Information Technology Reference
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9) } while there are some data pages which are not retrieved because of
overlapped page range
6.2.2
Performance Evaluation
Once again, the scope of simulator reported in Section
5
was extended to study
the response time and energy consumption of the single-class and hierarchical in-
dexing schemes in parallel air channels based on the input parameters presented
in
Table IV
.
6.2.2.1 Response Time.
Figure 24
shows the response time of broadcast
data in parallel air channel without and with indexing. From this figure, it can be
concluded that:
In the case of no indexing, the response time was constant and independent of
the number of channels in that without any indexing mechanism in place, the
mobile unit has to scan every data page in sequence until all required data pages
are acquired. Nevertheless, for a single channel environment, the response time
without an indexing scheme is less than with any indexing scheme. Moreover,
when indexing schemes are in force, the response time lessens as the number of
channels increases.
For inheritance and aggregation cases the response time decreases as the num-
ber of channels increases—as the number of channels increases, the length of
the broadcast decreases. The shorter the information in each channel, the lesser
the response time. However, the higher the number of channels, the higher the
probability of conflicts in accessing data residing on the different channels. As
a result, doubling the number of channels will not decrease the response time
by half.
For inheritance and aggregation indexing schemes, the single-class method
offers a better response time than the hierarchical method. The single-class
method accesses do not have to be started at the beginning of the broadcast.
When a probe takes place, the first class belonging to the set of classes to be
retrieved can be accessed directly. Other required classes are accessed in se-
quence. For the hierarchical method, on the other hand, any access has to be
started from the beginning of the broadcast, which makes the response time of
the hierarchical method longer.
Indexing based on the aggregation relationship offers a lower response time than
that of the inheritance relationship. Since the distribution of objects in the inher-
