Information Technology Reference
In-Depth Information
6.2.1
Retrieval Protocols
In case of parallel air channels, one has to account for switching between channels
when analyzing access time and power consumption. The switching time between
two different frequencies is assumed to be in the range of microseconds [51] .Dur-
ing the switching time, the pages that are being broadcast on different channels can
not be accessed by the mobile unit. In addition, the mobile unit, at each moment
of time can tune into one channel. Finally, we assumed that the power consump-
tion for switching between two channels is 10% of the power consumed in active
mode.
6.2.1.1
Hierarchical Method.
The following protocol shows the se-
quence of operations.
Hierarchical Protocol
1) Probe onto channel and retrieve offset to the next index
active
2) Do {Reach the next index
doze
3)
Retrieve the required index pages
active
4)
Do {Reach the next possible required data page
doze
5)
Retrieve the next possible required data page
active
6)
} while every possible required data page is
retrieved from the current broadcast
7)
} while there are un-accessed objects because of overlapped
page range
6.2.1.2 Single-Class Indexing Scheme. Similar to the single air
channel environment, we assume that the first page of every index contains infor-
mation indicating the location of each index class. The protocol below shows the
sequence of steps:
Single-Class Protocol
1) Probe onto channel and retrieve offset to the next index
active
2) do {Reach the next index
doze
3)
Retrieve offsets to the indexes of required classes
active
4)
Reach the next possible index
doze
5)
Retrieve the next possible required index page
active
6)
do {Reach the next possible index or data page
doze
7)
Retrieve the next possible index or data page
active
8)
} while not (all indexes and data of required classes are scanned)
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