Receiver techniques in spatial and temporal coded modulations for power efficient wireless communications.

摘要

The trend in mobile wireless communications is to design systems for both high performance and low power consumption. One approach is coded modulation, where spatial and/or temporal correlation is imposed in the transmitted signals. This thesis studies the receiver techniques for two important types of coded modulation. One is continuous phase modulation (CPM), which is coded modulation in the temporal dimension. The other is space-time coded modulation (STCM) with multiple transmit antenna systems, which is coded modulation in spatial-temporal dimensions. This thesis first considers the detection algorithms for Gaussian minimum shift keying (GMSK), the most commonly used CPM, in systems that use channel coding. One topic is the detection of low bandwidth-time-product ( BT) GMSK signals with both good power and bandwidth efficiency. We propose a two-stage MSK-type detector. Then we develop an adaptive soft output detector that enables higher coding gain through soft-decision decoding of the channel code. Another topic studied is the soft output detection of co-channel GMSK signals. We propose a soft output co-channel detection technique using a modified soft-output Viterbi algorithm for GMSK signals to achieve higher coding gain when the outer channel codes are used. For STCM, we study the channel estimation, detection and performance analysis of mobile wireless communication systems employing space-time block codes (STBC), where the channels exhibit flat Rayleigh fading with a significant amount of Doppler spread. Pilot symbol assisted modulation is developed to estimate the channels. Three channel estimators are derived and compared through both analysis and simulations. Maximum likelihood detection is formulated. Through analysis, we find the optimal linear detector. An interference cancellation detector is also developed to improve the performance of the linear detector. We derive the closed-form analytical expressions for the error rates of pilot symbol assisted STBC. Some important design issues are discussed through analysis.