With the progression of the microelectric mechanic technology and wireless transmission technology, the application of the wireless sensor network becomes much popular.
A wireless sensor network is a network system composed by at least one data collector and lots of sensors, and the communication between the respective components therein is wireless, so that the sensors and the data collectors can be arranged at will, and it is convenient and economical in time to lay out the sensor net system.
A sensor in a wireless sensor network is usually required to be power saving, low cost, and small size, and equipped with a environmental detection device so as to detect the subjects (such as temperature, color, sound, light, smoke and etc.) we are interested in the environment. The detected information is then transmitted to an information collector wirelessly, and then, the environmental status can be known based on the detected information received by the information collector, and relevant applications, such as calamity early warning, can be carried out.
Please refer to FIG. 1, which is a schematic diagram of a wired structural home environment monitoring system according to the prior art. As shown in FIG. 1, a local network includes a control center 11 and a plurality of cluster heads 13, where the cluster heads 13 and the control center 11 are linked by a wired network 12, using the wired protocols such as Power Line Communication (PLC), Ethernet, CAN Bus and etc. Each of the cluster head 13 communicates with a plurality of terminal devices 14 (i.e. end devices), and a star topology is thus shaped, wherein the terminal devices 14 could be a sensor, such as a sensor for temperature, moisture, brightness or smoke, a switch, an alarm, a light controller, an HVAC, a driver of doors and/or windows or an actuator for an emergency accident handle equipment (i.e. sprinkler, generator, exhaust fan and etc.). The wireless communication can be performed with a communication protocol being one selected from a group consisting of a ZigBee, a Z-Wave, a WiBree, a Bluetooth, an Insteon, a WiFi, a UWB and etc.
The terminal devices 14 transmit the detection messages to the cluster head 13 periodically, and then the detection messages are transmitted to the control center 11 via the wired network 12. The control center 11 is configured with corresponding condition and responses control rules. For example, while the smoke detection device transmits a message corresponding to a fire accident characteristic, the control center 11 announces an alarm and actuates an actuator of a sprinkler, etc. Furthermore, the control center 11 could be provided with a function of gateway and allows the user monitoring his home environment and ensuring his house safety via the internet, or sends emergency messages to the user's email or mobile phone.
Please refer to FIG. 2, which is a schematic diagram of a wireless structural home environment monitoring system according to the prior art. As shown in FIG. 2, a mesh network 22 are formed by a control center 21 and a plurality of cluster heads 23 via a wireless network protocol, and similarly each of the cluster head 23 communicates with a plurality of terminal devices 24 and thus a star topology is shaped, as stated in the preceding descriptions.
Based on the above-mentioned examples, an independent power source, generally as a battery, is required for the each of the terminal devices 14, 24 in a wired structural or wireless structural environment monitoring system. Since terminal devices 14, 24 would consume lots of power while detecting the environment status and transmitting the detection message to the cluster heads 13, 23, and the work for maintaining the large number of terminal devices and replacing the batteries thereof are very heavy, complicated, and consuming time, hence it is a important subject in the application of the wireless sensor network that saving the power of the terminal devices 14, 24 and thus prolonging the lifetime of the battery, and reducing the battery change frequency.
From the above description, in order to overcome the drawbacks in the prior art, a transmission power control method and device are provided by the inventor via the diligent research and perseverance working.