Multimedia Broadcasting in LTE Networks

Multimedia Broadcasting in LTE Networks

Antonios Alexiou (University of Patras, Greece), Christos Bouras (Computer Technology Institute & Press "Diophantus", Greece & University of Patras, Greece), Vasileios Kokkinos (Computer Technology Institute & Press "Diophantus", Greece & University of Patras, Greece), Andreas Papazois (Computer Technology Institute & Press "Diophantus", Greece & University of Patras, Greece) and George Tsichritzis (University of Patras, Greece)
DOI: 10.4018/978-1-4666-0017-1.ch011
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Abstract

Long Term Evolution (LTE) constitutes the latest step before the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the functionality to transmit MBMS over Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. In MBSFN transmissions, the achieved Spectral Efficiency (SE) is mainly determined by the Modulation and Coding Scheme (MCS) selected. This study proposes and evaluates four approaches for the selection of the MCS that will be utilized for the transmission of the MBSFN data. The evaluation of the approaches is performed for different users’ distribution and from a SE perspective. Based on the SE measurement, the approach that either maximizes or achieves a target SE for the corresponding users’ distribution is determined.
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Introduction

Long Term Evolution (LTE) constitutes the evolution of the 3rd Generation (3G) mobile telecommunications technologies. In order to enhance 3rd Generation Partnership Project’s (3GPP) radio interface, LTE utilizes Orthogonal Frequency Division Multiple Access (OFDMA) (Holma & Toskala, 2009). Moreover, 3GPP has introduced the Multimedia Broadcast/Multicast Service (MBMS) as a means to broadcast and multicast information to mobile users, with mobile TV being the main service offered (3GPP, 2010b; Holma & Toskala, 2009).

In the context of LTE systems, the MBMS will evolve into e-MBMS (“e-” stands for evolved). This will be achieved through increased performance of the air interface that will include a new transmission scheme called MBMS over Single Frequency Network (MBSFN). In MBSFN operation, MBMS data are transmitted simultaneously over the air from multiple tightly time-synchronized cells. A group of those cells which are targeted to receive these data is called MBSFN area (3GPP, 2010b). Since the MBSFN transmission greatly enhances the Signal to Interference plus Noise Ratio (SINR), the MBSFN transmission mode leads to significant improvements in Spectral Efficiency (SE) in comparison to multicasting over Universal Mobile Telecommunications System (UMTS). This is extremely beneficial at the cell edge, where transmissions (which in UMTS are considered as inter-cell interference) are translated into useful signal energy and hence the received signal strength is increased, while at the same time the interference power is largely reduced (Holma, 2009).

In this study, we evaluate the performance of MBSFN in terms of SE. In general, SE refers to the data rate that can be transmitted over a given bandwidth in a communication system. Several studies, such as (Rong et al., 2008), have shown that SE is directly related to the Modulation and Coding Scheme (MCS) selected for the transmission. Additionally, the most suitable MCS is selected according to the measured SINR so as a certain Block Error Rate (BLER) target to be achieved. Taking into account the above, we focus on a dynamic user distribution, with users distributed randomly in the MBSFN area and therefore experiencing different SINRs. Based on the measured SINRs, our goal is to select the MCS which should be used by the base stations when transmitting the MBMS data. For this purpose, we consider four approaches with different goals set in each one of them. More specifically:

  • The 1st approach selects the MCS that ensures that all users, even those with the lowest SINR, receive the MBSFN service (Bottom Up approach).

  • The 2nd approach selects the MCS that ensures the maximum SE for all users in the MBSFN area (Top Down approach).

  • The 3rd approach sets a predefined SE threshold for the area and selects the MCS that ensures that the average SE over the MBSFN area exceeds this threshold (Area-Oriented approach).

  • The 4th approach selects the MCS that ensures that at least the 95% of the users receive the MBSFN service with a predefined target SE (User-Oriented approach).

The remaining of the manuscript is structured as follows: the background section presents the related work in the specific field, as well as an overview of MBSFN architecture. Afterwards, we describe the methodology for calculating the SE of the MBSFN delivery scheme in the single-user case. The four approaches for selecting the MCS of an MBSFN area as well as the evaluation results are presented subsequently. Finally, the last two sections present the conclusions and the planned next steps. For the reader’s convenience, appendix A presents an alphabetical list of the acronyms used in the manuscript.

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