Celebrities touched down in Sin City on Sunday night for the 2012 Billboard Music Awards. This year's show is set to be both celebratory and commemoratory. Tributes have been planned for fallen musical legends Whitney Houston, Donna Summer and Adam MCA Yauch.  

I was at the Grammys, and what a curveball they were thrown when Whitney passed away [the day before the show], Billboard Music Awards co-executive producer Richard Beckman told Billboard.com. They did a good job with Jennifer Hudson, but obviously we had a bit more time, so we wanted to do something honoring such a remarkable performer.

Whitney Houston's commemoration will be undertaken by John Legend and Jordin Sparks. Sparks will take on Houston's biggest hit, I Will Always Love You.

Soundcheck helped ease the nerves a bit! So excited for tonight! Now starting glam for red carpet! Sparks tweeted to her fans on Sunday from the MGM Grand Garden Arena in Las Vegas. Sparks looked svelte and smiley on the red carpet in a cream, lace dress and strappy heels.

Presenters at the 2012 Billboard Music Awards, airing Sunday on ABC at 8 p.m. EST, include Charlie Sheen, Miley Cyrus, Gladys Knight, Julianne Hough and Wiz Khalifa. The nominations list is jam-packed with all of today's top stars in the music business, including Justin Bieber, Adele and LMFAO. Adele leads the pack with 18 nominations.

Newcomer Carly Rae Jepsen is one of the most-anticipated performers of the night, making her debut on the Billboard Music Awards stage.

I saw the rehearsal yesterday with Carly Rae Jepsen, Beckman told Billboard. When we booked her no one really knew her name, and now 'Call Me Maybe' is No. 4 on [the Billboard Hot 100] and No. 1 on iTunes, and her performance is terrific, really energetic.

Jepsen tweeted a photo to fans before the show of her primping for her big night. She thanked hairstylists Harry Josh and John Freida. Later, Jepsen tweeted, Sound check was so fun! Can't wait to play now. #BBMA let's start the show already, before hitting the red carpet. 

Check out the celebrity arrivals on the red carpet at the 2012 Billboard Music Awards.