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SAR systems designed for on-board space environments present different challenges when compared to other systems. Constraints in performance, size, weight, power consumption and image quality are aspects that need to be taken into consideration when developing on-board systems. This paper presents an evaluation of two different multi-core embedded architectures for the Backprojection algorithm suitable for small satellites. Single and multi-core implementations are discussed, as well as the computation of approximations for the most time-consuming operations of the algorithm. Two different commercially available systems were tested: Pynq-Z2 and Ultra96, which are compared in terms of execution time, power consumption and efficiency, and image quality., This work was supported by national funds through Fundação para a Ciência e a Tecnologia (FCT), under grants with references UIDB/50021/2020 (INESC-ID multi-annual funding) and project SARRROCA (PTDC/EEIHAC/31819/2017). Helena Cruz would like to acknowledge FCT for the support through grant with reference SFRH/BD/144133/2019.

Stochastic Computing has emerged as a competitive computing paradigm that produces fast and simple implementations of arithmetic operations, while offering high levels of parallelism, and graceful degradation of the results when in the presence of errors. IoT devices are often operate under limited power and area constraints and subjected to harsh environments, for which, traditional computing paradigms struggle to provide high availability and fault-tolerance. Stochastic Computing is based on the computation of pseudo-random sequences of bits, hence requiring only a single bit per signal, rather than a data-bus. Notwithstanding, we haven’t witnessed its inclusion in custom computing systems. In this direction, this work presents Stochastic Theater, a framework to specify, simulate, and test Stochastic Datapaths to perform computations using stochastic bitstreams targeting IoT systems. In virtue of the granularity of the bitstreams, the bit-level specification of circuits, high-performance characteristics and reconfigurable capabilities, FPGAs were adopted to implement and test such systems. The proposed framework creates Stochastic Machines from a set of user defined arithmetic expressions, and then tests them with the corresponding input values and specific fault injection patterns. Besides the support to create autonomous Stochastic Computing systems, the presented framework also provides generation of stochastic units, being able to produce estimates on performance, resources and power. A demonstration is presented targeting KLT, typical method for data compression in IoT applications., i-ETC : ISEL Academic Journal of Electronics Telecommunications and Computers, Vol 4, No 1 (2018): IoT: Internet of Things as field revolution

The emerging concept of smart cities demands for a large number of electronic devices, like sensors and actuators, distributed over several public spaces and buildings. The Internet of Things (IoT) has a key role in connecting devices to the Internet. However, the significant number of devices makes the maintenance task of the entire network difficult and expensive. To mitigate this problem, considerable research efforts have been made to develop energy-aware devices capable of self-sustainable operation, by harvesting their energy from various sources. In this paper, we study the possibility of harvesting energy from the light flowing in the Gigabit Passive Optics Network (GPON) to supply low-power devices. Since most cities already have a working GPON installation, using this installation to interconnect and power IoT devices can be a viable and less expensive solution, instead of installing new dedicated networks. This is also an interesting solution to convey communications and energy to low-power applications where access to the power grid is unfeasible. This study is focused in the 1550 nm wavelength, whose available optical power, in residential premises, is between -7 dBm and +2 dBm. With this range of optical power, and with a 30% efficiency photodiode, we show, for the worst-case scenario of the GPON, how it is possible to harvest 62 µW of energy at the Maximum Power Point (MPP)., i-ETC : ISEL Academic Journal of Electronics Telecommunications and Computers, Vol 4, No 1 (2018): IoT: Internet of Things as field revolution