LTE系统中MAC层调度与HARQ的研究

发布时间：2018-02-20 18:02

本文关键词： LTE MAC 调度算法 HARQ 信道质量指示　出处：《北京交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：为了提高移动通信业务的质量,以适应快速增长的用户数据量需求,也为了应对来自WiMax、Wi-Fi等无线宽带接入技术的挑战,2004年底3GPP开始了LTE(Long Term Evolution,长期演进)的标准化进程来更完善地使3G技术平滑过渡到4G技术。频谱带宽是无线通信系统中最珍贵的资源。一种无线调度算法的高效性主要表现在可以让错误链路上的无效数据传输最小化,尽量减少频谱资源的浪费,从而实现系统吞吐量的最大化。LTE提高了业务的服务质量和峰值速率,而其采用的HARQ(Hybrid Automatic Repeat Request,混合自动请求重传)就是一种可以有效确保高服务质量和高数据速率传输的关键技术。论文首先概括了移动通信系统简史和3GPP LTE相关的网络架构、性能指标与关键技术。简要介绍了调度算法与HARQ的研究现状以及本论文的主要研究内容和组织结构。同时对LTE MAC (Medium Access Control,媒体接入控制)子系统的模块功能进行了介绍,尤其对上下行调度功能模块和上下行HARQ功能模块进行了详细的描述。其次,详细介绍了用于非实时数据业务和实时数据业务的经典调度算法。并在比例公平调度算法的基础上提出了实时与非实时业务混合的综合调度算法,该算法在用户优先级的表达式中加入了时延影响因子。不仅能最大化系统吞吐量,还保证了服务业务的多样性。通过系统仿真,与比例公平调度算法在系统吞吐量、丢包率、数据速率公平性以及包超时延门限的公平性方面进行性能的比较,验证了该综合调度算法的有效性和实用性。最后,论文描述了协议中TDD系统HARQ ACK反馈方案及空口质量指标CQI(Channel Quality Indicator,信道质量指示)的相关知识,进而提出了一种基于UE空口质量的HARQ ACK/NACK复用反馈判决算法。该算法是基于HARQ ACK/NACK复用模式,是在4个下行链路子帧对应一个上行链路子帧,反馈结果存在二义性的情况时提出的。该算法基于UE空口质量进行判决,提高了判断的可靠性,并且减小了数据误判的次数,提高了系统资源的利用率。文中给出了该算法思想及其步骤。通过仿真与目前反馈方案进行比较,验证了该判决算法的有效性。
[Abstract]:In order to improve the quality of mobile communication services and adapt to the rapid growth of user data demand, In order to meet the challenge of wireless broadband access technology such as WiMax Wi-Fi, 3GPP started the standardization process of LTE(Long Term evolution in late 2004 to improve the smooth transition of 3G technology to 4G technology. Spectrum bandwidth is a wireless communication system. The efficiency of a wireless scheduling algorithm can be achieved by minimizing invalid data transmission on an error link. The waste of spectrum resources is minimized to maximize system throughput. LTE improves service quality and peak rate. HARQ(Hybrid Automatic Repeat request (hybrid automatic request retransmission) is a key technology which can effectively ensure high quality of service and high data rate transmission. Firstly, the brief history of mobile communication system and the network architecture related to 3GPP LTE are summarized. This paper briefly introduces the research status of scheduling algorithm and HARQ, as well as the main research content and organization structure of this paper. At the same time, the module functions of LTE MAC medium Access Control (Media access Control) subsystem are introduced. In particular, the uplink and downlink scheduling function modules and uplink and downlink HARQ function modules are described in detail. Secondly, the classical scheduling algorithms for non-real-time data services and real-time data services are introduced in detail, and a hybrid scheduling algorithm for real-time and non-real-time services is proposed on the basis of proportional fair scheduling algorithm. The algorithm not only maximizes system throughput, but also ensures diversity of service services. Through system simulation, proportional fair scheduling algorithm is applied to system throughput and packet loss rate. Data rate fairness and packet timeout delay threshold fairness are compared to verify the effectiveness and practicability of the proposed algorithm. Finally, this paper describes the HARQ ACK feedback scheme of TDD system and the channel quality indicator (CQI(Channel Quality indicator). Furthermore, a feedback decision algorithm for HARQ ACK/NACK multiplexing based on UE quality is proposed. The algorithm is based on HARQ ACK/NACK multiplexing mode and corresponds to one uplink sub-frame in four downlink subframes. When the feedback result is ambiguous, the algorithm is based on the quality of UE void, which improves the reliability of the judgment and reduces the number of data misjudgment. The idea and steps of the algorithm are given. The validity of the decision algorithm is verified by comparing the simulation with the current feedback scheme.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.5

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