Ad Hoc Networks

On-site analysis of a radio environment together with a decoding of transmitted frames is an essential process of wireless networks deployment. We have proposed the PHY and MAC handheld analyzer of IEEE 802.15.4 based communication, which thanks to the wide application of this standard mainly in the wireless automation domain can find the significant utilization for the testing and troubleshooting of wireless nodes complying with this standard. Within this paper the architecture, control and performance of the developed analyzer is introduced in detail.

In this paper the experimental evaluation of the most critical operational QoS enabling parameters for IEEE 802.11e, with respect to service differentiation and throughput provisioning, over pragmatic conditions, is realized, exploiting the NETMODE wireless testbed. Capitalizing on the guidelines and observations that stem from this experimental study, a novel, asynchronous policy based resource allocation mechanism aiming at network’s aggregate throughput maximization and stations’ throughput prerequisites satisfaction for inelastic traffic is proposed. The operational effectiveness of the proposed method under pragmatic networking conditions is evaluated and tested for various scenarios implemented over the considered wireless testbed.

A critical problem of wireless sensor networks is the network lifetime, due to the device’s limited battery lifetime. The nodes are randomly deployed in the field and the system has no previous knowledge of their position. To tackle this problem we use a mobile robot, that discovers the nodes around it and replaces the active nodes, whose energy is drained, by fully charged inactive nodes. In this paper we propose two localized algorithms, that can run on the robot and that decide, which nodes to replace. We simulate our algorithms and our findings show that all nodes that fail are replaced in a short period of time.

Tracking moving objects is one important feature of wireless sensor networks. It is of interest in intrusion detection, traffic monitoring, security applications, and environmental monitoring. Current approaches to event tracking either focus on ad-hoc solutions to track specific objects, or address specific sensors or transducers as sources of data. On the other hand, by addressing composite events as source of data, it is possible to obtain higher-level information that is computed cooperatively by the sensors themselves that aggregate and combine the low-level acquired data. To address tracking of composite event we propose a general approach based on query languages. Our proposal allows to express in a simple form the properties of the composite event to be tracked, and the attributes related to the tracked events that have to be reported to the user. We propose and an in-network query processing model that implements the language and that allows the sensors to track and collect data from a moving event in a dynamic and autonomous way. The results of simulation experiments show that the proposed approach allows to successfully track moving events by properly tuning some parameters of the system.

In this paper we investigate the limits of routing according to left- or right-hand rule (LHR). Using LHR, a node upon receipt of a message will forward to the neighbour that sits next in counter-clockwise order in the network graph. When used to recover from greedy routing failures, LHR guarantees success if implemented over planar graphs. This is often referred to as face-routing. In the current body of knowledge it is known that if planarity is violated then LHR is guaranteed only to eventually return to the point of origin. Our work begins with an analysis to enumerate all node configurations that cause intersections. A trace over each configuration reveals that left-hand rule is able to recover from all but a single case, the ‘umbrella’ configuration so named for its appearance. We use this information to propose the Prohibitive Link Detection Protocol (PLDP) that can guarantee delivery over non-planar graphs using standard face-routing techniques. As the name implies, the protocol detects and circumvents the ‘bad’ links that hamper LHR. The goal of this work is to maintain routing guarantees while disturbing the network graph as little as possible. In doing so, a new starting point emerges from which to build rich distributed protocols in the spirit of CLDP and GDSTR.

Wireless sensor network (WSN) localization technique remains an open research issue due to its challenges on reducing location estimation error and cost of localization algorithm itself. For a large mobile network localization cost becomes increasingly important due to the exponential increment of algorithmic cost. Conversely, sacrificing localization accuracy to a great extent is not acceptable at all. To address the localization problem of wireless sensor network this paper presents a novel algorithm based on cross-entropy (CE) method. The proposed centralized algorithm estimates location information of the nodes based on the measured distances of the neighboring nodes. The algorithm minimizes the estimated location error by using CE method. Simulation results compare the proposed CE approach with DV-Hop and simulated annealing (SA)-based localizations and show that this approach provides a balance between the accuracy and cost.

The explosive growth of wireless services in recent years illustrates the growing demand for communications, so the spectrum becomes more congested. We know that static spectrum allocation is a major problem in wireless networks. Generally, these allocations lead to an inefficient use of spectrum. To solve the problem of congestion, cognitive radio networks use dynamic spectrum access. In this paper, we use a technique based on auctions theory known for its simplicity and facilitates the allocation of scarce resources.

This paper proposes a rendezvous protocol for Cognitive Radio Ad Hoc Networks, RAC²E-gQS, which (1) utilizes the asynchronous and randomness properties of the RAC²E protocol and (2) grid Quorum System-based channel mapping (gQ-RDV) protocol taking into account channel heterogeneity. We show that the combination of the RAC²E protocol with the grid-quorum based channel mapping can yield a powerful RAC²E-gQS rendezvous protocol for asynchronous operation in a distributed environment assuring a rapid rendezvous between the cognitive radio nodes.

Wireless sensor networks have a wide variety of applications in many areas from detecting enemy targets in the military to monitoring patient health or water/gas usage in the civil. However, sensor devices are usually equipped with a limited power battery and deployed at a very high density in inaccessible environments. Therefore, it is impractical to change or maintain manually these sensor networks. In this paper, we have designed and implemented a general and extendable management framework called DIstributed Self-Organizing NEtwork management (DISON) framework to provide an autonomous management mechanism for WSNs. In DISON, sensor nodes exploit local knowledge or cooperate with other nodes to coordinate and adapt management and application tasks effectively according to their capabilities. To verify the efficiency of the proposed framework, we have evaluated DISON in a data collection application scenario, where DISON is used to optimize the number of active nodes. The simulation results show that running DISON reduces the energy consumption up to 30%, and also improves other key parameters such as the packet delivery rate and the end-to-end delay.

In this paper we present a key pre-distribution scheme adapting a deterministic approach. The distribution of keys to the nodes precedes a virtual arrangement of the nodes into a rectangular grid structure. Distribution of keys is based on projective planes and pairwise connectivity. If the nodes are mapped to the vertices of a graph then the shortest path between any two nodes (considering key-connectivity) is at most three. With a small memory, the nodes induce a network, which offers a trade-off between connectivity and resilience. The impact of resilience and connectivity can be controlled by choosing the number of rows and columns suitably. Another significant aspect of the proposed scheme is that the key-path between any pair nodes is not unique, which leads to a well-connected network.

Due to the critical resource constraints of wireless sensor nodes such as processing speed, memory size and energy supply, implementing security mechanisms, in particular key management schemes, is quite challenging. Motivated by the conference key establishment scheme proposed by Harn and Gong in [11], we propose LPKM (Lightweight Polynomial-based Key Management Protocol), a key management scheme for distributed WSNs. LPKM enables sensor nodes to establish different types of keys to bootstrap trust and secure one-to-one and one-to-many communications in a flexible, reliable, and non-interactive way. Moreover, LPKM can effectively mitigate or thwart the most common attacks to WSNs such as node clone attacks, node impersonation attacks, etc. In addition, LPKM can tolerate changes of network topology and incurs little computational and communication overhead. Our experimental results on MICAz motes show that LPKM can be efficiently implemented on low-cost sensor nodes. In particular, a MICAz mote running at a frequency of 8MHz can generate required group keys of 128-bit in a few milliseconds, at a cost of 6.12 KBytes ROM and 68 Bytes RAM.

In this work we study the interception of the requests performed by the mobile nodes in a wireless network. This interception can be achieved because a local cache is implemented in each wireless device. In that way, the nodes can serve the documents instead of forwarding the requests to the data servers. In our proposal, the interception is enhanced so it is also implemented when the mobile nodes create the route to the data servers. Using cross-layer information, the routing algorithm can discover the location of the documents disseminated across the network. By means of simulations, we evaluate the performance of the proposed interception mechanism. We study the effect of the network load, the expiration time of the documents, the requests pattern and the cache size on these cache mechanisms. Under all the assumptions the proposed scheme reduces the delay, the network traffic and the amount of timeouts when the servers are not reachable.

Service discovery protocols for mobile ad hoc networks attempt to overcome the inability to locate resources presented by networks in which prior knowledge of node identity and capability is not available. Existing approaches continue to rely on underlying address-based routing protocols in order to communicate with discovered services. These two-tier approaches generate routing overheads which negatively impact on performance and network scalability.

As high-powered mobile computing devices with wireless connectivity become increasingly ubiquitous, the need for routing protocols which can operate at increased network densities becomes more acute. Cross-layer approaches to service discovery in MANETs have attempted to optimize the discovery process through direct integration with underlying routing protocols, however additional steps are necessary to improve service discovery performance, network scalability and application throughput.

This paper describes the Service Discovery and Routing Protocol (SDRP), a novel service-oriented routing protocol for MANETs. This protocol eschews the use of network-wide unique addresses or underlying address-based routing protocols and focuses instead on routing only to and from nodes which provide services. A comparison with existing approaches demonstrates that this approach improves discovery success rates and application throughput at higher node densities.

We argue that the potential benefits of developing high-fidelity models of biological communication systems has enormous potential in terms of enhancing the understanding of biological systems and that such understanding is a major step towards detection and treatment of disease. By focusing on lysosomal enzyme response to stimuli, we demonstrate that the understanding of the protocols governing cellular communications is far from complete. We discuss some major challenges and outline promising approaches to reaching the next level.

A Substitution Network (SN) is a rapidly deployable temporary wireless network that should be dynamically integrated within an existing base network. They back-up the base network inorder to meet temporary network overloaded conditions to keep providing services and to ensure the network connectivity, which could not be achieved by the base network alone. Within this context, in this paper, we propose a solution considering SNs as a means for provisioning backup path for Mobile Network Operators (MNOs) microwave backhaul to overcome network overload due to excessive wireless data traffic. Our approach considers Software Defined Networking (SDN) technology due to its flexibility to integrate diverse future generations of switches as well as its centralized approach for decoupling control-plane and data-plane. Our solution is based on exploring the OpenFlow protocol. Based on our experimental results, we demonstrate the feasibility of our proposal, which allows verifying the effectiveness of adopting SNs based on SDN. Here, our approach is considered in the context of emerging economies, since, from past research, studies have shown that OPEX/CAPEX may not have the same impact in emerging countries as they have in developed countries.

Wireless SAN (WSAN) may include wired and/or wireless devices, PCs and control stations arranged in a heterogeneous distributed system. Instead of assuming that embedded device nodes (e.g. MicaZ or TelosB motes), gateways (e.g. PC running Linux) and control stations are disparate entities with their own programming and processing model, it should be viewed as a single heterogeneous distributed system, offering more uniformity, simplicity and flexibility. Enabling adaptivity in the higher layers of the network architecture such as the middleware and application layers, beside its consideration in the lower layers, becomes of high importance. In this paper we propose an approach to hide heterogeneity and offer a single common configuration and processing component for all nodes of that heterogeneous system. In particular, this proposal aims at providing an abstraction to facilitate development of adaptive Wireless Sensor and Actuator Network (WSAN) applications. The main contribution of this paper is how to design a middleware architecture with a single uniform component to work with such heterogeneous underlying parts as a WSAN. This advances the current state-of-the-art in middleware for WSANs, by providing a single component that abstracts the underlying differences in both devices such as PCs and motes and in communications such as TCP and proprietary stacks to create a global processor.

Wireless sensor networks can be extended to include numerous different sensing devices. Strain gauges are the most common nondestructive sensing elements for measuring surface strain. This paper discusses the design, for the wireless CiNet network, of a strain gauge measurement system, which would make strain measurements more flexible while opening new targets of application in addition to those that traditional wired strain measuring systems can offer. The calibration and validation of the wireless strain measurements as well as energy consumption issues are also brought under observation.

Vehicular Ad-Hoc Networks rely on a multi-channel architecture to support vehicle-to-vehicle and vehicle-to-infrastructure communications. Multiple service channels are assigned in the 5GHz spectrum for non-safety data transfer, while a unique control channel is used for broadcasting safety messages and service advertisements. Single-radio vehicular devices stay tuned on one radio channel at a time and alternately switch between channels to monitor safety messages and to access information and entertainment services; while dual-radio devices can simultaneously stay tuned on both types of channels. Multi-channel coordination, synchronization, and access are big challenges in VANETs; many design choices are still open issues in ETSI and IEEE standardization bodies. In this paper, counter-measures and recent trends in standardization bodies are discussed to cope with inefficiencies related to multi-channel operation for single-radio devices (e.g., inefficient spectrum utilization, synchronized frame collisions, bandwidth waste), and dual-radio devices (e.g., cross-channel interference, coexistence with single-radio devices).

We consider a scenario where a number of mobile networks, e.g. vehicles equipped with Mobile Routers, travel together interconnected in a dynamic mesh structure, here called Ad Hoc Interconnected Mobile Network or AIMNET. The mesh topology interconnecting the mobile networks not only facilitates inter-mobile-network communications, but more importantly allows sharing of Internet access available to individual Mobile Routers. We first discuss the route optimisation problem in AIMNET and the prefix delegation based solutions. We then propose a two-level addressing scheme that minimises the overhead and improves route optimisation. Then, we discuss routing in the AIMNET and provide experimental results to verify our proposals.

It is widely known that topology, wireless range, and the movement patterns of devices often impose severe limitations on the ability of devices to communicate in Mobile Wireless Ad-hoc Networks (MANETs). However, there has been less research into the effect of devices’ movement speeds on network connectivity. In this paper we will look at two commonly used MANET movement patterns, Working Day Movement (WDM) and Random Walk Movement (RWM). This report will demonstrate using both of these movement patterns, that the time between neighbour discovery scans called the inter-probe time, can have a drastic effect on network connectivity. We will suggest a mechanism to choose inter-probe times based on the movement speeds of devices which can efficiently detect more than 99% of encounters between mobile devices carried by pedestrians. We will then propose a dynamic approach (PISTONS) which allows devices to alter inter-probe times based on context whilst preserving much of the network connectivity.

We study in this paper heterogeneous delay tolerant networks formed by different classes of nodes. We assume that two hop is the forwarding strategy to deliver messages from a source node to destination node and the goal is to optimize the probability of delivering a message in the presence of different classes of mobiles, while satisfying a given energy budget. Using our model, in particular, we transform the joint energy constraint into separate constraints, one per class. This allows us to characterize the optimal strategies and provides us with a suitable framework for the design of multi-dimensional stochastic control algorithms that achieve optimal performance at runtime in spite of the lack of full information on the network state and in presence of different classes of mobiles. A thorough analysis of the convergence properties and stability of our algorithms is presented.

The initial IP Mobility protocol was first presented in 1993 for IPv4. The Mobile IP protocol solves the TCP/IP Layer 3 mobility, by assigning a permanent IP address to the mobile node. Mobile IP consists of both MIPv4 and MIPv6, but IPv4 has a couple of drawbacks, the main one being IP address exhaustion, making MIPv6 the future option for mobility protocol in IP Networks.The main goal of the mobility protocol is to enable network applications to operate continuously at the required quality of service for both wired and wireless networks. MIPv6 uses the existing IPv6 protocol to enable seamless roaming between different access points. MIPv6 on its own needs optimization techniques to improve the handover latency of the protocol and to minimize the latency. This paper proposes FMIPv6 protocol to minimize handover latency. Both MIPv6 and FMIPv6 protocols introduce some new terminologies as proposed by the Internet Engineering Task Force (IETF), which require prior familiarisation to understand the working of MIPv6 and FMIPv6.