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A resource allocation problem considering both efficiency and fairness in orthogonal frequency division multiple access (OFDMA) systems is studied. According to the optimality conditions, a downlink resource allocation algorithm consisting of subcarrier assignment and power allocation is proposed. By adjusting the tradeoff coefficient, the proposed algorithm can achieve different levels of compromise between efficiency and fairness. The well-known classic resource allocation policies such as sum-rate maximization algorithm, proportional fairness algorithm and max-min algorithm are all special cases of the proposed algorithm. Simulation results show that the compromise between efficiency and fairness can be continuously adjusted according to system requirements. 相似文献
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相位差矢量平均的干涉仪解模糊方法 总被引:2,自引:0,他引:2
针对多基线相位干涉仪逐次递推解模糊测角算法中存在的问题,研究通道间相位误差较大条件下干涉仪正确解模糊的方法.提出了一种基于1倍相位差测量值矢量平均的干涉仪解模糊方法,与直接使用1倍相位差测量值的常规干涉仪解模糊测角方法不同,该方法利用多次测量的无模糊1倍相位差测量值来构造相位矢量,对其进行矢量平均处理,提高1倍相位差的... 相似文献
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分数倍抽样率转换器的时变网络结构及其FPGA实现 总被引:4,自引:0,他引:4
提出了分数倍抽样率转换器的高效时变网络结构的设计方法,并用现场可编程门阵列(FPGA)实现.通过对分数倍抽样率转换器的多相结构与时变网络结构的比较,指出在实现分数倍抽样率转换器时,时变网络结构克服了分数延迟的问题,结构简单;整个设计采用并行工作方式以提高系统的运算速度;采用低抽样率下进行滤波运算,从而大大降低了运算量.以I/D=256/1 023倍抽样率转换器为例,用FPGA XC2V250-5来实现时变网络结构的设计,芯片利用率为61%,最高工作频率可达92.225 MHz. 相似文献
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空间交会对接微波雷达采用基于延迟锁定环(DDLL)、锁频环(FLL)和锁相环(PLL)的算法处理合作目标转发的直接序列扩频信号,获得入射信号的时延、频率及波达角(DOA)估计。针对当前基于DDLL, FLL和PLL(DFP)的算法没有充分利用接收信号有效信息的问题,该文提出一种基于极大似然估计(MLE)的低代价闭环跟踪(MLBT)算法。该算法利用代价函数的梯度正比于参数误差的特性,设计了参数误差鉴别器。在此基础上给出了相应的扩频信号多参数跟踪环路。分析并验证了鉴别器的方差特性,从而给出MLBT算法的参数估计均方根误差(RMSEs)下限。仿真实验验证了对MLBT算法参数估计均方根误差下限分析的正确性。此外仿真结果表明,MLBT算法相比DFP算法有限地增加运算量,同时获得了更优的参数估计性能。 相似文献
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多载波发射机设计与实现 总被引:1,自引:0,他引:1
根据目前常见的几种发射机结构,针对TETRA数字集群通信系统提出发射机指标,设计了一种数字中频发射机。该发射机可以实现多载波信号宽带发射,并且通过采用数字预失真(DPD)技术大大降低对发射机射频模块和功率放大器的要求。 相似文献
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A generalized ionospheric dispersion simulation method is presented to verify and test wideband satellite-ground-link radio systems for dispersion robustness. In the method, ionospheric dispersive effects on wideband radio waves are modeled as an allpass nonlinear phase system, thus greatly decreasing the need for signal priori information. To accurately simulate the ionospheric dispersion and reduce the implementation complexity, the system is decomposed into three new allpass subsystems: with a linear phase passing through zero frequency, a constant phase, and a nonlinear phase with zero-offset and quasi-parabolic form respectively. The three subsystems are implemented respectively by the combination of integer-interval delay and fractional delay filter, digital shifting phase and the complex-coefficient finite impulse response (FIR) filter. The ionospheric dispersion simulation can be achieved by cascading the three subsystems in a complex baseband and converting the frequency to a radio frequency. Simulation results show that the method has the ability to accurately simulate the ionospheric dispersion characteristics without knowing the signal priori information and has a low implementation complexity. 相似文献