Spread SCPC/FDMA, spread TDMA/FDMA and SSMA/FDMA transmission through A non‐linear satellite channel with an earth‐station off‐axis emission constraint

Abstract

This paper analyses and compares possible access schemes to be used in satellite networks with a large number of small earth‐stations. Basically, frequency division (FDMA), time division (TDMA), and spread spectrum multiple access (SSMA) are considered. For TDMA, one single carrier originated in one particular earth‐station is transmitted in each sub‐band and therefore a single‐channel‐per‐carrier system results (SCPC/FDMA). For TDMA and SSMA, it is assumed that groups of earth‐stations using either of these access schemes share the full available band in FDMA. The corresponding systems are thus TDMA/FDMA and SSMA/FDMA. Moreover, for SCPC/FDMA and TDMA/FDMA individual carriers may be spread to the extent that the available bandwidth is always fully occupied. Spectral efficiencies for these three access modes (Spread SCPC/FDMA, Spread TDMA/FDMA and SSMA/FDMA) are computed and compared for transmission through a non‐linear satellite channel and optimum operating points for the non‐linear amplifier are also determined. Comparisons are also performed for the situation in which transmitting earth‐stations are bounded to obey an off‐axis emission constraint.