10 Other layer 1 functions

05.013GPPGeneral descriptionPhysical layer on the radio pathTS

The transmission involves other functions. These functions may necessitate the handling of specific protocols between BS and MS. Relevant topics for these cases are:

1) The power control mechanisms which adjust the output level of the mobile station (and optionally of the base station) in order to ensure that the required quality is achieved with the less possible radiated power. Power levels with 2 dB steps have been defined for that purpose. This is described in 3GPP TS 05.08 (radio subsystem link control) and 3GPP TS 05.05.

2) The synchronization of the receiver with regard to frequency and time (time acquisition and time frame alignment). The synchronization problems are described in 3GPP TS 05.10 (synchronization aspects).

3) The hand‑over and quality monitoring which are necessary to allow a mobile to continue a call during a change of physical channel. This can occur either because of degradation of the quality of the current serving channel, or because of the availability of another channel which can allow communication at a lower Tx power level, or to prevent a MS from grossly exceeding the planned cell boundaries. In the case of duplex point‑to‑point connections, the choice of the new channel is done by the network (base station control and MSC) based on measurements (on its own and on adjacent base stations) that are sent on a continuous basis by the mobile station via the SACCHs. The requirements are specified in 3GPP TS 05.08 (radio subsystem link control).

4) The measurements and sub‑procedures used in the first selection or reselection of a base station by a mobile are specified in 3GPP TS 05.08 (radio subsystem link control). The overall selection and reselection procedures, together with the idle mode activities of a mobile are defined in 3GPP TS 03.22 (functions related to MS in idle mode and group receive mode and GPRS mode ).

5) The measurements and sub‑procedures used by an MS in selecting a base station for reception of a voice group or a voice broadcast call are specified in 3GPP TS 05.08 (radio subsystem link control). The overall voice group and voice broadcast cell change procedures, being similar to the reselection procedures related to the idle mode activities of an MS, are defined in 3GPP TS 03.22 (functions related to MS in idle mode and group receive mode and GPRS mode ).

6) For the adaptive speech traffic channels the inband signalling carries the required information to adapt the speech and channel codec modes to the propagation conditions. The coding of the in band signalling is specified in 3GPP TS 05.09 (Link adaptation). An example of codec adaptation algorithm is also provided in 3GPP TS 05.09 (Link adaptation).