【正文】 nsor node that we designed in the system is truly able to apply to inwell environment, it through the wireless sensor node security certification. At the same time, due to the special nature of the wireless network is that it can spread the wireless signal, we can easily locate staff for coal mine safety monitoring provides more protection.II. SYSTEM ARCHITECTUREThis system is a prehensive monitoring system which is bined with software and hardware. Hardware part includes wireless mobile nodes and fixed nodes which were deployed in the underground tunnel, the main function of them is to collect coal mine environment data and require person’s location. Software part refers to the PC monitoring software which is designed in VC++ is used to summarize and display the data of each node. Monitoring node is divided into mobile nodes and fixed nodes。s deployed in the underground roadway bees very convenient. As the mobile node is carried by the miner, it must be using wireless transmission method. This allows the mine to form a topology of Zigbee wireless sensor network. The fixed node in wireless sensor network is router device and the mobile node carried by miner is the end device. Normally, the router of Zigbee network has no sensor equipment。 it should be a portable and low power consumption node. So the mobile node we designed is only as small as a mobile phone, and it is by builtin lithium ion battery power supply. In power loss, the core processor CC2530 is a low power consumption chip, when it is in the sleep mode, it only need to use less then 1uA work current. In order to reduce power consumption as much as possible on the display, a 100*32 pixel matrix with no backlighting LCD screen was used. The battery’s capacity of the mobile node is 1500mAh, so it is enough to meet the miner’s long hour works in the underground. The battery charge management chip is TP4057, the maximum charge current can up to 500Ma.The mobile node circuit includes the gas concentration sensor and temperature sensor PT1000. As far as we know, many wireless sensor platforms use the digital type sensor. The munication between the digital sensor and the MCU need strict timing requirements. But considering the actual application, the wireless MCU usually has a realtime operating system in general, if we use the microputer to simulate the strict timing, it will affect the realtime of whole operating system. These two sensors output analog signals not digital signals. Only input this signal into a differential amplifier, can we get an appropriate signal that can be converted to a digital signal by an ADC mode within the CC2530 chip. In order to facilitate the carrying, external antenna was not used in our mobile node, instead of using a patch antenna. And we customize a shell like a cell phone size。 it makes the fixed node with the function of soundlight alarm. Considering that it may occur the emergency of without electricity, fixed node also builtin a lithiumion battery. Under normal conditions, lithiumion battery is in charging status, when external cable disconnect, fixed node is automatic switched to battery power, which can ensure the mobile node can deliver the information through fixed nodes in underground.Without regarding to fixed nodes’ portability, we have a customized shell that has excellent explosion properties, and the internal space is enough to hold down the GHz antenna. To ensure safety, all cables and the location of sensors are placed with particular glue sealed, so that it has a good seal.IV. POSITIONING FUNCTION One of the important functions of the wireless sensor networks is localization, especially in the underground tunnel, it relates to the safe of the miner39。s still very vulnerable to external disturbance, therefore it39。t need to add additional hardware design. We also do not need very precise time requirements. This technique is about with measuring the wireless signals strength in the propagation of the loss, to measure the distance between two nodes. Because of this method requires hardware equipment is less, algorithm is simple, so it has been using in many wireless munication field. Comprehensive all conditions, positioning on the use of RSSI ranging technique.A. Hardware Location EngineThe CC2431 wireless microcontroller chip produced by TI Company has a hardware location engine. From the software39。 meanwhile mobile node position is calculated by the PC software, so as to reduce the burden of mobile node puting. To calculate the mobile node location, there must be at least three reference nodes. We will regard router nodes as reference nodes in network, and record the X, Y coordinates of every reference node. Then we let the mobile node send signal to each reference node, so that each reference node can obtain a RSSI values, with these parameters, we can use trilateral measurement method to calculate the specified location of the mobile node. The simpler way give the mobile node to broadcast way to send data, then around it every router node would receive the data from the mobile node, thus obtains RSSI values. Once the mobile node number increasing network, this method will make router nodes more burden, because the every radio message that the router node receives will transmit from the low layer to the top layer. Finally the application layer will analyze data packets. In fact, the mobile node need not to broadcast transmitted data, other routing node can also receive the mobile node packets. Only child mobile nodes of the router node will continue to transmit the packet forwarding upward, the other router nodes will shield out the packet in the bottom of the protocol. In order to let all router nodes can receive the packet which sending by mobile nodes, and send its RSSI values up to the gateway node, we need to modify the relevant function in Z Stack protocol which is provided by TI. First we find the function named afIningData, it deals with