Tower Sector ID's

[Craig]

Thinking about the sector ID's (and locations) that Sprint towers seem to employ, I got to wondering a few things.

 

What is the advantage for Sprint of using sector ID's off of a given tower instead of just using the tower ID itself? Troubleshooting?

 

Does the location of the sector correlate to the "aiming point" for the given towers downtilt, or is it just an arbitrary location in the direction the sector faces?

 

The site near my house has recently stopped reporting location (at least on the sector that serves me). It now reports as unknown. It's been in this state for the last 36+ hours. Does this indicate anything? While I haven't seen roaming indicated in the status bar, my S3 is set up to show dual clocks on the lock screen when I am roaming and it's displayed this multiple times since the site stopped reporting sector locations. Ideas why?

 

I know it's multiple questions in a single thread, but I'm a multiple questions kinda guy.

[boomerbubba]

Thinking about the sector ID's (and locations) that Sprint towers seem to employ, I got to wondering a few things.

 

What is the advantage for Sprint of using sector ID's off of a given tower instead of just using the tower ID itself? Troubleshooting?

 

Does the location of the sector correlate to the "aiming point" for the given towers downtilt, or is it just an arbitrary location in the direction the sector faces?

 

The site near my house has recently stopped reporting location (at least on the sector that serves me). It now reports as unknown. It's been in this state for the last 36+ hours. Does this indicate anything? While I haven't seen roaming indicated in the status bar, my S3 is set up to show dual clocks on the lock screen when I am roaming and it's displayed this multiple times since the site stopped reporting sector locations. Ideas why?

 

I know it's multiple questions in a single thread, but I'm a multiple questions kinda guy.

 

As for why they are used, that much is pretty obvious. The "tower" is just a location. Your connection is actually to one of the sector radios on each site.

 

I assume you are talking about CDMA sectors, since they broadcast coordinates and LTE sectors do not. It is not a question of "advantage" for Sprint in using them. These sector IDs (Base Station IDs) are baked in the cake of the CDMA standard. Generally, the devices' own telephony is based on sectors. For some other purposes, Sprint does use its own site IDs. Presumably, Sprint's internal databases link from the more granular sector IDs to their own tower IDs comprehensively. So when troubleshooting based on sector, they can always know the tower.

 

As for your location question, be aware that some Sprint towers' sector radios do broadcast the actual tower location's coordinates, identical for each sector, while other towers broadcast a different, offset coordinate for each sector. I do not know why this is, but it is. In my own experience, it does seem that the size of the offset is proportional to the designed coverage size of each sector.

 

This subject is summarized in this FAQ comment, which contains a link to a fuller Sponsor thread:

[digiblur]

Think about your question.... now think about a duplex house. Should they have the same address or should they be address A and address B?

 

And yes, I believe the numbers correlate to position of the panel. I can't remember off hand but I think the 1X PN's the north sector is numbered first.

[WiWavelength]

And yes, I believe the numbers correlate to position of the panel. I can't remember off hand but I think the 1X PN's the north sector is numbered first.

 

Right, with rare exception, the N sector is the low numbered PN offset -- both for CDMA1X and EV-DO.

 

AJ

[tommym65]

Which leads me to an LTE question: I know that the engineering screens, the CDMA Field Test app, Netmonitor, etc., get and report the sector ID, and that it is the 1X ID, and they also get and report the BSLAT and BSLON, thus pinpointing the sector logical location (and the tower physical location in some places, including northern Illinois). LTE must generate some sort of ID field, in order for the phone to know what antenna it is connected to. Is there any way to find that LTE identification (if it exists), so that you can determine what different LTE antennas are seen by the phone, even if you can't directly see their locations? At least you'd know if you were seeing the same antennas, different antennas, new ones, etc., etc.

[boomerbubba]

Which leads me to an LTE question: I know that the engineering screens, the CDMA Field Test app, Netmonitor, etc., get and report the sector ID, and that it is the 1X ID, and they also get and report the BSLAT and BSLON, thus pinpointing the sector logical location (and the tower physical location in some places, including northern Illinois). LTE must generate some sort of ID field, in order for the phone to know what antenna it is connected to. Is there any way to find that LTE identification (if it exists), so that you can determine what different LTE antennas are seen by the phone, even if you can't directly see their locations? At least you'd know if you were seeing the same antennas, different antennas, new ones, etc., etc.

 

There are two IDs defined for LTE sectors and sites, and Sprint towers broadcast them both. There are no lat/lon coordinates broadcast for LTE.

• The Physical Cell ID, an integer between 1 and 507, is broadcast for each sector. This value is available on Samsung devices' LTE Engineering screens (labeled there as the Serving Cell) and on the Field Test screens on iPhone 5 handsets. Empirically,k we have discovered that the three sector IDs on a typical tower are offset from each other by a value of 169. (For example, 148, 317 and 486.)
  
• The Sector Cell Identity, a 28 bit integer/ This value is displayed on EVO LTE 4G handsets' LTE Engineering screen (IIRC, it is also labled Serving Cell.) The EVO displays this ID as a 8-digit hexadecimal value, but only the rightmost 7 digits after the leading zero are significant. Within those 7 digits, the first 5 digits are identical for each tower. The last 2 digits are 01, 02 and 03, representing the sector. The iPhone also displays this ID, but converts the value to an 8-digit decimal integer.
  

The only way to relate these IDs to Sprint site IDs, and thus to geographic coordinates, is to physically survey and catalog them in the field. This is being done in Sponsor threads for certain areas, notably Austin and New Orleans.

[jeremyandrew]

Another reason for having multiple sector ID's has to do with the way CDMA functions. Since everyone is sharing the same spectrum, each mobile must be assigned an individual code. There are only so many of these walsh codes available, so if you have 3 sector IDs, you effectively triple the number of users you can have. If you add another RF carrier to the site, you add another set of walsh codes that can be used.

 

If you've ever tried to make a phone call, had acceptable coverage and received the 'network busy' message, one very plausible explanation is that the site is out of walsh codes for the frequency that your handset is designed to hash to.

 

http://en.wikipedia.org/wiki/Walsh%E2%80%93Hadamard_code

 

When you think of a cell site, you can almost think of it as 3 individual sites sharing backahul. There are also other configurations, in the past week I visited 2, 3 and 6 sector sites in Central PA(although, in the Nortel world, a 6 sector CDMA site is actually two 3 sector sites in the same box)

 

 

This LTE info is good stuff though. I've been so busy reading Samsung's technical manuals that I haven't had a change to dig into the nuts and bolts of LTE

[digiblur]

I have heard and read about setting up a 6 sector site. It was kinda of boring without any cell site porn though.

 

-- "Sensorly or it didn't happen!"

 

 

[S4GRU]

We have one four sector site here in New Mexico. I've only seen one so far. Although two sector sites are very common here.

 

Robert via Samsung Note II via Tapatalk

 

 

[tommym65]

 

There are two IDs defined for LTE sectors and sites, and Sprint towers broadcast them both. There are no lat/lon coordinates broadcast for LTE.

• The Physical Cell ID, an integer between 1 and 507, is broadcast for each sector. This value is available on Samsung devices' LTE Engineering screens (labeled there as the Serving Cell) and on the Field Test screens on iPhone 5 handsets. Empirically,k we have discovered that the three sector IDs on a typical tower are offset from each other by a value of 169. (For example, 148, 317 and 486.)
  
• The Sector Cell Identity, a 28 bit integer/ This value is displayed on EVO LTE 4G handsets' LTE Engineering screen (IIRC, it is also labled Serving Cell.) The EVO displays this ID as a 8-digit hexadecimal value, but only the rightmost 7 digits after the leading zero are significant. Within those 7 digits, the first 5 digits are identical for each tower. The last 2 digits are 01, 02 and 03, representing the sector. The iPhone also displays this ID, but converts the value to an 8-digit decimal integer.
  

The only way to relate these IDs to Sprint site IDs, and thus to geographic coordinates, is to physically survey and catalog them in the field. This is being done in Sponsor threads for certain areas, notably Austin and New Orleans.

 

Boomerbubba: Thanks for your reply, it seriously helps my understanding. I should have been clearer in my post that I knew that BSLAT & BSLON were for the 1X transmitter, not LTE.

 

2 follow-on questions: 1. Does the IIRC show up anywhere on the GS3 engineering screens? It seems like this field is the only way to actually pin down the LTE cell ID, and I can't find it on my GS3. 2. Does the GS3 LTE Engineering Screen show LTE parameters even when the LTE signal is so weak that the phone is locked to CDMA? When I looked at the screen while in my house, it was showing an RSRP of -119, I believe from a transmitter about 3 miles south of me, which I know has LTE, while CDMA Field Test app was showing CDMA and Evdo RSSI's in the 90's, I think from a tower about 1.5 miles northeast which doesn't have LTE yet.

 

(LTE is so close that it's like Chinese water torture! Drip . . . Drip . . . Drip . . . )

 

Again, thank you for your reply.

[boomerbubba]

Boomerbubba: Thanks for your reply, it seriously helps my understanding. I should have been clearer in my post that I knew that BSLAT & BSLON were for the 1X transmitter, not LTE.

 

2 follow-on questions: 1. Does the IIRC show up anywhere on the GS3 engineering screens? It seems like this field is the only way to actually pin down the LTE cell ID, and I can't find it on my GS3.

 

IIRC = "If I remember correctly"

 

2. Does the GS3 LTE Engineering Screen show LTE parameters even when the LTE signal is so weak that the phone is locked to CDMA? When I looked at the screen while in my house, it was showing an RSRP of -119, I believe from a transmitter about 3 miles south of me, which I know has LTE, while CDMA Field Test app was showing CDMA and Evdo RSSI's in the 90's, I think from a tower about 1.5 miles northeast which doesn't have LTE yet.

 

The GS3 LTE Engineering screen typically shows the last ID and signal-strength data from the prior LTE connection even after the LTE signal is lost. So you have to be careful to look for the 4G icon on the phone's top status bar to confirm that the connection is alive.

[tommym65]

 

2 follow-on questions: 1. Does the IIRC show up anywhere on the GS3 engineering screens? It seems like this field is the only way to actually pin down the LTE cell ID, and I can't find it on my GS3.

 

Too many acronyms.

 

Does the Sector Cell ID show up anywhere on the GS3 engineering screens? The GS3 Serving Cell appears to be the Physical Cell ID, not the Sector Cell ID.

 

Later: Actually you answered this on Dec. 20 in another thread: No. Oh, well.

[boomerbubba]

Too many acronyms.

 

Does the Sector Cell ID show up anywhere on the GS3 engineering screens? The GS3 Serving Cell appears to be the Physical Cell ID, not the Sector Cell ID.

 

Later: Actually you answered this on Dec. 20 in another thread: No. Oh, well.

 

That's right. The Samsungs display only the Physical Cell ID. The EVOs display only the Cell Identity. The only device I know of that displays both in its native diagnostic screens is the iPhone 5.

 

There also are no third-party apps that I know of that will display and log all this, along with other useful information such as the RSRP signal strength, user geographic coordinates, and timestamp. These LTE data elements were not available in the Android telephony API until Jelly Bean, which does expose them in a standard way to app developers. A logging app could be developed now for Jellybean devices, but AFAIK (as far as I know) it has not been written yet.