Before revision:  For this model, we first estimate the time-varying long run component  by the kernel estimator, and then estimate the non-time-varying parameters in  short run component by the quasi maximum likelihood estimator (QMLE).
After revision:  For this model, we first estimate the time-varying long run component by the kernel estimator, and then estimate the non-time-varying parameters in GARCH-type short run component by the quasi maximum likelihood estimator (QMLE).