The cooperative communication techniques, wherein several transmitters and one receiver are implemented, can greatly increase the performance of a communication system. In fact, the cooperative communication has been launched since the fourth generation mobile systems. The two competing cooperative techniques are; relays and intelligent reflecting surfaces (IRS). It is known that the electromagnetic interference (EMI) can degrade a radio system performance. In this paper, the EMI, affecting an IRS-based communication system, is mathematically modeled and simulated. The interference level can be affected by the channel parameters which are the 5G path loss models. In order to improve the communication system performance, Alamouti codes are applied. The gain, offered by diversity codes “Alamouti", can reduce the degradation of the performance due to the EMI existence. The complete mathematical model is carried out as well as the simulation model. The simulation results show that the cooperative Alamouti-coded 5G radio systems have a satisfying performance even the EMI exists