Jitter Suppression for Very Low Latency Feedback Control Over NR

The 5G New Radio standard is intended to support delay and reliability critical use cases, reaching round-trip latencies at least as low as 1 milli-second, and error rates of the order of 10-6. This paper first summarizes why redundant transmission over independent wireless interfaces is beneficial to meet the reliability requirements. Redundant transmission then leads to a need for delay aligning control between the data paths. However, due to high bandwidth radio channel fading and the physical end-to-end delay itself, remaining high bandwidth jitter is shown to require a substantial back-off with respect to the URLLC delay requirement. The main contribution of the paper therefore proposes the use of UE and gNB combining of redundant decoded application control data, received over the wireless interfaces. Simulations show that the use of 3-4 independent and redundant data paths allows a 1 milli-second high reliability requirement to be met, at an error rate of 10-5, with a delay back-off of 25-30%, as compared to more than 400% without redundancy processing.