Enhanced Spread Spectrum Aloha (E-SSA), an emerging satellite return link messaging scheme

This paper presents a return link multiple-access scheme that enables low terminal cost and high transmission efficiencies for systems such as large-scale vehicles, satellite-based telemetry service systems, or industrial supervisory control and data acquisition (SCADA) systems. These terminals have low power, small antennas, and deliver short messages, and no power control method has been practically feasible for them. The presented return link multiple-access scheme employs asynchronous Spread Spectrum Aloha (SSA) techniques combined with a transmission control mechanism based on a signal-to-noise ratio (SNR) estimator of the received signal in the forward link to dynamically identify the proper conditions in the channel. The hub demodulator employs successive interference cancelation (SIC) at the packet level with a cyclic redundancy check (CRC). The normalized channel utilization is close to 2 bits/s/Hz with packet loss ratios (PLRs) of 10^-3-10^-4.