This paper proposes a cooperative Non-Orthogonal Multiple Access (NOMA) scheme for 5G systems, which leverages prior knowledge of users' messages to enhance system performance. In traditional NOMA, users with better channel conditions decode messages using successive interference cancellation. The proposed cooperative NOMA scheme utilizes this prior knowledge by having users with better channel conditions act as relays to assist users with poor connections. This approach improves reception reliability and achieves maximum diversity gain for all users. The system model consists of two phases: direct transmission and cooperative transmission. During direct transmission, the base station sends messages to users using NOMA principles. During cooperative transmission, users communicate via short-range channels to assist each other. The outage probability and diversity order of the cooperative NOMA scheme are analyzed, showing that it outperforms both orthogonal multiple access (MA) and non-cooperative NOMA schemes. The paper also discusses the challenge of system complexity in cooperative NOMA and proposes user pairing as a solution. User pairing is shown to be more effective when users have significantly different channel conditions. Numerical studies demonstrate that cooperative NOMA achieves higher rates and better performance than other schemes, especially at high SNR. The results confirm that cooperative NOMA can achieve maximum diversity gain for all users, regardless of their channel conditions. The paper concludes that optimizing power allocation in cooperative NOMA systems is a promising direction for further performance improvements.This paper proposes a cooperative Non-Orthogonal Multiple Access (NOMA) scheme for 5G systems, which leverages prior knowledge of users' messages to enhance system performance. In traditional NOMA, users with better channel conditions decode messages using successive interference cancellation. The proposed cooperative NOMA scheme utilizes this prior knowledge by having users with better channel conditions act as relays to assist users with poor connections. This approach improves reception reliability and achieves maximum diversity gain for all users. The system model consists of two phases: direct transmission and cooperative transmission. During direct transmission, the base station sends messages to users using NOMA principles. During cooperative transmission, users communicate via short-range channels to assist each other. The outage probability and diversity order of the cooperative NOMA scheme are analyzed, showing that it outperforms both orthogonal multiple access (MA) and non-cooperative NOMA schemes. The paper also discusses the challenge of system complexity in cooperative NOMA and proposes user pairing as a solution. User pairing is shown to be more effective when users have significantly different channel conditions. Numerical studies demonstrate that cooperative NOMA achieves higher rates and better performance than other schemes, especially at high SNR. The results confirm that cooperative NOMA can achieve maximum diversity gain for all users, regardless of their channel conditions. The paper concludes that optimizing power allocation in cooperative NOMA systems is a promising direction for further performance improvements.