Multicast Relay Beamforming in CDMA Networks: Nonregenerative Approach

Multicasting in wireless networks has considerable applications due to the broadcast nature of wireless channels. Leveraging code division multiple access (CDMA) technique, we proposed cooperative relay aided distributed beamforming to multicast single antenna source nodes and also to enjoy the benefits of space diversity. In this schema, multiple sources broadcast their messages to their respective group of multiple destinations using multiple relay nodes. CDMA technique is used to reduce multiple access interference (MAI) impairments at relaying nodes as well as at the destination nodes. Each relay acts as a linear precoding beamformer to reshape the source signal in the proper available code space. The relays process the received signals from the sources to enhance the destinations QoS. The linear beamforming matrices are optimized to minimize the relays power subject to hold the QoS requirement in term of SINR defined for each multicast group. The numerical examination of the proposed method shows performance improvement of the proposed approach over the orthogonal multiplexing access schemes like FDMA/TDMA and also fully spatial multiplexing schema.