DTT / WhiteSpace a technical brief

Transcription

1 BACKGROUND Digital Terrestrial Television (DTT) is a worldwide move happening as we speak, of moving wireless television signals from Analog to Digital. The move to DTT brings in enormous advantages to broadcaster, consumers, the government and the economy as a whole. DTT is bound by better standards and specifications and it will generate short term, medium term as well as long term benefits to all stakeholders including content providers, service providers, network operators, satellite companies, TV manufacturers and other equipment vendors. As in other tech standards, the world has chosen to adopt different DTT standards based on local priorities. The geographical map below shows the worldwide adoption of DTT standards in different countries: DVB-T ATSC ISDB-T DTMB

2 WHY DIGITAL TRANSMISSION» Efficient use of Frequency Spectrum DTT supports better compression with multiplexing techniques and hence can handle Up to 6 MPEG-2 SD or 12 MPEG-4 SD TV channels instead of 1 analog in the same bandwidth. DTT supports SFN where different transmitters use the same frequency channel to transmit the same signal as compared to MFN which utilizes different frequencies used by the transmitters to transmit the same signal to avoid interference problem. These lead to better use of spectrum for applications like TV White Space» Capability to have local content insertion. This is splicing of feed to replace the ad slots with local ads in local language. It helps the broadcaster to increase the revenue on the ad-sales by being able to sell same slot to different advertisers in different region. The consumer gets the advantage of the content of relevance.» Conditional Access or encryption (for free to air as well as pay services) enables content protection to prevent content piracy» Digital transmission provides improved reception quality & can Support SD/HD since digital transmission avoids the ghosting problem of analogue transmission as a result of multipath reflections and the snowy pictures which is caused by the weak signals» TV viewership is under pressure to keep delivering better quality of content to compete with other media delivery platforms DTT INFRA A typical infrastructure of DTT would have the headend infrastructure distributing the DTT Multiplex stream over telecom network or the satellite network or both to have redundancy path to multiple DTT transmitters. From these transmitters the services are transmitted using DTT standards to the household receivers. Distribution Path-2 Satellite Connectivity Headend Infra Distribution Path-1 Networked Connectivity

3 DTT AND DTH CO-EXISTENCE In conditions where the broadcaster is operating on both DTH and DTT segment due to larger coverage area will get to have the benefit of opex cost saving by choosing solution design of Benchmark where the broadcaster need not invest in two satellite segment cost - for DTH and DTT separately. Rather, with a common infrastructure setup, the broadcaster can operate and transmit the services in a single satellite bandwidth for DTH uplink containing DTT metadata for enabling the distribution to the Digital Terrestrial Transmission sites operating at SFN. This infrastructure will also cater in scenarios where the DTH has a relatively larger number of services with national and multiple regional services for the whole nation and the DTT transmission has to be limited to national with specific regional services. It is possible to limit the services at the DTT sites by dropping the unwanted services during the DTT steam re-generation. Satellite Connectivity DTH Common Headend Infra for DTH with DTT Gateway DTH to DTT adapter DTH to DTT adapter

4 WHITESPACE AN INTRODUCTION WHY WHITESPACE With the transition to DTT set in the roadmap in relatively larger number of countries, the spectrum is getting freed up for more innovative applications and one such is White Space. Television White Space refers to the unused frequencies in the TV Broadcast spectrum. Traditional analog transmission has buffer/guard channels between the active services for protecting broadcast interference between the services, these are no more required after the migration to DTT and also as explained in the initial part of this article DTT consumes relatively less bandwidth for the active services. Why WhiteSpace The aim of Television WhiteSpace is to enable a layer of Internet connectivity for the remote users in the footprint of the DTT transmission by using the backbone of ISP and the DTT infrastructure. WhiteSpace Advantages» Because of its lower frequency White Space signals can work in non-line of sight conditions and can travel through building, vegetation and other obstacles» White Space will act as a Super Wi-Fi to provide broadband connectivity because of the propagation properties of the signal» Apart from Internet connectivity White Space can also enable machine-to-machine communication DYNAMIC SPECTRUM ACCESS IEEE is the IEEE standard defining the Wireless Regional Area Network - WRAN for the use of Television WhiteSpace with much better coverage standard utilizes Cognitive Radio and this leads to Dynamic Spectrum Access. Dynamic Spectrum Access (DSA) is a set of technologies and techniques enabling radio communications devices to work on available radio spectrum. DSA ensures that devices have wireless bandwidth when and where they need it. The working principle of DSA is:» The user of a WhiteSpace device requests access to the WhiteSpace database» The user is registered and access is provided and authorised» The user can then make a request for available WhiteSpace channels» Available channels are assigned and authorised for a defined time period after which the channel availability needs to be verified and renewed

5 WHITESPACE ARCHITECTURE Regulatory bodies from various countries are defining standards and guidelines for the allocation of WhiteSpace for consumer use. Various trials and pilot projects are being undertaken in countries such as the US, UK, Singapore, India, The Philippines among others. These tests have proved that the WhiteSpace operation is safe and interference free for licensed broadcasters. The guidelines being defined by the frequency regulatory bodies include the technical and operational parameters of WhiteSpace devices WhiteSpace base stations, television band devices and the WhiteSpace database system the registration of unlicensed users with the database system, operational mechanisms between WhiteSpace devices etc. Typical sample architecture of the WhiteSpace 1. The TV-WS Base Station device connects to the spectrum controlling organization 2. The controller offers to the TVWS-BS a list pf registered databases 3. The TVWS-BS selects a geo-location database from the list and sends few parameters such as location 4. The database answers with the vacant frequency bands represented by few return parameters 5.The master device provides the available frequency information to the TVBD 6. The slave devices answer the master device with data confirmation TVBD 5 6 List of databases 1 2 TVWS-BS 3 4 DTT coverage database Geo-location database WHITESPACE FOR BROADBAND Several telecom and cable providers have moved into densely populated urban centers, by offering cable channels through broadband and vice versa. However, due to the heavy investment cost needed for implementing broadband services, these telecom and cable providers have not yet penetrated into remote terrains or lowdensity areas. WhiteSpace enables TV networks to bring in additional value added services such as broadband to remote areas. This enables current TV operators who have far flung TV networks, to have additional sources of revenue by providing Internet services. Benchmark has collaborated with hardware vendors to bring in important missing pieces of the DTT/Whitespace jigsaw, to serve the TV Broadcasters who are currently implementing DTT and would like to take advantage of the Whitespace benefits. Apart from providing specific hardware such as IEEE WRAN compliant modems and antennae, the Benchmark team will also support the installation, integration and if required the maintenance of such remote broadband networks.

6 ABOUT BENCHMARK Benchmark Broadcast Systems, is a consultant and technology partner for media and broadcast companies in Asia. Headquartered in Singapore, the Company has offices in Bangkok, Chennai, Delhi, Dhaka, Kuala Lumpur and Manila. Its on-site engineering, software programming, software & systems integration, testing and support services are highly specialised. It operates in network mode with senior managers functioning out of Singapore, Chennai, Delhi and Manila. Benchmark focuses on providing complete solutions for broadcast and post production applications. The spectrum starts from simple modules to complete turnkey systems integration services for setting up a totally new TV station or upgrading/modernising existing ones. The Company also provides a complete range of services from pre-sale consultancy, through to systems design and integration, installation, user training, support and even to managed services. Benchmark Broadcast s capabilities extend to configuration of comprehensive enterprise-wide solutions, application support, systems installation and customer training and, importantly, to development of customised solutions. When you absolutely, positively have to be on-air 24/7 BROADCAST SYSTEMS Benchmark Broadcast Systems (S) Pte Ltd 12 Tannery Road #09-05/06/07 HB Centre I Singapore Phone: Fax: info@benchmarkbroadcast.com