Active Antena Unit-AAU 5G/Remote Radio Unit- RRU 4G LTE Heatsink systems are using natural convection cooling due to some outstanding advantages such as low cost, high reliability, noiseless operation and hard environment operation. However, some main disadvantages such as a relatively low heat transfer and low heat dissipation density are to be solve by optimal heat sink fin design. So an analytic calculation and FEM simulation is required to efficiently design natural convection heat sinks according to the applied design constraints. This paper describes an optimal heatsink fin profile design with V shape angle to maximize natural cooling for Active Antenna Unit-AAU 5G. The proposal design is based from RRU 4G heatsink simulation and experiment results. Several core ICs of RRU 4G with high heat loss sources up to hundred W need to be dissipated by Aluminum heatsink and enclosure or housing. The RRU 4G natural cooling system is composed of parallel-straight plate heat sinks in order to find an optimum heat sink design based on an analytical calculation of Entropy energy and Heatsink Resistance but the AAU 5G Heatsink system is cooled by V sin plate heat sinks to improve heat exchange. The analytical calculation was applied to different heat sink profiles and FEM simulations were setup to evaluate thermal performance for RRU 4G/AAU 5G heatsink. Temperature measurements were carried out to validate the RRU 4G heatsink model and proposal design of AAU 5G heatsink is calculated by an analytical model and FEM simulation.  This paper will show an optimal calculation of AAU 5G housing heatsink fin to minimize manufacture and material cost.