wireless ad hoc networking

308 Wireless Ad Hoc Networking
decreases the data-transmitting power. Nevertheless, it is still possible for
node E to send data to F concurrently by using a different data channel
(e.g., channel 2).
According to the channel assignment algorithm of DCA-PC, nodes will
pick the first data channel which will not interrupt the data transmissions of
ongoing nodes or have a chance to be interrupted by the sending/receiving
data of other nodes. Channels that conform to the above conditions will
be the candidates and the first among of them will be selected for the
data transmission. A possible way to increase the throughput is for the
neighboring nodes that are transmitting data to be taken into consideration.
Assume that two nodes (say X and Y) are parts of a sender and receiver pair,
and that they are in the process of selecting a channel as the data channel
from several candidate channels. If there is an ongoing transmission by
two nodes (say C and D), and if at least one of the nodes X and Y is in
the control packages’ transmission range but outside the data packages’
transmission range of C and D, then the channel used by C and D is the
more suitable one for X and Y compared to the original one alloted by the
channel-selection algorithm to increase the channel reuse if available.
For example, the related locations of nodes and the channel utilization
are shown in Figure 11.4. Following DCA-PC, the candidate channels of
nodes X and Y are {1,2,3} and channel 1 must be selected as their data
channel. In our viewpoint, channels 2 and 3 have higher priority than
channel 1 because these two channels are used near by them but are still
available. More importantly, channel 3 will be the best choice in this case
if we count the selected times on them. Finally, nodes X and Y select
G
ch3
E
ch2
F
H
X
Y
C
ch3
D
Figure 11.4
Improving the channel selection manner of DCA-PC.