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Why the future of wireless is digital

As the amount of spectrum available for use by wireless mic operators continues to shrink, most microphone manufacturers (including Shure) are drawn increasingly towards digital wireless technology as part of the solution. But why exactly are digital wireless systems such a hot topic? How do they compare to traditional analogue systems? And what benefits, if any, do they bring to us as professionals? Throughout this article, we will try to shed some light on what’s driving digital wireless tech.

Firstly, let’s uncover some of the back story. It’s a well-known fact throughout the professional audio industry that clean spectrum available to wireless microphones and in-ear monitors is shrinking. In the years following the digital TV switchover (DSO), we’ve seen the amount of spectrum available to our industry reduce significantly. First to go was the 800MHz band (790–862MHz), which made way for next generation mobile broadband (4G) back in 2012. Then, in quick succession, Ofcom announced its plan to clear the 700MHz band within the coming years. On 17 October 2016 Ofcom announced that PMSE users need to vacate the 700MHz band by May 2020. In a short space of time, we will have lost access to nearly 50% of usable spectrum. To further compound the situation, additional announcements included granting so-called white-space devices permission to operate as secondary users in the UHF space – effectively introducing unlicensed, less predictable sources of potential interference. In short, the airwaves are becoming increasingly crowded with wireless tech as industries bid for more resource to feed our digital lives.

This growth in demand for wireless spectrum and the subsequent congestion has put significant pressure on wireless manufacturers to develop new technology able to maintain performance levels under progressively challenging circumstances.

“The airwaves are becoming increasingly crowded with wireless tech as industries bid for more resource to feed our digital lives”

Enter digital wireless systems…
Quite simply, the technology available to design professional-quality digital wireless systems has now advanced to a level where we can now run much higher channel counts in reduced clear spectrum. The improved efficiency is down to more predictable deviation of digital wireless signals when compared to a frequency-modulated analogue signal; this, in turn, allows for tighter channel-to-channel frequency spacing. In many cases, digital systems can deliver nearly twice the channel count in the same slice of spectrum as their analogue cousins. But at the same time, we shouldn’t be as simplistic to think that just because a system is digital it is more efficient. A critical criteria in determining spectral efficiency is the linearity of the transmitter and robustness of the filters in the receiver. The more the system costs, the better the performance in most cases. And lastly, good RF coordination and practise will also ensure that the deployment of large wireless system is a success.

With clean RF spectrum continuing to shrink — and demand for wireless mics and in-ears increasing each day — digital wireless technology will play a critical role in securing the future of wireless microphones at major events. The spectrum argument is clear, but what about the audio? How do digital systems sound when compared to their analogue counterparts?

Analogue vs digital audio is one of the most emotive topics in the business, and while the conclusion is mostly subjective across most devices (mixers, outboard processing, hi-fi, etc.), wireless systems are, in fact, a little different. For wireless microphones, the main difference between analogue and digital is how we modulate the RF carrier. Most analogue wireless system use frequency modulation (FM), and while this has proven to be a very robust and ultimately successful way of transmitting wireless audio, there are certain limitations to FM. Digital systems, for instance, have the ability to operate in far worse carrier-to-noise environments, meaning that even in ugly RF environments we get clean audio.

“With clean RF spectrum continuing to shrink, digital wireless technology will play a critical role in securing the future of wireless microphones at major events”

In order to maintain high dynamic range, analogue systems also use a process called companding — whereby the audio signal is compressed in the transmitter to accommodate the limited dynamic range of FM radio and then expanded at the receiver. This process, while almost undetectable in most high-quality analogue systems, can still lead to audible artefacts like “pumping” and “breathing”. Digital wireless systems convert analogue audio to a digital signal that modulates the radio carrier in discrete steps (think binary code: ones and zeroes). Since the transmission of a digital audio signal doesn’t require companding, it is possible to achieve audio with a wider, flatter frequency response. In other words, the digital audio signal arrives at the receiver unaffected by the radio link.

Spectral efficiency and audio transparency are the principle advantages of digital wireless systems, but the positives certainly don’t end there. Digital wireless operators can also expect greater battery life, as well as enhanced privacy through encryption — perfect for information-sensitive events such as corporate conferencing.

The bottom line
The long and short of it is, digital wireless technology has reached a point where we can now leverage the many advantages to address the challenge of our modern RF environment. And, while analogue systems will not have inherent signal latency, even this minor drawback (less than three milliseconds in Shure digital systems) isn’t enough to ignore the huge gains in spectral efficiency. After all, the situation isn’t going to get any better. Wireless communication (particularly mobile) is entrenched into our daily lives and will continue to develop at a fast pace. Consumers will continue to expect increasing amounts of wireless tech — with relatively plug-and-play usability — all of which need to operate in the limited amount of spectrum available. Continuing to develop spectrally efficient digital wireless systems is one of the key ways we can continue to operate at the level audiences expect under progressively challenging conditions.

 


Tuomo Tolonen is pro-audio group manager at Shure Distribution UK. This article originally oppeared on the Shure UK blog.

A mobile threat

The UK is internationally renowned not only for producing some of the best musical artists in the world, but also for developing an unrivalled live music industry that supports this creative wellspring, together with the high quality venues and events needed to support our abundance of talent.

Not only is this big business within the UK – just look at the number of music festivals and live concerts that take place every year – it’s a serious draw for festival tourism as well. We’ve been in this game for decades and it shows: we’re not talking about bands of the stature of The Beatles playing in rundown Gaumont cinemas with just a couple of Vox amps any more. Live music is a serious matter in the UK these days. We have the knowledge, the techs and the kit to do it right, and our world-class track record and production values speak for themselves.

But this vibrant industry is under threat, and from a surprisingly innocuous source: our mobile phones. Over the past ten years, the UK government has been auctioning off ever greater parts of the RF (radio frequency) spectrum for use by mobile phones and wireless-enabled computers, to ensure that the mobile telecommunications industry can keep pace with the insatiable consumer demand for wireless access. If you’re wondering what this has to do with music, it’s simple – mobile phones have increasingly been given the same radio frequencies to work on as our wireless stage technology, including wireless microphones, in-ear monitors and backstage communications.

This vibrant industry is under threat, and from a surprisingly innocuous source: our mobile phones

And without access to uninterrupted, clear RF, these devices can’t work reliably on stage, night after night, as they need to if our live music industry is to maintain the high production values it is renowned for.

A couple of decades ago, this wasn’t a problem. Most stage technology in those days was cabled, with only a few key performers using wireless kit at most. The mobile phone industry was in its infancy and was using a completely different part of the RF spectrum to operate. But as live shows became more ambitious, production managers and set designers increasingly came to rely on the freedom that wireless mics and monitoring could offer performers, releasing them from the hindrance of being permanently cabled.

If you’ve ever seen a show where one of the performers played while suspended on a wire high above the audience, or where the lead singer crowd-surfed or mingled with their public while continuing to perform, those performances were only possible because of wireless stage technology. At the same time, mobile telecommunications moved beyond simple cell phones with the introduction of the smartphone and other wireless computers, and the ongoing and ever-rising consumer demand for fast RF-based internet access from handheld devices began in earnest. This made the rights and licences to use RF spectrum big business in a way they never were before. Not coincidentally, over the last decade we have seen large swathes of the RF spectrum in the UK auctioned to the mobile sector, making the interference-free use of wireless technology by the live music industry much more difficult and unpredictable.

If we’re not careful, some of the fantastic, high-quality events and live shows we’re known for in this country could be under threat

Manufacturers of wireless technology, such as the company I work for, Shure, have tried to keep pace with the changes, making devices compatible with the new frequencies and designing kit that can operate with more efficient use of RF, and in harsher environments. But yet another set of government spectrum auctions is currently underway, and once completed in 2020, our industry will have lost roughly 50% of the usable spectrum. This will make the operation of wireless microphones and IEMs at some large events impossible due to the lack of sufficient interference-free spectrum. Technological advances can make the best of reduced RF availability, but eventually, there will be a limit.

The UK government was prevailed upon to find alternative RF spectrum that could be used by the live, theatre and broadcast industries, but it remains to be seen whether this block is actually usable and offers a viable replacement for what has been lost.

What will happen next? If we’re not careful, some of the fantastic, high-quality events and live shows we’re known for in this country could be under threat. The changes aren’t yet set in stone, though, and industry pressure groups such as BEIRG are doing their best. Nobody wants to denigrate the mobile phone industry (who would want to be without their smartphone these days?) but more key industry players emphasising the important contribution professional wireless technology makes to the UK’s economy and cultural capital would help our industry’s standing no end.

If you feel you can lend your voice to the cause, please get in touch.

 


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