Warm-started quantum sphere decoding via reverse annealing for massive IoT connectivity

With the continuous growth of the Internet of Things (IoT), the trend of increasing numbers of IoT devices will continue. To increase the network's capability to support a large number of active devices accessing a network concurrently, this work presents IoT-ResQ, a warm-started quantum annealing-based multi-device detector via quantum reverse annealing (RA). Unlike in typical quantum forward annealing (FA) protocol, IoT-ResQ's RA starts its search operation on a controllable candidate classical state, instead of a quantum superposition, and thus allows refined local quantum search around the initial state. This procedure can provide an opportunity of utilizing both conventional classical- and quantum-based detectors together in a hybrid synergy, to boost quantum optimization performance, mitigating the effect of quantum decoherence and noise on quantum hardware. In our evaluation, IoT-ResQ achieves nearly two to three orders of magnitude better BER and over 2X packet success rate with packet size of 32-byte compared to other quantum and conventional detectors at SNR 9 dB to support 48 active IoT devices with QPSK modulation (implying 48,000 deployed devices with 0.1% wake-up radio rate at a time), requiring ≈ 140 μs pure compute time for detection.