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On path to gigabit LTE, Sprint moving upload/download configuration closer to 12-1 traffic ratio

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6.2.1 BS–BS coexistence in case of unsynchronized LTE-Advanced TDD systems:

Unsynchronized LTE-Advanced TDD systems may co-exist in adjacent spectrum blocks by applying one or more of the following measures to reduce interference between base stations:

•Frequency separation: Interference into the networks of adjacent operators may be decreased by introducing guard bands. In this report it is not studied in detail how large such a guard band would need to be, though it is clear from previous studies (Reports ITU-R M.2146 0 [12], and ITU-R M.2113 0 [15]) that if this is used as a stand-alone solution, a large amount of spectrum would remain unused.

•Additional filtering and appropriate guard band: Additional filters may substantially reduce interference by decreasing the unwanted emissions from the transmitter and improving the selectivity on the receiver side. A guard band between spectrum used by adjacent operators is then necessary to allow for sufficient filter roll-off. The required size of such a guard band would depend on the necessary additional isolation and the ability of the filter. According to the analysis in this report, such filters would need to provide additional isolation in the range 36-73 dB, depending on the interference scenario (propagation environment and isolation available because of other considerations than the filter e.g. site-coordination, antenna characteristics).

•Co-ordination among network operators: Site engineering techniques such as transmitter antenna tilting, selection of antenna direction and careful deployment planning may reduce interference. However, it could be very difficult to implement practically as different operators may have different user distribution patterns, growth patterns, business and operational plans.

•A combination of the above

6.2.2 UE–UE coexistence in case of unsynchronized LTE-Advanced TDD systems:

The analysis indicates that interference may occur when the UEs are in close proximity but that for most scenarios this interference will occur rarely. For UEs, additional filters are not a realistic means for reducing interference.

 

 

Looking at the High Band Spectrum Depth map, Sprint owns 148-186MHz of high band spectrum in most major urban areas. Looking at the report I found on the study of "Coexistence of two time division duplex networks in the 2300-2400MHz band", using the same frequency separation practices, wouldn't Sprint be able to use some of the excess spectrum as guard bands to reduce the interference between a PCC (Config 1) and the SCC(s) (Config 2)? Using the current practices of the synchronous TDD-LTE system, each surrounding PCC would already be synchronized to each other and the SCC(s) would be synchronized as well to each other. This wouldn't need to be a nationwide concern as rural and most suburban settings could switch as a whole from Config 1 to Config 2 without introducing the asynchronous interference problems.

 

I realize this is all conceptual and spectrum would need to be contiguous (as pointed out above), but with the current use of 3CA it's evident that there are cases of that existing. Assuming the spectrum puzzle pieces align allowing multiple CA, would this scenario not be a viable option? Also, would HPUE help mitigate some of the UE-UE interference due to a wider flexibility of power output?

 

https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-M.2374-2015-PDF-E.pdf

http://www.fiercewireless.com/wireless/2017-how-much-low-mid-and-high-band-spectrum-do-verizon-at-t-t-mobile-sprint-and-dish-own

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Looking at the High Band Spectrum Depth map, Sprint owns 148-186MHz of high band spectrum in most major urban areas. Looking at the report I found on the study of "Coexistence of two time division duplex networks in the 2300-2400MHz band", using the same frequency separation practices, wouldn't Sprint be able to use some of the excess spectrum as guard bands to reduce the interference between a PCC (Config 1) and the SCC(s) (Config 2)? Using the current practices of the synchronous TDD-LTE system, each surrounding PCC would already be synchronized to each other and the SCC(s) would be synchronized as well to each other. This wouldn't need to be a nationwide concern as rural and most suburban settings could switch as a whole from Config 1 to Config 2 without introducing the asynchronous interference problems.

 

I realize this is all conceptual and spectrum would need to be contiguous (as pointed out above), but with the current use of 3CA it's evident that there are cases of that existing. Assuming the spectrum puzzle pieces align allowing multiple CA, would this scenario not be a viable option? Also, would HPUE help mitigate some of the UE-UE interference due to a wider flexibility of power output?

 

 

For one. There is spectrum gaps around 2568-2572 and 2614-2618 that kills continuity. The hodgepodge of EBS and BRS spectrum means that a market may have 100+ mhz of spectrum but how much of that is contiguous and usable for 15 / 20 MHz carriers? 

 

Sprint is deploying B41 carriers on B41HL (2500-2570 or 2620-2690) with small cells taking up the L or H (--> 40 MHz) portions depending on what the macro cells are deploying. Let's just say sprint has a contiguous 120 MHz from 2500-2560 and 2620-2680. 60 MHz is taken up by macros and 40 MHz is taken up by small cells. Then add in high capacity 2.5 sites which may broadcast up to 120 MHz from one radio antenna setup. 

 

So where do you get the spectrum needed to create the substantial guard bands which the white paper theorized? 

 

In addition in 3GPP Rel 14 36.300, this is stated, "For TDD CA, the downlink/uplink configuration is identical across component carriers in the same band and may be the same or different across component carriers in different bands."

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This all seems like a lot of work to get a horse with different size wheels on it's carriage.

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It seems like it would be better in the long run to get ca with b25/26 being the pcc and b41 scc than mess with trying to deploy different tdd configurations in the same market using huge swaths of spectrum as guard bands that could otherwise be utilized.

 

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For one. There is spectrum gaps around 2568-2572 and 2614-2618 that kills continuity. The hodgepodge of EBS and BRS spectrum means that a market may have 100+ mhz of spectrum but how much of that is contiguous and usable for 15 / 20 MHz carriers? 

 

Sprint is deploying B41 carriers on B41HL (2500-2570 or 2620-2690) with small cells taking up the L or H (--> 40 MHz) portions depending on what the macro cells are deploying. Let's just say sprint has a contiguous 120 MHz from 2500-2560 and 2620-2680. 60 MHz is taken up by macros and 40 MHz is taken up by small cells. Then add in high capacity 2.5 sites which may broadcast up to 120 MHz from one radio antenna setup. 

 

So where do you get the spectrum needed to create the substantial guard bands which the white paper theorized? 

 

In addition in 3GPP Rel 14 36.300, this is stated, "For TDD CA, the downlink/uplink configuration is identical across component carriers in the same band and may be the same or different across component carriers in different bands."

Any TDD configurations must be identical or separated enough that it doesn't cause catastrophic interference.

 

You cannot run adjacent tdd carriers using different frame configurations without substantial interference.

 

 

 

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Mixed with the continuous reminder on the current contingencies for carrier aggregation, your first point almost argues against the ability for carrier aggregation at all with your mention of a lack of contiguous spectrum. There are already locations that have valid 2CA and 3CA operating. The discussion was in regards to changing the configuration of components in those areas from 1 to 2.

 

The scenario you set up is asserting that small cells are currently present. That is a perfect example of where this can NOT work, yes, but is also heavily dependent upon small cells being present and currently they seem to be an exception rather than the rule for several markets. Now each of my posts has stated this is all "theory" and "conceptual", yet instead of discussing the possibilities you have merely demonstrated why it is currently not capable in your example. Is this thread not "On path to gigabit LTE..."? Interestingly, I see you also edited your previous post to remove your suggestion to look up white papers on the coexistence of TDD. There has been a more recent one done by GTI that discuses the path towards dynamic TDD, found below. An advantage brought up that I've never thought of is how switching to a configuration highly favoring uploads (most likely at night) allows the site to lower its power consumption.

 

http://lte-tdd.org/Resources/rep/2016-09-06/9424.html

IMG_1240.PNG

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The scenario you set up is asserting that small cells are currently present. That is a perfect example of where this can NOT work, yes, but is also heavily dependent upon small cells being present and currently they seem to be an exception rather than the rule for several markets. 

Small cells may be in more places than you think. Not sure what you are defining as "markets" if it is cities or our definition of markets. A lot of markets (the term we use as sprint markets)have small cells. Just think Pittsburgh, Cleveland, Columbus, and Cincinnati all have small cells. Those can't all be "main" markets I know the Pittsburgh market had a lot of GMOs that just started getting LTE.

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