Information Technology Reference
In-Depth Information
F
IG
. 7. A parallel broadcast of 4 channels with eight requested objects.
The access latency is directly dependent on the number passes over the broadcast
channels. One method of calculating the number of required passes over the broad-
cast channels is to analyze the conflicts between objects. For any particular object,
all objects in the same or succeeding page (column) and on a different row (channel)
will be in conflict. Thus, for any specific page (object) in the grid, there are
(
2
M −
2
)
conflicting pages (objects) in the broadcast except the last column (
Fig. 7
depicts a
request for eight objects from 4 parallel broadcast channels).
3 . 6
A c c e s s P a t t e r n s
The conflicts affect both the response time and power consumption. To reduce the
impact of conflicts, retrieval procedures should be enhanced by a scheduling protocol
that allows orderly retrieval of the requested objects during each broadcast cycle. One
could define a set of heuristics as follows to achieve this goal:
Eliminate the number of conflicts
.
Retrieve the maximum number of objects
.
Minimize the number of channel switches
.
As can be noted, the aforementioned set of heuristics sacrifices the number of
channel switches, hence power consumption, for reduced access latency. However,
there is always a trade off between the access time and power consumption. There-
fore, it would be interesting to investigate the effect of the reordered heuristic rules
on the power consumption and access latency.
