声源定位中的时延估计方法研究

时延估计是传声器阵列信号处理中的一项关键技术,其目的是估计出同源信号到达不同传声器时,由于传输距离不同而引起的时间差。首先对常用的多种基于时延估计算法进行了论述,并对具有代表性的3种TDE方法进行了仿真,通过综合比较揭示了各自的优缺点,最后给出了进一步的研究方向。     

A Cooperative Relay Selection for Two-Way Cooperative Relay Networks in Nakagami Channels

We investigate the performance of the best-worse relay selection strategy in a two way cooperative non-regenerative relay network, where the relay is selected to maximize the worst Signal to Noise Ratio (SNR) of two links. In contrast to existing work, we aim to provide a theoretical performance analysis for this scheme under the more practical Nakagami channel. Closed-form expression of the probability density function for the SNRs of both two links is derived, based on which the outage probability of the best-worse relay selection is obtained. It is shown that the best-worse relay selection scheme achieves full diversity gain. Furthermore, the asymptotic packet error ratio with SNR increasing is also analyzed through rigorous derivations. The accuracy of our derivation is validated by computer simulations.     

放大转发协同OFDM系统中的时域信道估计算法

考虑到在复杂街区环境中由于距离太远或者障碍物阻挡等原因,造成源节点和目的节点之间没有直接链路,而是利用多个中继进行协同传输的情景,该文针对放大转发协同OFDM系统,提出了一种时域信道估计算法。不同于传统的频域信道估计,该文利用一种特殊的梳状导频以及在中继节点上对导频做简单变换,通过时域的相关处理估计源节点经每一个中继节点到目的节点之间的等效信道冲激响应。在此基础上,为减小来自中继节点和目的节点的等效噪声对信道估计性能的影响,提出了时域LMMSE（Linear Minimum Mean Square Error）估计以及其简化形式,并推导了相应的Cramér-Rao界（CRB）。仿真结果表明,该文算法具有较好的均方误差性能;与直接时域信道估计相比,该文提出的简化时域LMMSE估计更接近于CRB。      

Time Delay Estimation Based on Entropy Estimation

Abstract--This paper presents a novel time delay estimation （TDE） method using the concept of entropy. The relative delay is estimated by minimizing the estimated joint entropy of multiple sensor output signals. When estimating the entropy, the information about the prior distribution of the source signal is not required. Instead, the Parzen window estimator is employed to estimate the density function of the source signal from multiple sensor output signals. Meanwhile, based on the Parzen window estimator, the Renyi＇s quadratic entropy （RQE） is incorporated to effectively and efficiently estimate the high-dimensional joint entropy of the multichannel outputs. Furthermore, a modified form of the joint entropy for embedding information about reverberation （multipath reflections） for speech signals is introduced to enhance the estimator＇s robustness against reverberation.     

无线中继网络中基于矩阵几何方法的统一延时分析

A lot of work has been focused on designing and analyzing various cooperative diversity protocols for wireless relay networks. To provide a unified queuing analytic framework, we formulate an embedded Markov chain, which turns out to be a Quasi-Birth-and-Death (QBD) process. Using the Matrix-Geometric method, we can analyze the average delay in a unified way. Theoreti-cal analysis is validated by simulation results. We show that the delay performances of Amplify-and-Forward or Decode-and-Forward (AF/DF) and incremental AF/DF schemes can be analyzed in the unified way. Thus, we can always choose the best cooperative diversity scheme in different scenarios for delay minimization.     

An Energy-Efficient Relay Selection Strategy Based on Optimal Relay Location for AF Cooperative Transmission

In this paper, an energy-efficient optimal relay selection strategy which is jointly optimized with the energy-efficient optimal power allocation scheme for AF cooperative transmission is proposed. The relay selection criterion is the distance from the potential relay to the corresponding optimal relay locations where the minimum transmission power of the source, the relay or their total can be achieved. In order to determine the optimal relay locations, a universal algorithm with low computational complexity and easy implementation is also presented. Simulations are conducted to validate our theoretical analysis. The results show that with the relay selected by the proposed strategy, the cooperative transmission can achieve considerably high energy-efficiency.     

多用户环境下定位精度的克拉美罗下限 与时延估计算法

本文针对码分多址(CDMA)系统,推导了基于到达时间(TOA)的移动台定位所具有的估计精度下限,给出了定位估计精度下限推导的具体步骤和下限表达式,分析了该下限所具有的物理意义,得到了定位精度下限与用户数无关的结论.同时,提出了在长码扩频条件下能够抑制多址干扰(MUI)的时延估计算法,进一步说明了精度下限的物理含义.最后在仿真的基础上对估计下限和新算法的性能进行了讨论.     

协作网络中基于中继选择的协作波束赋形算法

针对多中继网络中所有中继节点都参与协作的协作波束赋形方法,提出了一种基于选择的协作波束赋形算法。该方法将最小化系统中断概率作为目标,得到一个次优的中继节点选择门限,小于门限的中继节点被逐一剔除,从而保证了网络中的资源只分配给有用的中继节点,获得了分集增益。该选择方法需搜索次数和中继节点的个数相等,因此大幅降低了选择过程的复杂度。蒙特卡洛仿真表明,选择波束赋形算法可有效提高系统中断概率性能和网络能量效率。     

Cooperative Connectivity Models for Wireless Relay Networks

This paper considers the ways that cooperating terminals can be connected to each other in wireless relay networks and the constraints imposed by the availability of different system resources. A framework is developed that exposes the relationship between constraints on available system resources and the achievable combinations of communication links between cooperating terminals. Cooperative connectivity models defined by the achievable combinations of links are derived, associated with their minimum cost constraint sets, and mapped to diversity techniques presented in the literature. The constraints considered are the available number of orthogonal relaying channels, the ability of terminals to diversity combine signals on a single common channel, the ability of terminals to diversity combine signals on orthogonal channels, the ability of terminals to transmit signals on multiple orthogonal channels, and the ability of terminals to cancel the effects of interhop interference.     

协作分集中基于延迟时间的伙伴选择

在协作分集中如何及时有效选取合作伙伴是重点研究问题之一,制定一个合理可靠的选择标准是解决此问题的关键。依据传输路径的时延特性,提出以中继延迟时间最小为标准来进行协作伙伴的选择。对此选择标准在分集增益、信噪比、传输误比特率性能上进行了仿真分析,表明以此标准选择协作伙伴能够获得较好的分集性能,降低误码率,并且能够避免目的节点处因同时接收中继节点信息而造成干扰阻塞,是一种可靠的伙伴选择协议。     

Performance Modeling for Relay Cooperation in Delay Tolerant Networks

Delay tolerant networks (DTNs) rely on the mobility of nodes and sequences of their contacts to compensate for lack of continuous connectivity and thus enable messages to be delivered from end to end in a “store-carry-forward” way, where multiple relay nodes are usually employed in the message delivery process. In this paper, we focus on such relay cooperation and analytically explore its impact on the delivery performance in DTNs. Specifically, we first develop a continuous time Markov chain-based theoretical framework to model the complicated message delivery process in delay tolerant networks adopting the two-hop relay algorithm. We then derive closed-form expressions for both the expected delivery delay and the corresponding expected delivery cost, where the important relay behaviors of forwarding traffic for itself or for other nodes are carefully incorporated into the analysis.     

Cooperative Strategies and Capacity Theorems for Relay Networks

Coding strategies that exploit node cooperation are developed for relay networks. Two basic schemes are studied: the relays decode-and-forward the source message to the destination, or they compress-and-forward their channel outputs to the destination. The decode-and-forward scheme is a variant of multihopping, but in addition to having the relays successively decode the message, the transmitters cooperate and each receiver uses several or all of its past channel output blocks to decode. For the compress-and-forward scheme, the relays take advantage of the statistical dependence between their channel outputs and the destination's channel output. The strategies are applied to wireless channels, and it is shown that decode-and-forward achieves the ergodic capacity with phase fading if phase information is available only locally, and if the relays are near the source node. The ergodic capacity coincides with the rate of a distributed antenna array with full cooperation even though the transmitting antennas are not colocated. The capacity results generalize broadly, including to multiantenna transmission with Rayleigh fading, single-bounce fading, certain quasi-static fading problems, cases where partial channel knowledge is available at the transmitters, and cases where local user cooperation is permitted. The results further extend to multisource and multidestination networks such as multiaccess and broadcast relay channels.     

Relay Selection for Secure Cooperative Networks with Jamming

This paper deals with relay selection in cooperative networks with secrecy constraints. The proposed scheme enables an opportunistic selection of two relay nodes to increase security against eavesdroppers. The first relay operates as a conventional mode and assists a source to deliver its data to a destination via a decode-and-forward strategy. The second relay is used in order to create intentional interference at the eavesdropper nodes. The proposed selection technique jointly protects the primary destination against interference and eavesdropping and jams the reception of the eavesdropper. The new approach is analyzed for different complexity requirements based on instantaneous and average knowledge of the eavesdropper channels. In addition an investigation of an hybrid security scheme which switches between jamming and non-jamming protection is discussed in the paper. It is proven that an appropriate application of these two modes further improves security. The enhancements of the proposed selection techniques are demonstrated analytically and with simulation results.     

Competitive Resource Sharing Based on Game Theory in Cooperative Relay Networks

This letter considers the problem of resource sharing among a relay and multiple user nodes in cooperative transmission networks. We formulate this problem as a sellers’ market competition and use a noncooperative game to jointly consider the benefits of the relay and the users. We also develop a distributed algorithm to search the Nash equilibrium, the solution of the game. The convergence of the proposed algorithm is analyzed. Simulation results demonstrate that the proposed game can stimulate cooperative diversity among the selfish user nodes and coordinate resource allocation among the user nodes effectively.     

七元空间声阵应用时延估计定位的研究

弹丸在出膛和空中飞行时处于超声速运动状态.根据声学原理,可以利用超声速运动物体产生的激波来对其进行空间定位和跟踪.针对五元空间声阵存在定位精度较差等问题,提出了一种七元空间声阵探测的模型,以及利用被动声时延估计原理进行推导的定位算法.结合了七元空间声阵和五元空间声阵推导出的定位算法,分别利用同一组理想定点代入定位算法进...     

基于高斯小波变换的时延估计

在假设噪声为高斯白噪声的前提下构造相移滤波器,并证明原始信号经过它的输出（时延判定函数）的高阶导数不仅在时延处取到最大值而且具有较低的旁瓣;又利用时延判定函数的阶高斯变换恰好与其阶导数的磨光化成比例以及光滑信号与高斯白噪声的高斯小波变换系数的不同而设计了时延估计算法;最后给出仿真实例并收到了较好的效果。     

基于三阶累积量的多径时延估计

研究多径传输条件下的时延估计问题。利用三阶累积量的一维切片作为高阶统计量,结合相关算法原理,提出一种新的时延估计算法。为提高时延估计精度,对相关数据进行了加权处理。该算法可有效抑制空间相关高斯噪声或对称分布噪声,得到非高斯信号准确的时延估计。算法具有计算量小,易于实现的优点。仿真结果表明了该算法的有效性。     

基于HHT时频图的时延估计方法

时延估计方法主要有广义相关法、相位数据法以及自适应时延估计法等。对于水中爆炸冲击波这种瞬态、非平稳信号的时延估计,常用的时延估计方法存在一定的误差。针对爆炸冲击信号的特征,利用HHT变换在处理非平稳信号的优势,提出了一种基于希尔伯特黄时频图的时延估计方法。该方法首先将信号进行EMD分解,然后得出爆炸信号的时频图,最后根据时频图中能量最大的频率所对应的时间得出时延估计。仿真实验表明,该方法能够有效、精确地对爆炸冲击信号进行时延估计。     

Optimal Power Control in Cooperative Relay Networks Based on a Differential Game

In this paper, the optimal power control problem in a cooperative relay network is investigated and a new power control scheme is proposed based on a non‐cooperative differential game. Optimal power allocated to each node for a relay is formulated using the Nash equilibrium in this paper, considering both the throughput and energy efficiency together. It is proved that the non‐cooperative differential game algorithm is applicable and the optimal power level can be achieved.     

Multiple Relay Selection Based on Game Theory in Cooperative Cognitive Radio Networks

Due to the inefficiency of traditional fixed spectrum allocation policies, the paradox of apparent spec-trum scarcity occurs while most of the bands are under-utilized. This has prompted proposals for Dynamic spec-trum sharing (DSS), which explains why Cognitive radio network (CRN) has been widely accepted as a promising approach to settle inefficient usage of scarce available radio spectrum. As a subset of DSS, Dynamic spectrum leasing (DSL) strategy has been proposed based on game idea, where Primary user (PU) has an incentive to allow Cog-nitive users (CUs) to access its licensed spectrum for a fraction of time in exchange for revenue. This paper pro-poses an approach, named multiple relay selection based on Game theory (GTMRS), to optimize the utilities of PU and CUs as a whole, where a pricing-based spectrum leas-ing mechanism is applied. While the parameter price c is jointly determined by PU and CUs, all selected cognitive user's optimal cooperative powers can be satisfied through a non-cooperative game among themselves. Numerical re-sults show that more CUs are involved in the cooperation and both utilities of PU and CUs as a whole are improved, which means the whole system throughput is increased.