A code division access and switching method is applied to multibeam satellite for fixed service communications. In this article we present the system architecture, which consists of the Common Air Interface (CAI) and the onboard code switching mechanism. The CAl provides information traffic and Signaling control channels. The traffic channel access and modulation is based on a spectrally efficient CDMA (SE-CDMA) scheme for which we examined the bit error rate performance. The SE--CDMA can offer very low bit error rates at low signal to noise ratio while the available spectrum is re used in every beam (frequency reuse one). The on- board code switching mechanism is based on a Code Division Switch (CDS) for which we have evaluated the capacity, speed, and complexity. The CDS is a non-blocking switch with complexity linearly proportional to its size and can route calls from an uplink to a downlink beam without onboard demodulation and channel decoding. Finally, we present the satellite routing control and optimization mechanism. The system operates with demand assignment control. That is, channel bandwidth and switch connections are only assigned upon user request. The services provided are circuit switched calls for voice data and video and packet switched for data.
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