This paper presents a hierarchical approach to resource allocation inopen-access femtocell networks. The major challenge in femtocell networks isinterference management which in our system, based on the Long Term Evolution(LTE) standard, translates to which user should be allocated which physicalresource block (or fraction thereof) from which femtocell access point (FAP).The globally optimal solution requires integer programming and ismathematically intractable. We propose a hierarchical three-stage solution:first, the load of each FAP is estimated considering the number of usersconnected to the FAP, their average channel gain and required data rates.Second, based on each FAP's load, the physical resource blocks (PRBs) areallocated to FAPs in a manner that minimizes the interference by coloring themodified interference graph. Finally, the resource allocation is performed ateach FAP considering users' instantaneous channel gain. The two majoradvantages of this suboptimal approach are the significantly reducedcomputation complexity and the fact that the proposed algorithm only usesinformation that is already likely to be available at the nodes executing therelevant optimization step. The performance of the proposed solution isevaluated in networks based on the LTE standard.
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