Broadcast

This note describes how ATDI software can be used across current Analogue and Digital Broadcast Technologies in both TV and radio to optimise and roll out networks. Tools are included within ATDI planning tools for future technologies such as T-DAB and DTTV. The methods and sub-tools within tools such as ICS Telecom have come from our work with various broadcast customers including several national broadcast organisations as well as systems integrators supplying turnkey broadcast solutions.

These customers have either used our tools or have contracted ATDI to carry out work on their behalf to furthers their development of their broadcast networks.

General Broadcast Planning Methods

The following general modelling methods have application in broadcast networks and are included in ATDI planning tools. Please refer to the technologies section on microwave links for details of tools for transmission bearer planning.

• The ability to compute the coverage of ground area from a given transmitter type and specification to a given receiver type and specification considering both directional and omni-directional antennas.
• The ability to design and model all types of sectored broadcast antennas including those with down tilt. Antennas may be theoretical, mirroring administration masks or real, emulating reality and comparisons may be done between the two.
• The ability to compute the degree of interference suffered by subscribers from all sources on the same or adjacent channels. This includes the ability to view interference limited coverage across all combinations of culprit and victim networks. Interference includes considering varying protection ratios taken from ITU recommendations.
• The counting of subscriber population covered under a transmitter footprint with the addition of an irregular polygon limit. Includes the graphing subscribers by social category.
• The counting of area under a transmitter footprint but showing results over a variety of different urbanisation categories including roads, urban and suburban areas with the addition of an irregular polygon limit.
• The ability to link the planning tools via an Open Data Base Connectivity protocol to external databases such as Oracle or MS Access allowing the sharing of engineering data across a multi-discipline project team.

Specific Broadcast Planning Methods

Using ICS telecom, the spectrum co-ordinator/administrator can insert proposed sites and base station parameters either from database or directly on screen.He can then compute the resulting field strength for varying percentage of time and locations over differing path types (land, cold sea etc.) and can conclude whether the base station so defined is within the terms of the appropriate agreement or not. In the event of close co-ordination he can then go on to place the victim base stations or mobiles in the adjacent territory and analyse the degree of interference suffered.

The design and subsequently the roll our of broadcast networks to cover both analogue and new digital services is a well established process.

There is however great scope for automation in the methods and for optimisation of the engineering design to critically engineer the network to meet the customer requirements with the minimum transmitter and antenna system resources both initially and as the network develops.The specific methods noted below are some of the many tools employable to ensure that the planning team produce the most cost effective system.

The coverage calculated can be filtered to only display on specified ground use types such as suburban areas or roads. This then allows the planner to focus on the desired target user for the service. Similarly interference calculations over rural or open areas away from that target user can be ignored or reduced in consideration during automatic frequency planning.

Several views are possible once a coverage computation from a given sites or radio base station has been made. The best server view shows where on the ground mobiles would vote or register on the basis of signal strength. The simultaneous communications view shows which areas on the ground benefit from signal from several sites.

Once coverage has been assessed the operating frequency of the transmitter can be assigned automatically from a frequency list. Frequency planning can be set to consider either omni-directional or directional subscriber antennas.

With new digital services in both television and radio ICS Telecom incorporates methods of assessing the effects of both amplitude and phase of multiple arrivals at the subscriber antenna.

At the overlap if the incident signals are within capture of the receiver and if the differential delays between the various signals is within various guard intervals the effect may be constructive or destructive interference. This effect typical of the Single Frequency Network can be modelled.