Approaches to layered coding for dual-rate wireless video transmission

Visual communications over wireless networks require the efficient and robust coding of video signals for transmission over wireless links having time-varying channel capacity. The authors compare several schemes for encoding video data into two priority streams, thereby enabling the transmission of video data over wireless links to be switched between two bit rates. An H.261 (p×64) algorithm is modified to implement each candidate scheme. The algorithms are evaluated for a microcellular wireless environment and a clear-channel bit rate of 65 kb/s. The results show that by combining layering with automatic-repeat request (wireless-)link control, almost-wireline visual quality can be achieved