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在现有的分散定步长功率控制算法基础上,通过引入多个功率控制步长,得到一种改进的分散功率控制算法。通过分析可知,新算法具有更好的收敛精度,仿真结果表明与原有算法相比,本算法收敛速度获得了提高。 相似文献
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CDMA系统由于用户容量大、频谱利用率高等特点而优于其他多址方式,近年来在通信系统中得到越来越多的重视,如何克服多址干扰问题已成为提高CDMA系统容量的关键。而作为3G的关键技术之一的多用户检测技术,近年来取得了多个方面的发展。本文就TD—SCDMA系统的多用户检测技术(MUD)之一的最小均方误差(MMSE)技术进行了详细分析,并给出仿真结果。 相似文献
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3GPP长期演进(LTE)系统中femtocell密集部署时,femtocell之间会存在较强干扰,针对femtocell的下行干扰,提出了一种基于干扰级别的功率控制算法。根据设定的信干噪比(SINR)门限值,给femtocell用户设置相邻干扰标志,通过上行信道发送给femtocell,再转发给相邻femtocell,femtocell由收到的干扰标志数量划分级别,根据干扰级别进行不同的功率调整。仿真结果表明,该算法很好地提升了femtocell用户的低SINR,femtocell用户吞吐量比无功率控制情况下至少提高了2.1Mbps,达到了降低femtocell间干扰的目的。同时表明,femtocell部署越密集,控制效果更加明显。 相似文献
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在现今最流行的WCDMA这种制式的通信系统中,系统的容量是会受干扰限制的,如果可以降低用户的发射功率和对其他用户的干扰,都可以大幅提高系统的通信质量。功率控制在这方面起着极其重要的作用。如果将WCDMA系统中的功率控制过程比作一个博弈的过程。那么在系统中,功率控制的博弈论模型中的代价函数就可以用用户的发射功率的函数来表示,因此对功率控制的求解问题就可以把它转化为对某个函数的求解。 相似文献
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通过对几种典型的分布式功率控制算法进行仿真分析,得出了“完全分布式功率控制(FDPC)算法具有最低的算法复杂度,而改进的分布式功率控制(IDPC)算法则具有最优的收敛速度”的结论。 相似文献
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应用功率控制、波束赋形和多用户检测可以有效地消除和减少CDMA系统中的干扰。本文结合波束赋形和多用户检测的特性,提出一种应用波束赋形增益和多用户相关矩阵的解相关算法。基于算法的复杂性,提出一种区分聚集用户进行多用户检测的的算法。由于波束赋形能够消减主瓣波束之外的多用户干扰,对聚集移动台采用解相关检测达到减少运算量和消除多用户干扰的目的。对算法进行了仿真分析,证明了本算法的优越性。 相似文献
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在码分多址(CDMA)系统中,功率控制被认为是所有关键技术的核心,可以有效地克服远近效应和多址干扰的影响。提出了一种新的基于最小均方误差(MMSE)多用户检测的分布式功率控制算法。实验结果表明,该算法具有收敛速度快,功率控制效果好的优点,使用该算法可以有效降低系统内用户发射的总功率,同时系统容量也得到一定程度的提高。 相似文献
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Ali F. Almutairi Mohammed M. GabAllah 《Wireless Communications and Mobile Computing》2007,7(4):445-456
This paper examines the performance of a reduced rank minimum mean square error (MMSE) receiver‐based direct sequence code division multiple access (DS‐CDMA) system. For such system, when a large processing gain is employed, substantial time is consumed in computing the filter tap weights. Many schemes for reducing the complexity of the MMSE have been proposed in recent years. In this paper, computational complexity reduction of the MMSE receiver is achieved by using the K‐mean classification algorithm. The performance of the uncoded and coded systems are investigated for the full rank MMSE receiver and reduced rank MMSE receiver and results are compared in terms of bit error rate at different loading levels in both AWGN and fading channels. A system with the matched filter (MF) receiver is also presented for the purpose of comparison and an analytical pair‐wise error bound for the coded system is derived. In the adaptive implementation of the receivers, results show that good performance is achieved for the reduced rank receiver when compared to the full rank receiver in both coded and uncoded systems, while in the optimum implementation of the tap weights, the reduced dimension receiver performance experiences degradation when compared to the full rank scheme. Over the band‐limited channels considered, results for the reduced rank receiver also reiterate the fact that higher code rates tend to yield lower BER than that of low rate codes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Zvi Rosberg 《Wireless Networks》2007,13(4):551-564
The asymptotically combined optimal transmission power and rate control policy is derived for a DS-CDMA time varying fading
channel with multiple user classes, random spreading codes and a receiver using either a conventional matched filter (MF)
or a minimum mean square error (MMSE) multiuser detector. For a general objective function, the optimal policies are given
by closed form functions of a single Lagrangian multiplier. The optimal policies are demonstrated by an application, where
the transmission power is adapted to the channel fade variations, and the transmission rates are adapted to the tier containing
the mobile. The effect of the number of tiers on the optimal transmission rate are presented for MF and MMSE receivers in
an environment with Lognormal and Rayleigh fading. It is shown that with an MMSE receiver, there is a substantial increase
in the total transmission rate, whereas only a negligible increase exists with a MF receiver.
Zvi Rosberg received the B.Sc., M.A. and Ph.D. degrees from the Hebrew University of Jerusalem. During his graduated studies he was a
senior system analyst in the Central Computing Bureau of the Israeli government, where he was one of the chief designers of
a new on-line Israeli population registration system. After graduation he held a research fellowship at the Center of Operation
Research and Econometric (C.O.R.E.), Belgium and a visiting assistant professorship at the department of Business Administration,
University of Illinois. At 1980 he joined the Computer Science department, Technion, Israel where he was until 1990. From
1990 to 1999 he was with the Haifa Research Laboratory, Science and Technology, IBM Israel, holding a position of a Program
Manager of Communication Networks. From 2000 to 2001 he was with Radware Ltd., holding the chief scientist position. During
the year of 2002 he visited the ARC Special Research Centre for Ultra-Broadband Information Networks (CUBIN), University of
Melbourne. Currently he is an Associate/Professor at the Department of Communication Systems Engineering, Ben Gurion University,
Beer-Sheva.
Since 1980 he held summer research positions and a two year visiting position in IBM Thomas J. Watson Research Center, Yorktown
Heights. He also had summer research positions in the Department of Electrical and Computer Engineering, University of Massachusetts,
Amherst, Department of Electrical Engineering and Computer Science, University of California, Berkeley, the Radio Communication
Systems, Royal Institute of Technology (KTH) in Stockholm, the ARC Special Research Center for Ultra-Broadband Information
Networks (CUBIN), University of Melbourne, and the Department of EEE, City University, Hong Kong. Presently, he is serving
on the editorial board of the Wireless Networks (WINET) and the International Journal of Communication Systems. His research
interest, where he has published numerous papers, include: Narrowband and spread spectrum wireless communication, Radio resource
allocation and planning in cellular networks, Scheduling in wireless networks, Optical and ultra high speed networks, Control
in queueing networks, Analysis of algorithms in communication and computing systems and Internet technologies 相似文献
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This paper proposes transmission power control for vehicular ad hoc network (VANET) using fuzzy system. Despite the potential advantages of VANET especially for safety and intelligent transportation system, some challenges are discovered during the implementation of VANET. Main challenges emerge because of the dynamic environment and high mobility of vehicle. Furthermore, the interference due to the shared‐spectrum usage can significantly decrease the quality of signal. Fuzzy system is implemented to control the transmission power based on the signal to interference and noise ratio (SINR) difference with the targeted value of the receiver vehicle and the interference inflicted by the transmitter vehicle. The algorithm of fuzzy power control for VANET is proposed, and the performance is evaluated through the simulations. The results of simulations show that the proposed algorithm can increase SINR of vehicles especially the vehicles with SINR value below the target. Thus, the average of SINR and the throughput of the system can be increased as well. 相似文献
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为了优化长期演进(LTE)系统引入设备直传(D2D)通信后带来的同频干扰、系统边缘用户性能恶化问题,提出一种基于信干噪比(SINR)的多小区D2D通信资源分配方案,通过调整信干噪比阈值将部分蜂窝用户(CU)转化为D2D用户并释放频谱资源进而获得较佳的资源分配策略,同时提出一种基于小区间D2D竞争机制的配置算法有效降低小区间干扰.仿真表明,算法能够有效提升系统容量,并提升小区边缘D2D用户公平性. 相似文献
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This article proposes a new algorithm to improve the rate control efficiency of enhanced reverse link medium access control (RLMAC) in the code division multiple access (CDMA) 1x EV-DO release A(Rev. A) system. The new algorithm brings reverse access terminal (AT) pilot power to the RLMAC rate control procedure and makes it easier for a low pilot power user to increase its data rate when the system is slightly loaded and harder to decrease its date rate when the system is heavily loaded. Numerical results of system level simulations show that the new algorithm can bring higher system throughput, lower AT transmission power, and lower system load. 相似文献