A new method for obtaining side information in frequency-hop spread-spectrum systems

Information about the reliabilities of the received symbols is very beneficial in slow-frequency-hop communication systems. This information, referred to as side information, can be used to erase unreliable symbols at the input to an errors-and-erasures decoder. It is common that special redundant symbols, referred to as side information symbols, are included in each dwell interval of the frequency-hop transmission, and the demodulation of those symbols provides the side information. The corresponding decrease in the number of message symbols that can be sent in each dwell interval makes it desirable to develop alternative methods that do not require side information symbols. In this paper, one such alternative is proposed and evaluated for channels with catastrophic partial-band interference. It is shown that staggered interleaving of the code words and iterative errors-and-erasures decoding facilitates the erasure of unreliable symbols without the need for side information symbols. The performance of this method is compared with the performance of errors-only decoding and the performance of errors-and-erasures decoding with standard block interleaving and side information obtained from test symbols