Performance Analysis of Quality-Based Channel State Feedback Scheme for Wireless Multicast Systems With Greedy Scheduling

Abstract

Multi-group multicasting has recently attracted substantial attention. In this letter, we propose quality-based channel state information feedback (QCF) in multicast systems with greedy scheduling of multiple multicast groups, and present exact expressions for outage probability and average capacity of the multicast systems using QCF over independent Rayleigh fading channels. Further, we provide a method to determine the appropriate QCF threshold, and describe the relative feedback load of QCF with respect to full channel state information feedback. Our QCF scheme can significantly reduce the feedback load, simultaneously accomplishing negligible system performance loss.Index Terms-Wireless multicast, quality-based channel state feedback, average capacity, outage probability, feedback load.

Multicast Systems With Fair Scheduling in Non-identically Distributed Fading Channels

“…, M , and we have M m=1 K m = K. In each scheduling, the BS only serves one selected multicast group for data transmission during any given slot. We make the following assumptions [16], [19]:…”

“…Motivated by the greedy scheduling [9] applied in unicast systems, a greedy scheduling based scheme [16] was proposed for a wireless multicast system, where the BS needs to select the multicast group with the best channel quality for data transmission. The MSs in the same group are interested in the same information stream from the BS, and the affordable data rate is determined by the minimum received signal to noise ratio (SNR) among the MSs in a group.…”

“…Therefore, the objective of greedy scheduling is to maximize the minimum received SNR of the selected group. In [16], multicast system capacity performance was evaluated only for greedy scheduling, where all MSs' channels were assumed to follow independent and identically distributed (i.i.d.) fading.…”

Improved quality-based channel state feedback scheme in multicast systems with greedy scheduling

“…This scheme incurs a tolerable rate loss. In [7], a QCF scheme for multicast systems with greedy scheduling was proposed to reduce the feedback load with a negligible system performance loss, by which only the MSs whose instantaneous received SNRs are lower than a predetermined feedback threshold feed back their CSI to the BS. The reason is that the worst channel quality between the BS and the MSs in a multicast group is needed to determine the achievable capacity for that group.…”

“…To quantify the feedback load reduction by using the IQCF instead of the full CSI feedback (FCF) scheme [7], we define the normalized average feedback loadF as the ratio of the IQCF average feedback load to the FCF load. The IQCF average feedback load F I is given by…”