This paper investigates the impacts of network coding(NC) on user fairness from the network perspective in multiple access channels.Firstly,simultaneous outage is exploited as the metric to evaluate user fairness.To optimize it,a fairness-oriented physical layer NC scheme is proposed,in which users’ signals are superimposed in specific calculated proportion at relay and then decoded by maximal ratio combination(MRC) and serial interference cancellation(SIC) at destination.Furthermore,the influence of power allocation coefficient error on simultaneous outage is also analyzed to reveal its correlation with user fairness.Simulation results indicate that the proposed scheme can supply approximately equal performance promotion for each cooperation-participated user and outperform those without fairness consideration in terms of the employed metric. This paper investigates the impacts of network coding (NC) on user fairness from the network perspective in multiple access channels. Firstly, simultaneous outage is exploited as the metric to evaluate user fairness.To optimize it, a fairness-oriented physical layer NC scheme is proposed, in which users’ signals are superimposed in specific calculated proportion at relay and then decoded by maximal ratio combination (MRC) and serial interference cancellation (SIC) at destination. Futurertherm, the influence of power allocation coefficient error on simultaneous outage is to reveal its correlation with user fairness. Simulation result indicates that the proposed scheme can supply equivalent equal performance promotion for each cooperation-participating user and outperform those without fairness consideration in terms of the employed metric.