IBOC Update - Sep 15, 2004
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Kahn Continues Crusade Against IBOC AM HD Radio Standard
Long-time radio engineer and AM proponent Leonard Kahn is once again making waves, though not of the electromagnetic variety. Kahn, well known to many industry insiders as both a technical innovator and maverick, recently went public with a letter attacking the nighttime IBOC performance of WOR-AM (710) in New York City, claiming that an evening test "jammed" the signals of first-adjacent WLW (700) in Cincinnati. Buckley Broadcasting Director of Engineering Thomas Ray responded to Kahn's accusation as being completely unsubstantiated. Buckley Broadcasting owns WOR, and has been a strong proponent of Ibiquity's HD Radio system.
Kahn's point of view is reflective of some in the industry, both domestically and in neighboring Mexico and Canada, who fear the potential loss of secondary coverage that blanket authorization of AM IBOC digital may bring. But his stance against Ibiquity's approach is also marked by a 2003 petition to the FCC to set aside mandating an AM IBOC digital AM standard in order to permit evaluation of an alternative system he himself has developed, known as Compatible Amplitude Modulation-Digital, or by its acronym, CAM-D.
While Kahn has publicly revealed very little in the way of CAM-D's technical details, the system he now champions is widely believed to be a variation of an older technology that his company also developed; the Kahn/Hazeltine AM stereo system. Those who remember the long and tortuous history of AM stereo implementation may recall that the Kahn system relied largely on independent sidebands for the carriage of the encoded stereo multiplex information. Though the system eventually lost the industry standard contest to Motorola's C-Quam, CAM-D is an apparent attempt to build upon Kahn's original technology by adding a relatively low-rate data signal that would carry additional high frequency information not available because of the limited bandwidth imposed upon the analog sidebands by the NRSC spectral mask. Precisely by what means CAM-D's digital stream is compressed, encoded, and extracted is unclear, and is described only as "proprietary."
Many senior engineers in the industry have great respect for Kahn's historic record of creative development with sideband manipulation, exemplified in the late 1950's by his development of the Symmetra-Peak, an AM audio processor that greatly reduced audio asymmetry and a fundamental approach still embodied in modern AM processors. He is also credited for his development of Power Side, a unique approach to packing more energy into a single AM sideband for increased range. Even so, most engineers question whether his primarily analog approach can realistically expect to compete with the 34kp/s pure digital stream delivered by Ibiquity's AM HD Radio standard. Still more are troubled by the thought that if AM IBOC digital doesn't get off the ground soon, any improvement, no matter how well it protects existing coverage, may be too little, too late.
Even so, the debate over coverage trade-offs, along with objections from broadcasters in Canada and Mexico, are not likely to diminish in the short term.
The FCC is expected to issue a Report and Order specifying operational standards for both AM and FM IBOC digital operation soon.
Canada Hosts First Digital Multimedia Broadcast Demonstration
The Canadian Broadcast Corporation (CBC), in collaboration with Pixtree Technologies, Radioscape and Société Radio Numérique (SRN), recently demonstrated Digital Multimedia Broadcast (DMB) in Canada for the first time. The demonstration allowed members of the Canadian broadcast industry to get a first-hand look at DMB, a new multimedia broadcast standard proposed by South Korea that is totally compatible with the Eureka-147 system DAB now being deployed in Europe and Canada. As a supplemental service offered by DAB broadcasters, DMB would allow users to receive live video on mobile units such as personal digital assistants and cellular phones.
The CBC demonstration utilized a 320x240 display of streamed video multiplexed over a DAB network via an IP gateway. Canadian groups are currently considering a trial system somewhere on Canadian soil that would allow local broadcasters and consumers to gain exposure to the new technology. In Korean and Japan, both governments have cooperated to provide frequency allocations service for domestic commercial system deployment via direct broadcast satellites as well as terrestrial systems.
CBC/Radio-Canada was created as a Crown Corporation in 1936 by the Canadian government in response to what many Canadians felt was a disproportionate American influence in Canadian radio broadcasting. As Canada's public broadcaster, CBC/Radio-Canada provides services in English, French and eight Aboriginal languages in the North. CBC/Radio-Canada is mandated to provide radio, television and new media services incorporating a wide range of programming, and is said to have provided inspiration for the creation of America's Corporation of Public broadcasting in 1969 by Congress.
IBC Gives Attendees Look at latest DAB developments
While American broadcasters anxiously await a report and order that will codify IBOC DAB in the US, international broadcasters attending the International Broadcasters Conference in Amsterdam last week found plenty of evidence of DAB innovation and convergence on the show floor.
WorldDAB, the association supporting and promoting a global DAB standard and representing more than 80 organizations across 25 countries hosted the first European demonstration of Digital Multimedia Broadcasting at its booth. Co-exhibitor KBS (Korean Broadcasting System) was on hand to deliver the demonstration of terrestrial DMB using DAB over handheld receivers from Samsung, Perstel and On Timetek.
The Korean terrestrial DAB system will launch by the end of 2004, and will initially include 48 channels delivered to consumers free of charge.
Radioscape displayed its Broadcast System 5.0, a DAB broadcast platform designed for robust delivery of next generation data services, such as Digital Multimedia Broadcasting (DMB), first demonstrated at NAB 2003 in conjunction with Tanberg Television, Microsoft and NTL Broadcast. The company claims that the system's architecture has been improved in order to provide seamless integration of data applications over DAB from content provider to consumer. One example is the new WM9CAM, which encodes audio into the popular Windows Media 9 encoding standard, and the Datacam, which acts as a single portal to content providers - both support multicast IP capability. Another is the development of additional Forward Error Correction (FEC) features to increase the reliability of both multimedia and general data transmissions.
Radioscape also demonstrated what it bills as "the world's first complete Electronic Programming Guide (EPG) solution for Digital Radio. The EPG is broadcast using its Professional Broadcast System v.5, and is received and displayed using Radioscape's recently launched RS300L(tm) DAB module.
Digital Radio Mondiale, which has developed a non-proprietary digital broadcast system for medium and short-wave broadcasters was also on hand at the IBC, demonstrating the Digital Traveler, a DRM capable USB receiver produced by Coding Technologies. The organization also showed a variety of other DRM compatible consumer products including some designed specifically for the automotive market.
IBOC Across America
IBOC By State: Texas
Ibiquity has a list of stations that have licensed HD Radio technology and notes those that are on the air now. IBOC by State will look at various states and list the stations that are making the transition.
|KRGN-FM 102.9||Christian||Amarillo, TX||Family Life Communications, Inc.||No|
|KEDT-FM 90.3||Variety||Corpus Christi, TX||South Texas Public Broadcasting Systems Inc.||No|
|KCAF-AM 990||dark||Dallas-Ft. Worth, TX||Renaissance Radio, Inc.||No|
|KERA-FM 90.1||Nws/Tlk/Inf||Dallas-Ft. Worth, TX||North Texas Public Broadcasting Inc||No|
|KNTU-FM 88.1||Jazz/Clscl||Dallas-Ft. Worth, TX||University of North Texas||No|
|KSOC-FM 94.5||Hip Hop||Dallas-Ft. Worth, TX||Radio One Inc.||Yes|
|WRR-FM 101.1||Classical||Dallas-Ft. Worth, TX||WRR-FM, City of Dallas||No|
|KCHN-AM 1050||Ethnic||Houston-Galveston, TX||Multicultural Radio Broadcasting Group||No|
HD Radio Terminology
DRM: Digital Radio Mondiale. DRM was first conceived as a digital replacement for AM broadcasting below 30 MHz in 1998 by a consortium of world broadcast organizations, which has since expanded to include 81 members, including American broadcast manufacturers Harris Corp, Broadcast Electronics, and DRS Broadcast Technology (formerly Continental). Unlike the HD Radio AM IBOC digital system developed and licensed by Ibiquity, DRM encompasses a non-proprietary system architecture available to broadcasters and manufacturers alike.
Because channel bandwidth, emission mask requirements, and propagation vary with different regions and bands, four modes of operation are specified for DRM, offering greater levels of signal robustness in exchange for lower audio data rates. Like HD Radio AM, DRM can be transmitted in a hybrid (digital/analog simulcast) mode but with a significantly lower data rate than in its purely digital implementation.
Belar to Address IBOC Signal Monitoring at NAB Radio Show
With many large radio ownership groups now planning to accelerate their rollout of IBOC digital signals, broadcast engineers are asking tough questions about how they are going to measure the performance of new digital transmission systems. For example, which parameters are key to evaluating system performance? What parameters might the FCC may require broadcasters to routinely monitor? What types of instrumentation will be available to address those tasks?
In a brief interview with Radio magazine, Belar Laboratories' Mark Grant addressed some of the issues facing broadcaster's digital monitoring needs, and offered a preview of a talk he will give at the upcoming NAB Radio Show in San Diego in October. He is currently developing HD Radio monitoring products for his employer, which announced its licensing of the technology with Ibiquity last April.
The most obvious and basic need digital broadcasters face, says Grant, is for a high-quality source of decoded primary and secondary digital audio signals, both in AES/EBU digital and analog domains. But that's only the beginning. Digital modulation levels are important in assuring that sufficient headroom is maintained to prevent coding modulators from reaching digital zero. Because audio processing approaches to the compressed digital audio domain of HD Radio are very different than the hard limiting and clipping employed in analog FM broadcasting, greater care will have to be exercised in the digital domain.
Because HD Radio also carries ancillary data including static information such as station identification as well as dynamic information regarding programming, any monitoring solution will need to provide that data for monitoring purposes throughout the station, Grant added.
Another key function called for in hybrid signal monitoring is measuring time alignment between demodulated digital and analog signals. Due to the latency of decoded digital signals in receivers, analog audio must be delayed by up to six seconds to assure satisfactory performance when those receivers blend or transition from analog to digital and vice versa. This makes time alignment a parameter that broadcasters will need to measure, match, and maintain with precision.
Also of importance is the ratio of analog to digital carrier levels in hybrid and extended hybrid operation. According to Ibiquity specifications, these ratios must be maintained with the digital carrier operating 20dB below that of the analog carriers at all times.
Finally, there is a need to observe and monitor the robustness of the digital transmission. According to Grant, this is analogous to monitoring the bit error rate on a DAT tape. The presence of a quality indicator signal will assist broadcasters in detecting system problems before a signal degrades to the point where it becomes apparent to the listener.
Despite the obvious challenges of working with such a broad set of requirements, Belar is targeting January 2005 as a shipping date for their new HD Radio monitor product line.
Mark Grant will deliver his full presentation on IBOC monitoring during the 2004 NAB Radio Show on Oct. 8 at 8:45 a.m.
Harris Debuts DRM Upgrades at IBC
Harris demonstrated its support for the international DRM (Digital Radio Mondiale), demonstrating its new Flexstar DRM exciter upgrade package last week at the IBC show in Amsterdam. The integrated hardware/software platform is designed for simple incorporation into the company's established DX and new low-power Dax AM transmitters. The upgrade package features both a DRM modulator and content server. The content server encodes the audio and combines it with digital program information into one bandwidth-efficient, digital bitstream that is sent to the transmitter. The DRM modulator, situated inside the transmitter cabinet, accepts the digitally prepared signal and controls the transmitter to drive the digital signal to the receiver.
Visitors to the Harris booth were able to examine an operational Flexstar DRM exciter upgrade package integrated with a Dax 5kW AM transmitter, and hear its performance on a local DRM receiver.
"Until the simulcast mode is finalized, DRM will be used in the all-digital mode," said Don Spragg, high-power product engineer for Harris' Radio Broadcast Systems business. "Transmissions must be either all-digital DRM or a traditional analog signal. Broadcasters can't simply shut off transmitters that service their analog listeners to go completely digital at once. Instead, they may opt to program certain hours in DRM and others in analog. Our package provides an easy way to switch between formats, remotely or at the transmission site, whether for simple testing or actual programming."
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