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Digital Microwave Radio Network
Design in an IP Environment
Upcoming Revisions to TIA TSB 10F
George Kizer , Alcatel-Lucent
How did we get here?
Telecommunications Systems Bulletin 10
has been around for decades.
The current version, TSB 10F, was
adopted in 1994.
This version was intended to support the
recently created FCC Part 101 services
(a joint effort of TIA Fixed Point-to-Point
Microwave section and NSMA).
It also facilitated spectrum sharing with
PCS services during the 2 GHz band
transitions.
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How did we get here?
Path performance was defined on the basis of flat
fading and (now obsolete) rain fading methods
TSM defined interference analysis for analog FDM-FM,
analog video and digital signals
TSB 10F introduced the concept of T/I and ATPC for
non-rain fading paths
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How did we get here?
TSM 10F gained wide industry acceptance
It is strongly embedded in the FCC rules and regulations:
§ 22.602(j) (“TIA TSB 10-F or any standard successor”)
§ 24.237(a) (“TIA Telecommunications Systems Bulletin 10-F, "Interference Criteria for
Microwave Systems," May 1994, (TSB10-F)”)
§ 24 Appendix I To Subpart E (“EIA/TIA Bulletin 10-F”)
§ 27.1134(b) (“TIA Telecommunications Systems Bulletin 10-F, "Interference Criteria for
Microwave Systems," May, 1994 (TSB 10-F)”)
§ 101.3 ("TIA Telecommunications Systems Bulletin TSB 10, Interference Criteria for
Microwave Systems (TSB 10).")
§ 101.79(a) ("TIA TSB 10–F", "TSB 10" and "Telecommunications Industry Association’s
Telecommunications Systems Bulletin TSB 10")
§ 101.105(a)(5) ("TSB 10–F")
§ 101.79(a) (“TIA TSB 10-F”)
§ 101.95(a) (“TIA Bulletin 10-F or any standard successor”)
§ 101.105(a)(5)(i) & (ii) (“TSB 10-F or other generally acceptable good engineering
practice”)
§ 101.105(c) (“Telecommunications Industry Association's Telecommunications Systems
Bulletin TSB 10, "Interference Criteria for Microwave Systems" (TSB 10)”)
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Where are we now?
TSB 10F was primarily oriented to analog microwave transmission
Digital transmission design methodologies are not addressed
The many variations of T/I were not known or described
ATPC for rain dominated paths was not allowed
These limitations have led to contention within the industry
The current effort to update the standard addresses these issues
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TIA Committee TR-45 Working Group on Microwave Systems
Areas of Interest:
A) Automatic Transmit Power Control (ATPC) - Tom Willis, AT&T
B) Analog Systems Update - Will Perkins, Comsearch
C) Digital Systems Update - George Kizer, Alcatel-Lucent
D) Short and Long Term Objectives - Will Perkins, Comsearch
F) IP-based MW Radio Development and Deployment Guidelines – George Kizer,
Alcatel-Lucent
H) Combine Vertical and Horizontal Antenna Discrimination - Thu Nguyen, Radyn
I) Define T/I and C/I Criteria - Will Perkins, Comsearch
J) Define Availability and Quality - George Kizer, Alcatel-Lucent
K) Update Current Rain Models - Tom Willis/George Kizer, AT&T and Alcatel-Lucent
L) Part 25 Interference Methods - Thu Nguyen, Radyn
P) BAS 900 MHz FM STL Part 74 Coordination Procedures ( Brad Youngblood)
Areas related to IP (fixed and adaptive) point to point microwave radios.
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A) Automatic Transmit Power Control (ATPC)
Tom Willis, AT&T Labs
Currently ATPC is defined for multipath
dominated microwave paths. Can ATPC be used
on rain dominated paths and, if so, how can its
used be specified.
When operating in fixed mode, the operation of
the radio is not different than a current radio.
When operating in ACM mode, what is the
expected operation and how should ATPC be
managed?
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Automatic Transmit Power Control (ATPC)
Site Separation
A: 1.3 km
B: 3.9 km
C: 6.5 km
D: 9.0 km
11 km
10 km
A network model of area wide fading has been agreed to
based upon Bell Labs studies
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Automatic Transmit Power Control (ATPC)
Rain Intensity
d = 2.4 km
d = 2.7 km
A rain cell fading intensity model has been
agreed to
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Automatic Transmit Power Control (ATPC)
Bill Rummler is currently performing a Monte
Carlo analysis to determine the effects of rain
fading on various path configurations.
The expectation is to determine the path
configurations for which ATPC is applicable.
This task is still active.
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B) Analog Systems Update
Will Perkins, Comsearch
Annex A: Methods for Computing the Interference Objectives of
FM-FDM Receivers
ITU-R Recommendation SF.766 (1992) will be used for this
section.
Annex B: Methods for Computing the Interference Objectives of
Digital Receivers
This section is being addressed in other tasks.
Annex C
C/I Objectives for Digital Interference into FM-Video Receivers
This section has been updated.
Annex D: Methods for Computing the Interference Objectives of
AM-VSB Video Receivers
This section is unchanged.
This task is complete.
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C) Digital Systems Update
George Kizer, Alcatel-Lucent
Digital systems have a dispersive fade margin that
is not experienced in analog systems
Currently there is not industry accepted method
of estimating dispersive fading.
This task is addressing these issues and is still
active.
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D) Short and Long Term Objectives
Will Perkins, Comsearch
Short term objectives have been updated to
allow less restrictive over the horizon
estimations for paths blocked for K =
 paths.
This task is completed.
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F) IP-based MW Radio Guidelines
George Kizer, Alcatel-Lucent
The fixed microwave manufactures, service
providers and users are recognizing the world is
moving quickly into an Internet Protocol (IP)
environment.
Pressure to increase microwave radio bandwidth is
leading to the introduction of Adaptive Coded
Modulation (ACM) radios [also called Link Adaption
(LA) or Adaptive Modulation and Coding (AMC)].
Legacy equipment and system testing
methodologies need updating to address these
technologies new to microwave radios.
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What is an IP point to point microwave radio?
An IP radio operates in an Internet Protocol (IP)
environment.
One type overlays IP into a TDM radio transport
frame. Latency is minimized. Convenient for
drop and insert applications. TDM waiting time
jitter control requires synchronization.
The other encapsulates TDM traffic (pseudowire
DS1s and DS3s) into IP packets and transports all
traffic in native IP packets. Latency is greater.
TDM encapsulation requires synchronization.
Convenient for asymmetric traffic shaping.
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What is an ACM point to point microwave radio?
An Adaptive Coded Modulation (ACM) radio can
operate at different modes depending upon the
condition of the radio path.
During normal propagation conditions the radio
operates at high spectral efficiency (up to2048
QAM).
When path conditions degrade (e.g., during
multipath or rain fading), the radio changes
forward error correction and/or QAM mode (as
low as 4 QAM) to increase radio threshold (but
reduce transmission capacity as much as 3 to 1)
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What is an ACM point to point microwave radio?
An ACM radio requires the incoming traffic be
tagged to some form of Quality of Service (QoS).
Compatibility with the various QoS definitions is
an issue.
Routers seeing a variable bandwidth IP channel
may behave unpredictably. Using an ACM
qualified router is suggested.
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What are the new issues with IP microwave radio?
How do you measure the threshold of an IP radio?
(No, the answer is definitely not to measure it on an
encapsulated DSx or Ex channel!)
What is the concept of Dispersive Fade Margin
(DFM) when an ACM radio has two thresholds per
operating mode?
How should Automatic Transmitter Power Control
(ATPC) for when an ACM radio has multiple
transmission modes?
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New measurements for IP microwave radios
Historically we have used 10-6 BER in a TDM baseband
signal (such as DS1, DS3, STS-1, OC3, E1, E3 or STM0) as
the receiver threshold. That is meaningless in an IP
environment.
A single error in an IP packet causes that packet to be
lost. The effect is to promote a bit error into an
dropped frame in TDM traffic.
Proprietary encapsulation methods can reduce this
sensitivity, but the basic issue remains.
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Proposed IP fixed modulation radio threshold
We are proposing replacing Bit Error Ratio (BER) with
Frame Loss Rate (FLR):
FLR
= (bytes per frame) * (bits per byte)
* (probability of error event)
= (bytes per frame) * (bits per byte)
* (BER threshold / [errors per error burst])
Bits per byte = 8
BER threshold = traditional 10-6
For consistency and to limit the influence of multiple
errors we suggest using a specified byte packet.
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Proposed IP fixed modulation radio threshold
Assuming 20 errors per error burst:
BER
FLR (64 byte frame)
FLR (1518 byte frame)
10-3
3 x 10-2
6 x 10-1
10-6
3 x 10-5
6 x 10-4
10-9
3 x 10-8
6 x 10-7
10-12
3 x 10-11
6 x 10-10
BER = Bit Error Ratio
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FLR = Frame Loss Ratio
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Proposed IP ACM microwave radios threshold
For ACM radios there are TWO receiver thresholds:
a threshold at which the receiver switches
from a lower complexity (QAM) to the
reference complexity (up threshold = THup)
a threshold at which the receiver switches
from the reference complexity to the lower
complexity mode (down threshold = THdown).
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Proposed IP microwave radios threshold
Receiver flat fading time probability is inversely
proportional to fade margin or directly
proportional to receiver threshold:
PDFM
FFM
TH
= receiver multipath outage probability
 10-FFM/10  10TH/10
= flat fade margin
= normal RSL (dBm, negative value) – TH
= receiver threshold (dBm, negative value)
10THavg/10 = ½ [10THup/10 + 10THdown/10]
This simplifies to the following:
THavg = -3 + 10 log10 [10THup/10 + 10THdown/10]
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Proposed IP microwave radios DFM
Historically Dispersive Fade Margin (DFM) is measured
for a given radio threshold:
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Proposed IP microwave radios DFM
DFM is calculated based upon a W curve for minimum
and non-minimum dispersive fade:
North American Method
Bellcore (Telcordia)
Sw  
39.6
39.6
International Method
ITU-R
[eBn/3.8  eBm/3.8 ]df (MHz)
DFM (dB) = 39.6 – 10 log ( Sw )
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Proposed IP ACM microwave radios DFM
Traditional Dispersive Fade Margin (DFM) Curves
< replace with new threshold
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Proposed IP ACM microwave radios DFM
For ACM radios there are TWO receiver thresholds:
Threshold for transition to a lower QAM
Threshold for transition from a lower QAM
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Proposed IP ACM microwave radios DFM
New Dispersive Fade Margin (DFM) Curves
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Proposed IP ACM microwave radios DFM
PDFM
= dispersive multipath outage probability
 10-DFMavg/10
 10-Bavg /10
The basic dispersive fading outage models assume minimum
and non-minimum fading occurs for equal time.
10-DFMavg/10 = ½ [10-DFMsu/10 + 10-DFMsd/10]
10-Bavg/10 = ½ [10-Bsu/10 + 10-Bsd/10]
The subscripts “su” and “sd” represent “Switch Up” and
“Switch Down” respectively. These equations may be
simplified to the following:
DFMavg = 3 – 10 log10 [10-DFMsu/10 + 10-DFMsd/10]
Bavg = 3 – 10 log10 [10-Bsu/10 + 10-Bsd/10]
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IP ACM microwave radio unexpected consequences
The radio thresholds for an ACM radio are
always higher than the threshold for a fixed
modulation radio.
When changing from a fixed modulation IP
radio to an ACM radio, the path availability of
the reference modulation (and reference
capacity) is always reduced.
The availability of the priority traffic is always
significantly increased.
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New measurements for IP ACM microwave radios
Some parameters are new to radio systems:
Radio Transmission Capacity (Layer, 1, 2 or 3)
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What is an IP point to point microwave radio?
Layer 4
Application
Layer 3
IP Rate
Layer 2
Information Rate
Layer 1
Line Rate
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What is transmission rate for an IP radio?
Line Rate
Information Rate
IP Rate
Payload
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What is transmission capacity of an IP radio?
figure adapted from Understanding Carrier Ethernet Throughput, Metro Ethernet Forum, July 2010
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What is transmission throughput for an IP radio?
figure adapted from Understanding Carrier Ethernet Throughput, Metro Ethernet Forum, July 2010
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New measurements for IP ACM microwave radios
Some parameters are new to radio systems:
Frame Loss Rate (loss vs offered load – determine
overload point)
Latency (Delay at 90% capacity)
Frame Delay Variation (Frame Jitter)
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New measurements for IP ACM microwave radios
Some parameters are new to radio systems:
Back to Back Frames (burst tolerance)
Buffering Recovery Time
Reset Time
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New measurements for IP ACM microwave radios
Some parameters are important but not
currently being addressed by the TR-45 effort:
Routing, network stability and restoration
Processing of Priority Tagging (“Quality of
Service”) of competing traffic.
Security
Note that the above features typically behave differently
in IPV4 and IPV6 environments.
This task is completed.
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H) Combine Vertical and Horizontal Antenna
Discrimination
Thu Nguyen, Radyn
Antennas generally have a symmetrical antenna
pattern center around antenna boresight.
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Combine Vertical and Horizontal Antenna Discrimination
Most interference discrimination methods assume the path
is on a flat plane. For very short paths, this creates
significant estimation error.
A method to compensate for path vertical angle has been derived.
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I) Define T/I and C/I Criteria
Will Perkins, Comsearch
The difference between T/I and C/I are not
always understood within the industry.
Methods of estimating T/I with measured data is
not available is an issue.
What is the appropriate interference limit with
different T/Is are involved with ACM radios
This section addresses these issues.
This task is in process.
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J) Availability and Quality
George Kizer, Alcatel-Lucent
The concepts of Availability and Quality are
different in Europe and North America.
This task explains these differences and how they
affect performance estimates.
This task is completed.
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K) Update Rain Attenuation Models
Tom Willis, AT&T Labs
George Kizer, Alcatel-Lucent
Since 1994 rain models have evolved significantly
from Rain Zones to specific location rain rates.
The coefficients K and for point rain attenuation
have also evolved.
This section addresses these issues.
This task is completed.
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L) Update Part 25 Interference Methods and Limits
Thu Nguyen, Radyn
Objectives for coordination with Part 25 earth
stations have been updated.
This task is completed.
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P) Define Part 74 STL Audio Link Standards
Brad Youngblood, Micronet
Coordination objectives for analog and digital
systems and well as typical and worst case
receiver filters have been determined.
This task is completed.
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Questions?
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