  We consider a dynamic millimeter-wave network with integrated access and
backhaul, where mobile relay nodes move to auto-reconfigure the wireless
backhaul. Specifically, we focus on in-band relaying networks, which conduct
access and backhaul links on the same frequency band with severe constraints on
co-channel interference. In this context, we jointly study the complex problem
of dynamic relay node positioning, user association, and backhaul capacity
allocation. To address this problem, with limited complexity, we adopt a
hierarchical multi-agent reinforcement with a two-level structure. A high-level
policy dynamically coordinates mobile relay nodes, defining the backhaul
configuration for a low-level policy, which jointly assigns user equipment to
each relay and allocates the backhaul capacity accordingly. The resulting
solution automatically adapts the access and backhaul network to changes in the
number of users, the traffic distribution, and the variations of the channels.
Numerical results show the effectiveness of our proposed solution in terms of
convergence of the hierarchical learning procedure. It also provides a
significant backhaul capacity and network sum-rate increase (up to 3.5x)
compared to baseline approaches.
