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- Battery lifetime estimation for LoRaWAN communicationsPublication . Fialho, Vitor; Fortes, FernandoSmart Cities concept increased the number of end devices (ED) which allow the acquisition of parameters for further analysis and processing. The actual technologies based on Internet of Things (IoT) enable sensors connectivity to Internet. This feature allows real time acquisition of several physical data important for smart cities monitoring. In order to minimize the power consumption, Low Power Wide Area Networks (LPWAN) assumes an important role on the evolution and growing of wireless network sensors. In this particular type of network, LoRaWAN has taken the lead, among other technologies. Typically most end devices need to be powered with batteries, since they are in remote zones. Therefore one important issue to consider is the global power consumption of the end device building blocks: LoRa transceiver, microcontroller unit and sensor unit. This paper presents the study and simulation results supported on LoRa modulation parameters, in order to estimate the battery lifetime, which is useful for IoT remote sensing units. The achieved results denote it is possible to configure LoRa transceiver with similar parameters and different payloads, reaching the same battery lifetime.
- Wireless communication based on chirp signals for LoRa IoT DevicesPublication . Fialho, Vitor; Azevedo, FernandoThis paper presents the study of chirp signals for wireless communications between Internet of Thing devices used on low power wide area networks. Up and down chirp concept is introduced as well as the chirp spread spectrum concept. A computationally efficient symbol decoding method is presented based of discrete Fourier transform as an alternative to typical coherent detection. The proposed LoRa simulation model is implemented in MATLAB allowing the communication system evaluation based on bit error rate and packet error rate.
- Integer N synthesizer design for LoRa transceiversPublication . Fialho, VitorThis paper presents the study and design of an Integer N synthesizer model for three LoRa ISM bands: 430 MHz 868 MHz and 915 MHz. The proposed topology is composed by two voltage controlled oscillators working in two different bands. The presented model uses the same phase-frequency detector, charge pump and loop filter. This study is focused on dynamic and steady-state analysis in order to infer the synthesizer stability and bandwidth. The performed study shows that the settling time for all bands is less than 40 µs for a bandwidth of 102 kHz.
- Local oscillator phase noise model for EVM estimation and optimizationPublication . Fialho, Vitor; Fortes, Fernando; Vieira, ManuelaThis work presents a local oscillator (LO) phase noise model and its experimental validation for carrier to phase noise ratio (CPNR) and error vector magnitude (EVM) evaluation on a radio frequency (RF) transceiver. The proposed LO model is based on a type II charge pump phase locked loop with a combined phase noise source from the voltage controlled oscillator and input reference with a low pass characteristic. The obtained results of CPNR and signal to phase noise ratio are based on numerical simulations and validated with experimental measurements based on a commercial RF transceiver chip. The EVM of the transmitted RF channel is also measured and compared with CPNR.