I've now had a chance to test PMP450i 900MHz in a few different settings. The first setting I'll be talking about is a worse case scenario. This is a 1.4 mile completely non-LOS shot through multiple evergreen (Ponderosa) and deciduous (some sort of Elm I think) trees. Along with the trees, I'm also dealing with noise spikes from both paging and water meter systems on every channel at around -65dBm or worse. This is a lite urban environment of around 80k people.
From my house:
From the repeater site:
I've tried various links over the years... back in 2009 I used a Canopy 900MHz/FSK link with great results, only problem was that it was limited to around 6mbps aggregate (the maximum available)... and while stable, wasn't enough bandwidth. So the hunt continued. I had tried to use PMP450 3.65GHz using a 2' dish and could not get an SM to register, so no dice. I ended up buying some licensed 2.5GHz radios from Radwin and while it worked OK at times, it sometimes would have had huge swings in signal strength from -68dBm to -85dBm depending on the amount of foliage in the trees and rain/snow in the trees. The licensed 2.5 link would swing from being completely disconnected to getting about 40mbps HDX (using a 20MHz channel width no less!) at it's best. It was very unreliable, the link would fail over to my backup connection (gasp!) a poached WiFi backup through a coffee shop next door to me. I guess I should also mention this is my house... yes MY OWN HOUSE! I'm not sure why I keep choosing to live in places with poor LOS to my own service... I'm a glutton for punishment I guess, but that's also what I like about what I do... that's the whole reason I started this business was to play with new technology and figure out how to get myself the best service given the circumstances. If I can find some new radios that perform well given my horrible circumstances, and I can use it day in day out and be happy with it, I know that my clients will be happy too.
So back to the review... I'm using a point to point type configuration, with a Cambium PMP450i 900MHz AP on one side attached to a 12dBi yagi (N009045D003A), and a PMP450 900MHz SM attached to a 12dBi yagi on the other side. I'm using a 10MHz channel width. I tried a 20MHz channel width and could never get it to connect reliably with the amount of noise I'm experiencing. I also tried 5MHz, and 7MHz channel widths, and after extensive testing, given the noise floor issues, I settled on 10MHz as having the best bang for the buck. I also did some testing with 5ms vs. 2.5ms frames, and I ended up choosing 5ms frames, as I didn't see a huge difference in latency, and I prefer having a bit more bandwidth. It's the difference of like maybe 10% more bandwidth on average vs 10ms less latency.
As I've mentioned, every single channel has noise spikes of -65dBm or greater on a regular basis and you can see them happening on every refresh in a SA. We had a bet in the office that given the non-LOS issues and the noise spikes, that this link either wouldn't work at all, or would be taken down a few days after it was put up. After a few days of use, it was apparent that the link was solid and would remain in place. On link evals I typically get around 30mbps aggregate, and real world speed tests I see 25mbps or more every time. Latency is pretty good, despite the huge jumps in the noise floor. Not seeing any dropped packets, and if I switched to 2.5 ms frames, I could do some competitive gaming. I use VoIP and Skype regularly on this connection and whether it's 2.5 or 5ms, it works fine... jitter is the main killer for VoIP, and jitter isn't bad considering the overall poor conditions of this link.
It's been about a month now and I use it every day... so I can safely say that I won the office bet! Thank you to the folks at Cambium (you know who you are) for listening to your customers and investing time and money to develop a truly worthy successor to the tried and true 900MHz FSK radios! You guys have a winner on your hands!
Local Speedtest.net from my office server:
Latency & Jitter to our office servers using 1450 byte ICMP: