Abstract
We consider a heterogeneous MIMO-OFDMA based dense small cell (SC) system in which each macro cell base station (MBS) serves its coverage area with the help of small cell base stations (SBSs) through multi-hop wireless connections. The SBSs act as integrated access and backhaul (IAB) nodes that handle both access and backhaul traffics with wireless links. We first develop an optimal (sum-rate maximization) resource allocation (RA) algorithm which considers subcarriers/spatial subchannels assignment and the associated power allocations. We also present two low-complexity suboptimal RA schemes which, as verified by simulations, incur only minor performance loss in the high SNR region. Our RA algorithms can be applied to other multi-hop networks with general UE association rule and node location distributions. We study the channel aging effect caused by the time lag between the time channel state information (CSI) is measured and that when data transmission occurs. We show the benefit of channel prediction and the limit of a centralized RA approach. The advantages of frequency (channel) reuse and the multi-hop architecture are demonstrated as well. A related but perhaps more important system design issue for an IAB cellular network is the IAB node placement problem. With the given UE association rule and UE location distribution, we present systematic approaches to find the optimal node locations. For two special propagation models, we derive closed-form expressions for the node locations that maximizes a spectral efficiency lower bound. Numerical results validate the accuracy of our estimates based on either numerical evaluations or closed-form solutions.
Highlights
Heterogeneous networks (HetNets) that consist of macro and small cells were introduced by 3GPP for LTE advanced (LTE-A) and is considered for 5G Ultra-Dense Cellular Networks (UDCNs) [1]
We have 18 user equipments (UEs) uniformly distributed within the service area–a 60-degree sector of radius RC = 500 meters centered at the macro cell base stations (BSs) (MBS) with the two integrated access and backhaul (IAB) nodes (SBS 1, small cell base stations (SBSs) 2) placed on the angle bisector; see Fig. 1
The fading process associated with a time-varying channel is modelled as a third-order autoregressive process and the MBS who is in charge of resource allocation (RA) applies a Wiener predictor to improve the channel state information (CSI) precision
Summary
Heterogeneous networks (HetNets) that consist of macro and small cells were introduced by 3GPP for LTE advanced (LTE-A) and is considered for 5G Ultra-Dense Cellular Networks (UDCNs) [1]. A MULTI-HOP HetNet MODEL AND ITS TIME-FREQUENCY PLAN Consider a MIMO-OFDMA network in which an MBS is equipped with multiple antenna arrays, each is responsible for communicating with UEs and IABs within a sectorized service area. For if the resource distribution does not take the area-fairness into consideration, most resource will be given to the UEs in SC 1 which are closest to the MBS as such allocation is most sum-rate-efficient We return to this issue in Sections IV.B and VI.D. We return to this issue in Sections IV.B and VI.D Note that this T-F schedule represents the upper layer of our RA plan, i.e., we first partition the available T-F resources into several parts, each for serving a SC. We refer to such a l-tuple as a vector subcarrier (VC)
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