LTE基站中PDSCH高效并行计算的FPGA实现

提出一种第三代合作伙伴(3GPP)长期演进(LTE)基站中下行共享信道(PDSCH)中比特级信号处理并行计算方案,其并行运算是基于现场可编程门阵列(FPGA)的。由于下行控制信道中数据流量相对下行共享信道偏少,为了保证控制信道与共享信道下行数据的时序对齐,并且最大程度上节省硬件资源,以满足LTE系统测试要求,必须采用并行计算的处理方式。采用VHDL语言在Xilinx公司的Virtex-6系列FPGA芯片内成功对该方案进行了验证,并对其进行优化。     

LTE系统DCI格式检测及PDSCH传输方案的实现

物理下行控制信道(Physical Downlink Control Channel,PDCCH)承载着一个或多个终端的下行控制信息(DCI),UE通过解析DCI来得知用于PUSCH/PDSCH(物理上行共享信道/物理下行共享信道)传输的相关控制信息.提出了一种当UE被高层设置为用小区无线网络临时标识C-RNTI加扰的CRC进行PDCCH解码时,UE根据传输模式来确定DCI格式候选集合,进而盲检测DCI格式及确定PDSCH传输方案的DSP实现方法,该方法已经在TMS320C64x DSP中实现.将该方案应用于TD-LTE射频一致性测试系统的开发中,实际运行验证了该方案的可行性、高效性.     

LTE系统DCI格式检测及PDSCH传输方案确定的实现

PDCCH (Physical Downlink Control Channel,物理下行控制信道)承载着一个或多个终端的下行控制信息（DCI）,UE通过解析DCI来得知用于PUSCH/PDSCH（物理上行共享信道/物理下行共享信道）传输的相关控制信息。本文提出了一种当UE被高层设置为用小区无线网络临时标识C-RNTI加扰的CRC来进行PDCCH解码时,UE根据传输模式来确定DCI格式候选集合,进而盲检测DCI格式及确定PDSCH传输方案的DSP实现方法。该方法已经在TMS320C64xDSP中实现。将该方案应用于TD-LTE射频一致性测试系统的开发中,实际运行验证了该方案的可行性、高效性。     

WCDMA中高速下行物理共享信道的RAKE接收机

WCDMA R5版本协议引入了高速下行共享信道用于支持高速业务,为此增加了高速下行物理共享信道（HS—PDSCH）、高速下行控制信道（HS—SCCH）以及高速上行反馈信道（HS—DPCCH）。其中,HS—PDSCH在不同的环境下可以采用16QAM或者QPSK两种调制方式,文中提出了RAKE接收机的接收方案,并在瑞利衰落环境下进行了仿真,同时对仿真结果加以分析。结果表明,此RAKE接收机的性能能够满足接收要求,且易于实现。     

LTE-A中下行参考信号冲突的性能分析

在LTE-A标准中，下行用户级的解调参考信号会与物理广播信道以及主、辅同步信号等冲突。终端可以不接收冲突的资源块甚至整个PDSCH/ePDCCH数据，这将对LTE-A下行系统性能产生较大影响。针对资源冲突情况，系统分析了基站和终端多种解决策略以及相应的理论性能。通过性能仿真给出了冲突解决策略的链路级性能增益。结合仿真结果，建议设备和终端共同改进来约束终端行为并提高性能。     

基于LMS自适应算法的HS-PDSCH动态码道分配方法

高速下行分组接入技术（HSDPA）通过使用自适应调制编码、混合自动重传请求、快速凋度等关键技术,可以大大提高下行数据的传输速率。为了充分利用这些技术网络侧必须配置仅供HSDPA用户使用的PDSCH码道,因为PDSCH码道的共享性和普通R4码道的专用性,TD-SCDMA系统中必须在建立小区的时候建立PDSCH码道,一旦某些码道被HSDPA占用就不能再在这些码道上接入普通的R4业务。但系统对HSDPA下行流量的需求是时变的,因此固定不变的PDSCH码道配置就有可能造成码道资源的浪费。本文从侧重实现的角度提出了一种基于LMS自适应算法的HSDPA动态码道分配方法,可以由系统根据当前下行数据流量自行调整HSDPA码道配置,提高了TD-SCDMA系统中HS-PDSCH物理信道的利用效率和系统容量。     

基于TD- LTE系统的新型SNR和CQI映射方案

为了在链路自适应、混合自动重传、快速调度过程中最大程度地满足长期演进(LTE)系统的性能和吞吐量,提出了一种新型的信噪比(SNR)和信道质量指示(CQI)映射方案.这种新的方案通过系统链路级仿真得到信噪比和误块率之间的仿真曲线,然后通过区域拟合的方式得到SNR和CQI之间的关系.和传统的映射方案相比,它不仅易于实现和存...     

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。     

LTE系统中下行频域资源分配算法的研究

在LTE系统中,下行频选分配依据子信道质量选取最好的信道来传输业务,提高系统吞吐量。本文从无线资源分配角度出发,针对现有频选算法的不足,提出一种改进型频选与非频选结合分配算法,实现频选资源选取的最优化,同时在资源分配时将频选分配和非频选分配算法进行合并处理,通过比较频选UE度量值和非频选UE度量值来决定当前资源块组(resource block group,RBG)的分配方式。通过系统级仿真可知,在提高资源分配合理性的同时,可以提高系统整体吞吐量。     

LTE系统中上行数据组装过程研究与实现

介绍了LTE系统中上行数据组合过程的原理与特点,主要分析了LTE技术中逻辑信道优先级中采用的令牌桶算法,论述了逻辑信道资源分配机制与上行数据复用过程采用的方案。针对LTE技术中的逻辑信道复用与上行数据组装过程,提出了一种改进的可用于实现的数据组装方案。最后总结了LTE系统中逻辑信道映射的优势,根据现有方案实现的代码进行测试,验证方案的正确性。     

LTE系统中保证CCE分配公平性的算法

在LTE系统中,CCE是传输控制信息所用的物理资源,被上行调度和下行调度共用,若上行调度中所需CCE资源多并且调度快,那么下行调度中将没有或者只有很少的CCE资源可以使用,导致PDSCH中的RB浪费大,反过来PUSCH中RB浪费大。为了避免这个问题的发生,采取限制上下行调度中分配CCE的最大UE数目的方法来保证其公平性,同时提出计算上下行调度中分配CCE最大UE数目的算法,最后通过仿真证明该方法是可行的。     

Automated performance‐based design technique for an efficient LTE PDSCH implementation using SDSoC tool

System on a chip (SoC) creates massive design challenges for SoC‐based designers. The design challenges start from functional, architectural verification complexity and finally meeting performance constraints. In addition, heterogeneity of components and tools introduces long design cycles. The Software‐Defined System‐on‐Chip (SDSoC) developed by Xilinx is used to create custom SoC on a heterogeneous FPGA‐CPU platform. The SDSoC tool provides fast, flexible, and short design cycle to develop heterogeneous FPGA‐CPU platform. The objective of this paper is to introduce a new automated design technique to build a SoC on a heterogeneous FPGA‐CPU platform that meets design requirements using SDSoC tool. In this paper, the typical SDSoC design flow is introduced. In addition, a new automated SDSoC design technique is developed to design SoC on a heterogeneous FPGA‐CPU platform on the basis of performance metrics such as area, power, and latency. Design of physical downlink shared channel (PDSCH) in long‐term evolution (LTE) is presented as a case study. This paper provides the implementation of the transmitter and the receiver of the PDSCH in LTE using SDSoC tool and selects a platform that meets performance metrics constraints.     

Energy-saving scheduling for LTE multicast services

In the Long Term Evolution （LTE） downlink multicast scheduling, Base Station （BS） usually allocates transmit power equally among all Resource Blocks （RBs）, it may cause the waste of transmit power. To avoid it, this paper put forward a new algorithm for LTE multicast downlink scheduling called the Energy-saving based Inter-group Proportional Fair （EIPF）. The basic idea of EIPF is to calculate an appropriate transmitting power for each group according to its data rate respectively, and then follow the inter-group proportional fair principle to allocate RBs among multicast groups. The results of EIPF simulation show that the proposed algorithm not only can reduce the transmit power of BS effectively but also improve the utilization rate of energy.     

Resource allocation algorithm for LTE networks using fuzzy based adaptive priority and effective bandwidth estimation

In this paper, we propose a scheme to allocate resource blocks for the Long Term Evolution (LTE) downlink based on the estimation of the effective bandwidths of traffic flows, where users’ priorities are adaptively computed using fuzzy logic. The effective bandwidth of each user traffic flow that is estimated through the parameters of the adaptive β-Multifractal Wavelet Mode modeling, is used to attain their quality of service (QoS) parameters. The proposed allocation scheme aims to guarantee the QoS parameters of users respecting the constraints of modulation and code schemes (modulation and coding scheme) of the LTE downlink transmission. The proposed algorithm considers the average channel quality and the adaptive estimation of effective bandwidth to decide about the scheduling of available radio resources. The efficiency of the proposed scheme is verified through simulations and compared to other algorithms in the literature in terms of parameters such as: system throughput, required data rate not provided, fairness index, data loss rate and network delay.     

LTE中基于Turbo编码的速率匹配算法的DSP快速实现方案

针对现有TD-LTE终端测试仪表因信道编码处理速度慢导致下行达不到理论峰值速率问题,本文在深入研究了3GPP协议中的Rate Matching算法的基础上,提出了一种基于DSP芯片快速实现RM算法的方案,优化下行信道编码,利用地址置换代替数据置换以减小速率匹配的处理延时.通过对比代码优化前后的算法执行时间,表明基于该方案的RM算法具有较小的处理延时.此方案推动了TD-LTE终端测试仪表实现下行理论峰值速率,为加快LTE发展提供了动力.     

Network Performance Analysis of TCP-Based 3GPP LTE Time Division Duplex Systems

This paper deals with the determination of downlink (DL) and uplink (UL) channel split ratio for time division duplex (TDD) based long term evolution (LTE) networks. In a TDD system, UL and DL transmissions are carried out at different time intervals, but share the same frequency band. The TDD framing in LTE is adaptive in the sense that the DL to UL bandwidth ratio may vary with time. This paper proposes an adaptive split ratio (ASR) scheme for LTE networks to automatically adjust the bandwidth ratio of DL to UL, according to the current traffic profile, wireless interference, and transport layer parameters. This provides the maximum aggregate throughput in LTE systems. The performance analysis shows that ASR scheme outperforms static allocation in terms of higher aggregate throughput and better adaptively to network dynamics. Further, it is also observed that the ASR scheme performs well for LTE, compared to worldwide interoperability for microwave access (WiMAX) system.     

Integrated load‐based power saving for real‐time and nonreal‐time traffic in LTE‐TDD

Long‐Term Evolution (LTE) is a 4G wireless broadband technology developed by the Third Generation Partnership Project. Two duplex modes, namely, frequency division duplex and time division duplex (TDD), are defined in LTE for transmission in both downlink and uplink directions simultaneously. Power saving mechanisms for LTE‐frequency division duplex were proposed in the authors' previous work. Applicability of the previously proposed mechanisms to LTE‐TDD is investigated in this paper, and the idea of “virtual time” associated with the mapping mechanism from the virtual time domain to the actual time domain for different TDD configurations is proposed. With the help of the mapping mechanism, 3 revised power saving schemes are proposed to support real‐time user equipments and nonreal‐time user equipments in LTE‐TDD. Simulation study demonstrates the effectiveness of the mapping mechanism as well as the benefit of the proposed schemes in power saving efficiency and real‐time support in comparing with the standard‐based mechanism.