WO2016008516A1 - Précodage par projection spectrale pour émetteur mimo - Google Patents

Précodage par projection spectrale pour émetteur mimo Download PDF

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Publication number
WO2016008516A1
WO2016008516A1 PCT/EP2014/065229 EP2014065229W WO2016008516A1 WO 2016008516 A1 WO2016008516 A1 WO 2016008516A1 EP 2014065229 W EP2014065229 W EP 2014065229W WO 2016008516 A1 WO2016008516 A1 WO 2016008516A1
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Prior art keywords
multicarrier
group
symbols
symbol
transmitter device
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PCT/EP2014/065229
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English (en)
Inventor
Jaap Van De Beek
Branislav Popovic
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Huawei Technologies Co., Ltd
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Priority to PCT/EP2014/065229 priority Critical patent/WO2016008516A1/fr
Publication of WO2016008516A1 publication Critical patent/WO2016008516A1/fr

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    • 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
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03828—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/046—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
    • H04B7/0473—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking constraints in layer or codeword to antenna mapping into account
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/068—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission using space frequency diversity
    • 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
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03343—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/26265—Arrangements for sidelobes suppression specially adapted to multicarrier systems, e.g. spectral precoding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2634—Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation

Definitions

  • the present invention relates to a transmitter device for multicarrier wireless communication systems. Furthermore, the present invention also relates to a corresponding method, a computer program, and a computer program product.
  • OFDM Orthogonal Frequency Division Multiplexing
  • any of these necessary means to reduce the out-of-band emissions thus cause the practical transmitted signal to be different from a text-book OFDM signal.
  • Standards have recognized this and instead of specifying which particular power-reduction means to use (as in wireline standards), the very suppression-means is left to the vendors as a proprietary design and only a limit to the Error-Vector Magnitude (EVM) is specified in the standards, which is a measure of dissimilarity between a practically generated system and the text-book OFDM signal.
  • EEM-budgets guarantee that transmitted signals from different manufacturers are sufficiently similar and fulfil the requirements.
  • a traditional means to reduce the out-of-band emissions is the use of a low-pass filter in the transmitter.
  • PAPR Peak to Average Power Ratio
  • Emerging radio communication systems adapt their spectral containment to the changing radio environment. Not only is such spectral flexibility envisaged to provide more spectrum- efficient usage of the spectrum, it also will enable sharing of spectrum by multiple users with various levels of cooperation and coordination. As a result of the spectral flexibility, the out- of-band emission characteristics, and thus the interference, change with time. A transmitter for these future systems must thus have flexible means to adapt the suppression of out-of- band emissions to the reigning circumstances.
  • Cancellation subcarriers are reserved subcarriers not carrying any data and modulated such that the signal spectrum gets a desired shape. While the method of cancellation subcarriers in general is effective in the sense that it is an alternative to traditional spectrum-shaping filters which essentially reduce the effective length of the cyclic prefix in OFDM systems, the problem with this method is that the performance (spectral suppression) is often not good enough to meet requirements. Furthermore, often the PAPR of the transmitted signal is often changed to the worse. Finally, either a lot of additional transmit power is needed on the reserved subcarriers, or a lot of subcarriers (overhead) need to be reserved in order to obtain typical satisfactory out-of-band suppression performance, and either way is undesirable.
  • FBMC FilterBank MultiCarrier
  • this method also in general is effective to solve the cyclic-prefix consumption-problem, the problem with this method is that the performance (spectral suppression) is often not good enough to meet the requirements - spectral suppression is typically in the order of up to 10 dB.
  • the multiplicative weights are very different from 1 , and hence a large distortion is introduced by this transmitter operation.
  • the weights are the result of a nonlinear programming problem whose solution is performed by a numerical algorithm. This comes with a complexity problem. Finally, when a receiver employs a classical OFDM receiver this method comes with a performance loss in terms of reduced detection error probability.
  • the precoder linearly transforms the Kx 1 data vector d into a precoded vector, also of size Kx 1 (and hence using all subcarriers in the system) whose K elements always are linearly dependent according to the subspace's definition.
  • the K elements of the precoded vector then modulate the OFDM subcarriers.
  • the number of data symbols D is slightly smaller than the number of subcarriers K, D ⁇ K, and here the 0x 7 reduced data vector d is orthogonally precoded with a non-square size-( xD) matrix P 0 whose D columns form an orthogonal basis of same vector subspace as used for the projection precoder in the previous conventional method.
  • the precoder linearly transforms the 0x 7 data vector d into a precoded vector, also of size x 7 (and hence again using all subcarriers in the system) whose K elements always are linearly dependent according to the subspace's definition.
  • the resulting precoded vector resides in the same subspace and has the same spectral properties.
  • each of the D data symbols is associated with one of the D orthogonal base vectors. While an advantage of this method over the subcarrier weighting method and over the projection method, is that the data is orthogonally precoded (and hence can be recovered at a receiver that has knowledge of the precoder matrix Po without any error floor), the disadvantages of this method are however that the data rate is slightly reduced (compared to the other conventional precoder methods) and that with this precoder, in practice, the data cannot be recovered at a receiver without knowledge of precoder matrix Po. The distortion, when interpreted as an unknown additive distortion of the data vector d s simply too large that knowledge of Po is required in the receiver.
  • MIMO multiple-input, multiple-output
  • An objective of embodiments of the present invention is to provide a solution for multi- antenna systems which mitigates or solves the drawbacks and problems of conventional solutions.
  • a transmitter device for a multicarrier (multi-antenna) wireless communication system comprising a processor and a transmitter; wherein the processor is configured to
  • each transmission symbol is associated with one of K number of sub-carriers
  • each first group is associated with one of the K sub-carriers
  • each spatially precoded symbol is associated with one of T number of transmit antennas of the transmitter device;
  • each second group is associated with one of the T transmit antennas
  • multicarrier modulate the at least one spectrally precoded symbol to obtain a multicarrier signal s a for the at least one second group; and wherein the transmitter is configured to
  • the transmitter according to the first aspect of the present invention accomplish very low out- of-band emissions due to the two step precoding, i.e. first spatial precoding and thereafter spectral projection precoding.
  • the transmitter according to the first aspect of the present invention provides spectrum efficient modulation, and allows all existing MIMO diversity and multiplexing transmission schemes.
  • legacy receivers e.g. User Equipments in LTE
  • legacy receivers can receive the present multicarrier signals transmitted by the transmitter according to the first aspect without any modification or having additional hardware but still take advantage of the present invention.
  • Further advantages of the transmitter according to the first aspect of the present invention are:
  • the projection precoder of the present invention often leaves a small EVM and a negligible PAPR and these properties are inherited from the single-antenna systems in the prior art that use the projection precoder.
  • the projection precoder is of low transmitter complexity, i.e. few multiplications per subcarrier.
  • the error-rate at the transmitter can be made even smaller.
  • the transmission symbols may be any symbols for transmission including data symbols and pilot (or reference) symbols.
  • w f is a vector of spectrally precoded symbols
  • G is a projection matrix
  • w s is a vector of spatially precoded symbols
  • I is the identity matrix
  • A is a constraint matrix
  • H denotes the Hermitian transpose.
  • the first possible implementation form provides a projection precoder with a correction vector having a very small distortion. This is especially the case when the number of sub-carriers is large.
  • each element a k m of column k and row m of the constraint matrix A has the form: e
  • T g is a length of a cyclic prefix of a multicarrier symbol
  • T s T - T g
  • T is a total length of the multicarrier symbol
  • f m is a fixed precoder design-frequency
  • the advantage with the second possible implementation form is that the spectrum can be controlled or sculpted with a large degree of control through the precoder design frequencies. For instance can particular choices of these precoder design parameters accomplish that the spectrum of the signal is made very steep in the vicinity of the signal's frequency band, a steep spectral decay, whereas the out-of-band emission for frequencies further away from the signal's bandwidth is just sufficient to comply with any spectral regulations.
  • the constraint matrix A has the form:
  • T g is a length of a cyclic prefix of a multicarrier symbol
  • T s T - T g
  • T is a total length of the multicarrier symbol
  • N is an integer
  • k 0 , ... , /3 ⁇ 4_ ! are the subcarrier indices.
  • An advantage with the third possible implementation form is that very few parameters need to be set. It is a "one-size-fits-all" solution where only the signal's bandwidth and the basic OFDM parameters determine the particular form of the spectral precoder. In a scenario where the signal's bandwidth changes from one time instant to a next, this spectral precoder does not have to be redesigned (and signalled) with other parameters than the above mentioned.
  • the at least one spatially precoded symbol of said at least one second group are based on data transmission symbols and the remainder of the spatially precoded symbols of said at least one second group are based on reference transmission symbols.
  • the receiver may perform channel estimation with good performance since the pilot-carrying subcarriers pass the spectral precoder unchanged.
  • a method in a transmitter device for a multicarrier (multi-antenna) wireless communication system comprising:
  • each transmission symbol is associated with one of K number of sub-carriers
  • each first group is associated with one of the K sub-carriers
  • each spatially precoded symbol is associated with one of T number of transmit antennas of the transmitter device;
  • each second group is associated with one of the T transmit antennas
  • the method according to the second aspect of the present invention accomplish very low out-of-band emissions due to the two step precoding, i.e. first spatial precoding and thereafter spectral projection precoding. Also means to flexibly change the multicarrier signal's spectrum content is provided by the method according to the second aspect of the present invention. Furthermore, the method according to the second aspect of the present invention provides spectrum efficient modulation, and allows all existing MIMO diversity and multiplexing transmission schemes.
  • legacy receivers e.g. User Equipments in LTE
  • legacy receivers can receive the present multicarrier signals transmitted according to the method according to the second aspect without any modification or having additional hardware but still take advantage of the present invention.
  • the projection precoder of the present invention often leaves a small EVM and a negligible PAPR and these properties are inherited from the single-antenna systems in the prior art that use the projection precoder.
  • the projection precoder is of low transmitter complexity, i.e. few multiplications per subcarrier.
  • the error-rate at the transmitter can be made even smaller.
  • the projection precoder has the form:
  • each element a m of column k and row m of the constraint matrix A has the form:
  • T g is a length of a cyclic prefix of a multicarrier symbol
  • T S T - T g
  • T is a total length of the multicarrier symbol
  • f m is a fixed precoder design-frequency
  • the constraint matrix A has the form:
  • T g is a length of a cyclic prefix of a multicarrier symbol
  • T s T - T g
  • T is a total length of the multicarrier symbol
  • N is an integer
  • k 0 , ... , k K _ 1 are the subcarrier indices.
  • the present invention also relates to a multicarrier (multi-antenna) wireless communication system comprising at least one transmitter device according to the first aspect as such or according to any of the preceding implementation forms of the first aspect.
  • the multicarrier wireless communication system is an orthogonal frequency division multiplexing, OFDM, system.
  • the present invention also relates to a computer program with a program code for performing a method according to any method according to the second aspect, when the computer program runs on a computer. Further, the invention also relates to a computer program product comprising a computer readable medium storing said mentioned computer program thereon.
  • Said computer readable medium program comprises one or more of: ROM (Read- Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.
  • - Fig. 1 shows a transmitter device according to an embodiment of the present invention
  • FIG. 2 shows a flow chart of a method in a transmitter device according to an embodiment of the present invention
  • FIG. 3 illustrates a transmitter device according to an embodiment of the present invention
  • FIG. 4 illustrates a wireless communication system comprising embodiments of the present invention
  • - Fig. 5 shows spectra of a transmitted signal according to the present invention.
  • the invention disclosed herein therefore provides a two-step spatial-spectral precoder for multi-antenna systems where the first step performs the spatial precoding (MIMO precoding) of the transmissions symbols on a subcarrier basis (i.e. one precoder per subcarrier) and the second step performs the spectral precoding of the spatial-precoded output on a transmit antenna basis (i.e. one precoder per transmit antenna).
  • MIMO precoding spatial precoding
  • spectral precoding of the spatial-precoded output on a transmit antenna basis
  • OFDM and multicarrier modulation are used interchangeably in this disclosure. It is further to be understood that the present invention applies to all multicarrier systems based on an orthogonal set of underlying waveforms, in particular to OFDM systems which is based on the orthogonal set of orthogonal finite-length complex exponentials.
  • the transmitter device 100 comprises a processor 1 1 0 which is communicably coupled with a transmitter unit 120.
  • the transmitter device 100 further comprises multiple transmit antennas, namely T number of transmit antennas, where T is an integer.
  • the processor 1 10 is configured to receive a plurality of transmission symbols, wherein each transmission symbol is associated with one of K (integer) number of sub-carriers, indexed k 0 , ... , k K _ 1 .
  • the processor 1 1 0 is further configured to group the plurality of transmission symbols into a set of first groups, wherein each first group is associated with one of the K sub-carriers.
  • the processor 1 10 is further configured to spatially precode the transmission symbols of each first group to obtain spatially precoded symbols, wherein each spatially precoded symbol is associated with one of T number of transmit antennas, indexed a 0 , ... , a T of the transmitter device 1 00.
  • the processor 1 10 is further configured to group the spatially precoded symbols of all first groups into a set of second groups, wherein each second group is associated with one of the T transmit antennas of the transmitter device 100.
  • the processor 1 10 is further configured to spectrally precode at least one spatially precoded symbol of at least one second group by means of a projection precoder to obtain spectrally precoded symbols.
  • the processor 1 10 is further configured to multicarrier modulate the at least one spectrally precoded symbol to obtain a multicarrier signal s a for the at least one second group.
  • the transmitter 120 is configured to transmit the multicarrier signal s a for the at least one second group on its associated transmit antenna over the multicarrier wireless communication system 200.
  • the transmission symbols may be either data symbols or pilot (or reference) symbols.
  • the information carrying data symbols may be taken from a symbol constellation, and meant for transmission in one multicarrier symbol of the present multicarrier transmitter device 100.
  • the spatial precoding can take on any of the forms existing in the literature and/or conventional solutions, such as open-loop, closed-loop, diversity precoding, beamforming, etc.
  • MIMO transmission schemes appear in different forms.
  • several data streams are multiplexed, transmitted in parallel over the MIMO channel, and detected at the receiver.
  • This form can occur in two flavours: open-loop, where the transmitter has no knowledge about the channel state of the MIMO channel, and closed-loop where the transmitter has some knowledge about the channel state of the MIMO channel, typically based on feedback information received on a feedback communication channel from the receiver to the transmitter.
  • the spatial precoder "directs" the radio-signal over a beneficial spatial mode of the MIMO channel.
  • a single stream is transmitted and the spatial precoder provides means of diversity to the data transmission.
  • Data multiplexing typically is used in high-SNR regimes and diversity schemes are typically used in low-SNR regimes.
  • the order of the spatial precoding and the spectral precoding is indeed important in the present method, i.e. first spatial precoding and thereafter spectral precoding.
  • the alternative of performing spectral precoding prior to the spatial precoding is not attractive since general spatial precoding will destroy initial spectral precoding and cause the out-of- band emission to increase.
  • a projection precoder is used in embodiment of the present invention.
  • the projection precoder is particularly suitable for this as compared to other spectral precoders because it is the only known spectral precoder whose output signal can be represented as a sum of the input signal and a low-amplitude signal.
  • the projection precoder adds only a small distortion (the low-amplitude signal) to otherwise unchanged input values - small enough to impact the spatial precoder's operation only negligibly.
  • the projection precoder can operate on any kind of input signal, not necessarily data constellation values.
  • the spectral precoder is not restricted to operate on constellation symbols (as done in the conventional solutions of spectral precoders) but on any complex-valued numbers that are the result of a prior precoding step.
  • Fig. 2 shows a flow chart of a corresponding method in a transmitter device.
  • the method comprises receiving 300 a plurality of transmission symbols, wherein each transmission symbol is associated with one of K number of sub-carriers.
  • the method further comprises grouping 310 the plurality of transmission symbols into a set of first groups, wherein each first group is associated with one of the K sub-carriers.
  • the method further comprises spatially precoding 320 the transmission symbols of each first group to obtain spatially precoded symbols, wherein each spatially precoded symbol is associated with one of T number of transmit antennas of the transmitter device 100.
  • the method further comprises grouping 330 the spatially precoded symbols of all first groups into a set of second groups, wherein each second group is associated with one of the T transmit antennas.
  • the method further comprises spectrally precoding 340 at least one spatially precoded symbol of at least one second group by means of a projection precoder to obtain spectrally precoded symbols; multicarrier modulating 350 the at least one spectrally precoded symbol to obtain a multicarrier signal s a for the at least one second group; transmitting 360 the multicarrier signal s a for the at least one second group on its associated transmit antenna over the multicarrier wireless communication system 200.
  • Fig. 3 illustrates yet another embodiment of a transmitter device 1 00 according to the present invention.
  • the transmission symbols for transmission are grouped into first groups of transmission symbols associated with the same subcarrier among the available subcarriers at the transmitter device 100.
  • a spatial precoder For each subcarrier k 0 , ... , k K _ 1 , a spatial precoder carries out spatial precoding of the associated group of transmission symbols in each first group, resulting in spatially precoded symbols (weights), wherein each symbol is associated with one of the transmit antennas used by the transmitter device 100. There is no difference between weights and what in this disclosure denote symbols.
  • spatially precoded symbols are then grouped in second groups of spatially precoded symbols associated with the same transmit antenna used by the transmitter device 100.
  • a spectral projection precoder whose output signal can be represented as a sum of the input signal and a low-amplitude noise-like modulating signal, carries out spectral precoding of the second groups of spatially precoded symbols, resulting in spectrally precoded symbols, wherein each spectrally precoded symbol is associated with one of the many subcarriers used by the multicarrier system 200.
  • a multicarrier modulator employs multicarrier modulation on the spectrally precoded symbols generating a multicarrier signal to be transmitted by the associated transmit antenna.
  • the multicarrier signal is transmitted in the multicarrier wireless communication system by its associated transmit antenna of the transmitter device 100.
  • Fig. 4 illustrates a wireless communication system 200 comprising an embodiment of the present invention.
  • the transmitter 100 is implemented in a base station of a cellular system.
  • the system may e.g. be a 3GPP communication system such as LTE or LTE Advanced, but can be any other suitable multicarrier system.
  • four user devices e.g. User Equipment, UE, in LTE terminology
  • 400a, 400b, 400c,..., 400n are receiving downlink multicarrier multi-antenna transmission signals 5 from the base station.
  • the transmitted signal is a multicarrier signal spatially precoded and subsequently spectrally precoded according to the present invention.
  • the user devices 400a, 400b, 400c,..., 400n receives the multicarrier signals and demodulates and decodes the multicarrier signals.
  • the present transmitter device 100 is however not limited to downlink transmissions but can also be used in uplink transmissions or in inter-device communications in wireless communication systems without the downlink and uplink concepts.
  • the projection precoder is based on a constraint matrix A .
  • the resulting precoder turns for each OFDM symbol and for each transmit antenna the vector w s of spatially precoded weights into the vector w f , being the solution to the condition
  • projection precoder has the form
  • Two particular condition matrices A can, for instance, be used in equations (1 )-(3), according to the following two embodiments.
  • the matrix A reflects the condition that the spectrum of the emitted signal must have zeros at the predefined frequencies / 0 , / 1( ...,f M _ x .
  • the matrix A has as its entry on row m and column k, e T ' sine, ⁇ l + ⁇ )(k - f m T s ) (4)
  • each element a k of column k and row m of the constraint matrix A has the form
  • T g is a length of a cyclic prefix of a multicarrier symbol
  • T S T - T g
  • T is a total length of the multicarrier symbol
  • f m is a fixed precoder design-frequency.
  • the fixed precoder design-frequencies uniquely determine the spectral precoder. These frequencies also uniquely determine the spectrum of the resulting transmit signal. These frequencies can be chosen/used/deployed freely, and typically reside in the spectrum outside the desired signal's bandwidth. For different signal bandwidths and/or different out-of-band power emission requirements different sets of frequencies (and hence different precoders) are chosen/used/employed in the transmitter.
  • the matrix A reflects the condition that the multicarrier symbol's initial and last values, as well as the signal's first N derivatives in these time instants are zero.
  • the constraint matrix A has in this embodiment the form
  • T g is a length of a cyclic prefix of a multicarrier symbol
  • T S T - T g
  • T is a total length of the multicarrier symbol
  • N is an integer
  • k 0 , ... , k K _ 1 are the subcarrier indices.
  • the spectral precoding step is only applied to subcarriers not carrying pilot or reference symbols.
  • the pilot-carrying subcarriers therefore pass the spectral projection precoder step of the present transmitter 100 unchanged. This allows the receiver to perform channel estimation with the same performance as in a conventional reference system without spectral precoding.
  • the at least one spatially precoded symbol of the at least one second group are based on data transmission symbols and the remainder of the spatially precoded symbols of the at least one second group are based on reference (or pilot) transmission symbols.
  • Figs. 5 and 6 illustrate the performance of the present invention scheme as labelled "precoder, projection" compared to a traditional MIMO multiplexing scheme without any spectral precoding.
  • the Y-axis of Fig. 5 shows power spectral density and the X-axis shows the frequency offset.
  • the Y-axis of Fig. 6 shows probability of coded bit error and the X-axis shows the SNR in dB.
  • the figures show the performance of a rate 0.5 turbo-coded, QPSK modulated Long Term Evolution (LTE) system with 600 subcarriers operating in 5 MHz.
  • LTE Long Term Evolution
  • a key achievement of the present invention here is the fact that while suppressing the out-of-band emission significantly as shown in Fig. 5, the coded bit error rates are virtually unaffected as shown in Fig. 6.
  • the MIMO precoder used in these figures is an open-loop multiplexing scheme where two streams of information are multiplexed using a spatial precoder reflected by a 2x2 identity matrix on each subcarrier. This is similar to one of the operation modes in the LTE standard.
  • Other MIMO schemes than the multiplexing schemes addressed in the figures are likely to be robust to the effect of the spectral precoder. While the distortion will become visible for very high diversity orders (the more diversity a scheme provides, the more will the channel become Gaussian), it is likely that MIMO scheme with realistic, low diversity orders, still will be robust to this interference
  • any method according to the present invention may be implemented in a computer program, having a program code, which when run by processing means causes the processing means to execute the steps of the method.
  • the computer program is stored in a computer readable medium of a computer program product.
  • the computer readable medium may comprises of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.
  • the present transmitter device 100 may be a standalone device or an integrated part of another communication device, such as base stations (including micro, pico, and femto stations), remote radio heads, relay nodes, etc. However, the present transmitter device 100 may also be a standalone device or an integrated part of user devices having wireless communication capabilities and multiple antennas, such as smart phones, laptops, tablet computers, etc.
  • the present transmitter device comprise the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution.
  • means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.
  • the processors of the present transmitter device may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, processing means, or other processing logic that may interpret and execute instructions.
  • CPU Central Processing Unit
  • ASIC Application Specific Integrated Circuit
  • the expression "processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.
  • the processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Power Engineering (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Radio Transmission System (AREA)

Abstract

La présente invention concerne un dispositif émetteur pour un système de communication sans fil multiporteuse MIMO servant à réduire les émissions spectrales hors bande ou les lobes secondaires. Des symboles spectraux précodés sont ensuite regroupés pour chaque antenne, et un précodage spectral basé sur un précodage par projection est réalisé antenne par antenne avant d'appliquer une transformée de Fourier rapide inverse sur chaque voie d'antenne.
PCT/EP2014/065229 2014-07-16 2014-07-16 Précodage par projection spectrale pour émetteur mimo WO2016008516A1 (fr)

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Cited By (3)

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WO2018054446A1 (fr) * 2016-09-20 2018-03-29 Huawei Technologies Co., Ltd. Réception d'un signal ofdm précodé spatialement et spectralement
CN109075843A (zh) * 2016-03-15 2018-12-21 华为技术有限公司 极化频谱预编码传输
US20210067232A1 (en) * 2019-08-27 2021-03-04 Samsung Electronics Co., Ltd. System and method for providing channel recovery for angle domain sparse channels

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109075843A (zh) * 2016-03-15 2018-12-21 华为技术有限公司 极化频谱预编码传输
CN109075843B (zh) * 2016-03-15 2021-02-09 华为技术有限公司 极化频谱预编码传输
CN112688726A (zh) * 2016-03-15 2021-04-20 华为技术有限公司 极化频谱预编码传输
CN112688726B (zh) * 2016-03-15 2022-04-29 华为技术有限公司 极化频谱预编码传输
WO2018054446A1 (fr) * 2016-09-20 2018-03-29 Huawei Technologies Co., Ltd. Réception d'un signal ofdm précodé spatialement et spectralement
US20210067232A1 (en) * 2019-08-27 2021-03-04 Samsung Electronics Co., Ltd. System and method for providing channel recovery for angle domain sparse channels
US11539424B2 (en) * 2019-08-27 2022-12-27 Samsung Electronics Co., Ltd System and method for providing channel recovery for angle domain sparse channels
US20230077972A1 (en) * 2019-08-27 2023-03-16 Samsung Electronics Co., Ltd. System and method for providing channel recovery for angle domain sparse channels

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