Experimental Results
During each run of our test, the results are stored on the device's local memory. These results are discussed
in the sections given below.
Readings for Distributed System
Since each pair changes the channel according to their requirements, every channel change causes interference to some other link and leads to
another channel change. Thus, a larger proportion of time is spent in probing and changing channels. In the given set of readings, the links are
placed at a constant distance from each other. As observed, one Tx-Rx pair changes to a new channel once every 18 seconds on an average. This
phenomenon is called thrashing and is responsible for degrading performance of the system. In the image, the information is in following order:
timestamp of record, the link quality and RSSI of three channels and the selected channel number.
Readings for Centralized System
In the Centralized System, the Controller maintains a timeout between granting consecutive channel change requests. Hence, the time difference
between two consecutive channel changes is atleast equal to the timeout period (20 seconds in our implementation) as can be observed in the given
set of readings. This eliminates the major problem of thrashing discussed above. Also, the controller performs intelligent allotment of channels.
Thus, interference between links is kept to a minimum by the controller.In the image, the information is in following order:
timestamp of record, the link quality and RSSI of three channels and the selected channel number.
Readings for Hybrid System
Similar to the Centralized System, the Controller maintains a timeout and hence a time difference of atleast 20 seconds(in our implementation) is
observed between consecutive channel changes. Thrashing in the system is avoided if a hybrid channel allocation scheme is implemented. Also, since
the controller is just involved in transmission and reception of control packets, overhead data is reduced considerably. However, channel selection
is performed as in the Distributed Scheme and hence there can still be interference between the links. In the image, the information is in following order:
timestamp of record, the link quality and RSSI of three channels and the selected channel number.
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Since each pair changes the channel according to their requirements, every channel change causes interference to some other link and leads to
another channel change. Thus, a larger proportion of time is spent in probing and changing channels. In the given set of readings, the links are
placed at a constant distance from each other. As observed, one Tx-Rx pair changes to a new channel once every 18 seconds on an average. This
phenomenon is called thrashing and is responsible for degrading performance of the system. In the image, the information is in following order:
timestamp of record, the link quality and RSSI of three channels and the selected channel number.
