多跳蜂窝系统中固定中继节点支持的随机接入协议

针对多跳蜂窝移动通信环境,文章基于时分多址方式提出由固定中继节点支持的随机接入协议,并具体阐述了其系统模型。仿真结果表明,和以往研究相比,该协议的网络吞吐量明显提高,适用于未来的多跳蜂窝移动通信系统。     

下一代移动通信系统中的多跳通信

多跳通信可以在低功率消耗的情况下，实现无线信号的传输，并增加了蜂窝网络拓扑结构的灵活性，成为下一代移动通信技术中的研究热点。本文介绍了当前已经提出的多跳蜂窝网络系统，分析了多跳蜂窝通信的特性，并讨论了今后多跳蜂窝通信系统中的主要研究领域和问题。     

混合网络研究

自组织网和蜂窝网是移动通信系统的重要组成部分,融合两者的混合网络将可能成为未来移动通信系统的重要组成形式之一.文章介绍了混合网络的研究现状,分析了各网络模型的特性,并对混合网络中的关键技术问题,如框架结构、通信模式选择、信道分配、路由、计费、负载均衡,进行了探讨.文章认为混合网络通过其灵活的网络组建能力,不仅提高了对传统业务的支持,同时也为引入新服务创造了条件.自组织网络和蜂窝网络的融合将为构造下一代移动通信系统奠定基础.     

基于固定中继的盲区覆盖的研究

如何减小蜂窝小区的盲区覆盖一直是多跳蜂窝网络研究的热点问题。这里提出了一种新的在传统蜂窝小区中划分扇区并加入固定中继的系统模型。该系统模型通过数学模型解析了节点移动到盲区边缘或未完全进入盲区时的距离,并通过算法描述了盲区附近节点需要选择跳板节点的条件以及通过跳板节点连接到固定中继后再同基站通信的过程。该方法设计降低了掉话率,维持了正常通信,仿真证明了该方法的可行性。     

多跳蜂窝混合网络路由协议的研究

文章分析了多跳蜂窝混合网络的优势及存在的问题，提出了一种支持多跳蜂窝混合网络的路由协议HMCNRP。HMCNRP协议采用区域路由技术和代理注册机制，实现了工作模式选择智能化、转换灵活化，提高了网络的连通性和覆盖范围，增强了网络的鲁棒性。     

路由特性对IEEE802．11 DCF多跳网络容量的影响

使用数学分析方法研究基于IEEE 802.11 DCF的Ad Hoc网络中节点传输半径和路由策略选择问题.在节点均匀分布的多跳网络中,使用四种路由策略以及不同的节点传榆半径设王,试图找出能够使网络容量最大化的方案组合.计算结果表明,在节点密度一定的情况下,减小网络节点的传输距离有利于增加网络的容量,而在传输半径一定的条件下,使用能够导致长跳路由的策略,有利于提高网络容量.     

无线多跳网络中节点激励策略的研究

随着多跳蜂窝网的发展,协作通信成为热点问题,其中节点激励策略是研究重点.分析比较了Ad Hoc网络和多跳蜂窝网络中的激励策略.根据每种策略的优缺点,详细阐述了实现节点激励策略的关键因素,指出结合信誉和计费和有安全保证的激励策略才是下一代多跳网络节点协作问题的关键.     

基于C-RAN的5G无线接入网架构

在分析传统蜂窝结构的无线接入网面临越来越多的挑战的基础上,介绍了当前移动通信系统的发展趋势和需求,分析了第五代移动通信系统(5G)的研究目标以及对未来网络的要求.针对该问题,提出了基于C-RAN的新型5G无线接入网架构,并进一步阐述了5G通信系统网络架构的潜在关键技术,包括UND、虚拟化,SDN、NFV、CDN和绿色通信,为5G网络架构研究提供参考.     

蜂窝与ad hoc融合网络的路由算法

蜂窝网络与ad hoc网络作为两种不同性质的网络结合,可以提高系统的容量和吞吐量、扩大覆盖范围、均衡小区业务、提高用户下行传输速率等等。融合网络路由将不再是基于单一的蜂窝或是ad hoc网络的路由算法,而是在源和目的节点之间通过多跳、代理或是蜂窝网络建立一条最佳的路径。这里将介绍几种融合网络模型的路由算法,并重点介绍其中的一种算法。     

能耗均衡的无线传感网络不等环分层路由算法

针对无线传感器网络(Wireless Sensor Network,WSN)中邻近汇聚节点(sink)的传感节点负荷和能耗过载问题,基于整体网络能耗平衡目标,提出一种不等环的次优分层网络路由。在均匀分布的传感节点环境中,以sink为中心,按照拓扑距离进行分环多跳路由,理论推导了不等环半径,并考虑单跳能耗。实验分析仿真结果表明,该路由分层模型延长了网络生存周期,提高了节点利用效率,且达到网络内大部分节点能耗均衡的目标。     

Novel Section‐Based Joint Network Coding and Scheduling Scheme in WMNs: JNCS

Guaranteeing quality of service over a multihop wireless network is difficult because end‐to‐end (ETE) delay is accumulated at each hop in a multihop flow. Recently, research has been conducted on network coding (NC) schemes as an alternative mechanism to significantly increase the utilization of valuable resources in multihop wireless networks. This paper proposes a new section‐based joint NC and scheduling scheme that can reduce ETE delay and enhance resource efficiency in a multihop wireless network. Next, this paper derives the average ETE delay of the proposed scheme and simulates a TDMA network where the proposed scheme is deployed. Finally, this paper compares the performance of the proposed scheme with that of the conventional sequential scheduling scheme. From the performance analysis and simulation results, the proposed scheme gives more delay‐ and energy‐efficient slot assignments even if the NC operation is applied, resulting in a use of fewer network resources and a reduction in ETE delay.     

基于网络编码的无线网络多流问题研究

多流问题研究多对源、宿节点之间所能达到的最大吞吐。在无线网络中,解决该问题的关键在于量化无线干扰。由于网络编码能够在一定程度上克服无线干扰的影响,因此通过使用超边来描述编码发送,并构造关于超边的冲突图,可以实现对网络编码条件下无线干扰（以协议干扰模型为例）的量化,进而解决网络编码条件下的多流问题。此外,针对在超边冲突图中搜集所有极大独立集的NP难问题,提出了一种实用的搜集算法,并给出了相关的数字结果。     

一种新的下一代无线个人通信网络

下一代无线通信网络是以用户为中心和异构的,不仅支持网络的自动配置和适应性,而且使用扩展多跳的无线个域网(WPAN)。与此同时,它将以一种透明的方式向用户提供多种类型的服务,这就需要有效地把异构网络技术与不同类型的协议结合起来,形成一个完整的网络体系,网络整合的关键是通过IP技术来达到协议的整合。文中介绍一种新的适用于目前和未来无线个人通信及相关服务的无线个人通信网络架构及其关键技术。     

Performance Optimization of Interference-Limited Multihop Networks

The performance of a multihop wireless network is typically affected by the interference caused by transmissions in the same network. In a statistical fading environment, the interference effects become harder to predict. Information sources in a multihop wireless network can improve throughput and delay performance of data streams by implementing interference-aware packet injection mechanisms. Forcing packets to wait at the head of queues and coordinating packet injections among different sources enable effective control of copacket interference. In this paper, throughput and delay performance in interference-limited multihop networks is analyzed. Using nonlinear probabilistic hopping models, waiting times which jointly optimize throughput and delay performances are derived. Optimal coordinated injection strategies are also investigated as functions of the number of information sources and their separations. The resulting analysis demonstrates the interaction of performance constraints and achievable capacity in a wireless multihop network.      

Does the IEEE 802.11 MAC protocol work well in multihop wireless adhoc networks?

The IEEE 802.11 MAC protocol is the standard for wireless LANs; it is widely used in testbeds and simulations for wireless multihop ad hoc networks. However, this protocol was not designed for multihop networks. Although it can support some ad hoc network architecture, it is not intended to support the wireless mobile ad hoc network, in which multihop connectivity is one of the most prominent features. In this article we focus on the following question: can the IEEE 802.11 MAC protocol function well in multihop networks? By presenting several serious problems encountered in an IEEE 802.11-based multihop network and revealing the in-depth cause of these problems, we conclude that the current version of this wireless LAN protocol does not function well in multihop ad hoc networks. We thus doubt whether the WaveLAN-based system is workable as a mobile ad hoc testbed     

Cross-Layer Design for QoS Support in Multihop Wireless Networks

Due to such features as low cost, ease of deployment, increased coverage, and enhanced capacity, multihop wireless networks such as ad hoc networks, mesh networks, and sensor networks that form the network in a self-organized manner without relying on fixed infrastructure is touted as the new frontier of wireless networking. Providing efficient quality of service (QoS) support is essential for such networks, as they need to deliver real-time services like video, audio, and voice over IP besides the traditional data service. Various solutions have been proposed to provide soft QoS over multihop wireless networks from different layers in the network protocol stack. However, the layered concept was primarily created for wired networks, and multihop wireless networks oppose strict layered design because of their dynamic nature, infrastructureless architecture, and time-varying unstable links and topology. The concept of cross-layer design is based on architecture where different layers can exchange information in order to improve the overall network performance. Promising results achieved by cross-layer optimizations initiated significant research activity in this area. This paper aims to review the present study on the cross-layer paradigm for QoS support in multihop wireless networks. Several examples of evolutionary and revolutionary cross-layer approaches are presented in detail. Realizing the new trends for wireless networking, such as cooperative communication and networking, opportunistic transmission, real system performance evaluation, etc., several open issues related to cross-layer design for QoS support over multihop wireless networks are also discussed in the paper.     

Self‐adaptive routing protocols for integrating cellular networks,WLANs, and MANETs

A growing need to have ubiquitous connectivity has motivated our research to provide continuous connection between various wireless platforms such as cellular networks, wireless local area networks (WLANs), and mobile ad hoc networks (MANETs). In this paper, we consider integration at the routing layer and propose two adaptable routing protocols (IRP‐RD and IRP‐PD) that exploit topology information stored at the fixed network components (cellular base stations and WLAN access points) for the route discovery and maintenance processes. Our proposed protocols can provide connectivity to the cellular network and/or WLAN hotspots through multihop routing, while differ in the gateway discovery approach used. In IRP‐RD, multihop routes to gateways to the cellular network or WLAN hot spots are discovered on demand, while in IRP‐PD out of coverage users proactively maintain routes to the gateways. Furthermore, proposed protocols can be used in any heterogeneous scenario, combining a cellular network and WLANs operating in infrastructure or ad hoc (MANET) mode. We provide simulation results that demonstrate the effectiveness of the proposed integrated routing protocols and show the advantages and drawbacks of each gateway discovery approach in different heterogeneous scenarios. Copyright © 2006 John Wiley & Sons, Ltd.     

Energy-efficient joint relay node selection and power allocation over multihop relaying cellular networks toward LTE-Advanced

Cooperative relaying is emerging as an effective technology to fulfill requirements on high data rate coverage in next-generation cellular networks,like long term evolution-advanced (LTE-Advanced).In this paper,we propose a distributed joint relay node (RN) selection and power allocation scheme over multihop relaying cellular networks toward LTE-Advanced,taking both the wireless channel state and RNs’ residual energy into consideration.We formulate the multihop relaying cellular network as a restless bandit system.The first-order finite-state Markov chain is used to characterize the time-varying channel and residual energy state transitions.With this stochastic optimization formulation,the optimal policy has indexability property that dramatically reduces the computational complexity.Simulation results demonstrate that the proposed scheme can efficiently enhance the expected system reward,compared with other existing algorithms.     

Design and analysis of distributed utility maximization algorithm for multihop wireless network with inaccurate feedback

Distributed network utility maximization (NUM) is receiving increasing interests for cross‐layer optimization problems in multihop wireless networks. Traditional distributed NUM algorithms rely heavily on feedback information between different network elements, such as traffic sources and routers. Because of the distinct features of multihop wireless networks such as time‐varying channels and dynamic network topology, the feedback information is usually inaccurate, which represents as a major obstacle for distributed NUM application to wireless networks. The questions to be answered include if distributed NUM algorithm can converge with inaccurate feedback and how to design effective distributed NUM algorithm for wireless networks. In this paper, we first use the infinitesimal perturbation analysis technique to provide an unbiased gradient estimation on the aggregate rate of traffic sources at the routers based on locally available information. On the basis of that, we propose a stochastic approximation algorithm to solve the distributed NUM problem with inaccurate feedback. We then prove that the proposed algorithm can converge to the optimum solution of distributed NUM with perfect feedback under certain conditions. The proposed algorithm is applied to the joint rate and media access control problem for wireless networks. Numerical results demonstrate the convergence of the proposed algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

Improving Spatial Reuse in Multihop Wireless Networks - A Survey

In multihop wireless ad-hoc networks, the medium access control (MAC) protocol plays a key role in coordinating the access to the shared medium among wireless nodes. Currently, the distributed coordination function (DCF) of the IEEE 802.11 is the dominant MAC protocol for both wireless LANs and wireless multihop ad hoc environment due to its simple implementation and distributed nature. The current access method of the IEEE 802.11 does not make efficient use of the shared channel due to its conservative approach in assessing the level of interference; this in turn affects the spatial reuse of the limited radio resources and highly affect the achieved throughput of a multihop wireless network. This paper surveys various methods that have been proposed in order to enhance the channel utilization by improving the spatial reuse.