Research On Coverage Enhancement And Resource Allocation Of M2M Communications In LTE-Advanced Cellular Networks

Machine to Machine (M2M) communication is one of the hot topics in the current and future communication industry. With characteristics including wide coverage, low cost, backward compatibility and high system capacity, LTE-Advanced cellular networks would be an ideal platform for large M2M deployment.Nowadays the cellular networks are designed and optimized based on the Human-to-human(H2H) communication service features, and some unique M2M characteristics have not been taken into consideration. Under this circumstance, large M2M deployment in cellular networks would result in some great challenges. For example,when large number of M2M equipments start random access this process will make excessive server load and deteriorate H2H user’s quality of experience(QoE). To alleviate the adverse effect on H2H QoE, it is necessary to optimize the current cellular network to make it compatible with M2M features.In this thesis,three major research directions which are M2M communications coverage enhancement in special scenarios,resource scheduling in random access congestions with large number of M2M equipments and resource allocation in lower power M2M communications are studied.The research contents and innovation points are summarized as follows.1. In the study on M2M communications coverage enhancement, this thesis analyzes the quality of service (QoS) characteristics of the M2M communications in smart grids and provides novel schemes to realize a narrow-band M2M communication system which is embedded in the current broadband LTE network. Such an M2M system has low power consumption and enhanced coverage. Furthermore, we propose three receiving mechanisms based on Transmission Time Interval (TTI) Bundling to achieve wider coverage, lower power consumption and less commercial cost. An actual hardware and software platform is established to test the suggested schemes. Simulation results validate that a17～21dB gain of the coverage performance can be achieved compared with the current LTE systems.2. In the study on resource scheduling in random access congestions with large number of M2M equipments, M2M services are classified according to traffic characteristics, each type of M2M equipments form a cluster,in which different accses groups are formed based on location information.M2M devices start random access process in the form of groups. Accesspriorities based on access delay are considered,and the group with more sensitive delay has a higher priority. Resource blocks beared by Message3(Msg3) are scheduled with the use of group paging to signalling load due to large devices.Simulation results demonstrate that the proposed scheme is efficient to boost the success rate of random access and reduce different group’s access delay.3. In the study on resource allocation in lower power M2M communications, M2M devices with power limitation could report data to the eNB with the aid of mobile terminal devices which work as mobile relays and combine the D2D (device-to-device) technology and energy harvesting technologies in LTE-A. Energy consumption of mobile terminal device is compensated by energy harvesting. This article discusses optimization problems of how to determine the segmentation time coefficient and transmitting power. Furthermore an optimal relay selection scheme is proposed. Simulations results show that the relay could gain the best energy revenue with an appropriate segmentation time coefficient and transmitting power. And the proposed optimal relay selection scheme could notably improve system performance compared with the random relay selection scheme.