Trellis coded multiple access (TCMA)

Traditional methods for multiple access (MA) are FDMA (frequency division MA), TDMA (time division MA) and CDMA (code division MA). The MA technique in this paper treats time, frequency and user signature sequences as a common resource to all users in the system. The only separation between users is accomplished by the use of a TCM (trellis coded modulation) scheme which is unique for each individual user. This access method is called trellis coded multiple access (TCMA). Assuming an additive, white and Gaussian (AWGN) channel, optimal (in the maximum likelihood sequence detection, MLSD, sense) multi-user detection is considered. The detection performance for each user is investigated using the union bound evaluated through a generalization of the transfer function (TF) approach and also by means of simulations. This paper outlines the analysis method and also gives some numerical results for TCMA systems having two or four users. The modulation is chosen to be M-ary phase shift keying (MPSK) for all users and it is possible that all users share the same modulation as well as having the same envelope magnitude. Thus, the only feature specific for each user is the choice of the convolutional encoder component in this case.