Downlink and Uplink Cell Association With Traditional Macrocells and Millimeter Wave Small Cells

Abstract

Millimeter wave (mmWave) links will offer high capacity but are poor at penetrating into or diffracting around solid objects. Thus, we consider a hybrid cellular network with traditional sub 6 GHz macrocells coexisting with denser mmWave small cells, where a mobile user can connect to either opportunistically. We develop a general analytical model to characterize and derive the uplink and downlink cell association in view of the SINR and rate coverage probabilities in such a mixed deployment. We offer extensive validation of these analytical results (which rely on several simplifying assumptions) with simulation results. Using the analytical results, different decoupled uplink and downlink cell association strategies are investigated and their superiority is shown compared to the traditional coupled approach.Finally, small cell biasing in mmWave is studied, and we show that unprecedented biasing values are desirable due to the wide bandwidth. is with OFCOM, UK. M. Dohler (mischa.dohler@kcl.ac.uk) is with the Centre for Telecommunications Research (CTR), King's College London, UK. I. INTRODUCTIONTwo key capacity-increasing techniques for future cellular networks including 5G will be network densification and the use of higher frequency bands, such as millimeter wave (mmWave) [1], [2]. The main challenges to using mmWave frequencies are their high near-field pathloss (due to small effective antenna aperture) and very poor penetration into buildings. However, it is increasingly believed these challenges can be overcome, at least for outdoor-to-outdoor cellular networks, using high gain steerable antennas in a dense enough network with sufficient scattering[3]- [11]. Further, recent studies have shown that with such highly directional transmissions and sensitivity to blockage, a positive side effect is that interference is greatly reduced, and so in many or most cases, mmWave networks will be noise rather than interference-limited [10]- [13].Nevertheless, it is unrealistic to expect universal coverage with mmWave, especially indoors, and so a likely deployment scenario is that mmWave will co-exist with a traditional sub-6GHz cellular network. The mmWave small cells will be used opportunistically when a connection is possible, with the sub-6GHz base stations providing universal coverage, for both control signaling and for data when a mmWave connection is not available. The goal of this paper is to model and analyze such a hybrid network, considering in particular how user equipments (UEs) should associate with the two types of BSs in the uplink (UL) and downlink (DL). A. Related WorkDownlink and uplink associations are typically coupled, i.e. a UE connects to the same BS in the DL and UL. In the context of a heterogeneous network, downlink-uplink decoupling (DUDe) has been recently shown to significantly improve the network capacity (especially in the UL) by considering different association criteria for the UL and DL [14]. DUDe has been discussed in [2], [15], [16] as an interesting component for future cellular netw...

On the Capacity and the Optimal Sum-Rate of a Class of Dual-Band Interference Channels

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Resource allocation in 5G heterogeneous networks with downlink‐uplink decoupled access

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Coverage in Heterogeneous Downlink Millimeter Wave Cellular Networks

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