This work presents an instruction-set extension to the open-source RISC-V ISA (RV32IM) dedicated to ultra-low power (ULP) software-defined wireless IoT transceivers. The custom instructions are tailored to the needs of 8/16/32-bit integer complex arithmetic typically required by quadrature modulations. The proposed extension occupies only 2 major opcodes and most instructions are designed to come at a near-zero energy cost. Both an instruction accurate (IA) and a cycle accurate (CA) model of the new architecture are used to evaluate six IoT baseband processing test benches including FSK demodulation and LoRa preamble detection. Simulation results show cycle count improvements from 19% to 68%. Post synthesis simulations for a target 22nm FD-SOI technology show less than 1% power and 28% area overheads, respectively, relative to a baseline RV32IM design. Power simulations show a peak power consumption of 380 µW for Bluetooth LE demodulation and 225 µW for LoRa preamble detection (BW = 500 kHz, SF = 11).
This work demonstrates an ultra-low power, software-defined wireless transceiver designed for IoT applications using an open-source 32-bit RISC-V core. The key driver behind this success is an optimized hardware/software partitioning of the receiver's digital signal processing operators. We benchmarked our architecture on an algorithm for the detection of FSK-modulated frames using a RISC-V compatible core and ARM Cortex-M series processors. We use only standard compilation tools and no assembly-level optimizations. Our results show that Bluetooth LE frames can be detected with an estimated peak core power consumption of 1.6 mW on a 28 nm FDSOI technology, and falling to less than 0.6 mW (on average) during symbol demodulation. This is achieved at nominal voltage. Compared to state of the art, our work offers a power efficient alternative to the design of dedicated baseband processors for ultra-low power software-defined radios with a low software complexity.
International audienceThis work introduces the notion of multiple virtual logical networks on a single hardware NoC. It details how it can be implemented and describes the meta-routing mechanism used within. We define a virtual logical network as a network in which the neighborhood is not determined by physical locations in the physical topology. A node can conceptually be a neighbor of any other node even if physically they are not close and there is not a direct physical connection between them. These networks are virtually logically independent, and so let each application have its own separate network with its own topology and its own number of nodes. We present some exploitation of Virtual Logical Networks to demonstrate how this innovative idea can deal with routing efficiency, cache coherency as well as fault tolerance
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