Improving automatic link establishment through a new soft decision trellis decoder for the (24,12) Golay code

Automatic link establishment (ALE) is the term used to describe systems where the functions of encoding and decoding, modulation and demodulation, frequency management, and system control ate co-ordinated by the system during the start-up and transmission phases of communications. The US MILSTD-188-141A is currently the major standard addressing the subject of ALE. It defines a channel selection procedure, control protocol, and data transport to allow non-adaptive ALE. The MILSTD-188-141A uses a fixed 8 frequency shift keying modulation scheme, and the (24,12) extended Golay code. Under certain conditions this will not be sufficient to allow error free transmission of data. One way to combat this would be to use a more robust error correcting code, but this would no longer adhere to the standard, and would reduce the data throughput. As the standard does not specify a decoding method for the Golay code, an alternative way to improve the performance of the standard is to use a more effective decoding technique. This paper describes a new maximum likelihood trellis decoder for the (24,12) Golay code