Jan 2004

Broady Cash, ARINC

Slide 1

doc.: IEEE 802.11-04/0142r0

Submission

WAVE High Speed Testing

Wireless Access in Vehicular Environments

for the 5.9 GHz band

Jan 2004

Broady Cash, ARINC

Slide 2

doc.: IEEE 802.11-04/0142r0

Submission

Background

• Repeat testing for FreeSpace and Atheros 802.11a (not R/A)

• Testing in July showed failures with not enough explanation about the cause(s)

• Emphasis should be on equal dB margin zones, not equal size zones

Jan 2004

Broady Cash, ARINC

Slide 3

doc.: IEEE 802.11-04/0142r0

Submission

Test Description

• Testing performed at Maryland International Raceway, Budds Creek, MD.

• RSU antenna mounted on cherry picker.

• OBU equipped vehicle makes 10 passes through the zone at 35, 60, 80, 100, & 120 mph.

Jan 2004

Broady Cash, ARINC

Slide 4

doc.: IEEE 802.11-04/0142r0

Submission

Budds Creek

Jan 2004

Broady Cash, ARINC

Slide 5

doc.: IEEE 802.11-04/0142r0

Submission

RSU Antenna

Jan 2004

Broady Cash, ARINC

Slide 6

doc.: IEEE 802.11-04/0142r0

Submission

OBU Antenna

Jan 2004

Broady Cash, ARINC

Slide 7

doc.: IEEE 802.11-04/0142r0

Submission

Antenna Positions

July• RSU Antenna Height:

19 feet 5 inches• RSU bore sight angle:

20 Deg. from vertical• OBU Antenna Height:

4 feet• OBU bore sight angle:

25° from horizontal

August• RSU Antenna Height:

19 feet 9 inches• RSU bore sight angle:

20 Deg. from vertical• OBU Antenna Height:

4 feet• OBU bore sight angle:

35° from horizontal

Jan 2004

Broady Cash, ARINC

Slide 8

doc.: IEEE 802.11-04/0142r0

Submission

Communication Zone (CZ)July

• Wanted: same size CZ ~ 12-15 feet

• Atheros:

Attenuation: 42 dB

CZ ~13 feet• FreeSpace:

Attenuation: 29 dB

CZ ~15 feet

August• Wanted: equal dB margin

zones ~ 5 dB• Result: very different zones

(6 ft. vs. 14 ft.)Compromise:• Atheros : attn 26dB,

(15 dB margin)CZ ~20 ft.

• FreeSpace: attn 20dB(19 dB margin)CZ ~18 ft.

• Light beams used to limit CZ to 12 ft.

Jan 2004

Broady Cash, ARINC

Slide 9

doc.: IEEE 802.11-04/0142r0

Submission

Basic Protocol

BST

VST

Sleep

RSU OBU

Jan 2004

Broady Cash, ARINC

Slide 10

doc.: IEEE 802.11-04/0142r0

Submission

FreeSpace Protocol Details

• Service Channel protocol with ACK• BST transmitted in all 20 slots of a frame (L2) .• When the OBU receives the BST, a VST is

returned, in all slots of a single frame (L2).• If a Sleep is not received after 200 polls, the

OBU retransmits the VST (L7). If Sleep is not received within 16 msec of the BST, the “try” is terminated.

Jan 2004

Broady Cash, ARINC

Slide 11

doc.: IEEE 802.11-04/0142r0

Submission

Atheros Protocol Details

• DCF (ACK inherent)• RSU L2 transmits the BST up to 7 times (until

ACK)• When the OBU receives the BST, a VST is

returned. Up to 7 L2 attempts (until ACK)• If a Sleep is not received after 200 polls, the

OBU (L7) retransmits the VST. If Sleep is not received within 16 msec of the BST, the “try” is terminated.

Jan 2004

Broady Cash, ARINC

Slide 12

doc.: IEEE 802.11-04/0142r0

Submission

Measurements (35 to 100 mph)

• Nr of Tries – nr of L7 BST’s between light beam and final sleep

• Access Time – first light beam to first BST received at OBU

• Transaction Time – final BST to final sleep received at OBU

• Communication Time – first BST to final sleep received at OBU

Jan 2004

Broady Cash, ARINC

Slide 13

doc.: IEEE 802.11-04/0142r0

Submission

Measurements (120 mph)

• Nr of Tries – nr of L7 BST’s between light beam and final sleep

• Access Time – first light beam to first BST transmitted from RSU

• Transaction Time – final BST to final sleep transmitted from RSU

• Communication Time – first BST to final sleep transmitted from RSU

Jan 2004

Broady Cash, ARINC

Slide 14

doc.: IEEE 802.11-04/0142r0

Submission

Association

• FreeSpace requires association before transaction– RSU signal manually switched to “road coverage”

antenna until just before the zone reached, then signal restored to spot.

• Atheros OBU was “hardwired” to assume association with RSU complete

Jan 2004

Broady Cash, ARINC

Slide 15

doc.: IEEE 802.11-04/0142r0

Submission

Results

Jan 2004

Broady Cash, ARINC

Slide 16

doc.: IEEE 802.11-04/0142r0

Submission

ETC Scorecard

FreeSpace Atheros

Speed Runs Success Runs Success

35 10 10 10 10

60 10 10 10 10

80 10 10 10 10

100 10 10 10 10

120 10 10 10 10

Jan 2004

Broady Cash, ARINC

Slide 17

doc.: IEEE 802.11-04/0142r0

Submission

Number of Trials: FS, Atheros

FreeSpace• 49/50 runs succeeded

with one L7 BST try

• 1 run at 35 mph needed two L7 BST tries to complete the transaction

• OBU Did not receive first BST

Atheors• 49/50 runs succeeded

with one L7 BST try

• 1 run at 100 mph needed two L7 BST tries to complete the transaction

• OBU Did not receive first BST

Jan 2004

Broady Cash, ARINC

Slide 18

doc.: IEEE 802.11-04/0142r0

Submission

FreeSpace Access Time

FreeSpace Access Time

0

2

4

6

8

10

12

14

16

18

20

0 20 40 60 80 100 120 140

Vehicle Speed

Acc

ess

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 19

doc.: IEEE 802.11-04/0142r0

Submission

FreeSpace Access Time - Detail

FreeSpace Access Time - Detail

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100 120 140

Vehicle Speed

Acc

ess

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 20

doc.: IEEE 802.11-04/0142r0

Submission

Atheros Access Time

Atheros Access Time Data

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Vehicle Speed

Acc

ess

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 21

doc.: IEEE 802.11-04/0142r0

Submission

Atheros Access Time – Detail

Atheros Access Time - Detail

0

0.5

1

1.5

2

2.5

0 20 40 60 80 100 120 140

Vehicle Speed

Acc

ess

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 22

doc.: IEEE 802.11-04/0142r0

Submission

Access Time: Detail Histograms

0.5 1 1.5 2 2.5 3 3.50

5

10

15

20

25

Occu

rrenc

es

F r e e S p a c e

T i m e ( m s e c )0.5 1 1.5 2 2.5 3 3.50

5

10

15

20

25

T i m e ( m s e c )

Occu

rrenc

es

A t h e r o s

FreeSpace Atheros

Jan 2004

Broady Cash, ARINC

Slide 23

doc.: IEEE 802.11-04/0142r0

Submission

FreeSpace Transaction Time

FreeSpace Transaction Time

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140

Vehicle Speed

Tra

nsa

ctio

n T

ime

(mse

c)

Series1

Jan 2004

Broady Cash, ARINC

Slide 24

doc.: IEEE 802.11-04/0142r0

Submission

Atheros Transaction Time

Atheors Transaction Time

0

2

4

6

8

10

12

0 20 40 60 80 100 120 140

Vehicle Speed

Tra

nsa

ctio

n T

ime

(mse

c)

Series1

Jan 2004

Broady Cash, ARINC

Slide 25

doc.: IEEE 802.11-04/0142r0

Submission

Transaction Time

1 2 3 4 5 6 7 8 9 10 110

5

10

15

20

25

30

35

40

45A t h e r o s

Occu

rrenc

es

T i m e ( m s e c )1 2 3 4 5 6 7 8 9 10 11

0

5

10

15

20

25

30

35

40

45

T i m e ( m s e c )

Occu

rrenc

es

F r e e S p a c e

FreeSpace Atheros

Jan 2004

Broady Cash, ARINC

Slide 26

doc.: IEEE 802.11-04/0142r0

Submission

1 2 3 4 5 6 7 8 9 10 110

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Time (msec)

Pe

rce

nt

Ex

ce

ed

ed

FreeSpaceAtheros

Transactions Time CDFs

Jan 2004

Broady Cash, ARINC

Slide 27

doc.: IEEE 802.11-04/0142r0

Submission

FreeSpace Communication Time

FreeSpace Communication Time

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Vehicle Speed

Co

mm

un

icat

ion

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 28

doc.: IEEE 802.11-04/0142r0

Submission

FreeSpace Communication TimeFreeSpace Communication Time - Detail

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140

Vehicle Speed

Co

mm

un

icat

ion

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 29

doc.: IEEE 802.11-04/0142r0

Submission

Atheros Communication Time

Atheros Communication Time

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Vehicle Speed

Co

mm

un

icat

ion

Tim

e (m

sec)

Series1

Jan 2004

Broady Cash, ARINC

Slide 30

doc.: IEEE 802.11-04/0142r0

Submission

Observations

• Both radios completed all transactions.

• Each radio had one run with two L7 BST tries.

• Transaction Time for both radios is 6 msec or less, 95 % of the time.