将蓝牙rssi(信号强度)转换成距离的问题。没有准确的解决办法，但是有人做过一个拟合回归函数，其变化规律比较类似于rssi的变化规律，函数如下:
d = 10^(abs(rssi) - a / (10 * n))
A Bluetooth gateway is an electronic device that connects a Bluetooth product to other hardware. For instance, an audio or stereo BL gateway connects a Bluetooth-enabled device to an external speaker. In this article, our focus will be on a cellular BL gateway. Cellular BL gateways converge cellphone accounts with home landlines.