1. Overview of Previous Analysis for WAVE
Month 2002
doc.: IEEE /xxxr0
January 2004
Overview of Previous Analysis for WAVE
Justin McNew
Justin McNew, TechnoCom
John Doe, His Company

2. Traditional Scanning Passive scanning Active scanning
Month 2002
doc.: IEEE /xxxr0
January 2004
Traditional Scanning
Passive scanning
Requires waiting for Beacon reception
Beacons are not required for WAVE communications (see wave)
Introduces excessive latency for public safety applications that require immediate access to information transmitted in mobile environments
Active scanning
Requires excessive transmissions by mobile units
Clogs communications channels with densely populated OBU (mobile stations)
Justin McNew, TechnoCom
John Doe, His Company

3. Authentication & Association
January 2004
Authentication & Association
Authentication and association also affect latency of critical public safety applications (see wave)
Not utilized for most public safety applications
Requires Beaconing mechanism
Joining a network is not required to communication with WAVE devices
Justin McNew, TechnoCom

4. Channelization 10 MHz versus 20 MHz channels
Month 2002
doc.: IEEE /xxxr0
January 2004
Channelization
10 MHz versus 20 MHz channels
75 MHz allocation results in excessive unused bandwidth with 20 MHz channels
Seven 10 MHz channels provides ability to dedicate more channels to specific applications
Leftover 5 MHz reserved for future FCC allocation of spread spectrum ISM band below 5.85 GHz
Licensing of channels more robust (less overlap)
Utilize half-rate solution consistent with j
Consistent with expected delay spreads in outdoor and mobile environments
Justin McNew, TechnoCom
John Doe, His Company

5. January 2004
Basic MAC Simulations
Altered existing simulation models to represent WAVE environment and 10 MHz channels
No Beacons or association
6 Mbps data rate (QPSK modulation)
Simple simulation used to confirm can work for WAVE
Justin McNew, TechnoCom

6. PHY Parameters January 2004 Characteristics Value Comments aSlotTime
Calculated as aCCATime + aRxTxTurnaroundTime + AirPropagationTime + aMACProcessingDelay
aSIFSTime
32 s
Doubled from standard a value
aCCATime
 8 s
aRxTxTurnaroundTime
 2 s
Same as standard a value
aRxTxSwitchTime
 1 s
aAirPropagationTime
 4 s
Quadrupled to support up to 1200 meter range
aMACProcessingDelay
aPreambleLength
40 s
aPLCPHeaderLength
8 s
aCWmin 15
aCWmax
1023
Justin McNew, TechnoCom

7. Basic Simulation Results (cont’d)
January 2004
Basic Simulation Results (cont’d)
Generic simulation
Randomly distributed nodes.
10, 30, 50, 70, and 90 OBUs with 1 RSU
Network traffic
Unicast traffic sent from OBUs destined to RSU
Each OBU starts in different time (exponentially distributed with mean of 10 sec.)
Exponentially distributed inter-arrival time with mean of 0.1 sec
Average payload size of 64 bytes (smaller than anticipated)
Justin McNew, TechnoCom

8. Basic Results
January 2004
Justin McNew, TechnoCom

9. Realistic Simulation Case
January 2004
Realistic Simulation Case
OBU enter communication zone of an RSU at a reasonably consistent rate
OBU service table (OST) sent in response to periodically broadcast RSU service table (RST)
Single Exchange represented by Exchange Success Rate (ESR):
RSU
OBU
RST Broadcast
Delay
Unicast OST
Justin McNew, TechnoCom

10. January 2004
System Stability
An excessive number of OBU entering a communication zone will result in significant exchange failures
E.g. if 5 new OBUs enter the zone, the total number of OBUs that must be processed is the number of new OBUs plus the number of OBUs that failed for the last RST transmission
Failures can result from collisions of RSTs and/or OSTs
Realistically, not more than around 10 to 15 OBU can arrive in a communication zone on a large freeway within a 100 ms period
Justin McNew, TechnoCom

11. Simulation Parameters
January 2004
Simulation Parameters
Packet characteristics
RST Size: 490 bytes
Unicast OST size: 490 bytes
Vehicle to Vehicle:
Broadcast OST size: 250 bytes
Broadcast OST period: 100 ms
Randomly distributed over 100 ms interval (uniform)
6 Mbps data rate
Justin McNew, TechnoCom

12. January 2004
Simulation Results
RST Period
Justin McNew, TechnoCom

13. Summary 802.11 can support WAVE applications
January 2004
Summary
can support WAVE applications
Requires disabling various MAC features in certain instances
Beacons, authentication & association
10 MHz channels used in WAVE frequency band
Simulations indicate adequate capacity is available
Note: Resulting recommendations presented in wave
Justin McNew, TechnoCom