In the decentralized-TDMA (D-TDMA) protocol, the terminals select a free slot based on the frame information (FI) which is a representation of the status of each slot in the network. The FI, however, constitutes a large portion of the packet, which seriously compromises the per-packet transport capacity of the D-TDMA protocol. We therefore propose an opportunistic header management scheme for increasing the number of payload bytes without adversely affecting the performance of the D-TDMA. Our proposal is based on every terminal being able to choose between two techniques for transmitting their data packets. The first, based on the FI redundancies, lets the terminals transmit only the relevant information. The second compresses the FI with a lossless data compressor, i.e. the Huffman algorithm. Computer simulations were conducted for an urban environment in which vehicles are moving. The simulation results show that the proposed technique significantly increases the throughput without degrading the quality of the D-TDMA protocol.

Moving-picture transmission through narrow band and high bit error rate communication channels, such as a mobile communication channel, requires improved compression rate and enhanced error resilience. Variable-length codes are one of the essential techniques of compressing digital video information. This technique is used in various video coding schemes although a bit error in the channel impairs the synchronization of variable-length codewords, resulting in propagation of the error. With a hybrid video coding method in particular, which combines motion-compensation and transform coding, once an error is detected in the coded data, subsequent data cannot be decoded. Consequently, even an error-free portion of any data received must be discarded. To minimize the influence of an error in a channel on coded video data, this paper proposes a new video coding syntax which makes the best use of the self synchronizing characteristic of variable-length Huffman codes. Owing to the Huffman code's characteristic, the proposed coding syntax enables a decoder to decode the data portion that cannot be decoded, due to an error, by the conventional syntax without adding any redundancy. Computer simulation has verified the effectiveness of this proposed syntax in video coding with a very low bitrate and erroneous communication channel.