## 1 Introduction  
Radio Frequency Identification (RFID) is one of the most preferred auto-ID technologies among bar code, QR code etc. The word RFID illustrates that object is to be identified by transferring electromagnetic waves. Identification, monitoring and authentication are the significant features of the RFID. A variety of industries have applied RFID technology, from health department to inventory management to industry [1]. This phenomenon is also rapidly implementing to vehicle management over the decade. Parking lot, speed monitoring to electronic toll gate RFID is efficiently employed. Electronic toll collection (ETC) is one of the busiest and most economically beneficial sectors of vehicle transportation. Around the world, RFID is used in almost all ETC. Currently, there is a lane system where each lane has its own reader antenna and tolling booth. The system is therefore expensive to install since each reader has to be paired with a tolling booth. Each lane permits one car to pass the gate at a time hence there is delay to proceed the whole operation.  
Therefore, there must have a suitable model of ETC that operates fast and effortlessly at low cost. Figure 1 depicted the outline of the suggested model considering required parameters and corresponding possible issues.  
The proposed scenario for ETC is designed in such a way that two reader antennas (no. of antenna can be varied according to the toll gate area) installed at the top of the toll gate. The first and foremost concern is that total number of reader antennas can cover the total gate area. A variety of factors influence the installation mechanism, such as the height of the antenna position, the inclination angle, and the beamwidth. The red colored triangle and circle shape represent the possible issues. The tringle one depicts the reader collision, while two reader antennas are try to read the same tag attached on vehicle. The circle one represents the tag collision, when multiple vehicle respond to the same reader. Corresponding solutions are suggested to mitigate the problems. Modified pulse protocol is proposed for reader collision and M-ry tree algorithm for tag collision.  
The position of the reader antenna needs to account the variables such height, downtilt angle, and beamwidth to reduce the path loss and increase the signal strength. Two ray model is the best way to determine the signal strength [2; 3; 4]. Downtilt angle and beamwidth are required for maximize the coverage area [5; 6]. More than one reader antenna within operating region leads to reader collision. RFID functioning is affected in terms of inaccurate and slow readings due to this collisions. To prevent collisions, two mechanisms have been investigated: centralized and distributed. In the centralized method, a central server is responsible for synchronizing all readers and sharing resources. By using the distributed method, readers trade the required information directly to each other without the intervention of a central server [7]. The two methods are based on different protocols, such as the Class 1 Generation 2 UHF standard, Colorwave, and ETSI EN 302 208 [8; 9].  
On the other side, responding multiple tags at the same time creates tag collision leads to inaccurate vehicle identification. ALOHA-based and tree-based algorithms are used to prevent tag collisions [10].  
Figure 1: The outline of the complete model of the suggested method.