Space-time characteristics of frequency nonselective Rayleigh fading channels with applications to modeling, system design, and demodulation
Abstract
Space and time diversity combined systems, such as space-time coded modulation, have received great attention. The transmission characteristics of space and time on the base station (BS) and the mobile station (MS) over frequency nonselective Rayleigh fading channels are explored in this work by generalizing the well known Jakes' model. The new model may be employed in transmitting or receiving schemes that utilize multiple antennas at BS or MS. Various issues regarding the time and receiver diversity system design at BS are demonstrated, such as the optimal antenna separation design, performance alterations due to mobile location variations, system degradation due to insufficient space for the optimal antenna separation, multiple-antenna placement design, and the interleaving depth design. Pilot symbol assisted modulation (PSAM) is a common technique for channel estimation. Two dimensional space-time PSAM is investigated by applying the cross-correlation function derived for BS. Its application on MS is straightforward. It is shown that 2-D space-time PSAM performs better than applying 1-D PSAM on each antenna separately. In general, the 2-D space-time PSAM performs better when channel correlations are high. Consequently, the channel estimate mean square error (MSE) is smaller when the mobile is circling the BS, or at the end-fire location of an antenna pair. A further application of the 2-D space-time PSAM is cochannel interference detection. By estimating the multiplicative distortion of both the desired user and the interferer, a significant system performance improvement can be obtained compared with the conventional method of replacing the interferer power with Gaussian noise. A near-optimal detection of applying Viterbi algorithm and an MMSE interference suppression algorithm are simulated. The near-optimal decision is shown to be close to the lower bound performance.
Degree
Ph.D.
Advisors
Zoltowski, Purdue University.
Subject Area
Electrical engineering
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