Opportunistic interference alignment with 1-bit feedback in 3-cell interference channels

Opportunistic interference alignment (OIA) exploits channel randomness and multiuser diversity by user selection. The transmitter needs channel state information (CSI), which is usually measured on the receiver side and sent to the transmitter side via a feedback channel. Lee and Choi show that d degrees of freedom (DoF) per transmitter are achievable in a 3-cell MIMO interference channel assuming a fully informed network, where every user feeds back a real-valued variable to their own transmitter. This paper investigates the achievable DoF using only 1-bit feedback per user. We prove that 1-bit feedback is sufficient to achieve the optimal DoF d. Most importantly, the required number of users for OIA with 1-bit feedback remains the same as with real-valued feedback. Moreover, for a given system configuration, we provide an optimal choice of the 1-bit quantizer, which captures most of the capacity provided by a system with real-valued feedback.