Reducing the number of control packets while maintaining reliability is an important technical issue.In this paper, we propose a new transmission power control scheme to efficiently compensate for the changes of link quality according to the temperature. To reduce the packet overhead for power control, the temperature measured by sensors is utilized to adjust the transmission power level. By more accurately adjusting the transmission power, the closed-loop feedback process is additionally executed by using control packets.3.?Empirical ExperimentsTo analyze the change of link quality according to the temperature variation, we measured the RSSI in an indoor environment in which the temperature varied from 29 to 35 ��C.
Figure 1(a) shows the layout of the experimental environment.
Our experiment is performed in an empty office to minimize effects on link quality variation from sources other than the temperature. We use TELOSB motes with CC2420 radio chips [13]. The TELOSB mote has a 12-bit resolution SHT11 temperature sensor and an integrated PCB antenna. In the experiment, the transmission power is set to 0 dBm that is the maximum value of CC2420. The packet rate is one packet per 5 seconds. Figure 1(b) shows the distribution of the daytime peak temperature in Figure 1(a).Figure 1.The layout and temperature distribution. (a) Layout; (b) Temperature distribution.Temperature at Node 4 that is installed in the data sever is the highest.
We measure the RSSI between Node 4 and Node B in the situation where the temperature changes over 24 hours.
Figure 2 shows the RSSI corresponding to temperature variation at Node 4 (from 3 P.M. 20th October to 3 P.M. 21st October). The temperature variation is 6 ��C over 24 hours. Cilengitide The RSSI becomes lowest when temperature is highest around 3 P.M. On the contrary, when a temperature is low, RSSI is high with less fluctuation. We can easily observe the inversely proportional relationship between RSSI and temperature. In a high temperature, the link quality is reduced and irregular.Figure 2.The change of RSSI according to temperature.
As shown in Figure GSK-3 3, we measured the RSSI between a sink n
Many semiconductor materials have been tested for their suitability as ion sensors; in particular there is an emerging interest in the use of wide band gap semiconductors as sensitive chemical sensors. Gallium nitrides (GaN) are chemically stable semiconductors with high internal spontaneous and piezoelectric polarization, which make them very suitable materials to create very sensitive but robust sensors for the detection of ions, gases and polar liquids, particularly at high temperatures and in harsh environments [1,2].