Sample synchronization among diffrent USRP2s with seperate gigabit ethernet ports

Hi GRers,

We are planning to build a wideband MIMO system with 2 or more USRP2s.
Acording to the configuration in
a MIMO cable or HUB is used for connecting multiple USRP2s and just one
ethernet interface is used for connecting to host computer. The problem
data from multiple USRP2 is sharing the ethernet bandwidth which will
certainly be a bottleneck limiting the maximum available bandwidth.
What we are considering is parallelly use all the ethernet interfaces on
USRP2s for delievering sample to host computer. I guess for receiver
this can be done through use common 10MHz clock reference and 1PPS time
reference as well as timestamping the samples in FPGA. (Has this
timestamping already been done? How to use it on host computer?)
How about on transmitter side? How to synchronize the samples sent to

Thanks in advance.