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Colocation and Interference

Colocation and Interference. Marlon K. Schafer CTO KMS Wireless Global Solutions (509) 982-2181. Introduction. Colocation and interference, unfortunately, often go hand in hand.

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Colocation and Interference

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  1. Colocation and Interference Marlon K. Schafer CTO KMS Wireless Global Solutions (509) 982-2181 Marlon K. Schafer, CTO, KMS Wireless (509) 982-2181

  2. Introduction Colocation and interference, unfortunately, often go hand in hand. The goal is often not to eliminate all interference but rather to minimize it’s effect (to our systems and those of others). I live in an area rich in interference but I’ve been able to colo with other systems in such a way that we all work just fine and the customer’s win at the end of the day. The first thing you want to do is make sure you don’t locate your system where there is no available spectrum (see above). You also don’t want to go locating your systems where you’ll create problems for those already using the spectrum. Due diligence is the order of the day. Marlon K. Schafer, CTO, KMS Wireless (509) 982-2181

  3. Colocation Issues. • First, try not to have to colocate. Go where others are not. • If that won’t work you at least need to check out who’s already up there and pick technologies and channels so as to not cause interference to them. • If there’s DSSS in the area then you should usually use DSSS and pick different channels. Same for FHSS. • Physical separation will often go a long way in colocation issues too. Try to get 20 feet or more between antennas. • Don’t forget that your own antennas are colocated just like competitors antennas would be. • The more systems that need to be colocated the higher quality gear needs to be used throughout the system. Better radios and especially top quality antennas become increasingly important. Marlon K. Schafer, CTO, KMS Wireless (509) 982-2181

  4. Interference Issues • Interference is any signal received by your radio but isn’t your own signal. • It can come from some very unexpected places. In the graphic below the signal on the left (red means there’s a lot of interference being picked up) is from a local cell phone tower that’s about a mile away and a few degrees off to the side of my WPOP. The signal on the right is coming from the other end of that link. 30 miles away. • A phone call and 2 days later and AT & T had a bad remote radio fixed and we were in good shape again. MOST companies will work with you if they find out that they are creating new interference. • This situation could have been dealt with by using antennas with different polarity and/or physical location or patterns that caused them to not look at the offending signal. • If I’d have tried to build my WPOP in a location that started out like that my WISP would have been dead before it was even out of the starting gate. Marlon K. Schafer, CTO, KMS Wireless (509) 982-2181

  5. Interference Issues, Continued • There are basically two types of interference. • The kind that’s always there and always in the same place. • DSSS will normally deal with that better than FHSS as we can program around it if we know where it’s at. (Left hand example is a Wmux link.) • Or the kind that’s on and off in random places within the band (FHSS systems typically). • FHSS systems will deal with that better as they’ll fill in when the spectrum is available and just go past the bad spot while it’s bad. (Right hand example is BreezeCOM and does that all over the scale.) • There is also vertical and horizontal antenna polarization. This is all vertical, horizontal may be clear as can be. • Naturally there is always the option of choosing a new spectrum to work with…. Marlon K. Schafer, CTO, KMS Wireless (509) 982-2181

  6. Conclusion • Interference is a fact of life in the ISM and UNII bands. • Look be fore you leap. • Ask interfering parties, nicely, to stop before you get forceful with them. • Offer to fix other people’s problems just to get them out of your way. • Make sure you are correct with what you claim before you accuse anyone. • Hire professional help to help you design your network if you can afford to. • Hire professional help to help prove your interference case if the interfering company(s) will not work with you. Marlon K. Schafer, CTO, KMS Wireless (509) 982-2181

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