TD-LTE系统中资源调度技术的研究

首先阐述了TD-LTE系统中资源调度技术的重要性,介绍了资源调度技术中信道质量指示CQI信号的定义、反馈机制、以及周期性与非周期性CQI反馈区别。然后在实际TD-LTE系统环境中对CQI信号进行测试,并对结果做了简单的比较分析。最后详细比较了FD-LTE、HSDPA和TD-LTE系统中CQI的运作机制,总结得出TD-LTE系统在资源调度技术上具有高频率利用率、支持非对称业务、获得高吞吐速率以及节省上行信道资源等优势。     

TD-LTE主要功能——下行频率选择性调度（DLFSS）测试研究

TDLTE下行频选调度的主要原理是依据UE反馈的下行信道CQI信息,在频域上为UE分配较好的子带资源,来优化链路性能,避开小区间的干扰。本测试研究主要用来验证TD-LTE系统对下行频率选择性调度功能的支持,考察在不同加扰模式下下行频域选择性调度和非频域选择性调度的性能比较。     

TD-SCDMA测试仪中Uu接口的RRC消息关联方案研究

在TD无线网络测试中,测试仪表的空中接口的数据解码和分析质量有着举足轻重的作用。RRC子层在空中接口中属于接入层,空中接口的相关功能的实现,如无线承载的建立和实现等都是在RRC信令连接的基础上进行的,因此RRC子层消息的关联是空中接口呼叫合成的关键所在。本文以MOC信令流程为例,根据RRC信令连接是否建立在专用信道上,对专用信道和公共信道上建立的RRC消息分别提出了相应的关联方案。经过测试,该方案确实可行,达到了研究的预期目的。     

TD-SCDMA终端无线资源管理（RRM）测试初探

1 引言无线资源管理是对移动通信系统的空中接口资源的规划和调度,涉及到一系列与无线资源分配有关的内容。对TD-SCDMA系统以及终端设备来说,可靠和高效的无线资源管理策略和方法是提高系统性能和容量的重要保证。本文针对TD-SCDMA终端无线资源管理测试的几个主要方面进行介绍,包括空闲模式进程、连接模式下的移     

LTE MIMO中秩（RI）的意义及作用过程

LTE系统中,eNodeB根据UE上报的信道质量指示（CQI）和秩指示（RI）信息进行下行资源调度,分配所需的资源块和MCS,设定同时发送的码字数目。3GPP中对于CQI的上报方式和取值等信息定义比较明确,对于RI的描述则相对较少。分析和研究RI的意义、作用方式以及影响因素等内容,对全面理解LTE性能无疑会有很大帮助,以下予以详细论述。     

全新无线信道仿真平台专为新一代无线通信系统设计

无线通信系统越来越快的传输速度，要求空中接口具备更宽的带宽和更高的频谱效率。MIMO和波束赋形等先进技术已经成为提高无线系统性能的关键因素。除了利用标准无线信道模型验证基本功能外，在实验室中模拟真实的空中接口环境，进行设备级、应用级甚至网络级的测试是确保最终用户能够体验到预期性能的关键。伊莱比特公司（EB）日前推出一个全新的信道仿真平台，     

一种GEO卫星移动通信信道质量近似方法

在LTE移动通信系统中信道质量指示参数(Channel Quality Indicator,CQI)是自适应调制编码(AdaptiveModulation and Coding,AMC)技术的一项重要参数。由于GEO卫星信道存在较长的传输时延,为保证有效的AMC调整,对CQI进行预测是非常必要的。但是大多数预测算法的可预测时长受到输入序列的相关时间限制,而含有小尺度衰落影响的信号的CQI序列的相关时间远远小于所需预测时长,对获得的CQI序列进行预测是不现实的。针对这一问题,提出了一种使用仅含有大尺度衰落的CQI数据进行预测的近似方法。将获得的CQI序列平滑后去掉小尺度衰落的影响,余下的数据可以认为是只受大尺度衰落影响,其相关时间可以大大延长。通过对GEO卫星信道信道质量进行建模分析,对使用近似方法处理前后的CQI序列数据差距以及相关时间的变化进行了数值仿真,结果表明所提出的近似方法不会导致CQI数据产生较大的偏差,且近似后的序列具有较长相关时间。在此种近似方法处理下的CQI数据相关时间能够满足预测模型的需要,从而为保证GEO卫星移动通信系统中使用AMC的可行性和可靠性提供可能。     

cdma2000 1x EV-DV系统中信道质量指示符预测算法研究

cdma2000 1x EV-DV系统为了获得更好的系统性能,在前向链路应用前向链路信道质量指示符(Channel Qual-ty Indicator,CQI)来得到前向链路的信道质量。文章提出了两种CQI的预测方法,一种是根据过去CQI数值,然后采用数值方法来得到CQI的非线性数值逼进模型参数,然后,再应用这个模型对CQI进行外推预测;另一种CQI预测算法是基于对过去的CQI值进行归一化最小均方(N-LMS)预测。对两种CQI预测算法和传统的CQI处理方法分别进行了分析和仿真,从链路级证明了算法的有效性。     

LTE网络空中接口物理层PDSCH信道检测技术研究

随着国内LTE牌照的发放,大规模的LTE网络规划和部署势在必行。由于LTE扁平化的结构特点使得空中接口测试成为LTE网络监测的重点。物理层位于空中接口协议规范最底层,而PDSCH信道承载了物理层业务数据比特流,因此,PDSCH信道的检测成为物理层分析的核心模块。本文结合自主研发的LTE空中接口监测仪,对PDSCH信道检测技术进行探讨,仪器分析结果表明,提出的检测技术正确有效。     

TD-SCDMA空中接口物理层概述及其与WCDMA的比较

对TD-SCDMA移动通信系统空中接口的物理层的帧结构,以及物理层所采用的智能天线,联合检测,动态信道分配等关键技术进行了阐述。并与WCDMA系统的空中接口物理层作了比较。为TD-SCDMA无线系统和WCDMA无线系统的研究提供一定的参考数据。     

Proportional fair scheduling with reduced feedback

An opportunistic feedback technique is proposed for proportional fair (PF) scheduling in a downlink multi-user system. This technique requires each mobile station, the scheduling metric of which is higher than a threshold, to send one-bit feedback for PF scheduling. The scheduler determines the optimal modulation and coding scheme for a scheduled user based on channel quality indicator (CQI) update, which is sent on a longer period than the scheduling period. The simulation results indicate that PF scheduling with the proposed update scheme can achieve similar performance as PF scheduling with full CQI feedback. The feedback overhead can be reduced in comparison with typical PF scheduling provided that an optimal CQI update period is chosen.     

多载波MIMO传输系统中的信道质量信息压缩反馈新方法(英文)

In multi-user wireless communication systems,adaptive modulation and scheduling are promising techniques for increasing system throughput.However,for multi-carrier systems,they will lead to overwhelming user feedback overhead for Channel Quality Indication(CQI) in every subcarrier.In our work,novel CQI feedback schemes are proposed based on the recently proposed theory of Compressive Sensing(CS).First,the standard CS method is introduced to reduce CQI feedback overhead for multi-carrier Multiple-Input Multi...     

TD-LTE网络吞吐率最优原则研究

吞吐率是4G网络构成竞争优势的关键指标,影响吞吐率的因素众多,除网络质量关键因素外,吞吐率的差异取决于网络的调度算法,调度算法由UE和eNode B联合实现。UE完成信号监测后上报CQI和RI,eNode B根据调度算法输出TM、MCS、RB等信息,本文依据海量测试,分析得出了TD-LTE网络吞吐率遵循3大最优原则,为后续TD-LTE网络规划和优化提供理论依据。     

On capacity of quality-based channel-state reporting in mobile systems with greedy transmission scheduling

Greedy transmission scheduling achieves great capacity by maximally exploiting independent time-varying channels across different mobile users. The improvement in capacity, however, depends on the degree of completeness of the channel quality information (CQI) fed back from the receiver to the transmitter. To be motivated by an insight that too many CQI feedbacks may rather impair the capacity gain, due to causing congestion in feedback link, this letter proposes a quality-based CQI reporting (QBR) scheme where the CQIs are fed back to the transmitter only for receivers whose signal quality is above a predefined threshold. The capacity is provided in terms of the threshold and feedback-error rate. The results show that QBR achieves outstanding performance when the feedback error is present. In addition, it quickly approaches an unimpaired ideal capacity, as the number of users increases if the error is not assumed.     

基于TD-HSDPA系统的新型调度算法

通过对TD-HSDPA (TD-SCDMA高速下行分组接入技术)中关键技术的分析,研究了CQI(信道质量信息)的反馈时延对系统性能的影响,分析了信令开销与反馈准确性之间的联系;同时提出了一种基于TD-HSDPA系统的新型调度算法,此算法通过对调度流程和优先级计算方式的改进,能够有效地避免CQI反馈时延对于Node B(基站)快速调度器的调度效率和准确性的影响.通过对系统级仿真结果的分析,证明在系统负载持续增加的情况下,新算法能够有效地保证小区吞吐量和分组业务的延时性能.     

TD-LTE与TD-SCDMA系统共存子帧配比兼容分析研究

对于当前TD-LTE与TD-SCDMA系统邻频共存的情况,由于两者皆为TDD系统,所以TD-LTE必须与TD-SCDMA系统的子帧配比兼容以避免系统间干扰;给出了两者共存时兼容的子帧配比,研究了此子帧配比下TD-LTE的两种特殊时隙配比方案SSP5与SSP6,并从下行资源利用情况、单小区下行峰值吞吐量、基站可规避干扰距离等方面将两方案做了对比分析,指出SSP6能够更好地利用系统的下行资源,有利于提升系统容量。     

On Scheduling for Multiple-Antenna Wireless Networks Using Contention-Based Feedback

Multiuser diversity gain is an effective technique for improving the performance of wireless networks. This gain can be exploited by scheduling the users with the best current channel conditions. However, this kind of scheduling requires that the base station (or access point) knows some kind of channel quality indicator (CQI) information for every user in the system. When the wireless link lacks channel reciprocity, each user must feed back this CQI information to the base station. The required feedback load makes exploiting multiuser diversity extremely difficult when the number of users becomes large. To alleviate this problem, this paper considers a contention-based CQI feedback where only users whose channel gains are larger than a threshold are allowed to transmit their CQI information through a spread-spectrum based contention channel. Considering the capture effect in this contention channel, it is shown that i) the multiuser diversity gain can be exploited regardless of the number of transmit antennas at the base station and ii) the total system throughput exponentially approaches that of the full feedback scheme as the spreading code length of the contention channel linearly increases. In addition, it is also shown that multiuser diversity can be maintained with the feedback delay of time-variant channels. We also consider the issue of differentiated rate scheduling, in which the base station gives different rates to different subsets of mobiles. In this scenario, mobiles feed back their CQI with some access probability, and we show this technique causes only a negligible throughput loss compared to the case without supporting differentiated rate.     

An enhanced channel-quality indication (CQI) reporting scheme for HSDPA systems

A major evolution of UMTS standard is the high speed downlink packet access (HSDPA). One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes an enhanced CQI reporting scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The proposed scheme uses a dynamic threshold to filter off redundant CQI reports. With the proposed scheme, the battery capacity of UK can be conserved, maintaining the performance of traditional CQI reporting scheme.     

LTE系统中的一种频选调度方案

从无线资源分配的角度出发,提出了一种频选调度方案,旨在充分利用LTE系统频谱资源的前提下提高小区的吞吐量。频选调度方案设计的MAC层调度器可以按照UE上报的信道质量指示,将可以使用的资源分为不同的优先级,然后把最好的资源分配给相应的UE,实现频选调度策略。通过系统级仿真可知,该方案能提高用户的性能。     

An Opportunistic Channel Quality Feedback Scheme for Proportional Fair Scheduling

In this paper, we propose a channel quality information (CQI) feedback load reduction scheme for proportional fair scheduling (PFS) in wireless systems. The proposed scheme induces select users to feed back CQI only when the probability of selection is high. It is shown that the proposed scheme achieves system throughput comparable to the conventional scheme, where each and every user feeds back its CQIs, with significant feedback load reduction for each of the users.