Jordin Sparks and John Legend are to perform a tribute to late pop icon Whitney Houston at Sunday\'s Billboard Music Awards show in Las Vegas, ABC said Tuesday. Houston is to be posthumously honored with the 2012 Billboard Millennium Award at the event, which her daughter Bobbi Kristina and sister-in-law Pat are expected to attend. Julie Bowen and Ty Burrell are to serve as hosts of the ceremony at the MGM Grand Garden Arena. Houston drowned in a hotel bathtub Feb. 11 in Beverly Hills, Calif., after using cocaine. She was 48.