Constant-rate turbo-coded orthogonal frequency division multiplex videophony over UMTS

The ability of a Universal Mobile Telecommunications System (UMTS) framework to support interactive video communications is evaluated employing the inherently error sensitive, but high-compression H.263 video codec. A constant bit rate (CBR) is maintained and error-resilience is achieved by invoking a packet acknowledgement scheme, instructing both the local and remote reconstruction buffer to leave picture areas un-updated, if the packet was corrupted. Orthogonal frequency division multiplexing (OFDM) is employed to deliver the video signal over the dispersive worst-case Bad Urban COST 207 channel, assisted by binary Bose-Chaudhuri-Hochquenghem (BCH) and turbo codes. These channel codes are investigated comparatively, with the conclusion that due to the high error-resilience of the video packetisation and acknowledgement regime the increased power of the higher complexity turbo codec does not translate to substantially improved overall system robustness, although the bit error rate and acknowledgement flag error-rate is significantly reduced. The system is also compared to a 155 Mbps wireless ATM scheme. The video transceiver parameters are also summarised