Time to Switching Frequence

Hi All,

I have a project to monitoring ( air sniffer ) the data between GSM BTS and MS using UmTRX. Uplink Transmission is delayed 3 slots than downlink from specification. So when I sync. with BTS and get the downlink slot data, I must switch the freqs of receiver from downlink to uplink in less than 2 slots. When the program call 'usrp_dev->set_rx_freq(wFreq)', How much time does the UmTRX switch to the 'wFreq' ?

Thanks in advance.

Jiang WenYi