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AT&T/Verizon 700mhz vs Sprint 800mhz


RAvirani
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Having used AT&T Band 17 a lot and very recently, Verizon Band 13 (my work decided it would be a good decision to give me a hotspot) a question has arised. Why is it that AT&T and Verizon devices can hold a -116 to -120 dbm signal on 700mhz if I put them in my pocket while while sprint can barely hold a -110 800mhz signal in my hand? A it just how sprint has programmed their phones or does the iPhone 6S have a terrible Band 26 antenna because it seems like sprint should hold onto that band 26 signal down to -120 at the very least and be very reluctant to drop to 3G.

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Having used AT&T Band 17 a lot and very recently, Verizon Band 13 (my work decided it would be a good decision to give me a hotspot) a question has arised. Why is it that AT&T and Verizon devices can hold a -116 to -120 dbm signal on 700mhz if I put them in my pocket while while sprint can barely hold a -110 800mhz signal in my hand? A it just how sprint has programmed their phones or does the iPhone 6S have a terrible Band 26 antenna because it seems like sprint should hold onto that band 26 signal down to -120 at the very least and be very reluctant to drop to 3G.

Band 26 is 5/5 or 3/3 in most cases chances are the capacity may be pulling (breathing in) to limit the number of connections?

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I have wondered this as well, if I could have B26 at -120 I would never leave LTE and fall back to 3G. Usually by the ~112 dBm mark I fall back to 3G.

Yea...I've seen AT&T hold a steady -123 to -126 signal on Band 17...something just doesn't add up. If sprint would do this on B26 I think it's safe to say LTE coverage would match if not eclipse 3G coverage. Isn't that what sprint wants? It's also interesting that Sprint phones hold on to -118 to -122ish LTE on 1900mhz and 2500mhz...

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This is due to intended configuration and will differ across sites.

 

My opinion is that Sprint adjusts this threshold to best satisfy several conditions:

  1. Minimize the risk of missed incoming calls. An intermittent or poor LTE signal can increase the risk that eCSFB call flow will not successfully reach your device.
  2. Minimize interruption to data connectivity. Some older versions of the Nexus 5 radio firmware do not respect the network-side configuration parameters and will spend a longer period of time trying to handover to another LTE site as opposed to falling back to 3G. This causes active data sessions to fail and extends the period of time where the user will be unable to access data services. Newer firmware across most devices opts to reconnect to something as quickly as possible.
  3. Provide the best overall data experience. In conjunction with point 2, there are situations in which a 3G signal at a given location will actually provide more throughput and/or less timeouts than an LTE connection. You can test this yourself by performing a speed test next time this happens, then forcing your device into LTE-only mode, then performing another speed test. Again, this will not always be the case, but keep in mind that these points are in order of priority.

I have seen sites along highways and in rural areas which will consistently hold an LTE connection to a lower RSRP than urban sites.

 

Now, specifically in relation to AT&T and Verizon, it is true that Sprint's configuration will generally give up at higher signal levels. This is because the majority of 700 MHz LTE coverage from those carriers is deployed as 10x10 MHz. What's the difference? The wider carriers are capable of greater throughput at comparable power levels.

 

In other words, take a look at the performance of Sprint's 800 MHz 5x5 LTE in relation to the signal level. Find the signal level (say, -120 dBm or lower) where the throughput or stability would no longer be considered "usable" (time-outs, throughput in kilobits, etc.). Now, under most conditions, a 700 MHz 10x10 LTE carrier at that same power level would probably still be considered "usable" down to a slightly lower power level.

 

You can see it yourself by testing AT&T in an area where it only has 5x5 of 700 MHz spectrum, as well as by testing T-Mobile in an area where it has deployed 700 MHz. Of course, since T-Mobile supports VoLTE and has no comparable 3G fallback in many areas, they don't need to satisfy point 1 above, so you'll still see their devices sustain that connection beyond -120 dBm in some cases.

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In my own experience my iPhone and nexus 5 would always drop back to 3G around -112 and -115 at best. It's of no fault to the devices it's definitely how they have things setup. It was infuriating to me because LTE would work until it dropped and 3G would be terribly slow or useless.

 

On AT&T if SNR is really bad (which it's pretty saturated so it usually is) I'll drop around -118 or so. On a good day it may hold to -123 or so. I've been to quite a few of their 5x5 B17 areas, two counties over is one in fact, and 5 MHz B17 performs pretty well and hangs on pretty tight just like in 10 MHz areas. Another example of an AT&T 5x5 market is San Angelo, TX where i spent a few days last summer. I stayed put on B17 around -114 dbm indoors consistently. Even out in fringe areas 8 or so miles from a tower I had no issue with it.

 

Whatever sprint is doing with B26 in my market I don't agree with it and have found it infuriating from the beginning. I think they could manage it better, and I know they have at least in the KC metro.

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I don't even have B26 in 99% of my market, so Sprint has tweaked the heck out of B25. In some cases, my device doesn't fall back to 3G until the signal is -125dBm or weaker. With a 5x5 configuration, I think someone is much better off on 3G EVDO when the signal dips below roughly -115. It sure beats pulling hair out when web pages time out and texts fail to send.

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When Sprint starts rolling out VoLTE they're gonna have no choice but to turn that B26 up and make it cover as much as possible. Otherwise it'll be dropped call central. AT&T did the same when it rolled VoLTE out in my area. Makes for an easily congested B17, but that still works better than their HSPA 95% of the time.

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When Sprint starts rolling out VoLTE they're gonna have no choice but to turn that B26 up and make it cover as much as possible. Otherwise it'll be dropped call central. AT&T did the same when it rolled VoLTE out in my area. Makes for an easily congested B17, but that still works better than their HSPA 95% of the time.

I've noticed that B26 in my area has a terrible signal to noise ratio compared to B25 originating from the same tower. The full potential of B26 coverage has yet to be reached for Sprint in many areas.

 

Unfortunately, speeds will take an even bigger hit when that happens if the network isn't dense enough and properly balanced on the network side. As it stands today, 3G evdo pulls at least 1 Mbps everytime in my area (which pre NV era was 0.10 Mbps) which is way faster than B26. Hopefully Sprint figures out load balancing once 8t8r Sprint equipment replaces Clearwire equipment.

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In other words, take a look at the performance of Sprint's 800 MHz 5x5 LTE in relation to the signal level. Find the signal level (say, -120 dBm or lower) where the throughput or stability would no longer be considered "usable" (time-outs, throughput in kilobits, etc.). Now, under most conditions, a 700 MHz 10x10 LTE carrier at that same power level would probably still be considered "usable" down to a slightly lower power level.

 

You can see it yourself by testing AT&T in an area where it only has 5x5 of 700 MHz spectrum, as well as by testing T-Mobile in an area where it has deployed 700 MHz. Of course, since T-Mobile supports VoLTE and has no comparable 3G fallback in many areas, they don't need to satisfy point 1 above, so you'll still see their devices sustain that connection beyond -120 dBm in some cases.

I have used AT&T 5x5 B17 and there is no change the the device's ability/willingness to hold on to B17. The same goes for T-Mobile which I have also used (not very much but once or twice). Also in my experience, -118ish on B26 is a lot more usable than the -100 or so on 3G I would get it if I weren't on LTE.

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Im sure it depends on a lot of factors.  There is 700 vs 800 differnences yea.  But then on my N5 with B26 my phone will hold onto B26 forever.  I have seen as high as -140 but sensorly couldn't send packets past -135. 

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I've noticed that B26 in my area has a terrible signal to noise ratio compared to B25 originating from the same tower. The full potential of B26 coverage has yet to be reached for Sprint in many areas.

 

:td: That's Ericsson for you. The newer RRUS 31 B25 significantly outperforms the older RRUS 11 B25. AT&T is still using the old ones in my area, and even though they have twice the density of Sprint (and consistently higher signal strength), their band 2 SNR is much closer to what Sprint's used to be before the swap. Take a look -- same tower, same device, same location.

 

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Maybe one day they'll come up with some better band 26 equipment.

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I have used AT&T 5x5 B17 and there is no change the the device's ability/willingness to hold on to B17. The same goes for T-Mobile which I have also used (not very much but once or twice). Also in my experience, -118ish on B26 is a lot more usable than the -100 or so on 3G I would get it if I weren't on LTE.

 

One other contributing factor is the difference in 3G network:

  • AT&T is already thinning out their 2G GSM network in anticipation of full shutdown by January 2017.
  • LTE outperforms UMTS/HSPA at the cell edge even at 5x5 MHz bandwidth, so it wouldn't be as beneficial to fall back compared to falling back to eHRPD on Sprint.
  • Networks which are fully 3GPP will use SIB 13 to maintain continuity across 2G/3G/4G carriers. In other words, although optimized LTE-to-eHRPD handover is possible, the opposite is not. [Tim will correct me here if that problem has been solved now, but if that were the case, you would expect VoLTE to have been launched by now as it has the same problem].
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LTE outperforms UMTS/HSPA at the cell edge even at 5x5 MHz bandwidth, so it wouldn't be as beneficial to fall back compared to falling back to eHRPD on Sprint.

 

Doesn't LTE also outperform eHRPD/EVDO at the cell edge?

 

Networks which are fully 3GPP will use SIB 13 to maintain continuity across 2G/3G/4G carriers. In other words, although optimized LTE-to-eHRPD handover is possible, the opposite is not. [Tim will correct me here if that problem has been solved now, but if that were the case, you would expect VoLTE to have been launched by now as it has the same problem].

 

I'm slightly confused as to how this pertains to how weak a signal the device should hold on to...could you elaborate?

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Doesn't LTE also outperform eHRPD/EVDO at the cell edge?

That depends on how it's deployed. You can see it on Sprint's coverage map: there are some areas at the edge of coverage where they show LTE reaching farther than 3G (and in those areas you'll see it hold LTE down to a lower level), while others show the opposite. Yes, a 5x5 800 MHz LTE carrier may outperform a 1900 MHz EV-DO carrier in throughput at the cell edge, but keep in mind that the number one priority here is to ensure reliable voice service. It is entirely possible for a 1900 MHz CDMA voice carrier to have better reliability at the cell edge, and an 800 MHz CDMA voice carrier will definitely do so.

 

I'm slightly confused as to how this pertains to how weak a signal the device should hold on to...could you elaborate?

 

It's easier to see if you have a Samsung device (their engineering screen has a "SIB 13 received" indicator). Sprint has the capability to send your device from one LTE band to the other, but as far as I know, it doesn't have a direct method to tell your device to do so from a CDMA connection. On the other hand, if you're on an AT&T or T-Mobile device, the network can freely direct you between 2G/3G/4G using SIB 13.

 

That's one of the reasons AT&T and T-Mobile were able to implement SRVCC to keep voice calls active across 3G/4G handover, whereas Verizon cannot handover an active VoLTE call to CDMA.

 

--

 

I should additionally clarify something else. Although the network does control the LTE-to-eHRPD handover threshold, the device will only do so if there isn't an active data session. In other words, if you start something like, say, a Hangouts call, your device will stay on LTE up to the point where it actually loses the connection. Also keep in mind that it isn't strictly based on RSRP. The important numbers here are RSRQ and SINR.

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Does anyoneknow if the newer ALU RRUs for B25 significantly outperform the older ALU (Panasonic) B25 RRUs?  I am hoping Sprint eventually replaces all the old Panasonic B25 RRUs at all sites.

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That depends on how it's deployed. You can see it on Sprint's coverage map: there are some areas at the edge of coverage where they show LTE reaching farther than 3G (and in those areas you'll see it hold LTE down to a lower level), while others show the opposite. Yes, a 5x5 800 MHz LTE carrier may outperform a 1900 MHz EV-DO carrier in throughput at the cell edge, but keep in mind that the number one priority here is to ensure reliable voice service. It is entirely possible for a 1900 MHz CDMA voice carrier to have better reliability at the cell edge, and an 800 MHz CDMA voice carrier will definitely do so.

 

 

It's easier to see if you have a Samsung device (their engineering screen has a "SIB 13 received" indicator). Sprint has the capability to send your device from one LTE band to the other, but as far as I know, it doesn't have a direct method to tell your device to do so from a CDMA connection. On the other hand, if you're on an AT&T or T-Mobile device, the network can freely direct you between 2G/3G/4G using SIB 13.

 

That's one of the reasons AT&T and T-Mobile were able to implement SRVCC to keep voice calls active across 3G/4G handover, whereas Verizon cannot handover an active VoLTE call to CDMA.

 

--

 

I should additionally clarify something else. Although the network does control the LTE-to-eHRPD handover threshold, the device will only do so if there isn't an active data session. In other words, if you start something like, say, a Hangouts call, your device will stay on LTE up to the point where it actually loses the connection. Also keep in mind that it isn't strictly based on RSRP. The important numbers here are RSRQ and SINR.

Ok so two things. I understand what you said about LTE doing better in the data department but 3G winning when it comes to voice but isn't that irrelevant because sprint doesn't do VoLTE anyways? My second question is: isn't there a means by which an LTE call can be handed to CDMA semi-smoothly now (http://www3.alcatel-lucent.com/wps/DocumentStreamerServlet?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=Data_Sheets/SCG_R9-0_EN_Datasheet.pdf and http://lteworld.org/blog/evolution-single-radio-voice-call-continuity-srvcc see release 9)?

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Ok so two things. I understand what you said about LTE doing better in the data department but 3G winning when it comes to voice but isn't that irrelevant because sprint doesn't do VoLTE anyways?

The relevance to voice comes from the high risk that users with poor/intermittent LTE connectivity will be unable to receive calls reliably via eCSFB. Call reliability is Sprint's number one priority, as they are only just beginning to break away from the reputation they earned during the interruptions caused by Network Vision. Data reliability is a secondary priority, but it is still considered. AT&T doesn't have to worry about this because HSPA is going to perform worse anyway, and T-Mobile doesn't have to worry about this because they don't have low-band HSPA anywhere other than one market.

 

It's specified by the standard, but that doesn't mean it's fully supported by vendors or the network backend. Keep in mind that Verizon -- known for ubiquitous reliability -- skipped it entirely. My understanding is that Sprint is still working toward a working SRVCC solution for 3GPP2 as a prerequisite to VoLTE.

 

Sprint updated their Wi-Fi calling FAQ for 2016+ devices. This seems to signal that they're beginning to make some of the necessary back-end changes to eventually support SRVCC.

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One other contributing factor is the difference in 3G network:

  •  
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  • LTE outperforms UMTS/HSPA at the cell edge even at 5x5 MHz bandwidth, so it wouldn't be as beneficial to fall back compared to falling back to eHRPD on Sprint.
  •  
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Not my experience at all with at&t. I can drop LTE at -115 to -120 where B17 is performing at 1-2mbps and HSPA+ is performing at 5-8mbps at -96 signal. If signal is weak, I generally get better speeds on HSPA+. You're probably right, in theory, but in practice HSPA+ usually outperforms slow LTE areas.

 

I cannot think of one area where LTE is weak and slow, but HSPA+ is worse. It's generally agreed upon at Hofo that HSPA+ is a great fallback network.

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Not my experience at all with at&t. I can drop LTE at -115 to -120 where B17 is performing at 1-2mbps and HSPA+ is performing at 5-8mbps at -96 signal. If signal is weak, I generally get better speeds on HSPA+. You're probably right, in theory, but in practice HSPA+ usually outperforms slow LTE areas.

 

I cannot think of one area where LTE is weak and slow, but HSPA+ is worse. It's generally agreed upon at Hofo that HSPA+ is a great fallback network.

That's probably because most users have moved on to LTE phones and have left HSPA+ uncongested. I live very close to a T-Mobile tower and HSPA+ is usually faster than LTE now. I get 18 Mbps on faux 4G while LTE gets around 16 Mbps.
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Not my experience at all with at&t. I can drop LTE at -115 to -120 where B17 is performing at 1-2mbps and HSPA+ is performing at 5-8mbps at -96 signal. If signal is weak, I generally get better speeds on HSPA+. You're probably right, in theory, but in practice HSPA+ usually outperforms slow LTE areas.

 

I cannot think of one area where LTE is weak and slow, but HSPA+ is worse. It's generally agreed upon at Hofo that HSPA+ is a great fallback network.

At my house, AT&T's LTE is at about -114 to -118 and speeds are approx 1.5 down while HSPA is at -104ish and latency tests usually fail. If I don't disable LTE, my iPhone will hold it down to -126 or so.

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Not my experience at all with at&t. I can drop LTE at -115 to -120 where B17 is performing at 1-2mbps and HSPA+ is performing at 5-8mbps at -96 signal. If signal is weak, I generally get better speeds on HSPA+. You're probably right, in theory, but in practice HSPA+ usually outperforms slow LTE areas.

 

I cannot think of one area where LTE is weak and slow, but HSPA+ is worse. It's generally agreed upon at Hofo that HSPA+ is a great fallback network.

That is so not the case in my area. In most cases if I'm indoors somewhere and fall off LTE, H+ is sluggish as hell. There's like two places I can think of where H+ actually does work better and that's it. Not to mention one of the 850 channels keeps jamming making nothing work, not even calls.

 

Let me put it this way, AT&T H+ works so poorly in my county that Verizon EVDO running on PCS makes it look bad. Chicago OTOH is the complete opposite, it works almost everywhere.

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  • 9 months later...

Networks which are fully 3GPP will use SIB 13 to maintain continuity across 2G/3G/4G carriers. In other words, although optimized LTE-to-eHRPD handover is possible, the opposite is not. [Tim will correct me here if that problem has been solved now, but if that were the case, you would expect VoLTE to have been launched by now as it has the same problem].

 

Just an update on this: Sprint has implemented ORNL recently for several of the more prominent devices on their network (iPhone for example), allowing the network to push a device from 3G to LTE. Maybe we'll start to see more changes soon ;).

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