We consider energy-efficient Distributed Detection in wireless sensor networks. It is assumed that a group of sensors observe the same quantity in independent additive observation noises with possibly different variances. Each node computes a local statistic and communicates it to a fusion center over Rayleigh fading wireless channels.At the fusion,the linear minimum mean square error (LMMSE) is used. In this paper Two types of constraints are considered: 1) transmission power constraints at the nodes, and 2) the communication channel between the nodes and the decision center. we propose a optimal distributed estimation algorithm in energy-constrained wireless sensor networks. Finally, we demonstrate the applicability of our results through numerical examples.