Rehman started his career at Fulham and has also played at Norwich and Brighton.
He spent time on loan at Rangers' Championship rivals Blackpool earlier this season and has not played since Blackpool's win at Birmingham on 20 September.
Rehman added: "The fact the club are so open to the Asian community is a major thing for me too.
"I was invited up to the club to have a chat and have been really impressed with everything I've seen."
Rehman's arrival at Valley Parade has seen fellow defender Mark Bower go out on loan to League Two's bottom club Luton Town.
The centre-back has only made on start this season for City and joins Luton for a month.
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