I want to show some results we got from an install the other day, while also asking if we are understanding the results of the Link Status page. This is a 3.65 SM using 10mhz, at a distance of 6.5m using a reflector. We have been told that if we tried to put a 20meg profile on a link like this is would cause problems and use up more capacity at the tower becuase of the distance and it not having a signal strength of at least -64. From what we understand by looking at these photos, we think we could get a 20meg subrscriber to work on this link. SSR is at 0, beacons 100%, link test showing 30meg download, up and down efficiency at 100%, 8x/6x mimo and using a configured 20meg SM we ran a speed test and were able to get our profile.
What is a good SNR to have when looking at a link?
Whats a maximum distance you would install a high bandwidth profile, or is it all based on the results we are seeing below?
What are we seeing from the Receive Fragments Modulation (good or bad)?
Do you think this particlar link could hold a 20 meg profile and the customer see no issues and we would not be hurting our selves at the tower putting 20meg on that far out?
I assume you mean 6.5 km or 6.5 miles (not meters)... right?
In either case, I think you'd be safe to offer a 20 Mbps plan to this customer. The sector capacity is dependent on how much data is actually used, not the plan they are allowed. So, if you think this customer would consume the maximum bandwidth they are allowed all the time, it may be slightly riskier, but in my opinion, I would allow this.
From the screens you've provided, it looks like this SM is in 6X modulation most of the time, so he's doing fairly well, and the overall sector capacity (if ALL SMs are in 6x modulation) would be about 95 Mbps. If you factor an oversubscription rate into that total capacity, you can estimate approximately how many subscribers you can adequately service at various package speeds.
There's a very old (but still pertinent) discussion here, and another much more recent discussion here.
A good reference for the impact to the sector is the knowledge base article on the shared sector capacity concept here.
So the higher the mimo is working at is equal to less work actually being done at the AP meaning more subscribers?
We are stuck using a system with Localoop, based on their model we were told to expect (15) 20meg, (22) 10meg and (13) 4meg subscribers on each ap using 3.65 at 10mhz. We currently have a 100/100 DIA Fiber but can add more easily. Does that sound about right?
In essence, the higher the modulation the SM operates in, the faster the AP can complete its transmissions to that SM, "freeing it up" to complete transmissions to other SMs requiring it.
So, not really "less work" but "less time" dedicated to complete the data transfer.
One way to look at a model like that is this (I made some assumptions on Uplink expected throughputs):
15 * (20+3) + 20 * (10+2) + 13 * (4+1) = 674 Mbps
If ALL of the SMs on a given AP are in 6X modulation or better, you'll have ~90 Mbps capacity at any given point in time.
674 / 90 = 7.5
This 7.5 represents your "oversubscription rate". Meaning, that if ALL 48 SMs wanted their maximum rates ALL the time, you wouldn't be able to support it, but 7.5:1 oversubscription is very reasonable (and in my opinion, very conservative).
You can also model this using the PMP 450 Capacity Planner R14.1 v2 Tool, by inputting various SMs into the sector, to give you an estimated capacity. Then you can perform similar calculations to arrive at an oversubscription rate, given the capacity outputted from the tool (using actual subscriber modulations). If the number seems reasonable, then you should be good to go. Of course, different providers can tolerate different levels of oversubscription, and I invite folks with more direct experience in this field to comment further.
So when im told you can only use a 20meg with an signal strength of -64 or better thats just to ensure we are working on 8x, but even on 6x seeing results like we had that link is perfectly fine and wont degrade the network that much.
What SNR's do we need to be looking for?
I will try and play around with the Link Planner. Unfortunately, since Localoop is in "control" I dont have the exact info of how our Live network is built so I cannot build a model of what we have and see what we are actually capable of. You did however nail the upload throughputs!
With those figures stated (in your opinion), what is an oversubscription rate thats not conservative but say no more than 75%-80% to ensure we wont have customer issues. We are killing another company becuase they are so oversold and we never want our customers to talk about us like they do them.
For 3.65 on a 10 MHz channel, the following table is accurate:
Modulation Mode
Sensitivity (dBm)
T-put (Mbps)
CNR (dB)
256QAM (8x)
-66
125
32
64QAM (6X)
-73
90
24
16QAM (4X)
-80
60
17
QPSK (2X)
-86
30
10
QPSK (1X)
-86
15
8
The Carrier to Noise Ratio (CNR) is equivalent to the Signal to Noise Ratio (SNR) for this purpose. The reported values in the radio can vary given rf conditions present at the time of testing, but anything above 24 should be operating in 6X mode, which is consistent with the screen shots you shared in the first post.
The rule of thumb of -64 dB RSL is valid for 8x, when combined with the 32 CNR, meaning that you're at least 32 dB higher than the noise floor (i.e. the noise floor is -96 dB or better). In actual operation, it's tough to always ensure that ALL SMs are operating at maximum modulation. More often, we see customers that have a 6X acceptable deployment strategy, and base the sector capacity on this level.
With respect to your oversubscription rate question, we have seen values all over the map. Some operators are more tolerant than others, and the number you settle on usually comes through experience. Again, my opinions is that most providers should be able to tolerate 10:1 or even 12:1 without incurring the wrath of angry customers, but your mileage may vary.
