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 connection to the Internet of billionsof new IoT devices will continue. To increase network capa-bility to support a large number of active devices accessing anetwork (i.e.,massive IoT connectivity), this work presentsIoT-ResQ, a warm-started quantum annealing-based multi-device detector via quantum reverse annealing (RA). Whilein typical quantum forward annealing (FA) protocol, nothingbetween the initial superposition and the final solution canbe controlled, IoT-ResQ’s RA starts its search operation on acontrollable candidate classical state, instead of a quantumsuperposition and thus allows refined local quantum searcharound the initial state. This procedure can provide an op-portunity of utilizing both conventional and quantum-baseddetectors together synergically. For this, IoT-ResQ consistsof classical Fixed-complexity Sphere Decoder (FSD) and RA.In our evaluation, IoT-ResQ achieves two to three orders ofmagnitude better BER (10−5) than other quantum and con-ventional detectors at SNR 9 dB to support 48 devices withQPSK modulation, sufficiently satisfying a IoT frame decod-ing time-slot in LTE-A. To support 36 devices with QPSKunder 48 receiver antennas at SNR 11 dB, over 2×packet suc-cess rate in IoT-ResQ is observed with packet size of 32-byte,compared to other quantum and conventional detectors.