The Gaussian non-cooperative multiple access channel with Rayleigh fading

A model in which several users transmit simultaneously to a common receiver is described. The users do not cooperate, in the sense that they transmit their signals without concern and using any approach (e.g. time sharing) to maximize the transmission of information. An information-theoretic approach is used to find the set of information rates at which simultaneous reliable communication of messages of each user is possible. It is assumed that the transmitted signals are subject to Rayleigh fading. It is found that as the number of users approaches infinity, the capacity region shrinks and the channel capacity converges to a given value, and there is no way to increase the capacity of the noncooperative channel by increasing the power of the transmitted signals. The channel capacity C^∞ becomes independent of the signal-to-noise ratio as the number of senders goes to infinity. The only way to boost the capacity is by an increase in the available bandwidth. Spread spectrum techniques could prove useful in this case