**3.3 Experimental results on simulation model with three sinks**

In this subsection, through experimental results on the simulation model with three sinks, the effectiveness of the transmission power control introduced in our scheme is evaluated. In the following experimental results, the battery capacity of each sensor node was set to 0.2J, and the range of radio wave of high power transmission in each sensor node was set to 200 m and it of low power transmission in each sensor node was set to 150m.

As the first experiment on the simulation model with three sinks, it was assumed that the evaluation node marked in Fig.4 detected an abnormal value and transmitted the data packet with this abnormal value periodically, as in the above subsection 3.2. The routes used by

Autonomous Decentralized Control Scheme for Long-Term

me is extended by early switching to low power in high node density.

*evaluation node*

*evaluation node*

Fig. 8. Routes used by applying our scheme (*Te* = *E*×0.5J )

**3.4 Discussion** 

Operation of Large Scale and Dense Wireless Sensor Networks with Multiple Sinks 455

nsor nodes is shown, and the lifetime of the simulation model with three sinks, as in Figs.7, 8 and 9, is compared. From Figs.10, 11 and 12, it can be confirmed that the effect of our sche-

*evaluation node*

*evaluation node*

(c) 1 to 2000 data packets (d) 1 to 3000 data packets

To facilitate ubiquitous information environments by wireless sensor networks, their control mechanisms should be adapted to the variety of types of communication, depending on ap-plication requirements and the context. Currently, adaptive communication protocols for the long-term operation of the above ubiquitous sensor networks (Intanagonwiwat et al., 20-03; Silva et al., 2004; Heidemann et al., 2003; Krishnamachari & Heidemann, 2003; Wakabay-ashi et al., 2007) are under study. In

(a) 1 to 500 data packets (b) 1 to 1000 data packets

applying our scheme are shown in Figs.7, 8 and 9, where the number of sensor nodes is 1000. In Figs.7, 8 and 9, *Te* was set to 0.0J, *E*×0.5J, and *E*×0.9J, where *E* indicates the battery capaci-ty of each sensor node. Of the 3000 data packets transmitted from the evaluation node, the r-outes used by the first 500 data packets are illustrated in Figs.7, 8 and 9(a), those used by the 1000 data packets are in Figs.7, 8 and 9(b), those used by the 2000 data packets are in Figs.7, 8 and 9(c), and those used by a total of 3000 data packets are in Figs.7, 8 and 9(d). From Figs. 7, 8 and 9, it can be confirmed that the effect of our scheme is extended by early switching to low power.

Fig. 7. Routes used by applying our scheme (*Te* = 0.0J )

Next, it was assumed that data packets were periodically transmitted from a total of 20 sensor nodes placed in the set simulation area. In Figs.10, 11 and 12, the transition of the delivery ratio of the total number of data packets transmitted from a total of 20 randomly selected sensor nodes is shown, and the lifetime of the simulation model with three sinks, as in Figs.7, 8 and 9, is compared. From Figs.10, 11 and 12, it can be confirmed that the effect of our scheme is extended by early switching to low power in high node density.

Fig. 8. Routes used by applying our scheme (*Te* = *E*×0.5J )
