13 research outputs found
mmWave V2V Localization in MU-MIMO Hybrid Beamforming
Recent trends for vehicular localization in millimetre-wave (mmWave) channels include employing a combination of parameters such as angle of arrival (AOA), angle of departure (AOD), and time of arrival (TOA) of the transmitted/received signals. These parameters are challenging to estimate, which along with the scattering and random nature of mmWave channels, and vehicle mobility lead to errors in localization. To circumvent these challenges, this paper proposes mmWave vehicular localization employing difference of arrival for time and frequency, with multiuser (MU) multiple-input-multiple-output (MIMO) hybrid beamforming; rather than relying on AOD/AOA/TOA estimates. The vehicular localization can exploit the number of vehicles present, as an increase in a number of vehicles reduces the Cramr-Rao bound (CRB) of error estimation. At 10 dB signal-to-noise ratio (SNR) both spatial multiplexing and beamforming result in comparable localization errors. At lower SNR values, spatial multiplexing leads to larger errors compared to beamforming due to formation of spurious peaks in the cross ambiguity function. Accuracy of the estimated parameters is improved by employing an extended Kalman filter leading to a root mean square (RMS) localization error of approximately 6.3 meters
MmWave V2V Localization in MU-MIMO Hybrid Beamforming
Recent trends for vehicular localization in millimetre-wave (mmWave) channels include employing a combination of parameters such as angle of arrival (AOA), angle of departure (AOD), and time of arrival (TOA) of the transmitted/received signals. These parameters are challenging to estimate, which along with the scattering and random nature of mmWave channels, and vehicle mobility lead to errors in localization. To circumvent these challenges, this paper proposes mmWave vehicular localization employing difference of arrival for time and frequency, with multiuser (MU) multiple-input-multiple-output (MIMO) hybrid beamforming; rather than relying on AOD/AOA/TOA estimates. The vehicular localization can exploit the number of vehicles present, as an increase in a number of vehicles reduces the Cramr-Rao bound (CRB) of error estimation. At 10 dB signal-to-noise ratio (SNR) both spatial multiplexing and beamforming result in comparable localization errors. At lower SNR values, spatial multiplexing leads to larger errors compared to beamforming due to formation of spurious peaks in the cross ambiguity function. Accuracy of the estimated parameters is improved by employing an extended Kalman filter leading to a root mean square (RMS) localization error of approximately 6.3 meters
Hybrid Beamforming via the Kronecker Decomposition for the Millimeter-Wave Massive MIMO Systems
Despite its promising performance gain, the realization of mmWave massive
MIMO still faces several practical challenges. In particular, implementing
massive MIMO in the digital domain requires hundreds of RF chains matching the
number of antennas. Furthermore, designing these components to operate at the
mmWave frequencies is challenging and costly. These motivated the recent
development of hybrid-beamforming where MIMO processing is divided for separate
implementation in the analog and digital domains, called the analog and digital
beamforming, respectively. Analog beamforming using a phase array introduces
uni-modulus constraints on the beamforming coefficients, rendering the
conventional MIMO techniques unsuitable and call for new designs. In this
paper, we present a systematic design framework for hybrid beamforming for
multi-cell multiuser massive MIMO systems over mmWave channels characterized by
sparse propagation paths. The framework relies on the decomposition of analog
beamforming vectors and path observation vectors into Kronecker products of
factors being uni-modulus vectors. Exploiting properties of Kronecker mixed
products, different factors of the analog beamformer are designed for either
nulling interference paths or coherently combining data paths. Furthermore, a
channel estimation scheme is designed for enabling the proposed hybrid
beamforming. The scheme estimates the AoA of data and interference paths by
analog beam scanning and data-path gains by analog beam steering. The
performance of the channel estimation scheme is analyzed. In particular, the
AoA spectrum resulting from beam scanning, which displays the magnitude
distribution of paths over the AoA range, is derived in closed-form. It is
shown that the inter-cell interference level diminishes inversely with the
array size, the square root of pilot sequence length and the spatial separation
between paths.Comment: Submitted to IEEE JSAC Special Issue on Millimeter Wave
Communications for Future Mobile Networks, minor revisio
Majorization-Minimization Aided Hybrid Transceivers for MIMO Interference Channels
The potential of deploying large-scale antenna arrays in future wireless
systems has stimulated extensive research on hybrid transceiver designs aiming
to approximate the optimal fully-digital schemes with much reduced hardware
cost and signal processing complexity. Generally, this hybrid transceiver
structure requires a joint design of analog and digital processing to enable
both beamsteering and spatial multiplexing gains. In this paper, we develop
various weighted mean-square-error minimization (WMMSE) based hybrid
transceiver designs over multiple-input multiple-output (MIMO) interference
channels at both millimeter wave (mmWave) and microwave frequencies. Firstly, a
heuristic joint design of hybrid precoder and combiner using alternating
optimization is proposed, in which the majorization-minimization (MM) method is
utilized to design the analog precoder and combiner with unit-modulus
constraints. It is validated that this scheme achieves the comparable
performance to the WMMSE fully-digital solution. To further reduce the
complexity, a phase projection-based two-stage scheme is proposed to decouple
the designs of analog and digital precoder combiner. Secondly, inspired by the
fully-digital solutions based on the block-diagonalization zero-forcing (BD-ZF)
and signal-to-leakage-plus-noise ratio (SLNR) criteria, low-complexity MMbased
BD-ZF and SLNR hybrid designs are proposed to well approximate the
corresponding fully-digital solutions. Thirdly, the partially-connected hybrid
structure for reducing system hardware cost and power consumption is
considered, for which the MM-based alternating optimization still works.
Numerical results demonstrate the similar or superior performance of all the
above proposed schemes over the existing benchmarks.Comment: 13 pages, 8 figure
Dataset for Iterative matrix decomposition aided block diagonalization for mm-Wave multiuser MIMO systems
Considering the dearth for spectrum in the congested microwave band, the next generation of cellular communication systems is envisaged to incorporate part of the millimeter wave (mm-wave) band. Hence recently, there has been a significant interest in beamforming aided mm-wave systems. We consider a downlink multiuser mm-wave system employing a large number of antennas combined with a fewer radio frequency (RF) chains both at the base station (BS) and at each of the user equipment (UE). The BS and each of the UE is assumed to have a hybrid beamforming architecture, where a set of analog phase shifters is followed by digital precoding/combining blocks. In this paper, 1) we propose an iterative matrix decomposition based hybrid beamforming (IMD-HBF) scheme for a singleuser scenario, which accurately approximates the unconstrained beamforming solution, 2) we show that the knowledge of the angle of departure (AoD) of the various channel paths is sufficient for the block diagonalization (BD) of the downlink mm-wave channel and hence for achieving interference free channels for each of the UEs, 3) we propose a novel subspace projection based AoD aided BD (SP-AoD-BD) that achieves significantly better performance than the conventional BD, while still only requiring the knowledge of the AoD of various channel paths, 4) we use IMD-HBF in order to employ SP-AoD-BD in the hybrid beamforming architecture and study its performance with respect to the unconstrained system. We demonstrate using simulation results that the proposed IMD-HBF gives the same spectral efficiency as that of the unconstrained system in the single user scenario. Furthermore, we study the achievable sum rate of the users, when employing SP-AoD-BD with the aid of IMD-HBF and show that the loss in the performance with respect to the unconstrained system as well as the existing schemes is negligible, provided that the number of users is not excessive.
This dataset accompanies the publication: Rajashekar, Rakshith and Hanzo, Lajos (2016) Iterative matrix decomposition aided block diagonalization for mm-Wave multiuser MIMO systems. IEEE Transactions on Wireless Communications (doi:10.1109/TWC.2016.2628357).</span