A Stitch in Time and Frequency Synchronization Saves Bandwidth

Luong, Anh; Hillyard, Peter; Abrar, Alemayehu Solomon; Che, Charissa; Rowe, Anthony; Schmid, Thomas; Patwari, Neal

doi:10.1109/ipsn.2018.00016

Cited by 12 publications

(6 citation statements)

References 20 publications

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“…We use a Decawave DW1000 IR-UWB radio which supports IEEE 802.15.4a, and provide the timestamp of the arrival of the first arriving path [12]. For clock synchronization, we adopt radio frequency synchronization (RFS) method proposed in [13] where one node periodically broadcasts a reference unmodulated signal using a TI CC1200 narrowband transceiver and the other nodes compute carrier frequency offset and adjust their VCTCXO frequency. The CC1200 transceiver is also used to exchange data between nodes.…”

Section: Hardwarementioning

confidence: 99%

Collision Prediction from UWB Range Measurements

Abrar¹,

Luong²,

Spencer³

et al. 2020

Preprint

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The ability to predict, and thus react to, oncoming collisions among a set of mobile agents is a fundamental requirement for safe autonomous movement, both human and robotic. This paper addresses systems that use range measurements between mobile agents for the purpose of collision prediction, which involves prediction of the agents' future paths to know if they will collide at any time. One straightforward system would use known-location static anchors to estimate agent coordinates over time, and use the track to predict collision. Fundamentally, no fixed coordinate system is required for collision prediction, so using only the pairwise range between two agents can be used to predict collision. We present lower bound analysis which shows the limitations of this pairwise method. As an alternative anchor-free method, we propose the friend-based autonomous collision prediction and tracking (FACT) method that uses all measured ranges between nearby (unknown location mobile) agents, in a distributed algorithm, to estimate their relative locations and velocities and predict future collisions between agents. Using analysis and simulation, we show the potential for FACT to achieve equal or better collision detection performance compared to other methods, while avoiding the need for anchors. We then build a network of N ultra wideband (UWB) devices and an efficient multi-node protocol which allows all O(N 2 ) pairwise ranges to be measured in N slots. We run experiments with up to six independent robot agents moving and colliding in a 2D plane and up to four anchor nodes to compare the performance of the collision prediction methods. We show that the FACT method can perform better than either other method but without the need for a fixed infrastructure of anchor nodes.

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Section: Hardwarementioning

confidence: 99%

Collision Prediction from UWB Range Measurements

Abrar¹,

Luong²,

Spencer³

et al. 2020

Preprint

Self Cite

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“…After collecting ranging data by the positioning system, the position of the tag can be determined by solving the nonlinear distance equations. The system dealing with UWB positioning in this paper is based on TOA, the ranging measurements in these transceivers is performed based on the two-way ranging (TWR) in which the positioning system estimates the signal round-trip time (RTT) without a common time reference and eliminates the error due to imperfect synchronization [35,36]. The nonlinear observation model of distance equation is given as [37]:…”

Section: The Nonlinear Least-squares Solution Of Distance Equations Imentioning

confidence: 99%

Bias Analysis of Parameter Estimator Based on Gauss-Newton Method Applied to Ultra-Wideband Positioning

Wang

et al. 2019

Applied Sciences

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Ultra-wideband (UWB) is considered as a promising technology in short-distance indoor wireless positioning due to its accurate time resolution and good penetration through objects. Since the functional model of UWB positioning is nonlinear, the optimal solution is generally estimated by the way of continuous iteration. As an iterative descent method of high efficiency, the Gauss–Newton method is widely used to estimate the position. The nonlinear distance equations are linearized, and the solution can be found iteratively. Therefore, the nonlinear least-squares solution is generally biased even if the observations are normally distributed. In outdoor satellite positioning, the ranging distances are long enough so that the bias caused by nonlinearity is very small. However, in UWB positioning, the relative ranging error is large, and the positioning system is prone to become ill-posed, hence the bias due to nonlinearity is not negligible. In this study, both the statistical factor and geometric factor for bias in the nonlinear least-squares estimator of UWB positioning are discussed. In order to assess whether the linearized model is sufficiently approximate for the positioning estimation, a hypothesis test criterion based on Mahalanobis distance is proposed. The simulation and measurement experiments are performed to analyze the factors affecting the bias in UWB positioning. Experimental results are given to demonstrate that the linearization is valid and the bias in UWB positioning estimation can be neglected for the relatively high measurement precision. Moreover, for a positioning configuration, when the anchors are evenly distributed, the amount of nonlinearity is orthogonal to the ranging space of the design matrix, the UWB positioning estimation tends to be unbiased. Meanwhile, the hypothesis test based on Mahalanobis distance is carried out to determine the validity of the linearized model. When the bias is large for UWB positioning, the bias estimate can be used to correct the estimator to guarantee the unbiasedness for UWB positioning. Furthermore, the correction of parameter estimator bias is more effective in the case of relatively low measurement precision or ill-conditioned configuration.

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“…The Sitara features a single circuit board populated with a Texas Instruments CC1200 transceiver acting as the radio and a lowpower Nordic nRF52840 SoC as its µC. The SoC is equipped with a Bluetooth 5 transceiver to maintain high throughput of the raw IQ samples generated by the Texas Instruments CC1200 transceiver [15,16]. The Sitara relies on a Bluetooth connection for operation.…”

Section: Sitaramentioning

confidence: 99%

Sitara: Spectrum Measurement Goes Mobile Through Crowd-Sourcing

Smith

Luong

Sarkar

et al. 2019

2019 IEEE 16th International Conference on Mobile Ad Hoc and Sensor Systems (MASS)

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Software-defined radios (SDRs) are often used in the experimental evaluation of next-generation wireless technologies. While crowdsourced spectrum monitoring is an important component of future spectrum-agile technologies, there is no clear way to test it in the real world, i.e., with hundreds of users each with an SDR in their pocket participating in RF experiments controlled by, and data uploaded to, the cloud. Current fully functional SDRs are bulky, with components connected via wires, and last at most hours on a single battery charge. To address the needs of such experiments, we design and develop a compact, portable, untethered, and inexpensive SDR we call Sitara. Our SDR interfaces with a mobile device over Bluetooth 5 and can function standalone or as a client to a central command and control server. The Sitara offers true portability: it operates up to one week on battery power, requires no external wired connections and occupies a footprint smaller than a credit card. It transmits and receives common waveforms, uploads IQ samples or processed receiver data through a mobile device to a server for remote processing and performs spectrum sensing functions. Multiple Sitaras form a distributed system capable of conducting experiments in wireless networking and communication in addition to RF monitoring and sensing activities. In this paper, we describe our design, evaluate our solution, present experimental results from multi-sensor deployments and discuss the value of this system in future experimentation. CCS CONCEPTS• Networks → Wireless access points, base stations and infrastructure; • Hardware → Digital signal processing; Sensor devices and platforms.

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A Stitch in Time and Frequency Synchronization Saves Bandwidth

Cited by 12 publications

References 20 publications

Collision Prediction from UWB Range Measurements

Collision Prediction from UWB Range Measurements

Bias Analysis of Parameter Estimator Based on Gauss-Newton Method Applied to Ultra-Wideband Positioning

Sitara: Spectrum Measurement Goes Mobile Through Crowd-Sourcing

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