## 2 Related Work  
There is no research done yet to propose a complete model of RFID implementation in vehicle management at toll gate with no-lane concept. The proposed model has three parts: antenna installation, algorithms to avoid reader collision as well as tag collision. Contemporary research is considered and discussed here that can highlight the work done on each part distinctively. In [2], two ray model is used to investigate path loss effect of RFID system at different heights. Multi ray model is designed for line of sight communication (LoS) communication at mm wave frequency [4]. Frequency diversity is introduced in two ray propagation model for indoor and outdoor environment [3]. In [11], research revealed that when down tilting mechanism is used, a vertical beam focuses on the vehicle on the road and reduces interference outside of the beam. It is necessary to determine the downtilt angle of the antenna element in order to maximize the coverage range of the reader antenna. Mechanical downtilt angle (MDT) and electrical downtilt angle (EDT) are two common approaches. For mechanical methods, a site visit is necessary to calibrate the tilt angle. The electrical method, on the other hand, does not require site visit, but requires a control system and advanced technology to adjust the tilt angle when necessary [12]. As a result, MDT is the preferred method for simplicity and low cost. Thereafter, to mitigate reader collision multi-access methods are used which include frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and carrier sense multiple access (CSMA) [13; 14; 15]. In Class 1 Generation 2 UHF standard, FDMA uses two separate frequency channels to establish communication with tags [16]. Although this method reduces interference between readers, reader-to-tag collisions remain a problem. Furthermore, conventional passive tags do not have any on-board frequency tunning circuit, so they cannot identify specific readers of corresponding frequency channels. TDMA based Colorwave provides different time slots to interfering readers to avoid simultaneous transmission [17]. Each reader selects a different time slot or color to transmit. In the event that any adjacent reader chooses the same time slot, it reselects a new time slot. It is crucial for this method to ensure accurate time synchronization between participants. In CDMA, all tags must be code-designated and need extra on-board circuit, which makes the system complicated and expensive [16; 17]. ETSI EN 302 208 is one of the most advanced protocols for RFID applications. CSMA mechanism called 'Listen before Talk' is used in the above protocol. If the data channel is idle, the reader starts reading if it is not, it waits for random backoff time [13; 18]. Another distributed method, pulse protocol used for passive tags and the method can be made cost-effective. Pulse protocol uses two independent channels. The first is a control channel, and the second is a data channel. For reader-tag communication, a data channel is used. An investigation of the reader's action is conducted through the control channel [19; 20]. As the number of readers increases, collisions persist. Next, tag collision is reduced by probabilistic or deterministic approach. ALOHA based algorithms could reduce tag collisions but may take a long time to identify the tag, resulting in tag deprivation [10; 21]. The tree algorithm is a deterministic approach to receiving tag responses. By enquiing with the identifying number in the read cycle, the reader validates tags in the interrogation zone. There are three types of tree algorithms including collision tree, query tree, and binary tree [10]. A query tree protocol enquires with a series of prefixes. Tag compares the prefix with the tag ID and if the comparison is true, tag responds with the tag ID. A collision mode reader sends a 1-bit prefix query and splits the group into two subgroups.