【作者】 王奇；

【导师】 郑军；

【作者基本信息】 东南大学 ， 信息与通信工程， 2016， 硕士

【摘要】 随着移动互联网的快速发展和移动设备的快速普及,用户对于移动业务的需求也逐渐发生变化。在未来移动通信网络服务中,用户对于数据服务的需求将远远大于对于传统语音服务的需求,提高系统数据吞吐量已成为移动通信网络未来发展的主要课题。为此,移动通信网络在不断演进过程中引入了small cell网络的概念。Small cell网络作为未来移动通信网络中重要的组成部分,将极大的提高蜂窝系统覆盖范围和系统容量,为用户提供更快速的数据通信服务。但是small cell的大规模部署必然会极大增加蜂窝系统的能耗。因此,在保证smallcell网络性能的前提下,降低系统的能量消耗就成为目前small cell网络研究中的一个重要课题。本硕士论文研究small cell网络的能量效率问题,基于休眠调度和资源分配的方法,提出了分布式休眠调度机制、基于休眠模型的资源分配算法以及兼顾公平性的资源分配算法。论文首先提出了一种分布式休眠调度机制(Distributed On/Off Control Mechanism, D-OCM)。该休眠调度机制考虑small cell大规模部署的系统场景,每个小区基站(Small Cell Base Station, SBS)有休眠和作业两种状态,SBS可以主动进入休眠状态或是在休眠状态下被周围的基站通过广播信号的方式激活进入作业状态。为了实现这种分布式休眠调度机制,每个SBS必须通过其当前小区内的用户收集相邻小区的网络信息,并建立相应的网络信息表。每个SBS根据当前小区的负载状况和网络信息自主决定是否激活周围一个处于休眠状态的基站或是自身进入休眠状态。仿真结果表明,D-OCM调度机制可以在保证吞吐量的条件下,有效地降低系统的能量消耗；与传统的分布式休眠机制相比,D-OCM可以更好地降低系统的能量消耗。在分布式休眠调度机制的基础上,论文研究了网络拓扑结构发生变化时用户的资源分配问题。当一个小区被激活后,会收到多个用户的服务请求,新启动的SBS需要根据不同的资源块在每个用户处所受到的干扰不同,对资源块进行分配。为此,论文提出了一种基于休眠模型的资源分配(Resource Allocation Algorithm Based on Sleep Mode, RASM)算法。RASM算法将资源分配分成频谱分配和功率优化两步,其中将频谱分配问题建模成一个M×N的指派问题,并使用匈牙利算法求解最优分配方案。在频谱分配过程中,默认每个资源块的功率固定,因此新基站会与相邻基站产生严重的覆盖重叠。为此,论文进一步提出了一种功率优化算法,该算法让当前小区依次与相邻小区相互通信,并进行功率优化。仿真结果表明,RASM算法可以在保证系统吞吐量的条件下,有效降低系统能量消耗,提高能量效率。与随机资源分配策略相比较,RASM算法能够获得更好的系统性能。针对上述算法中忽视的公平性问题,论文提出了一种兼顾公平性的资源分配算法(Resource Allocation Algorithm Considering Fairness, RACF)。该算法首先采用一种多资源块(Resource Block, RB)分配算法,在每个用户发射功率固定的条件下,根据每个资源块在不同用户处受到的干扰不同,将多个资源块分配给用户。同时,在用户吞吐量较低时,采用一种资源块调整算法,通过小区内资源块调整和相邻小区资源块调整,为当前吞吐量较低的用户提供一个干扰较低的资源块,并通过对相邻小区资源块调整再次进行优化,在保证当前小区用户公平性的条件下使相邻小区系统性能不会出现明显下降。仿真结果表明,所提出的资源分配算法可以有效提升系统的吞吐量,所提出的资源块调整策略可以有效保证用户的公平性。更多还原

【Abstract】 With the rapid development of mobile Internet and rapid popularity of smart mobile devices, users’demand for mobile communication service is changing. In future mobile communication networks, users’demand for data service will be much more than that for void service. Increasing the data throughput of a mobile communication network has become an important research topic for future mobile communication networks. To achieve this objective, the concept of small cell networks has been introduced in mobile communication networks. As an important component of a future mobile communication network, a small cell network will be able to improving the capacity and coverage of a cellular network, and provide faster data communication service. However, the massive deployment of small cells will increase the energy consumption of a cellular system. Therefore, how to reduce the energy consumption of a cellular system while not affecting the performance of a small cell network has become an important research topic in small cell networks.This thesis studies the energy efficiency problem in small cell networks. Based on sleep scheduling and resource allocation, it proposes a distributed base station on/off mechanism, a sleep mode based resource allocation algorithm and a resource adjustment strategy with fairness for small cell networks.First, the thesis proposes a distributed base station on/off mechanism (D-OCM). D-OCM considers a macro-cell system with multiple small cells, where each small cell base station (SBS) has two states:sleep and working. A working SBS can actively go into a sleep state, while a sleep SBS can be activated by a neighbor SBS. To support D-OCM, each base station needs to maintain three tables to store relevant network status information on its neighbor base stations. Both the MBS and an SBS build the tables using the network status information collected from the users within their coverage. Each base station, either the MBS or an SBS, makes a decision to activate an SBS in a sleep state or to deactivate an SBS in a working state based on the traffic load within its coverage. Simulation results show that the proposed D-OCM mechanism can significantly reduce the energy consumption of the system as compared a traditional control mechanism.Based on D-OCM, the thesis further studies the resource allocation problem under the change of the network topology and proposes a resource allocation algorithm based on a sleep mode (RASM). The network topology changes when an SBS is deactivated or activated. A newly activated SBS will receive multiple requests from users and thus need to allocate resources for the users. RASM consists of two phases:spectrum allocation and power optimization. The spectrum allocation can be described as an MxN assignment problem, which can be solved by using a Hungarian algorithm. The power optimization of small cell can be performed through communication with neighbor small cells. Simulation results show that RASM can achieve higher energy efficiency than the random allocation algorithm.Given that D-OCM and RASM have not considered the user fairness problem, the thesis proposes a resource allocation algorithm considering user fairness (RACF). RACF consists of a resource block allocation algorithm and a resource block adjustment algorithm. The resource block allocation algorithm allocates multiple resource blocks for users based on the different interferences each resource block receives at different users under the condition that each user transmits at fixed power. Meanwhile, the resource block adjustment algorithm allocates a resource block with lower interference for a lower data rate user by adjusting the resource blocks in the current small cell and the resource blocks of neighbor small cells, and further optimize the resource block allocation by adjusting the resource blocks of neighbor small cells. The objective is to ensure the user fairness in the current small cell while not affecting the performance of neighbor small cells. Simulation results show that RACF can effectively improve the system throughput while effectively ensuring the user fairness.更多还原