无线认知网络概念与实例研究

提出了一种新的、以认知能力为基础的无线网络,称为无线认知网络。对无线认知网络进行了定义,对认知实体、认知进程和认知环境进行了分析和讨论,提出了无线认知网络的实体、网络、认知和控制4个关联层面,对无线认知网络的特点进行了阐述,并给出了技术上的挑战。在此基础上,从基础设施、层次结构和节点性质3个方面对无线认知网络进行了分类研究,在给出最小跨层设计原则与信息交换方法的基础上,提出了由基础层、网络适配层、应用开发环境层和应用逻辑层组成的4层软件体系结构。最后结合无线认知网络目前的惟一实例-认知无线电网络,对无线认知网络的实例化问题进行了讨论。     

无线认知传感器网络的研究

在无线传感器网络中引入认知无线电技术,构成无线认知传感器网络,可以减少ISM频段干扰,提高数据传输率。对无线认知传感器网络的研究目前已成为一个新的研究领域。介绍了无线认知传感器网络的概念,从无线认知传感器网络的节点、频谱感知、频谱决策、频谱共享、频谱迁移、网络层、传输层、应用层等方面综述了现有的研究成果,讨论了目前存在的问题和需要进一步研究的方向。     

认知无线电网络路由协议综述

认知无线电网络中的节点具有动态频谱接入的特点,进而产生可用频谱的不规则性,这与传统无线多跳网络有很大不同,从而导致了认知无线电网络路由面临新的挑战.在介绍认知无线电网络路由的特点之后,对路由协议进行了初步分类.然后着重分析了目前认知无线电网络较为重要的路由协议的主要机制,详细比较了路由协议的主要类别和特点,最后总结了好的认知无线电网络路由协议的特点,并对未来发展趋势进行了初步展望.     

一种多接口认知传感器网络体系结构

传统的单接口无线传感器网络由于同道干扰问题的存在,网络性能受到极大的限制。多接口无线网络技术是解决这一问题的有效方案。但是多接口无线传感器网络的频谱接入问题是多接口传感网大规模部署的关键一环。而认知无线电技术能够实现频谱的动态访问,即便是信道拥塞的情况仍能有效改善网络性能,并且在无线传感器网络中表现出较好的传输特性。本文提出一种基于连通支配集的多接口认知传感器网络体系结构。通过分析不难看出,提出的体系结构具有良好的扩展性和容错性能。     

认知无线电自组织网络MAC协议

随着无线频谱资源短缺问题的日益突出,认知无线电网络得到了广泛关注和研究.在这类网络中,媒体接入控制MAC协议是关键技术之一.特别是在认知无线电自组织网络中,因为缺乏中心基础设施的支持,MAC协议的设计面临着巨大的挑战.除了媒体接入控制等传统问题之外,这些挑战还包括如何保证主用户的业务质量,如何有效认知并管理频谱资源等.文中首先介绍了认知无线电自组织网络MAC协议的最新研究进展,然后对一些典型协议进行了比较分析,最后对未来的研究方向进行了探讨.     

基于能量优化的Ad hoc认知无线电网络组播路由启发式算法研究*

提出了两个Ad hoc认知无线电网络中基于能量优化的组播路由启发式算法。一个是基于经典的最短路径树的组播算法（shortest path tree algorithm,SPTA）,另一个是基于能量函数的组播启发式算法(energy function based heuristic algorithm,EFHA)。这两个算法都在考虑了认知无线电网络特性的基础上建立能量优化的组播树,从应用例子可以看出, EFHA算法明显优于SPTA算法,并且复杂度较低。     

基于能量优化的认知无线电网络组播路由协议

针对认知无线电网络节点动态频谱分配的特点,利用静态博弈方法,根据次用户占用频谱越宽所造成干扰越大,建立基于价格惩罚机制的古诺模型解决频谱分配问题,通过求解纳什均衡,频谱利用率达到最优。根据最小增量按需驱动思想建立了节约能量的组播树,提出基于能量优化的适用于认知无线电网络的按需组播路由协议。     

认知无线Mesh网络中一种协助的分布式组播调度算法

认知无线Mesh网络是下一代无线宽带通信系统的主要形式之一,它能通过使用授权网络未使用的频谱资源来提高网络带宽.组播是一种应用非常广泛的无线业务需求.本文主要研究CR-Mesh路由器和CR-Mesh终端之间的组播调度问题.由于CR-Mesh路由器和CR-Mesh终端具有可用信道异构的特征,这将导致无线业务组播的时间变长.本文的目标是最小化无线业务组播的时间,提出一种基于节点协助的分布式组播调度算法DAMSA,通过同组成员或者其他组成员的协助达到降低组播时间的目的.通过大量的仿真发现,我们提出的DAMSA算法不仅降低了无线业务需求的组播时间,而且提高了系统的吞吐量.     

认知无线电网络传输层协议设计探讨

认知无线电是当前的研究热点,然而对认知无线电网络传输层协议的研究却很少.本文从认知无线电的概念出发,介绍了TCP在无线环境中存在的问题,以及改进无线TCP性能所需要考虑的因素,结合认知无线电自身特点,指出了进行认知无线电网络传输层协议设计的思路.     

无线传感器网络中组播路由协议分析

无线传感器网络由小型无线通信传感设备密集部署形成。组播是一种将数据包从源节点有效传递到一组目的节点的基本路由服务技术。组播协议中,源节点到目的节点的一些路径可由多个目的节点共享,所共享的路径越大,总带宽消耗越低。在分析无线传感器网络基本特征的基础上,对无线传感器网络中现有的组播路由协议进行了分类分析和比较,最后对无线传感器网络组播路由协议的未来发展趋势提出展望。     

基于无线网络的分层组播拥塞控制策略研究

分析了分层组播拥塞控制协议的基本原理,针对当前存在的拥塞控制算法的不足,提出了使用单向延迟和pathload算法来判断网络拥塞情况,避免了接收端信息反馈给算法带来的复杂性和可扩展性的问题,并实现了一种适应于无线异构网络环境下分层组播拥塞控制策略WALM。仿真实验表明,WALM不但能比较好的适应无线网络环境,而且还具有比较好的TCP友好性。     

Block-level packet recovery with network coding for wireless reliable multicast

Reliable multicast, the lossless dissemination of data from one sender to a group of receivers, has a wide range of important applications in wireless networks. In this paper, we are interested in the reliable single-hop wireless multicast. As the wireless channel is inherently error prone, it is challenging to achieve high channel utilization in reliable wireless multicast. Most schemes proposed by now for reliable single-hop wireless multicast share the same weakness in that an entire frame will be retransmitted even if it has single error bit. To alleviate this problem, this paper presents an efficient reliable multicast scheme based on block-level ARQ and network coding technique. The new scheme breaks the data stream into blocks and retransmits only erroneous blocks (rather than the entire corrupted frame), where the novel network coding technique is further adopted to minimize the total number of block retransmissions. The theoretical analysis and simulation are conducted to demonstrate the performance of the new scheme and also some typical available schemes in terms of their bandwidth efficiency. The simulation and theoretical results indicate that new reliable wireless multicast scheme can significantly enhance the channel utilization, especially in the scenarios where bit error rate is high and the number of receivers is large.     

Design and implementation of light-weight mobile multicast for fast MIPv6

Mobile multicast is a research hotspot and can provide many applications. Some mobile multicast schemes have been proposed, but most of them introduce new entities and study construction algorithms of the dynamic multicast delivery structure which is heavyweight for wireless devices. In this paper, we propose a light-weight mobile multicast (LMM) scheme for Fast Mobile IPv6 which reduces the redundant operational overhead by simplifying multicast listener discovery (MLD) proxying. The LMM scheme implements simplified MLD proxying function on home agent to reduce the complicated multicast routing protocol and modifies MLD host part function on mobile node to reduce the multicast membership messages interaction. In order to solve the tunnel convergence problem, LMM also introduces a multicast tunnel combination and reconstruction algorithm. We set up a test-bed to evaluate the performance of LMM, and compare it with other mobile multicast schemes. The experimental results show that LMM reduces the multicast disruption time at handover. Based on the experimental results, we analyze the cost of LMM, and the results show that it has lower protocol cost than other schemes.     

Computation-Efficient Multicast Key Distribution

Efficient key distribution is an important problem for secure group communications. The communication and storage complexity of multicast key distribution problem has been studied extensively. In this paper, we propose a new multicast key distribution scheme whose computation complexity is significantly reduced. Instead of using conventional encryption algorithms, the scheme employs MDS codes, a class of error control codes, to distribute multicast key dynamically. This scheme drastically reduces the computation load of each group member compared to existing schemes employing traditional encryption algorithms. Such a scheme is desirable for many wireless applications where portable devices or sensors need to reduce their computation as much as possible due to battery power limitations. Easily combined with any key-tree-based schemes, this scheme provides much lower computation complexity while maintaining low and balanced communication complexity and storage complexity for secure dynamic multicast key distribution.     

一种优化时延的机会协同组播调度策略

无线组播面临的最大问题是各个用户信道状态的不均匀性和波动性,无法同时满足所有用户的服务质量需求。无线蜂窝通信系统中,为实现可靠组播,数据包不可避免地需要被重传多次,组播的时延也因此增加。本文我们首先分析了协同组播调度CMS策略的时延,并且推导了基于信道信息全知条件下的最小时延。另外,我们在部分信道信息未知条件下提出了一种机会协同组播策略来优化组播时延。仿真数据显示,我们提出的机会协同组播调度OCMS策略在时延性能上几乎达到了我们所分析的CMS策略的最小值而且明显优于其他调度策略。     

无线接入网络中组播拥塞控制机制的研究

随着无线技术的迅速发展和无线设备的日益普及,如何有效地提高传统的组播拥塞控制机制在无线网络中的性能是一个急需解决的课题。本文提出了一种新的组播拥塞控制机制,该机制通过对无线缝路上的随机丢失分组和网络中的拥塞丢失分组进行辨别并采取相应的处理措施,有效地提高了传统的组播拥塞控制机制在无线网络中的性能,同时保证了在有线网络环境中的TCP友好性。     

Application of reinforcement learning for security enhancement in cognitive radio networks

Cognitive radio network (CRN) enables unlicensed users (or secondary users, SUs) to sense for and opportunistically operate in underutilized licensed channels, which are owned by the licensed users (or primary users, PUs). Cognitive radio network (CRN) has been regarded as the next-generation wireless network centered on the application of artificial intelligence, which helps the SUs to learn about, as well as to adaptively and dynamically reconfigure its operating parameters, including the sensing and transmission channels, for network performance enhancement. This motivates the use of artificial intelligence to enhance security schemes for CRNs. Provisioning security in CRNs is challenging since existing techniques, such as entity authentication, are not feasible in the dynamic environment that CRN presents since they require pre-registration. In addition these techniques cannot prevent an authenticated node from acting maliciously. In this article, we advocate the use of reinforcement learning (RL) to achieve optimal or near-optimal solutions for security enhancement through the detection of various malicious nodes and their attacks in CRNs. RL, which is an artificial intelligence technique, has the ability to learn new attacks and to detect previously learned ones. RL has been perceived as a promising approach to enhance the overall security aspect of CRNs. RL, which has been applied to address the dynamic aspect of security schemes in other wireless networks, such as wireless sensor networks and wireless mesh networks can be leveraged to design security schemes in CRNs. We believe that these RL solutions will complement and enhance existing security solutions applied to CRN To the best of our knowledge, this is the first survey article that focuses on the use of RL-based techniques for security enhancement in CRNs.     

基于混沌映射组播技术的无线移动自组织网络路由研究

为解决无线移动自组织网络在高速运转过程中存在严重时延,导致组播困难的问题,本文提出一种基于混沌映射组播技术的无线移动自组织网络路由。引入数学群论中的直积,构造无穷混沌图谱节点;再通过强镜面性来给移动节点坐标进行映射处理,将整个无线移动自组织网络纳入超球面中;最后,利用超球面良好的拓扑性能来实现源节点组播信息及网络路由的维护。仿真实验表明：与当前网络路由相比,本新路由在时延、网络控制开销及分组投递指标上有明显的优势,特别是在规模较大时的优势更加明显。     

An effective scheduling scheme for multi-hop multicast in wireless mesh networks

With the utilization of concurrent transmission strategy, a throughput-enhanced scheduling scheme is devised for multicast service in wireless multi-hop mesh networks. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, the interference relationships are first characterized by introducing a graph transformation method. Based on the graph transformation, the multicast scheduling problem is converted to the graph coloring problem, and then a capacity greedy algorithm is designed to provide concurrent transmission scheduling so that the demanded multicast transmission rate can be achieved. Moreover, the necessary and sufficient conditions of multicast schedulable feasibility are derived. Through corresponding simulations, it is shown that the proposed strategy can enhance the throughput of wireless multi-hop multicast systems significantly.     

Subcarrier and power allocation for OFDMA-based multicast cellular networks using a coalitional game

The subcarrier and power allocation problem for orthogonal frequency-division multiple access (OFDMA)-based multicast cellular networks is investigated in this paper. Due to the intrinsic heterogeneity of the channel gains experienced by different multicast users, the conventional multicast schemes are highly conservative and spectrally inefficient. To address this issue, a novel multicast formulation is proposed where multiuser diversity inherent in OFDMA can be adaptively exploited by clustering users within a multicast group into smaller subgroups based on their channel gains. Subcarriers and power are then dynamically allocated to these subgroups to maximize the total multicast rate of the system. Coalitional game theory is adopted to model the group formation in which users can autonomously form coalitions with other users to compete for network resources. A low-complexity algorithm is proposed for the multicast coalitional game to reach multicoalitional equilibrium in which a sub-optimal performance can be obtained. Simulation results demonstrate that the proposed scheme outperforms the conventional unicast and multicast schemes while achieving a sub-optimal performance comparable to the exhaustive search scheme.