a MS sends a CHANNEL REQUEST to cell B, on its BCCH frequency.
This channel request is sent to cell B, but cell C can also catch it.
Cell C will start processing this channel request, because it is located on its BCCH frequency. Of course, the MS will not pursue this channel request with Cell C, but rather with cell B.
So that’s 1 ghost rach for cell C.
Same with HO ACCESS : the MS sends a HO access on the BCCH frequency of cell B (because the previous serving cell has allocated a target TCH on the BCCH TRX of cell B). This HO ACCESS is decoded by cell C, because it’s on its BCCH freq and it looks like a channel request (same message and burst format).
That’s 1 ghost rach for cell C.
Regards,
Pix