Azin Neishaboori

SINR-sensitive routing in wireless 802.11 mesh networks

Despite the many routing protocols to choose from in the existing wireless network literature, routing has remained a challenging problem in the actual deployment of wireless mesh and ad hoc networks. To address some of the issues involved with routing in wireless mesh networks, in this paper we attempt to make routing more sensitive to the dynamics of the network such as interference, traffic load and congestion. We introduce a link/load-sensitive metric using linkspsila idle time and average Signal to Interference Noise Ratio (SINR), as perceived by receiving nodes into link/path selection. We use this quantity as a secondary link metric to prevent instability that might happen due to frequent SINR variations. We therefore attempt to introduce better load balancing critical to mesh networks as the nodes closer to the base stations tend to be the natural bottlenecks of the network. We perform a simulation study to assess the performance enhancement due to this technique under different load conditions. We use ETX as primary link metric and observe throughput enhancement when a secondary SINR-based metric is incorporated in the link metric.

Energy saving strategies in WiFi indoor localization

Despite extensive research on WiFi indoor localization, very few solutions are widely deployed, largely due to their high energy consumption. In this paper, we propose several energy saving strategies with varying localization accuracy and energy consumption tradeoffs in WiFi indoor localization. Instead of localizing every single device, these strategies exploit short range low-power communication technologies, to localize clusters of mobile devices, via a representative cluster head. We propose various cluster head selection algorithms that offer different trade offs between localization accuracy and power consumption. The outcome of this work provides insights into the effectiveness and cost of a particular strategy depending on the needs of the application requiring varying localization service levels.

Up and away: A visually-controlled easy-to-deploy wireless UAV Cyber-Physical testbed

Cyber-Physical Systems (CPS) have the promise of presenting the next evolution in computing with potential applications that include aerospace, transportation, and various automation systems. These applications motivate advances in the different sub-fields of CPS such as mobile computing, context awareness, and computer vision. However, deploying and testing complete CPSs is known to be a complex and expensive task. In this paper, we present the design, implementation, and evaluation of Up and Away (UnA): a testbed for Cyber-Physical Systems that use Unmanned Aerial Vehicles (UAVs) as their main physical component. UnA aims to abstract the control of physical system components to reduce the complexity of UAV oriented CPS experiments. UnA provides APIs to allow for converting CPS algorithm implementations, developed typically for simulations, into physical experiments using a few simple steps. We present two scenarios of using UnAs API to bring mobile-camera-based surveillance algorithms to life, thus exhibiting the ease of use and flexibility of UnA.

On target coverage in mobile visual sensor networks

Recent advancements in manufacturing low-cost wireless battery operated cameras has made their application in Wireless Video Sensor Networks (WVSN) increasingly more feasible and affordable. The application of robotic sensing agents equipped with cameras in WVSNs, seems particularly promising in performing coverage tasks for ad hoc surveillance. Their application in this context can be specifically useful for surveying areas with little to no available or affordable infrastructure, or where quick deployment is necessary. In this paper, we address the target coverage problem for finding the minimum number of cameras, their placement, and orientation to cover arbitrarily located targets in an area of interest. We propose a computationally light-weight heuristic, where the number of used mobile cameras is close to those found by near-optimal algorithms. Specifically, we address this problem for non-uniform target distributions that naturally form clusters. Having light-weight heuristics will be particularly useful when the application is required to adapt to target mobility and/or is implemented in embedded systems. Our simulation study shows that when clusters are sufficiently separated, the required number of cameras found by our proposed method is very close to those acquired by the near-optimal algorithm, whereas the computational complexity of our algorithm is about ten times less. We also deploy our algorithm on a drone testbed using off-the-shelf components to verify its feasibility.

Argus: realistic target coverage by drones

Low-cost mini-drones with advanced sensing and maneuverability enable a new class of intelligent visual sensing systems. This potential motivated several research efforts to employ drones as standalone surveillance systems or to assist legacy deployments. However, several fundamental challenges remain unsolved including: 1) Adequate coverage of sizable targets; 2) Target orientation that render coverage effective only from certain directions; 3) Occlusion by elements in the environment, including other targets.In this paper, we present Argus, a system that provides visual coverage of wide and oriented targets, using camera-mounted drones, taking into account the challenges stated above. Argus relies on a geometric model that captures both target shapes and coverage constraints. With drones being the scarcest resource in Argus, we study the problem of minimizing the number of drones required to cover a set of such targets and derive a best-possible approximation algorithm. Building upon that, we present a sampling heuristic that performs favorably, while running up to 100x faster compared to the approximation algorithm. We implement a complete prototype of Argus to demonstrate and evaluate the proposed coverage algorithms within a fully autonomous surveillance system. Finally, we evaluate the proposed algorithms via simulations to compare their performance at scale under various conditions.

Wireless mesh networks based on CDMA

In this paper, we study hybrid contention-free/contention-based traffic management schemes in presence of delay-sensitive and delay-insensitive data in multihop CDMA wireless mesh networks. We suggest a greedy incremental contention-based ordering algorithm for contention-free schedules and also propose a time-scale-based framework for integration of contention and contention-free traffic management schemes. Further, for the contention-free phase, we propose a power control algorithm that gives an end-to-end throughput guarantee. With the aid of simulation, we observe the additional end-to-end throughput that can be achieved when scheduling and tight power control are applied.

Low Complexity Target Coverage Heuristics Using Mobile Cameras

Wireless sensor and actuator networks have been extensively deployed for enhancing industrial control processes and supply-chains, and many forms of surveillance and environmental monitoring. The availability of low-cost mobile robots equipped with a variety of sensors in addition to communication and computational capabilities makes them particularly promising in target coverage tasks for ad hoc surveillance, where quick, low-cost or non-lasting visual sensing solutions are required, e.g. in border protection and disaster recovery. In this paper, we consider the problem of low complexity placement and orientation of mobile cameras to cover arbitrary targets. We tackle this problem by clustering proximal targets, while calculating/estimating the camera location/direction for each cluster separately through our cover-set coverage method. Our proposed solutions provide extremely computationally efficient heuristics with only a small increase in number of cameras used, and a small decrease in number of covered targets.

Routing and Uplink-Downlink Scheduling in Ad Hoc CDMA Networks

In multihop ad hoc CDMA networks, uplink-downlink schedules are needed to forward packet flows throughout the network without conflict. Also, a routing algorithm and a power control mechanism are required to route the flows while satisfying the QoS needs of the users. To maximize bandwidth utilization efficiency, scheduling tables of minimum length are desired. We suggest an incremental contention-based algorithm as a heuristic distributed solution to the NP-hard uplink-downlink scheduling problem. Also, we propose a routing strategy that considers these schedules, i.e., integrated routing and scheduling.

Wireless mesh networking games

We address the coverage range extension of Wireless Mesh Networks (WMNs) by motivating traffic relaying by in-range network subscribers. Two different game models for non-cooperative users are discussed: a primary market model in which all in-range and out-of-range customers subscribe to one provider, and a primary-secondary market model in which some in-range customers are secondary providers and sell resources to out-of-range users. For the first market type, the relays may engage in packet-dropping for their own throughput gain, but we justify why this would likely not occur in the second market type. In both market models, we analyze the dynamics of the price charged by each provider and the traffic demanded by each subscriber. Additionally, we discuss possible options for underlying MAC protocols that are suitable for the games in play. We use an ALOHA-based framework to study the dynamics of the primary market, and an OFDMA-based framework to study the dynamics of the primary-secondary market. Lastly, we provide a simulation study for each model.

A relaying enticement mechanism for wireless CDMA mesh networks

In this letter, we propose an incentivized relaying scheme for CDMA-based wireless mesh networks for broadband Internet access. This scheme is applied to entice the users, i.e., mesh clients, in range of the mesh infrastructure (mesh routers) to relay traffic to those clients that are in range with them, but are out of communication range of the mesh routers. To apply this mechanism, in-range clients participate in a game through which they decide how to allocate their resources. The convergence and fixed point characteristics of this game are investigated in a numerical study