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Doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 1 IEEE 1588 over 802.11b Afshaneh Pakdaman San Francisco.

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Presentation on theme: "Doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 1 IEEE 1588 over 802.11b Afshaneh Pakdaman San Francisco."— Presentation transcript:

1 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 1 IEEE 1588 over 802.11b Afshaneh Pakdaman San Francisco State University John Eidson Agilent Laboratories, Palo Alto, CA Todor Cooklev San Francisco State University tcooklev@sfsu.edu

2 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 2 Outline Introduction EEE 1588 IEEE 802.11b IEEE 1588 Clock Synchronization over IEEE 802.11b Wireless Local Area Network Conclusions Future work

3 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 3 Clock synchronization is needed in various home, office, and industrial automation applications. Synchronization protocols are used to precisely synchronize independent clocks throughout a distributed system. Synchronization allows transactions between distributed systems to be controlled on time basis. Why do we need to synchronize the clock?

4 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 4 IEEE 1588 IEEE 1588 is a new standard for precise clock synchronization for networked measurement and control systems in the LAN environment. Sub-microsecond synchronization of real-time clocks Intended for relatively localized systems typical of industrial automation and test and measurement environments. Applicable to local areas networks supporting multicast communications (including but not limited to Ethernet)

5 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 5 IEEE 1588 (continued) Simple, administration free installation Support heterogeneous systems of clocks with varying precision, resolution and stability Minimal resource requirements on networks and host components. Develop a supplement to 1588 for operation over WLAN (future work).

6 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 6 1588 Timing Related Messages Four types of timing messages: Sync, Follow_Up, Delay_Req, Delay_Resp Issuing and response to these messages dependent on the ‘state’ of each clock The Sync and Delay_Req messages are time stamped when they sent and received

7 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 7 Detection of Sync messages Application layer Network protocol stack Sync and Delay_Req message detector Physical layer e.g. interface in Ethernet e.g. IEEE 802.11b in Ad Hoc mode

8 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 8 Timing Latency & Fluctuation msecs of delay and fluctuation Application layer Network protocol stack Physical layer < 100 nsecs of delay and fluctuation Application layer Network protocol stack Physical layer Repeater, Switch, or Router Repeaters & Switches: fluctuations ~100ns to usec Routers:fluctuations ~ms

9 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 9 802.11b PHY and MAC layer Data is exchanged between the MAC and the PHY by series of PHY-DATA requests issues by MAC and PHY-DATA. confirm primitives issued by PHY. The PHY layer indicated Last_Symbol_on_Air event to the MAC layer using PHY- TXEND.confirm.

10 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 10 At the other node: The PHY layer indicates the Last_Symbol_On_Air event to the MAC layer using the PHY_RXEND. indication primitive. PHY and MAC layer (continued)

11 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 11 PHY_TXEND.req PHY_TXEND.conf MAC PHY PLCP PHY_TXSTART. req PHY_TXSTART. confirm PHY_DATA.req Time PHY_DATA. confirm PMD_TXPWRLVL.req PMD_RATE.req PMD_ANTSEL.req PMD_TXSTART.req PMD_DATA.req PMD_RATE.req PMD_DATA.req PMD_RATE.req PMD_MODULATION.req PMD_DATA.req PMD_TXEND.req SYNC SFD LENGTH SIGNAL, SERVICE CRC PSDU PHY PMD TX Power RAMP on Scramble start CRC 16 start CRC 16 end TX Power RAMP off PLCP Transmit Procedure ---

12 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 12 Mapping 1588 over 802.11b Processing Delay Jitter between the Transmitter and Receiver devices Delay spread

13 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 13 Mapping 1588 over 802.11b (continued) Time stamp point Last_Symbol_on_Air This indication is observable by all the stations. It is readily available from the PHY layer in the form of either PHY_RXEND indication or PHY_TXEND indication.

14 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 14 LAST DATA BIT SAMPLED TX PORT TIMING TXCLK TX_PE TXD TX_RDY FIRST DATA BIT SAMPLED DATA RX PORT TIMING RXCLK RX_PE MD_RDY RXD Timing Diagram LSBDATA PACKETMSB LSBDATA PACKETMSB

15 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 15

16 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 16

17 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 17 Time interval between TX_RDY on Device A and MD_RDY on Device B falling edge

18 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 18 Time interval between TX_RDY on Device A and MD_RDY on Device B rising edge

19 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 19 Time interval between TX_PE on Device A and RX_PE on Device B falling edge

20 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 20 Time interval between TX_CLK, TX_RDY and MD_RDY falling edge

21 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 21 Time interval between TX_CLK, TX_RDY and MD_RDY falling edge

22 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 22

23 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 23

24 doc.: IEEE 802.11-04/1080r0 Submission September 2004 Todor Cooklev, SF State UniversitySlide 24 Conclusions State the meaning of the results in terms of synchronization, IEEE 1588 can be implemented over WLAN. TX_RDY and MD_RDY Falling edge looks best for implementing 1588. PHY jitter is 500 to 600 ns and the average offset is 7.35 us.


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