Satellite radio uses satellites and terrestrial repeaters to broadcast over 100 commercial-free music and talk channels across large areas. It provides CD quality audio to subscribers. Key points: - Signals are transmitted digitally from uplink stations to satellites then to fixed or mobile receivers. - Coverage is provided by multiple satellites using spot beams. Signals are amplified and retransmitted by the satellites. - Receivers use techniques like maximal ratio combining on multiple satellite signals for better reception. Audio is compressed using perceptual coding before transmission. - Content is protected using encryption and conditional access restricts signals to legitimate subscribers. - While offering unique features, satellite radio faces challenges from competition and high subscription/receiver costs

1. Satellite Radio – a technological overviewSagar Medikeri,2BV06EC060

2. Radio – Analog and DigitalIntroduction to Satellite RadioVarious Satellite Radio TechnologiesFuture of Satellite RadioSeminar Overview

3. Analog RadioHere, the audio signal is piggybacked on a carrier signal by means of analog modulation techniques like AM, FMDigital RadioHere, the audio signal is digitized and then transmitted using digital modulation techniques like QPSK, QAMRadio – Analog and Digital

4. Analog vs. Digital Radio

5. Satellite Radio - Market Players

6. Large area coverageCD quality audioSubscription basedCommercial-free contentLots of variety - 100s of channelsProgramming includes music, news, talk radio, sports, humorAudio associated metadata transmittedSome channels broadcast in 5.1 surround sound formatFCC does not regulate contentService features

7. How Satellite Radio works?Uplink Station, Satellite & Terrestrial Repeaters Control RoomTerrestrial RepeatersFixed Receivers

8. Satellite Technology

9. 1worldspace satellite spot beamsAsiastarAfristar

10. ATIS (Automatic Transmission Identification Service). In this scheme, there can be multiple uplink facilities. Each uplink facility has a station ID.2 or 3 Parabolic or Unfurlable Antennas are usedThe RF signal received by satellites is amplified by high power TWTAs operating in parallelRF power transmitted is 12 – 15 KWSatellites’ lifetime is 12 - 15 yearsSatellite Technology

11. Receiver Technology2320 MHz2332.5 MHzCarrier 1Carrier 2Carrier 34 MHz4 MHz4 MHz

12. Receiver TechnologySirius 1Carrier 1Carrier 1Sirius 2Carrier 2Carrier 375 MHzIF~ -50dBmMaximal-Ratio Combining for Signal DiversityBaseband ProcessorAntenna Tuner2.3 GHzDigitize, Demodulate, Error correction, DecryptDown conversion

13. Maximal Ratio CombiningAdderBaseband 1a1Retrieve the 3 Baseband signals75 MHzIFBaseband 2a2Best estimate of Baseband signalBaseband 3a3

14. Perceptual Audio CodingEntropy CodingFilter BanksQuantization & EncodingMUXAudioCompressed AudioPsychoacoustic ModelBit Allocation

15. Achieved by Hierarchical ModulationQPSK is embedded into 16QAMQPSK carries “High Priority” bits & QAM carries “Less Priority” bitsIn poor link conditions, at least QPSK is resolvedEconomizes BandwidthLink Adaptation

16. Used to limit reception to legitimate subscribersIntegrity of contentContent ProtectionElliptical Curve Cryptography (ECC) is used for encryption. ECC provides RSA level security with a smaller key. This reduces transmission overhead.Conditional Access

17. Receivers ($120) and Subscriptions (>$7/month) costlyStiff competition from iPod, Internet Radio, local FMSteady Attrition RatesSirius & XM still in debtBut, the technology developed for Satellite Radio will pave the way for Satellite Digital Media Broadcasting (S-DMB)Future of Satellite Radio

18. Painter, T., and A. Spanias. "Perceptual coding of digital audio." Proceedings of the IEEE 88 (2000)Wikipedia entries on, 1. Sirius Radio 2. XM Radio 3. PsychoacousticsGledhill J., MacAvock P., Miles R. Whitepaper on “Hierarchical Modulation”References

19. Thank You !!