Information Technology Reference
In-Depth Information
Extended Retrieval Protocol
1) Probe the channel and retrieve the offset to the next index.
2) Access the next index
3) Do {Search the index for the requested object
4) Calculate the offset of the object
5) Get the channel on which the object will be broadcast
6) } while there is an unprocessed requested object
7) Generate access patterns for the requested objects (using retrieval scheme)
8) Do {Wait for the next broadcast cycle
9) Do {Reach the first object as indicated by the access pattern
10) Retrieve the object
11) } while there is an un-retrieved object in the access pattern
12) } while there is an unprocessed access pattern
7.2.1 Performance Evaluation
To validate the feasibility of this approach, to compare and contrast them against
each other, and to show the trade-off between access latency and computational com-
plexity the scope of the simulator reported in Section
6
was extended. The extended
simulator emulates the process of accessing data from a hierarchical indexing scheme
for both the bottom up and the top down approaches discussed in Sections
3.6.1 and
cess time and power consumption.
The index structure can be transmitted in different fashions including:
A complete index is transmitted at the beginning of each broadcast in the first
channel before the data;
Index is distributed among the data elements;
Index is replicated and interleaved with the data elements; or
A dedicated channel is used to exclusively and continuously transmit the index
in a cyclic manner.
The experimental results indicated that repeated transmission of the index on a
separate channel provides the best response time. Hence, the following discussion is
limited to the employment of dedicated channel to broadcast the index structure.
User requests were randomly generated representing a collection of
K
objects in
the broadcast. In various simulations runs, the value of
K
was varied from one to
N × M
—in a typical user query of public data,
K
is much less than
N × M
. Finally,
to take future technological advances into account, parameters such as transmission
rate and power consumption in different modes of operation were fed to the simulator
as variable entities.