ANALOG WIRELESS QUEEN IS DEAD. LONG LIFE DIGITAL KING. But time for the next leap is already here.

A DECADE OF EVOLUTION

With the launch of the Sennheiser Evolution Wireless DX and the Shure QLX-D, RF manufacturers major league have achieved its overall analog to digital portfolio changeover. This took about 10 years. It started back in 2012 when Sennheiser was putting on orbit its admiral vessel the huge D9000. Digital wireless technology is now affordable and a piece of cake to use. Both Sennheiser and Shure brands had their own strategy, but the goals were the same: get rid of frequency modulation to transport analog signals and use the benefits of shift keying modulation to carry digital audio signals.

Beyer-Dynamic with the TG1000 system, Sound Device with the A10 system, Lectrosonics with the D2 have also crossed the line of the digital world. Audio-Technica got the 3000 digital series. Still Wysicom remains in the analog FM world with highly performant digital processing.

The benefits of digital wireless systems are incomparable.

For those who were about to rock the RF in the 80’s or 90’s todays achievements sound unbelievable. Old tech will certainly tell the newbies: “hey young fella I can tell ya things are so much easier for you kids today. Deploying 12 wireless mics was something in my time”.

First the arrival of Wi-Fi and DECT RF bands wireless microphones is a terrific new for nonprofessional users but for professional as well. These two natively frequency agile band sort out our RF spectrum in a way. Amateurs benefit the agility and ease of use of the Wi-Fi band in regards of their few channel needs while the corporate environment take all advantages of the DECT more robust standardized band.

Thus the golden UHF band remains dedicated to professional program making special event (PMSE) activities with all the reward of digital modulations:

1)??????????The intermodulation products are way further and not taken in account. This allows for equidistant grid frequency planning.

2)??????????Depending on the system, its power and audio quality spacing evolves from 600 KHz to 125 Khz. The resulting efficiency goes from 16 to 64 microphones inside a European 8 MHz DTT TV channel.

3)??????????The robustness versus interference of the transmission are a way better than analog ones and increase the operation range. Digital links are more reliable.

4)??????????Digital systems always offer the best of their audio in their quality mode all over their operating range.

The research and development investments made in the telecom industry have been beneficial to the Program Making and Special Event (PMSE) audio niche. Transmitters now benefit from all the battery, processing and emitting stage circuitry that have been developed. Today users can have a miniaturized digital pocket transmitter working all day long without any battery swap with very high linear RF amplifier. The comfort of use that techs, artists and TV anchors had been waiting for so long is here at last. However, within this 10 years’ time lapse we’ve seen shifts movement in the RF world in parallel. The telecom industry is pursuing its needs of RF spaces. They have eaten much of the UHF band that wireless microphone users were used to. used to. They are claiming to increase the baud rate spectrum efficiency again with upcoming the 5G.

In parallel to the quest for spectrum, the wireless industry faces the problem of latency. This is the main reason why only Lectrosonics offers a digital IEM (M2 Duet System). To date a fully digital wireless from mic to IEM at best inflicts 2.4ms of latency to the audio channel. The most sensitive persons (i.e. some drummers, vocalists, monitor engineers) can't bear to hear their performance in intra IEMs with a greater latency than 2.8ms. This leaves 0.4ms for network treatment (usually set at 1 ms) and console processing (few samples at today’s 96 kHz standard and half a millisecond at 48 kHz) which is not enough.

The next leap the major league is working hard on is Wireless Multi-Channel Audio Systems (WMAS). Quickly said WMAS is a bi-directional multiplexed base managed RF system contained within a UHF TV channel bandwidth (8 MHz for EU or 6 MHz for America). It employs new wideband modulation techniques to support the transmission of multiple audio links in one single wideband radio channel. The radio channel is shared among the devices (e.g. microphone, IEM, Intercom) via duplex (e.g. Time Division Duplex, TDD) and multiple-access schemes (e.g. Time Division Multiple Access, TDMA). Users could hold frequency agile transceivers that can receive and send low latency high quality audio.

?WMAS has considerable advantages and aims to solve several problems:

?????????????Use the current PMSE allocated spectrum, notably in the golden UHF range.

?????????????Improve further the spectrum efficiency by adding improved audio quality and flexibility during run-time as new value-adds.

?????????????Let the user choose to rise the audio channels amount or to surge audio quality (by playing on parameters such as codec audio debit and/or higher sample rate, RF robustness, or latency).

?????????????Develop the use of digital IEM.

?????????????Address new market opportunities such as immersive audio, conferences, and educational systems.

?????????????Use the forefront telecom progress technologies (Cognitive Radio?-CR-?and evolved Licensed Sharing Access -eLSA- ) to allow breakthroughs in more agile frequency management.

The European Telecommunications Standard Institute produced a paper in 2017 exposing the ins and outs of this technology based on Sennheiser R&D department works[2]. Sennheiser efforts had been then supported by Shure Inc, Microsoft and others to promote this opportunity in Americas. To lead their spectrum affairs Shure recruited Mr. Prakash Moorut previously leading Nokia's engagement on spectrum standardization and policy work. One of the first action of M. Moorut had been to build within Shure a worldwide team of spectrum specialist to monitor all opportunities and regional spectrum moves. Mr. Moorut is actively promoting the interests of his company and its business to the the USA Federal Communication Commission (FCC). But the commission is under influence of all stakeholder’s arguments and it debates pros and cons in particular with the cautious and influential National Association of Broadcasters (NAB).

Big challenges may arise from the decisions of the FCC. If it aligns its technological and regulation choices to those of ETSI, products could be available on the market within a few years. But the RF environment as well as the challenges faced by the Telecom industry are slightly different on both sides of the Atlantic Ocean. The FCC is sovereign in his kingdom where Lectrosonics and Shure are not aligned and compete in the high-end application domain. In addition, Cisco, Microsoft, Facebook, and Intel have the ear of the commission especially in the regarding the possible allocation of allocation 6Ghz and 7Ghz to licensed WMAS PMSE which these major companies refuse categorically. Multiple standards between EU and in America will complexify the development and increase R&D costs for a PMSE industry which is healthy but relatively minor compared to the other speakers around the RF table.

Let’s hope negotiations will be profitable soon for users. The RF congestion is clear, while the perpetual spectrum needs of a powerful telecom industry and GAFAMs is a continuous threat for PMSE utilization and development. The tremendous effort put in by Sennheiser and Shure on the evolution of their digital global portfolio evolution can ensure its confidence for some time. But it doesn’t postpone the urgent need for an agreement on a game changing technology.

Warm thanks to Andreas Wilzeck with Sennheiser, and Prakash Moorut with Shure for their precious answer to my questions and L. Hunsinger for the rereading.

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Sources

Apr. 21

https://www.tvtechnology.com/news/fcc-exploring-new-wireless-mic-technology

Aug. 21, Sept. 21

https://www.radioworld.com/tech-and-gear/wireless-mic-industry-debates-wmas-technology

Nov. 21

https://kab.net/debate-over-wmas-specifics-heats-up/

https://www.rsm.govt.nz/assets/Uploads/documents/consultations/2021-draft-five-year-spectrum-outlook-2022-2026/shure-response-to-5-year-outlook.pdf?

[1] https://www.radioworld.com/news-and-business/headlines/debate-over-wmas-specifics-heats-up

?[2] https://www.etsi.org/deliver/etsi_tr/103400_103499/103450/01.01.01_60/tr_103450v010101p.pdf