Somprakash Bandyopadhyay

A network-aware MAC and routing protocol for effective load balancing in ad hoc wireless networks with directional antenna

Use of directional antenna in the context of ad hoc wireless networks can largely reduce radio interference, thereby improving the utilization of wireless medium. Our major contribution in this paper is to devise a routing strategy, along with a MAC protocol, that exploits the advantages of directional antenna in ad hoc networks for improved system performance. In this paper, we have illustrated a MAC and routing protocol for ad hoc networks using directional antenna with the objective of effective load balancing through the selection of maximally zone disjoint routes. Zone-disjoint routes would minimize the effect of route coupling by selecting routes in such a manner that data communication over one route will minimally interfere with data communication over the others. In our MAC protocol, each node keeps certain neighborhood status information dynamically in order that each node is aware of its neighborhood and communications going on in its neighborhood at that instant of time. This status information from each node is propagated periodically throughout the network. This would help each node to capture the approximate network status periodically that helps each node to become topology-aware and aware of communications going on in the network, although in an approximate manner. With this status information, each intermediate node adaptively computes routes towards destination. The performance of the proposed framework has been evaluated on QualNet Network Simulator with DSR (as in QualNet) as a benchmark. Our proposed mechanism shows four to five times performance improvement over DSR, thus demonstrating the effectiveness of this proposal.

An adaptive MAC and idrectional routing protocol for ad hoc wireless network using ESPAR antenna

Use of directional antenna in the context of ad hoc wireless networks can largely reduce radio interference, thereby improving the utilization of wireless medium. To achieve this, we have proposed an adaptive MAC protocol, where each node keeps certain neighborhood information dynamically so that each node can avoid interference by keeping track of other communicating nodes at the instant of time. Moreover, appropriate mechanism for null steering of directional antennas in user terminals can help exchanging the neighborhood information in presence of on-going communication and can drastically improve the medium utilization through overlapping communications in different directions. Subsequently, we have proposed a modified link-state based table-driven routing protocol that captures the approximate network status periodically without generating lot of control traffic. It uses the directional capability of adaptive antenna for capturing, disseminating and using the network information for direction routing

A distributed mechanism for topology discovery in ad hoc wireless networks using mobile agents

Summary form only given. We have discussed a mobile multi-agent based framework to address the aspect of topology discovery in ad hoc wireless network environment. In other words, we have designed a multi-agent based protocol to make the nodes in the network topology aware. Our primary aim is to collect all topology-related information from each node in the network and distribute them periodically (as updates) to other nodes through mobile agents. The notion of stigmergic communication has been used through the implementation of a shared information cache in each node. Moreover, we have used a concept of link stability and information aging based on which a predictive algorithm running on each node can predict the current network topology based on the current network information stored at that node. We have demonstrated through performance evaluation of a simulated system that the use of mobile multi-agent framework would be able to make each node in the network topology aware without consuming large portion of network capacity. This would eventually help us to implement a proactive routing protocol without much overhead. Moreover, as a direct outcome of infiltrating topology information into the nodes, the foundations for designing distributed network management and implementing communication awareness get automatically laid.

An adaptive MAC protocol for wireless ad hoc community network (WACNet) using electronically steerable passive array radiator antenna

In the context of ad hoc networks, use of directional antennas can largely reduce the radio interference, thereby improving the utilization of wireless medium and consequently the network throughput. However, in order to fully exploit the capability of directional antennas, whenever a source and a destination engage in a communication, all the neighbors of source and destination nodes should know the direction of communication so that they can initiate new communication in other directions, thus preventing interference with on-going data communication. In our adaptive MAC protocol, each node keeps certain neighborhood information dynamically so that each node can keep a track of the direction of communication events going on in its neighborhood at that instant of time. Moreover, appropriate mechanisms for null steering of directional antennas in user terminals can help exchange the neighborhood information in the presence of on-going communication and can drastically improve the medium utilization through overlapping communications in different directions.

Agro-sense: Precision agriculture using sensor-based wireless mesh networks

Advances in wireless personal area networks have made the practical deployment of various services possible, which until a few years ago was considered extremely costly or labor intensive. We build such a wireless sensor network for precision agriculture where real time data of the climatologieal and other environmental properties are sensed and relayed to a central repository. The architecture comprises of three distinct sections - (a) the sensor-nodes (b) the wireless mesh network and (c) the actuation components. The sensors are selected based on the properties suited for the most common crops and we identify four such attributes. The sensor network is based on the IEEE-802.15.4 standard and we develop a new static routing algorithm suited for the sensing application. The algorithm overrides the deficiency of the Hierarchical Routing scheme inherent in the ZigBee specification where the Csklp addressing algorithm limits the possible depth of the network topology due to address wastage. The new algorithm maintains the hierarchical network topology and thus ensures routing at its optimal best. The algorithms for both addressing and routing are provided. The actuation components are also a part of mesh network and are activated wirelessly for controlling irrigation and fertigation.

Communication-aware mobile hosts in ad-hoc wireless network

A mobile, multi-hop wireless computer network, also termed an ad-hoc network, can be envisioned as a collection of routers, equipped with wireless transmitter/receiver, which are free to move about arbitrarily. The basic assumption in an ad-hoc network is that some nodes willing to communicate may be outside the wireless transmission range of each other but may be able to communicate if other nodes in the network are willing to forward packets from them. However, the successful operation of an ad-hoc network will be hampered if an intermediate node, participating in a communication between two nodes, moves out of range suddenly or switches itself off in between message transfer. The objective of this paper is to introduce a parameter, affinity that characterizes the strength of relationship between two nodes and to propose a distributed routing scheme between two nodes in order to find a set of paths between them which are more stable and less congested in a specific context. Thus, the communication in an ad-hoc wireless network can be effective by making the nodes in the system communication-aware in the sense that each node should know its affinity with its neighbors and should be aware of the impact of its movement on the communication structure of the underlying network.

Improving quality-of-service in ad hoc wireless networks with adaptive multi-path routing

The objective of this paper is to propose a mechanism for adaptive computation of multiple paths to transmit a large volume of data packets from a source s to a destination d in ad hoc wireless networks. We consider two aspects in this framework. The first aspect is to perform preemptive route re-discoveries before the occurrence of route errors while transmitting a large volume of data from s to d. Consequently, this helps find out dynamically a series of multiple paths in the temporal domain to complete the data transfer. The second aspect is to select multiple paths in the spatial domain for data transfer at any instant of time and to distribute the data packets in sequential blocks over those paths in order to reduce congestion and end-to-end delay. The performance of this approach has been evaluated to show the improvement in the quality of service. It has been observed that the mechanism allows any source to transmit a large volume of data to a destination without degradation of performance due to route errors. Additionally, it would help reduce significantly the end-to-end delay and the number of route-rediscoveries needed in this process.

Evaluating the performance of mobile agent-based message communication among mobile hosts in large ad hoc wireless network

In ad-hoc wireless network, each node acts as a mobile router, equipped with a wireless transmitter / receiver, which is free to move about arbitrarily. In this configuration, even if two nodes are outside the wireless transmission range of each other, they can still be able to communicate with each other in multiple hops. However, the dynamics of these networks as a consequence of mobility and disconnection of mobile hosts pose a number of problems in designing routing schemes for effective communication between any source and destination. Thus, even off-line communication between source and destination (e-mail, for example) would be inefficient, if not impossible, in a large ad hoc network structure. This paper introduces a scheme using mobile agent to address this issue. Mobile agent in this context would act as a messenger that would migrate from a source and carry the message from a source to a destination. A mobile agent can migrate off a source node with a message and navigate autonomously throughout the network to find out the destination in order to deliver this message. From the performance evaluation, it has been concluded that the proposed scheme consumes much less network resource compared to other routing schemes proposed in the context of highly dynamic large ad hoc network.

Multipath Routing in Ad Hoc Wireless Networks with Omni Directional and Directional Antenna: A Comparative Study

Several routing schemes have been proposed in the context of mobile ad hoc network. Some of them use multiple paths simultaneously by splitting the information among multitude of paths, as it may help to reduce end-to-end delay and perform load balancing. Multipath routing also diminishes the effects of unreliable wireless links in the constantly changing topology of ad hoc networks to a large extent. Route coupling, caused by the interference during the simultaneous communication through multiple paths between a pair of source and destination, severely limits the performance gained by multipath routing. Using node disjoint multiple paths to avoid coupling is not at all sufficient to improve the routing performance in this context. Route coupling may be reduced to a great extent if zone disjoint or even partially zone disjoint paths are used for data communication. Two paths are said to be zone disjoint if data communication through one path does not interfere with other paths. Large path length (number of hops) also contributes to the performance degradation resulting in high end to end delay. So zone disjoint shortest multipath is the best choice under high traffic condition. However, it is difficult to get zone disjoint or even partially zone disjoint multiple routes using omni-directional antenna. This difficulty may be overcome if directional antenna is used with each mobile node. In this paper, we have done a comparative study on the performance of multipath routing using omni-directional and directional antenna. The result of the simulation study clearly shows that directional antenna improves the performance of multipath routing significantly as compared to that with omni-directional antenna.

Topology Discovery in Ad Hoc Wireless Networks Using Mobile Agents

Extensive research on mobile agents has been rife with the growing interests in network computing. In this paper, we have discussed a mobile multi-agent-based framework to address the aspect of topology discovery in ad hoc wireless network environment. In other words, we have designed a multi-agent based protocol to make the nodes in the network topology aware. Our primary aim is to collect all topology-related information from each node in the network and distribute them periodically (as updates) to other nodes through mobile agents. The notion of stigmergic communication has been used through the implementation of a shared information cache in each node. Moreover, we have defined a concept of link stability and information aging based on which a predictive algorithm running on each node can predict the current network topology based on the current network information stored at that node. We have demonstrated through performance evaluation of a simulated system that the use of mobile multi-agent framework would be able to make each node in the network topology aware, without consuming large portion of network capacity. As a direct outcome of infiltrating topology information into the nodes, the foundations for designing efficient routing scheme, distributed network management and implementing communication awareness get automatically laid.