Emerging applications rely on wireless broadcast to disseminate time-critical information. For example, vehicular networks may exchange vehicle position and velocity information to enable safety applications. The number of nodes in one-hop communication range in such networks can be very large, leading to congestion and undesirable levels of packet collisions. Earlier work has examined such broadcasting protocols primarily from a MAC perspective and focused on selective aspects such as packet error rate. In this work, we propose a more comprehensive metric, the average system information age, which captures the requirement of such applications to maintain current state information from all other nearby nodes. We show that information age is minimized at an optimal operating point that lies between the extremes of maximum throughput and minimum delay. Further, while age can be minimized by saturating the MAC and setting the CW size to its throughput-optimal value, the same cannot be achieved without changes in existing hardware. Also, via simulations we show that simple contention window size adaptations like increasing or decreasing the window size are unsuitable for reducing age. This motivates our design of an application-layer broadcast rate adaptation algorithm. It uses local decisions at nodes in the network to adapt their messaging rate to keep the system age to a minimum. Our simulations and experiments with 300 ORBIT nodes show that the algorithm effectively adapts the messaging rates and minimizes the system age.

/pdf/minimizing-age-of-information-in-vehicular-networks-2jlm45t2fh.pdf

Minimizing age of information in vehicular networks

At some point in the future, how far out we do not exactly know, wireless access to the Internet will outstrip all other forms of access bringing the freedom of mobility to the way we access the we...

ACM SIGCOMM computer communication review

We address the problem of interference aware routing in multi-radio infrastructure mesh networks wherein each mesh node is equipped with multiple radio interfaces and a subset of nodes serve as Internet gateways. We present a new interference aware routing metric - iAWARE that aids in finding paths that are better in terms of reduced interflow and intra-flow interference. We incorporate this metric and new support for multi-radio networks in the well known AODV routing protocol to design an enhanced AODV-MR routing protocol. We study the performance of our new routing metric by implementing it in our wireless testbed consisting of 12 mesh nodes. We show that iAWARE tracks changes in interfering traffic far better than existing well known link metrics such as ETT and IRU. We also demonstrate that our AODV-MR protocol delivers increased throughput in single radio and two radio mesh networks compared to similar protocol with WCETT and MIC routing metrics. We also show that in the case of two radio mesh networks, our metric achieves good intra-path channel diversity.

/pdf/interference-aware-routing-in-multi-radio-wireless-mesh-3gcw7xdmih.pdf

Interference aware routing in multi-radio wireless mesh networks

Routing protocols for mobile ad hoc networks (MANETs) have been explored extensively in recent years. Much of this work is targeted at finding a feasible route from a source to a destination without considering current network traffic or application requirements. Therefore, the network may easily become overloaded with too much traffic and the application has no way to improve its performance under a given network traffic condition. While this may be acceptable for data transfer, many real-time applications require quality-of-service (QoS) support from the network. We believe that such QoS support can be achieved by either finding a route to satisfy the application requirements or offering network feedback to the application when the requirements cannot be met. We propose a QoS-aware routing protocol that incorporates an admission control scheme and a feedback scheme to meet the QoS requirements of real-time applications. The novel part of this QoS-aware routing protocol is the use of the approximate bandwidth estimation to react to network traffic. Our approach implements these schemes by using two bandwidth estimation methods to find the residual bandwidth available at each node to support new streams. We simulate our QoS-aware routing protocol for nodes running the IEEE 802.11 medium access control. Results of our experiments show that the packet delivery ratio increases greatly, and packet delay and energy dissipation decrease significantly, while the overall end-to-end throughput is not impacted, compared with routing protocols that do not provide QoS support.

/pdf/qos-aware-routing-based-on-bandwidth-estimation-for-mobile-2nzmm35cjd.pdf

QoS-aware routing based on bandwidth estimation for mobile ad hoc networks

Designing routing metrics is critical for performance in wireless mesh networks. The unique characteristics of mesh networks, such as static nodes and the shared nature of the wireless medium, invalidate existing solutions from both wired and wireless networks and impose unique requirements on designing routing metrics for mesh networks. In this paper, we focus on identifying these requirements. We first analyze the possible types of routing protocols that can be used and show that proactive hop-by-hop routing protocols are the most appropriate for mesh networks. Then, we examine the requirements for designing routing metrics according to the characteristics of mesh networks and the type of routing protocols used. Finally, we study several existing routing metrics, including hop count, ETX, ETT, WCETT and MIC in terms of their ability to satisfy these requirements. Our simulation results of the performance of these metrics confirm our analysis of these metrics.

/pdf/designing-routing-metrics-for-mesh-networks-49pmmbzjpj.pdf

Designing routing metrics for mesh networks

An admission control algorithm must coordinate between flows to provide guarantees about how the medium is shared. In wired networks, nodes can monitor the medium to see how much bandwidth is being used. However, in ad hoc networks, communication from one node may consume the bandwidth of neighboring nodes. Therefore, the bandwidth consumption of flows and the available resources to a node are not local concepts, but related to the neighboring nodes in carrier-sensing range. Current solutions do not address how to perform admission control in such an environment so that the admitted flows in the network do not exceed network capacity. In this paper, we present a scalable and efficient admission control framework - contention-aware admission control protocol (CACP) - to support QoS in ad hoc networks. We present several options for the design of CACP and compare the performance of these options using both mathematical analysis and simulation results. We also demonstrate the effectiveness of CACP compared to existing approaches through extensive simulations.

/pdf/contention-aware-admission-control-for-ad-hoc-networks-fi99qylqje.pdf

Contention-aware admission control for ad hoc networks

Load balancing is critical for improving performance in wireless mesh networks. The unique characteristics of mesh networks, such as static nodes and the shared nature of the wireless medium, invalidate existing solutions from both wired and wireless networks and introduce new challenges for providing load balancing. In this paper, we focus on addressing these challenges. We first formulate the objective of load balancing in mesh networks and provide a theoretical solution to optimally achieve this objective. Then, we investigate some existing practical approaches to load balancing in mesh networks and show that none of them sufficiently address these challenges and some may even cause non-optimal paths and forwarding loops. In response, we propose a new path weight function, called MIC, and a novel routing scheme, called LIBRA, to provide interferenceaware and multi-channel/multi-radio aware load balancing for mesh networks, while still ensuring routing optimality and loopfreedom. We use extensive simulations to evaluate our scheme by comparing it with both the theoretical optimal solution and existing practical solutions. The results show close-to-optimum performance and indicate that LIBRA is a good candidate for load balancing and routing in wireless mesh networks.

Interference-aware Load Balancing for Multihop Wireless Networks

The design of a routing protocol must be based on the characteristics of its target networks. The diversity of wireless networks motivates the design of different routing metrics, capturing different aspects of wireless communications. The design of routing metrics, however, is not arbitrary since it has a great impact on the proper operation of routing protocols. Combining a wrong type of routing metrics with a routing protocol may result in routing loops and suboptimal paths. In this paper, we thoroughly study the relationship between routing metrics and routing protocols. Our work provides important guidelines for designing routing metrics and identifies the specific properties that a routing metric must have in order to be combined with certain type of routing protocols.

http://www.ece.vt.edu/yyang8/papers/infocom08.pdf

Design Guidelines for Routing Metrics in Multihop Wireless Networks

Mobile navigation services are used by billions of users around globe today. While GPS spoofing is a known threat, it is not yet clear if spoofing attacks can truly manipulate road navigation systems. Existing works primarily focus on simple attacks by randomly setting user locations, which can easily trigger a routing instruction that contradicts with the physical road condition (i.e., easily noticeable).

In this paper, we explore the feasibility of a stealthy manipulation attack against road navigation systems. The goal is to trigger the fake turn-by-turn navigation to guide the victim to a wrong destination without being noticed. Our key idea is to slightly shift the GPS location so that the fake navigation route matches the shape of the actual roads and trigger physically possible instructions. To demonstrate the feasibility, we first perform controlled measurements by implementing a portable GPS spoofer and testing on real cars. Then, we design a searching algorithm to compute the GPS shift and the victim routes in real time. We perform extensive evaluations using a trace-driven simulation (600 taxi traces in Manhattan and Boston), and then validate the complete attack via real-world driving tests (attacking our own car). Finally, we conduct deceptive user studies using a driving simulator in both the US and China. We show that 95% of the participants follow the navigation to the wrong destination without recognizing the attack. We use the results to discuss countermeasures moving forward.

/pdf/all-your-gps-are-belong-to-us-towards-stealthy-manipulation-4n8vttt58q.pdf

Yaling Yang

Papers

Designing routing metrics for mesh networks

Contention-aware admission control for ad hoc networks

Interference-aware Load Balancing for Multihop Wireless Networks

Design Guidelines for Routing Metrics in Multihop Wireless Networks

All your GPS are belong to us: towards stealthy manipulation of road navigation systems