Degrees-of-Freedom Based on Interference Alignment with Imperfect Channel Knowledge

Abstract

The impact and benefits of channel state information (CSI) are analyzed in terms of degrees-of-freedom (DoFs) in a K-user interference network operating over time-selective channels, where the error variance of CSI estimation is assumed to scale with an exponent of the received signal-to-noise ratio (SNR). The original interference alignment (IA) scheme is used with a slight modification in the network. Then, it is shown that the DoFs promised by the original IA can be fully achieved under the condition that the CSI quality order, represented as a function of the error variance and the SNR, is greater than or equal to 1. Our result is extended to the case where the number of communication pairs, K, scales with the SNR, i.e., infinite K scenario, by introducing the user scaling order. As a result, this letter provides vital information to the system designer in terms of allocating training resources for channel estimation in practical cellular environments using IA.

A low-complexity design for robust SINR fairness in MIMO interference networks

“…On the other hand, CSI uncertainty in the context of IA was addressed in several recent studies, e.g., [6]- [8]. To this end, achievable DoF was studied for a MIMO interference network, assuming that the CSI is estimated at the transmitter through channel estimation [6] or obtained at the transmitter via feedback from the receiver [7]- [8]. However, these studies focused on the original IA scheme that is optimal only at high SNR and did not consider SINR fairness among users.…”

Robust transceiver optimization for underlay device-to-device communications

“…In the context of MIMO interference networks, the achievable DoF with imperfect CSI was studied with the assumption that CSI is estimated through channel estimation at the transmitter side [13] or obtained via quantized feedback from the receiver [14]. The transceiver optimization problem considering SINR fairness for MIMO broadcast and point-to-point systems was discussed in [15]- [17].…”