What would you like to do?
Have you read this post?
http://community.cambiumnetworks.com/t5/Licensed-Microwave/LAG-options-for-PTP-820S/m-p/72222#M559
You can use external switches to do the traffic combining, you can use internal LAG, or you can use MC-ABC.
Each of these options has tradeoffs:
MC-ABC combines the traffic at Layer 1 and is the most efficient way to use the channels. (Depending upon the configuration and the traffic, LAG may allow one link to be fully utilized while the other link is under utilized. LAG doesn't necessarily guarantee even traffic distribution.)
There's no additional cost with internal LAG. External LAG requires two drop cables per end, one for each link.
I hope this helps!
Dave