Multicast capacity and delay trade‐offs in ad hoc networks with random iid mobility model

In this paper, multicast capacity and delay trade‐offs of mobile ad hoc networks are considered under random independently and identically distributed (iid) mobility model. Compared with unicast, multicast can reduce the overall network load by a factor with high probability (whp) in static random ad hoc networks, where k is the number of destination nodes in a multicast session. So we firstly discuss whether the law still holds in mobile random ad hoc networks, and in this case what delay should be tolerated. Through the relation between average retransmissions and multicast capacity, we prove that order of multicast capacity is not achievable whp, and delay for multicast capacity is , where is the number of ad hoc nodes in the whole networks, and and c is a positive constant. Then achievable throughput whp is considered. The nearest neighbor transmission strategy is introduced by Grossglauser and Tse to achieve throughput which is so far the highest achievable unicast capacity. So the multicast capacity of mobile ad hoc networks under this strategy is studied. The analysis shows that under any multicast routing scheme based on the nearest neighbor transmission strategy, the upper bound on multicast capacity is whp. Then we propose a multicast routing and scheduling scheme by which mobile ad hoc networks can achieve throughput whp, and must tolerate total network delay. Copyright © 2009 John Wiley & Sons, Ltd.     

基于SDN的互联网域间路由研究

互联网流量的爆发式增长,叠加互联网流量固有的突发性特点,使得网络流量不均衡现象日益加剧。传统BGP协议由于缺乏全网拓扑和全局流量观,只能遵循标准BGP选路原则,在解决流量调度和负载均衡方面存在不足。针对BGP协议存在的局限性,研发了基于RR+的互联网骨干网流量调度系统,并应用于ChinaNet骨干网的网内中继、网间互联出口、IDC出口等多个流量优化场景。更进一步地,提出了一种基于SDN的互联网域间路由架构,通过在域间控制器之间交换BGP路由,无需在域内和域间运行BGP协议,极大地简化了网络协议,并能够实现灵活的流量调度和负载均衡。     

TD-SCDMA集群系统中部分宏分集组网前向容量分析

TD-SCDMA集群小区使用宏分集技术可以有效的克服大尺度衰落,保证信号质量。本文首先分析了在没有任何措施的前提下进行宏分集组网,但前向容量会随着宏分集基站数的增多而减少。在分析容量损失原因的基础上,我们进一步提出在终端利用Rake接收机对各路信号进行同步、相位调整,再进行最大比值合并,然后发送给用户,由此,前向容量大大提高。     

三网融合技术值得注意的几个问题

三网融合正在积极推进,其技术选择受到各方关注,为此而探讨几个主要问题：借助三网融合,展开适度竞争,有利于改善我国的网络环境,有线电视业参与三网融合竞争的基本条件;非对称DOC-SIS/HFC网络结构更有利于三网融合增值业务开发,Cable Modem和ADSL是当前宽带接入的主流技术,Cable Modem接入技术将在宽带市场竞争中胜出,而EPON＋EoC并非网络双向改造的最佳方案。针对有关的指导性文件,阐述相对固定的信道带宽更有利于有线电视联网和用户接入,提出两种技术与经济效益更好的方法,以增加传输容量,较8n（MHz）方式变更信道带宽更先进更合理。     

高效率基站Doherty功放的研究

随着无线通信系统的发展,人们对数据和信息的需求在不断的增加。功率放大器作为通信系统中最重要的模块之一,功放的性能对整个系统性能的影响至关重要。面对高速增长的移动数据业务和频谱资源短缺的威胁,高峰均比（PAR）的调制方式不断出现,如OFDM调制方式,这就对功放的线性度提出了较高的要求。为了保证信号的线性度,一般采用功率回退的方法来实现。以NXP公司的140W晶体管为模型,在ADS仿真软件中设计对称Doherty仿真电路。设计完成的功放电路能够在6dB功率范围内保持高效率工作。     

Realization of 2-D Variable IIR Digital Filter Structures with a Small Amount of Calculations for Coefficient Update

This paper proposes 2-D variable IIR digital filter structures with a small amount of calculations for coefficient update. The proposed realization method uses the 2-D parallel allpass structure derived from the separable denominator 2-D filter as the prototype structure for 2-D variable digital filters. In order to reduce the amount of calculations, all the redundant first-order complex allpass sections are combined by modularization of the variable structure. Furthermore, we can realize a very compact variable structure with a minimal number of first-order complex allpass sections by combining complex allpass sections with their complex conjugate allpass sections. Comparison of the calculation loads of the variable structures is presented to demonstrate that the amount of calculations for coefficient update of the proposed variable structure is far less than that of the original and the modular variable structure.     

Hybrid Chameleon Search and Remora Optimization Algorithm-based Dynamic Heterogeneous load balancing clustering protocol for extending the lifetime of wireless sensor networks

Clustering is an indispensable strategy that helps towards the extension of lifetime of each sensor nodes with energy stability in wireless sensor networks (WSNs). This clustering process aids in sustaining energy efficiency and extended network lifetime in sensitive and critical real-life applications that include landslide monitoring and military applications. The dynamic characteristics of WSNs and several cluster configurations introduce challenge in the process of searching an ideal network structure, a herculean challenge. In this paper, Hybrid Chameleon Search and Remora Optimization Algorithm-based Dynamic Clustering Method (HCSROA) is proposed for dynamic optimization of wireless sensor node clusters. It utilized the global searching process of Chameleon Search Algorithm for selecting potential cluster head (CH) selection with balanced trade-off between intensification and extensification. It determines an ideal dynamic network structure based on factors that include quantity of nodes in the neighborhood, distance to sink, predictable energy utilization rate, and residual energy into account during the formulation of fitness function. It specifically achieved sink node mobility through the integration of the local searching capability of Improved Remora Optimization Algorithm for determining the optimal points of deployment over which the packets can be forwarded from the CH of the cluster to the sink node. This proposed HCSROA scheme compared in contrast to standard methods is identified to greatly prolong network lifetime by 29.21% and maintain energy stability by 25.64% in contrast to baseline protocols taken for investigation.     

无人地震台站太阳能供电电源的使用与维护

作为我国国计民生的重要组成范畴,电源与供电技术的革新是时代发展的必然产物,它与电源使用需求之间有着密切的联系。产业革命之后针对高科技电源技术的应用成为了新时期供电技术发展的典范,太阳能电源凭借其节能、净化、安全等多重特点成为了无人地震台站用电的主要输出系统。文中从无人地震台站的基本供电特点出发,重点分析了特殊地区太阳能供电电源的使用及维护等问题。     

基于负载分类的交换式以太网的实时性研究

为了满足交换式以太网中部分数据的实时性,该文应用网络演算对周期性实时数据和突发性实时数据进行分析,同时对受控类负载采取负载分类的方法,赋以不同优先级并采用静态优先级队列的策略进行调度。仿真结果表明,负载分类的策略有效地将强实时负载任务的延迟控制在一定值内,同时大幅度降低了受控类负载的平均时延,特别是降低了较高优先级受控类负载的时延,从而提高了数据的实时性。     

An energy‐efficient utility‐based distributed data routing scheme for heterogenous sensor networks

A utility‐based distributed data routing algorithm is proposed and evaluated for heterogeneous wireless sensor networks. It is energy efficient and is based on a game‐theoretic heuristic load‐balancing approach. It runs on a hierarchical graph arranged as a tree with parents and children. Sensor nodes are considered heterogeneous in terms of their generated traffic, residual energy and data transmission rate and the bandwidth they provide to their children for communication. The proposed method generates a data routing tree in which child nodes are joined to parent nodes in an energy‐efficient way. The principles of the Stackelberg game, in which parents as leaders and children as followers, are used to support the distributive nature of sensor networks. In this context, parents behave cooperatively and help other parents to adjust their loads, while children act selfishly. Simulation results indicate the proposed method can produce on average more load‐balanced trees, resulting in over 30% longer network lifetime compared with the cumulative algorithm proposed in the literature. Copyright © 2014 John Wiley & Sons, Ltd.