Advances in mm-wave wireless links
by
Professor Stuart D Walker
University of Essex
Computer Science and Electronic Engineering
University of Warwick
29th April2016
The main mm-wave issues in the 5G context
• Non-line-of-sight (NLoS) usage is problematic
• Non-waveguide based technology is still emerging;
• Commercially-available chips are in reality, not in plentiful supply and
generally require complex additional circuitry if USB3.0, GbE or HDMI
interfaces are to be used;
• Beam-steering or new designs for compact omnidirectional antennas
may be needed.
• As a side issue, from a systems integration viewpoint, power
consumption is a concern which will require smart power
management in mobile applications
• Human body absorption and its side-effects cannot be neglected in
mobiles
Challenges in identifying spectrum above 6 GHz for 5G
• Spectrum at higher frequencies is already used for a range of important
services. 40% of the spectrum between 6 and 100 GHz is authorised for use
by Fixed Links, and 23% for Satellite services.
• Satellite operators looked to bands above 30/31 GHz, thereby avoiding the Ku
and Ka bands which are established and widely used by the satellite
community.
• The Ministry of Defence (MOD) indicated opposition to an International
Mobile Telecommunications (IMT) identification in certain bands between
40-95 GHz due to their specific satellite requirements.
• Ofcom’s current work on other bands suitable for mobile broadband use (but
not currently being considered for 5G) includes planned releases of spectrum
at 700 MHz, 2.3 GHz and 3.4 GHz and a proposal to vary the licence for the
1452-1492 MHz band to make it suitable for 4G Supplemental Downlink (SDL)
services.
Attenuation for Atmospheric Oxygen and Water Vapour
• On account of limited spectrum allowance (100 MHz @ 24 GHz) and rain/oxygen absorption in the 60 GHz band
(6.8 GHz from 57.1 GHz to 63.9 GHz); these frequencies are currently licence-free.
• Higher frequencies such as 71-76 GHz and 81-86 GHz avoid oxygen absorption overtones (but have greater rainfall
penalties) and are currently light-licensed.
• Even higher frequency usage through 100 GHz has been extensively reported and is now the subject of early
adoption in the US.
60GHz commercial offerings (SiBEAM)
UEssex has performed preliminary
experiments which demonstrated orbital
angular momentum (OAM) generation in
conjunction with commercial 60 GHz
antenna arrays. It is possible that OAM
may provide a further means for spatial
multiplexing.
The figure shows a commercial product
from SIBEAM which featured in the
OAM work described above. 60 GHz
connections were avoided by using
baseband signals to/from the TX/RX
chips to the active, steerable antenna
array.
A 4-Gbps uncompressed wireless OAM
experimental setup
SiBEAM Silicon CMOS antenna array
Data rates of ~3 Gbit/s are
possible over distances of
~19m. All standard
interfaces are provided so
uncompressed 4k UHDTV
signals were transmitted.
Wireless connection is
possible up to distance of
~19 m between the Laptop1
and the 802.11ad docking
station. (Full-duplex per
channel)
D2I was tested (LAN/WAN).
Limited to point-to-point!!
Throughput (Mb/s)
60GHz commercial offerings (Wilocity)
Distance (m)
Wireless card
Active antenna
Omnidirectional antenna characterisations
•
•
Omnidirectional antenna basic characterisations (left:
90° azimuth directivity, right: 330° azimuth directivity)
Connection was maintained
when Laptop was moved
around the dock
however, the link speed
(<2.4Gb/s) and the maximum
wired
1GbE
throughput
(<980Mb/s) was not constant
due to the characteristics of
the omnidirectional antennas
in both the dock and in the
Latitude
Reflection Experiment
Reflection experimental setup with one
mirror
•
•
Connection was maintained when
Laptop was moved around the dock
however, the link speed (<2.4Gb/s)
and the maximum wired 1GbE
throughput (<980Mb/s) was not
constant due to the characteristics
of the omnidirectional antennas in
both the dock and in the Latitude
Reflection experimental setup with two mirrors
•
It was impossible to get readings
at any other distances (by
adjusting D2 and M1) as the
direction of the beam could not
be controlled. A maximum
throughput speed of 950 Mb/s
was measured
Network Topological Rearrangement
•
•
In this scenario, the availability of the four different channel bands in the IEEE 802.11ad
standard allows the use of the different frequencies/channels to create a sparse interconnected
mesh topology, where the devices D1 and D5 are each used as hub gateways to RRH1.
Furthermore, it also shows the reuse of frequencies and channels between D2D connections.
Introduction to arrays
Multiple amplifier modular antenna
Standard modular antenna
PN
N
P
A
Splitter
P
Splitter
P/N
A
NA
NA
EIRP proportional to NAP
N
EIRP proportional to N2AP
The receiver has NO advantage!
Introduction to arrays
Standard modular antenna
P
Splitter
P/N
N
A
EIRP proportional to NAP
NA
Multiple amplifier modular antenna
P
Splitter
PN
N
EIRP proportional to N2AP
A
NA
The receiver has no advantage
Prototype IEEE 802.11ad High gain antenna array
Co-polar plot at 64 GHz
Current distribution plot showing complete signal
extinction
Cross-polar plot at 64 GHz
Prototype IEEE 802.11ad High gain antenna array
Splitter
P
~5dB advantage
Prototype IEEE 802.11ad Transmitter and Receiver Boards
•
•
•
•
Independent differential I & Q data lines
Pluggable low cost antenna facility
Phase matched data I/P & O/P
Covers the Entire IEEE 802.11ad frequency range
•
•
•
•
Tx gain adjustable for optimal performance
Tx 20dBm power output
Rx sensitivity -71dBm
Matching coaxial antenna gain 16dBi @
64GHz
Prototype IEEE 802.11ad Antenna Test Rig
1Gbps transmission system
Some concluding remarks…
•
Current issues are NLoS operation and the limited commercial availability of fullfunction chip-sets.
•
Several advertisers appear to have nothing to sell.
•
UEssex has placed itself in a good position for exploitation of this emerging
technology having appropriate radio test equipment and by being a partner in several
EU/EPSRC consortia in the 5G arena.
•
mobile devices will need to operate over a wide range of frequency bands, i.e. both
below and above 6 GHz.
•
A high-gain directional antenna is favored to compensate for the tremendous
propagation loss and reduce the shadowing effect.
•
mmWave signals have difficulties penetrating through solid materials
•
4k UHDTV live streaming up to 38 metres is possible