I realize it depends on the megapixels, frame rate, etc
Technically, no, none of that matters. What matters is bitrate. Yes, bitrate is going to mostly be a factor of frame-rate and resolution, but the nanostation (like any piece of network gear) does not care at all about fps, just mbps.
Distance and obstructions between the unit can also affect maximum throughput, as will other wifi gear in the area.
For the units you're talking about in an average setting you should be able to get about 45Mbps throughput. With a little bit of consideration paid to the install (picking a clear RF channel, proper aiming, positioning away from walls), you can get about 50-55 Mbps. You likely won't ever see more than 60Mbps of real throughput without a lot of luck.
How many cameras you can carry over 45-50Mbps will vary based on the camera itself (see other tests IPVM has done for bandwidth), but you should be able to get about 5-8 cameras on that link.
Would be feasible to use two pairs of radios?
We have these deployed with 12 3MP and 4 D1 cameras on a single link. We cap our 3MP bitrate at 4mbps VBR. The D1 is capped at 1024kbps VBR. We haven't seen a single issue, but it is using a Dahua DVR, not a real VMS, so there isn't much as far as reporting issues. Last time I checked at night, we were not close to saturating that link. The distance for that link is under 100'.
We have a second location that uses the same radios with 3 3MP cams, again VBR 4mbps capped. These have a Dahua NVR, so again, reporting is minimal, but have yet to have any issues, other than needing one reboot in 3 years in service.
A third location was recently installed with 5 3MP VBR 4mbps capped per radio (two sets) and at that location we are running DW Spectrum. Have yet to receive a single email about network issues. If you're not familiar with DWS, it usually nags you about network issues often. This site has been very quiet. So much so I checked the logs to be sure.
We have run 5 X 4MP cams from 200' to two back to back radios easily accommodating them and no issues.
As of today we are running 7 on ptp nanos m2 1/4 mile from each other at 48dcbms, in a unpolluted 2ghz area.
Thanks for all the replies. As always the input is very helpful.
Just to confirm, real world one way throughput of Nanostation M5s over short distances is in the order of 50Mbit/s, as opposed to the figures touted by Ubiquiti. This is primarily due to the processor performance (can't handle higher packets per second). So bigger packets = larger throughput.
Ubiquiti have recently launched the Nanobeam family of units. Similar pricing to Nanostations but with 560MHz processors instead of 400MHz. These should offer a significant throughput improvement, although the hard upper limit will be set by the 100Mbit/s Ethernet port.
Not quite. Ubiquiti has slightly confused matter by (a) rebranding some products and (b) having one product range (PowerBeam) with two different throughput capabilities.
So to clarify:
The new NanoBeam M product range is effectively a direct replacement for Nanostations and Nanostation Locos. 5GHz only, small, low cost and fully integrated. The new model has better antennas with cleaner radiation patterns and faster processors than the old models. See Ubiquiti - NanoBeam® M
The PowerBeam range is intended for longer distance links. For 5GHz it has larger dishes (12 inch, 16 inch or 20 inch) delivering higher gain. Radios and dishes come as separate components that need to be fitted together and unit prices are higher. Throughput performance depends upon the model. The 12 inch and 16 inch variants have effectively the same radio and processor as the Nanobeam Ms, so maximum performance should be similar but with less dropoff over distance. PowerBeams also have gigabit Ethernet ports. The 20 inch variant has a better processor and the radio technology is based upon 802.11ac rather than 802.11n. This is the only variant for which Ubiquiti quotes a 450 Mbps throughput. Again what people have seen in the real world is a quite a bit lower but it is still in the order of 250 Mbps
To get the full radio rates of the ac product, you need a clear 80MHz channel. Assuming you are installing in the US, you might find that difficult given the small amount of spectrum you currently have available. So in practice you may be limited to 60 or 40 MHz. Nevertheless even at 40MHz you should be able to reach sustained user rates well in excess of 100 Mbps. So you are probably right to go with the flexibility offered by the Powerbeam. The larger dishes will also provide more directivity and hence greater isolation from external interference.
For the price there is no real alternative that will offer better performance. If you are willing to pay quite a lot more then you can move to carrier grade 5GHz point to point solutions such as Infinet Wireless or Cambium. The main advantages of these products are custom radio modules that provide more robust connectivity, better quality antennas and automated zero outage channel change in the event of interference.
The final option is to use millimetric (60GHz). Over a 200m distance the Siklu EH600 will provide reliable full duplex Gigabit capacity, all in a small package weighing around 4 pounds and costing around $5000 per link. Here in Europe the band is licence free - not sure of the rules in the USA.