Effects of some nonuniform spatial demand profiles on mobile radio system performance

The design of future mobile radio systems will be based upon an estimated user demand. Systems probably will be engineered to serve the "average business day" spatial distribution of call attempts, which for the purpose of this study was assumed to be uniform. There will be day-to-day fluctuations about this long-term average, the magnitudes of which are only to be conjectured at this time. This paper compares the performance of computer simulated mobile radio systems operating with several demand profiles. The profiles were selected to give an indication of the effects on system performance of either uncompensated changes in average traffic or normal fluctuations which occur in the randomly offered traffic even when the long-term average value does not change. The dynamic channel assignment systems increased the traffic capacity at low blocking levels even over a perfectly designed fixed channel assignment system. In addition, it was found that the dynamic channel assignment systems were relatively insensitive to the periodic spatial demand distributions studied by this computer simulation. Even though new call attempts were made to fluctuate markedly between adjacent base stations within a reuse interval, the blocking rate of each base station remained constant. It appears that the blocking rate within a reuse interval depends (in the dynamic channel assignment systems) mainly on the average demand within that interval and not very strongly upon the distribution of that demand. In the fixed channel assignment system, uncompensated fluctuations in the spatial demand distribution away from the design value always degrade system performance.