说明：  基于RSSI的定位，已知发射节点的发射信号强度, 接收节点根据接收信号的强度, 计算出传播损耗, 利用理论的或经验的信号传播模型将传播损耗转化为距离, 然后再计算出节点的位置
(RSSI-based positioning, known to launch the node transmission signal strength, the receiving node according to received signal strength, transmission loss calculated using the theory or experience loss of signal propagation model will spread into the distance and then calculate the location of the node)