So, this is the idea…
Let’s say you have two TRXs with BCCH freq 20 and TCH freq 35.
Without BBH you get a TCH on freq 35. Very good level -60 dBm but low quality => interference.
Then the BSC assign you a TCH on the BCCH TRX ( freq 20 ). There you have the same level but better quality due to clear BCCH freq.
With BBH you get a TCH on the TCH TRX. Very good level but bad average quality due to very bad freq ( BCCH 20 or TCH 35) or both.
You perform a intracell HO and you get a TCH on the BCCH TRX. The same level again, but the same quality because of the average value on the hopping sequence ( freq 20 and freq 35 ).
Then you perform a new intracell HO and again… and again…
A loop with unknown end :- )
Of course performing this HO we keep the freq band ( it’s not inner zone to outer zone HO and vs… ).