cation in Release-16 primarily focused on stationary small cells. Further work on IAB in Release-17 is expected to enhance the feature set and improve on spectral efficiency and robustness. Also, performance enhancements are expected, for example, to support low-latency services over multiple hops. Specifically, the following IAB enhancements are expected to be defined in Release-17: Enhancements for resource multiplexing between child and parent links of an IAB node; CLI and interference mitigation improvements; Topology adaptation improvements; Routing improvements. It has also been proposed to support IAB node mobility, which enables IAB node deploy- ments on trains, buses, cabs, low and high-altitude drones, satellites, etc. At the time of writing this book, mobile IAB is not part of the 3GPP work plan; however, it may be added in the future. References 3GPP Technical Report 22.862 (2016). Service requirements for the 5G system; Stage1. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Report 38.874 (2019). Study on Integrated Access and Backhaul for NR. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 23.401 (2019). GPRS enhancements for E-UTRAN access. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 23.501 (2019). System Architecture for the 5G System; Stage 2. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 23.502 (2019). Procedures for the 5G system; Stage 2. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 33.210 (2019). Network Domain Security (NDS), IP network layer security. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 33.501 (2019) Security architecture and procedures for 5G system. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 36.300 (2019). E-UTRA and EUTRAN; Overall description; Stage 2. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.300 (2019). N