In this paper. we consider a downlink non-orthogonal multiple access (NOMA) system over Nakagami-m channels. The single-antenna base station serves two single-antenna NOMA users based on statistical channel state information (CSI). We derive the closed-form expression of the exact outage probability under a given decoding order. https://www.roneverhart.com/Ryukyu-Kobujutsu-Buki-Jutsu-Vol-2-DVD-with-Kiyoshi-Yogi/