The proliferation of sophisticated applications and services comes with diverse performance requirements. The 5G cellular network is advocated to support this diversity through an end-to-end network slicing. Even-though the slicing is not a novel concept, its implementation in the RAN still remains challenging. In this article, we aim to enforce the real time 5G slicing from radio resources perspective in a multi-cell system. For that, an exact optimization model is proposed. Due its high convergence time, heuristics are developed and evaluated with regard to the optimal model. Results are promising, as two heuristics are highly enforcing the real time RAN slicing.