We consider different scenarios for K-user relay-aided 
multiplexing of uplink and downlink communications, in 
the presence of interference.
The scenarios relate to the practical setup where 
a set A of K users uplinks to a base station B that downlinks 
to another set C of K-users, in the presence of an assisting 
relay R, in the presence of interference between the independent 
users in A and C, and under a global half-duplex constraint.  
In these settings we derive the  optimal region for the 
degrees-of-freedom, and then meet this region using simple 
interference neutralization and channel orthogonalization techniques.