Voice over Wi-Fi must have been a hot topic at the Voice on the Net conference: Microsoft said it is adding VoIP capabilities to its Windows CE operating system. Microsoft also said that Vonage will be its first service provider partner. Earlier this week, Vonage said that it will begin offering voice over Wi-Fi service, but didn't elaborate on what device customers would use to access the service. It's not clear if Vonage will offer voice over Wi-Fi handsets or if the service will hinge on the Windows CE devices.