Performing a Computer Radio Path Survey May 18, 2010 Perry Spetz President

1. Performing a Computer Radio Path Survey May 18, 2010 Perry Spetz President Industrial Control Links Auburn, CA

2. What we’re going to talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • What Could Possibly Go Wrong?

3. First lets talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • What Could Possibly Go Wrong?

4. Engineered System vs Guesswork Accurately predict the cost of the system Help with radio and component selection Identify need for towers, etc. Validate site locations Identify need for repeaters Identify potential problems Confirm that the system can actually work Why do a Path Survey?

5. Now lets talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • What Could Possibly Go Wrong?

6. Made up of 4 components: Radio Path Survey Software Topo Map Data Field Data - Lat/Longs & Site Details Equipment Specifications Computer Radio Path Survey. . . The real breakthrough came about earlier in this decade with the free availability of the software and map data over the Internet.

7. Used to cost $$$$ (typically $7,500 + maps) Now Available free over the Internet Radio Mobile www.cplus.org/rmw/english1.html Splat! www.qsl.net/kd2bd/splat.html . . . thanks to amateur radio enthusiasts and your tax dollars at work Based on ITS Irregular Terrain Model (Longley-Rice) (named for Anita Longley and Phil Rice, 1968) Radio Path Survey Software

8. The Longley–Rice model is a radio propagation model A method for predicting the attenuation of radio signals for a telecommunication link in the frequency range of 20 MHz to 20 GHz. Also known as the Irregular Terrain Model (ITM) Created in the 1960s for the needs of frequency planning in television broadcasting in the United States Was extensively used for preparing the tables of channel allocations for VHF/UHF Is the foundation for the Radio Mobile and Splat! software Free Documentation, FORTRAN and C code available from: U.S. Department of Commerce NTIA/ITS Institute for Telecommunication Sciences ( http://flattop.its.bldrdoc.gov/itm.html ) Radio Path Survey Software Longley-Rice Model

9. SRTM (Shuttle Radar Topography Mission) Based on raw data collected by Space Shuttle Endeavour in February 2000 Topo Map Data (SRTM) In order to gather topographic (elevation) data of Earth's surface, SRTM used the technique of interferometry. In interferometry, two images are taken from different vantage points of the same area. The slight difference in the two images allows scientists to determine the height of the surface. To get two images from different vantage points, a main antenna was installed in Space Shuttle Endeavour's cargo bay. The main antenna both transmitted and received radar signals. Once the shuttle was in space, a mast was deployed from a canister that was attached to the main antenna truss. The mast extended out 60 meters (200 feet). At the end of the mast, an outboard antenna acted as the second vantage point and received radar signals. More info on SRTM and technology used at: www2.jpl.nasa.gov/srtm/instr.htm

10. Customer supplies . . . Site GPS Coordinates Site Information Potential antenna locations (tanks, buildings, etc.) Limitations (such as community/neighborhood regulations) Potential obstacles Potential interference (other radios, cell/pager/TV/radio towers) Repeater options Field Data GPS list price < $100 (photo courtesy of Garmin, Inc.)

11. From Product Data Sheets . . . Radio Specifications Transmit Power Receiver Sensitivity Antenna Specifications Gain Type (Omni, Yagi, etc.) and Lobe Shape Antenna Cable Specifications Loss, per foot or per meter (at the operating frequency) Miscellaneous Other losses (connectors, lightening arrestors, etc.) Equipment Specifications

12. Typical Radio Data Sheet

13. Typical Antenna Data Sheet

14. Typical Antenna Cable Data Sheet

15. Now lets talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • What Could Possibly Go Wrong?

16. Field Survey – Instrumented or “Go out and Try It” Good secondary validation, but . . . Expensive and labor intensive Time consuming guesswork (antennas, elevations, etc.) Sometimes hard to achieve with real configuration (towers, etc.) Snapshot that doesn’t account for seasonal changes Computer Radio Path SurveyversusField Survey

17. Now lets talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • What Could Possibly Go Wrong?

18. To choose a technology, we need to determine: Speed/throughput required Environment and distances Topology (Master/Slave, Peer-to-peer) Selecting Radio Technologies • In general, LOWER frequencies . . . • Penetrate Better • Bend over hills better • Equipment available to operate at higher power • But . . • may be slower • are bulkier and more exposed (big antennas!) • may not be as secure (frequency hopping, encryption,etc.)

19. Now lets talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • Interpreting and Using the Results • What Could Possibly Go Wrong?

20. Computer Radio Path Survey. . .Getting started w/Radio Mobile Install Radio Mobile from: www.cplus.org/rmw/english1.html (full install is a little tedious!) or copy Radio Mobile folder from USB stick into your Programs Directory, and run the Visual Basic V6.0 SP6 installation “vbrun60sp6.exe” (much easier!).

21. Computer Radio Path Survey. . .Getting started w/Radio Mobile Start Radio Mobile Program ( rmweng.exe) and select the “File” menu.

22. Computer Radio Path Survey. . .Getting started w/Radio Mobile Select “Unit Properties”. Rename generic names of “Unit 1”, etc. to site names, then click on “Enter LAT LON or QRA” and enter site coordinates.

23. Computer Radio Path Survey. . .Getting started w/Radio Mobile Go back to “File” menu and select “Network Properties”. Under Parameters, enter minimum and maximum frequency range and additional loss “fudge factor”. I normally leave everything else alone.

24. Computer Radio Path Survey. . .Getting started w/Radio Mobile Under the “Topology” tab, copy the settings below . . .

25. Computer Radio Path Survey. . .Getting started w/Radio Mobile Under the “Systems” tab, create the radio/cable/antenna combinations that you will be using (if they don’t exist already) and save them with descriptive names using the “Add to Radiosys.dat” button. You can reuse these “system” definitions again and again.

26. Computer Radio Path Survey. . .Getting started w/Radio Mobile Under the “Membership” tab, select “Net 1” and “check” each unit that is part of the same network, then select the “System” being used at each site checked. Be sure to set the “Antenna height (at least for starters) and the “Antenna Direction” for directional sites (i.e. sites using Yagi antennas). Remember that Radio Mobile works in meters!

27. Computer Radio Path Survey. . .Getting started w/Radio Mobile Under the “Style” tab, I recommend starting with the settings below. You can change them later depending on what Fade Margin you feel is “Good” , “OK” and “Bad” when the radio paths are plotted on the map.

28. Computer Radio Path Survey. . .Getting started w/Radio Mobile Go back to the “File” menu and select “Map Properties”. Initially select one of the sites (under “Select a Unit”) that you suspect is kind of central to the system (like “City Hall”?). Set “Height” to the largest area that you think that the system covers. Sites outside of that area will not be plotted! Too large an area though will take forever to load.  Be sure that the “Adjust units elevation” and “Merge pictures” boxes are checked.

29. Computer Radio Path Survey. . .Getting started w/Radio Mobile Click on “Extract” and your computer will build the background topo image (from SRTM files that it downloads from the Internet) where colors represent elevations per the scale in the upper left hand corner.

30. Computer Radio Path Survey. . .Getting started w/Radio Mobile Under “View” select “Merge Pictures” if you want to overlay street maps or aerial photographs, and click on “Draw”. You’ll be asked if you want to keep the results (some are better than others!).

31. Computer Radio Path Survey. . .Getting started w/Radio Mobile Under the “Tools” menu, select “Radio Link” to get the plotted radio path(s) overlayed on the topo and street map images.

32. Computer Radio Path Survey. . .Getting started w/Radio Mobile You’ll also get a profile view window. You can see the results at the top change as you vary antenna heights, “systems” (radio/antenna/cable combinations) and operating frequencies for each radio link. Note how the losses are spelled out so that you can tell “what’s getting you”.

33. Computer Radio Path Survey. . .Getting started w/Radio Mobile If you go to “Edit” and select “Copy”, the clipboard in your PC will get the path data so that you can paste it into a text document. You can copy and paste the profile to so that the user can see the path information. If some paths look really ugly, consider changes to antenna elevations, gains, frequency, etc. Path Data: Distance between Reservoir and Pump House is 0.4 km (0.2 miles) True North Azimuth = 48.6°, Magnetic North Azimuth = 31.4°, Elevation angle = -21.2946° Terrain elevation variation is 145.1 m Propagation mode is line-of-sight, minimum clearance 1.9F1 at 0.2km Average frequency is 915.000 MHz Free Space = 83.6 dB, Obstruction = 0.4 dB, Urban = 0.0 dB, Forest = 9.8 dB, Statistics = 5.9 dB Total propagation loss is 99.8 dB System gain from Reservoir to Pump House is 141.0 dB ( yagi.ant at 48.6° gain = 6.0 dB ) System gain from Pump House to Reservoir is 141.0 dB ( yagi.ant at 228.6° gain = 6.0 dB ) Worst reception is 41.2 dB over the required signal to meet 70.000% of situations

34. Now lets talk about . . . • Why Do a Radio Path Survey? • What is a Computer Radio Path Survey? • Computer versus Field Study • Selecting Radio Technologies • How is a Computer Survey Performed? • What Could Possibly Go Wrong?

35. What Could Possibly Go Wrong?Interference and Fresnel Zones Well many things actually! Most people assume that the signal strength is simply not sufficient if a radio system doesn’t work. If you understand Interference and Fresnel Zones, you’ll start to understand some of the more common problems . Problem #1: Overwhelming “out of band” interference. I’ve seen this more times than you would ever imagine. The symptoms are easily identified when the radio reports high levels of background “noise” levels when no other radios in the system are transmitting. Keep in mind that radio reliability has everything to do with Signal to Noise ratio. The signal can still be weak if you give the radio a chance to dig it out without fighting off a bunch of noise. Solution: Bandpass filters usually nip this problem in the bud!

36. What Could Possibly Go Wrong?Interference and Fresnel Zones Problem #2: “I have clear “line of sight”, and my radios still don’t work!” Welcome to Fesnel Zone (multipath) problems! Solutions: Change antenna elevations, use a different path, change frequencies, etc. Good references links: www.zytrax.com/tech/wireless/fresnel.htm en.wikipedia.org/wiki/Fresnel_zone www.vias.org/wirelessnetw/wndw_04_08b.html www.titanwirelessonline.com/SearchResults.asp?Cat=90 The 1st Fresnel Zone is the one that gets you! 1st Fresnel Zone radius (miles) = 72.1 x Sqr root ((Obstacle Dist. x (Total Link - Obstacle Dist.)) / (Freq. in GHz x Total Link)) Obstacle free radius = 0.6 x 1st Fresnel Zone radius

37. Thank You For Your Time!