Research On Turbo Equalization Of Wireless Communication Systems

In the next generation wireless communication systems, the bandwidth and the modulation order increase greatly. In addition, they are expected to achieve higher terminal mobility, transmission quality, spectrum utilization and data rate. In such cases, there will be time- and frequency-selective fading in the future broadband wireless communication systems, as a joint iterative equalization and decoding algorithm, the"turbo equalization"approach has been shown remarkable ability in compensating for the system performance degradation, e.g., in the bit error rate, due to ISI. Therefore, Turbo receiver of single-carrier system and OFDM system has been researched according to the requirements of next generation wireless communication systems.For single-carrier system, a new class of equalization techniques, combining the turbo principle and frequency domain equalization is presented and applied to high order modulation formats, such as QPSK and 16QAM, thus improving the whole system's performance with higher bandwidth utilization and lower complexity.For OFDM system, a promising structure of Turbo Receiver is proposed, in which, the channel estimator, equalizer and decoder are jointed to construct a complete information feedback system. On one hand, it makes full use of OFDM's advantage to overcome frequency selective fading and reduce ISI. On the other hand, the channel estimator refines the estimation through the feedback from the decoder, thus improving the system's performance. At last, simulation results show the advantage of the structure.