# Study of 5G-NR-MIMO Links in the Presence of an Interferer
## 1 Introduction
Another assumption is that the transmitter and the interference's transmission are transmitted under the Orthogonal Space-Time Block Codes (OSTBC)-Alamouti scheme, also receive Alamouti decoder MRRC combiner with Maximum Likelihood (ML) search. The modulation is a Common Envelope (CE), to save energy and lower the Peak-to-Average Power Ratio (PAPR). Another assumption is that the interference occurs regularly, meaning that the statistical average of the product between the transmitter's symbols and the symbols of the receiver is different from zero [32]. In a military communication situation, Partial Band Noise (PBN) jammers [33], and smart jammers [21] are present. In these situations, a smart jammer learns and estimates the channel matrix between a legitimate transmission and his receiver. If we have a wide-band noise jammer [33] or even a PBN jammer [34], we can use the eigenvalue beamforming technique [35] and cancel the jammer effects with the null steering that eigenvalue beamforming will create [27]. In the smart jammer case, we must also control the MIMO array in the transmitter and in the receiver together, meaning also the CSI at the transmitter (CSIT). In recent years, significantly advanced interference cancellation techniques, such as MMSE-Interference Rejection Combining (MMSE-IRC) and MMSE-Maximal Ratio Combining (MMSE-MRC), have been developed and implemented in advanced LTE [15; 36; 37]. The next step is the new algorithm interference, and anti-jamming generation is required, especially under the assumption of TDD access and Ultra-Reliable and Low-Latency Communications (URLLC) in 5G requirements. These requirements are a binding reduction in the computing of the co-variance [36] matrix and the time estimation of the channel, on the transmitter and the receiver sides. In our future works, we will address these requirements in developing fitting algorithms. The purpose of this paper was to refine the challenge in order to deal with those impacts. We start by understanding the limitations of advanced diversity techniques as the OSTBC-Alamouti scheme, based only on the CSIR, without any closed loop-feedback. This article highlights the lack of re-feeding by focusing on the effects required for correction with the help of a control system. This closed-loop feedback creates and sends feedback that fixes the destructive multi-path and interference effects. In addition, the time response is reduced, and the channel with smart and effective CSIT is learned. These ideas open a window for other researchers. This study presents the impacts of an interferer or a smart jammer synchronizing with UE or with a small cell. Another purpose of this study was to enrich the importance of CSI Interference's Management (CSI-IM) [30] at the UE, at the macro base-station, or the small cells, in the same time, similar to the HetNet scenario. In unlicensed wireless communication, we clarify the importance of CSI-IM in transmissions, in an interferer or smart-jammer environment scenario. We illustrate these effects on the basic principle of MIMO techniques based on an open loop. Another purpose was to show that selective space techniques, such as eigenvalue beamforming and a null spacing matrix that reduces the effects of signal interference, are not enough to deal with highly dynamic interference or smart jammer attacks in the space domain. The main target is to overcome fluctuation channels in the time and frequency domain amid jammer or interferer issues. Our idea is to create more flexible scheduling in the next 5G-NR transceiver and in new radio access. This paper can be integrated with other papers regarding unique geometric scattering models for MIMO channels [4; 5]. Some studies work around modern communication with jammers [15; 21; 31; 36]. This paper and future studies will complement these papers and provide different points of view on this subject. We divide strategies handling multi-interference into two mechanisms.