Study On Application Of ISM Communication In The Mountain Road Portable Early Warning Device

With the implementation of the great development strategy, the mountain aera economy keeps a continued growing. The transportation demand increases greatly. Because of the worse mountain road condition and the shortage of traffic safety facilities, the road traffic accident increases day by day. To keep the growth of mountain aera economy and ensure the great development, the improvement of mountain traffic safety is imperative. The present measures of enhancing the mountain road traffic safety are strengthening the management of the drivers, improving the road condition, enhancing the vehicle safety technology property and so on.In this paper, the main object is a portable early warning device based on a RF transmission chip nRF905. This early warning system is a set of independent electronic equipment with initiative alarm and can improve the traffic safety effectively. The warning device is mostly applied in the vehicles which drive on the mountain road frequently. The early warning device sends and receives signals according to a certain communication protocol. When the signal of the opposite vehicles has been received, the warning device onboard gives alarm to avoid accidents.The main parts of the portable warning device are the wireless RF transmission chip and MCU. The chip nRF905 works in the ISM band and AT89LV51 is selected to be the control unit. This system has the advantages of low cost, simple peripheral circuits, and strong anti-jamming, low power consumption and good product stability. As the control unit of the portable warning device, AT89LV51 is in charge of setting the nRF905's state, controlling the signal transmission and alarm warning to the driver and so on.There is existence of a variety of interference factors in the practical application, such as noise, different time bases in vehicles. In will disturb the communication of the early warning system. In makes the early warning devices working in a disunity time basis, if the early warning devices communicate in a common procedure. There may be more than one device transmitting in a certain slot. It can cause interruption between devices, even more it can fail the whole early warning system. In this paper, pseudo-random sequence code-m sequence is adopted to control the communication procedure. It can guarantee the receiving of warning signals and improve the road traffic safety greatly.