The optimal design of the energy-efficient multiple-input multiple-output (MIMO) aided uplink ultra-reliable low-latency communications (URLLC) system is an important but unsolved problem. For such a system, we propose a novel absorbing-Markov-chain-based analysis framework to shed light on the puzzling relationship between the delay and reliability, as well as to quantify the system energy efficiency. We derive the transition probabilities of the absorbing Markov chain considering the Rayleigh fading, the channel estimation error, the zero-forcing multi-user-detection (ZF-MUD), the grant-free access, the ACK-enabled retransmissions within the delay bound and the interactions among these technical ingredients. Then, the delay-constrained reliability and the system energy efficiency are derived based on the absorbing Markov chain formulated. Finally, we study the optimal number of user equipments (UEs) and the optimal number of receiving antennas that maximize the system energy efficiency, while satisfying the reliability and latency requirements of URLLC simultaneously. Simulation results demonstrate the accuracy of our theoretical analysis and the effectiveness of massive MIMO in supporting large-scale URLLC systems.
翻译:对于这样一个系统,我们提议一个基于吸收链的新型吸收- Markov-链式分析框架,以揭示延迟和可靠性之间的模糊关系,并量化系统的能源效率。我们从吸收Markov链的过渡概率中得出吸收Markov链的最佳概率,考虑到Raylei的淡化、频道估计误差、零强制多用户探测(ZF-MUD)、无赠款访问、在延迟限制范围内由ACK带动的再传输以及这些技术要素之间的相互作用。然后,延迟限制的可靠性和系统能源效率是根据所拟订的吸收Markov链得出的。最后,我们研究用户设备的最佳数量和接收天线的最佳数量,以最大限度地提高系统的能源效率,同时满足URLC的可靠性和耐久性要求。模拟结果显示我们大规模LCLC的理论性分析的准确性。