FUNDAMENTALS OF MICROWAVE RADIO COMMUNICATION FOR IP AND TDM
1. 1
BASIC INTRODUCTION INTO MICROWAVE THEORY AND IP
APPLICATIONS
FUNDAMENTALS OF MICROWAVE RADIO
COMMUNICATION FOR IP AND TDM
Presented by: Richard Laine / Ivan Zambrano
Silicon Valley, CA.
2. Agenda
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Introduction……………………………………..………….…….A
What is Microwave……….…………………….………….…….B
• Spectrum……………………………………………………………….…..B.1
• A Terrestrial Microwave Link and Applications...……………………....B.2
• How Far can Microwave Go………………………………………..........B.3
• How Microwave Radios Communicate……………………………….....B.4
• How Repeaters Extend the Range……………………………………....B.5
• Microwave Tower Issues………………………………………………….B.6
• Causes of Microwave Disconnect Periods……………………………...B.7
L2 Radio Technology………..………………………………......C
Why Propagation…………………......…………..…………......D
Antennas and Feeder Systems.…………………….………….E
RF Protection……………………………………………………..F
4. • The field of terrestrial microwave communications is constantly experiencing a steady
technological innovation to accommodate the ever-demanding techniques telecom
providers and private microwave users employ when deploying microwave radios in their
cloud networks.
• In the beginning of this wireless evolution, the ubiquitous DS1s/E1s and DS3s/E3s
crisscrossed networks transporting mainly voice communications, data, and video.
• With the advent of Carrier Ethernet and IP, new techniques had to be developed to
ensure the new Layer 2 radios were up to par with the new wave of traffic requirements
including wideband online-streamed media. These new techniques come in the form of
Quality of Service (QoS), Traffic Prioritization, RF Protection and Design, Spectrum
Utilization, and Capacity Enhancement.
• With Carrier Ethernet and IP, network design becomes more demanding and complex in
terms of RF, Traffic Engineering, and QoS. However, the propagation concepts remain
unchanged from TDM link engineering while the link’s throughput of L2 radios doubles,
triples, or quadruples employing enhanced DSP techniques.
Introduction
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6. 6
Flushing ANSI
values
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Terrestrial Microwave?………..What is it?
A line-of-sight point-to-point wireless technology
for the transmission of Internet, voice, data, and
online-streamed media.
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Refracted Beam
Direct Beam
Reflected Beam
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Terrestrial Microwave?………..What is it? (cont'd)
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Terrestrial Microwave?………..What is it? (cont'd)
July 2013
60% F1
60% F1
20. Typical Relative Path Lengths with Clear Line of Sight (LOS)
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Path Length, mi (km)
6/7/8 GHz
11 GHz
18 GHz
23/38 GHz
100(160)5(8) 10(16)
• Path lengths in the different RF
bands are estimates only
• A path analysis is required to
calculate the reliability and
availability criteria.
Maximum EIRP (Effective
Isotropic Radiated Power) =
+55 dBW = +85 dBm
3(5)
July 2013
80 GHz
21. 21
Examples of Very Long IP Microwave Links for Air Traffic Control
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Adaptive Coding and Modulation for IP Backhaul
Throughput
[Mbit/s @ 7 MHz Ch BW]
(QPSK) 10
(16QAM) 20
(64QAM) 30
Example: 99.990% 99.995% 99.999% Rain Availability or Path Reliability
Fade Margin: 24 dB (20%) 31 dB (55%) 40 dB (25%)
Time
Fast Multipath or Slow Rain Fade
Best Effort Traffic
Less Critical
Traffic Critical Traffic
(256QAM) 40
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Coding Gain in AWGN Channels
• Coding gain in AWGN (Additive White Gaussian Noise) channels is defined as
the amount that the bit energy or S/N power ratio can be reduced under the coding
technique for a given Pb (bit error probability) or Pbl (block error probability)
Shannon Limit: Threshold, Eb/N0, below which
reliable communication can not be maintained! This
ratio can be considered a metric that characterizes the
performance of one system vs. another. The smaller
the ratio, the more efficient is the modulation and
detection process for a given Pb.
Pb
10-2
10-4
10-6
Uncoded
Coded
-1.6 dB-8 dB 16 dB
X dB of Coding Gain depending on modulation and BW
Eb/N
0
mNoEbNC log10//
With concatenated coding, the coded curve is steeper
than with Reed-Solomon alone.
Example: The C/N of a p-t-p radio featuring
4DS1/16QAM and Eb/N0 = 11.9 dB @ 10-6
equals: 11.9 dB + 10 log4 = 17.9 dB
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MLCM Signal Constellation
d
√2 d
1 0
Level 1
1 0
2d
1 0
Level 2
A set of 64 symbols is divided into subsets B0 & B1 with
increased minimum square distance. Error performance
of level 1 is determined by the minimum square distance
of the original partition. Then in order to increase “free
Euclidean distance,” coding (combination of block or
convolutional) is performed to the lower level. Hence the
total error performance is improved. Example (16QAM):
Code rate, R = (1/2+3/4+23/24+1)/4=3.2/4
B1 B0
C2 C0 C1 C3
Level 3
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Passive Reflector
"Billboard"
Site A
Single
Reflector
Site B
Terrain
Obstruction
Passive Repeater Arrangements
Site B
Site A
Terrain
Obstruction
Terrain
Obstruction
Double
Reflector
Double Reflector
July 2013
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Site A Beam Bender
(Back-To-Back
Parabolics)
Terrain
Obstruction
Site B
Beam Bender
Back-To-Back Parabolic Antennas
"Beam Bender"
Other Passive Repeater Arrangements
July 2013
30. Twist and Sway
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A B C
Antennas: HSX12-77 Antennas: HSX12-77
Beamwidth: ±0.35o Beamwidth: ±0.35o
425ft/130m
200ft/60m
425ft/130m
Daytime Tower Twist: ±10
±0.50 deflection angle
at 10 dB point
32. Causes of Traffic Disconnect - Outage
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• Rain outage (predictable and therefore acceptable) in access links above
about 10 GHz
• Equipment failure within the MTBF (Mean Time Between Failure) period
• Maintenance error or manual intervention (e.g., failure of a locked-on
module or path)
• Infrastructure failure (e.g., antenna, batteries, towers, power system)
• Low fade margin in non-diversity links
• Power fade (long-term loss of fade margin) in paths above about 6 GHz
July 2013
34. Eclipse Intelligent Node Unit
• The most compact nodal
solution on the market
• Single indoor unit
supporting multiple radio
paths
• Hot-swappable radio and
data access modules
• Support for all traffic types
• Cable-less traffic
connections
• Complete solution in one
box
34 AVIAT NETWORKS | July 2013
35. • Lower Losses than Couplers
• More ODUs per Antenna feed
• Fewer Antennas
• Increased system gain
• Reduces antenna sizes
• Less Tower Loading
• Radios’ features
• 5 to 38 GHz licensed operation
• Fully transparent to payload
• Up to 500 Mbit/s of TDM, Hybrid
TDM/Ethernet/IP, or all-IP throughput
• QPSK to 256-QAM
Networked Radios
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37. Radio Wave Propagation
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GEO, MEO,
and LEO
Satellites
Sky Wave
(MF, HF only)
REFRACTED WAVE
NON-REFRACTED (k=1) WAVETransmitting
Antenna
Receiving
Antenna
Troposphere
Ionosphere
Microwave link propagation is
influenced by REFRACTION,
REFLECTION, and DIFFRACTION
(not shown) wave propagation.
Ground Wave
(LF/MF only)
True Earth’s Curvature
MULTIPATH RAYS
July 2013
38. Ray Tracing Along a Profile
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• Not unlike outbound ripples from a pebble
tossed into a quiet pond, the outgoing microwave
wave front is circular. However, the only part of
the wave of interest is equal to the diameter
(aperture) of the antenna. Beyond the antenna’s
near field, and into the far field, the wave front is
flat, as shown. The ray(s), one direct (shown)
plus multipath rays (if any), are always
perpendicular (90o) to the wave front - thus only
one ray is assigned to each direct or multipath
route. All path profiles and engineering are based
upon ray analysis.
• Antennas serve only to provide maximum
coupling of the direct ray energy into the
waveguide feeder, to the exclusion of multipath
rays. Thus, optimum dish alignment is crucial
for minimum fading.
k = 1 (True Earth’s Radius)
Superrefraction (k>3)
Wavefront Ray 90o
Substandard
Refraction (k<1)
Possible
Obstruction
Possible
Decoupling,
Defocusing, or
Entrapment
Dry and High Valleys
Humid Wetlands
39. Carrier Ethernet Link Design Parameters
39
Flushing ANSI
values
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• NETWORK LAYOUT
• FIELD VERIFICATION
• MICROWAVE EQUIPMENT (Backhaul
Capacity, Link Aggregation, RF Band,
Diversity)
• LINK ANALYSIS (Google Map Study, Field
Survey, Geometry, Weather Patterns)
• LINK PERFORMANCE CALCS (ITU, Vigants)
• LINK AVAILABILITY CALCS (RF Protection,
Rain Outage)
• ACTIVE NODES and PASSIVE REPEATERS
• FREQUENCY STUDY (Interference,
Licensing, Antenna Selection)
• INFRASTRUCTURE (Shelter, AC/DC Power,
Site Security, Towers, Ice Shield, Air Con, etc.)
• ANTENNA FEEDER SYSTEM, (Structures,
Aesthetics, Transmission Lines)
• GROUNDING AND SAFETY
Towers >200ft (60-m)
Require Lighting,
Painting
Sections:
20-ft guyed,
25-ft Self Supp
Shelter
Elliptical
Waveguide, Coax
Atmospheric
Multipath
Millimeter Wave
Rain Attenuation
Refraction, k-Factor
Variations
Antenna Sizes,
Types, Alignment
Diversity
Type, Ant.
Spacing, XPIC
Path
Clearance
July 2013
Dust Cloud
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Reflector Antennas
Photos courtesy of Andrew Corporation
July 2013
Standard parabolic
Standard parabolic
(with radome) Shielded with radome
(high performance)
Higher F/B ratio
Spillover Effect Scattering Effect Diffraction Effect
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Antennas
• Used to efficiently radiate/receive the energy towards/from
the far-end of the link
• Important characteristics
– Gain / directivity / beamwidth
– Side lobe level
– Front-to-back ratio (F/B)
– Polarization (linear V/H, circular, dual V/H)
– Cross-polar discrimination
– VSWR
– Frequency operating range
– Mounting, weight, and wind loading
– Aesthetics
July 2013
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Antenna Alignment Issues
Antenna aligned on a side-lobe
Correct antenna alignment
July 2013
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Antenna Decoupling
• Angle of arrival may vary by as much as 1° on long paths
in humid areas at night; therefore larger antennas are
typically slightly uptilted during daytime periods
• Such variations may cause power fades and degraded
performance (loss of fade margin, increased outage) if
antennas are very directive
Variation in arrival angle
K=
K=4/3
K=-2
July 2013
50. Definitions
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• Protection Schemes provide a level of security from long-
term (>10 CSES/event – Consecutive Severely Errored
Seconds) outages and loss of data throughput, and
therefore improve Availability and reduce traffic
disconnects.
• Diversity Arrangements reduce the number and duration
of short-term (<10 CSES/event) outages (no traffic
disconnects) and therefore improve Performance.
July 2013
52. 1+1 Monitored Hot Standby Outdoor Node (cont’d)
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Tribs 1-20
Protection
Cable
ODU 600sp/hp/ep
Y-Cables
53. 1+1 Monitored Hot Standby Outdoor Node
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Equal split (3dB)
RF Splitter is also
possible with the
consequence of a
2dB link gain
penalty which
translates into a
58% degradation in
the hop’s error
performance and
perhaps larger
antennas!
ANTENNA
DATA
OUT
DATA IN
-1.6dB
-6.6dB
Tx A
Rx A
Tx B
Rx B
Asymmetric
RF
Coupler
INU/IDU errorless data
selection is frame-by-frame
-1.6dB
-1.6dB
Tx A or Tx B is on line
56. 1+1 Monitored Hot Standby Space Diversity - Outdoor Node
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Multipath forms essentially
in the vertical plane;
consequently, the antennas
should always be placed
vertically to achieve de-
correlated paths !
Main ANTENNA
DATA
OUT
DATA IN
Tx A
Rx A
Tx B
Rx B
INU errorless data
selection is frame-by-frame
Diversity ANTENNA
300 ms
Vertical antenna spacing from 3 – 23m
ITU-R P.530-13
RSLM
RSLD
-40 dB fade
-20 dB fade
58. Suggestions
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• Professional Affiliations News Websites
• IEEE
• LinkedIn www.bbc.com
www.foxnews.com
• Movies www.elpais.es
• The Pirates of Silicon Valley
• Social Network
• The Internship
• The Greatest Game Ever Played
• Flash of Genius
• Countries
• Spanish English
• Chile Australia
• Argentina New Zealand
Dubai
Canada
USA