Abstract: An improved coding and decoding process is disclosed to determine the ending state of a convolutional decoding using Viterbi algorithm without the use of tail bits. The most important information bits are first coded with a block code. The block code word and the rest of the information bits are then split into several bursts. Each burst is coded with a convolutional code. The most important information bit part of the block code word is then placed in the beginning of the code burst for the convolutional encoder. The parity bit part can be placed between the end of the most important information bit part and the end of the code burst. In the convolutional decoding process for each burst, the ending state is determined by detected valid block code word after combining the convolutional decoding processes for all the bursts. The performances of average BER and missed detection rate can be optimized by moving the placement of the parity bit in each message code burst.

Abstract: A method for transmitting random access signals from a mobile unit to a satellite or other control station which requires the transmission of less information than in conventional terrestrial cellular or proposed mobile satellite systems. According to the method, the mobile unit acquires synchronization from the satellite and transmits reduced random access information to the satellite, and the satellite calculates time adjustment information for the mobile units based on the reduced random access information. The random access information is reduced by predetermining a slot number for each mobile unit, and by transmitting only the odd or even status of the frame number desired by the mobile unit.