Bit error rate evaluation of a spectrally efficient CDMA scheme for geostationary satellite communications

Spectrally efficient CDMA (SE-CDMA) is a multiple access and modulation scheme proposed for multibeam geostationary communications satellites that provides fixed service directly to the end users. The SE-CDMA is designed to meet the service requirements for high spectral efficiency and low bit error rate (BER) given the on-board power limitations. Its implementation consists of a concatenated Reed-Solomon/turbo channel encoder, of a two step spreading operation isolating the satellite beams and users within each beam and of a M-ary PSK modulator. The up and down SE-CDMA links are considered to be coupled at the satellite by a CDMA routing circuit which performs a despreading and respreading operation. This paper presents the system architecture and the BER performance of the proposed SE-CDMA. Performance results show that the system can provide high spectral efficiency at very low BER and at low E_b/N₀