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 for unconditional variance by the kernel estimator, and then estimate the non-time-varying parameters in short run component by the quasi maximum likelihood estimator (QMLE).