This thesis contributes a new system in support of large scale people-centric sensing applications. Over the last decade, wireless sensor networking has developed into ar-guably the most active area in networking research. The state of the art largely follows an application-specific philosophy, where modest numbers of static wirelessly-connected sensor nodes are placed in the target environment in support of a single application. In a properly engineered network, sensor nodes are well-equipped and well-positioned to best provide the connectivity and sensing required by the application. Such networks are ill-suited, however, to the demands of a new class of applications focused on providing sensor information about people, their daily lives, and their environments. These people-centric applications require the ability to both sample very detailed information on the individual scale, and to provide a view of the urban landscape- a very large scale challenge. A new approach is required. Therefore, we propose the novel MetroSense architecture in support of people-centric sensing. While incorporating static infrastructure elements, to get large scale sensing cover-age the architecture primarily makes use of devices with embedded sensors, such as mobile

Breadcrumb systems (BCS) have been proposed to aid firefighters inside buildings by communicating their physiological parameters to base stations outside the buildings. In this paper, we describe the design, implementation and evaluation of an automatic and robust breadcrumb system for firefighter applications. Our solution includes a breadcrumb dispenser with an optimized link estimator that is used to decide when to deploy breadcrumbs to maintain reliable wireless connectivity. The solution includes accounting for realities of buildings and dispensing such as the height difference between where the dispenser is worn and the floor where the dispensed nodes are found. We also include adaptive power management to maintain link quality over time. Experimental results from our study show that compared

We present empirical measurements of the packet delivery performance of the latest sensor platforms: Micaz and Telos motes. In this paper, we present observations that have implications to a set of common assumptions protocol designers make while designing sensornet protocols – specifically – the MAC and network layer protocols. We first distill these common assumptions in to a conceptual model and show how our observations support or dispute these assumptions. We also present case studies of protocols that do not make these assumptions. Understanding the implications of these observations to the conceptual model can improve future protocol designs.

Abstract. Wireless sensor network protocols and applications, including those used for localization, topology control, link scheduling, and link quality estimation, make extensive use of Received Signal Strength Indication (RSSI) measurements. In this paper we show that inaccuracies in the RSSI values reported by widely used 802.15.4 radios, such as the CC2420 and the AT86RF230, have profound impact on these protocols and applications. Furthermore, we experimentally derive the response curves which translate actual RSSI values to the raw RSSI readings that the radios report and show that they contain non-linear and even noninjective regions. Fortunately, these curves are consistent across radios of the same model, making RSSI calibration practical. We present a calibration mechanism that removes the artifacts in the raw RSSI measurements, including ambiguities created by the non-injective regions in the response curves, and generates calibrated RSSI readings that are linear. This calibration removes many of the outliers generated when raw RSSI readings are used to estimate Signal to Noise (and Interference) ratios, estimate radio model parameters, and perform RF-based localization. 1

This paper presents the design and deployment experience of an air-dropped wireless sensor network for volcano hazard monitoring. The deployment of five stations into the rugged crater of Mount St. Helens only took one hour with a helicopter. The stations communicate with each other through an amplified 802.15.4 radio and establish a self-forming and self-healing multi-hop wireless network. The distance between stations is up to 2 km. Each sensor station collects and delivers real-time continuous seismic, infrasonic, lightning, GPS raw data to a gateway. The main contribution of this paper is the design and evaluation of a robust sensor network to replace data loggers and provide real-time long-term volcano monitoring. The system supports UTCtime synchronized data acquisition with 1ms accuracy, and is online configurable. It has been tested in the lab environment, the outdoor campus and the volcano crater. Despite the heavy rain, snow, and ice as well as gusts exceeding 120 miles per hour, the sensor network has achieved a remarkable packet delivery ratio above 99 % with an overall system uptime of about 93.8 % over the 1.5 months evaluation period after deployment. Our initial deployment experiences with the system have alleviated the doubts of domain scientists and prove to them that a low-cost sensor network system can support real-time monitoring in extremely harsh environments.

We present empirical measurements of the packet delivery performance of the latest sensor platforms: Micaz and Telos motes. In this article, we present observations that have implications to a set of common assumptions protocol designers make while designing sensornet protocols— specifically—the MAC and network layer protocols. We first distill these common assumptions in to a conceptual model and show how our observations support or dispute these assumptions. We also present case studies of protocols that do not make these assumptions. Understanding the implications of these observations to the conceptual model can improve future protocol designs.

At ever-increasing rates, we are using wireless systems to communicate with others and retrieve content of interest to us. Current wireless technologies such as WiFi or Zigbee use forward error correction to drive bit error rates down when there are few interfering transmissions. However, as more of us use wireless networks to retrieve increasingly rich content, interference increases in unpredictable ways. This results in errored bits, degraded throughput, and eventually, an unusable network. We observe that this is the result of higher layers working at the packet granularity, whereas they would benefit from a shift in perspective from whole packets to individual symbols. From real-world experiments on a 31-node testbed of Zigbee and softwaredefined radios, we find that often, not all of the bits in corrupted packets share fate. Thus, today’s wireless protocols retransmit packets where only a small number of the constituent bits in a packet are in error, wasting network resources. In this dissertation, we will describe a physical layer that passes information

Abstract—The dynamic nature of wireless communication and the stringent energy constraints are major challenges for the design of low-power wireless sensor network applications. The link quality of a wireless link is known for its great variability, dependent on the distance between nodes, the antenna’s radiation characteristic, multipath, diffraction, scattering and many more. Especially for indoor and urban deployments, there are numerous factors impacting the wireless channel. In an extensive experimental study contained in the first part of this paper, we show the magnitude of this problem for current Wireless Sensor Networks (WSNs) and that based on the overall connectivity graph of a typical multihop WSN, a large portion of the links actually exhibit very poor characteristics. We present a pattern based estimation technique that allows assessing the quality of a link at startup and as a result to construct an optimal neighbor table right at the beginning using a minimum of resources only. Our estimation technique is superior compared to other approaches where protocols continue to decide on the fly which links to use expending valuable energy both for unnecessary retransmissions and recursive link estimation. I.

Neighborhood relations are changing over time in wireless sensor networks due to different hardware or environmental effects. These effects and memory limitations require a balanced neighborhood management to ensure agility, stability, symmetry, and connectivity. The proposed neighborhood management protocol Mahalle is optimized with regard to these four criteria. Agility and stability are achieved by ALE, a new adaptive link estimator. 1.

The recent development of control applications over Wireless Sensor Networks (WSNs) imposes new approaches to the protocol design. These networks are characterized by the scarcity of energy supply and processing capabilities. Furthermore, existing protocol solutions are often based on the traditional OSI model, where communication layers are not optimized to support efficiently the reliability and latency requirements imposed by control applications. The critical aspects of wireless transmission have lead to a lack of protocols that are able to guarantee latency and quality of service under unreliable channel conditions. In this thesis, we design and implement a cross-layer protocol for WSNs in industrial automation, the Extended Randomized Protocol, which considers jointly physical layer aspects (as power control and duty cycling strategies), randomized MAC and routing. The protocol can be considered and extension of an already existing Randomized Protocol, and it is designed with the objective to maximize the network lifetime under the constraints of error rate and end-to-end delay in the packet delivery. As a relevant part of our activity, we have provided a complete test bed implementation of the protocol building a WSN with TinyOS and a large number of Moteiv’s Tmote Sky wireless sensors. An experimental campaign has been conducted in order to test the validity of the protocol solution we propose. Experimental results show that the protocol achieves the required successful packet reception rate and the latency constraints while minimizing the energy consumption. Despite the fact that improving solutions are necessary to take into account the problem of duplicated packets, our protocol solution seems to be a good candidate for WSN in industrial automation. i