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

Abstract

An open ITS platform combining interactive satellite services with other communication channels is being developed and evaluated in field trials within the SafeTRIP project [1]. 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-of-sight (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

The combined automatic repeat request and rate control mechanism in S‐band mobile interactive multimedia asynchronous return link—design background, parameter dimensioning and first experimental results

“…It can be observed that the T SDD performance in the laboratory tests increases with the background interference (caused by the background traffic load), as the IC process needs to remove higher interference power to decode the packets. In fact, the ESSA demodulator implementation in SafeTRIP is based on software defined radio [14] with a number of IC nodes connected in cascade.…”

“…It can be proven that the cases in which fragmentation and / or retransmissions are required can be expressed using Equation (14) by properly replacing the r.v. X as specified in Table I. (2) Case B: T bot < T ACK In this case, Equation (2) can be expressed as in Equation (15).…”

“…where Δr represents the impact of the queued packets corresponding to lower priority classes, as shown in Equation (19); the queuing theory provides compact expressions for the sojourn time E(S i ) of packets of any priority r > 1, as in Equation (20), but deriving a similar Equation to (14) for this case becomes highly complex because of the interdependencies between the parameters of the different service classes.…”

“…For this purpose, the parameter setting shown in Table II was applied, adding the 0.2 s delay caused by the set up time of the power amplifier to the T TX of 250 ms (which corresponds to one of the available configurations of the ESSA bursts [1]). T bot was dimensioned using Equation (14) to achieve a target T SDD = 3s for the Tr-mode with N = 0 and P = 1. The terminal load was kept significantly low to assume E(W) → 0 in Equation (8), that is, every packet finds an empty queue and is directly processed, whereas background load (varying interference) is applied at the demodulator side.…”

S‐MIM field trials results

“…Within the framework of the SafeTRIP project , an intelligent transport system open platform integrating the S‐MIM protocol has been developed and tested under real environment conditions. This in field evaluation of the platform represents the first on air test of the S‐MIM technology, although the E‐SSA wave form has already been validated on the field . With respect to these preliminary field trials of the E‐SSA wave form, the S‐MIM link layer (based on the Return Link Encapsulation (RLE) protocol ) has been developed and integrated in the open platform, providing thus statistics at link layer and Internet Protocol (IP) levels.…”