A Study Of Massive Accesses Of M2M Communication In Wireless Networks

In recent years, as the development and popularization of the Internet of Things and consumer electronics, M2M communication emerges as a new technology. M2M communication aims to provide automatic transmission and ubiquitous connections for massive M2M devices. On this purpose, it is necessary to integrate M2M communication into current cellular wireless communication systems, which are designed and optimized for H2H communication. However, the characteristics of M2M communication are far different from that of H2H communication, including the direction of services, data size, access and connection delay, data cycle, mobility, information priority, the number of devices, lifetime and energy efficiency. These different characteristics make it difficult to integrate M2M communication into cellular wireless communication systems. The main issue to deploy M2M network is to optimize the air interface, and the most difficult and important problem is the massive accesses of M2M devices. This thesis mainly investigates the massive accesses of M2M devices in wireless communication systems, including the following two aspects:1. The optimization algorithms for massive accesses of M2M devices in LTE networks are proposed. First, following the procedures of random access in LTE, the assumptions and models are built, and the random access in LTE networks is analyzed. The mathematical expressions of main performance parameters are derived. Then the correctness of analysis is verified by simulations and the performance of current LTE random access protocol is shown. Finally, based on the analysis, the optimization algorithms are proposed to guarantee the QoS for each M2M application and optimize spectrum efficiency and energy efficiency. The simulation results show the effectiveness of the proposed algorithms.2. The massive accesses of M2M communication in wireless local area network are studied based on the IEEE 802.11 specification. First, several MAC protocols of IEEE 802.11 are introduced, including DCF, EDCA and IEEE 802.11 ah, which is newly peoposed for M2M communication specially. Then the performances of these MAC protocols are verified by simulation in terms of throughput, access success probability, collision probability, the number of retransmissions, energy consumptions and access delay. It is shown that IEEE 802.11ah provide better performance than DCF and EDCA when the number of devices is large. However, IEEE 802.1 lah still cannot work well when the number of devices reaches 6000. So we optimize the IEEE 802.1 lah by decreasing the number and increasing the length of RAW slots to improve the throughput. Finally, several feasible solutions to enhance IEEE 802.11 ah are given based on the simulations and analyses.