Toward URLLC with Proactive HARQ Adaptation

Abstract

In this work, we propose a dynamic decision maker algorithm to improve the proactive HARQ protocol for beyond 5G networks. Based on Lyapunov stochastic optimization, our adaptation control framework dynamically selects the number of proactive retransmissions for intermittent URLLC traffic scenarios under time-varying channel conditions without requiring any prior knowledge associated with this stochastic process. It then better exploits the trade-off between Radio Access Network (RAN) latency, reliability and resource efficiency, which is still limited in its realization on current HARQ designs. We then evaluate the performance of several HARQ strategies and show that our proposal further improves latency over the reactive regime without affecting the resource efficiency such as fixed proactive retransmission while maintaining target reliability.

Proactive Resource Scheduling for 5G and Beyond Ultra-Reliable Low Latency Communications

“…We consider several levels of proactivity, different traffic rates and channel conditions. The results of this study pave the way for the design of an online decision maker framework enabling to dynamically choose the appropriate level of proactivity based on the network state [12].…”

Dynamic Resource Scheduling Optimization for Ultra-Reliable Low Latency Communications: From Simulation to Experimentation

“…Figure 5 compares the Complementary Distribution Function (CDF) of latency for different HARQ schemes: (i) Classic HARQ procedure, (ii) Fixed number of parallel RTXs, (iii) Proactive HARQ adaptation with a fixed maximum number of RTXs (R max = 10) as defined in [16] (iv) our proposed optimization (Dynamic HARQ) in which R max = amax a0 r n;aj . According to Figure 4, we select two pairs of (V, α) parameters: (25, 2) for good reliability and considerably low latency and (60, 0) for very good resource efficiency and latency.…”