Design of Efficient Multicast Protocol for IEEE 802.11n WLANs and Cross-Layer Optimization for Scalable Video Streaming

The legacy multicasting over IEEE 802.11-based WLANs has two well-known problems-poor reliability and low-rate transmission. In the literature, various WLAN multicast protocols have been proposed in order to overcome these problems. Existing multicast protocols, however, are not so efficient when they are used combining with the frame aggregation scheme of IEEE 802.11n. In this paper, we propose a novel MAC-level multicast protocol for IEEE 802.11n, named Reliable and Efficient Multicast Protocol (REMP). To enhance the reliability and efficiency of multicast services in IEEE 802.11n WLANs, REMP enables selective retransmissions for erroneous multicast frames and efficient adjustments of the modulation and coding scheme (MCS). In addition, we propose an extension of REMP, named scalable REMP (S-REMP), for efficient delivery of scalable video over IEEE 802.11n WLANs. In S-REMP, different MCSs are assigned to different layers of scalable video to guarantee the minimal video quality to all users while providing a higher video quality to users exhibiting better channel conditions. Our simulation results show that REMP outperforms existing multicast protocols for normal multicast traffic and S-REMP offers improved performance for scalable video streaming.

1 Introduction

The IEEE 802.11 wireless local area network (WLAN) [1] has been one of the most popular wireless access technologies due to its advantages of the high data rate, low cost, and easy deployment. Recently, most mobile devices such as laptops, PDAs, and mobile phones equip the WLAN interface for low cost and high speed Internet connectivity. In IEEE 802.11n [2], the physical layer (PHY) data rate increases to 600 Mbps. Also, IEEE 802.11n introduces an enhanced medium access control (MAC) protocol in order to reduce MAC layer overhead. One of key MAC enhancements of 802.11n is the aggregate MAC protocol data unit (A-MPDU) aggregation, which maximizes the throughput at the MAC layer.