Graph‐based resource allocation algorithms for multiuser downlink MIMO‐OFDMA networks

Multiuser multiple‐input multiple‐output orthogonal frequency division multiple access (MIMO‐OFDMA) is considered as the practical method to attain the capacity promised by multiple antennas in the downlink direction. However, the joint calculation of precoding/beamforming and resource allocation required by the optimal algorithms is computationally prohibitive. This paper proposes computationally efficient resource allocation algorithms that can be invoked after the precoding and beamforming operations. To support stringent and diverse quality of service requirements, previous works have shown that the resource allocation algorithm must be able to guarantee a specific data rate to each user. The constraint matrix defined by the resource allocation problem with these data rate constraints provides a special structure that lends to efficient solution of the problem. On the basis of the standard graph theory and the Lagrangian relaxation, we develop an optimal resource allocation algorithm that exploits this structure to reduce the required execution time. Moreover, a lower‐complexity suboptimal algorithm is introduced. Extensive simulations are conducted to evaluate the computational and system‐level performance. It is shown that the proposed resource allocation algorithms attain the optimal solution at a much lower computational overhead compared with general‐purpose optimization algorithms used by previous MIMO‐OFDMA resource allocation approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

MQBV: multicast quality of service swarm bee routing for vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) are witnessing in recent years a rapid development for road transmissions and are considered as one of the most important types of next generation networks, in which drivers can have access anywhere and anytime to information. However, vehicles have to deal with many challenges such as the links failures due to their frequent mobility as well as limited degrees of freedom in their mobility patterns. In this paper, we propose a new quality of service multicast and multipath routing protocol for VANETs, based on the paradigm of bee's communication, called multicast quality of service swarm bee routing for VANETs (MQBV). The MQBV finds and maintains robust routes between the source node and all multicast group members. Therefore, the average end‐to‐end delay and the normalized overhead load should be reduced, while at the same time increasing the average bandwidth and the packet delivery ratio. Extensive simulation results were obtained using ns‐2 simulator in a realistic VANET settings and demonstrated the efficiency of the proposed protocol. Copyright © 2013 John Wiley & Sons, Ltd.     

Service‐based high‐speed railway base station arrangement

To provide stable and high data rate wireless access for passengers in the train, it is necessary to properly deploy base stations along the railway. We consider this issue from the perspective of service, which is defined as the integral of the time‐varying instantaneous channel capacity. With large‐scale fading assumption, it will be shown that the total service of each base station is inversely proportional to the velocity of the train. Besides, we find that if the ratio of the service provided by a base station in its service region to its total service is given, the base station interval (i.e., the distance between two adjacent base stations) is a constant regardless of the velocity of the train. On the other hand, if a certain amount of service is required, the interval will increase with the velocity of the train. The aforementioned results apply not only to simple curve rails, like line rail and arc rail, but also to any irregular curve rail, provided that the train is traveling at a constant velocity. Furthermore, the new developed results are applied to analyze the on–off transmission strategy of base stations. Copyright © 2013 John Wiley & Sons, Ltd.     

服役温度对多壁碳纳米管/Li1.18Ni0.15Co0.15Mn0.52O2复合正极材料性能的影响

通过煅烧的方式制得多壁碳纳米管(MWCNT)质量分数为3%的MWCNT/Li1.18Ni0.15Co0.15Mn0.52O2锂离子电池复合正极材料,并测试了复合正极材料在不同服役温度环境下的电化学性能:-20和60℃下服役时,其放电容量分别高达169、303 mAh·g^-1,且展示出良好的倍率性能和循环稳定性。结合电化学阻抗测试结果可知,MWCNT均匀附着在层状粒子的表面,有效减少了电解液对电极材料的侵蚀,阻碍了表面膜的生成,同时提高了材料的电子电导率。     

一种牧场配料系统的设计与实现

提出了一种应用于移动Ad Hoc网络的分布式资源接纳控制机制,在目的节点和中间节点部署不同的资源接纳控制模块,能以接近通话或者分组传输的时间间隔适应网络的动态变化,为业务提供较好的QoS保障,并且能够支持多播及接收者异质性。仿真结果表明,添加资源接纳控制机制后,时延、抖动及丢包率分别降低了25.75%,51.76%和24.15%。     

小微数据包高效无线传输技术的发展和趋势

5G-NR和B5G系统都需能高效地支持小微数据包(块)的传输,且在不同的无线传输技术(如宽带或超低时延)之间快速灵活地切换.系统梳理和比较和小微数据包(块)相关的多种无线传输技术,如两步RACH、预配置授权和公共资源竞争等,分析它们对3GPP各个系统和各个RAN协议的影响和复杂度优劣等,并进一步展望其未来发展和应用趋势...     

装备战备完好性及其影响因素分析

介绍了装备战备完好性的概念和国外装备战备完好性的研究现状,在用战备完好率和使用可用度来度量装备战备完好性的基础上,从装备研制和使用两方面系统地分析了影响战备完好性的主要因素并提出解决思路。     

以面向市场的科技创新体制推进企业转型

上海市电信有限公司在对中国电信集团公司提出的转型战略深入思考和探索后,提出自身实施科技创新的立足点:面向市场、服务转型.本文介绍了上海电信进行以市场为导向的科技创新工作的4个方向,其中总结了上海电信在近几年所获得的成绩以及未来贯彻落实集团转型战略的具体工作措施.     

短信多业务平台架构的研究

本文针对当前短信业务越来越丰富的趋势,着重分析了在短信多业务并存下的号码路由问题,提出了一种新的基于业务分发路由方式的短信多业务平台架构,以解决当前短信多业务并存中的诸多问题.     

内容计费及其技术路线

基于传统语音业务利润率下降的现实,阐述了内容服务价值链的形成原因和组成,并提出建设一套能够为电信运营商所用、所管、所利的内容计费平台的必要性.最后,概要说明了内容计费平台的建设原则和两种技术方案与适用条件.