共查询到20条相似文献,搜索用时 46 毫秒
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针对高速高动态接收机在长伪码周期、大频偏情况下的快速捕获问题,该文提出一种基于码相位压缩相关器与快速傅里叶变换(CCPC-FFT)的双驻留伪码快速捕获方法。在第一驻留阶段,利用码相位压缩相关器对相邻码相位进行快速、粗略的压缩搜索,同时利用FFT算法完成对多普勒频偏的并行捕获;在第二驻留阶段,利用传统的相关积分方法对第一驻留捕获的所有码相位进行逐个精确搜索。给出了系统性能的理论分析模型,并通过蒙特卡洛仿真验证了理论分析的正确性。最后仿真结果表明:新方法在平均捕获时间上比2维压缩相关(TDCC)捕获方法进一步缩短,同时提高了频偏的捕获带宽和精度,且针对长码的捕获比其他基于FFT的方法节省资源。 相似文献
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Many investigations of hybrid selection (HS) diversity assume maximal ratio combining (MRC) of the selected branches. However, a coherent detector needs to dwell on the received signal for some time before it can produce accurate channel estimates for fading compensation, a requirement that appears inconsistent with the branch switching that occurs in a selection diversity receiver. Motivated by this observation, we derive in this letter analytical results on the switching rate and average dwell time of a selection diversity receiver where M out of a total of N independent branches are selected for combining. We show that the switching rate can be many times the Doppler frequency, while the average dwell time can be a small fraction of the reciprocal Doppler frequency. The brevity of the dwell times suggests difficulty in obtaining channel state information, which in turn calls into question performance analyses of idealized HS/MRC structures. Our results also suggest that HS/MRC should be frame-based, rather than continuously acting in time 相似文献
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针对载波多普勒下的伪码捕获问题,分析了基于分段相关-视频积累方法的多驻留伪码捕获系统的最优性能。推导了正交双通道检测器的检测概率和虚警概率表达式,给出了多驻留系统的捕获时间均值表达式;通过采用遗传算法对系统进行优化设计,增大了系统的多普勒容限,降低了捕获时间;分析了驻留级数、多普勒和载噪比等对捕获系统性能的影响。研究成果可用于指导扩频系统接收机伪码捕获模块的设计。 相似文献
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Handover request queueing has been extensively analyzed as a handover protection scheme for future cellular networks. In this frame, however, while channel holding time distribution and cell boundary crossing rate have been modeled, the distribution of the allowed queue waiting time-i.e., the handover dwell time-has remained an open question from the modeling standpoint. In this frame, this paper proposes a model of the handover dwell time in circular cells' coverage. The agreement between modeling and simulation results is very satisfactory. A fitting of an asymptotic behavior of the handover dwell-time distribution with a truncated Gaussian function is also provided, measuring the fitting goodness in various test cases. The practical insights the model can provide are also outlined in the paper 相似文献
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This paper is concerned with the problem of delay-dependent stability analysis for a class of two-dimensional (2D) discrete switched systems described by the Roesser model with state delays. First, the concept of average dwell time is extended to 2D switched systems with state delays. Then, based on the average dwell time approach, a delay-dependent sufficient condition for the exponential stability of the addressed systems is derived. All the results are formulated in terms of linear matrix inequalities (LMIs), which can be solved efficiently. A numerical example is given to illustrate the effectiveness of the proposed method. 相似文献
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Xian Wang Pingzhi Fan 《Communications Letters, IEEE》2007,11(2):158-160
Channel holding time is fundamental to teletraffic analysis of wireless cellular networks. This quantity depends on user's mobility which can be characterized by the dwell time, and the traffic model which is associated with the unencumbered session time. In this paper, under a general assumption on the distributions of unencumbered session time and dwell time, the characteristics of new call channel holding time and handoff call channel holding time are investigated. Analytical formulae for the distributions of new call channel holding time and handoff call channel holding time are derived 相似文献
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Multiple Dwell Serial Search: Performance and Application to Direct Sequence Code Acquisition 总被引:1,自引:0,他引:1
The technique of multiple dwell serial search is described and analyzed. The advantage of the multiple dwell procedure is that the examination interval need not be fixed, allowing incorrect cells to be quickly discarded, which in turn results in a shorter search time than is possible with a fixed dwell time procedure. This type of search scheme is particularly useful for direct sequence code acquisition in a spread-spectrum communication system. An expression for the generating function is obtained from a flow graph representation of the multiple dwell technique. The generating function is used to develop expressions for the mean and variance of the search time in terms of the following parameters: the dwell times, the detection probability, the false alarm probability, and the false alarm penalty time. Coherent detector characteristics are then used to investigate the performance of the multiple dwell technique for direct sequence code acquisition. It is shown that the multiple dwell procedure can significantly reduce the expected acquisition time from that obtained with a single dwell system. The most significant improvement is obtained by using a two-dwell system. Additional but nominal improvement is gained when more than two dwells are employed. 相似文献
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针对相控阵雷达波束快速扫描能力,提出了一种基于时间指针的相控阵雷达在线脉冲交错调度算法。首先建立了雷达驻留任务模型并分析了调度约束条件,然后引入时间指针来指向当前调度分析时刻,分别从波束的角度和脉冲的角度分析了驻留任务交错的几种方式,并给出了三种脉冲重叠方式的时间约束条件,最后在满足时间和能量资源约束的条件下,选取综合优先级最高的雷达驻留任务进行调度。仿真结果表明,与基于收益的调度算法相比,此算法能有效地降低任务丢失率,提高时间利用率和能量利用率。 相似文献
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根据数字阵列雷达的信号处理特征,提出了一种应用于数字阵雷达的波束驻留调度算法.该调度算法以一种在线脉冲交错技术为基础,它使得不同的驻留任务能在满足系统时间和能量资源约束的条件下交错执行,其中,驻留等待期可用来执行其它驻留的发射或接收子任务且不同驻留任务的等待期可在时间上相互重叠.仿真结果表明,由于驻留任务等待期和接收期的充分利用,与传统波束驻留调度算法相比,此算法能有效地降低各类任务丢失率,从而获得更高的系统实现价值率. 相似文献
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该文针对机载组网雷达,在单目标跟踪场景下,研究了雷达辐射参数与航迹规划联合优化问题。首先,推导了包含各雷达辐射功率、驻留时间、发射信号高斯脉冲长度和信号带宽等射频辐射参数以及各载机速度、朝向角等平台运动参数的贝叶斯克拉默-拉奥下界(BCRLB)表达式,以此作为表征目标跟踪精度的衡量指标;推导了含有各雷达辐射功率、驻留时间等射频辐射参数以及各载机速度、朝向角等平台运动参数的机载组网雷达被截获概率,以此作为表征机载组网雷达射频隐身性能的衡量指标。在此基础上,建立了面向目标跟踪的机载组网雷达辐射参数与航迹规划联合优化模型,以最小化机载组网雷达的目标估计误差BCRLB为优化目标,以满足给定的系统射频资源、载机机动能力和预先设定的被截获概率阈值为约束条件,对各载机飞行速度、朝向角以及各机载雷达辐射功率、驻留时间、发射信号高斯脉冲长度和信号带宽进行联合优化设计,以提升机载组网雷达的目标跟踪精度。最后,针对上述优化问题,结合粒子群算法,采用5步分解迭代算法进行求解。仿真结果表明,与现有算法相比,所提算法能够在满足一定射频隐身性能要求的条件下,有效提升机载组网雷达的目标跟踪精度。 相似文献
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针对复杂环境下对低可观测运动目标探测的迫切需求,该文在系统回顾近几年频控阵雷达国内外发展现状、频控阵雷达阵列结构设计及波束形成、距离和角度的联合估计等技术的基础上,提出了基于空距频聚焦的频控阵雷达信号新方法。充分利用频控阵雷达提供的发射波形自由度、阵元位置自由度、波束方位与距离相关性以及凝视观测的特点,即在空间(角度)、距离和频率(多普勒)的灵活自由度和能量集性,实现空-距-频聚焦和联合参数估计。仿真分析表明该方法具有提高复杂环境下雷达微弱动目标检测和参数估计的潜力,在杂波和干扰抑制、动目标精细化处理等方面有广阔的应用前景。 相似文献
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A 2-D random-walk mobility model for location-management studies in wireless networks 总被引:3,自引:0,他引:3
In this work, a novel two-dimensional (2-D) random-walk mobility model is proposed, which can be used for studying and analyzing the location-area crossing rate and dwell time of mobile users in wireless networks. The development and application of the model under two cell structures, namely the square and hexagon cells, have been detailed. The analytical results obtained for location-update rates and dwell times have been validated using simulated and published results. The highlights of the model are its simplicity, minimal assumptions, and adaptability to conduct both "location-crossing rate" and "dwell-time" studies using the same model with slight modifications for either the square or hexagon cells. Using symmetry of mobile-user movement, a reduced number of computational states was achieved. A novel wrap-around feature of the model facilitates reduced assumptions on user mobility, which has also resulted in considerably reduced mathematical computation complexity. A regular Markov chain model was used for computing the average location-area crossing rate. A slightly modified model with absorbing states was used to derive the dwell time. This is the first model of its kind that can be used for studying area-crossing rates. To further emphasize the flexibility of the model, we have extended the model to study an overlapped location-area strategy. The study and analysis of overlapped locations areas has hitherto been difficult due to the complexity of the models. 相似文献
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旋翼目标是机载毫米波脉冲多普勒雷达低空与地面目标中的首要识别对象,由于其回波频谱展宽与波长成近似反比关系,使其在毫米波段呈现低信杂比、弱特征现象。本文首先在分析毫米波雷达旋翼目标特性的基础上,针对旋翼识别难题,对雷达系统前端的波束驻留时间、脉冲重复周期、杂波抑制性能、相参积累脉冲数、频综器相位噪声谱密度等参数设计提出了新的要求;之后,设计了专用目标识别软件平台,并给出了面向工程应用的专用目标识别软件总体结构,提出了利用噪声归一化的频谱数据预处理技术、识别结果积累策略以及多普勒频谱层析图分析等信号处理方法;最后,利用实测数据提取特定的特征对目标进行识别分类,并对部分中间结果进行了详细分析,实验结果验证了本文方法的有效性,对旋翼和固定翼目标具有良好的分类识别性能。 相似文献
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编队飞机由于间距很小,常规低分辨雷达无法直接从距离和方位上分辨架次.本文提出一种基于距离—多普勒二维联合处理的群目标分辨方法.发射线性调频脉冲信号,将观测时间内的若干次回波在距离维和多普勒维分别转换为单频信号的叠加,再联合距离-多普勒二维信息估计协方差矩阵,用超分辨信源数估计算法——新的改进盖氏圆盘法分辨目标架次.这种方法可以直接地给出判决结果,适用于各种飞行状态、低信噪比环境或波束驻留时间较短的情况,而且和重频参差工作模式相兼容,尤其适合中、高重频工作方式. 相似文献