Reliability-oriented intra-frequency dual connectivity for 5G systems: Configuration algorithms and performance evaluation

Abstract

The 5th Generation (5G) New Radio (NR) interface is expected to continue utilising the existing homogenous networks for some time in the near future serving a wide range of use cases, one of those cases is Ultra-Reliable Low Latency Communications (URLLC) services. For URLLC, short data packets must be correctly transmitted and received within very short latency up to 1ms with a reliability of 99.999%. There are several options being proposed to meet this difficult design target. One very promising suggested solution is the dual connectivity with data duplication, where the same packet is duplicated and independently transmitted via two different nodes. This work uses a system-level simulation to study how the data duplication at PDCP level for dual connectivity is functioning, where every copy of the designated packet is sent via the two connections that a certain User Equipment (UE) is connected. The studied scenario is a homogeneous network of 21 macro cells of 500m inter-site distance. The scenario is first optimized for the single connectivity mode, which supports less than 1Mbps URLLC offered load while meeting the IMT2020 latency requirements. As we enable dual connectivity, in a URLLC traffic only scenario, it is shown that dual connectivity provides some noticeable gain by enabling the support of up to 1.5Mbps URLLC load within the URLLC requirements but not improving the low load criteria in comparison to single connectivity results due to the low interference condition in single connectivity. As a second stage, the gain of DC is studied when the URLLC traffic coexist with a heavy full buffer background eMBB traffic. Results show that a latency gain as well as higher load support than the single connectivity case can be obtained by dual connectivity, however the sensitivity of this gain on the scenario conditions is very high. Finally, an enhanced duplication configuration is added, that is if a packet is successfully sent through one of the links and correctly decoded at the UE, the duplicated copy transmission on the other link is cancelled (i.e. the packet is dropped at the network side). This results in a significant performance improvement in terms of the latency and supported URLLC load especially at relatively high load because it avoids the queuing delay.