Adaptive equalization of frequency selective indoor wireless communication channels

We examine the performance of adaptive linear, T/2 fractionally spaced and decision feedback equalizers (LE, FSE and DFE) for digital communication systems over indoor wireless channels (IWC) affected by frequency selective fading. The channel is modeled as both fixed and time-varying channels, and the data transmission rate is 10 Mbits/s. The simulation results show that, with differential encoding, the quadrature phase shift keying (DQPSK) modulation scheme outperforms 4-state and 8 state trellis coded modulations (DTCM4 and DTCM8), when the DFE with the least mean square (LMS) algorithm (DFE LMS) is used. While DTCM4 has better BER performance than DTCM8 with the DFE LMS over time-varing channels, the reverse conclusion can be obtained over fixed channels. When the recursive least square (RLS) algorithm is applied instead of the LMS algorithm, the systems with the DFE RLS can achieve slightly better bit error rate (BER) performance than those with the DFE LMS