# Real-Time Location-Positioning Technologies for Managing Cart Operations at a Distribution Facility
## 3 An RFID-Enabled Real-Time Cart-Locating Platform for Mail Facilities  
RFID, which uses electromagnetic fields to establish wireless data communications, is a key enabler for our proposed application. In this section, we present the architecture of this RFID-enabled platform for managing cart operations at distribution facilities. Our project team successfully developed a system based on this architecture, and this system was implemented in a large and busy AMC in an Asian city. The details of the implementation are given in Section 4. With this platform, the AMC is also able to: (i) promptly locate carts loaded with mail bags of departing flights and reduce mail delays; (ii) reduce misplacements of mail bags to ULDs; and (iii) analyze cart movements and derive insights into managing the cart operations from the data collected. This actual implementation also demonstrates the practicality of the platform.  
Our platform consists of the ordinary key components of RFID platforms: tags, readers and middleware. Active RFID is adopted for our platform because of its higher tracking ability. The benefits of active RFID over the passive one in this application are its longer read range (i.e., the maximum distance that the tags and the reader can communicate) and its capability of continuously and automatically tracking the objectives, although the active one is more expensive and needs battery to supply power to the tags [48]. In our application, RFID tags are affixed to the carts in the facility. Each tag has an ID, which is unique in the information system; since each tag is associated with exactly one cart, the tag ID can be used to identify the cart. Several positioning readers are installed at different locations within the facility such that the tags can be positioned by using the estimated angles of arrival communication signals between the readers and the tags and the signal strengths. An illustration of the principle of this locating method is given in Section 4. The middleware establishes the data linkage between the positioning readers and the main information system of the company or organization so that the staff can retrieve real-time locational information about all the carts to facilitate the circulation of mail bags within the facility. Information related to each mail bag (e.g., destination of the mails) is available in the system so that staff can acquire the desired information whenever needed. Mobile applications can be developed on portal electronic devices, such as smartphones and tablets, to provide staff members with an access to the required information from the system in the highly dynamic environment of the facility. From the mobile application, the users can send a request to the platform for locating the carts loaded with mail bags of the selected flights on the map of the facility in real time. Signal lights connected with the RFID tags are installed on the carts so that the users can use the mobile application to send visual signals from the selected carts for effective on-spot searching. In addition to the information about the cart locations, the mobile application also hasthe capability of providing the planned loading times of the mail bags to the ULDs using the latest flight schedule obtained from the airport authority such that the staff members can realize the urgencies of the loading tasks. Figure 1 depicts the flows of information and visual-signal requests on our proposed RFID-enabled platform. The historical data about the cart locations also be analyzed to provide intelligence for improving the staging operations at the mail facility. Examples of such offline data analytics are provided in Section 4.2. In summary, our proposed platform can facilitate mail bags circulating at both operational and analytical levels by the capabilities of real-time tracking of carts, reducing misplacements of mail bags to flights and performing intelligence and analytics on operational enhancement. The overall benefits of the system are as follows.