**4. Adaptive modulation for OFDM system using fuzzy logic interface**

In a OFDM system using lower order modulators such asBPSK, 4 QAM and 8 QAM will improve Bit Error Rate (BER) but decreases spectral efficiency and speed, on the other hand employing higher order modulators such as 64 QAM, 128 QAM, 256QAM and 512 QAM will increase spectral efficieny and speed but result in poor BER. So to achieve good trade-off between spectral efficiency and overall BER (Bit Error Rate). Adaptive modulation is used.
