共查询到20条相似文献,搜索用时 15 毫秒
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远近效应和多径衰落会降低WCDMA收发器的性能.快速功率控制的广泛应用就是为了减小这种不良影响,这样就需准确地估计出接收信号的信干比.文中在传统SIR估计方法的基础上,提出了一种改进SIR估计的方法.此方法考虑并消除了多径间的干扰,克服了其它现有方法在精确度、复杂度和实时性方面的不足.经仿真验证,文中提出的SIR估计方法相比传统算法更为精确. 相似文献
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功率控制是TD-SCDMA系统正常工作所必须的,外环功率控制为内环功率控制提供SIR参考值。为此提出了一种门限报告算法,该算法通过统计误块数和误块容忍周期来决定是否调整目标信干比,同时还给出了具体参数的公式,可以较好地实现3GPP中对外环功率控制的要求。 相似文献
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基于正交解扩的信干比估计方法 总被引:1,自引:0,他引:1
研究了TDD-CDMA(时分双工-码分多址)系统中的SIR(信干比)估计问题。现有的SIR估计方法准确度依赖于信道条件和观测时间,而TDD-CDMA系统复用时隙短,车速条件下信道变化剧烈的特点使得估计准确度降低。针对这种情况,提出了一种基于正交解扩的SIR估计方法。通过COSSAP仿真对比结果表明,该方法在瑞利衰落信道和AWGN(加性高斯白噪声)信道条件不同调制方式下,从低SIR到高SIR的很大范围内都有比较好的性能。 相似文献
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ZhouHua YangDacheng 《电子科学学刊(英文版)》2004,21(4):278-288
Signal-to-Interference Ratio(SIR) is a very important metric of communication link quality. For wireless cellular systems, several control mechanisms, such as power control mechanisms, rate control mechanisms, and allocation of radio resource, are based on SIR estimation.In previous researches, most of researchers concentrated on WCDMA systems, in which pilot symbol is time-multiplexed with data symbol; the method developed in this case is not feasible for cdma2000 systems where pilot symbol is code-multiplexed with data symbol. This paper first develops the SIR estimators based on the reverse pilot channel and then derives the approximate analytic expression for its Mean Squared Error (MSE) function, the accuracy of which is validated through simulation. It is shown that the MSE of the new SIR estimator is significantly smaller than that of other widely used SIR estimators, especially in low SIR case. Finally, the estimate quality of the proposed method is further improved by long-termly averaging the sample interference. 相似文献
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在蜂窝无线通信系统设计中,基于信号干扰比(SIR)测量的功率控制方法得到广泛的应用。该文提出多输入多输出(MIMO)天线蜂窝系统中的基于SIR测量的分布式功率控制(DPC)方法。该方法通过控制移动台或者基站的发射功率可以达到以下两个目标的其中之一:(1)最小化所有基站或者移动台的平均接收SIR中断概率;(2)在满足目标SIR要求的前提下最小化平均发射功率。数值仿真结果显示,该文提出的DPC方法在低的计算复杂度下,可以达到降低SIR中断概率和减小发射功率的目的。 相似文献
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基于信号干扰比(SIR)测量的归一化功率控制在无线蜂窝系统中有着广泛的应用。论文提出TD-SCDMA系统中的基于SIR测量的二阶快速收敛分布式功率控制算法,使用当前功率和前次功率共同参与运算控制移动台发射功率。仿真结果表明,论文提出的二阶快速收敛DPC算法在相同的传播环境下比DPC和SOPC具有更快的收敛速度。 相似文献
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In this article,a modified susceptible-infected-removed(SIR) model is proposed to study the influence of diversity of node anti-attack abilities on the threshold of propagation in scale-free networks.In particular,a vulnerability function related to node degree is introduced into the model to describe the diversity of a node anti-attack ability.Analytical results are derived using the mean-field theory and it is observed that the diversity of anti-attack of nodes in scale-free networks can increase effectiv... 相似文献
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Shaowei Wang Fangjiang Huang Mindi Yuan Sidan Du 《International Journal of Communication Systems》2012,25(2):254-269
In this paper we study the resource allocation problem for the multiuser orthogonal frequency division multiplexing (OFDM)‐based cognitive radio (CR) systems with proportional rate constraints. The mutual interference introduced by primary user (PU) and cognitive radio user (also referred to secondary user, SU) makes the optimization problem of CR systems more complex. Moreover, the interference introduced to PUs must be kept under a given threshold. In this paper, the highest achievable rate of each OFDM subchannel is calculated by jointly considering the channel gain and interference level. First, a subchannel is assigned to the SU with the highest achievable rate. The remaining subchannels are always allocated to the SU that suffers the severest unjustness. Second, an efficient bit allocation algorithm is developed to maximize the sum capacity, which is again based on the highest achievable rate of each subchannel. Finally, an adjustment procedure is designed to maintain proportional fairness. Simulation results show that the proposed algorithm maximizes the sum capacity while keeping the proportional rate constraints satisfied. The algorithm exhibits a good tradeoff between sum capacity maximization and proportional fairness. Furthermore, the proposed algorithm has lower complexity compared with other algorithms, rendering it promising for practical applications. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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The Signal‐to‐Interference Ratio (SIR) has been highlighted in the literature to be a most efficient criterion for several methods aiming at reducing the effects of cochannel interference, e.g., diversity reception, dynamic channel allocation and power control. In this paper we address the problem of how to obtain fast and accurate measurements of this parameter in a practical context. We develop a general SIR estimation technique for narrow‐band cellular systems that is based on a signal subspace approach using the sample covariance matrix of the received signal. Simulation results using the frame structure in the GSM system show that the SIR can be estimated to within an error of 0.3 dB after only 200 ms, or within an error of 0.1 dB after only 0.6 seconds. 相似文献
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Hanho Wang Kyunbyoung Ko Choongchae Woo 《International Journal of Communication Systems》2012,25(3):404-413
Motivated by the difficulty in measuring channel state information between heterogeneous primary and secondary systems, we propose a signal‐to‐interference‐noise ratio (SINR)‐based spectrum sharing policy. In the proposed spectrum sharing policy, a secondary user who does not cause SINR outage at the primary receiver is admitted to share the primary user's spectrum. In this article, we analyze the achievable rate of a secondary user and for whom the achievable rate is maximized in the SINR‐constrained spectrum sharing. The maximized achievable rate is determined by the ratio of the distance between the secondary transmitter and the primary receiver to the distance between the secondary transmitter and receiver, and it is proportional to the distance ratio. In conclusion, secondary links with large distance ratio can support high data rate applications so long as SINR constraint of the primary user is guaranteed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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In this paper, the effect of wireless internet traffic on the functionality of a radio resource metric estimation (RME) applicable to a TDD‐CDMA system which incorporates a multirate transmission scheme (such as multicode and multislot) with simple call admission control algorithm is investigated. A solution for efficient inter‐working between the physical layer and the higher layers is proposed, a resource metric mapping function (RMMF) that can deliver information about the state of the current channel load condition by the monitoring of signal‐to‐interference ratio (SIR) bursts and also the availability of a code pool by estimating the mean and the standard deviation of SIR bursts. This function is defined and demonstrated by means of an average raw BER mapping diagram as a function of the mean and the standard deviation of SIR bursts according to the multirate transmission method. By using this kind of mapping function combined with throughput estimation, the radio resource allocation algorithm can successfully reflect the current interference and mobile radio channel characteristics. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Haiwen Liu Jiuhuai Lei Yulong Zhao Wenyuan Xu Yichao Fan Tiantian Wu 《ETRI Journal》2013,35(2):344-347
This letter presents a compact dual‐mode tri‐band bandpass filter by using a short‐circuited stub‐loaded stepped‐impedance resonator (SIR) and a short‐circuited stub‐loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short‐circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even‐odd mode theory. For demonstration purposes, a tri‐band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured. 相似文献
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主要对SIR滤波器在两方面进行了改进。采用了DGS结构和新型的耦合方式,增强了耦合,为滤波器提供了更多的零点抑制寄生通带的影响。根据理论原理,设计了基于4阶低通原型滤波器结合新结构的SIR带通滤波器,通过HFSS仿真结果看出,该方法能够有效抑制带外寄生通带的影响,对寄生通带的抑制可以达到40dB左右。 相似文献
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基于SIR平衡的功率控制可能存在正反馈的问题,从而使得系统不稳定.讨论了在加性高斯白噪声及Rayleigh衰落信道下,CDMA上行链路闭环功率控制系统的SIR上限问题.通过折衷考虑系统的容量与QoS要求,可以确定临界稳定时的目标SIR上限,在设计功率控制算法时,目标SIR只有满足上限要求,才能确保CDMA系统稳定. 相似文献
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Dongwoo Kim 《Communications Letters, IEEE》2002,6(1):13-15
With signal-to-interference ratio (SIR) based call admission control, a newly arriving call is accepted only if the received SIR is greater than an admission threshold. Since a large threshold often leads to unnecessary denials of the admission requests, the threshold should be selected within a certain upper bound. In this paper, the upper bounds of the admission threshold is provided, which achieves a prespecified level of admission-denying rate in power-controlled DS-CDMA mobile systems 相似文献
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1 IntroductionRecently ,OrthogonalFrequencyDivisionMul tiplexing (OFDM)usesFFTtomultiplexdatasym bolsoversubcarrierstoimplementhigh bit ratedatatransmissionoverwirelesschannels,andhasbeenappliedinseveralcommunicationfields,suchasDig italAudioBroadcast (DAB) ,DAB ,AsymmetricalDigitalSubscriberLoop ,IEEE 80 2 1 1a ,andHIPERLANⅡ .However,OFDMisverysensitivetofrequencyoffsetandfrequencyspreadowingtofrequencydifferenceandrelativemovementbetweentransmittersandreceivers.Thisisahind… 相似文献
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研究了无线数据网络中的信道分配策略,提出了基于信干比(Signal to Interference Ratio,SIR)的动态信道分配(Dynamic Channel Assignment,DCA),通过判断用户的SIR情况来分配空闲信道,并且建立了无线数据网络的排队论模型。仿真分析了网络的呼叫延迟概率和呼叫延迟超时概率这两个重要的性能指标,结果显示在系统高负载情况下,本文提出的基于SIR的DCA相对于传统的信道分配方法能够获得更好的效果,从而实现了对高负载网络的优化。 相似文献