Showing papers on "Wireless mesh network published in 2001"

Investigating the energy consumption of a wireless network interface in an ad hoc networking environment

Abstract: Energy-aware design and evaluation of network protocols requires knowledge of the energy consumption behavior of actual wireless interfaces. But little practical information is available about the energy consumption behavior of well-known wireless network interfaces and device specifications do not provide information in a form that is helpful to protocol developers. This paper describes a series of experiments which obtained detailed measurements of the energy consumption of an IEEE 802.11 wireless network interface operating in an ad hoc networking environment. The data is presented as a collection of linear equations for calculating the energy consumed in sending, receiving and discarding broadcast and point-to-point data packets of various sizes. Some implications for protocol design and evaluation in ad hoc networks are discussed.

Capacity of Ad Hoc wireless networks

Abstract: Early simulation experience with wireless ad hoc networks suggests that their capacity can be surprisingly low, due to the requirement that nodes forward each others' packets. The achievable capacity depends on network size, traffic patterns, and detailed local radio interactions. This paper examines these factors alone and in combination, using simulation and analysis from first principles. Our results include both specific constants and general scaling relationships helpful in understanding the limitations of wireless ad hoc networks.We examine interactions of the 802.11 MAC and ad hoc forwarding and the effect on capacity for several simple configurations and traffic patterns. While 802.11 discovers reasonably good schedules, we nonetheless observe capacities markedly less than optimal for very simple chain and lattice networks with very regular traffic patterns. We validate some simulation results with experiments.We also show that the traffic pattern determines whether an ad hoc network's per node capacity will scale to large networks. In particular, we show that for total capacity to scale up with network size the average distance between source and destination nodes must remain small as the network grows. Non-local traffic-patterns in which this average distance grows with the network size result in a rapid decrease of per node capacity. Thus the question “Are large ad hoc networks feasible?” reduces to a question about the likely locality of communication in such networks.

Routing with guaranteed delivery in ad hoc wireless networks

Abstract: We consider routing problems in ad hoc wireless networks modeled as unit graphs in which nodes are points in the plane and two nodes can communicate if the distance between them is less than some fixed unit. We describe the first distributed algorithms for routing that do not require duplication of packets or memory at the nodes and yet guarantee that a packet is delivered to its destination. These algorithms can be extended to yield algorithms for broadcasting and geocasting that do not require packet duplication. A by product of our results is a simple distributed protocol for extracting a planar subgraph of a unit graph. We also present simulation results on the performance of our algorithms.

An analysis of the optimum node density for ad hoc mobile networks

Abstract: An ad hoc mobile network is a collection of nodes, each of which communicates over wireless channels and is capable of movement. Wireless nodes have the unique capability of transmission at different power levels. As the transmission power is varied, a tradeoff exists between the number of hops from source to destination and the overall bandwidth available to individual nodes. Because both battery life and channel bandwidth are limited resources in mobile networks, it is important to ascertain the effects different transmission powers have on the overall performance of the network. This paper explores the nature of this transmission power tradeoff in mobile networks to determine the optimum node density for delivering the maximum number of data packets. It is shown that there does not exist a global optimum density, but rather that, to achieve this maximum, the node density should increase as the rate of node movement increases.

QoS issues in ad hoc wireless networks

Abstract: Ad hoc wireless networks consist of mobile nodes interconnected by multihop communication paths. Unlike conventional wireless networks, ad hoc networks have no fixed network infrastructure or administrative support. The topology of the network changes dynamically as mobile nodes join or depart the network or radio links between nodes become unusable. This article addresses some of the quality of service issues for ad hoc networks which have started to receive increasing attention in the literature. The focus is on QoS routing. This is a complex and difficult issue because of the dynamic nature of the network topology and generally imprecise network state information. We present the basic concepts and discuss some of the results. The article concludes with some observations on the open areas for further investigation.

Distributed topology construction of Bluetooth personal area networks

Abstract: Wireless ad hoc networks have been a growing area of research. While there has been considerable research on the topic of routing in such networks, the topic of topology creation has not received due attention. This is because almost all ad hoc networks to date have been built on top of a single channel, broadcast based wireless media, such as 802.11 or IR LANs. For such networks the distance relationship between the nodes implicitly (and uniquely) determines the topology of the ad hoc network. Bluetooth is a promising new wireless technology, which enables portable devices to form short-range wireless ad hoc networks and is based on a frequency hopping physical layer. This fact implies that hosts are not able to communicate unless they have previously discovered each other by synchronizing their frequency hopping patterns. Thus, even if all nodes are within direct communication range of each other, only those nodes which are synchronized with the transmitter can hear the transmission. To support any-to-any communication, nodes must be synchronized so that the pairs of nodes (which can communicate with each other) together form a connected graph. Using Bluetooth as an example, this paper first provides deeper insights into the issue to link establishment in frequency hopping wireless systems. It then introduces the Bluetooth topology construction protocol (BTCP), an asynchronous distributed protocol for constructing scatternets which starts with nodes that have no knowledge of their surroundings and terminates with the formation of a connected network satisfying all connectivity constraints posed by the Bluetooth technology. To the best of our knowledge, the work presented in this paper is the first attempt at building Bluetooth scatternets using distributed logic and is quite "practical" in the sense that it can be implemented using the communication primitives offered by the Bluetooth 1.0 specifications.

Core assisted mesh protocol for multicast routing in ad-hoc Networks

Abstract: A method of providing multicast routing for use in ad hoc broadcast networks, such as wireless and mobile networks. The method is described within a protocol referred to as core-assisted mesh protocol, or CAMP. The method departs from traditional tree-structured multicast protocols and utilizes multicast meshes in which the network need not be flooded with control or data packets to establish routing paths. Each router configured for CAMP is capable of accepting unique packets arriving from any neighbor in the mesh, wherein packets are forwarded along reverse shortest paths to the receiver. Multiple cores may be defined for a group wherein the loss of a single core does not prevent packet flow. Routers for sender-only hosts are allowed to join the multicast mesh in simplex mode, and in certain cases may join without the sending of a join request.

Bluetrees-scatternet formation to enable Bluetooth-based ad hoc networks

Abstract: Bluetooth is an open specification for short-range wireless communication and networking, mainly intended to be a cable replacement between portable and/or fixed electronic devices. The specification also defines techniques for interconnecting large number of nodes in scatternets, thus enabling the establishment of a mobile ad hoc network (MANET). While several solutions and commercial products have been introduced for one-hop Bluetooth communication, the problem of scatternet formation has not yet been dealt with. This problem concerns the assignment of the roles of master and slave to each node so that the resulting MANET is connected. We introduce two novel protocols for forming connected scatternets. In both cases, the resulting topology is termed a bluetree. In our bluetrees the number of roles each node can assume are limited to two or three (depending on the protocol), thus imposing low slave management overhead. The effectiveness of both protocols in forming MANETs is demonstrated through extensive simulations.

Distributed topology control for wireless multi-hop sensor networks

Abstract: The following description provides direction-based topology control to a distributed wireless multi-hop network. The network includes multiple potentially mobile nodes. Each node sends a discovery message in all directions. Each node discovers a set of neighboring nodes using a set of incoming signals from the neighboring nodes that are responsive to the discovery message. Responsive to receiving the incoming messages, each node makes a local decision about a substantially optimal transmission power with which to communicate with at least a portion of the discovered neighboring nodes. The decisions are based on the incoming signals and are also independent of positional information (e.g., latitude and longitude). Each node in the network maintains communications with the decided portion of nodes to provide connectivity between each of the nodes.

Ad hoc relay wireless networks over moving vehicles on highways

Abstract: Ad hoc networks can be formed on highways among moving vehicles, each equipped with a wireless LAN device However, during times of low traffic density, it is likely that such networks are disconnected This paper tests the hypothesis that the motion of vehicles on a highway can contribute to successful message delivery, provided that messages can be relayed---stored temporarily at moving nodes while waiting for opportunities to be forwarded further Using vehicle movement traces from a traffic microsimulator, we measure average message delivery time and find that it is shorter than when the messages are not relayed We condclude that ad hoc relay wireless networks, based on wireless LAN technologies, have potential for many emerging applications of this kind

System and method for coordinating bandwidth usage of a communication channel by wireless network nodes

Abstract: A system and method is provided for coordinating wireless bandwidth usage of a common frequency band by wireless nodes in two disjoint networks, such as an infrastructure (“IS”) network and an ad hoc (“AH”) network. When AH nodes move into the transmission range of an access point of the IS network, they register with the access point and listen to the access point to tell them when they are allowed to transmit data over a given transmission channel. The access point coordinates the bandwidth usage by broadcasting ad hoc mode poll signals to indicate that the ad hoc nodes may transmit over the channel, and sending infrastructure mode poll signals to indicate that a wireless node in the IS network can transmit over the given channel. The access point makes a fraction of the bandwidth available for communications by the wireless AH nodes in its transmission range, while guaranteeing the rest of the bandwidth for wireless nodes in the IS network.

Finding a Maximal Weighted Independent Set in Wireless Networks

Abstract: This paper introduces MWIS, a distributed algorithm for the efficient determination of a maximal weighted independent set in the topology graph G of a wireless network. Motivated by the observation that the problem of partitioning wireless nodes into clusters easily reduces to the problem of finding a maximal weighted independent set of nodes, the proposed algorithm is described by taking into account two main characteristics of wireless networks, namely, the broadcast nature of the wireless medium and the possibility to support nodes mobility. MWIS is executed at each node by means of fast message triggered procedures that require the sole knowledge of the topology local to the node. Moreover, its time complexity is proven to be bounded by a topology dependent parameter of the network (the stability number ?(G) of the network topology graph G), rather than by the invariant number n of the network nodes. Based on this result, and by using a well known result about ?(G) in the theory of random graphs the paper concludes with a brief discussion on the average time complexity of MWIS.

Join process method for admitting a node to a wireless mesh network

Abstract: A join process (Fig. 5) is disclosed for a wireless mesh topology network. In the network, nodes have multiple spatial coverage sub-sectors together covering a larger sector angle and a node can establish connection with other nodes located in directions covered by its sub-sectors. The join process (Fig. 5) adds a joining node to the network and includes having the joining node listen (504) to sub-sectors at a specific receiving frequency for a defined time. Thereafter, the network node changes (506) its sub-sectors and its receiving frequencies according to a defined timing and sequence. Active network nodes transmit (508) organized invitation data packets on defined sectors, frequencies and timing, based on relative location and relative angle orientation deduced from sub-sectors already in use for existing internal network communication. This reduces frequency interference in the network and reduces time required for the join process.

Scalable multicasting: the core-assisted mesh protocol

Abstract: Most of the multicast routing protocols for ad hoc networks today are based on shared or source-based trees; however, keeping a routing tree connected for the purpose of data forwarding may lead to a substantial network overhead. A different approach to multicast routing consists of building a shared mesh for each multicast group. In multicast meshes, data packets can be accepted from any router, as opposed to trees where data packets are only accepted from routers with whom a “tree branch” has been established. The difference among multicast routing protocols based on meshes is in the method used to build these structures. Some mesh-based protocols require the flooding of sender or recieved announcements over the whole network. This paper presents the Core-Assisted Mesh Protocol, which uses mesh for data forwarding, and avoids flooding by generalizing the notion of core-based trees introduced for internet multicasting. Group members form the mesh of a group by sending join requests to a set of cores. SImulation experiments show that meshes can be used effectively as multicast routing structures without the need for flooding control packets.

Medium access control in a network of ad hoc mobile nodes with heterogeneous power capabilities

Abstract: MAC layer protocols for wireless ad hoc networks typically assume that the network is homogeneous with respect to the transmit power capability of individual nodes in the network. The IEEE 802.11 MAC protocol has been popular for use in ad hoc networks. We investigate the performance of this protocol when it is used in a network with nodes that transmit at various power levels. We show that overall throughput is lower than the throughput of a network in which all nodes transmit at identical power levels. In addition, low power nodes have a disadvantage in accessing the medium due to higher levels of interference from the high power nodes. We consider propagating the control messages generated by a node wishing to initiate communication to distant nodes so that they may forbear transmissions for some time, thereby allowing clear access to the initiating node. We find that the overhead incurred due to the additional message transmissions outweighs the potential gain achieved by propagating these messages. This indicates that the signalling mechanism used in the IEEE 802.11 standard or the variants thereof are not sufficient to alleviate the loss in throughput and the lack of fairness engendered by networks that are heterogeneous with regard to the transmit power capabilities of individual nodes.

Mobility-adaptive protocols for managing large ad hoc networks

Abstract: We propose a new protocol for efficiently managing large ad hoc networks, i.e., networks in which all nodes can be mobile. We observe that, since nodes in such networks are not necessarily equal in that they may have different resources, not all of them should be involved in basic network operations such as packet forwarding, flooding, etc. In the proposed protocol, a small subset of the network nodes is selected based on their status and they are organized to form a backbone (whence the name "backbone protocol" or simply B-protocol to our proposed solution). The B-protocol operates in two phases: first the "most suitable" nodes are selected to serve as backbone nodes, then the selected nodes are linked to form a backbone which is guaranteed to be connected if the original network is. The effectiveness of the B-protocol in constructing and maintaining in face of node mobility and node/link failure a connected backbone that uses only a small fraction of the nodes and of the links of the original networks is demonstrated via simulation. The obtained results show that both the selected backbone nodes and the links between them in the backbone are considerably smaller than the nodes and the links in the flat network.

Longevity of routes in mobile ad hoc networks

Abstract: An ad hoc network is a collection of mobile nodes where communication takes place through the wireless medium and in the absence of any fixed infrastructure. Direct communication is only possible between neighboring nodes and hence multi hop communication becomes necessary for distant nodes. It is essential that a routing protocol is used by a source node to discover a route to the destination node so that it can successfully transmit its message via the intermediate nodes. The lifetime of a particular route is dependent on the speed and direction of movement of all the nodes involved in the route. In this paper, we investigate the expected lifetime of a route so that the route discovery protocol can be invoked at the right time without disrupting the communication. We argue that if the movement pattern of the nodes is absolutely deterministic then the lifetime of a route can be determined exactly. On the other hand, a chaotic mobility pattern will bring in uncertainty to the lifetime of the route. We calculate the expected lifetime for different mobility models.

PatchODMRP: an ad-hoc multicast routing protocol

Abstract: We propose an ad-hoc multicast routing protocol, referred to as PatchODMRP. PatchODMRP extends the ODMRP (on-demand multicast routing protocol), which is a mesh-based multicast routing protocol proposed for ad-hoc networks. In ODMRP, the nodes that are on the shortest paths between the multicast group members are selected as forwarding group (FG) nodes, and form a forwarding mesh for the multicast group. The ODMRP reconfigures the forwarding mesh periodically to adapt it to the node movements. When the number of sources in the multicast group is small, usually the forwarding mesh is formed sparsely and it can be very vulnerable to mobility. In this case, very frequent mesh reconfigurations are required in ODMRP, resulting in a large control overhead. To deal with this problem in a more efficient way, PatchODMRP deploys a local patching scheme instead of having very frequent mesh reconfigurations. In PatchODMRP, each FG node keeps checking if there is a symptom of mesh separation around itself. When an FG node finds such a symptom, it tries to patch itself to the mesh with local flooding of control messages. Through a course of simulation experiments, the performance of PatchODMRP is compared to the performance of ODMRP. The simulation results show that PatchODMRP improves the data delivery ratio, and reduces the control overheads. It has also been shown that the performance gain is larger when the degree of node mobility is bigger.

Energy efficient broadcasting for situation awareness in ad hoc networks

Abstract: Ad hoc wireless networks and sensor networks have nodes with limited battery power, and broadcasting is an important operation in such networks. In this paper, we consider energy efficient one-to-all and all-to-all broadcast communications in such power constrained networks. It is assumed that nodes have power control and can adjust the range of their transmissions. Given a network of N nodes in a playing field of size D/spl times/D, we establish a lower bound and present a simple scheme for a source-to-all broadcast operation. Using simulations we show that the average energy cost of broadcasting from any source is within 25% of this lower bound in a network of 100 nodes in a 500 m/spl times/500 m and a 1000 m/spl times/1000 m area. In the situation awareness application, each node periodically transmits a small packet of 60 bytes to all other nodes in the network. For this all-to-all broadcast communication, we present a cluster scheme when nodes are allowed to transmit long distances, and a chain based scheme when nodes are limited to short distances. Our schemes for situation awareness significantly improve the life of the network compared to schemes with direct transmissions.

Apparatus, and associated method, for utilizing antenna information determinative of antenna operation in a wireless mesh network

Abstract: Apparatus, and associated method, for facilitating use of an antenna assembly forming a portion of a communication station, such as a node of a wireless mesh network. Antenna information is determined and stored at a routing table of the node. The antenna information is combined with an IP address or other identifier of another node to which a data packet is to be communicated. The antenna information is utilized to define characteristics to be exhibited by the antenna assembly to best facilitate communication of the data packet between the nodes.

Mesh networks for broadband access

Abstract: Broadband wireless access systems must satisfy exacting technical and commercial requirements. In this paper, the author describes a novel approach that uses Internet-like routing to bridge the infamous 'last mile'.

Hamiltonian cycle protection: a novel approach to mesh WDM optical network protection

Abstract: Designing a protection scheme for a mesh WDM network is a challenging task. Extending the concept of the SONET self-healing ring in the mesh topology by using multiple rings to cover a mesh is inefficient in network resource usage. Mesh-based schemes can yield an optimal solution in network resource usage, but entails complicated switch reconfigurations when network element fails. In addition, mesh optimization needs traffic demands as input, therefore is not applicable to dynamic traffic. We introduce a novel mesh WDM network protection scheme-Hamiltonian cycle protection (HCP)-that is simple, efficient and applicable to dynamic traffic. HCP performs traffic grooming in spare resource space by consolidating spare capacity into as few links as possible, thus minimizing the number of spare switch ports and reducing spare link capacity. HCP can simplify the network recovery process by minimizing the number of nodes involved in switch reconfigurations and enabling the switch reconfiguration to be performed at coarse granularity.

Apparatus, and an associated method, for facilitating synchronization in a wireless mesh network

Abstract: Apparatus, and associated method, by which to synchronize nodes in a wireless mesh network, such as a fixed broadband network or a moving ad-hoc mesh network. Time stamps are added to data packets at a reference node defined pursuant to a pseudo hierarchy. The data packets are communicated by the reference node to a receiving node. The time stamp information is extracted therefrom, to provide an indication of a time reference value from which the time stamp information is formed. Registers are maintained at the nodes with updated values of the timing information, used in time synchronization between the nodes of the mesh network.

Ad hoc on-demand backup node setup routing protocol

Abstract: An ad hoc wireless network provides infrastructureless data networking, where users have network services while they are continually moving. Instructureless, and mobility are properties of the ad hoc wireless networks. Furthermore, each move of the mobile host affects the change of network topology, and affects the change of the transmission route. There are numerous routing protocols developed for ad hoc wireless networks, and they may be generally categorized as table-driven or source-initiated on-demand. However, the properties of the ad hoc wireless networks still affect those routing algorithms. The ad hoc backup node setup routing protocol (ABRP) is proposed to lead us pay move attention on the intrinsic properties of the ad hoc wireless networks. It provides a more complete consideration of the routing quality. According to the proposed ABRP, the destination can receive some more routes in a period of time. Those routes from the source node to the destination node may give us ways to analyze and find some good backup routes to get more help for reconnection when a link failure occurs. The backup route information can be saved in a specific on-the-route node. The enables the backup routes to be rapidly found and traced back to these nodes when there are situations such as disconnection or connection loss. Moreover, the ABRP provides a backup node mechanism to reconnect maintenance quickly, so meeting the property of ad hoc wireless networks.

Addressing and routing in wireless mesh networks

Abstract: The present invention is directed to a method and apparatus for forwarding and/or addressing a packet in a wireless network, wherein an address information of a protocol layer lower than a network layer is added to the packet, which address in-formation indicates the geographical location of a destination node and which can be changed during forwarding of the packet through said wireless network. The packet is then forwarded within the wireless network based on a difference be-tween the geographical location of a present node and the destination node. This location based addressing makes packet forwarding easier in dynamic mesh net-works, because each node (10) can decide into which direction to forward incom-ing packets based only on the information in the packet header and its own loca-tion.

A Minimal Bluetooth-Based Computing and Communication Platform

Abstract: In this technical note we present an autonomous wireless communication and computing platform and its applications. The system is based on a Bluetooth communication module and a microcontroller. It is designed for a minimum use of resources while still being flexible. This platform is being used to set up large ad hoc networks, e.g. for collaborative remote sensing. In general, it can be used as a small but generic wireless networking node.

Impact of virtual channels and adaptive routing on application performance

Abstract: Research on multiprocessor interconnection networks has primarily focused on wormhole switching, virtual channel flow control, and routing algorithms to enhance their performance. The rationale behind this research is that by alleviating the network latency for high network loads, the overall system performance would improve. Many studies have used synthetic workloads to support this claim. However, such workloads may not necessarily capture the behavior of real applications. In this paper, we have used parallel applications for a closer examination of the network behavior. In particular, the performance benefit from enhancing a 2D mesh with virtual channels (VCs) and a fully adaptive routing algorithm is examined with a set of shared-memory and message passing applications. Execution time and average message latency of shared memory applications are measured using execution-driven simulation and by varying many architectural attributes that affect the network workload. The communication traces of message passing applications, collected on an IBM-SP2, are used to run a trace-driven simulation of the mesh architecture to obtain message latency. Simulation results show that VCs and adaptive routing can reduce the network latency to varying degrees depending on the application. However, these modest benefits do not translate to significant improvements in the overall execution time because the load on the network is not high enough to exploit the advantages of the network enhancements. Moreover, this benefit may be negated if the architectural enhancements increase the network cycle time. Rather, emphasis should be placed on improving the raw network bandwidth and faster network interfaces. Index Terms—Adaptive routing, architectural simulation, interconnection network, mesh network, performance evaluation, virtual channels. E

Apparatus and associated method, for dynamically selecting frequency levels upon which to define communication channels

Abstract: Apparatus, and associated method, for dynamically selecting frequencies upon which to define communication channels in a communication system, such as a wireless mesh network. Frequency levels are selected for global use throughout the entire mesh network. And, frequency levels upon which to define local communication channels for individual nodes of the mesh network are also selectable.

Expansion planning for wireless network

Abstract: The present invention is directed to a method and system for planning an expansion of a constantly changing wireless network. Node parameters of networks nodes of the wireless network are stored in a database (109). The network is monitored by regularly reading node specific data stored at the network nodes, and the database (109) is constantly updated node parameters a combined coverage area achieved by the network nodes is calculated. Thereby, the actual network coverage is available at any given point in time to plan network changes, to understand how good the coverage is in a particular area, and to make marketing and business decisions.