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(De)synchronicity schedules
Active
Active
Active
Sleeping
Sleeping
1
2
3
4
5
6
7
8
9 10
1
2
3
4
5
6
7
8
9 10
Active
Active
Sleeping
Sleeping
1
2
3
4
5
6
7
8
9 10
1
2
3
4
5
6
7
8
9 10
Slots in a frame
Slots in a frame
DESYDE schedules
Active
Active
Transmit
Listen
Sleeping
Sleeping
1
2
3
4
5
6
7
8
9 10
1
2
3
4
5
6
7
8
9 10
Active
Active
Sleeping
Sleeping
1
2
3
4
5
6
7
8
9 10
1
2
3
4
5
6
7
8
9 10
Slots in a frame
Slots in a frame
(a)
2-by-2 grid topology.
(b)
Example of (De)synchronicity schedules (top) and DESYDE schedules (bot-
tom) for the 2-by-2 grid.
Fig. 6.
Comparison between (De)synchronicity and DESYDE schedules on the 2-by-2 grid
To illustrate the effect of the above three differences, consider the
2
by
2
grid in Fig-
ure 6(a). An example of the resulting wake-up schedule of the four nodes is illustrated
in Figure 6(b) for both (De)synchronicity (top) and DESYDE (bottom). In this exam-
ple, the frame contains
10
slots, and the four schedules reported (for each approach) are
those of the four nodes in the grid, arranged in the same order as in Figure 6(a). Fig-
ure 6(b) (top) shows the schedules of nodes using the algorithm presented in this paper.
One can see that the left nodes are synchronized for communication at slots
2
−
4
, while
the right ones are active at slots
5
7
. In other words, upper nodes are synchronized
with lower ones (being active at the same slots) and left nodes are desynchronized with
right.
The schedules of nodes when using DESYDE are presented in Figure 6(b) (bottom).
Here upper transmission slots are synchronized with lower reception slots and left active
slots are desynchronized with right active slots. More precisely, at slot
2
, the upper left
node transmits when the lower left node receives, while the right nodes are synchronized
for communication at slot
5
. The lower left node sends its data to the base station at slot
7
and forwards that of the upper left node at slot
9
. The lower right node does the
same at slots
4
and
6
, respectively. Thus, with both approaches we observe the same
coalitions as in our schematic model in Figure 6(a). On the one hand, DESYDE allows
nodes to adapt their active time based on the (static) traffic load and therefore prolongs
the network lifetime. However, one disadvantage is that DESYDE is not well suited for
−
