Coordinated SINR balancing techniques for multi-cell downlink transmission

In this paper, we consider the network multiple-input multiple-output (MIMO) where the base stations (BS) exchange only channel state information (CSI) to jointly design their transmission strategy. We particularly focus on a signal-to-interference-plus-noise ratio (SINR) balancing problem. First, the achievable rate regions with symmetric complex (SC) and asymmetric complex (AC) signaling techniques are invetigated. It is observed that the AC signaling shows a substantial gain over the SC signaling in terms of maximizing the worst-user rate as the system signal-to-noise-ratio (SNR) increases. After establishing the optimal SINR balancing algorithm with the SC signaling, we confirm the effectiveness of the AC signaling by proposing an efficient balancing scheme which outperforms the SC signaling scheme over all SNR regime.