User Relaying in a Two-User MIMO Broadcast Channel

A novel user relaying scheme based on bit concatenation is proposed for a two-user multiple input multiple output(MIMO) broadcast channel (BC). In broadcasting phase, a part of information for a destination user is concatenated to data for a relaying user and transmitted to a relaying user. The destination user receives the part of information via the relaying user in relaying phase in addition to the data in broadcasting phase. Achievable rate region of the proposed scheme is derived and an algorithm to characterize the boundary of the rate region is proposed. Our analysis and simulations show that the proposed user relaying in a MIMO BC expands the achievable rate region of a zero-forcing dirty paper coding (ZF-DPC) in a MIMO BC without relaying.