Traffic Aided Uplink Opportunistic Scheduling with QoS Support in Multiservice CDMA Networks

In this letter, we address the problem of resource allocation with efficiency and quality of service (QoS) support in uplink for a wireless CDMA network supporting real‐time (RT) and non‐realtime (NRT) communication services. For RT and NRT users, there are different QoS requirements. We introduce and describe a new scheme, namely, traffic aided uplink opportunistic scheduling (TAUOS). While guaranteeing the different QoS requirements, TAUOS exploits the channel condition to improve system throughput. In TAUOS, the cross‐layer information, file size information, is used to improve fairness for NRT users. Extensive simulation results show that our scheme can achieve high system throughput in uplink wireless CDMA systems, while guaranteeing QoS requirements.     

Analysis of Traffic Distribution and Blocking Probability in Future Wireless Networks

Future wireless networks are envisioned to provide good quality multimedia services to mobile users anywhere at anytime. Traditional analysis of teletraffic in such networks assumes that call arrivals follow a Poisson process, as each cell is being modeled as an M/G/c/c queueing system. This does not reflect the real situation since handoff traffic arrivals are not generally Poissonian. In this paper, we propose to model each cell in future wireless networks as a G/G/c/c queueing system. As such a model has not been explicitly addressed in the literature, our main contribution is to propose a solution which enables to evaluate both traffic distribution and blocking probability within each cell of the service area. Result analysis reveals that coefficient of variation of call arrivals has more impact on the network performance than coefficient of variation of channel holding time.     

On Blocking Probability of Multi-Beam CDMA Systems Using SBF Array Antennas

In wireless cellular systems, a code division multiple access (CDMA) technology with array antennas can significantly reduce interferences by taking advantage of the combination of spreading spectrum and spatial filtering. We investigate blocking probabilities of multi-beam CDMA systems using switched beamforming (SBF) array antennas considering non-homogeneous traffic loading over a cell which may cause traffic congestion and introduce large blocking probability in a hot-spot area. We also propose a feasible main beamwidth deployment and a beam reassignment (BR) method to mitigate the hot-spot beam, named the hot-beam. The feasible main beamwidth deployment suggests that we can relieve the hot-beam situation by deploying the feasible main beamwidth which can guarantee below 1% blocking probability. Using the BR method, the blocking probability of hot-beam and total blocking probability over a cell are significantly reduced. Further, it is shown that the feasible traffic load ratio of the hot-beam to the lightly loaded beam is significantly enhanced when the total blocking probability of the cell is maintained below 1%. Hyunduk Kang received the B. Eng. degree in electronics engineering from the Dong-A University, Busan, South Korea, in 1997, and the M.S. degrees in information and communications engineering from the Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea, in 1999. He is currently a Ph.D. candidate in information and communications engineering from the GIST. His current research interests include performance analysis and resource management of next generation mobile communications and wireless sensor networks. Seokjin Sung received the B.Eng. degree in radio science and communication engineering from the Hong-Ik University, Seoul, South Korea in 2002, and the M.S. degree in information and communications engineering from the GIST, Gwangju, South Korea in 2004. He is currently a Ph.D. candidate in information and communications engineering from the GIST. His research interests are in the areas of adaptive smart antenna system design and analysis for moving-user environments. Insoo Koo received the B.Eng. degree in electronics engineering from the Kon-Kuk University, Seoul, South Korea, in 1996, and the M.S. and Ph.D. degrees in information and communications engineering from the GIST, Gwangju, South Korea, in 1998 and 2002, respectively. From 2002 to 2004, he was with the GIST as a Research Professor. In 2005, he joined the University of Ulsan where he is presently an Assistant Professor. His current research interests include next generation mobile communications and wireless sensor networks. Kiseon Kim received the B.Eng and M.Eng from the Seoul National University, all in electronics engineering, in 1978 and 1980, and the Ph.D. degree from the University of Southern California, Los Angeles, in 1987, in electrical engineering-systems. From 1988 to 1991, he was with Schlumberger in Texas, as a Senior Development Engineer where he has been involved in development of telemetry systems. From 1991 to 1994, he was a Computer Communications Specialist for Superconducting Super Collider Lab., in TX, where he has built telemetry logging and analysis systems for high energy physics instrumentations. Since joining the GIST, in 1994, he is presently a Professor. His research interests include wideband digital communications system design, analysis and implementation.     

CDMA功率控制研究中目标SIR设置的上限

基于SIR平衡的功率控制可能存在正反馈的问题,从而使得系统不稳定.讨论了在加性高斯白噪声及Rayleigh衰落信道下,CDMA上行链路闭环功率控制系统的SIR上限问题.通过折衷考虑系统的容量与QoS要求,可以确定临界稳定时的目标SIR上限,在设计功率控制算法时,目标SIR只有满足上限要求,才能确保CDMA系统稳定.     

Call Admission Control Algorithms in OFDM-based Wireless Multiservice Networks

Orthogonal frequency division multiplexing (OFDM) is becoming a fundamental technology in future generation wireless communications. Call admission control is an effective mechanism to guarantee resilient, efficient, and quality-of-service (QoS) services in wireless mobile networks. In this paper, we present several call admission control algorithms for OFDM-based wireless multiservice networks. Call connection requests are differentiated into narrow-band calls and wide-band calls. For either class of calls, the traffic process is characterized as batch arrival since each call may request multiple subcarriers to satisfy its QoS requirement. The batch size is a random variable following a probability mass function (PMF) with realistically maximum value. In addition, the service times for wide-band and narrow-band calls are different. Following this, we perform a tele-traffic queueing analysis for OFDM-based wireless multiservice networks. The formulae for the significant performance metrics call blocking probability and bandwidth utilization are developed. Numerical investigations are presented to demonstrate the interaction between key parameters and performance metrics. The performance tradeoff among different call admission control algorithms is discussed. Moreover, the analytical model has been validated by simulation. The methodology as well as the result provides an efficient tool for planning next-generation OFDM-based broadband wireless access systems.

码分多址（CDMA）技术和公用空中接口综述

本文主要讨论数字移动通信中扩频码分多址技术，阐明了ＣＤＭＡ体制的优越之外，分析了ＣＤＭＡ的关键技术，全面介绍了ＣＤＭＡ系统设计的基本原则和ＩＳ－９５－Ａ空中接口标准的含义。     

基于CDMA的IMT-2000空中接口方案简介

围绕第三代移动通信系统IMT - 2 0 0 0标准 ,各国间正展开激烈的竞争 ,提交ITU的地面候选方案多达 10种。由于CDMA具有容量大、频谱利用率高、频率规划方便等优点 ,IMT - 2 0 0 0候选标准已基本上统一到基于CDMA方案上。本文先简要介绍了第三代CDMA空中接口的特征 ,然后分别介绍呼声最高的两种方案的空中接口标准 :W -CDMA和cdma2 0 0 0。     

分布式数字交换网络阻塞概率的研究

全分散控制数字程控交换系统广泛采用分布式数字交换网络,其阻塞概率和设备配置是设计中必须考虑的重要问题。本文对近期报导的基于３ 种阻塞成分的算法作了明显改进,提出了不受通信模块数量限制的通用计算方法,并使得计算简化和规则化     

时隙光突发交换网络阻塞性能分析模型

文章介绍了基于时隙的光突发交换网络的结构及其特点，提出了相应的时隙化多波长多光纤系统阻塞分析模型，仿真结果表明该模型准确地反映了光纤数和帧长等网络参数变化对网络阻塞特性的影响．对于评估时隙突发交换网络性能和设计实现参数具有重要意义。     

UMTS/WCDMA空中接口方案的物理层协议

简要介绍第三代移动通信系统的研究现状,并对欧洲通用移动通信系统ＵＭＴＳ／ Ｗ ＣＤＭＡ 空中接口方案的物理层协议进行深入探讨。     

基于Erlang-B的阻塞率仿真实现

本文根据爱尔兰B公式,分析实现了阻塞率仿真,仿真结果表明：随着话务量的增加,阻塞率也在增加,当话务量增加到一定大小时,阻塞率增加趋势有所减缓。     

An Evaluation Model for Integrated Services on Wireless Broadband CDMA Networks

This paper proposes a performance evaluation approach for integrated voice and data services on a broadband code division multiple access (CDMA) network. For random access schemes, the dynamic behavior of a CDMA channel infers that we must be cautious with a performance judgment. We must be especially careful when choosing a mathematical model that has to include the effect of dynamic error rates. The approach shown in this paper is to employ a Poisson error model that takes the occurrence of errors as a Poisson process with the occurring rate dependent on the channel traffic. Based on this assumption, we developed a continuous-time Markov chain model to evaluate the throughput and delay performance. This approach can certainly apply to the evaluation of many integrated services protocols.     

Delay-on-Demand: A Signaling Protocol to Reduce Blocking Probability in Optical Burst-Switching Networks

Optical burst switching (OBS) is emerging as one promising switching paradigm for the next generation optical networks. To support multiple services in burst-switching networks, the OBS paradigm should support some quality-of-service (QoS) provisioning. A major design issue in such networks is to reduce the blocking probability of the bursts arising due to resource contention at the intermediate core router. In this paper, we propose a signaling protocol which we call ‘Delay-on-Demand’ (OBS-DoD), to reduce blocking probability and support QoS in optical burst-switching networks. The proposed scheme guarantees that at least one of the bursts succeeds depending on its priority, propagation delay from the ingress router, and the burst-size when contention occurs at the core router. For this, we use a control packet to delay, in case of a contention, the transmission of bursts at the ingress router. We compare the performance of our proposal, by simulation, with an earlier proposed scheme, and show that the proposed OBS-DoD outperforms the earlier scheme in reducing the blocking probability. For simulation, we generated bursty traffic using an M/Pareto distribution.     

基于CDMA技术的光接入网

提出了采用ＣＤＭＡ实现光纤搪入网的一般方案,讨论了光ＣＤＭＡ中的光扩频编码技术,信道间干扰的消除,功率控制等关键技术,并对光纤接入网的几种接入方法作了详细的分析比较。     

Approximating the Outage Probability of the Pilot Channel for IS‐95‐Based Cellular CDMA Systems in the Soft Handover Region

This letter presents an approximation of the outage probability of the pilot channel that can be used for CDMA cell planning. The approximation can determine system parameters for soft handover in IS‐95‐based cellular CDMA downlink design. Computer simulations show that our analytical results agree with empirical results.     

CDMA无线网络中的突发数据业务延时分析

本文对CDMA无线网络中的突发数据业务的延时性能进行了分析。与以往的工作相比，本文假设数据流量模型为Markov到达过程(而非简单的泊松过程)，并从理论上对系统延时性能进行了分析。本文首先为数据子系统建立了完整的Markov模型，并运用矩阵几何技术求解该Markov链；然后计算数据包延时的概率分布函数(而非简单的平均延时)。仿真结果表明系统建模和延时分析方法是正确的。     

与窄带微波系统共享频段的CDMA系统性能分析

本文分析了与窄带微波系统共享频段的ＣＤＭＡ系统的误码性能，给出了ＤＳ／ＣＤＭＡ接收机使用一个多径判决反馈滤波器后的计算机模拟数值结果。     

Spatial Averages of Coverage Characteristics in Large CDMA Networks

The aim of the present paper is to show that stochastic geometry provides an efficient computational framework allowing one to predict geometrical characteristics of large CDMA networks such as coverage or soft-handoff level. The general idea consists in representing the location of antennas and/or mobile stations as realizations of stochastic point processes in the plane within a simple parametric class, which takes into account the irregularities of antenna/mobile patterns in a statistical way. This approach leads to new formulas and simulation schemes allowing one to compute/estimate the spatial averages of these local characteristics in function of the model parameters (density of antennas or mobiles, law of emission power, fading law etc.) and to perform various parametric optimizations.     

Up- and Downlink Admission/Congestion Control and Maximal Load in Large Homogeneous CDMA Networks

This paper proposes scalable admission and congestion control schemes that allow each base station to decide independently of the others what set of voice users to serve and/or what bit rates to offer to elastic traffic users competing for bandwidth. These algorithms are primarily meant for large CDMA networks with a random but homogeneous user distribution. They take into account in an exact way the influence of geometry on the combination of inter-cell and intra-cell interferences as well as the existence of maximal power constraints of the base stations and users. We also study the load allowed by these schemes when the size of the network tends to infinity and the mean bit rate offered to elastic traffic users. By load, we mean here the number of voice users that each base station can serve.