This work considers the 5G new radio (5G-NR) frame structure through the 3GPP channel model in Rural-Macro (RMa) scenario. A graph-based channel-coding scheme to ensure data-security to the intended user/destination in a MIMO-cooperative communication network in presence of an external passive eavesdropper is proposed. For this purpose, two graphs: mathcal{G} {M}( mathrm{V} {M}, mathcal{E} {M}, mathrm{W} {M}) , mathcal{G} {E}( mathrm{V} {E}, mathcal{E} {E}, mathrm{W} {E}) corresponding to the source-relay-destination, source-relay-eavesdropper are considered in MIMO-channels environment respectively. The channel coding scheme, based on the inverse graph Fourier transformation (IGFT) of the mathcal{G} {M} , is proposed to create increased bit/symbol errors at the eavesdropper along with the MIMO-diversity gain at the main user. The GFT of mathcal{G} {M} based postcoder is used at the destination to detect the transmitted symbols whereas GFT of mathcal{G} {E} with/without postcoder at the eavesdropper is used to estimates the signal. Physical layer security (PLS) scheme based on the difference of BERs between destination and the eavesdropper is proposed. © 2021 IEEE.