Month Year doc.: IEEE 802.15-08/0xxxxr0 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. 1 Page 1 Kiran Bynam, Samsung

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

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

BAN Applications requiring Ranging Game application Body posture detection Tracking applications

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

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.

Time Of Arrival (TOA) – 1 TOA/TWR – Two way ranging (Single packet exchange) T0 T1 time TOF TResponse TOF Dev A Transmits signal Dev B receives the signal Dev B Respond back to dev A 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

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

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 T1 T’0 T’1 time TOF TResponse TOF TOF TDelay = 2*TResponse TOF Dev A Tx signal Dev B rx signal Dev B Respond back to dev A Dev A rx response from Dev B Dev A Tx signal Dev A rx response from Dev B Dev B rx signal Dev B Respond back to dev A 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

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 A* Transmits signal Dev* B receives the 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

Time Of Arrival (TOA) – 5 TOA Localization (circle geometry): Anchor1 (x1, y1) A3 Anchor3 (x1, y1) A2 Anchor2 (x1, y1) M Mobile Node (xm, ym) Anchors A1, A2 & A3 are centers of circles. Three circles will pass through one common point for a single solution. 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

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 2 Rx signal Anchor 2 Rx signal Anchor 1 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

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.

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

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

Angle of Arrival (AOA) AOA could be an alternative solution to TOA/TDOA Lower requirements in terms of synchronization and clock precision Two anchors are sufficient for 2D-positioning and three for 3D-positioning AOA requires precise calibration at anchor nodes Cost increases with size and size may not be reduced

Comparison chart Ranging Techniques Advantages Disadvantages TOA Highly accurate for wide bands transmission as synchronization accuracy is high   Clock drift issue Clock accuracy in nodes   Clock synchronization is required RSS Less complexity Effected by channel dynamics AOA Localization technique Number of anchors required for 2-D and 3-D positioning are lesser than TOA technique. Multi-path effects changes phase of a signal and can yield large positioning errors. Requires array of antenna

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

Ranging scheme for UWB Hybrid of TOA/TDOA Accuracy of up to 3 cm Code sequences are used for transmission Use of CDMA to allow multiple localizers at same time in same area

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