Robust Hybrid Beam-Forming for Non-Orthogonal Multiple Access in Massive MIMO Downlink

This paper presents hybrid precoding for a non-orthogonal multiple access (NOMA) transmission scheme in a millimeter wave (mmWave) massive MIMO (mMIMO) downlink. In hybrid precoding, the analog precoder is obtained by the orthogonalization of the users’ channel vectors to minimize inter-beam interference. The digital precoder consists of a zero-forcing precoder to minimize inter-user interference. In order to break the barrier of one user per beam, we utilize the NOMA within the beam for power domain multiplexing among users. Simulation results show the proposed scheme’s efficacy compared to the state-of-the-art schemes and provide 1.48 times better sum-rate performance at 10 dB received SNR.

Optimising the Massive MIMO Downlink in the Presence of Power Amplifier Nonlinearities

<p>Massive MIMO is known for its high level of spectral efficiency in multipath rich environments. We present a detailed Massive MIMO cell system using maximum-ratio transmission (MRT) and zero-forcing (ZF) where energy efficiency is taken into account. This is done through the use of a realistic model of moderate performance and hence moderate cost power amplifiers (PAs) for the base station downlink, which could be applied in a practical Massive MIMO system. In the process of detailing the linear aspects of the Massive MIMO system, results for the normalisation factor and array gain are derived, which as far as the author is aware are original. These results are used to derive an expression to optimise the downlink signal-to-interference-and-noise-ratio (SINR) in a linear system, which is also original as far as the author is aware. A process is outlined to optimise the downlink SINR when nonlinear PAs are used and a simulation of a cell system is performed where the benefits of applying the nonlinear optimisation process are demonstrated.</p>

Optimising the Massive MIMO Downlink in the Presence of Power Amplifier Nonlinearities

<p>Massive MIMO is known for its high level of spectral efficiency in multipath rich environments. We present a detailed Massive MIMO cell system using maximum-ratio transmission (MRT) and zero-forcing (ZF) where energy efficiency is taken into account. This is done through the use of a realistic model of moderate performance and hence moderate cost power amplifiers (PAs) for the base station downlink, which could be applied in a practical Massive MIMO system. In the process of detailing the linear aspects of the Massive MIMO system, results for the normalisation factor and array gain are derived, which as far as the author is aware are original. These results are used to derive an expression to optimise the downlink signal-to-interference-and-noise-ratio (SINR) in a linear system, which is also original as far as the author is aware. A process is outlined to optimise the downlink SINR when nonlinear PAs are used and a simulation of a cell system is performed where the benefits of applying the nonlinear optimisation process are demonstrated.</p>

Sum Rate Analysis for Massive MIMO Downlink With MRC Beamforming and User Selection

Average allocation of data rate to each user is inefficient since the resource a base station can allocate is limited. Thus, user selection and user scheduling need to be applied into multi-user massive multiple-input multiple-output (MIMO) downlink system. In this paper, we mainly focus on the methods of user selection. First, we establish a downlink system model including transmission model and channel model. Then, two user-rate based user selection algorithms via the signal-to-interference-plus-noise-ratio (SINR) are proposed, where the SINR is generated by MRC beamforming. Finally, simulation results are provided to compare the performance of two proposed algorithms and their fairness towards selected users. In the simulation results, location-based selection algorithm and random selection algorithm are jointly compared. The second proposed algorithm possesses the highest total sum-rate and is the optimal algorithms among the four algorithms.

Using a Sorted QR Decomposition Algorithm for Multiuser MIMO Downlink Transmission

MIMO is a wireless technology that uses large scale antennas to transfer more data at the same time and to increase spectral efficiency. To achieve high data rate with less bandwidth we use decomposition algorithm. Among various de-composition algorithm QR decomposition algorithm outperforms low bit error rate(BER), but the computational complexity is prohibitively high when the system incorporates large number of antennas. This paper presents a low computational sorted QR decomposition (SQRD) algorithm for MIMO.SQRD uses precoding technique at the transmitter which decomposes the channel that can sent in parallel.