REUSE: A combined routing and link scheduling mechanism for wireless mesh networks

Increasing the capacity of wireless mesh networks has motivated numerous studies. In this context, the cross-layer optimization techniques involving joint use of routing and link scheduling are able to provide better capacity improvements. Most works in the literature propose linear programming models to combine both mechanisms. However, this approach has high computational complexity and cannot be extended to large-scale networks. Alternatively, algorithmic solutions are less complex and can obtain capacity values close to the optimal. Thus, we propose the REUSE algorithm, which combines routing and link scheduling and aims to increase throughput capacity in wireless mesh networks. Through simulations, the performance of the proposal is compared to a developed linear programming model, which provides optimal results, and to other proposed mechanisms in the literature that also deal with the problem algorithmically. We observed higher values of capacity in favor of our proposal when compared to the benchmark algorithms.     

On the end-to-end flow allocation and channel assignment in multi-channel multi-radio wireless mesh networks with partially overlapped channels

The performance of wireless mesh networks (WMNs) can be improved significantly with the increase in number of channels and radios. Despite the availability of multiple channels in several of the current wireless standards, only a small fraction of them are non-overlapping and many channels are partially overlapped. In this paper, we formulate the joint channel assignment and flow allocation problem for multi-channel multi-radio WMNs as a Mixed Integer Linear Program (MILP). Unlike most of the previous studies, we consider the case when both non-overlapped and partially overlapped channels are being used. We consider an objective of maximizing aggregate end-to-end throughput and minimizing queueing delay in the network, instead of the sum of link capacities, since the traffic characteristics of a multi-hop WMN are quite different from a single hop wireless network. Our static channel assignment algorithm incorporates network traffic information, i.e., it is load aware. Our formulation takes into consideration several important network parameters such as the transmission power of each node, path loss information, the signal to interference plus noise ratio at a node, and the frequency response of the filters used in the transmitter and receiver. We show by simulations that our MILP formulation makes efficient use of the spectrum, by providing superior channel assignments and flow allocations with the addition of partially overlapped channels, without the use of any additional spectrum. We also justify the need to consider alternative objective functions such as, minimizing average queueing in the network. We also propose a polynomially bounded heuristic algorithm to scale the proposed algorithm to bigger network topologies.     

Routing Internet traffic in heterogeneous mesh networks: Analysis and algorithms

In practical wireless mesh networks (WMNs), gateways are subject to hard capacity limits on the aggregate number of flows (in terms of bit rate) that they can support. Thus, if traffic is routed in the mesh network without considering those constraints, as well as the traffic distribution, some gateways or intermediate mesh routers may rapidly get overloaded, and the network resources can be unevenly utilized. To address this problem, in this paper we firstly develop a multi-class queuing network model to analyze feasible throughput allocations, as well as average end-to-end delay, in heterogeneous WMNs. Guided by our analysis, we design a Capacity-Aware Route Selection algorithm (CARS), which allocates network paths to downstream and upstream Internet flows so as to ensure a more balanced utilization of wireless network resources and gateways’ fixed connections. Through simulations in a number of different network scenarios we show that the CARS scheme significantly outperforms conventional shortest path routing, as well as an alternative routing method that distributes the traffic load on the gateway nodes to minimize its variance.     

Integrated connection-level and packet-level QoS controls over wireless mesh networks

This paper focuses on integrating connection-level and packet-level QoS controls over wireless mesh network (WMN) to support applications with diverse QoS performance requirements. At the connection-level, the dynamic guard based prioritized connection admission control (DG-PCAC) provides prioritized admission with relative connection blocking probabilities and end-to-end deterministic minimum bandwidth allocation guarantees. DG-PCAC is enabled by dynamic guard based logical link configuration controls (LCCs), which provides relative differentiated capacity limits for prioritized admission classes. At the packet-level, the optimal rate delay scheduler (ORDS) dynamically allocates link bandwidth to the admitted flows of prioritized traffic classes; with the objective to minimize deviation from relative delay targets with minimum bandwidth guarantees according to traffic classes. Two realizations of the ORDS are presented, namely optimal scheduling policy via dynamic programming (DP) algorithm, and neural network (NN) based heuristic to alleviate computational complexity. Performance results show that the DG-PCAC enables consistent performance guarantees under non-stationary arrivals of connection requests. Performance results also show that the performance of the NN based scheduling heuristic approaches to that of the DP based optimal ORDS scheme.     

WMN中的干扰避免部分重叠信道分配算法

针对无线mesh网络(wireless mesh networks,WMN)中存在的信道干扰问题,提出一种基于部分重叠信道(partially overlapping channels,POC)的负载平衡且干扰避免的信道分配算法。通过基于Huffman树的通信接口分配方法连接邻居节点的接口;根据网络干扰情况,对链路进行迭代信道分配,使用静态链路调度保证网络连接;利用启发式算法优先为重要程度较高的链路分配无干扰时隙,对链路调度进行优化。仿真结果表明,在具有混合流量的WMN中,所提算法可以显著提升网络吞吐量,降低网络干扰与平均丢包率,改善网络性能。     

基于UWB的无线传感器网络跨层优化模型研究

跨层设计是提高无线传感器网络整体性能的一种有效方法。在综合考虑MAC层调度、物理层功率控制、网络层路由三方面因素的基础上,结合超宽带技术大带宽、低信号功率的特点,以实现网络最大数据传输速率为目标,构建了基于超宽带技术的无线传感器网络跨层优化模型。仿真实验表明：模型最优解可有效提高网络数据传输速率;物理层功率控制对优化结果有着至关重要的影响。这证明以构建、求解优化模型的方式解决跨层设计问题是切实可行的,同时也为解决大规模超宽带传感器网络数据传输问题提供了一条新的解决思路。     

User density sensitive P2P streaming in wireless mesh networks

Link rate allocation is very important for supporting high video playback rate in Peer-to-Peer video streaming. Although many studies can be found on resource allocation in P2P streaming in wired networks, very few studies have studied the problem in wireless networks, especially in Wireless multi-hop Mesh Networks (WMNs), which is still challenging. To maximize the users’ satisfaction of P2P streaming in WMNs, this paper focuses on link rate allocation problem and proposes a fully distributed algorithm to efficiently utilize the upload and download bandwidth of wireless mesh nodes. We first build an efficient P2P streaming system based on the experimental results from real deployment of our wireless mesh testbed. Then we design an efficient distributed algorithm based on the solution to a linear optimization model, which optimizes towards a user-density-related objective to decide the best streaming rates among peers. Our scheme is resilient to network dynamics that is characteristic in wireless multi-hop peer-to-peer networks. The simulation experiments demonstrate the significant performance enhancement by using the proposed rate allocation algorithm in WMNs.     

超宽带传感器网络跨层优化模型应用研究

跨层设计是提高无线传感器网络整体性能的一种有效方法。在综合考虑MAC层调度、物理层功率控制、网络层路由三方面因素的基础上,结合超宽带技术大带宽、低信号功率的特点,以实现网络最大数据传输速率为目标,构建了超宽带传感器网络跨层优化模型,并提出了适用于大规模网络的数据传输解决方法。实验结果表明,模型最优解可有效提高网络的数据传输速率,同时该优化模型还可用于解决大规模网络数据传输问题。这证明以构建、求解优化模型的方式解决跨层设计问题是切实可行的。     

Optimal joint routing and link scheduling for real-time traffic in TDMA Wireless Mesh Networks

We investigate the problem of joint routing and link scheduling in Time-Division Multiple Access (TDMA) Wireless Mesh Networks (WMNs) carrying real-time traffic. We propose a framework that always computes a feasible solution (i.e. a set of paths and link activations) if there exists one, by optimally solving a mixed integer-nonlinear problem. Such solution can be computed in minutes or tens thereof for e.g. grids of up to 4 × 4 nodes. We also propose heuristics based on Lagrangian decomposition to compute suboptimal solutions considerably faster and/or for larger WMNs, up to about 50 nodes. We show that the heuristic solutions are near-optimal, and we exploit them to gain insight on the schedulability in WMN, i.e. to investigate the optimal placement of one or more gateways from a delay bound perspective, and to investigate how the schedulability is affected by the transmission range.     

Enhanced MAC protocol to support multimedia traffic in cognitive wireless mesh networks

With the advanced physical layer techniques such as multiple-input and multiple-output (MIMO) and orthogonal frequency-division multiplexing (OFDM), transmission real-time 2D/3D contents and applications becomes more and more necessary in wireless networks for the amazing growing in demand of customers. However, the low efficiency of medium access control (MAC) protocol degrades the performance of real-time traffic greatly in multihop, wireless and mobile environment. Focusing on supporting real-time multimedia traffic in cognitive wireless mesh networks (WMNs), an enhanced MAC protocol is proposed. And the contribution of this paper is twofold: (1) An efficient carrier sense multiple access with collision avoidance (CSMA/CA) compatible time division multiple access (TDMA)-like MAC protocol called T-MAC is proposed, which aims to improve the system performance by allocating more channel access time in centralized manner and decreasing overhead. (2) An optimal adaptive scheduling scheme is proposed to support real-time multimedia applications and guarantee QoS for different priority traffic, which aims to find the optimized schedule among all possible sequences of concurrent transmissions by minimizing the occupied resources. Detailed simulation results and comparison with IEEE 802.11e MAC scheme show that the proposed T-MAC can effectively improve quality of service (QoS) for multimedia traffic in terms of throughput, end-to-end delay and packet loss rate, which also manifests that T-MAC is an efficient multimedia applications transmission scheme for mobile terminals and MAPs in cognitive WMNs.     

Utility-based scheduling in wireless multi-hop networks over non-deterministic fading channels

In this paper, an innovative scheduling scheme is proposed for interference-limited wireless multi-hop networks with non-deterministic fading channels. The scheduling problem is considered as a network utility maximization (NUM) problem subject to link rate constraints. By jointly taking into account of the link scheduling and the statistical variations of signal and interference power, the convex sets for the NUM are derived. Two types of non-deterministic fading channels (i.e., Rayleigh fading channel and Ricean fading channel) are characterized into our NUM models as examples. To solve the convex optimization problem, the subgradient projection method based on dual decomposition is employed. Then, a heuristic algorithm is designed for the TDM mode wireless multi-hop networks by minimizing the discrepancy between the expected network cost and the optimal one in each timeslot. At last, the source–destination session rate and network utility are evaluated in a dedicated wireless multi-hop network scenario. The numerical results demonstrate that the session rates convergence and the network utility is improved by our proposed scheme.     

Enhancing multi-hop communication over multi-radio multi-channel wireless mesh networks: A cross-layer approach

The multi-channel multi-radio technology represents a straightforward approach to expand the capacity of wireless mesh networks (WMNs) in broadband wireless access scenarios. However, the effective leveraging of this technology in WMNs requires (i) enhanced MAC protocols, to coordinate the access to multiple channels with a limited number of radio interfaces, and (ii) efficient channel allocation schemes, to mitigate the impact of co-channel interference. The design of channel assignment schemes and MAC protocols is strictly interrelated, so that joint design should be considered to optimize the mesh network performance. In this paper, a channel assignment and fast MAC architecture (CAFMA) is proposed, which exploits the benefits provided by the multi-channel multi-radio technology to (i) enhance the performance of multi-hop communications, (ii) maximize the resource utilization, and (iii) support differentiation of traffic classes with different quality of service (QoS) requirements. CAFMA is designed with a cross-layer approach and includes (1) a novel MAC scheme, which provides multi-channel coordination and fast data relaying over multi-hop topologies, and (2) a distributed channel allocation scheme, which works in cooperation with the routing protocol. Simulation results confirm the effectiveness of CAFMA when compared with other single-layer and cross-layer solutions for multi-radio multi-channel WMNs.     

Joint routing, scheduling, and power control for multichannel wireless sensor networks with physical interference

Reliability and real-time requirements bring new challenges to the energy-constrained wireless sensor networks, especially to the industrial wireless sensor networks. Meanwhile, the capacity of wireless sensor networks can be substantially increased by operating on multiple nonoverlapping channels. In this context, new routing, scheduling, and power control algorithms are required to achieve reliable and real-time communications and to fully utilize the increased bandwidth in multichannel wireless sensor networks. In this paper, we develop a distributed and online algorithm that jointly solves multipath routing, link scheduling, and power control problem, which can adapt automatically to the changes in the network topology and offered load. We particularly focus on finding the resource allocation that realizes trade-off among energy consumption, end-to-end delay, and network throughput for multichannel networks with physical interference model. Our algorithm jointly considers 1) delay and energy-aware power control for optimal transmission radius and rate with physical interference model, 2) throughput efficient multipath routing based on the given optimal transmission rate between the given source-destination pairs, and 3) reliable-aware and throughput efficient multichannel maximal link scheduling for time slots and channels based on the designated paths, and the new physical interference model that is updated by the optimal transmission radius. By proving and simulation, we show that our algorithm is provably efficient compared with the optimal centralized and offline algorithm and other comparable algorithms.     

Application-aware scheduling for VoIP in Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are seen as a means to provide last mile connections in Next Generation Networks (NGNs). Because of their auto-configuration capabilities and the low deployment cost WMNs are considered to be an efficient solution for the support of multiple voice, video and data services in NGNs. This paper looks at the optimal provision of resources in WMNs for Voice over IP (VoIP) traffic, which has strict performance requirements in terms of delay, jitter and packet loss. In WMNs, because of the challenges introduced by wireless multi-hop transmissions and limited resources, providing performance quality for VoIP comparable to the voice quality in the traditional circuit-switched networks is a major challenge.This paper analyses different scheduling mechanisms for TDMA-based access control in mesh networks as specified in the IEEE 802.16-2004 WiMAX standard. The performance of the VoIP applications when different scheduling mechanisms are deployed is analysed on a variety of topologies using ns-2 simulation and mathematical analysis. The paper concludes that on-demand scheduling of VoIP traffic – typically deployed in 802.11-based WMNs – is not able to provide the required VoIP quality in realistic mesh WiMAX network scenarios and is therefore not optimal from a network operator’s point of view. Instead, it is shown, that continuous scheduling is much better suited to serve VoIP traffic. The paper then proposes a new VoIP-aware resource coordination scheme and shows, through simulation, that the new scheme is scalable and provides good quality for VoIP service in a wide range of network scenarios. The results shown in the paper prove that the new scheme is resilient to increasing hop count, increasing number of simultaneous VoIP sessions and the background traffic load in the network. Compared to other resource coordination schemes the VoIP-aware scheduler significantly increases the number of supported calls.     

无线传感器网络中基于最小延时的数据汇集树构建与传输调度算法

无线传感器网络的数据通信模式问题是目前的研究热点,针对现有的无线传感器网络数据汇集算法延时较大这一不足,对最小延时数据汇集树和传输调度问题进行了研究。提出一种基于度约束的汇集树构建算法(DCAT)。该算法按照 BFS 方式遍历图,当遍历到每个节点时,通过确定哪些节点与汇点更近来确定潜在母节点集合。然后,选择图中度数最小的潜在母节点作为当前被遍历节点的母节点。此外,为了在给定的汇集树上进行高效地数据汇集,还提出两种新的基于贪婪的TDMA传输调度算法：WIRES-G 和 DCAT-Greedy。利用随机生成的不同规模的传感器网络,参照当前最新算法,对文中方法的性能进行了全面评估。结果表明,与当前最优算法相比,文中调度算法与文中汇集树构建算法结合起来,可显著降低数据汇集的延时。     

无线mesh网络中效用与链路强度联合优化的覆盖多播

支持多播通信是无线mesh网络(WMNs)的一个重要应用.采用基于效用的定价机制,通过拉格朗日(Lagrange)对偶分解法获得一个基于价格的分布式算法.以该分布式算法为核心,作为mesh网络中数据流速率和链路强度调整的优化策略,每条链路根据自己的拥塞状况合理地定价,通过价格机制来调节链路的强度和数据流的速率,使网络净效用最大化.实验结果表明该算法是有效可行的.     

WSN中基于最小延时的数据汇集树构建与传输调度算法

针对现有的无线传感器网络数据汇集算法延时较大的不足,对最小延时数据汇集树和传输调度问题进行了研究。提出一种基于度约束的汇集树构建算法(DCAT)。该算法按照BFS方式遍历图,当遍历到每个节点时,通过确定哪些节点与汇点更近来确定潜在母节点集合。然后,选择图中度数最小的潜在母节点作为当前被遍历节点的母节点。此外,为了在给定的汇集树上进行高效的数据汇集,还提出两种新的基于贪婪的TDMA传输调度算法:WIRES-G和DCAT-Greedy。利用随机生成的不同规模的传感器网络,参照当前最新算法,对所提方法的性能进行了全面评估。结果表明,与当前最优算法相比,将所提调度算法与所提汇集树构建算法结合起来,可显著降低数据汇集的延时。     

The WICKPro protocol with the Packet Delivery Ratio metric

Wireless mesh networks (WMNs) with chain topologies are very useful in road and railroad transportation or in tunnel and mine applications. The proposed protocols for WMNs usually support best-effort traffic or some kind of Quality of Service (QoS). However, some applications such as remote-controlled machines in industrial control networks have hard real-time (HRT) requirements, i.e., strict deadlines. For this reason, this paper incorporates the Packet Delivery Ratio (PDR) metric into the WICKPro (WIreless Chain networK Protocol) protocol, a HRT protocol for WMNs with chain topologies which uses a token-passing approach. WICKPro is a Medium Access Control (MAC) protocol based on the ideas of the Timed-token protocol and the cyclic executive. The incorporation of the PDR metric lets calculate the needed time to be reserved where packet retransmissions can be accommodated while satisfying HRT traffic constraints. Moreover, the feasibility of using the PDR metric in a token-passing protocol is shown. Since WICKPro has been designed to work on top of IEEE 802.11, we made a testbed using commercial 802.11 wireless cards and compared the WICKPro’s performance with the 802.11 protocol and three specific protocols for WMNs with chain topologies.     

云环境下异构无线传感器网络节点调度改进算法

针对大规模传感器网络节点异构性突出、调度困难,传统节点调度算法在大规模传感器网络环境下效率低等问题,提出了基于云计算的节点调度模型,并设计了该模型下的节点调度改进算法。通过将节点算法的执行迁移至云端,由云端调度节点。通过OMnet＋＋对改进算法与云端融合数据处理进行仿真实验表明：改进算法可以有效地延长网络生存周期,并且随着数据量的增加,云端处理融合数据耗时相对平稳。相比较传统节点调度算法,改进算法在能量与耗时指标上表现更优。     

可变频宽无线网络中信道频谱分配与链路调度

考虑信道频宽对链路传输距离和链路间干扰的影响,对可变频宽无线网络现有的累积干扰模型进行了改进,并基于改进的干扰模型对可变频宽无线网络的信道频谱分配和链路调度问题进行了建模分析。设计了一种两层优化算法对信道频谱分配和链路调度问题进行解耦,提出了一种考虑链路负载需求满足程度的链路优先级指标,启发式地构建并发传输信道分配矩阵的方法。仿真结果表明,两层优化算法能够在合理时间内收敛,启发式方法能够高效地构建并发传输信道分配矩阵。