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`09/202729
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`3OOR OcUdU7,' O 14 (cid:39)(cid:40)(cid:38)(cid:3)1998
`Apparatus and Method For Transmitting Information
`a n d"
`Apparatus and Method For Receiving Info--ation
`
`I
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`Field of the invention
`
`The present invention relates to concepts for digital
`broadcasting and, in particular, concepts for digital
`broadcasting suited for fading channels for wireless
`communication.
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`Background of the Invention
`
`Satellite-based broadcasting systems provide an adequate
`communication link only in rural areas, in which only a
`small number of e.g. bridges exist. Additionally, rural
`areas usually do not have skyscrapers. Skyscrapers as well
`as bridges or, generally, densly built-up areas are
`obstacles to satellite-based communication systems, since
`carrier frequencies used for such communication links
`involve that a channel between a sender, e.g.., a satellite,
`and a receiver, i. e. a mobile or stationary receiver, is
`characterised by the line of visual contact (line of sight)
`between the sender and the receiver. If a skyscraper comes
`into the line of visual 'bontact, i.e., the transmission
`channel between the satellite and the receiver, which may be
`positioned in a car, the received signal power will decrease
`substantially.
`
`Generally, it can be stated that in wireless systems (radio
`systems), changes in the physical environment cause the
`channel to fade. These changes include both relative
`movement between transmitter and receiver and moving
`scatters/reflectors in the surrounding space. In theoretical
`studies of wireless systems, the real channels are usually
`modelled so that they result in trackable analysis. The two
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 1
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`major classes of fading characteristics are known as
`Rayleigh and Rician. A Rayleigh-fading environment assumes
`no line of sight and no fixed reflectors/scatters. The
`expected value of the fading is zero. If there is a line of
`sight, this can be modelled by Rician-fading, which has the
`same characteristics as the Rayleigh-fading, except for a
`non-zero expected radio.
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`Modern digital broadcasting systems know several means for
`reducing the impact of a channel fading. These concepts
`comprise channel coding on the one hand and several kinds of
`diversity on the other hand. The European standard for
`digital audio broadcasting (DAB),
`set out in Radio
`iBroadcasting Systems; Digital Audio Broadcasting (DAB) To
`Mobile, Portable and Fixed Receivers, ETS 300 401, ETS I -
`European Telecommunications Standards Institute, Valbonne,
`France,
`February 1995,
`uses
`differential quadrature
`phase-shift keying (DQPSK) as modulation technique. The
`channel encoding process is based on punctured convolutional
`coding, which allows both equal and unequal error
`protection. As a mother code, a convolutional code having a
`code rate of 1/4, a constraint length 7, and octal
`polynominals is used. The puncturing procedure allows the
`effective code rate to vary between 8/9 and 1/4. Channel
`coding by means of punctured convolutional codes is
`described in "Punctured Convolutional Codes of Rate (n-l)/n
`and Simplified Maximum Likelihood Decoding", J. Bibb Cain et
`al., IEEE Transactions on Information Theory, Vol. IT-25,
`No. 1, January 1979.
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`Punctured convolutional codes can be used in connection with
`many modulation techniques, such as OFDM, BPSK, QAM, etc.
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`Different channel encoding techniques are outlined in
`"Channel Coding with Multilevel/Phase Signals", Gottfried
`Ungerboeck, IEEE Transactions on Information Theory, Vol. IT
`28, No. 1, pages 55 to 66, January 1982.
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 2
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`Bitstreams encoded by means of a convolutional encoder can
`be decoded by a decoder, in which the well-known Viterbi
`algorithm is implemented. This algorithm is capable of using
`the channel state information (see P. Hoeher "TCM on
`Frequency-Selective Length-Mobile Fading Channels", Proc.
`Tirrenia International Workshop Digital Communication,
`Tirrenia, Italy, September 1991). The Viterbi algorithm can
`be modified to provide reliability estimates together with
`the decoded sequence. This enables soft decoding. By
`applying a soft-output Viterbi algorithm, an improvement of
`about 2 dB is obtained in comparison to systems that
`implement "hard" decision.
`
`Description of Prior Art
`
`With reference to Fig. 6, a simplified overview of a
`transmitter receiver system described in the European DAB
`Standard is illustrated. The transmitter receiver system
`generally comprises a transmitter section 60 and a receiver
`section 70. The transmitter section 60, in the simplest
`case, comprises a bitstream source 62, a channel encoder 64
`and a transmitter 66. The receiver section 70, in the
`simplest case, comprises a receiver 72 and a channel decoder
`74.
`
`Fig. 7 illustrates a transmitting receiving setup providing
`for time diversity as well as space diversity. The
`transmitter section 60' comprises the bitstream source 62
`and the encoder 64 that have already been described with
`respect to Fig. 6. In addition, the receiver section 60'
`comprises a first transmitter 66a and a second transmitter
`66b. Both transmitters 66a and 66b are fed by the same
`signal output by the encoder 64 that is duplicated by a
`duplicator 67.
`
`To obtain time diversity, a delay element 68 is coupled
`between the duplicator 67 and the second transmitter 66b.
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 3
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`In the case of satellite communication, the transmitters 66a
`and 66b are realised by two satellites that reside on
`different orbital positions spaced apart from each other.
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`The first channel is defined by the line of sight between
`the first transmitter and the receiver, for example, a car,
`whereas the second channel is defined by the line of sight
`between the second transmitter 66b and the car that
`comprises the receiving section 70'. In the scenario, in
`which the car travels on a street to the right and to the
`left of which are high buildings, the possibility is
`
`increased that the car will receive the transmitted signal
`from at least one satellite.
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`When the case is considered, in which the car is driving
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`through a tunnel or under a bridge, the lines of sight to
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`both transmitters 66a and 66b are interrupted. The time
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`diversity method implemented by this system shown in Fig. 7,
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`however, ensures that the'receiver will not be affected by
`the interrupted channel, since the transmission signal is
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`delayed by the delay stage 68. Optimally, no transmission
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`interruption will result, when the delay time is equal to or
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`greater than the travelling time of the car through the
`tunnel or under the bridge. Thus, the receiving section
`
`will, once again, receive the transmission signal sent by
`
`the transmitter 66a, when it was under the bridge, via a
`channel 2. Naturally, the receiving section 70' comprises
`another delay stage 78. As it is shown in Fig. 7, the delay
`stage 78 of the receiving section has to be in the channel
`that has not been delayed in the transmitter section. Thus,
`the signals at the output of the receivers 72a and 72b are
`identical, when the delay values of the delay stages 78 and
`68 are equal.
`
`A decision stage 79, which is symbolised as a switch in Fig.
`7, determines which channel provides the signal with the
`better signal to noise ratio. When it is determined that
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 4
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`(cid:76)(cid:17)
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`channel 1 provides the stronger signal, the decision stage
`79 is operative to conduct the signal received by the
`receiver 72a into the channel decoder 74
`When it is
`determined in block 79 that the signal transmitted over the
`other channel (channel 2) is the stronger one, the decision
`stage 79 is operative to conduct the signal received by the
`receiver 72b to the channel decoder 74.
`
`To summarise, the system illustrated in Fig. 7 comprises the
`following essential features:
`
`the signal output by the encoder 64 is duplicated by the
`duplicator 67;
`
`exactly the same signals, whether delayed or not, are
`transmitted via both channels;
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`(cid:16)
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`(cid:16)
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`the signals transmitted over both channels are derived
`from the bitstream output by the bitstream source 62 in
`exactly the same way by means of the encoding process
`carried out in the redundancy adding encoder 64
`(repetition code);
`
`the decision stage 79 compares the signal to noise ratio
`of both channels and selects the channel in which the
`signal having the better signal to noise ratio is
`transmitted;
`
`the signal transmitted via the other channel is
`discarded; and
`
`the channel decoder 74 only uses one channel, i.e., the
`channel determined by the decision stage 79, for channel
`decoding.
`
`Besides the technique of channel encoding using a redundancy
`adding encoder like a convolutional encoder, different types
`of diversity, e.g., time diversity and space diversity, can
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 5
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`be implemented to ease the impact of fading channels.
`
`The bitstream source 62 can be implemented as an audio
`encoder as defined by ISO-MPEG. It provides a bitstream
`comprising useful information, i.e., encoded spectral values
`of a block of. audio samples, and side information. To
`enhance the robustness of the communication link, a forward
`error correction encoding is performed by the convolutional
`encoder 64. In general, the convolutional encoding procedure
`generates redundancy in the transmitted datastream in order
`to provide ruggedness against transmission distortion.
`
`Usually, convolutional encoders consist of a specific number
`of shift registers and a number of XOR gates. The
`convolutional encoder described in the ETS Standard is a
`convolutional encoder having a code rate of 1/4. This means
`that the convolutional encoder produces four output bits for
`one input bit. As it is well known in the art, each output
`bit is derived from the current input bit and a specific
`combination of a certain number of preceding input bits
`stored in the. shift registers. The specific combination of
`the current input bit and certain preceding input bits for
`each encoder output bit is defined by the so-called
`generator polynominals. The octal forms of the generator
`polynominals defined in the ETS 300 401 are 133, 171, 145
`and 133.
`
`The encoded bitstream can be punctured for raising the code
`rate from 1/4 to another code rate, e.g., 8/9. "Puncturing"
`means that certain bits in the convolutional encoder output
`bits are discarded and not forwarded to the transmitter 66.
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`Thus, puncturing operates to again reduce redundancy in an
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`encoded bitstream, which has been added by the convolutional
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`encoder.
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`The transmitter 66 may comprise usual transmitter elements,
`such as a QPSK modulator, an IFFT block (IFFT = Inverse Fast
`Fourier Transform) for performing orthogonal frequency
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 6
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`division multiplexing, a guard interval inserter, a
`synchronisation sequence inserter and modulation 'means for
`modulating the signal onto a high frequency carrier.
`
`Analogously, the receiver 72 comprises an HF front end, an
`analog/digital converter, and a QPSK demodulator. The signal
`output by the receiver is input in the decoder 74. The
`decoder 74 is operative to decode the encoded bitstream
`output by the receiver 72. In modern communication systems,
`the decoder 74 implements the above-outlined soft-input
`Viterbi algorithm. As it has already been outlined, the
`Viterbi decoder performs a maximum likelihood decoding using
`the channel state information, which is also called
`"metric". Different algorithms are known for Rician and
`Rayleigh channels.
`
`Especially in satellite-based communication systems, design
`engineers are confronted with strong demands for reducing
`transmitter power. Reduced transmitter power directly
`translates into system costs. Generally, the costs for
`designing and transporting the satellite(s) into its (their)
`orbital position(s) are directly proportional to the power
`supply needed on board of the satellite. Higher transmitter
`power on board of the satellite also means higher energy
`producing capabilities of the satellite. Thus, it can be
`stated that, under costs aspects, reducing transmitter power
`is essential.
`
`Therefore, the system described in Fig. 7 is disadvantageous
`in that, in the receiver, only one channel is used for
`retrieving information, whereas the other channel is
`discarded. In extreme situations, in which one channel has
`faded totally, no transmitter power from one transmitter,
`i.e., one satellite, will reach the receiver. Normally,
`however, the channels will not fade totally. Instead, both
`channels will fade more or less. Thus, the decision stage 79
`has to select one out of two useful signals. When the case
`is considered that both signals output by the receivers 72a
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 7
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`and 72b have identical signal to noise ratios,-, only one
`signal is selected, whereby the transmitter power from the
`satellite transmitting via the other channel is wasted
`totally.
`
`Summary of the Invention
`
`It is the object of the present invention to provide an
`apparatus and method of transmitting information and an
`apparatus and method of receiving information, which result
`in better receiver output signal quality and/or reduced
`transmitter power demands.
`
`In accordance with a first aspect of the present invention,
`this object is attained by an apparatus for transmitting
`information, comprising a bitstream source for providing a
`bitstream representing the information; a redundancy adding
`encoder for generating an encoded bitstream based on the
`bitstream provided by the bitstream source wherein the
`encoder is arranged to output, for a first number of input
`bits, a second number of output bits, the second number of
`output bits having at least twice as many output bits as the
`first number of input bits, and wherein the second number of
`output bits includes two portions of output bits, each
`portion of output bits individually allowing the retrieval
`of information represented by the first number of input
`bits, and the first portion of output bits being coded based
`on the bitstream in a different way with respect to the
`second portion of output
`bits;
`a partitioner for
`partitioning the second number of output bits into the two
`portions of output bits; and a transmitter for transmitting
`the output bits of the first portion via a first channel and
`the output bits of the second portion via a second channel,
`the second channel being spatially different from the first
`channel.
`
`In accordance with a second aspect of the present invention,
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 8
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`this object is attained by an apparatus for.receiving
`information, the information being represented by an encoded
`bitstream, the encoded bitstream being encoded such that its
`redundancy is at least doubled with respect to a bitstream
`from which the encoded bitstream is derived, and that, for a
`first number of bits of the bitstream, the encoded bitstream
`comprises a second number of bits, the second number of bits
`having at least twice as many bits as the first number, and
`wherein the second number of bits includes two portions of
`bits, each portion of bits individually allowing the
`retrieval of information represented by the first number of
`bits, and the first portion of the bits being encoded in a
`different way with respect to the second portion of bits,
`the apparatus comprising a receiver for receiving the first
`portion of bits via a first channel and the second portion
`of bits via a second channel, the first and the second
`channels being spatially different from each other; a
`combiner for combining the first and the second portions;
`and a decoder for decoding the coded bitstream by removing
`redundancy from the coded bitstream, the decoder using the
`first and second portions of bits combined by the combiner.
`
`In accordance with a third aspect of the present invention,
`this object is attained by a method of transmitting
`information, comprising the following steps: providing a
`bitstream representing the information;
`generating a
`redundancy added encoded bitstream based on the bitstream
`provided in the step of providing, wherein for a first
`number of input bits, a second number of output bits is
`generated, the second number of output bits having at least
`twice as many output bits as the first number of input bits,
`and wherein the second number of output bits includes two
`portions of output bits, each portion of output bits
`individually
`allowing
`the
`retrieval
`of
`information
`represented by the first number of input bits, and the first
`portion of output bits being coded based on the bitstream in
`a different way with respect to the second portion of output
`bits; partitioning the second number of output bits into the
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 9
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`two portions of output bits; and transmitting the output
`bits of the first portion via a first channel and the output
`bits of the second portion via a second channel, the second
`channel being spatially different from the first channel.
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`In accordance with a fourth aspect of the present invention,
`this object is attained by a method of receiving
`
`information, the information being represented by an encoded
`bitstream, the encoded bitstream being encoded such that its
`redundancy is at least doubled with respect to a bitstream
`from which the encoded bitstream is derived, and that, for a
`first number of bits of the bitstream, the encoded bitstream
`comprises a second number of bits, the second number of bits
`having at least twice as many bits as the first number, and
`wherein the second number of bits includes two portions of
`bits, each portion of bits individually allowing the
`retrieval of information represented by the first number of
`bits, and the first portion of the bits being encoded in a
`different way with respect to the second portion of bits,
`the method comprising the following steps: receiving the
`first portion of bits. via a first channel and the second
`portion of bits via a second channel, the first and the
`second channels being spatially different from each other;
`combining the first and the second portions; and decoding
`the coded bitstream by removing redundancy from the coded
`bitstream, wherein the first and second portions of bits
`combined in the step of combining are used in the step of
`decoding.
`
`The present invention is based on the finding that, although
`there are two physically different channels both channels
`are considered as one single channel from the viewpoint of
`the channel decoder located in the receiving section. This
`means that the channel decoder in the. receiving section does
`not know that the signals it decodes stem from two
`physically, i. e. spatially, different channels. However,
`the inventive system, in fact, provides two different
`physical channels to allow for time and/or space diversity.
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 10
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`.;The
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`space diversity can be obtained by two terrestrial
`transmitters, by two satellite transmitters or by one
`satellite transmitter and one terrestrial transmitter.
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`In accordance with the present invention, an apparatus for
`transmitting information comprises a bitstream source for
`providing a bitstream representing the information. A
`redundancy adding encoder for generating an encoded
`bitstream based on the bitstream provided by the bitstream
`source is arranged to output, for a first number of input
`bits, a second number of output bits, the second number of
`output bits having at least twice as many output bits as the
`number of input bits, and wherein the second number of
`output bits includes two portions of output bits, each
`portion of output bits individually allowing the retrieval
`of information represented by the first number of input
`bits, and the first portion of output bits being coded based
`on the bitstream in a different way with respect to the
`second portion of output bits. A means for partitioning,
`i.e., a partitioner, receives the output of the redundancy
`adding encoder and partitions the second number of output
`bits into the two portions of output bits. Means for
`transmitting transmit the output bits of the first portion
`via a first channel and the output bits of the second
`portion via a second channel, wherein the second channel is
`spatially different from the first channel.
`
`In accordance with another aspect of the present invention,
`an apparatus for receiving information comprises a receiver
`for receiving the first portion of bits via a first channel
`and the second portion of bits via a second channel, a
`combiner for combining the first and the second portions and
`a decoder for decoding the coded bitstream by removing
`redundancy from the coded bitstream, the decoder using the
`first and second portions of bits combined by the combiner.
`
`This inventive transmitter receiver concept provides the
`following advantages:
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 11
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`two channels allow time and/or space diversity,
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`the partitioner partitions rather than duplicates the
`output signal of the encoder into two portions of output
`bits;
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`the combiner in the receiver combines rather than
`selects the signals received from both channels and
`feeds the combined signal into the channel decoder;
`
`the signals from both channels are used for decoding all
`the time;
`
`in the best case, in which the signal powers in both
`channels are identical, transmitter power used for
`transmitting via each channel can be halved at least,
`thus, halving system costs with respect to the system
`illustrated in Fig. 7; and
`
`when the transmitter powers are not changed, the signal
`quality output by the
`channel
`decoder can be
`considerably improved.
`
`Brief Description of the Drawings
`
`The foregoing and other objects, features and advantages of
`the invention will become more readily apparent from the
`following detailed description of preferred embodiments
`which proceeds with reference to the drawings.
`
`Fig. 1 shows a principle overview of a transmission
`receiving system in accordance with the present
`invention, comprising an inventive transmitter and
`an inventive receiver.
`
`Fig. 2 shows a more detailed block diagram of the
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`(cid:87)
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 12
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`(cid:16) 13 (cid:16)
`
`transmission receiving system shown in Fig. 1, in
`which time and space diversity are embodied.
`
`Fig. 3 shows a detailed block diagram of an inventive
`transmitter section.
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`Fig. 4 shows an input bit sequence and an output bit
`pattern of a convolutional encoder used in an
`inventive transmitter section.
`
`Fig. 5 shows a detailed view of an inventive receiver
`section.
`
`Fig. 6 shows a generalised block diagram of a prior art
`transmitting receiving system.
`
`Fig. 7 shows a block diagram of a transmitter receiver
`system implementing time and space diversity, in
`which the output of the transmitter encoder is
`duplicated and a channel selection is performed in
`the receiver.
`
`Description of Preferred Embodiments
`
`In Fig. 1 a general block diagram of an inventive apparatus
`for transmitting 100 and an inventive apparatus for
`receiving 200 is illustrated. The transmitting apparatus 100
`comprises a bitstream source 110, a redundancy adding
`encoder 120 and a partitioner 130. The bitstream source 110
`may be an MPEG encoder as described above. The encoder 120
`is generally a redundancy adding encoder for generating an
`encoded bitstream on its output, wherein the encoder 120 is
`arranged to output, for a first number of input bits, a
`second number of output bits, the second number of output
`bits having at least twice as many output bits as the first
`number of input bits. This means that the encoder 120
`implements a code rate equal to or less than 1/2. As it is
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 13
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`known in the art, the code rate is defined by the number of
`input bits divided by the number of output bits produced by
`the encoder based on the number of input bits. In other
`words, a code rate 1/2 means that for each input bit, two
`output bits are produced. Analogously, a code rate of 1/3
`means that for each input bit, three output bits are
`produced. Similarly, a code rate of 3/8 means that for three
`input bits, eight output bits are produced.
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`The code rate of the encoder 120 is set to be smaller than
`1/2, such that the second number of output bits can be
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`sub-divided into two portions of output bits, such that each
`portion of output bits individually allows the retrieval of
`information represented by the first number of input bits
`This means that a decoder 220 located in the receiving
`apparatus is able to retrieve information represented by the
`bitstream output by the bitstream source 110 when only one
`channel, i.e., channel 1 300 or channel 2 400 provides a
`useful signal, whereas the other channel has faded totally.
`
`Another feature of the encoder 120 is that the first portion
`
`of output bit is coded based on the bitstream in a different
`way with respect to the second portion of output bits. In
`contrast to a simple repetition code in which redundancy is
`doubled by simply duplicating a signal to transmitted coded,
`the channel decoder 220 capabilities are enhanced, since the
`signal is transmitted over the channels 300 and 400 are
`
`derived from the bitstream output by the bitstream source
`110 independently of each other. The partitioner 130 feeds
`means for transmitting, i.e., a transmitter, 140 for
`transmitting the first portion of output bits via the first
`channel 300 and the second portion of output bits via the
`second channel 400. It is to be noted that both channels 300
`and 400 are spatially different from each other.
`
`As usual, a channel between the transmitter and the receiver
`is defined by the line of sight connection between the
`transmitter and the receiver. Thus, two channels are
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 14
`
`

`

`(cid:13)(cid:3)
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`(cid:47)I.
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`(cid:16) 15 (cid:16)
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`different from each other when a mobile receiver...has moved
`with respect to a single transmitter, or when two
`transmitters exist positioned in different locations, e.g.,
`orbital positions. In this case, it does not play any role
`whether the receiver is a mobile or a stationary receiver.
`
`Thus, the transmitting means 140 may comprise one
`transmitter, e.g., one satellite and a delay stage, such
`that two different channels are created between the single
`transmitter and a mobile receiver, when the mobile receiver
`is at a first position and between the single transmitter
`
`and the mobile receiver when the mobile receiver has moved
`to a second position after the period defined by the delay
`stage in the transmitter. This concept is called time
`diversity for mobile receivers. Naturally, it is not
`possible to create two channels different from each other
`between a single stationary transmitter and a stationary
`receiver.
`
`Alternatively, as it is described with reference to Fig. 2,
`the transmitting means 140 comprise two transmitters
`positioned in
`different locations, to obtain space
`diversity.
`
`The receiving apparatus 200 illustrated in Fig. 1 comprises
`receiving means 240a and 240b, the receiving means, i.e.,
`the receiver, comprising a first receiver 240a for receiving
`the first portion of output bits transmitted via the first
`
`channel 300 and a second receiver 240b for receiving the
`second portion of output bits via the second channel 400.
`
`In accordance with the present invention, the output signals
`of the receiving means 240a and 240b are combined in a
`combiner 230 such that the output signals of both receivers
`
`are used in the channel decoder 220.
`
`Fig. 2 illustrates a transmission receiving system in
`accordance with the preferred embodiment of the present
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`31
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 15
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`

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`-16 -
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`invention. The transmitting apparatus comprises, as already
`
`described in Fig. 1, the bitstream source 110, the encoder
`
`120 generally termed as forward error correction, the
`partitioner 130 and transmitting means comprising a first
`satellite 140a, a second satellite 140b and a delay stage
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`140c.
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`The receiving apparatus comprises the channel decoder 220,
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`the combiner 230 and the receiving means (Rx) comprising the
`
`first and second receivers 240a, 240b and a delay stage
`
`240c. The transmitting apparatus and the receiving apparatus
`are "connected" by the first channel 300 and the second
`channel 400.
`
`By using the delay stages 140c and 240c, which are
`
`positioned in opposite channels, time diversity is
`
`implemented in the transmission receiving system shown in
`Fig. 2. Furthermore, by means of the provision of two
`transmitters, i.e., the first satellite 140a and the second
`satellite 140b, space diversity or spatial diversity is
`implemented into the inventive transmission receiving
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`20
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`system.
`
`With reference to Fig. 3, a more detailed block diagram of
`
`the transmitting apparatus is described. The encoder 120 in
`the transmitting apparatus is implemented as a convolutional
`
`encoder in accordance with the present invention. As it is
`
`shown in Fig. 3, the convolutional encoder comprises three
`generator polynominals, i.e., a first generator polynominal
`gl 121, a second generator polynominal g2 122 and a third
`generator polynominal g3 123. Thus, the convolutional
`
`encoder 120 has a code rate of 1/3, since, for one input
`bit, the encoder produces
`three output bits. The
`
`transmitting apparatus shown in Fig. 3 further comprises a
`
`puncturing unit 125 that reduces the number of bits, i.e.,
`the number of output bits, such that an even number of
`output bits to be transmitted over the first and second
`channel is obtained. The puncturing unit 125 is connected to
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 16
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`

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`the partitioner 130, that, in accordance with the preferred
`embodiments
`of
`the
`present
`invention,
`comprises
`a
`parallel-to-serial converter and a demultiplexer to
`demultiplex
`the
`serial
`bitstream
`produced
`by
`the
`parallel-to-serial converter into two bitstreams. The block
`diagram in Fig. 3 further comprises the delay stage 140c of
`transmitting means. The first transmitter and the second
`transmitter are not shown in Fig. 3.
`
`Thus, the first portion of output bits is transmitted via
`the first channel, whereas the second portion of output bits
`is delayed by the delay stage, transmitted via the second
`channel.
`
`With reference to Fig. 4, the functionality of the
`convolutional encoder 120, the puncturing unit 125 and the
`partitioner 130 will be described. In Fig. 4, an input bit
`sequence having bits 401, 402 and 403 is illustrated. The
`convolutional encoder 120 will produce three parallel
`arranged output bits 411, 412 and 413 for each input bit
`401, 402 and 403. The .notation of the output bits 411 to 413
`relates to the channel, over which the respective bit is
`transmitted. Thus, bits termed E are transmitted over the
`early satellite, i.e., satellite 140a (Fig. 2), whereas the
`bits termed L are transmitted over the late satellite, i.e.,
`the satellite 140b (Fig. 2), which input is delayed by the
`delay stage 140c. The bit termed X is not transmitted at
`all. This bit is discarded by the puncturing unit 125 to
`obtain a second number of output bits, which is an even
`number. In accordance with the preferred embodiment of the
`present invention, an even number of output bits to be
`
`transmitted by the transmitting means 140 (Fig. 1) is
`required, since two channels exist and the number of bits
`transmitted over each channel are equal in the preferred
`embodiment. it has to be noted that equal numbers of bits in
`each channel are not esential for the present invention.
`
`othe
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`The output of the puncturing unit 125 is fed into a
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`33
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`Petitioner Sirius XM Radio Inc. - Ex. 1011, p. 17
`
`

`

`(cid:47)
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`......................
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`(cid:16) 18 (cid:16)
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`parallel-to-serial converter