Mobile TV can be watched on a smart or 3G mobile phone, such as the LG Vu or Samsung SCH u620 smart phone. Both AT&T Wireless and Verizon Wireless offer mobile TV services. For Verizon, it is VCAST TV and for AT&T, it is AT&T Mobile TV. Both AT&T and Verizon Mobile TV use MediaFLO technologies from Qualcomm to broadcast the VHF (719 MHz Center frequency) digital TV signals to the mobile phones. Mobile TV service from different carrier bundle different set of TV channels in its broadcast (in the range of 10 to 12 TV channels in a basic package).
Mobile TV service does not use the mobile phone network to transmit the TV signals. Instead, it uses a separate network to distribute, transmit and broadcast the TV signals to the mobile phones. It only uses the mobile phone network to provide interactivity and user authorization with the TV service provider IPTV Streaming Service. Since the 3G mobile phone network from AT&T and Verizon are both capable to carry IP traffic, it seems to be obvious that the simplest implementation for mobile TV is using IPTV. A good example is AT&T already using IPTV in its U-verse service (internet, phone and TV).
To understand why mobile TV does not use IPTV, the unicast nature of the mobile phone network needs to be explained. The current 3G (UMTS, EVDO) mobile phone network are designed to carry unicast traffic only, i.e. point to point connection needs to be establish between the user and the Media server in order for the network to deliver the TV traffic to the mobile phone. Since TV is a broadcast service, i.e. a point to multipoint connection is required for mobile TV service. To implement point to multipoint connection, the mobile phone network needs to set up an IP connection between the Media server and each mobile user receiving the broadcast simultaneously. These many connections will easily overrun the capacity of the mobile phone network and blocks other voice and data traffic that needs to use the network.
For mobile TV to use IPTV, the IP multicast feature needs to be implemented on the mobile phone network. Multicasting is the technique of transmitting a single video signal simultaneously to multiple end users. All viewers receive the same signal at the same time but there are no separate streams (connections) for each recipient. IP multicast is widely used in the delivery of broadcast TV services over IP networks. It significantly reduces the amount of bandwidth required to transmit high quality IPTV content across a network. This is because only a single copy of every video stream needs to be sent to a router, which in turn makes a copy of that stream for the requesting devices. Not only does multicast reduce the bandwidth requirements of the network but the processing power of the Media server can also be kept relatively low because it only transmits one copy of an IPTV stream at a time.
Although the current 3G mobile network from AT&T and Verizon does not have IP multicast, however, the next 3G mobile network upgrade from both carriers may include the IP multicast feature. For AT&T Wireless, the next network upgrade will be HSPA (High Speed Packet Access) which supports the MBMS (Multimedia Broadcast Multicast Services) feature. For Verizon Wireless, the next upgrade will be EVDO Rev A which supports the BCMCS (Broadcast and Multicast Services) feature. Hence, the future mobile TV service from both AT&T Wireless and Verizon Wireless may use IPTV implementation.