On the sum capacity of the Y-channel
Anas Chaaban, Aydin Sezgin, A. Salman Avestimehr · 2011
A model where three users communicate with each other via a relay is considered. Users do not receive other users' signals via a direct link, and thus the relay is essential for their communication. Each user wants to broadcast one message to each other user. The sum-capacity is studied, and upper bounds and lower bounds are given. If all nodes have the same power, the sum-capacity is characterized to within a gap of 2 bits or a factor of 4 for all values of channel coefficients.