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too, the requirement of traffic reduction
is much more compelling in wireless ad-
hoc networks, where the communication
bandwidth ability is usually limited to ap-
proximately 1 MBps. It is worth noticing,
that the reduction of traffic also reduces the
involvement of other MHs, due to constraints
in their processing power and autonomy.
already explained in Section “Information
Discovery/Provision In Wireless Mobile
Ad-hoc Networks”).
2. The second requirement is addressed by a
technique that uses a concise, feature-based
representation of the query with reducing
length. The reducing-length representation
(a.k.a transcoding) drastically degrades
traffic, while reducing the computation
performed at each MH as well.
3. The additional traffic produced by the third
requirement is addressed by a twofold tech-
nique: (1) Policies to constraint the number
of MHs involved for the propagation of
the answers, by exploiting any MHs that
were involved during the propagation of
the query. (2) By allowing such MHs to
prune the propagation of answers, based
on a property of the previously described
representation.
3
In CBMIR over wired P2P networks, should
a matching music excerpt be found, it can
immediately be returned to the querying
node, since the querier is directly accessible
(through its IP address). In contrast, in wire-
less ad-hoc networks the answers to a query
have to be propagated back to the querier
via the network (the querier is not directly
accessible), burdening further traffic.
The aforementioned issues can be addressed,
to a certain extent, by algorithms proposed for the
problem of routing in wireless ad-hoc networks,
though, these approaches consider neither the pe-
culiarities of searching for CBMIR purposes nor
the size of the transferred data, since music data
are considerably larger than routing packets.
Research related to the application of CBMIR
in wireless ad-hoc P2P networks is so young,
that to our best knowledge the work by Karydis,
Nanopoulos, Papadopoulos, Katsaros, and Mano-
lopoulos (in press) is the only one to examine the
issue of CBMIR in ad-hoc wireless networks.
Accordingly, to address the requirements
posed by the wireless medium, Karydis et al. (in
press) proposed the following techniques:
outline of the searching procedure
The problem of finding similar music sequences
in a MANET requires a searching procedure,
which will detect MHs in the MANET that have
similar sequences, find those sequences in the
MHs and return them back to the querier. The
already described requirements of the wireless
framework formulate the examined searching
procedure in the following way:
1.
There is no prior knowledge of the data MHs
store; that is, the querier has no knowledge
of the location of the required data.
1. To fulfil the first requirement, breadth-first
searching is performed over the wireless
ad-hoc network using knowledge about
neighboring MHs (obtained by probing
neighborhood at specific time points). This
approach can cope with mobility, maintain
increased final recall and constraint the
drawbacks of flooding, for example, exces-
sive traffic due to multiple broadcasts (as
2.
MHs that have qualifying sequences have
to be reached in a way that addresses their
mobility and minimises traffic. Due to their
relative positions and the preferred tolerance
to traffic (see Figure 1) all such nodes may
not be possible to reach.
3.
At each reached MH, the qualifying se-
quences have to be detected by detaining
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