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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Ranging as a requirement for BAN and study on existing ranging schemes Date Submitted: May 12, 2008

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Ranging as a requirement for BAN and study on existing ranging schemes Date Submitted: May 12, 2008 Source: Giriraj Goyal, Kiran Bynam, Ranjeet Kumar Patro, Arun Naniyat, Seung-Hoon Park, Noh-Gyoung Kang, Jaeseung Son, EunTae Won Contact: Giriraj Goyal, giriraj.g@samsung.com, Samsung Electronics Voice: +91 80 41819999, E-Mail: giriraj.g@samsung.com Re: [] Abstract: Brief overview of existing ranging techniques Purpose: To identify ranging as a requirement for BAN applications set and present brief study on existing ranging mechanisms. Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual's) or organization's). The material in this document is subject to change in form and content after further study. The contributor's) reserve's) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and in May’08 it would be made publicly available by P802.15.

  2. Agenda • Ranging applications • Ranging as a Requirement criterion for BAN • Existing Ranging and localization Techniques

  3. Ranging applications • GPS based application • Radar applications • Ship navigation • Tracking ‘search & rescue’ • Inventory • Security and surveillance

  4. BAN Applications requiring Ranging • Game application • Body posture detection • Tracking applications

  5. Common Ranging Techniques • Time-of-Arrival (TOA) • TOA/TWR • DTOA • TOA/OWR • TDOA • Received signal strength (RSS) • Angle-of-Arrival (AOA)

  6. Assumptions with ranging techniques • Direct line of sight • Static channel condition • Anchor (reference) nodes and the nodes are static when distances are measured. • Anchor nodes positions are known to each other.

  7. Time Of Arrival (TOA) – 1 • TOA/TWR – Two way ranging (Single packet exchange) T0 T1 time TOF TResponse TOF Dev B Respond back to dev A Dev A Transmits signal Dev B receives the signal Dev A receives response from Dev B • TOF = Time of flight for signal from Dev A to Dev B • TResponse = Turnaround time for Dev B to respond back to Dev A (Prescribed Protocol Delay and/or Processing Time) Distance (between A and B) estimation done by A

  8. Time of Arrival (TOA) - 2 Range estimation with TOA/TWR is affected by : • Relative clock drift between A and B • Clock accuracy in A and B • Prescribed response delay

  9. Time Of Arrival (TOA) – 3 • TWR with Double packet exchange; known as DTOA (Differential Time of Arrival) • DTOA is a modification of TOA/TWR technique, to remove effects of protocol/response delay (turn around time) Random Time Delay T0 T’1 T1 T’0 time TDelay = 2*TResponse TOF TOF TOF TResponse TOF Dev B rx signal Dev A Tx signal Dev A Tx signal Dev A rx response from Dev B Dev B Respond back to dev A Dev A rx response from Dev B Dev B Respond back to dev A Dev B rx signal • TOF = Time of flight for signal from Dev A to Dev B • TResponse = Turnaround time for Dev B to respond back to Dev A (Prescribed Protocol Delay and/or Processing Time) Distance (between A and B) estimation done by A

  10. Time Of Arrival (TOA) - 4 • OWR – One way ranging, If Terminals are synchronized to a common clock, direct OWR can be used. T0 T1 time TOF Dev* B receives the signal Dev A* Transmits signal • TOF = Time of flight for signal from Dev A to Dev B • * Device A and Device B are isochronous Distance (between A and B) estimation done by B

  11. A1 Anchor1 (x1, y1) A2 Anchor2 (x1, y1) M Mobile Node (xm, ym) A3 Anchor3 (x1, y1) • Anchors A1, A2 & A3 are centers of circles. • Three circles will pass through one common point for a single solution. Time Of Arrival (TOA) – 5 TOA Localization (circle geometry): Calculate Algorithm for drawing circle trajectory and finding common point of intersection Estimation • 3 anchors with known positions (at least) are required to retrieve a 2D-position • 4 anchors with known positions (at least) are required to retrieve a 3D-position

  12. Time Of Arrival (TOA) - 6 • TDOA (Time Difference of Arrival) localization is a modification of TOA localization technique T0 Mobile* Tx time TOF 2 Anchor 2* Rx T2 Anchor 2 sends T2 info to Anchor 1 TDOA Estimation TOF 3 Anchor 3* Rx Anchor 3 sends T3 info to Anchor 1 T3 TOF 1 Anchor 1* Rx T1 Mobile Node M Tx signal Anchor 1 Rx signal Anchor 2 Rx signal Anchor 2 Rx signal Reference time • Time of flight information by anchor nodes can be calculated by any of TOA method. • Example shows Time Difference by a anchor node (anchor 1) can be calculated by any reference time if TOA/OWR ranging method

  13. Time Of Arrival (TOA) - 7 TDOA Localization (hyperbola geometry): Calculate A3 Anchor3 (x1, y1) Algorithm for drawing hyperbolic trajectory and finding point of intersection A1 Anchor1 (x1, y1) A2 Anchor2 (x1, y1) M Mobile Node (xm, ym) Estimate Note: 3 anchors with known positions (at least) are required to retrieve a 2D-position • Anchors A1, A2 & A3 are Foci of Hyperbola • Hyperbolas are drawn for locus of M with • and as constant.

  14. Received Signal Strength (RSS) – 1 Data link Processing unit Anchor/reference node Nodes required being located • -Devices calculate ranges to their neighbors • Location is jointly estimated using collective information • Location Accuracy/ Range Extension

  15. Received Signal Strength (RSS) – 2 • RSS is an alternative solution to TOA/TDOA as it lowers requirements in terms of synchronization and clock precision • The Disadvantages are – • RSSI requires precise channel behavioral model • This technique is sensitive to channel inconsistency

  16. Angle of Arrival (AOA) AOA could be an alternative solution to TOA/TDOA -Lower requirements in terms of synchronization and clock precision • AOA requires precise calibration at anchor nodes • Cost increases with size and size may not be reduced

  17. Comparison chart

  18. Ranging challenges • MAC role/computation complexities • Energy attenuation • Multi-path channel • Clock synchronization

  19. Reference • 15-04-0581-07-004a-ranging-subcommittee-final-report.doc • http://rfdesign.com/mag/radio_uwb_technology_locationaware/

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