Grant Free Non Orthogonal Multiple Access: A Key Enabler for 6G IoT
The proliferating number of devices with short payloads as well as low power budget has already driven researchers away from classical grant based access schemes that are notorious for their large signalling overhead as well as power consuming retransmissions. Instead, light weight random access protocols have been re investigated and their throughput has been improved in orders of magnitude with sophisticated yet still low complex transceiver algorithms. In fact, grant free access has been identified as a key medium access control technique for providing massive connectivity in machine type communications in cellular networks. In this paper, we show that grant free access combined with non orthogonal transmission schemes is a promising solution for 6G Internet of Things (IoT) We present novel and promising results for deep learning (DL) based techniques for joint user detection and decoding. Then, we propose a multi layered model for GF NOMA for power efficient communications. We also discuss resource allocation issues to enable the co existence of GF NOMA with other orthogonal or even grant based schemes. Finally, we conclude with proposed research directions for medium access towards enabling 6G IoT.
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