【作者】 崔杰；

【导师】 常永宇；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2010， 博士

【摘要】 本文研究了时分同步码分多址接入(Time Division Synchronous Code Division Multiple Access, TD-SCDMA)的演进系统及其先进的无线资源管理(Radio Resource Management, RRM)技术。所涉及的TD-SCDMA的演进系统主要可以分为两大类：基于码分多址接入(Code Division Multiple Access, CDMA)的系统以及基于正交频分多址接入(Orthogonal Frequency Division Multiple Access, OFDMA)的系统；而研究的RRM算法主要包括：基于TD-SCDMA高速下行分组接入(TD-SCDMA High Speed Downlink Packet Access, TD-HSDPA)反馈时延控制的快速调度(Fast Packet Scheduling, FPS)算法、基于TD-HSDPA的正交可变扩频因子(Orthogonal Variable Spreading Factor, OVSF)码字重用算法、TD-SCDMA长期演进(TD-SCDMA Long Term Evolution, TD-LTE)的二维调度和资源分配算法、基于干扰避免的OFDM自适应资源分配(Adaptive Resource Allocation, ARA)算法以及基于物理资源块(Physical Resource Block, PRB)重用的TD-LTE三维调度和资源分配算法,最后本文还分析了TD-SCDMA与TD-LTE共存的系统性能。TD-SCDMA演进不仅需要系统架构的升级优化,更需要物理(Physical, PHY)层和媒体接入控制(Medium Access Control, MAC)层关键技术的不断创新和优势组合。本文介绍的TD-SCDMA演进系统有基于CDMA的TD-HSPA/TD-HSPA+和基于OFDMA的TD-LTE/TD-LTE+,并且对其标准化过程和关键技术进行了分析,包括智能天线(Smart Antenna, S A)、联合检测(Joint Detection, JD)、自适应调制编码(Adaptive Modulation and Coding, AMC)、混合自动重传请求(Hybrid Auto Repeat reQuest, HARQ)、多输入多输出(Multiple Input Multiple Output, MIMO)天线和OFDM技术等；同时对于未来通信中的无线资源的基本结构和算法也做了简要的介绍。通过对系统结构及特性的研究,本文讨论了基于TD-SCDMA演进系统的系统级仿真方法论,提出了多种相应的仿真模型和参数假设；并针对TD-HSPA和TD-LTE的不同点,对仿真器进行了差异性设计。本文的研究点主要包含下几个部分：首先,在TD-HSDPA中,系统利用高速下行共享信道(High Speed Downlink Shared CHannel, HS-DSCH)作为业务信道来传输不同用户的数据流,并引入了两个共享控制信道：HS-DSCH的共享控制信道(Shared Control CHannel for HS-DSCH, HS-SCCH)和HS-DSCH的共享信息信道(Shared Information CHannel for HS-DSCH, HS-SICH),用于基站(NodeB)和用户设备(User Equipment, UE)控制信息的交互；在TD-HSDPA协议中规定了不同信令交互的定时关系,由于采用共享反馈的机制,信道质量指示(Channel Quality Indicator, CQI)的反馈在常规的调度策略模式下传输往往会有很大的时延；特别是当系统负载较大时,NodeB所接收到的反馈CQI已经无法准确体现用户当前的信道情况,因此本文提出了一种基于TD-HSDPA反馈时延控制的调度策略,通过有效地改善TD-HSDPA系统中的用户调度和信道资源分配方式来对抗信令交互的时延特性,提高反馈的实时性和有效性,从而提升通信系统性能。其次,TD-HSDPA采用了OVSF码作为其物理信道的扩频码,其扩频因子最大可取16；由于受到扩频码字数目的限制,TD-HSDPA和TD-SCDMA一样,是一种典型的资源受限的CDMA系统,本文通过智能天线波束赋形时产生的空间隔离特性,在TD-HSDPA引入空间维资源的概念,提出了一种OVSF码字重用算法,允许满足智能天线空间隔离度要求的用户群共享同一码字,从而大幅提升了系统容量,增进了用户满意度。第三,TD-LTE中所采用的OFDMA是一种很有前景的物理层技术,由于引入了频域资源,需要更复杂的时频调度算法来挖掘更丰富的多用户分集,本文研究了跨层设计的二维调度和资源分配算法,通过对MAC层的时域分组调度(Time Domain Packet Scheduling, TDPS)和PHY层的频域资源分配(Frequency Domain Resource Allocation, FDRA)的不同组合的性能评估,论证了跨层设计的方式能够很好的考虑HARQ重传,给重传数据较高的优先级,并且能保证用户之间的公平性,为系统带来较高的性能增益。第四,本文考虑了OFDMA系统中多径时延超过保护间隔(Guard Interval, GI)的场景,并分析了由此带来的相应符号间干扰(Inter-Symbol Interference, ISI)和载波间干扰(Inter-Carrier Interference, ICI);而为了完成OFDMA系统的小区内干扰消除,大多数的文献都将研究重心放在接收端的数字信号处理(Digital Signal Processing, DSP)算法上,本文创新性地提出了一种自适应的资源分配算法,通过利用非满载系统资源分配的灵活性来避免由GI不足带来的小区内干扰,从而不需要在接收端对DSP模块进行硬件升级,只需要通过软件升级即可完成干扰消除,降低了系统的复杂度。第五,本文在TD-LTE系统的原有资源基础上,研究通过新的关键技术来增加频谱利用效率。通过将智能天线应用在TD-LTE系统,在原有时频资源的基础上,引入空间资源,使TD-LTE的二维无线资源扩容成三维。新算法对满足空间隔离度的用户进行PRB重用,使系统性能得到了本质的提高。第六,本文研究了TD-SCDMA与TD-LTE双系统共存场景的系统性能,通过对于双系统的联合仿真,分析了不同方向业务之间的干扰情况,并且根据相应的结果曲线总结了不同场景下系统间对抗干扰所需的邻道干扰比(Adjacent Channel Interference power Ratio, ACIR)隔离度。更多还原

【Abstract】 Time Division Synchronous Code Division Multiple Access (TD-SCDMA) evolution and advanced radio resource management (RRM) technologies are researched in this dissertation. The mainstream TD-SCDMA evolution can be categorized into two types:systems based on Code Division Multiple Access (CDMA) and systems based on Orthogonal Frequency Division Multiple Access (OFDMA). Several novel RRM technologies are involved here, such as the novel fast packet scheduling (FPS) algorithm considering feedback delay in TD-SCDMA High Speed Downlink Packet Access (TD-HSDPA) systems, the novel strategy of orthogonal variable spreading factor (OVSF) code reusing in TD-HSDPA, the packet scheduling and resource allocation schemes in TD-SCDMA Long Term Evolution (TD-LTE), the novel adaptive resource allocation (ARA) algorithm in OFDMA with insufficient guard interval. under fractional load, and the three-dimension scheduling and resource allocation scheme based on physical resource block (PRB) reusing. Moreover, the co-existence performance of TD-SCDMA and TD-LTE are studied.TD-SCDMA evolution not only needs the upgrade in system fundamental architecture, but also the innovation and optimization in key technologies on physical (PHY) layer and medium access control (MAC) layer. TD-HSPA/TD-HSPA+ based on CDMA and TD-LTE/TD-LTE+ based on OFDMA are introduced by this dissertation, while the standardization and key technologies of TD-SCDMA evolution are analyzed, such as smart antenna (SA), joint detection (JD), adaptive modulation and coding (AMC), hybrid auto repeat request (HARQ), multiple input multiple output (MIMO) antenna, and OFDM algorithm; the framework and schemes of future RRM are also mentioned. Through the analysis of the features and structures of TD-SCDMA evolution, the system level simulation methodology is discussed. The correlative simulation modules and assumptions of parameters are designed, and the simulator also takes the differences between TD-HSPA and TD-LTE into account. Our research work can be composed of following 6 parts:Firstly, TD-HSDPA adopts high speed downlink shared channel (HS-DSCH) as the traffic channel to transmit packet data for different users, and it has two shared control channels for interaction between base station (NodeB) and user equipment (UE):shared control channel for HS-DSCH (HS-SCCH) and shared information channel for HS-DSCH (HS-SICH). In TD-HSDPA, due to the timing relationship of high speed (HS) channels, the feedback information of channel quality indicator (CQI) are always delayed under the conventional scheduling schemes; especially, when the traffic load is heavy, the CQI received by NodeB can no longer represent the current channel condition for users. In order to maintain the efficiency of feedback information, a novel scheduling scheme for feedback delay control is proposed. As the new scheme utilizes users’scheduling and channel allocation, the interaction delay can be greatly shortened, and the system performance can be improved remarkably.Secondly, OVSF is adopted in TD-HSDPA for physical channel spreading, and the spreading codes can be up to 16. Similar to TD-SCDMA, TD-HSDPA is a kind of resource-limited systems whose spreading codes are finite in a given time slot. The proposed OVSF codes reusing algorithm introduces spatial domain into TD-HSDPA by using spatial filter of SA beam-forming, and the users who have passed the spatial filter can share same codes, which enhances the system capacity and improve the quality of service (QoS).Thirdly, OFDM is considered as one of the most promising technologies for future multimedia wireless systems that require reliable and high-rate data transmission. As subcarrier resource is exploited, more complicated scheduling algorithms are required to achieve richer multi-user diversity. We investigate the combined performance of HARQ aware cross-layer design RRM in TD-LTE downlink systems, which is generally composed of time domain packet scheduling (TDPS) at MAC layer and frequency domain resource allocation (FDRA) at PHY layer, and the simulation results shows that the cross-layer design algorithm can guarantee the users’fairness and bring more performance gain for TD-LTE downlink.Fourthly, a more practical scenario, in which multi-path delay is longer than the guard interval (GI), is considered in this dissertation, and the intra-cell inter-symbol interference (ISI) and inter-carrier interference (ICI) are re-analyzed. Most of the existing literatures focus on the digital signal processing (DSP) algorithms at the receiver for reducing the intra-cell interference of OFDMA systems. However, instead of the conventional complicated DSP algorithms, we propose a novel adaptive resource allocation scheme, in which RA flexibility of fractional load is utilized to avoid intra-cell interference.Fifthly, in TD-LTE, we adopt SA to improve spectrum utilizing efficiency. Through the beam-forming, spatial dimension resources are introduced into TD-LTE, and the RRM schemes are extended to three-dimension. The proposed scheme makes the users who have passed spatial filter reuse the same PRB, which enhances the system throughput remarkably.Finally, the co-existence performance of TD-SCDMA and TD-LTE are studied. By the cooperative simulation of double systems, we analyze the interference with different traffics, and find out the required adjacent channel interference power ratio (ACIR) value in different scenarios from the simulation results.更多还原