2.9 Encoder and Decoder

The encoder encodes the each 4-bit block into a 7-bit code word. This code word is fed into the system, at this time the output of the decision block will be the received code word rather than received bits. These code words may contain erroneous bits. The decoder will perform error check by taking 7bit blocks from the received bit stream of code words .It calculates the syndrome of each received code word. This syndrome is used to find the error pattern using syndrome LUT. Finally the corrected code word is generated and the data bits are recovered from each corrected code word.

3 Simulation Results

In this section we will discuss the simulation results of BPSK, QPSK, QAM and the obtained results are compared with theoretical values.

3.1 BPSK and QPSK with Rectangular Pulse Shaping Filter

The performance of BPSK and QPSK system in terms of BER vsEb/No is evaluated in Matlab. Both the QPSK and BPSK has same performance curves. The following figure show the BER curve for the simulated and theoretical system. It can be seen the two curves overlap each other. 

Fig3.1: Simulation results of BPSK & QPSK with Rectangular Pulse Shaping

There is no difference between the simulation and the theoretical curves of Eb/N0  vs  BER for three modulation schemes .In this context 8QAM  provides better performance than BPSK & QPSK .