Abstract
Simultaneous random access of massive machine type communications (MTC) devices are expected to cause congestion in the radio access network. Not only the performance of MTC, but the coexisting human to human (H2H) communications would also degrade dramatically without an appropriate medium access control (MAC) protocol. However, most existing solutions focus on the random access procedure without dealing with the sunsequent data transmission procedure. In this paper, we firstly derive a packet size threshold based on the capacity analysis of slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) protocols. Then a novel hybrid S-ALOHA/TDMA MAC protocol (HSTMAC) is presented for massive MTC access, in which the resources are separated for beta distributed machine to machine (M2M) traffic with small size packets and high priority H2H traffic with large size packets. Considering access class barring (ACB) scheme as an overload control method, the system equilibrium under arbitrary retransmission limit is analyzed rigorously, which can provide insights on quality of service (QoS) guarantee. Finally, a dynamic pre-backoff (DPBO) algorithm is designed for load balance by adaptively scattering the highly synchronized M2M traffic over the transmission interval. Numerical and simulation results validate our analysis and show that the HSTMAC protocol is superior to pure S-ALOHA protocol and pure TDMA protocol. The proposed DPBO algorithm can achieve a higher success probability and resource utilization ratio with a much reduced average delay than that of uniform pre-backoff (UPBO) scheme.
Highlights
Machine type communication (MTC), known as machine to machine (M2M) communication, is envisioned as a main enabler for the Internet of Things (IoT) [1,2]
A simplified model of the random access procedure in long term evolved (LTE)/LTE-A networks is depicted in Figure 1a, which shows that four handshake messages are needed before a successful data
A simplified model of the random access procedure in LTE/LTE-A networks is depicted in Figure 1a, which shows that four handshake messages are needed before a successful data transmission[10]
Summary
Machine type communication (MTC), known as machine to machine (M2M) communication, is envisioned as a main enabler for the Internet of Things (IoT) [1,2]. A simplified model of the random access procedure in LTE/LTE-A networks is depicted, which shows that four handshake messages are needed before a successful data transmission[10]. The packet sizes of many M2M applications are usually small, some of them even on the order of of bits or bytes (e.g., health or environment monitors and alarm devices) [17]. The authors in [19] demonstrated that the supportable arrival rate of one-stage protocol, like slotted-ALOHA (S-ALOHA), is higher that the supportable arrival rate of one-stage protocol, like slotted-ALOHA (S-ALOHA), is higher than that of two-stage protocol, like time division multiple access (TDMA), if the payload size is small. In [20], the LTE/LTE-A random access procedure was tailored exclusively for M2M traffic to reduce the signaling overhead.
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