Overview of Wireless Mesh Networks
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paper_title: Wireless mesh networks: a survey

paper_content:

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.
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paper_title: Wireless Mesh Networks: WMN Overview, WMN Architecture

paper_content:

WMN, the Wireless Mesh Network is a promising technology in providing the last mile broadband access. In a WMN, a mesh client can access the Internet through formed wireless mesh routers which are interconnected in a multi-hop fashion. This paper is a quick technical overview and covers: WMN overview (i.e., fundamental concept, technology, standards, etc.) and WMN architecture (i.e., network and node architectures, components, applications, etc.) Finally, a list of issues requiring further research is deliberated.
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paper_title: Directional virtual carrier sensing for directional antennas in mobile ad hoc networks

paper_content:

This paper presents a new carrier sensing mechanism called DVCS (Directional Virtual Carrier Sensing) for wireless communication using directional antennas. DVCS does not require specific antenna configurations or external devices. Instead it only needs information on AOA (Angle of Arrival) and antenna gain for each signal from the underlying physical device, both of which are commonly used for the adaptation of antenna pattern. DVCS also supports interoperability of directional and omni-directional antennas. In this study, the performance of DVCS for mobile ad hoc networks is evaluated using simulation with a realistic directional antenna model and the full IP protocol stack. The experimental results showed that compared with omni-directional communication, DVCS improved network capacity by a factor of 3 to 4 for a 100 node ad hoc network.
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paper_title: IEEE 802.11s MAC Fundamentals

paper_content:

The tremendous success of the Institute of Electronics and Electrical Engineering (IEEE) 802.11 wireless local area network (WLAN) standard led to severe competition. Due to Wi-Fi Alliance (WFA)'s marketing, 802.11 became a universal solution for wireless connectivity. However, still a WLAN depends on wired infrastructure that interconnects the central access points (APs). To become independent of backbone networks leading to cheap deployments, the traditional single-hop approach needs to be replaced by wireless mesh networks (WMNs). Since several years, the research community develops routing protocols designed for wireless multi-hop networks. With 802.11s an integrated WMN approach is under development that adds the necessary functionality for interworking, security and routing. As its medium access control (MAC), 802.11s relies on the existing schemes. However, the current 802.11 MAC has been designed for wireless single-hop networks. Its application to WMNs leads to low performance. The capacity of the wireless medium can hardly be exploited. Thus, 802.11s provides an optional MAC that has been specifically designed for WMN. In this paper we explain the fundamental operation of the 802.11s MAC, explain its extensions and provide detailed simulation results on their performance.
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paper_title: Dynamic and efficient tuning of IEEE 802.11 for multimedia applications

paper_content:

In order to exploit the properties of multimedia applications in IEEE 802.11-based wireless networks in more appropriate ways, we interest in the dynamic and efficient tuning of the MAC protocol by taking into account the inherent characteristics of this kind of applications. We focus on the try limit parameter used at the 802.11 MAC layer to limit the number of retransmissions of a data frame by a source until the reception of a link-level acknowledgment from the destination. Based on analytical preliminaries, we determine the optimal value of this parameter in order to achieve an expected average end-to-end delay or a maximum packet loss rate. Moreover, an approximated value of the try limit parameter optimizing both QoS criteria (delay and packet loss rate) could also be obtained. Furthermore, these values are approximated dynamically using a simple algorithm that is easily implementable in 802.11 protocol.
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paper_title: Dynamic Tuning of the IEEE 802.11 Protocol to Achieve a Theoretical Throughput Limit

paper_content:

In wireless LANs (WLANs), the medium access control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel. In this paper we focus on the efficiency of the IEEE 802.11 standard for WLANs. Specifically, we analytically derive the average size of the contention window that maximizes the throughput, hereafter theoretical throughput limit, and we show that: 1) depending on the network configuration, the standard can operate very far from the theoretical throughput limit; and 2) an appropriate tuning of the backoff algorithm can drive the IEEE 802.11 protocol close to the theoretical throughput limit. Hence we propose a distributed algorithm that enables each station to tune its backoff algorithm at run-time. The performances of the IEEE 802.11 protocol, enhanced with our algorithm, are extensively investigated by simulation. Specifically, we investigate the sensitiveness of our algorithm to some network configuration parameters (number of active stations, presence of hidden terminals). Our results indicate that the capacity of the enhanced protocol is very close to the theoretical upper bound in all the configurations analyzed.
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paper_title: Multi-channel mac for ad hoc networks: handling multi-channel hidden terminals using a single transceiver

paper_content:

This paper proposes a medium access control (MAC) protocol for ad hoc wireless networks that utilizes multiple channels dynamically to improve performance. The IEEE 802.11 standard allows for the use of multiple channels available at the physical layer, but its MAC protocol is designed only for a single channel. A single-channel MAC protocol does not work well in a multi-channel environment, because of the multi-channel hidden terminal problem . Our proposed protocol enables hosts to utilize multiple channels by switching hannels dynamically, thus increasing network throughput. The protocol requires only one transceiver per host, but solves the multi-channel hidden terminal problem using temporal synchronization. Our scheme improves network throughput signifiantly, especially when the network is highly congested. The simulation results show that our protocol successfully exploits multiple hannels to achieve higher throughput than IEEE 802.11. Also, the performance of our protocol is comparable to another multi-hannel MAC protocol that requires multiple transceivers per host. Since our protocol requires only one transceiver per host, it an be implemented with a hardware complexity comparable to IEEE 802.11.
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paper_title: Traffic and Interference Aware Scheduling for Multiradio Multichannel Wireless Mesh Networks

paper_content:

This paper proposes a scheduling scheme for wireless mesh networks that are capable of multiple channel access and equipped with multiple radio interfaces. The proposed scheme is interference and traffic aware in that it increases the overall achievable throughput of the network by eliminating the interference between the wireless mesh routers and maximizes the satisfaction ratios of all active sessions by accounting for the sessions' data rate requirements. Simulation results show that the proposed scheme outperforms the Tabu-based scheduling scheme and yields good tradeoffs between the achievable throughput of the network and the satisfaction ratios of the sessions.
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paper_title: Wireless mesh networks: a survey

paper_content:

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.
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paper_title: Channel control for multi-radio multi-channel wireless mesh networks

paper_content:

IEEE 802.11 wireless local area networks (WLANs) technologies are being considered as potential turnkey solutions for constructing infrastructures of wireless mesh networks (WMNs). With known experiments and simulation results, performances at the transport layer, including the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), have not been doing satisfactorily for connections passing through multiple hops using 802.11 technologies. Data throughput usually drops significantly when a connection has to go through more than three wireless hops. Since UDP is a simple connectionless protocol, its performance failure indicates that the design of 802.11 Medium Access Control (MAC) protocol may not be competent to handle traffic on the wireless mesh networks. In this paper, a multi-radio multi-channel wireless mesh network architecture with a novel MAC protocol design is proposed. The MAC protocol extends the Request-to-Send/Clear-to-Send message pair in 802.11 for channel reservation operations. Only two stations at an instant can have the sole possession of a specific channel with an announced duration. During this duration, the two stations can establish a connection for sending multiple segments to each other, if needed. This per-hop reservation concept can further be deployed into multi-hop wireless networks, and high throughput data rate should be achievable for multi-hop TCP and UDP connections.
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paper_title: SSCH: slotted seeded channel hopping for capacity improvement in IEEE 802.11 ad-hoc wireless networks

paper_content:

Capacity improvement is one of the principal challenges in wireless networking. We present a link-layer protocol called Slotted Seeded Channel Hopping, or SSCH, that increases the capacity of an IEEE 802.11 network by utilizing frequency diversity. SSCH can be implemented in software over an IEEE 802.11-compliant wireless card. Each node using SSCH switches across channels in such a manner that nodes desiring to communicate overlap, while disjoint communications mostly do not overlap, and hence do not interfere with each other. To achieve this, SSCH uses a novel scheme for distributed rendezvous and synchronization. Simulation results show that SSCH significantly increases network capacity in several multi-hop and single-hop wireless networking scenarios.
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paper_title: Optimization of Resource Allocation in Multi-radio Multi-channel Wireless Mesh Networks

paper_content:

Multi-channel communication in a Wireless Mesh Network with routers having multiple radio interfaces significantly enhances the network capacity. Efficient channel assignment is critical for realization of optimal throughput in such networks. This paper addresses the channel assignment problem for multi-channel multi-interface (radio) wireless mesh networks. We focus on static wireless mesh networks where multiple non-overlapping channels are available for each wireless interface. In this network environment, our objective is to find a fixed channel assignment which maximizes the number of bidirectional links that can be activated simultaneously, subject to interference constraints. We present a mixed integer linear programming models for solving the fixed channel assignment problem with multiple radios. Detailed computational results are presented and discussed to validate the algorithm.
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paper_title: Utilizing Multiple Channels With Fewer Radios in Wireless Mesh Networks

paper_content:

Wireless mesh networking (WMN) is regarded as a low-cost technology for rapid wireless network deployment. However, in a single-channel WMN, the overlapped transmission ranges between relaying mesh points could introduce serious interference. Using multiple radios over multiple channels can decrease the interference and improve the capacity of a WMN, but it increases the cost of a mesh point. One possible solution to balance between interference, hence performance, and cost is utilizing fewer radios that switch among multiple channels instead of using per-channel radios. In this paper, we propose a channel-switching method, called the traffic-aware switching scheme (TRASS), for a mesh point with a limited number of radios. TRASS utilizes the existing IEEE 802.11 mechanisms, i.e., hybrid-coordination-function-controlled channel access and power saving, to avoid packet loss during channel switching. A TRASS mesh point monitors the occupied channel time to schedule radios that switch among channels. The implemented TRASS demonstrates 75% throughput improvement by (2, 1), i.e., two-channel single-radio, over (1, 1). (3, 2) and (3, 1) achieve 69.8% and 39.7%, respectively, of the throughput of (3, 3) in the simulated TRASS.
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paper_title: Throughput Improvement in Multi-Radio Multi-Channel 802.11a-Based Wireless Mesh Networks

paper_content:

Single-radio mesh routers operating on a single channel suffer from low throughput due to collisions. Equipping mesh routers with multiple radios operating on non-overlapping channels can significantly improve the throughput. However, the assignment of channels to radios in a multi-radio mesh network is a challenging task. In this paper, we propose a channel assignment algorithm, TICA (Topology-controlled Interference-aware Channel-assignment Algorithm), which significantly improves network throughput by minimizing interference within the mesh network using a novel approach of controlling the network topology based on power control before intelligently assigning the channels to the multi-radio mesh routers, as well as guaranteeing network connectivity.
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paper_title: A multi-radio unification protocol for IEEE 802.11 wireless networks

paper_content:

We present a link layer protocol called the multi-radio unification protocol or MUP. On a single node, MUP coordinates the operation of multiple wireless network cards tuned to non-overlapping frequency channels. The goal of MUP is to optimize local spectrum usage via intelligent channel selection in a multihop wireless network. MUP works with standard-compliant IEEE 802.11 hardware, does not require changes to applications or higher-level protocols, and can be deployed incrementally. The primary usage scenario for MUP is a multihop community wireless mesh network, where cost of the radios and battery consumption are not limiting factors. We describe the design and implementation of MUP, and analyze its performance using both simulations and measurements based on our implementation. Our results show that under dynamic traffic patterns with realistic topologies, MUP significantly improves both TCP throughput and user perceived latency for realistic workloads.
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paper_title: MAC Design for Interference Issues in Multi-Channel Wireless Mesh Networks

paper_content:

IEEE 802.11 wireless local area networks (WLANs) have been considered as potential solutions for constructing infrastructures of wireless mesh networks (WMNs). For connections going through multiple wireless hops, the interference and transmission range issue at physical layer, terminal problems at link layer, and unsatisfactory performance at transport layer may render 802.11 Medium Access Control (MAC) protocol inappropriate for wireless mesh networks. In fact, the hidden and exposed terminal problems magnify if interference range is multiple times wider than transmission range. The multi-radio multi-channel WLAN is a possible solution for multi-hop mesh networks. In this paper, a multi-channel MAC protocol is extended to combat the interference range and the hidden terminal problems for multi-hop wireless mesh networks. Besides, thorough simulation results indicate that the design offers excellent throughput performance in WLAN environments.
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paper_title: A List-Based Medium Access Control algorithm in IEEE 802.11 wireless mesh networks

paper_content:

The Head-Of-Line (HOL) blocking problem is one of major reasons for degradation of the performance in wireless mesh networks (WMNs). Since IEEE 802.11 MAC handles packets as the First-In, First-Out (FIFO) policy, devices having frames to transmit may stay in back-off stage for a long time due to a HOL-blocked packet. To resolve the HOL blocking problem, we propose a novel scheduling algorithm called as List-Based Medium Access Control (LBMAC). Our LBMAC algorithm improves the network performance by alleviating the HOL blocking problem and reducing the excessive back-off time. We design the LBMAC based on CSMA/CA algorithm so as to easily incorporate with IEEE 802.11 standards. Performance evaluation shows that our algorithm achieves better performance than IEEE 802.11 MAC protocol.
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paper_title: Review of Routing Protocols and It's Metrics for Wireless Mesh Networks

paper_content:

WMNs are low-cost internet access networks built on cooperative routing over a backbone composed ofstationary wireless routers. In hybrid mesh WMNs both client mesh and backbone has ability to forward the data to destination. Many ad hoc routing protocols have been adapted to work in WMN without considering the differences between both technologies. Due to the differences between ad hoc network and WMN network, many Researchers started to revisit the routing protocol design of existing wireless mesh networks (WMNs), especially of IEEE 802.11 networks, and ad hoc networks from the perspectives of WMNs which provide internet for large distances area and consist of two tiers where the heterogeneity exists between them, the heterogeneity between backbone nodes and client nodes are many, for example, the backbone nodes are immobile with a fixed location and high capacity while the client nodes are mobile devices with low capacity and must take care of power consumption and mobility. However, these perspectives should be taken care of in designing the routing protocol to enhance the routing algorithm in order to work well in WMN. There are two ways to enhance the performance of routing protocol in WMN. One way is to improve the metric used in the selection path, the second way is to modify the routing algorithms by considering new characteristics of WMN or integrating the routing protocols with other technologies. In this paper, we present a detailed review of current state-of-the-art routing protocol and its metric for wireless mesh networks in order to provide a better understanding of the research challenges in WMN routing protocol.
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paper_title: A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks

paper_content:

An ad hoc mobile network is a collection of mobile nodes that are dynamically and arbitrarily located in such a manner that the interconnections between nodes are capable of changing on a continual basis. In order to facilitate communication within the network, a routing protocol is used to discover routes between nodes. The primary goal of such an ad hoc network routing protocol is correct and efficient route establishment between a pair of nodes so that messages may be delivered in a timely manner. Route construction should be done with a minimum of overhead and bandwidth consumption. This article examines routing protocols for ad hoc networks and evaluates these protocols based on a given set of parameters. The article provides an overview of eight different protocols by presenting their characteristics and functionality, and then provides a comparison and discussion of their respective merits and drawbacks.
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paper_title: A review of routing protocols for mobile ad hoc networks

paper_content:

Abstract The 1990s have seen a rapid growth of research interests in mobile ad hoc networking. The infrastructureless and the dynamic nature of these networks demands new set of networking strategies to be implemented in order to provide efficient end-to-end communication. This, along with the diverse application of these networks in many different scenarios such as battlefield and disaster recovery, have seen MANETs being researched by many different organisations and institutes. MANETs employ the traditional TCP/IP structure to provide end-to-end communication between nodes. However, due to their mobility and the limited resource in wireless networks, each layer in the TCP/IP model require redefinition or modifications to function efficiently in MANETs. One interesting research area in MANET is routing. Routing in the MANETs is a challenging task and has received a tremendous amount of attention from researches. This has led to development of many different routing protocols for MANETs, and each author of each proposed protocol argues that the strategy proposed provides an improvement over a number of different strategies considered in the literature for a given network scenario. Therefore, it is quite difficult to determine which protocols may perform best under a number of different network scenarios, such as increasing node density and traffic. In this paper, we provide an overview of a wide range of routing protocols proposed in the literature. We also provide a performance comparison of all routing protocols and suggest which protocols may perform best in large networks.
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paper_title: A peer-to-peer zone-based two-level link state routing for mobile ad hoc networks

paper_content:

A new global positioning system (GPS)-based routing protocol for ad hoc networks, called zone-based hierarchical link state (ZHLS) routing protocol, is proposed. In this protocol, the network is divided into nonoverlapping zones. Each node only knows the node connectivity within its zone and the zone connectivity of the whole network. The link state routing is performed on two levels: focal node and global zone levels. Unlike other hierarchical protocols, there is no cluster head in this protocol. The zone level topological information is distributed to all nodes. This "peer-to-peer" manner mitigates traffic bottleneck, avoids single point of failure, and simplifies mobility management. Since only zone ID and node ID of a destination are needed for routing, the route from a source to a destination is adaptable to changing topology. The zone ID of the destination is found by sending one location request to every zone. Simulation results show that our location search scheme generates less overhead than the schemes based on flooding. The results also confirm that the communication overhead for creating and maintaining the topology in the proposed protocol is smaller than that in the flat LSR protocol. This new routing protocol provides a flexible, efficient, and effective approach to accommodate the changing topology in a wireless network environment.
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paper_title: Optimized Link State Routing Protocol (OLSR)

paper_content:

This document describes the Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. The protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. The key concept used in the protocol is that of multipoint relays (MPRs). MPRs are selected nodes which forward broadcast messages during the flooding process. This technique substantially reduces the message overhead as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. In OLSR, link state information is generated only by nodes elected as MPRs. Thus, a second optimization is achieved by minimizing the number of control messages flooded in the network. As a third optimization, an MPR node may chose to report only links between itself and its MPR selectors. Hence, as contrary to the classic link state algorithm, partial link state information is distributed in the network. This information is then used for route calculation. OLSR provides optimal routes (in terms of number of hops). The protocol is particularly suitable for large and dense networks as the technique of MPRs works well in this context.
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paper_title: Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers

paper_content:

An ad-hoc network is the cooperative engagement of a collection of Mobile Hosts without the required intervention of any centralized Access Point. In this paper we present an innovative design for the operation of such ad-hoc networks. The basic idea of the design is to operate each Mobile Host as a specialized router, which periodically advertises its view of the interconnection topology with other Mobile Hosts within the network. This amounts to a new sort of routing protocol. We have investigated modifications to the basic Bellman-Ford routing mechanisms, as specified by RIP [5], to make it suitable for a dynamic and self-starting network mechanism as is required by users wishing to utilize ad hoc networks. Our modifications address some of the previous objections to the use of Bellman-Ford, related to the poor looping properties of such algorithms in the face of broken links and the resulting time dependent nature of the interconnection topology describing the links between the Mobile Hosts. Finally, we describe the ways in which the basic network-layer routing can be modified to provide MAC-layer support for ad-hoc networks.
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paper_title: Mobility-Aware Hybrid Routing Approach for Wireless Mesh Networks

paper_content:

Wireless mesh networks (WMNs) are attractive as a new communication paradigm. Ad hoc routing protocols for WMNs are classified into: (a) proactive, (b) reactive, and (c) hybrid approaches. In general, proactive routing is more suitable for a stationary network, while reactive routing is better for a mobile network with a high mobility. In many applications, a node in WMN is mobile but it can fluctuate between being mobile and being stationary. Therefore, a hybrid routing approach with the ability to adapt to node mobility could improve the performance of WMNs. In this paper, we propose a Mobility-aware Hybrid Routing (MHR) approach for WMNs, which varies its routing between reactive and proactive to adapt to node mobility. The MHR basically uses a reactive approach for route discovery, and as a proactive approach it maintains the route entry in the routing table unless the route fails due to node movement, even if the route is not used. In this paper, the MHR approach was applied to AODV, and herein called AODV-MHR. Its performance was compared with that of AODV and OLSR by simulation. The simulation results showed that AODVMHR could achieve the advantages of both reactive and proactive routing approaches in performance.
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paper_title: Source-tree routing in wireless networks

paper_content:

We present the source-tree adaptive routing (STAR) protocol and analyze its performance in wireless networks with broadcast radio links. Routers in STAR communicate to the neighbors their source routing trees either incrementally or in atomic updates. Source routing trees are specified by stating the link parameters of each link belonging to the paths used to reach every destination. Hence, a router disseminates link-state updates to its neighbors for only those links along paths used to reach destinations. Simulation results show that STAR is an order of magnitude more efficient than any topology-broadcast protocol, and four times more efficient than ALP, which was the most efficient table-driven routing protocol based on partial link-state information reported to date. The results also show that STAR is even more efficient than the dynamic source routing (DSR) protocol, which has been shown to be one of the best performing on-demand routing protocols.
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paper_title: A location management protocol for hierarchically organized multihop mobile wireless networks

paper_content:

We consider the problem of location management in a large, hierarchically organized multihop mobile network, where the switches comprising the infrastructure as well as the endpoints (terminals) may be mobile. Such networks are common in applications such as battlefield networks, disaster management, law enforcement, etc. We present a novel network architecture and location management protocol that accommodates switch mobility and, using a new concept called "roaming level", allows the updating procedure to be controlled on a per endpoint basis. We discuss simulation results on the variation of performance with the speed, roaming level and call frequency of endpoints. Our results show that at high endpoint speeds or low call frequencies a significant decrease in the control overhead can be obtained in comparison to traditional schemes.
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paper_title: Optimized Link State Routing Protocol (OLSR)

paper_content:

This document describes the Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. The protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. The key concept used in the protocol is that of multipoint relays (MPRs). MPRs are selected nodes which forward broadcast messages during the flooding process. This technique substantially reduces the message overhead as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. In OLSR, link state information is generated only by nodes elected as MPRs. Thus, a second optimization is achieved by minimizing the number of control messages flooded in the network. As a third optimization, an MPR node may chose to report only links between itself and its MPR selectors. Hence, as contrary to the classic link state algorithm, partial link state information is distributed in the network. This information is then used for route calculation. OLSR provides optimal routes (in terms of number of hops). The protocol is particularly suitable for large and dense networks as the technique of MPRs works well in this context.
---
paper_title: Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers

paper_content:

An ad-hoc network is the cooperative engagement of a collection of Mobile Hosts without the required intervention of any centralized Access Point. In this paper we present an innovative design for the operation of such ad-hoc networks. The basic idea of the design is to operate each Mobile Host as a specialized router, which periodically advertises its view of the interconnection topology with other Mobile Hosts within the network. This amounts to a new sort of routing protocol. We have investigated modifications to the basic Bellman-Ford routing mechanisms, as specified by RIP [5], to make it suitable for a dynamic and self-starting network mechanism as is required by users wishing to utilize ad hoc networks. Our modifications address some of the previous objections to the use of Bellman-Ford, related to the poor looping properties of such algorithms in the face of broken links and the resulting time dependent nature of the interconnection topology describing the links between the Mobile Hosts. Finally, we describe the ways in which the basic network-layer routing can be modified to provide MAC-layer support for ad-hoc networks.
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paper_title: A routing protocol for packet radio networks

paper_content:

Abstract : The authors present a new distance-vector routing protocol for a packet radio network. The new distributed routing protocol, Wireless Routing Protocol (WRP), works on the notion of second-to-last hop node to a destination. WRP reduces the number of cases in which a temporary routing loop can occur and also provides a mechanism for the reliable transmission of update messages. The performance of WRP has been compared quantitatively by simulations with that of distributed Bellman-Ford (DBF), DUAL (a loop-free, distance-vector algorithm), and an ideal link-state algorithm (ILS) that represents the state of the art of Internet routing in a highly dynamic environment. The simulation results indicate that WRP is the most efficient of the algorithms simulated in a wireless environment.
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paper_title: Global state routing: a new routing scheme for ad-hoc wireless networks

paper_content:

In an ad-hoc environment with no wired communication infrastructure, it is necessary that mobile hosts operate as routers in order to maintain the information about connectivity. However with the presence of high mobility and low signal/interference ratio (SIR), traditional routing schemes for wired networks are not appropriate, as they either lack the ability to quickly reflect the changing topology, or may cause excessive overhead, which degrades network performance. Considering these restrictions, we propose a new scheme especially designed for routing in an ad-hoc wireless environments. We call this scheme "global state routing" (GSR), where nodes exchange vectors of link states among their neighbors during routing information exchange. Based on the link state vectors, nodes maintain a global knowledge of the network topology and optimize their routing decisions locally. The performance of the algorithm, studied in this paper through a series of simulations, reveals that this scheme provides a better solution than existing approaches in a truly mobile, ad-hoc environment.
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paper_title: A wireless hierarchical routing protocol with group mobility

paper_content:

In this paper we present a hierarchical routing protocol in a large wireless, mobile network such as found in the automated battlefield or in extensive disaster recovery operations. Conventional routing does not scale well to network size. Likewise, conventional hierarchical routing cannot handle mobility efficiently. We propose a novel soft state wireless hierarchical routing protocol-Hierarchical State Routing (HSR). We distinguish between the "physical" routing hierarchy (dictated by geographical relationships between nodes) and "logical" hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). HSR keeps track of logical subnet movements using home agent concepts akin to Mobile IP. A group mobility model is introduced and the performance of the HSR is evaluated through a detailed wireless simulation model.
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paper_title: Optimized Link State Routing Protocol (OLSR)

paper_content:

This document describes the Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. The protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. The key concept used in the protocol is that of multipoint relays (MPRs). MPRs are selected nodes which forward broadcast messages during the flooding process. This technique substantially reduces the message overhead as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. In OLSR, link state information is generated only by nodes elected as MPRs. Thus, a second optimization is achieved by minimizing the number of control messages flooded in the network. As a third optimization, an MPR node may chose to report only links between itself and its MPR selectors. Hence, as contrary to the classic link state algorithm, partial link state information is distributed in the network. This information is then used for route calculation. OLSR provides optimal routes (in terms of number of hops). The protocol is particularly suitable for large and dense networks as the technique of MPRs works well in this context.
---
paper_title: A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks

paper_content:

An ad hoc mobile network is a collection of mobile nodes that are dynamically and arbitrarily located in such a manner that the interconnections between nodes are capable of changing on a continual basis. In order to facilitate communication within the network, a routing protocol is used to discover routes between nodes. The primary goal of such an ad hoc network routing protocol is correct and efficient route establishment between a pair of nodes so that messages may be delivered in a timely manner. Route construction should be done with a minimum of overhead and bandwidth consumption. This article examines routing protocols for ad hoc networks and evaluates these protocols based on a given set of parameters. The article provides an overview of eight different protocols by presenting their characteristics and functionality, and then provides a comparison and discussion of their respective merits and drawbacks.
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paper_title: A review of routing protocols for mobile ad hoc networks

paper_content:

Abstract The 1990s have seen a rapid growth of research interests in mobile ad hoc networking. The infrastructureless and the dynamic nature of these networks demands new set of networking strategies to be implemented in order to provide efficient end-to-end communication. This, along with the diverse application of these networks in many different scenarios such as battlefield and disaster recovery, have seen MANETs being researched by many different organisations and institutes. MANETs employ the traditional TCP/IP structure to provide end-to-end communication between nodes. However, due to their mobility and the limited resource in wireless networks, each layer in the TCP/IP model require redefinition or modifications to function efficiently in MANETs. One interesting research area in MANET is routing. Routing in the MANETs is a challenging task and has received a tremendous amount of attention from researches. This has led to development of many different routing protocols for MANETs, and each author of each proposed protocol argues that the strategy proposed provides an improvement over a number of different strategies considered in the literature for a given network scenario. Therefore, it is quite difficult to determine which protocols may perform best under a number of different network scenarios, such as increasing node density and traffic. In this paper, we provide an overview of a wide range of routing protocols proposed in the literature. We also provide a performance comparison of all routing protocols and suggest which protocols may perform best in large networks.
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paper_title: Modified Optimized Link State Routing (M-OLSR) for Wireless Mesh Networks

paper_content:

Wireless mesh networks (WMNs) are a type of radio-based network systems which require minimal configuration and infrastructure. One of the factors that influence the performance of WMNs is the underlying routing protocol used. Here, we propose one such routing protocol, called M-OLSR, which is a variant of OLSR, a traditional link-state protocol developed to meet the requirements of mobile adhoc networks MANETs. Our approach improves the throughput and packet delivery ratio, while minimizing routing overhead and delay, by choosing a stable path for packet forwarding through static routers. Simulation results demonstrate that, for WMNs, the M-OLSR outperforms OLSR in terms of throughput, packet delivery ratio, and routing overhead.
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paper_title: Location-aided routing (LAR) in mobile ad hoc networks

paper_content:

A mobile ad hoc network consists of wireless hosts that may move often. Movement of hosts results in a change in routes, requiring some mechanism for determining new routes. Several routing protocols have already been proposed for ad hoc networks. This report suggests an approach to utilize location information (for instance, obtained using the global positioning system) to improve performance of routing protocols for ad hoc networks.
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paper_title: Signal Stability based Adaptive Routing (SSA) for Ad-Hoc Mobile Networks

paper_content:

Ad hoc networks have no spatial hierarchy and suffer from frequent link failures which prevent mobile hosts from using traditional routing schemes. Under these conditions, mobile hosts must find routes to destinations without the use of designated routers and also must dynamically adapt the routes to the current link conditions. This article proposes a distributed adaptive routing protocol for finding and maintaining stable routes based on signal strength and location stability in an ad hoc network and presents an architecture for its implementation. Interoperability with mobile IP (Internet protocol) is discussed.
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paper_title: A novel distributed routing protocol to support ad-hoc mobile computing

paper_content:

This paper presents a new, simple and bandwidth-efficient distributed routing protocol for ad-hoc mobile networks. Unlike the conventional distributed routing algorithms, our protocol does not attempt to consistently maintain routing information in every node. In an ad-hoc mobile network where mobile hosts are acting as routers and where routes are made inconsistent by mobile host movements, we employ a new associativity-based routing scheme where a route is selected based on nodes having associativity states that imply periods of stability. In this manner, the routes selected are likely to be long-lived and hence there is no need to restart frequently, resulting in higher attainable throughput. The association property also allows the integration of ad-hoc routing into a BS-oriented wireless LAN environment, providing fault tolerance in times of base station (BS) failures. The protocol is free from loops, deadlock and packet duplicates and has scalable memory requirements. Simulation results obtained reveal that shorter and better routes can be discovered during route re-constructions.
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paper_title: IPv6 flow handoff in ad hoc wireless networks using mobility prediction

paper_content:

In an ad hoc wireless network, mobile hosts are acting as routers and the network topology is constantly changing due to node mobility. The disruptions can cause serious degradation for real-time session. This paper describes a new protocol, the flow oriented routing protocol (FORP), for routing real-time IPv6 flows (e.g., voice and data) in highly mobile ad hoc wireless networks. A new concept called "multi-hop handoff" is introduced to anticipate topological changes and perform rerouting, thus limiting the disruption of a flow due to the changing topology. The performance of the proposed scheme is compared to other routing approaches.
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paper_title: Performance evaluation for routing protocols in wireless mesh networks

paper_content:

In this paper, we address on-demand routing protocols by focusing on Dynamic Source Routing (DSR) protocol and Ad hoc On-demand Distance Vector (AODV) routing protocol in Wireless Mesh Network (WMN). We use the OPNET to establish the simulation models of DSR and AODV protocols in WMN. Simulation and results show that, DSR protocol based on dynamic source routing is not suitable for wireless transmission, while AODV protocol based on purpose-driven routing is suitable for wireless transmission with rapid change of network topology.
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paper_title: A review of routing protocols for mobile ad hoc networks

paper_content:

Abstract The 1990s have seen a rapid growth of research interests in mobile ad hoc networking. The infrastructureless and the dynamic nature of these networks demands new set of networking strategies to be implemented in order to provide efficient end-to-end communication. This, along with the diverse application of these networks in many different scenarios such as battlefield and disaster recovery, have seen MANETs being researched by many different organisations and institutes. MANETs employ the traditional TCP/IP structure to provide end-to-end communication between nodes. However, due to their mobility and the limited resource in wireless networks, each layer in the TCP/IP model require redefinition or modifications to function efficiently in MANETs. One interesting research area in MANET is routing. Routing in the MANETs is a challenging task and has received a tremendous amount of attention from researches. This has led to development of many different routing protocols for MANETs, and each author of each proposed protocol argues that the strategy proposed provides an improvement over a number of different strategies considered in the literature for a given network scenario. Therefore, it is quite difficult to determine which protocols may perform best under a number of different network scenarios, such as increasing node density and traffic. In this paper, we provide an overview of a wide range of routing protocols proposed in the literature. We also provide a performance comparison of all routing protocols and suggest which protocols may perform best in large networks.
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paper_title: A distributed routing algorithm for mobile wireless networks

paper_content:

We present a loop-free, distributed routing protocol for mobile packet radio networks. The protocol is intended for use in networks where the rate of topological change is not so fast as to make “flooding” the only possible routing method, but not so slow as to make one of the existing protocols for a nearly-static topology applicable. The routing algorithm adapts asynchronously in a distributed fashion to arbitrary changes in topology in the absence of global topological knowledge. The protocol's uniqueness stems from its ability to maintain source-initiated, loop-free multipath routing only to desired destinations with minimal overhead in a randomly varying topology. The protocol's performance, measured in terms of end-to-end packet delay and throughput, is compared with that of pure flooding and an alternative algorithm which is well-suited to the high-rate topological change environment envisioned here. For each protocol, emphasis is placed on examining how these performance measures vary as a function of the rate of topological changes, network topology, and message traffic level. The results indicate the new protocol generally outperforms the alternative protocol at all rates of change for heavy traffic conditions, whereas the opposite is true for light traffic. Both protocols significantly outperform flooding for all rates of change except at ultra-high rates where all algorithms collapse. The network topology, whether dense or sparsely connected, is not seen to be a major factor in the relative performance of the algorithms.
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paper_title: Performance evaluation for routing protocols in wireless mesh networks

paper_content:

In this paper, we address on-demand routing protocols by focusing on Dynamic Source Routing (DSR) protocol and Ad hoc On-demand Distance Vector (AODV) routing protocol in Wireless Mesh Network (WMN). We use the OPNET to establish the simulation models of DSR and AODV protocols in WMN. Simulation and results show that, DSR protocol based on dynamic source routing is not suitable for wireless transmission, while AODV protocol based on purpose-driven routing is suitable for wireless transmission with rapid change of network topology.
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paper_title: A highly adaptive distributed routing algorithm for mobile wireless networks

paper_content:

We present a new distributed routing protocol for mobile, multihop, wireless networks. The protocol is one of a family of protocols which we term "link reversal" algorithms. The protocol's reaction is structured as a temporally-ordered sequence of diffusing computations; each computation consisting of a sequence of directed link reversals. The protocol is highly adaptive, efficient and scalable; being best-suited for use in large, dense, mobile networks. In these networks, the protocol's reaction to link failures typically involves only a localized "single pass" of the distributed algorithm. This capability is unique among protocols which are stable in the face of network partitions, and results in the protocol's high degree of adaptivity. This desirable behavior is achieved through the novel use of a "physical or logical clock" to establish the "temporal order" of topological change events which is used to structure (or order) the algorithm's reaction to topological changes. We refer to the protocol as the temporally-ordered routing algorithm (TORA).
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paper_title: A review of routing protocols for mobile ad hoc networks

paper_content:

Abstract The 1990s have seen a rapid growth of research interests in mobile ad hoc networking. The infrastructureless and the dynamic nature of these networks demands new set of networking strategies to be implemented in order to provide efficient end-to-end communication. This, along with the diverse application of these networks in many different scenarios such as battlefield and disaster recovery, have seen MANETs being researched by many different organisations and institutes. MANETs employ the traditional TCP/IP structure to provide end-to-end communication between nodes. However, due to their mobility and the limited resource in wireless networks, each layer in the TCP/IP model require redefinition or modifications to function efficiently in MANETs. One interesting research area in MANET is routing. Routing in the MANETs is a challenging task and has received a tremendous amount of attention from researches. This has led to development of many different routing protocols for MANETs, and each author of each proposed protocol argues that the strategy proposed provides an improvement over a number of different strategies considered in the literature for a given network scenario. Therefore, it is quite difficult to determine which protocols may perform best under a number of different network scenarios, such as increasing node density and traffic. In this paper, we provide an overview of a wide range of routing protocols proposed in the literature. We also provide a performance comparison of all routing protocols and suggest which protocols may perform best in large networks.
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paper_title: A peer-to-peer zone-based two-level link state routing for mobile ad hoc networks

paper_content:

A new global positioning system (GPS)-based routing protocol for ad hoc networks, called zone-based hierarchical link state (ZHLS) routing protocol, is proposed. In this protocol, the network is divided into nonoverlapping zones. Each node only knows the node connectivity within its zone and the zone connectivity of the whole network. The link state routing is performed on two levels: focal node and global zone levels. Unlike other hierarchical protocols, there is no cluster head in this protocol. The zone level topological information is distributed to all nodes. This "peer-to-peer" manner mitigates traffic bottleneck, avoids single point of failure, and simplifies mobility management. Since only zone ID and node ID of a destination are needed for routing, the route from a source to a destination is adaptable to changing topology. The zone ID of the destination is found by sending one location request to every zone. Simulation results show that our location search scheme generates less overhead than the schemes based on flooding. The results also confirm that the communication overhead for creating and maintaining the topology in the proposed protocol is smaller than that in the flat LSR protocol. This new routing protocol provides a flexible, efficient, and effective approach to accommodate the changing topology in a wireless network environment.
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paper_title: Scalable Routing Protocol for Ad Hoc Networks

paper_content:

In this paper we present a scalable routing protocol for ad hoc networks. The protocol is based on a geographic location management strategy that keeps the overhead of routing packets relatively small. Nodes are assigned home regions and all nodes within a home region know the approximate location of the registered nodes. As nodes travel, they send location update messages to their home regions and this information is used to route data packets. In this paper, we derive theoretical performance results for the protocol and prove that the control packet overhead scales linearly with node speed and N3/2 with increasing number of nodes. These results indicate that our protocol is well suited to relatively large ad hoc networks where nodes travel at high speed. Finally, we use simulations to validate our analytical model.
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paper_title: Mobility-Aware Hybrid Routing Approach for Wireless Mesh Networks

paper_content:

Wireless mesh networks (WMNs) are attractive as a new communication paradigm. Ad hoc routing protocols for WMNs are classified into: (a) proactive, (b) reactive, and (c) hybrid approaches. In general, proactive routing is more suitable for a stationary network, while reactive routing is better for a mobile network with a high mobility. In many applications, a node in WMN is mobile but it can fluctuate between being mobile and being stationary. Therefore, a hybrid routing approach with the ability to adapt to node mobility could improve the performance of WMNs. In this paper, we propose a Mobility-aware Hybrid Routing (MHR) approach for WMNs, which varies its routing between reactive and proactive to adapt to node mobility. The MHR basically uses a reactive approach for route discovery, and as a proactive approach it maintains the route entry in the routing table unless the route fails due to node movement, even if the route is not used. In this paper, the MHR approach was applied to AODV, and herein called AODV-MHR. Its performance was compared with that of AODV and OLSR by simulation. The simulation results showed that AODVMHR could achieve the advantages of both reactive and proactive routing approaches in performance.
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paper_title: Review of Routing Protocols and It's Metrics for Wireless Mesh Networks

paper_content:

WMNs are low-cost internet access networks built on cooperative routing over a backbone composed ofstationary wireless routers. In hybrid mesh WMNs both client mesh and backbone has ability to forward the data to destination. Many ad hoc routing protocols have been adapted to work in WMN without considering the differences between both technologies. Due to the differences between ad hoc network and WMN network, many Researchers started to revisit the routing protocol design of existing wireless mesh networks (WMNs), especially of IEEE 802.11 networks, and ad hoc networks from the perspectives of WMNs which provide internet for large distances area and consist of two tiers where the heterogeneity exists between them, the heterogeneity between backbone nodes and client nodes are many, for example, the backbone nodes are immobile with a fixed location and high capacity while the client nodes are mobile devices with low capacity and must take care of power consumption and mobility. However, these perspectives should be taken care of in designing the routing protocol to enhance the routing algorithm in order to work well in WMN. There are two ways to enhance the performance of routing protocol in WMN. One way is to improve the metric used in the selection path, the second way is to modify the routing algorithms by considering new characteristics of WMN or integrating the routing protocols with other technologies. In this paper, we present a detailed review of current state-of-the-art routing protocol and its metric for wireless mesh networks in order to provide a better understanding of the research challenges in WMN routing protocol.
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paper_title: Performance evaluation for routing protocols in wireless mesh networks

paper_content:

In this paper, we address on-demand routing protocols by focusing on Dynamic Source Routing (DSR) protocol and Ad hoc On-demand Distance Vector (AODV) routing protocol in Wireless Mesh Network (WMN). We use the OPNET to establish the simulation models of DSR and AODV protocols in WMN. Simulation and results show that, DSR protocol based on dynamic source routing is not suitable for wireless transmission, while AODV protocol based on purpose-driven routing is suitable for wireless transmission with rapid change of network topology.
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paper_title: Research on Routing Protocol Applied to Wireless Mesh Networks

paper_content:

Broadcast storm problem and congestion question can be found in the routing protocol DSR when we research on the routing protocol of wireless Mesh network. In this paper an advanced routing protocol was proposed, it improved DSR by transmitting the packets based on the distance threshold and congestion threshold. The simulation results show that the improved routing protocol has bigger throughput than before.
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paper_title: Evaluation of multi-radio extensions to AODV for wireless mesh networks

paper_content:

Due to their self-configuring and self-healing capabilities, as well as their low equipment and deployment cost, Wireless Mesh Networks (WMNs) based on commodity hardware present a promising technology for a wide range of applications. Currently, one of key challenges that WMN technology faces is the limited capacity and scalability due to high levels of interference, which is typical for multi-hop wireless networks. A simple and relatively low-cost approach to address this problem that has recently been proposed is the use of multiple wireless network interfaces (radios) per node. Operating the radios on each node on different, non-overlapping channels allows making more efficient use of the radio spectrum and thereby reducing interference and contention. In this paper, we evaluate the performance of the Ad-hoc On-demand Distance Vector (AODV) routing protocol in a Multi-Radio Wireless Mesh Network. Our simulation results show that under high traffic load conditions, Multi-Radio AODV (AODV-MR) is able to efficiently utilize the increased spectrum, and proves to be far superior to single radio AODV. We therefore believe that AODV-MR is a promising candidate for multi-radio WMNs.
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paper_title: Performance evaluation for routing protocols in wireless mesh networks

paper_content:

In this paper, we address on-demand routing protocols by focusing on Dynamic Source Routing (DSR) protocol and Ad hoc On-demand Distance Vector (AODV) routing protocol in Wireless Mesh Network (WMN). We use the OPNET to establish the simulation models of DSR and AODV protocols in WMN. Simulation and results show that, DSR protocol based on dynamic source routing is not suitable for wireless transmission, while AODV protocol based on purpose-driven routing is suitable for wireless transmission with rapid change of network topology.
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paper_title: Joint channel assignment and routing for throughput optimization in multi-radio wireless mesh networks

paper_content:

Multi-hop infrastructure wireless mesh networks offer increased reliability, coverage and reduced equipment costs over their single-hop counterpart, wireless LANs. Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment and routing is essential for throughput optimization of mesh clients. Efficient channel assignment schemes can greatly relieve the interference effect of close-by transmissions; effective routing schemes can alleviate potential congestion on any gateways to the Internet, thereby improving per-client throughput. Unlike previous heuristic approaches, we mathematically formulate the joint channel assignment and routing problem, taking into account the interference constraints, the number of channels in the network and the number of radios available at each mesh router. We then use this formulation to develop a solution for our problem that optimizes the overall network throughput subject to fairness constraints on allocation of scarce wireless capacity among mobile clients. We show that the performance of our algorithms is within a constant factor of that of any optimal algorithm for the joint channel assignment and routing problem. Our evaluation demonstrates that our algorithm can effectively exploit the increased number of channels and radios, and it performs much better than the theoretical worst case bounds.
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paper_title: Joint Routing and Channel Assignment in Multi-Radio Wireless Mesh Networks

paper_content:

This paper considers the problem of how to maximize throughput in multi-radio multi-channel wireless mesh networks. With mathematical model based on radio and radioto-radio link, we introduce a scheduling graph and show that the feasibility problem of time fraction vector is equal to the problem of whether the scheduling graph is [M]-colorable, where M is the number of slots in one period. We use this equivalence property to derive a sufficient condition of feasibility, and then, using this sufficient condition, we mathematically formulate the joint routing and channel assignment problem as a linear programming problem. Finally, we use vertex coloring to get a feasible schedule and lift the resulting flows. We prove that the optimality gap is above a constant factor. The numeric results demonstrate the effectiveness of our proposed algorithm.
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paper_title: Joint Disjoint Path Routing and Channel Assignment in Multi-Radio Multi-Channel Wireless Mesh Networks

paper_content:

Due to the reduction of equipment cost and the demand of higher capacity, Wireless Mesh network (WMN) router devices usually have several interfaces and work on multichannels. Jointing channel allocation, interface assignment and routing (JCIAR) can expressively enhance the network capacity. In this paper, regarding the characteristic of network node and network traffic, we formulate the JCIAR problem as a two-stage optimization problem. In the first stage, we will obtain the optimal throughput of network regarding radios and channel constraints over set of predetermined disjoint paths. In the second stage, basing on the flows value obtained from the first stage, channel allocation and interface assignment are solved distributedly to obtain the optimal network throughput. The argument and evaluation show the advantage of our method in comparison with other existing method in terms of implementation scheme and network performance.
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paper_title: MRS: a simple cross-layer heuristic to improve throughput capacity in wireless mesh networks

paper_content:

Wireless Mesh Networks (WMNs) are an emerging architecture based on multi-hop transmission. ISPs considers WMNs as a potential future technology to offer broadband Internet access. Therefore, in WMNs, the throughput capacity of the wireless backbone becomes a key factor, limiting the scalability in terms of users able to effectively take advantage of the network. Increasing the effective throughput capacity will support WMNs become a very cost-effective solution for wireless ISPs.Based on the analysis of the theoretical capacity bound derived by Gupta et al., we propose MRS (Mesh Routing Strategy), a novel cross layer routing solution. MRS is specifically designed for Wireless Mesh Networks, where routing is challenging due to the unreliable wireless medium. Traditional routing paradigms are not able to overcome this issue, resulting in an average throughput experienced by the network far lower than the theoretical throughput capacity bound. This paper shows how a cross-layer approach will consistently improve the throughput experienced by large-scale multi-hop networks. We show through simulation that our proposal increases throughput while reducing the average transmitted power. Furthermore, MRS limits interference and gets closer to the theoretical throughput capacity bound.
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paper_title: Cross-layer optimization of wireless multi-hop networks with network coding

paper_content:

In this paper we present a cross-layer algorithm for joint optimization of congestion control, routing, and scheduling in wireless multi-hop networks with network coding. We introduce virtual flow variables in the formulation of capacity region of the networks. The utility maximization problem subject to constraints on the capacity region is solved using dual decomposition and subgradient method, based on which a new queuing model is obtained and which also can result in a cross-layer algorithm for distributed implementation. The new queuing model can facilitate coding operations and reduce coding complexity. Simulation results show that network coding in the proposed joint optimization algorithm can interact adaptively and optimally with other components in different layers, and thus yield higher performance than the routing scheme without network coding.
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paper_title: Cross-Layer Design of Wireless Mesh Networks with Network Coding

paper_content:

We investigate the optimal design of a multihop wireless mesh network equipped with multiple orthogonal wireless channels and multiple radios. Specifically, we focus on solutions that can efficiently utilize the limited resource to support multiple unicast applications by routing and network coding. We propose a cross-layer optimization framework where the broadcasting feature of the wireless environment, which plays an important role in realizing the achievable gain of network coding, is taken into account. Moreover, we propose a network code construction scheme based on linear programming, with which the possible achievable Coding+MAC gain could be significantly increased. Delay constraints are also included in the network code construction formulation so that the possible impact of the extra decoding delay to the TCP/IP performance can be reduced without changing the upper-layer protocols. The proposed network design based on cross-layer optimization results in significant increase in network throughput.
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paper_title: Using Cross-layer Heuristic and Network Coding to Improve Throughput in Multicast Wireless Mesh Networks

paper_content:

Wireless mesh networks (WMNs) receive much research interests because of their reliability, scalability and low cost. Obtaining high-throughput for multicast applications (e.g. video streaming broadcast) in WMN is challenging due to the interference and the change of channel quality. Cross-layer design and network coding are approaches which have been recently received considerable attention for high-throughput problem in wireless networks. In this paper, we propose an approach namely CLNC (Cross-Layer Network Coding) which is a combination of the above approaches to improve throughput in multicast wireless mesh networks. Our simulation results show that when the number of receivers is high CLNC's throughput is higher at least 30% than that of known methods such as AODV, DSDV and DSR and higher than that of MAODV. Moreover, PDR (Packet Delivery Ration) of CLNC is higher than that of MAODV and DSDV.
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paper_title: Joint channel assignment and routing for throughput optimization in multi-radio wireless mesh networks

paper_content:

Multi-hop infrastructure wireless mesh networks offer increased reliability, coverage and reduced equipment costs over their single-hop counterpart, wireless LANs. Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment and routing is essential for throughput optimization of mesh clients. Efficient channel assignment schemes can greatly relieve the interference effect of close-by transmissions; effective routing schemes can alleviate potential congestion on any gateways to the Internet, thereby improving per-client throughput. Unlike previous heuristic approaches, we mathematically formulate the joint channel assignment and routing problem, taking into account the interference constraints, the number of channels in the network and the number of radios available at each mesh router. We then use this formulation to develop a solution for our problem that optimizes the overall network throughput subject to fairness constraints on allocation of scarce wireless capacity among mobile clients. We show that the performance of our algorithms is within a constant factor of that of any optimal algorithm for the joint channel assignment and routing problem. Our evaluation demonstrates that our algorithm can effectively exploit the increased number of channels and radios, and it performs much better than the theoretical worst case bounds.
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paper_title: Routing Algorithm for Network Coding Based Multicast

paper_content:

Network coding (NC) is one of the most important breakthroughs on the theory of information transmission and processing. Network coding can improve the performance of multicast by performing encoding operations at intermediate nodes. There are two steps should be realized while using network coding in multicast communication: one is finding proper transmission paths from source to multi-receivers and the other is determining the coding scheme. For the latter problem, a variety of methods have been proposed. However, little research about the former has been done in the present work. In this paper, we present a detailed routing algorithm for network coding based multicast. Simulations based on this algorithm show that, for network coding based multicast, performance in terms of achievable throughput and bandwidth consumption has been improved to some extend over the traditional IP multicast.
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paper_title: Embracing wireless interference: analog network coding

paper_content:

Traditionally, interference is considered harmful. Wireless networks strive to avoid scheduling multiple transmissions at the same time in order to prevent interference. This paper adopts the opposite approach; it encourages strategically picked senders to interfere. Instead of forwarding packets, routers forward the interfering signals. The destination leverages network-level information to cancel the interference and recover the signal destined to it. The result is analog network coding because it mixes signals not bits. So, what if wireless routers forward signals instead of packets? Theoretically, such an approach doubles the capacity of the canonical 2-way relay network. Surprisingly, it is also practical. We implement our design using software radios and show that it achieves significantly higher throughput than both traditional wireless routing and prior work on wireless network coding.
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paper_title: Centralized channel assignment and routing algorithms for multi-channel wireless mesh networks

paper_content:

The IEEE 802.11 Wireless LAN standards allow multiple non-overlapping frequency channels to be used simultaneously to increase the aggregate bandwidth available to end-users. Such bandwidth aggregation capability is routinely used in infrastructure mode operation, where the traffic to and from wireless nodes is distributed among multiple interfaces of an access point or among multiple access points to balance the traffic load. However, bandwidth aggregation is rarely used in the context of multi-hop 802.11-based LANs that operate in the ad hoc mode. Most past research efforts that attempt to exploit multiple radio channels require modifications to the MAC protocol and therefore do not work with commodity 802.11 interface hardware. In this paper, we propose and evaluate one of the first multi-channel multi-hop wireless ad-hoc network architectures that can be built using standard 802.11 hardware by equipping each node with multiple network interface cards (NICs) operating on different channels. We focus our attention on wireless mesh networks that serve as the backbone for relaying end-user traffic from wireless access points to the wired network. The idea of exploiting multiple channels is particularly appealing in wireless mesh networks because of their high capacity requirements to support backbone traffic. To reap the full performance potential of this architecture, we develop a set of centralized channel assignment, bandwidth allocation, and routing algorithms for multi-channel wireless mesh networks. A detailed performance evaluation shows that with intelligent channel and bandwidth assignment, equipping every wireless mesh network node with just 2 NICs operating on different channels can increase the total network goodput by a factor of up to 8 compared with the conventional single-channel ad hoc network architecture.
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paper_title: Joint Routing and Channel Assignment in Multi-Radio Wireless Mesh Networks

paper_content:

This paper considers the problem of how to maximize throughput in multi-radio multi-channel wireless mesh networks. With mathematical model based on radio and radioto-radio link, we introduce a scheduling graph and show that the feasibility problem of time fraction vector is equal to the problem of whether the scheduling graph is [M]-colorable, where M is the number of slots in one period. We use this equivalence property to derive a sufficient condition of feasibility, and then, using this sufficient condition, we mathematically formulate the joint routing and channel assignment problem as a linear programming problem. Finally, we use vertex coloring to get a feasible schedule and lift the resulting flows. We prove that the optimality gap is above a constant factor. The numeric results demonstrate the effectiveness of our proposed algorithm.
---
paper_title: Joint Disjoint Path Routing and Channel Assignment in Multi-Radio Multi-Channel Wireless Mesh Networks

paper_content:

Due to the reduction of equipment cost and the demand of higher capacity, Wireless Mesh network (WMN) router devices usually have several interfaces and work on multichannels. Jointing channel allocation, interface assignment and routing (JCIAR) can expressively enhance the network capacity. In this paper, regarding the characteristic of network node and network traffic, we formulate the JCIAR problem as a two-stage optimization problem. In the first stage, we will obtain the optimal throughput of network regarding radios and channel constraints over set of predetermined disjoint paths. In the second stage, basing on the flows value obtained from the first stage, channel allocation and interface assignment are solved distributedly to obtain the optimal network throughput. The argument and evaluation show the advantage of our method in comparison with other existing method in terms of implementation scheme and network performance.
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paper_title: Characterizing the capacity region in multi-radio multi-channel wireless mesh networks

paper_content:

Next generation fixed wireless broadband networks are being increasingly deployed as mesh networks in order to provide and extend access to the internet. These networks are characterized by the use of multiple orthogonal channels and nodes with the ability to simultaneously communicate with many neighbors using multiple radios (interfaces) over orthogonal channels. Networks based on the IEEE 802.11a/b/g and 802.16 standards are examples of these systems. However, due to the limited number of available orthogonal channels, interference is still a factor in such networks. In this paper, we propose a network model that captures the key practical aspects of such systems and characterize the constraints binding their behavior. We provide necessary conditions to verify the feasibility of rate vectors in these networks, and use them to derive upper bounds on the capacity in terms of achievable throughput, using a fast primal-dual algorithm. We then develop two link channel assignment schemes, one static and the other dynamic, in order to derive lower bounds on the achievable throughput. We demonstrate through simulations that the dynamic link channel assignment scheme performs close to optimal on the average, while the static link channel assignment algorithm also performs very well. The methods proposed in this paper can be a valuable tool for network designers in planning network deployment and for optimizing different performance objectives.
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paper_title: Network coding-based multicast scheduling for throughput enhancement in wireless ad hoc network

paper_content:

Since network coding is very useful for increasing the total throughput in wireless networks, it has recently gained much attention. However, there is few works focusing on network coding in the cyclic topology network, in which six nodes are connected to form a cluster. Considering the case that each node's regional information is required to be exchanged among all the nodes in the cyclic network, we proposed a heuristic multicast scheduling scheme. At each time slot, only the designated group of nodes can transmit data simultaneously. For this reason, we considered the distributed power control to reduce interference. With our proposed scheme, it can be shown that the total throughput is substantially improved using wireless network coding. In addition, we analyzed the appropriate range of node locations, from which we can evaluate the corresponding system performance. Finally, the simulation results indicate that if the nodes are distributed almost evenly in an area, lower energy consumption and improved throughput can be achieved.
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paper_title: Physical Layer Network Coding

paper_content:

A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). This paper shows that the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacity-boosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to straightforward network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. And in doing so, PNC can potentially achieve 100% and 50% throughput increases compared with traditional transmission and straightforward network coding, respectively, in multi-hop networks. More specifically, the information-theoretic capacity of PNC is almost double that of traditional transmission in the SNR region of practical interest (higher than 0dB). We believe this is a first paper that ventures into EM-wave-based network coding at the physical layer and demonstrates its potential for boosting network capacity.
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paper_title: A Novel Channel Assignment Algorithm for Multicast in Multi-radio Wireless Mesh Networks

paper_content:

With the development of Internet, many new applications with obvious multicast character come forth and become popular, which increase the importance of multicast in Internet especially in wireless access networks where the bandwidths of networks are very limited. In this paper, we consider the problem of channel assignment for multicast in multi-radio wireless mesh networks (WMNs), which have not been studied up to now. We propose a novel channel assignment strategy called UCAS based on unidirectional link model, and give an efficient greedy vertex coloring algorithm called BFVC. Finally, the results of simulations demonstrate the efficiency of the algorithms presented in this paper.
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paper_title: Minimum Interference Channel Assignment in Multi-Radio Wireless Mesh Networks

paper_content:

In this paper, we consider multi-hop wireless mesh networks, where each router node is equipped with multiple radio interfaces and multiple channels are available for communication. We address the problem of assigning channels to communication links in the network with the objective of minimizing overall network interference. Since the number of radios on any node can be less than the number of available channels, the channel assignment must obey the constraint that the number of different channels assigned to the links incident on any node is atmost the number of radio interfaces on that node. The above optimization problem is known to be NP-hard. We design centralized and distributed algorithms for the above channel assignment problem. To evaluate the quality of the solutions obtained by our algorithms, we develop a semidefinite program formulation of our optimization problem to obtain a lower bound on overall network interference. Empirical evaluations on randomly generated network graphs show that our algorithms perform close to the above established lower bound, with the difference diminishing rapidly with increase in number of radios. Also, detailed ns-2 simulation studies demonstrate the performance potential of our channel assignment algorithms in 802.11-based multi-radio mesh networks.
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paper_title: Multicast Algorithms for Multi-Channel Wireless Mesh Networks

paper_content:

Multicast is a key technology that provides efficient data communication among a set of nodes for wireless multi-hop networks. In sensor networks and MANETs, multicast algorithms are designed to be energy efficient and to achieve optimal route discovery among mobile nodes, respectively. However, in wireless mesh networks, which are required to provide high quality service to end users as the "last-mile" of the Internet, throughput maximization conflicting with scarce bandwidth has the paramount priority. We propose a level channel assignment (LCA) algorithm and a multi-channel multicast (MCM) algorithm to optimize throughput for multi-channel and multi-interface mesh networks. The algorithms first build a multicast structure by minimizing the number of relay nodes and hop count distances between the source and destinations, and use dedicated channel assignment strategies to improve the network capacity by reducing interference. We also illustrate that the use of partially overlapping channels can further improve the throughput. Simulations show that our algorithms greatly outperform the single-channel multicast algorithm. We observe that MCM achieves better throughput and shorter delay while LCA can be realized in distributed manner.
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paper_title: Superimposed code based channel assignment in multi-radio multi-channel wireless mesh networks

paper_content:

Motivated by the observation that channel assignment for multiradio multi-channel mesh networks should support both unicast and local broadcast1, should be interference-aware, and should result in low overall switching delay, high throughput, and low overhead, we propose two flexible localized channel assignment algorithms based on s-disjunct superimposed codes. These algorithms support the local broadcast and unicast effectively, and achieve interference-free channel assignment under certain conditions. In addition, under the primary interference constraints2, the channel assignment algorithm for unicast can achieve 100% throughput with a simple scheduling algorithm such as the maximal weight independent set scheduling, and can completely avoid hidden/exposed terminal problems under certain conditions. Our algorithms make no assumptions on the underlying network and therefore are applicable to a wide range of MR-MC mesh network settings. We conduct extensive theoretical performance analysis to verify our design.
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paper_title: A topology control approach for utilizing multiple channels in multi-radio wireless mesh networks

paper_content:

We consider the channel assignment problem in a multi-radio wireless mesh network that involves assigning channels to radio interfaces for achieving efficient channel utilization. We propose the notion of a traffic-independent base channel assignment to ease coordination and enable dynamic, efficient and flexible channel assignment. We present a novel formulation of the base channel assignment as a topology control problem, and show that the resulting optimization problem is NP-complete. We then develop a new greedy heuristic channel assignment algorithm (termed CLICA) for finding connected, low interference topologies by utilizing multiple channels. Our extensive simulation studies show that the proposed CLICA algorithm can provide large reduction in interference (even with a small number of radios per node), which in turn leads to significant gains in both link layer and multihop performance in 802.11-based multi-radio mesh networks.
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paper_title: Network Coding for Efficient Multicast Routing in Wireless Ad-hoc Networks

paper_content:

Network coding is a powerful coding technique that has been proved to be very effective in achieving the maximum multicast capacity. It is especially suited for new emerging networks such as ad-hoc and sensor networks. In this work, we investigate the multicast routing problem based on network coding and put forward a practical algorithm to obtain the maximum flow multicast routes in ad-hoc networks. The "conflict phenomenon" that occurs in undirected graphs will also be discussed. Given the developed routing algorithm, we will present the condition for a node to be an encoding node along with a corresponding capacity allocation scheme. We will also analyze the statistical characteristics of encoding nodes and maximum flow in ad-hoc networks based on random graph theory.
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paper_title: Optimization models for fixed channel assignment in wireless mesh networks with multiple radios

paper_content:

The combination of multiple radio nodes in conjunction with a suitably structured multi-hop or mesh architecture has the potential to solve some of the key limitations of present day wireless access networks that are based on single-radio nodes. This paper ad- dresses the channel assignment problem for multi-channel multi-interface (radio) wireless mesh networks. We focus on static wireless mesh networks where multiple non- overlapping channels are available for each wireless inter- face. In this network environment, our objective is to find a fixed channel assignment which maximizes the number of bidirectional links that can be activated simultaneously, subject to interference constraints. We present two mixed integer linear programming models for solving the fixed channel assignment problem with multiple radios. Detailed computational results on various grid topologies are also presented and discussed.
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paper_title: Architecture and algorithms for an IEEE 802.11-based multi-channel wireless mesh network

paper_content:

Even though multiple non-overlapped channels exist in the 2.4 GHz and 5 GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel. As a result, these networks rarely can fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. This prevents them from being used as an ISP's wireless last-mile access network or as a wireless enterprise backbone network. In this paper, we propose a multi-channel wireless mesh network (WMN) architecture (called Hyacinth) that equips each mesh network node with multiple 802.11 network interface cards (NICs). The central design issues of this multi-channel WMN architecture are channel assignment and routing. We show that intelligent channel assignment is critical to Hyacinth's performance, present distributed algorithms that utilize only local traffic load information to dynamically assign channels and to route packets, and compare their performance against a centralized algorithm that performs the same functions. Through an extensive simulation study, we show that even with just 2 NICs on each node, it is possible to improve the network throughput by a factor of 6 to 7 when compared with the conventional single-channel ad hoc network architecture. We also describe and evaluate a 9-node Hyacinth prototype that Is built using commodity PCs each equipped with two 802.11a NICs.
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<format>
Title: Overview of Wireless Mesh Networks

Section 1: INTRODUCTION
Description 1: Introduce Wireless Mesh Networks (WMNs), their components, applications, and challenges.

Section 2: MEDIUM ACCESS CONTROL (MAC) PROTOCOL FOR WIRELESS MESH NETWORKS
Description 2: Discuss MAC protocols for WMNs, their types, classifications, and proposed schemes for performance improvement.

Section 3: ROUTING PROTOCOLS FOR WIRELESS MESH NETWORKS
Description 3: Provide an overview of routing protocols for WMNs, including classifications, specific protocol details, and their performance in different scenarios.

Section 4: CROSS-LAYER AND NETWORK CODING IN MULTI-CAST MULTI-RADIO MULTI-CHANNEL WMNS
Description 4: Describe the role of cross-layer optimization and network coding in enhancing the throughput and performance of multicast multi-radio multi-channel WMNs.

Section 5: DIRECTIONS FOR FURTHER RESEARCH
Description 5: Suggest potential future research directions in the area of WMNs for enhancing performance and addressing current challenges.

Section 6: CONCLUSIONS
Description 6: Summarize the key points discussed in the paper and the potential benefits of WMNs coupled with cross-layer optimization and network coding.
</format>
