Serviceorientiertes Mehrkanal-Beaconing in Fahrzeug-Ad-hoc-Netzen

The interconnection of vehicles is an important topic concerning
the enhancement of traffic safety and trffic efficiency. Therefore,
vehicles exchange position and state information with each other to
establish an awareness level for the calculation of collision
probabilities with their neighbors. To recognize critical safety
situations it is essential to receive information reliably.
However, these systems are typically based on wireless ad-hoc
networks that cannot guarantee reliable packet transmission. This
is especially the case in situations where a high number of
communication nodes exist. The aim of this work at hand is the
definition of a beaconing algorithm that enables the establishment
of a desired awareness level for critical safety situations
especially in high density traffic scenarios. First, representative
scenarios for collision detection and collision avoidance were
specified and metrics for the evaluation of the beaconing
algorithms were defined. Based on these metrics the performance of
beaconing algorithms with different static periodical update rates
was evaluated. It is presented that these kinds of beaconing
algorithms cannot provide sfficient results with respect to the
required constant information throughput in high density traffic
situations. To provide a high awareness level for each vehicle in
its individual situation in spite of an unreliable communication
channel a service-oriented beaconing approach is dened in this
work. It is based on a request/response communication scheme to
compensate particular packet loss. Hereby, a broadcast and a
unicast occurrence of the algorithm are defined accordingly to the
corresponding representative scenarios. It is presented that the
service-oriented beaconing approach provides a signicant benefit
with respect to the information throughput for low and middle
traffic density situations. However, in high density situations the
benefit of this approach is decreasing due to the increased
communication overhead. This is a result of using one single
communication channel. To achieve a high awareness level also in
high density trac situations, a signi- cant modification was
defined. Therefore, the usage of multiple communication channels
was introduced to distribute the communication load over several
channels. It is specified to send all service responses on a
dedicated service channel to reduce the load on the control channel
where the service requests are transmitted. After an extensive
evaluation of the multi-channel utilization in vehicle ad-hoc
networks using IEEE 802.11p it is shown that the multi-channel
version of the service-oriented beaconing approach can achieve
significant benefits concerning the information throughput for the
collision detection and collision avoidance scenarios even in high
density traffic situations.