1 research outputs found
On the Degrees of Freedom for Opportunistic Interference Alignment with 1-Bit Feedback: The 3 Cell Case
Opportunistic interference alignment (OIA) exploits channel randomness and
multiuser diversity by user selection. For OIA 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
degrees of freedom (DoF) per transmitter are achievable in a 3-cell MIMO
interference channel assuming perfect real-valued feedback. However, the
feedback of a real-valued variable still requires infinite rate. In this paper,
we investigate 1-bit quantization for opportunistic interference alignment
(OIA) in 3-cell interference channels. We prove that 1-bit feedback is
sufficient to achieve the optimal DoF in 3-cell MIMO interference channels
if the number of users per cell is scaled as . Importantly,
the required number of users for OIA with 1-bit feedback remains the same as
with real-valued feedback. 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. Using our new 1-bit feedback
scheme for OIA, we compare OIA with IA and show that OIA has a much lower
complexity and provides a better rate in the practical operation region of a
cellular communication system