Optimal signaling and detector design for M-ary communication systems in the presence of multiple additive noise channels

An M-ary communication system is considered in which the transmitter and the receiver are connected via multiple additive (possibly non-Gaussian) noise channels, any one of which can be utilized for the transmission of a given symbol. Contrary to deterministic signaling (i.e., employing a fixed constellation), a stochastic signaling approach is adopted by treating the signal values transmitted for each information symbol over each channel as random variables. In particular, the joint optimization of the channel switching (i.e., time sharing among different channels) strategy, stochastic signals, and decision rules at the receiver is performed in order to minimize the average probability of error under an average transmit power constraint. It is proved that the solution to this problem involves either one of the following: (i) deterministic signaling over a single channel, (ii) randomizing (time sharing) between two different signal constellations over a single channel, or (iii) switching (time sharing) between two channels with deterministic signaling over each channel. For all cases, the optimal strategies are shown to employ corresponding maximum a posteriori probability (MAP) decision rules at the receiver. In addition, sufficient conditions are derived in order to specify whether the proposed strategy can or cannot improve the error performance over the conventional approach, in which a single channel is employed with deterministic signaling at the average power limit. Finally, numerical examples are presented to illustrate the theoretical results.     

Optimal channel switching in multiuser systems under average capacity constraints

In this paper, the optimal channel switching problem is studied for average capacity maximization in the presence of multiple receivers in the communication system. First, the optimal channel switching problem is proposed for average capacity maximization of the communication between the transmitter and the secondary receiver while fulfilling the minimum average capacity requirement of the primary receiver and considering the average and peak power constraints. Then, an alternative equivalent optimization problem is provided and it is shown that the solution of this optimization problem satisfies the constraints with equality. Based on the alternative optimization problem, it is obtained that the optimal channel switching strategy employs at most three communication links in the presence of multiple available channels in the system. In addition, the optimal strategies are specified in terms of the number of channels employed by the transmitter to communicate with the primary and secondary receivers. Finally, numerical examples are provided in order to verify the theoretical investigations.     

冷/温混合贮备系统最优切换及视情维修决策

针对周期性切换冷/温混合贮备系统,研究其最优切换以及视情维修决策,在系统劣化建模的基础上,分析系统结构和切换式运行维修特性,制定基于周期切换和检测的离线视情维修策略.首先,通过分析系统运行与备用设备交替使用、维修过程中的状态转移特性,推导各检测周期时刻系统状态概率分布模型以及各维修活动的概率;然后,以系统有限时间范围内平均费用率最小为目标建立解析优化模型,以决策最优切换周期和维护阈值,并采用遗传算法对模型进行求解;最后,以汽轮发电机定子冷却水泵系统为对象验证策略和模型的正确性和有效性,并对参数进行灵敏度分析.实验结果表明,所提出离线视情维修策略能够有效地降低系统的维修成本.     

Dynamic Output Feedback Control of Switched Linear Systems

This paper is devoted to stability analysis and control design of switched linear systems in both continuous and discrete-time domains. A particular class of matrix inequalities, the so-called Lyapunov--Metzler inequalities, provides conditions for open-loop stability analysis and closed-loop switching control using state and output feedback. Switched linear systems are analyzed in a general framework by introducing a quadratic in the state cost determined from a series of impulse perturbations. Lower bounds on the cost associated with the optimal switching control strategy are derived from the determination of a feasible solution to the Hamilton--Jacobi--Bellman inequality. An upper bound on the optimal cost associated with a closed-loop stabilizing switching strategy is provided as well. The solution of the output feedback problem is based on the construction of a full-order linear switched filter whose state variable is used by the mechanism for the determination of the switching rule. Throughout, the theoretical results are illustrated by means of academic examples. A realistic practical application related to the optimal control of semiactive suspensions in road vehicles is reported.     

基于开关矩阵的多通道信号切换设备研制

为提高多通道信号系统的硬件资源利用率和信道切换效率,使用AD75019型宽信号范围模拟开关矩阵为核心设计了一款信号切换设备;设备支持外接电源和内置电池的双电源供电模式,并可通过触摸式液晶屏完成通道间连接状态的配置,确保了设备使用的便利性和灵活性;同时接口采用了高密度接插件进一步减小了设备的体积和重量,提高了产品的便携性;测试试验证明,信号切换设备实现了 32输入至32输出通道之间任意组合的连接和切换,且配置完成后的通道切换响应时间小于100 ms,使用该设备避免了多通道信号系统中整理线缆和插拔接口的工作,能够显著的提高系统的信道切换效率和配对可靠性,可广泛应用于大型测量、控制和试验系统中.     

多信道无线通信功率分配的最优化决策

研究了基于有损Gilbert-Elliott信道的多信道无线通信功率分配的最优化决策问题,利用部分可观测的马尔可夫决策过程（POMDP）和数学语言建立并描述理论模型,提出了具有一般性的功率分配方案,并给出问题的最优决策的各项性质和特征。在三维信道的通信系统上,进一步给出最优决策的空间结构,利用线性规划仿真验证了其正确性,并分析了最优决策随信道转移概率的变化趋势。     

基于分簇和Stackelberg博弈的D2D资源分配策略

当前,车辆密集通信场景下存在通信资源利用率低、DUE(D2D user)用户通信质量差等问题。针对上述问题,提出了一种基于分簇和Stackelberg博弈的D2D(device to device)资源分配策略,以解决DUE用户功率分配、信道匹配问题。首先,基于每个信道内DUE用户之间干扰最小原则,该模型对所有DUE用户进行分簇;然后,对于CUE(cellular user)用户与DUE用户簇,构建一对多的Stackelberg主从博弈模型,通过复用链路干扰参数和簇内干扰参数的迭代更新,优化每个DUE用户的发射功率;最后,利用匈牙利算法实现DUE用户簇与CUE用户的最佳信道匹配,最大化DUE用户的容量和。仿真结果表明,与基于价格迭代、等功率分配和高能效干扰约束的几种功率分配算法相比,所提算法能有效提升DUE用户的总容量。     

A new joint strategy of radio channel allocation and power control for wireless mesh networks

For wireless mesh networks, it is critical to allocate the limited number of radio channels efficiently while mitigating the co-channel inference to improve network performance. For this reason, after extensively reviewing the related work, we present a new joint radio channel allocation (RCA) and power control (PC) strategy for wireless mesh networks. First, we formulate the RCA problem as a multiple objective optimization problem, with the constraints of transmission power and traffic data rates, while effective channel utilization (ECU) is chosen as the target metric for optimization. Second, we incorporate the channel status into the model of MAC protocols, including as signal-to-noise ratio (SNR) and transmission power. Consequently, the PC is incorporated into the ECU for channel allocation. Third, we propose to directly maximize the ECU to find both optimal radio channel and transmission power. The resulting strategy is a fully distributed RCA/PC algorithm without relying on a coordination mechanism among mesh routers. Our extensive simulation results have demonstrated that the proposed algorithm significantly outperforms the existing RCA strategies and the standard MAC protocols in performance such as throughput, packet dropping, delay and delay jitter.     

Dependent data broadcasting for unordered queries in a multiple channel mobile environment

Data broadcast is a promising technique to improve the bandwidth utilization and conserve the power consumption in a mobile computing environment. In many applications, the data items broadcast are dependent upon one another. However, most prior studies on broadcasting dependent data are restricted to a single broadcast channel environment, and as a consequence, the results are of limited applicability to the upcoming mobile environments. In view of this, we relax this restriction and explore the problem of broadcasting dependent data in multiple broadcast channels. By analyzing the model of dependent data broadcasting, we derive several theoretical properties for the average access time in a multiple channel environment. In light of the theoretical results, we develop a genetic algorithm to generate broadcast programs. Our experimental results show that the theoretical results derived are able to guide the search of the genetic algorithm very effectively, thus leading to broadcast programs of very high quality.     

无线网络中具有信道感知的期望能耗最小化策略研究

随着无线网络技术的快速发展,节省能耗已成为构建绿色无线网络的一个非常重要的课题。由于信道的时变特性,在无线通信中利用好的信道状态能够获得更高的能量利用率。从整个无线网络的数据传输能耗出发,提出一种基于最优停止理论的数据传输期望能耗最小化策略(E²CMS)。E²CMS策略延迟数据的传输直到找到最好的期望信道状态,同时考虑了最大传输延迟和给定的接收端功率。首先,构建具有QoS约束的能耗最小化问题;接着,通过最优停止理论证明E²CMS策略是一种纯粹的阈值策略;然后,通过逆向归纳法求解定点方程,以求出功率阈值;最后,在典型的小尺度衰落信道模型中进行仿真实验,将E²CMS策略与多种不同的传输调度策略进行对比。结果表明,E²CMS策略具有更小的单位数据平均能耗,显著提高了网络性能。     

相依多模失效下冷贮备系统最优切换及视情维护决策

针对存在冲击影响的冷贮备系统,研究其最优切换及视情维护决策问题.首先,在系统结构和切换式运行和维护特性分析的基础上,制定基于周期切换和状态检测的切换式离线视情维护策略;其次,建立累积冲击过程影响下系统退化所致的软失效和极端冲击过程所致的硬失效竞争可靠性模型;再次,通过分析两类冲击过程影响下系统运行与备用设备交替使用、维修过程中的状态转移特性,重点推导各检测周期时刻系统状态概率分布的迭代计算模型;然后,以系统平均费用率最小为目标,建立解析决策模型,以求解系统的最优切换周期和维护阈值.最后,以矿井主通风系统为案例验证策略及模型的有效性,并分析模型对参数的灵敏度.结果表明,系统的最优维修策略随机冲击影响的不同而变化显著.     

Hybrid circuit-switched network for on-chip communication in large-scale chip-multiprocessors

Large-scale chip-multiprocessors (CMPs) need a scalable communication structure characterized by low cost, low power, and high performance to meet their on-chip communication requirements. This paper presents a hybrid circuit-switched (HCS) network for on-chip communication in the large-scale CMPs. The HCS network, which is Advanced Microcontroller Bus Architecture (AMBA) compatible, is composed of bufferless switches, pipeline channels, and network interfaces. Furthermore, packets are transferred in a hybrid transmission scheme. If a message has only one packet, the transmission scheme for this message is packet switching. Conversely, if a message contains multiple packets, the transmission scheme for this message is circuit switching. We evaluate HCS networks with different channel depths and then compare the HCS network with the Stanford elastic buffer (EB) network. Our results show that the HCS network with two-depth channel requires 83% less power and occupies 32% less area compared with the EB network. Furthermore, under maximum frequency and single traffic, the HCS network with two-depth channel provides 37% lower zero-load latency, 390% higher maximum throughput per unit power, and 19% higher maximum throughput per unit area compared with the EB network.     

Adaptive Distributed Dynamic Channel Allocation for Wireless Networks

Channel allocation schemes in a mobile computing (wireless) environment can be either static or dynamic. Static allocation offers negligible channel acquisition time and zero message complexity and works well at a low system load; the performance steadily decreases as system load increases since many calls are dropped. In the case of even temporary hot spots many calls may be dropped by a heavily loaded switching station even when there are enough idle channels in the interference region of that station. On the other hand, dynamic schemes provide better utilization of the channels at higher loads albeit at the cost of higher channel acquisition time and some additional control messages. Our purpose in the present paper is to propose a combined channel allocation scheme so that each switching station can tune to its own load independent of other stations in its interference region; the objective is to minimize the call drop rate and at the same time maintain a minimum average channel acquisition time and minimum control message complexity.     

蓝牙数据广播性能分析与自适应分组选择策略

分析了蓝牙GFSK调制方式在加性高斯白噪声信道(AWGN)下的比特错误率(BER)与平均接收信噪比的关系,推导了ACL数据分组的重传概率与平均接收信噪比的函数表达式,并且计算出了各个数据分组在不同信噪比的情况下广播重传次数和传输吞吐量.为了提高蓝牙在噪声环境下的广播性能,提出了一种自适应数据分组选择策略,通过在不同的信噪比情况下选择合适的分组类型进行广播而获得最大的广播吞吐量,给出了分组类型切换的信噪比门限值.仿真计算结果表明了该策略的有效性.     

Optimal transmission schemes for parallel and fading Gaussian broadcast channels with an energy harvesting rechargeable transmitter

We consider an energy harvesting transmitter sending messages to two users over parallel and fading Gaussian broadcast channels. Energy required for communication arrives (is harvested) at the transmitter and a finite-capacity battery stores it before being consumed for transmission. Under off-line knowledge of energy arrival and channel fading variations, we obtain the trade-off between the performances of the users by characterizing the maximum departure region in a given interval. We first analyze the transmission with an energy harvesting transmitter over parallel broadcast channels. We show that the optimal total transmit power policy that achieves the boundary of the maximum departure region is the same as the optimal policy for the non-fading broadcast channel, which does not depend on the priorities of the users, and therefore is the same as the optimal policy for the non-fading scalar single-user channel. The optimal total transmit power can be found by a directional water-filling algorithm. The optimal splitting of the power among the parallel channels is performed in each epoch separately. Next, we consider fading broadcast channels and obtain the transmission policies that achieve the boundary of the maximum departure region. The optimal total transmit power allocation policy is found using a specific directional water-filling algorithm for fading broadcast channels. The optimal power allocation depends on the priorities of the users unlike in the case of parallel broadcast channels. Finally, we provide numerical illustrations of the optimal policies and maximum departure regions for both parallel and fading broadcast channels.     

一种基于有限信道的能量高效节点调度机制

在低负载、低功耗无线传感器网络中,节点状态切换的能量消耗因为用于数据传输的能量较小而变得不可忽略。针对此问题,提出了结合多信道技术与时分多路访问( TDMA)技术的节点调度算法。该算法设计了基于接收端的连续时隙分配策略以减少节点状态切换次数,并且在可用无线信道有限的约束条件下,提出了信道分配与时隙调整机制,实现了时隙重用并最小化有限信道约束对优化节点状态切换次数的影响。仿真实验结果表明,当可用无线信道数为3~5时,算法能够有效地改善节点能量效率。当可用无线信道数大于3之后,算法能够获得优化的数据汇聚时间。     

碳限额与交易政策下电动汽车动力电池制造商梯次利用决策

随着我国电动汽车保有量迅速增长,大量退役动力电池亟需回收和利用.对此,研究碳限额与交易政策下电动汽车动力电池制造商开展梯次利用业务决策.针对由一个动力电池制造商、一个零售商和一个梯次利用商组成的闭环供应链,分别构建制造商不开展和开展梯次利用业务两种模式下闭环供应链模型.用Stackelberg博弈理论求得均衡解,通过理论比较和数值分析探究关键参数对最优决策和制造商模式选择的影响.研究发现,制造商最优碳减排水平随碳交易价格增加而增加,随碳减排成本系数增加而降低,随消费者低碳偏好系数增加而增加.制造商开展梯次利用业务并非总是最好选择,需满足以下条件:1)可梯次利用比例高于一定阈值;2)制造商为开展梯次业务而投入的成本小于一定阈值;3)制造商梯次利用单位收益高于一定阈值且梯次利用商梯次利用单位收益低于一定阈值.     

Improved eigenanalysis canceler based on data-independent clutter subspace estimation for space-time adaptive processing

The eigenanalysis canceler(EC)method which is suitable for nonhomogeneous clutter can suppress clutter efectively by discarding the eigenvectors of small eigenvalues,which is a well-known subspace-based space-time adaptive processing(STAP)method.However,the computational complexity of conventional EC STAP method is huge due to the eigenvalue decomposition.Moreover,the corresponding performance would be degraded signifcantly by the subspace leakage phenomenon,since the clutter subspace is not strictly confned to a low-rank subspace any more.Therefore,an improved EC STAP method based on the data-independent clutter subspace estimation is proposed to reduce the computational complexity,where the clutter subspace is rapidly constructed by sampling the prolate spheroidal wave functions(PSWF)non-uniformly.In order to deal with the subspace leakage phenomenon,the proposed EC-PSWF STAP method is modifed based on the covariance matrix taper(CMT)to obtain the covariance matrix by re-establishing the noise floor.The corresponding performance of proposed method is evaluated by using the numerical simulation.     

CNR中基于多用户Q学习的联合信道选择和功率控制

针对认知无线网络中多用户资源分配时需要大量信道和功率策略信息交互,并且占用和耗费了大规模系统资源的问题,通过非合作博弈模型对用户的策略进行了研究,提出一种基于多用户Q学习的联合信道选择和功率控制算法。用户在自学习过程中将采用统一的策略,仅通过观察自己的回报来进行Q学习,并逐渐收敛到最优信道和功率分配的最优集合。仿真结果表明,该算法可以高概率地收敛到纳什均衡,用户通过信道选择得到的整体回报非常接近最大整体回报值。     

Pricing strategy in a dual-channel and remanufacturing supply chain system

This article addresses the pricing strategy problems in a supply chain system where the manufacturer sells original products and remanufactured products via indirect retailer channels and direct Internet channels. Due to the complexity of that system, agent technologies that provide a new way for analysing complex systems are used for modelling. Meanwhile, in order to reduce the computational load of searching procedure for optimal prices and profits, a learning search algorithm is designed and implemented within the multi-agent supply chain model. The simulation results show that the proposed model can find out optimal prices of original products and remanufactured products in both channels, which lead to optimal profits of the manufacturer and the retailer. It is also found that the optimal profits are increased by introducing direct channel and remanufacturing. Furthermore, the effect of customer preference, direct channel cost and remanufactured unit cost on optimal prices and profits are examined.