DVB-RCT (Digital Video Broadcasting - Return Channel Terrestrial) provides a method by which the DVB-T platform (and in theory also the DVB-T2 platform, but DVB-T2 probably trialled first about 5 years after last DVB-RCT field trial) can become a bi-directional, asymmetric data path using wireless between broadcasters and customers. DVB-T when completed with DVB-RCT can be used not only for interactive TV (voting, quiz, etc.), but also for light IP telecommunication services. Without this method, various degrees of interactivity can be offered, without implying any return channel back from the user to the service provider: Data Carrousel or Electronic Programs Guides (EPG) are examples of such enhanced TV services which make use of “local interactivity”, without any return path from customer to provider. To implement interactive services having a closely coupled and real-time relationship with the TV programs (e.g. interactive advertising, tele-voting, tele-quiz), a low latency return channel technology is mandatory, and this is the goal of the DVB-RCT.
By 2006, Runcom, the main developer of DVB-RCT, had abandoned it (no deployments due to mobile phone penetration) and switched the expertise to portable WiMax modems and infrastructure, later adding LTE. Many people mistakenly think DVB-RCT would have allowed viewers to browse the Internet. Partially the mistaken Internet belief was due to the "It's TV" Proposal in Ireland in 2000/2001 and RTE-NL (now 2RN) 1999 field trials assisted by Runcom.
But peak time speeds using existing TV mast infrastructures would have provided about 1.2 Kbit/s or less. It could only have been used for in program voting or purchase of broadcast advert items (TV or Teletext, or later MHP / MHEG5 broadcast), very little per downloaded content. DVB-RCC, the cable version of DVB-RCT, never succeeded in competing against Cablelabs DOCSIS. Internet by Satellite did use DVB-RCS, the satellite version of DVB-RCT, but Ka-Sat and others have been deploying satellite versions of DOCSIS since 2005.
It was projected in 2001 that revenues from TV commerce would exceed revenues from e-commerce in the home by 2008. T-commerce clearly requires a return path from the home back to the digital TV service provider. The current scenario of UHF/VHF bands shows a very congested spectrum in several countries that could be a real problem for the introduction of new services.
From a pure technical point of view, DVB-RCT is built around technologies for digital transmission and information theory; in addition to the benefits of first generation OFDM technology for broadband portable and mobile services, Multiple Access OFDM included in the DVB-RCT specification provides the following characteristics:
| Downstream Channel (DS) | OFDM, ETS 300 744 (DVB-T) compliant | |
| Return Interaction Channel | Multiple Access OFDM (MA-OFDM) | |
| Forward Interaction Channel (US) | Embedded in DS, compliant with ETS 300 744 (DVB-T) | |
| OFDM Carrier set | 1024 (1K), 2048 (2K) | |
| OFDM Carrier spacing (CS) | ~1K, ~2K, ~4K | |
| Transmission modes | 6 modes (as combination of 3 CS and 2 Carrier set) | |
| Carrier shaping | Nyquist, Rectangular | |
| Guard Interval | 1/8, 1/16, 1/32 (for Rectangular shaping only) | |
| Transmission Frames | TF1, TF2 | |
| Data randomization | PRBS with polynomial: 1+X14+x15 | |
| Modulation | QPSK, 16QAM, 64QAM | |
| Useful data payload per burst | 18, 27, 36, 54, 81 bytes (1 burst = 144 modul. Symbols) | |
| Channel codes | Turbo or concatenated (Reed-Solomon + Convol.) | |
| Interleaving | Random Interleaver - PRBS with polynomial: 1+X3+x10 | |
| Burst Structures | BS1, BS2, BS3 | |
| Frequency hopping | for BS1 only (optional) | |
| Medium Access Schemes | MAS1, MAS2, MAS3 (as combinations of BS and TF) | |
| Net Bit rate /carrier (range) | 0.6 kbit/s - 15 kbit/s (depending on the mode) | |
| Service range | Up to 65 km (cell radius) | |
| Channelisation | 6, 7, 8 MHz channels are supported |