3. AutoNet 2006
What is a VANET ?
Vehicular Ad-hoc
Networks
Individual nodes
different from traditional
wireless nodes
No power constraint
Nodes mostly mobile
Extends existing
infrastructure
Vehicle-Vehicle
Communication
Vehicle-
Infrastructure
Communication
4. AutoNet 2006 4
F o r w a r d r a d a r
C o m p u t i n g p l a t f o r m
E v e n t d a t a r e c o r d e r ( E D R )
P o s i t i o n i n g s y s t e m
R e a r r a d a r
C o m m u n i c a t i o n
f a c i l i t y
D i s p l a y
(GPS)
- Human-Machine Interface
- Navigation system
5. AutoNet 2006 5
• Processing power: comparable with a Personal Computer + a few
dozens of specialized processors
• Communication: typically over a dedicated channel:
Dedicated Short Range Communications (DSRC)
•In the US, 75 MHz at 5.9 GHz;
•In Europe, 20 MHz requested but not yet allocated)
• Envisioned protocol: IEEE 802.11p
• Penetration will be progressive (over 2 decades or so)
6. AutoNet 2006
V2V/V2I Communication-based
Automotive Applications
From an application benefit viewpoint, V2V/V2I
applications can be classified as
Safety Applications
Convenience Applications
Commercial Applications
6
Safety
7. AutoNet 2006
among those listed, safety-oriented applications are of special
interest because they are expected to significantly reduce the
fatalities and economic losses caused by traffic accidents
7
ConvenienceCommercial
12. AutoNet 2006
Commercial Applications
RVP/D: Remote Vehicle
Personalization/Diagnostics
SA: Service Announcements
CMDD: Content, Map
or Database Download
RTVR: Real-Time Video Relay
13. AutoNet 2006
V2V/V2I Application Characterization
and Classification
Application Characteristics
describe properties directly related to the applications themselves
13
14. AutoNet 2006
Classification Criteria: Network
Attributes
Networking Attributes
characterize the fundamental aspects of network design for communication-
based automotive applications
14
18. AutoNet 2006
Application Classification (2)Group applications into 7 generic classes:
Accommodate the applications of interest
Class Name Representative Applications
1 Event-Driven Short-Message Broadcast SVA, EEBL, PCN, RHCN, and RCN
2 Scheduled (Periodic) Short-Message
Broadcast
CCW ( Cooperative Collision Warning),
CVW (Cooperative Violation Warning)
3 On-Demand Short-Message Broadcast SA (Service Announcements)
4 Financial Transaction Short-Message
Unicast
RVP/D (Remote Vehicle Personalization/Diag)
TOLL (Free Flow Tolling)
5 Non-Financial Transaction Short-
Message Unicast
TP, PAN, PSL
6 File Download CMDD (Contents, Map or Database
Download)
7 Video Streaming RTVR (Real-Time Video Relay)
18
- Only (7 generic classes) application models
- Individual applications are simple extensions from the generic models
SVA: Stopped or Slow Vehicle Advisor
EEBL: Emergency Electronic Brake Light
PCN: V2V Post Crash Notification
RHCN: Road Hazard Condition Notification
RFN: Road Feature Notification
TP: Traffic Probe
PAN: Parking Availability Notification
PSL: Parking Spot Locator
19. AutoNet 2006
Performance Metrics for Communication-
based Automotive Applications
We mainly concentrate on safety applications, since they are the initial focus of automotive
industry
Necessity to introduce novel application-level metrics to accurately capture performance trends of safety applications
19
Level Metric Description Classes
Network Packet Delivery Ratio packets received / packets transmitted 1, 2, 3, 4, 5, 6
Network Per-Packet Latency packet reception time – packet transmission
time
1, 2, 3, 4, 5
Application T-window Reliability prob. of receiving at least one transmitted
packet within a given time interval
1, 2, 3
Application Time-to-Successful
Reception
application-level packet reception latency 1, 2, 3
Application QoS Metrics end-to-end packet delay, jitter, and throughput 7
20. AutoNet 2006
ADVANTAGES
Reducing the likelihood of collision at intersections.
Reducing the likelihood of road departure crashes.
Providing more accurate and timely road condition
alerts.
20
21. AutoNet 2006
DISADVANTAGES
The whole system cannot be work without network
connectivity
This process can be done if and only if every vehicle
should active their communication system
21
22. AutoNet 2006
APPLICATIONS
Using V2V communication, when a vehicle on the
road acts abnormally, e.g., deceleration exceeding a
certain threshold, dramatic change of moving
direction, major mechanical failure, etc., it becomes
an abnormal vehicle (AV). An AV actively generates
Emergency Warning Messages (EWMs), which
include the geographical location, speed, acceleration
and moving direction of the AV, to warn other
surrounding vehicles. A receiver of the warning
messages can then determine the relevancy to the
emergency based on the relative motion between the
AV and itself.
22
23. AutoNet 2006
FUTURE SCOPE
The authors are currently investigating efficient communication
mechanisms to disseminate CoTEC’s road traffic congestion
information to vehicles approaching the congested area.
Using this information, vehicles would be able to modify their route,
and select alternative ones that avoid the congested area.
An interesting research area would then be to investigate how to
efficiently couple V2V-based road traffic monitoring mechanisms with
cooperative traffic management strategies.
Such coupling should be studied in large scale scenarios in order to
better understand the impact on road traffic conditions, and the
capability of cooperative systems to efficiently distribute road traffic
flows.
23
24. AutoNet 2006
CONCLUSION
Cooperative vehicular communications open new
possibilities to develop advanced traffic monitoring
solutions in next-generation ITS systems.
In this context, this paper has presented CoTEC, a novel
distributed technique using V2V communications to
detect and characterize traffic congestion.
The proposed technique includes mechanisms to
compensate the impact of radio propagation on the
accurate estimation of traffic density, and to account for
the gradual market introduction of cooperative vehicular
communications.
24
Appropriately lower the tone:
we attempted to be as general and as thorough as possible, we acknowledge that future analysis of a broader set of
applications may uncover other important characteristics. Indeed, it is our hope that the work presented here will
inspire others to research and expand the list as future applications are explored and developed. However, as we will
show, this list covers a sufficiently broad range of applications to be a useful reference tool for application and network
designers.
Key point:
These attributes, summarized in Table 3, are more or less, are determined by the application characteristics discussed in the previous section,
Key point:
1. Notice that most of the safety applications have a medium-sized effective application range (i.e., a few hundred
meters to 1 kilometer), since safety messages, such as vehicular kinematics status or road conditions, are only
relevant to other vehicles within a moderate geographical region. Exceptions are the CCW and CVW applications,
which have a small application effective range because they require the closer monitoring of vehicles in
their direct neighborhood (i.e., within 200 meters). Conversely, convenience applications generally require a
medium or large effective range (i.e., up to a few kilometers), because it is vital for drivers to know the congestion
situation or traffic condition at this range for effective detour or trip planning. Similarly, commercial
applications also tend to have a large effective range in order to access remote commercial service providers4.
2. Most safety applications (e.g., EEBL, RHCN and SVA) and a few convenience applications (e.g., CRN, TP
and TOLL) are initiated by the events happening on the road, such as vehicle collisions, detection of road
hazards (e.g. ice, oil), sudden braking, or detection of traffic congestion. If no such events happen, these
applications will not be invoked. Among safety applications, CCW and CVW are unusual because they rely on
the periodical message updates to monitor the neighboring vehicles’ driving status, regardless of safety events.
On the other hand, most convenience applications and commercial applications are triggered on-demand by
vehicle occupants, rather than by any safety event on the road or the vehicle itself.
3. The potential recipients of application messages, in most safety applications (e.g., SVA and EEBL), are vehicles
within a specific zone (i.e., behind the vehicle which detects the event and originates the safety message). Thus,
safety applications can be summarized as one-to-a-zone recipient patterns5. At the same time, convenience and
commercial applications vary from application to application: some convenience applications (e.g. TOLL) and
commercial applications (e.g., RVP/D, CMDD, and RTVR) have point-to-point (one-to-one)modes, while other
convenience applications (e.g., CRN) and commercial applications (e.g., SA) are fundamentally one-to-a-zone
in nature.
4. “Event” is an important concept in safety applications, and a few convenience applications, because it is an event
that initiates the application operations. In our study, we also characterize safety events via several properties
of events, including event duration, event correlation, and event detectors. Consistent with our conjecture, we
find that safety events drastically vary from application to application. For example, sudden braking (EEBL)
is a one-shot event, while road hazard/feature events (RHCN or RFN) are persistent events. Also, different
instances of RHCN or RFN events caused by the same road hazard/feature are more likely to be correlated with
each other, in contrast to the totally independent PCN events. Even though the study of event characteristics
is not directly used in the network design conducted in Section 4.2, we believe that such an analysis can help
future network designers better capture the data traffic patterns induced by event-driven safety applications.
Key point
1. The message packet format is determined by the type of application (from the perspective of user benefit).
Normally, safety and convenience applications use light-weight shortmessages in theWSMP format, to improve
network resource efficiency. Commercial applications, on the other-hand, generally prefer the traditional heavyweighted
IP format to be compatible with existing Internet commercial services.
2. The network-layer routing protocol is one essential component in a network stack, differentiating the reachability
and recipient patterns of various applications. Most safety applications utilize multi-hop geocast routing
protocols6, because of the one-to-many communication nature in safety applications. CCW and CVW applications,
instead, use the single-hop broadcast scheme to announce the periodic update in their direct neighborhood.
Convenience and commercial applications either use geocast/broadcast protocols to announce messages
in a region (for advertisement service like SA, or traffic congestion notification like CRN), or exploit unicast
protocols to forward packets to a given destination (for financial transactions like TOLL, or data download from
infrastructure like CMDD).
3. The method by which the network routing protocol is triggered is another interesting design choice to be examined
in our study. Event-driven safety applications (e.g., SVA, EEBL and CRN) require the event-triggered
mechanism in network protocols, periodic-based safety applications (e.g., CCW and CVW) mandate the periodic
beacon (or hello message) mechanism, and user-initiated convenience and commercial applications (e.g.,
SA, RVP/D and PSL) are triggered in an on-demand fashion.
4. The involvement of infrastructure in network design and application development is another key issue for consideration7.
Normally, as a rule of thumb, safety applications often do not assume the participation of road-side
infrastructure. On the contrary, infrastructure can facilitate the design of convenience applications as well as
enable commercial applications by providing the gateway to the existing Internet infrastructure8. As a side note,
the involvement of infrastructure also complicates the design of security solution. We believe that security solutions
for V2V applications are different from that for V2I applications, depending on whether PKI structure can
be utilized. Also, the gateway to the Internet requires the compatibility of V2V/V2I security solutions with the
existing Internet security solutions.
Motivation of classification and generalization: the obvious similarity between applications!
(1) RHCN and RFN are nearly the same, except that the type of safety warning
messages are different: RHCH is about road hazards, while RFN is about road features. (2) PCN and RHCN are also
similar except for the number of event originators: PCN has a sole message host, while RHCN has multiple message
hosts. Even though this difference gives rise to different levels of data traffic burstiness from event generation, the
network protocol stacks for these two applications are still similar to each other. (3) Also, CCWand CVWapplications
can be categorized into the same type, although the former is a V2V application whereas the latter is a V2I application.