Wlan Mesh Primer

A WLAN mesh network is a fully IEEE 802.11-based wireless network that employs multihop communications to forward traffic en route to and from wired Internet entry points. Recently standardized IEEE 802.11a 7 and 802.11g 8 WLAN standards have substantially increased data rates of WLAN networks by using spectrally efficient modulation schemes (up to 54 Mbps). Upcoming IEEE 802.11n standard based on Multiple-input Multiple-output (MIMO) techniques promises to increase data rates further (up to...

Editors

Yan Zhang received a Ph.D. degree from the School of Electrical & Electronics Engineering, Nanyang Technological University, Singapore. From August 2004 to May 2006, he worked with NICT Singapore, National Institute of Information and Communications Technology (NICT). From August 2006, he has worked with Simula Research Laboratory, Norway (http www.simula.no ). Dr. Zhang is on the editorial board of International Journal of Network Security and is currently serving as the series editor for...

Countermeasures to Selfish Misbehavior

The problem of selfish behavior in multihop wireless networks is studied and a solution called Catch is proposed 27 . It assumes that most of the nodes are honest and cooperative. They collectively prevent a minority of selfish nodes from malicious action, e.g., packet dropping. In game theory parlance, Catch assures that cooperation is an evolutionarily stable strategy. The scheme uses anonymous messages, in which the identity of the sender is hidden, to tackle two critical problems. First,...

Other Topologybased Routing Protocols for Wireless Mesh Networks

Many routing protocols have been proposed for wireless multihop networks. This section lists a few other routing protocols. It is by no means exhaustive. For extensive information, the reader is referred to the World Wide Web. Topology Dissemination Based on Reverse-Path Forwarding (TBRPF) has been standardized in IETF as experimental RFC 3684 19 . It is a proactive routing protocol. TBRPF is used in a few installations and products of WMNs. Dynamic on-demand MANET routing protocol (DYMO) is...

Electrical Engineering

A promising new technology, wireless mesh networks are playing an increasingly important role in the future generations of wireless mobile networks. Characterized by dynamic self-organization, self-configuration, and self-healing to enable quick deployment, easy maintenance, low cost, high scalability, and reliable services, this technology is becoming a vital mode complementary to the infrastructure-based wireless networks. Wireless Mesh Networking Architectures, Protocols and Standards is the...

Shah I Rahman

13 IEEE 802.16 WiMAX Mesh YAN ZHANG, KEAN-SOON TAN, PENG-YONG KONG, Spectrum CLEMENS KLOECK, VOLKER BLASCHKE, HOLGER JAEKEL, FRIEDRICH K. JONDRAL, DAVID GRANDBLAISE, JEAN-CHRISTOPHE DUNAT, AND SOPHIE GAULT 15 Wireless Mesh Networks Case Study Fire Emergency Management and Market CARLES GOMEZ, PAU PLANS, MARISA CATALAN, JOSEP LLUIS FERRER, JOSEP PARADELLS, ANNA CALVERAS, JAVIER RUBIO,

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Radio access networks (RAN), 484 Radio access technology (RAT), 477 Radio auction agent (RAA), 489 Radio aware optimized link state Radio resource goods (RRGs), 485 Radio technology, choice of, 15 Radio usage policy, 51 RADIUS authentication mechanism, 522 analysis of, 314-316 Reachability graph, of the network, 66 Reactive protocols, 117 Ready to receive (RTR) messages, 165 Real-time multiplayer games, 352-354 Real-time polling service (rtPS), 450 (RSSI), 76, 443 Receiver-initiated channel-hop...

Congestion Control in WLAN Mesh

The original 802.11 MAC and all its recent enhancements (e.g., 802.11e 10 , 802.11i 11 , 802.11k 16 ) are designed primarily for single-hop wireless networks. Multihop data forwarding is central to WLAN mesh networks. Neither 802.11 DCF nor 802.11e EDCA provides any QoS over a multihop WLAN network. Each MP contends for the channel independently, without any regard for what is happening in the upstream or downstream nodes. One of the consequences is that a sender with backlogged traffic may...

Medium Access Control Protocols For Multiradio Wireless Mesh Networks

The design of MAC protocols is important in MR-WMNs compared to the single-radio WMNs because of additional challenges faced by the former. This section presents a few of the recently proposed MAC protocols for MR-WMNs. These protocols are the MCSMA 24 , the ICSMA 8 , and the 2P-TDMA 25 . These protocols are explained in detail in Section 1.7.1 through Section 1.7.3. The MCSMA MAC protocol 24 , is similar to an FDMA system. In this medium access scheme, the available bandwidth is divided into...

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Of the OLSR protocol (RFC 3626 13 ) as described in Section 4.5.3. Instead of IP addresses as in 13 it uses MAC addresses and can work with arbitrary routing metrics such as the air-time metric of Section 4.6.1. Furthermore, it defines a mechanism for the distribution of addresses of nonmesh WLAN clients in the RA-OLSR mesh. The link state is the value of the link metric and is used in the shortest path computation. Therefore, a link metric field is associated to each reported neighbor in hello...

Backhaul and Access Traffic Separation

Since an MP is only a logical entity, it is possible to physically collocate it with an AP or implement it on a device that also acts as an application end point, i.e., in addition to participating in the mesh and forwarding frames on behalf of other MPs, it also generates its own application traffic. In both cases, one single device has to forward a mixture of mesh traffic (with four-address frame formats) and BSS traffic (with three-address frame formats). Handling of these two different...

Routing Protocols

The default routing protocol in the access cubes is an OLSR implementation called olsrd 42 , which uses the LQE, a nonstandard feature. This mechanism uses the expected transmission count (ETX) 12 metric to choose the most appropriate route by combining link quality and the number of hops per path. The ETX for each link is obtained as NLq*iq, where LQ is the measured quality of the link between a node and a neighbor in one direction and NLQ is the link quality measured in the opposite...

Pointto Multipoint and Mesh Networking Modes

Figure 13.1 compares the PMP and mesh topologies. In PMP mode, a Base Station (BS) performs the centric role to coordinate and relay all communications. The Subscriber Station (SS) under the management of the BS has to communicate with BS before transmitting data with other SSs. This architecture is exactly similar to cellular networks. Under certain situations, e.g., emergency or disaster scenarios, PMP mode may not be suitable for timely and efficient deployment while mesh mode serves as an...

Dynamic Source Routing Protocol DSR

DSR is one of the pioneering routing protocols for MANETs. DSR is being standardized in the IETF MANET working group 2 . DSR is a well-known, reactive routing protocol. It computes a route only if one is needed. The route discovery consists of route request and route reply. The route request is broadcast into the wireless network. However, instead of setting the (reverse) paths in the routing tables of the nodes, the route request collects the addresses of the traversed nodes on its way to the...

Info

Where FDR and RDR are the forward delivery ratio and reverse delivery ratio, respectively. The FDR is the estimated value of the probability of a data packet successfully received at a receiver over a given link. Similarly, the RDR is the estimation of the probability of the ACK packet successfully received at the sender of the data packet over a given link. In Equation 1.1, the denominator term of the RHS, containing the product of FDR and RDR, represents the expected probability of a...

Hardware Requirements

Form factor and weight Firefighters should carry several seeds in addition to their own FT. These devices must be small and light enough for them to carry. Indoor and outdoor operation FTs and seeds are expected to be used mainly indoors, while ONs are defined as outdoor devices. Network nodes should therefore be able to operate in both indoor and outdoor scenarios. Batteries The battery life of the nodes should ensure full operation throughout a fire incident.

Phy

Figure 5.4 The IEEE 802.11e MAC architecture. queue and its own set of EDCA parameters. The differentiation in priority between ACs is realized by setting different values for the EDCA parameters. The EDCA parameters include (1) arbitration interframe space number (AIFSN), (2) minimum contention window (CWmin), (3) maximum contention window (CWmax), and (4) transmission opportunity (TXOP) limit. AIFS is the period of time the wireless medium is sensed idle before the start of a frame...

IEEE 80211e MAC Protocol

The IEEE 802.11e standard draft defines a number of QoS enhancements to IEEE 802.11 4 . Two main functional blocks are defined in IEEE 802.11e (1) the channel access functions and (2) the traffic specification (TSPEC) management. The channel access function defines a new coordination function called the hybrid coordination function (HCF). HCF has two modes of operation a contention-based protocol called enhanced distributed channel access (EDCA) and a polling mechanism called HCF controlled...

IEEE 80211 DCF Protocol

The IEEE 802.11 standard specifies two medium access methods (1) distributed coordination function (DCF) that builds on CSMA CA and (2) point coordination function (PCF) providing contention-free access 1 . Because PCF requires a central control entity, i.e., a point coordinator, it is rarely used in WMNs. Instead, the DCF protocol is widely adopted in WLANs and WMNs. Additionally, because of its robustness and flexibility, many advanced MAC protocols are also based on the IEEE 802.11 DCF...

Multiradio Mesh

Multiple radio nodes are effectively full duplex, i.e., they can receive on channel c1 on one interface while simultaneously transmitting on channel c2 on another interface, thereby doubling the node throughput (in principle). For example, consider the path 1 2 3 in Figure 2.4. Let R denote the maximum possible transmit rate over one hop (i.e., 1 2). With one radio, node 2 spends roughly half the time receiving from node 1 and the other half transmitting to node 3. Consequently, if the source...

References

Vollbrecht, J. Carlson, and H. Levkowetz. Extensible authentication protocol (EAP). RFC 3748, June 2004. 2. I.F. Akyildiz, X. Wang, and W. Wang. Wireless mesh networks A survey. Computer Networks, vol. 47, p. 445-487, 2005. 3. P.G. Argyroudis and D. O'Mahony. Secure routing for mobile ad hoc networks. IEEE Communications Surveys and Tutorials, vol. 7, no. 3, 2003. 4. V. Bahl. Mesh networking. In Mesh Networking Summit 2004 Making Meshes Real, 2004. 5. S. Buchegger and J....

Conclusions

This chapter presented a survey of current research efforts for multimedia communications support over WMNs. WMNs are particularly challenging because of their multihop structure, the mobility of network nodes, and the unreliable nature of the wireless channel. While most of the studies (routing protocols, priority mechanisms, and rate control techniques) have focused on throughput and packet loss performance of WMNs, in general, further investigation is required to provide QoS for real-time...

Current PSDR Communication Technology

The mainstay of public safety communications has been and still is LMR, also known as professional mobile radio or private mobile radio (PMR). Traditional LMR systems provide analog voice communication for closed user groups over dedicated ultra high frequency (UHF) or very high frequency (VHF) bands. Modern LMR systems are digital and have limited data capabilities. The two most relevant standards are digital and the Association of Public Safety Communications Official (APCO) Project 25 (P25)...

Throughput Model between an Access Point and Users

The design of cell size in WMN for urban coverage can be considered from two folds. First, the cell radius should be less than rmax to maintain an acceptable data rate. Second, the cell radius should be larger than rmin to lower the handoff probability. In each cell, users share the medium and employ the carrier sense multiple access with collision avoidance (CSMA CA) MAC protocol to communicate with an AP. We assume that the users are uniformly distributed on the road with density DM (Users...

Characteristics of WMN

One of the key features of WMNs is the ability to dynamically self-organize and self-configure. The nodes in a WMN automatically detect neighbor nodes and establish and maintain network connectivity in an ad hoc fashion, typically implemented at the network layer through the use of ad hoc routing protocols 11 . The self-configuring nature of WMNs allows easy and rapid deployment. WMNs also have the ability to dynamically adapt to changing environments and to essentially self-heal in case of...

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AAA server, 185, 188 Access categories (ACs), 155 Access One network devices, 521 Access points (APs), 50, 80 ACK packet, 30, 32 Active attacks, to WMNs, 193 Active nodes, 292 Active scanning, 339 Adaptive dejitter buffers, 349 Adaptive modulation and coding (AMC), 432 Adaptive multirate wideband (AMR- WB) encoder, 348 Address resolution protocol (ARP), 26 Ad hoc mesh networks, 188 Ad hoc on-demand distance vector routing protocol (AODV), 115, 122-125, 377, 521 Ad hoc traffic indication message...

Authentication Protocols

Two novel authentication protocols are described to illustrate the provision of sufficient and efficient authentication for WMNs. The first protocol is the WDAP 53 for IEEE 802.11 WMNs. The WDAP provides dual authentication for a WS and its corresponding AP in a wireless network by an AS, and sets up a session key for confidential communications between the WS and the AP if the authentication is successful. The second protocol is the SUMP 21 that is originally designed for multihop ad hoc...

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Figure 1.8 Example topology for 2P-TDMA. respectively. There are two issues in this case (a) the network interface that first initiates the packet (e.g., 1.A) will result in carrier sensing at the other network interface (1.B) on the same node even if they are placed several meters apart and (b) even if the interfaces 1.A and 1.B simultaneously begin transmission of their DATA packets without leading to mutual carrier sensing and subsequent back-off, the interface at node 1, which first...

Fisher Rputung Prptocol

Figure 4.1 Classification of routing protocols. compute a route only when it is needed. This reduces the control overhead but introduces a latency for the first packet to be sent due to the time needed for the on-demand route setup. In proactive routing protocols, every node knows a route to every other node all the time. There is no latency, but permanent maintenance of unused routes increases the control overhead. Hybrid routing protocols try to combine the advantages of both the philosophies...

Game Theory

Game theory is a tool for modeling and analyzing situations with strategic interactions. Since the pioneering work of von Neumann and Morgenstern 36 , game theory concepts and methods have been used in various domains, from economics to politics, biology, or telecommunications. Formally, a game is constituted with a set of players, each having the possibility to choose the best strategy in a given space so as to obtain the greatest payoff 37 . The expected outcome of a game is to reach an...

Mesh Routing And Forwarding

Wireless routing has been a topic of research interest for over a decade. Routing frames from a wireless host by the backbone network to the appropriate intra-, inter-, or gateway-node through dynamic RF environments has been a major challenge to date. WLAN mesh routing protocol adapts earlier works of IETF MANET Work Group as well as wireless spanning tree protocols (STP) are specified 1 . The terms mesh path selection and mesh forwarding are used to describe selection of single-hop or...

Contention Free MAC Protocols for Synchronized Mesh Networks

Currently, most of the current WMNs are based on 802.11 MAC or its derivatives due to the asynchronous operation of mesh nodes. However, if all mesh nodes are synchronized with each other, contention-free MAC protocols can be used to improve the network performance. One of the most popular contention-free MAC protocols is defined in IEEE 802.16 2 , also called WiMax. The 802.16 MAC protocol is designed to support point to multipoint (PMP) and mesh network models. Utilizing TDMA and originally...

Protocols for Mesh Nodes Equipped with Directional Antennas

MAC protocols designed for WMNs typically assume omnidirectional antennas that transmit radio signals to and receive them from all directions. When two nodes are communicating, all other nodes in the vicinity have to remain silent, which has a negative impact on the network capacity. Therefore, the network capacity diminishes with an increase in the number of nodes 15 . With directional antennas (including smart antennas), two pairs of nodes located in each other's radio vicinity may...

Common Channel Framework

An optional common channel framework (CCF) is proposed to enable the operation of single-radio devices in a multichannel environment. The CCF assumes that each node is equipped with a single half-duplex transceiver and nodes in the network or in the same cluster share a common control channel. To legacy devices (STAs and AP) and MPs that do not support the CCF, the common channel appears as any other 802.11 channel and their operation remains unaffected. Using the CCF, node pairs or clusters,...

Bs Manoj And Ramesh R

2 Multiradio Multichannel Mesh RAJIV VIJAYAKUMAR, ARINDAM DAS, SUMIT ROY, AND HUI MA 3 IEEE 802.11-Based Wireless Mesh ASHISH RANIWALA, RUPA KRISHNAN, AND TZI-CKER CHIUEH 4 Routing in Wireless Mesh 113 MICHAEL BAHR, JIANPING WANG, AND XIAOHUA JIA 5 Medium Access Control in Wireless Mesh Networks 147 MICHELLE X. GONG, SHIWEN MAO, SCOTT F. MIDKIFF, AND BRIAN HART 6 Security in Wireless Mesh 183 RAINER FALK, CHIN-TSER HUANG, FLORIAN KOHLMAYER,

Ad hoc Ondemand Distance Vector Routing Protocol AODV

Aodv Protocol Images

AODV is a very popular routing protocol for MANETs. It is a reactive routing protocol. Routes are set up on demand, and only active routes are maintained. This reduces the routing overhead, but introduces some initial latency due to the on-demand route setup. AODV has been standardized in the IETF as experimental RFC 3561 4 . There are several implementations available, for instance, AODV-UU of Uppsala University 10 . Further information on AODV can be found in 11,12 . Recently, an adaptation...

Innovative Multimedia Applications

The interest in WMNs is rapidly growing. One of the reasons is that they can provide connectivity in scenarios and conditions that cannot be easily supported by other architectures. In future, the new functionalities offered by WMNs will be exploited by a number of advanced applications ranging from traditional multimedia applications to innovative ones, such as intervehicle multimedia communications and multiplayer gaming. However, typical users expect to be able to use multimedia services...

Contents

11.2 Survey of multiple antenna 11.2.1 Beamforming and antenna 11.2.2 Diversity and space-time 11.2.3 Spatial 11.3 Overview of wireless mesh 11.3.1 Characteristic aspects of wireless mesh networks 369 11.3.2 Challenges in wireless mesh networks and possible 11.4 Multiple antenna techniques for wireless mesh networks 373 11.4.1 Increase capacity and 11.4.2 Improve routing 11.4.3 Increase energy 11.4.4 Other performance 11.5 Conclusions and

General Concepts Of Routing Protocols 431 Classification of Routing Protocols

The main task of routing protocols is the path selection between the source node and the destination node. This has to be done reliably, fast, and with minimal overhead. Especially, there has to be a path computed if there exists one. In general, routing protocols can be classified into topology-based and position-based routing protocols cf. Figure 4.1 . Topology-based routing protocols select paths based on topological information, such as links between nodes. Position-based routing protocols...

Routing Metrics

We now turn our attention to the problem of routing in mesh networks for a given CA. We do not discuss the various options for routing protocols themselves usually one of the well-known routing protocols developed for ad hoc networks will suffice. Instead, we focus on the choice of routing metric used by the routing protocol. The simplest routing metric, the hop count shortest path , has been widely used in existing ad hoc routing protocols. However, it will generally fare poorly in mesh...

Physical Layer And Mac Layer Overview

IEEE 802.16 defines three different PHY specifications for PMP mode in the 2-11 GHz frequency band. Each of these air interfaces is able to work together with the MAC layer to provide a reliable end-to-end link. WMAN-SCa a single carrier SC modulation technology WMAN-OFDM a 256-carrier OFDM modulation, in which Time Division Multiplex Access TDMA mechanism is utilized for multiple access this air interface is mandatory for license-exempt bands WMAN-OFDMA a 2048-carrier OFDM modulation, in which...

Topology Control Schemes For Multiradio Wireless Mesh Networks

In WMNs, topology control refers to the alteration of network topology by modifying one or more parameters such as mobility, location, transmission power, directionality of antennas, and the status of network interfaces. This section presents the objectives of topology control and the existing solutions for topology control in WMNs. 1.9.1 Objectives of Topology Control Protocols The network capacity is influenced by the network topology and therefore, altering the topology can increase the...

WiMAX Simulator

Wimax Architecture Qualnet

Figure 13.13 illustrates the protocol structure of the WiMAX mesh MAC protocol stack. One of the functionalities of the mesh network entry protocol component is selection of sponsor node, which will involve communication exchange of unicast MSH-NENT from the new entry node and broadcast MSH-NCFG control messages from Figure 13.13 WiMAX mesh simulator protocol structure. Figure 13.13 WiMAX mesh simulator protocol structure. the sponsor node. In the design, the network entry process has been...

Scheduling Mshnent in Control Subframe

In the mesh mode, transmission opportunities in the control subframe and minislots in the data subframe are separated. Each node competes the control channel access. The contention consequence in the control subframe does not have effect on the data transmission during the data subframe of the same frame. There are two different messages in the control subframes MSH-NENT and MSH-NCFG. Accordingly, there are two scheduling algorithms defined for these two messages. In this section, we will...

Advanced Topology Discovery

The most fundamental element of any network management is the ability to visualize the location and interconnectivity of nodes as well as the utilization of network resources in this case wireless channels at each location. This is especially important for larger scale WMN as they need to coexist with, rather than compete with, other residential and office wireless LANs. The three research questions here are the following. First, how to utilize multiple radios and potentially smart antennas...

Introduction

Wireless mesh network WMN is a radical network form of the ever-evolving wireless networks that marks the divergence from the traditional centralized wireless systems such as cellular networks and wireless local area networks LANs . Similar to the paradigm shift, experienced in wired networks during the late 1960s and early 1970s that led to a hugely successful and distributed wired network form the Internet WMNs are promising directions in the future of wireless networks. The primary...

Numerical Investigations

The numerical investigations are based on grid topologies aiming to evaluate the effect of the number of active links on different performance aspects of the system. Even though grid topologies may not represent realistic mesh network configurations, they facilitate a detailed and systematic discussion on the performance of different algorithms. As an example a topology with 64 nodes and 40 active links in a 8 x 8 grid is shown in Figure 9.4. The coefficients of the objective function are...

Wlan Mesh Security

Ieee 802 11s Mesh Data Frame Format

This is a mandatory feature of 802.11s draft standard, which utilizes 802.11i-based security mechanisms to enable link security in a WLAN mesh network. 802.11i 16 provides link-by-link security in a WLAN mesh network. End-to-end security may be layered on top of WLAN mesh security, e.g., IP security IPSec VPN . The link access protocol is based on 802.11i Robust Security Network Association RSNA security and supports both centralized and distributed IEEE 802.1x-based authentication and key...

Energy Management in PMP Mode

Listening Interval Sleeping Interval

The amendment 802.16e 7 adds mobility component for WiMAX and defines both physical and MAC layers for combined fixed and mobile operations in licensed bands. Due to the promising mobility capability in IEEE 802.16e, the mechanism in efficiently managing the limited energy is becoming very significant since a Mobile Subscriber Station MSS is generally powered by battery. For this, sleep mode operation has been recently specified in the MAC protocol 7,16,34 . Figure 13.5 shows the wake mode and...

Design Issues In Multiradio Wireless Mesh Networks

The primary advantages of using an MR-WMN are the improved capacity, scalability, reliability, robustness, and architectural flexibility. Notwithstanding the advantages of using a multiradio system for WMNs, there exist many challenges for designing an efficient MR-WMN system. This section discusses the issues to be considered for designing an MR-WMN. The main issues can be classified into architectural design issues, MAC design issues, routing protocol design issues, and routing metric design...

Intramesh Congestion Control

With 802.11 MAC, each MP contends for the channel independently, without any regard for what is happening in the upstream or downstream nodes. One of the consequences is that a sender with backlogged traffic may rapidly inject many packets into the network, which would result in local congestion for downstream nodes. In wired networks and WLANs, one of the effective tools to combat congestion has been end-to-end flow control implemented at the higher layers of the network stack. For instance,...

Mesh Deterministic Access

The MDA is an optional access method that allows MPs to access the channel with lower contention than otherwise in selected periods. The goals are to utilize channel bandwidth more efficiently and to provide better QoS for periodic traffic. The method sets up contention-free time periods called MDA opportunity MDAOP in mesh neighborhoods where a number of MDA-supporting MPs may potentially interfere with each other. For each MDAOP period, supporting MPs are allowed to access the channel in a...

Aloha and Slotted Aloha

The first contention-based MAC protocol is Aloha, developed in the early 1970s by Abramson at the University of Hawaii 6 . The basic operation of Aloha is as follows nodes can transmit whenever they have a packet to send. The receiver needs to acknowledge successful receipt of the data packet. If a collision occurs and the packet is corrupted, the sender does not receive an acknowledgment ACK within the time-out period. Then, the sender waits for a random amount of time and retransmits the...

Mup

Figure 1.5 A representation of the MUP architecture. Therefore, channel selection or switching refers to selection or switching of radio interfaces, respectively. It is, therefore, a significant requirement to have every node in the network to use the same set of orthogonal channels for its interfaces. This, however, leads to a limitation where the number of radio interfaces that can be attached to any node in the network, as per MUP, limited by the number of orthogonal channels in the system....

Secure Unicast Messaging Protocol

SUMP is mainly designed to mitigate the threats of sinkhole and wormhole attacks for multihop ad hoc sensor networks. Most other authentication protocols for multihop ad hoc sensor networks, e.g., SNEP 36 , are vulnerable to these attacks because they require nodes to maintain parent node information. The SUMP does not require a sensor node to store parent node information, thus mitigates sinkhole and wormhole attacks. In SUMP, the base station, which is equivalent to the GN in a WMN,...

Interference Assumption

The IEEE 802.16 mesh mode depends on a common assumption that there is no interference more than two hops away, for instance, the physical neighbor list building, or the MSH-NCFG and MSH-DSCH messages listening and broadcasting. This assumption may lead to a discrepancy from the realistic environment and needs further investigation. For example, there are lots of nodes in a city's dense area. The interference may propagate several hops away. In such a case, the interference has a great impact...

Cognitive Radio Architecture

Cognitive Radio Architecture

Since CRs provide operation in different frequency bands using different modulation forms, the underlying structure is built upon SDRs. SDRs also have the ability to operate on several bands simultaneously which increases the utility for a dynamic resource allocation over different transmission standards. In addition to SDRs, which have to meet the local regulations regarding the new downloaded software, CRs have to be designed in a way that their choices of the operational parameters will meet...

Cross Layer Routing Approach

The interference in wireless networks dramatically degrades the network performance. The interference is directly related to the transmission power. Larger transmission power means more reliable links with higher capacity. On the other hand, larger transmission power also means more interference, thus, less network throughput. Therefore, to provide the routing layer with the information of the lower layers can help to find more reliable and higher capacity paths. A cross-layer routing...

Scheduling Mshncfg in Control Subframe

Distributed election scheduling is defined to determine the next transmission time NextXmtTime of a node's MSH-NCFG during its current transmission time XmtTime. There are two fields NextXmtMx and XmtHoldoffExponent in MSH-NCFG to determine the next eligibility interval. Here, the eligibility interval refers to the duration in which the node can transmit in any slot and is given by The length of the eligibility interval is equal to the difference between the upper bound and the lower bound,...

PSDR Command and Communication Structure

Command And Communications Structure

To understand the requirements of PSDR communications, it is important to consider the typical command and control structure used in emergency and disaster recovery situations. The Incident Command System ICS is one of the predominant emergency response management systems. The ICS provides a generic framework for the coordination and management of emergency response and disaster recovery operations, where various agencies of different jurisdictions and disciplines are involved. One of the key...

Interflow and Intraflow Interference

The bandwidth issue is even more severe for multihop WMNs where in order to keep the network connected all nodes operate over the same radio channel. This results in substantial interference between transmissions from adjacent nodes on the same path as well as neighboring paths reducing the end-to-end capacity of the network 1,2 . Figure 3.2 depicts an example of such interference. Hearing-range neighbors of '3' Sense-range neighbors of '3' Neighbors of 3's sense-range neighbors Figure 3.2...

WMN Systems and Standards

Several companies e.g., Tropos Networks, Firetide, Motorola, Strix, and PacketHop have realized the potential of WMNs and have started offering mesh networking products for a range of application scenarios, including PSDR communications. Most of these products are based on commodity IEEE 802.11 hardware to leverage the low cost and high performance of this technology. However, a majority of these commercial systems implement their own proprietary mesh protocols for routing and network...

Multimedia Characteristics And Quality Of Service Requirements

In contrast to generic data communications, multimedia communications have more stringent QoS requirements that must be fulfilled to provide an acceptable service. In particular, multimedia traffic is characterized by strong time sensitivity and inelastic bandwidth requirements. Multimedia packets, in fact, must be available at the decoder before their playback time deadline to allow an undistorted media reconstruction. Packets that are not received before their deadline become useless....

Uncoordinated Distributed Scheduling

Uncoordinated distributed scheduling serves the temporary communication between two nodes. The algorithm is based on a three-way-handshake mechanism Figure 13.11 . MSH-DSCH Grant confirmation Direction 0 Figure 13.11 Three-way-handshake process. In uncoordinated distributed scheduling, mesh distributed schedule MSH-DSCH message, which transmits in the data subframe, is the most important message in the scheduling process. An MSH-DSCH message carries the following fields 1 availabilities IE,...

Coordinated Distributed Scheduling

Similar to uncoordinated distributed scheduling, MSH-DSCH message plays a significant role in the whole scheduling process. Unlike the MSH-DSCH message taking place in data subframe in uncoordinated distributed scheduling, the MSH-DSCH in coordinated distributed scheduling occurs in control subframe. The transmission opportunity of MSH-DSCH in coordinated distributed scheduling follows a similar distributed election algorithm as in Section 13.4.4. That is, the distributed election scheduling...

Hybrid Wireless Mesh Protocol HWMP

HWMP is the default routing protocol for WLAN mesh networking. Every IEEE 802.11s compliant device will be capable of using this routing protocol. The hybrid nature and the configurability of HWMP provide good performance in all anticipated usage scenarios 28 . The foundation of HWMP is an adaptation of the reactive routing protocol AODV 4 to layer 2 and to radio-aware metrics called radio metric AODV RM-AODV . A mesh node, usually a mesh portal, can be configured to periodically broadcast...

Design Objective And Challenges

While WMNs can extend network coverage and potentially increase network capacity, they can also impose unique challenges on MAC protocol design. The first and foremost challenge stems from the ad hoc nature of WMNs. In the absence of fixed infrastructure that characterizes traditional wireless networks, control and management of WMNs have to be distributed across all nodes. Distributed MAC is a much more challenging problem than centralized MAC. For multichannel MAC protocols, distributed...

Multiple Antenna Techniques For Wireless Mesh Networks

As seen from Section 11.3, the employment of multiple antennas could improve the performance of the WMNs from different aspects. Generally, in order to meet the challenges in the WMNs, the functions of the multiple antenna techniques could be classified into many different parts increase the capacity and throughput, improve the routing performance, increase energy efficiency, and many other performance improvements. Section 11.4.1 through Section 11.4.4 illustrates the above-mentioned functions...

Interest for a Distributed and Collaborative Approach

Several measurements performed by the Shared Spectrum Company have shown that the level of activity was very low in many allocated spectrum bands 2 . This revealed the existence of spectrum holes in spectrum usage, within the fully allocated bands. Unfortunately, there is no model to predict when and for how long a given spectrum band will be used. Accordingly, opportunistic and smart algorithms should be developed to identify these holes and use them as needed, while authorized by the...

Outlook And Open Issues

Wireless mesh networking is a topic that now attracts great attention from industrial companies and universities. Big efforts are under way to develop working mesh standards. There are many companies selling wireless mesh devices. And there are already many working installations of wireless mesh networks around the world. The core idea of wireless mesh networks forwarding of packets over multiple wireless hops is a new quality in wireless communications. It can make devices ''truly wireless.''...

Protocols And Open Issues

The growing deployment of wireless technology in everyday scenarios actively fosters the evolution of wireless networks into what will be the network infrastructure of our future. Recently, WMNs emerged as a key technology for a variety of new applications that require flexible network support. As an evolution of multihop mobile ad hoc wireless networks MANETs , the so-called mesh network configuration maintains the ad hoc communication structure that consists of two architectural levels mesh...

QoS Scheme For WiMax Mesh Mode

In the mesh mode, the transmission opportunities in the control sub frame and the minislots in the data subframe are separated. Each node competes the control channel access. The contention consequence in the control subframe does not affect the data transmission during the data subframe of the same frame. Hence, the contention process in the control subframe is elaborated for deriving the performance metrics. In the distributed scheduling, MSH-DSCH message plays a significant role in the whole...

Hardware Platform

Hardware Mesh Access Cube

We only added hardware to the access cubes to build the CC and FTs, as the seeds and ONs could be implemented on the default platform. We developed an FT prototype composed of an access cube connected to a PDA, which acts as a graphical user interface. Figure 15.2 illustrates this setup, in which the Ethernet interface was used to connect the personal digital assistant PDA to the access cube. Another option would be to use an IEEE 802.11b interface. Advanced firefighter equipment would include...

Smooth Topology Changes

We analyzed reactivity to smooth topology changes in an emulated emergency scenario inside a building. We positioned our WMN testbed in a realistic way, with natural multihop communications i.e., without using iptables to emulate coverage . Figure 15.8 illustrates a scenario in which a firefighter walks into a burning building following the path from A to D. The FT of the moving firefighter communicates with node D while the firefighter follows the aforementioned path. At the beginning of the...

Contributors

Research King's College London, United Kingdom Siemens AG Corporate Technology Munich, Germany Nachrichtentechnik Universit t Karlsruhe Karlsruhe, Germany Wireless Networks Group Technical University of Catalonia Barcelona, Spain Wireless Networks Group Technical University of Catalonia Barcelona, Spain Engineering National Chiao-Tung University Hsinchu, Taiwan People's Republic of China Science Stony Brook University Stony Brook, New York Engineering University of Washington, Seattle,...

WMN Architecture

Wired Link

We can differentiate between three basic types of WMN architectures infrastructure mesh, client mesh, and hybrid mesh 9 . Figure 16.2 is an example of an infrastructure WMN. The mesh routers collectively provide a wireless backbone infrastructure. In this architecture, clients have a passive role and do not contribute to the mesh infrastructure. In a client mesh architecture Figure 16.3 , the network is made up of user devices only and no dedicated network infrastructure is involved. Since...

Multi Radio Link Quality Source Routing Mrlqsr Protocol

In a wireless mesh network, some degradation in throughput might be expected over five or six hops. Channel interference could result in lower throughput if the nodes are too close to each other or if the power is too high for the area. WMN routing protocols should select paths based on observed latency and wireless environment as well as other performance factors, resulting in the best possible throughput across the network. To increase the capacity of the wireless mesh networks, nodes might...

Radio Aware Optimized Link State Routing RAOLSR

RA-OLSR protocol is an optional, proactive routing protocol of the emerging IEEE 802.11s standard. It follows closely the specification Root node configured Mesh portal announcements configured Root node configured Mesh portal announcements configured On-demand routing tree to root node

Wireless Dual Authentication Protocol

Deauthentication Request

Before going into the details of WDAP, we first give a brief overview of the authentication scheme in 802.11i 19 , the security standard used in 802.11 WMNs. As discussed in Section 6.1.3, 802.11i provides strong user-based authentication through the use of the 802.1x 20 standard and the EAP. The mutual authentication in 802.11i requires a UN to exchange a PMK with the AS before setting up a connection with an AP. The negotiation request packets are forwarded to the AS by the AP using RADIUS,...

Wlan Mesh Basic Services 1231 WLAN Frame Formats

WLAN mesh frame formats reuse IEEE 802.11 MAC frame formats defined 9 and extend them appropriately for supporting ESS mesh services. MAC frame header is appended with a mesh forwarding control field, which is a 24-bit field that includes a time to live TTL field for use in multihop forwarding to eliminate the possibility of infinite loops and a mesh E2E sequence number for use in controlled broadcast flooding and other services. This field is present in all frames of type extended with subtype...

Overview Of Wireless Mesh Networks

Broadband wireless systems are envisioned to provide ubiquitous access to end users, providing high-quality voice services, video, and other multimedia contents. As various next-generation wireless networks evolve around broadband services, the WMN attract great interests. The WMNs offer huge possibilities for community networks to provide access to homes and businesses, and could be used to connect public access sites throughout a community 2 . The basic architecture of WMNs could be...

Swarm Intelligence

SI is an artificial intelligence technique based on the study of collective behavior in decentralized and self-organized systems, which was introduced by Beni and Wang in 1989, in the context of cellular robotic systems. SI is defined as the emergent collective intelligence of groups of simple agents 33 . Computational intelligence structures at the system level emerge from unstructured starting conditions using powerful interaction mechanisms, while the action of each individual appears random...

Frame Format

The OFDM PHYof the system supports the frame-based transmission with the frame length 0.5 ms, 1 ms, or 2 ms. Figure 13.4 illustrates the frame structure for the OFDM physical layer operating in TDD mode. Each frame consists of a DL subframe and an UL subframe. The Tx Rx transition gap TTG is used to separate the DL and UP subframes and allows the terminal to change operation from reception to transmission. Similarly, the Rx Tx transition gap RTG is used to separate the UL and DL subframes and...

Types of PSDR Communication Networks

Conceptual Network Diagrams

As defined in the SAFECOM report 2 , we can differentiate between the following types of PSDR communication networks. Personal area networks PANs interconnect various devices carried by individual first responders. For example, fire fighters might be equipped with devices to detect hazardous gas or to monitor their vital statistics, geographical location, or oxygen tank status. These devices are connected wirelessly by a PAN. An incident area network IAN is a temporary network created for the...

Open Issues

Scalability is a quite desirable feature of WMNs. With the support of this feature, the network performances including user throughput and even the quality of service QoS e.g., delay, jitter, and packet loss rate can still be maintained as network coverage and users increase. In the following, we will discuss some interesting issues in WMNs, from the viewpoint of scalability. It goes without saying that the multihop communications can extend the coverage of an AP with more hops and or longer...

Gateway Load Balancing In Wireless Mesh Networks

Gateway nodes connect a WMN to the wired network, generally to the Internet. Therefore, traffic aggregation happens at gateway nodes which essentially limits the WMN's capacity. In addition to the limited capacity, the gateway node particularly expends much more energy for handling large number of packets it forwards, and this high energy consumption leads to quicker failure of gateway nodes in energy constrained WMNs. Therefore, gateway load balancing assumes significance in order to achieve...

Optimized Link State Routing Protocol OLSR

Wireless Mesh Networks Olsr

OLSR is a popular proactive routing protocol for wireless ad hoc networks. It has been developed at INRIA and has been standardized at IETF as Experimental RFC 3626 13 . Further information on OLSR can be found in 14,15 . OLSR uses the classical shortest path algorithm based on the hop-count metric for the computation of the routes in the network. However, the key concept of OLSR is an optimized broadcast mechanism for the network-wide distribution of the necessary link-state information. Each...

Design Issues In Wireless Mesh Networks

There are many issues that need consideration when a WMN is designed for a particular application. These design issues can be broadly classified into architectural issues and protocol issues. The architectural design issues and protocol design issues are described in Section 1.4.1 and Section 1.4.2. 1.4.1 Network Architectural Design Issues A WMN can be designed in three different network architectures based on the network topology flat WMN, hierarchical WMN, and hybrid WMN. These categories...