On energy efficiency of geographic opportunistic routing in lossy multihop wireless networks

Geographic opportunistic routing (GOR) is an emerging technique that can improve energy efficiency in lossy multihop wireless networks. GOR makes local routing decision by using nodes?? location information, and exploits the broadcast nature and spatial diversity of the wireless medium to improve the packet forwarding reliability. In this paper, our goal is to fully understand the principles and tradeoffs in GOR, thus provide insightful analysis and guidance to the design of more efficient routing protocols in multihop wireless networks. We propose a local metric, one-hop energy efficiency (OEE), to balance the packet advancement, reliability and energy consumption in GOR. We identify and prove important properties about GOR on selecting and prioritizing the forwarding candidates in order to maximize the expected packet advancement. Leveraging the proved properties, we then propose two localized candidate selection algorithms with O(N ³) running time to determine the forwarding candidate set that maximizes OEE, where N is the number of available next-hop neighbors. Through extensive simulations, we show that GOR applying OEE achieves better energy efficiency than the existing geographic routing and blind opportunistic routing schemes under different node densities and packet sizes.     

Throughput oriented forwarders selection analysis for opportunistic routing in wireless mesh network

Opportunistic routing explicitly takes advantage of the broadcast nature of wireless communications by using a set of forwarders to opportunistically perform packet forwarding. A key issue in the design of opportunistic routing protocols is the forwarder list selection problem. This paper proposes a novel routing metric which shows the end-to-end throughput and a corresponding throughput oriented opportunistic routing forwarder-selecting algorithm throughput oriented forwarders selection (TOFS) through analyzing forwarding characteristics of forwarders. The algorithm puts forward a constraint mechanism that controls the number of forwarders by constraint of throughput for forwarders selection, achieving a better balance between number of forwarders and effective link stability by introducing the factor of transmission time. Simulation results show that the algorithm can improve the network end-to-end throughput effectively over existing methods.     

SOAR: Simple Opportunistic Adaptive Routing Protocol for Wireless Mesh Networks

Multihop wireless mesh networks are becoming a new attractive communication paradigm owing to their low cost and ease of deployment. Routing protocols are critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along predetermined paths and face difficulties in coping with unreliable and unpredictable wireless medium. In this paper, we propose a Simple Opportunistic Adaptive Routing protocol (SOAR) to explicitly support multiple simultaneous flows in wireless mesh networks. SOAR incorporates the following four major components to achieve high throughput and fairness: 1) adaptive forwarding path selection to leverage path diversity while minimizing duplicate transmissions, 2) priority timer-based forwarding to let only the best forwarding node forward the packet, 3) local loss recovery to efficiently detect and retransmit lost packets, and 4) adaptive rate control to determine an appropriate sending rate according to the current network conditions. We implement SOAR in both NS-2 simulation and an 18-node wireless mesh testbed. Our extensive evaluation shows that SOAR significantly outperforms traditional routing and a seminal opportunistic routing protocol, ExOR, under a wide range of scenarios.     

Environment-Driven Opportunity Forwarding Cross-Layer Optimization for Ubiquitous Wireless Networks

In this paper, an environment-driven cross-layer optimization scheme is proposed to maximize packet forwarding efficiency. The proposed algorithm is aimed to improve the performance of location-based routing protocol in respect of greedy forwarding and avoid void regions for ubiquitous wireless networks. In greedy forwarding mode, we use a new routing metric IAPS which can estimate the forwarding distance, link quality and the difficulty of channel access during the process of the next hop node selection. When the packet forwarding comes into a local minimum, the proposed scheme uses an opportunistic forwarding method based on competitive advantage to bypass the void regions. NS2 simulation results indicate that the proposed algorithm can improve network resource utilization and the average throughput, and reduce congestion loss rate of wireless multi-hop network comparison with existing GPSR algorithm.     

EFT: a high throughput routing metric for IEEE 802.11s wireless mesh networks

In this paper, we present a throughput-maximizing routing metric, referred to as expected forwarding time (EFT), for IEEE 802.11s-based wireless mesh networks. Our study reveals that most of the existing routing metrics select the paths with minimum aggregate transmission time of a packet. However, we show by analyses that, due to the shared nature of the wireless medium, other factors, such as transmission time of the contending nodes and their densities and loads, also affect the performance of routing metrics. We therefore first identify the factors that hinder the forwarding time of a packet. Furthermore, we add a new dimension to our metric by introducing traffic priority into our routing metric design, which, to the best of our knowledge, is completely unaddressed by existing studies. We also show how EFT can be incorporated into the hybrid wireless mesh protocol (HWMP), the path selection protocol used in the IEEE 802.11s draft standard. Finally, we study the performance of EFT through simulations under different network scenarios. Simulation results show that EFT outperforms other routing metrics in terms of average network throughput, end-to-end delay, and packet loss rate.     

ad hoc网络中一种基于信任模型的机会路由算法

由于ad hoc网络具有缺乏足够的物理保护、拓扑结构动态变化、采用分布式协作、节点的带宽和计算能力有限等特点,导致传统的路由安全机制不再适合ad hoc网络路由协议的设计。最近当前研究热点之一的机会路由能够在链路不可靠的情况下充分利用无线广播和空间多样性的特性提高网络的吞吐量。因此,考虑在机会路由中引入信任相似性概念设计信任机会路由,建立了基于节点信任度和最小成本的信任机会转发模型,提出了最小成本的机会路由算法MCOR,并对算法进行了理论上的分析和证明。最后采用仿真实验对该算法进行验证,又与经典机会路由协议ExOR以及其他经典的信任路由协议TAODV和Watchdog-DSR进行性能对比。仿真结果表明,MCOR算法能够防范恶意节点的攻击,在吞吐量、端到端时延、期望转发次数(ETX)和成本开销等方面都比其他3种协议表现出性能上的优势。     

On selection of forwarding nodes for long opportunistic routes

Opportunistic routing is a promising routing paradigm which increases the network throughput. It forces the sender’s neighbors, who successfully overheard the transmitted packet, to participate in the packet forwarding process as intermediate forwarding nodes. As a seminal opportunistic routing protocol, MORE combines network coding idea with opportunistic routing to eliminate the need for strict coordination among active forwarding nodes. In this paper, we show that MORE performance does not scale well with the route length, especially when the route length goes beyond two hops. Also, we found that MORE fails to establish a working opportunistic route in sparse networks. Clearly, the network throughput is directly influenced by both the quantity and quality of forwarding nodes, and their cooperation order. In this paper, we propose a new forwarder selection mechanism which considers the route length, link qualities, the distance from the source, and nodes density. It eliminates the occasional route disconnectivity happening in MORE and improves the quality of the established opportunistic routes. The simulation result indicates that our proposal always outperforms MORE when dealing with long opportunistic routes.

     

无线传感器网络中基于最优转发集的协作式编码传输协议

针对当前大多数据传输协议没有充分利用无线信道的广播特性这一问题,本文提出了基于网络编码的机会路由协议NCOR（Network Coding based Opportunistic Routing protocol）.首先,通过分析网络端到端传输代价,本文提出了最优转发集构造机制以最小化传输代价.此后,NCOR在转发集内执行节点协作式编码传输以保证传输可靠性.最后,理论分析了NCOR的传输可靠性结论.仿真实验表明NCOR可适用于不同的链路环境,且在保证可靠传输的同时,大幅降低了网络能耗.     

无线多跳网络中一种基于网络编码的机会路由

近年来机会路由和网络编码是两种利用无线信道广播特性提高网络性能的新兴技术。相比传统的静态路由决策,机会路由利用动态和机会路由选择减轻无线有损链路带来的影响。网络编码可以提高网络的资源利用率。但编码机会依赖于多个并发流所选路径的相对结构。为了创造更多的网络编码机会和提高网络吞吐量,本文提出了一种基于流间网络编码的机会路由(ORNC)算法。在ORNC中,每个分组转发的机会路径选择是基于网络编码感知的方式进行的。当没有编码机会时,采用背压策略选择下一跳转发路径以平衡网络负载。仿真结果表明本文提出的ORNC算法能够提高无线多跳网络的吞吐量。     

On Maximizing Transmission Reliability for Real-Time Routing in Multi-hop Wireless LANs

Three factors have been often shown to significantly affect the reliability of real-time transmission in wireless local area networks—transmission rate, power, and packet size. We analyze these factors and determine the optimal combination of factors subject to time constraints that yields the most reliable transmission of real-time data. We propose a cross-layer framework to jointly design the routing and MAC protocol combined with our optimization approach. The approach under a non-real-time routing protocol that produces a path metric is compared with a real-time routing protocol. Additionally, the real-time routing protocol enhances a guaranteed rate with our approach. Our experiments reveal that real-time performance in terms of miss ratio and throughput is significantly increased in lossy link and heavy traffic environments. Miss ratio and average throughput are improved by up to 30% over a state-of-the art routing protocol and 35% over a MAC protocol, respectively.     

High throughput route selection in multi-rate wireless mesh networks

Most existing Ad-hoc routing protocols use the shortest path algorithm with a hop count metric to select paths. It is appropriate in single-rate wireless networks, but has a tendency to select paths containing long-distance links that have low data rates and reduced reliability in multi-rate networks. This article introduces a high throughput routing algorithm utilizing the multi-rate capability and some mesh characteristics in wireless fidelity （WiFi） mesh networks. It uses the medium access control （MAC） transmission time as the routing metric, which is estimated by the information passed up from the physical layer. When the proposed algorithm is adopted, the Ad-hoc on-demand distance vector （AODV） routing can be improved as high throughput AODV （HT-AODV）. Simulation results show that HT-AODV is capable of establishing a route that has high data-rate, short end-to-end delay and great network throughput.     

一种新的基于部分网络编码的机会路由机制

网络编码能够提升无线网络传输性能,网络中的节点若采用传统的全网络编码,必须等待所有的数据包到达后才能进行解码,而这将造成网络的延迟。通过将部分网络编码和机会路由相结合,提出了一种新的路由协议(ORoPNC),该协议可以降低网络编码延迟,提高网络的稳定性。同时,设计了一种新的转发策略——ETXoEC。在这一策略下,转发节点的选取决定于当前链路状态和节点的剩余能量。仿真结果表明,网络的延迟降低了25%左右,能量消耗也得到了较好的平衡,整个网络的稳定性得到进一步提高。     

Congestion Aware Geographic Routing Protocol for Wireless Ad Hoc and Sensor Networks

Geographic routing protocols forward packets according to the geographical locations of nodes. Thus, the criteria used to select a forwarding node impacts on the performance of the protocols such as energy efficiency and end-to-end transmission delay. In this paper, we propose a congestion aware forwarder selection (CAFS) method for a geographic routing protocol. To design CAFS, we devise a cost function by combining not only the forward progress made to a packet but also the amount of energy required for packet forwarding, forwarding direction, and congestion levels of potential forwarders. Among the potential forwarders, CAFS selects the next forwarder having the minimum cost. In our simulation studies, we compare the performance of CAFS with those of the maximum progress (MP) method and the cost over progress (CoP) method in various network conditions. The results show that compared with MP, the length of a routing path in terms of the number of hops becomes longer when CAFS is used. However, the shorter hop distance helps to avoid unnecessary retransmissions caused by packet loss in a wireless channel. In addition, since CAFS considers congestion levels of candidate forwarders, it reduces the queuing delay in each forwarder. Therefore, CAFS is superior to the MP and the CoP in terms of the energy consumption, end-to-end packet transfer delay, and the successful packet delivery rate.     

ABC-MC: A new multi-channel geographic forwarding scheme for wireless sensor networks

Improving throughput and delay is an important challenge in multi-hop wireless sensor networks. In this work, we propose ABC-MC, a simple multi-channel geographic forwarding scheme. ABC-MC is based on ABC which is a lightweight and reliable routing protocol where nodes do not need to set up or maintain routing/neighbor tables. A unique feature of ABC-MC is that it uses a channel pre-negotiation mechanism to reduce delay. Another unique feature of ABC-MC is that it takes into account the channel usage information within a few (e.g., three) hops in channel selection to reduce interference. Experimental results show that ABC-MC outperforms other protocols in terms of the average delay and throughput performance.     

Contention-based forwarding for mobile ad hoc networks

Existing position-based unicast routing algorithms which forward packets in the geographic direction of the destination require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages each node sends out periodically.

Due to mobility, the information that a node receives about its neighbors becomes outdated, leading either to a significant decrease in the packet delivery rate or to a steep increase in load on the wireless channel as node mobility increases. In this paper, we propose a mechanism to perform position-based unicast forwarding without the help of beacons. In our contention-based forwarding scheme (CBF) the next hop is selected through a distributed contention process based on the actual positions of all current neighbors. For the contention process, CBF makes use of biased timers. To avoid packet duplication, the first node that is selected suppresses the selection of further nodes. We propose three suppression strategies which vary with respect to forwarding efficiency and suppression characteristics. We analyze the behavior of CBF with all three suppression strategies and compare it to an existing greedy position-based routing approach by means of simulation with ns-2. Our results show that CBF significantly reduces the load on the wireless channel required to achieve a specific delivery rate compared to the load a beacon-based greedy forwarding strategy generates.     

A Priority Based Opportunistic Routing Mechanism for Real-Time Voice Service in Mobile Ad hoc Networks

Traditional routing protocols send traffic along pre-determined paths and have been shown ineffective in coping with unreliable and unpredictable wireless medium which is caused by the multi-path fading. The most difference between the opportunistic routing and the traditional routing mechanism is that the opportunistic routing mechanism can use several lossy broadcast links to support reliable transmission. In this paper, an opportunistic routing mechanism for real-time voice service is proposed. This mechanism is based on the dynamic source routing (DSR) protocol with some modifications, the routing messages of DSR are used to construct the forwarder list, which guides the data packets forwarding process. The forwarder nodes have priorities to restrict the number of duplicated packets. Simultaneous flows can be supported well by our mechanism. Simulations show that our mechanism can effectively decrease the data packets transmission times and the amount of the control messages and reduce the end-to-end delay for real-time voice service, the quality of service can be supported well over the unstable wireless channel.     

A novel slot scheduling technique for duty-cycle based data transmission for wireless sensor network

The duty cycling process involves turning a radio into an active and dormant state for conserving energy. It is a promising approach for designing routing protocols for a resource-constrained Wireless Sensor Networks (WSNs). In the duty cycle-based WSNs, the network lifetime is improved and the network transmission is increased as compared to conventional routing protocols. In this study, the active period of the duty cycle is divided into slots that can minimize the idle listening problem. The slot scheduling technique helps determine the most efficient node that uses the active period. The proposed routing protocol uses the opportunistic concept to minimize the sender waiting problem. Therefore, the forwarder set will be selected according to the node's residual active time and energy. Further, the optimum routing path is selected to achieve the minimum forwarding delay from the source to the destination. Simulation analysis reveals that the proposed routing scheme outperforms existing schemes in terms of the average transmission delay, energy consumption, and network throughput.     

A novel real-time scheme for (m,k)-firm streams in wireless sensor networks

The multimedia transmission based real-time applications have posed a big challenge to wireless sensor networks (WSNs) where both reliability and timeliness need to be guaranteed at the same time, to support an acceptable Quality of Service (QoS). The existing real-time routing protocols, however, are not able to meet the QoS requirements of realtime applications because of the inherent resource constraint of sensor nodes and instability of wireless communication. Therefore, we propose a real-time scheme in this paper, including a QoS-aware routing protocol and a set of fault recovery mechanisms, for (m,k)-firm based real-time applications over WSNs. A local status indicator which is specially devised for (m,k)-firm stream, is used for intermediate nodes to monitor and evaluate their local conditions. The proposed routing protocol takes into account of packet deadline, node condition and remaining energy of next hop, to make optimal forwarding decision. Additionally, according to the stream QoS and node condition, the proposed fault recovery mechanisms are utilized for nodes to handle the congestion, link failure and void problems occurred during transmission and remain the desired reliability and timeliness requirements. The proposed scheme has been well studied and verified through simulations. The results have proved the efficiency of the proposed scheme in terms of high successful transmission ratio, small end-to-end delay and long lifetime of network.     

基于动态规划法的无线Mesh网络QoS路由算法和性能评价

该文针对时延敏感的多媒体业务吞吐率和传输可靠性的考虑,在无线Mesh网络中,引入动态规划和跨层设计方法设计QoS路由算法。在假设的网络模型上,提出了一个新的基于MAC层信息的综合凸规划路由准则,以及基于此实现的路由算法CPRMQS,详细给出了利用动态规划法解决路由优化问题的算法流程和样例分析。最后通过仿真验证了该算法的可行性,并给出了基于DSR扩展协议的性能评价,其中包括吞吐率和延时等性能。     

Optimal backpressure routing for wireless networks with multi-receiver diversity

We consider the problem of optimal scheduling and routing in an ad-hoc wireless network with multiple traffic streams and time varying channel reliability. Each packet transmission can be overheard by a subset of receiver nodes, with a transmission success probability that may vary from receiver to receiver and may also vary with time. We develop a simple backpressure routing algorithm that maximizes network throughput and expends an average power that can be pushed arbitrarily close to the minimum average power required for network stability, with a corresponding tradeoff in network delay. When channels are orthogonal, the algorithm can be implemented in a distributed manner using only local link error probability information, and supports a “blind transmission” mode (where error probabilities are not required) in special cases when the power metric is neglected and when there is only a single destination for all traffic streams. For networks with general inter-channel interference, we present a distributed algorithm with constant-factor optimality guarantees.