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EV-DO over LTE at signal edge?


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There’s something that I’ve been curious about regarding a phone’s ability to run on LTE versus EV-DO.

 

That make me optimistic for LTE 800 in your area when it arrives in the future. LTE 800 should roughly be the same dBm signal strength as CDMA 800. However, it will start petering out between -90dBm and -95dBm RSSI. So anything in the 80's should be quite good.

 

So when LTE 1900 is deployed on your tower, it will not likely reach your house. But LTE 800 should. The only wild card are the devices.

 

Robert via CM9 Kindle Fire using Forum Runner

 

Yeah, I figured that much. I've gotten pretty good EVDO on 1900, over 2 meg, but from reading on here it sounds like LTE doesn't hold up quite as good on the fringe.

 

No, EV-DO tends to be the more robust airlink. So, all other factors being equal, LTE will likely have somewhat less range than will post Network Vision EV-DO. However, LTE coverage should be similar to pre Network Vision EV-DO coverage.AJ

 

I’ve been seeing posts like those I quoted above in various threads about how a phone will likely lose its LTE signal before its EV-DO signal. Since both EV-DO and LTE currently run on 1900MHz, why would LTE cut out before EV-DO? I read through the very informative article comparing RSSI and RSRP, but I may have failed to connect the dots.

 

I'm still irked that I can't latch onto this tower from my home a little over two miles away. But, with potential like this, I can wait.

 

Sent from my EVO using Tapatalk

This could be because of two reason. It seems that the LTE Signal threshold, certain dBm where LTE would connect and disconnect, was set very very high, and the new android update on Sprint phones is supposed to address that. Also, they might just have the tower in some sort of "test mode" where the tower won't broadcast a full strength signal...therefore you wouldn't be albe to get a signal probably more than 1000 yards away.

 

(nothing I just said has been verified, its just my educated guess)

 

Could it have something to do with this? Granted, this threshold was probably set high because it was a test site, but it sounds like Sprint could theoretically set a less extreme threshold once LTE is fully deployed. The only other thing I could think of might have to do with how the data is handled. Would data transferred over LTE be more sensitive to some kind of packet loss?

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My favorite quote on this :)

 

Reports are that VZW is deploying LTE 750 for coverage breadth first, density second. So, only some sites get LTE overlay the first go round. If that is true in a given area, then LTE to EV-DO cannot be an apples to apples coverage comparison -- at least, not yet.

 

That said, my expectations for LTE have tempered somewhat from empirical observation of VZW's and Sprint's LTE roll outs. LTE does seem to be a more fragile airlink than does EV-DO. And that is almost to be expected, as LTE is made up of hundreds of small subcarriers that, individually, are not as robust as is a single spread spectrum carrier.

 

Now, maybe the disparity is a function of devices that are still relatively early in the LTE development cycle. After all, EV-DO development is going on a decade, is now very mature. So, newer LTE devices may continue to improve radio performance. But I do think that we have to consider the real possibility that Sprint's LTE 1900 will usably cover only 80-90 percent of the underlying CDMA1X/EV-DO 1900 footprint.

 

AJ

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Because the LTE signal is more fragile and cannot push data on a weak signal like EVDO can.

 

The LTE signal and EVDO signal strength should be the roughly the same at the same distance from the tower (if you are measuring both in RSSI).

 

However, LTE will stop being effective around -95dBm and EVDO will be able to work until approximately -105dBm. So if you are standing in a place with a -100dBm EVDO signal, you would also have a -100dBm LTE signal. But your device will probably not show LTE in your signal indicator because it cannot connect and be useful at that strength.

 

Does that make sense?

 

With LTE 800, the -95dBm threshold will be farther out from the site than LTE 1900, giving more coverage.

 

Robert via Samsung Galaxy S-III 32GB using Forum Runner

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Because the LTE signal is more fragile and cannot push data on a weak signal like EVDO can.

 

The LTE signal and EVDO signal strength should be the roughly the same at the same distance from the tower (if you are measuring both in RSSI).

 

However, LTE will stop being effective around -95dBm and EVDO will be able to work until approximately -105dBm. So if you are standing in a place with a -100dBm EVDO signal, you would also have a -100dBm LTE signal. But your device will probably not show LTE in your signal indicator because it cannot connect and be useful at that strength.

 

Does that make sense?

 

With LTE 800, the -95dBm threshold will be farther out from the site than LTE 1900, giving more coverage.

 

Robert via Samsung Galaxy S-III 32GB using Forum Runner

 

Offsetting that a little, considering the total changes effected by NV relative to legacy EVDO, I have read here that the radiated power should be about "20 percent" higher due to the proximity of the radio to the antenna. And presumably there is a similar improvement in the tower's receive strength since the coax losses go away there, too. But if that "20 percent" is a linearly absolute change in wattage, it would only amount to about one decibel. Am I right about interpreting that?

 

BTW, I will be a natural test subject for all of this theory when LTE finally comes to Austin. At my desk these days, my RSSI dBm levels vary a few decibels up and down from -95.

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Offsetting that a little, considering the total changes effected by NV relative to legacy EVDO, I have read here that the radiated power should be about "20 percent" higher due to the proximity of the radio to the antenna. And presumably there is a similar improvement in the tower's receive strength since the coax losses go away there, too. But if that "20 percent" is a linearly absolute change in wattage, it would only amount to about one decibel. Am I right about interpreting that?

 

BTW, I will be a natural test subject for all of this theory when LTE finally comes to Austin. At my desk these days, my RSSI dBm levels vary a few decibels up and down from -95.

 

I've seen it written somewhere that the maximum anticipated NV gain ever to be experienced in ideal situations is 3dBm over legacy 1x/EVDO to NV 1x/EVDO. Since the maximum threshold between LTE and EVDO is approximately 10dBm (between -95dBm and -105dBm RSSI), this will be far different than the maximum 3dBm difference between legacy and NV. So, therefore, we can anticipate LTE 1900 should offer less coverage than legacy EVDO. If you use Cloud RF to model the difference, in an ideal flat area, you get about a one mile difference on a 300' boomer with no downtilt.

 

So I think LTE 1900 coverage should be quite good in most urban/suburban locations, except in those places with poor site spacing (like Baton Rouge). But tertiary and rural markets will look like LTE swiss cheese until LTE 800 arrives toward the end of 2013.

 

I appreciate your offer of being a S4GRU guinea pig.

 

Robert

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I've seen it written somewhere that the maximum anticipated NV gain ever to be experienced in ideal situations is 3dBm over legacy 1x/EVDO to NV 1x/EVDO.

 

That seems very reasonable. I have seen a 3-6 dB figure quoted as typical loss each way from sending modulated RF via coax up/down the physical tower. If Sprint can reduce or eliminate that loss by using RRUs and sending unmodulated digital data via coax or fiber up/down the physical tower, a 3 dB gain on each half of the link budget seems tenable.

 

AJ

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I've seen it written somewhere that the maximum anticipated NV gain ever to be experienced in ideal situations is 3dBm over legacy 1x/EVDO to NV 1x/EVDO. Since the maximum threshold between LTE and EVDO is approximately 10dBm (between -95dBm and -105dBm RSSI), this will be far different than the maximum 3dBm difference between legacy and NV. So, therefore, we can anticipate LTE 1900 should offer less coverage than legacy EVDO. If you use Cloud RF to model the difference, in an ideal flat area, you get about a one mile difference on a 300' boomer with no downtilt.

 

So I think LTE 1900 coverage should be quite good in most urban/suburban locations, except in those places with poor site spacing (like Baton Rouge). But tertiary and rural markets will look like LTE swiss cheese until LTE 800 arrives toward the end of 2013.

 

I appreciate your offer of being a S4GRU guinea pig.

 

Robert

 

For what it is worth (probably not much) but I read a report saying 2dB from Sprint installing new/modern antennas + 3dB from Sprint switching to RRU's.

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Wow, this is all great info, thanks! Using Netmonitor, my signal seems to be fluctuating between -88 and -96dBm while at work, which seems to be in-line with what "Rx Power" reads under "1X Engineering." However, my power under "EVDO Engineering" seems to be a little lower, more in the -91 to -97dBm range.

 

According to something else I read, it's not LTE itself that really drains battery power, it's switching back and forth from LTE to EV-DO. Given that -95dBm is likely where it will switch (from what I understand), wouldn't people who are operating in that area likely to see battery issues if they have their phone on LTE/CDMA mode?

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Check your PN offsets. You sound like you may be idling on different CDMA1X and EV-DO sites.

 

AJ

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Check your PN offsets. You sound like you may be idling on different CDMA1X and EV-DO sites.

 

AJ

 

Under 1X Engineering, I’m seeing something that just says “PN,” and under EVDO Engineering, I’m seeing “Active Set Pilot PN.” These are the only things I could find that refers to pseudo noise, and they both read 9.

 

On a side note, what does “RX Signal Strength” refer to under EVDO Engineering? It’s usually in the range of 90-100 with no unit, and there’s no negative sign in front of it. It seems to move independently of “Rx Power” (which sits at -0.50dBm when my 3G icon is inactive).

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When LTE 800 arrives, could someone explain how it will work? Will 1900 be phased out or will there be signal at both frequencies? If so, which signal will a particular phone use and how it is decided?

 

Thanks.

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Check your PN offsets. You sound like you may be idling on different CDMA1X and EV-DO sites.

 

AJ

 

Are different sites on evdo and 1x necessarily bad? I have seen that happen more then once, especially when your phone is receiving two distant sites at about the same signal strength, especially if their are a lot of evdo users on one tower.

 

 

Sent from my EVO LTE

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When LTE 800 arrives, could someone explain how it will work? Will 1900 be phased out or will there be signal at both frequencies? If so, which signal will a particular phone use and how it is decided?

 

Thanks.

 

Signal will be available on both frequencies, along with 2500/2600Mhz in hot spot areas. You device will have thresholds where it will jump from one frequency to another. Might be related to a lack of signal or the carriers might be overloaded.

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When LTE 800 arrives' date=' could someone explain how it will work? Will 1900 be phased out or will there be signal at both frequencies? If so, which signal will a particular phone use and how it is decided?

 

Thanks.[/quote']

 

Signal will be available on both frequencies' date=' along with 2500/2600Mhz in hot spot areas. You device will have thresholds where it will jump from one frequency to another. Might be related to a lack of signal or the carriers might be overloaded.[/quote']

 

And most likely the priority will be 1900 > 800 > 2600.

 

Although, it may also be 1900 > 2600 > 800. In this scenario, it would likely only go from 190 to 800 when 1900 capacity starts to fill.

 

Robert via CM9 Kindle Fire using Forum Runner

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Hopefully Sprint will fully acquire Clearwire in the next two years and make 2600 the priority where available and fill up that high capacity carrier first...

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Hopefully Sprint will fully acquire Clearwire in the next two years and make 2600 the priority where available and fill up that high capacity carrier first...

 

Agreed. Ideally, the priority order should be 2600 > 1900 > 800.

 

Robert via CM9 Kindle Fire using Forum Runner

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Agreed. Ideally, the priority order should be 2600 > 1900 > 800.

 

Robert via CM9 Kindle Fire using Forum Runner

 

I was thinking the exact same thing, mainly because 2600 will have a smaller footprint per site than 1900, and same with 1900 vs 800. The key here will be how all the thresholds are configured so devices aren't hanging onto the higher frequencies for dear life before switching down to a lower frequency. Sprint really has a huge trump card against the other providers for coverage, and they need to play it right. ;)

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As long as Clearwire remains separate from Sprint, I would not expect Sprint LTE mobiles to be able to select Clearwire TD-LTE of their own volition. In fact, Clearwire LTE will probably utilize a different MNC (the 3GPP equivalent of SID). As such, a Sprint LTE mobile will always utilize the Sprint network unless a Sprint eNodeB redirects it to to the Clearwire TD-LTE offload network. In other words, the mobile will not decide when to offload to Clearwire; Sprint will call the shots.

 

AJ

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As long as Clearwire remains separate from Sprint, I would not expect Sprint LTE mobiles to be able to select Clearwire TD-LTE of their own volition. In fact, Clearwire LTE will probably utilize a different MNC (the 3GPP equivalent of SID). As such, a Sprint LTE mobile will always utilize the Sprint network unless a Sprint eNodeB redirects it to to the Clearwire TD-LTE offload network. In other words, the mobile will not decide when to offload to Clearwire; Sprint will call the shots.

 

AJ

 

Yes, this is the most likely scenario. :(

 

Robert

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An intriguing albeit unlikely possibility is that Sprint could use a separate MNC for LTE 800, too.

 

AJ

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As long as Clearwire remains separate from Sprint, I would not expect Sprint LTE mobiles to be able to select Clearwire TD-LTE of their own volition. In fact, Clearwire LTE will probably utilize a different MNC (the 3GPP equivalent of SID). As such, a Sprint LTE mobile will always utilize the Sprint network unless a Sprint eNodeB redirects it to to the Clearwire TD-LTE offload network. In other words, the mobile will not decide when to offload to Clearwire; Sprint will call the shots.

 

AJ

 

Sprint and Clearwire had an interesting discussion of how their new network would integrate. They seem pleased that there were formal 3GPP standards that allowed for "mock" sites allowing a clearwire site to look like a sprint site. I don't really understand the technical aspects but it seemed like as far as network, hand-offs, and all other things that would seem to be a problem with two separate networks are gone (so they say).

 

webcast:

http://cc.talkpoint.com/well001/071812a_hr/?entity=1_X5JEDJ6

 

It's pretty interesting - did you get a chance to listen to it?

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