认知无线网络中基于进化博弈的动态频谱接入*

研究了认知无线网络环境中基于价格动态性的动态频谱接入,即不同的授权网络服务商以不同的价格将空闲频谱出售给认知网络,且认知用户可以根据自己获得的报酬动态地接入不同的网络。为最大化认知网络的效用,提出了基于进化博弈的动态频谱接入方案。仿真结果表明,当认知用户群体到达进化均衡时,接入每个主网络的认知用户数量的比例达到稳定状态,最大化了认知用户和网络的效用。     

动态频谱访问无线网络的连通性分析

与传统无线网络不同,在动态频谱访问无线网络中,授权用户对分配的频段具有优先使用权,非授权用户网络的连通性受授权用户的分布和授权用户对频段的使用行为的影响.基于连续渗流理论,证明当授权用户较为稀疏或者负载较轻时,非授权用户可以构成部分连通的网络;反之,当授权用户较为密集并且负载较重时,无法部署部分连通的非授权用户网络.此外,在授权用户和非授权用户共享1个信道的情况下,给出了非授权用户网络存在部分连通性的必要条件.仿真实验数据验证了理论分析的正确性.     

Dynamic spectrum access and network selection in heterogeneous cognitive wireless networks

In this paper, we propose a cross-layer architectural framework for network and channel selection in a heterogeneous cognitive wireless network (HCWN). Existing research on heterogeneous wireless networks primarily focuses on network selection among available networks, while research on cognitive networks mainly focus on improvising efficient sensing and spectrum sharing algorithms. In this paper, we introduce a novel probabilistic model for channel classification based on its adjacent channels’ occupancy within the spectrum of an operating network. Further, we utilize a Analytic Hierarchical Process for categorizing user applications, followed by prioritizing them based on performance metrics. Finally, a modified Hungarian algorithm is implemented for channel and network selection among secondary users. The effectiveness of our approach is evaluated for different scenarios of HCWN. Simulation results show that our approach provides a 60% and 64% improvement in blocking probability over greedy and first-come-first-serve (FCFS) algorithms, respectively. Additionally, our proposed algorithm results in 22% enhancement in spectrum utilization and 50% increase in throughput over greedy and FCFS schemes.     

基于二分图的两级动态异构网络选择方案

通信技术的发展,使多种接入技术并存的异构网络成为未来通信网络的发展趋势,随着用户业务QoS需求的提高和传输带宽的增加,现有的网络选择算法已经不能满足用户高质量的通信需求。针对异构无线网络频谱资源日益紧缺的问题,提出了由用户端和网络端共同参与的两级动态网络选择方案。该方案包括灰度关联分析法和二分图联合优化匹配算法,通过用户端和网络端的共同决策,算法在有效满足移动用户业务服务质量需求的前提下,优化了系统吞吐量,均衡了网络负载。仿真实验表明,相对传统算法,该方案极大地提高了异构网络频谱资源利用率并降低了用户在无线网络间的切换概率,实现了用户需求和网络资源的合理配置。     

基于POMDP的信道感知接入算法

在认知无线电中,为了最大化次用户的吞吐量,同时对主用户的干扰低于预定值,提出一种基于POMDP的信道感知接入算法。次用户将主用户信道在时间轴上细分成等间隔的时隙,在每个时隙开始时,次用户从频谱感知、以较高的功率接入信道和以较低的功率接入信道三种可选策略中选择最优的策略。将次用户的选择过程建模成一个POMDP问题,并采用一些相应的最优策略求解。计算机仿真结果验证了算法的有效性。     

速率期望比较下的宽带频谱接入简化算法

为解决认知无线网络中宽带频谱感知模式的计算量大和感知时间延长等问题,提出了一种基于速率的认知无线网络低复杂度宽带频谱感知算法。在宽带频谱感知的基础上,设定选择条件,对信道的期望传输速率进行比较,确定需要感知的信道,以实现减少认知无线网络次用户系统的信道感知时间和感知计算量的目标。经过仿真实验分析对比表明,该算法可以有效地平衡次用户系统吞吐量最大化和主用户系统的干扰之间的矛盾。     

认知无线电网络的伺机频谱接入策略

提出了一种伺机频谱接入策略,用于由移动用户构成的认知无线电网络环境。提出的方案中,将每个可获得的信道划分成由N个时隙构成的TDMA帧,并且为每个激活的认知用户分配一个区别于其他激活用户的时隙。允许节点以一定的接入概率充分利用分配给其他激活用户的时隙进行通信。评估了提出的伺机频谱共享策略对系统吞吐量和能耗性能的影响。     

Aprojected gradient based game theoretic approach for multi-user power control in cognitive radio network

The fifth generation (5G) networks have been envisioned to support the explosive growth of data demand caused by the increasing traditional high-rate mobile users and the expected rise of interconnections between human and things. To accommodate the ever-growing data traffic with scarce spectrum resources, cognitive radio (CR) is considered a promising technology to improve spectrum utilization. We study the power control problem for secondary users in an underlay CR network. Unlike most existing studies which simplify the problem by considering only a single primary user or channel, we investigate a more realistic scenario where multiple primary users share multiple channels with secondary users. We formulate the power control problem as a non-cooperative game with coupled constraints, where the Pareto optimality and achievable total throughput can be obtained by a Nash equilibrium (NE) solution. To achieve NE of the game, we first propose a projected gradient based dynamic model whose equilibrium points are equivalent to the NE of the original game, and then derive a centralized algorithm to solve the problem. Simulation results show that the convergence and effectiveness of our proposed solution, emphasizing the proposed algorithm, are competitive. Moreover, we demonstrate the robustness of our proposed solution as the network size increases.     

基于认知无线电网络的动态频谱分配

针对无线通信网络中频谱日益紧缺的问题,对基于认知无线电网络的动态频谱分配技术进行研究,提出一种保护信道和排队相结合的动态信道分配方案。该方案在不影响主用户业务的情况下,为因主用户到达而切换的次用户预留保护信道,对新到达的次用户采用排队策略。如果系统中主用户或者次用户因服务完毕而离开时,队列中的次用户则可按一定的次序使用空闲可用的子信道。仿真结果表明,与仅预留保护信道和仅使用队列缓冲器的方案相比,该方案能有效降低系统的总体失败率,提高分配性能,且对次用户的平均吞吐量和平均延迟影响较小。     

认知无线网络中基于无休止多臂赌博机模型的多用户频谱接入机制

针对如何协调多个认知用户择机接入多段空闲频域信道的问题,提出了一种基于无休止多臂赌博机(RMAB)模型的动态频谱接入机制。首先,考虑到实际环境下认知用户的信道感知误差,推导出能有效处理感知误差的Whittle索引值算法,该算法通过历史经验积累给予每个信道一定的信任值,并综合考虑在当前信任值下选择每个信道的立即收益与未来收益的多少,选择出需要感知接入的信道;其次,对于多个认知用户接入相同信道时产生冲突的问题,提出了基于多标拍卖的协调机制,通过多标拍卖的方式处理认知用户之间的冲突。仿真结果表明,在相同的环境中,所提出的频谱接入机制与未处理误差的或者未采用多标拍卖的接入机制相比,认知用户获得的吞吐量更大。     

On the optimal,fair and channel-aware cognitive radio network reconfiguration

In this work, we focus on the Joint Channel Assignment and Routing (JCAR) problem in Cognitive Radio Networks (CRNs) and especially on the optimal reconfiguration of secondary networks under the presence of primary users. Secondary CRN users need to adapt their transmission channels promptly, while effectively limit additional or escalating system modifications triggered by the intertweaved primary user activity. Our approach takes into consideration the underlying spectrum switching dynamics and concurrently aims at a fair resource allocation among the active network flows. We take an optimization perspective and formulate the JCAR and network reconfiguration problems as mixed integer linear programs, addressing fairness concerns as well. We propose a heuristic approach which is based on a sequential reduced search space methodology, in order to obtain efficiently solutions of otherwise tough and demanding reconfiguration problems. The operation, effectiveness and performance of the proposed mechanisms are evaluated through analysis and simulations under various working conditions. The obtained numerical results indicate the benefits of the proposed schemes in terms of overhead performance and their scaling properties with respect to more realistic and thus demanding topologies.     

基于演化博弈的多用户网络选择算法

无线通信技术的发展和演进,使得多种广域蜂窝网和大量无线局域网共存、重叠。针对热点区域,密集分布的大量用户同时发起同种业务请求应用场景,提出一种基于演化博弈的多用户网络选择算法,依据选择网络的用户数设计效用函数,给出了演化博弈的复制动态方程。与RSSI算法的对比仿真结果表明：该算法能快速达到演化均衡,用户平均收益高于RSSI算法,接入网络的用户分布更均衡,能合理利用网络资源。     

Performance improvement for applying network virtualization in fiber-wireless （FiWi） access networks

Fiber-wireless （FiWi） access networks, which are a combination of fiber networks and wireless networks, have the advantages of both networks, such as high bandwidth, high security, low cost, and flexible access. However, with the increasing need for bandwidth and types of service from users~ FiWi networks are still relatively incapable and ossified. To alleviate bandwidth tension and facilitate new service deployment, we attempt to apply network virtualization in FiWi networks, in which the network＇s control plane and data plane are separated from each other. Based on a previously proposed hierarchical model and service model for FiWi network virtualization, the process of service implementation is described. The performances of the FiWi access networks applying network virtualization are analyzed in detail, including bandwidth for links, throughput for nodes, and multipath flow transmission. Simulation results show that the FiWi network with virtualization is superior to that without.     

认知无线网络中动态频谱接入性能分析

认知无线电技术利用频谱空洞进行通信,有效缓解了频谱资源紧缺问题,动态频谱接入是其核心技术。网络中主用户对授权频谱的使用效率较高时,次用户接入网络无法完成符合QoS要求的通信,只有当主用户频谱效率在一定门限值下时网络才适合次用户接入。有限频谱空洞资源只能满足有限次用户的通信需求,为了保证通信质量,网络在固定的主用户频谱效率下只能接入适量的次用户。提出用强制优先排队理论对认知无线网络中的动态频谱接入过程进行模拟,通过仿真对次用户的切换概率、阻塞概率两个QoS因子进行分析,在给定的QoS条件下,得到了网络适合次用户接入的主用户频谱效率门限值,以及在固定的主用户频谱效率下网络适合接入次用户的量。     

跨洋航空网络的频谱共享博弈模型

提出一种跨洋航空网络中主干网络的频谱共享博弈模型。该模型综合考虑了主用户和所有次级用户的收益,主用户可在保证自身收益最大的前提下对各次级用户进行有效的频谱分配;各次级用户根据主用户的最佳单位定价改变请求带宽以获得最大收益。给出了该模型的静态博弈纳什均衡与动态博弈收敛结果,通过与次级用户收益的最优化模型进行比较,验证了用该模型解决跨洋航空网络中主干网络上的频谱分配问题具有公平性。     

认知无线Mesh网络中基于概率的贪婪频谱决策技术研究

认知无线电网络传统的频谱决策方法中次用户根据不同的判据选择信道,会引起信道竞争和拥塞。针对认知无线Mesh网络中基于概率的频谱决策方法,提出一种贪婪信道选择算法,当发生频谱切换时,其结合改进的抢占优先(相似文献   

A knowledge-based approach to the local area network design problem

Computer networks are an essential tool for people in business, industries, government, and schools. With the rapid rate of change in network technology and products, and the emergence of highly sophisticated network users, network design has become an increasingly complex task. Although the computer society aims at agreeing to a series of international standards for describing network architectures, the design of a computer network remains an ill-structured problem that lends itself perfectly to expert systems solutions. We propose an expert system that is able to design local area networks meeting the requirements specified by the user. Rules and guidelines pertaining to local area network design are formulated and incorporated into the knowledge base. The system is built on an object-oriented paradigm. The object-oriented approach and the hierarchical rule structure paradigm are discussed. We also employ the blackboard technique through which rules can access dynamic objects conveniently.     

Queuing-Based Dynamic Channel Selection for Heterogeneous Multimedia Applications Over Cognitive Radio Networks

In this paper, we propose a dynamic channel-selection solution for autonomous wireless users transmitting delay-sensitive multimedia applications over cognitive radio networks. Unlike prior works that seldom consider the requirement of the application layer, our solution explicitly considers various rate requirements and delay deadlines of heterogeneous multimedia users. Note that the users usually possess private utility functions, application requirements, and distinct channel conditions in different frequency channels. To efficiently manage available spectrum resources in a decentralized manner, information exchange among users is necessary. Hence, we propose a novel priority virtual queue interface that determines the required information exchanges and evaluates the expected delays experienced by various priority traffics. Such expected delays are important for multimedia users due to their delay-sensitivity nature. Based on the exchanged information, the interface evaluates the expected delays using priority queuing analysis that considers the wireless environment, traffic characteristics, and the competing users' behaviors in the same frequency channel. We propose a dynamic strategy learning (DSL) algorithm deployed at each user that exploits the expected delay and dynamically adapts the channel selection strategies to maximize the user's utility function. We simulate multiple video users sharing the cognitive radio network and show that our proposed solution significantly reduces the packet loss rate and outperforms the conventional single-channel dynamic resource allocation by almost 2 dB in terms of video quality.      

混合共享认知无线网络信道分配算法

混合频谱共享是适应认知用户不同地理分布的有效频谱共享模式。信道分配是无线通信网络中关键的问题之一,近年来得到了广泛研究。集中式信道分配算法是最常用的算法形式,但在认知无线电网络这种分布式系统中,集中式算法不易实现。将混合共享认知无线网络的信道分配问题构建为一对一的匹配博弈,提出了分布式用户-信道匹配算法。该算法数学复杂度低,且能够达到稳定匹配。仿真结果表明,算法收敛时间短,稳定匹配状态下的平均传输速率与使用匈牙利算法的最优分配算法所获得传输速率相接近,远优于随机分配算法的传输速率。     

Analytical modeling for spectrum handoff decision in cognitive radio networks

Cognitive Radio (CR) is an emerging technology used to significantly improve the efficiency of spectrum utilization. Although some spectrum bands in the primary user’s licensed spectrum are intensively used, most of the spectrum bands remain underutilized. The introduction of open spectrum and dynamic spectrum access lets the secondary (unlicensed) users, supported by cognitive radios; opportunistically utilize the unused spectrum bands. However, if a primary user returns to a band occupied by a secondary user, the occupied spectrum band is vacated immediately by handing off the secondary user’s call to another idle spectrum band. Multiple spectrum handoffs can severely degrade quality of service (QoS) for the interrupted users. To avoid multiple handoffs, when a licensed primary user appears at the engaged licensed band utilized by a secondary user, an effective spectrum handoff procedure should be initiated to maintain a required level of QoS for secondary users. In other words, it enables the channel clearing while searching for target vacant channel(s) for completing unfinished transmission. This paper proposes prioritized proactive spectrum handoff decision schemes to reduce the handoff delay and the total service time. The proposed schemes have been modeled using a preemptive resume priority (PRP) M/G/1 queue to give a high priority to interrupted users to resume their transmission ahead of any other uninterrupted secondary user. The performance of proposed handoff schemes has been evaluated and compared against the existing spectrum handoff schemes. Experimental results show that the schemes developed here outperform the existing schemes in terms of average handoff delay and total service time under various traffic arrival rates as well as service rates.