Additional switching nodes: Not a panacea for congested wireless networks

Traditionally, service providers have been adding Mobile Switching Centers (MSCs) in their wireless networks whenever they run out of capacity. In an analysis of a large metropolitan network, we observed something seemingly counter-intuitive: additional MSCs do not necessarily add call capacity and they can sometimes even cause decreased network capacity. The apparent anomaly can be intuitively explained by noting that it is the all important call capacity that brings revenue to the operator. A new MSC in a network will always enhance total processing capacity but its introduction will also result in increased inter-MSC signaling for mobility handling. For a given total processing capacity, as mobility handling demand goes up, the remaining capacity for call processing goes down. In this paper, we establish a methodology for predicting capacity exhaust in an expanding network and also present practical suggestions for avoiding network congestion. Even though the analysis was done for a network with traditional monolithic switches, the methodology can be applied towards next generation distributed architecture components as well.