Abstract
The escalating scarcity of the spectrum has led to reuse the spectrum bands already occupied by the existing services. Hence, the interference situations between already activated services and the proposed future technologies rise rapidly. Accordingly, this paper sheds light on the spectrum sharing of coexisting of high altitude platform system (HAPS) user and an incumbent Long Term Evolution (LTE) networks that are intended for future applications. Moreover, the spectrum sharing has evaluated based on the interference to noise ratio (INR) and the carrier to interference plus noise ratio (CINR). Accordingly, optimistic results obtained at this juncture illustrate the feasibility of coexistence of both systems in 3.6 GHz band.