Exploiting Combination Techniques in Random Access MAC Protocols: Enhanced Contention Resolution ALOHA

Recently, random access (RA) protocols have acquired new interest from the scientific community not only in satellite communication scenarios but also due to the opening of new fields as smart grid and machine-to-machine (M2M) applications. Unslotted ALOHA-like RA protocols are very attractive for such applications thanks to the low complexity transmitters and to their complete avoidance of synchronization requirements. Evolutions of the ALOHA protocol employ time diversity through proactive replication of the packets but this diversity is not fully exploited at the receiver. The novel RA protocol named enhanced contention resolution ALOHA (ECRA) is presented, which goes beyond the limitation introducing combination techniques in the receiver algorithm. The behaviour of ECRA is investigated through mathematical analysis and simulations for two combination techniques, selection combining (SC) and maximal-ratio combining (MRC). Approximations of the packet error rate (PER) for unslotted RA protocols, including ECRA, well suited for the low channel load regime is also presented. Furthermore, ECRA and recently presented RA protocols, are analyzed in terms of different metrics, including spectral efficiency, showing that ECRA is able to largely outperform both slotted and unslotted schemes. Part of the material in this paper was presented at the 2013 International ITG Conference on Systems, Communications and Coding (SCC). This work is a first draft and is currently under finalization for a journal submission. Federico Clazzer is with the Institute of Communication and Navigation (Satellite Networks Department) of the German Aerospace Center (DLR), Muenchener Str. 20, 82234 Wessling, Germany. E-mail: [email protected]. Christian Kissling is with Triagnosys Gmbh Zodiac Aerospace, Argelsrieder Feld 22, 82234, Wessling, Germany. E-mail: [email protected]. Mario Marchese is with the Department of Electrical, Electronic, and Telecommunications Engineering, and Naval Architecture (DITEN), Via Opera Pia 13, 16145 Genova, Italy. E-mail: [email protected].