During his studies at MIT, he participated in the cooperative program at AT&T Bell Laboratories, during which he worked on digital circuit design and binaural hearing.
After obtaining his PhD in 1967, he joined AT&T Bell Laboratories' research division in Murray Hill, NJ as a member of technical staff.
He was promoted vice-president of Research in 1998, succeeding Sandy Fraser, where he managed broad programs in communication, computing, and information sciences.
Rabiner was the first to publish the scaling algorithm for the Forward–Backward method of training of HMM recognizers.
His research showed how to successfully implement an HMM system based on either discrete or continuous density parameter distributions.