The Design And Implementation Of DSRC Protocol Software In ETC System

Europe, America and Japan had started researching electronic toll collection system in the 1900 s.China began researching dedicated short range communication protocols in the early of 2000 s, and officially released it in 2007, which unified communications rules between RSU and OBU. Many domestic research companies focused on three aspects: RSU equipment, OBU equipment, DSRC protocol development. This thesis accomplishes DSRC software, according to GB\T20851. The purpose is to achieve the protocol functions, improve transaction efficiency and reduce communication time.This thesis is based on arm + linux platform. Respectively, the physical layer, data link layer, application layer and devices application layer are designed and implemented. The physical layer is completed using the RF chip BK5823.BK5823 driver is loaded into the linux kernel in the form of modules. Since DSRC protocol is unequal agreement, the software of two ends are inconsistent. RSU data link layer is implemented with a state machine. The state machine in RSU has four states and a dozen events. The state machine in OBU has only one state, and OBU is a passive device. The design of data link layer protocol was refered to ?stop and wait protocol?. In the data link layer, this thesis uses a hash table as the data structure storing in the frame, while taking advantage of the many functions of linux(asynchronous notification, memory allocation, interrupt upper and lower parts,etc.) to ensure the real-time communication. The main application layer is T-KE design. The design of T-KE includes encoding and decoding,segmentation and re-segmentation. Application layer described by ASN.1 abstract language uses eclipse plugin as ASN.1 compiler. ASN.1 structures can be successfully mapped to the C language structure. It uses PER encoding and decoding library to achieve conversion bitstream. The ideas of segmentation and re-segmentation refered to the ideology of fragmentation and reassembly in TCP\IP protocol. Application layer also implements the B-KE and I-KE’s interface functions. I-KE layer has two state machines. The I-KE state machine of RSU has four states, while the OBU has three states. It primarily designs ICC card and PSAM modules in application device layer. This thesis uses Watchdata card as ICC card and PSAM. This thesis operates TimeCOS card based on ISO7816 protocol. It establishes a folder in TimeCOS card, and achieves a secure transmission function.It uses access permission, information identification, the ciphertext transmitssion. Finally, it tests for each module. RSU module, OBU module, secure transmission module were tested. Test cases used normal and non-normal frame frame for testing, the results were consistent with expectations. The test results showed that this protocol software had a good performance, in line with the function DSRC protocol.