HARQ–ARQ interaction method for LTE‐based mobile satellite communication system

Hybrid automatic repeat request (HARQ) and automatic repeat request (ARQ) of the terrestrial long‐term evolution (LTE) system are designed considering the very short propagation delay of terrestrial environment. Therefore, when HARQ and ARQ are applied to the LTE‐based mobile satellite communication system, the inefficiency is caused by the long propagation delay of satellite environment. This paper proposes the interaction method between HARQ and ARQ for the decrease of inefficiency in the LTE‐based mobile satellite communication system. The existing concept of layered architecture about HARQ and ARQ is also maintained in our interaction method. Simulation results reveal that our proposed scheme can provide the larger spectrum efficiency than that of the non‐interaction scheme in all environments. The performance improvement can be up to 2.04 times through the interaction method. Copyright © 2014 John Wiley & Sons, Ltd.     

LTE中ARQ的机制研究及算法改进*

本文主要研究了LTE中的ARQ机制,并针对ARQ确认算法中每次组装状态报告只是固定添加未接收到的PDU的SN号或分段信息而可能导致资源浪费的问题,提出了一种自适应确认算法,通过设定不同的基准参数,采用不同的偏移算法,有效的提高了系统的确认效率和资源利用率,从而使系统获得了较高的吞吐量。     

应用于SAW-less LTE接收机中的高线性度下变频器

本文提出一种基于0.18 μm CMOS 工艺的高线性度下变频器。该下变频器应于直接下变频架构的LTE接收机中,并可以使之省去高成本的深表面波(SAW)滤波器。所提出的下变频器由跨导级、无源混频器、电流缓冲器、跨阻级和直流失调消除环路等五部分组成。其中,电流缓冲器为无源滤波器在高频范围内提供低阻抗负载,减小了由带外阻塞信号引起的电压摆幅,从而改善了下变频器的线性度。与传统电路结构相比,该方法可以提高输入三阶交调截断点(IIP3)4.5 dB以及输入二阶交调截断点(IIP2)11 dB。测试结果表明,该下变频器转换增益为29.5 dB,噪声系数为12.7 dB,IIP3为13 dBm,IIP2大于62 dBm。     

基于校正子的第一类混合ARQ及其性能分析

基于校正子的计算提出了一种第一类混合ARQ (HARQ) 方案,该HARQ采用Reed-Solomon (RS)码作为纠错子系统,将检错功能巧妙融于译码过程中。对系统误比特率和吞吐量的分析与仿真表明,短码宜采用前向校正子结构,长码宜采用后向校正子结构,而系统的吞吐量与可靠性之间的最佳折衷,可以通过选择恰当的最大重传次数实现。     

LTE系统一种高效率准动态部分频率复用方案

部分频率复用(FFR)是下一代移动通信系统中提升系统容量与边缘用户性能的核心技术之一.准动态FFR在增益与额外开销的平衡上具有明显优势,成为优化静态FFR技术的主要研究方向.本文提出了一种新的准动态FFR方案,以很低的额外开销,同时达到提高系统容量和改善边缘用户性能的目的.通过在LTE系统级仿真平台上的仿真,论文对算法的适用场景、增益和代价进行了深入分析.     

LTE中一种基于负载均衡的自优化切换算法

在3GPP LTE自组织网络（SON）中,面向整体切换性能的自优化算法明显优于面向个别性能的算法.本文针对EWPHPO算法无法对小区负载进行动态调整,也无法对单个过载小区的切换参数进行及时调整,从而导致掉话率等指标不能得到有效控制的问题,提出了兼顾整体切换性能和负载均衡的WPLBHO算法.通过仿真并与EWPHPO算法在相同环境下的仿真结果进行比较,我们的算法在保持切换失败率基本不变的情况下,使掉话率降低约20%、乒乓效应降低约5%,从而使系统整体切换性能（HP）提升约25%;同时,使系统平均过载时间下降近50%.因此我们的算法使系统整体性能得到了明显改善.     

LTE中一种改进的基于探测参考信号的定时估计算法

研究了LTE系统中探测参考信号(SRS)的定时同步方法。由于基本的滑动相关算法和传统的后向搜索算法不能有效地消除相关过程中旁瓣峰值的影响,不适用于SRS的定时同步。因此,针对SRS的时频结构特点,提出一种改进的后向搜索算法。该方法通过将本地序列与接收序列在时域上相关得到定时度量函数,并重新定义门限值,通过结合门限和新的搜索技术来确定第1径的位置,从而得到正确的定时采样点。仿真结果表明,所提方法的估计性能优于滑动相关算法和传统的后向搜索算法,有效地消除了旁瓣峰值的影响,提高了SRS的正确定时概率。相比传统的后向搜索算法,所提方法的估计性能提高了6倍左右。     

Design of broadband class-F power amplifier for multiband LTE handsets applications

A broadband class-F power amplifier for multiband LTE handsets applications is developed across 2.3-2.7 GHz. The power amplifier maintains constant fundamental impedance at the output matching circuit which is operating for broadband. The nearly zero of second harmonic impedance and nearly infinity of third harmonic impedance are found for highly efficient class-F PA. The harmonic control circuits are immersed into the broadband output matching for fundamental frequency. For demonstration, the PA is implemented in InGaP/GaAs HBT process, and tested across the frequency range of 2.3-2.7 GHz using a long-term evolution signal. The presented PA delivers good performance of high efficiency and high linearity, which shows that the broadband class-F PA supports the multiband LTE handsets applications.     

Small‐cell planning in LTE HetNet to improve energy efficiency

Cell planning is one essential operation in wireless networks, and it significantly affects system performance and cost. Many research efforts consider the cell planning problem with identical base stations (BSs) or to construct a new network on the region without any infrastructure. However, long‐term evolution (LTE) adopts heterogeneous network, which allows operators to tactically deploy small cells to enhance signal coverage and improve performance. It thus motivates us to propose a small‐cell planning problem by adaptively adding low‐powered BSs with the limitation of budget to an existing network to increase its energy efficiency, which is defined by the ratio of network throughput to the amount of energy consumption of BSs. We consider 2 types of LTE small cells, namely, microcells and picocells, and develop different clustering strategies to deploy these cells. Based on the available resource and traffic demand in each cell, we then adjust the transmitted power of the deployed BS with energy concern. Experimental results demonstrate that our small‐cell planning solution can achieve high‐energy efficiency of LTE networks, which means that BSs can better use their transmitted energy to satisfy the traffic demands of user devices. This paper contributes in proposing a practical problem for cell planning with heterogeneous network consideration and developing an efficient solution to provide green communications.     

3GPP LTE中基于HARQ技术的吞吐量性能研究

简要介绍了LTE系统下行链路中的混合自动请求重传(HARQ)技术原理。为证明HARQ对LTE系统吞吐量性能的改善,分别在QPSK、16QAM和64QAM三种调制方式下,对系统不加HARQ、强制重传及加入HARQ时系统的吞吐量性能进行了分析研究。仿真结果表明,加入HARQ时系统吞吐量明显提高,且提高范围介于未加HARQ及强制重传之间,证明了HARQ技术可有效改善LTE系统吞吐量性能,提高LTE系统的传输质量。     

UEs Power Reduction Evolution with Adaptive Mechanism over LTE Wireless Networks

At present, the major drawback for mobile phones is the issue of power consumption. As one of the alternatives to decrease the power consumption of standard, power-hungry location-based services usually require the knowledge of how individual phone features consume power. A typical phone feature is that the applications related to multimedia streaming utilize more power while receiving, processing, and displaying the multimedia contents, thus contributing to the increased power consumption. There is a growing concern that current battery modules have limited capability in fulfilling the long-term energy need for the progress on the mobile phone because of increasing power consumption during multimedia streaming processes. Considering this, in this paper, we provide an offline meaning sleep-mode method to compute the minimum power consumption comparing with the power-on solution to save power by implementing energy rate adaptation (RA) mechanism based on mobile excess energy level purpose to save battery power use. Our simulation results show that our RA method preserves efficient power while achieving better throughput compared with the mechanism without rate adaptation (WRA).     

A dynamic paging scheme for long‐term evolution mobility management

In long‐term evolution, the service area is partitioned into several tracking areas (TAs), which comprise one or more cells (the radio coverages of base stations). The TAs are grouped into TA list (TAL). When an incoming call arrives, the network attempts to connect to the user equipment (UE) by paging the cells in the UE's TAL, which may incur large paging traffic that significantly consumes the limited radio resources. To resolve this issue, this paper proposes a dynamic paging scheme that determines the paging sequence of cells in real time according to the UE movement and call behavior. We compare the performance of the dynamic paging with that of the previously proposed Cell‐TA‐TAL (CTT) paging. Our study indicates that the dynamic paging outperforms the CTT paging when movement pattern is regular and the UE moves frequently. Copyright © 2013 John Wiley & Sons, Ltd.     

Efficient allocation of LTE downlink spectral resource to improve fairness and throughput

For the current generation of cellular communication systems, long‐term evolution (LTE) has been the major protocol to support high‐speed data transmission. It is critical to allocate downlink spectral resource in LTE, namely, resource blocks (RBs), but the issue is not well addressed in the standard. Therefore, the paper develops an efficient RB allocation algorithm with 4 mechanisms to improve both fairness and throughput in LTE. For fairness concern, our RB allocation algorithm uses a resource‐reservation mechanism to prevent cell‐edge user equipments from starvation, and a credit‐driven mechanism to keep track of the amount of resource given to each user equipment. For throughput concern, it adopts both weight‐assignment and RB‐matching mechanisms to allocate each RB to a packet according to its flow type and length. Through simulations, we demonstrate that the proposed RB allocation algorithm can significantly increase both throughput and fairness while reducing packet dropping and delays of real‐time flows, as compared with previous methods.     

3GPP LTE/WLAN无线融合技术研究进展

总结了4种在无线侧实现长期演进(LTE)系统与无线局域网(WLAN)相互融合的技术方案.在分析传统的核心网融合方案不足之处的基础上,重点介绍了无线融合在3 GPP R12和R13阶段的研究进展和标准化情况,讨论了各方案对终端、演进型节点B(eNodeB)和WLAN的影响,综合对比了每种方案的特征、优缺点及应用场景,为运营商部署LTE/WLAN融合网络提供了思路.     

一种用于手持移动终端的九频段平面印制天线

提出了一种应用于手持移动终端的九频段平面印制天线,该天线结构紧凑,尺寸为20 mm×28 mm×0.8 mm.利用弯折单极子、寄生地枝和耦合分枝激励起了五个谐振模式,并通过三个调节片和位于馈电点附近的阶梯形过渡结构改善了各个谐振模式的阻抗匹配,从而拓展了天线的工作带宽通过分析该天线关键参数对带宽性能的影响,对关键参数进行了优化,得到了满足性能要求的天线结构.天线样品的实测-6 dB阻抗带宽为700～1 008 MHz和1 692～2 984 MHz,覆盖了LTE700/2300/2500,GSM850/900,DCS/PCS/UMTS和2.4-GHz WLAN频段;工作频带内具有良好的辐射性能     

LTE系统中下行预编码技术

长期演进技术（LTE,Long Term Evolution）采用正交频分复用（Orthogonal Frequency Division Multiplexing）和多输入多输出（Multiple-Input Multiple-Output）相关技术作为其无线网络演进的标准。MIMO是下一代无线移动通信的关键技术之一,它通过使用多天线来抑制信道衰落,能够获得比传统单输入单输出（Single Input,Single Output）系统更高的信道容量,在实际中有广泛的应用。文中主要研究了LTE系统中MIMO下行链路的预编码技术以及相关仿真算法。仿真结果表明了LTE系统中预编码技术的有效性。     

应用于LTE上行链路的D-MMSE-FE 均衡算法

为克服线性均衡性能的局限性及避免传统判决反馈均衡器的高复杂度,提出了一种判决反馈均衡算法D-MMSE-FE。该均衡器先是分析线性MMSE均衡的结果成分,并根据最小均方误差准则计算出均衡器的前、后向传递函数,形成反馈链路,提高均衡器性能。将该种均衡器应用于TDD-LTE 1×2 SIMO上行链路中,在协议中常用的信道下进行了计算机仿真,仿真结果表明,TDD-LTE 1×2 SIMO均衡器相对于线性均衡器使系统性最多可提高达2 dB。     

High performance parallel turbo decoder with configurable interleaving network for LTE application

In this paper, a high performance parallel turbo decoder is designed to support 188 block sizes in the 3rd generation partnership (3GPP) long term evolution (LTE) standard. A novel configurable quadratic permutation polynomial (QPP) multistage network and address generator are proposed to reduce the complexity of interleaving. This 2ⁿ-input network can be configured to support any 2ⁱ-input $(0\le i\le n)$ network. Furthermore, it can flexibly support arbitrary contention-free interleavers by cascading an additional specially designed network. In addition, an optimized decoding schedule scheme is presented to reduce the performance loss caused by high parallelism. Memory architecture and address mapping method are optimized to avoid memory access contention of small blocks. Moreover, a dual-mode add–compare–select (ACS) unit implementing both radix-2 and radix-4 recursion is proposed to support the block sizes that are not divided by 16. Implemented in 130 nm CMOS technology, the design achieves 384.3 Mbps peak throughput at clock rate of 290 MHz with 5.5 iterations. Consuming 4.02 mm² core area and 716 mW power, the decoder has a 1.81 bits/cycle/iteration/mm² architecture efficiency and a 0.34 nJ/bit/iteration energy efficiency, which is competitive with other recent works.     

Application layer forward error correction for multicast streaming over LTE networks

The next step beyond third generation mobile networks is the Third Generation Partnership Project standard, named Long Term Evolution. A key feature of Long Term Evolution is the enhancement of multimedia broadcast and multicast services (MBMS), where the same content is transmitted to multiple users located in a specific service area. To support efficient download and streaming delivery, the Third Generation Partnership Project included an application layer forward error correction (AL‐FEC) technique based on the systematic fountain Raptor code, in the MBMS standard. To achieve protection against packet losses, Raptor codes introduce redundant packets to the transmission, that is, the forward error correction overhead. In this work, we investigate the application of AL‐FEC over MBMS streaming services. We consider the benefits of AL‐FEC for a continuous multimedia stream transmission to multiple users and we examine how the amount of forward error correction redundancy can be adjusted under different packet loss conditions. For this purpose, we present a variety of realistic simulation scenarios for the application of AL‐FEC and furthermore we provide an in‐depth analysis of Raptor codes performance introducing valuable suggestions to achieve efficient use of Raptor codes. Copyright © 2012 John Wiley & Sons, Ltd.     

LTE channel throughput assessment and comparison under different terrain

In evolved UMTS terrestrial radio access network, long‐term evolution is known as the fourth‐generation mobile network with a leading radio performance metric as a throughput and signal‐to‐noise ratio (SNR) that affect the radio links. In this paper, we analytically describe the different long‐term evolution propagation model and measure and compare the throughput and SNR on different Doppler frequencies. To validate the performance of channel, we implement network on 3 standard models, viz, as pedestrian (EPA), vehicular (EVA), and typical urban (ETU) at different Doppler frequency (5, 70, 300, and 750 Hz), and different value of SNR (10, 13, 16, and 19 dB) on downlink channel and measured the channel throughput rate. We conclude that a performance of the channel for high SNR values severely affected by the high value of the Doppler frequency while for the channels at low SNR values is a negligible effect with high Doppler frequency.