inShare Oakland: Officials zeroing in on source of police radio interference

[jland138]

From the Oakland Tribue (via the San Jose Mercury News):

City and AT&T officials said Monday they have identified and are working to fix a problem with the city's unreliable public safety radio system that failed during a protest when President Barack Obama was in Oakland last month.
...
City officials on Monday said the problem stems from interference from AT&T cell phone towers, and antennas on 16 towers have been temporarily disabled while the problem is addressed.

Link: Oakland: Officials say unreliable police radio system possibly caused by interference from one cell network - San Jose Mercury News

 

[officer_415]

I saw this story on the news tonight. The notion that all of the extensive problems with Oakland's radio system have been caused by interference from AT&T cell sites is ridiculous. Oakland is desperate for an easy fix so they don't have to admit that they squandered $18 million in taxpayer money on a worthless radio system. They should join the EBRCSA before wasting any more money trying to salvage it.

 

[mibzzer15]

+1 on joining EBRCS.But I also would not want to see them throw 18$ million down the drain.

 

[officer_415]

+1 on joining EBRCS.But I also would not want to see them throw 18$ million down the drain.

Most of that cost was subscriber radios that can be reprogrammed to work with EBRCS. A consultant conducted a study of the City of Oakland system two years ago and determined Oakland’s radio system as having 7 million dollars in current value for radios and 1.5 million dollars in current value for system infrastructure. So they're really not throwing away that much money...

 

[MattSF]

here's the Chron article on the same subject, a few more details on the situation.

Oakland police radio culprit: cell towers - SFGate

 

[WayneH]

So if AT&T's "850" (in cellular it refers to 870-894) is causing interference I wonder why Verizon is not? AT&T runs the A-band around here with Verizon covering the majority of the B-band (the latter half of 850). AT&T definitely pushes out some power though, much more than Verizon.

 

[JT-112]

Totally different radio access methods (high power TDMA vs. lower CDMA).

I wouldn't doubt that AT&T has cranked up the TX power to compensate for having less GSM cells on the air, in fact, I'd count on it.

 

[officer_415]

Oakland admits that the AT&T interference may not explain all of their issues, so they're looking at other possibilities...such as interference from T-Mobile. It's much more convenient if the problems are someone else's fault, rather than their own faulty engineering.

 

[Ben96cal]

re: interference

So for the people who don't fully understand. Why would interference from freq in the same range interfere with Oakland but not other systems in the area that are in the same range or for even the previous Oakland system?

 

[officer_415]

So for the people who don't fully understand. Why would interference from freq in the same range interfere with Oakland but not other systems in the area that are in the same range or for even the previous Oakland system?

That's an excellent question that you should ask the radio techs in Oakland.

 

[inigo88]

Most of AT&T's system in metro areas seems to be UMTS (CDMA) in the 870 MHz range (with some 1.9 GHz stuff). Honestly I haven had my phone revert to GSM in a while. Given the nature of CDMA and the fact that all the sites share the same UARFCN frequencies, I don't understand how they would detrimentally affect the Oakland system. I could imagine there would be some bleed over, but not 20 MHz of it.

Oakland made the same mistake agencies before them have made (and more will make in the future): They tried to convert from analog to P25 digital without adding a sufficient number of sites. Digital is "supposed" to perform the same as analog in lab tests, but I have seen countless instances where agencies needed additional sites to cover the same coverage area their analog systems could sufficiently cover to begin with. They did add Gwin, the Oakland Hills site, but it was at first only for fill-in and was only recently added to the simulcast system.

Similcasting is very complicated, and requires a significant amount of fine tuning antenna downtilts and Tx delays to reduce multipath. I suspect that the firm who engineered their system was relying on CQPSK and P25 LSM to handle the multipath issue, but I think a great deal of fine tuning is still necessary to get everything to work. I believe Oakland's problems are the result of poor simulcast engineering rather than some stray cell towers. Otherwise why don't we see this problem in every other major metropolitan area?

 

[EnidPuceflange]

Normally cell sites don't cause interference. However, if you try to get very clever with them, and mix a GSM signal and a UMTS signal on the same frequency, you get interference and lots of it. At least, that's what my drinking buddy told me.

That would account for why it's AT&T specifically.....

He also mentioned that one of the RF images was in the GPS band....I wonder how that would play with the GPS receivers on the simulcast sites?

 

[brey1234]

Oakland qrm

AT&T Denies Cell Phone Towers Interfere With Oakland Police Radios « CBS San Francisco

 

[jland138]

If you haven't seen this, here's an update after AT&T did an investigation into the interference issues.

Oakland Police Still Dealing With Radio Issues Despite Earlier Fix « CBS San Francisco

 

[officer_415]

Gee what a surprise, AT&T is not the cause of their problems. Here are some good excerpts:

So what's going on? “It’s really easy to blame somebody else,” said engineering consultant Bill Ruck with CSI Telecommunications in San Francisco.

Ruck said other cities with similar P25 systems are not having similar interference problems and blaming AT&T may be a way to distract attention from other issues.

“Clearly the problem has multiple dimensions,” he said. “A little bit of too much old stuff, a little bit of not well thought out new stuff, a little bit of poor training.”

But several experts CBS 5 has talked to, including Ruck, said [EBRCS] is the way to go. “Traditionally Oakland has wanted to march to their own drummer and has not been willing to get involved. It may require admission that we made a bad decision, which they don’t like to do politically,” he said.

 

[low3oh]

I enjoyed the comments portion, stating that Cruise's portable was a moto.. it's clearly a unity portable.

 

[officer_415]

"This radio works in this one building in downtown Oakland, so it must have been AT&T..."

 

[low3oh]

Any updates? I have heard that AT&T will be turning their sites back on.

 

[officer_415]

CBS did another story about lack of security at Oakland's radio sites. They already showed the problems with the Seneca site in a previous report. This time they visited the Gwin site, which doesn't even have a fence. Barry Donelan, president of the Oakland Police Officers Association, was appalled by the lack of security, while David Cruise, Oakland's public safety systems advisor, said "I don't see what's unsecure about that site." This is the same person who was confident that the bulk of the problems were caused by interference to the system by AT&T cell towers, which has proven not to be the case.

Oakland Police Radio Towers Lacking Security, Controls « CBS San Francisco

 

[WayneH]

“You couldn’t easily shut the whole thing down just by climbing up that tower,”
You don't need to climb the tower to cut the coax, you can do that safely at the bottom where it comes out of the shelter without a ladder. No coax to tower, site shut down.

But a nearby regional public safety radio system used by almost every other city and county in the East Bay has transmission towers that are protected by a tall fence, barbed wire and 24 hour monitoring.
The colo building where EBRCS, ALCO, COCO, etc are has surveillance cameras at every corner and a tall fence with barbed wire like they say. Yet I know for a fact when copper theft occurred at a different COCO location (who commonly uses cameras) they could not find the footage nor were aware it happened. If we even walk on the property during the day without calling ahead it's like a terrorist attack in progress. So despite the security it's still not very well managed, regardless of fences or cameras.