Due to the frequent topology changes in most wireless networks, low-power Neighbor Discovery (ND) is essential for many Wireless Sensor Networks (WSNs) and Internet of Things (IoT) applications. In this work, we present UWB-ND, a low-power ND protocol for ultra-wideband (UWB) radio networks that are becoming increasingly popular in IoT applications. To conserve energy, these IoT applications typically rely on other low-power radio technology such as Bluetooth Low Energy (BLE) for ND, requiring the integration of auxiliary radios in all nodes. Utilizing specific characteristics of UWB radios such as efficient Channel Activity Detection (CAD) and varying preamble modulation, UWB-ND introduces a low-power ND approach specific to UWB radios. Our evaluation shows that UWB-ND can reduce ND power consumption by 50%, compared to the state-of-the-art PI-based approach.

Positioning plays an important role in many IoT applications. Ultra-wideband (UWB)-based positioning is an alternative to GPS in indoor environments due to its multipath resilience and its accuracy and precision. In the presence of a large number of targets to localize, conventional UWB localization fails to provide a practical location update rate. UWB concurrency in conjunction with self-localization has been used in both time-based and phase-based localization making the targets to localize (tags), a relatively passive device with the sole role of receiving wireless packets and calculating its own location. More recently, phase-based concurrent angle estimation also offloaded the hardware complexity and cost to the anchors instead of the tags. In this work, our anchor-oriented approach combines inter-anchor and intra-anchor concurrency for phase-based localization but also allows time-based localization. Our experimental evaluation on a testbed consisting of Decawave platform shows that our technique is not only practical but also performant.

Ultra-wideband (UWB) is becoming a major localization technology enabler for the indoor environment. Traditional localization systems rely on time-of-arrival (ToA)-based methods such as two-way ranging (TWR) and time difference of arrival (TDoA). Such solutions cannot scale due to interference from multiple devices sharing the same part of the wireless spectrum. One solution is to use concurrent transmissions for a more efficient use of air time. Concurrency-based localization systems that utilize ToA cannot satisfy the accuracy requirements of many applications due to hardware time scheduling limitations. Angle of Arrival (AoA) is a promising solution that can provide scalability and accuracy when used in a concurrent transmission scheme. UWB radio platforms like Decawave DWM1002 with dual-UWB-chip design have made it possible to accurately measure AoA by calculating the phase difference of arrival (PDoA). State-of-the-art AoA estimation has then been extended to build self-localization systems with an unlimited number of tags and to handle multiple sources at the same time. These methods require tags with dual-chip design which adds cost and complexity. In this paper, we investigate the idea of estimating AoA on single-chip (single-antenna) tags receiving concurrent UWB signals from dual-chip anchors (intra-anchor concurrency). We call our system Single-Antenna AoA Estimation (SA-AoA). As opposed to inter-anchor concurrency, intra-anchor concurrency consists of receiving two concurrent packets from two different chips of the same anchor. By estimating AoA on single-chip tags, SA-AoA reduces the design complexity and the cost of tags by at least 50%. Our results suggest that the single-antenna AoA can achieve performance similar to dual-antenna AoA estimation.

Pose estimation is a building block for many location-based applications, such as safety applications in a construction site. Ultra-WideBand (UWB) Radios have been widely used for localization and can be used in pose (location and orientation angle of the object) estimation primarily because of the accuracy with which these radios can estimate the arrival time of radio signals. Current UWB pose estimation solutions do not perform adequately in Non-Line of Sight (NLoS) conditions. Some of these existing solutions in pose estimation rely on two or more types of sensors to tackle the NLoS challenge. These methods suffer from data fusion complexity, making the system not generalizable and limited to some specific simple environments, such as labs. In this paper, we propose ViPER, a UWB-based pose estimating system using only UWB radios. Our goal is to reduce the effects of the NLoS without the inclusion of any auxiliary sensors. ViPER uses low-pass filter, anchor and reference selection method to reduce the effect of NLoS in the measurements. It also estimates the pose of the entities using an optimization problem. We have evaluated ViPER in real- world highway construction and parking lot setting. We find that it improves the average packet reception ratio by 117% and decreases the error rate by 70% over the state of the art in Non-Line of Sight situation.

The angle of arrival (AoA) estimation is one of the commonly used techniques for indoor localization. Ultrawideband (UWB) radios facilitate AoA estimation through the measurement of the phase difference of arrival (PDoA) at multiple receiver antennas. Concurrent transmissions in UWB radios aim to increase the efficiency of localization systems by exploiting wireless interference. This paper first investigates the feasibility of AoA estimation with UWB radios in a concurrent scheme. State-of-the-art UWB indoor localization solutions use time difference of arrival (TDoA) in a concurrent scheme. These solutions rely on accurate timestamping of the concurrently received packets. However, due to the scheduling uncertainty of the UWB transmitter platform used in this area, an unavoidable timing jitter of 8 ns causes up to 2.4 m of the localization error. Therefore, the accuracy of solutions based on concurrent TDoA relies on additional timestamp correction, which adds to the complexity of the system. Our results show that concurrent AoA estimation remains unaffected by the transmitter scheduling uncertainties. AoA-based localization techniques face two main challenges: (1) front-back ambiguity of AoA for antenna array of size two; and (2) AoA measurement device's unknown tilting. This paper then presents AnguLoc, an efficient and scalable indoor localization system that makes use of concurrent AoA estimation to reduce the number of required packet exchanges. AnguLoc uses an Angle Difference of Arrival (ADoA) technique, also generalizable to sequential AoA, to overcome the front-back angle measurement ambiguity problem, and to work with unknown tag tilting. We evaluate AnguLoc in an office environment on a recently introduced platform, Decawave PDoA node (DWM1002). Our results show that AnguLoc is 4 times faster than sequential AoA and improves the localization accuracy by up to 44.33% compared to state-of-the-art concurrency-based indoor localization solutions without relying on additional timestamp correction.

Clean Cooking is essential to maintain a healthy lifestyle. However, many people in developing economies do not have access to clean cooking. To promote clean cooking, first, we need to understand the cooking patterns in the household, and second, design interventions over those patterns. We also need to understand the grid and power supply readiness to support electricity-based clean cooking initiatives. In this paper, we provide an affordable and scalable energy monitoring system solution to instrument the cooking pattern in peri-urban Nepal. Our design consists of off-the-shelf power meters, minor changes in sockets/wiring at homes, data upload using cellular radio, and standard dashboard and analysis in the cloud. We deployed the system in 35 households in peri-urban Nepal and collected data from early August until the middle of October 2019. Our preliminary study indicates: 1) Cellular data access is a viable way to upload instrumentation data to the Internet in studies of this nature. 2) Data integrity and reliability are closely coupled with user behaviors and cellular reliability. 3) Deployment can be centralized instead of distributed, and cost can be affordable. 4) Continuous data collection from about three months shows poor power quality in the area.

Concurrent ranging exploits features of the channel impulse response (CIR) of received packets to allow an ultra-wideband (UWB) initiator node to concurrently measure the distance from multiple UWB responder nodes. Concurrent ranging enables indoor localization systems to reduce the required number of ranging packet exchanges, leading to less air utilization and energy consumption, and faster location update rate. Despite the research in this area, it is still challenging to build a practical UWB concurrent ranging system for real-world environments. Existing concurrent ranging solutions are not scalable because (1) they require strong assumptions about either the responders or the environment and (2) they fail to maintain the ranging accuracy in longer distances due to errors caused by clock drift. In this work, we present R3, a Reflection Resilient Ranging solution, to address these critical scalability issues in UWB concurrent ranging. R3 makes use of the difference in the time deviation of ranging signals to detect concurrent responders and it is equipped with a clock skew correction method that enables accurate concurrent ranging in long distances. We evaluate R3 using Decawave DW1000 UWB chip by deploying the radio nodes in an office environment. Our results show that R3 effectively detects concurrent ranging peaks in the presence of strong multipath. When we equip R3 with a clock skew correction method, it reduces the concurrent ranging error induced by clock drift by at least 54 cm in long distances (>50 m) and by more than 97% in average when the ranging response delay is arbitrarily large.

Ultra-wideband signals have been used for accurate ranging and localization application during the last few years. State of the art UWB ranging applications can estimate the distances with less than a 5 cm error. Existing localization solutions create their own ranging traffic. In this paper, we investigate the possibility of piggybacking the information required by ranging application over existing network traffic. In addition, we study the feasibility of piggybacking of sensing information over ranging traffic and finally, we propose our technique for Simultaneous Ranging and Communication (SRAC) in UWB networks which adaptively changes the ranging mode from active to passive by using either ranging traffic or sensing traffic to accomplish the ranging and sensing goals while reducing the network traffic to minimum possible. We integrated our proposed solution to RIOT operating system and evaluated its performance over a mesh of UWB-enabled nodes. Our results indicate almost 40% reduction in network traffic.

The growth of the Internet of Things and the trends to deploy more sensors everywhere has led to search for cost effective ways to connect the devices to the Internet. In the most common network architecture for home IoT, the devices use low-power wireless or WiFi to connect to an AP and access the Internet backend. We present a study on the feasibility and efficiency of an alternate network architecture for home IoT. In the proposed architecture, sensors and devices are directly attached to WiFi access points and utilize the computing resources of WiFi APs. We design and implement several sensing applications based on the proposed architecture and report on the performance and limitations of the approach. We find that the proposed architecture allows WiFi APs to become the computational, networking, and storage host for sensing applications without degrading the AP's primary function of providing Internet access to the home users.