MobiTV has hit the 4-million subscriber mark, adding a million subscribers in the last six months as well as the six months before that, reports RCRNews. It has also announced a combination unicast/multicast system, so that if 50 subscribers are watching the same channel in one sector it will switch from unicast to multicast—saving on backhaul. CTO Kay Johansson also said that the time required to change channels is now less than a second, putting it on par with other TV services. The time required to change channels is important—when mobile TV first came out the lag in changing channels was an inhibitor to uptake. (release)

• MobiTV Passes 3 Million Mark, Re-signs Sprint Deal