9 research outputs found
Common Codebook Millimeter Wave Beam Design: Designing Beams for Both Sounding and Communication with Uniform Planar Arrays
Fifth generation (5G) wireless networks are expected to utilize wide
bandwidths available at millimeter wave (mmWave) frequencies for enhancing
system throughput. However, the unfavorable channel conditions of mmWave links,
e.g., higher path loss and attenuation due to atmospheric gases or water vapor,
hinder reliable communications. To compensate for these severe losses, it is
essential to have a multitude of antennas to generate sharp and strong beams
for directional transmission. In this paper, we consider mmWave systems using
uniform planar array (UPA) antennas, which effectively place more antennas on a
two-dimensional grid. A hybrid beamforming setup is also considered to generate
beams by combining a multitude of antennas using only a few radio frequency
chains. We focus on designing a set of transmit beamformers generating beams
adapted to the directional characteristics of mmWave links assuming a UPA and
hybrid beamforming. We first define ideal beam patterns for UPA structures.
Each beamformer is constructed to minimize the mean squared error from the
corresponding ideal beam pattern. Simulation results verify that the proposed
codebooks enhance beamforming reliability and data rate in mmWave systems.Comment: 14 pages, 10 figure
Massive MIMO Performance - TDD Versus FDD: What Do Measurements Say?
Downlink beamforming in Massive MIMO either relies on uplink pilot
measurements - exploiting reciprocity and TDD operation, or on the use of a
predetermined grid of beams with user equipments reporting their preferred
beams, mostly in FDD operation. Massive MIMO in its originally conceived form
uses the first strategy, with uplink pilots, whereas there is currently
significant commercial interest in the second, grid-of-beams. It has been
analytically shown that in isotropic scattering (independent Rayleigh fading)
the first approach outperforms the second. Nevertheless there remains
controversy regarding their relative performance in practice. In this
contribution, the performances of these two strategies are compared using
measured channel data at 2.6 GHz.Comment: Submitted to IEEE Transactions on Wireless Communications,
31/Mar/201
Advanced Quantizer Designs for FDD-Based FD-MIMO Systems Using Uniform Planar Arrays
Massive multiple-input multiple-output (MIMO) systems, which utilize a large
number of antennas at the base station, are expected to enhance network
throughput by enabling improved multiuser MIMO techniques. To deploy many
antennas in reasonable form factors, base stations are expected to employ
antenna arrays in both horizontal and vertical dimensions, which is known as
full-dimension (FD) MIMO. The most popular two-dimensional array is the uniform
planar array (UPA), where antennas are placed in a grid pattern. To exploit the
full benefit of massive MIMO in frequency division duplexing (FDD), the
downlink channel state information (CSI) should be estimated, quantized, and
fed back from the receiver to the transmitter. However, it is difficult to
accurately quantize the channel in a computationally efficient manner due to
the high dimensionality of the massive MIMO channel. In this paper, we develop
both narrowband and wideband CSI quantizers for FD-MIMO taking the properties
of realistic channels and the UPA into consideration. To improve quantization
quality, we focus on not only quantizing dominant radio paths in the channel,
but also combining the quantized beams. We also develop a hierarchical beam
search approach, which scans both vertical and horizontal domains jointly with
moderate computational complexity. Numerical simulations verify that the
performance of the proposed quantizers is better than that of previous CSI
quantization techniques.Comment: 15 pages, 6 figure