In this paper, we derive asymptotic expressions for the ergodic capacity of the multiple-input multiple-output (MIMO) keyhole channel at low SNR in independent and identically distributed (i.i.d.) Nakagami-$m$ fading conditions with perfect channel state information available at both the transmitter (CSI-T) and the receiver (CSI-R). We show that the low-SNR capacity of this keyhole channel scales proportionally as $\frac{\mathrm{SNR}}{4} \log^2 \left(1/{\mathrm{SNR}}\right)$. With this asymptotic low-SNR capacity formula, we find a very surprising result that contrary to popular belief, the capacity of the MIMO fading channel at low SNR increases in the presence of keyhole degenerate condition. Additionally, we show that a simple one-bit CSI-T based On-Off power scheme achieves this low-SNR capacity; surprisingly, it is robust against both moderate and severe fading conditions for a wide range of low SNR values. These results also extend to the Rayleigh keyhole MIMO channel as a special case.
翻译:在本文中,我们以独立和同样分布的(i.d.) Nakagami-$m$d) 光模版状态信息,在发射机(CSI-T)和接收机(CSI-R)都可获得的完美频道状态信息的情况下,以独立和同样分布的(i.d.) Nakagami-$d) 淡化条件,在低SNR 中,多投入多输出(MIIMO) 键眼通道的性能无症状。我们表明,这个关键孔频道的低SNR能力,与美元(fraft) {SNR} 4}\log%2\ left(1/ mathrm{SNR ⁇ right) 一样,成比例的一比特的CSI-T能力,达到了这一低SNR能力;令人惊讶的是,它对于一个范围很广的低SNRIK关键值的特殊的中度和严重淡化条件,具有很强。