MIMO Beamforming for QoS Enhancement via Analog, Digital and Hybrid Relaying

Quality-of-service (QoS) of multimedia broadcast/multicast service (MBMS) is the most challenging issue that needs to be addressed for next generation wireless broadcasting. Multiple-input/multiple-output (MIMO) and multihop relay technologies are viable options for improving QoS of MBMS. For stable MBMS, the average throughput of overall cell region must be guaranteed. Nevertheless, severe throughput degradation may occur in the outer region of multicells due to significant interference from neighboring cells or relay stations, thereby limiting the overall performance. This paper describes an effective technique, which combines MIMO and two-hop relay, to guarantee the QoS of edge users. We assume that the channel between the base station (BS) and the fixed relay station (FRS) is line-of-sight (LOS). First, we define a criterion needed to install the FRS. Second, we construct a weight matrix for hybrid relaying having lower complexity than digital relaying. Finally, we propose a user scheduling algorithm which can be adapted to analog relaying (amplify and forward), digital relaying (decode and forward) and hybrid relaying (filter, amplify and forward). The simulation results show that the proposed method can improve both the QoS of edge users and the sum-rate.