Enabling Ultra-Reliable and Low-Latency Communications through Unlicensed Spectrum

© 2018 IEEE. In this article, we aim to address the question of how to exploit the unlicensed spectrum to achieve URLLC. Potential URLLC PHY mechanisms are reviewed and then compared via simulations to demonstrate their potential benefits to URLLC. Although a number of important PHY techniques help with URLLC, the PHY layer exhibits an intrinsic trade-off between latency and reliability, posed by limited and unstable wireless channels. We then explore MAC mechanisms and discuss multi-channel strategies for achieving low-latency LTE unlicensed band access. We demonstrate, via simulations, that the periods without access to the unlicensed band can be substantially reduced by maintaining channel access processes on multiple unlicensed channels, choosing the channels intelligently, and implementing RTS/CTS

Unlocking Unlicensed Band Potential to Enable URLLC in Cloud Robotics for Ubiquitous IoT

Cloud robotics (CR) support extremely high reliability and low-latency communications in ubiquitous Internet of Things applications. However, many of those applications currently rely on wired connection, limiting their use within the confines of Ethernet/optical links. Some wireless solutions such as Wi-Fi have been considered, but failed to meet the stringent criteria for latency and outage. On the other hand, cellular technology possesses expensive licensing. Thus, the Third Generation Partnership Project (3GPP) is actively working on New Radio in the unlicensed band for incorporating ultra-reliable low-latency communications (URLLC) into fifth generation and beyond communication networks. In this article, we aim to study the feasibility of URLLC in an unlicensed band specifically for CR applications. We open up various use cases and opportunities offered by the unlicensed band in achieving latency and reliability constraints for robotics applications. We then review the regulatory requirements of unlicensed band operation imposed by 3GPP and explore its medium access challenges for CR due to the shared use of unstable wireless channels. Finally, we discuss the potential technology enablers to achieve URLLC using the unlicensed band for the ubiquitous CR applications

Fast Iterative Semi-Blind Receiver for URLLC in Short-Frame Full-Duplex Systems with CFO

IEEE We propose an iterative semi-blind (ISB) receiver structure to enable ultra-reliable low-latency communications (URLLC) in short-frame full-duplex (FD) systems with carrier frequency offset (CFO). To the best of our knowledge, this is the first work to propose an integral solution to channel estimation and CFO estimation for short-frame FD systems by utilizing a single pilot. By deriving an equivalent system model with CFO included implicitly, a subspace based blind channel estimation is proposed for the initial stage, followed by CFO estimation and channel ambiguities elimination. Then refinement of channel and CFO estimates is conducted iteratively. The integer and fractional parts of CFO in the full range are estimated as a whole and in closed-form at each iteration. The proposed ISB receiver significantly outperforms the previous methods in terms of frame error rate (FER), mean square errors (MSEs) of channel estimation and CFO estimation and output signal-tointerference- and-noise ratio (SINR), while at a halved spectral overhead. Cramér-Rao lower bounds (CRLBs) are derived to verify the effectiveness of the proposed ISB receiver structure. It also demonstrates high computational efficiency as well as fast convergence speed