Joint Load Balancing and Interference Mitigation in 5G Heterogeneous Networks

Abstract

We study the problem of joint load balancing and interference mitigation in\nheterogeneous networks (HetNets) in which massive multiple-input\nmultiple-output (MIMO) macro cell base station (BS) equipped with a large\nnumber of antennas, overlaid with wireless self-backhauled small cells (SCs)\nare assumed. Self-backhauled SC BSs with full-duplex communication employing\nregular antenna arrays serve both macro users and SC users by using the\nwireless backhaul from macro BS in the same frequency band. We formulate the\njoint load balancing and interference mitigation problem as a network utility\nmaximization subject to wireless backhaul constraints. Subsequently, leveraging\nthe framework of stochastic optimization, the problem is decoupled into dynamic\nscheduling of macro cell users, backhaul provisioning of SCs, and offloading\nmacro cell users to SCs as a function of interference and backhaul links. Via\nnumerical results, we show the performance gains of our proposed framework\nunder the impact of small cells density, number of base station antennas, and\ntransmit power levels at low and high frequency bands. We further provide\ninsights into the performance analysis and convergence of the proposed\nframework. The numerical results show that the proposed user association\nalgorithm outperforms other baselines. Interestingly, we find that even at\nlower frequency band the performance of open access small cell is close to that\nof closed access at some operating points, the open access full- duplex small\ncell still yields higher gain as compared to the closed access at higher\nfrequency bands. With increasing the small cell density or the wireless\nbackhaul quality, the open access full- duplex small cells outperform and\nachieve a 5.6x gain in terms of cell-edge performance as compared to the closed\naccess ones in ultra-dense networks with 350 small cell base stations per km2 .\n