Louise Lamont

Quality of service routing in ad-hoc networks using OLSR

In an ad-hoc network, all communication is done over wireless media, without the help of wired base stations. While many routing protocols have been developed to find and maintain routes based on a best-effort service model, quality-of-service (QoS) routing in an ad-hoc network is difficult because the network topology may change constantly and the available state information for routing is inherently imprecise. In this paper, we discuss how to support QoS routing in OLSR (optimized link state routing protocol, one of the routing protocols under study by the IETF MANET Working Group). We develop heuristics that allow OLSR to find the maximum bandwidth path, show through simulation that these heuristics do improve OLSR in the static network case, and finally, we prove that for our ad-hoc network model, two of the heuristics are indeed optimal (i.e., guarantee that the highest-bandwidth path between any two nodes is found).

Implementing a fully distributed certificate authority in an OLSR MANET

OLSR (optimal link state routing) is one of the four base routing protocols being considered for use with MANETs (mobile ad hoc networks) by the lETFs MANET working group. OLSR belongs to the proactive class of routing protocols in which the connection setup delay is minimized at the expense of the heavier control traffic load on the wireless channel. Existing IETF draft proposals on OLSR does not yet address security issues. Although a PKI (public key infrastructure) based security is deemed more appropriate for MANETs including OLSR MANETs, care should be taken to ensure that such an infrastructure does not add to the already heavy control traffic load in OLSR and, as much as possible, the existing OLSR control packets are utilized to support such infrastructures as well. In this paper we describe our approach in which a PKI is tightly coupled with an OLSR MANET at the network layer level and the OLSR control packets are leveraged to support various security related activities as well. We have implemented a fully distributed CA (certificate authority) and integrated it with an existing implementation of OLSRv4 (OLSR for IP version 4). Intricate details of our implementation are presented to develop insights into the key aspects of the proposed solution.

Medium Access Control for Unmanned Aerial Vehicle (UAV) Ad-Hoc Networks With Full-Duplex Radios and Multipacket Reception Capability

Recent advances in interference cancellation and signal-processing techniques can enable full-duplex radios and multipacket reception (MPR), which will have significant impact on medium access control (MAC) schemes. In this paper, we propose a MAC scheme in unmanned aerial vehicle (UAV) ad-hoc networks with full-duplex radios and MPR. To efficiently handle the highly mobile environment of a UAV ad-hoc network, a token-based technique is used to update information in the network as well. The MAC schemes in the presence of perfect and imperfect channel state information (CSI) are formulated as a combinatorial optimization problem and a discrete stochastic optimization problem, respectively. Simulation results show the effectiveness of the proposed MAC.

The Performance of Greedy Geographic Forwarding in Unmanned Aeronautical Ad-Hoc Networks

The availability of accurate location information (for airborne purposes) in unmanned aeronautical ad-hoc networks (UAANETs) makes it possible to deploy geographic routing mechanisms as the main communication protocol in such networks. However, the performance of geographic routing is not obvious, especially for sparse networks (i.e., networks with low connectivity levels). In this paper, the main goal is to explore the effects of network sparsity on the performance of greedy geographic forwarding and to determine in different scenarios the percentage of source-destination pairs that can successfully establish communication based on greedy geographic forwarding only. To that end, Monte Carlo simulations have been performed to collect statistics in estimating the performance of UAANETs in sparse situations. Simulation results show that greedy geographic forwarding can be used for less critical applications of UAANETs. However, for applications with guaranteed delivery requirements, other alternatives should be combined with greedy geographic forwarding.

Integrating WLANs & MANETs to the IPv6 based Internet

This paper presents a novel approach to integrate wireless local area network (WLANs) and mobile ad hoc networks (MANET) to the Internet protocol version 6 (IPv6) based Internet. In the proposed network architecture, the mobiles, connected as a MANET, employ the optimized link state routing (OLSR) protocol for routing within the MANET. Gateways are used to connect MANETs to the Internet. This paper extends the functionality of OLSR to support mobile IP (MIP). This functionality is essential in a scenario where a node moving into an OLSR MANET needs to auto-configure its care-of-address and to propagate a binding update message containing its new care-of-address to its home agent and its correspondent node(s) located on the Internet. Automatic mode-detection and switching capability is also introduced in each mobile node to facilitate handoffs between WLANs and MANETs. Mobility management across WLANs and MANETs is achieved through mobile IPv6 (MIPv6). A real test-bed is constructed to demonstrate the viability of the proposed approach. Results from a performance evaluation on this test-bed are presented. Efficiency of handoffs between WLANs and MANETs is measured in terms of delay and packet loss. The impact of OLSR based route discovery and packet propagation, and mobile IPv6 features such as movement detection and address auto-configuration on the handoff latency and packet loss are quantified. These performance benchmarks and metrics provide in assessment of the impact of the aforementioned system features on the QoS parameters associated with handoffs.

Proactive QoS routing in ad hoc networks

In this paper, we analyze the advantages and disadvantages of the proactive QoS routing in ad-hoc networks. We discuss how to support bandwidth QoS routing in OLSR (Optimized Link State Protocol), a best-effort proactive MANET routing protocol. Using OPNET, we simulate the algorithm, exploring both traditional routing protocol performance metrics and QoS-specific metrics. Our analysis of the simulation results shows that the additional message overhead generated by the proactive QoS routing have a negative impact on the performance of the routing protocol. Given the negative results, we identified research areas that would be worthwhile investigating in order to obtain better performance results.

Communication architectures and protocols for networking unmanned aerial vehicles

A fundamental but challenging problem in cooperation and control of multiple unmanned aerial vehicles (UAVs) is efficient networking of the UAVs over the wireless medium in rapidly changing environments. In this paper, we introduce four communication architectures for networking UAVs and review some military communication standards applicable to UAV communications. After discussions of pros and cons of each communication architecture, we conclude that a UAV ad hoc network is the most appropriate architecture to network a team of UAVs, while a multi-layer UAV ad hoc network is more suitable for multiple groups of heterogeneous UAVs. By comparing various legacy and next-generation military data link systems, we highlight that one important feature of the next-generation waveforms is their capability of Internet protocol (IP) based ad hoc networking, which allows UAVs to communicate with each other in a single- or multi-layer UAV ad hoc networks.

Multilateration localization in the presence of anchor location uncertainties

Multilateration is a fundamental localization technique for wireless sensor network applications. Classical multilateration techniques typically assume that the anchor locations are known and error free, an assumption that is always not valid in practice. Although the popular total least squares (TLS) method is able to take into account such errors in general, it requires that the noise components in the formulated data matrices be identically, independently distributed. In multilateration localization, however, it can be shown that the noise components in the formulated equations are algebraically related. In this paper, we formulate multilateration for sensor localization based on the use of the constrained total least squares (CTLS) method. By assuming that distance measurement errors are relatively small and can be neglected, we show that the CTLS solution leads to a weighted least squares problem. Computer simulations are used to demonstrate the effectiveness and performance of the proposed technique.

Combined Reactive-Geographic routing for Unmanned Aeronautical Ad-hoc Networks

As a result of high mobility of Unmanned Aerial Vehicles (UAVs), designing a good routing protocol is challenging for Unmanned Aeronautical Ad-hoc Networks (UAANETs). Geographic-based routing mechanisms are seen to be an interesting option for routing in UAANETs due to the fact that location information of UAVs is readily available. In this paper, a combined routing protocol, called the Reactive-Greedy-Reactive (RGR), is presented for UAANET applications, which combines the mechanisms of the Greedy Geographic Forwarding (GGF) and reactive routing. The proposed RGR employs location information of UAVs as well as reactive end-to-end paths in the routing process. Simulation results show that RGR outperforms existing protocols such as Ad-hoc On-demand Distance Vector (AODV) in search UAANET missions in terms of delay and packet delivery ratio, yet its overhead is similar to traditional mechanisms.

A token circulation scheme for code assignment and cooperative transmission scheduling in CDMA-based UAV ad hoc networks

Code division multiple access (CDMA) ad hoc networks have been considered a promising multiple-channel networking architecture for connecting tactical platforms in battle fields. In this paper we consider a network of a swarm of unmanned aerial vehicles (UAVs) that are used in a tactical surveillance mission. The UAVs are assumed to have multiuser detection capability and form a CDMA-based ad hoc network. A token circulation scheme is proposed to conduct functions required at the medium access control layer including detection of hidden/lost neighbors, code assignment and schedule-based cooperative transmission scheduling. In the proposed scheme, a token continuously circulates around the network based on the “receive-forward” module. Through circulation of the token, each UAV can detect its hidden and/or lost neighbors in near real-time, assign codes enabling the spatial reuse of code channels without incurring code collision, and schedule data transmissions in a cooperative and distributed manner. In addition, the proposed scheme is able to take advantage of multiuser detection functionality and allows for simultaneous transmissions from multiple transmitters to a same receiver. The performance of the proposed token circulation scheme is evaluated, both analytically and through simulations. It is shown that the latency of the token is at most linearly proportional to the network size, and the average delay of a data packet increases with either the packet generation rate or the network size. The results also show that the proposed token circulation scheme is suitable for large-scale CDMA-based UAV ad hoc networks with even heavy network traffic load.