Delay-tolerant space-time codes: An overview

In basic cooperative diversity systems, diversity is implemented by providing multiple routes through a network of single-antenna nodes. A potentially powerful cooperative strategy is to apply space-time codes (STCs) in a distributed fashion to the above virtual antenna array. However, owing to the nodes arbitrary geographical locations and individual oscillators, the system is fundamentally asynchronous. This will damage some of the key properties of the STCs and can lead to substantial performance degradation. The delay-tolerant STC is one efficient way to overcome such a problem. This paper presents an overview of delay-tolerant property and recent research efforts on design of delay-tolerant STCs. The design can be carried out by different criteria such as full-diversity order, minimum error probability, minimum mean square error etc. In addition, the feedback information can be utilized to further improve the performance of delay-tolerant STCs.