Networking Reference
In-Depth Information
The behavior of these five mechanisms has been compared
with the original IEEE 802.11p under medium and high
vehicular density, with a traffic volume varying between
40 vehicles/km and 80 vehicles/km. In a first phase,
simulations were run in order for each of the above
algorithms to be optimized with regard to the different
parameters that have an impact on their performance. The
tested values and those that achieved the best performance
for each parameter are shown in Table 1.1. In the case of
IEEE 802.11p, a value of 7 has been used for CW min . This is
equivalent to the value mentioned in the standard for the
access category with the second highest priority [THE 10].
Tested values
Optimal value
1 s, 5 s, 10 s, 20 s
T update
0.25, 0.5, 1, 2
PER min / PER max 5%/10%, 10%/15%, 15%/20%
1, 1.1, 1.2, 1.3, 1.4
100 m, 150 m, 200 m, 250 m
200 m
d col
40, 50, 60
CW max
2, 2.5, 3, 3.5
D max
Table 1.1. Optimal values for the different parameters
of the algorithms
The metric used for this optimization and for the
comparison was the beaconing reception probability at a
distance of less than 200 m from the source vehicle. This
metric is considered to be particularly suitable because it
includes in a single value both the probability of collision and
the probability of an expired beacon. Moreover, because a
beacon that cannot be sent with the required time delay
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