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.     

具有双层系统的分扇区CDMA小区上行链路容量

码分多址系统与传统的时分多址和频分多址系统相比,在各方面都具有优势,尤其是能提供更好的服务质量和更大容量,因而成为第三代移动通信系统的核心技术。通过在小区中划分扇区能进一步提升系统容量,在扇区中又引入双层系统,可以显著提高该扇区内容量。由于CDMA系统是噪声受限系统,因此以信干比为标准,分析具有双层系统的分扇区CDMA小区系统的上行链路容量。最后通过仿真结果证明了该系统上行链路容量相对普通小区系统上行链路容量的提升。     

码分多址反向链路调度算法与处理时延的关系

研究了码分多址反向链路数据传输采用不同的调度算法受系统处理时延影响的程度，这种影响与信道估计误差有关，也与传输速率的更新时间有关。通过对CDMA2000的动态系统级仿真，其结果显示反向链路上的最大速率与轮询结合的算法、最小路径损耗算法、以及轮询算法在有处理时延时吞吐量性能都会降低，其中最大速率与轮询结合的算法降低的程度最小，轮询算法降低程度最大，最小路径损耗算法介于中间。性能降低也与快衰信道类型相关，信道变化越快算法性能受到的影响越大。提出了一种对调度算法的改进方法，即根据移动台处理时延的变化，为近期处理时延较小的移动台分配更多的资源，结果表明该方法改善了系统吞吐量。     

非完备功控CDMA无线网络上行准入控制算法及性能分析

本文研究了非完备功控宽带CDMA无线网络上行准入控制问题。首先为非完备功控CDMA网络上行链路建立了系统模型，然后设计相应的准入控制算法，其中无线资源被划分为供各类用户专用的部分和在各类用户之间共享的部分。为了利用非实时用户可以容忍延时的特点，又引入了队列结构以降低阻塞率。通过对算法进行Markov分析，从理论上计算了用户阻塞率和平均吞吐率性能。仿真结果验证了理论模型的正确性。     

Delay Analysis of Packet Scheduling with Multi-Users Diversity in Wireless CDMA Systems

There have been a number of studies that investigate efficient packet scheduling schemes to support quality of service of multiple real-time data users and to increase capacity of non-real-time users sharing a wireless channel. We consider the problem of scheduling transmissions of multiple data users sharing the same wireless channel so as to satisfy delay or throughput and present a general packet scheduling, called MBCS (Multi-users Best Channel Scheduling) which takes advantage of the multi-user diversity of a mobile wireless system. In this paper, a queuing model that represents radio resource management for supporting packet data services is developed for the purpose of evaluating the performance of wireless CDMA systems. Numerical results show that delay performance of the proposed scheduler is higher than that of the Single-user Best Channel Scheduler (SBCS) depending on the time-varying channel status.Sungkyung Kim is a Ph. D. student in the collage of information & Communications at University of Korea, Seoul, Korea. She received her B.S. and M.S. degree in electrical engineering from Korea University in 1999 and in 2001, respectively. From March 2001 to August 2004, she worked at the Electronics Telecommunications Research Institute, Daejeon, Korea, as a member of research engineer. Her research interests include MAC protocol, radio resource control, packet scheduling, and system performance evaluation at system level in wireless access networks.Chung Gu Kang received his B.S. degree in Electrical Engineering from the University of California, San Diego in 1987 and his M.S. and Ph.D. degrees both in Electrical and Computer Engineering from the University of California, Irvine, in 1989 and 1993, respectively. While working on his Ph.D. dissertation from June 1991 to May 1992, he also was with the Aerospace Corporation in El Segundo, California, as a part-time member of technical staff (MTS). After graduation in 1993, he joined Rockwell International in Anaheim, California, where he has been working on the signaling system no. 7 and other telecommunication systems development. Since March 1994, he has been with College of Information & Communications at the Korea University, Seoul, Republic of Korea, as a full professor. His research interests include next generation mobile radio communication system and broadband wireless networks, with special emphasis on physical layer/medium access control layer design and performance analysis. During the academic year of 2000, he has been a visiting scholar at Center for Wireless Communication and also a visiting professor at Department of Electrical & Computer Engineering in University of California at San Diego (UCSD). He is a member of IEEE COMSOC, IT, and VT, and a member of KICS and KITE.     

智能天线对CDMA系统上行链路的影响

智能天线技术将信号处理由空域、时域、码域扩展到了空域，它已成为第3代移动通信系统的关键技术之一。本文结合IS－95和cdma2000系统的特点，仿真并分析智能天线对CDMA系统上行链路性能的影响。     

LTE系统上行链路调度算法研究

长期演进(Long Term Evolution,LTE)已经成为4G无线技术标准。目前,LTE分组调度的下行链路调度被大多数研究者研究,上行链路的研究相对较少。针对上行链路调度无法保证实时业务分组在延迟期限内传输,存在公平性较差、分组丢弃多的问题。因此,提出了一种新的上行链路调度算法。该算法根据实时业务的延迟约束条件建立目标整数线性规划模型,再根据目标整数线性规划模型进行调度。实验结果表明,该算法能保证实时业务分组在延迟期限内传输,适用于实时业务,能确保公平性,最小化分组丢弃,具有较好的适用性。     

CDMA系统中上行链路发射功率控制理论的研究

综述了CDMA系统上行链路发射功率控制研究的一些基本理论。首先从控制系统的角度出发,将反向闭环功控问题抽象为标准的控制过程,其中的输入输出量可看作控制系统的各个分量。在此基础上综述了现有的控制策略,阐述了功率控制器的设计,重点是控制步长的设计。最后讨论了需要进一步研究的问题。     

Effects of Array Weight Errors on Parallel Interference Cancellation Receiver in Uplink Synchronous and Asynchronous DS‐CDMA Systems

This paper investigates the impacts of array weight errors (AWE) in an antenna array (AA) on a parallel interference cancellation (PIC) receiver in uplink synchronous and asynchronous direct sequence code division multiple access (DS‐CDMA) systems. The performance degradation due to an AWE, which is approximated by a Gaussian distributed random variable, is estimated as a function of the variance of the AWE. Theoretical analysis, confirmed by simulation, demonstrates the tradeoffs encountered between system parameters such as the number of antennas and the variance of the AWE in terms of the achievable average bit error rate and the user capacity. Numerical results show that the performance of the PIC with the AA in the DS‐CDMA uplink is sensitive to the AWE. However, either a larger number of antennas or uplink synchronous transmissions have the potential of reducing the overall sensitivity, and thus improving its performance.     

CDMA多小区上行接纳控制

提出了一种在CDMA系统中基于多小区负荷因子增长估计的上行接纳控制算法。在新呼叫到达时,不仅考虑接纳小区的负荷因子增长,同时考虑相邻小区的负荷因子增长,通过理论分析给出了相邻小区负荷因子增长估计的方法。仿真结果表明,基于多小区负荷因子增长估计的接纳控制算法比基于单小区的接纳控制算法能更有效地提高判决精度,降低错误接纳概率和中断概率,保证已连接用户的QoS要求。     

Channel Adaptive Power Control in the Uplink of CDMA Systems

In this paper, we propose an adaptive power control algorithm using optimal control theory for CDMA cellular systems. With linear quadratic control, each mobile transmits to achieve a desired SIR under the fast varying environment of practical CDMA cellular systems. We apply Kalman filter theory to estimate a channel variation which is vulnerable to nonconstant link gain, mutual interference and uncertain noise. Through simulation comparison with DCPC algorithm, the suggested power control algorithm shows an increased uplink channel capacity.

Optimum Uplink Power/Rate Control for Minimum Delay in CDMA Networks

We derive a new joint power and rate control rule with which we can minimize the mean transmission delay in CDMA networks for a given mean transmission power. We show that it is optimal to respectively control the power inverse‐linearly and the rate linearly to the square root of channel gain while maintaining the signal‐to‐interference ratio at a constant. We also show that the proposed joint power/rate control rule achieves excellent performance results in terms of the probability of the instantaneous delay being within a target delay against one‐dimensional control schemes.     

Application‐layer community‐oriented uplink scheduler for CDMA networks

This paper focuses on community‐based mobile applications and delivers an efficient application‐layer uplink scheduler for the collection of community responses in CDMA networks, capable of pursuing the best possible compromise between delay and radio resource constraints. The scheduling problem is mathematically formulated and solved, based on a novel probabilistic approach inspired by the birthday paradox. Results of the proposed approach are presented and analyzed. Copyright © 2008 John Wiley & Sons, Ltd.     

CDMA直放站设计漫谈

通过对CDMA直放站的干扰、切换、前向反向链路预算问题的分析，提出设置CDMA直放站时，应注意的事项。     

The Effect of On-Off Scheduling to the Required Transmit Power in Systems with Fast Power Control

Physical layer channel-aware scheduling may significantly improve coverage and throughput of IP based services in wireless cellular networks, and the feasibility of such schedulers is actively studied within 3G and 4G systems. A channel-aware scheduler requires access to instantaneous channel state information in order to direct transmission to users with favorable channel conditions. In frequency division duplex (FDD) systems, this requires a fast feedback channel between mobile and base stations, and the overhead of the feedback control channel should be kept as low as possible.In this paper, we study the effect of control channel overhead to on-off scheduling (OOS) when fast transmit power control is applied in data and control channels. On-off scheduling is a simple channel-aware scheduling algorithm, where transmission to a user is suspended if the transmit power exceeds a given threshold. On-off scheduling is applied on the data channel while control channel is always on so that the scheduler is able to obtain channel state information from active users. The gain of OOS strongly depends on the power ratio between control and data channels, and increased interference due to control signaling and decreased interference due to channel-aware scheduling should be jointly considered in system design. Gains in the required transmit power are translated into gains in coverage and capacity assuming WCDMA parameters, and the results can be applied, e.g., when designing scheduling algorithms and corresponding signaling formats for WCDMA uplink.     

CDMA前反向链路平衡问题以及导频功率的优化配置

CDMA中应该先确定话务模型,然后根据有效容量确定反向链路的有效半径,再通过改变前向链路的参数达到前反向链路的平衡.最后,在链路平衡的条件下,根据小区负载的情况来配置导频功率.     

LTE上行接入技术研究

上行接入为用户设备UE（UserEquipment）接入网络提供上行支撑,是移动通信不可或缺的重要组成部分。优秀、高效的上行接入技术可以大大提高上行链路的频谱效率,增加系统容量,扩大覆盖范围,最大化的减小时延。本文通过对LTE（LongTimeEvolution）标准中上行接入技术的研究,较为全面地对LTE环境下上行接入进行了分析和介绍。     

The Other-Cell Interference Calculation of Forward Link Channel in Multicode CDMA Systems

This paper analyzes the other-cell interference of forward link channel in multicode CDMA system supporting a voice and data service. In this system, voice communication can be served by a basic code and data service can be supported by multiple codes. Using this analysis, we can get the approximated capacity of forward link. We describe the effect of data user activity and received power level ratio between a data service and a voice service. Also, this paper describes the forward link capacity and the power ratio of data power to voice power according to the change of FER threshold for data service.     

CDMA基站上行干扰的定位和清除

重点介绍如何有效地进行CDMA基站上行干扰的定位和清除,详细介绍干扰定位和清除的方法和流程,并给出复杂干扰定位和清除案例。     

CDMA网络规划的上行功率迭代算法

该文提出了一种用于CDMA网络规划的的上行功率迭代算法。在迭代的过程中,移动台根据各个基站的负载情况,动态地选择所连接的基站,使发射功率最小,最终使移动台的发射功率和基站处的干扰功率收敛。对算法的收敛性给出了理论分析,仿真结果验证了理论分析的正确性。该算法便于计算机实现,可用于实际的网络规划。