# digital communication system block diagram

What technological innovations and development are necessary to realize 5G – the fifth generation of wireless communications technology? Therefore at the input side, first we convert these non electrical signals into electrical signals then process these electrical signals and finally convert them back into the original form (non electrical) at the receiving end. Of them all, we have the main types with general classification, mentioned in the above figure. This is due to the transmission characteristics of the channel. Hence, the output will be the carrier signal at high input. The following figure illustrates an example for a quantization error, indicating the difference between the original signal and the quantized signal. If a 1 occurs at the incoming signal, then there occurs a transition at the beginning of the bit interval. This is the type of digital modulation technique used for data transmission in which instead of one bit, two or more bits are transmitted at a time. Uniform quantization is achieved at µ = 0, where the characteristic curve is linear and no compression is done. The destination also works as a transducer at the receiving end. Linear Predictive Coding (LPC) is a tool which represents digital speech signals in linear predictive model. Figure 1.1-1 illustrates the functional diagram and the basic elements of a digital communication system. Digital communication is one of the most commonly used mode of communication in the current scenario. Because it is much easier to process electrical signals in comparison to other non electrical signals. An intruder with no official access is never allowed to crack them. Following is the block diagram of Adaptive delta modulator. The various massage is the form of words, group of word, code, symbol, sound signal etc. To find the process of obtaining this ASK modulated wave, let us learn about the working of the ASK modulator. If there are ‘n’ number of connections, then the frame is divided into ‘n’ time slots. With these features, the spread spectrum signals are highly resistant to interference or jamming. The diagram is as follows. This binary or digital information has many types and forms, which are discussed further. Name five types of internal noise. The following figure shows the image of an eye-pattern. This chipping code is nothing but the spreading code which is multiplied with the original message and transmitted. These combinations act as demodulators and the decision circuit chooses which output is more likely and selects it from any one of the detectors. The received signal is demodulated as well as converted again from analog to digital. This signal to get converted into digital, has to undergo sampling and quantizing. There are a few techniques which have paved the basic path to digital communication processes. We have so far discussed mutual information. The pair of bits are recovered here from the original data. Hence, the interpretation of eye pattern is an important consideration. The Asynchronous ASK detector consists of a half-wave rectifier, a low pass filter, and a comparator. A greater value of figure-of-merit will be an advantage. The error probability should be very low, nearly ≤ 10-6 for a reliable communication. The bandwidth required for this coding is greater. Switching & Transmission Prof. Murat Torlak Digital Modulation Overview: In digital wireless communication … The above equation states that the input sequence of uncorrelated binary sequence {ak} is changed into a sequence of correlated three level pulses {ck}. The quality of a Quantizer output depends upon the number of quantization levels used. This process helps in effective utilization of the bandwidth. Information is the source of a communication system, whether it is analog or digital. The bandwidth efficiency of M-ary FSK decreases and the power efficiency increases with the increase in M. This is called as M-ary Phase Shift Keying (M-ary PSK). We can observe from the above pattern that the over-lapping of information is done, which leads to mixing up and loss of information. If the wavelength increases, the frequency of the signal decreases. View Answer: Answer: Source, Transmitter, Channel, Receiver, Destination. The amplitude of the carrier signal, takes on M different levels. There are many M-ary modulation techniques. In a communication system, the transmitter is located at one place, the receiver is located at some other place (maybe far or near) separate from the transmitter and the channel is that physical medium that connects them. Now, the parity bits are again added and the whole data is again encoded. Coherent ASK Detector, Baseband transmission and Optimal Reception of Digital Signal, Information and entropy, Matrix description of Linear Block Codes, Convolution Codes: Encoding, Spread Spectrum Modulation Etc. The decision circuit chooses which output is more likely and selects it from any one of the envelope detectors. The end or start of a bit will not be indicated and it will maintain the same voltage state, if the value of the previous bit and the value of the present bit are same. There are two types of Bi-phase Encoding. It is a type of quantization error, which usually occurs in analog audio signal, while quantizing it to digital. If the signal x(t) is sampled above the Nyquist rate, the original signal can be recovered, and if it is sampled below the Nyquist rate, the signal cannot be recovered. Multiplexing was first developed in telephony. The name duo-binary means doubling the binary system’s transmission capability. M represents a digit that corresponds to the number of conditions, levels, or combinations possible for a given number of binary variables. While the transition is from Low to High for the input bit 0. This is the technique which helps to collect the sample data at instantaneous values of message signal, so as to reconstruct the original signal. The output of the XNOR gate along with the carrier signal is given to the balance modulator, to produce the DPSK modulated signal. NRZ codes has a disadvantage that the synchronization of the transmitter clock with the receiver clock gets completely disturbed, when there is a string of 1s and 0s. Both the mid-rise and mid-tread type of uniform quantizers are symmetric about the origin. In the demodulation process the original message signal is recovered back from the modulated signal. As an Amazon Associate I earn from qualifying purchases. DPSK is a technique of BPSK, in which there is no reference phase signal. Entropy can be defined as a measure of the average information content per source symbol. Block Diagram of Basic Communication System: Fig. The name Eye Pattern was given from its resemblance to the human eye for binary waves. The sampling done here is the sample-and-hold process. Announcement: Group Work 8 follow up. Sampling frequency is the reciprocal of the sampling period. 1. Block Diagram of Basic Communication System: Fig. In the communication system, the maximum effect of the noise is in the channel. For LPC, the predictor co-efficient values are determined by minimizing the sum of squared differences (over a finite interval) between the actual speech samples and the linearly predicted ones. The spectral envelope is represented in a compressed form, using the information of the linear predictive model. This decreases the data bit rate to half, which allows space for the other users. For a 1, the voltage level gets a transition from + to – or from – to +, having alternate 1s to be of equal polarity. The serial data input is given to the XNOR gate and the output is again fed back to the other input through 1-bit delay. The block diagram of DPCM Receiver consists of a decoder, a predictor, and a summer circuit. Following is the diagram for the same. If we consider an event, there are three conditions of occurrence. Here n is greater than k. The transmitter adds redundant bits which are (n-k) bits. This is also called as Stair-case waveform, in accordance with its shape. Delta Modulation gives a better output than PCM. A line code is the code used for data transmission of a digital signal over a transmission line. Hence with $L_{min} = H(\delta)$, the efficiency of the source encoder in terms of Entropy $H(\delta)$ may be written as, $$\eta = \frac{H(\delta)}{\overline{L}}$$. The delta demodulator comprises of a low pass filter, a summer, and a delay circuit. Block Diagram of Communication System Main building blocks of the communication system in electronics are-*Source of information *Input transducer *Transmitter *Channel *Receiver *Destination All these basic building blocks of communication system are shown in the block diagram below-Block Diagram of Communication System Following is the block diagram of a delta modulator. FSK is a scheme of frequency modulation. The transmission losses of the channel and other factors affecting the quality of the signal, have to be treated. Very easy design of the modulator and the demodulator, Slope Over load distortion (when Δ is small). The design of the modulator and the demodulator is simple. For example, in telegraphy, we use Morse code, in which the alphabets are denoted by Marks and Spaces. A number of signals were combined to send through a single cable. Where Sk is the output of the discrete memoryless source and bk is the output of the source encoder which is represented by 0s and 1s. The signal droop is caused at places where the signal is non-zero at 0 Hz. The frequency of the output signal will be either high or low, depending upon the input data applied. Both the spread spectrum techniques are popular for their characteristics. The amount of uncertainty remaining about the channel input after observing the channel output, is called as Conditional Entropy. There are two variations in Unipolar signaling −. Let us assume that the source has an alphabet with k different symbols and that the kth symbol Sk occurs with the probability Pk, where k = 0, 1…k-1. The timing circuit determines the sampling times. This technique is used to transmit a signal over a single communication channel, by allotting one slot for each message. Fig. There are different methods for demodulating a FSK wave. The main function of a transmitter is to process an electrical signal obtained from the input transducer. Information or input signal. It is denoted by r and the value of r is r < 1. The Fourier Transform is the extension of Fourier series for non-periodic signals. There are two types of Companding techniques. A square law detector is one whose output voltage is proportional to the square of the amplitude modulated input voltage. (2) Digital In digital technology, the data are generated and processed in two states: High (represented as 1) and Low (represented as 0). The signals modulated with these techniques are hard to interfere and cannot be jammed. The synchronous detector is a coherent one, while asynchronous detector is a non-coherent one. Minimal phase estimation error at the receiver. As the sampling interval is reduced, the signal correlation will be higher. It is denoted by C and is measured in bits per channel use. The following figure quotes an example for blocks of data and stream of data, used for transmission of information. The following figure depicts this clearly. PSD is the Fourier Transform of Auto-Correlation (Similarity between observations). In this video the block diagram of basic digital communication system is discussed. Hence in this method, we have as many as 729 (3^6) combinations for signal and 256 (2^8) combinations for bits. Now, after a while, sender 1 hops to the other frequency and sender 2 uses the first frequency, which was previously used by sender 1. The bandwidth efficiency of M-ary PSK decreases and the power efficiency increases with the increase in M. So far, we have discussed different modulation techniques. The modulated ASK signal is given to the half-wave rectifier, which delivers a positive half output. Cyclic codes are used for error correction. The hardware implementation in digital circuits, is more flexible than analog. Signal processing functions such as encryption and compression are employed in digital circuits to maintain the secrecy of the information. This is called as frequency reuse. In this type of coding, the transition is done at the middle of the bit-interval. 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