EEE Science

Report on Digital Communication System

Executive Summery

In this project, Digital Communication System using QPSK Modulation is analyzed and simulated. The main aim of the thesis is to achieve the best digital communication using QPSK modulation and reduce the effect of noises in the communication channel. This thesis details the software implementation of a modern digital communication system and digital modulation methods. The digital modulation schemes considered here include both baseband and Quadrature Phase Shift Keying (QPSK) techniques. The proposed communication system will serve as a practical tool useful for simulating the transmission of any digital data. We use the MATLAB programming to simulate the communication project and simulated portion are attached and discuss briefly. There are some steps of any digital communication model. We discuss each of the steps using necessary diagram and try to understand the reader nicely about digital communication system where we told about Linear Predictive Coding (LPC) in source coding, PLL and all the modulation technique specially the Quadrature Phase Shift Keying (QPSK) in detail for using in the digital communication. The proposed communication system will serve as a practical tool useful for simulating the transmission of any digital data. The various modules of the system include analog to digital converters, digital to analog converters, encoders/decoders and modulators/demodulators. The results show the viability of a QPSK modulated digital communications link.


Communication has been one of the deepest needs of the human race throughout recorded history. It is essential to forming social unions, to educating the young, and to expressing a myriad of emotions and needs. Good communication is central to a civilized society.

The various communication disciplines in engineering have the purpose of providing technological aids to human communication. One could view the smoke signals and drum rolls of primitive societies as being technological aids to communication, but communication technology as we view it today became important with telegraphy, then telephony, then video, then computer communication, and today the amazing mixture of all of these in inexpensive, small portable devices.

Initially these technologies were developed as separate networks and were viewed as having little in common. As these networks grew, however, the fact that all parts of a given network had to work together, coupled with the fact that different components were developed at different times using different design methodologies, caused an increased focus on the underlying principles and architectural understanding required for continued system evolution.

The possible configurations of the link are numerous, so focus was maintained on a typical system that might be used in satellite communications. For this reason convolution channel coders and QPSK modulation were chosen. Additionally, channel effects were primarily modeled as the combination of band laired additive white Gaussian noise (AWGN) and signal attenuation. The results of this link on speech transmission show the various gains and tradeoffs that are realized as data passes through the entire system; the quantitative performance is measured by the probability of bit error, Pe, and the effect various signal to noise ratios have on this probability.

The idea of converting an analog source output to a binary sequence was quite revolutionary in 1948, and the notion that this should be done before channel processing was even more revolutionary. By today, with digital cameras, digital video, digital voice, etc., the idea of digitizing any kind of source is commonplace even among the most technophobic. The notion of a binary interface before channel transmission is almost as commonplace. For example, we all refer to the speed of our internet connection in bits per second.

There are a number of reasons why communication systems now usually contain a binary interface between source and channel (i.e., why digital communication systems are now standard). These will be explained with the necessary qualifications later, but briefly they are as follows:

– Digital hardware has become so cheap, reliable, and miniaturized, that digital interfaces are eminently practical.

– A standardized binary interface between source and channel simplifies implementation and understanding, since source coding/decoding can be done independently of the channel, and, similarly, channel coding/decoding can be done independently of the source.

This thesis studies the Digital Communication System for Quadrature Phase Shift Keying (QPSK) modulation used in digital communications. Software implementation is performed in the MATLAB programming languages and consists of separately coding and interfacing the various functions of the system. By modularizing the various functions which are performed on the data from source to destination, it becomes convenient to change individual sections of the link and model the effects of different transmission conditions on data as it is passed through the channel. The modules of the link include source encoders/decoders, channel encoders/decoders, modulators/demodulators, and channel effects.


We use Quadrature Phase Shift Keying (QPSK) Technique in the Digital communication system for better signal transmit and receive in the communication model.

In chapter one, the use and necessary of digital communication in our life has been presented in brief.

In chapter two, we describe the basic digital communication system and channel model which is use in this thesis.

In chapter three, source coding is described briefly. The source encoder is responsible for producing the digital information which will be manipulated by the remainder of the system.

In chapter four, we describe the channel coding in brief and the goal of channel coding is told which allows the detector at the receiver to detect and/or correct errors which might have been introduced during transmission. We use AWGN in the channel coding and it is also presented.

In chapter five, we describe the modulation technique of the digital communication in which Quadrature Phase Shift Keying (QPSK) is described elaborately.

In chapter six, the channel equalization and adaptive filtering are presented in brief.

In chapter seven, we described the demodulation of the communication model used in the thesis.

In chapter eight, we demonstrate the simulation result of QPSK modulation. The software for the simulation, we use the MATLAB platform.

A conclusion was made in chapter nine.

Literature Review

Chapter 2


In this chapter, we describe the basic digital communication system and channel model which is use in this thesis. The model is a simple model of digital communication system. The model is broken into its constituent functions or modules, and each of these is in turn described in terms of its affects on the data and the system. Since this model comprises the entire system, both the source coding and channel equalization are briefly described. In chapters 3 through 8, these two areas will be covered in detail, and the specific algorithms and methods used in the software implementation will be addressed in detail.

We organize this chapter as follows. First, we review some basic notions from digital communications. We present one basic model of digital communication system. We then talk about source encoding and decoding, channel encoding and decoding, modulation, digital interface and channel effects.


Communication systems that first convert the source output into a binary sequence and then convert that binary sequence into a form suitable for transmission over particular physical media such as cable, twisted wire pair, optical fiber, or electromagnetic radiation through space.

Digital communication systems, by definition,are communication systems that use such a digital sequence as an interface between the source and the channel input (and similarly between the channel output and final destination).

Figure 2.1 in the basic digital communication model the first three blocks of the diagram (source encoder, channel encoder, and modulator) together comprise the transmitter .The source represents the message to be transmitted which includes speech, video, image, or text data among others. If the information has been acquired in analog form, it must be converted into digitized form to make our communication easier. This analog to digital conversion (ADC) is accomplished in the source encoder block. Placing a binary interface between source and channel. The source encoder converts the source output to a binary sequence and the channel encoder (often called a modulator) processes the binary sequence for transmission over the channel.

The last three blocks consisting of detector/demodulator, channel decoder, and source decoder form the receiver. The destination represents the client waiting for the information. This might include a human or a storage device or another processing station. In any case, the source decoder’s responsibility is to recover the information from the channel decoder and to transform it into a form suitable for the destination. This transformation includes digital to analog conversion (DAC) if the destination is a human waiting to hem or view the information or if it is an analog storage device. If the destination is a digital storage device, the information will be kept in its digital state without DAC. The channel decoder (demodulator) recreates the incoming binary sequence (hopefully reliably), and the source decoder recreates the source output.


The source encoder and decoder in Figure 2.1 have the function of converting the input from its original form into a sequence of bits. As discussed before, the major reasons for this almost universal conversion to a bit sequence are as follows: inexpensive digital hardware, standardized interfaces, layering, and the source/channel separation theorem.
The simplest source coding techniques apply to discrete sources and simply involve representing each successive source symbol by a sequence of binary digits. For example, letters from the 27symbol English alphabet (including a space symbol) may be encoded into 5-bit blocks. Since there are 32 distinct 5-bit blocks, each letter may be mapped into a distinct 5-bit block with a few blocks left over for control or other symbols. Similarly, upper-case letters, lower-case letters, and a great many special symbols may be converted into 8-bit blocks (“bytes”) using the standard ASCII code.

For example the input symbols might first be segmented into m – tupelos, which are then mapped into blocks of binary digits. More generally yet, the blocks of binary digits can be generalized into variable-length sequences of binary digits. We shall find that any given discrete source, characterized by its alphabet and probabilistic description, has a quantity called entropy associated with it. Shannon showed that this source entropy is equal to the minimum number of binary digits per source symbol required to map the source output into binary digits in such a way that the source symbols may be retrieved from the encoded sequence.

Some discrete sources generate finite segments of symbols, such as email messages, that are statistically unrelated to other finite segments that might be generated at other times. Other discrete sources, such as the output from a digital sensor, generate a virtually unending sequence of symbols with a given statistical characterization. The simpler models of Chapter 2 will correspond to the latter type of source, but the discussion of universal source coding is sufficiently general to cover both types of sources, and virtually any other kind of source.

The most straight forward approach to analog source coding is called analog to digital (A/D) conversion.


The channel encoder and decoder box in Figure 2.1 has the function of mapping the binary sequence at the source/channel interface into a channel waveform.

One of the advantages of digital communications over analog communications is its robustness during transmission. Due to the two state nature of binary data (i.e. either a 1 or a 0), it is not as susceptible to noise or distortion as analog data. While even the slightest noise will corrupt an analog signal, small mounts of noise will generally not be enough to change the state of a digital signal from I to 0 or vice versa and will in fact be ‘ignored’ at the receiver while the correct information is accurately recovered.
Nevertheless, larger amounts of noise and interference can cause a signal to be demodulated incorrectly resulting in a bit stream with errors at the destination. Unlike an analog system, a digital system can reduce the effect of noise by employing an error control mechanism which is used prior to modulation. The channel encoder performs this error control by systematically introducing redundancy into the information bit stream after it has been source encoded but prior to its transmission. This redundancy can then be used by the receiver to resolve errors that might occur during transmission due to noise or interference.

The channel decoder performs the task of decoding the received coded bit stream by means of a decoding algorithm tailored for the encoding scheme. Error control of this variety that allows a receiver to resolve errors in a bit stream by decoding redundant information introduced at the transmitter is known as Forward Error Correction (FEC). The price paid for employing FEC is the increased bit rate and complexity of the transmitter and receiver.


The digital modulator serves as an interface between the transmitter and the channel. It serves the purpose of mapping the binary digital information it receives into waveforms compatible with the channel. In baseband modulation, the output waveforms we simple voltage pulses which take predefined values corresponding to a 1 or 0. However, many channels, such as a satellite channel, are not suited for backhand communication and require the incoming data to be modulated to a higher frequency, referred to as the carrier frequency, so it can be converted to an electromagnetic wave that will propagate through space to its destination ( a satellite or a ,round station) This type of modulation, known as band pass modulation, varies one of the following three parameters of the carrier frequency based on the incoming digital bit stream: amplitude, frequency or phase. These modulation types are commonly known as Amplitude Shift Keying (ASK). Frequency Shift Keying (FSK) and Phase Shift Keying (PSK) respectively.

The digital detector/demodulator reverses the process and extracts the binary baseband information from the received modulated signal which has been subjected to noise, interference, loss, and other distortions. The demodulator produces a sequence of binary values which are estimates of the transmitted data and passes it on to the channel decoder.


The interface between the source coding layer and the channel coding layer is a sequence of bits. However, this simple characterization does not tell the whole story. The major complicating factors are as follows:

– Unequal rates: The rate at which bits leave the source encoder is often not perfectly matched to the rate at which bits enter the channel encoder.

– Errors: Source decoders are usually designed to decode an exact replica of the encoded sequence, but the channel decoder makes occasional errors.

– Networks: Encoded source outputs are often sent over networks, traveling serially over several channels; each channel in the network typically also carries the output from a number of different source encoders.

The first two factors above appear both in point-to-point communication systems and in networks. They are often treated in an ad hoc way in point-to-point systems, whereas they must be treated in a standardized way in networks. The third factor, of course, must also be treated in a standardized way in networks.


During transmission, the signal undergoes various degrading and distortion effects as it passes through the medium from the transmitter to the receiver. This medium is commonly referred to as the channel. Channel effects include, but are not limited to, noise, interference, linear and non linear distortion and attenuation. These effects are contributed by a wide variety of sources including solar radiation, weather and signals front adjacent channels. But many of the prominent effects originate from the components in the receiver. While many of the effects can be greatly reduced by good system design, careful choice of filter parameters, and coordination of frequency spectrum usage with other users, noise and attenuation generally cannot be avoided and are the largest contributors to signal distortion.

In digital communication systems, a common quantity used to determinate whether a signal will be detected correctly is the ratio of energy per bit to spectral noise power density, Eb / No, measured at the detector. The higher the Eb, the lower the resulting bit error rate (BER), the probability of bit error, Pb Unfortunately, a high Eb demands greater power consumption at the transmitter; in some cases, it may be unfeasible to obtain a high Eb due to transmitter size or power limitations as in the case of satellite transmission.

The digital communication system described consists of an ordered grouping of various modules which operate on an input data sequence. In practice, these modules or resources are not dedicated to a single source/destination, but they me shared by multiple sources and their destinations to achieve optimum utilization.

In a digital system, the transmission bit rate is an important system resource. A given information source of bandwidth B, sampled at 2B samples/second using q bits per sample results in a data rate, R, of 2Bq bits per second. With a compression ratio C, the data rate from the source encoder is Rs = RIC bits per second. Channel coding by a factor n leads to a coded data rate of Rc = Rs n bits per second; R, is the system transmission bit rate. These bits we then used by the modulator to form the transmission waveforms which have to be accommodated within the available bandwidth. At the receiver these steps m performed in the reverse order to recover the information sequence.

Chapter 3


In the digital communication system model described previously, the source encoder is responsible for producing the digital information which will be manipulated by the remainder of the system. After the digital signal is acquired from the analog information, the source encoder subjects it to a wide range of processing functions, the goals of which are to compactly represent the information. Speech, image, and textual information each have their own unique characteristics that require different source encoding techniques. Depending on the information source, different digital signal processing functions are implemented to remove the redundancies inherent in the given signal. The specifics of the speech compression techniques used in this thesis are detailed below.

In this chapter we describe the source coding and then its related speech compression, Linear predictive coding (LPC) and Code excited linear prediction (CELP).The use of these in digital communication in source coding. And we also describe the LPC in large as we use it in the source coding in our digital communication thesis.


Since the frequency content of spoken language is confined to frequencies under 4000 Hz, it is reasonable to use a sampling frequency of 8000 Hz. Using 16 bit linear Pulse code modulation (PCM) as the quantization method results in a bit rate of 128 kbps. Subsequent analysis, coding, and compression of speech are performed on segments or frames of 20 to 30 ms duration.

There are two broad categories of speech coding/compression. Both categories are concerned with representing the speech with the minimum number of applicable parameters while also allowing the speech to be intelligibly reproduced; both are loss in nature.

The first category deals with waveform coders which manipulate quantities in the speech signal’s frequency representation. Typical analysis tools of waveform coders are the Discrete Fourier Transform (DFT) and the Discrete Wavelet Transform (DWT), both of which transform the time signal to its frequency domain representation. In this case, compression might potentially be achieved by retaining the frequency components with the largest magnitudes.

The second category of speech compression deals with voice coders, or vocoders for short. Vocoders attempt to represent speech as the output of a linear system driven by either periodic or random excitation sequences as shown in Figure 3.1.

A periodic impulse train or a white noise sequence, representing voiced or unvoiced speech, drives an all pole digital filter to produce the speech output. The all pole filter digital filter models the vocal tract.

Additionally, estimates of the pitch period and gain parameters are necessary for accurate reproduction of the speech. Due to the slowly changing shape of the vocal tract over time, vocoders successfully reproduce speech by modeling the vocal tract independently for each frame of speech and driving it by an estimate of a separate input excitation sequence for that frame. Most vocoders differ in performance principally based on their methods of estimating the excitation sequences.


Linear Predictive Coding (LPC) is one of the most powerful speech analysis techniques, and one of the most useful methods for encoding good quality speech at a low bit rate. It provides extremely accurate estimates of speech parameters, and is relatively efficient for computation. This document describes the basic ideas behind linear prediction, and discusses some of the issues involved in its use.

Linear prediction model speech waveforms are same by estimating the current value from the previous values. The predicted value is a linear combination of previous values. The linear predictor coefficients are determined such that the coefficients minimize the error between the actual and estimated signal. The basic equation of linear prediction is given as follows:
LPC starts with the assumption that the speech signal is produced by a buzzer at the end of a tube. The glottis (the space between the vocal cords) produces the buzz, which is characterized by its intensity (loudness) and frequency (pitch). The vocal tract (the throat and mouth) forms the tube, which is characterized by its resonances, which are called formants. For more information about speech production, see the Speech Production OLT.
LPC analyzes the speech signal by estimating the formants, removing their effects from the speech signal, and estimating the intensity and frequency of the remaining buzz. The process of removing the formants is called inverse filtering, and the remaining signal is called the residue.
The numbers which describe the formants and the residue can be stored or transmitted somewhere else. LPC synthesizes the speech signal by reversing the process: use the residue to create a source signal, use the formants to create a filter (which represents the tube), and run the source through the filter, resulting in speech.
Because speech signals vary with time, this process is done on short chunks of the speech signal, which are called frames. Usually 30 to 50 frames per second give intelligible speech with good compression.

A. Speech Production

When a person speaks, his or her lungs work like a power supply of the speech production system. The glottis supplies the input with the certain pitch frequency (F0). The vocal tract, which consists of the pharynx and the mouth and nose cavities, works like a musical instrument to produce a sound. In fact, different vocal tract shape would generate a different sound. To form different vocal tract shape, the mouth cavity plays the major role. To produce nasal sounds, nasal cavity is often included in the vocal tract. The nasal cavity is connected in parallel with the mouth cavity. The simplified vocal tract is shown in Fig 3.2.

The glottal pulse generated by the glottis is used to produce vowels or voiced sounds. And the noise-like signal is used to produce consonants. ..or unvoiced sounds.

B. Linear Prediction Model

An efficient algorithm known as the Levinson-Durbin algorithm is used to estimate the linear prediction coefficients from a given speech waveform.

Assume that the present sample of the speech is predicted by the past M samples of the speech such that

Where the prediction of is is the kth step previous sample, and ak are called the linear prediction coefficients.

The transfer function is given by

Because ε(n), residual error, has less standard deviation and less correlated than speech itself, smaller number of bits is needed to quantize the residual error sequence. Equation can be rewritten as the difference equation of a digital filter whose input is ε (n) and output is s (n) such that

The implementation of the above equation is called the synthesis filter and is shown in Figure 3.5.

If both the linear prediction coefficients and the residual error sequence are available, the speech signal can be reconstructed using the synthesis filter. In practical speech coders, linear prediction coefficients and residual error samples need to be compressed before transmission. Instead of quantizing the residual error, sample by sample, several important parameters such as pitch period, code for a particular excitation, etc are transmitted. At the receiver, the residual error is reconstructed from the parameters.


Although the data rate of plain LPC coders is low, the speech reproduction, while generally intelligible, has a metallic quality, and the vocoder artifacts are readily apparent in the unnatural characteristics of the sound. The reason for this is because this algorithm does not attempt to encode the excitation of the source with a high degree of accuracy. The CELP algorithm attempts to resolve this issue while still maintaining a low data rate.

Speech frames in CELP are 30 ms in duration, corresponding to 240 samples per frame using a sampling frequency of 8000 Hz. They are further partitioned into four 7.5 ms sub frames of 60 samples each. The bulk of the speech analysis/synthesis is performed over each sub frame.

The CELP algorithm uses two indexed codebooks and three lookup tables to access excitation sequences, gain parameters, and filter parameters. The two excitation sequences are scaled add summed to form the input excitation to a digital filter created from the LPC filter parameters. The codebooks consist of sequences which are each 60 samples long, corresponding to the length of a sub frame.

CELP is referred to as an analysis by synthcsis technique.
Figure 3.6 shows a schematic diagram of the CELP analyzer/coder. The stochastic codebook is fixed containing 512 zero mean Gaussian sequences. The adaptive codebook has 256 sequences formed from the input sequences to the digital filter and updated every two sub frames. A code from the stochastic codebook is scaled and summed with a gain scaled code from the adaptive codebook.

The result is used as the input excitation sequence to an LPC synthesis filter. The output of the filter is compared to the actual speech signal, and the weighted error between the two is compared to the weighted errors produced by using all of the other codewords in the two codebooks. The codebook indices of the two codewords (one each from the stochastic add adaptive codebooks), along with their respective gains, which minimize the error are then coded for transmission along with the synthesis filter (LPC) parameters. Because, the coder passes each of the adaptive and stochastic codewords through the synthesis filter before selecting the optimal codewords.

Chapter 4


We considered the problem of digital modulation by means of M=2k signal waveforms, where each waveform conveys k bits of information. We observed that some modulation methods provide better performance than others. In particular, we demonstrated that orthogonal signaling waveforms allow us to make the probability of error arbitrarily mail by letting the number of waveforms M → ∞ provided that the SNR per bit γb ≥ 1.6 dB. Thus, we can operate at the capacity of the Additive White Gaussian Noise channel in the limit as the bandwidth expansion factor Be =W/R→∞. This is a heavy price to pay, because Be grows exponentially with the block length k. Such inefficient use of channel bandwidth is highly undesirable.

In this and the following chapter, we consider signal waveforms generated from either binary or no binary sequences. The resulting waveforms are generally characterized by a bandwidth expansion factor that grows only linearly with k. Consequently, coded waveforms offer the potential for greater bandwidth efficiency than orthogonal M ary waveforms. We shall observe that. In general, coded waveforms offer performance advantages not only in power limited applications where RIW<1, but also in bandwidth limited systems where R/W > 1.

We begin by establishing several channel models that will be used to evaluate the benefits of channel coding, and we shall introduce the concept of channel capacity for the various channel models, then, we treat the subject of code design for efficient communications.


In the model of a digital communication system described in chapter 2, we recall that the transmitter building block; consist of the discrete input, discrete output channel encoder followed by the modulator. The function of the discrete channel encoder is to introduce, in a controlled manner, some redundancy in the binary information sequence, which can be used at the receiver to overcome the effects of noise and interference encountered in the transmission of the signal through the channel. The encoding process generally involves taking k information bits at a time and mapping each k bit sequence into a unique n bit sequence, called a code word. The amount of redundancy introduced by the encoding of the data in this manner is measured by the ratio n/k. The reciprocal of this ratio, namely k/n, is called the code rate.

The binary sequence at the output of the channel encoder is fed to the modulator, which serves as the interface to the communication channel. As we have discussed, the modulator may simply map each binary digit into one of two possible waveforms, i.e., a 0 is mapped into s1 (t) and a 1 is mapped into S2 (t). Alternatively, the modulator may transmit q bit blacks at a time by using M = 2q possible waveforms.

At the receiving end of the digital communication system, the demodulator processes the channel crurrupted waveform and reduces each waveform to a scalar or a vector that represents an estimate of the transmitted data symbol (binary or M ary).The detector, which follows the demodulator, may decide on whether the ‘transmitted bit is a 0 or a 1. In such a case, the detector has made a hard decision. If we view the decision process at the detector as a form of quantization, we observe that a hard decision corresponds to binary quantization of the demodulator output. More generally, we may consider a detector that quantizes to Q > 2 levels, i.e. a Q ary detector. If M ary signals are used then Q ≥ M. In the extreme case when no quantization is performed, Q = M. In the case where Q > M, we say that the detector has made a soft decision.

A. Binary Symmetric Channel

Figure 4.1: A composite discrete-input, discrete output channel

Let us consider an additive noise channel and let the modulator and the demodulator/detector be included as parts of the channel. If the modulator employs binary waveforms and the detector makes hard decisions, then the composite channel, shown in Fig. 4.1, has a discrete-time binary input sequence and a discrete-time binary output sequence. Such a composite channel is characterized by the set X = {0, 1} of possible inputs, the set of Y= {0, 1} of possible outputs, and a set of conditional probabilities that relate the possible outputs to the possible inputs. If the channel noise and other disturbances mum statistically independent errors in the transmitted binary sequence with average probability P then,

P(Y = 0 / x = 1) = P(Y = 1 / x = 0) = P

P(Y = 1 / x = 1) = P(Y = 0 / X = 0) = 1- P
Thus, we have reduced the cascade of the binary modulator, the waveform channel, and the binary demodulator and detector into an equivalent discrete-time channel which is represented by the diagram shown in Fig 4.1. This binary-input, binary-output, symmetric channel is simply called a binary symmetric channel (BSC).

B. Discrete Memory Less Channel

The BSC is a special can of a more general discrete-input, discrete-output channel. Suppose that the output form the channel encoder are q ary symbols, i.e., X={x0, x1,…,xq -1) and the output of the decoder consists of q ary symbols, where Q ≥M =2q.

Figure 4.2: Binary symmetric channels

If the channel and the modulation are memory less, then the input-output characteristics of the composite channel, shown in Fig. 4.1, are described by a set of qQ conditional probabilities.

C. Waveform Channels

We may separate the modulator and demodulator from the physical channel, and consider a channel model in which the inputs are waveforms and the outputs are waveforms. Let us assume that such a channel has a given bandwidth W, with ideal frequency response C(f) =1 within the bandwidth W, and the signal at its output is corrupted by additive white Gaussian noise. Suppose that x (t) is a band-limited input to such a channel and y (t) is the corresponding output, then,

y(t) = x(t) + n(t)

Where n(t) represents a sample function of the additive noise process.


For (n,1) convolution codes, each bit of the information sequence into the encoder results in an output of n bits. However, unlike block codes, the relationship between information bits and output bits is not a simple one-to-one mapping. In fact, each input information bit is ‘convolved’ with K-1 other information bits to form the output n bit sequence. The value K is known as the constraint length of the code and is directly related to its encoding and decoding complexity as described below in a brief explanation of the encoding process.

For each time step, an incoming bit is stored in a K stage shift register, and bits at predetermined locations in the register are passed to n modulo 2 adders to yield the n output bits. Each input bit enters the first stage of the register, and the K bits already in the register are each shifted over one stage with the last bit being discarded from the last stage.

The n output bits produced by the entry of each input bit have a dependency on the preceding K-1 bits. Similarly, since it is involved in the encoding of K-1 input bits in addition to itself, each input bit is encoded in nK output bits. It is in this relationship that convolutional coding derives its power. For larger values of K, the dependencies among the bits increased the ability to correct more errors rises correspondingly. But the complexity of the encoder and especially of the decoder also becomes greater.

convolutional code encoder
Shown in Figure 4.3 is the schematic for a (2,1) encoder with constraint length K= 3 which will serve as the model for the remainder of the development of convolutional coding. In the coder shown, the n = 2 output bits are formed by modulo 2 addition of the bits in stages one and three and the addition of bits in stages one, two, and three of the shift register.

Chapter 5


In this chapter, we describe the basic Modulation Technique and emphasis on QPSK Modulation which is use in this thesis. We are trying to show how QPSK Modulation is used in digital communication system. In digital transmission systems, the data sequence from the channel encoder is partitioned into L bit words, and each word is mapped to one of M corresponding waveforms according to some predetermined rule, where M = 2L. We shall see later, in a QPSK modulation system, the incoming sequence is separated into words of L = 2 bits each and mapped to M = 22 = 4 different waveforms. During transmission, the channel causes attenuation and introduces noise to the signal. The net result is the formation of a version of the original signal which may not be detected correctly by the receiver. If the errors are too numerous, the channel decoder may not be able to resolve the information correctly. Baseband modulation using the simple binary symmetric channel model is briefly discussed, and the details of QPSK modulation are then presented.

We organize this chapter as follows. First, we review some basic from Modulation Technique. We present basic modulation of Amplitude Shift-keying (ASK), Frequency Shift-keying(FSK),Phase Shift-keying(PSK), Binary Phase Shift-keying (BPSK) and Quadrature Phase Shift-keying(QPSK). We then talk about Quadrature Phase Shift-keying(QPSK) in detail and try to show the use of QPSK in digital communication system.


In many situations, for example in radio frequency transmission, data cannot be transmitted directly, but must be used to modulate a higher frequency sinewave carrier. The simplest way of modulating a carrier with a data stream is to change the amplitude of the carrier every time the data changes. This technique is known as amplitude shift -keying.

The simplest form of amplitude shift-keying is on- off keying, where the transmitter outputs the sinewave carrier whenever the data bit is a ‘1’, and totally suppresses the carrier when the data bit is ‘0’. In other words, the carrier is turned ‘on’ for a ‘1’, and ‘off ‘ for a ‘0’.This form of amplitude shift-keying is illustrated in figure below:

Figure 5.1: an ASK signal (below) and the message (above)

In order to generate an amplitude shift-keyed (ASK) wave form at the Transmitter a balanced modulator circuit is used (also known as a linear multiplier). This device simply multiplies together the signals at its two inputs, the output voltage at any instant in time being the product of the two input voltages. One of the inputs is a.c. coupled; this is known as the carrier input. The other is d.c. coupled and is known as the modulation (or signal) input.

In order to generate the ASK waveform, all that is necessary is to connect the sine wave carrier to the carrier input, and the digital data stream to the modulation input, as shown in figure below:

Figure 5.2: ASK generation method

The data stream applied to the modulator’s modulation input is unipolar, i.e. its ‘0’ and ‘1’ levels are 0 volts and +5volts respectively. Consequently.

(1) When the current data bit is a ‘1’ , the carrier is multiplied by a constant, positive voltage, causing the carrier to appear, unchanged in phase, at the modulator’s output.

(2) When the current data bit is a ‘0’, the carrier is multiplied by 0 volts, giving 0 volt as at the modulators output.

At the Receiver, the circuitry required to demodulate the amplitude shift- keyed wave form is minimal.The filter’s output appears as a very rounded version of the original data stream, and is still unsuitable for use by the “Receiver’s digital circuits. To overcome this, the filter’s output wave form is squared up by a voltage comparator.

5.2 Frequency Shift-keying

In frequency shift -keying, the signal at the Transmitter’s output is switched from one frequency to another every time there is a change in the level of the modulating data stream For example, if the higher frequency is used to represent a data ‘1’ and the lower ferquency a data ‘0’, the reasulting Frequency shift keyed (FSK) waveform might appear as shown in Figure below:

Figure 5.3 An ASK waveform

The generations of a FSK waveform at the Transmitter can be acheived by generating two ASK waveforms and adding them together with a summing amplifier.

At the Receiver, the frequency shift-keyed signal is decoded by means of a phase-locked loop (PLL) detector. The detector follows changes in frequency in the FSK signal, and generates an output voltage proportional to the signal ferquency.

The phase-locked loop’s output also contains components at the two carrier frequencies; a low-pass fillter is used to filter these components out.

The filter’s output appears as a very rounded version of the original data stream, and is still unsuitable for use by the Receiver’s digital circuits. To overcome this, the filter’s output waveform is squared up by a voltage comparator. Figure below shows the functional blocks required in order to demodulate the FSK waveform at the Receiver.

5.3 Phase Shift keying (PSK)

In phase shift keying the phase of the carrier sinewave at the transmitter’s output is switched between 0 º and 180 º, in sympathy with the data to be transmitted as shown in figure below:

Figure 5.3: phase shift keying

The functional biocks required in order to generate the PSK signal are similar to those required to generate an ASK signal. Again a balanced modulator is used, with a sinewave carrier applied to its carrier input. In contscast to ASK generation, however, the digital signal applied to the madulation input for PSK generation is bipolar, rather than unipolar, that is it has equal positive and negative voltage levels.

When the modulation input is positive, the modulator multiplies the carier input by this constant level. so that the modulator’s output signal is a sinewave which is in phase with the carrier input.

When the modulation input is negative, the modulator multiplies the carrier input by this constant level, so that the modulatior’s autput signal is a sinewave which is 180 º out of phase with the carier input.

At the Receiver, the frequency shift-keyed signal is decoded by means of a squaring loop detector. This PSK Demodulator is shown in figure below:


In binary phase shift keying (BPSK), the transmitted signal is a sinusoid of fixed amplitude it has one fixed phase when the data is at one level and when the data is at the other level the phase is different by 180 º . If the sinusoid is of Amplitude A it has a power :

Ps = 1/2 A2
A = Root over (2 Ps)

BPSK(t) = Root over (2 Ps) Cos (ω0t)
BPSK(t) = Root over (2 Ps) Cos (ω0t+π )
= – Root over (2 Ps) Cos (ω0t)

In BPSK the data b(+) is a stream of binary digits with voltage levels which, we take to be at +1V and – 1 V. When b(+) =1V we say it is at logic 1 and when b(+)= -1V we say it is logic 0. Hence, BPSK(t) can be written as:

BPSK(t) = b(t) Root over (2 Ps) Cos (w0t)

In practice a BPSK signal is generated by applying the waveform Coswo as a carrier to a balanced modulator and applying the baseband signal b(+) as the modulating signal. In this sense BPSK can be thought of as an AM signal similar as PSK signal.

5.5 Quadrature Phase Shift Keying (QPSK)

In this section the topics of QPSK modulation of digital signals including their transmission, demodulation, and detection, are developed. The material in this section and the related coding of this system are both based on transmission using an AWGN channel model which is covered at the end of this section. Some of the techniques discussed below are specifically designed for robustness under these conditions.

Because this is a digital implementation of a digital system, it is important to note that the only places where analog quantities occur are after the DAC, prior to the actual transmission of the signal, and before the ADC at the receiver. All signal values between the source encoder input and modulator output are purely digital. This also holds for all quantities between the demodulator and the source decoder.

A. Background

QPSK modulation is a specific example of the more general M ary PSK. For M ary PSK, M different binary words of length L = log2 M bits are assigned to M different waveforms. The waveforms we at the same frequency but separated by multiples of φ = 2π/M in phase from each other and can be represented as follows:

, =

with i = 1, 2, … M. The carrier frequency and sampling frequency are denoted by fc and fs respectively.

Since an M ary PSK system uses L bits to generate a waveform for transmission, its symbol or baud rate is 1IL times its bit rate. For QPSK, there we M = 4 waveforms separated by multiples of ( = ) radians and assigned to four binary words of length L = 2 bits. Because QPSK requires two incoming bits before it can generate a waveform, its symbol or baud rate, D, is one half of its bit rate, R.

B. Transmitter

Figure 5.2 illustrates the method of QPSK generation. The first step in the formation of a QPSK signal is the separation of the incoming binary data sequence, b, into an in phase bit stream, b1, and a quadratic phase bits ream, bQ, as follows. If the incoming data is given by b = bo, b1, b2, b3, b4…. where bi are the individual bits in the sequence, then, bI = bo, b2, b4 ……(even bits of b) and bQ= b1, b3, b5 …… (odd bits). The digital QPSK signal is created by summing a cosine function modulated with the bI, stream and a sine function modulated by the bQ stream. Both sinusoids oscillate at the same digital frequency, ω0=2π fc / fs radians. The QPSK signal is subsequently filtered by a band pass filter, which will be described later, and sent to a DAC before it is finally transmitted by a power amplifier.

Figure 5.4 QPSK Modulator
B.1 Signal Constellation

It is often helpful to represent the modulation technique with its signal space representation in the I Q plane as shown in Figure 5.3. The two axes, I and Q, represent the two orthogonal sinusoidal components, cosine and sine, respectively, which are added together to form the QPSK signal as shown in Figure 5.2. The four points in the plane represent the four possible QPSK waveforms and me separated by multiples of n/2 radians from each other. By each signal point is located the input bit pan which produces the respective waveform. The actual I and Q coordinates of each bit pair are the contributions of the respective sinusoid to the waveform. For example, the input bits (0, 1) in the second quadrant correspond to the (I,Q) coordinates, ( 1,1). This yields the output waveform I + Q = cos (ω0n) + sin (ω0n). Because all of the waveforms of a QPSK have the same amplitude, all four points are equidistant from the origin. Although the two basis sinusoids shown in Figure 5.2 are given by cos (ω0n) and sin (ω0n), the sinusoids can be my two functions that are orthogonal.

Figure 5.3 Signal Constellation of QPSK

B.2 Filtering

The QPSK signal created by the addition of the two sinusoids has significant energy in frequencies above and below the carrier frequency. This is due to the frequency contributions incurred during transitions between symbols which are either 90 degrees or 180 degrees out of phase with each other. It is common to limit the out of band power by using a digital band pass filter (BPF) centered at ωo. The filter has a flat pass band and a bandwidth which is 1.2 to 2 times the symbol rate.

C. Receiver

The receiver’s function consists of two steps: demodulation and detection. Demodulation entails separating the received signal into its constituent components. For a QPSK signal, these are the cosine and sine waveforms carrying the bit information. Detection is the process of determining the sequence of ones and zeros those sinusoids represent.

C.1 Demodulator

The demodulation procedure is illustrated below in Figure 5.4. The first step is to multiply the incoming signal by locally generated sinusoids. Since the incommoding signal is a sum of sinusoids, and the receiver is a linear system, the processing of the signal can be treated individually for both components and summed upon completion.

Figure 5.4: QPSK Demodulator and Detector

Assuming the received signal is of the form

r(n) = AI cos(ω0 n) + AQ sin (ω0 n)

where AI and AQ are scaled versions of the bI and bQ bitstreams used to modulate the signal at the transmitter. The contributions through the upper and lower arms of the demodulator due to the cos(ω0 n) input alone are

rci = AI cos(ω0 n) cos (ω0 n+ ө)

rcQ = AI cos(ω0 n) sin (ω0 n+ ө)

where ө is the phase difference between the incoming signal and locally generated sinuso¬ids. These equations can be expanded using trigonometric identities to yield.

C.2 Detection

After the signal r(n) has been demodulated into the bitstreams dj(n) and dQ(n), the corresponding bit information must be recovered. The commonly used technique is to use a matched filter at the output of each LPF as shown in Figure 5.4. The matched filter is an optimum receiver under AWGN channel conditions and is designed to produce a maximum output when the input signal is a min or image of the impulse response of the filter. The outputs of the two matched filters are the detected bitstreams bdj and bdO, and they are recombined to form the received data bitstream. The development of the matched filter and its statistical properties as an optimum receiver under AWGN conditions can be found in various texts.

5.6 AWGN Channel

The previously introduced BSC channel modeled all of the channel effects with one parameter, namely the BER; however, this model is not very useful when attempting to more accurately model a communication system’s behavior. The biggest drawback is the lack of emphasis given to the noise which significantly corrupts all systems.

The most commonly used channel model to deal with this noise is the additive white Gaussian noise (AWGN) channel model. The time results because the noise is simply added to the signal while the term ‘white’ is used because the frequency content is equal across the entire spectrum. In reality, this type of noise does not exist and is confined to a finite spectrum, but it is sufficiently useful for systems whose bandwidths are small when compared to the noise power spectrum.

Chapter 6


Equalization is partitioned into two broad categories. The first category, maximum likelihood sequence estimation (MLSE), entails making measurements of impulse response and then providing a means for adjusting the receiver to the transmission environment. The goal of such adjustment is to enable the detector to make good estimates from the demodulated distorted pulse sequence. With an MLSE receiver, the distorted samples are not reshaped or directly compensated in any way; instead, the mitigating techniques for MLSE receiver is to adjust itself in such a way that it can better deal with the distorted samples such as Viterbi equalization.
The second category, equalization with filters, uses filters to compensate the distorted pulses. In this second category, the detector is presented with a sequence of demodulated samples that the equalizer has modified or cleaned up from the effects of ISI. The filters can be distorted as to whether they are linear devices that contain only feed forward elements (transversal equalizer), or whether they are nonlinear devices that contain both feed for ward and feedback elements (decision feedback equalizer) the can be grouped according to the automatic nature of their operation, which may either be preset or adaptive.
They are also grouped according to the filter’s resolution or update rate.
Symbol spaced
Pre detection samples provided only on symbol boundaries, that is, one sample per symbol. If so, the condition is known.
Fractionally spaced
Multiple samples provided for each symbol. If so, this condition is known.

An adaptive equalizer is an equalization filter that automatically adapts to time-varying properties of the communication channel. It is frequently used with coherent modulations such as phase shift keying, mitigating the effects of multipath propagation and Doppler spreading. Many adaptation strategies exist. A well-known example is the decision feedback equalizer, a filter that uses feedback of detected symbols in addition to conventional equalization of future symbols. Some systems use predefined training sequences to provide reference points for the adaptation process.
Adaptive equalization is capable of tracking a slow time varying channel response. It can be implemented to perform tap weight adjustments periodically or continually. Periodic adjustments are accomplished by periodically transmitting a preamble or short training sequence of digital data that is known in advance by the receiver. The receiver also detects the preamble to detect start of transmission, to set the automatic gain control level, and to align internal clocks and local oscillator with the received signal. Continual adjustments are accomplished by replacing the known training sequence with a sequence of data symbol estimated from the equalizer output and treated as known data. When performed continually and automatically in this way, the adaptive procedure is referred to as decision directed. Decision directed only addresses how filter tap weights are adjusted-that is with the help of signal from the detector. DFE, however, refers to the fact that there exists an additional filter that operates on the detector output and recursively feed back a signal to detector input. Thus with DFE there are two filters, a feed forward filter and a feed back filter that processes the data and help mitigate the ISI.
Adaptive equalizer particularly decision directed adaptive equalizer, successfully cancels ISI when the initial probability of error exceeds one percent. If probability of error exceeds one percent, the decision directed equalizer might not converge. A common solution to this problem is to initialize the equalizer with an alternate process, such as a preamble to provide good channel error performance, and then switch to the decision directed mode. To avoid the overhead represented by a preamble many systems designed to operate in a continuous broadcast mode use blind equalization algorithms to form initial channel estimates. These algorithms adjust filter coefficients in response to sample statistics rather than in response to sample decisions.
Automatic equalizer use iterative techniques to estimate the optimum coefficients. The simultaneous equations do not include the effects of channel noise. To obtain a stable solution to the filter weights, it is necessary that the data are average to obtain, stable signal statistics or the noisy solution obtained from the noisy data must be averaged considerations of algorithm complexity and numerical stability most often lead to algorithms that average noisy solutions. The most robust of this class of algorithm is the least mean square algorithm.

Suppose we have an FIR filter with adjustable coefficient {h(k),0<k<N-1}. Let x(n) denote the input sequence to the filter, and let the corresponding output be {y(n)}, where
y(n) = n=0,….M

Suppose we also have a desired sequence d(n) with which we can compare the FIR filter output. Then we can form the error sequence e(n) by taking the difference between d(n) and y(n). That is,
e(n)=d(n)-y(n), n=0,….M
The coefficient of FIR filter will be selected to minimize the sum of squared errors.
Thus we have

where, by definition,
rdx(k)= 0 ≤ k ≤ N-1
rxx(k)= 0 ≤ k ≤ N-1
We call rdx(k) the cross correlation between the desired output sequence d(n) and the input sequence x(n), and rxx(k) is the auto correlation sequence of x(n).
The sum of squared errors ε is a quadratic function of the FIR filter coefficient. Consequently, the minimization of ε with respect to filter coefficient h(k) result in a set of linear equations. By differentiating ε with respect to each of the filter coefficients, we obtain,

∂ε /∂h(m)=0, 0 ≤ m ≤ N-1
and, hence
rxx(k-m)=rdx(m), 0 ≤ k ≤ N-1
This is the set of linear equations that yield the optimum filter coefficients.
To solve the set of linear equations directly, we must first compare the autocorrelation sequence rxx(k) of the input signal and cross correlation sequence rdx(k) between the desired sequence d(n) and input sequence x(n).
The LMS provides an alternative computational method for determining the optimum filter coefficients h(k) without explicitly computing the correlation sequences rxx(k) and rdx(k). The algorithm is basically a recursive gradient (steepest-descent) method that finds the minimum of ε and thus yields the optimum filter coefficients.
We begin with the arbitrary choice for initial values of h(k), say h0(k). For example we may begin with h0(k)=0, 0 ≤ k ≤ N-1,then after each new input sample x(n) enters the adaptive FIR filter, we compute the corresponding output, say y(n), from the error signal e(n)=d(n)-y(n), and update the filter coefficients according to the equation
hn(k)=hn-1(k)+ Δ.e(n).x(n-k), 0 ≤ k ≤ N-1, n=0,1,…..
where Δ is called the step size parameter, x(n-k) is the sample of the input signal located at the kth tap of the filter at time n, and e(n).x(n-k) is an approximation (estimate) of the negative of the gradient for the kth filter coefficient. This is the LMS recursive algorithm for adjusting the filter coefficients adaptively so as to minimize the sum of squared errors ε.
The step size parameter Δ controls the rate of convergence of the algorithm to the optimum solution. A large value of Δ leads to a large step size adjustments and thus to rapid convergence, while a small value of Δ leads to slower convergence. However if Δ is made too large the algorithm becomes unstable. To ensure stability, Δ must be chosen to be in the range
0< Δ < 1/10NPx
Where N is length of adaptive FIR filter and Px is the power in the input signal, which can be approximated by
Px ≈ 1/(1+M)



Let us assume that we have a signal sequence x(n) that consists of a desired signal sequence, say w(n), computed by an AWGN interference sequence s(n). The two sequences are uncorrelated.

The characteristics of interference allow us to estimate s(n) from past samples of the sequence x(n)=s(n)+w(n) and to subtract the estimate from x(n).

The general configuration of the interference suppression system is shown in the entire block diagram of the system. The signal x(n) is delayed by D samples, where delay is chosen sufficiently large so that the signal components w(n) and w(n-D), which are contained in x(n) and x(n-D) respectively, are uncorrelated. The out put of the adaptive FIR filter is the estimate

s(n) =

The error signal that is used in optimizing the FIR filter coefficients is e(n)=x(n)-s(n). The minimization of the sum of squared errors again leads to asset of linear equations for determining the optimum coefficients. Due to the delay D, the LMS algorithm for adjusting the coefficients recursively becomes,
hn(k)=hn-1(k)+ Δ.e(n).x(n-k-D), k=0,1,…..N-1

Chapter 7


Function of receiver consists of two parts:

A. Demodulation

B. Detection

Demodulation is the act of extracting the original information-bearing signal from a modulated carrier wave. A demodulator is an electronic circuit used to recover the information content from the modulated carrier wave. Coherent Demodulation is accomplished by demodulating using a local oscillator (LO) which is at the same frequency and in phase with the original carrier. The simplest form of non-coherent demodulation is envelope detection. Envelope detection is a technique that does not require a coherent carrier reference and can be used if sufficient carrier power is transmitted.

Although the structure of a non-coherent receiver is simpler than is a coherent receiver, it is generally thought that the performance of coherent is superior to non-coherent in a typical additive white Gaussian noise environment. Demodulation entails separating the received signal into its constituent components. For a QPSK signal, these are cosine and sine waveforms carrying the bit information. Detection is the process of determining the sequence of ones and zeros those sinusoids represent.


The first step is to multiply the incoming signal by locally generated sinusoids. Since the incoming signal is a sum of sinusoids, and the receiver is a linear system, the processing of the signal can be treated individually for both components summed upon completion. Assuming the received signal is of the form

r(n)=Ai cos(ω0n)+Aq sin(ω0n)

where Ai and Aq are scaled versions of the bi and bq bit stream used to modulate the signal at the transmitter. Due to cos(ω0n) input alone,

rci(n)= Ai cos(ω0n) cos(ω0n+Ө)


rcq (n)= Ai cos(ω0n) sin(ω0n+Ө)

where Ө is the phase difference between incoming signal and locally generated sinusoids. Similarly for sin(ω0n) portion of the input r(n),

rsi(n)= Ai sin(ω0n) cos(ω0n+Ө)……….7.1


rsq(n)= Ai sin(ω0n) sin(ω0n+Ө)………..7.2


For the received data to be interpreted and detected correctly there needs to be coordination between the receiver and transmitter. Since they are not physically connected, the receiver has no means of knowing the state of the transmitter. This state includes both the phase argument of the modulator and the bit timing of the transmitted data sequence. The receiver must therefore extract the desired information from the received digital signal to achieve synchronization. A common means of accomplishing synchronization is with a PLL. A phase-locked loop or phase lock loop (PLL) is a control system that generates a signal that has a fixed relation to the phase of a “reference” signal. A phase-locked loop circuit responds to both the frequency and the phase of the input signals, automatically raising or lowering the frequency of a controlled oscillator until it is matched to the reference in both frequency and phase. PLL compares the frequencies of two signals and produces an error signal which is proportional to the difference between the input frequencies. The error signal is then low-pass filtered and used to drive a voltage-controlled oscillator (VCO) which creates an output frequency. The output frequency is fed through a frequency divider back to the input of the system, producing a negative feedback loop. If the output frequency drifts, the error signal will increase, driving the frequency in the opposite direction so as to reduce the error. Thus the output is locked to the frequency at the other input. This input is called the reference and is often derived from a crystal oscillator, which is very stable in frequency. At first the received signal is raised to 4th power. Then it is passed through a 4th order band pass filter and frequency divider. Thus the two sinusoid outputs used to demodulate the received signal are produced.


The signals [equation (7.1) and (7.2)] are passed through corresponding envelop detector and threshold comparator to obtain I data and Q data. An envelope detector is an electronic circuit that takes a high-frequency signal as input, and provides an output which is the “envelope” of the original signal. The capacitor in the circuit stores up charge on the rising edge, and releases it slowly through the resistor when the signal falls. The diode in series ensures current does not flow backward to the input to the circuit. Then threshold comparators compare the signals with their values and generate the I data and Q data. These are recombined by switching device to form received bit stream.


Figure 7.1: DETECTION

7.4 AWGN Channel

During transmission, the signal undergoes various degrading and distortion effects as it passes through the medium from transmitter to receiver. This medium is commonly referred to as the channel. Channel effects include but are not limited to noise, interference, linear and non linear distortion and attenuation. These effects are contributed by a wide verity of sources including solar radiation, weather and signal from adjacent channels. But many of the prominent effects originate from the components in the receiver. While many of the effects can be greatly reduced by good system design, careful choice of filter parameters and coordination of frequency parameter usage with other users, noise and attenuation generally can not be avoided and are the largest contributors to signal distortion.

The most commonly used channel model to deal with noise is the additive white Gaussian noise (AWGN) channel model. The name results because the noise is simply added to the signal while the term white is used because the frequency content is equal across the entire spectrum. In reality this type of noise does not exists and is confined to a finite spectrum, but it is sufficiently useful for systems whose bandwidth are small compared to the noise power spectrum. When modeling a system across an AWGN channel, the noise must first be filtered to the channel prior to addition.

Chapter 8



The section describes the performance of QPSK Modulation for speech.The simulation was done using MATLAB 7 platform.

All codes for this chapter are contained in Appendix A. An adaptive filter is used in these routines. All of the repeatedly used values such as cosine and sine are retrieved from look up tables to reduce computation load.


A speech signal is transmitted through the entire system. In each case speech signals are obtained from the internet. These are short segments of speech data of 6-7 seconds. From the speech signal 30874 samples are taken.

These samples are then quantized. Here 4 bit PCM is used (as 8 bit or higher PCM takes longer time during the simulation) to obtain a total of 123496 bits from 30874 samples.

The bits are divided into even bits and odd bits using flip flop. Here for simplicity and for the purpose of better understanding only 8 bits are shown on the figure instead of 123496 bits. Consider that the bit sequence is 11000110.

The even bits (1010) are modulated using a carrier signal (sine wave) and odd bits (1001) are modulated using the same carrier signal with 90 degree phase shift (cosine wave). The modulation process is explained explicitly in the previous sections. In the case of odd data cosine wave represents 1 while cosine wave with 180 degree phase shift represents 0. On the other hand in the case of even data sine wave represents 1 and sine wave with 180 degree phase shift represents 0. The odd data and even data are modulated separately in this way and then added using a linear adder to obtain QPSK modulated signal. This signal is passed through a band pass filter and transmitted through the channel.

8.3 Channel and receiver

In this system AWGN channel is considered. As the signal passes through the channel it is corrupted by AWGN noise. AWGN command in MATLAB is used to generate this noise. Here SNR is taken sufficiently large to avoid possibility of bit errors. Bit error rate and the performance of the system depend highly on the SNR which is discussed later in this chapter. To remove this AWGN interference sequence from the received signal the signal is passed through an adaptive filter. The adaptive filter uses LMS algorithm which is explained explicitly in the previous sections. Then the desired signal is obtained.

This desired signal is then passed through the demodulation process. At first it is passed through a PLL to obtain necessary carrier signal. Here for simplicity the angle generated by PLL is considered zero. At one side this desired signal is demodulated with sine wave to obtain even data while on the other side it is demodulated by cosine wave to obtain odd data.

Then these signals are passed through corresponding envelop detector and threshold comparator to obtain odd data and even data. When data is greater than .75 then it detected as 1 on the other hand when data is less than .75 then it is detected as 0. After that a switching device is used to combine odd data and even data.

Then this bit stream is passed through the decoder and the received speech signal is obtained. This received signal can be heard using soundsc command

Here theoretical Eb/N0 vs. BER curve for QPSK is shown



In this project the details of a digital communication system implementation using QPSK modulation and adaptive equalization have been discussed. Pulse-code modulation (PCM) is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a numeric (usually binary) code. PCM can facilitate accurate reception even with severe noise or interference. An adaptive equalizer is an equalization filter that automatically adapts to time-varying properties of the communication channel. It is frequently used with coherent modulations. It is useful for estimating and suppressing AWGN interference. Lastly, QPSK is an efficient modulation scheme currently used by modem satellite communication links.
We studied QPSK modulation technique through out the project. Instead of using other modulation techniques such MSK, 8-QPSK, 16-QPSK etc we used 4-QPSK in this project. QPSK is a quaternary modulation method, while MSK is a binary modulation method. In QPSK, the I and Q components may change simultaneously, allowing transitions through the origin. In a hypothetical system with infinite bandwidth, these transitions occur instantaneously; however, in a practical band-limited system (in particular, a system using a Nyquist filter) these transitions take a finite amount of time. This results in a signal with a non-constant envelope. MSK performed in such a way that the transitions occur around the unit circle in the complex plane, resulting in a true constant-envelope signal. Using 8-QPSK and 16-QPSK techniques higher data rate and higher spectral efficiency can be achieved but BER also increases. The performance of MSK, 8-QPSK, 16-QPSK techniques is better but implementation of these techniques is complex. 4-QPSK is simpler and easy to implement. Its spectral efficiency is not higher than that of 8-QPSK, 16-QPSK but it provides lower BER. In this project we performed the simulation of 4-QPSK modulation technique using MATLAB platform accurately and without any error. The system is flexible enough in accommodating any speech signal or analog signal. Digital communication systems can be implemented using QPSK modulation.


Report on Real State Sector of Bangladesh


Back ground of the study:

Bachelor of Business Administration (BBA) program of  World University of Bangladesh (WUB) requires each student to  complete an internship for at least three months with an organization and submit a report based on internship assignment. The scope of the application of theoretical knowledge of marketing gathered from BBA program has widened by interacting with the customers of THL during internship program.

Emerging competitors are fighting to gain substantial market share, though THL is considered as a leader in real estate sector.  In the arena of competitive market environment it has become significantly important for any company to analyze its performance of different marketing strategies in order to survive in the volatile market environment as well as to manage companies’ operations efficiently and effectively for achieving its objectives. This report is tailored to focus on the marketing activities of THL that is performing to retain market share and uphold the growth. 


Name of Association: Real Estate & Housing Association of Bangladesh

Year of Establishment: 1991

No of Member in 1991: 11

No of Member in 2008 (June): 320

No of Apt. units Delivered by the Developer in last 20 year: 56,000 (App.)

No of Apt. units Delivered by the Developer per year (2009): 7500-8500 units

No of Plot units Delivered by the Developer per year: 4500-5500 units.

Approx. turnover per year: 1,250 Crore Taka (Tk. 12.50 billion)

Contribution revenue to Govt.: 100 Crore Taka (Tk. 1.00 billion)

Direct Employment-

  1. Architects: 400 nos

b. Graduate Engineer: 2000 nos

c. Diploma Engineer: 8000 nos

d. Management Official: 14000 nos.

e. Direct Labour Skilled & unskilled : 1.5 million (15 Lacs ).

f. Contribution to GDP: 12-14 %.


The main reasons why real estate business developed in Dhaka city are as follows:
a. Scarcity of open space in the important areas of the city
b. Hazards of purchasing land
c. Hazards of construction of building
d. Rapid increase in population of Dhaka
e. Decrease in the rate of bank interest
f. Price of land and apartments is increasing day by day
g. Rent of the apartments is comparatively higher than the rent of privately constructed flats
h. Open Market Economy. Remittance of foreign currency is very easy
i. Security
j. Service facilities such as garbage disposal, central satellite TV connection, apartment’s services saves time, roof top facilities, lift and so on.


Real estate business especially apartment projects has started in late 1970s in DhakaCity. But from early ’80s the business started to grow and flourish. At present, more than 250 companies are active in business but 95% business is still dominated by of top 10 Companies. Present market is growing at the rate 15%


 I. Broad Objectives:

The broad objective of this report is to measure the marketing activities performing by the “Marketing & Sales Department of “Tropical Homes Ltd.”

II. Specific Objectives:

The specific objectives of this report are:

a. To make THL familiar with the readers and future researchers.

b. Take a closure look on the activities, policies and practices of THL.

c. Take look on the overall real estate sector of Bangladesh.

d. Identify the target market and market segmentation of THL.

e. Prepare a recommendation for THL


This internship report mainly focus on the activities of “Marketing & Sales Department” of THL. In this report, I discussed the things those I have observed at the time of my internship in that department. I have reviewed the overall marketing and sales activities of THL and at the end I give a recommendation for “Marketing & Sales Department” of THL.   Though this is not a research type report, I do not include any findings in it. My internship period was from 1st June, 2009 to 30th August, 2009 and all of my report focuses all those activities that I had observed at that time.


The study is carried out using both primary and secondary data.

Primary data collection: To prepare this report, the primary data was collected mainly through the survey as official assignment during the time of internship. Other methods are-

a. Observation.

b. Interview.

c. Telephone Interview.

d. Personal Interview.

e. Oral & Informative interview with the officers and employees of the “Marketing &

Sales Department “of THL.

Secondary data collection:  The secondary data have been collected from different publications of REHAB, different journals of THL, and related magazines and journals. I have used data collected from company publications with a view to observe the THL’s marketing activities, policies and company practices.


There were some limitations which have made my work a little bit harder. The limitations may be termed as follows-

a)      I have no previous experience about the preparation and organization of the internship report.

b)      It was not so much possible for me to get the exact information about some of the departments because of maintaining the secrecy.

c)      I did not get sufficient information about the real estate sector of Bangladesh.

d)     The executives of some departments were so busy that they could not give me sufficient time.

e)      The web resources were also not ample to get sufficient help


a)      THL-Tropical Homes Ltd.

b)      REHAB- Real Estate And Housing Association of Bangladesh


Tropical Homes Limited (THL) is estate of the art builder and one of the fastest growing real-estate developers in Bangladesh since 1996. The company allows the members to serve the nation ultimately in a different angle very smartly.

It is just a matter of long term planning on any environment friendly geographical location. Of course it involves so many factors in deciding about that. It has taken twenty two projects in different locations in Dhaka (till June 2009). Already it has completed about eight projects. THL is little a bit slow but steady in persuasion of its goal.

The management personnel, managers, executives, architects, engineers and staffs members are serving for the enhancement of efficiency of the company so that the company serves the clients better. Departmentalization is specially taken care for systematic and coordinated operation of the company activities. A panel of advisors, consultants and patrons are also continuously working for its enrichment of products and services.

THL was established with the primary goal of providing first-grade quality service and takes a leadership role in the Real Estate market. Throughout the year THL’s dedications to quality and diligence in remaining technically astute have been the key ingredients of it’s success in several clients’ engagements. THL has been able to maintain long-term relationship with distinctions and pride. While the trend in many businesses has been to diversify, this basic trend has guided THL to diversify its activities.

THL emphasizes it’s capabilities in undertaking large complex development projects, and shares the commitment with clients in meeting stringent deadlines and objectives. The company pride itself in being able to make the difference between a project that is delayed and a job that is well done within a reasonable time frame. It is totally a customer focus company and serve it’s best to make them smile.










Dr.Md. Rezaul Karim Chairman Marketing & Sales. MBBS, PhD
Mr. Rabiul Hoque  Managing Director. Administration MSc. MBA
Dr. Sanjita Akhter Director. Development MBBS, FCGP


Managing DirectorThe main responsibility of the managing director is to manage and supervise the entire department including Accounts & Finance, Consumer Care, Land Procurement, Admin & Human Resources Management, Logistic, Legal, and Information Technology.

Chairman­ THL’s chairman is the director of “Marketing and Sales” department. His responsibilities are to maintain the managers and executives of this department. He has the authority to finalize the sales.

Director The Director of THL manages and supervises “Engineering” and “Land Development” department.

Total Employees -Around 200 persons.


The Company incorporated to Joint Stock Companies, Bangladesh on April 21, 1996 under the company act of 1994 and under section 34 of the company act.


Address: House # Planners Tower (6th floor) 13/A, Bipanon C/A, Bir Uttam C.R Datta Road, Banglamotor, Dhaka-1000

Contact: Telephone # 8614280, 9344452 Fax # 8652153,


Web Address:

Company Registration No: C-30581(1797)/1996, April 21, 1996

Company’s TIN NO: 142 200 8445/CO.15 TEX AREA-5, DHAKA.

Dhaka City Corporation’s (DCC) Trade License No.: 157190.

Company Vat No- 9131051985. 



  • To maintain the highest standards in developing commercial properties.
  • To maintain the highest standards in developing homes for individuals.
  • To create safe homes.
  • To provide a fine blend of the traditional and contemporary design.
  • To provide feeling of living in a home with ultimate comfort.
  • To provide professional and personalized services of the highest integrity.
  • To become an international referral for buyers and investors.
  • To provide high quality Customer Relationship Management.
  • To develop and train staff.


  • Maintain outstanding service to its clients.
  • Maintain a high standard of quality of finish.
  • Maintain a safe environment.
  • Maintain value for many.
  • Continue good communications procedures.
  • Continue to promote a sense of corporate identity within all the staff team.
  • Continue to provide staff training to providing Excellence Customer Care.
  • Continue develop ‘Brand Name’.
  • Marketing and promoting to individuals quality homes in Bangladesh.
  • Marketing and promoting to won luxury homes for investment or comfort living.


Dhaka is a densely populated city but with inadequate housing facility and quality of life, especially for the middle & lower middle class people. Tropical Homes Ltd. is committed to improve the quality of life of these people by offering good quality, low cost apartment affordable to all of customers. High- rise and mixed-use projects being more advantageous and cheaper, we have diverted our attention more to this area and now it is a highly acclaimed name & trendsetter in the market. Big and exclusive commercial building, joint venture project housing complex, within our field of interest. Innovation, dynamism and perfection lead us to ultimate satisfaction of our customers and that is our goal


Our objective is to create vest employ, make urbanization with modern facilities which will ensure safe environment and where quality will not be compromised. Innovation, dynamism and perfection lead us to ultimate satisfaction of our customers and that is our objective.


Five major attributes make the cornerstone of THL’s success:


The standards which set for the company and which govern it’s engagements constantly reinforce it’s goal of brining the highest level of professionalism to all it’s engagements. The company exists to serve it’s clients those who are directed to meet this commitments. THL reflects this commitment to quality through the activities of it’s managers and executives, who are personally involved in quality related activities such as planning, goal-setting, employee recognition, progress reviews and meeting with customers. They project and reinforce the Company’s quality values in a consistent manner and engage all levels of management to co-operate in this effort. THL’s management is responsible for reinforcing the firm’s vitality by infusing each assignment with integrity and excellence of effort. Consistency in meeting user objectives with a shared sense of concern accounts for it’s reputation of excellence and reliability.


Teamwork within THL Occurs when people work in a community of shared technical, personal and economic interests. To successfully carry out their missions THL’s employees are assigned to projects where their technical disciplines complement one another in achieving the customer’s business objectives. But there is more. THL maintain just first class interpersonal relationship within it’s office & beyond. Within the workplace there is a sense enthusiasm and eagerness to demonstrate technical proficiency by working together to produce the best results possible. THL fosters a team spirit and the founders of the company have this idea of close co-operation in mind at the very beginning.


The managers and executives of the company are directly involved in each project. Every assignment is important. If customer has a problem, they make it their problem. They know customers want a timely and accurate resolution. The customers rely on them and value their trust and confidence very highly. They know customer is their boss. They satisfy these needs by remaining constantly available to their customers and allocating the kind of resources their customers may need & they provide the best solution in a timely manner. Customers are the center of their enterprise and they will take necessary actions to support customers’ success every time. They believe that only by understanding the customers needs a company can deliver superior service and stay ahead of competitors.


THL believes that the best way to improve productivity is to give its people the opportunity to learn, contribute to the process and develop each individual’s own sense of achievement. THL’s major strength lies in its pool of professionals and their substantial backgrounds in the real estate industry. In a spirit of co-operation, the professionals have succeeded in meeting the goals of some of the most complex assignments. It is their demand for excellence that the enthusiasm they bring to consulting, which has contributed to the THL ‘s success.


Long-term success can only be assured by cultivating new ideas. That is the way THL encourages its people to be creative, gives them the means to see their ideas realized.


a)      Amin Mohammad Foundation Ltd.

b)      Asset Development & Holdings Ltd.

c)      Bashati Consortium Ltd

d)     The Structural Engineers Ltd.

e)      East West Property Development (pvt.) ltd.

f)       Concord Condominium Ltd.

g)      Building Technology & Ideas Ltd.

h)      Rangs Properties Ltd.

i)        Navana Real Estate Ltd.

j)        Oriental Real Estate LTD.

k)      Sheltec Ltd.

l)        Suvastu Development Ltd.


Sl. No.

Project’s Name

Description & Location


Shalley Homes


6-Storied Apartment Buildingion
373, 22 Free School Street
Hatirpul, Dhaka.


Planners Tower


15-Storied CommercialBuilding

13/A, Bipanon C/A, Bir Uttam C.R Datta Road, Banglamotor, Dhaka-1000



Rahman Tropical Tower 14-Storied Apartment Building
52-52/1-52/5, Purana Paltan Line, Dhaka.
Phone: 9331489


Tropical Kishwer


14-Storied Apartment Building
52-52/1-52/5, Purana Paltan Line, Dhaka.
Phone: 9331489,


Tropical Prime


6-Stroried Apartment Building
130, West Nakhalpara, Tejgaon, Dhaka.
Phone: 8117736, 01


Tropical Srabonti


6-Storied Apartment Building
Plot No. 1, Road No. 9, Sector-6, Uttara.
Phone: 01819-25


Tropical Sony 6-Storied Apartment Building
35/A, Gopibagh (3rd Lane)
Phone: 7121607, 01819-253353


Tropical Razia Palace


14-Storied Commercial-cum-ApartmentBuilding
26/1, Chamelibagh, Dhaka.
Phone: 9331489,


Gulmohor 12-Storied Apartment Building
19/2, Garden Road, Kawranbazar, Dhaka
Phone: 8152505, 01


Gulfesha Plaza


15-Storied CommercialBuilding
69, Outer Circular Road,
Moghbazar, Dhaka.


Boro Bazar
6-Storied Shopping Centre
104, Green Road, Dhaka.
Phone: 8127603, 01713-040490


Tropical M. L. Point
16-Storied Commercial-cum-ResidentialBuilding
43, New Circular Road, Moghbazar, Dhaka.


Pacific Homes


10-Storied Commercial-cum-ResidentialBuilding
1 & 2 (New) East Tejturi Bazar, Farmgate, Dhaka


Kader Tropical Heights


15-Storied Commercial-cum-Residential Building
10 Hatkhola Road, Dhaka.
Phone: 7121607


Highway Homes
9-Storied Commercial & 9,15 Storied Residential Building
Ka 32/6, Shahzadpur, Progoti Sarani,


Kunjan Homes


13-Storied Residential Building
55, Box Nagar, Zoo Road, Mirpur, Dhaka.
Phone: 8031865


Tropical Mirage


6-Storied Apartment Building
Plot No. 135, Road No. 12/A
West Dhanmondi, Dhaka



The “Marketing & Sales Department” of THL is one of the most important departments of THL. In this department, there are one manager, one assistant manager and two executives. They are smart, energetic, experienced and high educated. They are capable of handling clients and selling the products in the efficient and effective way.


The markets of THL for its existing and up coming projects are highly segmented. This segmentation is mainly based on the location, price of the land, and size of the apartments. The segmented areas are:

a) Segmentation – I   :Baridhara, Gulshan, Banani, DOHS, Uttara.
b) Segmentation – II: Dhanmondi, Kalabagan.
c) Segmentation – III: Shegunbagicha, Shantinagar, Kakrail, Malibagh.
d) Segmentation – IV: Mirpur.
e) Segmentation – V: Banglamotor, Eskaton..
f) Segmentation – VI  :(For office building) Motijheel, Dilkusha,

, Kawran Bazar, Pantha Path etc. 


  1. Dhanmondi.
  2. Uttara
  3. Siddeshawari
  4.  College Gate.
  5. Panthapath
  6. Mirpur
  7. Malibagh
  8. Chamelibagh
  9. Mohakhali DOHS. 


In Bangladesh, there are more or less 500 real estate companies are working. Some of them are REHAB members and some of them are not. No matter whether they are REHAB member or not, the main activity of any Real Estate Company is to sell their products. At the end of my graduation, as a student of Marketing, I had done my internship in THL’s “Marketing & Sales Department”. I worked there for three months and closely observed all the activities of employees of “Marketing & Sales Department”. Again all the employees of “Marketing & Sales Department”, helped me lot to understand and realize how a sales person market and sell the products. Now I am giving the broad description of all the marketing activities of THL –


The first and foremost activity of THL’s “Marketing & Sales Department” is to prepare the advertisement which will be given to the daily newspapers. THL gives ads frequently on the newspapers (per week minimum one ads is given). THL gives main ads mostly on “The Daily Prothom- Alo” and “The Daily Ittefaq”. THL also gives classified ads on different daily news papers. In the main ads, names of four or five upcoming and existing projects, flat size, handover date etc are given. At the below part of the main ads, the name of the company, telephone numbers of the company, mobile numbers of the marketing executives are given. For the preparation of the ads, the Promotion Manager of THL is responsible. His responsibilities are to prepare and develop ads to attract the clients. After preparing the ads, he shows the ad to the management of THL and after approving the particular ad by the management, finally the ad is given to the daily news paper on the previously fixed date.

3.3.2 Media User by the Developers:



Advertisement in News paper


Advertisement in Magazine


Advertisement on Television


Harding (Display)


Neon (Display)


Mail sort or News letter sending




Publishing Brochure





The busyness of the “Marketing & Sales Department” increases in that day, when the ad comes on the newspaper. In that day, all the executive officers remain busy for the whole day long. The prospect and proposed clients make phone calls after seeing the ads on newspapers. The executives receive phone calls, give description of the particular project, and tell them about project location, available flat size, present condition of the construction works, handover date, booking money etc. The executives do not share the price over the phone. Because it is strictly prohibited by the management of THL. But they always invite the clients to come at the office so that after sitting together both of them can discuss about the price.

After that, client/s come to the head office and sits with that particular marketing executive and discusses everything. The executive officer shows the floor plan, design, layouts etc. and make the customer understand all the things. Again here the price of the flat or the commercial spaces, booking money, price of the car parking, handover date etc. are discussed. It may not happen that, at the first time the prospect client purchase the product. Bargaining starts among both of them and sometimes it takes a lot of time and some times a few days to reach both of them in a unique decision.  Some clients want to visit the project and the executive took the client/s to the particular project. Through this process, the client/s has a practical idea about the project. After that, the interested client/s come to the head office and sits with the executive for the discussion process described before.           


In some cases, the executive officer took the client to sit with the management of THL and if the client offered the price which seems reasonable to the management, then the flat or commercial space is sold. As the head of the “Marketing and Sales Department”, the Chairman of THL, Dr. Md. Razaul Karim sits with client/s for the purpose of final sales. Then the prospect client pays the booking money and become the original client and a member of THL family.  The activities of the “Marketing and Sales Department” came to an end when the “Deed of Agreement” between that client/s and the company is mutually signed. As the representative of the company, the Managing Director of THL, Mr. Rabiul Hoque came into an agreement with that client/s through the “Deed of Agreement”.


Market Survey is an important activity of THL’s “Marketing and Sales Department”. But these surveys are not done by the executives of the “Marketing and Sales Department”. THL takes “Intern” from reputed universities and through these “Interns”, the surveys are accomplished. Before sending the “Interns” for survey, the executives of “Marketing and Sales Department” give proper instructions and guidelines to do the survey. These surveys are basically done to know the projects of different developers in those locations, where THL have existing projects or THL wants to take projects.


  1. Duplex homes
  2. Simplex homes
  3. Luxury Apartments
  4. Furnished Apartments.
  5. Commercial Space
  6. Shopping Complex
  7. OfficeBuilding
  8. Commercial Showroom.


1. Application for allotment of apartments should be made on the prescribed application form duly signed by the applicant along with the earnest money. THL has the right to accept or reject any application without assigning any reason thereto.
2. On acceptance of an application, THL will issue allotment letter to the applicant on which the applicant/allottee shall start making payment as per the schedule of the project. Allotment of apartments is made on first come first serve basis.
3. Payments of earnest money, instalments, car parking costs, additional works and other charges shall be made by cheque, bank draft or pay order directly in the name of THL against which the receipts will be issued. Bangladeshis residing abroad may remit payments in foreign exchange by TT or DD in the name of THL.

4. Payments of instalments and all other charges are to be made on due dates according to the schedule. THL may issue reminders to the allot tee, but notwithstanding the issue of reminders, the allot tee must adhere to the schedule to ensure timely completion of construction.  Allotte

5. THL may arrange HBFC/Bank loan (if available) for allot tees according to the existing rules and regulations of the authority concerned.

6. Delay in payments beyond the schedule date will make the allot tee liable to pay delay charge for every 30 days on the amount of the payment delayed. If the payment is delayed beyond 60 days, THL have the right to cancel the allotment. In such an event, the amount paid by the allot tee will be refunded after deducting the earnest money and after allotment of the cancelled apartment.

7. Connection fees/charges security deposits and other incidental expenses relating to gas, water, sewerage and electric connections are included in the price of apartments. THL will make those payments directly to the authorities concerned on the allot tee’s account.
8. Limited changes in the specifications, design and/or layout of the apartments and other facilities may be made by THL in larger overall interest or due to unavoidable reasons

9. THL may cancel an allotment for non-payment of instalments in disregard of reminders and after final intimation to the allot tee by registered post at the address given in the application form.

10. The allottee shall be required to execute an agreement with THL for safeguarding the interests

11. The possession of the apartment shall be duly handed over to the allot tee on completion and full payment of instalments and other charges and dues. Till then the possession will rest with THL. If the project is completed before the stipulated time, the allot tee shall have to make full payment before taking possession.

12. The allottees will become equally divisible undivided and undemarketed shareholders of total acres of the scheduled land of the project in respective apartment. After all the dues and instalments are paid by the purchaser according to the requirements and schedule for payment and after the completion of the construction, the vendors shall execute a registered sale deed in favour of the purchaser transferring share of land of the project in the demised apartment.

13. After taking over of apartment of the project, the allot tee (s) must consult with THL prior to undertaking any structural or layout changes within the apartment complex. Failure to do so will be at the sole risk of the allottee.

14. THL shall not be liable if the completion period of the construction of the projects is affected by unavoidable circumstances beyond the control of the company, like natural calamities, political disturbances, strikes and changes in the fiscal policy of the state etc.

15. For the purpose of effective management and maintenance of the building the purchaser of the apartment shall form and constitute a mutual benefit cooperative society under the Co-operative Society’s Act 1940. The society shall be entrusted with the management and maintenance of the building. The rules, regulations and by laws of the co-operative society relating to management and maintenance of the building shall be binding upon all the purchasers/owners of the apartments.


In Bangladesh, there is no policy guideline for the real estate sector. However, Real Estate and Housing Association of Bangladesh (REHAB), the national coordinator of the private real estate developers has proposed a policy guideline for the sustainable development of this sector. Some of the important guidelines of REHAB are stated below:

  1. Government and private real estate developers should play their role equally in the land development process of the urban and per-urban areas.
  2. The role of the private sector housing in the urbanization process should be evaluated properly while formulating urbanization related projects and policies.
  3. Several laws and regulations (stated in section 10.00) which have become obsolete should be updated immediately. There are some conflicts and duplicity among the laws which should be taken care of.
  4. While formulating the Structure plan, the business of the private real estate developers should be given utmost priority. In this regard, land banking system can be a handy tool.
  5. Proper subdivision planning and zoning laws would help the private developers to cope with the policies and provisions of the structure plan.
  6. The registration system for the private real estate sector should be rescheduled within acceptable terms.
  7. The designs or plan for the private real estate projects should be approved by RAJUK.
  8. 30% land area of any project to be kept aside for road, drainage and public utility service purpose.
  9. For the better utilization of the scarce land resource, high rise buildings should be patronized.
  10. Government’s control over the land value and house rent should be   strengthened.
  11. The Building Construction Act, 1996 and other government building codes should be enforced strictly.
  12. No private developers should be permitted to construct the housing scheme outside the proposed expansion zone of the structure plan.


1. THL should stables the latest service marketing strategy, which will provide satisfaction for the valuable customer and it is the demand for the time.

2. Internet, the information supper high way, which is a modern way of marketing, so, when THL will start internet marketing, customer will get easily access about the THL product and service.

3. THL did not provide 24 hours customer service facilities.

4. Scarcity of man power (Marketing & Sales Department) for distributing service to the existing and target customer.

5. Direct sales agents are not inspired by their sales commission, remuneration and inadequate performance reward.

6. Marketing and Sales policy is not up to the demand for the present time.

7. For the time THL is not providing any type of training program and workshops for the employees manage customers smoothly and increase sales & services.


During my tenure as in “Intern” in THL, my placement was in “Sales & Marketing Department”. I worked there for three months where I encountered some issues that I thought should catch the THL’s management’s attention to re-examine. THL is one of the topmost developers in the country and it has been operating quite successfully. Although it has a healthy and steady growth in sales development of apartment and shopping complex, the organization needs to address some of the bottlenecks found out at the time of internship programme conducted for the concerned study .In an attempt to solve various problems so far identified in this study, the following recommendations can be put forward, which are given below, are from observational point of view:

THL should implement the best service providing strategy that will ensure more value for the existing and target customers.

  1. When the THL should implement internet marketing then our existing client and potential client will be very effective in this point of view.
  1. THL should provide 24hours online service to the customers to solve their problems and queries.
  1. “Marketing and Sales Department” should run in the most efficient and effective way. For ensuring better service THL should recruit more people in this department.
  1. Marketing Team (Direct Sales Agents) is less motivated in their job. They are not satisfied with their sales commission. THL should provide them a fixed sales commission and some rewards like the best performer should be rewarded annually.
  1. The managers and executives of “Sales & Marketing Department” should give more sincere attention to solve the customers’ problems.
  1. “Sales & Marketing Department” should encourage in order to career development of the employees. By doing so, THL will be able to increase the performance of the employees.
  1. THL should take protective measures so that it can be ensured that the services provided by its employees are free to get in its highest limit. This will help clients to come out from the fear of false transaction.
  1. THL should wishes to the clients in different occasions. It will create an extra value for the clients and make them more pleased and positive about the company.
  1. Before selling apartments or commercial spaces, “Sales & Marketing Department” should meticulously verify the applicant’s income from salary, status and other required particulars because many clients have a tendency to furnish erroneous information in their applications.
  1. THL’s direct marketing effort must be implemented more precisely and elaborately to ensure maximum market coverage both for existing and proposed clients.
  1. Arrangement for offering attractive gifts & prizes for the clients and target clients should be made so that the numbers of clients are increasing day by day.
  1. They should apply some promotional activity to raise its sale.
  1. Evaluation for the good performance of the employees by introducing award and incentives.


Today Bangladesh stands on the juncture of economic emancipation. The stage is set for rapid growth and development in every sector of the economy. The real estate sector is also experiencing significant changes. ‘Professionalism’ is the key word for success now a days and in the years to come. Only those companies which have a total commitment to this sector will thrive. THL is determined to play a leading role in the development of the real estate sector in the twenty –first century. THL has worked towards building a strong foundation and establishing a professional corporate identity for the company. Today, in the field of real estate development, though THL is new, but in future, it will be a recognized leader which will be respected for its achievements, professional ethics and innovative concepts. THL’s corporate philosophy is however based on a very simple principle – “A friend in need”. To this end, THL is constantly working towards upgrading and improving every aspect of it’s activity. THL emphasises to keep on improving it’s overall operations. It is because of this unrelenting quest for excellence that THL have earned the goodwill of so many of it’s customers. Today THL is poised for a new phase of dynamic growth. THL’s human resource is well trained and motivated, It’s financial fundamentals are strong and it has an excellent goodwill in the market. THL’s vision is to constantly set challenging goals. THL will continue to expand and diversify and be an example of a progressive company, playing a dynamic role in the economic development of Bangladesh. THL is a newly formed company dedicated to build a ‘beautiful tomorrow’ for the people of Bangladesh. Strong leadership, total commitment and personal care orientation have already created a strong image of the company in the apartment market. With a firm belief in the potential and track record of the hard working management of the company, customers are assured of obtaining the best value against their investment. Every single client of the company is treated with most personal attention. The ultimate policy of the company is to retain a life long relationship with THL’s home-owners. For every project development, before entering in designing the project, a group of experts plan and design the project taking into considerations its location, environment, surroundings, urban facilities and some other important factors that ensure maximum comfort and convenience for the target dwellers. THL’s architects and consultants relentlessly give maximum time and effort to respond to modern days need and changes concerning function, aesthetics and technology. Their every development embraces the importance of all latest facilities and amenities with maximum air, light and ventilation. THL has a strong project management team. Each and every phase of construction is planned, determined, supervised and engineered by a strong group of experts who have a large experience in some major local and foreign constructions. Only for this Project Management Team, THL can hand over its projects before the stipulated time guaranteeing a quality construction with superb finishing. Each and every suggestion of THL’s valued customers is greatly emphasized at every phase of project construction. Since the customer satisfaction is the main motto, THL’s customer service department always stands beside the customers to give the best possible friendly service. Customer service people always ready to welcome the clients whenever they need. THL’s aim is not only to meet the international standard, but to exceed it by setting new standard in design, construction and service.

THL is filled with optimism and promises of rosy tomorrow with its fleet of highly qualified professional engineers, architects, efficient technical personnel with high capability to meet the challenges of the 21st century. THL is an efficient and socially responsible participant in infrastructural construction sector and committed to organizational pursuit of excellence in its undertakings. THL aspires to make a significant and lasting contribution to the nation’s development and quality of life. THL provide its clients with competitive pricing, quality materials and workmanship and completion of project on schedule as well as post completion attention to ensure complete satisfaction.