Evolved Packet System (EPS): The LTE and SAE Evolution of 3G UMTS

6.4 Broadcast and Multicast

This section describes the broadcast and multicast service, as specified by the 3GPP documents. This service is known as MBMS (Multimedia Broadcast and Multicast Service).

From a general perspective, the benefit of broadcast and multicast on networks is that multiple subscribers can receive the same data at the same time, sent only once on each link. For the radio interface, the obvious benefit is that in a given cell, the radio resource cost is limited to what is needed for one transmission in a given cell, for the sake of radio interference and capacity. The gain on terrestrial interfaces is not also not negligible, as the interfaces between the content source and the radio equipment will also benefit from broadcast techniques.

Back to history, GSM networks already offers a text-based broadcast service known as SMSCB (Short Message Service Cell Broadcast). The SMSCB is limited to low bit rate data, transmitted to all subscribers in a given set of cells over a shared broadcast radio channel. The capacity of the GSM broadcast channel is quite limited, as it only allows sending a block of 88 bytes of text every eight 51-multiframe (approximately 2 seconds), which provides a maximum bit rate of around 350 bits per second.

As described below, MBMS has a much broader set of rates and applications, allowing multimedia types of data to be delivered.

MBMS shall not be confused with ‘IP Multicast’ – the multicast solution proposed by IETF. IP Multicast can, ...