Performance Elevation Criteria for OFDM under AWGN Fading Channel using IEEE 802.11a

Abstract

11 basic OFDM system architecture explaining how the modulation is being done and how then it is being transmitted. This figure also explain how the same signal is received and demodulated using the efficient N-point FFT. The most widely used modulation schemes used in OFDM as per IEEE 802.11a standard are BPSK, 16-QAMand 64-QAM [7]. Figure 2.1 Basic OFDM system architecture The theoretical expressions of symbol error rate (SER) for various uncoded OFDM schemes are as follows. For BPSK system,(BER and SER) …(1) …(2) …(3) In OFDM transmission, out of the available bandwidth from-10 MHz to +10 MHz, only subcarriers from-8.125 MHz to +8.125 MHz are used. This means that the signal energy is spread over a bandwidth of 16.25 MHz, whereas noise is spread over bandwidth of 20 MHz (-10 MHz to +10 MHz), i.e. ….(4) Simplifying Equation 13, we get Es / Eb > nDSC / nFFT. In an OFDM system, the transmission of cyclic prefix does not carry any extra information. The signal energy is spread over time T d T cp whereas the bit energy is spread over the time T d i.e.