# Ultra-Low-Power Wide Range Backscatter Communication Using Cellular Generated Carrier +
## 1 Introduction
Specifically, this article makes the following key contributions:  
1. The received signal power of the forward link i.e., between the transmitter (Tx) and the backscatter device (BD), in both indoor and outdoor condition is evaluated while utilizing an in-house built sophisticated 3D ray tracing simulator and a real city map data, at four different frequencies i.e., 200 MHz, 500 MHz, 700 MHz, and 900 MHz. The acquired simulation results shows that, for a considered case study, the mean received power levels at outdoor BDs are around -33 dBm, -42 dBm, -45.5 dBm, and -48 dBm at 200 MHz, 500 MHz, 700 MHz, and 900 MHz, respectively. Similarly, for indoor BDs, the received power level varies with respect to the frequency of operation and outdoor to indoor building penetration loss. 2. The signal propagation at backscatter link i.e., between the BD and the receiver, is investigated in both the indoor and outdoor condition while utilizing 3 GPP indoor hotspot model and ITU-R D2D outdoor model, respectively. For different combinations of forward and backscatter link distances, the received power at the reader is found at four considered frequencies. The obtained results for a considered case study configuration show that cellular based AmBC system is able to provide a sig nificantly high received power to the reader in an outdoor environment at 200 MHz with BD-reader distance up to 60 m. Whereas, at 500 MHz, the mean received power at the reader is above \(-140\) dBm for up to 50 m BD-reader distance in an outdoor environment. Promising coverage results are obtained for indoor BD communicating with the indoor reader at 200 MHz centre frequency. The received power level is clearly found higher than \(-140\) dBm at indoor readers at 200 MHz frequency, even with high building penetration loss model. 3. For energy harvesting, a significantly high received power level at the BD is required, therefore, the energy harvesting at the backscatter device is assessed at 200 MHz and 500 MHz frequency of operation in an outdoor environment, and only for LoRa backscatter technology. The obtained results show the time that is required for harvesting the energy as a function of different energy harvesting efficiencies. 4. Finally, the coverage outage ratio with respect to the receiver sensitivity level of three radio technologies i.e., LoRa backscatter, NB-IoT, and BLE, is evaluated in both indoor and outdoor conditions. Interestingly, for a considered case study, a zero outage is found with LoRa and NB-IoT technology at 200 MHz in an outdoor environment for up to 60 m BD-reader distance. It is fascinating to learn from the obtained simulation results that, even at 900 MHz frequency, both LoRa and NB-IoT offer a zero outage ratio for BD-reader distance up to 35 m. It highlights the potential of LoRa backscatter and NB-IoT technology for those outdoorAmBC applications that do not require placing the reader more than 35 m away from the BD. The remaining part of the article is organized, as follows. Section 2 outlines different low power wide area network technologies, and it briefly describes backscatter communication and its application in a smart city environment. Section 3 provides the details of three propagation models; those are considered for the simulation work of this article. Section 4 explains the simulation methodology adopted, and it gives details about the simulation environment, simulation cases, and simulation modeling parameters. Section 5 discusses the acquired simulation results. Finally, Section 6 concludes the article.