||Imagine you're the person in the white truck at the back of the
line. What information would you like to have? You want enough
information to help you decide if you should get off at the next exit.
Is there a blocked lane ahead, and if so, where? Is there an accident
that needs to be cleared? Is there a special event, or is this just
Now, imagine you're in one of the cars on the other side of the
road. Most likely, you passed whatever is causing the slow down. If
you could talk to the people on the other side of the road, you could
tell them exactly what's going on.
"It is estimated that over half of traffic congestion in the US is
caused by incidents." "Incident related traffic congestion will cost
the US public over $75 billion in the year 2005 in lost productivity
assuming an average rate of $10/hour lost due to congestion, and also
results in the waste of over 8.4 billion gallons of fuel." (From Incident
Management: Detection, Verification, and Traffic Management, US
Federal Highway Administration, Sep 1998.
||These are two different ways of categorizing applications, but
they're pretty similar.
platooning - vehicles travel together closely spaced for
increased road capacity, vehicles controlled by computer
Each of these classes of applications has different requirements.
||Take a look at each of these websites to get an idea of what each
||If you're not familiar with 802.11 wireless networks, I'd
encourage you to find some other references online
DIFS - distributed inter-frame spacing
SIFS - short inter-frame spacing
ACK - link-layer ACK (don't confuse with TCP ACK)
ACKs are only used for unicast, not for broadcast
||Helps with hidden node problem.
In ad-hoc network, send RTS to destination (since there's no BS)
RTS/CTS is typically not used in vehicular networks.
||We'll look at specific approaches to dissemination, aggregation,
and routing later in the semester
||Like with the wireless networking topic, if you aren't familiar
with network security, especially public key (PKI), consult other
references. These topics will come up again later in the course.
||How do Alice and Bob agree on the key value?
||The main thing here is that we want to ensure that the public key
of Bob is actually Bob's public key, i.e., the person who signed this
message is really that person (no forgeries)
||If you find an interesting paper, always take a look at the list
of references to see if there are others you should look at. This
also can let you know about other conferences or journals you should
be following. Typically, ACM and IEEE conferences/journals are the