Modeling human mobility in obstacle-constrained ad hoc networks

In this paper we present a mobility model for ad hoc networks consisting of human-operated nodes that are deployed in obstacle-constrained environments. According to this model, the network nodes move around the obstacles in a way that resembles how humans bypass physical obstructions. A recursive procedure is executed by each node at its current position to determine the next intermediate destination point until the final destination point is reached. The proposed mobility model is validated using real-life trace data and studied using both mathematical analysis and simulations. Furthermore, the model is extended to incorporate several operational aspects of ad hoc networks in mission critical scenarios, where it is best applicable. These extensions include hierarchical node organization, distinct modes of node activity, event-based destination selection and impact of the physical obstacles on signal propagation. The model is implemented as an add-on module in Network Simulator (ns-2).     

Security considerations in ad hoc sensor networks

In future smart environments, ad hoc sensor networks will play a key role in sensing, collecting, and disseminating information about environmental phenomena. As sensor networks come to be wide-spread deployment, security issues become a central concern. So far, the main research focus has been on making sensor networks feasible and useful, and less emphasis has been placed on security. This paper analyzes security challenges in wireless sensor networks and summarizes key issues that need be solved for achieving security in an ad hoc network. It gives an overview of the current state of solutions on such key issues as secure routing, prevention of denial-of-service, and key management service.     

Reactive routing for mobile cognitive radio ad hoc networks

Although more than a decade has passed from the proposal of the Cognitive Radio paradigm, in these years the research has mainly focused on physical and medium access issues, and few recent works focused on the problem of routing in cognitive networks. This paper addresses such a problem by evaluating the feasibility of reactive routing for mobile cognitive radio ad hoc networks. More specifically, we design a reactive routing protocol for the considered scenario able to achieve three goals: (i) to avoid interferences to primary users during both route formation and data forwarding; (ii) to perform a joint path and channel selection at each forwarder; (iii) to take advantage of the availability of multiple channels to improve the overall performance. Two different versions of the same protocol, referred to as Cognitive Ad-hoc On-demand Distance Vector (CAODV), are presented. The first version exploits inter-route spectrum diversity, while the second one exploits intra-route spectrum diversity. An exhaustive performance analysis of both the versions of the proposed protocol in different environments and network conditions has been carried out via numerical simulations. The results state the suitability of the proposed protocol for small mobile cognitive radio ad hoc networks.     

Secure hosts auto-configuration in mobile ad hoc networks

All existing routing protocols of Mobile Ad Hoc networks (MANET) assume that IP addresses of hosts are already configured before they join the network. In traditional schemes, this task is delegated to the dynamic host configuration protocol (DHCP [R. Droms, Dynamic host configuration protocol, RFC 2131, March 1997]), which allots an IP address to each requesting node. However, this process can not be applied in the context of MANET because of the lack of infrastructure and the great mobility that characterize them. A manual management of the addresses can be considered as long as the number of nodes remains reasonable. On the other hand, it is not possible any more since the network reaches a certain size. Some works proposed solutions to allow an automatic configuration of the nodes, i.e. without human intervention. Unfortunately these processes, often inspired of the traditional wired networks, are not always well adapted to MANET and appear relatively greedy concerning for example the delay, the address space or the bandwidth. Moreover, they apply only to ideal networks in which all nodes can trust each other. In this manner, they do absolutely not consider the security aspects and are thus not adapted to a real use in potentially hostile environment. In this paper, we propose a node auto-configuration scheme which uses the buddy system technique to allocate the addresses, as well as an algorithm allowing to authenticate the participants inside the network.     

An adaptive transmission-scheduling protocol for mobile ad hoc networks

Transmission-scheduling protocols can support contention-free link-level broadcast transmissions and delay sensitive traffic in mobile, multiple-hop packet radio networks. Use of transmission-scheduling protocols, however, can be very inefficient in mobile environments due to the difficulty in adapting transmission schedules. The paper defines a new adaptive and distributed protocol that permits a terminal to adapt transmission assignments to changes in topology using information it collects from its local neighborhood only. Because global coordination among all the terminals is not required and changes to transmission assignments are distributed to nearby terminals only, the protocol can adapt quickly to changes in the network connectivity. The two key parameters that affect the ability of the protocol to adapt to changes in connectivity are the rate of connectivity changes and the number of terminals near the connectivity changes. Using simulation, we determine the ranges for these parameters for which our adaptive protocol can maintain collision-free schedules with an acceptable level of overhead. The stability of the protocol is also characterized by showing that the protocol can quickly return to a collision-free transmission schedule after a period of very rapid changes in connectivity. Our channel-access protocol does not require a contention-based random-access phase to adapt the transmission schedules, and thus its ability to adapt quickly does not deteriorate with an increase in the traffic load.     

Load balancing and resource reservation in mobile ad hoc networks

To ensure uninterrupted communication in a mobile ad hoc network, efficient route discovery is crucial when nodes move and/or fail. Hence, protocols such as Dynamic Source Routing (DSR) precompute alternate routes before a node moves and/or fails. In this paper, we modify the way these alternate routes are maintained and used in DSR, and show that these modifications permit more efficient route discovery when nodes move and/or fail. Our routing protocol also does load balancing among the number of alternate routes that are available. Our simulation results show that maintenance of these alternate routes (without affecting the route cache size at each router) increases the packet delivery ratio. We also show that our approach enables us to provide QoS guarantees by ensuring that appropriate bandwidth will be available for a flow even when nodes move. Towards this end, we show how reservations can be made on the alternate routes while maximizing the bandwidth usage in situations where nodes do not move. We also show how the load of the traffic generated due to node movement is shared among several alternate routes. In addition, we adaptively use Forward Error Correction techniques with our protocol and show how it can improve the packet delivery ratio.     

Minimizing Intermediate Multicast routing for dynamic multi-hop ad hoc networks

A Minimizing Intermediate Multicast Routing protocol （MIMR） is proposed for dynamic multi-hop ad hoc networks. In MIMR, multicast sessions are created and released only by source nodes. In each multicast session process, the source node keeps a list of intermediate nodes and destinations, which is encapsulated into the packet header when the source node sends a multicast packet. Nodes receiving multicast packets decide to accept or forward the packet according to the list. Depending on topology matrix maintained by unicast routing, the shortest virtual hierarchy routing tree is constructed by improved Dijkstra algorithm. MIMR can achieve the minimum number of intermediate nodes, which are computed through the tree. No control packet is transmitted in the process of multicast session. Load of the network is largely decreased. Experimental result shows that MIMR is flexible and robust for dynamic ad hoc networks.     

A cluster based mobility prediction scheme for ad hoc networks

The ad hoc networks are completely autonomous wireless networks where all the users are mobile. These networks do not work on any infrastructure and the mobiles communicate either directly or via other nodes of the network by establishing routes. These routes are prone to frequent ruptures because of nodes mobility. If the future movement of the mobile can be predicted in a precise way, the resources reservation can be made before be asked, which enables the network to provide a better QoS. In this aim, we propose a virtual dynamic topology, which on one hand, will organize the network as well as possible and decreases the impact of mobility, and on the other hand, is oriented user mobility prediction. Our prediction scheme uses the evidence theory of Dempster–Shafer in order to predict the future position of the mobile by basing itself on relevant criteria. These ones are related to mobility and network operation optimisation. The proposed scheme is flexible and can be extended to a general framework. To show the relevance of our scheme, we combine it with a routing protocol. Then, we implemented the prediction-oriented topology and the prediction scheme which performs on it. We implemented also a mobility prediction based routing protocol. Simulations are made according to a set of elaborate scenarios.     

Analysis of coalition formation and cooperation strategies in mobile ad hoc networks

This paper focuses on the formal assessment of the properties of cooperation enforcement mechanisms used to detect and prevent selfish behavior of nodes forming a mobile ad hoc network. In the first part, we demonstrate the requirement for a cooperation enforcement mechanism using cooperative game theory that allows us to determine a lower bound on the size of coalitions of cooperating nodes. In the second part, using non-cooperative game theory, we compare our cooperation enforcement mechanism CORE to other popular mechanisms. Under the hypothesis of perfect monitoring of node behavior, CORE appears to be equivalent to a wide range of history-based strategies like tit-for-tat. Further, adopting a more realistic assumption taking into account imperfect monitoring due to probable communication errors, the non-cooperative model puts in evidence the superiority of CORE over other history-based schemes.     

Performance of PKI-based security mechanisms in mobile ad hoc networks

Security for ad hoc network environments has received a lot of attention as of today. Previous work has mainly been focussing on secure routing, fairness issues, and malicious node detection. However, the issue of introducing and conserving trust relationships has received considerably less attention. In this article, we present a scalable method for the use of public key certificates and their revocation in mobile ad hoc networks (MANETs). With the LKN-ad hoc security framework (LKN-ASF) a certificate management protocol has been introduced, bringing PKI technology to MANETs. In addition a performance analysis of two different revocation approaches for MANETs will be presented.     

Secure routing in mobile wireless ad hoc networks

We discuss several well known contemporary protocols aimed at securing routing in mobile wireless ad hoc networks. We analyze each of these protocols against requirements of ad hoc routing and in some cases identify fallibilities and make recommendations to overcome these problems so as to improve the overall efficacy of these protocols in securing ad hoc routing, without adding any significant computational or communication overhead.     

SPREAD: Improving network security by multipath routing in mobile ad hoc networks

We propose and investigate the SPREAD scheme as a complementary mechanism to enhance secure data delivery in a mobile ad hoc network. The basic idea is to transform a secret message into multiple shares, and then deliver the shares via multiple paths to the destination so that even if a certain number of message shares are compromised, the secret message as a whole is not compromised. We present the overall system architecture and discuss three major design issues: the mathematical model for the generation and reconstruction of the secret message shares, the optimal allocation of the message shares onto multiple paths in terms of security, and the multipath discovery techniques in a mobile ad hoc network. Our extensive simulation results justify the feasibility and the effectiveness of the SPREAD approach.

Onto scalable wireless ad hoc networks: Adaptive and location-aware clustering

Clustering is a widely used solution to provide routing scalability in wireless ad hoc networks. In the literature, clustering schemes feature different characteristics and purposes, however few schemes are context-aware. This work proposes a new solution called Distributed and Location-aware Clustering (DiLoC), a clustering scheme designed to operate in indoor environments, providing mechanisms to gather context location information in order to ease the maintenance of clusters, thus resulting in a stabler network topology in order to provide a scalable network topology for an efficient routing. DiLoC considers three distinct approaches, regarding the characteristics of the deployment environment, aiming to cover infrastructure-less, infrastructure and hybrid network scenarios. DiLoC was evaluated and compared with a similar clustering scheme, featuring the stability, amount of clustered nodes and network load. Included results demonstrate a scalable algorithm with a significant high stability.     

Relaying in mobile ad hoc networks: The Brownian motion mobility model

Mobile ad hoc networks are characterized by a lack of a fixed infrastructure and by node mobility. In these networks data transfer can be improved by using mobile nodes as relay nodes. As a result, transmission power and the movement pattern of the nodes have a key impact on the performance. In this work we focus on the impact of node mobility through the analysis of a simple one-dimensional ad hoc network topology. Nodes move in adjacent segments with reflecting boundaries according to Brownian motions. Communications (or relays) between nodes can occur only when they are within transmission range of each other. We determine the expected time to relay a message and compute the probability density function of relaying locations. We also provide an approximation formula for the expected relay time between any pair of mobiles.     

An MAC protocol supporting multiple traffic over mobile ad hoc networks

This letter presents the design and performance of a multi-channel MAC protocol that supports multiple traffics for IEEE 802.11 mobile ad-hoc networks.The dynamic channel selection scheme by receiver decision is implemented and the number of the data channel is independent of the network topology.The priority for real-time traffic is assured by the proposed adaptive back off algorithm and different IFS.The protocol is evaluated by simulation and the results have shown that it can support multiple traffics and the performance is better than the performance that IEEE 802.11 standard provides.     

Mobility–capacity–delay trade-off in wireless ad hoc networks

We show that there is a trade-off among mobility, capacity, and delay in ad hoc networks. More specifically, we consider two schemes for node mobility in ad hoc networks. We divide the entire network by cells whose sizes can vary with the total number of nodes n, or whose size is independent of the number of nodes. We restrict the movement of nodes within these cells, calculate throughput and delay for randomly chosen pairs of source–destination nodes, and show that mobility is an entity that can be exchanged with capacity and delay. We also investigate the effect of directional antennas in a static network in which packet relaying is done through the closest neighbor and verify that this approach attains better throughput than static networks employing omnidirectional antennas.     

Secure position-based routing protocol for mobile ad hoc networks

In large and dense mobile ad hoc networks, position-based routing protocols can offer significant performance improvement over topology-based routing protocols by using location information to make forwarding decisions. However, there are several potential security issues for the development of position-based routing protocols. In this paper, we propose a secure geographic forwarding (SGF) mechanism, which provides source authentication, neighbor authentication, and message integrity by using both the shared key and the TIK protocol. By combining SGF with the Grid Location Service (GLS), we propose a Secure Grid Location Service (SGLS) where any receiver can verify the correctness of location messages. We also propose a Local Reputation System (LRS) aiming at detecting and isolating both compromised and selfish users. We present the performance analysis of both SGLS and LRS, and compare them with the original GLS. Simulation results show that SGLS can operate efficiently by using effective cryptographic mechanisms. Results also show that LRS effectively detects and isolates message dropping attackers from the network.     

Location safety protection in ad hoc networks

Many routing protocols and applications developed for ad hoc networks rely on location information of participating nodes. The exposure of such information, however, presents significant safety threats to the networks. In this paper, we investigate the problem of preventing an adversary from locating (and thus destroying) nodes based on their location information they disclose in communications. Our idea is to reduce location resolution to achieve a desired level of safety protection. We define the safety level of a geographic region to be the ratio of its area and the number of nodes inside it. The higher safety level a region has, the less attractive for an adversary to search over it for the nodes. When a node has to disclose its location, it can compute a cloaking box that meets a desired level of safety requirement and report that as its current location information. To implement this simple idea, there are several challenges. First, each cloaking box must be as small as possible in order to minimize the impact of reduced location resolution on the efficiency of network operating and applications. Second, nodes must be able to compute their cloaking boxes without having to reveal their accurate position. Finally, given a sequence of cloaking boxes, they must not be correlated to refine an area whose safety level is less than the requirement. Our research addresses these challenges with cost-effective solutions in the context of both stationary and mobile ad hoc networks. We evaluate the performance of our techniques through both mathematical analysis and simulation. In addition, we present a new geographic routing protocol which can work with blurred location information and evaluate the impact of location resolution reduction on the performance of this technique.     

Enabling SIP-based sessions in ad hoc networks

The deployment of infrastructure-less ad hoc networks is suffering from the lack of applications in spite of active research over a decade. This problem can be solved to a certain extent by porting successful legacy Internet applications and protocols to the ad hoc network domain. Session Initiation Protocol (SIP) is designed to provide the signaling support for multimedia applications such as Internet telephony, Instant Messaging, Presence etc. SIP relies on the infrastructure of the Internet and an overlay of centralized SIP servers to enable the SIP endpoints discover each other and establish a session by exchanging SIP messages. However, such an infrastructure is unavailable in ad hoc networks. In this paper, we propose two approaches to solve this problem and enable SIP-based session setup in ad hoc networks (i) a loosely coupled approach, where the SIP endpoint discovery is decoupled from the routing procedure and (ii) a tightly coupled approach, which integrates the endpoint discovery with a fully distributed cluster based routing protocol that builds a virtual topology for efficient routing. Simulation experiments show that the tightly coupled approach performs better for (relatively) static multihop wireless networks than the loosely coupled approach in terms of the latency in SIP session setup. The loosely coupled approach, on the other hand, generally performs better in networks with random node mobility. The tightly coupled approach, however, has lower control overhead in both the cases. This work was partially done while the author was a graduate student in CReWMaN, University of Texas at Arlington. Dr. Nilanjan Banerjee is a Senior Research Engineer in the Networks Research group at Motorola India Research Labs. He is currently working on converged network systems. He received his Ph.D. and M.S. in computer science and engineering from University of Texas at Arlington. He received his B.E. degree in the same discipline from Jadavpur University, India. His research interests include telecom network architectures and protocols, identity management and network security, mobile and pervasive computing, measures for performance, modeling and simulation, and optimization in dynamic systems. Dr Arup Acharya is a Research Staff Member in the Internet Infrastructure and Computing Utilities group at IBM T.J. Watson Research Center and leads the Advanced Networking micropractice in On-Demand Innovation Services. His current work includes SIP-based services such as VoIP, Instant Messaging and Presence, and includes customer consulting engagements and providing subject matter expertise in corporate strategy teams. Presently, he is leading a IBM Research project on scalability and performance of SIP servers for large workloads. In addition, he also works on different topics in mobile/wireless networking such as mesh networks. He has published extensively in conferences/journals and has been awarded seven patents. Before joining IBM in 2000, he was with NEC C&C Research Laboratories, Princeton. He received a B.Tech degree in Computer Science from the Indian Institute of Technology, Kharagpur and a PhD in Computer Science from Rutgers University in 1995. Further information is available at Dr. Sajal K. Das is a Professor of Computer Science and Engineering and also the Founding Director of the Center for Research in Wireless Mobility and Networking (CReWMaN) at the University of Texas at Arlington (UTA). His current research interests include sensor networks, resource and mobility management in wireless networks, mobile and pervasive computing, wireless multimedia and QoS provisioning, wireless internet architectures and protocols, grid computing, applied graph theory and game theory. He has published over 400 research papers in these areas, holds four US patents in wireless internet and mobile networks. He received Best Paper Awards in IEEE PerCom’06, ACM MobiCom’99, ICOIN’02, ACM MSwiM’00 and ACM/IEEE PADS’97. He is also recipient of UTA’s Outstanding Faculty Research Award in Computer Science (2001 and 2003), College of Engineering Research Excellence Award (2003), the University Award for Distinguished record of Research (2005), and UTA Academy of Distinguished Scholars Award (2006). He serves as the Editor-in-Chief of Pervasive and Mobile Computing journal, and as Associate Editor of IEEE Transactions on Mobile Computing, ACM/Springer Wireless Networks, IEEE Transactions on Parallel and Distributed Systems. He has served as General or Program Chair and TPC member of numerous IEEE and ACM conferences. He is a member of IEEE TCCC and TCPP Executive Committees.     

Non-interactive key establishment in mobile ad hoc networks

We present a new non-interactive key agreement and progression (NIKAP) scheme for mobile ad hoc networks (MANETs), which does not require an on-line centralized authority, can non-interactively establish and update pairwise keys between nodes, is configurable to operate synchronously or asynchronously, and supports differentiated security services w.r.t. the given security policies. NIKAP is valuable to scenarios where pairwise keys are desired to be established without explicit negotiation over insecure channels, and also need to be updated frequently.