SDMA系统DL方案阻塞率的仿真

多址接入技术是无线通信系统设计的一个重要因素,未来无线通信系统将广泛采用空分多址（SDMA）接入技术来提高系统容量。比如在频分复用（FDMA）,时分复用（TDMA）,码分复用（CDMA）。介绍了Erlang-B分布这一典型的业务分配模型,并考虑了SDMA系统中DL信道分配机制,给出了理论推导,并采用一般的排队论模型对数字蜂窝移动通信系统中SDMA技术进行仿真。仿真结果表明：采用DL信道分配机制以后,用户可以在同一时间共享同一信道。     

CDMA／SDMA系统性能分析

空分多址接入技术（SDMA）可以通过信号不同的空间传播路径来区分用户，从而提高了蜂窝移动通信系统容量．而此技术又可以和其他多址方式相互兼容，比如频分多址，时分多址，码分多址．CDMA／SDMA系统就是码分多址和空分多址两种接入技术相结合的系统．该系统可通过时空编码实现的．文中分析此种系统的性能，并与多用户环境下的CDMA系统进行了比较．     

一种适用于教学实验的SDMA系统设计与实现

本文简要介绍了空分多址(SDMA)的基本原理,设计并实现了一种适用于教学实验的∞MA软件仿真系统.本软件系统可工作在两种模式下,为多个移动用户提供不同的互不干扰的空分信道,以第四维的多址方式接人基站.实验者可设置通信过程中的各种参数并观察其对整个系统性能的影响.该实验系统有助于实验者更好地理解和掌握SDMA技术,同时具有良好的可扩展性,并可与其他多址仿真系统有效地结合.     

在GPRS系统中网络实现SDMA

介绍了GPRS系统和SDMA技术以及智能天线技术,给出了在GPRS系统中网络实现SDMA的方法。     

SDMA技术在泉州PHS网络上的应用

通过对SDMA技术原理的简要说明以及现网部署后的效果分析,给出了该技术在PHS网络上的应用策略,可作为高话务区域内缓解资源紧张状况的一种补充手段。     

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。     

基于智能天线的空分多址(SDMA)技术及其应用

该文在简介阵列信号处理和智能天线的基础上,讨论了空分多址(SDMA)技术的概念、特点和其对于蜂窝通信系统的性能贡献。着重分析了SDMA与传统多址技术以及多用户检测技术的结合应用情况。     

下行多用户MIMO-OFDMA/SDMA系统动态资源分配

该文对下行多用户MIMO-OFDMA/SDMA系统动态资源分配算法进行了研究,在满足各种约束条件的前提下,以最大化系统吞吐量为目标建立了相应的优化模型。由于最优解难以获得,将整个优化过程分两步完成,第1步定义了一个用于度量配置多根天线的用户空间兼容性的指标,并根据该指标提出了相应的调度算法;第2步提出了两种次优的资源分配算法。仿真结果表明,所提算法优于传统的随机调度算法,与功率复用策略结合时,所提算法的性能接近于基于用户选择的最优分配算法的性能。     

轻轻松松降低GSM系统阻塞率

目前数字移动网正处于飞速发展时期,每天都有大量的用户加入其中,这不可避免地会引起基站信道的拥塞。由于移动用户的随意性,网络规划和实际的用户分布总有一定程度的差距。在一个本地网内,总有一些基站比较空,另一些基站的信道阻塞率比较高。降低信道阻塞率的方法有很多,诸如全向改定向、同心圆、微蜂窝等。但从发现问题、规划设计、现场勘测、鉴定合同、前期准备、供货商提供软件到工程正式开始,这是一个漫长的过程。在此期间,维护人员面对较高的阻塞率,若能充分调用网络的原有资源,运用一些简单的办法,也可达到降低阻塞率的目的。嘉兴地…     

多用户MIMO系统中基于快速匹配调度的有限反馈SDMA

提出了一种能高效利用多用户分集和空分复用增益的有限反馈空分多址(SDMA,space division multiple access)方法。首先利用子空间扰动的方法构造了一种具有分簇结构的多用户预编码码本。基于该码本,进一步给出了一种新型的多用户机会调度算法,该算法利用码本的簇结构实现对信道条件匹配的用户组进行快速的机会调度,同时确定被调度用户的首选码字。仿真结果表明,在蜂窝网络中,与传统的有限反馈SDMA方法相比,所提方法可以在不明显增加反馈开销的前提下显著提高系统吞吐量。     

Traffic Models and Blocking Probabilities for Two-Fold and Three-Fold SDMA Communication Systems

Spectrum efficiency is a constant challenge in the design of wireless networks. Space-division-multiple-access (SDMA) is a promising approach to achieve higher spectral efficiency which reuses bandwidth via multiplexing signals based on their spatial signature. Several different studies have shown that SDMA can effectively improve system capacity in a mobile environment. In this paper, we present a new Markov chain traffic model for a duplicate-at-last (DL) approach [IEE Proceedings on Communication 146 (1999) 303] in two-fold and three-fold SDMA systems. Simplified blocking probability formulations for two-fold and three-fold SDMA are also derived. Simulations based on a common method of spatial separation check for channel allocation in SDMA are presented to evaluate the probability of successfully creating two-fold and three-fold SDMA channels. The simulation, as well as analytical, results indicate that the SDMA system can reduce the blocking probability of the calls and result in more traffic loading than a traditional cellular system. The results also show that our simplified approaches not only can reduce the computational complexity, but can also accurate approximate two-fold and three-fold SDMA performance. Wen-Jye Huang received the B.S. degree in electrical engineering from Tatung Institute of Technology, Taipei, Taiwan, in 1991, the M.S. degree in electrical engineering from Ohio University, Athens, OH, in 1997, and the Ph.D. degree in electrical engineering from The Pennsylvania State University, University Park, PA, in 2001. Since 2002, he joined the Department of Electrical Engineering, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan, as an assistant professor. His research activities include smart antenna, SDMA, and MC-CDMA techniques. John F. Doherty received the B.S. degree (with honors) in engineering science from the College of Staten Island, City University of New York, in 1982, the M.Eng. degree in electrical engineering from Stevens Institute of Technology, Hoboken, NJ, in 1985, and the Ph.D. degree in electrical engineering from Rutgers University, New Brunswick, NJ, in 1990. He was an integrated circuit reliability engineer with IBM, from 1982 to 1984. From 1985 to 1988, he was member of the technical staff at AT&T Bell Laboratories, working in sonar signal processing. In 1990, he joined the Electrical and Computer Engineering Department, Iowa State University, Ames, as an assistant professor and Harpole Entair fellow. He is currently an associate professor of electrical engineering with The Pennsylvania State University, University Park. His current research activities include interference rejection in wireless communication systems, spatial-division multiple-access techniques, and radar target detection techniques. He is a former AFOSR summer faculty research fellow at the Rome Laboratory, Rome, NY, and an Army Research Office Young Investigator.     

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.     

Blocking Probability Based Hierarchical Storage Design in VoD Systems

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Comparison between the Spectral Efficiency of SDMA Systems and Sectorized Systems

In this paper we present a comparison of the spectral efficiency of Spatial Division Multiple Access systems with conventional omni-directional and sectorized systems. Our analysis attempts to incorporate the effect of co-channel interference (CCI) for users sharing the same channel within a cell (intra-cell interference) as well as the CCI from other cells (inter-cell interference). To determine the outage probability we utilize exact results for combined Rayleigh and Log-normal shadowing in conjunction with a generic antenna pattern. The study is limited to the forward link only and the switched-beam approach. Results are provided for the outage probability and spectral efficiency for various reuse distances and blocking probabilities. These demonstrate that under most conditions, SDMA systems have higher spectral efficiency than conventional omni-directional or sectored systems. Nevertheless under certain conditions such as high blocking probabilities or large reuse distances, the spectral efficiency of SDMA systems is lower than conventional systems.     

Low complexity resource allocation and scheduling algorithms for downlink SDMA systems

The downlink zero-forcing beamforming strategy in the case of random packet arrivals is investigated. Under this setting, the relevant fairness criterion is the stabilization of all buffer queues which guarantees a bounded average delay for all users. It has been shown that allocating resources to maximize a queue-length-weighted sum of the rates is a stabilizing policy. However, the high complexity of user selection and the feasible rates determination for optimal scheme may prevent the real-time scheduling operation. Two low complexity algorithms are provided taking the channel state, queue state and orthogonality into account. In particular, the authors pick the first user with the largest product between channel gain and queuing length, and select the remaining users to construct candidate user set based on the greedy user selection method or channel orthogonal user selection method. Then, the power and rate allocation for the selected users are implemented based on the modified water-filling method. The complexity of the proposed algorithms is analyzed. The average delay and average throughput are studied in homogeneous scenarios and heterogeneous scenarios, respectively. Simulation results show that the proposed algorithms can take full advantage of the multi-user diversity gain and provide average delay (or throughput) and fairness improvement compared with channel-aware-only schemes.     

An efficient power management scheme with SDMA for IEEE 802.15.3 WPANs

IEEE 802.15.3 is devised for short‐distance wireless connectivity within a wireless personal area network (WPAN). In WPANs, a power management (PM) mechanism is used for power saving. The PM enables devices to sleep for one or more superframes in order to conserve power. Space division multiple access (SDMA) is a new technology to optimize performance of current and future mobile communication systems. In this paper, we propose an SDMA‐based PM scheme, called enhanced min‐degree searching (EMDS) for WPANs. EMDS orders the streams among multiple devices to minimize the total wake‐up times. In this scheme, every device that can transmit data at the same time is checked using the SDMA. The total wake‐up times will be reduced substantially if the majority of the devices can transmit data at the same time. Simulation results show that the performance of the proposed EMDS outperforms that of the existing approaches. Copyright © 2013 John Wiley & Sons, Ltd.     

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     

两跳中继OFDMA蜂窝网络下行链路呼叫阻塞率分析

本文首先提出了一种分析OFDMA蜂窝网络下行链路呼叫阻塞率的方法,在此基础上进一步分析了加入两跳中继的OFDMA蜂窝网络呼叫阻塞率.OFDMA蜂窝网络的每个呼叫接入都需要随机数量的子载波来满足用户传输速率的需求,传统GSM及CDMA网络的容量分析方法不能应用到OFDMA网络系统中.本文根据用户对子载波的需求量,把接入用户分成不同的服务类型,以多维马尔可夫链为数学模型分别分析传统和两跳中继OFDMA蜂窝网络下行链路呼叫阻塞率,最终通过数值计算分析各种参数对系统性能的影响,数值分析结果表明加入中继后的两跳中继OFDMA蜂窝网络下行链路容量比传统网络有显著的提升.     

Outage Probability in Full Spectrum Reuse Cellular Systems with Discontinuous Transmission

Co-channel interference has a very strong impact on the performance of cellular mobile radio systems; a performance measure to evaluate its effect is the outage probability. This work presents an analytical general formula for the outage probability evaluation in full spectrum reuse cellular systems with discontinuous transmission. In particular, both Nakagami and Rician fading along with log-normal shadowing have been considered in the signal propagation model. In addition, the discontinuous transmission strategy is considered. The results are applied to the throughput evaluation of a packet cellular radio network based on the slotted Aloha protocol.