Header compression increases the transmission throughput and improves the quality of service in error prone environments. ROHC (robust header compression) is an IETF (Internet engineering task force) standard, which is used to compress the network and transport headers to save the precious air interface of mobile communication systems. The U-mode of ROHC profile 1 is suitable for transmission of packets without a feedback channel. However, in error prone environments, ROHC U-mode may lose synchronization between the compressor and decompressor due to bursts of errors in wireless communications. This results in unnecessary packet loss, which has severe detrimental effects on video quality. In this paper, the causes of context damage are analyzed for U-mode, and its effects on H.264 video quality and packet loss are demonstrated. A scheme to minimize the occurrences of context damage is proposed. Using the proposed scheme, packet loss rate reduces significantly for ROHC U-mode.

The 3G mobile-IP networks currently being developed will support end-to-end enhanced real-time multimedia services. End-to-end IP enables very high flexibility for transmission over a mobile network. Conversational services require the use of the Real-time Transport Protocol (RTP), which is typically deployed on top of UDP/IP, to facilitate acceptable quality of service at the receiver. The main drawback of using RTP/UDP/IP is the relatively large overhead imposed by these headers (at least 40/60 bytes in each packet), which leads to significant spectral inefficiency, particularly for low-bit rate speech applications. This paper examines current header compression techniques, CRTP & ROCCO, for multimedia services over IP and examines their performance in mobile channel environments.