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F IG . 28. Optimal number of broadcast channels.
objects from four different broadcasting schemes. The 4 broadcasting schemes have
1, 2, 4, and 8 parallel channels. This test was performed with up to 40 pages in each
broadcast. The results show that it is always advantageous to use more broadcast
channels, especially when relatively a few objects are requested. While there will be
more conflicts between objects, this does not quite counteract the shorter broadcast
length of the many-channel broadcasts. This is especially evident when only a few
objects in a broadcast are being accessed.
7 . 2 O r d e r e d A c c e s s L i s t
Based on the results reported in Sections 7.1 and 3.6 , in order to balance and to
compromise between the access time and power consumption, the general access
protocol for an indexed broadcast parallel channel configuration should be modified
[48,49,53,61] . The goal was to use heuristics that generates an ordered access list of
requested objects that reduces:
The number of passes over the air channels, and
The number of channel switches.
With reference to the discussion in Section 7 , during the search step, the index is
accessed to determine the offset and the channels of the requested objects. With this
information available a sequence of access patterns to pull objects from the air chan-
nels during each broadcast cycle is generated (see Section 3.6 ). Finally the retrieval
step is performed following the generated access patterns. The extended protocol is
as follows:
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