11 Lower Layer Procedures

03.523GPPLower layers of the GSM Cordless Telephony System (CTS) radio interfaceStage 2TS

11.1 CTSBCH transmission

The CTS-FP shall transmit the CTSBCH on the selected CTSBCH frequency (indicated by the Frequency Management procedure in the RR upper layer, see subclause 12.2.2) at the maximum permitted output power.

11.2 CTSBCH timeslot management

In order to further reduce the interference between two CTS-FP and to ease the detection of the CTSBCH of neighbour CTS-FP (for GSM-CTS Phase 2), the timeslot position of the CTSBCH within the TDMA frame where the CTSBCH is transmitted shall not be fixed from one 52-multiframe to another.

A mechanism of CTSBCH timeslot shifting shall be performed on the CTSBCH while the CTS-FP is in RR Idle state (see subclause 12.1). This mechanism shall fulfil the following requirements:

– the shifting sequences of CTSBCH timeslot positions shall be predictable;

– a high number of shifting sequences shall be generated from a minimum number of parameters.

The mechanism of CTSBCH timeslot shifting is optional while the CTS-FP is in RR Active state (see subclause 12.1), i.e. has established a dedicated RR connection to a CTS-MS. A flag shall indicate in the CTSBCH-SB information bits whether the CTSBCH timeslot shifting is currently performed or not (see subclause 10.1.4).

11.3 CTSBCH-FB detection

When triggered by the upper layers, the CTS-MS shall attempt to detect the CTSBCH-FB on the CTSBCH frequency given by the upper layers. When the CTSBCH-FB is detected, it is used by the CTS-MS to update its frequency synchronisation to the CTS-FP.

11.4 CTSBCH-SB decoding

When triggered by the upper layers, the CTS-MS shall attempt to decode the CTSBCH-SB on the CTSBCH frequency given by the upper layers. The decoding of the CTSBCH-SB allows the CTS-MS to update its time synchronisation to the CTS-FP.

The CTSBCH-SB information bits shall be sent to the RR upper layer of the CTS-MS: see subclause 12.2.3.

11.5 Discontinuous transmission (DTX)

DTX shall be used by the CTS-FP and the CTS-MS. The DTX procedure specified in the relevant GSM 06 series specifications and in GSM 05.08 subclause 8.3 shall be employed.

11.6 Interference measurements

A procedure shall be implemented in the CTS-FP by which it estimates the interference level on the uplink frequencies of the Generic Frequency List (GFL).

In the same manner, the CTS-MS shall estimate the interference level on the downlink frequencies of the GFL.

Such interference measurements are periodically triggered by the RR upper layer, i.e. the AFA algorithm: the list of frequencies of the GFL which are to be measured, the required number of samples per frequency and the allowed measurement period, shall be specified.

11.7 MS timing offset measurements

When triggered by the upper RR layer, the CTS-FP shall measure the MS timing offset (as specified in GSM 05.10) of the bursts received on the CTS radio interface, i.e. Synchronisation Bursts (SB) and Normal Bursts (NB). The measurements shall be reported to the RR upper layer.

The requirements on the measurement precision are intended to allow the control of the CTS-FP service range, as defined in subclause 12.2.4.