Multi-rate ALOHA Protocols for Machine-Type Communication

ALOHA-based medium access control (MAC) protocols are very popular in long-range wireless networks, where carrier-sense mechanisms are not much effective. In particular, pure or slotted ALOHA is used in many wireless technologies designed to support Machine-Type Communication (MTC), despite the very well-known scalability limits of the protocol. To mitigate the problem, some MTC technologies feature multiple transmission rates and, more importantly, advanced receivers that can detect the modulation scheme of a packet on the fly, without the need to transmit the packet header at a known basic rate. In this paper we propose two multi-rate MAC protocols, named Multirate-Split Slotted ALOHA (MSSA) and Multirate ALOHA Reservation Protocol (MARP), which are designed to better exploit such multi-rate capabilities of the wireless technologies. By means of extensive simulations, we show that our protocols can substantially improve the performance of the legacy ALOHA protocol in the specific scenario of MTC, characterized by a massive number of nodes, which sporadically transmit short packets.