aspects of vehicular wlan implementation
Download
Skip this Video
Download Presentation
Aspects of Vehicular WLAN Implementation

Loading in 2 Seconds...

play fullscreen
1 / 33

Aspects of Vehicular WLAN Implementation - PowerPoint PPT Presentation


  • 111 Views
  • Uploaded on

Aspects of Vehicular WLAN Implementation. Roger Berg Vice President - Technology and Product Development DENSO INTERNATIONAL AMERICA, INC. LA Laboratories. Contents. Identify Use cases Application Requirements Necessary Technology Innovate Technology Solutions Prioritization

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Aspects of Vehicular WLAN Implementation' - shellie-farmer


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
aspects of vehicular wlan implementation

Aspects of Vehicular WLAN Implementation

Roger Berg

Vice President - Technology and Product Development

DENSO INTERNATIONAL AMERICA, INC.

LA Laboratories

contents
Contents
  • Identify
    • Use cases
    • Application Requirements
    • Necessary Technology
  • Innovate
    • Technology Solutions
      • Prioritization
      • Channelization
      • Synchronization
      • Latency
  • Implement
    • Simulation
    • Feasibility Platform HW & SW
  • Insure
    • Test and Evaluation
    • Comparison to analytical and simulated results
slide3

Identify: United States Vehicle Safety Scenarios

autonomous sensors

limited sensor range

Cooperative sensors

sensor range extension

Motor vehicle crashes are the leading cause of death for every age from 2 to 33 years old.

However, US vehicle crash related death rates have flattened.

The trend and focus must move from crash mitigation to crash prevention.

Safety improvements have come from crash mitigation.

Goal for 2010: < 1.0 fatalities / 100 M VMT

identify vsc in the usa
Identify: VSC in the USA

Safety

Mobility

Reduce US Transportation inefficiency

3.6 Billion hours of vehicle delay / yr

5.7 Billion gallons of wasted fuel

Reduce highway fatalities

US DOT #1 priority

$230B/yr

$70B/yr

February 2004 FCC authorized

75 MHz in the 5.9 GHz band

for exclusive use of ITS.

DSRC is proposed as the critical communications link

US DOT envisions DSRC units

in every new motor vehicle for life

saving communications capability

DSRC WAVE

WIRELESS ACCESS FOR VEHICULAR ENVIRONMENTS

For interoperability

nation wide…

Specification

Feasibility

a public standard

of operation

must be created

Development

1998

2006

2009

Government wants to have standard capable for both V2V and V2R communications.

identify applications requirements
Identify: Applications & Requirements

SAE

VSCC

ISO TC204 WG16

WAVE IEEE 1556

ICDN NAWG ITS

OTHER

Latency, range, mobility, security, …

Focus:

requirements of groups of applications (range of required values)

identify vehicular applications requirements
Identify: Vehicular applications requirements
  • Top 7 Vehicle Safety Applications
  • Intersection Collision Warning and Avoidance (Vehicle-to-Roadside-to-Vehicle)
  • Left Turn Assistance (Vehicle-to-Vehicle)
  • Cooperative Forward Collision Warnings (Vehicle-to-Vehicle)
  • Pre-crash sensing (Vehicle-to-Vehicle)
  • Emergency Electronic Brake light Signaling (Vehicle-to-Vehicle)
  • Curve Speed/Rollover Warnings (Vehicle-to-Roadside-to-Vehicle)
  • Pre-crash Sensing (Vehicle-to-Vehicle)
  • Preliminary Common Communications System Requirements
  • 50 - 100 ms access latency and update rates
  • 250+ km/hr mobility
  • Scalable on the basis of vehicle traffic density
  • Dynamic message routing
  • 10 - 500 m radio link range
  • Shared communication channel
  • Message payload 2 - 5 kbytes
  • Data rates 2 - 12 Mbps
identify technology improvement
Identify: Technology improvement

Channelization Scheme for Vehicle/Public Safety & Private Applications

Control

Channel

Service

Channel

Service

Channel

Service

Channel

Service

Channel

Service

Channel

Service

Channel

High Priority

Vehicle Safety

CH 172

5860 MHz

CH 174

5870 MHz

CH 176

5880 MHz

CH 178

5890 MHz

CH 180

5900 MHz

CH 182

5910 MHz

CH 184

5920 MHz

  • Channelization solution to:
  • provide priority to vehicle/public safety message traffic
  • provide guaranteed and configurable message latency
  • allow channel capacity to be adaptively allocated
innovate i channel main goals
Innovate: i-Channel Main Goals
  • Prioritization
    • Public/Vehicle Safety is guaranteed highest priority
    • Channelization latency is predictable and configurable
  • Synchronization
    • RSU not necessary for synchronization
    • Messaging is organized into Safety/Non-Safety time slots
    • Provides synchronization in overlapping RSU communication zones
    • No restrictions EXCEPT channel switching priority based on i-Channel rules
    • Non-Safety operation is flexible as long as i-Channel rules are followed
  • Adaptive Channel Access
    • Allows available system capacity to be allocated to Non-Safety when Public Safety is not needed
    • Allows full system capacity to be allocated to Public Safety when necessary

Main Features: Prioritizes Safety, reduces latency, supports non-RSU communications.

innovate safety non safety systems
Innovate: Safety & Non-Safety Systems

SAFETY (ADAPTIVE)

NON-SAFETY (FIXED)

  • Safety Slot:
    • An adaptive time slot.
    • High-Priority Safety Messages transmitted only during Safety time slot.
    • Lower Priority Safety Messages may also be transmitted during the Safety time slot.
    • 802.11e QoS ensures highest priority messages get first access to RF medium.
    • OBUs and RSUs monitor the Safety Channel during the Safety time slot.
    • All devices stay on Safety Channel until High-Priority Safety Messages have not been transmitted or received for a predetermined period of time.
    • Once this predetermined time expires, Safety time slot ends, Non-Safety time slot begins.
  • Non-Safety Slot:
    • A fixed time slot. Guarantees return to Safety Channel to meet latency requirements.
    • OBUs and RSUs may change channels at will.
    • High-Priority Safety Messages may not be transmitted, even if tuned to the Safety Channel.

Separate the Safety and Non-Safety operations.

innovate architectural concept
Innovate: Architectural Concept

Focus: Specification of control mechanism for channel/system isolation.

innovate i channel parameters
Innovate: i-Channel Parameters

First

HP

Last

HP

First

LP or NS

Last

LP or NS

TNS

TIDLE

TTUNE

TTUNE

TNS-TX

Tc = One Adaptive I-Channel Cycle

TNS-TX Time left over for Non-Safety Communication. This time period is fixed to TNS – (2 x TTUNE).

TIDLE Idle time that follows the last High Priority Safety Message (TX or RX).

TTUNE Time allocated for receiver settling after a channel change.

TNS Time allocated for Low Priority Non-Safety Communication. This time period is fixed.

slide12

Tune to Safety Channel;

Complete all pending High-Priority Safety (HP S);

While verifying all High-Priority Safety has been completed,

exchange Low-Priority Safety (LP S);

HP S

HP S

HP S

HP S

HP S

LP S

LP S

LP S

LP S

LP S

Tune Back to Non-Safety Channel.

DSRC Band

Safety Channel

Time

Non-Safety Channel(s)

Paused

Paused

Paused

HP S

HP S

LP S

LP S

HP S

HP S

LP S

LP S

Adaptive Duration

for HP Safety

Fixed Duration

for Non-Safety

Fixed Duration

for LP

Innovate: i-Channel Cycle

>> x2

Zoom Out

1 t idle init
1) T idle Init

Safety Channel

Non-Safety Channel(s)

0

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

Idle Timer [ms]

t idle 1 5
T idle = 1.5

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

Idle Timer [ms]

1.5

2 hp radio 0
2) HP Radio 0

Radio 0 HP

0

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

(2) Idle Timeris reset every time aHP Safety messageis received OR transmitted by any OBU or RSU in the network.

Idle Timer [ms]

t idle 1 0
T idle = 1.0

Radio 0 HP

1.0

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

(2) Idle Timeris reset every time aHP Safety messageis received OR transmitted by any OBU or RSU in the network.

Idle Timer [ms]

hp radio 1
HP Radio 1

Radio 0 HP

Radio 1 HP

0

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

(2) Idle Timeris reset every time aHP Safety messageis received OR transmitted by any OBU or RSU in the network.

Idle Timer [ms]

t idle 3 5
T idle = 3.5

Radio 1 LP

Radio 0 HP

Radio 1 HP

3.5

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

(2) Idle Timeris reset every time aHP Safety messageis received OR transmitted by any OBU or RSU in the network.

Idle Timer [ms]

t idle timeout
T idle Timeout

Radio 1 LP

Radio 0 HP

Radio 1 HP

Timeout

Legend

HP Safety Message from Radio 0

HP Safety Message from Radio 1

LP Safety Message from Radio 1

Innovate: i-Channel Timing

Channel Switch timing is derived solely from HP Safety Messages.

(1) Idle Timeris initialized upon entering the Safety Slot.

(2) Idle Timeris reset every time aHP Safety messageis received OR transmitted by any OBU or RSU in the network.

(3)The Idle Timertimes out when it reached a predetermined value. Then, the radio MAY tune away from safety.

(4) Even if the radio does not tune away during the fixed non-safety period,

HP Safety messagesSHALL NOT be sent during that time.

Idle Timer [ms]

nodes enter high awareness mode ha periodically

Innovate: How do nodes and networks synchronize?

Nodes enter High Awareness mode (HA) periodically

Nodes enter HA, e.g. every 1 or 2 seconds, and

stay on the safety channel during the next NS period looking for other nodes within communication distance.

Nodes in a network enter High Awareness mode at different times

Node 0

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

HA

HP

LP

NS

HP

LP

NS

Node 1

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

HA

Node 2

HP

LP

NS

HP

LP

NS

HP

LP

HA

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

Node 3

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

NS

HP

LP

HA

HP

LP

NS

HP

LP

NS

HP

LP

NS

t0

tf

High Awareness = Stay on Safety Channel during Non-Safety period.

innovate follow the leader
Innovate: Follow the Leader

Last

HP

Last

HP

Follow

Me!

LEADER

TIDLE

TNS = TSRCH

TIDLE

Go to High Awareness

In High Awareness

“Follow Me”

Returning

THA Timeout

Other Network Detected

HP

TX

Last

HP

FOLLOWERS

TIDLE

TIDLE

Following

Searching

RX Follow Me Packet

“Follow the Leader” allows two clusters to join very quickly.

slide22

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

HP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

LP S

HP S

LP S

High-Awareness (instead of NS)

HP S

LP S

HP S

LP S

HP S

HP S

LP S

LP S

HP S

HP S

HP S

LP S

LP S

Innovate: i-Channel Multiple Networks

Radios in different networks (i.e. unsynchronized)

Radios in the same network (i.e. synchronized)

i-Channel High-Awareness Mode

Radio 0

RX

F

Radio 1

TX

F

Acquire Radio 0 Network

Networks Merged

innovate high awareness
Innovate: High Awareness

Equal Size Clusters

Unequal Size Clusters

Equal Size Clusters

Unequal Size Clusters

THA = 1.0

THA = 1.0

Simulation data shows switching times independent of network size and mobility

implement channelization latency problem
Implement: Channelization Latency Problem
  • All channel switching causes delays,
    • unless a radio is camped on a channel continuously.
  • All 802.11 systems have delays for medium access.
    • CSMA/CA access and back-off and
    • impacts of hidden nodes, interference, propagation delay, …
  • 802.11 packet latency depends on circumstances, environment, number of nodes, dynamics, loading, …
  • How can we isolate these impacts to determine the performance of a given channel switching method?

How can we effectively compare channel switching methods?

implement useful measure of latency
Implement: Useful Measure of Latency
  • DEFINITION: Channelization latency is the component of packet latency attributable to delays caused by the multi-channel management system.
  • Time delay between:
    • Packet arrival in MAC transmit queue from upper layer, and
    • Radio tuned to channel corresponding to that MAC queue.
  • Thus, Packet Latency =
    • Channelization latency
    • + Queue delay
    • + Access delay
    • + Propagation delay
    • + Process delay in receiver

Channelization Latency is a measure of the efficiency of the channel switching.

implement expected latency analytic
Implement: Expected Latency (analytic)

Expected Latency for HP and LP Safety and Non-Safety

___ HP Safety

___ LP Safety

___ Non-Safety

T_IDLE = 0.005

T_NS = 0.050

T_TUNE = 0.002

  • Computation of expected value of channelization latency according to:
    • Probability of packet arrival relative to channel switching system time;
    • Probability of channel change latency given load.
implement measured latency simulations
Implement: Measured Latency (simulations)

T_IDLE = 0.005

T_NS = 0.050

T_TUNE = 0.002

  • Measured actual channelization latency from ns2 simulations with varying degrees of high priority safety load.
slide29

Implement: Tools for prototype

10 / 20 MHz Band

Width Selection

Adjustable TX Pout

(1dB incremental)

WAVE Frequency

Channel Selection

Variable Data Rate

t-ns

T-ns setting

T-idle setting

T-High Awareness setting

WAVE Prototype Communications Module Support Tool

insure expected vs measured latency prototype
Insure: Expected vs. Measured Latency (prototype)

T_IDLE = 0.005

T_NS = 0.100

T_TUNE = 0.002

  • Measured packet latency from WRM prototypes with very low loading and few units:
    • low loading approximates zero queue delay;
    • few units approximates zero access delay;
    • thus, packet latency approximates channelization latency.

Measurements using radio module prototype confirm Analytical & Simulation analysis.

insure other evaluation tools
Insure: Other Evaluation Tools

Automatic data plotting

conclusion
Conclusion
  • Identified
    • Application requirements are the center point
    • Analyze technology deficiencies
  • Innovated solutions
    • Prioritize, channelize, synchronize with low latency
  • Implemented
    • Simulation and feasibility HW & SW
  • Insured
    • Match theory/simulation to implementation results
    • Test tools validate innovative implementation
ad