Maximizing the SDMA Mobile Radio Capacity Increase by DOA Sensitive Channel Allocation

In a cellular mobile radio system an SDMA (Space Division Multiple Access) component can be implemented for the reuse of radio channels physically incorporated by time, frequency or code slots. Since SDMA is based on the spatial separation of different users operating in the same channel, a DOA (Direction of arrival) sensitive channel allocation scheme is essential for maximizing system capacity. In this paper we present the Eigenvector method, a computationally efficient algorithm to do this job. We also present simulation results on the Eigenvector method operating in a typical urban mobile radio cell. The simulated blocking probabilities are then used to predict the capacity increase which can be expected after adding an SDMA component to a conventional mobile radio system.     

Dynamic Spatial Channel Assignment for Smart Antenna

The paper describes an optimal dynamic channel assignment algorithm for smart antennas. This algorithm can deal with the Spatial Division Multiple Access (SDMA) and traditional channel multiple accesses (FDMA, TDMA, or CDMA) simultaneously to enlarge the capacity of communication systems. This algorithm has several merits, including less computer time, the largest capacity, and avoidance of co-channel interference. The paper also describes the idea of a spatial channel pattern, in which several users can share a channel. Several simulation results are presented in the paper.     

The Performance of Space-Time Processing for Suppressing Narrowband Interference in CDMA Communications

The requirement to suppress narrowband interferences in CDMA communications stems from the overlay concept, i.e., coexistence of different types of signals in the same frequency band. The conventional approach to rejecting the narrowband interferences has been to whiten the received signal containing the interference, prior to spread spectrum demodulation. In this paper, it is proposed to achieve the interference rejection through spatial processing. The main benefit of this approach is its robustness with respect to the interference bandwidth. Stepping up from single domain spatial processing to space-time processing provides degrees of freedom for both overlay interference cancellation and diversity combining. Two space-time architectures, cascade and joint-domain, are studied and compared to a Rake receiver preceded by a whitening filter. Main contributions of the paper are the development of analytical expressions of (1) the efficiency of each method, (2) the p.d.f.'s of the output SNR in a Rayleigh fading environment, and (3) the error probability associated with each method. The analysis therein demonstrates that the joint-domain architecture outperforms the cascade configuration, which in turn is superior to the whitening filter-Rake combination.     

蜂窝通信的空分多址:概念、算法和性能

蜂窝通信采用空分多址正在移动通信领域引起广泛关注。本文对空分多址的基本概念、空间信道模型及其知识利用、上下行链路的实现方法和算法、以及对系统性能的改善等诸方面,进行了比较全面的论述。对目前空分多址研究中值得关注的问题,表达了作者的观点。     

一种低复杂度空-时选择性干扰消除方法

提出了一种行之有效的将智能天线技术同多用户检测技术结合的空-时接收方法,并对其参数进行了优化。它根据误码率信息有选择地实施干扰消除,先并行消除低误码率用户信号的影响,再检测高误码率用户信号。它复杂度低,计算效率高,易于实时实现,具有很好的应用价值。蒙特卡洛仿真实验表明,该方法可以显著改善码分多址移动通信系统的性能。     

智能天线及其在数字电视中的应用

阐述了智能天线的基本概念、关键技术,并针对数字电视传输中遇到的问题提出了将智能天线用于DTF的设想,介绍了国外将智能天线用于车载HDTV的研究进展,指出了智能天线有待研究的课题.     

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.     

A new approach to peer-to-peer wireless LANs based on ultra wide band technology

The advent of Ultra Wide Band (UWB) technology offers a unique opportunity to consider a new type of peer-to-peer wireless Local Area Network (LAN) that requires neither access at a peak data rate commensurate with the full bandwidth of the medium nor a conventional medium access protocol. Rather, due to the extraordinarily high bandwidth afforded by UWB, which is typically much greater than the peak bandwidth required by any ad-hoc radio node, one might imagine a network for which pairs of nodes are interconnected by one or more dedicated (non-shared) radio channels created by time, frequency, or code division multiplexing. In this paper, we consider a network containing N ad-hoc nodes and 2N independent radio channels. Starting with (1) an N × N power matrix, where element p _i,j represents the power needed for a successful transmission from node i to node j including the effects of path loss and shadow fading, and (2) a second N × N traffic matrix where element t _i,j represents the exogenous traffic originating from node i and destined for node j, we seek to assign radio channels and multi-hop route the traffic between source-destination pairs such that the resulting connectivity pattern and traffic flow minimize the average transmit energy needed to deliver a packet between an arbitrarily chosen pair of nodes. With no medium access protocol needed, collisions cannot occur and retransmissions become unnecessary. Moreover, the available capacity grows with the number of channels created (or, alternatively, as some common set of channels are re-used on a non-interfering basis via sufficient spatial separation). In this fashion, such a UWB ad-hoc network takes on the characteristics of a multi-hop Wavelength-Division Multiplexed (WDM) network well known from the multihop lightwave network art, although the constraints and dynamics are certainly different. Since the optimum connectivity and flow problem is shown to be NP hard, several heuristics are considered and compared. These heuristics seek, first, to establish a “good” connectivity graph, and then to flow the traffic in an optimum fashion. Our results suggest that application of these techniques may provide a distinct wireless LAN advantage achievable only via UWB radio technology, and several opportunities for future work based on this novel approach to ad-hoc local area radio networks are identified and discussed. Marc Krull received his B.S. degree in electrical engineering from Brown University in 2001 and his M.S. degree in electrical engineering from the University of California, San Diego in 2004. His graduate research focused on the investigation of energy efficient routing protocols for ultrawideband networks. He is currently with Raytheon Companys Intelligence and Information Systems division in Aurora, Colorado, where he is involved in software development for satellite ground systems. Anthony Acampora is a Professor of Electrical and Computer Engineering at the University of California, San Diego, and is involved in numerous research projects addressing various issues at the leading edge of telecommunication networks, including the Internet, ATM, broadband wireless access, network management and dense wavelength division multiplexing. From 1995 through 1999, he was Director of UCSDs Center for Wireless Communications, responsible for an industrially funded research effort which included circuits, signal processing, smart antennas, basic communication theory, wireless telecommunications networks, infrastructure for wireless communications, and software for mobility. Prior to joining the faculty at UCSD in 1995, he was Professor of Electrical Engineering at Columbia University and Director of the Center for Telecommunications Research, a National Science Foundation Engineering Research Center. He joined the faculty at Columbia in 1988 following a 20-year career at AT&T Bell Laboratories, most of which was spent in basic research where his interests included radio and satellite communications, local and metropolitan area networks, packet switching, wireless access systems, and lightwave networks. His most recent position at Bell Labs was Director of the Transmission Technology Laboratory where he was responsible for a wide range of projects, including broadband networks, image communications, and digital signal processing. At Columbia, he was involved in research and education programs concerning broadband networks, wireless access networks, network management, optical networks and multimedia applications. He received his PhD. in Electrical Engineering from the Polytechnic Institute of Brooklyn and is Fellow of the IEEE and a former member of the IEEE Communication Society Board of Governors. Professor Acampora has published over 160 papers, holds 33 patents, and has authored a textbook entitled An Introduction to Broadband Networks: MANs, ATM, B-ISDN, Self Routing Switches, Optical Networks, and Network Control for Voice, Data, Image and HDTV Telecommunications. He sits on numerous telecommunications advisory committees and frequently serves as a consultant to government and industry.     

Performance of the EY-NPMA Protocol

The throughput of the Elimination Yield Non-pre-emptive Priority Multiple Access (EY-NPMA) protocol, which has been chosen as the medium access control (MAC) protocol for HIPERLAN, is simulated. Connection between users is based on a statistical model of path loss with power law against distance and 6 dB log-normal shadowing. It is shown that the throughput performance of the EY-NPMA protocol in networks of moderate size and with small proportion of hidden nodes is satisfactory. For a fully connected network, the throughput reaches 0.85 at an offered traffic of 1 and remains at this level. The maximum throughput reduces gradually when the number of hidden node pairs in the network is increased. With 11% of hidden nodes in the network the peak throughput falls to 0.6.     

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。     

智能天线在多径信道中的性能仿真与分析

首先讨论了自适应阵列天线算法原理,然后通过对采用LMS算法的智能天线在多径信道中抗多径干扰性能的仿真,进一步分析了多径干扰对智能天线性能的影响。结果表明,智能天线阵列的抗多径干扰性能受信号空间分布、信号幅度等因素的影响。     

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.     

HIPERLAN Receiver Design Issues: Noise Performance and Frequency Offset Compensation

This paper is concerned with some physical layer issues for HIPERLAN. First, the noise performance required of each class of receivers in HIPERLAN is determined. Secondly, the effect of frequency offset on the performance of equalisers is investigated and various techniques for joint equalisation and frequency offset compensation are studied. It is shown that by employing a decision feedback equaliser incorporating a second order phase locked loop, the effect of both the intersymbol interference and frequency offset can be significantly reduced. Using such a technique, the packet error ratio (PER) of a HIPERLAN radio link in a multipath channel is found by simulation.     

多用户环境下阵列响应的闭式盲估计方法

本文通过剖析多径多用户环境下阵列输出信号二阶统计量的数据结构,提出了一种基于特征分解的闭式阵列响应盲估计方法,该方法适用于任何几何形状的阵列和未校准的阵列,且对信号特性和传播参数（散射源分布和入射角散布范围）的约束极少。理论分析与仿真结果是在近程该方法能够有效地进行阵列响应估计和信号分离,在空分多址（ＳＤＭＡ）的实现方面具有较强的实用性。     

智能天线系统中信道空分复用问题的研究

本文阐述了智能天线（ｓｍａｒｔ ａｎｔｅｎｎａ）空分复用系统中的重要概念－信道方向图的概念,提出子一种高效的搜算算法,用于解决信道复用中的组合寻优问题。最后以本文的搜索算法为基础进行仿真,得到了关于智能天线系统中有关信道复用的若干有用结论。     

椭圆形阵列天线的方向特性研究

对椭圆形阵列天线的方向特性进行了研究,证明了直线阵和圆环阵是椭圆形阵的特例。给出了椭圆形天线阵及在椭圆的中心和两个焦点上分别或同时加上一个阵元的情形下天线阵的方向性函数,并绘制了相应的方向性图,仿真计算结果表明在椭圆的中心和焦点处加上阵元可有效地降低副瓣,同时又不增加阵列的孔径。     

智能天线在OFDM系统中的应用

将智能天线引入OFDM系统可以克服限制系统容量的符号间干扰(ISI)和同道干扰(CCI)。文中首先介绍了数字波束形成,其次介绍了OFDM系统,最后介绍了智能天线自适应系统在OFDM系统中的位置和权值的计算问题。