Research On Differential Transmitting And Receiving In Wireless Communications

Differential communication attracts more ettention these days, but its cost of performance loss is still unsatisfactory. To improve the performance of differential communication, our researches focus on the differential modulation and differential detection. In the dissertation, the factors that affect the performance of differential communication are investigated. The dissertation proposes the promising solutions to enhance the performance by focusing on three fields: differential modulation process, signal's constellation and differential detection.The thesis presents a detailed analysis on the decision metric of Multiple-Symbol Differential Detection (MSDD) of differentially modulated signal. We achieve the maximum-likelihood decision metrics based on a complete receiving signal model, and show the relationship between the metrics and the channel state information and therefore show the performance of differentially receiving in wireless communication more accurately.A modified decision-feedback MSDD is proposed in the dissertation, which can improve the performance of MSDD especially when the number of receiving symbols is relatively small. And we have studied the frequency shift estimation when the received differentially modulated signal's carrier is biased. We estimate the frequency shift by the differential methods which makes the differential transceiver more feasible to compensate the received signal.In order to improve the performance under the fading channel, we have investigated the differential receiving with diversity when multiple receiving attennas are exploited. And a new differential receiving scheme with diversity is proposed, which adopts the advantage of MSDD and the diversity and array gains of multiple receiving antennas.The thesis presents a new differential modulation, Coherent Amplitude and Differential Phase Shift Key (CADPSK). Compared with Differential Amplitude and Phase Shift Key (DAPSK), it achieves better performance while reducing the complexity of the detection of amplitude part of signal. In the dissertation, the performance of CADPSK has been well studied, and the constellation is optimized based on the theoretical analysis.By the above efforts, the quality of differential communications is enhanced at Tx end and Rx end, and the more satisfied trandoff between complexity and performance is obtained.