Basic capacity calculation methods and benchmarking for MF-TDMA and MF-CDMA communication satellites

This paper introduces basic capacity calculation methods for circuit switched, multiple-beam, low earth orbit (LEO) communication satellites that use MF-TDMA and MF-CDMA schemes. Capacity is defined as the number of simultaneous duplex channels that a satellite can support for a given data rate and bit error rate. This paper integrates the bandwidth limit and the power limit on capacity, and derives the equations by which the capacity of a MF-TDMA or a MF-CDMA system can be calculated using key system parameters. Therefore, these methods enable system designers to quickly estimate the communication system capacity when key system parameters are known. The paper uses the Iridium and Globalstar systems for benchmarking by comparing the results obtained from the analytical methods with the 1,100 and 2,5000 simultaneous channels reported by Iridium and Globalstar, respectively. The analytic capacity estimate matches reported single satellite capacities to within 6%, but the predictions are sensitive to various loss assumptions made in the link budget. Copyright c © 2004 John Wiley & Sons, Ltd.