I'd jokingly talk with the Cambium guys about when we finally can get some Xeon 
processors in our AP's. Imagine.... 

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From: "af" <af@af.afmug.com> 
To: "af" <af@af.afmug.com> 
Cc: "matt mangriotis" <matt.mangrio...@cambiumnetworks.com> 
Sent: Friday, October 23, 2020 9:32:44 AM 
Subject: Re: [AFMUG] [ External ] Re: 450 and 450i AP CPU limit on throughput? 



The original 450 AP and SM were roughly the same PPS, and had similar limits… 
the AP having more FPGA gates, it has some additional resources to handle more 
things. In practice, in a typical network with mixed packet sizes, this ends up 
around 55-60 Mbps in a 20 MHz channel (PPS did improve over time going from 13k 
when they were first released, to ~20k these days… but we reached the limit of 
what those chips could do). 



The good news is that 450i, 450b and the new MicroPoP radios are all built 
using a next generation FPGA (SoC), which has embedded ARM processors, and with 
Release 20, we’ve unlocked some serious gains in PPS on these bad boys… 
effectively increasing PPS by 250% or more (from ~40k to >100k). If it’s a 
budget-constrained site, I might suggest a MicroPoP as an upgrade, depending on 
how many SMs you need to serve (and how far away they are). 



Standards-based chipsets have a distinct advantage in this area because the 
MAC/PHY is baked into the ASIC chip and does what it does very well… but limits 
the flexibility on what can be done. With our current approach, nearly anything 
is possible given time and resources, because everything down to Layer 1 is 
coded into that FPGA… but it adds a bit of cost. 



Matt 




From: AF <af-boun...@af.afmug.com> On Behalf Of Ken Hohhof 
Sent: Friday, October 23, 2020 8:21 AM 
To: 'AnimalFarm Microwave Users Group' <af@af.afmug.com> 
Subject: [ External ] Re: [AFMUG] 450 and 450i AP CPU limit on throughput? 




Not talking about sustained speed keys (finally gone in the 450b) but the point 
at which you haven’t maxed out the RF capability but the CPU horsepower becomes 
the limiting factor and you can’t get any more pps through it. I think the SMs 
also have this issue, but less likely to be a problem unless using them in PTP 
mode or having a small number of very high bandwidth customers. 



Or maybe you are saying the APs never had the CPU limitation like the SMs, but 
I’m pretty sure they did. Each generation 450, 450i, 450m having a more 
powerful CPU. Although not as powerful as we might think from the price, I 
guess maybe the result of using a processor core in an FPGA, it seems like 
lowly WiFi chips have more CPU power. I think most of us were surprised to find 
the limitation could be CPU not RF. 




From: AF < [ mailto:af-boun...@af.afmug.com | af-boun...@af.afmug.com ] > On 
Behalf Of Adam Moffett 
Sent: Friday, October 23, 2020 6:42 AM 
To: [ mailto:af@af.afmug.com | af@af.afmug.com ] 
Subject: Re: [AFMUG] 450 and 450i AP CPU limit on throughput? 




I thought the limitation was on what a single SM did. 

.....maybe mistaken. 




On 10/23/2020 12:14 AM, Ken Hohhof wrote: 




Does anyone know off the top of your head what the current CPU limited max 
throughput is for 450 vs 450i APs? Not based on RF characteristics but packet 
processing in the CPU. 



I keep thinking at one time 450 APs were only capable of maybe 20 Mbps but that 
can’t be right because I have some doing over 40. I think Cambium said that 
firmware tweaking kept raising that number. 



I’m asking because I have one lone site with a 450 and an omni, and maybe a 
dozen subs scattered through the entire 360 degrees. So while I am going to 
need more throughput, it just doesn’t justify 4 sectors, and the cables are in 
conduit and I think we only ran 4 cables and we have 2 backhauls. And it occurs 
to me what I need isn’t sectors, it’s to increase the channel width to 30 MHz 
(450) or 40 MHz (450i). But will a 30 MHz channel really help if the 450 AP is 
pps limited by the CPU? I’m OK with replacing the 450 with a 450i if necessary. 
Most sites we have at least 4 sectors, so mostly 20 MHz channels. But an omni 
with a 40 MHz channel would use the same amount of spectrum as 4 sectors and 20 
MHz channels. 





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