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.

中文翻译：

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通过免许可频谱实现超可靠和低延迟的通信


在本文中，我们旨在解决如何利用未授权频谱来实现 URLLC 的问题。对潜在的 URLLC PHY 机制进行了审查，然后通过模拟进行比较，以证明它们对 URLLC 的潜在好处。尽管许多重要的 PHY 技术有助于 URLLC，但 PHY 层在延迟和可靠性之间表现出内在的权衡，这是由有限且不稳定的无线通道造成的。然后，我们探讨 MAC 机制并讨论实现低延迟 LTE 免许可频段接入的多通道策略。我们通过模拟证明，通过在多个非授权信道上维护信道接入过程、智能地选择信道以及实施RTS/CTS，可以大大减少无法访问非授权频段的时间。