Effects of radio propagation path loss on DS-CDMA cellular frequency reuse efficiency for the reverse channel

Analysis techniques for quantitatively describing the impact of propagation path loss and user distribution on wireless direct-sequence code-division multiple-access (DS-CDMA) spread spectrum systems are presented. Conventional terrestrial propagation models which assume a d⁴ path loss law are shown to describe modern cellular and personal communication system channels, poorly. A two-ray propagation model and path loss model derived from field measurements are used to analyze the impact of path loss on the frequency reuse efficiency of DS-CDMA cellular radio systems. The analysis shows that the frequency reuse efficiency (F) of the reverse channel with a single ring of adjacent cells can vary from a maximum of 71% in d ⁴ channels with a favorable distribution of users, to a minimum of 33% in d² channels with a worst-case user distribution. For three rings of adjacent users, F drops to 58% and 16%, respectively. Using the two-ray model, it is shown that F can vary over a wide range of values due to the fine structure of propagation path loss