**Introduction**
Real-time detection of parking spaces plays a crucial role in achieving intelligent management of parking lots and improving the utilization of available spaces. It is also an essential requirement for modernizing parking management systems. The development of parking space detection systems has gone through three main stages: ground loop detection, gate control, and real-time position detection. The level of detection technology directly affects the efficiency and performance of these systems. With the rapid advancement of sensor technologies, the accuracy and reliability of parking detection have significantly improved.
The traditional first two generations of parking detection systems are often bulky, complex to install, and lack scalability, energy efficiency, and real-time capabilities. These limitations make them unsuitable for the fast-growing demand in modern parking environments. To address these challenges, new technologies such as WiFi and RFID have been introduced to enhance system performance and reduce costs.
WiFi is a short-range wireless communication technology that uses radio waves for data transmission. It offers wide coverage, with a radius of up to 100 meters, and high-speed data transfer, reaching up to 54 Mbps. Additionally, it has a low entry barrier, allowing devices supporting WiFi to connect easily with proper permissions. In parking space detection systems, WiFi is used to transmit data from sensor nodes to the central system, eliminating the need for cumbersome wiring and reducing both cost and energy consumption. This makes the system more scalable and flexible.
Radio Frequency Identification (RFID) is a non-contact automatic identification technology that uses radio frequency signals for communication. Operating at the 2.4 GHz band, RFID reduces the requirements for system equipment and minimizes sensitivity to frequency deviations. Its integration into parking space detection systems helps standardize equipment and improves the accuracy of vehicle tracking. The unique vehicle ID associated with each RFID tag allows for quick and accurate identification of parked vehicles.
This paper presents a scalable AMR-based parking space detection system that integrates WiFi and RFID technologies. By combining these technologies, the system significantly reduces the cost, complexity, and power consumption while enhancing detection accuracy and system scalability.
**1. System Design**
**1.1 Parking Space Detection System Design**
The parking space detection system consists of several key components: a server, a wireless router, a parking space display, an RFID reader, and AMR (Anisotropic Magneto-Resistive) sensor nodes. The server processes the data uploaded by the sensor nodes and sends the results to the display. It also communicates with the RFID reader to issue commands. The wireless router establishes a local area network, connecting all parts of the system. The parking space display provides real-time updates on the status of each parking spot.
The RFID reader acts as a network controller, managing both uplink and downlink data and commands. The AMR sensor nodes function as slave nodes, collecting magnetic field data and transmitting it wirelessly to the RFID reader. This two-way communication ensures accurate and efficient data exchange.
The system employs a star topology, where the RFID reader serves as the central hub, and the AMR sensor nodes operate as peripheral nodes. This design enhances system stability and scalability.
**1.2 System Circuit Design**
The circuit design of the parking space detection system includes:
1. **AMR Sensor Node Circuit**: This includes the power supply section, magnetic field acquisition module, data preprocessing unit, and RF transceiver.
2. **RFID Reader Circuit**: This consists of the RF transceiver, WiFi module, data processing unit, and control unit.
The power supply for the AMR sensor node is managed by the TI APL5312-33, which regulates the input voltage of 4.2 V to 3.3 V. The magnetic field detection is performed using the MMC2122MG AMR sensor, known for its small size, high sensitivity, and low power consumption. It features an integrated I²C bus, eliminating the need for external A/D conversion.
The microcontroller used in the AMR sensor node is the MSP430F2618, which offers low power consumption and high performance. It communicates with the CC2500 radio frequency chip via SPI and uploads preprocessed data to the RFID reader. The RFID reader’s RF transceiver includes the CC2500 and CC2591 modules, which enhance signal strength and receiver sensitivity, making the system suitable for long-range wireless applications.
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