IBOC (In Band On Channel) Technology for DIgital Radio.

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The engineering world has been working on the development and evaluation of IBOC transmission for some time. The NRSC began evaluation proceedings of general DAB systems in 1995. After the proponents merged into one, Ibiquity was left in the running for potential adoption. In the fall of 2001,the NRSC issued a report on Ibiquity's FM IBOC. This comprehensive report runs 62 pages of engineering material plus 13 appendices. All of the system with its blend-to analog operation as signals levels changes. The application of the FM IBOC has been studied by the NRSC and appears to be understood and accepted by radio engineers. AM IBOC has recently been studied by an NRSC working group as prelude to its adoption for general broadcast use .Its was presented during the NAB convention in April. The FM report covers eight areas of vital performance concerns to the broadcaster and listener alike .If all of these concerns can be met as successfully by AM IBOC, and the receiver manufactures rally to develop and produce the necessary receiving equipment. The evaluated FM concerns were audio quality, service area, acquisition performance, durability, auxiliary data capacity, and behavior as signal degrades stereo separation and flexibility.
The FM report paid strong attention to the use of SCA services on FM IBOC. About half of all the operating FM stations employ one or more SCAs for reading for the blind or similar services. Before going to the description of FM IBOC system, it is important to discuss the basic principles of digital radio, and IBOCtechnology.

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IBOC (In Band On Channel) Technology for DIgital Radio.

  1. 1. 6/13/2014 1 ครк™©2012 Hai….! Welcome
  2. 2. In Band On Channel Technology For Digital Radio Ashik S R ashikask@live.com 6/13/2014 2 ครк™©2012
  3. 3. INTRODUCTION In Band On Channel (IBOC) is a hybrid method of transmitting digital , analog radio signals broadcast simultaneously on the same frequency. By utilizing additional digital subcarriers or sidebands, digital information is “multiplexed” on an AM or FM analog, thus avoiding re-allocation of the broadcast bands. However, by putting RF energy outside of the normally- defined channel, interference to adjacent channel stations is increased when using digital sidebands. IBOC does allow for multiple program channels, though this can entail taking some existing subcarriers off the air to make additional bandwidth available in the modulation baseband. On FM, this could eventually mean removing stereo. On AM, IBOC is incompatible with analog stereo, and any additional channels are limited to highly- compressed voice, such as traffic and weather. Eventually, stations can go from mode(both analog and digital) to all digital, by eliminating the baseband monophonic audio. Digital Radio 6/13/2014ครк™©2012 3 In Band On Channel Technology For Digital Radio
  4. 4. A small screen attached to the digital receivers displays text and pictures. Text, data and images can be diffused at the scale of a country or a region. Visteon's MACH DSP combined with iBiquity technology brings HD Radio to reality 6/13/2014 7ครк™©2012
  5. 5. 6/13/2014 ครк™©2012 8 IBOC: a new system In Band On Channel Compatible with the current analogue radio formats. Utilises the existing AM and FM bands by attaching a digital side-band signal to the standard analogue signal. For digital compression, the IBOC uses a perceptual audio coder (PAC).
  6. 6. 6/13/2014 ครк™©2012 10 IBOC technologies from USADR and iBiquity Digital The IBOC technology allows digital audio broadcasting without the need for new spectrum allocations for the digital signal. It provides for enhanced sound fidelity, improved reception and new wireless data services. This enhancement to AM and FM will offer tremendous growth opportunities for broadcasters, manufacturers, retailers and automotive manufacturers.
  7. 7. 6/13/2014 ครк™©2012 16 Basics of IBOC • The IBOC technology is used to transmit CD-quality audio signals to radio receivers along with such data as station, song and artist identification, stock and news information and local traffic and weather updates. • The broadcasters can use the existing radio spectrum to transmit AM and FM analogue simultaneously with higher quality digital signals. • The system employs multiple digital signaling techniques, such as redundant sidebands, blend, first adjacent cancellation and code and power combining. • To compress the audio data and increase transmission without losing sound quality, it uses the PAC audio-compression technology.
  8. 8. 6/13/2014 ครк™©2012 17 An integral part of iBiquity Digital’s AM and FM digital broadcast technology, the PAC audio-compression technology utilizes advanced signal processing and psycho- acoustic modeling to interpret human hearing and eliminate redundancies and irrelevancies in the audio signal. iBiquity Digital has designed the PAC technology for Internet broadcasting as well. Companies will use the PAC technology to encode and decode music, talk and information programming that will be delivered over the Internet. iBiquity Digital’s PAC technology will also be used in satellite digital radio. Audio quality at a given compression rate is a crucial factor for satellite digital radio. With PAC technology, a high audio quality can be obtained at various bitrates.
  9. 9. FM hybrid IBOC waveform  Low-level digital sidebands are added to each side of the analogue signal.  The bandwidth is limited to 200 kHz from the centre frequency.  Restricting the digital sub- carriers to 70kHz.  This minimises interference to the analogue host and adjacent channels without exceeding the existing spectral mask.  This bandwidth is wide enough to support a robust, hybrid IBOC service with virtual CD-quality audio that mirrors the coverage of existing analogue radio stations. 6/13/2014 ครк™©2012 18 Fig. 1: FM hybrid IBOC power spectral density
  10. 10. 6/13/2014 ครк™©2012 20 Advanced FEC Allows the combination of both side bands. Provide additional signal power gain and coding gain. Base line hybrid system Simultaneously transmits 96 kbps of error – protected signals. Digital audio information and auxiliary services. Dual side band structure Enables the use of frequency diversty. Combat the effects of multipath fading & interference. IBOC technology employs redundant information placed in the upper and lower sidebands to ensure that the system performs in all radio environments. It further combats interference through first adjacent canceller (FAC) technology. FAC cancels the effects of a strong analogue adjacent channel station that can easily wipe out a digital sideband. This patent- pending technology greatly increases the chances of a sideband survival and, when combined with redundant sideband implementation, provides robust digital reception under all interference conditions.
  11. 11. 6/13/2014 ครк™©2012 21 Since QPSK has a bandwidth efficiency of two bits per second per hertz, it supports an information bitrate that is sufficient for transmission of virtual CD-quality audio in the bandwidth available. Orthogonal frequency-division multiplexing (OFDM) allows frequency-division multiplexing of many QPSK-modulated sub-carriers in an orthogonal fashion such that each sub-carrier does not interfere with its adjacent sub-carriers. This offers a high level of robustness in a multipath channel. When combined with FEC coding and interleaving, the digital signal’s robustness is enhanced further. The OFDM structure supports FEC coding techniques that maximize performance in the non-uniform interference environment. The most important coded bits can modulate OFDM carriers that are located in the most protected regions of the channel.
  12. 12. Multipath interference from multiple sources 6/13/2014 ครк™©2012 22
  13. 13. 6/13/2014 ครк™©2012 23 Block diagram of the IBOC DAB transmitter Encodes the audio For blending purpose Ensure that the compressed data is robust To produce the DAB base band signal Up convert the base band signal
  14. 14. 6/13/2014 ครк™©2012 24 Auxiliary services Ancillary Services Opportunistic Data 120 kbps Reducing Audio quality & FEC parity. Up to 32 kbps- intermittently multiplexed with the audio. Service Flexibility
  15. 15. 6/13/2014 ครк™©2012 25 Why delay in adoption? The IBOC technology is not free from problems: Low-power FM stations are prone to Interference. Receivers used for radio-reading services for the blind may also be impacted. IBOC licensing and service rules have not been adopted yet. iBiquity is the only IBOC vendor, stations willing to use the IBOC technology will have no choice but to make arrangements with iBiquity.
  16. 16. 6/13/2014 ครк™©2012 26 Let me Conclude We have discussed about: • Digital Radio • Benefits of DAB • RDS • PAC used in IBOC • USADR, iBiquity •Service flexibility. IBOC technology a hybrid method of transmitting digital and analog radio signals simultaneously on same band. Through this technology HD radio could make a reality. And let us hope that HD radio become familiar soon to Indians too.
  17. 17. 6/13/2014 ครк™©2012 27 Credits Slides prepared: Ashik.S.R Seminar presented: Ashik.S.R Guidance: Alex Shobana RajKumar Special Thanks to Sri. Justin Raj Thapas The Principal ,CPTC www.facebook.com/ashik.ask

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