BROADCASTING

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BROADCASTING

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This section presents some specific aspects related to planning of access networks of analogue broadcasting services (FM, TV, DTT, DVB-H, DAB, etc.).

The planning process is based on the common steps specified in access network planning section,  although some aspects are presented for a better adaptation to the networks being planned.

Then, steps of access network planning process are listed, noting in each one when necessary, the points to which the user must pay special attention to the planning of broadcasting networks.

NEEDS ANALYSIS - CONFIGURATION

Cartography. Typically, this network type requires the use of rural cartography, terrain models with resolution between 100 and 25 meters. On the other hand, it may be convenient to determine the reception effect in urban areas, for that purpose it is advisable to use morphography layers that associate losses to these areas or layers of urban altimetry with buildings details.

Calculation method. Most common methods for planning broadcasting services vary depending on the planning environment and purpose. The most used are:

oITU-R Rec. 526 or Deygout method, are the most used to simulate emission from centers located in rural environments. The estimation of signal received inside cities is usually carried out in the same way, taking into account that reception thresholds in these environments are much higher, or, if urban cartography is available, using the option of atimetry multiple layers and applying a resolution to calculations similar to the building model's one.

oITU-R Rec. 1546 may be useful in cases where sufficiently detailed cartography (DTM resolutions greater than 100 meters) is not available. In addition, these methods are applicable to distances greater than 100 km, which may result in a better estimation than deterministic methods, which are unreliable in long distances. Finally, its use is advisable when simulating effects of possible interference for short time (1% or 5%).

Methods proposed by the International Telecommunication Union (ITU) are standard and very useful; However, they do not always ideally fit the propagation in all environments.

PARAMETERIZATION OF STATIONS

Reception threshold. The reception threshold parameter to be used in the receivers radio parameters receivers is usually the reference field defined in international recommendations and standards, being usual to work in terms of electric field. It is common to work with different reception thresholds depending on the environment (like rural, urban, dense urban, etc.). In this case, the user can use morphographic layers that introduce a clutter factor associated with each terrain type or play in coverage studies with different ranges that fit the proposed thresholds.

Radiant systems. Radiant broadcasting systems are composed of one or more radiant elements that configure an array with particular emission characteristics.

NETWORK PLANNING

Receivers Orientation. It is important to note that receivers linked to each coverage study automatically orient their antenna towards their associated transmitter in the coverage study. When the receiving antenna is directive, this aspect is important since its associated transmitter signal level has maximum gain of the receiving antenna while the other signals are attenuated from other azimuths.

Best server per signal. In different network planning studies involving different stations, it is necessary to have a standad to determine the desired transmitter (best server) at each point. In order to consider a transmitter as best server, it is necessary to exceed the associated receiver threshold in the coverage study. Particular care must be taken not to set different thresholds for receivers of different coverage studies since in this case inconsistencies may occur when selecting the best server in zones with signal levels between these thresholds.

Overlapping. It is important, once the emission parameters have been determined for a new station as well as its frequency, to check the interference that this station may cause on the environment and, vice versa, the interference that the environment elements can cause on the New station service area. The multicoverage study "overlapping" result allows the identification of possible conflict zones with stations nearby.