ng scheme for digital audio. The MPEG-2 audio tests showed that AAC meets the requirements referred to as "transparent" for the ITU at 128 kbps for stereo, and 320 kbps for 5.1 audio. It is used in both traditional handsets and smartphones. 9.12.2.1.2 Delivery Methods Mobile TV can be delivered via two sets of technologies namely cellular and broadcast as shown in Figure 9.9: Broadcast Technologies: DVB-H, MediaFlo and T-DMB are the three key mobile TV broadcast technologies that are currently gaining momentum primarily in Europe, USA and South Korea respec- tively. A broadcast service is defined as a unidirectional point to multipoint service in which data is transmitted from a single source to multiple terminals within the broadcast service area. Broadcast can be considered as a push service where a response (feedback) for a service is not required from the customers. Cellular Technologies: MBMS and BCMCS are the two key 3G multicast and broadcast technologies envisioned by 3GPP and 3GPP2 respectively for mobile TV. A multicast service is defined as a unidirectional point to multipoint service in which data is transmitted from a single source to a multicast group within the designated multicast service area. Only those users who have the subscription and are active can receive the multicast communications. Unlike broadcast, multicast users need a return channel to interact with cellular networks in order to receive services. 9.12.2.2 DVB The Digital Video Broadcasting - Handheld (DVB-H) technology standard was published as EN 302 304 by ETSI in November 2004. EN 302 304 defines physical layer specifications designed to enable 5 The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. IMS, Services and Applications Cellular technologies Mobile Operators CDMA2000 BCMCS Broadcast technologies Broadcast DVB-H Content Provider Operators T-DMB Mobile Operators/ MediaFLO Wholesellers Figure 9.9 Mobile TV key technologies DVB-H the efficient deliv