Information Technology Reference
In-Depth Information
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(a)
(b)
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Fig. 1.
An example of connectivity degradation in multichannel MANET. The config-
urations are: (a) 1 channel; (b) 2 channels, 1 interface for each node; (c) 4 channels, 2
interfaces for each node.
and network load into consideration. This channel assignment problem is proved
to be NP hard [15]. The highly mobile character of VANET makes the prob-
lem even harder. In [25], the authors evaluated the QoS indicators of VANET
through simulations. They found that delay and jitter are usually within toler-
ance, but delivery ratio and connection lifetime are dicult to meet the QoS
requirements. Thus, sacrificing connectivity for the channel diversity seems not
suitable for VANET. On the other hand, vehicles have much fewer energy and
hardware constraints than handheld mobile devices. Consequently, we attempt to
preserve the VANET connectivity by relax the energy and hardware constraints
a bit. A connectivity invariant multichannel assignment protocol can not only
benefit the VANET QoS, but also make the other protocol design independent
to the multichannel method and preserve the layered network architecture.
In our previous work [24], we proposed a multichannel assignment method
based on road topology (MIMC-Road), which can keep the same connectivity
as single channel network. In this paper, we first generalize the previous solu-
tion by answering how to keep the connectivity while utilizing the multichannel
resources using the Pigeon Hole Principle. With the invariant connectivity, we
further present a channel usage based dynamic channel assignment method. Each
node monitors the channel usages of its own active channels and exchange the
channel usage information with the neighbors. With the collected channel us-
age information, the node can switch from a crowded channel to a channel with
sparse nodes, while still keeping the connectivity intact. The method is fully
distributed and insensitive to the mobility, which makes it suitable to be used
in VANET.
In the rest of the paper, after reviewing the related work in Section 2, we
discuss how to keep the network connectivity invariant in Section 3. In Section
4, we describe the details of the channel usage based multichannel assignment
method. The evaluations are presented in Section 5 and the conclusion is in the
last section.
2 Related Work
A lot of papers have studied the Single Interface Multi-Channel protocols (SIMC)
using channel hopping methods. A fast switching and time synchronization are
