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NV/LTE Breaking point(s)


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Ok so, who knows the numbers and wants to do the math?

 

What is the maximal consistent/sustained throughput of a fully completed standard sprint NV tower (not considering any backhaul limits)?

 

Let's assume we start with the current deployment makeup, then consider the effect (if any) of adding smr800 then lte800

 

- There are ho.w many RRU's in a standard deployment?

- Each RRU's max aggregated sustained throughput is?

- Max single subscriber sustained throughput is?

- Max number of subscribers able to be served (not necessarily at max sustained throughput) simultaniously per RRU?

- known bottlenecks in the chain that would affect either/or single or aggregate user experience?

 

 

What I am looking for is the # of subscribers and/or the sustained bandwidth point at which an NVE tower becomes over-saturated and starts degrading users experience.

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The breaking point in which overloading occurs could either be due to an overloaded carrier channel or overloaded backhaul. Cell splitting can take a single cell site broadcasting one carrier in all directions to a carrier that broadcasts several different carriers using the same spectrum. The addition of new channels effectively allows a cell site to become two sites operating in the same space adding further capacity. Backhaul has a set bandwidth according to the back haul provider which under ideal conditions is never exceeded.

 

cellsplitting.png

 

spectrume.png

 

Overloading occurs when a carrier channel is over burdened beyond it's capacity or the back haul link has to0 little bandwidth for the demand.

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For fiber-backhauled sites, backhaul can be taken out of the equation as a limitation. For microwave sites, you'd have to load things up pretty heavily to hit backhaul limits, but you could reach them one hop down the chain by putting three 5x5 carriers on each of three sectors and saturating those sectors (e.g. two PCS and one SMR). Still hard to do though, considering that we're talking about hundreds of megabits per second, more bandwidth than a residential cable provider (with DOCSIS 3) offers a comparable number of subscribers.

 

Realistically, to start with Sprint has one 5x5 LTE carrier per sector, and three sectors per site. In ideal real-world conditions, you get around 35 Mbps of bandwidth per sector on the download side, which in today's world is the side that you have to worry about (upstream capacity is 15 or so Mbps per 5MHz carrier). So that's 105M of capacity per cell, spread over whoever's in that cell (could be a mile radius, could be 2-3x that, could be one-third that).

 

If you add another 5MHz PCS carrier in, double those capacity numbers, spread over the same subscriber footprint. You may only need to do this on one sector, depending on load...35 Mbps (I've seen 32 Mbps down and 12 Mbps up on a speed test on Sprint LTE before) goes a long way in a smartphone-heavy mobile setting when no one is torture-testing their connection constantly.

 

If you add a 5MHz SMR carrier in, that's another 35 Mbps on that sector, though the additional range may give you more users on that carrier than on the others. But that can be balanced out with the proper network intelligence (people with better signals stay on PCS).

 

35 Mbps assumes two receive antennas and 64QAM modulation (six bits per Hz of frequency per second before error correction), which is reasonable for areas with good LTE service on any currently-available LTE phone. Higher data rates could happen if a phone and a base station had more antennas interfacing with each other (3x? or better MISO or MIMO rom the phone's perspective). But I doubt that will happen in the near future.

 

If you add in Clear TD-LTE, you have a ton of capacity per sector per channel, since there's 20 MHz of bandwidth that can be configured in a variety of download-upload ratios. If Clear configures it for 3:1, you've got the equivalent of a 15MHz FD-LTE carrier on the download side, plus a 5MHz carrier on the upload side. So similar upload speeds to the macro-cell network (using 16QAM modulation, which should still work at 2500/2600MHz for the distances we're talking about), but with download capacity in excess of 100 Mbps per channel, assuming two receive antennas and good signals on both (enough to do 64QAM).

 

Any more questions? :)

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