Error Control Coding for the N-User mod-2 Multiple-Access Channel

The efficient use of transmission facilities often requires the sharing of resources by a number of users. Commonly used methods of shared media access are time division multiple access (TDMA), frequency-division multiple access (FDMA), code-division multiple access (CDMA), carrier-sense multiple access (CSMA), etc. We propose a different approach to designing an N-user multiple access system for the binary input binary adder channel. When all users are sending data, the total rate of information transfer is equal to the time-share rate. However, when fewer than N users are active, the unused channel capacity is used to achieve error control. The extent of error control is inversely proportional to T, the number of active users. We present in detail two coding schemes; the first based on cyclic block codes, particularly BCH codes and Reed-Solomon codes, and the second based on convolutional codes.