Info Frx
52. E. Setton, X. Zhu, and B. Girod, ''Congestion-optimized multi-path streaming of video over ad hoc wireless networks,'' in Proceedings of the IEEE International Conference on Multimedia and Expo, vol. 3, Taipei, Taiwan, pp. 1619-1622, June 2004. 53. K. Madepalli, P. Gopalakrishnan, D. Famolari, and T. Kodama, ''Voice capacity of IEEE 802.11b, 802.11a and 802.11g wireless LANs,'' in Proceedings of the IEEE Global Telecommunications Conference GLOBECOM , vol. 3, pp. 1549-1553, December 2004....
Contents 1
2.1.1 802.11 Mesh 2.1.2 Capacity 2.1.2.1 Single-radio, single-channel mesh networks a 2.1.2.2 Single-radio, multichannel mesh networks 55 2.1.2.3 Multiradio 2.2 Radio usage 2.3 Channel assignment and 2.3.1 Channel assignment 2.3.1.1 Interfering 2.3.2 Formulations and 2.3.2.1 Integer linear 2.3.2.2 Graph-theoretic 2.3.4 Routing
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
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
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
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...
Info Bcx
equipped with directional antennas, 158-161 trade-offs and constraints in, 177-178 Merkle hash tree, 219 Mesh access points MAPs , 395 protocol, 401-402 Mesh beaconing, 400-402 MeshCluster, 208 opportunity MDAOP , 175 Meshdynamics, 208 Mesh federation, 191 Mesh link operations, 399-400 Mesh mode in, IEEE 802.16 WiMAX basic capabilities negotiation in, 444-445 frame format, 439-441 node authorization in, 443-444 node registration in, 444 scheduling data subframe, 447-449 scheduling MSH-NCFG in...
Info Xdb
Wireless mesh networking is the ideal technology for providing quick-and-easy network access where network infrastructure is hard to install or has been destroyed. Wireless mesh network WMN is equally suited to the low-cost extension of network access to a wide area. Typical deployment scenarios include public safety networks, home networks, office networks, and public access networks. For example, in public access networks, WMN deploys wireless routers, called wireless mesh points MPs on light...
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
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...
CrossLayer 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,...
References Lsi
3. Wireless MAN Working Group, http wirelessman.org 5. IEEE 802.16-2001, IEEE Standard for Local and Metropolitan Area NetworksPart 16 Air Interface for Fixed Broadband Wireless Access Systems,'' April 2002. 6. IEEE 802.16a-2003, IEEE Standard for Local and Metropolitan Area Networks Part 16 Air Interface for Fixed Broadband Wireless Access Systems Amendment 2 Medium Access Control Modifications and Additional Physical Layer Specifications for 2-11 GHz,'' April 2003. 7. IEEE 802.16e D5-2004,...
PSDR Command and Communication 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
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...
References Ppk
1. Kean, T.H., et al., The 9-11 Commission Report,'' http www.9-11commission. gov report 911Report.pdf accessed January 2006 . 2. SAFECOM Program, US Department of Homeland Security, Statement of Requirements for Public Safety Wireless Communication and Interoperability,'' Version 1.0, March 2004, http www.safecomprogram.gov SAFECOM accessed January 2006 . 3. Telecommunications Industry Association TIA , APCO Project 25 System and Standards Definition,'' TIA EIA Telecommunication Systems...
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,...
Airtime Routing Metric
The airtime link metric is proposed as the default radio-aware routing metric for basic interoperability between IEEE 802.11s devices. It reflects the amount of channel resources consumed for transmitting a frame over a particular link. The path with the smallest sum of airtime link metrics is the best path. The correct term for nodes of IEEE 802.11s mesh networks is mesh point. In this chapter, we use the term mesh node. The airtime cost ca for each link is calculated with the following...
WMN Architecture
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...
MultiRadio LinkQuality 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
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...
Contents Lim
8.2 Gateway load balancing in wireless mesh networks 267 8.2.1 Moving boundary-based load balancing 268 8.2.1.1 Shortest path-based moving boundary 8.2.1.2 Load index-based moving boundary 8.2.2 Partitioned host-based load 8.2.2.1 Centralized host partitioning-based load 8.2.2.2 Distributed host partitioning-based load 8.2.3 Probabilistic striping-based load balancing 273 8.2.3.1 All node probabilistic striping approach 273 8.2.3.2 Boundary node probabilistic striping 8.3 Center loading in...