基于信道认知在线可定义的电力线载波通信方法

常规的电力线载波技术在规定的频带范围采用固定的工作频率通信,不能适应复杂、时变、差异性的电网信道特性,通信性能和业务保障差。为提高面向智能电网应用的电力线载波通信技术的可靠性、灵活性与覆盖率,满足智能配用电业务通信需求,提出一种基于信道认知在线可定义的电力线载波通信方法,使载波通信可根据中低压配电网电力线信道实际情况,在150 k Hz^10 MHz跨频带范围内自适应选择合适的工作频率和通信带宽。从而打破传统电力线载波通信工作频率窄带和宽带的分割,实现基于信道认知结果的电力线载波通信参数"在线定义"。在给出所提出方法实现架构的基础上,着重探讨基于等效复数基带和收发端双加窗的数字前端、基于无线电信号接收因子的中短波电台检测、以及前导序列辅助下的频率选择等关键技术。仿真和现场实际测试证明了所提电力线载波通信方法的有效性,通过节点自主认知信道环境并自适应选择工作频率,提高了载波通信链路的可靠性和单跳覆盖率,对未来电力线载波技术在智能电网中的应用具有推动作用。

认知电力线载波通信技术在配电网的应用

电力线信道环境复杂多变,为了提供可靠、稳定的通信支撑,文章提出了一种认知电力线载波通信技术。该技术通过信道特性认知而自适应地选择最佳工作频段,同时利用数字前端技术、次优对数概率比技术及快速频率认知的点对点MAC协议等关键技术,可极大减小系统的丢包率。认知电力线载波通信系统在国网绍兴供电局多个配电网场景进行了测试和验证,结果表明,通过信道认知技术,在不同测试线路均能找到一个最佳通信频段,确保系统的可靠通信。

认知无线电网络基于QoS的监听时间与资源联合分配

以最大化所有认知无线电用户(CRU)的吞吐量为目标,同时保证每个CRU的服务质量(Qo S)约束,研究了联合最优监听时间和资源分配问题,并基于此提出了一种监听时间与资源联合分配算法。在多信道认知无线电网络中,频谱监听和资源分配都会影响网络的吞吐量。兼顾二者的联合优化问题可以被分解为两个子问题:固定监听时间的资源分配问题,以及固定资源分配策略的最优监听时间一维穷举搜索问题。提出的算法可以通过穷举搜索获得最优监听时间,并通过次梯度算法获得最优资源分配策略。仿真结果表明,提出的最优监听时间与资源分配算法可以最大化认知无线网络的吞吐量;此外,各认知用户的Qo S需求也能得到保证。

认知无线电网络中最优分组长度设计

为满足不同种类多媒体应用的服务质量需求,研究了一个多等级多信道认知无线电网络中的资源分配问题。根据时延和吞吐量为该网络模型定义一个效用函数并最大化这个效用函数的期望值。首先用不考虑传输功率分配的"浪费功率的方式"设计分组长度。然后在选择分组长度时考虑传输功率分配提出一种基于贪婪算法的改进方式,得到了最优分组长度和相应的传输功率。MATLAB的仿真结果表明,在传输功率受限下,当达到相同效用值时,改进方式和"浪费功率的方式"相比能减小传输功率,并取得更加合理的分组长度,而且能更好地满足带宽需求,这是由于改进方式不仅考虑了各个信道上数据包的到达时间间隔,还考虑了信道增益。

认知无线网络的改进资源管理算法研究

提出了一种基于资源认知信道的接入算法,可用于认知无线电环境下的无线资源管理。对资源认知信道上传输的每个分组——数据域部分采用了基于联合检测的扩频码,而控制域部分则分别采用了5种不同的信道接入协议。分析并仿真了认知用户在资源认知信道上的成功接入概率以及吞吐量性能。

水下智能跨域异构网络设计

面向未来联合作战、体系作战的战略需求,针对水下信息跨介质出入水传输的难题,本文提出一种面向未来的异构网络体系架构,对水下认知跨域异构网络进行分析和研究。结合无线信道、水声信道和认知网络的特点,提出一种水面/水下智能跨域通信系统,对我国实施水下战略有一定借鉴意义。

空间分集选频调制解调器的设计与实现

针对空间分集选频技术体制在两重空间分集站型下的应用,设计并实现了新型散射调制解调器。介绍了两重空间分集选频调制解调器的组成,描述了基本工作原理,进而阐述了实时信道认知技术、链路反馈控制技术和突发散射解调技术的设计思路和实现方案。采用无线信道模拟器及微波收发信机搭建测试系统并进行室内模拟测试,测试结果表明,空间分集选频调制解调器的性能优于传统调制解调器4 dB,证实了新型调制解调器的优越性。

CPC辅助终端接入网络策略研究

根据当前无线网络环境中多网络共存情形,结合自组织网络,提出一种CPC辅助用户终端接入网络策略。方案采用马尔科夫方法分析系统模型,并分析系统状态平衡时各状态之间转移情况,通过比较系统的业务阻塞率以及切换阻塞率分析系统的性能。最后对方案进行仿真,直观显示方案的性能。

Link Maintenance Scheme for OFDM-Based Cognitive Radio Ad Hoc Networks

Transmission among the cognitive users(CUs)' is always interrupted by the primary users(PUs)' reclaim of the spectrum and the fading effect of wireless channels.To maintain reliable continuous communication among CUs,an efficient scheme for link maintenance in OFDM-based cognitive radio Ad Hoc networks is proposed in this paper.In the scheme,redundant sub-channels(RSC) are employed by CUs to tackle the outage problem caused by the PUs' reclaim of the spectrum and wireless fading effect in the transmission.Meanwhile,backup sub-channels(BSC) are arranged to help select sub-channels with better channel quality.Additionally,to lower the overhead and improve the accuracy of the spectrum sensing,a partial sensing module is designed to enable the CUs to inherit and update the original idle spectrum list until it expires.Simulation results show that the proposed scheme can realize higher throughput and lower sensing overhead with slight reduction of the forced termination probability(FTP) performance compared to the existing approaches.

Throughput optimization for multi-channel cooperative CR under reporting channel errors

To overcome the problem of channel fading and noise uncertainty,cooperative spectrum sensing(CSS)is developed to enhance the sensing performance in cognitive radio networks(CRNs).Considering that the non-ideal reporting channels of CSS can cause an adverse impact on the detection performance,the throughput maximization problem for multi-channel CSS cognitive radio under reporting channel errors is investigated.While providing all the primary users with sufficient protection,the average throughput of secondary users(SUs)is maximized by jointly optimizing the sensing duration,detection threshold and SU assignment.To address the non-convex optimization problem,the optimal energy detection threshold is derived first.Then,a sub-optimal greedy algorithm is proposed to obtain the optimal sensing duration and the optimal SU assignment.Analysis and simulation results show that the proposed algorithm can output the same performance as the exhaustive search algorithm at a much lower level of complexity.It is also shown that the impact of imperfect reporting channels should be considered especially in low signal-to-noise ratio environments and the reporting channel errors significantly reduce the performance of CSS.

Dempster-Shafer （D-S） algorithm with credit scale in spectrum sensing

In cognitive radio, the detection probability of primary user affects the signal receiving performance for both primary and secondary users significantly. In this paper, a new Dempster-Shafer （D-S） algorithm with credit scale for decision fusion in spectrum sensing is proposed for the purpose to improve the performance of detection in cognitive radio. The validity of this method is established by simulation in the environment of multiple cognitive users who know their signal to noise ratios （SNR） and a central node. The channels between the cognitive users and the central node are considered to be additive white Ganssian noise （AWGN）. Compared with traditional data fusion rules, the proposed D-S algorithm with credit scale provides a better detection performance.

Fundamental capacity for peak interference power constrained cognitive radio relay networks

A Cognitive radio communication link is possible to be interrupted easily when its physical channel suffers severe fading. Relay technology is an effective way to mitigate the fading effect of wireless channels in a network. Based on the highest achievable rate of the relay channels, this paper considers a cognitive radio relay network where the secondary transmitter communicates with the receiver through the best relay node under the peak power constraint of a primary receiver. Intuitively, the secondary transmission can benefit from an intermediate relay node chosen from N possible nodes. To quantify this benefit, outage probability of cognitive radio relay networks is derived and also the closed-form expressions for outage capacity and ergodic capacity of cognitive radio relay networks are obtained in Rayleigh fading channels. Numerical simulation results are provided to show that the outage capacity and ergodic capacity benefit tremendously by properly increasing the number of relaying nodes.