2,506 research outputs found
MmWave Massive MIMO Based Wireless Backhaul for 5G Ultra-Dense Network
Ultra-dense network (UDN) has been considered as a promising candidate for
future 5G network to meet the explosive data demand. To realize UDN, a
reliable, Gigahertz bandwidth, and cost-effective backhaul connecting
ultra-dense small-cell base stations (BSs) and macro-cell BS is prerequisite.
Millimeter-wave (mmWave) can provide the potential Gbps traffic for wireless
backhaul. Moreover, mmWave can be easily integrated with massive MIMO for the
improved link reliability. In this article, we discuss the feasibility of
mmWave massive MIMO based wireless backhaul for 5G UDN, and the benefits and
challenges are also addressed. Especially, we propose a digitally-controlled
phase-shifter network (DPSN) based hybrid precoding/combining scheme for mmWave
massive MIMO, whereby the low-rank property of mmWave massive MIMO channel
matrix is leveraged to reduce the required cost and complexity of transceiver
with a negligible performance loss. One key feature of the proposed scheme is
that the macro-cell BS can simultaneously support multiple small-cell BSs with
multiple streams for each smallcell BS, which is essentially different from
conventional hybrid precoding/combining schemes typically limited to
single-user MIMO with multiple streams or multi-user MIMO with single stream
for each user. Based on the proposed scheme, we further explore the fundamental
issues of developing mmWave massive MIMO for wireless backhaul, and the
associated challenges, insight, and prospect to enable the mmWave massive MIMO
based wireless backhaul for 5G UDN are discussed.Comment: This paper has been accepted by IEEE Wireless Communications
Magazine. This paper is related to 5G, ultra-dense network (UDN), millimeter
waves (mmWave) fronthaul/backhaul, massive MIMO, sparsity/low-rank property
of mmWave massive MIMO channels, sparse channel estimation, compressive
sensing (CS), hybrid digital/analog precoding/combining, and hybrid
beamforming. http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=730653
Feedback-Aware Precoding for Millimeter Wave Massive MIMO Systems
Millimeter wave (mmWave) communication is a promising solution for coping
with the ever-increasing mobile data traffic because of its large bandwidth. To
enable a sufficient link margin, a large antenna array employing directional
beamforming, which is enabled by the availability of channel state information
at the transmitter (CSIT), is required. However, CSIT acquisition for mmWave
channels introduces a huge feedback overhead due to the typically large number
of transmit and receive antennas. Leveraging properties of mmWave channels,
this paper proposes a precoding strategy which enables a flexible adjustment of
the feedback overhead. In particular, the optimal unconstrained precoder is
approximated by selecting a variable number of elements from a basis that is
constructed as a function of the transmitter array response, where the number
of selected basis elements can be chosen according to the feedback constraint.
Simulation results show that the proposed precoding scheme can provide a
near-optimal solution if a higher feedback overhead can be afforded. For a low
overhead, it can still provide a good approximation of the optimal precoder.Comment: 7 pages, 5 figures, to appear at the IEEE International Symposium on
Personal, Indoor and Mobile Radio Communications (PIMRC) 201
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