E-SSA satellite messaging return channel: Performance analysis and field trials results

An open ITS platform combining interactive satellite services with other communication channels is being developed and evaluated in field trials within the SafeTRIP project. Prototyping and in-field validation of a novel waveform for messaging return channel over satellite for land mobile is an important objective of the project. The overall system architecture has recently been standardized by ETSI under the name of S-MIM (S-band Mobile Interactive Multimedia). The messaging protocol, described in the Part 3 of the standard, is based on the Enhanced Spread Spectrum Aloha (E-SSA). Its main asset resides in the low power required at the transmitter, which will allow the reuse of off-the-shelf power amplifiers and low-cost omnidirectional antennas. This paper will present a comprehensive summary of previous E-SSA performance analysis from simulations and the first field trials results using the E-SSA waveform. The presented results have been derived from static and mobile field trials carried out in Germany with fully functional E-SSA modulator and demodulator prototypes and the EUTELSAT10A satellite. Results for the static and mobile performance of the E-SSA demonstrator with an omni-directional antenna under Line-ofsight (LOS) conditions are presented. The measured Packet Error Rates of transmissions via satellite at different terminal power levels confirm the theoretical link budget calculations for single and multiple simultaneously transmitting terminals. The degradation due to fading effects of the transmission channel under mobile conditions has been measured during the trials to approx. 3 dB. The resulting overall required transmitter power in the multi-user scenario of the trials setup has been only -3 dBW to reach a high QoS under mobile conditions. This value confirms the suitability of the E-SSA waveform for interactive mobile services for the mass market.