Changing times
Feb 1, 1999 12:00 PM, Gregory A. DeTogne
In the dawn of the wireless world, audio professionals approached each day with a strong measure of apprehension. Although the passage of time and evolution of technology have calmed those initial fears, the initial skepticism was rooted in more than the anticipated fear of the unknown. As anyone who was there can attest, the first wireless mic systems were a far cry from the products available in the modern marketplace.
Despite the shortcomings of early wireless mic systems, credit should be given to the technological pioneers who developed them; it was their efforts that established the groundwork that will lead us into the 21st century with power and flexibility. Today, a vital and maturing wireless marketplace is coming of age, not only in the world of audio, but also in such realms as computer networking, telephone and Internet access. For manufacturers, meeting wireless needs is no longer just a question of realizing performance goals; it is one of meeting increasingly diverse market expectations.
Sandy LaMantia, president and CEO of Shure Brothers, Evanston, IL, said, "The next century will be rich in information and driven by communication. Successful wireless manufacturers will be the ones who accurately forecast which technologies will serve wide-ranging user requirements best."
These same players will also need to adapt to a global marketplace where a growing number of regulatory edicts will govern wireless spectrum real estate in an attempt to parcel out a pie which may simply not have enough for everybody. Most wireless designers know such constraints and limitations will affect wireless integrators. They feel, however, that much of today's wireless hardware will remain viable for most applications well into the next decade. As users and system integrators become more enlightened about the ways in which they can solve both the current and upcoming conflicts, matters will continue to improve.
Although his responsibilities are global in scope, Edgar Reihl, principal RF engineer at Shure, has been kept busier than usual right here in the United States. Reihl leads the formidable task of unraveling the true impact of two recent regulatory actions taken by the FCC that have sent shock waves of uncertainty through the audio industry. The first concerns the establishment of digital television (DTV) transmission standards and the 10-year transition period allotted broadcasters for the mandatory changeover from analog to digital broadcasting. The second, which has probably created as much confusion as the first, involves the reallocation of four of the upper UHF TV channels to public safety communications.
To understand the scope of the challenges to wireless system operation the first of these FCC actions poses both today and for tomorrow, it is important to realize that most professional wireless audio systems operate on unused channels in the VHF and UHF TV bands according to guidelines listed under Part 74 of current FCC rules. Within the Part 74 bands, wireless systems are classified as secondary users, meaning that they must not interfere with primary users, namely TV broadcasters, and they must accept that primary users may cause interference with their operation. Most commonly, wireless systems circumvent potential clashes with broadcasters by using unoccupied TV channels.
DTV and wireless With the advent of digital television broadcasting, however, the finite number of unused channels is decreasing rapidly. During the duration of the DTV transition period scheduled for completion in 2006, the number of on-air TV signals may double because of the FCC's decision that broadcasters should make the switch from analog to digital easier on consumers by broadcasting in both formats on separate channels until consumers have time to convert their old televisions or buy new digital sets. The best way to determine if the wireless mic gear you are currently using conflicts with the new scheduled DTV assignments is to consult the FCC's Table of Allocations (available on the FCC Web site: www.fcc.gov). Wireless users need not rush to this chart in a state of panic. Reihl said that most new DTV assignments will be between channels 2 and 51, which is well below the range of most professional-grade UHF wireless mic systems.
Because the FCC plans to assign only four new DTV stations in channels 66 through 69, Reihl said, "Most areas of the United States will still have enough open channels available to satisfy all but the largest wireless installations."
In the event of a conflict, Reihl said, "With a frequency-agile system, just turn to another channel. On most systems, compatible frequencies are grouped for easy avoidance of specific TV channels. If you have a non-synthesized system incapable of changing to a non-conflicting frequency, you will probably have to re-tune it. Shure, like most manufacturers, provides this service to its users for a nominal fee."
What is more interesting is that research suggests that wireless systems may be able to coexist with DTV signals more easily than with analog TV signals. This conclusion is based in part on the fact that DTV signals are spread out more uniformly than analog TV signals, thereby posting lower peak power levels. If you look at a DTV signal on an analog TV or listen to one on a wireless receiver, what you will experience is that it is essentially noise-like because of the digital nature of the transmission (see Figure 1). Therefore, wireless receivers using noise-squelch circuitry will interpret DTV signals as noise and suppress them. It should be noted, however, that even with squelch circuitry, the DTV signal energy is still present. As is always the case, whether or not a wireless system will be usable depends upon the relative strength of the transmitter signal compared to that of the undesired DTV station.
Public safety With all of the ruckus recently generated by the FCC's DTV ruling, the last thing wireless mic users wanted to hear about was the establishment of new public safety bands that will be used by police, firefighters, rescue squads and other emergency service providers. Thanks to the Balanced Budget Act of 1997 in which the U.S. Congress directed the FCC to allocate up to 24 MHz of spectrum between TV channels 60 and 69 for their application, these bands will become a reality. As originally proposed, the FCC ruling would have dedicated TV channels 63 and 64 (764 MHz and 776 MHz) plus 68 and 69 (794 MHz and 806 MHz) to public safety operations. All existing TV stations and secondary users of wireless systems using these bands would have had to abandon these frequencies.
"Wireless users were almost completely lost in the shuffle," Reihl said.
In response to the FCC decree, Shure [and other manufacturers] filed formal comments requesting that wireless audio transmitters be allowed to maintain their secondary user status within these bandwidths. When all was said and done, the FCC granted the request. The success of this regulatory advocacy has benefited the entire audio industry by retaining legal use of these important channels.
"It's useful to realize another issue regarding the new public safety bandwidths," Reihl said. "The FCC determined that now is also a good time to implement digital transmission for these users. To accomplish this, new equipment needs to be developed, which will take time, and existing wireless audio components need to be made usable for the foreseeable future."
The FCC has designated the lower public safety bands (TV channels 63 and 64) for base-to-mobile transmission and the upper bandwidths (TV channels 68 and 69) for mobile-to-base transmission.
"For the wireless user, this means that the bottom 3 MHz of TV channels 63 and 68 and the top 3 MHz of channels 64 and 69 will be occupied by narrowband digital transmissions," Reihl said. "The top 3 MHz of channels 63 and 68 and the bottom 3 MHz of channels 64 and 69 will be used by wideband digital transmissions. Interference from narrowband signals is much easier to avoid. Because public safety frequency selection will most likely continue to be handled by regional planning committees, it shouldn't be difficult to determine in advance which frequencies will need to be avoided."
All things considered in the regulatory world here in the United States, now is a good time to examine the future of wireless hardware technologies and the state of wireless market needs around the globe. Can such a thing as world wireless actually exist? Technically, it is a fairly safe bet that it could. Legally, however, it may be doubtful, given the number of different bandwidth plans embraced by various countries around the world. After all, the equivalent of our FCC in Sri Lanka-or any other agency regulating such matters anywhere else-might not want to provide audio professionals with a single device capable of operating on bandwidths that it had banned from wireless use. It would, in most cases, be unlikely, thereby limiting the number of countries in which such a device could be legally sold. Within the context of a global platform, Rob Cappucci, director of wireless products for Shure, predicts that the day will ultimately arrive when wireless mic systems are offered that allow users and systems integrators alike to forget about technology completely.
"Wireless audio will be self-sufficient," Capucci said. "You won't even have to remember that there's an RF transmitter and receiver. A wireless system will simply be one that doesn't have cords. You'll be able to turn it on like a light switch, and it will work. It may be capable of both voice and data communications. The business of locating open channels and then monitoring them to make sure they are free from interference will be unnecessary. The system will do all of that for you. If you add more channels yourself or if the church next door buys a dozen of its own systems in the future, your wireless system will continue to take care of itself and function flawlessly."
You cannot help but wonder what kind of role digital designs may play within this view of the future. Steve Johnson, Shure vice president of marketing, sees wireless audio following a technically enabling path where digital will reign, but he will not exclude the use of other analog-based platforms.
"Analog, digital, VHF, UHF-we have a tendency to get hung up on these terms," Johnson said. "At various points during the progression of wireless audio, VHF was perceived as better than what people referred to as FM band. Then UHF was better than VHF, and digital was better than analog. Just as we experienced with the evolution of the cordless telephone in the consumer world, there will come a time in the future when we all realize that each one of the current wireless technologies available has its share of advantages and limitations. For instance, a well-designed VHF system can sound as good as a UHF system in certain applications, while a digital system may actually sound worse than analog at times. It's all dependent upon what a given system's goals are and the purpose that needs to be fulfilled.
"The future will be driven by users," Johnson said. "Successful manufacturers will be those who meet user needs by offering flexible systems that allow them to buy into whatever part of the dream they need at a price they can afford."
Many within the industry today feel that digital's recent entry into the wireless mic market has taken such a disruptive route with the arrival of the low-priced, 16-bit products seen within the last year.
"These low-priced digital systems are a lot like a point-and-shoot camera," Johnson said. "They deliver a lot to the user but not everything. Whatever you think about their presence in the marketplace, you have to admit it's a pretty good start. For better or worse, they've set the tone for tomorrow by establishing certain expectations and an idea of what digital should do at what kind of price. The wireless market can be fickle. Groundbreaking products don't necessarily require a lot of research and development."
Given the likely prospect of a wireless future where the current allowable spectrum space becomes even more scarce, other frequency allocations will be necessary. Among the alternatives available are Part 90 business-band channels and the consumer product-dominated but license-free Part 15 bands at 900 MHz and 2,400 MHz that permit the use of spread-spectrum transmission. Out of all of these, there is no spectrum space that is definitively better than what wireless audio currently occupies.
"Higher power is permitted, but spectrum space and current hardware technologies severely limit the number of systems you can use simultaneously," Reihl said of spread spectrum possibilities. "Regulations governing that of transmission aren't favorable either. There are pitfalls with all the alternatives. For right now, sharing space with TV broadcasters still appears to be the way to go."
Be warned that this may not remain the status quo forever. As with anything else viewed through the sometimes cloudy sphere of a crystal ball, nothing can be said about tomorrow with absolute certainty until we actually arrive there. Educate yourself and your clients, and remain prepared or change.
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