CDMA系统中一种快速有效的盲波束形成方法

利用DS-CDMA系统的工作原理,提出一种基于鲍威尔法的最大化阵列输出功率的盲波束形成方法．只需检测相关器解扩后输出信号移相合并的功率,即可求出用于搜索的共轭方向,自适应地调整阵列天线中各阵元的相位,使形成波束指向期望用户的来波方向．该方法降低了系统复杂度．数值仿真结果表明,鲍威尔法与类似优化算法相比,提高了波束形成的稳定性,减少了计算量,并在同等收敛精度下具有更优的方向图．单信号入射时本方法的迭代次数和乘法次数约为同类方法的10％,双信号入射时的计算量进一步减小至同类方法的2％．     

An Approach to a Method of Construction of (F, K, 1) Optical Orthogonal Codes from Block Design

(F, K, 1) Optical orthogonal codes (OOC) are the best address codes applied to optical code division multiple access (OCDMA) communication systems, but the construction of the codes is very complex. In this paper, a method of construction of the OOC from block design is discussed and a method of computer aid design is presented, by which we can construct desired (F, K, 1) OOC easily.     

The Capture Analysis of Constant Modulus Approach for Blind Multiuser Detection

This paper analyzes the lock/capture behavior of constant modulus approach (CMA) for blind multiuser detection. Conditions under which CMA locks on the desired signal and when it captures the interferer are derived.     

Capacity Estimation in Multiple-Chip-Rate DS/CDMA Systems Supporting Multimedia Services

This paper is concerned with capacity estimation in multiple-chip-rate (MCR)DS/CDMA systems supporting multimedia services with different informationrates and quality requirements. Considering both power spectral density (PSD)over a radio frequency (RF) band and the effect of RF input filtering onthe receiver, capacity that satisfies the requirementof the bit energy-to-interference PSD ratio is derived.The optimum value of the received power which causes the leastinterference for other users while maintaining an acceptablequality-of-service(QoS) requirement is also derived. The results show that system performanceisstrongly affected by a selected channel assignment strategy. Therefore, it is critical to efficiently assign radio resources in MCR-DS/CDMA systems that support high capacity and a low blocking rate.     

准同步CDMA及其在卫星移动通信中的应用

研究了一种新颖的多址准同步CDMA方式，理论推导了准同步CDMA性能表达式，在性能评价的基础上，构造了两放新的扩频码集，分析表明，采用新码集时，准同步CDMA性能要远优于异步CDMA，最后分析了卫星移动通信系统反向信道采用准同步CDMA时的性能。     

CDMA蜂窝网中功率控制对系统容量的影响

ＣＤＭＡ蜂窝网中存在远近效应，必须引入功率控制。功率控制对系统容量有极大的关系。本针着重功率控制精度以系统容量的影响，提出功率控制的高斯误差颁假设，并得到系统容量随功率控制变化的规律及可参考的计算方法。     

The Capture Analysis of Constant Modulus Approach for Blind Multiuser Detection

1 Introduction Multiple-access interference (MAI) due to many simultaneous users constitutes the main limitation of DS-CDMA systems. Multiuser detection techniques can efficiently suppress MAI and substantially increase the capacity of CDMA systems. Over …     

PERFORMANCE OF MULTIUSER DETECTION FOR CDMA SYSTEM IN A FLAT RAYLEIGH FADING ENVIRONMENT

In a CDMA communication network using conventional signal detection, system capacity is limited and its performance is degraded by the multi-access interference (MAI). Multiuser detection, which makes use of cross-correlation information between spread spectrum codes, can reduce or eliminate the MAI in a Gaussian channel so as to mitigate the near-far effects and increase the system capacity. This paper extends the multiuser detector to a flat Rayleigh fading CDMA environment, and discusses the bit error rate of typical multiuser detection algorithms in such a environment by combining theoretical analysis and computer simulation. It is shown that multiuser detection is superior to conventional detections in the flat Rayleigh fading channels.     

Power Control for Link Quality Protection in Cellular DS-CDMA Networks with Integrated (Packet and Circuit) Services

The problem of admission control in a DS-CDMA network carrying a heterogeneous mix of traffic is addressed. In an interference limited system such as DS-CDMA, admission of a new user impacts the performance of all other users, as well as the system capacity. The admission process is concerned with two factors: (1) maintaining the QoS of active users, (2) allocating bandwidth to new users. We propose a simple power control algorithm and prove that it is optimal in the sense of maintaining active link quality while maximizing free capacity for new admissions. The algorithm scales the powers of active links appropriately to achieve link protection and improved tolerance of the link to new interference from bursty sources. This algorithm can be used to overlay bursty packet data services without compromising QoS of active circuits.     

Performance modeling and evaluation of data/voice services in wireless networks

Application-level performance is a key to the adoption and success of the CDMA 2000. To predict this performance in advance, a detailed end-to-end simulation model of a CDMA network is built to include application traffic characteristics, network architecture, network element details using the proposed simulation methodology. We assess the user-perceived application performance when a RAN and a CN adopt different transport architectures such as ATM and IP. To evaluate the user-perceived quality of voice service, we compare the end-to-end packet delay for different vocoder schemes such as G.711, G.726 (PCM), G.726 (ADPCM), and vocoder bypass scheme. By the simulation results, the vocoder bypass scenario shows 30% performance improvement over the others. We also compare the quality of voice service with and without DPS scheduling scheme. We know that DPS scheme keep the voice delay bound even if the service traffic is high. For data packet performance, HTTP v.1.1 shows better performance than that of HTTP v.1.0 due to the pipelining and TCP persistent connection. We may conclude that IP transport technology is better solution for higher FER environment since the packet overhead of IP is smaller than that of ATM for web browsing data traffic, while it shows opposite effect to the small size voice packet in RAN architecture. We show that the 3G-1X EV-DO system gives much better packet delay performance than 3G-1X RTT. The main conclusion is that end-to-end application-level performance is affected by various elements and layers of the network and thus it must be considered in all phases of the development process. Jae-Hyun Kim He received the B.S., M.S., and Ph.D. degrees, all in computer science and engineering, from Hanyang University, Ansan, Korea, in 1991, 1993, and 1996 respectively. In 1996, he was with the Communication Research Laboratory, Tokyo, Japan, as a Visiting Scholar. From April 1997 to October 1998, he was a post-doctoral fellow at the department of electrical engineering, University of California, Los Angeles. From November 1998 to February 2003, he worked as a member of technical staff in Performance Modeling and QoS management department, Bell laboratories, Lucent Technologies, Holmdel, NJ. He has been with the department of electrical engineering, Ajou University, Suwon, Korea, as an assistant professor since 2003. His research interests include QoS issues and cross layer optimization for high-speed wireless communication. Dr. Kim was the recipient of the LGIC Thesis Prize and Samsung Human-Tech Thesis Prize in 1993 and 1997, respectively. He is a member of the Korean Institute of Communication Sciences (KICS), Korea Institute of Telematics and Electronis (KITE), Korea Information Science Society (KISS), and IEEE. Hyun-Jin Lee received the B.S. degree in electrical engineering from Ajou University, Suwon, Korea, in 2004, and is working toward the M.S. degree and Ph. D. degree in electrical engineering at Ajou University. He has been awarded Samsung Human-Tech Thesis Prize in 2004. His research interests QoS, especially network optimization and wireless packet scheduling. He is a member of the KICS. Sung-Min Oh received the B.S. and M. S. degrees in electrical engineering form Ajou University, Suwon, Korea, in 2004, and is working toward the Ph. D. degree in electrical engineering at Ajou University. His research interests QoS performance analysis and 4G network. He is a member of the KICS. Sung-Hyun Cho received his B.S., M.S., and Ph.D. in computer science and engineering from Hanyang University, Korea, in 1995, 1997, and 2001, respectively. From 2001 to 2005, he has been with Samsung Advanced Institute of Technology, where he has been engaged in the design and standardization of MAC and upper layers of B3G, IEEE 802.16e, and WiBro systems. He is currently a MAC part leader in the telecommunication R&D center of Samsung Electronics. His research interests include 4G air interface design, radio resource management, cross layer design, and handoff in wireless systems.