Efficient Optimal and Suboptimal Joint Access Point Association and Radio Resource Allocation in WLANs

The centralized joint access point (AP) association and radio resource allocation problem in time-sharing based dense WLANs with heterogeneous station (STA) throughput demands and identical AP transmission power is considered in this paper. The problem is formulated as an NP-hard single non-zero programming (SNZP) optimization problem with three different throughput-based objective functions, including the maximal aggregate (MA) throughput, the max-min fair (MMF) throughput and the proportionally fair (PF) throughput. To solve the NP-hard SNZP problem, based on the optimal branch-and-bound (BnB) searching approach, two novel efficient algorithms, the optimal BnB and the suboptimal depth-first BnB (DF-BnB) algorithms, are proposed, which can be used as convenient performance benchmarks in the study of the problem considered. The complexity of the proposed algorithms is analyzed theoretically. Numerical results are presented to investigate and compare the performance and complexity of the proposed algorithms under the three different design criteria, which can help in choosing an appropriate cost function objective in practical system design.