Abstract
In this paper, we consider a multi-user full-duplex (FD) massive multiple-input multiple-output (MIMO) system. The FD base station (BS) is equipped with large-scale antenna arrays, while each FD user is equipped with two antennas (one for transmission and the other one for reception). We assume that the channel state information (CSI) is imperfect, and no instantaneous CSI of loop interference (LI) channel is obtained. On the basis of low-complexity uplink beamforming and downlink precoding techniques, i.e. maximum-ratio combining/maximum-ratio transmission (MRC/MRT) and zero-forcing reception/zero-forcing transmission (ZFR/ZFT), the asymptotic expressions of signal-to-interference-plus-noise ratio (SINR) of uplink and downlink are derived respectively when the number of antennas of the BS tends to infinity. Based on the asymptotic SINR expressions, we first analyse the spectral efficiency (SE) performance assuming that the generalized power scaling scenario is adopted. Through the theoretical derivation, it is shown that the detrimental impact of the LI can be eliminated by the very large number of antennas at the BS if the power scaling scenario is appropriately applied, as well as the interference caused by the imperfect channel estimation, the multi-user interference (MUI) and inter-user interference (IUI). Then, we propose power allocation (PA) scenarios to maximize the energy efficiency (EE) and the sum SE with the constraint of maximum powers at the BS and users. The simulation results verify the accuracy of the asymptotic method, we also validate the effectiveness of the EE and the sum SE maximization PA algorithms. We show that adopting the PA scheme to maximize the sum SE can make the multi-user FD massive MIMO system outperform the half-duplex (HD) counterpart regardless of the level of LI.
Highlights
The fourth generation (4G) wireless system has come to the mature stage, and with the booming development of all kinds of mobile smart terminals, the mobile Internet traffic in the recent years grows exponentially, which will increase by 1000 times beyond 2020
7 Conclusions In this paper, we consider a multi-user FD massive multiple-input multiple-output (MIMO) system, where the base station (BS) is equipped with large-scale antenna arrays, while each FD user is equipped with two antennas
The linear processing techniques of maximum-ratio combining/maximum-ratio transmission (MRC/MRT) and ZFR/ZFT are adopted at the BS to process the signals
Summary
The fourth generation (4G) wireless system has come to the mature stage, and with the booming development of all kinds of mobile smart terminals, the mobile Internet traffic in the recent years grows exponentially, which will increase by 1000 times beyond 2020. 2.1 Imperfect channel estimation phase In [12] and [13], it made an assumption that the residual LI can be regarded as additive noise after applying some novel LI mitigation scenarios, on the basis of knowing the CSI of GLI to compute the filter matrices [15] It may work in the conventional MIMO systems where the antennas deployed at the relay or BS are in a small quantity. With the growth of the number of transmit and receive antennas at the relay or BS, the dimension of GLI increases, and in order to obtain the CSI of GLI, the length of pilot sequence τ should satisfy τ ≥ N which is unprocurable in the massive MIMO systems owing to the limited duration of channel coherent time.
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