ARQ in Multibeam Opportunistic Beamforming Under Outage - QoS Performance

Scheduling in a downlink channel based on partial channel state information at the transmitter, is carried out through a multibeam opportunistic beamforming technique. Within a more practical perspective, this paper first presents a transmission strategy where a minimum rate per user is required, which in a wireless fading scenario, can be only guaranteed under a certain system outage constraint. An automatic repeat request (ARQ) is proposed to combat the system outage, so that it increases the system reliability, which stands as a possible Quality of Service (QoS) indicator for the system behaviour. Closed form expressions for the ARQ gain are obtained together with its maximum scheduling delay performance. The derived expressions are then tested via simulations in several transmission scenarios.