MD4452/4454 Dual and Quad Backhaul Configurations
MD4250 Two RadioMD4350 Three RadioMD4452 Four Radio Two DownlinksMD4454 Four Radio Four DownlinksMD4488 Four Radio Two AP radiosMD4355 Mobile Mesh NodeMD4455 Four Radio with Mobility ScannerUbiquiti Bullet, Mesh Enabled

MD4452 Four Radio Two Downlinks   
MD4454 Four Radio Four Downlinks


The capacity and “backhaul structure” of a mesh benefit from a root or relay nodes having multiple downlink radios. 
MD4452-AAIA  employs two backhaul downlinks to enable branching of the backhaul. It also has one uplink and one service radio.  In the illustration below, the use of multiple downlinks supports two separate mesh branches. If  a wired Ethernet link is attached to it, then the MD4452 configures itself as a root node and merges data from the two branches.
MD4454-AAAA has all four radios as downlinks. This dictates that the node can only be used as a root node - there are no uplinks so it cannot be used as a relay node also. The primary use of the MD4454 is to provide four separate branches of the mesh tree with each branch using a different type of antenna to support specific range/coverage (see below). Since each radio uses a separate 802.11a channel, the full TCP/IP throughput of each radio results in a total of 4X of each sub tree feeding into the root.