WO2016000761A1 - Procédé et appareil de codage spatio-temporel entrelacé - Google Patents

Procédé et appareil de codage spatio-temporel entrelacé Download PDF

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Publication number
WO2016000761A1
WO2016000761A1 PCT/EP2014/063953 EP2014063953W WO2016000761A1 WO 2016000761 A1 WO2016000761 A1 WO 2016000761A1 EP 2014063953 W EP2014063953 W EP 2014063953W WO 2016000761 A1 WO2016000761 A1 WO 2016000761A1
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Prior art keywords
space
time coded
coded block
sequence
data
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PCT/EP2014/063953
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English (en)
Inventor
Majid NASIRI KHORMUJI
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Huawei Technologies Co., Ltd.
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Priority to PCT/EP2014/063953 priority Critical patent/WO2016000761A1/fr
Publication of WO2016000761A1 publication Critical patent/WO2016000761A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols

Definitions

  • the aspects of the present disclosure relate generally to wireless communication systems and in particular to channel coding and estimation in a multi antenna radio channel.
  • the quality of data transmitted over wireless communication channels is often complicated by the volatility of the medium which suffers from effects such as fading i.e. random variation in signal strength over time, interference from other users, variability between UE devices, etc.
  • the effects of fading in wireless communication channels are generally addresses through the use of diversity techniques.
  • One appealing diversity technique is antenna diversity where different antenna ports are configured to have access to independent radio channels. Channel independence can be obtained for example by physically locating the antenna ports a distance apart where adequate channel independence can typically be achieved by a distance equal to half the wavelength of the associated carrier frequency.
  • a second channel may have access to a channel with better signal strength, thereby providing protection against fading channels.
  • MIMO techniques have quickly gained popularity and are penetrating large-scale standards based communication systems.
  • a MIMO radio link is one where either or both the transmitting end as well as the receiving end are equipped with multiple antenna elements.
  • a key feature of MIMO systems is the ability to use multi-path propagation, traditionally a drawback of wireless communications systems, to improve data rates provided to users.
  • Diversity in MIMO systems is typically achieved by using transmission schemes that employ a space-time code (STC) to transmit multiple copies of the data from separate antennas. Numerous STC transmission schemes have been developed for various MIMO configurations.
  • STC space-time code
  • Characteristics of the radio channels between transmitters and receivers are not available beforehand and need to be learned and/or estimated during data transmission.
  • Much of the channel state information (CSI) used to improve data transfer can be learned either implicitly or explicitly from the received noisy signals. It has become common practice to facilitate estimation of the channel at the receiver by transmitting some pre-determined symbols, referred to as pilot symbols, pilot signals, or reference symbols, multiplexed or comingled in with the data symbols (i.e. information-bearing symbols) as they are transmitted.
  • pilot symbols are used by the receiver to estimate the channel between transmit and receive antennas, then these channel estimates are utilized to perform decoding of received data signals.
  • pilot assisted channel estimation The process of transmitting predetermined pilot symbols and estimating the channel based on those pilot symbols is referred to as pilot assisted channel estimation and is common practice in many of the current standardized wireless communication systems, such as Long Term Evolution (LTE) and LTE-Advanced (LTE-A) being developed by the third generation partnership project (3GPP).
  • LTE Long Term Evolution
  • LTE-A LTE-Advanced
  • 3GPP third generation partnership project
  • Estimating the channel gains affecting the pilot symbols is generally accomplished by interpolation of the estimated channel gains over the pilot symbols.
  • the pilot-assisted communication provides a simple implementation but suffers from two main issues: a loss of spectral efficiency resulting from a reduction in the symbol slots available for data transmission, and propagation of channel estimation errors to the decoder at the receiver which adversely affects performance of data recovery.
  • Imperfect channel estimation at the receiver degrades performance of a communication system.
  • the received signal can be viewed as a noisy version of the transmitted signal with the transmitted symbol constellations being scaled and rotated by a complex gain or channel gain. Having knowledge of this channel gain at the receiver allows signal decoding to achieve a lower block error rate (BLER) than when decoding is performed without an estimate of the channel gain.
  • BLER block error rate
  • the channel estimation noise which is the error resulting from the channel estimator using the transmitted pilot symbols, propagates to the space-time receiver or linear combiner.
  • the error then passes to the demodulator or decoder where the estimation noise reduces end-to-end performance, for example block error rate (BLER), bit error rate (BER), or symbol error rate (SER) for a given spectral efficiency or the maximum achievable spectral efficiency for a given BLER, BER or SER.
  • BLER block error rate
  • BER bit error rate
  • SER symbol error rate
  • the performance of the decoder for a given encoder-decoder pair depends on the quality of the channel estimation: a more accurate channel estimate yields a lower BLER leading to better quality of service.
  • the maximum performance is achieved when the receiver has perfect knowledge of the true channel gain. In practice however, there is a loss in performance because channel estimates computed in a receiver differ from the true channel gains due to estimation noise.
  • optimization of the power allocation may be achieved by a technique known as power boosting where the transmitter transmits the pilots symbols with a higher average power than is used for transmission of the data symbols.
  • Power boosting consumes additional power which is a valuable resource, especially in mobile devices.
  • Power boosting is not suitable for use in systems with peak power constraints and since many of today's systems place peak power constraints on transmitted symbols, power boosting is not always available as a solution to the estimation noise problem.
  • transmitting pilot symbols with higher power leads to severe interference between neighboring transmitters that are using the same time-frequency resources for transmission of the data and pilot symbols.
  • pilot contamination that occurs when multiple transmitters transmit their pilot symbols over the same time -frequency resources leading to a bottleneck in channel estimation.
  • a channel estimate based on a pilot symbol quickly becomes outdated and is no longer correlated with the true channel gain affecting the transmitted data symbols. Therefore, increasing transmission power does not help alleviate this problem.
  • the transmitter can multiplex higher numbers of pilot symbols into a given set of resource blocks.
  • Using a larger number of pilot symbols improves channel estimation and is also suitable for fast varying channels but these improvements come at a price.
  • the main cost is a reduction in spectral efficiency due to the additional time-frequency resources consumed by transmission of the additional pilots.
  • this approach is not suitable for standardized systems where the pilot density and associated time-frequency mapping are fixed by the standards.
  • the improvement in channel estimation is obtained: without consuming additional power; without transmitting additional legacy pilot symbols; and without any error propagation.
  • the disclosed methods and apparatus described herein do not increase the complexity of the decoding per transmitted data packet while providing flexibility in the radio communications.
  • the disclosed embodiments also provide a mechanism to reduce the overhead due to transmission of legacy pilot symbols thereby improving spectral efficiency.
  • an apparatus including a transmitter having a plurality of antennas, and a processing apparatus coupled to the transmitter.
  • the processing apparatus is configured to: segment a stream of information bits to form a plurality of data packets; generate a plurality of symbol sequences, wherein each symbol sequence in the plurality of symbol sequences corresponds to one data packet in the plurality of data packets; apply space-time coding to each symbol sequence in the plurality of symbol sequences to create a plurality of space-time coded block sequences, wherein each space-time coded block sequence comprises a plurality of space-time coded blocks; interlace the space-time coded blocks from the plurality of space-time coded block sequences to form an interlaced space-time coded block sequence; and provide the interlaced space-time coded block sequence to the transmitter.
  • the transmitter is further configured to transmit the interlaced space-time coded block sequence using the plurality of antennas.
  • the processing apparatus is further configured to receive a channel quality feedback signal (indicating a quality of the channel used for transmitting the interlaced space time coded block sequence) and to segment the stream of information bits and interlace the space time coded blocks based on the received channel quality feedback signal.
  • a channel quality feedback signal indicating a quality of the channel used for transmitting the interlaced space time coded block sequence
  • the processing apparatus is configured to receive a channel quality indicator, CQI, index as the channel quality feedback signal.
  • the space-time coded blocks of one or more of the space-time coded block sequences spans a plurality of coherence intervals, wherein a coherence interval comprises at least one of a coherence time and a coherence bandwidth.
  • the plurality of antennas comprises two antennas and the space-time coding comprises Alamouti coding.
  • the processing apparatus is further configured to add error detection information to each data packet in the plurality of data packets, wherein one or more error detection algorithms may be used to generate the error detection information.
  • the error detection information comprises cyclic redundancy check bits.
  • an apparatus including a receiver configured to receive a radio frequency signal and to produce based on the received radio signal a data signal, wherein the data signal comprises a plurality of data packets, and a processing apparatus coupled to the receiver and configured to receive the data signal.
  • the processing apparatus is configured to: decompose the data signal into a plurality of space-time coded block sequences, wherein each space-time coded block sequence corresponds to a single data packet; decode a first space-time coded block sequence in the plurality of space-time coded block sequences to recover a first data packet; regenerate a noiseless symbol block sequence based on the first data packet; combine the regenerated noiseless symbol block sequence with the first space-time coded block sequence to produce one or more pilot signals; and determine a channel estimate based on the one or more pilot signals.
  • the processing apparatus is configured to perform a cyclic redundancy check on the first data packet and, when the cyclic redundancy check result associated with the first data packet is a pass, use the regenerated noiseless symbol block sequence used to determine the channel estimate and, when the cyclic redundancy check result associated with the first data packet is a fail, not use the regenerated symbol block sequence to determine the channel estimate.
  • combining the regenerated noiseless symbol block sequence comprises a linear combination of the regenerated noiseless symbol block sequence with the received signal associated with the regenerated noiseless symbol block sequence.
  • the processing apparatus is further configured to decode a second space-time coded sequence in the plurality of space-time coded sequences based on the channel estimate.
  • a method for transmitting information in a wireless communication system comprising: segmenting a stream of information bits to form a plurality of data packets; generating a plurality of sequences of modulated symbols wherein each sequence of modulated symbols corresponds to one data packet in the plurality of data packets; space-time coding each sequence of modulated symbols in the plurality of sequences of modulated symbols to generate a plurality of space-time coded block sequences, wherein each space-time coded block sequence corresponds to one data packet in the plurality of data packets; interlacing the plurality of space-time coded block sequences to form a single interlaced space-time coded block sequence; and transmitting the interlaced space-time coded block sequence using a plurality of antennas.
  • the method further comprises adding error detection information to each data packet in the plurality of data packets.
  • the error detection information comprises a cyclic redundancy check.
  • the method further comprises adding one or more pilot symbol blocks to the interlaced space-time coded block sequence.
  • the method further comprises receiving a channel quality feedback signal and wherein the segmenting and interlacing are based on the received channel quality feedback signal.
  • the above and further objects and advantages are obtained by a method for receiving information in a wireless communication system.
  • the method includes: receiving a data signal; decomposing the data signal into a plurality of space-time coded block sequences, where each space-time coded block sequence corresponds to a data packet.
  • a first space-time coded block sequences from the plurality of space-time coded block sequences is decoded to recover a first data packet.
  • a noiseless symbol block sequence is regenerated based on the first data packet.
  • the noiseless symbol block sequence is combined with the first space-time coded block sequence to produce one or more pilot signals, and the pilot signals are used to determine a channel estimate.
  • the channel estimate is used to decode a second space-time coded block sequence in the plurality of space-time coded block sequences to recover a second data packet.
  • Figure 1 illustrates a conventional space-time coded symbol block
  • Figure 2 illustrates a block diagram of a transmitter incorporating aspects of the disclosed embodiments
  • Figure 3 illustrates a process for creating an interlaced sequence of space-time coded blocks incorporating aspects of the disclosed embodiments
  • Figure 4 illustrates a pictorial diagram of steps used to form a interlaced sequence of space-time coded blocks incorporating aspects of the disclosed embodiments
  • Figure 5 illustrates a block diagram of an estimator incorporating aspects of the disclosed embodiments
  • Figure 6 illustrates a block diagram of a receiver incorporating aspects of the disclosed embodiments
  • Figure 7 illustrates a graph of performance improvements provided by a system incorporating aspects of the present disclosure
  • Figure 8 illustrates a graph comparing spectral efficiency of a conventional system to an embodiment of the present disclosure
  • Figure 9 illustrates a block diagram of a transceiver appropriate for practicing embodiments of the present disclosure
  • Figure 10 illustrates a flow chart of a method for transmitting data in a wireless communication system incorporating aspects of the disclosed embodiments.
  • Interlaced STC offers an alternative to conventional space-time coding transmission schemes and provides enhanced spectral efficiency without consuming additional time, frequency, or power resources.
  • Interlaced STC enables improved channel estimation in radio links using STC.
  • the source information bits are segmented into data packets and converted to a sequence of STC blocks, and then the sequences of STC blocks from different data packets are interlaced or comingled to create a single interlaced sequence of STC blocks to be transmitted from a multi-antenna transmitter.
  • the receiver then progressively improves its channel estimates through a process referred to as noiseless pilot expansion which takes advantage of the interlaced sequence of STC blocks to re-generate additional pilot symbols throughout the decoding process.
  • Interlaced STC can be advantageously employed with any appropriate STC scheme and with any number of transmit antennas; however, as an aid to understanding, specific example embodiments will be illustrated using a simple second order STC scheme known as the Alamouti space-time code and a transmitter having two antennas.
  • a simple second order STC scheme known as the Alamouti space-time code and a transmitter having two antennas.
  • the conventional Alamouti space- time code is a simple second order STC designed for two transmit antennas and one or two receive antennas. To understand the Alamouti code, consider transmission of two modulated symbols, x and a 2 , transmitted from two antennas.
  • the Alamouti space-time scheme transmits a copy of each symbol, x and a 2 , from each antenna respectively followed by a negated conjugate of the second symbol,— a 2 , form antenna 1 and a conjugated version of the first symbol, a , from the second antenna thereby creating a space-time coded (STC) block 100 of 4 symbols as illustrated in Figure 1.
  • the STC block 100 produced by the Alamouti STC is a two by two matrix of symbols having time 1 12 as one dimension, shown horizontally progressing from right to left, and a second spatial dimension 106 corresponding to the two antennas 108, 110 shown horizontally.
  • the symbols may be separated in frequency rather than time yielding a STC block 100 where the horizontal axis is frequency.
  • the second order Alamouti STC has a rate of one, i.e. two symbols are transmitted over two time slots.
  • a space-time code block may include more time slots and/or more antennas yielding a higher order matrix or STC block with a larger number of symbols.
  • the transmitter multiplexes pilot symbols, referred to herein as legacy pilot symbols, in with the coded modulated data symbols of different data packets over each coherence interval. These transmitted legacy pilot symbols are then used by the receiver to generate channel estimates through conventional channel estimation techniques, and the channel estimates can then be used to decode the first interlaced coded data packet. Decoding can be achieved for example by using a nearest neighbor decision rule.
  • the receiver has access to the known decoded modulated symbols and can use this knowledge along with the transmitted legacy pilot symbols to re-estimate the channel over each block.
  • the updated channel estimates can then be used for decoding subsequent data packets.
  • the signals of the two consecutive received noisy data symbols of the first packet need to be rearranged to enable a process referred to herein as orthogonal noiseless pilot expansion which generates new pilot symbols from the modulated data symbols of the first packet. Pilot expansion is achieved through optimal linear processing which enables orthogonal pilot expansion.
  • the channel estimates can be updated to provide more accurate estimates for decoding subsequent data packets.
  • the receiver has access to better and better estimates of the channel through continual use of orthogonal pilot expansion to create new virtual pilot symbols.
  • This approach of transmitting joint pilot and data symbols enables the receiver to use orthogonal pilot expansion to progressively enhance the quality of its channel estimates in systems using STC.
  • the improvement in channel estimation is obtained: without consuming additional power; without transmitting additional legacy pilot symbols; and without any error propagation.
  • the disclosed methods and apparatus described herein do not increase the complexity of the decoding per transmitted data packet while providing flexibility in the radio communications.
  • the disclosed embodiments also provide a mechanism to reduce the overhead due to transmission of legacy pilot symbols thereby improving spectral efficiency. In certain embodiments, when the first packet can be decoded blindly, transmission of legacy pilot symbols may completely eliminated.
  • FIG. 2 illustrates an embodiment of a transmitter 200 configured to transmit data using interlaced STC.
  • the transmitter 200 uses a processing apparatus 258 to convert raw data bits 206 into an interlaced sequence of STC blocks 244.
  • the transmitter 200 includes a radio frequency transmitter 256 that has an antenna array 248 configured to transmit the interlaced sequence of STC blocks 244 generated by the processing apparatus 258.
  • Two key features of the transmitter 200 are parallel coding and block-wise interlacing 216. These features will be discussed in more detail below.
  • Transmitter 200 is configured to operate in a closed loop mode where a feedback signal 208 is received by an interlacing controller 210 and used to determine a set of transmission parameters 218 (e.g. transmitted from a User Equipment).
  • the feedback signal 208 could include a channel quality indicator (CQI) index providing the transmitter 200 with information about the quality and condition of the radio channel over which the interlaced sequence of STC blocks 244 is being transmitted by the radio frequency transmitter 256.
  • CQI channel quality indicator
  • the reported CQI can be any information indicating a condition of the radio channel.
  • the CQI could be an index associated with a signal-to-noise ratio (SNR) or signal-to-interference-plus-noise ratio (SINR) or channel estimation quality index or any other value that allows determination of transmission parameters 218 by the interlacing controller 210.
  • the CQI includes an index value that may be used to select transmission parameters 218 from a look-up table (LUT).
  • the transmission parameters 218 being selected by the interlacing controller 210 include a segmentation vector a for segmentation of raw data bits 206 into data packets 220, a coding rate Rj used by the encoder 222, a modulation order j which selects the desired modulation scheme, and an interlacing parameter /?j used to determine how the STC coded blocks 236 are interlaced to form an interlaced sequence of STC blocks 244 which are transmitted by the antenna array 248 in the radio frequency transmitter 256.
  • the raw data bits 206 to be transmitted by the transmitter 200 are received from a source 202 and are prepared as a block of B bits.
  • the raw data 206 is received from a source 202 external to the processing apparatus 258 or alternatively the raw data may be generated by software modules within the processing apparatus 258. In certain embodiments the raw data may be received from multiple sources 202.
  • the raw data 206 may also be encoded and packaged prior to segmentation 204.
  • the raw data 206 is segmented 204 to form smaller blocks of packetized raw data 220.
  • the number of raw data packets 220 or parallel streams 252 is denoted by K.
  • the K blocks of packetized raw data 220 are processed in parallel by K parallel streams indicated generally by numeral 252.
  • Segmentation 204 of the raw data 202 is based on the segmentation vector a, which is one of the interlacing parameters 218 determined by the interlacing controller 210 and is used to create each block of packetized raw data 220.
  • Each parallel stream 252 processes the raw packetized data 220 in the same or at least a similar way 254 (e.g. having the same elements, like CRC 224, encoder 222, modulator 226, space time encoder 228, but different parameters for these elements).
  • an error detection encoder 224 is used to add error detection information to create packetized raw data plus error detection information 230.
  • the error detection information allows a receiver to determine whether the decoded data block is correct or not.
  • the error detection encoder is a cyclic redundancy check (CRC), however any appropriate error detection encoding may be advantageously employed.
  • the type of error detection encoding 224 may be packet specific and may differ from those used for other parallel streams 252 or other data packets 220.
  • the error detection information or CRC bits will be used for an unconventional purpose when enhancing the channel estimation.
  • the raw packetized data with CRC 230 then undergoes channel encoding 222 to create a coded data packet 232.
  • the channel encoder 222 may include error correction encoding
  • the encoder block 222 includes a mother error correction encoder 238 followed by rate matching 240 and possibly a bit-interleaver 242. [0050] The coded data packet 232 is next passed to a modulator that generates coded modulated data packet 234 that is made up of a sequence of coded modulated symbols.
  • the modulated symbols 234 are grouped and passed to a space-time encoder 228 to generate space-time coded matrices 236, referred to herein as STC blocks 236.
  • the space-time encoder 228 may be a second order STC such as an Alamouti code where two modulated symbols are used to generate a STC block 236 that is a square matrix with four elements as illustrated in Figure 1.
  • the processing 254 is completed and the raw packetized data 220 is converted into STC blocks 236, the STC blocks 236 from each parallel stream 252 are interlaced 216 to create an interlaced sequence of STC blocks 244.
  • the interlacing 216 includes one or more blocks of legacy pilot symbols 250 in the interlaced sequence of STC blocks 244 to enable channel estimation prior to decoding of the first data packet.
  • Each block of legacy pilot symbols 250 includes an orthogonal set of pilot symbols that may be arranged in a diagonal matrix or block and multiplexed into the interlaced sequence of STC blocks 244.
  • the interlaced sequence of STC blocks 244 are then sent to the radio frequency transmitter 256 where they can be transmitted with the antenna array 248.
  • the antenna array 248 includes a number of antennas at least as large as the spatial dimension of the STC blocks 244 being transmitted.
  • the interlacing 216 is determined by a set of interlacing parameters ⁇ where each /?j determines which portion of the STC blocks from each sequence of STC blocks 236 are interlaced within each coherence interval.
  • FIG. 3 illustrates a flow chart of an exemplary encoding process 300 for converting raw data, such as raw data 206, into an interlaced sequence of STC blocks 244.
  • the encoding process 300 is appropriate for use in transmitter 200 described above with reference to Figure 2 and illustrates an exemplary embodiment of a second order process 300 having two parallel streams 302, 304.
  • any number of parallel streams may be advantageously employed with a corresponding STC algorithm appropriate for the desired number of parallel streams and number of antennas to be used for transmission.
  • the process 300 begins by receiving raw data 306 such as raw data 206 where the raw data 306 contains a number B of information bits.
  • a segmentation process 308 separates the raw data bits 306 into two packets of raw data 310 where each packet B l and B 2 is processed in a similar fashion by the two parallel paths 302, 304.
  • the size of each data packet B l and B 2 is determined by corresponding interlacing parameters referred to as a segmentation vector a, which may be predetermined or selected by a controller such as interlacing controller 210 described above, based on CQI feedback from a receiver.
  • Error detection bits are then added to each data packet 310 using an error detection coding scheme 312 such as a CRC to create data packets 314 containing both segmented raw data and error detection bits CRC.
  • an error detection coding scheme 312 such as a CRC to create data packets 314 containing both segmented raw data and error detection bits CRC.
  • a different error detection coding scheme may be used by different parallel streams 302, 304 or on subsequent data packets.
  • Channel coding and rate matching is applied 316 to create packets of coded bits 318 for each parallel stream C l , C 2 .
  • the coded bits 318 are then modulated 320 to form streams of coded modulated symbols 322.
  • Each stream of coded modulated symbols is then passed to a STC scheme 324, such as the second order Alamouti STC scheme described above, to create sequences of STC blocks 326, where each STC block is a matrix with one dimension corresponding to the number of antenna elements in the antenna array being used to transmit the data and the second dimension corresponding to a number of time slots which is determined by the STC scheme being used.
  • the sequences of STC blocks 326 are then interlaced and pilot symbol blocks are added to form the interlaced sequence of STC blocks 330, such as the interlaced sequence of STC blocks 244 described above.
  • FIG 4 illustrates a pictorial diagram of the STC 324 and interlacing 328 steps of the exemplary encoding process 300 where the STC scheme 324 is an Alamouti STC and interlacing 328 is done in a uniform fashion.
  • a stream of modulated symbols 322 is represented by the modulated symbols of stream 1 , 402, and the modulated symbols of stream 2, 404.
  • the two modulated symbol streams 402, 404 are processed by an STC scheme 406, such as STC 324, which in the example illustrated in Figure 4 is an Alamouti STC 406, to produce a sequence of STC blocks 408.
  • an Alamouti STC produces four element blocks of symbols containing two symbols from the stream of modulated symbols 402, 404, to produce each STC coded block 408.
  • the two sequences of STC blocks 408, 410 are then block- wise interlaced 412 with each other.
  • alternating one STC coded block such as STC block 414 and 418, is taken from each sequence of STC coded blocks 408, 410 to form the interlaced sequence of STC blocks 420.
  • the interlaced sequence of STC blocks 420 is transmitted from right to left with the block of pilot symbols 422 being transmitted through a pair of antennas 426, 428 as indicated by the arrows labeled Antenna 1 , 426, and Antenna 2, 428, followed by the first STC block 414 of the first STC block sequence 408, then the first STC block 418 of the second STC block sequence 410, and continuing on in this fashion until all the interlaced STC blocks 420 are transmitted in the coherence interval.
  • the spatial dimension 430 is depicted vertically and time is depicted horizontally from right to left.
  • fj is a function denoting the channel estimation which is based on the legacy pilot symbols x p (if any were transmitted), the correctly decoded modulated data symbols of the earlier packets Xd 1 i x d 2 i ' " > x dj_ ⁇ the received noisy signals y v associated with the transmitted pilot symbols (if any), and the received noisy signals ⁇ 3 ⁇ 4, ⁇ 3 ⁇ 4 2 , , ydj_ x associated with the correctly decoded modulated data symbols Xd 1 i x d 2 > " ' > x d _ -
  • Any desired channel estimation method may be chosen, for example a minimum mean square error (MMSE) estimator or a maximum likelihood (ML) estimator.
  • D ⁇ di , dz , ⁇ ⁇ , Xd j _ 1 ⁇ denotes a function which selects a block of modulated symbols from the correctly decoded packets; i.e. those packets that pass the CRC.
  • Function ) in equation (1) denotes symbol combining in order to determine equivalent "new" pilot symbols based on modulated symbols of the correctly decoded packets dl , dz , ⁇ ⁇ ⁇ , x d j _ 1 -
  • Function g 2 ⁇ - denotes the processing for signal combining which will be discussed in more detail below.
  • FIG. 5 illustrates a block diagram of a general channel estimation scheme 500 appropriate for use in a receiver configured to receive the interlaced sequence of STC blocks such as the interlaced sequence of STC blocks 244 described above or another appropriate interlaced sequence of STC blocks.
  • the estimator 500 will provide channel estimates hj whose quality improves on average data transmission progresses, i.e. as j progresses.
  • the estimator 500 receives a sequence regenerated modulated symbols 502 ⁇ ⁇ ⁇ j X ⁇ . ⁇ that have been regenerated from decoded received data packets.
  • a corresponding set of noisy data signals 516 is generated from the selected noisy signals 508 l by a signal combining process 522 5 , 2 ( - A channel estimator 518 can use the legacy pilot symbols 524 pand the additional pilot symbols 514 along with the received noisy legacy pilot signals 526 y v and the set of noisy data signals 516 to update the channel estimates 528 hj .
  • the transmitter may use longer term statistics of the channel such as the coherence time and/or coherence bandwidth of the channel to determine how many parallel streams, which data rates, and how many symbols of each packet should be multiplexed within each coherence time and coherence bandwidth.
  • the coded modulated symbols of a particular packet of data, packet j, that are passed to the same space-time encoder should be kept together and should be located close to each other and in proximity of the coded modulated symbols of the previous packets, packets 1 to j— 1, as well as the legacy pilot symbols, if any legacy pilot symbols are used.
  • the transmission parameters are selected so that interlacing causes the multiplexed coded modulated data symbols and the legacy pilot symbols to span the same coherence time and bandwidth. This provides that within a given time-frequency frame having a size equal to the coherence time and bandwidth, there are coded modulated data symbols from several data packets. When this is done the quality of the channel estimation can be refined for subsequent data packets. Robust channel estimation for earlier packets can be ensured by optimizing placement in the time-frequency grid as well as optimizing the packet length, the associated data rate, and the number of coded modulated data symbols placed within each coherence bandwidth and time.
  • the placement of the coded modulated symbols of earlier packets within the time-frequency grid should be accomplished such that it reduces the amount of interference from neighboring nodes which are using the same time-frequency resources. This can be achieved for example by using the structure of the reference symbols and the control region of neighboring nodes to place the coded modulated symbols of the first packet to avoid potential interference and to enable initial robust channel estimation.
  • feedback from the receiving nodes allows a transmitter to dynamically adapt placement of the coded modulated symbols.
  • Using feedback and dynamic placement provides for a more flexible radio transmission allowing a network controller to schedule use of time-frequency resources in a way that improves the quality of channel estimation. For radio links where the given coherence bandwidth and time can be obtained from long term statistics of the channel, it is beneficial to increase the number of coded modulated symbols places in each coherence bandwidth and time as the number of parallel streams increases.
  • the first data packet will be decoded blindly, i.e. decoded without channel estimates or with a blind channel estimation. Then the following data packet can be decoded coherently using channel estimates based on the first decoded data packet. In these embodiments the first data packet takes the place of legacy pilot symbols thereby freeing up resources that would have been consumed by legacy pilot symbols for transmission of data symbols.
  • the coded modulated symbols and legacy pilot symbols are interlaced so that coded modulated symbols from a data packet span the correlated channel.
  • a typical measure of the correlated channel is based on the coherence time as discussed above.
  • the coherence interval is the amount of time over which the channel remains approximately constant and depends on the mobility of the users. The faster a user moves the smaller the associated coherence interval becomes. For example, in a channel where the coherence interval or time is T c , a solution for a system using Alamouti space-time coding would be to use at least one legacy pilot symbol for each antenna and at most (T c — 2)/2 coded modulated symbols belonging to different data packets.
  • system performance which is dependent on uncontrollable factors such as the mobility of users and number of users, may be optimized by adjusting the controllable factors such as the number of parallel streams, and the number of legacy pilot symbols and coded modulated symbols mapped within a coherence interval.
  • controllable factors such as the number of parallel streams, and the number of legacy pilot symbols and coded modulated symbols mapped within a coherence interval.
  • a system can allow for variable numbers of coded modulated symbols from different data packets in each coherence interval.
  • a receiver for receiving an interlaced sequence of STC blocks such as the interlaced sequence of STC blocks 244 produced by the transmitter 200 includes two specialized components configured for decoding the interlaced sequence of STC blocks. These include sequential decoding where earlier transmitted data packets are decoded first and used to support decoding of subsequent data packets, and orthogonal noiseless pilot expansion where noiseless coded modulated symbols are re-generated from a decoded data packet and used as pilot symbols to improve the quality of channel estimation. Progressive noiseless pilot expansion was introduced above with respect to equation (1).
  • FIG. 6 illustrates a block diagram of an exemplary embodiment of a receiver structure 600 configured to receive an interlaced STC signal with two codebooks, or parallel streams, that have been encoded with an Alamouti STC at the transmitter (e.g. the transmitter 200), such as the sequence of coded symbol blocks 326 described above with reference to Figure 3.
  • the receiver 600 is configured to decode an interlaced sequence of STC blocks including two parallel streams or data packets.
  • the receiver 600 may be expanded to decode an interlaced sequence of STC blocks created from any number of parallel streams or data packets without straying from the spirit and scope of the present disclosure.
  • the receiver 600 includes a radio frequency receiver 642 to receive a radio frequency signal and provide a baseband signal 646 y to a processing apparatus 644.
  • the noisy baseband signal 646 y is passed to a de-multiplexer 604 which decomposes the received noisy baseband signal 646 y ' to a set of received noisy baseband signals associated with the transmitted legacy pilot symbols y Pl , y P2 and each coded modulated symbol y d , y d2 , 648 and y ds , y d4 650.
  • the data packets are decoded sequentially with the first packet 614 being decoded first by a first decoder 608 and the second packet 616 being decoded second by a second decoder 612.
  • Decoding of the second packet 616 is improved through the use of re-generated pilot symbols y d , y d2 derived by orthogonal noiseless pilot expansion 610 from the decoded first data packet 614.
  • the first channel estimators 618, 620 obtain estimates of the channel, h 1:1 , h 1 2 based on the received noisy signals associated with the first pilot symbols y v , y P2 respectively.
  • Alamouti linear combining 622 is used to create combined signals y d , y d2 . Then the combined signals y d , y d2 over the first two time slots are fed to the first demodulator/decoder 624 to produce the decoded data of the first packet 614.
  • Orthogonal noiseless pilot expansion 610 is then performed beginning by checking the CRC result 632 of the first packet. If the CRC passes, which means the data of the first packet 614 was decoded correctly, the data of the first packet is then used for orthogonal noiseless pilot expansion 610, otherwise expanded pilots for the failed data packet are not generated. When the CRC passes, the decoded information bits of the first data packet are re-encoded 630 and re -modulated 628 to create noiseless modulated data symbols 652 x d x d2 .
  • the noiseless modulated data symbols 652 x d x d2 are combined with the received noisy baseband signals associated with the coded modulated symbols of the first data packet y dl , y d2 to be used as new pilot signals 654 y dl , y d2 to improve channel estimation in the second decoder 612.
  • the channel estimators 634, 636 of the second channel 612 uses both the noisy baseband signals associated with the transmitted legacy pilot symbols y p , y P2 and the signals associated with the re-generated pilot symbols y d , 3 ⁇ 4 2 ⁇ re-generate channel estimates 656 h 2>1 , 3 ⁇ 42,2 navm g improved quality.
  • the second decoder 612 then proceeds in a fashion similar to the first decoder 608 where Alamouti linear combining 638 is used to create combined signals y d3 , y d4 . Then the combined signals y ds , y d4 over the first two time slots are fed to the second demodulator/decoder 640 to produce the decoded data of the second packet 616.
  • the improvements result from two advantages gained from the larger number of virtual pilot symbols. First the increased number of measurements reduces the effect of measurement noise allowing the channel to be estimated more accurately. Secondly, because the number of equivalent pilot symbols is increased, i.e.
  • the legacy pilot symbols plus the re-generated symbols based on the correctly decoded data of earlier data packets the actual channel experienced by the pilot symbols becomes more correlated to the channel experienced by the data symbols.
  • Continually updating the channel estimates based on recently decoded data packets combats channel out-dating and is important for fast-varying channels.
  • the enhanced channel estimates generated for the second packet are closer to the actual channel experienced by the coded modulated symbols of the second transmitted data packet. This, therefore, provides the second channel decoder with access to an improved channel estimate and hence the performance of the decoder becomes closer to that of a decoder that has perfect knowledge of the channel.
  • the error propagation in the receiver from the first parallel stream to the second parallel stream is avoided by using the CRC result to select only correctly decoded data packets for pilot expansion.
  • the receiver may initiate an automatic repeat request (ARQ) to have the first data packet retransmitted.
  • ARQ automatic repeat request
  • the transmitter retransmits the data packet until the receiver successfully decodes the data, i.e. the CRC passes.
  • the decoded packet can then be used to re-generate the coded modulated symbols that become additional pilot symbols used by the second channel estimator.
  • the initial packet needs to be stored in a buffer.
  • the second decoder may proceed using only the original transmitted pilot symbols for channel estimation.
  • transmission of the additional CRC bits with every packet is too expensive.
  • the receiver may request that the CRC bits be based on a larger combined packet and orthogonal noiseless pilot expansion be based on the larger combined packets.
  • Linear combining such as the linear combining 626 illustrated in the second order receiver embodiment 600 described above with reference to Figure 6, is performed during orthogonal noiseless pilot expansion because the modulated symbols from the first packet over two consecutive time slots are correlated and interfere with one another.
  • the receiver under a sequential decoding has already received and decoded signals for a first data packet.
  • the signals associated with the first data packet are given by equation (2):
  • x d j denotes the modulated data symbol associated with antenna j
  • h j is the channel estimate for the signal received over antenna j
  • Zj is additive white Gaussian noise (AWGN)
  • the receiver after the decoding of the first data packet has access to the modulated data symbols x dl , and x d2 from the first packet. To improve channel estimation for the second packet the receiver re-estimates the channel gains of the second channel x and h 2 prior to decoding of second packet. However, since the channels interfere with each other the two signals are linearly combined to provide separable signals for re-estimation. This is accomplished by first rewriting equation (2) in vector form as shown in equation (3):
  • the above analysis is based on a second order system that interleaves two parallel streams with two antennas.
  • the above techniques of orthogonal noiseless pilot expansion can be applied to system with larger numbers of antennas and parallel paths without straying from the spirit and scope of the present disclosure.
  • the next decoder sees an improved channel estimate resulting in lower channel estimation noise fed to the decoder thereby improving the decoding success rate of the second data packet.
  • the improved decoding success rate allows the transmitter to choose transmission schemes with higher data rates.
  • the first packet which is the packet decoded with a lower quality channel estimate, carries a lower rate while the second packet caries a higher rate due to the improved channel estimates.
  • the transmitter maintains a constant rate over all parallel streams, the later packets can achieve a higher successful decoding rate.
  • the effective throughput improves both when the later packets are transmitted with a higher rate as well as when the all packets are transmitted at a constant rate.
  • T c denotes the coherence time in number of symbols
  • T p denotes the number of pilot symbols per coherence time
  • P d denotes the average power consumed by the data symbols
  • Pp denotes the average power consumed by the pilot symbols
  • N 0 is the variance of the AWGN at the receiver
  • T c denotes the coherence time in number of symbols
  • T p denotes the number of pilot symbols per coherence time
  • P d denotes the average power consumed by the data symbols
  • P d denotes the average power consumed by the data symbols in packet i
  • h j i denotes the estimated channel from antenna j for decoding of packet i
  • an d %2k denotes two consecutive interlaced modulated symbols from packet k.
  • FIG. 7 illustrates a graph 700 illustrating the relative power gain of the proposed interlaced Alamouti coding scheme with respect to the baseline Alamouti scheme, i.e. the power gain for achieving the same rate, as a function of the coherence time.
  • relative power gain is plotted along the vertical axis 702 in decibels (dB)
  • coherence time in number of symbols is plotted along the horizontal axis 704.
  • the uniform power allocation across the resource elements is considered and the gain is computed for high SNR when the difference becomes saturated.
  • the graph 700 shows that the interlacing scheme disclosed herein offers a gain which can provide up to a 3 dB power gain at high SNR which is equivalent to 1 bit/s/Hz.
  • This yields a transmitter with two parallel streams, such as transmitter 200 as described above with the number of parallel streams 252 set to 2, i.e. K 2.
  • the coded symbol blocks from both parallel streams are interlaced uniformly over all coherence blocks.
  • the spectral efficiency is used in order to optimize the design parameters.
  • the mobile device or user equipment reports its channel quality indicator (CQI), for example a SNR index, to the interlacing controller, such as interlacing controller 210, that chooses the corresponding rate, segmentation parameter a and interlacing parameter /?, as illustrated in the transmitter 200 of Figure 2.
  • CQI channel quality indicator
  • Table 1 shows an example of modulation and coding schemes (MCS) for a 4-bit CQI that may be used for an interlaced Alamouti scheme using quadrature phase shift keyed (QPSK), 16 symbol quadrature amplitude modulation (16QAM) and 64 symbol quadrature amplitude modulation (64QAM).
  • QPSK quadrature phase shift keyed
  • 16QAM 16 symbol quadrature amplitude modulation
  • 64QAM 64 symbol quadrature amplitude modulation
  • the Gain, in dB of power gain, shown in Table 1 is computed when 90% of the maximum spectral efficiency is achieved.
  • the Gain is Table 1 shows that the power gain can be up to 2 dB for the LTE system described above.
  • the disclosed interlacing embodiments provide more gain due to the improved channel estimation at the receiver. Table 1.
  • FIG. 8 illustrates a graph 800 showing the performance for 64QAM which was summarized in Table 1 with index 16.
  • the graph 800 shows signal-to-noise ratio in dB on the horizontal axis 804 and spectral efficiency as a Rate in bits/s/Hz along the vertical axis 802.
  • the gain of nearly 2.1 dB is in agreement with that predicted in by the above analysis and illustrated in graph 700 of Figure 7.
  • FIG. 9 illustrates a block diagram of one embodiment of an apparatus for wireless communications 900 appropriate for use as the transmitter 200 or receiver 600 described above and with reference to Figure 2 and Figure 6 respectively.
  • the apparatus 900 includes a processing apparatus 902 (or processor 902) coupled to a computer memory 904, a radio frequency transmitter 906, a radio frequency receiver 908, and a user interface (UI) 910.
  • UI user interface
  • interaction with a user is not required, and in these embodiments the UI 910 may be omitted from the apparatus 900.
  • the apparatus 900 may be used as mobile station such including various types of wireless communications user equipment, such as cell phones, smart phones, tablet devices, etc.
  • the term computer refers to any computing device including a processing apparatus such as the processing apparatus 902 coupled to a computer memory such as the computer memory 904.
  • the processing apparatus 902 is appropriate for use as the processing apparatus
  • the processing apparatus 902 may be a single processing device or may comprise a plurality of processing devices including special purpose devices such as for example it may include digital signal processing (DSP) devices, microprocessors, or other specialized processing device as well as one or more general purpose processors.
  • DSP digital signal processing
  • the memory 904 is coupled to the processing apparatus 902 and may be a combination of various types of computer memory such as for example volatile memory, non-volatile memory, read only memory (ROM), random access memory (RAM) or other types of computer memory and stores computer program instructions which may be organized as method groups including an operating system, applications, file system, as well as other computer program instructions for other desirable computer implemented methods such as methods that support transmitting and/or receiving the sequences of interlaced STC block sequences or orthogonal noiseless pilot expansion techniques disclosed herein. Also included in the memory 904 are program data and data files which are stored and processed by the computer program instructions.
  • the radio frequency transmitter 906 is coupled to the processing apparatus 902 and configured to transmit radio frequency signals based on digital data 912 exchanged with the processing apparatus 902.
  • the radio frequency transmitter 906 is appropriate for transmitting the interlaced sequences of STC blocks 244 described above and with reference to Figure 2.
  • the radio frequency transmitter 906 includes multiple antenna elements capable of simultaneously transmitting independent radio frequency signals.
  • the transmitted radio frequency signals may include symbol sequences such as the interlaced space-time coded symbol sequences 330 or the multiplexed pilot and data packets 244 transmitted by the transmitter 200.
  • the radio frequency receiver 908 is coupled to the processing apparatus 902 and is configured to receive radio frequency signals which may include CQI information from a receiving node (not shown), or alternatively in receiving node the radio frequency receiver 908 may include one or more antennas configured to receive interlaces space- time coded symbol sequences such as the sequences 330 described with reference to Figure 3 or the multiplexed pilot and data packets 244 transmitted by the transmitter 200.
  • the radio frequency receiver 908 is appropriate for use as radio frequency receiver 642 of receiver 600 and provides digital information 914 describing the received signals to the processing apparatus 902.
  • the radio frequency receiver and the radio frequency transmitter 906 may include analog circuitry to condition the received signal and analog to digital converters to digitize received RF signals at a desired sampling rate, such as about 30 megahertz (MHz) sample rate, and send the digitized RF signals 914 to the processing apparatus.
  • the radio frequency transmitter 906 may include digital to analog converters to convert digital data 914 received by the RF transmitter 906 from the processing apparatus 902 into analog signals along with analog circuitry to condition the analog signals produced by the digital to analog converter in preparation for transmission.
  • the UI 910 may include one or more well-known user interface elements such as a touch screen, keypad, buttons, as well as other elements for inputting data with a user.
  • the UI 910 may also include a display unit configured to display a variety of information appropriate for a user equipment or access node and may be implemented using any of well-known display types such as organic light emitting diodes (OLED), liquid crystal display (LCD), as well as less complex elements such as LEDs or indicator lamps, etc.
  • OLED organic light emitting diodes
  • LCD liquid crystal display
  • the communications apparatus 900 is appropriate for creating and transmitting the interlaced sequence of STC blocks or performing the orthogonal noiseless pilot expansion techniques disclosed herein.
  • FIG. 10 illustrates a flow chart of a method 1000 for creating an interlaced STC transmission scheme according to an embodiment of the present invention.
  • the method 1000 receives 1002 a channel quality feedback signal (such as a CQI index) from a receiver or other device receiving the interlaced sequence of STC blocks 1016 produced by method 1000.
  • the reported CQI e.g. reported by a User Equipment
  • the CQI can be any information indicating a condition of the radio channel.
  • the CQI could be an index associated with a signal-to-noise ratio (SNR) or signal-to-noise-plus-interference (SINR) or any other value that allows determination of transmission parameters, such as transmission parameters 218 described above.
  • SNR signal-to-noise ratio
  • SINR signal-to-noise-plus-interference
  • the selected transmission parameters include a segmentation vector such as the segmentation vector a, which in certain embodiments may be a scalar value, and an interlacing parameter, such as the interlacing parameters ⁇ described above, and in certain embodiments may include additional parameters such as the coding rate and modulation and coding scheme used when preparing data for transmission.
  • a block of information bits is then segmented 1004 according to the selected segmentation parameter to create a set of data packets that will be processed in parallel.
  • Error detection information 1006 is added to each data packet to allow a receiver to determine if the received data packets have been decoded correctly. Any suitable error detection coding scheme may be used, for example in certain embodiments the error detection information include a CRC. Different data packets may use different error detection schemes as desired.
  • the set of data packets is then encoded in preparation for transmission and a sequence of modulated symbols is created 1008 for each encoded data packet.
  • Each sequence of modulated symbols is space-time encoded 1010 to form a sequence of STC blocks such as the sequence of STC blocks 236 described above with reference to Figure 2.
  • the sequences of STC blocks are then interlaced 1014 to form a single interlaced sequence of STC blocks 1016.
  • one or more orthogonal blocks of pilot symbols such as the block of pilot symbols 422 illustrated in Figure 4, may be multiplexed into the interlaced sequence of STC blocks 1016 to enable channel estimation at the receiver prior to decoding the first data packet.
  • FIG 11 illustrates a flow chart of a method 1100 for decoding an interlaced space-time coded block sequence according to an embodiment of the present invention.
  • the method 1100 is appropriate for decoding the interlaced STC block sequence produced by the method 1000 illustrated in Figure 10 and described above.
  • the method begins by receiving 1102 a data signal that has been formatted as an interlaced STC block sequence such as any of the interlaced STC block sequences described above.
  • the interlaced STC block sequence is then decomposed 1102 into a set of STC block sequences where each STC block sequence corresponds to a data packet.
  • a first STC block sequence is then decoded 1106 to recover the original data packet.
  • legacy pilot symbols are included in the interlaced STC block sequence which may be used to generate channel estimates to improve the decoding 1106.
  • the first data packet can be decoded blindly, i.e. without the aid of pilot symbol supported channel estimation.
  • the first data packet is then used to regenerate 1108 noiseless STC blocks corresponding to the STC blocks in the first STC block sequence.
  • These regenerated STC blocks are then combined 1110 with the received noisy signals to produce a set of equivalent pilot signals. This combining can be achieved for example by the maximum ratio- combining described above with reference to equation (4).
  • the equivalent pilot signals can then be used along with any legacy pilot signals that may have been included in the received data signal to determine 1112 improved channel estimates.
  • each transmitted data packet includes error detection information.
  • error detection information such as CRC bits
  • CRC bits When error detection information, such as CRC bits, is available it can be used to control whether equivalent pilot signals are generated from the received data packet. If the error detection information indicates that a data packet was not decoded correctly, this data packet isn't used to generate equivalent pilots.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Radio Transmission System (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un appareil de transmission d'informations dans un système de communications sans fil comprenant un émetteur ayant une pluralité d'antennes et configuré pour transmettre une séquence de blocs de symboles codés spatio-temporellement, et un appareil de traitement couplé à l'émetteur et configuré pour fournir la séquence de blocs de symboles codés spatio-temporellement à l'émetteur. L'appareil de traitement est configuré pour : segmenter un flux de bits d'informations pour former une pluralité de paquets de données; générer une pluralité de séquences de symboles qui correspondent chacune à un paquet de données de la pluralité de paquets de données; appliquer un codage spatio-temporel sur chaque séquence de symboles afin de créer une pluralité de séquences de blocs codés spatio-temporellement; entrelacer les blocs codés spatio-temporellement à partir de la pluralité de séquences de blocs codés spatio-temporellement pour former une séquence de blocs codés spatio-temporellement entrelacés; et envoyer la séquence de blocs codés spatio-temporellement entrelacés à l'émetteur.
PCT/EP2014/063953 2014-07-01 2014-07-01 Procédé et appareil de codage spatio-temporel entrelacé WO2016000761A1 (fr)

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WO2024067598A1 (fr) * 2022-09-29 2024-04-04 维沃移动通信有限公司 Procédé et appareil de modulation, procédé et appareil de démodulation, et dispositif, système et support de stockage

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WO2024067598A1 (fr) * 2022-09-29 2024-04-04 维沃移动通信有限公司 Procédé et appareil de modulation, procédé et appareil de démodulation, et dispositif, système et support de stockage

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