HD Proponents Seek Protection for "No New Spectrum"

An interesting trial-balloon was floated last month in Radio World. In it, John Kean, one of the founding employees of NPR Labs (who was let go in a reshuffle this past August) suggested that the FCC’s spectrum allocation rules be revised to better “protect” FM-HD Radio sideband signals.
Before going any further, it’s best to cover some history. HD Radio was adopted by the FCC in 2000 primarily on the premise that the system used “no new spectrum.” In fact, FM-HD signals double the spectral footprint of FM stations — but HD’s proponents got around this by appropriating fallow spectrum the FCC leaves between stations as the stations’ own allocation.
This fallow spectrum, called an “emissions mask,” was initially intended to prevent spurious and transitory transmissions from one station interfering with a neighbor; the mask was never intended to be used as “add-on” spectrum to host new radio services. Yet this is precisely how HD Radio works: the digital sidebands that constitute the technology reside firmly within the emissions mask, filling it completely (and, in some instances, ovewhelming it).
Thus “no new spectrum” has and continues to be a canard, while the imposition of HD has wholly redefined what a radio “channel” actually is. At the time the FCC first approved the HD rollout, it admitted that interference between neighboring stations was possible, and the years have certainly borne that out.
Kean argues that the FCC’s current allocation rules are primarily designed to protect neighboring stations from the potential interference of an HD broadcaster, but do not adequately protect that HD broadcaster from interference from other stations. Studies conducted by NPR over the last decade show that interference between FM-HD and analog signals do degrade the quality of the digital sidebands. This is one of the reasons why the FCC allowed stations to increase the power level of their sidebands, and also allows them to asymmetrically deploy them in hopes of mitigating station-to-station interference.
These workarounds work best when there is only two interfering stations in the mix: an FM-HD station and an analog neighbor. However, what happens when analog stations’ signals encroach on an FM-HD station’s sidebands on both sides? The sidebands carry redundant data so that if one gets interfered with there’s still enough data available to maintain a listenable digital signal. But if an FM-HD broadcaster experiences interference to both of its sidebands, the redundancy (and listenability) of its FM-HD signal may be significantly compromised.
Kean’s solution is to get the FCC to formally recognize the FM-HD sidebands as a specifically protected use of the spectrum, in such a way so that analog stations would be statutorily mandated to reconfigure their own signal patterns to minimize interference to digital signals. In many cases, this might involve analog stations having to reconfigure their antennas to provide quasi-directional signals away from their HD neighbors.
Can of worms alert: the vast majority of FM broadcasters in the United States have decided not to adopt HD because of its operational complexibilities and lack of a demonstrable return-on-investment. Will these stations take kindly to being forced to adjust their own signals in order to accommodate a digital service whose adoption is totally voluntary? Revising the FCC’s FM spectrum allocation rules is an incredibly heavy-handed way of attempting to address interference concerns which are inherent to the design of the HD system itself.
Fortunately, there may be an alternative to the tedious yet contentious idea of allocation reform. What if a technological fix existed that improved HD Radio reception on the receiver-side? For several years now, DigitalPower Radio has claimed to do just this. DPR has developed algorithms that are hard-coded into receiver chips that can help to increase the robustness of wireless digital signal reception.
DPR has made multiple entreaties to HD Radio’s proprietor, iBiquity Digital Corporation, which did result in a meeting of the minds in 2013, though the results of that encounter have never been fully disclosed, and iBiquity’s public position has never moved from the notion that integrating DPR technology into its system is a non-starter. The reason for this is that iBiquity’s entire business model has been based on the closed and proprietary nature of its technology; adding a third-party into this mix would crack the black box that surrounds HD Radio’s intellectual property.
Fortunately, iBiquity now reports to a parent company, DTS, who acquired it and the HD Radio system earlier this year in a $172 million deal. DTS has many commonalities with DPR: both are companies who develop and market algorithmic technologies to improve the robustness of digital audio systems, and both rove far beyond the broadcast space in their endeavors. One of the reasons why DTS bought iBiquity was to acquire a conduit into the automotive space for the provision of wireless data and audio services. As non-broadcasters, the advantages of working with DPR may be more obvious to those who rarely venture outside the radio broadcast sandbox.
Furthermore, DPR’s technology also claims to increase the amount of data any given digital wireless channel can carry. If this is true, than integrating it into the HD Radio system would theoretically allow FM-HD stations to reduce the footprint of their digital sidebands, which would certainly reduce the risk of harmful interference between them and neighboring analog stations. Broadcasters will inherently chafe at this suggestion because it would involve “giving up” veritable slivers of spectrum that they’ve colonized under shady pretenses over the last fifteen years.
As the incremental tweaking of HD Radio continues, the inherent compromises made to its initial design are becoming more noticeable. A logical way to address these issues is to tweak the system design itself — not to force those broadcasters who opted out of a voluntary system to make accommodations for it.