Methods and corresponding systems for allocating resources in a communications system includes determining feasible sets of subchannels for allocation to a user subject to an allocation constraint. In one approach, a constraint matrix representing constraints for allocating subchannels to users in allocations of selected subchannels is computed, subject to the allocation constraint. Then a vector containing metrics corresponding to allocations of selected subchannels to the communication links is estimated. A binary decision vector representing an allocation of the subchannels to the users is computed using binary integer processing. In another approach a greedy heuristic allocation is used. The allocation constraint can be a restriction limiting multiple subchannels allocated to a user to be adjacent to one another. The metrics can be weighted capacities of allocations of selected subchannels to the users.