A mobile communications system comprising a base station as a network controller, one or more relay nodes (804, 805) and one or more mobile communication terminals (802, 803) acting as a source of communications sessions to the base station, the base station being configured: to transmit a request message for measurement information to a plurality of infrastructure units, comprising the one or more relay nodes (804, 805) and the one or more mobile communication terminals (802, 803); to receive, in response to the request message, the measurement information from the infrastructure units; to analyse the measurement information to identify all potential communications paths between at least two of the infrastructure units; to detect from the analysis of the measurement information a relative quality of the communications paths; to organise the infrastructure units into a plurality of subgroups (1110, 1120) based on the relative quality of the communications paths; to create a look-up table from the analysis of the measurement information that contains a plurality of active edges, the active edges being all of the communications paths that have a relative quality above a threshold quality, the look-up table linking, for each of the one or more relay nodes, the active edges that are incoming to that relay node with relevant source communications sessions from an infrastructure unit of the same subgroup as that relay node into the active edges that are outgoing from that relay node with relevant combined communications sessions to an infrastructure unit of the same subgroup as that relay node; and to transmit at least a part of the look-up table to each of the infrastructure units, the at least a part of the look-up table being relevant to the infrastructure unit. to transmit a request message for measurement information to a plurality of infrastructure units, comprising the one or more relay nodes (804, 805) and the one or more mobile communication terminals (802, 803); to receive, in response to the request message, the measurement information from the infrastructure units; to analyse the measurement information to identify all potential communications paths between at least two of the infrastructure units; to detect from the analysis of the measurement information a relative quality of the communications paths; to organise the infrastructure units into a plurality of subgroups (1110, 1120) based on the relative quality of the communications paths; to create a look-up table from the analysis of the measurement information that contains a plurality of active edges, the active edges being all of the communications paths that have a relative quality above a threshold quality, the look-up table linking, for each of the one or more relay nodes, the active edges that are incoming to that relay node with relevant source communications sessions from an infrastructure unit of the same subgroup as that relay node into the active edges that are outgoing from that relay node with relevant combined communications sessions to an infrastructure unit of the same subgroup as that relay node; and to transmit at least a part of the look-up table to each of the infrastructure units, the at least a part of the look-up table being relevant to the infrastructure unit.