Congestion measures and capacity constraints in spread spectrum networks

When can a call be admitted to a radio network and when should it be blocked due to congestion in the network? In order to answer such a question, we need to be able to compute traffic constraints that are imposed by quality of service considerations. This is a nontrivial problem with an interesting spatial aspect, as users are distributed amongst the receivers, and may be in motion. The great benefit of spread spectrum is that the traffic constraints turn out to be “macroscopic”, in the sense that the constraints are only imposed on the overall traffic in relatively large geographical areas. This averaging over space is a form of statistical multiplexing, and simplifies the analysis of mobility, fading, and burstiness, although we do not directly consider these issues in the present paper. It implies that we can dimension a network, and control the admission of calls, without needing to predict at call admission the future fading levels of individual mobiles throughout the lifetimes of their calls.