This paper introduces a cooperative Non-Orthogonal Multiple Access (NOMA) scheme for 5G systems, which leverages the prior knowledge of better channel conditions to enhance system performance. The proposed scheme consists of two phases: the Direct Transmission Phase and the Cooperative Phase. In the Direct Transmission Phase, the base station sends messages to users based on NOMA principles, and users with better channel conditions can decode messages intended for others. In the Cooperative Phase, users cooperate via short-range communication channels to improve reception reliability for users with poor connections. The outage probability and diversity order of the cooperative NOMA scheme are analyzed, showing that it can achieve maximum diversity gain for all users. To reduce system complexity, user pairing is proposed, where users with more distinctive channel gains are paired together. Numerical studies demonstrate that cooperative NOMA outperforms both orthogonal MA and non-cooperative NOMA, achieving higher outage capacity and better performance at high signal-to-noise ratios.This paper introduces a cooperative Non-Orthogonal Multiple Access (NOMA) scheme for 5G systems, which leverages the prior knowledge of better channel conditions to enhance system performance. The proposed scheme consists of two phases: the Direct Transmission Phase and the Cooperative Phase. In the Direct Transmission Phase, the base station sends messages to users based on NOMA principles, and users with better channel conditions can decode messages intended for others. In the Cooperative Phase, users cooperate via short-range communication channels to improve reception reliability for users with poor connections. The outage probability and diversity order of the cooperative NOMA scheme are analyzed, showing that it can achieve maximum diversity gain for all users. To reduce system complexity, user pairing is proposed, where users with more distinctive channel gains are paired together. Numerical studies demonstrate that cooperative NOMA outperforms both orthogonal MA and non-cooperative NOMA, achieving higher outage capacity and better performance at high signal-to-noise ratios.