16 research outputs found
Achievable Rates and Training Overheads for a Measured LOS Massive MIMO Channel
This paper presents achievable uplink (UL) sumrate predictions for a measured
line-of-sight (LOS) massive multiple-input, multiple-output (MIMO) (MMIMO)
scenario and illustrates the trade-off between spatial multiplexing performance
and channel de-coherence rate for an increasing number of base station (BS)
antennas. In addition, an orthogonal frequency division multiplexing (OFDM)
case study is formed which considers the 90% coherence time to evaluate the
impact of MMIMO channel training overheads in high-speed LOS scenarios. It is
shown that whilst 25% of the achievable zero-forcing (ZF) sumrate is lost when
the resounding interval is increased by a factor of 4, the OFDM training
overheads for a 100-antenna MMIMO BS using an LTE-like physical layer could be
as low as 2% for a terminal speed of 90m/s.Comment: 4 pages, 5 figure
An Overview of Massive MIMO Research at the University of Bristol
Massive MIMO has rapidly gained popularity as a technology crucial to the
capacity advances required for 5G wireless systems. Since its theoretical
conception six years ago, research activity has grown exponentially, and there
is now a developing industrial interest to commercialise the technology. For
this to happen effectively, we believe it is crucial that further pragmatic
research is conducted with a view to establish how reality differs from
theoretical ideals. This paper presents an overview of the massive MIMO
research activities occurring within the Communication Systems & Networks Group
at the University of Bristol centred around our 128-antenna real-time testbed,
which has been developed through the BIO programmable city initiative in
collaboration with NI and Lund University. Through recent preliminary trials,
we achieved a world first spectral efficiency of 79.4 bits/s/Hz, and
subsequently demonstrated that this could be increased to 145.6 bits/s/Hz. We
provide a summary of this work here along with some of our ongoing research
directions such as large-scale array wave-front analysis, optimised power
control and localisation techniques.Comment: Presented at the IET Radio Propagation and Technologies for 5G
Conference (2016). 5 page
Temporal Analysis of Measured LOS Massive MIMO Channels with Mobility
The first measured results for massive multiple-input, multiple-output (MIMO)
performance in a line-of-sight (LOS) scenario with moderate mobility are
presented, with 8 users served by a 100 antenna base Station (BS) at 3.7 GHz.
When such a large number of channels dynamically change, the inherent
propagation and processing delay has a critical relationship with the rate of
change, as the use of outdated channel information can result in severe
detection and precoding inaccuracies. For the downlink (DL) in particular, a
time division duplex (TDD) configuration synonymous with massive MIMO
deployments could mean only the uplink (UL) is usable in extreme cases.
Therefore, it is of great interest to investigate the impact of mobility on
massive MIMO performance and consider ways to combat the potential limitations.
In a mobile scenario with moving cars and pedestrians, the correlation of the
MIMO channel vector over time is inspected for vehicles moving up to 29 km/h.
For a 100 antenna system, it is found that the channel state information (CSI)
update rate requirement may increase by 7 times when compared to an 8 antenna
system, whilst the power control update rate could be decreased by at least 5
times relative to a single antenna system.Comment: Accepted for presentation at the 85th IEEE Vehicular Technology
Conference in Sydney. 5 Pages. arXiv admin note: substantial text overlap
with arXiv:1701.0881
Performance characterization of a real-time massive MIMO system with LOS mobile channels
The first measured results for massive MIMO performance in a line-of-sight
(LOS) scenario with moderate mobility are presented, with 8 users served in
real-time using a 100-antenna base Station (BS) at 3.7 GHz. When such a large
number of channels dynamically change, the inherent propagation and processing
delay has a critical relationship with the rate of change, as the use of
outdated channel information can result in severe detection and precoding
inaccuracies. For the downlink (DL) in particular, a time division duplex (TDD)
configuration synonymous with massive multiple-input, multiple-output (MIMO)
deployments could mean only the uplink (UL) is usable in extreme cases.
Therefore, it is of great interest to investigate the impact of mobility on
massive MIMO performance and consider ways to combat the potential limitations.
In a mobile scenario with moving cars and pedestrians, the massive MIMO channel
is sampled across many points in space to build a picture of the overall user
orthogonality, and the impact of both azimuth and elevation array
configurations are considered. Temporal analysis is also conducted for vehicles
moving up to 29km/h and real-time bit error rates (BERs) for both the UL and DL
without power control are presented. For a 100-antenna system, it is found that
the channel state information (CSI) update rate requirement may increase by 7
times when compared to an 8-antenna system, whilst the power control update
rate could be decreased by at least 5 times relative to a single antenna
system.Comment: Submitted to the 2017 IEEE JSAC Special Issue on Deployment Issues
and Performance Challenges for 5G, IEEE Journal on Selected Areas in
Communications, 2017, vol.PP, no.99, pp.1-