Space-time coding for MIMO systems: High rates and low decoding complexity

As a fading countermeasure, space-time techniques have recently received a lot of attention. In the literature, it is proven that multiple transmit antenna systems have the advantage of increased channel capacity. However, due to the coding/decoding principle, space-time techniques introduce higher decoding complexity and high implementation costs. Therefore, multiple transmit antenna systems must provide a solution for the decoding complexity and offer quality performance to compensate for the extra costs. The dissertation focuses on two sub-fields: system design for noncoherent multiple transmit antenna communications and space-time trellis code design for coherent multiple transmit antenna communications, towards the goal of high performance and low, or moderate, decoding complexity.; For noncoherent multiple transmit antenna communications, unitary space-time codes are constructed from Alamouti's scheme with amplitude/phase shift keying (APSK) signals. We show that unitary Alamouti codes with APSK signals have larger diversity products than those with PSK signals while the complexity of their maximum-likelihood (ML) decoding algorithm is comparable. Specifically, our codes have larger diversity products than unitary Alamouti codes with PSK signals at rates 1.5, 2.5, 3, 3.5, 4, and 4.5 bits/s/Hz. The proposed 4 bits/s/Hz code has a 2 dB gain over the same rate unitary Alamouti codes with PSK signals. We also propose a 5 bits/s/Hz noncoherent modulation scheme, which has the same BER performance as the 4 bits/s/Hz differential orthogonal space-time modulation with comparable decoding complexity.; This dissertation also examines the detection performance of noncoherent modulation schemes in fading channels. Two classes of decision-feedback differential detection (DF-DD) schemes, multiple block detection based DF-DD and linear-prediction-based DF-DD, are proposed to improve detection performance of various noncoherent modulation schemes.; For coherent multiple transmit antenna communications, we construct a number of super-orthogonal space-time trellis codes that satisfy the equal eigenvalue criterion for codewords of arbitrary length. Under the proposed structure, the classic results in set-partitioning for spectrally efficient signals are modified to maximize the diversity products of the proposed codes. The resultant codes have larger diversity products and better performance than the existing super-orthogonal space-time trellis codes at rates 2.5, 3, 3.5, and 4 bits/s/Hz.