Training on Pasolink +

Technical Center Group NEC India

AgendaAgenda

RF Microwave Fundamentals Digital Microwave Radio Theory a) Introduction – Features, Configurations and

Upgradability b) Parameters and Specifications c) DMR Subsystem Digital Microwave Radio Practical

a) System Installation b) Antenna Installation

c) Commissioning Local Craft Terminal

RF Microwave RF Microwave FundamentalsFundamentals

Basic Microwave Radio Basic Microwave Radio SystemSystem

Ways of communication in Telecom industry:1) Cable2) Microwave radio3) Optical fiber4) Satellite

Advantages of Microwave :1) Easy and quick installation2) Medium is free

Disadvantages of Microwave:Medium is exposed to many uncertainty

Wave Propagation in the Wave Propagation in the atmosphereatmosphere

For No atmosphere With atmosphere

Snell’s law:Ray bends towards the denser medium of the two media

Atmosphere Multipath Atmosphere Multipath PropagationPropagation

Multipath propagation occurs when there are more than one ray reaching the receiver. Multipath transmission is the main cause of fading.Multipath can happen when dN/dh varies with height.dN= Atmosphere dh= Height.

Ground based duct:The atmosphere has a very dense layer at the ground with a thin layer on top of it. There will be nearly total reflection from this layer boundary.

Elevated duct:The atmosphere has a thick layer in some height above ground. If both the Transmitter and the receiver are within the duct, multiple rays will reach the receiver. If one is inside and other is out side the duct, nearly no will reach the receiver

Formation of a duct :

During day time the sun heats the ground giving convection and a well mixed atmosphere. A calm night will give radiation from the warm ground, giving temperature inversion. This in turn gives a region near ground where dM/dh<0, resulting in a ground based duct.

Just after sunrise in morning, the ground is heated by sun again, and the convection starts near ground. The ground based duct rises, resulting in an elevated duct.

This region is

Cooled by grounddM/dh<0

dM/dh>0

Daytime

Convection mixes

The atmosphere

Calm night

No Convection temperature inversion

Morning

Ground based duct

rises to become an elevated duct

Terrain ProfilesTerrain Profiles

1) Line of sight2) Fresnel Zone

Line of sight between transmitter and receiver is a straight line and ray bending due to K-value variation is added to the terrain heights.

The modification of terrain heights is given by(d1.d2)/(12.74.k)

K=1.33 for (5 to 15 Kms) and 0.66 for longer path lengths (15-30 Kms)

There must be a clearance for the first Freznel zone to avoid diffraction loss in addition to free space loss.

Fresnel ZoneFresnel Zone

F1

d1 d2

D1 D2First fresnel zone is defined as the locus ofPoints having maximum energy lobe from Trans.antenna to Receiver Antennad3-(d1+d2)=λ/2Where d3=D1 + D2 refer to figure.λ =wavelength

For practical application the radius F1May be approximated by the formula:

F1= 17.3 (d1.d2/f.D)

Where f is the freq in GHzD=d1+d2 the total path length in Km

Survey:Field work:Confirmation of LOS (checking critical obstacles)Verification of position and altitudes of the sitesChecking of site, road accessAvailability of power (Exiting shelters and towers)Propagation conditionMake interference measurementsFinally prepare a report with required optimum tower heights.

Difficult areas for Microwave linkOver water pathsHigh reflection coefficient.High ducting probability.Rice and wheat fields Strong ground reflectionDesert areaMultipath fading

Microwave AntennaMicrowave Antenna

The parabolic Antenna is the most commonly used antenna in MicrowaveRadio-relay systems.

Antenna parameters: 1)`Antenna gain : Gain is approximated by the formulae Gain = 17.8 + 20 log (D.f) dBi Where D = Antenna diameter [m] & F = Frequency in GHz

2) VSWR Standard type Antenna : 1.06 to 1.15 typically High performance Antenna : 1.04 to 1.06 typically VSWR= Reflected power/ incident power

3) Cross polarization: A good cross-polarization enables full utilization of the frequency band by using Vertical and Horizontal polarization.

4) Beam width: The half power beam width of an antenna is defined as the angular width of the main beam at –3 dB point.

Free Space Loss and Power Free Space Loss and Power BudgetBudget

Power received at any point from a radiated antenna is inversely proportionalto square of distance between them and radiating freq.

It can be defined by formula:Lfs= 92.45 +20 log(f.d)Where Lfs= Free space lossPower budget:

Tx Rx

Tx power o/p = +21 dBmLosses (feeder + branching) = 3.0 dBTx Antenna Gain = 36.5 dBFree space loss = 130 dBRx Antenna Gain = 36.5 dBFeeder loss Rx = 1.2 dBNominal input level = -40.2 dBReceiver Threshold = -80 dBmFading margin = 39.8 dB

PrecipitationTransmission of microwave signal above 10 GHz is vulnerable to precipitation.The energy is attenuated due to radiation (scattering) and absorption(heating).

ScatteringRadio waves are a time varying electromagnetic field, the incident field willinduce a dipole moment in the raindrop. The rain drop will also have the same time Variation as the radio waves and will act as an antenna and reradiate the energy.As rain drop-antenna have low directivity it will radiate energy arbitrary directionand add to loss.

AbsorptionWhen the wavelength becomes small (High freq. < 18GHz) relative to the raindrop size more energy is absorbed by heating of the raindrop.

Why vertical polarization favorable at high freq.:As the rain-drop increases in size they depart spherical shape and get extended in thehorizontal direction. For freq. higher than 18 GHz the wavelength is generally in mm.So these rain-drops attenuate horizontally polarized waves than the vertical polarized.

Raindrop shapes

1mm 1.5mm 2mm 2.5mm

Why Fading Margin:

RxI/Plevel

-40dBm

-80dBmoutage

Receiver Threshold

Nominal I/P level

Atmosphericdisturbance

Fading events are mainly caused by multipath fading and fading due to precipitation.So larger the fading margin better the system performance.This can be achieved by higher tx o/p, larger (Gain) antennas,lower threshold levelAnd reduced path length etc.Multipath Fading:

Fading due to layering of the atmosphere is the dominating factor of degradation of radio-relays.Transmitted waves that receives at the receiver refracted from the troposphere or reflected from the ground other than wanted signals are added to it.The phase and amplitude relationship determines the resulting I/p signal at the receiver.1) Flat fading= complete link length fading 2) Selective fading= selective lengths of link

Diversity:

The common forms of diversity in LOS links freq. And space or combination of both. Lately angle diversity is also introduced.

Space Diversity:Placing two antennas vertically separated at the receiver tower so only one antennaIs located in a power minimum range.

Overcoming the effects of Overcoming the effects of multipathmultipath

Freq. Diversity: This protection technique takes advantage of the freq. Selectivity of the multipath Fading. But the as the freq. Bandwidth is costlier in India this technique is rarely being used.

Switching sections:By switching or combining the different channels (in freq. Diversity)/ Rx. signals(from main antenna and space diversity antenna) carrying the same signal, it is possible to attain an improvement.

Hot Standby configuration:Reduces the system outage due to equipment failures.

Hybrid Diversity:

1+1 hot standby system having space diversity at one of the radio sites.

Combined Diversity:

When using space diversity and frequency diversity at the same time.

Angle diversity:

Two antenna feedhorns are slightly off the boresight, giving a duelbeam parabolic dish antenna.

Digital Microwave Radio Theory–Digital Microwave Radio Theory–Pasolink +Pasolink +

Pasolink Family TreePasolink Family Tree

Introduction to Pasolink FamilyIntroduction to Pasolink Family

256 QAM

128 QAM

64 QAM

32 QAM

16 QAM

8 PSK

4 PSK

0 3.5 7.0 14.0 28.0 40.0 56.0 [ MHz ]

Adjacent CH Spacing

MODULATION

Pasolink +

3000 S

Pasolink Mx

Pasolink V4

●

● ● ●

● ● ● ●

5E1 10E1 20E1 40E1

2E1 4E1 8E1 16E1

●

●

●

STM-1

2X STM-1

STM-1

STM-1

IDU ConvergenceIDU Convergence

1+1 system with OPT Interface card

Current Type IDU

1+1(3U)

1+0 system with OPT Interface card

1+0(1U)

The PASOLINK+ system provides interface types for SDH Optical , Electrical and LAN. The PASOLINK+ system provides interface types for SDH Optical , Electrical and LAN. The The

transmission signals are 1 to 2 x STM-1, 10/100 Base-T(X) signals. transmission signals are 1 to 2 x STM-1, 10/100 Base-T(X) signals.

Pasolink+ CapacityPasolink+ Capacity

Antenna and ODU

(Direct Mount 1+0) (11 – 52 GHz)

ODU – IDU CompatibilityODU – IDU Compatibility

MK- I ODU(TRP-XXG-1AA)

MK-II ODU(TRP-XXG-5AA)

MK-I IDU(MDP-150MB7T-2 or 1) C NC

MK-II IDU (or Enhance IDU)(MDP-150MB7T-2B or 1B) Note1 C

ODU

IDU

Note1-- Connected with reduced Power (MK-I ODU power)

C--- Fully connectableNC-- Not Connected