3GPP TS45.005 p.42:
For a BTS on a RACH or PRACH with a random RF input, the overall reception performance shall be such that less than 0,02 % of frames are assessed to be error free.
So random noise should be decoded as a noise for 99.98% of the time
0.02% of the noise could be understood as a request, by mistake.
There are 51 RACH-blocks in 240ms (approx)
so that’s 765,000 RACH blocks / hour
0.02% * 765,000 = 153 ghost rach per hour are “accepted” by 3GPP. In other words, if a BTS is located in an area without any traffic (anechoic room, for example), the number of ghost RACH self-generated should be less than 153 / hour.
Can you please shed some light on that matter that for a request to be considered as RACH it should GMSK modulated & BSIC needs to be decoded to consider it as RACH request.
It means Ghost rach should happen only in rare cases.
Looking for your reply.
sory, i missed your post.
Rach requests do not contain the BSIC.
Yes, they are GMSK modulated. But that doesn’t allow noise detection. EM Noise could “sound” like a GMSK signal.
Yes, Ghost RACH are rare, if they are just noise. But sometimes, some equipments generates a signal which is exactly containing a sequence of 900MHz phase modulated symbols. In this casse, it is decoded as a RACH.