• Power Control enables the mobile station and/or the BTS to increase or decrease the transmission power on a per-radio link basis.
• Power Control is separately performed for the uplink and downlink. In both cases the BSC is responsible for initiating Power Control; the mobile station and the BTS adopt transmit power according to the BSC Power Control commands.
• Measurements while a mobile station is active on a call, it has the responsibility of PROVIDING measurement data about the performance of the air-interface to its serving BTS so that the serving BSC can decide if a power control should be performed. ALSO the serving BTS measures the performance of the air-interface. WHEREAS the mobile station measures the performance of the downlink, the BTS measures the performance of the uplink.

Downlink measurements The mobile station measures and reports the following measurements to the BSC regarding the performance of the downlink:

• Strength of the signal being received from its serving BTS (in dBm).
• Quality of the signal being received from its serving BTS (in bit error rate).

Uplink measurements The BTS measures and reports the following measurements to the BSC regarding the performance of the uplink:

• Strength of the signal being received from the mobile station.
• Quality of the signal being received from the mobile station.

Periodically measuring the mobile station measures periodically the performance of the downlink, and sends the measurements in the SACCH (Slow Associated Control Channel) via the serving BTS to the BSC every SACCH multi-frame. This corresponds to the transmission of data every 104 TDMA frames or 480 Ms. The base station measures the quality of the uplink. Also, it transfers the measurements in the SACCH to the BSC every 480 ms.

Signal strength when the BSC notices that the signal strength of a particular radio link measured on the uplink becomes below the lower pre-defined threshold because the mobile station moves away from the BTS, it sends a Power Control command to the mobile station to increase its transmit power (MS_TXPWR) by a pre-defined STEP (typically 2 DB).

Downlink measurements The mobile station measures and reports the following measurements to the BSC regarding the performance of the downlink:

Uplink measurements The BTS measures and reports the following measurements to the BSC regarding the performance of the uplink:

Periodically measuring the mobile station measures periodically the performance of the downlink, and sends the measurements in the SACCH (Slow Associated Control Channel) via the serving BTS to the BSC every SACCH multi-frame. This corresponds to the transmission of data every 104 TDMA frames or 480 Ms. The base station measures the quality of the uplink. Also, it transfers the measurements in the SACCH to the BSC every 480 ms.

Signal strength when the BSC notices that the signal strength of a particular radio link measured on the uplink becomes below the lower pre-defined threshold because the mobile station moves away from the BTS, it sends a Power Control command to the mobile station to increase its transmit power (MS_TXPWR) by a pre-defined step (typically 2 dB).