In Idle mode, the MS listens only to the BCCH of its serving cell. It will decode all System Information messages sent on this channel. Some of these SI msg (SI5 and SI5bis, as far as i recall) lists all the neighbors cells declared for this serving cells (actually, it justs lists down the neighbors’ BCCHs).
The MS measures the RXLEV of the serving’s BCCH and the RXLEV of all neighbors declared in the SI msg.
In Dedicated mode, the MS does not measure the BCCH RXLEV of its serving cell. It measures the TCH RXLEV of the serving only. Plus, of course, the RXLEV neighbors. It will report back those measures to the BTS, but because there might be a lot of neighbors, it will limit the report to the serving’s RxLev and the 6 strongest neighbors’ RxLev.
I don’t know if that answers your question..
FYI, Synch. channel has nothing to do with all this.