Cooperative Multicast for Multi-Connected XR Devices with Joint HARQ Processing

In this paper, we investigate the multi-connectivity for Extended Reality (XR) devices, having both a direct link and an indirect link to the same Next-Generation Node B (gNodeB). The indirect link is established through a cooperating 5th generation (5G) tethering device positioned in proximity to the XR device. Our study focuses on point-to-multipoint (PTM) multicast transmission to the XR device and the nearby 5G tethering device, emphasizing their cooperative interaction. We conduct this investigation under a spatially consistent channel model, quantifying the performance in terms of block error rate (BLER). Furthermore, we propose algorithms for processing joint hybrid automatic repeat request (HARQ) feedback (FB) in 5G multicast sessions. These algorithms are designed for multicast sessions, where User Equipment (UE)s actively cooperate, aiming to enhance the spectral efficiency of multiconnected XR devices by minimizing HARQ retransmissions. The resulting increase in spectral efficiency contributes to the overall capacity improvement of the network. Our link-level simulations demonstrate that multi-connectivity for XR yields a 0.8 dB gain for a 10% BLER target. Additionally, the proposed joint HARQ FB processing algorithm provides approximately a 7% gain in spectral efficiency.