An Adaptive Hybrid ARQ Algorithm for Video Multicasting over WiMAX Network

• Main Authors: Chang-Wei Liu, 劉昌瑋
• Other Authors: Yung-Chang Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/80335587921648070244

碩士 === 國立清華大學 === 電機工程學系 === 96 === In recent years, the demand for transmitting multimedia over wireless environment is greatly needed. With IEEE 802.16, also called world interoperability for microwave access (WiMAX), technology coming to maturity in the next few years, the demand for high data rate, high capacity and QoS to each user can be satisfied. The IEEE 802.16 MAC layer supports two kinds of topology. One is point-to-multipoint architecture and the other is mesh topology. In PMP architecture, there is a central base station (BS) and several subscriber stations (SSs) in one sector. Although the IEEE 802.16 can satisfy the demand for each user, packet loss can’t be avoided in the wireless environment. The quality of multimedia will be greatly degraded with the increasing packet loss rate in the wireless radio environment. Forward error correction (FEC) techniques and automatically repeat request (ARQ) are the preferred error control schemes for unicast or multicast. In this thesis, a novel Hybrid ARQ (HARQ) algorithm is proposed for video multicasting over WiMAX network. The proposed algorithm adopts Reed-Solomon erasure correction code (RS code) at packet level instead of at bit level. With traditional RS code at packet level, BS needs to send original data packets and constant number of redundant packets in one transmission group. The proposed algorithm adaptively adjusts the number of redundant packets to conserve the bandwidth in lower packet loss rate. If the packet loss rate increases continuously, the proposed algorithm adjusts the number of data packets and redundant packets adaptively. In the end, the number of retransmitted packets is reduced and the multimedia can be protected more robustly.