An integrated design of STBC and signal alignment in MIMO Y channels

摘要

This paper presents the integration of distributed space-time block coding (STBC) and signal alignment (SA) in multiple-input multiple-output (MIMO) Y channels where multiple terminals communicate with each other in a bi-directional manner via the relay. The objective is to take advantage of the STBC diversity gain without losing much of the high bandwidth efficiency in MIMO Y channel schemes with SA alone. The proposed deployment of STBC represents a form of cooperative coding between the terminals and is referred to as networked MIMO. Specifically, by a thoughtful design of pre-processing vectors and scheduling of transmissions, the signals with mutual information in bi-directional links between terminals are aligned into proper spatial dimensions according to the selected space-time block code. The transmission schemes are also optimized to reduce computational complexity and improve time slot utilization. It is demonstrated with simulations that the proposed design in a three-user MIMO channel offers significant coding gain of 25 dB at the bit error rate (BER) of 10-3 over the conventional MIMO channel signaling in Rayleigh fading channels. This improvement is achieved at the expense of reducing the bandwidth efficiency by a factor of 7/2.