Sunday, March 06, 2005

HD Radio thoughts, speculation and technical info

This started out as a short essay on IBOC radio and it sort of grew a little. Honestly, I was going to trash it, but it's big enough that I am going to publish it anyway. I just hate to waste that much text!

03/25/04 Update: I've gotten some interesting e-mail on this work. As a result, I've made some changes and additions to the HTML version of this paper. I'll probably get the PDF done at some point.

I've been doing some hard thinking about FM IBOC and realize it has some potential. This is a *long* post, but if you are interested in IBOC, HD radio, there is probably something here for you of interest. I've been pretty vocal on the technical issues, particularly on the AM side of things. AM IBOC may not ever fly and I am convinced it is stillborn today. --We just don't know it yet and there is work to be done, despite industry claims it is ready to go.

FM IBOC brings a lot of choice to the table and one facet of it in particular really interests me. Multi-stream capability. The current specifications clearly provide for more than one audio stream per IBOC station. This essay really was the result of some hard thinking about that. --Take it for what it is worth and please do let me know what that ended up being for you! --Thanks.

I've also got some real HD radio samples on the way. When those arrive, I'll edit and repost the old samples page and put 'em there. (EDIT: They have arrived and can be found here.) Links will be provided from here. I expect to have what I need to do this in the next week or so.

You can also download this essay as a PDF file, if that works better for you. Be aware, the resources portion of the PDF and this introductory information will slowly grow out of date. The best info, related to this work, will be here on OpenGeek. The PDF file represents the original version of this work and no longer contains the information the Internet HTML version does. I will address this at a later date, once the document reaches a stable point.

And here, finally, is the monster:

Digital Radio: What is it
and how will it affect Radio as we know it today?

This essay is a brief look at Digital Radio technology, it's technical issues, potential benefits and potential pitfalls as I see them today. Some statements presented in this essay are speculative and should be treated as such.

What is IBOC, HD Radio, Digital, etc... ?

IBOC stands for In Band On Channel with HD Radio being the marketing catchphrase for the IBOC Technology powering digital radio in the US today. To put this in very simple terms, IBOC/HD Radio is the new digital radio signal, broadcast along with or on top of, depending on your point of view, an existing radio stations traditional analog signal, with the idea being to allow both types of broadcast to co-exist going forward.

We are at the early stage of HD Radio technology implementation. I believe it's important to express how this technology affects us now while many decisions are being made. This paper represents my view, I encourage you to express yours as well. The more voices we have, both positive and negative, the better the end product will be for all of us.

While HD Radio is broadcast in addition to existing analog signals, the long term plan, put forward by Ibiquity the creator of the IBOC system, is to transition to an all digital system at some time in the future, making existing radios obsolete. Frankly, I don't see this happening for a very long time given the number of existing radios in use today. Let's just say the potential exists for all digital stations and leave things right there for the foreseeable future.

Ideally, existing radios will not be significantly impacted by the additional digital information. On FM this is turning out to be largely true. On AM the reality is a bit different as I will explain below.

My aim for this essay is to communicate in fairly simple terms how digital radio, using IBOC technology will change radio as we know it today. FM IBOC and AM IBOC differ enough that many aspects of this paper will not apply equally to both technologies. Some general technology speculation is offered, along with technical links and other resources, for those interested in learning more.

How FM IBOC and AM IBOC differ

While the core technology is the same on both AM and FM, the implementation is different. These differences are largely a factor of existing radio tolerance to the new signals and compatibility with existing broadcast regulations, not the IBOC technology itself. These differences are significant enough to warrant a comparison with some level of technical detail.

While both systems share the same modulation technology the traditional bandwidth allocation differences between AM and FM have significant implications on the AM band.

In a nutshell, the implementation of IBOC on the FM band is superior in every way to AM IBOC making FM IBOC viable and AM IBOC questionable at best at this time.


AM IBOC features a total RF bandwidth of 30Khz per IBOC station. The innermost (closest to the center carrier frequency) 10Khz of this contains 5Khz traditional analog audio with the outer 20Khz of bandwidth being the new digital information. (Remember, the total RF broadcast bandwidth is twice the audio bandwidth.) This outer 20Khz can be broken roughly into two 10Khz layers that differ only in their radiated power, with the greater radiated power going to the outermost 10Khz of digital transmission.

The total radiated power, for IBOC transmission, is typically 1/100th of the total analog power. A 25Kw AM station would be transmitting 250watts of IBOC information, for example.

Testing indicates the IBOC signal, despite being a fraction of that required for analog, is able to provide solid service inside the 60dbu contour. This contour is the area of coverage, unique to each broadcast site, where an acceptable signal is present at all times. Receivers located outside of this contour may well see an acceptable level of service, service is not a guarantee.

All of this yields 32Kbps of digital information per AM IBOC station, in addition to its 5Khz of analog audio. This bit-rate is the upper-limit for a hybrid (analog and digital) AM IBOC station. AM Stations are free to make analog digital tradeoffs to better address the needs of their listeners. It is possible for AM stations to adjust their analog signal component at the expense of digital bandwidth. The IBOC system will allow up to 8Khz of analog audio bandwidth.

Reference implementations allow for 15Khz stereo audio digital broadcasts. Depending on how the public receives highly compressed audio, two monophonic limited bandwidth (6Khz?) sub-channels may be a viable option. AM IBOC digital bit rates are about half that available on the better satellite radio service channels.

Night time AM IBOC remains problematic, at this time, because the wide signals required combined with night-time AM propagation introduce more noise than can be reasonably tolerated on existing analog gear.

All digital AM IBOC stations are likely to see higher bit rates though I know of no plans for this at this time.

The HD Radio codec, responsible for transforming the analog audio to and from the digital domain, is a hybrid codec similar to the mp3pro low bitrate codec. All audio below about *5Khz is encoded in the usual way to be reproduced on the receiver end. Higher frequency audio is artifically reproduced by the receiver with the help of some additional information encoded into the audio bitstream. Together these two techniques provide the listener with the perception of a fairly wide audio bandwidth at the expense of accuracy on the higher frequencies.

(I don't have precise figures for this and the cutoff point can be adjusted. The idea here being to simply make people aware of the tradeoffs made in the HD radio technology where higher frequency audio is concerned.)

AM IBOC Technical Implications

Traditional AM band allocations are 10Khz, meaning most quality AM stations, broadcasting 10Khz of audio, overlap today. For daytime operation, this has been a minor problem at best in that many radios are limited to less total audio bandwidth and daytime propagation properties keep this interference to a minimum. Most of the problems we see today, with AM analog broadcasting, occur at night where signal propagation is far greater than daytime.

An analog AM radio, will continue to suffer from overlapping stations, beat tones, noise and other common AM issues. However, an AM IBOC radio will operate largely outside these issues within it's coverage area, at the expense of analog listeners however.

Without going too deep, AM radio has been plagued by it's simple nature, making it particularly suceptable to noise. This combined with poor regulation over the years has left the band largely unusable for most programming, other than talk, sports and ethnic/niche music programming.

Analog improvements, such as AM Stereo and noise limiting, have strong potential even today, however our regulatory decisions over the years have marginalized this to a point where most of the AM listening public remains largely unaware of the benefits and sharply limited in their ability to take best advantage of them.

AM IBOC further complicates the mix in that it degrades the existing analog signal, particularly with quality wideband radios, while bringing modest to average potential for improvement in return. The big question being how people will respond to the changes and if the improvements are worth the trade offs for those using existing radios.

Existing analog AM radio listeners, depending on the gear they are using, will experience increased noise, due to IBOC signals overlapping with existing analog ones, as a minimum.

Users of quality AM gear will experience a reduction in service quality in that IBOC stations are limited to 5Khz of analog audio and analog AM Stereo broadcasts are not able to exist with IBOC digital broadcasts. Additionally, the harsh filtering required to keep the analog audio in check at 5Khz, causes significant audio distortion audible on even marginal AM radios in use today. These filters are necessary "brick wall" types because any analog spillover into the IBOC portion of the broadcast can easily overwhelm the low-powered IBOC signal, rendering it unusable far sooner than it otherwise would be.

AM IBOC brings near FM quality improvement to the table, along with a more binary listening experience. Either an AM station will be listenable or not. The digital audio will be highly compressed, using a hybrid wavelet compression scheme that replicates frequencies artificially above 10Khz or so to bring the total audio bandwidth up to 15Khz. In terms of pure audio frequency response, this is an improvement over other AM broadcast technologies, on par with the quality FM audio service we have enjoyed for years.

For many, this is an improvement over the somewhat messy analog situation we have today. The combination of low bit-rate and aggressive compression techniques do bring audible artifacts to the table however. How much of an improvement this really is will depend on listener expectations and the program material being broadcast.

In addition, the artificial spectral reproduction of higher frequencies reduce the overall accuracy of the audio made available to the listener.

To sum this up, existing analog AM radios, of all types, will be impacted by the addition of IBOC broadcasts, with marginal to good digital improvements in return. What is not known, at this time, is how the average listener will respond. Will the reduced level of service be easily tolerated, or not? Will AM listeners move on to FM with it's increased quality and choice potential or choose other technologies, such as satellite radio or podcasts or simply tune out entirely? Given the audio artifacts, AM IBOC will be less competitive than FM IBOC will be in this regard, making the risk / reward ratio less favorable where AM IBOC is concerned.

Given the aggressive audio compression, quality analog broadcast tecnhiques combined with noise limiting technology available today, remain competetive with AM IBOC transmissions.

There is no clear path forward that keeps impact to a minimum. I believe additional work will need to be done in order to properly move the AM band forward without losing the utility of the many AM radios in service today.

AM radio, being a technology close to my own heart, has been largely marginalized in recent years from the onslaught of many new technologies. Despite this, many people today still consider AM a viable technology in times of need, or for niche programming.

AM radio has a long history of public service and, despite the considerable challenges of the medium, has provided much value to our society, particularly in times of need. I harbor serious concerns about it's continued viability, given the reduced level of service to existing radio gear IBOC implementation will bring, particularly given the aggressive audio compression necessary to maintain an acceptable audio bandwidth.

At this early stage, the overall fate of AM radio, as we know it today, is unclear. Ideally, the radio industry will take conservative steps until we know more and can make solid choices from there. There is a strong case for AM broadcast remaining mostly analog.

At this time, I remain unconvinced AM IBOC makes good sense to implement, given the strong potential and sharply reduced level of service tradeoffs present in analog technologies, such as AM Stereo and impulse noise blanking.


FM IBOC features a total RF bandwidth of a little under 400Khz. The innermost 200Khz is naturally the FM analog signal, essentially unchanged from the FM service we know today.

FM signals are more complex than AM ones, often including audio, data sub-carriers and the stereo portion of the broadcast as well. This additional complexity is made possible through the greater degree of discrimination possible on the FM receiver side.

The IBOC portion of the signal, extends another 100Khz in either direction from the primary center carrier frequency, meaning an FM IBOC station will occupy a total of 400Khz of RF bandwidth. There are two modes of transmission in the hybrid analog / digital mode as well; namely standard and extended. Early standard systems in use today do not make full use of their portion of the FM channel in that IBOC signals are not right up against the analog portion of the channel, keeping impact to existing receivers to a minimum. Current standard mode systems only make use of about the outer 70 percent of the 100Khz IBOC allotment. (Per sideband) The innermost 30 percent remains unused, leaving a gap between the analog signal and the IBOC one.

However, the multi-channel capability and additional data bitrates made possible by filling this gap are likely to result in the extended hybrid mode seeing wider use. This mode provides allows for a higher total bitrate on the order of about 150Kbps. IBOC transmission in this mode will likely have a greater impact on analog receivers, particularly wide band IF ones.

As with AM IBOC, total radiated power is a fraction of the analog signal with this ratio being 1/100. A 50Kw analog FM station would then transmit 500Watts of IBOC signal. This amount of power is sufficient to provide service within the 60dbu coverage contour typical of analog broadcasts.

The greater bandwidth allowances on the FM band, bring the peak total IBOC digital bit-rate up to a little above 96Kbps per IBOC station. This is considerably higher than the more limited AM IBOC is capable of. The IBOC signal does not mandate a reduction in audio bandwidth for analog FM Stereo signals. I do not know the effect on FM sub-carrier services at the time of this writing. Peak FM IBOC bit rates are 150 percent greater than that available on the better satellite radio service channels.

The much higher peak bit-rate bring more choice and quality options to the table. Broadcasters will, for the first time, be able to bring multiple programming streams to their listeners in a practical way.

The number of streams determines the overall bit rate available to each particular stream. If a station were to choose 3 streams, they could have one 48Kbps stream and two 24Kbps streams in addition to their analog signal for a total of up to 4 program channels, for example. Or a more conservative choice could be made where three streams are made available to the listener with the higher quality 48Kbps stream duplicating the analog program for robustness.

Another alternative would be to simply broadcast the same program on both the digital and analog systems at the same time, taking best advantage of the ~96Kbps bit rate and the more robust error correction. (robustness) Early systems, on the air at this time, make use of this approach.

It is possible also to trade signal robustness for a bit more bandwidth in the sub-channels. FM stations, operating in a fairly benign topology, could reduce their robustness and offer more aggressive sub-channel bit rates (24Kbps) and still retain their 96Kbps quality primary channel, for example.

Use of the extended hybrid digital mode will allow for higher bitrates overall, with no channel seeing more than 96Kbps total for audio. The original bandplan for this extended mode was 40-50Kbps of data bandwidth, National Public Radio has proposed this additional bandwidth be configured to allow more audio broadcasts as well. They call this Tomorrow Radio. In addition to the choices mentioned above, higher bitrate audio channels will be possible when stations are operating in extended hybrid mode. It may be possible for a station to run three audio streams at 48Kpbs for example. Work in this area is ongoing and the information I present here is early.

Finally, the potential exists for data services to be carried along with audio ones. While both AM and FM IBOC have this potential, the higher bit rates of FM IBOC present more potential in this area.

FM IBOC is not restricted at night because existing radios and the wavelength of FM both combine to properly discriminate between analog FM broadcasts and the new IBOC digital ones well enough to allow full time service.

FM IBOC audio frequency response can reach 22Khz. This is an improvement, in sheer audio frequency response, on par with digital CD audio. The hybrid nature of the digital encoding process does introduce the potential for artifacts, however these will be limited to the upper frequency range and are likely to be easily tolerated by the average listener.

As with AM IBOC, only a portion of the audio is directly encoded with the higher frequencies being artifically replicated at the receiver end. I don't have hard numbers for the cutoff point at this time. Spectral analysis of early HD radio samples lead me to believe audio above 10 to 12Khz is artifically reproduced in the receiver.

How this will be received will depend on the processing techniques used, program material, and total audio bitrate. Subchannels are likely to see a maximum of 48Kbps per channel available.

FM IBOC Technical Implications

Although it is possible for FM IBOC signals to overlap with other analog FM stations, current frequency allocations in many markets, keep this to a minimum. Additionally, the modulation technique used by IBOC combined with it's fractional power levels will keep this from being an issue in all but a small number of cases because the IBOC signal is largely invisible to analog FM detectors. This is perhaps, the biggest differentiator between the FM implementation and the AM one, besides overall peak bit rate and the potential for multiple audio streams.

The additional choice potential FM IBOC brings to the table is it's strongest attribute, making the HD Radio moniker a bit misleading. Overall audio will not be "high definition" in the sense that HDTV is higher definition, because the peak bit rates available at this time limit the overall quality of the audio received. Instead, the HD Radio system only conveys the perception of higher bandwidth audio, due to the hybrid encoding system and it's artificial spectral reproduction of the higher frequencies.

However, the audio experience, potential quality issues aside, will be a more consistent one overall. FM multi-path 'fuzz' will not be an issue when listening to an IBOC broadcast. For many, sensitive to noise and multi-path, the quieter and more consistant broadcast may well make up for any audio accuracy issues.

When compared to satellite services, the additional bit rates are likely to make the 'HD Radio' tag more appropriate, when the higher 96Kpbs bitrates are used.

It is worth noting, FM IBOC implementation will have a negative effect on "Dxers", those listeners who either depend on fringe area coverage, or choose to seek it for entertainment purposes. It is also worth nothing, existing translators already have begun to enroach on these listeners today. Over time, the expected growth of radio and the additional choice provided by IBOC broadcasts has the potential to balance the loss of distant signals for many listeners.

Unlike AM, the implementation of FM IBOC will have little overall effect on existing listeners in that the technology will go largely unnoticed on existing radio gear. The extended hybrid mode may change this, but is not likely to exceed the negative impact found in all AM IBOC systems. Additionally, FM stations wil be free to choose their operating mode, trading analog signal quality for number of digital channels where AM IBOC is an all or nothing affair.

General IBOC Technical Implications

The digital processing required will introduce a delay into the audio chain, making "on air" monitoring difficult. Additionally, the digital audio is buffered, making real-time broadcasts questionable. Perhaps some of these, such as sporting events, will need to remain analog for the most crisp experience. This buffer can cause a disjointed experience when a receiver falls back to analog mode, then jumps forward into digital mode again. This can be largely mitigated in the receiver and is moot for digital only programming.

All audio is encoded and compressed. Those building digital music library systems, may find their programming quality reduced below expectations due to re-encoding necessary for IBOC digital transmission.

Audio broadcasts, received via the HD Radio IBOC system, do not have the accuracy of either analog methods or quality compressed audio. The primary limiting factor remains the peak bitrate available. In the future, the higher bitrate (~300Kpbs) possible on all digital FM stations may provide a remedy for this. However, plans for this are largely still on the drawing board. The IBOC transmission technology has been developed, but receiver implementation and codec technology is a work in progress.

Despite years of planning, IBOC is not yet "cooked" in that we are still seeing new ideas come forward for how to best use the bit stream to deliver programming to the listener. This means current IBOC implementations will offer the basic level of service, with enhancements planned over time as our understanding of the technology and demand grow.

Unlike analog broadcast improvements, changes to the digital bit stream can require changes to both the transmitter and receiver side in order to be fully realized to the listener. These changes, given solid initial planning and some over engineering in the receiver, can largely be software related, keeping potential issues to a minimum. However, the potential for early receiver obsolescence is much higher than the general public is used to, given the long service life of their existing analog gear.

Early adopters may well find their HD Radio capable of only a sub-set of the total programming in the future, or may find selecting that programming to be difficult due to user interface issues. Given the rapidly advancing state of the art in digital encoding, it is very likely this will continue for some time yet. It is not yet possible to know if the weight of existing HD Radio gear will hold the technology back, or if listeners will be willing to upgrade / purchase new radio gear to take advantage of improvements still to come.

Additionally, digital technologies have proven less robust in the face of adverse conditions and over extended periods of time than analog methods. The more binary nature of the listening experience (either you get the signal or you don't) could be a problem on occasion. Having to "reset" the receiver, or perform other computer related workaround tasks will bring a level of complexity to the ordinary radio, some listeners may not be accustomed to. This additional complexity will also create new user interface challenges as well. HD radios won't be as simple as traditional analog ones currently are capable of being.

While these issues are not show stoppers by any means, they are going to need to continue to be addressed until everyone has the right expectations. Put simply, HD radio is going to have some teething pains for a few years yet.

IBOC is not an open technology like AM or FM radio is. Every transmitter and receiver will include a royalty to cover the use of the patented IBOC technology. While this helps bring a standard to all digital radios, it also puts a private entity at the center of the radio industry that all parties must depend on and pay to make use of the RF spectrum. This does raise public interest concerns in that we won't see competition for digital radio and will see cost built into both broadcast and receive parts of the process.

Ideally we will see Ibiquity, the owner of the IBOC technology, provide RAND (reasonable and non-discriminatory) licensing terms for those interested in providing IBOC / HD Radio related products and services. Without these terms, there is little incentive for both innovation and cost reduction of IBOC related services and radio gear. Additionally, software radio technologies are still developing at this time. Most of this work is Open Source. Will HD Radio broadcasts remain invisible to software radios due to licensing issues? Should they be, given the public interest in the radio spectrum? These and other questions surrounding the licensing of the IBOC technology remain a growing concern in the longer term that should be addressed before the use of the technology becomes to pervasive.

I have not seen plans for providing part 15 hobby level radio capability at this time. If we are to continue to encourage digital radio broadcasts, we should also encourage a more open use of the technology as well.

Ok, so how does this change radio for me?

This is the fun part, where I just throw out a bunch of things I believe IBOC to be capable of. Some of these are a reality today, others may or may not happen depending on how things evolve. --Take with two large grains of salt and enjoy!

Right now, FM stations all across the country are implementing basic IBOC signals. These signals duplicate existing programming in the digital form, allowing listeners to take best advantage of both broadcast forms on their new radios. This first stage will bring the basic technology improvements and changes to existing radio broadcasts. Ideally, these will be enough to drive HD Radio forward into the next stage, where increased choice, through multi-streams comes into play.

Once the basic services are up and running, broadcasters are going to begin programming their different streams. This will be an interesting time in that we will see new programming without having to invest in new stations for each additional programming choice. Additionally, the ability to offer more than one programming choice should make the risk of that choice easier to bear because existing streams would be largely unaffected. I expect to see more risks taken resulting in a more diverse set of programming choices for the average radio listener.

Success in the streams will also depend on receiver manufacturer support and planning / implementation issues. If the interface is rushed, or the streams are poor quality, etc.. listeners could largely ignore them. This is also true where expectations are concerned. The general HD Radio marketing catchphrase may not be appropriate in this regard. The NPR "Tomorrow Radio" might be better able to manage and set listener expectations where overall quality and program content are concerned.

AM IBOC stations, being more limited, will largely concentrate on bringing a better experience to their existing listeners while trying to limit the reduction in service at the same time.

There is the real possibility of AM IBOC not seeing much adoption at all given the issues. Despite the considerable engineering acumen of the IBOC team, the case for continued analog AM innovation and transmission remains strong, particularly given the audio accuracy and night time broadcast tradeoffs in IBOC. The digital return is minor, given the heavy AM tradeoffs. There is clear demand for better quality AM service, but I honestly don't expect IBOC to fit the bill at this stage. More work needs to be done and analog methods deserve greater consideration than they are currently being given.

I see no public demand for digital radio, only better radio. Where FM IBOC is concerned, the technology has strong potential to provide both. As I wrote above, AM IBOC is doubtful in this regard.

Back on the subject of choice, we might see a blend of program types become an option on both AM and FM bands. Talk programming, for example on FM becomes interesting where multiple streams are concerned. It's possible to carry multiple viewpoints, or provide program rotation/repeat cycles that bring a particular show to a wider audience not otherwise able to normally listen, though multiple schedules on different streams. This makes live broadcast of talk programming possible in all markets without having to force listeners into schedules they find uncomfortable, for example.

On AM, given the basic technical issues are resolved, music programming may be viable again as well. The upper limit on peak bit rate may well prove too low for this. Early tests on classical and jazz music are favorable. It must be noted these programs represent best case material for the codec due to their harmonic content. IBOC must be evaluated on a program by program basis to better understand what works well and what doesn't.

The additional choice and low cost of daily listening, compared to the recurring fees found on satellite radio systems, combined with a local presence should give radio an incentive to provide programs better adapted to a particular audience along with national program formats with less risk than is possible today with analog only systems. Multi-stream capability will power this, IMHO.

These are near-term expectations. In the longer term, FM IBOC presents some interesting possibilities. This is the pie in the sky part. Take your second grain of salt here -both if you didn't get started with one!

Digital radios, in Europe, are being fitted with download capability. The primary goal is being able to time shift broadcasts. This option, combined with multiple streams, here in the US, may well present listeners with choices not possible until now.

Here is one example: A station decides to run a special show at a specific time. Listeners could cache the program for listening later, or perhaps choose not to listen and play another cached show, or switch to another stream. Programming possibilities in this environment allow for new formats not possible with analog broadcasts today. To me, this is perhaps the most compelling possibility IBOC brings to the table.

Subscription services may become available, though I think those are better suited to satellite, Internet stream, and pod cast type delivery systems. I don't want to see these on radio, so I'm not going to write much about them.

Although there are no current plans for this, that I know of, it seems natural to include a media slot on future HD radios for downloaded content. As listeners consume their favorite program on a regular basis, they would be receiving portable content at the same time for their ongoing loyalty. Such content could be pictures, special release music files, hyper links, or simply text data or documents relevant to their local area, such as concert schedules, promotional discounts, and other localized information.

It is early, but there is another good use for removable media storage: namely pod cast like replay of programs, or distribution of pod cast like programs using the IBOC system instead of the Internet. The added value here would be ease of use combined with the station being able to air promotional programming related to the pod cast in question.

Market saturation with digital IBOC capable radios is going to take a while. Being able to "record" a broadcast onto some removable media, such as a USB memory key type device, would enable owners of IBOC capable radios to get the most use out of them. A car radio could be caching late evening programming for use during work, for example. Such a cache could also be used to playback favorite program segments, or provide entertainment outside of a coverage area.

Sadly, the legal landscape we see today makes these things nothing more than a dim reality, but it could yet happen. Perhaps the growing market pressure of satellite and Internet delivery systems will help this along a bit.

The digital nature of IBOC also allows for blanket coverage with advantages over analog means, such as RDS. Some small portion of the data could be used to tell a radio when it can switch to an identical program as a listener moves between service areas. This information could also be used to schedule time shift requests for listening later in a manner similar to satellite PVR video systems do today.

IBOC does allow for data transmission as well as audio broadcasts. I didn't discuss this much earlier because the focus of this paper was on the radio listener, for the most part. Stations can choose to devote a portion of their bitstream to data applications, not directly targeted at the average radio user. These applications include commercial controlling, tracking and automation applications not well served by existing and more expensive technologies. These applications hold the potential for additional station revenue. This may be a good thing for radio listeners in that healthy radio stations may be better able to provide live and local programming. However, it may be that overall audio quality and choice may suffer as well with data profits simply going to the station bottom line with no improvements in return for the listener.

I did get one interesting comment on the multi-stream that is worth noting here. The potential for multiple FM streams may result in reduced AM service in that the AM programming can simply be moved to a stream, thus making the expense of an AM station unnecessary. In this case, we may lose AM stations, or others may choose to operate them in new and creative ways. Either way, it is worth noting the broadcast giants have little incentive to operate multiple stations when they can use one, more powerful and capable one to hold their different programming offerings. Will they choose to further consolidate or will they simply provide more options given the new capability offered to them? If AM stations are freed, will we lose them, or will others fill the gap and try new programming to compete?


We are entering an interesting radio time, particularly for FM radio. IBOC holds strong potential for greater choice than we have today. There are technical challenges to overcome yet, particularly on AM. Increased choice and reduced risk are the biggest benefits I see IBOC bringing to the table. Quality has the potential for being greater than satellite and most Internet delivery systems with the added advantage of being inexpensive for the listener over the longer term.

This paper represents a best case view for FM IBOC as much as it does an overall reference to the technology put into basic terms. Many factors may well contribute to the IBOC picture that sharply reduce the overall value delivered to the listener. I have tried to present many of these here for your consideration.

Going forward, I believe the increased choice potential outweighs the technical problems on FM and am eager to see radio grow in that direction. Content is king, and I would rather see more of it, that I have a chance at enjoying, than continue on the path we are on now. IBOC on FM will provide a vehicle that will make that happen with less risk than currently required today to "break the mold" so to speak. Lets hope that part of things begins to happen sooner rather than later.

I have mixed opinions about AM IBOC and welcome your comments and insight. I hope the right decisions will be made regarding AM IBOC and feel it is important for everyone to continue to express whatever view they have on that topic. My personal view is not favorable in that the value added to AM does not outweigh the value lost in existing services. (Loss of AM Stereo, increased noise, limited analog bandwidth, etc...)

Why this paper? I evaluate technology as part of my day to day activities. A long interest in radio, prompted me to look at IBOC and write what I have learned so far. The story is not over yet by any means. We shall see just how much I have wrong over the next few years.

From time to time, this paper will see updates and changes as the IBOC HD Radio landscape continues to evolve.

I hope you have enjoyed reading this as much as I did writing it! Please direct any comments / suggestions and (gasp!) errors to:


(At the moment, this section is incomplete. Look for additional links and some brief commentary on the significance of each one here in the near future.) -- Creator/owner of the IBOC technology. -- Various white papers detailing technical implementation details and core technology elements. -- Source for podcasts. While not directly relevant to this paper, I used the term several times. This should clear things up if you have questions. Enjoy a few while you are there! - Rather sales like treatment of HD radio, but does have links to actual HD radio gear for reference / comparison. -- Interesting information about bitrates and multi-stream technology progress. -- Negative view of IBOC. I don't agree fully with this work, but include it here because many of the points given apply to the delicate AM IBOC discussion. Worth a read on that basis alone. -- This is an informative page that details FM noise expectations where multi-stream is concerned.

Have an additional IBOC resource to share? Drop it into a comment below, or shoot me an e-mail. I'll add it to the list.


Blogger worldsupercaster said...

HD Radio is a defective technology resulting in more problems and false claims then benefits.
More here:

March 01, 2006 6:05 AM  

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