# Smart Warehouses: Rationale, Challenges and Solution Directions
## 4 Results
### RQ-4: What Are the Currently Adopted Technologies for Realizing Smart Warehouses? Many developments are intertwined and part of the whole process. When we analyze the current technologies, the same pattern can be observed. Most technologies that are implemented to realize a smart warehouse are either on a system level or on a data-providing level. On a data-providing level, RFID is clearly present in the papers. RFID is linked to technologies such as IoT and various operation management systems. In this chapter, the summary of the technologies, as presented in Figure 5, is described in detail. RFID technology can be seen as \"one of the most important technologies in IoT\" [24], it is key for the automated warehousing systems [14; 26]. An RFID-based intelligent warehouse management system (RFID-IWMS) realizes the effective management of spacing, automatic recognition, and tracking of goods in the whole warehouse process, and the exchange of real-time data between operations and the WMS [16]. To develop a \"smart\" self-adjusting warehouse, it is required to apply RFID-tags to both inventory items and warehouse storage equipment. In this machine-to-machine (M2M) network, the shelves or parts of the shelves are automatically allocated to other locations [25]. Together with a dy  
Figure 5: Summary of frequency of adopted technologies. namic bottom-up approach linked to an IoT infrastructure, enabling the system to have self-organizing behavior and interconnecting all warehouses within the supply chain [29, 32]. An IoT-based WMS is a WMS in which all incoming/outgoing products and activities are controlled, and deviation in order quantity can be automatically managed and solved [3, 22, 30]. Integrated WMSs (iWMS) and communication networks (cabled/wireless) are linked with smart labels (barcodes, RFID, automatic identification (Auto-ID)) and facilitate identification, storage, tracking, and control for all incoming and outgoing goods at a warehouse [13]. The use of a CO in WMS creates a product-driven system that represents products, resources, and workers. In short, an IoT-approach in which communication and decision making are endorsed to secure joint, reactive, and smart operations [23]. Enhanced with CoT, everything is seen as a \"thing\", allowing heterogeneous resources to be amassed and abstracted to the variation in demand [21]. Finally, the WMS should also be integrated with the enterprise resources planning (ERP) system to manage and control all data and support supply chain decision-making and planning [13]. The application of path development algorithms and ceiling-mounted cameras will allow the AGVs to be self-instructing and cope with alterations. The purpose of the mounted cameras is tracking and dynamic control [15]. Further development in robotics could include the interaction between all robotics, conveyor belts [18], and other technological applications on site. Differentiated probabilistic queuing (DPQ) is suggested for the scheduling of the AGVs. With DPQ, priority can be given to the different orders coming in. Possible forms of priority are the willingness to pay and the urgency of order [20]. Besides AGVs, artificial reality (AR) can be embedded in warehouses by having the employees use smart glasses in their work. AR speeds up processes, and employees do not have to use hand mobile devices to scan/operate warehouse products and instruments [27, 28]. Another system to optimize labor resources, reduce in-warehouse travel distance, and define order-picking priority could be the OPOS. The OPOS interacts with the WMS for the stock and data storage [19]. To determine operations workflow and keep risk management into consideration, a workflow decision support system (WDSS) is suggested. The WDSS is integrated with RFID, the analytical hierarchy process (AHP), and case-based reasoning (CBR). AHP allows both quantitative and qualitative criteria to be taken into consideration. CBR uses former solutions to help in the current decision-making [17].