Channel feedback reduction for wireless multimedia broadcast multicast service systems

With the increasing demand of wireless multimedia services, the multimedia broadcast multicast service (MBMS) is an emerging technology which is adopted in new wireless communication standards to enhance multimedia data transmission. In an MBMS system, all the users subscribing to the service receive multimedia data via the broadcast channel from the base station (BS). To ensure the quality of the broadcast, the MBMS users feedback their channel state information (CSI) to the BS. The BS then selects the best transmission mode according to the users´ feedbacks to achieve the optimal result. This CSI feedback operation results in increasing feedback load with the number of users and hence reduces the spectrum efficiency. In this paper, a novel method is proposed to reduce the feedback load of the MBMS systems. The proposed method let the users determine individually whether feeding back their CSI will be critical for the BS to select the transmission mode. If not, a user does not feedback. Different decision rules at the users incur different degrees of MBMS rate loss, which is mathematically analyzed. Through simulations, we show that the proposed method can significantly reduce the CSI feedback load with only a slight impact on the MBMS rate.