KKW_ELTX_DCOM

                                                                                                                                               Name of Experiment :-Experimental study of Quadrature Phase shift keying  The  Quadrature Phase Shift Keying  QPSK  is a variation of BPSK, and it is also a Double Side Band Suppressed Carrier  DSBSC  modulation scheme, which sends two bits of digital information at a time, called as  bigits . Instead of the conversion of digital bits into a series of digital stream, it converts them into bit pairs. This decreases the data bit rate to half, which allows space for the other users. QPSK Modulator The QPSK Modulator uses a bit-splitter, two multipliers with local oscillator, a 2-bit serial to parallel converter, and a summer circuit. Following is the block diagram for the same. At the modulator’s input, the message signal’s even bits (i.e., 2 nd  bit, 4 th  bit, 6 th  bit, etc.) and odd bits (i.e., 1st bit, 3 rd  bit, 5 th  bit, etc.) are separated

                                                                                                                                                  Name of Experiment :-Experimental study of generation and detection of Direct spread spectrum system(DSSS). A collective class of signaling techniques are employed before transmitting a signal to provide a secure communication, known as the  Spread Spectrum Modulation . The main advantage of spread spectrum communication technique is to prevent “interference” whether it is intentional or unintentional. The signals modulated with these techniques are hard to interfere and cannot be jammed. An intruder with no official access is never allowed to crack them. Hence, these techniques are used for military purposes. These spread spectrum signals transmit at low power density and has a wide spread of signals. Pseudo-Noise Sequence A coded sequence of  1s  and  0s  with certain auto-correlation properties, called as  Pseudo-Noise coding sequence  is

  Name of Experiment :-Implementation of Convolutional   Code Using MATLAB Convolutional Codes In convolutional codes, the message comprises of data streams of arbitrary length and a sequence of output bits are generated by the sliding application of Boolean functions to the data stream. In block codes, the data comprises of a block of data of a definite length. However, in convolutional codes, the input data bits are not divided into block but are instead fed as streams of data bits, which convolve to output bits based upon the logic function of the encoder. Also, unlike block codes, where the output codeword is dependent only on the present inputs, in convolutional codes, output stream depends not only the present input bits but also only previous input bits stored in memory. For generating a convolutional code, the information is passed sequentially through a linear finite-state shift register. The shift register comprises of (-bit) stages and Boolean function generators. A convolut

                                                                                            Name of Experiment :-Implementation of Linear Block Code Using MATLAB Linear Block Codes In the linear block codes, the parity bits and message bits have a linear combination, which means that the resultant code word is the linear combination of any two code words. Let us consider some blocks of data, which contains  k  bits in each block. These bits are mapped with the blocks which has  n  bits in each block. Here  n  is greater than  k . The transmitter adds redundant bits which are  n − k bits. The ratio  k/n  is the  code rate . It is denoted by  r  and the value of  r  is  r < 1 . The  n − k  bits added here, are  parity bits . Parity bits help in error detection and error correction, and also in locating the data. In the data being transmitted, the left most bits of the code word correspond to the message bits, and the right most bits of the code word correspond to the parity bits. Syst

                                                                                          Name of Experiment :-Experimental study of Binary Phase shift  keying  Binary Phase Shift Keying  B P S K This is also called as 2-phase PSK or Phase Reversal Keying. In this technique, the sine wave carrier takes two phase reversals such as 0° and 180°. The modulation of BPSK is done using a balance modulator, which multiplies the two signals applied at the input. For a zero binary input, the phase will be  0°  and for a high input, the phase reversal is of  180° . Following is the diagrammatic representation of BPSK Modulated output wave along with its given input. The output sine wave of the modulator will be the direct input carrier or the inverted  180 ° p h a s e  s h i f t e d  input carrier, which is a function of the data signal.                PRE TEST                                                                         THEORY                         PRACTICAL                        

                                                                                          Name of Experiment :-Experimental study of Frequency shift  keying  Frequency Shift Keying  F S K  is the digital modulation technique in which the frequency of the carrier signal varies according to the digital signal changes. FSK is a scheme of frequency modulation. The output of a FSK modulated wave is high in frequency for a binary High input and is low in frequency for a binary Low input. The binary  1s  and  0s  are called Mark and Space frequencies. The following image is the diagrammatic representation of FSK modulated waveform along with its input.               PRE TEST                                                                         THEORY                         PRACTICAL                                                                                                                                            POST TEST Reference:-  Manual