## 1 Introduction  
The Internet of Things (IoT) is a concept that has evolved in the last decade to provide internet connectivity to objects that we use in everyday life. The versatility of these objects knows no limits. They can be generic devices such as bicycles, motors, home appliances, tools of any kind, and devices such as temperature, humidity, air quality, or inertial measurement unit sensors. These objects are also usually equipped with extra hardware that constitutes mainly a processing unit and a transceiver for digital communications. Consequently, this hardware enables objects to communicate with one another or to send information to the internet [1]. The IoT concept aims to provide an extra layer of intelligence to these objects by enabling remote access. Furthermore, it allows interaction among several objects to achieve a high operational efficiency [2, 3]. Accordingly, the IoT concept has attracted the attention of many industries where automation plays a key role. Applicationscan be found in home and industrial automation, medical aids, energy management, automotive, smart cities, etc.  
Moreover, Low-Power Wide-Area Networks (LPWANs) have emerged to provide the communication means that have enabled the IoT concept. Most LPWAN technologies can, in principle, provide the required internet connectivity to millions or even billions of objects. This communication revolution can be attributed to the LPWAN's capability to establish long-range communication links that go up to several kilometers while using low-power transceivers [4]. Moreover, due to the low production cost, LPWAN transceivers are massively deployed in large-scale environments, i.e., on the scale of cities or even countries.  
During the last decades, Software-Defined Radio (SDR) technology has also become a very popular and powerful prototyping tool [5,6]. Before the introduction of SDR technology, researchers and manufacturers relied only on custom-made expensive hardware and simulation tools. Although simulation tools can be very powerful in describing any physical behavior, they cannot include all the physical variables that are associated with complex engineering problems. On the other hand, SDR technology can provide a physical prototype that can be subjected to testing scrutiny. A noticeable trend in recent years is that SDR technology is used as a final product for many communication system technologies due to the decreasing production costs.  
In this paper, we make use of SDR technology to design the physical layer for LPWAN communication systems. The design steps are generic and can be deployed with any LPWAN standard. However, we adopted the DASH7 Alliance Protocol (D7A) [7]. This communication standard was selected to represent IoT communication systems because its specification is freely available [8], and an open-source software stack is ready to use [9]. The proposed SDR implementation of the DASH7 standard was validated using simulation and experimental analyses. Furthermore, we provided raw DASH7 signals that were recorded using the SDR front-end in indoor and suburban environments to test our implementation; these data sets were correctly labeled, and the accurate positions of every transmitted signal were reported, which can be used in various applications, including localization.  
In the following section, several LPWAN technologies will be presented, and a brief introduction to SDR technology will be provided. The DASH7 Alliance Protocol and our SDR implementation are presented in Sections 4 and 5. In Section 6, we present simulation and experimental results that consolidate our implementation capabilities, followed by the discussion of the achieved results in Section 7. Subsequently, conclusions are drawn in Section 8. Finally, several technical appendices are presented to serve as tutorial material to understand common coding and decoding techniques used in telecommunication systems.