Multisite throughput of a mobile data radio link

In a single-site system, the uplink channel (from the mobile units to the site) has a throughput of 0.184 if pure ALOHA transmission protocol is used. The downlink channel throughput (from the site to the mobile units) for a single-site system is one because the transmissions are scheduled and no conflict occurs. To widen the service area and to increase system throughput for the single-site system without using additional frequency channels, multiple transmitter/receiver sites can be used. Throughput in both directions (uplink and downlink) and optimal site assignment in the downlink channel are calculated using an iterative method. Formulas are derived for two- and three-site systems. For systems with more than three sites, the three-site formulas can be used in an approximate method. Results produced by this method are within 1 or 2% of those generated by software simulations. For simplicity, FM capture is assumed to depend on the received signal level difference between the two strongest signals. Calculations are given assuming the message error rates are known