Wireless Blog

The Wireless Blog from Unwired Insight discusses the latest developments in wireless networks and services, including the new technologies and architectures of LTE and LTE-Advanced. For expert advice on 2G, 3G and 4G mobile systems and standards, including GSM, UMTS, LTE and LTE-Advanced, please contact us.

Mobile broadcasting comes of age in LTE eMBMS

Photograph of Alastair BrydonAt this month’s International Consumer Electronics Show  (CES 2013) in Las Vegas, Verizon Wireless announced plans to launch a video broadcast service based on eMBMS, the LTE variant of the 3GPP Multimedia Broadcast Multicast Service (MBMS). Amid reports that a number of network operators are considering eMBMS, Verizon took the opportunity of CES to demonstrate eMBMS in action, in collaboration with Ericsson and Qualcomm, and to reveal its plans to launch services early in 2014.

For many years it has been recognised that the point-to-point delivery of video services is a major drain on the capacity of mobile networks and that broadcasting would be a much more efficient approach in situations where the same content is being sent to multiple users. There have been a number initiatives to satisfy this need, including dedicated mobile broadcasting networks, such as Digital Video Broadcasting-Handheld (DVB-H) and Digital Multimedia Broadcasting (DMB), and adaptations to cellular networks, such as MBMS. However, these have met with limited commercial success to date. There have been various reasons for this, including the cost of deploying high quality services, the need for special terminals, and limited picture quality. A problem with broadcast services is that consumers are becoming increasingly accustomed to consuming multimedia content as and when they want to, for example using personal video recorders (PVRs) and online “catch-up” services, rather than being constrained to a broadcaster’s schedule. However, there are certain occasions when broadcasting comes into its own, such as during major live news or sports events. Also, there may be opportunities to broadcast certain material to the memories of mobile devices, to be consumed later, rather like a mobile PVR. As well as providing video and audio broadcasts, the same approach could be used to deliver software, games and music to mobile devices. Given the potential for network operators to off-load large quantities of point-to-point multimedia traffic during these occasions, there remains considerable interest in a flexible, efficient mobile broadcasting system that requires minimal changes to existing networks. 

MBMS was first introduced into the 3GPP specifications in Release 6, in 2005, with the aim of enabling multicasting or broadcasting of multimedia content over 3G UMTS radio access networks. While the technology was effective, the service was not a great success. One of its weaknesses was the limited capacity that could be set aside in a UMTS radio access network, which restricted the number and/or quality of channels it could deliver. A typical configuration would be five channels running at 256kbit/s.

In 3GPP Release 9, in 2009, MBMS was enhanced to take advantage of the capabilities of the LTE radio interface, with the potential to enable more attractive services. The faster throughput and greater capacity of the LTE interface offer the prospect of more channels at higher quality and the flexible allocation of resources in LTE avoids the need to dedicate spectrum permanently, which was a weakness of 3G MBMS solutions. Instead, the channels required by a broadcast can be set up and cleared down in an LTE network as and when required. A particularly attractive feature of the LTE radio interface is that it can provide broadcast services across a set of cells as a Single Frequency Network (SFN), whereby all of the cells delivering a particular broadcast channel can operate on the same frequencies, providing they are closely synchronised. Rather than causing interference to each other, the signals can be combined constructively. This is particularly helpful near cell boundaries, where coverage and interference problems are generally at their worst. Modelling by Qualcomm suggests that eMBMS could offer a substantial broadcasting capability. For example, if a network operator with 10MHz LTE spectrum temporarily allocated 60% to eMBMS it could deliver 16.9Mbit/s of user throughput in an urban environment.

3GPP Release 11,  under development during 2012 and 2013, introduces a number of further benefits, including new video coding to enable higher frame rates and picture resolution, and improved error correction.

It remains to be seen whether network operators can find the right combination of service propositions, content and pricing to exploit the full benefits of LTE’s broadcasting capabilities, but with multimedia services consuming more and more network capacity the benefits could be substantial. More than ever eMBMS provides network operators with the tools for the job.

Dr Alastair Brydon has worked in digital radio communications for over 25 years. He provides expert advice on 2G, 3G and 4G mobile systems and standards including GSM, UMTS and LTE. He has written over 40 reports on the development of wireless technologies and services and has acted as an expert witness in major patent disputes.

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