and we assume the observation time of $\Delta t_o =10$ years.

**SKA mock data:** For the case of SKA, we follow the prescription given in Refs. [@Klockner:2015rqa; @Martins:2016bbi] to produce the mock data of redshift drift. It is shown in Refs. [@Klockner:2015rqa; @Martins:2016bbi] that if SKA could have the full sensitivity and detect a billion galaxies, the evolution of the frequency shift in redshift space would be estimated to a precision of one percent. Thus, we consider the following two scenarios:

1.  For SKA Phase 1, in our simulation, we produce 3 mock data of the drift $\Delta v$ in redshift bin centered on $z_{i}=[0.1,0.2,0.3]$ with velocity uncertainties $\sigma_{\Delta v}$ respectively of $3\%$ in the first bin, $5\%$ in the second bin and $10\%$ in the third bin. The redshift interval $\Delta z$ is 0.1 for each bin and the timespan $\Delta t_o$ is 40 years. Note that although a timespan of 40 years is long integration time, it can be as a benchmark scenario to improve sensitivity and redshift coverage in the full SKA configuration.

2.  For SKA Phase 2, we generate 10 mock data of the drift $\Delta v$ in ten redshift bins. The mock data are covering 