無線網絡中的選擇

　　由于其擴展范圍、易實現(xiàn)性和較小的代碼尺寸，低GHz、低數(shù)據(jù)速率的無線網絡通常是亞GHz專有協(xié)議的最佳選擇。

　　設計者知道無線發(fā)送數(shù)據(jù)有多種選擇。這些包括簡單的命令和控制方案，如遙控鑰匙（RKE）和車庫門開啟器，和更復雜的無線局域網。本文介紹了各種選擇和它們的局限性，因為它們涉及到為工業(yè)應用選擇無線網絡。

　　RKE系統(tǒng)通常用于汽車鎖定和解鎖的門，提供了一個良好的例子，簡單的命令和控制中的應用。在RKE應用，一個命令從鑰匙到汽車接收機發(fā)送。響應一個正確接收的命令，汽車要么鎖定要么解鎖。

　　Receivers in similarly made automobiles can theoretically accept packets sent from any similar model key fob. However， the car will only accept commands from the unique key fob assigned to it. Security protocols like rolling code generators and security encryption are utilized to transmit a unique ID from the key fob to the car. In this way， a driver’s key fob is not able to unlock a similar model car.

　　In the case of automobile RKE， the key fob operator typically hears the locks being engaged. If this audible feedback “click” is not heard， the operator simply presses the button again， completing the feedback loop. To put it in simple terms， if you don’t hear the car unlock， you press the button again until you do.