A.3 MS requirements
3GPP45.010GSM/EDGE Radio subsystem synchronizationTS
The MS shall comply to the following requirements.
A.3.1 Provision of time difference information
The reception epoch criterion used for clocking the timebase shall be as close as possible to line of sight path reception epoch so that the timing advance when the MS is stationary is as close as possible to the double propagation delay. However the quantization mentioned in subclause A.1.1 does not impose any additional requirement on the resolution of the measurement.
A.3.2 After each successful circuit-switched handover
After each successful circuit-switched handover the MS shall give to the new BTS the sum of the observed time difference and the last timing advance value received from the old BTS, if required by the BTS encoded as subclause A 1.1.
A.3.3 Synchronized or a pseudo synchronized handover
When a synchronized circuit-switched or packet-switched handover, or a pseudo synchronized circuit-switched handover occurs, the MS shall synchronize to the new BTS and shall use as initial timing advance value the value calculated modulo 256 from the observed time difference between the two BTS, the real time difference and the last timing advance value received from the previous BTS, according to subclause A.1.3. Calculated values between 230 and 255 shall be regarded as negative timing advance. The Real Time Difference (RTD) is in the case of pseudo synchronized handover given with the handover command and in the case of synchronized handover set to 2500*INT(OTD/2500+0,5) by the MS. If the initial timing advance value calculated is outside the range 0 to TAmax the MS shall do as follows:
– if the initial timing advance value calculated is greater than TAmax, the cell shall be considered as out of range. The MS shall, if it attempts to transmit on the new cell, use a timing advance value of TAmax as the initial timing advance value. Whether the MS transmits on the new cell or not depends on the NCI bit as specified in 3GPP TS 44.018;
– if the initial timing advance value calculated is less than 0, the MS shall use a timing advance value of 0 as the initial timing advance value.
Annex B (informative):
CTSBCH timeslot shifting properties for CTS-MS synchronization
The determination of TN for CTS-MS synchronization is eased by specific properties of the CTSBCH timeslot shifting procedure. Three successive CTSBCH detection and decoding are always sufficient to set TN.
The CTSBCH shifting procedure may be either active or not. This is signalled by a flag in the CTSBCH-SB (see 3GPP TS 45.002).