Indoor localization is of great importance for a range of pervasive applications, attracting many research efforts in the past two decades. Most radio-based solutions require a process of site survey, in which radio signatures are collected and stored for further comparison and matching. Site survey involves intensive costs on manpower and time. In this work, we study unexploited RF signal characteristics and leverage user motions to construct radio floor plan that is previously obtained by site survey. On this basis, we design WILL, an indoor localization approach based on off-the-shelf WiFi infrastructure and mobile phones. WILL is deployed in a real building covering over 1600 m2, and its deployment is easy and rapid since site survey is no longer needed. The experiment results show that WILL achieves competitive performance comparing with traditional approaches.

WILL: Wireless Indoor Localization without Site Survey

Indoor localization is of great importance for a range of pervasive applications, attracting many research efforts in the past two decades. Most radio-based solutions require a process of site survey, in which radio signatures are collected and stored for further comparison and matching. Site survey involves intensive costs on manpower and time. In this work, we study unexploited RF signal characteristics and leverage user motions to construct radio floor plan that is previously obtained by site survey. On this basis, we design WILL, an indoor localization approach based on off-the-shelf WiFi infrastructure and mobile phones. WILL is deployed in a real building covering over 1600m2, and its deployment is easy and rapid since site survey is no longer needed. The experiment results show that WILL achieves competitive performance comparing with traditional approaches.

/pdf/will-wireless-indoor-localization-without-site-survey-srk10dfb4s.pdf

WILL: Wireless indoor localization without site survey

Geographic routing offers a radical departure from previous topology-dependent routing paradigms through its use of physical location in the routing process. Geographic routing protocols eliminate dependence on topology storage and the associated costs, which also makes them more suitable to handling dynamic behavior frequently found in wireless ad-hoc networks. Geographic routing protocols have been designed for a variety of applications ranging from mobility prediction and management through to anonymous routing and from energy efficiency to QoS. Geographic routing is also part of the larger area of context-awareness due to its usage of location data to make routing decisions and thus represents an important step in the journey towards ubiquitous computing. The focus of this paper, within the area of geographic routing is on wireless ad-hoc networks and how location information can benefit routing. This paper aims to provide both a comprehensive and methodical survey of existing literature in the area of geographic routing from its inception as well as acting as an introduction to the subject.

A Survey of Geographical Routing in Wireless Ad-Hoc Networks

We address the problem of control-channel jamming attacks in multi-channel ad hoc networks. Deviating from the traditional view that sees jamming attacks as a physical-layer vulnerability, we consider a sophisticated adversary who exploits knowledge of the protocol mechanics along with cryptographic quantities extracted from compromised nodes to maximize the impact of his attack on higher-layer functions. We propose new security metrics that quantify the ability of the adversary to deny access to the control channel, and the overall delay incurred in re-establishing the control channel. We also propose a randomized distributed scheme that allows nodes to establish a new control channel using frequency hopping. Our method differs from classic frequency hopping in that no two nodes share the same hopping sequence, thus mitigating the impact of node compromise. Furthermore, a compromised node is uniquely identified through its hop sequence, leading to its isolation from any future information regarding the frequency location of the control channel.

/pdf/mitigating-control-channel-jamming-attacks-in-multi-channel-42h1vbtzr5.pdf

Mitigating control-channel jamming attacks in multi-channel ad hoc networks

Tracking mobile targets in wireless sensor networks (WSNs) has many important applications. As it is often the case in prior work that the quality of tracking (QoT) heavily depends on high accuracy in localization or distance estimation, which is never perfect in practice. These bring a cumulative effect on tracking, e.g., target missing. Recovering from the effect and also frequent interactions between nodes and a central server result in a high energy consumption. We design a tracking scheme, named t-Tracking , aiming to achieve two major objectives: high QoT and high energy efficiency of the WSN. We propose a set of fully distributed tracking algorithms, which answer queries like whether a target remains in a “specific area” (called a “face” in localized geographic routing, defined in terms of radio connectivity and local interactions of nodes). When a target moves across a face, the nodes of the face that are close to its estimated movements compute the sequence of the target’s movements and predict when the target moves to another face. The nodes answer queries from a mobile sink called the “tracker”, which follows the target along with the sequence. t-Tracking has advantages over prior work as it reduces the dependency on requiring high accuracy in localization and the frequency of interactions. It also timely solves the target missing problem caused by node failures, obstacles, etc., making the tracking robust in a highly dynamic environment. We validate its effectiveness considering the objectives in extensive simulations and in a proof-of-concept system implementation.

Local Area Prediction-Based Mobile Target Tracking in Wireless Sensor Networks

Wireless sensor networks are formed by small sensor nodes communicating over wireless links without using a fixed network infrastructure. Sensor nodes have a limited transmission range, and their processing and storage capabilities as well as their energy resources are also limited. Routing protocols for wireless sensor networks have to ensure reliable multi-hop communication under these conditions. We describe design challenges for routing protocols in sensor networks and illustrate the key techniques to achieve desired characteristics, such as energy efficiency and delivery guarantees. We give a survey of state-of-the-art routing techniques with a focus on geographic routing, a paradigm that enables a reactive message-efficient routing without prior route discovery or knowledge of the network topology. Different geographic routing strategies are described as well as beaconless routing techniques. We also show the physical layer impact on routing and outline further research directions.

Routing in Wireless Sensor Networks

Beaconless georouting algorithms are fully reactive and work without prior knowledge of their neighbors. However, existing approaches can either not guarantee delivery or they require the exchange of complete neighborhood information. We describe two general methods for completely reactive face routing with guaranteed delivery. The beaconless forwarder planarization (BFP) scheme determines correct edges of a local planar subgraph without hearing from all neighbors. Face routing then continues properly. Angular relaying determines directly the next hop of a face traversal. Both schemes are based on the select-and-protest principle. Neighbors respond according to a delay function, but only if they do not violate a planar subgraph condition. Protest messages are used to remove falsely selected neighbors that are not in the planar subgraph. We show that a correct beaconless planar subgraph construction is not possible without protests. We also show the impact of the chosen planar subgraph on the message complexity. With the new circlunar neighborhood graph (CNG) we can bound the worst case message complexity of BFP, which is not possible when using the Gabriel graph (GG) for planarization. Simulation results show similar message complexities in the average case when using CNG and GG. Angular relaying uses a delay function that is based on the angular distance to the previous hop. We develop a theoretical framework for delay functions and show both theoretically and in simulations that with a function of angle and distance we can reduce the number of protests by a factor of 2 compared to a simple angle-based delay function.

Message-efficient beaconless georouting with guaranteed delivery in wireless sensor, ad hoc, and actuator networks

We have developed TakaTuka, a Java Virtual Machine optimized for tiny embedded devices such as wireless sensor motes. TakaTuka requires very little memory and processing power from the host device. This has been verified by successfully running TakaTuka on four different mote platforms. The focus of this paper is TakaTuka’s optimization of program memory usage. In addition, it also gives an overview of TakaTuka’s linkage with TinyOS and power management. TakaTuka optimizes storage requirements for the Java classfiles as well as for the JVM interpreter, both of which are expected to be stored on the embedded devices. These optimizations are performed on the desktop computer during the linking phase, before transferring the Java binary and the corresponding JVM interpreter onto a mote and thus without burdening its memory or computation resources. We have compared TakaTuka with the Sentilla, Darjeeling and Squawk JVMs.

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Optimized java binary and virtual machine for tiny motes

Beaconless or contention-based geographic routing algorithms forward packets toward a geographical destination reactively without the knowledge of the neighborhood. Such algorithms allow greedy forwarding, where only the next hop neighbor responds after a timer-based contention using only three messages (RTS, CTS, and DATA) per forwarding step. However, existing contention-based schemes for recovery from greedy failures do not have this property. In this paper, we show that recovery is possible within this 3-message scheme: the Rotational Sweep (RS) algorithm directly identifies the next hop after timer-based contention and constructs a traversal path that ensures progress after a greedy failure. It uses a traversal scheme (called Sweep Circle) that forwards a message along the α-shape of the network and provides recovery paths shorter or equal to the prominent face routing with Gabriel graph planarization. An alternative traversal scheme (called Twisting Triangle) provides even shorter routes on average, as shown by simulations. They both also reduce per-node overall network contention delays. We prove that both traversal schemes guarantee delivery in unit disk graphs. Our traversal schemes avoid planarization and are easy to implement, based merely on the evaluation of a function of a neighbor node's relative position. They can also be used for boundary detection and improve path-length in conventional beacon-based routing.

Optimizing Communication Overhead while Reducing Path Length in Beaconless Georouting with Guaranteed Delivery for Wireless Sensor Networks

Communication in mobile ad hoc networks and intermittently connected networks usually requires multihop routing. While ad hoc routing protocols target the connection establishment in a changing environment, communication in intermittently connected networks requires end-to-end delivery without established connections. We present DT-DYMO, a combination of ad hoc routing based on the established Dynamic MANET On-demand Routing protocol and mechanisms for in-network storage and delivery likelihood prediction. DT-DYMO uses a route discovery mechanism in order to find the destination or nodes that are likely to be able to deliver the message in the future. We present simulation results for wireless network scenarios with high mobility and temporary network disconnection. The results show that we can significantly increase the delivery rate in mobile scenarios and thus can overcome the limitations of traditional ad hoc routing. On the other hand, DT-DYMO provides faster delivery than opportunistic message passing schemes that rely only on delivery likelihood estimation.

Stefan Rührup

Papers

Routing in Wireless Sensor Networks

Message-efficient beaconless georouting with guaranteed delivery in wireless sensor, ad hoc, and actuator networks

Optimized java binary and virtual machine for tiny motes

Optimizing Communication Overhead while Reducing Path Length in Beaconless Georouting with Guaranteed Delivery for Wireless Sensor Networks

DT-DYMO: Delay-Tolerant Dynamic MANET On-demand Routing