共查询到20条相似文献,搜索用时 15 毫秒
1.
Chieh-Ho Lee Chung-Ju Chang Wen-Ho Sheen 《Wireless Communications, IEEE Transactions on》2008,7(1):78-83
The letter proposes a method to analyze the system capacity of uplinks with imperfect SIR-based power control in direct sequence/code division multiple access (DS/CDMA) cellular systems with the multipath fading. It considers the received signal-to-interference ratio (SIR) as a random variable due to imperfect SIR-based power control. Based on assumptions regarding the average received SIR, a set of linear equations for the average received power on each uplink is derived. An outage-based system capacity can be then obtained according to the feasibility of the average received power vector and the average bit error rate. Finally, by applying central limit theorem, a closed-form solution for system capacity is approximately derived. Results show that numerical results of the closed-form solution have a good match with simulation results, which supports the validity of the proposed capacity analysis method. 相似文献
2.
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。 相似文献
3.
4.
5.
《Communications Letters, IEEE》2007,11(3):258-260
Since the capacity of CDMA networks is interference-limited, it is vital to have a call admission control (CAC) mechanism to preserve the signal quality in terms of the signal-to-interference-and-noise ratio (SINR). SINR-based CAC schemes compare the SINR of the incoming call with a threshold value (SINRth). The call is accepted if the SINR is greater than SINRth, otherwise it is rejected. The choice of the SINRth value is restricted by two opposing factors: the signal quality and the network utilization. Setting SINR th at high value is desirable to increase the signal quality. However, a high SINRth value increases the blocking probability (Pb) and reduces the network utilization. An upper bound of SINRth (SINRth_ub) in CDMA systems with imperfect power control has been determined. However, the accuracy of that upper bound is questionable since the possibility of power control (PC) infeasibility has not been taken into consideration. Also, the analysis used the normal distribution to model SINR instead of the widely-accepted lognormal distribution. Moreover, the noise and the inter-cell interference were ignored. In this letter, we derive a more accurate upper bound by taking the possibility of PC infeasibility into consideration and by using the lognormal distribution of SINR for imperfect PC. In addition, our analysis takes the noise and the inter-cell interference into account 相似文献
6.
时分复接码分多址系统中预瑞克与空时编码技术 总被引:2,自引:0,他引:2
提出了一种适用于时分复接码分多址系统的发射分集,即预瑞克与空时格状编码调制相结合方案。采用预瑞在代替瑞克,在接收机中采用单径瑞克就可实现多径分集,可以简化接收机结构和节约费用。计算机仿真结果表明,在多径衰落下,所提出方案的性能比仅采用空时码好。在最小均方误差意义下预瑞克抽头数应与多径数相同。所提出新型星座图-8APK(振幅相位键控)可以用来构造了一个空时码,此空时码性能比由8PSK构造的具有相同结构的空时码好。 相似文献
7.
Forward Link Performance Analysis in CDMA Distributed Antenna Systems with Imperfect Channel Estimation 总被引:1,自引:0,他引:1
CHEN Peng WU Wei-lingInformation Engineering School Beijing University of Posts Telecommunications Beijing P. R. China 《中国邮电高校学报(英文版)》2005,12(1)
1 Introduction The Distributed Antenna (DA) system has been proposedas a promising antenna architecture for the future wirelesscommunication systems[1~10]. In the DA systems, with remote antennas, the presentcellular structure is removed and cells are not divided geo graphically, but according to the user needs. That is, ac cording to the channel estimates computed via pilot signals,the Processing Node (PN) continuously measures the chan nels between the mobiles and the remote ante… 相似文献
8.
《Signal Processing, IEEE Transactions on》2006,54(10):3947-3956
Power control is an important factor for direct-sequence code division multiple access (DS-CDMA) cellular radio systems to achieve higher communication link quality and better system capacity. In order to track the desired signal-to-interference-plus-noise ratio (SINR) under round-trip delay, multiple access interference (MAI), channel fading, and noise, a time delay-based state-space model is developed for representing the tracking error dynamics and a state feedback controller is introduced for SINR tracking control. Then the power tracking problem can be regarded as a control problem. In this paper, a robust$H_infty$ power tracking control design is proposed to achieve a robust optimal SINR tracking from the minimization of the worst-case effect point of view. This robust optimal power tracking design problem can be transformed to solving the eigenvalue problem (EVP) under some linear matrix inequality (LMI) constraints. The LMI Matlab toolbox can be used to efficiently solve the EVP via convex optimization to achieve a robust optimal SINR tracking design. Under the proposed distributed framework, the information of channel gain is not needed. 相似文献
9.
The performance of the code-division multiple-access/packet-reservation multiple-access (CDMA/PRMA) protocol for a Nakagami-m frequency selective fading channel is obtained by simulation for mixed voice/data traffic 相似文献
10.
区间C/I平衡多区蜂窝CDMA系统的性能 总被引:1,自引:0,他引:1
本文研究多区蜂窝CDMA系统的性能。采用区间载扰比(C/I)平衡技术控制移动台和基台的发射功率以补偿路径损失和对数阴影的综合影响,用蒙特卡诺模拟方法计算了区间C/I平衡蜂窝CDMA系统的中断概率,研究了相邻小区数和不同标准偏差的对数阴影对系统性能的影响以及微蜂窝CDMA系统的总用户数和小区数的关系,并同区内C/I平衡蜂窝CDMA系统的性能进行了比较。 相似文献
11.
An Uplink Short-Term Fading Prediction-Based Power Control Method for DS/CDMA Cellular Radio Systems
In previous research, a new multi-step SIR-based powercontrol, referred to as short-term fadingprediction-based (SFP-based) method, has been proposedfor DS/CDMA downlink power control. Simulation resultsshowed that the SFP method outperforms the originalmulti-step SIR-based power control. In this paper, wefurther investigate the behavior of the SFP methodapplied to uplink. Simulation results show that theSFP method still performs better than the originalmulti-step SIR-based method. Although the uplinkperformance is still poorer than the downlink usingSFP power control method instead of the originalmulti-step SIR-based method, the improvement amount ofSFP-based method compared to the multi-step SIR-basedmethod in uplink is larger than that in downlink. 相似文献
12.
本文就CDMA蜂窝系统中的功率控制问题进行了讨论,其中包括功率控制误差的考虑以及功率控制源的选择,在以往的分析中,常常只考虑基于距离的功率,选择,本文引入了对实际环境下基于导频功率的选择考虑,给出了两种方法的比较,数值计算结果显示后者在系统容量上有一定的改善。 相似文献
13.
The CDMA cellular system can provide more capacity than AMPS systems and the hierarchical layer of cells is required for system design. However, system performance and capacity is degraded due to the cochannel interference between microcell and macrocell if a single frequency channel is shared. This paper proposes three multi-channel access schemes where various frequency channels are assigned for microcell and macrocell. Performances of channel capacity, blocking probability and blocking ratio in uplink and downlink are evaluated. Due to channel segregation and thus the cochannel interference among macrocell and microcell are minimized, the proposed scheme 3 where all channels are accessible sequentially in macrocell and microcell performs the best in system capacity and blocking probability than the other schemes. 相似文献
14.
15.
Young-Long Chen Jyu-Wei Wang Yung-Sheng Lin Jyh-Horng Wen 《Wireless Personal Communications》2008,46(3):269-284
Power control mechanisms are essential for CDMA wireless communication systems to enhance user capacity. In this paper, we
propose a novel power control scheme which combines transmission rate management with power adjustments for multimedia CDMA
cellular systems. In the proposed scheme, a fuzzy logic controller (FLC) is first used to dynamically infer a suitable transmission
rate for each service. Then a selective power control (SPC) scheme is used to adjust the transmission power for each service
in order to maintain an acceptable signal-to-interference ratio (SIR). Numerical results show that the proposed scheme outperforms
the original SPC and the Lagrangian relaxation technique and power control (LRPC) methods in outage probability, average transmission
rate, probability of unsuccessful transmission, and probability of changes in transmission rates.
相似文献
Jyh-Horng Wen (Corresponding author)Email: |
16.
17.
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。 相似文献
18.
19.
20.
SimulationofPowerControlandDiversityofCellularCDMARomanPichna;QiangWang;VijayK.Bhargava;JialinZou;RonKerr(UniversityofVictori... 相似文献