Why Digital?

The principal advantage of digital microwave links is that digital information can be transmitted without degradation and then reconstructed at its destination, within predictable limits. A digital signal can also be compressed, reducing the information that has to be conveyed. This reduces the bandwidth requirements of transmission systems.

The other main advantages of digital microwave links are as follows:

	Digital transmissions are more 'Robust', are error free, and predictable under most conditions.
	Digital transmissions makes more efficient use of spectrum and have better threshold margins.
	Digital transmissions have a more rectangular spectrum mask/ better adjacent channel rejection

Practical Considerations
Despite the advantages that digital wireless technology offers in terms of the live coverage of outside broadcasts and news gathering, digital technology is still a trade off between best quality, delay, and rugged RF. If you are looking for the best quality MPEG 2, with 64 QAM COFDM modulation, is the answer. On the other hand, QPSK modulation provides an extremely robust RF signal for use in difficult locations. No one permutation will give you best quality with rugged modulation and/or minimum delay.

No one permutation will give you best quality with rugged modulation and/or minimum delay. When choosing a digital wireless camera system or planning an event you must decide what are your priorities:

	Best quality?
	Minimum bit rate?
	Minimum or no delay?
	Rugged Modulation?
	Narrow bandwidth?

In the early days of digital wireless cameras, engineers tended to use QPSK modulation for sporting and other events. However, as confidence in digital wireless cameras has grown, engineers have started using 16QAM (low delay mode), with promising results, even in sports stadiums.

“What is the range?” is a question that you often hear from people who are not familiar with using wireless cameras. The traditional answer is, “As far as the nearest receive point”. To a great extent this is still true but a recent test in Rome, under operational conditions, provided extensive coverage of Saint Peter's Square from a rooftop receive point, 500 metres away. During another test, in Hong Kong, signals from a 100mW D-Cam were received 40 kilometres away using only a 0.9m dish and feed at the receive site.

Why Gigawave?
The benefits of Gigawave Digital Technology

Low Delay Compression Techniques
COFDM Modulation
Outstanding RF Performance

Over the past two years, there has been a quiet revolution in the live coverage of major sporting events, and other outside broadcasts. Suddenly, viewers are seeing things from a new perspective, thanks to digital wireless camera systems.

Cameramen, especially those using a Steadicam or similar rig, are now able to go where they please to get that special shot, freed from the constraints of an umbilical cable.

Digital Compression
Digital Compression Techniques
Basic Principles of MPEG

All Gigawave digital transmitters and receivers (except the D-Cam 'Clip-on') are available with a choice of both MPEG 2 and 'Wavelets' compression. These 'plug-in' modules can easily be changed on-site, or upgraded as new compression techniques evolve, thanks to the unique modular design of Gigawave digital microwave links. The choice between MPEG 2 and 'Wavelets' compression depends on the application and/or RF environment in which the link is used.

MPEG 2 /Wavelets Application Guide:
With all Gigawave digital links, you choose the encoding that best suits your particular application:

Digital Modulation
Digital Modulation Techniques
Basic Principles of COFDM

The new generation of Gigawave digital microwave links all use DVB-T compliant COFDM modulation The 'plug-in' COFDM modulator can be switched to operate in 64QAM, 16QAM and QPSK modes, whilst the corresponding receiver demodulator automatically 'senses' the operating mode.

Digital modulation Offers
		Either vastly increased threshold margins compared with equivalent analogue FM (eg QPSK threshold extended by more than 20 dB - equivalent to increasing transmitter power by 100 times!)
		Or increased payload. Digital modulation packs more ‘bits’ into each megahertz of RF bandwidth (eg 64 QAM has 4 times the bit/MHz ratio compared with QPSK) at the expense of threshold margin (12 dBs less than QPSK)
		Increased protection ratios compared with analogue, because the unwanted signal does not have the coherence of an analogue signal, and appears like noise.

COFDM
		Resilient to multipath. Actually, COFDM benefits from multipath reflections!
		Improved robustness as a result of Forward Error Correction.
		Theoretically perfectly rectangular spectrum shaping and discrimination between carriers as a result of the orthogonal coding employed. This enables adjacent channel operations, with the protection ratio being determined solely by the orthoganality of the coding, and the linearity of the RF amplifiers.
		Basic Principles of COFDM

Digital RF
Advanced RF technology based on experience
Digital Transmission Techniques

Gigawave engineers have designed a new range of 'state of the art' transmitters from 100mW to 1 Watt, in which every component has been harmonised to work in a digital environment.

Specially designed linear up/down converters, IF/RF amplifiers, and power amplifiers, essential for the higher orders of modulation such as 64QAM, have been matched with digitally optimised antennas, resulting in exceptional RF performance.

The superior RF performance of the 100mW D-Cam transmitter, when matched with the high dynamic range of the latest MVL-D2 receiver is such that it requires only a single receive point with Fanbeam antenna for most normal OB locations, including sports stadiums. The same technology enhances the performance of point to point and other digital microwave links.

The Gigawave Guide to Digital Microwave Technology:
For more detailed information we have produced a simple guide to digital encoding, modulation and transmission techniques. It contains all you need to know about digital broadcasting.

Digital Television Basics
Digital Compression Techniques
Digital Modulation Techniques
Digital RF Transmission