Radio Link Supervision

For each active radio channel, a counter “S” is

•decremented by 1 each time an SACCH frame cannot be decoded (BFI=1)

•Incremented by 2 each time a valid SACCH frame is received is received

The value of S gives a measure of the “quality” of uplink radio link

Initial value of S = BS_RADIO_LINK_TIMEOUT

•If S reaches N_BSTXPWR_M, a radio link recovery is triggered

•If S reaches 0, a radio link failure is detected

RADIOLINK_TIMEOUT_BS > RADIOLINK_TIMEOUT is important because the mobile must release the radio channel first.

Optimal setting for RLT parameters will give the call time for recovery in case of degraded call quality and not just regard it as radio link failure. Therefore this can reduced drop calls specially for radio link fault cases due to burst interference or blind areas owing to high rise buildings or shadowing.