The variable bit rate nature of compressed video remains a major challenge to the transmission of real-time video over mobile CDMA cellular networks. Indeed, H.263 and MPEG-4 video bitstreams can exhibit high peak rates and frequent rate variations, which are difficult to support in 2.5G and 3G mobile networks. In this paper, we consider smoothing schemes to minimize the peak rate, variance, and average bandwidth of the transmitted signal, in order to obtain a lower bit-error-rate and thus, a higher received video quality than if unsmoothed video were transmitted. By introducing a delay in the decoding process, the video output stream can be buffered at the video decoder end: this buffering capability is used in order to perform real-time smoothing of the video streams. The transmitter chooses among the set of rates provided by the IS-95B or cdma2000 standards, in a mobility scenario, in order to support the rate variations. We simulate two end-to-end video communication systems based on IS-95B and cdma2000. They consist of an H.263 codec, an H.223 multiplexer, a rate management system and the physical layer components of the IS-95B and cdma2000 standards. The transmitted signal is subject to multipath fading and multiple-access interference, obtained by simulating all the other users in the cell. Results show a significant gain in the video quality obtained through smoothing of the video streams.
['C.-D. Iskander', 'P.T. Mathiopoulos']
Online smoothing of VBR H.263 video for the CDMA2000 and IS-95B uplinks