Local Gan-Gross-Prasad conjecture for unitary groups: Trace formula approach for epsilon dichotomy

The purpose of this paper is to provide a proof independent of the theta-lifting for the epsilon-dichotomy of the local Gan-Gross-Prasad conjecture of real unitary groups for tempered L-parameters. The approach is based on the local trace formula and endoscopic character identities following Waldspurger and Chen-Luo.