# Smart Parking: A Literature Review from the Technological Perspective
## 1 Introduction  
The Internet of Things (IoT) has changed the habitual behavior of people, giving them many comfort improvements. This effect is allowing IoT solutions to grow rapidly [1]. Some research works have pointed out that the number of IoT devices connected to the Internet is increasing exponentially and will be nearly 77 billion by 2025 [2; 3; 4; 5; 6; 7]. The Internet of Things (IoT) refers to the interconnection and exchange of data among devices/sensors [8], and most of IoT applications involve particular requirements such as long-reach, low data rate, low energy consumption, and profitability. Moreover, user network coverage may increase with cellular network technologies. However, cellular network technologies provide too much power to the devices, which is why IoT applications have driven wireless transmission technologiessuch as Low-Power Wide-Area Network (LPWAN). This technology provides long range connections: approximately 10-40 km in rural areas and 1-5 km in urban areas [1; 8]. Because of the growth of IoT and cloud systems, smart cities have great opportunities in terms of technological developments and accessibility, creating a revolution in some aspects of people's lives [9]. Smart city applications are being implemented in many countries, as they improve the quality of life of their citizens and help reduce environmental pollution by optimizing time and fuel consumption [10]. Smart parking is popular among smart cities, as described in articles of the industry [11; 12]. These papers highlight that smart parking reduces congestion, increases revenue, has a pricing system that is adjusted based on the demand for availability on-peak hours, and reinforces traffic laws by using cameras to detect violators among others. Parking space search is one of the most important activities in a city, reaching up to 31% of ground usage in big cities [13]. On average, a vehicle is moving 10% of the time, and the rest of the time it remains stopped either temporarily or permanently, as mentioned in [14]. The common method used to find a parking space is manual as discussed by the authors of [15]. Approximately 30% of vehicles on the street are looking for parking, and the average time to do is ~7-8 min. In cities with high vehicular congestion, finding an available parking spot can be a waste of time and resources. The authors of [16] found that, in areas such as Los Angeles, vehicles looking for parking spots produced over 730 tons of carbon dioxide and burnt 47,000 gallons of gas. The inconvenience created by the need for finding a parking slot causes some drivers to park in unauthorized zones, plus increasing vehicular congestion and carbon dioxide emissions. For instance, if drivers had access to a database containing information about parking spots in real-time, there would be more opportunities for selecting an appropriate route to a desired parking slot. Autonomous vehicles are part of the smart parking initiative, as they consider mobility, fuel consumption, and journey time. Long-range Autonomous Valet Parking (LAVP) presents a novel approach, making an autonomous vehicle temporary park in a car park within an urban area. The authors of [17] state that the Scheduling Center is the core, as it coordinates the nearest route to a drop-off place and find the best car park. This approach will benefit users by providing a reservation system in a cost-effective manner. Other approaches, like [18], suggests that customers use an Android application to reserve a parking place in advance. In this solution, the authors propose using a trolley to move the car to the reserved spot by using a genetic algorithm. There are several works that aim to provide a classification of some components of a smart parking solution [13; 19; 20; 21; 22; 23]. First, [PERSON] and [PERSON] [19] denote a classification of parking systems, where the authors list several types that refer to assisted parking search (APS), Information Systems (IS), payment, automated parking, reservation, park assistant among others.