Update on the current status of DVB in Europe

Several different implementations of DVB are currently under discussion. The main difference lays in the method of signal modulation and error correction which influences the type of transmission line used. The following list gives an overview (Wikipedia, 2007):

• DVB-S for the signal transmission through satellites. A new specification DVB-S2 is currently under preparation.
• DVB-C for the signal transmission through cabel networks.
• DVB-T for the signal transmission through terrestrial base stations in the VHF or UHF frequency band. A new specification DVB-T2 is currently under preparation.
• DVB-H for the asynchronous terrestrial signal transmission to mobile receivers (Handhelds).
• DVB-IPI for the signal transmission through IP based networks, for example the Internet (Internet Protocol Infrastructure).
• DVB-RC(S/C/T) Return Channel for the transmission of data services, for example broad band Internet.
• DVB-SI for the transmission service information
• DVB-SH for the signal transmission between satellite and mobile device. 
• DVB-CBMS (Convergence of Broadcast and Mobile Services) The ad hoc Group CBMS was formed in March 2001 (under the name UMTS) to draw up technical specifications and guidelines for applications and services that utilise 'co-operation' between broadcast and mobile telecommunications platforms.

DVB is a standard mainly used for digital TV broadcast and was developed by the international DVB Project for fix or portable devices in the indoor, outdoor or mobile environment (vehicles). It builds upon -and is largely compatible with- the existing DVB-T standard for terrestrial broadcast. The standard describes several extensions to DVB-T, specifically adapted to the requirements of the mobile reception and transmission environments. Various national audiovisual organisations estimate the date of analogue switchover to take place in 2012.

The European Commission announced in 2007 that it will further promote this standard and give it a higher priority compared to other solutions. Several countries have already launched Digital TV broadcast for handheld units, such as Italy and Finland, and an increasing number of handsets supporting DVB-H is available to the mobile consumer. A survey conducted by EMBC among the EU member states revealed in Q1 2007 the following results:

Commercial DVB-H services have been launched in 2006 in Italy and Finland. Commercial DVB-H services are also expected to be launched in the Czech Republic and the Netherlands in 2007. In addition there have been DVB-H trials in more than half of the 22 responding countries. In total, DVB-H trials and services have been conducted or are on offer in over three-fourths of all responding countries. A DMB trial was also conducted in one country in Band IV. Two MediaFLO trials were also conducted in one country in Band V.

The introduction of DVB-T in Band IV/V is well underway in Europe, however the status of the introduction can be divided into two groups. One-half of the 22 responding countries have four or more DVB-T multiplexes in operation. (8 with 4-6 multiplexes and 3 with 7-9 multiplexes) and the other half have 1-3 DVB-T multiplexes, of which 6 are on a trial basis.  The national results of the GE06 agreement identify more resources for DVB-T than currently in use; of the 18 countries which could report the conference results for their countries, 17 reported allocations of 6-8 or more layers. This represents a substantial increase to current usage for 7 countries of 5-8 additional layers and of 2-4 additional multiplexes for 6 countries. (EMBC, 2007).
 
The following table shows the status of DVB-H availability world wide (DVB-H, 2007)

The DVB-H standard specifies the system requirements for both the physical layer as well as the lower protocol layers. The focus of these specifications lies on handheld terminals; light weight consumer devices having limited dimension, limited processing power and without external power supply, that impose severe constraints on the transmission system. Such requirements include low power consumption to prolong battery life, increased error robustness to facilitate mobile operation at high vehicle speed and data rates of 10 Mbit/s per channel to offer broadcast equivalent services. Further restrictions apply to the use of diversity antennas, to seamless radio cell handover and to the compatibility to existing DVB-T networks.

The physical radio transmission is based on DVB-T. Thus, COFDM multi-carrier modulation is employed and several constellation levels (e.g. QPSK, 16-QAM) can be selected. Compared to DVB-T, a new 4k modulation mode (in addition to 2k and 8k) is available and an extra channel bandwidth of 5 MHz can be chosen for applications not using the traditional broadcasting bands and channel rasters. In situations where the 2k or 4k mode is used, the OFDM symbol interleaver allows in-depth interleaving for increased error robustness.

Most of the DVB-H essential extensions are provisioned at the protocol layer, such that compatibility with DVB-T networks is ensured. Four important features can be discerned, that together form the DVB-H codec: Time slicing, IP interfacing, Protocol Encapsulation (MPE) and Enhanced Error Correction. For more details on the protocol, please see the specification documents.

DVB-SH (DVB – Satellite service to Handheld) is a radio interface technology designed to provide broadcast services to handset terminals via an hybrid terrestrial & satellite network infrastructure. The terrestrial network is deployed to provide optimal coverage in urban areas whilst satellite segment can complement coverage over the rest of a country.

DVB-SH intends to re-use some DVB-H technologies (OFDM modulation, time slicing, IP datacasting). The main modifications allow to improve the reception quality in mobile propagation environment thanks to efficient coding scheme (turbo code) allowing very low coding rate and to extended time interleaving at physical layer.
The mixture of satellite and terrestrial broadcasting technology encompasses high-power, geostationary satellites and low-power terrestrial repeaters, both operating in the 2170-2200 MHz frequency band. This 30 MHz spectrum is an IMT2000 band allocated to Mobile Satellite Systems. It is currently available in Europe and Asia. This band is adjacent to the T-UMTS Frequency Division Duplexing downlink band (2110 – 2170 MHz), which enables technology and implementation synergies with the UMTS technology at the terminal and terrestrial repeater level (a similar principle to the Chinese STiMi).

The satellites can provide outdoor and indoor coverage in rural areas under spot beams. The satellites are complemented by terrestrial repeaters to address indoor coverage in urban areas, where satellite signals suffer severe blockages. Terrestrial repeaters are designed to be co-sited with 2G & 3G cellular base stations and share their antennas, minimizing environmental impact. Terrestrial Repeaters installed in urban areas retransmit satellite programs on the same frequency and allow coverage to be extended inside buildings. Synchronization between the terrestrial repeaters and the satellite allows the receiver to see the satellite signal as a simple echo of the terrestrial repeater signal. This concept system has been validated with experiments carried out within the European MoDiS and Maestro R&D programs, and recently during a trial conducted by the French Space Agency in Toulouse.

DVB-SH may deploy some technology elements of DVB-H standard. The main differences with DVB-H lies with the replacement of the convolutional code and the reed Solomon code by a turbo code allowing low coding rate such as 1/3 or even 1/5. In addition, an enhanced “time interleaver” allows to enhance the time interleaving from a few milliseconds (DVB-H) to several hundred milliseconds and even further. These new feature prevent to add any additional error correction scheme and time interleaving schemes at higher layer such as MPE-FEC protocol to combat the mobile propagation conditions.

Two main radio interface configurations are foreseen:

• “Hybrid Satellite & terrestrial” or “Terrestrial only” which is expected to correspond to nine TV programs at a mean encoding rate of 256 Kbit/s and an MPEG2-TS level of 2.5 Mbit/s.
• “Terrestrial only” signal which is expected to corresponds to eighteen TV programs at a mean encoding rate of 256 Kbit/s and an MPEG2-TS level of 5 Mbit/s.
  

Standardization of DVB-SH is on-going in the DVB Project (EMBC, 2007).

Source: PTV