To solve the problem that the low capacity in hot-spots and coverage holes ofconventional cellular networks, the base stations (BSs) having lower transmitpower are deployed to form heterogeneous cellular networks (HetNets). However,because of these introduced disparate power BSs, the user distributions amongthem looked fairly unbalanced if an appropriate user association scheme hasn'tbeen provided. For effectively tackling this problem, we jointly consider theload of each BS and user's achievable rate instead of only utilizing the latterwhen designing an association algorithm, and formulate it as a network-wideweighted utility maximization problem. Note that, the load mentioned aboverelates to the amount of required subbands decided by actual rate requirements,i.e., QoS, but the number of associated users, thus it can reflect user'sactual load level. As for the proposed problem, we give a maximum probability(max-probability) algorithm by relaxing variables as well as a low-complexitydistributed algorithm with a near-optimal solution that provides a theoreticalperformance guarantee. Experimental results show that, compared with theassociation strategy advocated by Ye, our strategy has a speeder convergencerate, a lower call blocking probability and a higher load balancing level.
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