doc.: ieee 802.11-04/1080r0 submission september 2004 todor cooklev, sf state universityslide 1 ieee...

September 2004

Todor Cooklev, SF State University

Slide 1

doc.: IEEE 802.11-04/1080r0

Submission

IEEE 1588 over 802.11b

Afshaneh PakdamanSan Francisco State University

John Eidson Agilent Laboratories, Palo Alto, CA

Todor CooklevSan Francisco State University

[email protected]

September 2004


Slide 2

doc.: IEEE 802.11-04/1080r0

Submission

Outline

• Introduction• EEE 1588• IEEE 802.11b• IEEE 1588 Clock Synchronization over

IEEE 802.11b Wireless Local Area Network

• Conclusions• Future work

September 2004


Slide 3

doc.: IEEE 802.11-04/1080r0

Submission

• 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?Why do we need to synchronize the clock?

September 2004


Slide 4

doc.: IEEE 802.11-04/1080r0

Submission

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)

September 2004


Slide 5

doc.: IEEE 802.11-04/1080r0

Submission

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).

September 2004


Slide 6

doc.: IEEE 802.11-04/1080r0

Submission

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

September 2004


Slide 7

doc.: IEEE 802.11-04/1080r0

Submission

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

September 2004


Slide 8

doc.: IEEE 802.11-04/1080r0

Submission

Timing Latency & Fluctuation

msecs of delay and fluctuation

Application layer


Physical layer< 100 nsecs of delay

and fluctuation

Application layer


Physical layer

Repeater, Switch, or

RouterRepeaters & Switches:fluctuations ~100ns to usecRouters:fluctuations ~ms

September 2004


Slide 9

doc.: IEEE 802.11-04/1080r0

Submission

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.

September 2004


Slide 10

doc.: IEEE 802.11-04/1080r0

Submission

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)

September 2004


Slide 11

doc.: IEEE 802.11-04/1080r0

Submission

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

SY

NC

SF

DLE

NG

TH

SIG

NA

L, SE

RV

ICE

CR

CP

SD

U

PHY

PMD

TX Power RAMP on Scramble start

CRC 16 start

CRC 16 end

TX Power RAMP

off

PLCP Transmit Procedure

------

---

September 2004


Slide 12

doc.: IEEE 802.11-04/1080r0

Submission

Mapping 1588 over 802.11b

• Processing Delay

• Jitter between the Transmitter and Receiver devices

• Delay spread

September 2004


Slide 13

doc.: IEEE 802.11-04/1080r0

Submission

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.

September 2004


Slide 14

doc.: IEEE 802.11-04/1080r0

Submission

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

LSB DATA PACKET MSB

LSB DATA PACKET MSB

September 2004


Slide 15

doc.: IEEE 802.11-04/1080r0

Submission

September 2004


Slide 16

doc.: IEEE 802.11-04/1080r0

Submission

September 2004


Slide 17

doc.: IEEE 802.11-04/1080r0

Submission

Time interval between TX_RDY on Device A and MD_RDY on Device B falling edge

September 2004


Slide 18

doc.: IEEE 802.11-04/1080r0

Submission

Time interval between TX_RDY on Device A and MD_RDY on Device B rising edge

September 2004


Slide 19

doc.: IEEE 802.11-04/1080r0

Submission

Time interval between TX_PE on Device A and RX_PE on Device B falling edge

September 2004


Slide 20

doc.: IEEE 802.11-04/1080r0

Submission

Time interval between TX_CLK, TX_RDY and MD_RDY falling edge

September 2004


Slide 21

doc.: IEEE 802.11-04/1080r0

Submission

Time interval between TX_CLK, TX_RDY and MD_RDY falling edge

September 2004


Slide 22

doc.: IEEE 802.11-04/1080r0

Submission

Time interval TX_RDY and MD_RDYfalling edge

0

20

40

60

80

100

120

Time Microsecond

Da

ta s

am

pli

ng

10

00

.00%

20.00%

40.00%

60.00%

80.00%

100.00%

120.00%

Frequency

Cumulative %

September 2004


Slide 23

doc.: IEEE 802.11-04/1080r0

Submission

Time interval TX_RDY and MD_RDYfalling edge

050

100150200250300350400450500

Time Microsecond

Da

ta s

am

pli

ng

10

00

.00%

20.00%

40.00%

60.00%

80.00%

100.00%

120.00%

Frequency

Cumulative%

September 2004


Slide 24

doc.: IEEE 802.11-04/1080r0

Submission

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.

doc.: ieee 802.11-04/1080r0 submission september 2004 todor cooklev, sf state universityslide 1 ieee...

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