We integrate a prototype WiFi Time-of-Flight (ToF) ranging and po- sitioning system in the WiSHFUL software platforms and hardware radios for experimental prototyping. Users can have access to ToF measurements as well as computed positions through uni ed pro- gramming interfaces that make possible to investigate innovative positioning and networking solutions

Cordob\ue9s De La Calle, H.

Gallo, P.

Garlisi, D.

Giannoulis, S.

Giustiniano, D.

Moerman, I.

Rea, M.

Maurizio Rea

Hector Cordobes

Domenico Giustiniano

Domenico Garlisi

Pierluigi Gallo

Spilios Giannoulis

Ingrid Moerman

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Poster

Cordobés De La Calle, H.

GARLISI, Domenico

GALLO, Pierluigi

Archivio istituzionale della ricerca - Università di Palermo

Poster: Integration of WiFi ToF Positioning System in the Open,Flexible and Adaptive WiSHFUL ArchitectureMaurizio ReaIMDEA Networks InstituteMadrid, SpainHector CordobesIMDEA Networks InstituteMadrid, SpainDomenico GiustinianoIMDEA Networks InstituteMadrid, SpainDomenico GarlisiCNIT & University of PalermoPalermo, ItalyPierluigi GalloCNIT & University of PalermoPalermo, ItalySpilios GiannoulisIMECGhent, BelgiumIngrid MoermanIMECGhent, BelgiumABSTRACTWe integrate a prototype WiFi Time-of-Flight (ToF) ranging and po-sitioning system in the WiSHFUL software platforms and hardwareradios for experimental prototyping. Users can have access to ToFmeasurements as well as computed positions through unified pro-gramming interfaces that make possible to investigate innovativepositioning and networking solutions.1 INTRODUCTIONResearch on indoor localization techniques has gained an immenseinterest lately, with many contributions such as [3–5, 8] that haveconcretely shown that achieving accurate positioning capabilitiesin indoor areas is possible. However, as of today, there is lack ofaccess to ranging and positioning systems for experimentation. Theavailability of such system would allow to design novel position-ing algorithms and introduce innovate networking protocols thatexploit location data.We take advantage of the flexibility of WiSHFUL architecture [1]and the unified programming interfaces (UPIs) to act on the designof WiFi radio subsystems and integrate a prototype ranging andpositioning system in a modular and platform agnostic architec-ture. The WiSHFUL software architecture allows focusing on novelnetwork programs, without the hassle of setting up a dedicatedtestbed, a key feature that can be hardly find anywhere else. Theintegrated system provides raw Time-of-Flight (ToF) measurementsand position data in near real-time for a number of WiFi nodes asclients.2 WIFI TOF POSITIONING SYSTEMOur WiFi ToF positioning system can estimate in near real-time thelocation based on ToF measurements, and without requiring anyPermission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor profit or commercial advantage and that copies bear this notice and the full citationon the first page. Copyrights for third-party components of this work must be honored.For all other uses, contact the owner/author(s).WiNTECH’17, October 20, 2017, Snowbird, UT, USA© 2017 Copyright held by the owner/author(s).ACM ISBN 978-1-4503-5147-8/17/10.https://doi.org/10.1145/3131473.3133334DBCentral	  Localization	  Unit(CLU)𝐀𝐏𝟏 𝐀𝐏𝟐𝐀𝐏𝐍FWWFB43	  DriverUDP 𝑀𝐴𝐶)*+,-)𝑇𝑜𝐹targetposition(𝑇𝑜𝐹1, . . , 𝑇𝑜𝐹4)Figure 1: Current architecture of WiFi ToF positioning sys-tem [6].input from inertial sensors [6]. In order to compare the performanceof our system with others from academia and industry, our systemhas also participating to the Microsoft Indoor Localization Compe-tition 2016 [2]. The system was ranked 5th out of ten teams in thefinal. 5 APs were deployed over a challenging and uncontrollablespace of more than 500m2, with a final average position accuracyof 3.17m. More APs allow to achieve better accuracy.Figure 1 gives a high level overview of the current architecturefor ranging and positioning. The system is orchestrated by the Cen-tral Location Unit (CLU), that controls the rest of the nodes (APs andtarget devices), computes the ranges and positions, and makes dataavailable to be exploited by other applications through a database.The CLU issues measurement rounds to the APs. Measurementsare scheduled using a time division approach, where only one APat each time can measure the ToF to the target devices.Measurements are performed by eachAP using amodified FWWFfirmware. These measurements may be related to different targets,as the system allows the continuous tracking of multiple targets.The CLU receives raw ToF measurements from the APs. After thisset of measurements is received, the CLU estimates the distancefrom each AP to each intended target. For that, different approacheshave been developed to adapt the algorithms to different scenarios.DBGlobal	  Control	  ProgramCLULocal	  Control	  Program WMPB43	  Driver𝐀𝐏𝟏𝐀𝐏𝟐𝐀𝐏𝐍UPI-­‐N𝑇𝑜𝐹init_local_control(𝐴𝑃+)start_injection(𝑀𝐴𝐶./012.)targetstart_clu (𝑀𝐴𝐶./012.,	  𝐶ℎ𝑖𝑝𝑠𝑒𝑡./012.,	  [𝐴𝑃9, . . , 𝐴𝑃+])	  UDP𝑀𝐴𝐶./012.𝑇𝑜𝐹pos(𝑇𝑜𝐹9, . . , 𝑇𝑜𝐹+)set_hostapd_confUPI-­‐Nget_posFigure 2: Envisioned architecture of WiFi ToF positioningsystem integrated in the WiSHFUL framework.As not all WiFi chipsets behave the same, the database includes in-formation about chipset offset that has been calibrated beforehand.Only one calibration step is needed, and the process does not needto be repeated. Methods to automatically estimate the chipset havebeen investigated and will be integrated in a next version of thesystem.Using the estimated distances, a multi-lateration algorithm isused to make a position estimation. This algorithm makes use theWeighted Non-Linear Least Square (NLLS) techniques to computethe position from this initial value. The NLSS algorithm is imple-mented using the Newton-Gauss method with line-search for thestep-size, a well-known method for this problem. Our implementa-tion takes into account that as a result of quantization errors in therange estimation, divergence problems may occur in the algorithm.As such, we perform pre-filtering of the data to remove the sideeffects of quantization. As for the initial position for the computa-tion, we use the one given by a linear least square (LLS) algorithm,having the advantage of being computationally efficient.3 INTEGRATION OF POSITIONING SYSTEMINWISHFULA high level illustration of the envisioned architecture wherein weintegrate the WiFi ToF ranging and positioning system in WiSH-FUL is shown in Fig. 2. This new architecture allows us to takeadvantage of the versatility of WiSHFUL’s design for experimenta-tion. In WiSHFUL, the Local Control Program (LCP) manages andcontrols the single device, while the Global Control Program (GCP)manages and controls with a group of devices. In our integratedsystem, the LCP controls the deployment-specific Local Monitoring& Configuration Engine. The latter injects traffic to target nodesand gathers raw ToF measurements. In order to achieve the highestflexibility in the proposed architecture, the firmware used in theLocal Monitoring & Configuration Engine is based on the Wire-less MAC Processor (WMP) [7] rather than the modified FWWFfirmware as done so far.The LCP sends the ToF measurements to the GCP in batches. TheGCP forwards the measurements received by NAPs to the CLU, thatis responsible of computing first the distance to the device and thenits position. Experiments from users can be performed remotelyaccessing the w.iLab.2 testbed (covering an area of 66x20.5m),1 withall the APs running the WMP firmware on Alix boards. Nodes canbe either static or dynamic (using Turtlebot II Robotic Platformsin the w.iLab.2 testbed), thus making possible to study variouscompelling scenarios.Users have access to raw ToF measurements as well as computedpositions using unified programming interfaces (UPIs) to investi-gate various applications such as novel positioning algorithms anddesigning location-aware link and networking protocols. The visionis that the capability to exploit positioning information for servingan increasing number of users with a given amount of resources inpower, time and frequency, can help to better manage networks.1http://doc.ilabt.imec.be/ilabt-documentation/ACKNOWLEDGMENTSThis work has been funded by the European Commission in theframework of the H2020 project WiSHFUL (Grant agreement no.645274),REFERENCES[1] H2020 WiSHFUL project. http://www.wishful-project.eu.[2] Microsoft Indoor Localization Competition 2016. https://www.microsoft.com/en-us/research/event/microsoft-indoor-localization-competition-ipsn-2016.[3] Kotaru, M., Joshi, K., Bharadia, D., and Katti, S. Spotfi: Decimeter levellocalization using wifi. In ACM SIGCOMM Computer Communication Review(2015), vol. 45, ACM, pp. 269–282.[4] Lymberopoulos, D., Liu, J., Yang, X., Choudhury, R. R., Handziski, V., andSen, S. A realistic evaluation and comparison of indoor location technologies:Experiences and lessons learned. In Proceedings of the 14th International Conferenceon Information Processing in Sensor Networks (2015), IPSN ’15, ACM, pp. 178–189.[5] Mariakakis, A. T., Sen, S., Lee, J., and Kim, K.-H. Sail: Single access point-basedindoor localization. In Proceedings of the 12th Annual International Conference onMobile Systems, Applications, and Services (2014), MobiSys ’14, ACM, pp. 315–328.[6] Rea, M., Fakhreddine, A., Giustiniano, D., and Lenders, V. Filtering noisy802.11 time-of-flight ranging measurements from commoditized wifi radios.IEEE/ACM Transactions on Networking PP, 99 (2017), 1–14.[7] Tinnirello, I., Bianchi, G., Gallo, P., Garlisi, D., Giuliano, F., and Gringoli,F. Wireless mac processors: Programming mac protocols on commodity hardware.In INFOCOM, 2012 Proceedings IEEE (2012), IEEE, pp. 1269–1277.[8] Vasisht, D., Kumar, S., and Katabi, D. Decimeter-level localization with a singlewifi access point. In Proceedings of the 13th Usenix Conference on NetworkedSystems Design and Implementation (Berkeley, CA, USA, 2016), NSDI’16, USENIXAssociation, pp. 165–178.

Integration of WiFi ToF Positioning System in the Open, Flexible and Adaptive WiSHFUL Architecture

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Integration of WiFi ToF Positioning System in the Open, Flexible and Adaptive WiSHFUL Architecture

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