# Making Shopping Easy for People with Visual Impairment Using Mobile Assistive Technologies
## 4 Discussion  
In this study we have presented different approaches, techniques, and technologies to help PVI navigate and identify products while shopping. We classified the shopping approaches into preparing a list of what to purchase and navigating inside the store to identify items on the shelves. Solutions for shopping list preparation used some techniques, such as CV, OCR and STT, to read list details from PVI and store them in a database. During shopping, audio messages are given to PVI about shopping items stored in the database using TTS. Shopping preparation makes it easy for users to buy from a list, but it has some limitations: it assumes that the shopper already knows what they wish to buy on their trip [8], and this is not always the case. Also, shopping may take a long time. Shopping is not simply buying items on a list. For people without visual impairment, shopping also entails opportunistically exploring new products or brands, engaging in cultural learning about tastes, and making different choices based on occasional sales [89]. Some solutions require taking an image of the shopping list, but it is difficult for PVI to take a good quality image. Researchers have also developed multiple solutions to help PVI navigate and identify products using RFID and NFC for tag based systems. RFID tags have some benefits: their signals can penetrate walls and obstacles, which cover a wide area, and reuse existing infrastructures, resulting in cost reduction [90]. Also, PVI do not need to be in a certain direction to receive messages from the tagged item [91]. Moreover, the tag does not need to be within the line of sight of the RFID reader which allows it to be placed inside items. However, there are some drawbacks: to setup the environment, hundreds of RFID tags need to be installed, which is costly. Information overload is another major problem, as it is overwhelming to receive information about all the items in the store at the same time and attempt to use this information to identify various objects [56]. Another significant limitation is that these systems are used only in a restricted environment in which objects have been tagged, and these tags need regular maintenance. Sometimes, RFID tags are attached to items like the liquid in metal cans, which reflect the radio waves during communication. Using RFID technology with glass causes a reflection of the radio waves, which affects the system outcome. NFC tags have the following benefits: PVI can simply touch the NFC tag with an NFC reader, such as a smartphone, to begin the required service. NFC readers read information stored in the tags, which enables PVI to get product information. Moreover, by using NFC tags, researchers can build low-cost indoor navigation systems. NFC technology also has a very low response time, because the time required to transfer data from an NFC tag to a mobile device and generate the walking path to the items is short. They also provide accurate position and orientation information, so the orientation of the user to the destination is facilitated. Moreover, NFC tags work well in unclean environments and do not require a direct line of sight between the reader and the tags. Finally, PVI do not have to carry large or bulky devices--only their smartphones. However, there are some drawbacks: NFC tags are not as effective and efficient as Bluetooth or Wi-Fi Direct when it comes to data transfer rates. NFC can only send and receive very small packets of data, so real-time positioning cannot be provided in the NFC Internal system. Also, PVI must be inside the reading area in order to identify NFC tags and must have an NFC-equipped smartphone. Moreover, researchers developed multiple solutions to help PVI navigate and identify products using CV techniques. CV techniques rely on visual tags, such as QR codes, barcodes, and AR markers, or utilize information about the objects' physical features.