认知无线网络中基于Vandermonde预编码的认知用户可达比特率研究

在认知无线网络中,主用户与认知用户要求在频率选择性衰落信道下与它们各自相应的接收机进行同时通信.主用户与认知用户之间的干扰必须尽可能消除以实现两者的频谱共享.本文提出了认知正交频分复用(OFDM)中采用Vandermonde预编码的预编码多址接入(PDMA)策略,它有效利用认知信道的频率选择性构成频率波束成型器.在主用户干扰受限和最优功率分配策略下,采用Vandermonde预编码可使认知用户达到高比特传输率.理论推导过程均采用数值计算与仿真得到证明.数值计算与仿真结果表明,最优输入功率分配策略可使认知用户对主用户不产生干扰的前提下获得可达比特传输率(ABR).同时,数值仿真验证了理论推导过程.在认知无线网络中,采用Vandermonde预编码器构成PDMA,认知用户接收机信噪比与主用户目标速率均可以显著影响认知用户的可达比特率.     

Achievable bit rates of cognitive user with Vandermonde precoder in cognitive radio network

In cognitive radio network (CRN) where primary user (PU) and secondary user (SU) wish to communicate with their corresponding receivers simultaneously over frequency selective fading channels,the interference between PU and SU should be eliminated in order to realize spectrum sharing.Precoder division multiple access (PDMA) that implements Vandermonde precoder in cognitive orthogonal frequency division multiplexing (OFDM) is proposed,which benefits from the frequency selectivity of the cognitive channel to ...     

认知无线电网络中基于需求的频谱资源分配算法研究

认知无线电网络中,已有的分配算法未考虑用户的需求,这样会导致需求小的用户分配到更多的资源。为解决上述问题,提出基于需求以及联合比例公平两种频谱分配算法,这两种算法均将用户需求作为频谱分配时需要考虑的因素。仿真结果表明,基于需求以及联合比例公平算法比原算法更能满足各用户的需求。     

Cooperative detection of primary user emulation attacks in CRNs

Cognitive radio networks (CRNs) can improve the utilization of the spectrum by making use of licensed spectrum in an opportunistic manner. With such purpose, coexistence mechanisms among CRN nodes or secondary users and legitimate users of the spectrum or primary users are defined. However, due to the particular features of CRNs, new security threats arise, such as the primary user emulation (PUE) attack, which is the most challenging among all. With the aim of detecting such kind of attacks, in this paper we propose a cooperative localization method specifically suited to CRNs which relies on TDoA measurements and Taylor-series estimations. Simulations results show the goodness of the proposed method and its suitability to typical CRN scenarios.     

认知Ad-Hoc网络中一种实时信道分配路由协议

针对认知无线Ad Hoc网络中授权用户的活动将影响认知用户间路由稳定性的问题,提出了一种实时信道分配路由协议。该协议采用动态源路由协议(DSR)的路由发现机制,在路由建立阶段,提出综合路由度量标准来选择路由;在数据发送阶段引入IN MESSAGE数据包,使路由中间节点可以掌握其下一跳节点信道环境的变化,从而进行实时信道分配。仿真对比表明,实时信道分配路由协议有效提高了分组的投递率,减少了路由重建次数。     

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.     

双阈值能量检测的无线电网络协作频谱感知

针对认知无线电网络中协作频谱感知使能耗增加而降低网络寿命的问题,提出了一种双阈值能量检测的协作频谱感知方案.利用基于双阈值的能量检测方法最大化网络吞吐量,使能耗低于一个阈值同时保护主用户不受次用户的干扰.利用凸优化分析来获得感知时间和检测阈值的最佳值.仿真结果表明,方法能有效权衡网络吞吐量与能量效率之间的关系,相比传统的频谱感知方法,具有明显的优越性.     

认知无线电中一种n步串行信道感知策略

为了提高频谱感知的整体性能,基于链路层多认知用户集中式协作感知思想,提出一种带缓冲区的双周期n步串行协作感知机制.该机制利用多认知用户分时、分段协作提高频谱感知效率,建立频谱池缩短被中断用户切换延迟时间,使用离散马尔可夫模型对感知参数建模,通过求解最优搜索步长和双感知周期比,提高认知用户频谱感知性能和QoS.仿真实验结果显示,该算法在感知效率、被迫中断概率和中断时间方面均优于随机搜索和传统串行搜索策略.     

利用在线异常感知的无线电网络抗SSDF攻击协作频谱感知方案

该文提出了一种时空频率CSS框架,用于检测和跟踪CR网络中的恶意用户和异常测量。联合频谱感知和恶意用户识别问题构成优化问题,且利用固有稀疏到频谱占用和恶意用户发生。提出的方案利用在线异常感进行实时识别和跟踪,通过节点位置信息获得了改进的性能,可有效处理错过或不正确的位置信息,以及PU功率级噪声SU测量。实验结果表明,提出的方案在协作感知中能够有效克服感知数据错误化(SSDF)攻击。此外,提出的方案优于现有的较为先进的基于PCA方法,具有足够的灵活性来抵御SU网络中的各种攻击。     

On power allocation for a cognitive radio network with hybrid spectrum sharing

In this study we propose a hybrid spectrum sharing scheme based on power control by combining Overlay with Underlay schemes,to improve radio spectrum efficiency.In the scheme,the secondary users dynamically switch their operational states between Overlay and Underlay according to the spectrum occupancy.Thus the dynamics of the primary network is first modeled with a discrete-state Markov process to find the time fraction of secondary users in the Overlay state and that in the Underlay state,which leads to the capacity model of the hybrid spectrum sharing system.Under the criterion of maximizing capacity,the power allocation of the cognitive network is researched and the optimum power allocation for secondary users is deduced.As a result,the maximum achievable capacity of the cognitive network is obtained.Simulations are given to prove the analysis further.Theoretical and simulated results indicate that hybrid spectrum sharing based on power control provides a higher capacity than single Overlay and Underlay systems for the cognitive network,i.e.,hybrid spectrum sharing can further improve radio spectrum efficiency.     

Optimizing channel selection for cognitive radio networks using a distributed Bayesian learning automata-based approach

Consider a multi-channel Cognitive Radio Network (CRN) with multiple Primary Users (PUs), and multiple Secondary Users (SUs) competing for access to the channels. In this scenario, it is essential for SUs to avoid collision among one another while maintaining efficient usage of the available transmission opportunities. We investigate two channel access schemes. In the first model, an SU selects a channel and sends a packet directly without Carrier Sensing (CS) whenever the PU is absent on this channel. In the second model, an SU invokes CS in order to avoid collision among co-channel SUs. For each model, we analyze the channel selection problem and prove that it is a so-called “Exact Potential” game. We also formally state the relationship between the global optimal point and the Nash Equilibrium (NE) point as far as system capacity is concerned. Thereafter, to facilitate the SU to select a proper channel in the game in a distributed manner, we design a Bayesian Learning Automaton (BLA)-based approach. Unlike many other Learning Automata (LA), a key advantage of the BLA is that it is learning-parameter free. The performance of the BLA-based approach is evaluated through rigorous simulations and this has been compared with the competing LA-based solution reported for this application, whence we confirm the superiority of our BLA approach.     

认知无线电网络中基于需求的多小区频谱分配算法

提出一种认知无线电网络中基于需求的多小区频谱分配算法。使用图论着色模型,结合频谱质量分级概念,根据小区内需求情况,该算法将网络中周期检测到的可用频谱分配给各个认知小区,最大化满足需求的同时,为业务提供服务质量保障。仿真结果表明：与原有算法相比,该算法能更好地满足网络需求。     

On neighbor discovery in cognitive radio networks

A cognitive radio node is a radio device capable of operating over multiple channels. As a result, a network consisting of one or more cognitive radio nodes can adapt to varying channel availability in its geographical region by dynamically changing the channel (or channels) nodes are using for communication.     

E-band transceiver monolithic microwave integrated circuit in a waveguide package for millimeter-wave radio channel emulation applications

Dear editor, In the development of 5G prototype systems and termi-nal demonstration platforms,a wireless channel emulator plays a crucial role in the test and v...     

OFDM系统中有效信道长度跟踪方案*

为获得更为精确的有效信道长度,在分析最大似然（ML）信道估计算法对有效信道长度具有依赖性的基础上,提出将粗搜索策略与逐次插值逼近法相结合的有效信道长度跟踪方案,跟踪信道长度的变化。理论分析和仿真结果表明,在时变信道环境下,该算法可以有效跟踪信道长度的变化,提高ML信道估计器的估计性能。     

一种基于测距的无线传感网sybil攻击检测方法

提出一种基于测距的sybil攻击检测方法,各个节点通过测距找出各自邻居节点中可能为sybil节点的可疑节点,再通过邻居节点之间交换信息找出sybil节点。仿真实验表明,该方法具有如下特点：代价小,不要求高精度测距,准确性高,不引入特殊节点,不因特殊节点失效而使算法失效,不需全局信息。特别适合低成本,资源缺乏,工作在恶劣环境中的分布式无线传感器网络。     

一种多信道Ad hoc认知无线电网络密钥交互协议*

针对现有密钥协商协议没有考虑Ad hoc认知无线电网络多信道这一缺陷,提出一种多信道密钥协商协议（multi channels key agreement protocol,MCKAP）,通过建立多重图和替换广播操作减少信道冲突,优化协商路径提高共享密钥协商效率,利用信道属性为节点间选择合理位置,避免主用户干扰。该方案能有效地利用多信道提高共享密钥协商效率。最后通过理论分析和仿真实验证明该协议适用于Ad hoc认知无线电网络,具有较好的执行效率。     

On detecting co-resident cloud instances using network flow watermarking techniques

Virtualization is the cornerstone of the developing third-party compute industry, allowing cloud providers to instantiate multiple virtual machines (VMs) on a single set of physical resources. Customers utilize cloud resources alongside unknown and untrusted parties, creating the co-resident threat—unless perfect isolation is provided by the virtual hypervisor, there exists the possibility for unauthorized access to sensitive customer information through the exploitation of covert side channels. This paper presents co-resident watermarking, a traffic analysis attack that allows a malicious co-resident VM to inject a watermark signature into the network flow of a target instance. This watermark can be used to exfiltrate and broadcast co-residency data from the physical machine, compromising isolation without reliance on internal side channels. As a result, our approach is difficult to defend against without costly underutilization of the physical machine. We evaluate co-resident watermarkingunder a large variety of conditions, system loads and hardware configurations, from a local laboratory environment to production cloud environments (Futuregrid and the University of Oregon’s ACISS). We demonstrate the ability to initiate a covert channel of 4 bits per second, and we can confirm co-residency with a target VM instance in $<$ 10 s. We also show that passive load measurement of the target and subsequent behavior profiling is possible with this attack. We go on to consider the detectability of co-resident watermarking, extending our scheme to create a subtler watermarking attack by imitating legitimate cloud customer behavior. Our investigation demonstrates the need for the careful design of hardware to be used in the cloud.     

认知无线电网络中基于信任度的频谱感知技术

提出了一种在认知无线网络控制信道带宽受限条件下基于信任度的双门限协同频谱感知算法。首先每个认知用户基于双检测门限独立进行频谱感知,但只有部分可靠的认知用户通过控制信道向认知无线网络基站发送本地感知结果。当所有的用户都不可靠时,选取信任度最高的认知用户发送本地感知结果进行判决。理论分析和仿真表明,同常规能量检测算法相比较,该算法能够在控制信道带宽受限条件下,以较少的网络开销获得更好的频谱感知性能。