Tandberg HD Microwave Links

Recognising a requirement for the very highest transmission quality, which until now has not been fully addressed by any other microwave link manufacturer, Giga-Com has formed a unique partnership with TANDBERG Television to develop the MLV-T series.

Currently, it is commonplace to heavily compress video content during transmission to the home and this makes it more important than ever to present the direct-to- home encoders with as clean a feed as possible, and maintain the very highest quality standards throughout the content acquisition and editing processes.  It is this requirement that sets the standard for the contribution and distribution phase.

Many broadcasters find it preferable to only lightly compress their C&D feeds. This provides the best quality outcome and can also reduce the encoding delay times as well as aid accurate editing.

The new MLV-T family of versatile point to point links has been designed for exactly this application. The MVL-T is the result of a joint development between TANDBERG Television and Giga-Com with the simple aim of combining the unequalled encoding performance of TANDBERG Television with the satellite derived RF expertise of Giga-Com. The resulting solution provides the best performing, most versatile, feature-rich portable link system on the market.

The system shares similar 2 box architecture to the standard MLV-series links with the same RF head units and highly ergonomic mechanical packaging but control units are based on the TANDBERG Television E5788 encoder and RX1290 decoder.

The E5788 encoder was chosen as the standard compression engine for this solution because it is so powerful and versatile. The unit offers both MPEG-2 HD and SD encoding, and a software upgrade allows both encoders to be used simultaneously to provide 2 separate services out of the box when required. Both encoders are advanced and highly-tuned for excellent video performance as well as low encoding latency, and both are 4:2:2 capable.  This powerful encoder is coupled to the latest generation, DVB-S2 modulator providing highly efficient transmission.

DVB-S2 modulation is normally associated with satellite transmission but was chosen for this application because it provides several advantages over more conventional COFDM solutions.  Whilst it is possible to use COFDM, in practice the multipath capability offered by COFDM is not utilized in a point to point environment. The limitations of COFDM are therefore present without providing a tangible benefit, and include the fact that most COFDM systems are designed for bandwidths up to 8MHz and therefore the systems have a practical bit rate limit of approximately 24Mb/s with 64QAM. In contrast, using DVB-S2 allows wider bandwidths to be used, and the advanced error-correction used with DVB-S2 provides a considerable efficiency advantage. This system is therefore able to achieve bitrates of up to 80MB/s using DVB-S2 8PSK modulation and there are plans to increase this even further in the future.

What this enables is the transmission of very high quality 4:2:2 encoded material, with minimum delay and the possibility to use the optional REMUX card to add more services.

The REMUX card is one of a number of options for the E5788 and adds a multiplexing capability providing 3 x ASI inputs. This makes the system capable of transmitting several services over a single RF link. Other options include extra audio cards (to add a further 2 stereo channels) and the BISS option card to provide secure encryption. RAS is also available as a software option.

A standard E5788 would finish at the modulator stage and would provide a 70MHz IF output. With this system, an additional Giga-Com option card is fitted performing multiple additional functions as follows;
•    Accepts the DVB-S2 output from the modulator
•    Provides a 48VDC feed from the E5788 power supply
•    Interfaces with the controller in the E5788 and establishes a control connection with the transmitter head unit, containing the final frequency up-converter and power amplifier.
•    For convenience, offers a bi-directional audio talk-back path between the encoder and the RF head unit
The Giga-Com card therefore acts as an interface between the E5788 and the RF head-unit, allowing the head-unit to be configured and controlled from the font panel of the E5788.

The receive control unit is based on the RX1290 decoding engine repackaged by Giga-Com with a form factor to match the E5788 and including the following features:
•    MPEG-2 or H.264 decoding hardware provided as standard
•    HD or SD capability
•    4:2:2 HD or SD with the MPEG-2 decoder
•    Optional down-conversion from HD to SD
•    Optional support for simultaneous 4 stereo audio decodes
•    Low latency option
•    ASI input
•    DVB-S2 QPSK / 8PSK L-band inputs (X3) and 70MHz input (X1)
•    Configurable outputs (X3) lockable to provide HD-SDI, SD-SDI
•    Composite monitoring output
•    Component video output for monitoring HD on a projector or PC monitor
An advanced front-panel provides comprehensive control of the receive RF head unit and also includes a full colour switchable 4:3/16:9 monitor for display of the decoded video directly for monitoring.

As with the standard MLV-series, 70MHz, DC power and control signalling with audio talk-back circuit are carried over a single coax, triax or fibre optic cable.