Research On Ser Performance Of Cooperative Relay Orthogonal And Non-orthogonal Transmission Systems

Collaborative communication technology forms a virtual multiple-input multiple-output(MIMO)system similar to distributed antennas by users sharing each other's antennas.It can break through the limitations of traditional MIMO systems in terms of device requirements.Non-Orthogonal Multiple Access(NOMA)technology as a new multiple access technology can greatly improve the spectrum efficiency of the system.The performance formulas of channel capacity and pairwise error probability(PEP)in the cooperative multi-relay orthogonal transmission system and the power domain cooperative NOMA system are too complicated,which greatly increases the difficulty of system performance optimization.The derivation of the closed formula is of great significance to further improve the performance of the system.Therefore,this paper extends the simplified method of the symbol error rate(SER)formula of the cooperative single relay orthogonal transmission system to the multi-relay orthogonal transmission system and the single Following the research in the NOMA system.The main work includes the following two points:(1)Based on the cooperative multi-relay AF system model,first construct the Signal Interference Noise Ratio(SINR)formulas of the two communication user nodes,and calculate the approximate value under high SINR conditions to satisfy the form of harmonic mean,Combined with MGF's SER calculation formula,the SER asymptotically tight approximation formula of the system with simple structure is derived.Based on the asymptotic tight approximation formula of the total SER of the system,under the condition that the total power is fixed,with the goal of minimizing the overall SER of the system,the optimal power allocation scheme between the source and relay nodes is determined.Monte Carlo simulation results prove that under high signal-to-noise ratio(SNR)conditions,the formula can fit the actual simulation value well,thus verifying the accuracy of the formula.The determined optimal power distribution scheme has better system performance than the general scheme.(2)Based on the uplink single-relay AF cooperative NOMA system model,the signal-to-interference ratio(SINR)formulas of the two communication weak user nodes are first constructed,and then the SER fairness assumption is adopted to satisfy the harmonicmean MGF simplifies the conditions.Combined with the SER calculation formula of MGF,under the condition of high SNR,the SER asymptotically tight approximation formula of the system with simple structure is derived.Monte Carlo simulation results prove that the formula can accurately describe the SER performance of non-ideal serial interference cancellation(SIC)system when the SNR is high.Under the condition that the total power is limited,with the goal of minimizing the overall SER of the system,the optimal power allocation factor is solved,and the optimal power allocation relationship between the total power of the two weak user nodes and the relay amplification and forwarding power is determined.The Monte Carlo simulation verifies that the SER performance fairness of the two weak user nodes meets the constraints under the optimal power allocation scheme.