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码分多址卫星通信系统的网络容量较小,而功率控制不理想使其容量进一步降低。本文给出了功率下的中断概率公式,由此计算功率控制误差对系统容量的影响。 相似文献
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文章从卫星通信系统的功率控制原理入手,提出了一种适合CDMA卫星通信系统的功率控制方法;给出了精准的功率控制时的系统容量,通过推导给出的中断概率公式和例举的CDMA卫星通信系统实际数据,将功率控制误差对于系统容量的影响进行了仿真.仿真结果表明,当标准方差不断增大,系统的中断概率增大,系统容量随之显著减小;而采用精准的功率控制技术,可以有效改善系统性能. 相似文献
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In this paper, two new efficient detection algorithms, Type 1 (T1) with better complexity-performance tradeoff and Type 2
(T2) with lower complexity, are derived from one generalized framework for multiple-input multiple-output (MIMO) communication
systems. The proposed generalized detection framework constructed by parallel interference cancellation (PIC), group, and
iteration techniques provides three parameters and three sub-algorithms to generate two efficient detection algorithms and
conventional BLAST-ordered decision feedback (BODF), grouped, iterative, and B-Chase detection algorithms. Since the group
interference suppression (GIS) technique is applied to the proposed detection algorithms, the complexities of the preprocessing
(PP) and tree search (TS) can be reduced. In (8,8) system with uncoded 16-QAM inputs, one example of the T1 algorithm can
save complexity by 21.2% at the penalty of 0.6 dB loss compared with the B-Chase detector. The T2 algorithm not only reduces
complexity by 21.9% but also outperforms the BODF algorithm by 3.1 dB. 相似文献
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K波段卫星通信系统的抗衰落对策 总被引:2,自引:0,他引:2
本文概述了K波段卫星通信系统发展的优越性和巨大潜力。简单介绍了该波段卫星通信系统的衰落影响因素,提出了三各抗衰落对策,位置分集、自适应资源共享技术、自适应调制技术,并加以重点讨论。同时也分析了各种抗衰落技术的优势及存在问题。 相似文献
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卫星通信系统中的多址接入协议 总被引:1,自引:0,他引:1
简述了卫星通信中多址协议的分类和影响多址协议性能的因素,重点介绍了三种预约多址协议PRMA-HS、PRMA/CDMA和Butst Reservation CDMA,并分析了它们的性能. 相似文献
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卫星通信系统调制方式的研究 总被引:2,自引:0,他引:2
本文从卫星通信的特性出发 ,针对其带限和非线性的信道特性 ,提出了各种PSK调制方式 ,这类调制方式是利用已调信号包络恒定、频谱占有率低以及经由非线性信道而产生的频谱扩展和频率失真小等特点 ,使卫星通信的已调信号和特殊信道达到良好的匹配。本文还对相干载波提取中的锁相环提出了一种改进方法。 相似文献
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Admission Control Algorithms for Cellular Systems 总被引:1,自引:0,他引:1
This paper evaluates call admission control algorithms for a cellular or microcellular system. Algorithms are evaluated based on two Quality of Service (QoS) metrics: the new call blocking probability, which is the probability that a new call is denied access to the system, and the forced-termination probability, which is the probability that a call that has been admitted will be terminated prior to the call's completion. Three novel algorithms are presented: the Weighted Sum Scheme, the Probability Index Scheme, and the Hybrid Control Scheme. The weighted sum scheme uses the weighted sum of the number of calls underway in various cells when making the admission decision. The probability index scheme computes a probability index, which reflects the forced-termination probability of a new call arrival, and admits those calls with low probability indexes. The hybrid control scheme combines these two approaches. These novel algorithms are compared with three known algorithms: the Reservation Scheme in which a specific number of channels are reserved in each cell for handoffs, the Linear Weighting Scheme in which the admission decision depends on the total number of calls underway in a group of cells, and the Distributed Admission Control Scheme in which the admission decision depends on the projected overload probabilities in the cell at which the new call arrives and adjacent cells. We show that the Hybrid Control Scheme yields the best performance, particularly during periods when load differs from the expected level. We also show that the simple Reservation Scheme performs remarkably well, often superior to more complex schemes that have been proposed. 相似文献
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在3GPP协议规范中对外环功率控制算法没有定义,由各设备生产和制造商决定。TD-SCDMA系统每时隙下服务用户数较WCDMA系统每帧下服务用户数明显减少;另外,采用了自适应的智能天线技术,适合WCDMA的外环功率控制算法不能直接适用于TD-SCDMA,提出了一种先进的自适应功率调整步长的外环功率控制算法。由于外环功率控制参数对系统性能影响较大,基于自适应智能天线技术,给出了不同参数下外环功率控制算法的性能,可用于TD-SCDMA网络的规划优化。 相似文献
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MIMO即多输入多输出通信技术,因其可以增大信道容量,而被广泛应用于各类通信系统中。在卫星通信系统中应用MIMO技术,主要面临同道干扰和噪声两个问题。文中介绍了克服同道干扰的MIMO卫星通信线性检测系统,并为解决上述问题,在输入端引入扩频技术和接近香农极限的LDPC编码,而在输出端进行解扩和译码,既减小了同道干扰,又明显削弱了噪声,从而实现了良好的性能。 相似文献
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《Photonics Technology Letters, IEEE》2006,18(19):1984-1986
Maximum likelihood sequence detection represents the most efficient technique in the electrical domain to combat fiber impairments such as polarization-mode dispersion and group-velocity dispersion. In order to successfully apply this technique, it is mandatory to estimate some key channel parameters needed by the Viterbi processor. We propose a simple and effective solution based on the least-mean-square algorithm to perform such an estimation. 相似文献
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非对称PCMA卫星信号的截获方法 总被引:1,自引:0,他引:1
近年来PCMA等卫星通信新技术的应用对卫星通信信号的截获提出了更高的要求,通过分析PCMA卫星通信系统的工作原理,借鉴多用户检测技术中串行干扰抵消的基本思想,提出一种针对非对称PCMA信号的截获方法,并进行了性能仿真。仿真结果表明,在没有任何先验信息的情况下,可以实现对非对称PCMA信号中双方信号的截获和解调。 相似文献
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Within the last five years, there has been a cultural shift from wired landlocked connectivity to pervasive wireless information
access. Most emerging mobile devices are now equipped with some form of embedded wireless radio. The expectations of high
data rates and increased battery longevity have put tremendous pressure on all aspects of wireless system design.The goal
of our projects at the Center for Multimedia Communication at Rice is to develop powerefficient wireless enabled mobile devices.
In this paper, we will consider the control and coding issues to increase active access time of mobile communication devices.
In particular, we develop scheduling algorithms which adaptively change the transmission power and rate, based on both the transmission queue backlog and the channel conditions. Thepacket level control algorithms exploit burstiness of data
streams and channel variations to trade packet queuing delay with the average transmit power. The wide range of data rates
dictated by the scheduler and our power efficiency objective is effectively met by a multi-antenna transceiver. We design
non-coherent space-time codes for high mobile speeds, and space-time feedback strategies for low mobility applications. This
paper highlights some of the proposed methods and presents some preliminary results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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In this paper, we investigate a geosynchronous earth orbit(GEO) and low earth orbit(LEO)coexisting satellite communication system. To decrease the interference imposed on the GEO user caused by LEO satellites, we propose a joint beammanagement and power-allocation(JBMPA) scheme to maximize signal-to-interference plus noise ratio(SINR) at the GEO user, whilst maintaining the ongoing wireless links spanning from LEO satellites to their corresponding users. Specifically, we first analyze the overla... 相似文献
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