Point To Point Microwave Transmission

ContentsMicrowave Radio BasicsRadio Network Planning AspectsRadio Network Planning ProcessRadio wave PropagationLink Engineering & ReliabilityInterference AnalysisPtP MW Transmission IssuesUseful Formulae

What is Transport ?Transport is an entity that carries information between Network Nodes

Information is sent over a carrier between Network Nodes.

Carrier is sent over a Transmission Media

Commonly used Transmission Media :Copper CablesMicrowave RadioOptical FiberInfra Red Radio

Microwave Radio BasicsBasic ModulesConfigurationApplicationsAdvantages

Microwave Radio - ModulesMicrowave Radio Terminal has 3 Basic Modules

Digital Modem : To interface with customer equipment and to convert customer traffic to a modulated signalRF Unit : To Up and Down Convert signal in RF RangePassive Parabolic Antenna : For Transmitting and Receiving RF Signal

Two Microwave Terminals Forms a HopMicrowave Communication requires LOS

Basic Hardware ConfigurationsNon Protected or 1+0 Configuration

Protected or 1+1 Configuration, also known as MHSB

In MHSB Modem and RF Unit are duplicated

Microwave Radio Capacity ConfigurationsCommonly Used Capacity Configurations

4 x 2 Mbpsor 4 x E1

8 x 2 Mbpsor8 x E1

16 x 2 Mbpsor 16 x E1

155 MbpsorSTM1

Microwave Radio - ApplicationsAs Transport Medium inBasic Service Networks

Mobile Cellular Network

Last Mile Access

Private Networks

Microwave Radio AdvantagesAdvantages over Optical Fiber / Copper Cable SystemRapid Deployment

Flexibility

Lower Startup and Operational Cost

No ROW Issues

Low MTTR

Microwave Radio - ManufacturersFew well known Radio ManufacturersNokiaNeraNECSiemensDigital Microwave CorporationFujitsuEricssonAlcatelHariss

Microwave Network Planning AspectsNetwork ArchitectureRoute ConfigurationChoice of Frequency Band

Network ArchitectureCommon Network ArchitecturesSpur or Chain

Star

Ring

Mesh

Combination of Above

Spur ArchitectureBCDEAFor N Stations N-1 Links are requiredNth station depends on N-1 LinksSpur Architecture

Star ArchitectureFor N Stations N-1 Links are requiredEach Station depends on Only 1 LinkBCDEAStar Architecture

Loop ArchitectureFor N Stations N Links are requiredRoute Diversity is available for all stationsBCDEALoop Architecture

Loop protection is effective against faults, which are caused by e.g.

power failure

equipment failure

unexpected cut of cable

human mistake

rain and multipath fading cutting microwave radio connections

BTSDN2 or METROHUBMW RADIOSINGLE MODE MW LINKHSB MODE MW LINKCOPPER CONNECTION Figure 2. Primary solution where loop masters (DN2) are co- located in the BSC.To Next BSCTo Next BSCBSC

Figure 3. Solution of using remote loop master (DN2) co-located in a remote BTSTo Next BSCTo Next BSC

Mesh ArchitectureEach Station is Connected to Every OtherFull Proof Route ProtectionFor N sites (Nx2)-1CDEAMesh ArchitectureB

Typical Network ArchitectureBGDEITypical ArchitectureJFACTypical Network Consist of Rings and Spurs

Network Routes & Route CapacitiesInter- City routes - BackboneBackbone routes are planned at Lower Frequency Bands2, 6 and 7 GHz Frequency Bands are usedBackbone routes are normally high capacity routesNominal Hop Distances 25 40 KmIntra City routes - AccessAccess routes are planned at Higher Frequency Bands15,18 and 23 GHz Frequency Bands are usedNominal Hop Distance 1 10 Km

Frequency BandsFrequency Band 7, 15, 18 and 23 GHz are allowed to Private Operators for deployment in Transport Network

15,18 and 23 GHz bands are used for Access Network7 GHz band is used for Backbone NetworkDifferent Channeling Plans are available in these bands to accommodate different bandwidth requirementsBandwidth requirement is decided by Radio Capacity offered by the Manufacturer

Microwave Propagation

Free Space PropagationMicrowave Propagation in Free Space is Governed by Laws of Optics Like any Optical Wave , Microwave also undergoes

RefractionReflection

Free Space Propagation - RefractionRay bending due to layers of different densities

Bent Rays In Atmosphere

Free Space Propagation - RefractionIn effect the Earth appears elevated Earth elevation is denoted by K FactorK Factor depends on Rate of Change of Refractivity with heightK= 2/3 Earth appears more elevated K= 4/3 Earth appears flatter w.r.t K=2/3K= Ray Follows Earth Curvature

Free Space Propagation - RefractionEffect of Refractivity Change K = 2/3Actual Ground K = 4/3

Free Space Propagation ReflectionsMicrowaves are reflected overSmooth SurfacesWater Bodies

Reflected Signals are 180 out of phaseReflection can be a major cause of outagesLink needs to be planned carefully to avoid reflections

RF Propagation ReflectionsReflections can come from ANYWHERE - behind, under, in-front6 cm difference can change Path geometry

Fresnel ZoneThe Fresnel zone is the area of space between the two antennas in which the radio signal travels.For Clear Line of Sight Fresnel Zone Should be clear of obstaclesIt is depands on Distance and Frequency

FRESNEL ZONES1st Fresnel ZoneMid Path

FRESNEL ZONE CLEARANCES1ST Fresnal Zone = 17.3 (d1*d2)/f(d1+d2) d1 = Distance in Kilometers from Antenna A to mid pointd2 = Distance in Kilometers from Antenna B to mid pointf = Frequency in GHzAd1d2B

RF propagationFirst Fresnel Zone

RF propagationFree space versus non free spaceNon-free spaceLine of sight requiredObjects protrude in the fresnel zone, but do not block the path

Free Space Line of sightNo objects in the fresnel zoneAntenna height is significantDistance relative short (due to effects of curvature of the earth)

FRESNEL ZONE & EARTH BULGED2/8Earth BulgeHeight = D2/8 + 43.3D/4F 43.3D/4F 60% first Fresnel ZoneD = Distance Between AntennasH

Midpoint clearance = 0.6F + Earth curvature + 10' when K=1First Fresnel Distance (meters) F1= 17.3 [(d1*d2)/(f*D)]1/2 where D=path length Km, f=frequency (GHz) , d1= distance from Antenna1(Km) , d2 = distance from Antenna 2 (Km)Earth Curvature h = (d1*d2) /2 where h = change in vertical distance from Horizontal line (meters), d1&d2 distance from antennas 1&2 respectivelyClearance for Earths Curvature 13 feet for 10 Km path200 feet for 40 Km pathFresnel Zone Clearance = 0.6 first Fresnel distance (Clear Path for Signal at mid point) 30 feet for 10 Km path57 feet for 40 Km pathRF PropagationAntenna Height requirements

Microwave Network Planning ProcessDesign BasisLine of Sight SurveyLink Engineering Interference Analysis

NNYYRF Nominal Planning (NP)/ Application for Frequency LicenseDefine BSC BordersEstimate BSC LocationsPreliminary Transmission Planning and LOS Checking for possible BSCsFinalize BSC LocationsMicrowave Link Planning and LOS Checking for BTSsUpdate LOS Reports, Frequency Plan, Planning Database, Equipment SummaryCustomer to apply SACFA based on Nokia Technical InputsChange BTS Prime Candidate?Change BTS Prime Candidate?Figure 1. Microwave Link Planning ProcessPlanning Process

Design BasisChoice of Radio Equipment

Fresnel Zone Clearance Objectives

Availability / Reliability Objectives

Interference Degradation Objectives

Tower Height & Loading Restrictions

Microwave Network Planning ProcessMap Study for feasibility of Line of Sight and Estimating Tower HeightsActual Field Survey for refining map data and finalizing Antenna HeightsLink Power Budgeting & EngineeringFrequency and Polarization AssignmentsInterference Analysis (Network Level)Final Link Engineering (Network Level)

Map StudySOI Maps are available in different Scales and Contour Intervals1:50000 Scale Maps with 20 M Contour Interval are normally used for Map StudySites are Plotted on MapContour values are noted at intersectionsIntersection with Water Bodies is also notedAMSL of Sight is determined by Interpolation

Map StudyVegetation height (15-20m) is added to Map DataPath Profile is drawn on Graph for Earth Bulge Factor (K) =4/3 and 2/3Fresnel Zone Depths are Calculated & Plotted for Design Frequency BandAntennae Heights are Estimated for Design Clearance Criteria

Field SurveyEquipment Required Data RequiredGPS Receiver- Map Study Data CameraMagnetic Compass AltimeterBinocular / TelescopeFlashing MirrorFlagsInclinometerBalloon Set Measuring Tapes

Field SurveyField SurveyMap Data ValidationGathering Field inputs (Terrain Type, Average Tree/Obstacle Height, Critical Obstruction etc.) Line of Sight Check, if feasible ,using flags, mirror Data related to other stations in the vicinity , their coordinates, frequency of operation, antenna size, heights, power etc.Proximity to Airport / Airstrip with their co-ordinatesField inputs are used to refine existing path profile data , reflection point determination, reflection analysis

RF propagationEnvironmental conditionsLine of SightNo objects in path between antennaa. Neighboring Buildingsb. Trees or other obstructionsInterferencec. Power lines

FadingPhenomenon of Attenuation of Signal Due to Atmospheric and Propagation Conditions is called Fading

Fading can occur due to RefractionsReflectionsAtmospheric Anomalies

FadingTypes of FadingMultipath FadingFrequency Selective FadingRain Fading

Multipath FadingMultipath fading is caused due to reflected / refracted signals arriving at receiverReflected Signals arrive withDelayPhase ShiftResult in degradation of intended Signal

Space Diversity Radio Configuration is used to Counter Multipath Fading

Frequency Selective FadingFrequency Selective Fading Due to Atmospheric anomalies different frequencies undergo different attenuation levelsFrequency Diversity Radio Configuration is used to Counter Frequency Selective Fading

Rain FadingFrequency Band > 10 GHz are affected due to Rain as Droplet size is comparable to WavelengthsRain Fading Occur over and above Multipath and Frequency Selective FadingHorizontal Polarization is more prone to Rain Fades Path Diversity / Route Diversity is the only counter measure for Rain Fade

Drop Shape and Polarization2.0mm1mm1.5mm2.5mmAs raindrops increasein size, they get moreextended in the Horizontaldirection, and thereforewill attenuate horizontalpolarization more thanvertical polarization

Fade MarginMargin required to account for Fading Fade Margin

Higher Fade Margin provide better Link Reliability

Fade Margin of 35 40 dB is normally provided

Link Engineering & ReliabilityLink BudgetingReliability PredictionsInterference Analysis

Hop ModelOutdoor UnitStation BIndoor UnitTrafficOutdoor UnitStation AIndoor UnitTraffic

Link Power BudgetReceived Signal Level = RxlRxlB = TxA LA + GA Fl + GB LB

WhereTXA = Trans Power Station ALA = Losses at Station A (Misc.)GA = Antenna Gain at Station AFl = Free Space LossesGB = Antenna Gain at Station BLB = Losses at Station BRxlB = Rx. Level at Station B

RXL must be > Receiver Sensitivity always

Link Power Budget Receiver Sensitivity Lowest Possible Signal which can be detected by Receiver is called Receiver Sensitivity or Threshold

Threshold Value is Manufacturer SpecificDepends on Radio Design

Higher (-ve) Value Indicates better Radio Design

Link EngineeringSoftware Tools are usedInputs to the toolSight Co-ordinatesPath Profile DataTerrain Data & Rain DataEquipment DataAntenna DataFrequency and Polarization DataTool OutputAvailability Prediction

RF propagation Simple Path Analysis Concept (alternative)

Link Engineering InterferenceInterference is caused due to undesirable RF Signal Coupling

Threshold is degraded due to interference

Degraded Threshold results in reduced reliability

Link Engineering InterferenceExamples of Undesirable RF Couplings

Finite Value of XPD in Antenna is the Prime CauseSolution : Use of High Performance Antenna

F1HVCross Poler Coupling

Link Engineering InterferenceExamples of Undesirable RF Coupling

Receiver Filter Cut-off is tapperedSolution : Use Radio with better Specifications

F2Adjacent ChannelF1

Link Engineering InterferenceExamples of Undesirable RF Coupling

Finite value of FTB Ratio of Antenna is Prime CauseSolution : Antenna with High FTB Ratio

Front to BackT : HiR : LowT : HiR : LowT : LowR : HiT : LowR : Hi

Link Engineering InterferenceExamples of Undesirable RF Coupling

Solution : Choose Antenna Heights such a way there is no LOS for over reach

Over ReachT : LowR : HiT : HiR : LowT : HiR : LowT : LowR : HiT : LowR : HiT : HiR : Low

Link Engineering InterferenceInterference is calculated at Network LevelInterference due to links Within NetworkOutside Network (Links of other Operators)Interfering Signal degrades Fade MarginEngineering Calculation re-done with degraded Fade Margin

Link Engineering InterferenceCounter Measures Avoid Hi-Lo violation in loopFrequency DiscriminationPolarization DiscriminationAngular DiscriminationHigh Performance AntennaeLower Transmit Power , if possible

DN2 PORT ALLOCATION:

ET (Exchange Terminal) PortDN2 Port

20 PortDN2P1P3P5P7P9P11P13P15P17P19P2P4P6P8P10P12P14P16P18P20DN2 to BSC ConnectionDN2 to Network connection

BTS4ET33

STANDARD MICROWAVE RADIO FIU 19 TRIBUTARY ALLOCATION FOR LOOP PROTECTION

FIU 1 FIU2FB1FB2FB1FB2LOOP 1LOOP2 Loop Protection with Hardware Protection

PtP Microwave Transmission - IssuesLink Performance is Seriously Affected due toAtmospheric Anomalies like Ducting Ground ReflectionsSelective FadingExcessive Rains InterferencesThunderstorms / High Winds causing Antenna MisalignmentEarthingEquipment Failure

Some Useful Formulae

Link BudgetRx BAB+GA+GB-Lfs-ArainBRainfsAABGALGTxRx+--+=

d=1km ---> L = 124 dBmd=2km ---> L = 130 dBm

d=1km ---> L = 121 dBmd=2km ---> L = 127 dBm

39 GHz26 GHzExamplesFree Space Lossd = distance in kilometers f = frequency in GHz

RF PropagationBasic loss formula

Propagation Loss

d = distance between Tx and Rx antenna [meter]PT = transmit power [mW]PR = receive power [mW]G = antennae gain

Pr ~ 1/f2 * D2 which means 2X Frequency = 1/4 Power2 X Distance = 1/4 Power

Useful Formulae Earth BulgeEarth Bulge at a distance d1 Km

= d1 * d2 / (12.75 * K) Meter

Where d2 = (d d1) Km (d Km Hop Distance) K = K Factor

Useful Formulae Fresnel ZoneNth Fresnel Zone Depth at a distance d1 Km

= N * 17.3 * ( (d1*d2) / (f * d) ) 1/2 Meter

Where d2 = (d d1) Km d = Hop Distance in Km f = Frequency in GHz N = No. of Fresnel zone (eg. 1st or 2nd )

Tower Height Calculation :

Th = Ep + C + OH + Slope Ea

C = B1 + F

Slope = (( Ea Eb) d1)/ D

F = 17.3 ((d1xd2)/f X D) -1/2

B = (d1 x d2) / (12.75 x K )

Where, Th = Tower HeightEp = Peak / Critical ObstructionC = Other lossesB1 = Earth BuldgeF = Fresnel ZoneOH = Overhead ObstructionEa= Height of Site AEb= Height of Site Bd1= Dist. From site A to Obstructiond2= Dist. From site B to ObstructionD = Path Distancef= FrequencyK= 4/3

d1d2Ea Ep Eb

Useful Formulae Antenna GainAntenna Gain

= 17.6 + 20 * log10 (f *d) dBi See Note

Where d= Antennae Diameter in Meter f= Frequency in GHz

Note # Assuming 60% Efficiency

Useful Formulae Free Space LossFree Space Loss

Fl= 92.4 + 20 * log10 (f *d) dB

Where d = Hop Distance in Km f = Frequency in GHz

Useful Formulae Geo Climatic FactorGeo Climatic Factor

G = 10 T * (Pl)1.5

Where T= Terrain Factor= 6.5 for Overland Path Not in Mountain= 7.1 for Overland Path in Mountain= 6.0 for Over Large Bodies of Water Pl = Pl factor

Useful Formulae System GainSystem Gain = (Transmit Power + ABS(Threshold) ) dB

Fade Margin = FM = (Nominal Received Signal Threshold) dB

Path Inclination = ABS ((h1 + A1) (h2 + A2) ) / dWhere h1 = Ant. Ht. At Stn A AGL Meterh2 = Ant. Ht. At Stn B AGL Meter A1 = AMSL of Stn A MeterA2 = AMSL of Stn B Meterd = Hop Distance in KM

Useful Formulae Fade Occurrence FactorFade Occurrence Factor = = G * d 3.6 *f 0.89 * (1+ ) -1.4

WhereG = Geo Climatic Factord = Hop Distance in Kmf = Frequency in GHz = Path Inclination in mRad

Useful Formulae Outage ProbabilityWorst Month Outage Probability (One Way) % = OWM

OWM % = * 10 (FM/10)

Annual Unavailability (One Way) % = OWM * 0.3Assuming 4 Worst Months in a Year

Annual Availability (Two Way) % = 100-(OWM*0.3*2)

Thank You

Ashish Shah ADA Cellworks - Mumbai+91 9892548266 ashish.shah@adacellworks.com