Training Module on
Learning today……
Understanding Microwave link : applications,
configuration, operating parameters, system calculations
Line of Sight requirements and Antenna Heights
Antenna Installation alignment and its parameters,
safety and quality
MW Link Installations and commissioning :
standard practices : NEC’s approach
Concluding : General site issues: questions &
1
excerpt from the Scientific American
July 1892
In the specification to one of his recent patents, Thomas A. Edison says:
“I have discovered that if sufficient elevation be obtained to overcome the curvature of the earth’s surface
and to reduce to the minimum the earth’s absorption, electric signaling between distant points
can be carried on by induction without the use of wires.”
• Operates on a “Line-of-sight" principle
• Use Two antennas aimed directly at one another • Transmit Digitally modulated Microwave
Frequencies through free space from one terminal to another
• Typically transmit simultaneously in both
directions (Full Duplex)
4 0 0 1 0 0 2 0 0 3 0 0 0 . 5 1 . 0 1 .5 2 . 0 2 .5 3 . 0 3 . 5 4 . 0 4 .5 5 . 0 T y p i c a l P a t h P r o f i l e D i s ta n c e ( m il e s ) Line of sight Point to Point MW
FWS (Point-to-Point Transport) and FWA (BWA, Access) Hops
POP – Point of Presence PB X CPE CPE
Nodal (Hub) Site
155 Mbit/s Sonet/SDH FWS (Fixed Wireless System) Hop
CPE
ClearBurst MB Point-to-Multipoint FWA (Fixed Wireless Access) Broadband
Links CPE – Customer’s Premises Equipment: - Frame Relay - Video Conference - Sonet/SDH (PTP) - ATM Switch
- LAN/IP - Base Station - T1/E1 - POTS - Sonet/ SDH - ISDN
FWS and FWA (BWA) Radio Hops
Sonet/SDH NxOC-3 or NxSTM-1 Backbone FWS (Radio-Relay) Hop
OC-12 or STM-4 Fiber Ring
Long Distance 2xT1/E1 Unlicensed Hop
Short Distance 4xT1/E1 Hops Access Hops
Short Distance SONET/SDH Hop
X X
Transport Hop
Fiber and MW transmission media in GSM/CDMA Networks
23 GHz (OC-3) 38 GH z (N x DS1) 18 GHz ( N x DS1 ) 18 GH z (DS3) BTS BSC MTSO (MSC) BSC
(DS3 or OC-3NxOC-3 ) or 155 (Nx0C-3) Self-Healing Ring
BTS BTS
BTS
FWS Microwave Applications
PCS/Cellular Site Interconnection MTSO (MSC) - Switching Office BTS - Base Station
BSC - Base Station Controller
Some Attributes of Digital Microwave Radios
• Superior availability - route security (no cable cuts)
• Rapidly expandable and upgradeable, in-service if protected
• High quality - no multihop “noise” addition
• Rapid deployment over difficult terrain and into urban areas
• Economical - no copper or fiberoptic cable deployment
• Robust to fading and interference
• Insensitive to antenna feeder system and long-delayed on-path echoes
• Highly efficient data and broadband transport
• Exacting in-service visibility of radio hop performance with NMS
• Seamless interconnectivity to an ever-expanding digital transport (fiberoptics and other), PABX/MSC switch, and LAN/IP world.
1 M H z 1 0 M H z 1 0 0 M H z 1 G H z 1 0 G H z 1 0 0 G H z 1 0 1 2 1 0 1 4 M ic r o w a v e s A M B r o a d c a s t R a d io U H F T e le v is io n F M B r o a d c a s t R a d io V H F T e l e v i s io n M o b il e R a d io S h o r t w a v e R a d io M o b ile R a d io V i s ib le L ig h t F i b e r O p t ic s 1 0 0 0 m ( 3 0 0 K H z ) 1 m m ( 3 0 0 G H z ) 1 c m ( 3 0 G H z ) 1 0 c m ( 3 G H z ) 1 m ( 3 0 0 M H z ) 1 0 m ( 3 0 M H z ) 1 0 0 m ( 3 M H z )
3xDS3/OC-3/STS-3 4xDS3, 4xE3/STM-1 Capacity GHz T1/E1 DS3 or 28 T1 E3 or 16 E1 Frequency Band: 2 6 8 13 18 23 Backbone Transport 2 T1/E1 4 T1/E1 42 11 37 16 T1 NxOC-3/STM-1 10 Network Management Element Manager SNMP Interface 1:N Backbone & Access Unlicensed 1-5mi/2-8km 5-10mi/8-17km 7-15mi/12-25km >15-60mi/25-100km Access
Broadband Wireless Access (FWA)
26 8 E1
Typical Path Lengths:
Example of capacity and frequency bands
CEPT PDH Hierarchy 140 Mbit/s (1920 Ch) 1 2... 1 2. .. 2 3 1 30/31* 4 E1 E2 E3 16 34 Mbit/s (480 Ch) 1 2 3 4 E3 34.368 Mbit/s (480 Ch) 8.448 Mbit/s (120 Ch) 2.048 Mbit/s (30/31 Ch) PCM Channel Banks M34-140 Radio MUX 1st Order
CEPT Hierarchy is the international TDM digital standard everywhere except North America (USA, Canada), Taiwan, Korea and Japan.
1 2 3 4 M8-34 3rd Order E4 Skip Mux M2-8 2nd Order M2-34 Skip mux VF/data/LAN/IP and teleconferencing circuits 16 x 2.048 Mbit/s E1 Trunks PDH -Plesiochronous (asynchronous) Digital Hierarchy
*30 VF Channels with signaling channel or 31x64 kbit/s Data Channels (no signaling)
TDM: CEPT PDH Hierarchy Voice Channel Equivalent 1 30 120 480 1920/1890* Desig-nation E0 E1 E2 E3 E4 No. of E1 Trunks 30/31 = 1E1 1 4 16 64/63* Bit Rate (kbit/s) 64 2,048 8,448 34,368 139,264 Line Code AMI HDB3 HDB3 HDB3 CMI *63 E1 (1890 VF ch) are mapped in Synchronous Digital Hierarchy (SDH) AMI, HDB3, & CMI codes are bipolar.
Cable types: 120Ω Twisted Pair, 75Ω Coax (Length/type assigned for 6 dB maximum loss) Ref: ITU-T G.703, G.704
CEPT PCM Analog-Digital PCM Quantizing Code is A-Law
SDH Fundamentals: Rates Line Rate (Mbit/s) SDH Signal PDH Signal # E1 (2048 kbit/s) VF Transport 2.048 VC - 12 1 30 34.368 VC - 3 16 480 51.84 Sub-STM-1* 21 630 139.264 VC - 4 64 1,920 155.52 STM - 1 63 1,890 622.08 STM - 4 252 7,560 2488.32 STM - 16 1,088 30,240 9953.28 STM - 64 4,032 120,960
SDH Synchronous Digital Hierarchy
PDH Plesiochronous Digital Hierarchy
*Sub-STM-1 RR-STM, STM-0 = 51 Mbit/s for Radio Relay) Ref.: ITU-R Rec. F.750-3 (1997)
Radio or Fibre
Fibre 1:N Radio or Fibre
SDH Fundamentals: Mux
Note: Bold indicates commonly available multiplexer interface
RRRP NNI
SDH Synchronous Digital Hierarchy STM Synchronous Transport Module
VC Virtual Container
TU Tributary Unit
TUG Tributary Unit Group
AU Administration Unit
AUG Administration Unit Group ATM Asynchronous Transport Mode RRRP Radio-Relay Reference Point NNI Network Node Interface
Sub-STM-1 = RR-STM (52 Mbit/s for radio) = STM-0 ATM x4 Pointer Processing Multiplexing Aligning Mapping DS1 VC11 TU11 VC3 VC12 VC2 TUG-2 TUG-3 VC3 VC4 AU4 AUG STM-N E1 DS1 DS2 E3 DS3 E4 x1 x1 x1 x1 x3 x3 x3 x7 x3 AU3 x1 TU12 TU-3 x1 Sub-STM-1 TU-2
Circulator, Filter (CBN) Waveguide RF RF Circulator, Filter (CBN) Waveguide f [GHz] Channel BB = Baseband e.g. 155 Mbit/s Classical Design Channel Demodulator 16 - 128 QAM Modulator 16 - 128 QAM IF = Intermediate frequency e.g. 140 MHz RF = Radio frequency e.g. 7.5 GHz, 18.7 GHz TX Transmitter RX Receiver
• Outdoor Units (ODUs) are software configurable so that capacity upgrades can be made without climbing towers. • Indoor Units (IDUs) support capacities of 2/4E1, 4/8E1,
16E1, E3, 4/8DS-1, or DS3 and are frequency
independent so that they can be used with any ODU of like capacity.
– Minimal Installation time
– Single coaxial cable connection between IDU and ODU – Dual polarity DC input of (±21.6 to ±60 VDC)
– Adjustable transmit output power
– Frequency/channel setting via keypad or laptop PC – Diagnostic loopbacks accessible via laptop PC
Line Interfac
e
MUX MOD
DEMUX DEMOD AGC N - p l e x o r
LIU Input MUX PLL TX FPGA TX IF PLL TX IF RX FPGA DEMUX Frame Frame Sync Private Link DEMOD Lock Low BER (>1e-9) High BER (>1e-3)AGC
ODU Communication N - p l e x o r ALC ≈ ≈ PA IF LO RT 1848 PLL Synth Up Conv. Osc
Unlock
Synth TX Offset Voltage Synth TX Main Loop Unlock
Synth TX Offset Loop Unlock
Synth Rx Main Loop Unlock Synth Rx Offset Loop Unlock Synth Rx Offset Loop Voltage
TX Synth RX Synth LNA PA 70MHz 310MHz 2158MH z 1778MH z Line Interfac e MUX MOD
DEMUX DEMOD AGC N - p l e x o r
LIU Input MUX PLLTX FPGA TX IF PLL TX IF
RX FPGA DEMUX Frame Frame Sync Private Link
DEMOD Lock Low BER (>1e-9) High BER (>1e-3)
AGC ODU Communication N -p l e x o r ALC ≈ ≈ PA IF LO RT 1848 PLL Synth Up Conv. Osc Unlock
Synth TX Offset Voltage Synth TX Main Loop Unlock
Synth TX Offset Loop Unlock
Synth Rx Main Loop Unlock Synth Rx Offset Loop Unlock Synth Rx Offset Loop Voltage
TX Synth RX Synth LNA PA 70MH z 310MH z 2158MH z 1778MH z
Far End SP Far End RF Plug-in
Near End RF Plug-in Near End
SP
Protection and Diversity
Protection Schemes and
Protection and Diversity
The Need for Protection and Diversity
In the past, short traffic interruptions without traffic disconnect in microwave links were often acceptable to many private users.
Expectations changed with the digital microwave
transport of MSC-cell site data, ATM, high speed data transfer, teleconferencing, imaging (medical, etc.), and such technology as the new digital mobile trunking
systems.
Excessive numbers of short fade hits (circuit
interruptions) are now barely tolerable, except in LAN/IP transport and access (millimeterwave) hops impacted by rain cells, long-term outages (traffic
87
Protection Schemes
*Reverse Channel Switch command from far end receivers ** If FD is permitted
Equipment degradation, failure:
– 1+1, hot-standby or on-line modules …HS – 1:N, one standby for >2 modules ……..HS
Antenna system misalignment, failure:
– Split transmitters + RCS* ………….HS+ST – Two-dish hybrid diversity** ….HD, SD+ FD – Self-healing ring (loop) architecture …..SR
Protection Types
1+1 hot-standby protection ……….HS
1+1 on-line (paralleled elements) protection ...HS
1:N module protection ……….HS
1:N multiline protection ……….HS or HS+FD
Split transmitters with RCS* ……….……...HS+ST
Self-healing ring (or loop) architecture …….….SR
*Reverse Channel Switch command triggered by the dual failure (outage) of both far-end receivers
C B N 10dB C B N 1+0 Equipment Protection - "1+1 HSB" Configuration RPS RPS f1 f1a f1 f1a f1` f1b f1` f1b f1a f1a TX TX Station B Station A Ch. 1 (STM-1) (STM-1)Ch. 1 DM RX f1b DM RX f1b 10dB OP PR f1b PR TX MD f1b TX MD OP OP PR MD MD RX f1a RX f1a DM DM PR OP
1+0 Equipment Protection - Space Diversity f1 f1a f1 f1a f1` f1b f1` f1b C B N Station B Station A Ch. 1 (STM-1) RPS RPS (STM-1)Ch. 1 f1b PR TX MD f1b TX MD OP OP PR MD MD f1a f1a TX TX C B N RX f1a RX f1a DM DM PR OP CBN CBN DM RX f1b DM RX f1b OP PR
Frequency (GHz) Minimum Spacing (m) Ideal Spacing (m) 6,8 4,5 10 7 4,5 10 13 2,5 5 15 2,0 5
Typical spacing for SD
∆ ∆
Microwave Radio Technology - Space Diversity
DM RX TX MD CBN Main + DM RX TX MD CBN Main + STM-1 STM-1 CBN Div RX Length compensation CBN Div RX
TX MD Ch. 1 (STM-1) DM RX horizontal f1a f1b Ch. 1 (STM-1) DM RX TX MD f1a f1b horizontal 140 MHz 140 MHz CBN CBN Ch. 2 (STM-1) DM RX TX MD f1a f1b TX MD Ch. 2 (STM-1) DM RX vertical f1a f1b vertical 140 MHz MHz140 PW PW CBN CBN OP2 f1 OP2 f1 V f1 OP1 f1 OP1 f H
Block Diagram - 2+0 Configuration with XPIC
Clock synchronization Data compensation V V H H 2 Waveguide pro Station
Microwave Radio Technology - Frequency Diversity f1a f3a f1b RPS CBN Channel 1 MD TX MD TX DM f3b RX RX DM f1 f3 f f3 f3a f3 f3a f1 f1a f1 f1a f3’ f3b f3’ f3b f1’ f1b f1’ f1b
Hot-Standby & Space Diversity
Hot Standby Terminal Hot Standby Terminal with
Space Diversity Receivers
*
* Power splitters in digital radios are always asymmetrical, not 3/3 dB as in analog radios, as data are errorlessly switched - not combined as are analog radio basebands. A 3/3 dB RF receiver splitter provides no protection benefits over the 1/7 dB splitter, and will lower fade margins 2 dB for 58% more outage time.
Splitter/Combiners
Waveguide Coupler Primary Path
Insertion Loss Standby Pass Insertion Loss
6 dB unequal coupler 1.6 dB 6.4 dB
RFD Configurations
1+0 1+1 HH
Cost-effective method of providing T1/E1 trunk redundancy in mixed radio, fiberoptics, span lines.
Protects against Path, Site, and Equipment Failures with
non-protected radio repeaters - lowers costs ~40%.
Only protection from long-term periods of unavailability
due to fiber cuts, power fades such as heavy rain at higher frequencies, infrastructure failures, etc.
Operation, fault location, testing, and maintenance are
simplified.
A ring-closure microwave hop (perhaps longer or with
degraded performance) or other T1/E1 trunk for ring closure (fiber, leased line) is necessary.
Benefits of Ring Protection
Component mountings- IF Module
The IF Module (IFM)
consists of the following items:
TX IF assembly
RX IF assembly
dB dB dB dB 2 * S yn 2 * Syn DC DC CPU dB dB High integrated RF Module RF Diplexer Modulare ODU-Design IF Antenna
OP f1 H V STM-1 DPU EOW Modulator Demodulator Power Supply IDU
Broad Band Filter
ODU
coax. cable
Frequencies 7 up to 38 GHz Operation mode 1+0 with integrated antenna
In some cases of interest in an offer because of the lowest price
OP f1 H V Frequencies 7 up to 38 GHz STM-1 DPU EOW Modulator Demodulator Power Supply
Broad Band Filter
ODU
coax. cable
wave guide
IDU 155-16/128 LS
Operation mode 1+1 HSB with integrated antenna Frequencies 7 up to 38 GHz f1 H V BK DPU EOW Modulator Demodulator Power Supply DPU EOW Modulator Demodulator Power Supply ODU ODU Coupler coax. cable Slave-IDU Master-IDU 1,3 dB 6,3 dB
Operation mode 1+1 HSB with integrated antenna Frequencies 7 up to 38 GHz f1 H V BK DPU EOW Modulator Demodulator Power Supply DPU EOW Modulator Demodulator Power Supply ODU ODU Coupler coax. cable Slave-IDU Master-IDU 1,3 dB 6,3 dB
Operation mode 4+0 or 2x(1+1) dual polarized CCDP with XPIC STM-1 DPU EOW Modulator Demodulator Power Supply DPU EOW Modulator Demodulator Power Supply 4 x IDU 155-16/128 LS OMT Waveguide Wave -guide STM-1 Frequencies 7 up to 38 GHz f1 f1 H V f3 f3 OP1 OP3 OP2 OP4
ODU LX – Adjacent Channels ODU S – 1 Ch. to be left ODU ODU Coupler STM-1 DPU EOW Modulator Demodulator Power Supply DPU EOW Modulator Demodulator Power Supply STM-1 ODU ODU Coupler
Operation mode 4+0, coupler version in dual polarized ACAP STM-1 DPU EOW Modulator Demodulator Power Supply DPU EOW Modulator Demodulator Power Supply 4 x IDU OMT Waveguide Wave -guide STM-1 f2 f1 H V f4 f3 OP1 OP3 OP2 OP4 Frequencies 7 up to 38 GHz ODU ODU Coupler STM-1 DPU EOW Modulator Demodulator Power Supply DPU EOW Modulator Demodulator Power Supply STM-1 ODU ODU Coupler
90°
H horizontal
Frequency Patterns - Transmission via 2 Polarizations
1. Polarization 2. Polarization V: vertical Orthomode transducer (OMT) V TX MD DM RX f1a f1b CBN f1 f1 TX MD DM RX f1a f1b CBN f1 f1 H V H Waveguide V Waveguide H
Operational parameters and system planning
Microwave Frequency Required
Necessary Antenna Gain
Maximum Distance between terminals
Receive Signal Level Margin
TX
Terms of Microwave Radio Technology - System Overview
Max. power e.g. +31 dBm [1.25 W] Output power min. power e.g. -73 dBm [50 pW] Fading margin Free space attenuation e.g. 143.9 dB
(Distance d = 50 km) (Frequency: f = 7.5 GHz) (d[km]f[GHz]) log 20 92.4 0 a = + ⋅ ⋅ CBN waveguide e.g. 5.3 dB CBN waveguide Antenna gain e.g. 41.4 dB Antenna gain e.g. 41.4 dB CBN waveguide CBN waveguide e.g. 5.3 dB System attenuation (e.g. 71.7 dB) Input power RX System gain
SYSTEM GAIN (to 10-3 BER or LOF) Top of Bay Antenna Port 1 2 3 Transmitter Output Interface Repeater Station Top of Bay Antenna Port RSL IN 1 2 3 Receiver Input Interface SYSTEM GAIN. dB XMTR Power Out - RCVR RSL In
(for 10-3 BER) at the Antenna
Ports. Typically 100 dB
NPL - NET PATH LOSS. dB Waveguide In Site A to Waveguide
Out at Site B. Typically 60 dB (Excluding Fade Activity)
RECEIVER RSL INPUT. dB RSL = XMTR Power Out - NPL
THERMAL FADE MARGIN. dB TFM = System Gain - NPL
NET PATH LOSS (NPL) FREE SPACE LOSS
(NO FADE)
Terminal Station EIRP = P0 - Lf + Ga (FCC/ETSI Constraints)
Ga
Lf
P0
Receive signal level calculation
RSL(dBm) = Tx power(dBm) + Tx antenna gain(dBi)
Free Space Loss(dB) – Branching Loss – Feeder
cable loss + Rcv antenna gain (dBi) where
Free Space Loss(dB) = 32.4 + 20logF +20logD where: D is Kms, F is MHz
For example:
Given: Path Distance of 10 Kms, Radio Frequency is 7 GHz,
Tx Power is 20 dBm, and Antenna Gain(both sides) is 38 dBi
•Free Space Loss = 32.4+20log(10)+20log(7000)
= 32.4+20+76.90 = 129.30 dB
Receive signal level margin
• Directly determines the availability of the link by providing threshold “cushion” against signal fade due to environmental conditions, i.e. rain, snow, hail, etc.
• Rain data for geographic location is needed to calculate availability once RSL margin is known.
System Gain, Net Path Loss
RF Signal, Noise, and Interference Levels
Static and Dynamic Thresholds
Microwave Spectral Efficiency
QAM, QPSK Modulation
DSSS, OFDM/COFDM Signal Spreading
Microwave Spectrum Calculations
Co-Channel Dual Polarization (CCDP)
Latency
ATPC and DTPC
Frequency Bands, Interference, Terrain Scatter
Frequency Band Selection
Technical Topics that define Digital Radio Hops
ATPC and DTPC
DTPC – Dynamic Transmit Power Control (TRuepoint, Galaxy 23) ATPC – Automatic Transmit Power Control (all other radios)
ATPC or DTPC, features that reduce transmit powers except with far-end receiver alarms during deep fades, are occasionally assigned to some microwave links for one of the following reasons:
Prevents receiver front-end overload in higher frequency links assigned high rain fade margins
Complies with FCC (and other) EIRP constraints in short hops,
<17 km in the 6 GHz bands and <5 km at 10 and 11 GHz,
Prevents receiver overload in shorter 6, 10, and 11 GHz paths
requiring large antennas in frequency-congested areas
Reduces interference levels at hubbing sites and into adjacent
DTPC/ATPC
-10 -20 -30 -40 -50 -60 -70 -80 R ec ei ve S ig n al L ev el , d B m +20 +10 0 -10 0 10 20 30 40 50 60 1-Hour of Rain Fade Activity, MinutesT ra n sm itt er O u tp u t P o w er , d B m F ad e D ep th , d B 0 -10 -20 -30 -40 -50 -60 -70
Transmit and Receive RF Levels During 1-Hour Fade Activity in a High Fade Margin (60dB) 23 GHz DTPC Link.
RSL follows fades below the “setting point”, -45 dBm in this example
RSL w/DTPC Fade Depth, RSL w/o DTPC Outage Threshold No Outage DTPC RSL Setting Point -45 dBm Transmitter Output 10-6 BER Receiver Overload Error-free
Time RSL ATPC Off ATPC On Fading Stopped Fading 7/10 dB 7/10 dB 15/18 dB BER = 10 -11 BER = 10 -6 10 –6 Th + 15/18 dB Un-Fading
Useful Formulas
For English (ft, mi, GHz, dB) Metric (m, km, GHz, dB) Path Loss 96.6 + 20 log f + 20 log D 92.4 + 20 log f + 20 log D Earth’s curvature 0.67 d1d2/k d1d2/12.7k F1 radius 72.1 (d1d2/f D)0.5 17.3 (d
1d2/f D)0.5
Fn radius F1 (n)0.5 F
1 (n)0.5
Dish gain (55% efficiency) 7.5 + 20 log f + 20 log d 17.8 + 20 log f + 20 log d Dish BW, degrees 66/fd 20/fd Div. dish separation 1200 D/f h(t) 127D/f h(t) Multipath delay, nsec Fn /2f Fn/2f NOTATION: f = frequency, GHz D = path length
k = k-factor (4/3rds, etc.) d1, d2= distances (d1 + d2 = D) h(t) = Tx dish height above n = Fresnel zone number the reflection plane F1 = 1st Fresnel zone radius
d = dish diameter
Important to know…
Site Details Address, Lat-Long,
Azimuth wrt North, equipment layout
Access
/permission/approach road
Link Budget Expected Receive level/
Fade Margin Tx Planner/Operator
Frequency of operations and Tx power; Type of antenna, Height of antenna, Polarization LOS cleared
Cabling details External alarm
termination details/color code NMS IP address/DCN planning /cabling/router/convert er Traffic E1/STM1
Frequency Sub Band [GHz] Duplex [MHz] 10 350 10224 10574 350 10252 10602
Capacity BW [MHz] / Channel Raster
16 E1 28
8 E1 14
4 E1 7
2 E1 3.5
25 MHz Channel Filter Bandwidth
16 E1 CAPACITY
5.5 MHz 14 MHz 5.5 MHz
Understanding Frequency plan
Co- and adjacent-channel interference Low fade margins
Antenna k-factor decoupling
Antenna misalignments
Dispersive (spectrum-distorting) fades
Ducting, defocusing, and obstruction fades
EMI and other environmental effects
Effective diversity arrangements lessen the impact of otherwise unacceptable conditions: