Cooperative communications based on rateless network coding in distributed MIMO systems [Coordinated and Distributed MIMO]

In cellular distributed antenna systems, cooperation among base stations or remote antenna units to exploit multiple-input multiple-output gains could mitigate interference as well as provide more spatial diversity, which could significantly improve overall spectrum efficiency. However, most existing cooperation schemes require perfect synchronization, which is difficult and even impossible in practical distributed multi-user systems. When synchronization is not perfect, cooperative communication performance severely degrades. Orthogonal channel assignment among collaborating stations with rateless network coding allows synchronization to be performed independently, and provides a coding scheme with close-to-capacity performance. In this article we discuss how to construct cooperative communication schemes based on rateless network coding in distributed MIMO systems. Specifically, we propose two cooperation strategies: single-source cooperation based on rateless coding and multisource cooperation based on rateless network coding. The proposed cooperative strategies are applicable to both uplink cooperation among users and downlink cooperation among BSs or RAUs in cellular DASs, providing a parameter-flexible, encoding-simple, and bandwidth-efficient cooperative solution.