Coding for FFH-CDMA Systems - Part II: System Design

For pt.I see ibid., p.Z000319-23, (2006). In part I of this paper, the channel capacity per dimension of a fast frequency-hoping code division multiple-access (FFH-CDMA) with unquantized detector outputs was evaluated and it showed that hard limiting of outputs can significantly degrade capacity. In this paper, a coded FFH-CDMA system whose maximum likelihood receiver works with unquantized outputs is considered. With a matched bit-to-symbol conversion in transmitter, it is shown that a proper design criterion is to maximize symbol Hamming distance. Based on this new criterion, a search algorithm was developed and many good convolutional codes were found. Analytical and simulation results corroborated the effectiveness of the proposed design criterion