Smart parking systems present one of the essential infrastructure concepts that enable Internet of Things (IoT) in Smart cities. Finding a free parking lot plays a role in reducing traffic congestion, gas emissions, and increasing the quality of life of people living and working in it. Therein, the fundamental part of every smart parking system is the detection of vehicle presence, which is usually employed by devices comprised of power-hungry sensors. This paper gives an extension to state-of-the-art by a systematic in-depth overview of technologies used for the smart parking detection realization consuming mW of power. Deeper insights on the real-scenario performances and power consumption of most popular sensor devices and Low Power Wide Area (LPWA) radio technologies available today (LoRa, Sigfox and NB-IoT) are provided. The results show that based on the architectures of IoT system, lowest consumption is for LoRa devices. Further, analysis of power consumption of commercial LPWA-based Smart parking sensor device is provided along with battery estimation lifetime, which is especially important for the deployment of future smart parking solutions. Battery lifetime heavily depends on the number of parking lots exchanges and based on the less frequent changes, the estimated battery lifetime is approximately 7 years. Inspired by the limitations of power-hungry and relatively expensive smart parking sensor devices, two strategies for the optimization are proposed: first one is based on the premise where a drop in received signal strength of the LPWA device can serve as the presence of the vehicle in the parking lot, while the second one proposes a big picture on a novel architecture for harvesting the surrounding energy and using the same for circuitry wake-up therefore saving the energy.

智能停车系统提出了在智能城市中启用物联网（IoT）的基本基础设施概念之一。寻找免费停车场在减少交通拥堵，瓦斯排放以及提高居住和工作的人们的生活质量方面发挥着作用。其中，每个智能停车系统的基本部分是检测车辆的存在，这通常由耗电传感器组成的设备采用。本文通过系统深入地概述了用于消耗功率为mW的智能停车检测实现技术的最新技术，对现有技术进行了扩展。提供了对当今最流行的传感器设备和低功耗广域（LPWA）无线电技术（LoRa，Sigfox和NB-IoT）的真实场景性能和功耗的更深入的了解。结果表明，基于物联网系统的架构，LoRa设备的功耗最低。此外，提供了基于商用LPWA的智能停车传感器设备的功耗分析以及电池估计寿命，这对于部署未来的智能停车解决方案尤其重要。电池寿命在很大程度上取决于更换停车场的次数，并且根据不频繁的更换，估计电池寿命约为7年。受耗电且价格相对昂贵的智能停车传感器设备的局限性启发，提出了两种优化策略：第一种是基于这样的前提：LPWA设备的接收信号强度下降可以作为车辆的存在在停车场，