  In this paper, we study the problem of topology optimization and routing in
integrated access and backhaul (IAB) networks, as one of the promising
techniques for evolving 5G networks. We study the problem from different
perspectives. We develop efficient genetic algorithm-based schemes for both IAB
node placement and non-IAB backhaul link distribution, and evaluate the effect
of routing on bypassing temporal blockages. Here, concentrating on millimeter
wave-based communications, we study the service coverage probability, defined
as the probability of the event that the user equipments' (UEs) minimum rate
requirements are satisfied. Moreover, we study the effect of different
parameters such as the antenna gain, blockage and tree foliage on the system
performance. Finally, we summarize the recent Rel-16 as well as the upcoming
Rel-17 3GPP discussions on routing in IAB networks, and discuss the main
challenges for enabling mesh-based IAB networks. As we show, with a proper
network topology, IAB is an attractive approach to enable the network
densification required by 5G and beyond.
