A Design Of RFID-based PKE Base Station

The old vehicle access system (remote keyless entry system, RKE) is a one-way authentication from vehicle to key,ith the risks of co-channel interference and data being copied for retransmission, and also depends on user’s actively operation. So the security, intelligence, convenience should be improved, which stimulates new vehicle access system (passive keyless entry system, PKE) research. Therefore a new design of PKE base station is presented in this paper, with the hardware, software logic, system schedule all are detailed. The distribution of magnetic field within the vehicle room is studied furthermore, which greatly support the key location deterrnination. Moreover, a new Manchester decoding software algorithm is introduced to replace the hardware decoding, by using which the system is allowed to be optimized heavily while filter the digital noise mixed in the digital data effectively. At last, security of vehicle access system especially the relay attack is in deep-research, to over take the security risk, distance bounding protocol and also it’s implementation within vehicle access system are introduced creatively for the first time. It is certified by the validation that, this scheme could work steadily and effectively, with some technical difficulties solved successfully, so this paper is full of value for engineering and academic research.The main work of this paper is listed as follows:1. Background, A clear research background is laid out by studying the performance of the current car access, pointing out the defects on security, intelligence, convenience. Finally a new vehicle access system based on RFID (radio frequency identification) is presented.2. Scheme, A scheme of vehicle access based on RFID is presented, with its flow as follows, trigger to search keys, anti-collision, mutual authentication, to determinate the key location, execute the PKE function. High RF link (433.92MHz), low RF link (125kHz), bus communication among vehicle modules, and diagnostic system based on KWP2000protocol all are introduced.3. Implementation of hardware and software, MC9SXEP100works as the MCU within PKE base station, ATA5279for LF signal transmitter, ATA5724for RF signal receiver, meanwhile LIN, KLINE communication bus are implemented by taking advantage of serial communication interfaces on chip. For software, a timer based on real time interrupt module could be easily achieved, and each task is divided into several statuses. CPU switching from different tasks according to status machine, namely multitask scheduling by the timer.4. Test&analysis of PKE system. First, electromagnetic fields inside the vehicle, is deeply researched by the means of simulation and calibration. For example the irregular room inside the car, the number and relative position of LF antennas, material of car all could affect the distribution of electromagnetic fields inside the vehicle greatly, which means blind spot or overflow. Later, the Manchester decoding algorithm is tested by running the radio frequency link. The test shows that this algorithm could decode data correctly as well as effectively suppress noise pulse. Parameters that are important to Manchester decoding such as the acceptable maximum noise pulse width, edge fluctuation margin all are in deep-research. At the last, all the possible attacks are listed, especially relay attack, therefore the distance bounding protocol is introduced to vehicle access system, and an implementation of distance bounding protocol for vehicle access is presented in this paper creatively.