Oh yeah, one more note.
On the timing of the interference starting, that was also about the time that the leaves filled all the trees in our part of Alabama.
We had a general degredation of signal with most of our customers in the last three weeks.
In fact we had to swap out several integrated SM’s with connectorized to keep the service up.
We learned the hard way about giving ourselves enough head-space with signal strength to accomadate the seasonal changes (leaves on trees) when we do installs.
I have had to let two customers out of their contract last month because of poor signal due to the foilage growth this year.
Reay Culp
Sylacauga, Al
I appreciate your comments as always and I believe this is a good discussion and an important one.
My question remains; how are we as WISPs going to deal with -39dB at 1/4 mile and -57 at 4 miles (probably much less than this due to terrain)?
Here is the problem with the RFID systems as I see it.
1. The power level is legal and needed to penetrate stacks of boxes on pallets. It’s not going to change.
2. The frequency they are using is 906-924, and they aren’t going to change bands.
3. The system does not have any GPS sync (not that it would help)
4. They can change the operating center frequency, and by law they have to work with you in co-ordinating frequencies (he who gets there first wins).
In my opinion, this would be no different than another operator coming into town in which case frequency co-ordination is the ONLY answer. If you have a better answer, I’d love to hear it.
Does this suck? You bet. Is it going to severely impact Canopy operators? Definitely. Is it going away? Nope. This is the price we pay for free spectrum.
It may be possible to construct Faraday cages to reduce the level escaping the dock. They just need to drag the pallet through. They are not going to pay for that (or at least not the whole thing) and it won’t be cheap. I did find some info on shielding: http://www.hollandshielding.com/faraday … dtents.php.
Alternately, higher AP density may be another solution however that is going to get pricey.
Also, while ideally we want to be -77 or better, not all marginal links are problematic. For example:
LUID: 006 : MAC: State: IN SESSION (Encrypt Active)
Site Name :
Software Version : CANOPY 7.3.6 Oct 24 2005 12:06:56
Software Boot Version : CANOPYBOOT 3.0
FPGA Version : 070605 (DES Sched) P9
Session Timeout: 0, AirDelay 520 (approximately 14.48 miles (76440 feet))
Session Count: 1, Reg Count 1, Re-Reg Count 0
RSSI (Avg/Last): 1225/1241 Jitter (Avg/Last): 6/4 Power Level (Avg/Last): -80/-79
DnRate(SM): 1200 DnLimit(SM): 1200 UpRate(SM): 400 UpLimit(SM): 400 (kbit)
LoUpCIR(SM): 0 LoDnCIR(SM): 0 (kbps)
Rate : VC 22 Rate 1X/1X
I too have noticed some increased Jitter with new foliage.
Thanks Jerry,
I have not heard back from the Walmart engineer yet on what it is that they are going to do exactly.
To date, their system is still turned off.
I purchased one of those BumbleBee handheld sprectrum analyzers and I intend to monitor their site on occasion to see if I can determine their response.
Of course I will post our findings.
By the conversation I had with the Walmart engineer, they are going to slide their freq range up above 915, allowing us the lower range.
Reay Culp
Sylacauga,Al
One thing I want to make clear is that he wanted to assure me that Walmart would do whatever it takes to not interfere with our system.
Just turning it off so quickly was a great immediate response on their part.
Might be a sector for the infamous /configuration.html freq’s
What is that?
on 7.x sms or aps, it gives access to additional frequencies for testing only. we have used 900 mhz (900.0) for testing purposes before with good results - but it’s not exactly fcc legal.
http://169.254.1.1/configuration.html , for example
unfortunately, although we visited walmart on friday and emailed corp friday as well, we’ve received little response. We got this email on Monday after posting some spectrum screen shots online on a discussion board on www.part-15.org:
Hello Jay,
I am one of the members Motorola group in Bentonville-AR and I also work with the Motorola RFID division.
There were two spectrum plots (one at a store and one at a DC) that found their way to our group and I am keen on knowing the exact locations (addresses) that these were observed at.
Sincerely,
Prashant Bh.
Jay,
Have you been able, using a SM, to pinpoint the interference at the store?
Reay