一种LTE系统中基于半动态门限的RACH信号检测算法

针对LTE系统,文章提出一种基于半动态门限的随机接入信道(RACH)信号检测算法。该算法首先根据虚警概率计算判决门限系数,然后与信号能量均值相乘得到峰值门限。分析和仿真结果表明,该方法在信道条件恶劣的仿真环境下,对RACH信号检测具有良好的效果。     

WCDMA随机接入信道的数学建模及性能分析

文章主要讨论了宽带码分多址(WCDMA)网络中无线小区随机接入信道(RACH)的数学建模方法及性能分析.首先介绍了WCDMA的RACH及信息发送方式,然后描述了RACH随机接入过程的时隙ALOHA接入方式,并在此基础上重点分析了RACH数学建模的方法和详细过程,给出了RACH吞吐量的计算公式,最后,对RACH的性能进行了分析.     

LTE接入信道结构及容量研究

在设计规划和维护LTE网络时需重点关注LTE网络的接入性能指标,为了适应不同业务和用户环境,PRACH可根据不同业务负荷和小区覆盖距离进行优化调整。介绍了LTE-FDD移动通信系统接入信道中PRACH和RACH的概念、相关资源配置、时频结构、PRACH配置和接入距离之间的关系、PRACH容量相关无线参数,通过分析PRACH配置参数之间的关系,推导出各种配置下PRACH承载的容量。     

基于Ad hoc网络的退避算法研究

在移动Ad hoc网络中,无线信道由多个节点共享,合理协调多个节点访问共享信道的媒体接入控制(MAC,Medium Access Control)协议是移动Ad hoc网络的关键技术之一。退避算法在MAC协议中起着至关重要的作用。针对目前退避算法存在的问题,本文提出了一种改进算法,根据网络节点发送数据包成功与否,预测网络信道空闲或繁忙的趋势,应用趋势合理地调节退避算法中节点发送数据时退避值的大小,并通过Omnet++软件对算法进行了仿真分析对比。     

LTE中随机接入过程的解析及工程实现

LTE中进行随机接入的功能是实现UE和网络的同步,对于UE只有通过随机接入过程与系统上行同步之后,才能被系统调度进行上行传输。针对随机接入信道在LTE中的实现过程以及随机接入中涉及到的具体参数进行了详细研究,并且通过仿真对ZC序列在RACH中的相关特性进行分析,最后结合实际工程应用给出了在飞思卡尔的8157上的实现方式。     

无线信道动态树碰撞解决算法的性能分析

一般的随机访问信道(RACH)，延时特性只有均值，很难有明确的上限保证，所以对部分实时业务性能难以保证。树型算法则可以对日前处理的业务提供明确的延时上限，然而一般的固定树型算法对于无线信道的业务波动情况没有适应能力，例如树型分支固定，只能适合一定强度的到达业务，其他情况下会导致信道利用率下降和延时增加。本文针对随机访问信道协议，在固定树型算法的基础上，结合随机接续协议，给出了一种混合动态树型算法，目的是提高一般树型算法的信道利用率，保证延时指标的上限。     

基于多载波的宽带无线接入策略的研究

呼叫接入控制是无线通信中保证用户服务质量的关键技术之一。本文提出了一种在多业务环境下,基于多载波通信的优先强占接入策略:当剩余无线资源不能接纳实时业务的呼叫时,实时业务呼叫强占部分非实时业务占用的子载波来保证实时业务的接入,与此同时增加了非实时业务的传输时延。本文通过二维Markov链模型对系统进行了建模和性能参数(呼叫阻塞概率及系统频带利用率)的求解。通过与保护信道策略和无优先策略的比较可以看到:优先强占策略将接入控制和服务质量保证有机地结合在一起,既保证了用户的QoS,又大大降低了系统中的实时业务用户的呼叫阻塞概率,提高了系统资源的利用率。     

移动Ad Hoc网络中一种分布式QoS保证的多址接入协议

基于随机竞争和冲突解决的思想,本文为多跳移动Ad Hoc网络提出了一种分布式服务质量(QoS)保证的多址接入(QMA)协议.该协议中,节点在发送业务分组前利用预报突发进行竞争接入,节点根据业务分组时延情况和最早失效优先原则确定预报突发的长度,所发预报突发能持续到最后的节点优先获得接入.同时,具有实时业务的节点可以按照其优先级在更早的竞争微时隙中开始发送预报突发,而有非实时业务的节点只能在前面竞争微时隙空闲的情况下,才能在后面的微时隙开始发送预报突发,因此发送实时业务的节点可以比发送非实时业务的节点更优先接入信道,从而在移动Ad Hoc网络中实现了对多媒体业务的QoS保证.最后利用OPNET仿真评估了QMA协议的多址性能,并与IEEE 802.11e协议的性能做了比较,结果表明QMA协议可以提供较高的吞吐量和较低的实时业务时延.     

一种新的紫外光自组织通信网络MAC层避退算法

紫外光自组织通信网络是把紫外光与自组织网络相结合的,能够利用自组织网络的多跳特性来克服紫外光距离有限性的通信网络。为了使紫外光自组织通信网络中各个节点能够对有限的信道资源进行充分与公平的利用,需要对网络协议栈中的第二层——媒介接入控制层上的传统算法进行优化。本文以媒质接入控制层(MAC,Media Access Control)传统上采用的二进制指数退避算法为基础,以提高公平性为目的,提出了依据退避计数器值的随机选取是否合理,继而采取相应的奖励惩罚机制的新算法。研究结果表明:新算法提高了无线紫外光自组织通信网络中各节点接入信道的公平性,并在信道吞吐量和信道接入公平性之间达到了一个较好的折衷。     

一种工业无线自适应退避竞争接入方法的研究

在工业网络中,无线通信已经成为一个研究热点。传统的轮询方法具有可靠、稳定的优点,但对于子节点猝发的异常数据不能做到实时监测。设计一种保证工业异常数据实时接入信道的自适应退避竞争调度方法,该方法以轮询方式作为基础通信方式,并设计超帧结构以提供数据接入时隙,同时采用自适应退避竞争的方法避免信道碰撞。实验结果表明,异常数据以此方式接入信道具有较高的实时性和可靠性,满足工业对异常数据传输的苛刻要求。     

Novel Radio Link Buffer Management Schemes for End-User Multi-class Traffic in High Speed Packet Access Networks

The requirement to provide multimedia services with QoS support in mobile networks has led to standardization and deployment of high speed data access technologies such as the High Speed Downlink Packet Access (HSDPA) system. HSDPA improves downlink packet data and multimedia services support in WCDMA-based cellular networks. As is the trend in emerging wireless access technologies, HSDPA supports end-user multi-class sessions comprising parallel flows with diverse Quality of Service (QoS) requirements, such as real-time (RT) voice or video streaming concurrent with non real-time (NRT) data service being transmitted to the same user, with differentiated queuing at the radio link interface. Hence, in this paper we present and evaluate novel radio link buffer management schemes for QoS control of multimedia traffic comprising concurrent RT and NRT flows in the same HSDPA end-user session. The new buffer management schemes—Enhanced Time Space Priority (E-TSP) and Dynamic Time Space Priority (D-TSP)—are designed to improve radio link and network resource utilization as well as optimize end-to-end QoS performance of both RT and NRT flows in the end-user session. Both schemes are based on a Time-Space Priority (TSP) queuing system, which provides joint delay and loss differentiation between the flows by queuing (partially) loss tolerant RT flow packets for higher transmission priority but with restricted access to the buffer space, whilst allowing unlimited access to the buffer space for delay-tolerant NRT flow but with queuing for lower transmission priority. Experiments by means of extensive system-level HSDPA simulations demonstrates that with the proposed TSP-based radio link buffer management schemes, significant end-to-end QoS performance gains accrue to end-user traffic with simultaneous RT and NRT flows, in addition to improved resource utilization in the radio access network.     

一种基于CoMP的随机接入方案

提出了一种新的基于协作多点传输和接收（CoMP）技术的多发随机接入流程,并根据 随机接入的目的和业务类型设计了接入优先级,在此基础上设计了一种新的随机接入方案, 对 不同类型的随机接入请求提供不同的接入机制,以保证边缘用户的接入性能和满足不同业务 的QoS需求。仿真结果表明,与LTE标准随机接入方案相比,该方案对系统整体接入性能略有 提高,且大大提高了边缘高优先级用户的接入性能。     

TSM系统中随机接入成功率的分析

TSM是从GSM到TD-SCDMA系统的一个过渡标准，在TD—SCDMA的开发过程中，各大开发商在TSM上花费了很多功夫。对于任何一个移动通信系统，都需要随机过程，随机接入能力将直接影响到一个系统的性能，所以很有必要对TSM系统的随机接入过程进行认真的分析与研究。本文将介绍TSM系统中的随机接入过程及其接入能力。最后对结论做简单的仿真和分析。     

Resource Allocator for Non Real-Time Traffic in Wireless Networks Using Fuzzy Logic

Providing efficient access to a large user population with variantservice requirements in wireless communications networks poses a verychallenging problem. Resource allocation in the wireless domain shouldtake into account bandwidth limitations and fading effects inherent towireless channels, while accommodating for resource constraintsencountered in wireline networks. In this paper, a fuzzy resourceallocator is proposed in order to facilitate the efficient allocation ofnetwork resources in the wireless domain. The network preferentiallyallocates its resources to real-time (RT) traffic sources. Usingeffective transmission rate statistics of non real-time (NRT) trafficdsources as a measure of fading channel conditions, the fuzzy allocatoroptimally allocates the remaining resources to NRT traffic. Simulationsshow that the fuzzy allocator can reduce delay and incurs fewerretransmissions for NRT traffic. An overall improvement in wirelesschannel utilization is demonstrated.     

基于5G系统的随机接入前导检测算法

针对已有的随机接入前导算法存在难以在实际基站中实现以及算法运算量大的缺点,文章提出了5G随机接入前导检测算法。首先将接收到的信号经过发送端的逆过程处理得到频域前导,然后生成频域ZC序列并进行分组,将各个组内频域ZC序列相加并与频域前导相关,最后通过设置阈值来检测前导序列,利用多天线分集梳理修改相对阈值的累积分布函数,根据相对检测阈值确定绝对检测阀值,即相对检测阈值与时变噪声电平的乘积。仿真结果表明,与频域固定阈值前导检测算法相比,在加性高斯白噪声信道中,所提算法的正确检测概率性能提升了1 dB;在节拍延迟线(TDLC300-100)信道中,所提算法的正确检测概率性能提升了2 dB。     

Hopfield neural‐network‐based dynamic resource allocation scheme for non‐real‐time traffic in wireless networks

Dynamic resource allocation (DRA) plays a fundamental role in current and future wireless networks, including 3G systems. In this paper, a scheduling DRA scheme for non‐real‐time (NRT) packet services in wireless system is proposed based on the use of Hopfield neural networks (HNN). The scheme exploits the fast response time of HNN for solving NP optimization problems and has been particularized for the downlink transmission in a UMTS system, although it could be easily extended to any other radio access technology. The new DRA scheme follows a delay‐centric approach, since it maximizes the overall system resource utilization while minimizing the packet delay. Simulation results confirm that the proposed HNN‐based DRA scheme is effective in supporting different types of NRT services, while achieving efficient utilization of radio resources. Copyright © 2008 John Wiley & Sons, Ltd.     

A low-complexity beamforming-based scheduling to downlink OFDMA/SDMA systems with multimedia traffic

In this paper, we propose a low-complexity beamforming-based scheduling scheme utilizing a semi-orthogonal user selection (SUS) algorithm in downlink orthogonal frequency division multiple access (OFDMA)/space division multiple access (SDMA) systems to support multimedia traffic. One of the challenges in the multi-dimensional (space, time, and frequency) radio resource allocation problem for OFDMA/SDMA systems is its high complexity, especially to simultaneously satisfy the quality of services (QoS) requirements for various traffic classes. In the literature, the SUS algorithm is usually applied to the single-class traffic environment, but extending the SUS algorithm to the multimedia environment is not straightforward because of the need to prioritize the real-time (RT) users and the non-real-time (NRT) users. To solve this problem, we propose the concept of urgency value to guarantee the fairness of the NRT as well as the best effort (BE) users while satisfying the delay requirement for the RT users. Simulation results show that, when traffic load is greater than 0.5, the proposed scheduling algorithm can improve the fairness performance by more than 100% over the most recently proposed algorithms.     

多级业务CDMA随机接入技术研究

针对卫星通信系统的特点,研究了结合CDMA和随机接入协议的扩频随机接入方式。在卫星通信的传播时延较长和短数据通信为主的情况下,这种接入技术能根据分组数据等业务的不同需求,实现满足多优先级业务的接入。理论分析和仿真结果表明,这种接入技术可以提高系统的综合性能。     

TD-LTE网络随机接入前导码规划分析

TD-LTE网络随机接入是终端接入网络的必经过程,是用户进行初始连接、切换、连接重建立以及重新恢复上行同步的唯一策略,其失败率会影响TD-LTE网络的接入性能。本文中重点介绍TD-LTE网络随机接入前导码的精细规划,以及随着网络割接调整而实施的前导码自动规划。     

Maximization of user satisfaction in OFDMA systems using utility‐based resource allocation

In order to keep and/or expand its share of the wireless communication market and decrease churn, it is important for network operators to keep their users (clients) satisfied. The problem to be solved is how to increase the number of satisfied non‐real time (NRT) and real time (RT) users in the downlink of the radio access network of an orthogonal frequency division multiple access system. In this context, the present work proposes a method to solve the referred problem using a unified radio resource allocation (RRA) framework based on utility theory. This unified RRA framework is particularized into two RRA policies that use sigmoidal utility functions based on throughput or delay and are suitable for NRT and RT services, respectively. It is demonstrated by means of system‐level simulations that a step‐shaped sigmoidal utility function combined with a channel‐aware opportunistic scheduling criterion is effective toward the objective of user satisfaction maximization. Copyright © 2014 John Wiley & Sons, Ltd.