Roger Federer French Open 2015
Roger Federer will face a big test against the big-serving Iva Karlovic in the semifinals of the Gerry Weber OpenReuters

Roger Federer will be expecting a barrage of aces when he plays Ivo Karlovic in the semifinals of the Gerry Weber Open in Halle on Saturday.

Federer was his usual best in the quarterfinals, easing past Florian Mayer in straight sets 6-0, 7-6 (1) to setup a semi against the big-hitting Karlovic.

"I'm happy this week is going well," Federer was quoted as saying by ATP's official website after the handsome win. "This was clearly a total different opponent to the first two. I got more chances off his second serve, I was able to get into rallies easier and I had a good serving day. I thought I played very well.

"I think [Florian] brings a different challenge to the table because of his shot-making. He plays a different type of shots than other players do and I think I quite enjoyed that challenge. I had to focus very hard at the end to play a good breaker."

Federer will know those break points will not come as easily if Karlovic finds his serving groove again. The big Croatian set an ace record in his quarterfinal match against Tomas Berdych, firing home 45 of those rippers to stun his Czech opponent.

More serves of the same kind, and Federer will have to dig deep to topple Karlovic.

"I'm extremely happy about the record," Karlovic said. "Hitting aces helps a lot, you can avoid the volleys. I was surprised when I was told on court after the match how many aces I hit.

"I didn't know it was that many. Hopefully I can continue like that in the semifinal."

The second semifinal of the Wimbledon lead-up tournament will be between Japanese sensation Kei Nishikori and Italian Andres Seppi, with Indian interest then coming into play as Rohan Bopanna and his Romanian doubles partner Florin Mergea facing Eric Butorac and Scott Lipsky for a place in the final.

Where to Watch Live

Roger Federer vs Ivo Karlovic is scheduled to begin at 1 pm local time (4.30 pm IST, 12 pm BST, 7 am ET). That semifinal will be followed by Kei Nishikori vs Andreas Seppi (not before 4 pm local time start), before the day's action is completed with the doubles semifinal, involving Bopanna. Live coverage of all the tennis will be on Ten Action in India. The Queen's tournament, which has Andy Murray still in action, will be live on Star Sports and

Viewers in the US can watch both tournaments live on ESPN3, with the live stream option on Watch ESPN. Sky Sports is the place to be to watch the matches live in the UK, while the action can also be live streamed on Sky Go.

Audience across the world can watch both the ATP tournament semifinals via live streaming online on the official ATP website.