Network topologies and spectrum efficiency of High and Low Tower Broadcast Networks

I have made a study, comissioned by Broadcast Networks Europe (BNE), on network topologies and spectrum efficiency of High and Low Tower Broadcast Networks. The study is based on results from computer simulations made in a software that I created specifically for this work.

Below follows excerpts from the Executive Summary and Background sections in the final report of this study. The full report can be downloaded further down in the end of this blog post.

Existing terrestrial broadcasting networks are based on high power transmissions from high towers and masts. The high tower infrastructure is usually supplemented by in-fill transmitters using low to medium height towers to cover areas where the high tower transmissions do not reach, for instance due to terrain irregularities and shadowing. Additional sites are also sometimes needed to tailor coverage areas to deliver regional broadcast content.

Using high towers and masts is a cost-efficient solution to provide broadcasting services, i.e. where the same content is consumed simultaneously by a large audience over a large area. The higher the mast, the larger the coverage area, meaning that a limited number of high power transmitters can be used to cover very large areas and populations. In practice there is a limitation of the maximum height of a mast for technical and cost reasons. Most European countries use broadcasting masts and towers with heights in the range 150-300 meters to efficiently provide the required coverage. The optimal height depends on surrounding terrain, coverage requirements, cost considerations, the need for regional services and other national or local conditions.

For many years the broadcasting infrastructure was the only nationwide terrestrial infrastructure to provide radiocommunication services to the general public. However, when public mobile networks were rolled-out they were generally established using low tower infrastructures. The two main reasons were that mobile cell sizes are limited by the available output power of the handsets and that cell sizes need to be small enough to provide the necessary capacity to serve all active users in each cell.

Based on the almost universal availability of low tower infrastructure for mobile networks it has been suggested that this infrastructure may also be used for broadcasting purposes, possibly replacing the traditional high tower broadcasting infrastructure. A number of important issues will need to be analysed and addressed in this context. In this study two key aspects are considered; number of sites and potential spectrum gain;
for comparison of high tower (HT) based architecture with low tower (LT) based architecture for terrestrial broadcasting.

To investigate the feasibility of different network configurations for the transmission of digital terrestrial television (DTT), alternative network architectures with different power levels and transmitting antenna heights (300 m, 50 m and 30 m) have been studied for fixed reception with rooftop antennas. In all cases Single Frequency Network (SFN) design and DVB-T2 technology was used.

 The full report can be read here.

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