With the popularization of Internet-of-things (IoT) and wireless communication systems, a diverse set of applications in smart cities are emerging to improve the city-life. These applications usually require a large coverage area and minimal operation and maintenance cost. To this end, the recently emerging backscatter communication (BC) is gaining interest in both industry and academia as a new communication paradigm that provides high energy efficient communications that may even work in a battery-less mode and, thus, it is well suited for smart city applications. However, the coverage of BC in urban area deployments is not available, and the feasibility of its utilization for smart city applications is not known. In this article, we present a comprehensive coverage study of a practical cellular carrier-based BC system for indoor and outdoor scenarios in a downtown area of a Helsinki city. In particular, we evaluate the coverage outage performance of different low-power and wide area technologies, i.e., long range (LoRa) backscatter, arrow band-Internet of Things (NB-IoT), and Bluetooth low energy (BLE) based BC at different frequencies of operation. To do so, we carry out a comprehensive campaign of simulations while using a sophisticated three-dimensional (3D) ray tracing (RT) tool, ITU outdoor model, and 3rd generation partnership project (3GPP) indoor hotspot model. This study also covers the energy harvesting aspects of backscatter device, and it highlights the importance of future backscatter devices with high energy harvesting efficiency. The simulation results and discussion provided in this article will be helpful in understanding the coverage aspects of practical backscatter communication system in a smart city environment.

The present study introduces an inkjet-printed flexible coplanar waveguide (CPW) patch antenna array concept. Single antenna and four-element antenna arrays were characterized, which were attached to a sub-miniature version A (SMA) connector via an innovative solderless, 3-D printed "plug and play type" tightener. &#xD;Furthermore, indoor wireless communication and internet of things (IoT) scenarios with commonly used wall materials including gypsum and plywood board, on which the patch antennas and antenna arrays can be attached, were also presented. In order to validate the concept, design and fabrication iterations in parallel with numerical and experimental investigations were executed. To elaborate, single antenna and antenna array configurations without and with wall materials were characterized to see their functionality at 2.4 GHz resonance frequency with beyond 300 MHz bandwidth, respectively. The results demonstrated that the investigated configurations fulfill the short-range radio transmission and can be utilized, e.g. for indoor backscattering type communications and wireless sensing applications, as an affordable and versatile alternative for their conventional counterparts. Being attached to their corresponding background materials, single antenna specimens were measured to have return losses beyond 18 dB and peak gains around 1 dBi while higher peak gains above 6 dBi were detected for antenna arrays.&#xD;Moreover, the antenna arrays can enable multiple-input and multiple-output (MIMO) communication. The proposed arrays had diversity performance in terms of return losses higher than 15 dB, isolation more than 20 dB, envelope correlation coefficient (ECC < 0.001), diversity gain (DG > 9.95 dB), mean effective gain (MEG < -3 dB), power ratio factor (k < 0.5 dB), and channel capacity loss (CCL < 0.4 bits/s/Hz).