无线Mesh网络集中式信道分配算法设计

以集中式无线Mesh网络(WMN)为基础,分析和研究了传统多信道分配算法,并在此基础上提出了以节点优先级和分组为特点的多接口多信道分配算法(Channel Assignment based on Rank of Node and Link group,CAR-NL),该算法结合节点分级和链路负载预期评估机制,通过节点链路分组按级分配信道。通过仿真实验表明,该算法能有效提高无线Mesh网络多业务流并发执行时系统整体吞吐量,并实现较低的丢包率。     

A fairness adaptive TDMA scheduling algorithm for wireless sensor networks with unreliable links

Wireless sensor networks consist of a large number of wireless sensor nodes that organize themselves into multihop radio networks. With different link quality, different distance to the sink, nodes in a network are not treated equally, especially in a network with high traffic. In this paper, we propose a fairness adaptive time division multiple access scheduling algorithm (FATS) considering the fairness of network resource allocation. This algorithm, combining several heuristic algorithms, can assign network resources to the nodes to lead to maximizing the minimum end‐to‐end packet delivery success ratio. Because the wireless link is usually time‐varying, this algorithm can also assign the time slots to the nodes adaptively and energy‐efficiently according to the variation of link quality. We define several criteria for the slot assignment and adjustment. The change in slot assignment can be finished quickly during normal packet transmission, which causes little affect to the network. Meanwhile, considering the required data rate, FATS can achieve the maximum transmission capacity of the network with specified static or dynamic reliability. The simulation results show that the FATS can significantly reduce the difference of the end‐to‐end packet delivery ratio, track the variation of link quality quickly, and achieve the fairness of resource allocation.Copyright © 2012 John Wiley & Sons, Ltd.     

Introducing Fairness-Efficiency Trade-off for Energy Savings in Wireless Cooperative Networks

The focus of this paper is on a wireless cooperative network architecture, where a group of users exploits short-range wireless links to share the costs of a cellular download. To maximize the efficiency of the communication system, an optimization of parameters such as download time, monetary cost, and energy consumption can be implemented. Following this approach different portions of data shall be assigned for download to the involved users, which will then cooperatively exchange the contents on the short-range link. However, the policy of task assignment to the user terminals has a direct influence on the payoff of the single users, raising fairness issues in real implementation scenarios. Focusing on the energy savings introduced by the wireless cooperative network, in this paper we address the fairness issue by relying on game theoretic bargaining solutions. These solutions, have intrinsic properties to nicely model the duality between fairness and efficiency in the performances. An optimal trade-off algorithm between efficiency and fairness is then introduced, allowing the service coordinator to select the most appropriate bargaining solution and energy savings allocation under different constraints on fairness.     

RPR环网中的一种带宽公平分配算法

首先讨论了RPR网络中的公平性原则,然后结合该原则引入了一种适合于RPR网络的公平分配方案,基于该方案提出了一种能满足RPR环网性能要求的公平分配算法。该算法通过采用控制的方法为共享某链路的各数据流合理地分配带宽资源,从而达到:(1)各流的速率达到稳定;(2)链路缓存的占有量稳定到一个目标值;(3)链路带宽得到充分利用且实现公平分配。同时该算法能顺次协同地处理完网络中的各个链路,从而能够实现整个RPR环网的公平性与高的链路带宽利用率,达到RPR协议所要求的目标。给出了该算法的代码描述并对其作出稳定性分析,然后通过仿真对其性能进行了验证。     

协作系统中基于比例公平的资源分配方法

针对多用户协作中继系统中的资源分配问题,提出了一种在满足用户速率比例公平约束条件下的新算法。该算法先将由2个时隙组成的中继用户传输链路转换为一个等效信道链路,将涉及子载波分配、中继选择和功率分配的组合优化问题转化为分步的次优化问题。该算法在等功率分配情况下,根据各用户速率比例公平系数进行初步子载波数目分配;以瞬时信道增益最佳原则,进行剩余子载波数目分配及具体子载波分配,同时完成中继选择;在速率比例公平约束条件下推导出次优化功率分配的闭式表达式,从而完成各子载波上的功率分配。仿真结果表明,该算法在有效提高系统容量的同时,保证了各用户速率之间的比例公平性。     

Link scheduling with power control for throughput enhancement in multihop wireless networks

Joint scheduling and power control schemes have previously been proposed to reduce power dissipation in wireless ad hoc networks. However, instead of power consumption, throughput is a more important performance concern for some emerging multihop wireless networks, such as wireless mesh networks. This paper examines joint link scheduling and power control with the objective of throughput improvement. The MAximum THroughput link Scheduling with Power Control (MATH-SPC) problem is first formulated and then a mixed integer linear programming (MILP) formulation is presented to provide optimal solutions. However, simply maximizing the throughput may lead to a severe bias on bandwidth allocation among links. To achieve a good tradeoff between throughput and fairness, a new parameter called the demand satisfaction factor (DSF) to characterize the fairness of bandwidth allocation and formulate the MAximum Throughput fAir link Scheduling with Power Control (MATA-SPC) problem is defined. An MILP formulation and an effective polynomial-time heuristic algorithm, namely, the serial linear programming rounding (SLPR) heuristic, to solve the MATA-SPC problem are also presented. Numerical results show that bandwidth can be fairly allocated among all links/flows by solving the MILP formulation or by using the heuristic algorithm at the cost of a minor reduction of network throughput. In addition, extensions to end-to-end throughput and fairness and multiradio wireless multihop networks are discussed.     

802.11无线网状网中基于时频信道的准动态信道分配算法

该文首次在多天线多信道802.11无线网状网中提出了时频信道的概念。时频信道是通过在时间和频率两个维度划分无线资源取得的。这种划分方法增加了信道数量,使信道划分更加精细,为提高系统的信道利用率做了准备。在时频信道的基础上,提出了准动态信道分配算法。该算法可以和现有的固定信道分配算法结合,实现准动态信道分配,根据链路上负载变化,取得最大的吞吐量。该算法先根据固定信道分配算法为各链路分配相同数量的时频信道,剩余部分当作公共信道。在通信过程中,各链路首先使用分配给自己的信道和空闲的公共信道。如果分配给一个链路的信道不够,且别的链路上的信道有空闲,该链路还可以暂时使用这些空闲信道。理论分析和仿真结果证明该算法可以有效提高系统的吞吐量。     

Cross-Layer Design for End-to-End Throughput and Fairness Enhancement in Multi-Channel Wireless Mesh Networks

In this paper, we study joint rate control, routing and scheduling in multi-channel wireless mesh networks (WMNs), which are traditionally known as transport layer, network layer and MAC layer issues respectively. Our objective is to find a rate allocation along with a flow allocation and a transmission schedule for a set of end-to-end communication sessions such that the network throughput is maximized, which is formally defined as the maximum throughput rate allocation (MRA) problem. As simple throughput maximization may result in a severe bias on rate allocation, we take account of fairness based on a simplified max-min fairness model and the proportional fairness models. We define the max-min guaranteed maximum throughput rate allocation (MMRA) problem and proportional fair rate allocation (PRA) problem. We present efficient linear programming (LP) and convex programming (CP) based schemes to solve these problems. Numerical results show that proportional fair rate allocation schemes achieves a good tradeoff between throughput and fairness.     

无线mesh网络中基于效用最优的联合信道分配和功率分配算法

该文针对多信道无线mesh网络,采用基于效用最优的定价机制,提出了一种功率-干扰价格模型,并基于该模型提出了一种分布式联合信道分配和功率分配算法。每个节点根据自己所消耗功率状况合理地定功率价格,并根据自己所受干扰状况合理地定干扰价格。通过功率价格和干扰价格来调节链路的信道分配和功率分配,使网络效用最大化。仿真结果表明:所提出的算法能够快速、平稳地收敛到近似最优解。同时还仿真了网络可用信道数目、节点射频数目和功率对系统性能的影响,可以为网络配置提供参考。     

Subcarrier allocation and bit loading algorithms for OFDMA-based wireless networks

Orthogonal Frequency Division Multiple Access (OFDMA) is an emerging multiple access technology. In this paper, we consider OFDMA in the context of fixed wireless networks. This paper addresses the problem of assigning subcarriers and bits to point-to-point wireless links in the presence of cochannel interference and Rayleigh fading. The objective is to minimize the total transmitted power over the entire network while satisfying the data rate requirement of each link. We formulate this problem as a constrained optimization problem and present centralized algorithms. The simulation results show that our approach results in an efficient assignment of subcarriers and transmitter power levels in terms of the energy required for transmitting each bit of information. However, centralized algorithms require knowledge of the entire network topology and channel characteristics of every link. In a practical scenario, that would not be the situation and there is a need for distributed rate allocation algorithms. To address this need, we also present a distributed algorithm for allocating subcarriers and bits in order to satisfy the rate requirements of the links.