small changes for multi usrp support
It turns out that our usrp_lib.cpp can be used also with multiple USRPs extending the number of antenna ports we can use or allowing for distributed deployments. Assuming that the USRPs are synchronized by an external source or gps, simply specify sdr_addrs = "addr0=192.168.10.2,addr1=192.168.30.2,clock_source=external,time_source=external"; in the RU section. If you want to use only one channel of each USRP also specify the subdevice tx_subdev = "A:0"; rx_subdev = "A:0" There was only one minor fix in the usrp_lib.cpp needed to allow for this config.