US005907582A
`United States Patent
`5,907,582
`(11) Patent Number:
`[45] Date of Patent:
`May25, 1999
`Yi
`
`
`(15
`
`[54] SYSTEM FOR TURBO-CODED SATELLITE
`DIGITAL AUDIO BROADCASTING
`
`[75]
`
`Inventor: Byung Kwan Yi, Derwood, Md.
`
`[73] Assignee: Orbital Sciences Corporation, Dulles,
`Va.
`
`[21] Appl. No.: 08/908,045
`
`Filed:
`Aug. 11, 1997
`[22]
`Tint. C08.cessssescssssseseecsosssseneeesscssnnmseenseess HO04J 13/00
`[SL]
`[52] U.S. Ch.eens I75/259; 375/200; 370/342;
`370/208
`ssieevesesiesniess STS2OO, 2585
`........
`[58] Field of Search.
`375/260,267,347; 370/208, 209, 320,
`342, 486; 455/3.2, 103, 132, 133, 137,
`12.1, 427, 506
`
`(56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`Asystem and method for broadcasting an audio signal in a
`turbo-coded satellite digital audio broadcasting system is
`provided that utilizes the combination of a turbo coding
`system having code combining and code diversity tech-
`niques to lower the power required for transmittal and to
`transmit at a higher code rate of % by utilizing the punc-
`turing sequence and a pilot signal assisted orthogonal
`4,881,241
`11/1989 Pommier et al... 375/260
`CDMA; the invention includes an improved receiver system
`§,191,598
`3/1993 Backstrom et al. wo... 375/347
`that uses modified RAKE receivers in order to mitigate the
`
`5,278,863=1/1994 Briskman wo... 375/200
`Rayleigh multipath fading, shadowing, and temporal block-
`.........:00000 370/312
`5,283,780
`2/1994 Schuchmanet al.
`
`age and improve performance. The invention further uses a
`5/1994 Murphy etal. wees 370/312
`5,315,583
`
`terrestrial gap filler network having a reduced amountof gap
`6/1994 Briskman .....e.-sccssssssseeseeeseoenee 375/200
`5,319,673
`
`fillers.
`wee 371/434
`5,406,570
`4/1995 Berrou etal. .
`4/1995 HOW ..ccccccsscsscsscsrsssesesestenereeseees 375/340
`§,408,502
`
`8/1995 Tzukermanetal. .....0....0... 375/259
`5,438,590
`
`5,446,747
`8/1995 Berto cevseessssnsnssuseeesecesasseenee 3TU/AS
`
`5,485,485
`1/1996 Briskman etal...
`wee 375/200
`§,544,156
`8/1996 Teder etal. .....
`wee 370/342
`
`5,570,356
`sass 370/476
`10/1996 Finneyetal....
`
`5,588,022
`...--.-sccessecseceeene 375/216
`12/1996 Dapperet al.
`
`5,657,325
`8/1997 Louetal....
`von 370/334
`
`5,671,221
`9/1997 Yang. eveeoe
`vase 370/320
`
`5,691,974 11/1997 Zehavi etal....
`wee 370/203
`3/1998 Kostreski et al.
`sscsssscssosssesseus 4553.1
`5,729,825
`
`
`5/1998 Gilhousen.......
`ven 375/200
`5,751,761
`
`6/1998 Dent cevsoorsonsecrnnseensseeeeeesareee 370/479
`5,764,646
`6/1998 Kaks ...ccccosssecesrseessesssreresenceeee S7D/232
`5,771,226
`
`Primary Examiner—Young T. Tse
`Attorney, Agent, or Firm—McDermott, Will & Emery
`
`[57]
`
`ABSTRACT
`
`31 Claims, 6 Drawing Sheets
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 1
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 1
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 1 of 6
`
`5,907,582
`
`
`roadcastingStation
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`
`
`10
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 2
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 2
`
`

`

`U.S. Patent
`
`May25, 1999
`
`Sheet 2 of 6
`
`5,907,582
`
`12
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 3
`
`Channel 32 Sequence #2
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`102
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`FIG. 2
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 3
`
`

`

`U.S. Patent
`
`May25, 1999
`
`Sheet 3 of 6
`
`5,907,582
`
`Jasnpung
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`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 4
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 4
`
`
`

`

`May 25, 1999
`
`Sheet 4 of 6
`
`5,907,582
`
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 5
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 5
`
`
`
`

`

`U.S. Patent
`
`May25, 1999
`
`Sheet 5 of 6
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`5,907,582
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 6
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 6
`
`
`
`

`

`U.S. Patent
`
`May25, 1999
`
`Sheet 6 of 6
`
`5,907
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`582
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 7
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 7
`
`
`

`

`5,907,582
`
`1
`SYSTEM FOR TURBO-CODED SATELLITE
`DIGITAL AUDIO BROADCASTING
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`This invention relates to a Digital Audio Broadcasting
`(DAB) system for the wide-area distribution of multiple
`channels of audio programming, andin particular to a DAB
`system and method having improved receiver performance
`through coding gain from code diversity and packet
`combining, and distributed gapfiller network.
`2, Description of the Prior Art
`Several DAB methods and systems have been proposed
`for Direct Broadcast Satellite Radio that essentially broad-
`casts digital audio signals for reception by fixed and mobile
`receivers. Such DAB systems and methods heretofore have
`yet
`to overcome problems that affect
`the overall system
`performance so as to make it commercially feasible. The
`most significant problems in DAB systems are signal
`shadowing, fading, and temporal blockage. Shadowing
`problems are dominated by factors such as the intermittent
`blockage of the line of sight to the receiver from thesatellite
`by natural or man-made objects. For example, in suburban
`environments tree shadowing is the prominent signal
`impairment, while in urban environments, buildings cause
`the major shadowing effect. Fading problems are mainly
`caused by multipath signals to the mobile receiver in sub-
`urban and urban environments. Signal fading can be miti-
`gated by adapting temporal diversity techniques such as time
`diversity and spatial diversity. Conventional time diversity
`schemes operate on the samesignal so as to randomize the
`outage patterns through interleaving, data repetition, and/or
`someform of channel coding. Conventionalspatial diversity
`techniques operate on the samesignalusing a dual satellite
`schemeand/or an antennadiversity technique for remedying
`shadowing and temporal blockages.
`Conventional DAB systems and methods have sought to
`mitigate the problems of multipath fading and foliage
`attenuation by employing two geosynchronous satellites.
`U.S. Pat. Nos. 5,319,673 and 5,278,863 to Briskman dis-
`close a polarization diversity technique in a spread spectrum
`system (either direct sequence or
`frequency hopping
`schemes) that employs frequency diversity to combatfading
`in a frequency selective channel. A conventional Code
`Division Multiple access (CDMA)system, using two geo-
`synchronous satellites and a dual diversity technique is
`utilized, however,
`the Briskman system cannot provide
`seamless high performance service overthe entire coverage
`area, since conventional CDMA system performance is
`limited by self-interference. Self-interference is induced by
`the cross-correlations of the Pseudo Noise (PN) sequences
`used for the different program channels. Furthermore, the
`Briskman system employs a dual polarization approach to
`separate signals from twosatellites, the receiver then select-
`ing the stronger of the two broadcasts of the samesignal.
`Whilea dual satellite system increases the probability that a
`mobile orfixed receiver has line-of-sight contact with one of
`at least two satellites, the unselected satellite’s signal must
`be separated and eliminated from further signal processing,
`otherwise, the weaker signal acts like added noise to the
`stronger signal. Additionally, preserving the polarization in
`
`10
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`2
`the mobile signal path is very difficult because the reflected
`signals tend to invert the polarization. Therefore, conven-
`tional DAB systemsare inefficient in power and bandwidth
`usage whereby performance is inadequate for subscription-
`grade quality of service.
`Finally, even with two satellites, signal blockage,
`shadowing, and fading problems continue to occur in urban
`and suburban environments. Conventional DAB systems
`have sought to solve this problem by employing a network
`of gap filler transmitters to provide the signal when both
`satellites are blocked from view. However, such network of
`gap fillers transmitting the same broadcastsignal increases
`the self-interference problem, which in tum increases the
`cost and complexity of the gap filler network because of the
`desire to use increased transmit power levels to combat
`self-interference. Previous attempts to solve this problem
`have been inadequate for subscription grade service given
`the intended DAB service area (continental United States)
`and the pervasiveness of the shadowing/fading problem;this
`has created new cost problems whereby gap fillers are
`required in virtually all urban and suburban locations.
`Therefore,
`the DAB method and system of the present
`invention advantageously provides a way to reduce the
`numberand costof such gapfillers anda critical solution to
`the overall network design problem. The DAB method and
`system of the present invention advantageously utilizes code
`diversity (whereby two different non-self-interfering turbo
`encoded signals are transmitted and substantially combined
`inside the receiver)
`to provide improved performance
`through higher coding gains, fewer gapfillers, and reduced
`transmit powerlevel requirements from either of each of the
`satellite or the gap fillers.
`Other DAB systems have used dual antennas and a
`Viterbi-algorithm method over a fading channel to reduce
`the affects of signal fading in the received signal. U.S. Pat.
`No. 5,191,598 to Backstrom et al. discloses a system for
`receiving radio signals on at least two mutually spaced
`antennas and a receiver to process samples of the signal
`using a Viterbi-algorithm thereby reducing signal fading.
`Various antenna diversity schemes also have been used and
`these are characterized by the orthogonal polarization of the
`broadcast signals. For example, in U.S. Pat. No. 5,485,485
`to Briskman, a dual antenna system is disclosedthat selects
`the stronger of two signals having substantially the same
`content and frequency. The dual antenna approach requires
`two physical antennas on the mobile receiving station which
`is inconvenient and expensive as multiple antennas are
`installed on the vehicle’s roof, and their employmentillus-
`trates the severity of the reception problems of conventional
`DAB systems. Additionally, the performance gain due to a
`dual-antenna system is minimal unless the receiver uses
`extensive signal processing techniques to accurately com-
`pensate for the angle of arrival. The method and system of
`the present invention solves these problems by advanta-
`geously utilizing RAKE receivers to combine multipath
`signals from satellites and gapfillers at the DAB receiver.
`U.S.Pat. No. 5,544,156 to Tederet al. discloses a system
`and methodfor coherently demodulating an uplink signal in
`a multirate, CDMA system. However, the receiver perfor-
`mance of the conventional CDMA and/or Viterbi based
`coding systems is limited by multiple access channel inter-
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 8
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 8
`
`

`

`3
`ference and does not provide performance and coding gains
`at the level provided by the presentinvention. Asa result, the
`present invention uses a Turbo Code method and system
`along with Orthogonal Code Division Multiple Access
`(OCDMA)techniques to advantageously eliminate the
`effects of multiple access interference and provide high
`coding gain, which results in robust DAB reception at lower
`overall powerlevels.
`Finally, an error coding system using turbo codes, i.e.,
`codes that associate with parallel concatenation of two
`convolutional codes separated by an interleaver,is disclosed
`in U.S. Pat. No. 5,446,747 to Berrou and U.S. Pat. No.
`5,406,570 to Berrou et al. While such systems have accept-
`able coding gain they do not address the dual-signal path
`case or the benefits provided through the use of code
`combining and codediversity. These codes do not transmit
`interleaved data elements, but only transmit uninterleaved
`data elements and parity check elements from both uninter-
`leaved and interleaved sequences. The present invention
`transmits uninterleaved and interleaved data elements with
`corresponding coded data elements to two separate signal
`paths, and at the turbo decoder, combines these two elements
`advantageously to achieve an effective overall code rate “4
`from the simultaneous reception and combination of two
`code rate % signals,
`thereby providing significantly
`improved performance.
`The present
`invention is aimed at overcoming these
`different drawbacks of the priorart.
`
`4
`It is a further object of the present invention to provide
`high powered pilot channels to assist the receiver to acquire
`synchronization of the signals from multiple satellites and
`gap filler transmitters.
`Finally, the present invention can provide advantageously
`a terrestrial gap filler network for retransmission of the
`uplinked satellite signals in areas where there is a high
`probability that signals from both satellites might be
`blocked, with proper built-in signal propagation delay to
`compensate for the signal delay through the satellite path. A
`variable delay is applied to each gapfiller signal so as to
`accommodate propagation delays on the satellite paths,
`including Doppler shift associated with the normally
`encountered daily motion of the satellites in their respective
`geosynchronous orbit locations. In this way, each gap filler
`transmitter in a given service area retransmits the same
`signals as the two satellites so as to align the satellite-
`delivered and gapfiller delivered signals in time at each
`receiver in the gap filler’s service area. So long as the delay
`spread is maintained to less than one bit period, orthogo-
`nality of the OCDMA signals is maintained at the RAKE
`receiver, and the satellite, gap filler, and multipath reflection
`signals can be combined in the receiver to overcome the
`problemsof conventional systems.
`Accordingly,
`the present
`invention provides a digital
`audio broadcasting (DAB) system adapted to broadcast
`signals of digital radio information and to reduce multipath
`fading, signal shadowing and temporal blockage having a
`broadcast source having a transmitter for transmitting a first
`turbo encoded broadcast signal and a second turbo encoded
`broadcastsignal that includes the digital radio information,
`wherebythe first and second turbo encoded broadcastsig-
`It is an object of the present invention to provide an
`nals are transmitted at a code rate of 4 on at least one
`improved DAB methodand system using an implementation
`predetermined path, for example, the first turbo encoded
`of turbo code over two complementary satellite links in the
`broadcastsignal ona first path toafirst satellite, the second
`DAB system to allow the reduction of the satellite trans-
`turbo encoded signal on a second path to a secondsatellite
`mitter output power.
`source, and/or the first and second turbo encoded broadcast
`It is an object of the present invention to increase the
`signals to a network of gap fillers that have delay circuitry
`coverage area with a minimum numberof gap fillers using
`for delaying the first and second turbo encoded broadcast
`the high coding gain of the turbo code.
`signals to compensate for propagationsignal delay through
`the first and second satellites. The first
`turbo encoded
`Anotherobject of the present invention is to provide code
`diversity at a code rate of 4 coupled with packet combining
`broadcast signal consists essentially of uninterleaved data
`to result in an overall system coderate of %4. Acode diversity
`and parity check elements. The second turbo encoded broad-
`scheme, coupled with a code combining scheme advanta-
`cast signal consists essentially of interleaved data and parity
`geously provides improved performance through very high
`check elements. The system has at least one transmitter for
`coding gain, allows the reduction of transponder output
`transmitting the first and second turbo encoded broadcast
`power, and provides seamless service over the coverage area
`signals on separate signal paths to each of the first and
`with a minimum number of required gap fillers. Code
`second satellite sources, respectively, and for transmitting
`diversity and packet combining are used to mitigate Ray-
`the first and second satellite sources to the network of gap
`leigh multipath fading, shadowing, and temporal blockage.
`fillers. The system has a plurality of receivers for receiving
`Yet another object of the present inventionis to provide a
`the first and second turbo encoded broadcast signals, the
`DAB system using a synchronous Orthogonal Code Divi-
`receivers are located at or near the surface ofthe earth, each
`of the receivers has circuitry for outputting the digital radio
`sion Multiple Access (OCDMA) scheme for DAB
`information from the first and second turbo encoded broad-
`applications, e.g. CD Quality Radio, messaging transmis-
`sion and Internet download server, so as to completely
`cast signals. The receiver includes an antenna connected for
`eliminate self interference from other audio channels
`receiving radio frequency (RF) signals consisting of spread
`signals of the first and second turbo encoded broadcast
`signals. The receiver has downconverter meansfor convert-
`ing the RF signal to the baseband frequencyof thefirst and
`second DAB encoded broadcast signals.
`Accordingly the present invention provides a method of
`communicating an audio signal
`from a transmitter to a
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 9
`
`SUMMARYOF THE INVENTION
`
`encountered with the use of a conventional CDMA system.
`Another object of the present invention is to provide a
`DAB system having dual RAKE receivers, arranged
`whereby one RAKE receiveris used to combinethesatellite,
`gap filler, and multipath signals associated with each of two
`complementary satellite data streams.
`
`5,907,582
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 9
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`

`

`>
`receiver using Turbo Coding in a digital audio broadcast
`(DAB) system. The method includes encoding the audio
`signal according to the Turbo Code at a 4 rate punctured to
`a code rate of %, combining a first pilot signal and a
`predetermined number of channels of encoded audiosignals
`using an orthogonal CDMA(OCDMA) modulator, whereby
`As illustrated in FIG. 1, a DAB system 100 is described
`the OCDMA modulatorconsists essentially of an orthogonal
`according to an embodiment of the present invention. The
`Walsh sequence ofW,, W,, W2, .. . W3, to formafirst turbo
`DAB system 100 provides for the improved digital broad-
`encoded broadcast signal containing thefirst pilot signal and
`casting of a signal having program data and information,
`the encoded audio signals of the predetermined channels,
`such as, for example, digital radio information, CD Quality
`transmitting the first turbo encoded broadcast signal on a
`Audio, Messaging, Internet downloads and the like. The
`first path having thefirst pilot signal transmitted at a higher
`DAB system 100 has an uplink earth station or transmitter
`power, The method includes encoding the audio signal
`102 designed for fixed-feeder transmission (SHF or higher
`having been interleaved according to the Turbo Codeat a 4
`frequency) to a plurality of separately spaced satellites in
`rate puncturedto a rate of 4, combining a second pilotsignal
`geosynchronous orbits, which for ease of illustration are
`and the interleaved encoded audio signals of the channels
`shown by dual satellites 104 and 106. The transmitter 102
`using the OCDMA modulator, the OCDMA modulator con-
`can provide a plurality of uplink audio data signals A,, for
`sists essentially of an orthogonal Walsh sequence of W,.,
`example, uplink signals A, and A, to each ofsatellites 104
`Woz, Waa... -
`» We to form a second turbo encoded
`and 106 spaced apart
`in a geosynchronous orbil. Such
`broadcast signal containing the second pilot signal and the
`satellite transmissions can be by wayof fixed-feeder trans-
`interleaved encoded audio signal of the predetermined
`missionlinks to the geosynchronoussatellites or to a web or
`channels, and the second turbo encoded broadcast signalis
`network of low orbital satellites enabling switching trans-
`transmitted on a second path having the secondpilot signal
`mission such as GPS and the like. The DAB system 100 also
`W,,. transmitted at a higher power. The method includes, at
`has a plurality of receivers 108, whether fixed or mobile, for
`the receiver, receiving the first and second turbo encoded
`receiving such audio data signals A, after they are retrans-
`broadcast signals, demodulating a selected channel of the
`mitted to a footprint or coverage area represented as a
`first and second turbo encoded broadcast signals using said
`plurality of downlink paths from the satellites 104 and 106.
`orthogonal Walsh sequence, whereby the demodulation of
`The DAB system 100 advantageously can broadcast signals
`the first and second turbo encoded broadcast signals is
`A, terrestrially from the uplink station 102 to a plurality of
`adapted to use separate RAKE receivers so as to optimally
`gap fillers 110 along land-lines, optical networks, micro-
`combine the audio signal from the first and second turbo
`wave ground networks or the like. The gap fillers 110
`encoded signals received from the first and second paths.
`transmit both uplink signals A, and A,, in connection with
`The method demultiplexes the first and second turbo
`a continuously adaptive propagation delay scheme to
`encoded broadcast signals so as to separate systematic audio
`accommodate timing shifts caused by variations in the
`signals from multiplexed systematic sequences and parity
`satellite paths, Gap fillers operate to fill gaps in the reception
`sequences, and further the combining of an uninterleaved
`ofthe satellite signal data, for example, high density areas
`systematic sequence X, and interleaved systematic sequence
`having acute problems of fading or shadowing. Such gaps
`X, in conjunction with a code diversity combining of the
`can be the result of signal path blockage or fading such as,
`first and second turbo encoded broadcastsignals achieves an
`overall code rate “4.
`for example, urban areas where there is a high probability
`that buildings will block signals A, or A,, or both.
`The adaptive propagation delay L12 system compensates
`for the difference between the propagation delay through
`satellites and the propagation delay through the terrestrial
`gap filler 110 network. The delay system includes, in this
`case, two delays; one to align the gap filler’s transmission of
`the A, signal with the A, signal transmitted bysatellite 104,
`and oneto alignthe gapfiller’s transmission ofthe A, signal
`with the A, signal transmitted by satellite 106. The arrival
`delay spread of the signals from satellites, gap filler
`transmitter, and reflected multipaths is thereby maintained
`within one bit period to preserve the orthogonality of the
`synchronous OCDMA system,to eliminate self-interference
`at the RAKE receiver. In this manner, the DAB system 100
`can transmit the audio data signals. Additionally, the present
`invention advantageously can allow for the transmission and
`reception of the digitized program data and information in a
`highly efficient, reliable and cost effective manner, so as to
`better manage transmitter power and bandwidth resources.
`According to an embodiment ofthe present invention, the
`DAB system 100 utilizes a time diversity scheme that
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 10
`
`The features and advantages of the present invention will
`become more clearly appreciated from the following
`description, taken in conjunction with the accompanying
`drawings, in which like elements are denoted bylike refer-
`ence numerals and in which:
`FIG. 1 is a schematic illustration of a DAB method and
`system;
`FIG, 2 illustrates a DAB transmission method and system
`indicating the flow of audio data in the DAB system;
`FIG, 3 illustrates a method and system of turbo encoding
`the program data signal for transmission of a channel of
`audio data in relation to FIG, 2;
`FIG.4 illustrates and is used in explaining the method of
`implementing a punctured pattern for the output of the turbo
`encoder andthe creation and subsequent transmission of the
`two complementary data signals in relation to FIGS. 2 and
`3;
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 5 illustrates a DAB receiver and methodof receiving
`the audio data signals in the DAB system; and
`
`5,907,582
`
`6
`FIG, 6 illustrates and is used in explaining a method of
`decoding the audio data signal received in relation to FIG.
`5.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 10
`
`

`

`5,907,582
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`10
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`15
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`8
`directly spread by the Walsh sequences W, and W,, without
`implements a Turbo Code (TC) iterative channel coding
`scheme. The Turbo Coding scheme combines several simple
`turbo encoding. Encoded audio data and information on
`codes in parallel to communicate audio program data and
`Channels 1 through 31 are spread and sequenced with Welsh
`information in the signals to each uplink path (A,, A,) so as
`codes W, through W,, for transmission via the Al path,
`to provide for receiver performance at or near theoretical
`Similarly, encoded and interleaved audio data and informa-
`Shannon’s limit, such as, for example, in the range of 0.3 to
`tion on channels 33 through 63 are spread and sequenced
`0.7 dB signal-to-noise ratio at a bit error rate of 107% for the
`with Walsh codes W,,, through W,,, for transmission via the
`Binary Phase Shift Keying (BPSK) modulation scheme. The
`A; path. All 64 Walsh sequences are generated by the
`DAB system 100 advantageously provides a high perfor-
`Hadamard matrix, and each sequence is thus orthogonal to
`mance TC scheme achieving the code rate of %4 as described
`every other sequences including delayed versionsofitself,
`herein in relation to FIGS. 2-4. In this manner, the present
`unless the delay spread exceeds onebit period. The orthogo-
`invention advantageously provides temporal diversity
`nality results in the self interference free spread spectrum
`through a TC implementation, thereby reducingthe satellite
`operation of the OCDMA. The spread circuitry 116 outputs
`transmitter output powerand resulting in improved coverage
`the spread sequence of Channels 0 through 31 to the
`area with a minimum number ofgapfillers.
`combiner 118 for ultimate transmission to satellite 104 and
`As shown in FIG. 2,
`the transmitter 102 includes a
`to the gap filler 110, and Channels 32 through 63 to
`plurality of channels for sending the audio data signal, for
`combiner 118 for ultimate transmission to satellite 106 and
`example, a 31 Channel DAB transmission system. For ease
`to gap filler 110.
`of illustration, Channels 3 through 30 are not shown. The
`As shown in FIG.3, the turbo encoder 122 includes an
`transmitter 102 includes pilot signal generators 112 and 114
`interleaver 132 between two constituent recursive convolu-
`for generating pilot signals PS1 and PS2. Thepilot signal
`tional encoders 134 and 136 to permute incoming digital
`generators send pseudo-random noise (PN) sequences PN,
`audio information sequence in random fashion. The permu-
`and PN, on Channels 0 and 32. The PN sequences PN, and
`tation breaks the cross correlation between the two turbo
`PN,are spread by Walsh codes W, and W,,. Subsequently,
`encoded sequences. The operation of the constituent encod-
`pilot signal PS, on Channel 0 is combined with the first
`ers 134 and 136 can be described by the polynomial
`turbo encoded audio signal and sentasafirst turbo encoded
`representation,
`broadcast signal via signal path A,. Pilot signal PS, on and
`30
`Channel 32 is combined with a second turbo encoded audio
`signal and sent as a second turbo encoded broadcastsignal
`via signal path A,. The pilot signals are transmitted at a
`higher poweror rate than the individual signals of the audio
`data channels. Pilot signals PS, and PS, are used by the
`receiver 108 to acquire and maintain synchronization of the
`first and second turbo encoded broadcast signals for each
`channel on the A, and A, paths, and to obtain the predeter-
`mined numberof strongest multipath signals for the RAKE
`receiver,
`
`35
`
`As is illustrated in FIGS. 2 and 3, the transmitter 102
`provides Channels 1 through 31 with the broadcast program-
`ming or digital audio data and information from the source
`channels to respective audio encoders 120. The output of
`each audio encoder for channels 1-31is provided to a turbo
`encoder 122. Each turbo encoder 122 has two separate
`outputs designated 124 and 126. Non-interleaved outputs
`multiplexed with parity bits on output 124 are spread by
`Welsh codes W, through W.,, and combined together with
`the spreadpilot signal W,, for transmission as signal A, to
`satellite 104 andto the gapfiller 110. Interleaved outputs are
`similarly multiplexed with parity bits on output 126, are
`spread with Walsh codes W,, and W,, and combined with
`the other spread pilot signal W,,, for transmission as signal
`A, to satellite 106, and to the gapfiller 110.
`The spread circuitry 116 operates accordingto an orthoga-
`nal Code Division Multiple Access (OQCDMA) scheme to
`spread the PN sequences generated forpilot signals PS, and
`PS,, encoded audio program data and information, orinter-
`leaved encoded audio program data and information with a
`Walsh code sequence in a known manner and represented
`herein by the sequence W,, W,, W., .
`.
`. W,, for a system
`supporting 31 channels of CD-quality stereo audio.The pilot
`signals PS, and PS, generated for Channels 0 and 32 are
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`(a)
`(1, gy/ga)=(1, 1+4D°/14D+D?+D*+D")
`Conventional octal representation for the illustrated codeis
`(g,, 82)=(21, 37). Here, the g, represents the feed forward
`connection, and the g, represents the feed back connection.
`The constituent codes are illustrated as identical with each
`having four memory elements (D). However, the present
`inventionis notlimited by this particular polynomial nor by
`the number of memory elements. The parity sequence out-
`puts of two encoders 134 and 136are input to puncturers 138
`and 140 to generate two different punctured sequences
`described in greater detail in FIG. 4. These punctured parity
`sequence outputs are multiplexed with X, and X, represent-
`ing the unaltered source sequences d, and d,, at MUX 142
`and at MUX 144, respectively. The turbo encoder 122
`associated with cach audio channel can advantageously
`process broadcast programming or encoded audio data
`according to puncturing patterns discussed herein to com-
`bine the audio data and the parity data onto two carriers for
`subsequent advantageous use by an iterative decoding pro-
`cess in the turbo decoder 172 of each receiver 108.
`In operation, the original audio program data sequences,
`represented as d, in FIG. 3, are supplied to the turbo encoder
`122, which outputs an unaltered copy of the systematic
`audio data X, to one input of MUX 142. The audio data d,
`Is also supplied to the first constituent recursive encoder 134,
`which supplies parity output Y,, to one input of the first
`puncturer 138 and to one input of the second puncturer 140.
`The audio data d, are also supplied to interleaver 132. The
`second constituent encoder 136 is supplied with an inter-
`leaved audio program data signal d,,. Unaltered interleaved
`signal d,, is supplied in systematic form as sequence X, to
`one input of MUX 144 for ultimate transmission to signal
`path 126. A copyof d,, is supplied to the second constituent
`encoder 136, which encodes each interleaved bit of audio
`data and generates a parity sequence Y., which is supplied to
`both puncturers 138 and 140.
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 11
`
`Petitioner Sirius XM Radio Inc. - Ex