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ABSTRACT

The article investigates the coverage achievable by three different network configurations for delivering high quality multicast video services to mobiles: conventional broadcast High Power High Tower (HPHT), mobile cellular Low Power Low Tower (LPLT), and mixed structures.

Different spectrum efficiencies, transmitter distance and power, and receiver characteristics are considered, representing a range of possible network scenarios.

The study actually models generic radio interfaces with particular characteristics. Nevertheless, the choice of the parameters reflects configurations in use in 4G or currently under discussion for 5G, preferred over similar/better performing DVB T2Lite or NGH (Next Generation Handheld) broadcast technologies, to facilitate the user terminal implementation (smartphones and tablets).

The results clearly indicate that the best solution in terms of Capex/ Opex for running the network is represented by the cooperative approach where most of the rural/suburban coverage is provided by the HPHT network and the LPLT cellular networks are used to complete the coverage, especially in densely populated urban areas.

This allows avoiding the installation and operation of thousands of LPLT transmitters, with a very significant reduction of the corresponding network costs.

INTRODUCTION

The mobile communications sector is characterized by an exponentially increasing traffic demand for high quality mobile multimedia services, a significant portion of which identifiable with linear Television (TV) and scheduled broadcast (point-to-multipoint) distribution.

Current 3G and 4G mobile networks can deliver video services, but were primarily designed for two-way and one-to-one services, in the form of on-demand videoclips (e.g., YouTube), generally with limited quality of service (QoS), on a best effort basis.

Using the current unicast approach, video streaming represents a serious challenge for mobile operators, that will face the risk of overloading their very expensive frequency resources.

While 3G and 4G standards have been extended by a broadcast specification (MBMS, Multimedia Broadcast Multicast Service), that allows for the delivery of content to an arbitrary number of mobile viewers in a typical cell, the use case is not fully compliant with the requirements of TV Media Companies, that need to deliver “live high quality video content” (High Definition, HD) at guaranteed QoS (without buffering time) to millions of viewers at affordable price.

A big challenge is the requirement to deliver linear video content to a large number of viewers simultaneously (in the same cell or across many cells).

This is being considered in the framework of the 5G initiatives, where a heated debate is running about the choice of the best network infrastructure for providing digital mobile/portable IP-multicasting services, based on an evolution of the 4G e-MBMS protocol.

In recent years, an evolution of the LTE-A (4G) technology, called LTE-A+, has been proposed by Technische Universitat Braunschweig to allow for the implementation of the “Tower Overlay” concept, Ilsen et al (1).

This consists of transmitting broadcast services to mobiles from a traditional broadcast infrastructure, based on large cells, representing a more efficient delivery solution to cope with a high number of users consuming simultaneously the same service within a given coverage area.

LTE-A+ proposes additional features to the LTE standard, like longer cyclic prefixes (CP), that are necessary to support the HPHT broadcast environment. This paves the way to cooperation between the cellular and broadcasting networks, in order to reach all mobile devices without the need to add a specific broadcast receiver in the devices.

To verify the proposed approach in the field, Rai CRIT launched in 2015 an experimental trial in the Aosta Valley. During this trial, two data streams, DVB-T2 and LTE-A+, shared the same UHF channel in time-division: the first one conveyed conventional HDTV programs to domestic DVB-T2 receivers, and the second one conveyed a flow intended for LTE-A+ devices.

Meanwhile, a simulation study was started to understand the strengths and the weaknesses of the different network structures. The goal was finding the best solution for delivering high quality video to mobiles at limited network costs and affordable price for the customers.

This article describes the above mentioned simulation analysis of the performance achievable by three different network infrastructures: (i) conventional broadcast HPHT, (ii) mobile cellular LPLT, and (iii) mixed network structures.

A wide range of spectrum efficiencies, transmitter distances and powers, as well as receiver characteristics have been considered, to represent different possible scenarios for the delivery of multicast 5G video services to portable/mobile terminals.