1. doc.: IEEE 15-08-0426-02-004e SubmissionSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Time Synchronization for IEEE802.15.4e MAC] Date Submitted: [July, 2008] Source: [ChangSub Shin, Wun-Cheol Jeong, Soyoung Hwang, Anseok Lee, Seong-Soon Joo] Company [ETRI] Address [161 Gajeong-dong Yuseong-gu, Daejeon, Korea] Voice:[+82-42-860-1668], FAX: [+82-42-869-1712], E-Mail:[shincs@etri.re.kr] Re: [IEEE P802.15.4e Call For proposal] Abstract:[This document proposes time synchronization solution for IEEE802.15.4e MAC] Purpose:[This document is a response to call for preliminary proposals] 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 may be made publicly available by P802.15. July 2008 ChangSub Shin et al

2. doc.: IEEE 15-08-0426-02-004e SubmissionChangSub Shin et alSlide 2 Time Synchronization for IEEE802.15.4e MAC ChangSub Shin, Wun-Cheol Jeong, Soyoung Hwang, Anseok Lee, Seong-Soon Joo ETRI July 2008 This work has been supported by the Ministry of Knowledge Economy (MKE) of the Republic of Korea under Grants 2008-F-052.

3. doc.: IEEE 15-08-0426-02-004e Submission Beacon enabled mode Only for tree topology using StartTime value can’t support mesh topology Beacon scheduling algorithm is required in case of collision, beacon frame is lost Traffic overhead with periodic beacon frames Non beacon mode Can’t support TDMA Require long idle listening high power consumption Time Synchronization with IEEE802.15.4-2006 MAC July 2008 ChangSub Shin et alSlide 3

4. doc.: IEEE 15-08-0426-02-004e Submission Considerations Network-Wide Time Synchronization with beacon without beacon operate in multi-hop mesh topology peer-to-peer communication Simple and Reliable guarantee time accuracy within error boundary Robust in change of topology Time Synchronization for IEEE802.15.4e MAC July 2008 ChangSub Shin et alSlide 4

5. doc.: IEEE 15-08-0426-02-004e Submission Contention based Beacon with Adjusting Sync Offset (CB- ASO) CSMA/CA before sending a beacon frame Inform the beacon sync offset with beacon frame Receiver adjusts the next start time of beacon using sync offset Network-Wide Time Synchronization with Beacon (1/1) July 2008 ChangSub Shin et alSlide 5 Active DurationInactive Duration back-off sync offset Beacon Sync Offset

6. doc.: IEEE 15-08-0426-02-004e Submission Directional Time Diffused Synchronization (DTDS) Sending timestamp in one direction with Sync frame Relaying Sync frame with implicit ACK Refrain backward flooding with the depth of hopping offer the information of superframe structure Network-Wide Time Sync without Beacon (1/6) July 2008 ChangSub Shin et alSlide 6 A C B D F G IH J E 1-hop 2-hop 3-hop Sync-source Frame Control Destination Address Source Address Superframe structure Broadcast- Ack Address Hop- distance count Sequence Num timestamp broadcast Sync Frame

7. doc.: IEEE 15-08-0426-02-004e Submission Time Stamp and Clock Adjusting Estimated sending time MAC-PHY interface delay time + PHY delay time use timestamp defined in IEEE802.15.4-2006 Clock compensation Using simple liner-regression Network-Wide Time Sync without Beacon (2/6) July 2008 Backoff MAC Insert Timestamp value (interface delay + PHY modulation delay) CCAModulation and TX PHY Modulation and TX PHY Sender Receiver Get Timestamp value ChangSub Shin et alSlide 7

8. doc.: IEEE 15-08-0426-02-004e Submission Merits Simple Robust in failure of device Independent on network topology Flexible and adaptable Low traffic overhead Low synchronization error Support of global time information Network-Wide Time Sync without Beacon (3/6) July 2008 ChangSub Shin et alSlide 8

9. doc.: IEEE 15-08-0426-02-004e Submission Simple time sync test Hardware platform MCU : MSP430 RF : CC2420 Oscillator max skew : 20 ppm Synch packet interval : every 4 minute test test packet interval : every 1.1 second test Network-Wide Time Sync without Beacon (4/6) July 2008 ChangSub Shin et al

10. doc.: IEEE 15-08-0426-02-004e Submission Design issues Clock error value Time duration of basic time slot Error boundary Guard time of basic time slot Re-synchronization interval Network-Wide Time Sync without Beacon (5/6) July 2008 ChangSub Shin et al

11. doc.: IEEE 15-08-0426-02-004e Submission Design time slot unit 2400–2483.5 MHz O-QPSK PHY : max 133 bytes Preamble : 4 bytes SFD : 1 bytes PHR : 1 bytes Max PSDU size : 127 bytes Pure max Tx time => 4.256 ms (133 bytes) We have to consider proper value in implementation => 1 tx + turn around time + 1 ack + 2 guard time Example value of slot unit => 625 symbols (10ms in 2.4) Network-Wide Time Sync without Beacon (6/6) July 2008 ChangSub Shin et al

12. doc.: IEEE 15-08-0426-02-004e Submission Thank you very much for your attention Any Questions? ChangSub Shin et alSlide 12