  In this paper, we consider the downlink in a K-tier heterogeneous network in
the presence of Nakagami-m fading and noise. For such a system, we derive
closed-form approximations of coverage probability and average rate achievable.
A piece-wise linear approximation is employed in obtaining the simplified
expressions. The proposed results are verified numerically through simulations.
A comparison with existing work shows that the proposed work is a good
approximation.
