B. S. Manoj

Communication challenges in emergency response

primary challenge in responding to both natural and man-made disasters is communication. This has been highlighted by recent disasters such as the 9/11 terrorist attacks and Hurricane Katrina [2, 5, 6]. A problem frequently cited by responders is the lack of radio interoperability. Responding organizations must work in concert to form a cohesive plan of response. However, each group—fire, police, SWAT, HazMat—com-municates with radios set to orthogonal frequencies , making inter-agency communications extremely difficult. The problem is compounded as more local, state, and federal agencies become involved. The communication challenges in emergency response go far beyond simple interop-erability issues. Based on our research, practical observation of first responder exercises and drills, and workshop discussions, we have identified three categories of communication challenges: technological, sociological, and organizational. These three major areas are key to developing and maintaining healthy and effective disaster communication systems. The primary technological challenge after a disaster is rapid deployment of communication systems for first responders and disaster management workers. This is true regardless of whether the communications network has been completely destroyed (power, telephone, and/or network connectivity infrastructure), or, as in the case of some remote geographic areas, the infrastructure was previously nonex-istent. Deployment of a new system is more complicated in areas where partial communication infrastructures remain, than where no prior communication networks existed. This can be due to several factors including interference from existing partial communication networks and the dependency of people on their prior systems. Another important obstacle to overcome is the multi-organizational radio interoperability issue. To make future communication systems capable of withstanding large-or medium-scale disasters, two technological solutions can be incorporated into the design: dual-use technology and built-in architectural and protocol redundancy. Dual-use technology would enable both normal and emergency operational modes. During crises, such devices would work in a network-controlled fashion, achieved using software agents within the communication

Quality of service provisioning in ad hoc wireless networks: a survey of issues and solutions

An ad hoc wireless network (AWN) is a collection of mobile hosts forming a temporary network on the fly, without using any fixed infrastructure. Characteristics of AWNs such as lack of central coordination, mobility of hosts, dynamically varying network topology, and limited availability of resources make QoS provisioning very challenging in such networks. In this paper, we describe the issues and challenges in providing QoS for AWNs and review some of the QoS solutions proposed. We first provide a layer-wise classification of the existing QoS solutions, and then discuss each of these solutions.

A dynamic core based multicast routing protocol for ad hoc wireless networks

Ad hoc wireless networks are self-organizing dynamic topology networks formed by a collection of mobile nodes through radio links. Minimal configuration absence of infrastructure and quick deployment make them convenient for emergency situations other than military applications. Multicasting plays a very crucial role in the application of Ad hoc networks. As the number of participants increases scalability of the multicast protocol becomes an important issue. Among the existing multicast protocols On Demand Multicast Routing Protocol (ODMRP) perfo exhibits a high packet delivery ratio even at high mobility. But ODMRP suffers from higher control overhead as the network size and the number of sources increase.In this paper we propose an efficient multicast routing protocol for Ad hoc wireless networks. This protocol reduces the control overhead by dynamically classifying the sources into Active and Passive categories. The control overhead is significantly reduced by about 30% compared to ODMRP which contributes to the scalability of the protocol. We study the effectiveness of the proposed multicast routing protocol by simulation studies and the results show that the multicast efficiency is increased by 10--15% and packet delivery ratio is also improved at high network load.

Multi-hop cellular networks: the architecture and routing protocols

Multi-hop cellular network (MCN) is an architecture proposed by Lin and Hsu (see INFOCOM 2000. IEEE, 2000) for wireless communication & MCNs combine the benefits of having a fixed infrastructure of base stations and the flexibility of ad-hoc networks. They are capable of achieving much higher throughput than current cellular systems, which can be classified as single-hop cellular networks (SCNs). This work concentrates on MCNs and SCNs using the IEEE 802.11 standard for wireless LANs. We provide a general overview of the architecture and the issues involved in the design of MCNs, in particular the challenges to be met in the design of a routing protocol. We extend the work of Lin and Hsu to enhance the throughput of such networks further. We propose a routing protocol for use in such networks. We conduct extensive experimental studies on the performance of MCNs and SCNs under various load conditions (both TCP and UDP). Then studies clearly indicate that MCNs with the proposed routing protocol are a viable alternative for SCNs, in fact they provide much higher throughput.

Dynamic Coverage Maintenance Algorithms for Sensor Networks with Limited Mobility

Sensor networks consist of small wireless sensor nodes deployed randomly over an area to monitor the environment or detect intrusion. The coverage provided by sensor networks is very crucial to their effectiveness. Many of the important applications of sensor networks demand autonomous mobility for the sensor nodes. Early failure of sensor nodes can lead to coverage loss that requires coverage maintenance schemes. In this paper, we propose dynamic coverage maintenance (DCM) schemes that exploit the limited mobility of the sensor nodes. The main objective of coverage maintenance is to compensate the loss of coverage with minimum expenditure of energy. We propose a set of DCM schemes which can be executed on individual sensor nodes having a knowledge of only their local neighborhood topology. We propose four algorithms to decide which neighbors to migrate, and to what distance, such that the energy expended is minimized and the coverage obtained for a given number of live nodes is maximized. The decision and movement is completely autonomous in the network, and involves movement of one-hop neighbors of a dead sensor node. We also propose an extension to these algorithms, called cascaded DCM, which extends the migrations to multiple hops. We have also compared the performance of the different algorithms in terms of the improvement in coverage, average migration distance of the nodes, and the lifetime of the network

CogNet: a cognitive complete knowledge network system

The benefits of using cognitive information at the physical layer, as in cognitive radios, are many. In this article, we propose CogNet -- a cognitive complete knowledge network system -- which makes use of a large amount of information that can be gained from the experience of each node to improve the overall network and user performance. CogNet gathers, processes, analyzes, and stores information available through a variety of devices and protocols to build an omnipresent, distributed repository that holds the spatiotemporal, network-experience information. The inexpensiveness and plentifulness of storage resources and increasing processing power in handheld devices help accelerate the development of CogNet-like systems. Our contribution in this article is the proposal of the architecture and of the communication elements, as well as a transport layer application of CogNet as a proof of concept for possible application scenarios of such a system. We also present performance evaluation of CogTCP, the CogNetenabled TCP, which exploits the transport layer experience of other nodes for improved performance. From our experiments, we found that the use of cognitive information is very useful for networking.

A Realistic Small-World Model for Wireless Mesh Networks

Small-world network concept deals with the addition of a few Long-ranged Links (LLs) to significantly bring down the average path length (APL) of the network. The existing small-world models do not consider the real constraints of wireless networks such as the transmission range of LLs, limited radios per mesh router, and limited bandwidth for wireless links, therefore, we propose C-SWAWN (Constrained Small-World Architecture for Wireless Network) model for Wireless Mesh Networks (WMNs). We then propose three LL addition strategies for reducing APL to the centrally placed Gateway node in WMNs. In moderately large WMNs, a 43% reduction in APL to Gateway can be achieved with the addition of 10% LLs (with respect to number of mesh routers) in our C-SWAWN model with greedy LL addition strategy. Detailed studies show realistic performance benefits with application of small-world concept in WMNs.

A Neural Network Based Cognitive Controller for Dynamic Channel Selection

In this paper, we present an application of the Cognitive Networking paradigm to the problem of dynamic channel selection in infrastructured wireless networks. We first discuss some of the key challenges associated with the cognitive control of wireless networks. Then we introduce our solution, in which a Neural Network-based cognitive engine learns how environmental measurements and the status of the network affect the performance experienced on different channels, and can therefore dynamically select the channel which is expected to yield the best performance for the mobile users. We carry out performance evaluation of the proposed system by experimental measurements on a testbed implementation; the obtained results show that the proposed cognitive engine is effective in achieving performance enhancements with respect to state-of-the-art channel selection strategies.

A New Energy Efficient Protocol for Minimizing Multi-Hop Latency in Wireless Sensor Networks

In wireless sensor networks, efficient usage of energy helps in improving the network lifetime. As the battery of a sensor node, in most cases, cannot be recharged or replaced after the deployment of the sensors, energy management becomes a critical issue in such networks. In order to detect an event, a sensor network spends majority of the time in monitoring its environment, during which a significant amount of energy can be saved by placing the radio in the low-power sleep mode. This can be achieved by using a dual frequency radio setup. However, such energy saving protocols increase the latency encountered in setting up a multihop path. We, in this paper, propose a reservation scheme, latency minimized energy efficient MAC protocol (LEEM), which is a novel hop-ahead reservation scheme in a dual frequency radio to minimize the latency in the multihop path data transmission by reserving the next hops channel a priori. Thus, in a multihop sensor network, a packet can be forwarded to the next hop, as soon as it is received by a sensor node, which helps in eliminating the delay incurred for setting up the path. Simulation results show that LEEM consumes lesser power and reduces end-to-end latency by around 50% than that of the existing schemes

Link life based routing protocol for ad hoc wireless networks

Due to the highly dynamic topology and absence of any fixed infrastructure, stability of selected path is of prime importance in ad hoc networks. The frequent route failure and high control overhead in routing protocols lead to degraded system performance. This paper proposes a stability based distributed adaptive routing protocol for ad hoc networks, which uses the worst case lifetime of wireless links, which is obtained by linear regression of the variation of distance between nodes as the routing metric. An efficient beaconing mechanism, load balancing, pro-active and reactive route reconfiguration mechanisms are also studied with the protocol. The protocol is supported with simulation using GloMoSim.