4G移动通信系统的热点技术及其发展动态

简述了4G系统的特点,并介绍了4G中的OFDM、软件无线电、智能天线、IPv6等新技术,依靠这些复杂的技术,4G系统得以实现100Mbps的传输速度,为人们提供高质量的数据服务。文章最后指出了4G未来的发展动态。     

UMTS性能增强技术研究

指出开发UMTS性能增强技术的关键驱动因素,介绍了扩容天线、多用户检测和软件无线电技术的基本原理与功能,并提出了一种面向分组的体系结构。     

基于RTDS的一种直流触发角测量方法及其实现

随着我国电力系统的发展和计算机漱硬件技术的提高,RTDS实时数字仿真系统由于其具备建立闭环仿真环境等的优点在我国得到了越来越广泛的应用。提出了一种基于RTDS的闭环交直流混联系统的直流触发角测量方法。在介绍了直流触发角测量原理和RTDS改进点火脉冲算法的基础上,提出了可用于直流控制保护设备控制测试分析和系统分析研究用的直流触发角测量方法．并基于RTDS控制模块库元件和自定义（UDC功能进行了仿真实现。最后,就我国桌特高压直流输电系统的电气参数和南瑞继保自主．研发的特高压直流控制保护系统样机,通过与实际控制保护系统直流触发角测量录波软迹的比较．验证了所提方法的有效性。     

在线SDN控制器性能监控器设计与研究

随着网络规模和网络数据流量的变大,软件定义网络控制器性能问题可能成为网络瓶颈,为了在动态负载情况下仍然可以获取控制器准确的性能状态,设计了一个在线的性能监控器框架,并定义了控制器时延性能衡量指标Lpdex.在一款广泛使用的FloodLight控制器中实现了性能监控器的简单原型,经过实验评估,验证了控制器性能监控器的可行性和Lpdex可在线准确地反映控制器在不同负载情况下时延性能的变化.     

Software‐defined networking approach for enhanced evolved packet core network

The evolved packet core (EPC) network is the mobile network standardized by the 3rd Generation Partnership Project and represents the recent evolution of mobile networks providing high‐speed data rates and on‐demand connectivity services. Software‐defined networking (SDN) is recently gaining momentum in network research as a new generation networking technique. An SDN‐based EPC is expected to introduce gains to the EPC control plane architecture in terms of simplified, and perhaps even software‐based, vendor independent infrastructure nodes. In this paper, we propose a novel SDN‐based EPC architecture along with the protocol‐level detailed implementation and provide a mechanism for identifying information fields exchanged between SDN‐EPC entities that maintains correct functionality with minimal impact on the conventional design. Furthermore, we present the first comprehensive network performance evaluation for the SDN‐based EPC versus the conventional EPC and provide a comparative analysis of 2 networks performances identifying potential bottlenecks and performance issues. The evaluation focuses on 2 network control operations, namely, the S1‐handover and registration operations, taking into account several factors, and assessing performance metrics such as end‐to‐end delay (E2ED) for completion of the respective control operation, and EPC nodes utilization figures.     

Software‐defined network‐enabled opportunistic offloading and charging scheme in multi‐unmanned aerial vehicle ecosystem

Unmanned aerial vehicles (UAVs) are autonomous fliers, which can play different roles in modern day applications. In one of the important role, UAVs can act as aerial data forwarding nodes for communication range enhancement in remote areas. UAVs form a web of drones, which can be geo‐distributed across a large area to serve various applications. However, the two major contradicting challenges with respect to multi‐UAV networks are channel congestion and flight time enhancement. The use of effective data transmission techniques to handle congestion can lead to higher battery dissipation, which in turn end up in the reduction in flight time. However, it is utmost necessity to provide an effective framework, which can provide a viable solution for handling congestion in multi‐UAV networks while enhancing the flight time of UAVs. To handle these issues, software‐defined network (SDN)–enabled opportunistic offloading and charging scheme (SOOCS) in multi‐UAV ecosystem is designed in this paper. In this scheme, an opportunistic offloading scheme is proposed, which uses an SDN‐based control model to handle congestion issues. Apart from this, an opportunistic energy‐charging scheme is designed, wherein the UAVS can either replenish their batteries using solar plates or they can wirelessly charge energy from charging points deployed at various geo‐distributed locations. The proposed scheme is evaluated using a simulation‐based study over the realistic deployment of charging points in Chandigarh City, India. The results obtained show the superiority of SOOCS over other variants of its category in terms of end‐to‐end delay, throughput, and hand‐over latency.     

Nature‐inspired meta‐heuristic algorithms for solving the load balancing problem in the software‐defined network

The growth of the networks has difficult network management. Recently, a concept called software‐defined network (SDN) has been proposed to address this issue, which makes network management more adaptable. Control and forwarding planes are separated in SDN. The control plane is a centralized logical controller that controls the network. The forwarding plane that consists of transfer devices is responsible for transmitting packets. Because the network resources are limited, optimizing the use of resources in the networks is an important issue. Load balancing improves the balanced distribution of loads across multiple resources in order to maximize the reliability and network resources efficiency. SDN controllers can create an optimal load balancing compared to traditional networks because they have a network global view. The load‐balancing problem can be solved using many different nature‐inspired meta‐heuristic techniques because it has the NP‐complete nature. Hence, for solving load balancing problem in SDN, nature‐inspired meta‐heuristic techniques are important methods. However, to the best of our knowledge, there is not a survey or systematic review on studying these matters. Accordingly, in the area of the load balancing in the SDN, this paper reviews systematically the nature‐inspired meta‐heuristic techniques. Also, this study demonstrates advantages and disadvantages regarded of the chosen nature‐inspired meta‐heuristic techniques and considers their algorithms metrics. Moreover, to apply better load balancing techniques in the future, the important challenges of these techniques have been investigated.     

SDN‐DMM for intelligent mobility management in heterogeneous mobile IP networks

Mobility management applied to the traditional architecture of the Internet has become a great challenge because of the exponential growth in the number of devices that can connect to the network. This article proposes a Software‐Defined Networking (SDN)‐based architecture, called SDN‐DMM (SDN‐Distributed Mobility Management), that deals with the distributed mode of mobility management in heterogeneous access networks in a simplified and efficient way, ensuring mainly the continuity of IP sessions. Intent‐based mobility management with an IP mapping schema for mobile node identification offers optimized routing without tunneling techniques, hence, an efficient use of the network infrastructure. The simplified mobility control API reduces both signaling and handover latency costs and provides a better scalability and performance in comparison with traditional and SDN‐based DMM approaches. An analytical evaluation of such costs demonstrated the better performance of SDN‐DMM, and a proof of concept of the proposal was implemented in a real environment.     

数据中心网络中相关感知流量整合算法

随着大数据、云计算不断融入人们的日常生活,作为支撑其发展的基础设施--数据中心网络的能耗也在急剧增长。为了解决这个问题,学术界提出了能量感知路由（Energy-Aware Routing,EAR）。EAR的主要思想是通过将流量需求聚集在网络链路的子集,并睡眠未使用的网络设备以节省能量。但是在流量低谷时期频繁地切换网络设备模式可能会导致网络振荡甚至网络性能下降。因此提出了一种相关感知流量整合（Correlation-Aware Traffic Consolidation,CATC）算法。提出了基于软件定义网络（Software Defined Network,SDN）的CATC模型,即在流量整合时考虑了流之间的相关性,并结合链路速率来实现更高的节能。在流量约束和链路容量约束下将CATC模型转换为一个最优流量分配问题,并提出CATC算法来求解。仿真结果显示,与现有的节能算法相比,CATC算法在仅仅增加极少网络延迟的同时可以为数据中心网络节省大约45%的能量。     

Evolutionary gaming approach for decision making of Tier‐3 Internet service provider networks migration to SoDIP6 networks

With the increasing number of Internet of Things (IoT) devices, current networking world is suffering in terms of management and operations with lack of IPv4 addresses leading to issues like network address translation (NAT) proliferation, security and quality of services. Software‐defined networking (SDN) and Internet Protocol version 6 (IPv6) are the new networking paradigms evolved to address related issues of legacy IPv4 networking. To adapt with global competitive environment and avoid all existing issues in legacy networking system, network service providers have to migrate their networks into IPv6 and SDN‐enabled networks. But immediate transformations of existing network are not viable due to several factors like higher cost of migration, lack of technical human resources, lack of standards and protocols during transitions, and many more. In this paper, we present the migration analysis for proper decision making of network transition in terms of customer demand, traffic engineering, and organizational strength with operation expenditure for network migration using evolutionary gaming approach. Joint migration to SDN‐enabled IPv6 network from game theoretic perspective is modeled and is validated using numerical results obtained from simulations. Our empirical analysis shows the evolutionary process of network migration while different internal and external factors in the organization affect the overall migration. Evolutionary game in migration planning is supportive in decision making for service providers to develop suitable strategy for their network migration. The proposed approach for migration decision making is mostly applicable to fairly sustained service providers who lack economics, regulation/policy, and resources strengths.