Microwave Basics

Wireless Transmission Microwave Basics WT CoTr Training November 2004 Kari Halinen

Microwave Radios •

Connection between two points  – Transmitter/ Receiver  stations  –using freely propagating radio waves

•

The advantages of microwave are:

•

•

Fast deployment

•

Cheap equipment and low operating costs (almost free transmission medium)

•

Can be part of standardized equipment configuration

•

Flexible adaptation to a wide range of link lengths

•

Can be made available almost everywhere

The drawback of microwaves: •

Limited amount of free spectrum, spectrum administration necessary

•

Difficult planning in regions with differing weather conditions (rain periods, monsoons)

•

Sensitive against external damaging

Path calculation process TARGETS •availability •error performance

interdependency

NETWORK CONFIGURATION •path lengths •orientation

DESIG N Use of 

New design round if  needed

•capacity •modulation

Ptx

•Diversity •Protection

method

Prxth Interference

Ga • Availability  Availability •Error performance

1) Topology, interference condition and i nterdependent!!!  performance are tightly interdependent!

2) Both error performance and availability objectives should be fulfilled (often – above 17GHz - availability dominates)

Points to consider  •

Operating band •

•

•

•

below or above 17 GHz (rain attenuation)

Choice of frequencies and polarization •

often higher frequencies for shorter hops

•

availability of channels

•

interference situation

Path design •

full Fresnel zone clearance

•

beware of reflections!

Modulation method •

effect on system value

•

tolerance to interference

Points to consider (cont.) •

Tx power  • •

•

•

•

automatic/ adjustable transmitted level !?

Rx threshold power  •

•

effect on interference

capacity, modulation method

 Antenna gain •

higher frequency brings higher gain

•

control of interference

Protection method •

possible effect on system value

•

HSB, ( space diversity usually below 17 GHz only)

Hop design and overall network performance •

Meeting the error performance and availability targets

Characteristics of frequency bands Frequency band (GHz)

7

8

13

15

Hop length (km)  Antenna diameter (m) Dominating fading type

20-70

20-50

5-40

0.6-3

0.6-3

multipath

multipath

Polarization

V&H

V&H

V&H

V&H

V&H

V&H

V

V

V

 Atmospheric attenuation (db/km)  Attenuation due rain (dB/km) 20mm/h

-

-

-

0.03

0.1

0.2

0.1

0.12

12

-

-

-

-

1

2

3

5

7

5-30

18

23

26

38

58

5-25

3-18

2-15

1-6

10E-3, integration time one second

•

Degraded Minutes (DM): bit error ratio BER>10E-6, integration time one minute

•

Errored Seconds (ES): intervals of one second containing at least one error 

•

Residual Bit Error Ratio (RBER): the BER under nonfading conditions measured over 15 minutes or more

In practice the design is most often based on SES if error  performance is considered to be the limiting factor 

Link Availability •

Link availability is the percentage of time when the link is in operation •

Link is unavailable when the Bit Error Ratio (BER) is greater than 10 -3 for  at least 10 consecutive seconds

•

Unavailable time ends when BER for each second is better than 10 -3 for  at least 10 consecutive seconds. These ten seconds are considered to be available time Grade

Availability

Unavailability

Unavailable per year 

High grade

99.999%

0.001%

5.3 min

Medium grade

99.995%

0.005%

26.3 min

Local grade

99.94%

0.06%

5.3 hours

Integrated Network Planning NetAct Planner  Radio Planner 

WCDMA Planner 

2G Radio Network Planning

Quality Planner  Field Measurement Analysis

Rollout Planner  Site Acquisition & Project Tracking

3G Radio Network Planning

Common Database & Environment

Link Planner  Microwave Link Planning

Transmission Planner  Transmission and ATM/IP Network Planning

NetAct Link Planner  •

Integrated microwave link planning tool for 2G, 2.5G and 3G •Line

of sight checking

•Interference analysis •Intermodulation

analysis

•Link performance calculations •

Multi-user platform •WindowsTM

based

•OracleTM database

Link Planner Features 2D and 3D Views •

In 2D view, a planner can •

•

See •

Network connections

•

Link types

•

Frequencies

•

Capacities

•

BTS routes

•

Interference

View •

•

Site visibility with Fresnel clearance

3D view is a “bird” view •

3D visualization of a map

Link Planner Features Line of Sight Support •

•

In 2D view, a planner can see •

Site visibility

•

Site visibility with Fresnel zone

In 3D view, a planner can have • „A bird view‟ to check LOS

•

With Line Of Site  –wizard, a planner  can find out •

LOS and/or Fresnel clearance

•

Obstruction or clearance in meters

•  And

generate a Report for findings

Link Planner Features Height Profile With Height profiler, a planner can •

•

view profile of  •

Between 2 sites

•

From Site to point

•

Between 2 points

•

Point to multipoint

visualize •

Fresnel Zones

•

Reflections

•

Clearance / Obstruction

•

Hop length

•

Diffraction loss

•

locate obstacles

•

minimize antenna heights

Network Design Link Power Budget and Availability •

•

Supported calculations •

ITU-R P.530-10

•

ITU-R P.530-7

•

Vigants

Supported diversities •

Frequency diversity

•  Angle

diversity

•

Space diversity

•

Space(2) + frequency diversity

•

Space(4) + frequency diversity

Network Design Interference Analysis •

Interference analyses • • • • • •

•

Interference wizard Cumulative analyze Co & adjacent channel cases Report 2D map view visualization Threshold degradation

Intermodulation analyses • •

Report Graphical display

Link Planner Benefits Feature

Benefit

2D and 3D views

• A planner is

Line of Sight support

• A planner can

Height profiler 

• A planner can

Link database

•Enables

Templates

•Enables

Flags and filters

•Enables

Equipment database

•Enables

Point-to-multi point support

•Enables

able to use digital map information for link planning. With 3D view planner is able watch the link as a bird. run Line of Sight checks and can generate report for this. Initial planning can be done in office thus increasing productivity. display the profile of the link and see line of sight and Fresnel zone clearance. sharing created microwave links between all planners. Planners can work with those microwave links they are responsible. Increases productivity. efficient planning of microwave links as commonly used link and hub configuration can be saved to the Link database. Increases productivity and consistency of the plans. operator to define flags and filters for links to organise and display them efficiently. operator to define commonly used microwave radios, antennas and feeders into common database. Increases consistency of plans. operator to analyse point-to-multi point microwave radio equipment in planning of microwave radio network.

Link Planner 4.2 New Features Feature

Description

ITU-T G821/826 support

• A Planner can

Height Profiler  enhancements

•Supports

 Absolute antenna location support

define required availability calculation rules accordingly.

links over multi-resolution map.

•Obstacle

locator enables identification of obstacles along link profile. And obstacle coordinates & height identification on report and Map View. •Enables

specifying antennas in precise location either to relative to property or  to absolute GPS position. •Link

calculations and visualisation between antennas will be done according these absolute locations.

High/low conflict report  Automatic rain zone calculation

• A planner can

generate a report that tells if the plan has high/low frequency band conflicts inside the links. •The

tools will calculate rain zone based on coordinates.

Enhanced equipment availability modelling

• A planner can

Map Info link export

• A planner can

define different MTTR value for each property, which allows different values for Urban / Suburban / Rural sites. export link data from Link Planner to MapInfo-application.