The Research Of Resource Scheduling Algorithms And Mac Layer Implementation Of Simulation Platform In TD-LTE System

With the presence of real-time multimedia applications, Long Term Evolution represents an emerging and promising technology for providing a broadband ubiquitous Internet access. To face the ever growing demand for packet-based mobile broadband systems, the3GPP has introduced the LTE as the next step of the current3G mobile networks. An enhanced access network (i.e., the E-UTRAN, Evolved-UMTS Terrestrial Radio Access Network) and an evolved core network have been defined. At the present, more than280mobile operators from90countries worldwide have already stated a commitment to LTE. Starting from this premise, it is clear that the optimization of all LTE aspects is a topic worth of investigation for both industry and academia communities.Next-generation broadband wireless system standards, e.g.,3GPP long term evolution (LTE) and IEEE802.16(WiMAX), consider orthogonal frequency division multiple access (OFDMA) as the preferred multiple access scheme, especially for the downlink. In a LTE system, the frequency channel is divided into orthogonal subcarriers. The problem of allocating the subcarriers, bits, power to different users for better system performance has always been a research focus. To take advantage of the multiuser diversity resulted from the variation in channel conditions among the users, it has become an interesting and challenging problem to efficiently allocate the resources such as subcarriers, bits, and power. Most of current research concentrates on solving the resource-allocation problem for all users together in a centralized way, which brings about high computational complexity and makes it impractical for real system.Therefore, a coalitional game framework for downlink multi-user resource allocation in long term evolution (LTE) system is proposed, based on the divide-and-conquer idea. The goal is to maximize the overall system data rate under the constraints of each user’s minimal rate requirement and maximal transmit power of base station while considering the fairness among users. In this framework, a coalitional formation algorithm is proposed to achieve optimal coalition formation and a two-user bargaining algorithm is designed to bargain channel assignment between two users. The total computational complexity is greatly reduced in comparison with conventional methods. The simulation results show that the proposed algorithms acquire a good tradeoff between the overall system throughout and fairness, compared to maximal rate and max-min schemesTo verify the performance of the proposed algorithms, a NS-3based TD-LTE system-level simulation platform is established. The simulation platform implements radio protocol stack for LTE system, especially for MAC layer. Moreover, end-to-end IP connectivity is supported on the platform. This platform provides the functionality of logical channel multiplexing, resource allocation and adaptive modulation and coding (AMC) via eNode B MAC and UE MAC entities. With the platform, simulations for the proposed algorithms and classic resource allocation algorithms are established and compared for further analysis.