nk/downlink allocation alignment levels. and alignment can be considered, especially when using 28 GHz deployment with a larger signal attenuation. 3GPP is also addressing another dimension with interference, namely, RIM, which is looking at longer-distance interference (within a network), experienced sometimes with TD-LTE networks when radio conditions support such a propagation situation. The study conducted looked at methods to identify such a situation in a network and the necessary actions to mitigate the impact. The RIM aspects are also covered with ongoing work, as seen in [9]. 15.2.4 Integrated Access and Backhaul The Integrated Access and Backhaul (IAB) is creating support for the 3GPP-specified wireless backhaul operation using the same bands being used for access. The operation has similarities with the LTE-based relay operation defined in the 3GPP Release 10 spec- ifications as part of LTE-Advanced work [10], but relays were not deployed widely in the field. The transmission would be using the same band as the actual access operation, avoiding the need for fiber connection to every site. The so-called donor gNB would be then having fiber connectivity. The IAB operation is being defined for both FR1 and FR2 ranges, but naturally at higher frequency bands there are more resources available for the backhaul operation. The IAB architecture model is as follows [11]: The interfacing between the donor and the IAB node is based on the CU/DU split, with an additional adaptation layer with the RLC Layer to handle the routing infor- mation, since there can be multiple IAB nodes in a chain. The interface between the donor and IAB nodes is called F1*, with the PDCP and SDAP in the CU side in line with the 3GPP higher layer functional split. The F1* func- tional split is not visible for the UE, but the UE assumes being connected to a regular gNB in any case. 15 5G Phase 2 and Beyond IAB Node IAB Donor 5G Core Figure 15.6 IAB architecture and functional split. The radio connection ends in the Mobile Termination (MT)