LTE synthesizer locking time

I am trying to extract the required specs for an LTE synthesizer, focusing on the required locking time for the synthesizer, is it the TDD guard period that imposes the strictest limitation on the synthesizer locking time, or is there something else that requires faster locking?

I am facing the same problem so i need to know if you have reached anything , by making a survey i found most of who have done LTE synthesizer took the locking time about 30 to 40 us , but without explanation for how we calculate it , also if there is anyone can help us in understanding the frequency hopping in LTE systems and thanks in advance