Not getting timestamp when pps is disable in basic station

I am getting issue that not getting timestamp in uplink frame with basic station wenever i disable the pps is disable in station.conf file. Also when pps is false at that time Gateway not sending any time sync request to server.

My station.conf file look like below.
/* If slave-X.conf present this acts as default settings /
“SX1301_conf”: { /
Actual channel plan is controlled by server /
“lorawan_public”: true, /
is default /
“clksrc”: 1, /
radio_1 provides clock to concentrator /
path to the SPI device, un-comment if not specified on the command line e.g., RADIODEV=/dev/spidev0.0 /
“device”: “/dev/spidev0.0”,/
freq/enable provided by LNS - only HW specific settings listed here /
“radio_0”: {
“type”: “SX1257”,
“freq”: 865400000,
“rssi_offset”: -166.0,
“tx_enable”: true,
“antenna_gain”: 0
“radio_1”: {
“type”: “SX1257”,
“freq”: 866385000,
“rssi_offset”: -166.0,
“tx_enable”: false
chan_multiSF_X, chan_Lora_std, chan_FSK provided by LNS /
“station_conf”: {
“routerid”: “70:F8:E7:FF:FE:10:B3:1D”,
“euiprefix”: “::0”,
“log_file”: “~temp/station.log”,
“log_level”: “XDEBUG”, /
“log_size”: 10000000,
“log_rotate”: 3,
“TC_TIMEOUT”: “2s”,
“gps”: “/dev/smd7”,
“pps”: “gps”,
“radio_init”:"/usrdata/ start",