WiMAX实时业务数据下行调度算法的仿真与改进

WiMAX是下一代无线城域网(WMAN)技术,支持实时与非实时等多种业务,由IEEE 802.16协议定义.协议定义了多种QoS调度类型,但并没有定义具体的带宽调度策略,而WiMAX的下行相对于上行来说是更容易造成传输瓶颈.文章提出一种针对实时业务流的优化方案,BS进行下行调度时对实时业务集中调度,根据网络状况对分组进行动态丢弃,大大减少了在网络拥挤情况下的带宽使用和分组延迟,优化了抖动,保证了更好的QoS.文中以VoIP业务为例对NS2进行仿真.仿真结果表明,通过对下行分组队列算法的合理优化,能更好地改善系统性能、提高吞吐量、减少时延和减少缓冲区需求.     

无线Mesh网络中基于公平的EDCA算法研究

针对无线Mesh网络的网络特性,分析无线Mesh网络中的EDCA算法,提出了一种基于公平的EDCA算法,详细讨论了该算法的具体实现过程及参数变化规则,通过仿真验证了该算法提高网络的公平性同时改善网络性能,还可以达到对不同业务流的业务区分。     

无线Mesh网络中基于拥塞概率的EDCA算法研究

针对无线Mesh网络的网络特性,分析了无线Mesh网络中的EDCA算法,提出了一种基于拥塞概率的CPEDCA算法,详细讨论了该算法的具体实现过程及参数的动态调整方法,通过仿真验证了该算法对网络性能的提高,同时可以实现不同业务流间的业务区分。     

基于无线Mesh网络技术构建无线城市

无线Mesh网络(WMN)可以和多种无线网络系统,如无线局域网(WLAN)、无线城域网(WMAN)等相结合,改善无线网络的性能,提高网络的覆盖范围.以WMN网络技术在IEEE 802系列标准中的发展为基础,提出了一种无线城市的覆盖方案,最底层网络覆盖采用WiFi+wireless Mesh技术,WiMAX网络与WiFi...     

应用于二维Mesh结构片上网络的区域转弯路由算法

本文针对二维Mesh结构片上网络,在转弯模型的基础上提出一种新的路由算法——区域转弯算法,以获得更低的延迟时间和更高的吞吐率.该算法利用当前节点的X坐标,将整个Mesh网络划分为两个部分,目的节点X坐标小于当前节点X坐标的实行西优先算法,反之实行北最后算法.仿真结果表明,该算法相比于XY路由算法,平均延迟时间有所降低,当负载为40cycles/message时,延迟时间降低最大,为13.99%.吞吐率在负载为20cycles/message时最大提高13.56%.     

无线Mesh网络中激励机制研究

为了激励无线Mesh网络中自私节点转发数据,通过分析节点自私行为激励的原因和目标,将适用于无线Mesh网络中对节点自私行为的四类激励机制进行比较.讨论了无线Mesh网络博弈模型,并对无线Mesh网络中重复博弈模型进行理论分析.针对节点的自私行为提出了基于博弈论与信誉相结合的激励方案.仿真实验表明,该方案不仅降低了基于信誉的复杂度又能有效激励更多自私节点转发数据,从而提高了网络的整体性能.     

IEEE 802.16中改进的QoS动态分层调度算法设计

WiMAX(IEEE802.16)为每个节点提供实时业务和非实时业务,并对不同的业务提出了QoS保证服务。调度算法是WiMAX为分类业务提供QoS保证的重要技术。本文提出一种用于WiMAX系统PMP模式下的动态调整优先级的分层调度算法DAPQ,DAPQ算法由基站(BS)和用户站(SS)共同实现,为不同优先级的业务流动态分配带宽,可以为系统提供更好的公平性,并有效的减少时延。仿真结果表明,本文提出的算法在一定程度上降低了rtPS业务的时延和丢包率。     

基于链路选择因子的高速无线个域网自适应时隙调度算法

本文提出了一种基于链路选择因子的高速无线个域网自适应时隙调度算法.在利用服务曲线对网络QoS需求进行建模的基础上,结合由链路质量获得的实时最优帧长,算法可以得出各个链路的选择因子.同时,选择因子的控制参数k能够决定调度算法的偏重点是链路质量还是业务QoS.仿真结果表明,该算法能在保证网络公平性的基础上有效地提高系统吞吐量.     

移动Mesh网络定位系统研究

提出了一种基于移动Mesh网络的定位系统,利用Mesh节点作为"锚"节点,建立相对坐标系,移动终端通过测量与"锚"节点之间距离,并通过TDOA定位算法获得自身相对位置信息。对移动Mesh网络定位系统可行性问题进行探讨,主要对移动Mesh网络条件下实现终端定位的性能进行了探讨,并对定位误差进行了必要的仿真验证。仿真结果表明该系统定位精度较高,可实现基于移动Mesh通信网络的终端定位功能。     

WiMAX系统中的MAC层与网络层接入算法问题探讨

宽带无线接入技术作为无线城域网(Wireless Metropolitan Area Networks)中最具发展潜力的接入技术之一,正受到业界越来越多的关注。IEEE802.15系列规范(也称为WiMAX)的制定,就是为了适应宽带无线接入的快速发展,并为之提供一个全球统一的标准。本文主要研究WiMAX系统网络的常见网络拓扑结构,介绍Mesh网络的帧结构和MAC层的集中式和分布式接入调度算法。     

Designing multihop wireless backhaul networks with delay guarantees

As wireless access technologies improve in data rates, the problem focus is shifting towards providing adequate backhaul from the wireless access points to the Internet. Existing wired backhaul technologies such as copper wires running at DSL, T1, or T3 speeds can be expensive to install or lease, and are becoming a performance bottleneck as wireless access speeds increase. Longhaul, non-line-of-sight wireless technologies such as WiMAX (802.16) hold the promise of enabling a high speed wireless backhaul as a cost-effective alternative. However, the biggest challenge in building a wireless backhaul is achieving guaranteed performance (throughput and delay) that is typically provided by a wired backhaul. This paper explores the problem of efficiently designing a multihop wireless backhaul to connect multiple wireless access points to a wired gateway. In particular, we provide a generalized link activation framework for scheduling packets over this wireless backhaul, such that any existing wireline scheduling policy can be implemented locally at each node of the wireless backhaul. We also present techniques for determining good interference-free routes within our scheduling framework, given the link rates and cross-link interference information. When a multihop wireline scheduler with worst case delay bounds (such as WFQ or Coordinated EDF) is implemented over the wireless backhaul, we show that our scheduling and routing framework guarantees approximately twice the delay of the corresponding wireline topology. Finally, we present simulation results to demonstrate the low delays achieved using our framework.     

Throughput-range tradeoff of wireless mesh backhaul networks

Wireless backhaul communication is expected to play a significant role in providing the necessary backhaul resources for future high-rate wireless networks. Mesh networking, in which information is routed from source to destination over multiple wireless links, has potential advantages over traditional single-hop networking, especially for backhaul communication. We develop a linear programming framework for determining optimum routing and scheduling of flows that maximizes throughput in a wireless mesh network and accounts for the effect of interference and variable-rate transmission. We then apply this framework to examine the throughput and range capabilities for providing wireless backhaul to a hexagonal grid of base stations, for both single-hop and multihop transmissions for various network scenarios. We then discuss the application of mesh networking for load balancing of wired backhaul traffic under unequal access traffic conditions. Numerical results show a significant benefit for mesh networking under unbalanced loading.     

移动WiMAX网络端到端QoS解决方案的研究

本文根据移动WiMAX的组网特点和业务流分类,深入分析了无线承载和IP传输承载的QoS机制,给出了一种无线承载和IP传输承载的QoS对应的映射方案,从而解决移动WiMAX系统中端到端的QoS问题.     

WiMAX Mesh网络技术分析

WiMAX是近来新兴的无线宽带接入技术之一,具有高带宽、长距离的特性,正受到越来越多的关注。与点对多点(PMP)模式相比,Mesh模式更是具备覆盖范围广、系统容量高、组网灵活等诸多优势。分析了WiMAXMesh网络的拓扑结构特点以及MAC帧定义,简要阐述了网络控制机制与新节点入网流程,对Mesh模式下的调度机制进行了细致分析和对比,在最后指出了后期的研究重点和关键技术。     

QoS Differentiation for IEEE 802.16 WiMAX Mesh Networking

Recently IEEE 802.16 WiMAX has attracted a lot of attention in wireless networking research and applications. To enable a flexible and cost-effective deployment, mesh networking mode is defined in WiMAX standard. In this paper, we introduce a system model of WiMAX mesh networking with the focus on entry process, frame structure, centralized and distributed scheduling. The state-of-the-art WiMAX mesh networking research is reviewed. In addition, we propose an effective QoS differentiation scheme for the IEEE 802.16 WiMAX mesh networks. Both collocated scenario and general topology are theoretically analyzed and compared. Illustrative numerical examples are presented to demonstrate the effectiveness of the proposed strategy. The impact of key parameters on the performance is discussed for differentiating multiple classes of services. Several open issues are summarized as a guideline for future topics in WiMAX mesh networking research.     

Integration of IEEE 802.11 WLANs with IEEE 802.16-based multihop infrastructure mesh/relay networks: A game-theoretic approach to radio resource management

One of the promising applications of IEEE 802.16 (WiMAX)-based wireless mesh/relay networks is to provide infrastructure/backhaul support for IEEE 802.11-based mobile hotspots. In this article we present an architecture for integrating IEEE 802.11 WLANs with IEEE 802.16-based multihop wireless mesh infrastructure to relay WLAN traffic to the Internet. The major research issues in this integrated architecture are outlined and related work is reviewed. A game-theoretic model is developed for radio resource management in this integrated network architecture. In particular, a multiplayer bargaining game formulation is used for fair bandwidth allocation and optimal admission control of different types of connections (e.g., WLAN connections, relay connections, and connections from standalone subscriber stations) in an IEEE 802.16 base station/mesh router. Both connection-level and inconnection-level performances for this bandwidth management and admission control framework are presented     

WiMAX femtocells: a perspective on network architecture, capacity, and coverage

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner. The idea is to overlay low-power and low-cost base station devices, Femto-APs, on the existing cellular network, where each Femto-AP provides high-speed wireless connection to subscribers within a small range. In particular, Femto-APs can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage, using a single access technology such as WiMAX. In this article we consider a WiMAX network deploying both macro BSs and Femto-APs, where it is assumed that Femto-APs have wired backhaul such as cable or DSL and operate on the same frequency band as macro BSs. Simulation results show that significant areal capacity (throughput per unit area) gain can be achieved via intense spatial reuse of the wireless spectrum. In addition, Femto-APs improve indoor coverage, where the macro BS signal may be weak. Motivated by the gains in capacity and coverage offered by femtocells, we review the state of the art of this "infant" technology, including use cases and network deployment scenarios, technical challenges that need to be addressed, and current standardization and industry activity.     

A low complexity mechanism for congestion notification in rural IPSec‐enabled heterogeneous backhaul networks

Management in wireless backhaul networks is a challenging task, especially in rural and isolated environments. In these scenarios, the backhaul network usually consists of a set of heterogeneous wireless links that provide limited and variable bandwidth to the access networks, often 3G/4G small cells. Because of the highly constrained nature of this type of backhaul network, intelligent and joint management in both the backhaul network and the access network is crucial in order to avoid performance degradation caused by traffic congestion. In order to avoid the saturation in the backhaul network, access networks should consider the backhaul state when taking decisions in the admission control and scheduling procedures. However, no standardized mechanisms currently exist for sharing management information between both networks. In this work, we propose to use the Explicit Congestion Notification (ECN) bit in the outer IP headers present in the Iuh 3GPP IPSec‐enabled interfaces in order to notify the backhaul congestion state to the access network. We analyze for the referred scenario, compatibility and security details, validating our approach by running numerically simulations and implementing the notification mechanism. Our low complexity approach offers 2% accuracy and backhaul update latency lower than 10 ms during 80% of the time, which makes the solution appropriate for admission control and scheduling intervals in small cells.     

WiMAX组网方案研究

本文研究了基于OFDM技术的WiMAX小区规划方案,给出了各种提高频谱效率的方案;然后对WiMAX与现网的融合进行了分析,给出了紧耦合和松耦合两种方法,并就基于IPv6的WiMAX核心网机制进行了阐述;最后对基站的无线互联方案进行了探讨.     

Maximizing the Network Stability in Mobile WiMAX Mesh Networks

Resource scheduling and routing tree construction in WiMAX mesh centralized scheduling are not defined in the standard and thus are subject to extensive research. In this paper, we consider routing and scheduling in a WiMAX-based mesh network. We assume that nodes are not necessarily stationary, but rather mobile with a mobility that may yield to frequent topology changes (e.g., failure of existing links and creation of new transmission links). We model the joint routing and scheduling as an optimization problem whose objective is either to determine a minimum length schedule by maximizing spectrum spatial reuse or maximizing the network lifetime by routing around the less stable RF-links, while satisfying a set of (uplink/downlink) end-to-end demands. While solving the problem with the two objectives, we study the tradeoffs between these two objectives. We show that minimizing the schedule length forces the joint routing and scheduling problem to generate a routing tree and feasible transmission groups which favor higher spectrum spatial reuse (and hence higher system throughput), irrespective of the robustness of the selected transmission links. In addition, we show that maximizing the network stability or lifetime yields the selection of different routing trees and slot assignments which do not necessarily result in shorter schedule length. We perform numerical experiences where we compare the performances of our proposed models with respect to the network stability and resource spatial reuse.