PATHLOSS TRAINING COURSE
INTRODUCTION To PATHLOSS March 17, 2009 NEC Corporation Islamabad 1 NEC Internal Use Only
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GENERAL PROGRAME OUTLINE Path Loss program is organized into the 8 following modules: Module 01: Module 02: Module 03: Module 04: Module 05: Module 06: Module 07: Module 08:
Summary Terrain Data Antenna Heights Worksheets Diffraction Reflection Multipath Network
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COURSE OUTLINE • • • • •
Module 01: Module 02: Module 03: Module 04: Q&A
Summary Terrain Data Antenna Heights Worksheet
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Module 1: SUMMARY MODULE
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Module 1: SUMMARY MODULE
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Module 1: SUMMARY MODULE
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Module 1: SUMMARY MODULE
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Module 1: SUMMARY MODULE
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Module 2: Terrain Data Module
• • • • •
Basic procedures to create a Terrain Profiles Survey Angle calculation Global 30 ARC Second Database SRTM Database. Profile Generation
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module (cont’d)
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Module 2: Terrain Data Module GTOPO30
• GTOPO30 is a global digital elevation model (DEM) with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer). • GTOPO30, completed in late 1996, was developed over a three year period . • The absolute vertical accuracy of GTOPO30 varies by location according to the source data. • The full resolution have a vertical accuracy of + or - 30 meters.
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Module 2: Terrain Data Module SRTM • SRTM is a 90m Digital Elevation Data for the entire world. • Originally produced by NASA, is a major breakthrough in digital mapping of the world, and provides a major advance in the accessibility of high quality elevation data for large portions of the tropics and other areas of the developing world. • The NASA Shuttle Radar Topographic Mission (SRTM) has provided digital elevation data (DEMs) for over 80% of the globe. • The SRTM data is available as 3 arc second (approx. 90m resolution) DEMs. • A 1 arc second data product was also produced, but is not available for all countries. 25 NEC Internal Use Only
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Module 3: Antenna Height Module
• • • • • • •
Basic Operations, Setting Clearance Criteria, Clearance Calculation at a point, Antenna height Considerations, Setting Antenna Heights, Optimizing Antenna heights, Report Generations
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Module 3:Antenna Height Module (cont’d)
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Module 3:Antenna Height Module (cont’d)
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Module 3:Antenna Height Module (cont’d)
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Module 3:Antenna Height Module (cont’d)
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Module 4: Worksheet Module
• • • • • •
Overview Antenna Configurations Reliability Options Diversity options Microwave Worksheet Options Look up Tables
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 4: Worksheet Module (cont’d)
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Module 5: Diffraction Module
• • • •
Overview, Diffraction loss variation with K-factor Diffraction loss variation with different algorithms Diffraction loss variation with height variation
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Module 5: Diffraction Module (cont’d)
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Diffraction of microwave beam occurs when the beam center line grazes over an obstacle and RF energy reaching the far antenna is attenuated.
•
Diffraction creates a small shadow region where some energy is re directed in a narrow and rapidly diminishing wedge toward total shadow.
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Module 5: Diffraction Module (cont’d) • • • •
The actual amount of diffraction is dependent upon: The Fresnel Zone Radius of the wave front at the obstruction point The Size and Shape of the obstruction and The Reflectivity of the obstruction.
3rd
2nd 1st Fresnel Zones
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Module 5: Diffraction Module (cont’d)
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Module 5: Diffraction Module (cont’d)
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Module 5: Diffraction Module (cont’d)
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Module 5: Diffraction Module (cont’d)
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Module 5: Diffraction Module (cont’d)
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Module 6: Reflection Module
• • • •
Reflective Plan Definition, Terrain Roughness, Variable Parameters, Dispersion Analysis,
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Module 6: Reflection Module
•Reflection occurs when radio waves strike: • A smooth surface such as water, sheet of Ice in winter • A smooth earth • The boundary between the adjacent atmospheric layers of different densities.
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Module 6: Reflection Module (cont’d)
Depending on the length of the reflected path, the reflected wave may arrive at the receive antenna either:
• • •
In phase, Out of phase or Partially out of phase
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Module 6: Reflection Module (cont’d)
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Module 6: Reflection Module (cont’d)
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Module 6: Reflection Module (cont’d)
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Module 6: Reflection Module (cont’d)
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Module 6: Reflection Module (cont’d)
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Module 6: Reflection Module (cont’d)
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Module 7: Multipath Module
• • •
Overview, Constant Gradient Method Variable Gradient Method
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Module 7: Multipath Module
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Module 7: Multipath Module (Cont’d)
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Module 7: Multipath Module (Cont’d)
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Module 7: Multipath Module (Cont’d)
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Module 7: Multipath Module (Cont’d)
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Module 7: Multipath Module (Cont’d)
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Module 8: Network Module
• • •
Overview, Interference calculation procedure, Interference Calculations
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Module 8: Network Module (Cont’d)
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Module 8: Network Module (Cont’d)
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Module 8: Network Module (Cont’d)
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Module 8: Network Module (Cont’d) The simplified RL networks are used to illustrate the calculation procedure.
RECTANGULAR NETWORK
TRIANGULAR NETWORK 71 NEC Internal Use Only
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Module 8: Network Module (Cont’d) Obtain the following information to determine where interference analysis is needed in the network: Frequency Bands If the network frequency plan uses different frequencies then there is no need to analyze these links for interference. For example use of 7 and 13 GHz bands together.
Available Frequency Pairs For example a two frequency plan as opposed to a four frequency plan. Number of pairs determine how often the frequencies are repeated. System Layout ( to scale) This will indicate possible cases of interferences in the network 72
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Module 8: Network Module (Cont’d) Distance between paths Distances over 150 Km an be ignored, however short distances or co located sites must be analyzed for interference. Terrain Mountains between sites will block an interfering signal, however sites located on mountain tops must be investigated for possible interference. Exaggerated Azimuths 90 – 180 degrees may not require interference analysis. 73 NEC Internal Use Only
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Module 8: Network Module (Cont’d) Antenna Patterns These should be based on polarizations schemes such as HH, VV, HV, VH used in the network and shall be available for both, the victim receiver and the interfering transmitter.
Path Calculations These should include: Victim Path, Interfering Path and interfering path to victim receiver.
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Module 8: Network Module (Cont’d) • Consider any of the following options to meet the required interference objectives: • Antenna Changes: • Use larger diameter antenna to increase gain • Use High performance antennas to achieve higher levels of discrimination • X pole discrimination
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Adjust Power Output
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Use other frequency assignments
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Module 8: Network Module (Cont’d)
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THANK YOU
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