A method of dynamically configuring a frequency division duplex tree-structured multiple-hop wireless backhaul network for a communications system, the network comprising a congregate node connected to the communications system, a plurality of access points (120- i), each access point having associated amounts of incident bidirectional traffic to be conveyed to and from the congregate node, and a plurality of bidirectional wireless links (130- i) adapted to convey the traffic between the access points (120- i) and the congregate node, the method comprising: computing a bandwidth request associated with each link from the traffic amounts associated with each node connected by the link; allocating bandwidth within a first frequency division duplex band of the predetermined available spectrum to each link in a first sub-network of the network based on the computed bandwidth requests associated with those links in the first sub-network; and allocating bandwidth within a second frequency division duplex band of the predetermined available spectrum to each link in a second sub-network of the network based on the computed bandwidth requests associated with those links in the second sub-network; and wherein each of the allocating steps in the first sub-network and the second sub-network respectively comprises: provisionally allocating bandwidth within the respective first frequency division duplex band and the second frequency division duplex band to each link in the respective first sub-network and the second sub-network based on the bandwidth requests associated with the links and a provisional guard band amount; computing a scaling factor that, if applied to the provisional bandwidth allocation, would make the total provisionally allocated bandwidth equal to the available bandwidth of the band; adjusting the provisional guard band amount (660, 670) depending on a comparison between the provisional guard band amount scaled by the computed scaling factor and a lower limit on the guard band amount; repeating the provisional allocating, computing, and adjusting (650, 660, 670) until the provisional guard band amount scaled by the computed scaling factor converges; and scaling the provisional bandwidth allocation by the computed scaling factor. computing a bandwidth request associated with each link from the traffic amounts associated with each node connected by the link; allocating bandwidth within a first frequency division duplex band of the predetermined available spectrum to each link in a first sub-network of the network based on the computed bandwidth requests associated with those links in the first sub-network; and allocating bandwidth within a second frequency division duplex band of the predetermined available spectrum to each link in a second sub-network of the network based on the computed bandwidth requests associated with those links in the second sub-network; and wherein each of the allocating steps in the first sub-network and the second sub-network respectively comprises: provisionally allocating bandwidth within the respective first frequency division duplex band and the second frequency division duplex band to each link in the respective first sub-network and the second sub-network based on the bandwidth requests associated with the links and a provisional guard band amount; computing a scaling factor that, if applied to the provisional bandwidth allocation, would make the total provisionally allocated bandwidth equal to the available bandwidth of the band; adjusting the provisional guard band amount (660, 670) depending on a comparison between the provisional guard band amount scaled by the computed scaling factor and a lower limit on the guard band amount; repeating the provisional allocating, computing, and adjusting (650, 660, 670) until the provisional guard band amount scaled by the computed scaling factor converges; and scaling the provisional bandwidth allocation by the computed scaling factor.