WO2016078724A1 - Procédé d'estimation de canal en présence d'interférence - Google Patents

Procédé d'estimation de canal en présence d'interférence Download PDF

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WO2016078724A1
WO2016078724A1 PCT/EP2014/075205 EP2014075205W WO2016078724A1 WO 2016078724 A1 WO2016078724 A1 WO 2016078724A1 EP 2014075205 W EP2014075205 W EP 2014075205W WO 2016078724 A1 WO2016078724 A1 WO 2016078724A1
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Prior art keywords
channel
reference signal
signal
interfering
interfering signals
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PCT/EP2014/075205
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English (en)
Inventor
Ansgar SCHERB
Aravindh Krishnamoorthy
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Telefonaktiebolaget L M Ericsson (Publ)
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Priority to PCT/EP2014/075205 priority Critical patent/WO2016078724A1/fr
Publication of WO2016078724A1 publication Critical patent/WO2016078724A1/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
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • 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
    • H04L25/021—Estimation of channel covariance
    • 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
    • H04L25/022—Channel estimation of frequency response
    • 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
    • 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
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0242—Channel estimation channel estimation algorithms using matrix methods
    • H04L25/0244—Channel estimation channel estimation algorithms using matrix methods with inversion
    • 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
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0256—Channel estimation using minimum mean square error criteria
    • 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
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0258—Channel estimation using zero-forcing criteria

Definitions

  • the present disclosure generally relates to a technique for performing channel estimation. More specifically, and without limitation, a method and a device are provided for performing channel estimation based on a reference signal received in the presence of an interfering signal.
  • elCIC Enhanced Inter-Cell Interference Coordination Challenges in Heterogeneous Networks
  • the existing elCIC techniques include subframe alignment, i.e., the subframes of an interfering macrocell and a serving picocell or femtocell are aligned. Since their control and data channels overlap with each other, so-called Almost Blank Subframes (ABSFs) are introduced at the interfering macrocell. In the ABSFs, no control or data signals but only reference signals are transmitted.
  • ABSFs Almost Blank Subframes
  • the reference signal of the serving cell overlaps in time and frequency with an interfering reference signal of another cell, so that channel estimation based on the reference signal of the serving cell is compromised, if not impossible.
  • the method may further comprise the step of receiving the received signal.
  • the received signal may correspond to a transmission of the reference signal.
  • the received signal may be interfered by a transmission of the one or more interfering signals.
  • the "transmission of a reference signal” and the “transmission of one or more interfering signals” may refer to the respective signals as transmitted by a
  • the channel may be estimated for less channel components than a number of channel components received in the receiving step or receivable on the channel.
  • the channel may be estimated for L channel components being less than the N channel components of the received signal. L may be a fraction of N.
  • the filtering may include a mapping that maps the reduced number of (e.g., L) channel components to the number of (e.g., N) channel components received in the receiving step or receivable on the channel (and/or vice versa).
  • the L channel components for which the channel is estimated may correspond to L subcarriers.
  • the mapping may not necessarily map the estimated L channel components one-to-one onto a proper subset of L subcarriers.
  • the mapping may include any linear mapping from L dimensions to N dimensions, e.g., in the frequency domain.
  • the mapping may include any linear mapping with rank L, e.g., in the frequency domain.
  • the processing may include the step of computing a linear combination of the reference signal and the one or more interfering signals.
  • the linear combination may be applied to the received signal, e.g., by multiplication.
  • the processing may include multiplying a Hermitian conjugate of the linear combination with the received signal.
  • a result of the filtering may estimate the channel for the time of the transmission of the reference signal.
  • the method may provide a coarse channel estimation.
  • the filtering may not involve time averaging.
  • the reference signal and the interfering signal may overlap in time and frequency.
  • the interference may be time synchronous.
  • the reference signal and the one or more interfering signals may be (at least substantially) synchronized.
  • the linear combination may be computed based on a correlation of the reference signal as sent and the one or more interfering signals as sent.
  • the correlation may be a scalar product of the corresponding sequences.
  • the linear combination may be computed according to
  • Goo Sref + ⁇ k l..n ⁇ 3 ⁇ 4 S if (k) , wherein the symbol S re r represents the reference signal, and the symbol S,f (k) represents the k-th interfering signal of the one or more interfering signals.
  • the symbol c1 ⁇ 2 represents diagonal elements of an inverse of the correlation, e.g., between the reference signal and one of the one or more interfering signals.
  • the processing may further depend on a channel covariance, e.g., of the estimate of the channel on which the reference signal is transmitted and/or further estimates of one or more channels on which the one or more interfering signals are transmitted.
  • a channel covariance e.g., of the estimate of the channel on which the reference signal is transmitted and/or further estimates of one or more channels on which the one or more interfering signals are transmitted.
  • a sum of squares of absolute values of the estimate for the channel used for transmitting the reference signal may be
  • the channel covariance may be time-averaged separately for each of the reference signal and the one or more interfering signals (i.e., for each of the channels).
  • the diagonal elements of the correlation may include the channel covariance.
  • the processing may further depend on a noise power measured at the device.
  • the diagonal elements of the correlation may include the noise power.
  • the received signal may be included in one Orthogonal Frequency-Division
  • Each of the reference signal and the interfering signal may be transmitted as one OFDM symbol.
  • the OFDM symbol transmitted for the reference signal and the one or more OFDM symbols transmitted for the one or more interfering signals may be (at least substantially) synchronized.
  • a length of the OFDM symbol of each of the reference signal and the one or more interfering signals may be equal, e.g., including the N channel components (e.g., the N subcarriers in the frequency domain).
  • the one or more interfering signals may occupy (at least substantially) the same OFDM subcarriers used by the reference signal.
  • a length of the finite impulse response of the filtering may be shorter than or equal to the length of the OFDM symbol.
  • the length of the finite impulse response may be an integer fraction of the OFDM symbol length.
  • the filtering may result in a coarse channel estimation without time averaging over multiple OFDM symbols.
  • the filtering may include a window filter in the time domain or an equivalent thereof in the frequency domain.
  • the filtering may include a sine filter.
  • the filtering may be cyclically applied to the OFDM symbol.
  • a length of the time window may be equal to or shorter than a total delay spread of delay profiles for the reference signal and the one or more interfering signals.
  • the total delay spread may be equal to the sum of the delay spreads of each of the reference signal and the one or more interfering signals.
  • the delay spread may be computed based on a mean delay of the delay profile and/or a root mean square delay of the delay profile.
  • the filtering may be sensitive to subcarriers that are spaced apart in the frequency domain, e.g., by N/L subcarriers and/or according to a coherence bandwidth of the channel.
  • the filter may be characterized by the reduced number of L channel components compared to the number of N channel components (or resource elements) in the OFDM symbol, i.e., L ⁇ N.
  • a computer program product comprises program code portions for performing any one of the steps of the method aspect disclosed herein when the computer program product is executed by one or more computing devices.
  • the computer program product may be stored on a computer-readable recording medium.
  • the computer program product may also be provided for download via a data network, e.g., the telecommunications network using the channel and/or the Internet.
  • a device for performing channel estimation from a received signal comprising a superposition of a reference signal with one or more interfering signals.
  • the device comprising a processing unit adapted to process the received signal based on both the reference signal and the one or more interfering signals; and a filtering unit adapted to filter a result of the processing for estimating a channel on which the reference signal is received.
  • a mobile terminal is provided.
  • the mobile terminal is connected or connectable to a cellular telecommunications network via a wireless channel based on a reference signal transmitted on the channel.
  • the mobile terminal includes the device according to the above aspects.
  • Fig. 1 schematically illustrates a heterogeneous network
  • Fig. 2 schematically illustrates a time-frequency grid including cell-specific
  • FIG. 3 shows a schematic block diagram of a device for performing channel estimation in the network of Fig. 1;
  • Fig. 4 shows a flowchart for a method of performing channel estimation impiementable by the device of Fig. 3;
  • Fig. 5 shows a schematic block diagram of a processing chain in a mobile
  • Fig. 6 schematically illustrates further details of a first embodiment of the
  • Fig. 7 schematically illustrates a variant of the first embodiment of the device of
  • FIG. 8 schematically illustrates further details of a second embodiment of the device of Fig. 3;
  • Fig. 9 shows a diagram for comparing channel power of a wireless channel underlying a numerical simulation and estimated by the device of Fig. 7;
  • Fig. 10 shows a diagram of mean square error as a function of signal to
  • Fig. 1 schematically illustrates a telecommunications network 100 as an exemplary environment for implementing the technique.
  • the telecommunications network 100 includes cells 102 and 104 in which mobile device 110 and 112 wirelessly accesses the telecommunications network 100 via basis stations 106 and 108, respectively.
  • the basis stations 102 and 106 are also to refer to as evolved Node B (or eNodeB) in an LTE implementation or as Access Point (AP) in a WLAN implementation.
  • the base station 106, 108 may be part of an Internet Protocol Connectivity Access Network (IP-CAN).
  • IP-CAN Internet Protocol Connectivity Access Network
  • the cells 102 and 104 of the telecommunications network 100 overlap.
  • HetNet heterogeneous network
  • the picocell 102 is overlaid by the macrocell 104.
  • Each of the cells 102 and 104 transmits a reference signal.
  • the mobile device 110 is wirelessly connected to the cell 102 by estimating a downlink channel from the base station 106 to the mobile device 110.
  • a channel frequency response for the wireless transmission between the base station 106 and the mobile device 110 is estimated.
  • the mobile device 112 is wirelessly connected to the cell 104 and estimates the wireless channel between the base station 108 and mobile device 112.
  • the following description focuses for clarity on the channel between the cell 102 and the mobile device 110 considering the cell 104 as an interferer.
  • the technique is directly applicable also for estimating the other channel between the cell 104 and the mobile device 112 considering the cell 102 as the interferer.
  • the designation of primary reference signal and secondary reference signal may be interchanged.
  • the term "mobile”, as used herein, does not necessarily require that the mobile device is moving.
  • the mobile device may also encompass any portable device that is at least temporarily operated at a certain position with the cell 102 or 104.
  • the channel estimate may be time-dependent even while the mobile device 110 is not moving, e.g., due to a rotation of the mobile device and/or moving objects within the wireless channel.
  • Fig. 2 schematically illustrates resource elements in a time-frequency grid 200, e.g. on the downlink channel between the mobile station 106 and the mobile device 110.
  • Time is shown on the horizontal axis 204 in Fig. 2.
  • Frequency is shown on the vertical axis 206 in Fig. 2.
  • the time-frequency grid 200 shown in Fig. 2 covers one subframe 204 in the time direction.
  • One subframe includes two slots 208.
  • OFDM Orthogonal Frequency Division Multiplexing
  • the time-frequency grid 200 shown in Fig. 2 includes 12 subcarriers in the frequency direction 206, which corresponds to one Resource Block (RB) per slot 208.
  • RB Resource Block
  • Resource Element corresponds to the complex value transmitted or received at the subcarrier k in the OFDM symbol I.
  • a predefined reference signal is transmitted.
  • the REs 202 are collectively referred to as the reference signal 202.
  • the reference signal transmitted by each of the cells 102 and 104 is also referred to as a Cell-specific Reference Signal (CRS).
  • CRS Cell-specific Reference Signal
  • MIMO Multiple Input Multiple Output
  • the reference signal 202 illustrated in Fig. 2 is transmitted on antenna port 0. While the reference signal for one antenna port are transmitted, all other antenna ports used by the MIMO channel are muted.
  • the transmission of the CRS 202 in the cell 102 may be viewed as a single antenna port transmitting the CRS 202, since the other antenna ports remain muted during the transmission.
  • the technique is descripted in what follows for a single antenna port without loss of generality.
  • the channel to be estimated may relate to the wireless transmission from the antenna port transmitting the reference signal 202 to any one of the one or more receive antennas, e.g., of the mobile device 110.
  • the reference signal 202 transmitted by the cell 102 is subjected to interference by those reference signals 202 that are synchronously transmitted on the same frequency by the cell 104.
  • Such interference is possible, e.g., in LTE- Advanced systems including an enhanced Inter- Cell Interference Coordination (elCIC) according to standard document 3GPP TS 36.300 (e.g. Version 12.3.0) for heterogeneous networks (also abbreviated by "HetNets").
  • elCIC Inter- Cell Interference Coordination
  • FIG. 3 schematically illustrates a block diagram of a device 300 for performing channel estimation.
  • a receiving unit 302 is provided with a received signal that includes both contributions of the reference signal 202 transmitted by the cell 102 and an interfering reference signal 202 transmitted by the cell 104. While the reference signals 202 transmitted by the cells 12 and 104, respectively, are transmitted at corresponding times and frequencies, the value of the REs
  • the receiving unit provides the received signal in the frequency domain to a processing unit 304, which analyzes the received signal based on the reference signal 202 as transmitted by the cell 102 and the interfering signal 202 as
  • the processing partly estimates the channels for the transmission from the cells 102 and 104, e.g., to the extent possible given the correlation properties of the transmitted signals.
  • a result of the processing is provided to a filtering unit 306, which extracts the channel estimate for the downlink channel from the base station 106.
  • the device 300 may be included in any one of the mobile devices 110 and 112.
  • Fig. 4 shows a flowchart for a method 400 of performing channel estimation.
  • a signal is received.
  • the received signal is, besides noise and/or unknown interference, a combination of the reference signal 202 as received at the device 300 from the cell 102 and an interfering signal as received at the device 300, e.g., the interfering reference signal 202 from the cell 104.
  • the received signal is processed in a step 404 based on the signals as transmitted. From the processed signal, the channel estimate is extracted in a filtering step 406.
  • the device 300 may be operated according to the method 400. E.g., the steps 402 to 406 may be performed by the units 302 to 306, respectively.
  • the channel impulse response in the time domain or the channel frequency response in the frequency domain is estimated according to a linear channel model. If the interfering signal transmitted by the cell 104 was absent, the channel could be estimated with the linear channel model and the usual assumptions as to consistency of the channel model, i.e., existence of a solution of the model.
  • the solution may be uniquely defined by an optimization criterion. E.g., the channel estimate minimizes a square error or any other optimization criterion.
  • a typical signal processing chain 500 for channel estimation in the mobile device 110 is shown in the block diagram of Fig. 5.
  • a Coarse Channel Estimation block 300 which uses a scheme with minimal assumptions, e.g., least- squares, to perform a first-level channel estimation (also referred to as coarse channel estimate, h_c).
  • Minimal assumptions have the benefit that the coarse channel estimates contain all the information present in the received signal so that parameter estimation can be performed efficiently.
  • the first-level channel estimates, h_c are used for further estimating parameters such as frequency offset, Doppler spread and delay spread of the channel in the Parameter Estimation block 502. These parameters are then processed for, e.g. filtered, to generate parameters of high reliability in a Parameter Processing block 504.
  • the filtering in the block 502 includes time averaging over multiple OFDM symbols, I, or slots 208, which are used to process the coarse channel estimates h_c to generate channel estimates in a Channel Estimates Processing block 506.
  • the REs of the reference signal 202 within the same OFDM symbol are collectively referred to as a reference symbol. The technique may be applied for each reference symbol separately.
  • the reference symbol transmitted by the cell 102 is represented by a sequence s 1 including N complex numbers.
  • the last term, v, represents a noise component on the channel
  • the symbol h x is a column vector representing the channel estimate in the frequency domain (also referred to as the channel frequency response).
  • MMSE Minimum Mean Square Error
  • channel estimation is performed in the presence of known time- synchronized intra-frequency reference symbol interference.
  • Data interference is not considered, e.g., as it is absent in ABSFs or unknown and, thus, a contribution to the noise term in Eq. (1).
  • a first conventional approach of ignoring the interference for the purpose of the coarse channel estimation leads to coarse channel estimates that have high noise.
  • a second conventional approach of a simple joint estimation is only possible in the least-square sense as the linear system is under-determined. Noteworthy, two N length sequences, which do not interfere with each other under cyclic correlation, do not exist as they would demand 2N orthogonal dimensions in an N dimensional space. Consequently, a conventional joint estimation technique relying upon all N channel components is not feasible. In both cases the quality of the coarse channel estimates and the following outputs is significantly hampered. A low quality of the channel estimation degrades the system performance and throughput. If they existed, the joint estimation technique would have worked.
  • a first embodiment of the device 300 uses only assumptions Al and A2.
  • a block diagram for the first embodiment of the device 300 in the processing chain 500 is schematically illustrated in Fig. 6.
  • a second embodiment of the device 300 uses the three assumptions Al, A2 and A3.
  • a block diagram for the second embodiment of the device 300 embedded in the processing chain 500 is schematically illustrated in Fig. 8.
  • the second embodiment achieves an even lower computational complexity than the first embodiment.
  • an implicit assumption about constancy of channel estimates along the time direction within an OFDM symbol is made, which is reasonable for interference scenarios such as HetNet, e.g., since high-speed motion is unlikely to occur along with a synchronized interferer as the primary contribution to a varying channel is the frequency shift due to motion.
  • An offset due to a mismatch of the Local Oscillator (LO) at the receiver may be corrected prior to downlink initiation.
  • LO Local Oscillator
  • the assumption Al is that the reference signal (also referred to as primary reference sequence) and the one or more interfering signals (also referred to as interfering reference sequences) are linearly independent.
  • a combined channel is defined by stacking one channel after another, including the reference signal followed by the one or more interfering signals.
  • the assumption A2 is that delay spreads of an impulse response of the combined channel is less than the OFDM symbol length.
  • the assumption A2 is reasonable (e.g., for LTE) as mobile telecommunications systems (such as LTE) cope with delay spreads that are less than the cyclic prefix length by design. For example, two times the cyclic prefix length (i.e., for one interferer) is less than the OFDM symbol length.
  • the assumption A3 is that among N interferes, (N + 1) times the highest delay spread is less than the ODFM symbol length, and that the reference signals (e.g., as transmitted) exhibit good correlation properties for time lags (i.e., time differences between the reference signals) up to the highest delay spread.
  • the assumption A3 requires that one can find sequences that do not interfere with each other under cyclic correlation up to a certain time lag.
  • Good correlation properties means that a circular auto-correlation and/or a circular cross-correlation of the corresponding sequences is non-zero for zero time lag and substantially zero for time lags up to the length of the highest delay spread.
  • the one or more interferes e.g., neighboring picocells
  • use circularly shifted CRS sequences for the primary and secondary reference signals with time-shifts greater than the highest delay spread or cyclic prefix length special methods are not required since the sequences would be orthogonal up to some time lag.
  • Both the first embodiment and the second embodiment can be implemented in the frequency domain and/or in the time domain. In what follows, the focus is on frequency domain implementations.
  • the first embodiment implements a joint least square-like coarse channel estimator, which uses the known reference signal and the known interfering signal (e.g., a primary reference sequence and an interfering reference sequence) in the processing step 404.
  • the mapping in the step 406 is generated from, or representable by, the first few columns of a Discrete Fourier Transform (DFT) matrix.
  • DFT Discrete Fourier Transform
  • the second embodiment uses the known reference signal and the known interfering signal (e.g., a primary reference sequence and an interfering reference sequence) in the processing step 404 to generate a modified reference sequence.
  • the modified reference sequence is a linear combination of the reference signal and the interfering signal.
  • the modified reference signal processed with an existing coarse channel estimator, followed by a low-pass filter in the filtering step 406.
  • the mapping generated from, or representable by, the first few columns of a Discrete Fourier Transform (DFT) matrix and its Hermitian conjugate is applied in the filtering step 406.
  • DFT Discrete Fourier Transform
  • the coarse channel estimator is suboptimai.
  • the noise in the coarse channel estimates is then directly related to the circular auto-correlation and cross-correlation values for non-zero time lags.
  • the second embodiment still achieves a valuable suboptimai channel estimation.
  • all embodiments are applicable, e.g., whenever the assumptions Al and A2 are fulfilled.
  • D denote the first L columns of the N x N OFT matrix
  • M denote the square matrix formed by picking rows from D that are N/L rows apart, starting with the first row.
  • M is the L x L DFT matrix, which is not essential for the technique.
  • An expansion matrix E is constructed according to
  • the channel estimate is mapped or expanded to length N in the frequency direction.
  • the expansion matrix is also applicable to a time-averaged channel estimate.
  • the Hermitian conjugate of the expansion matrix, E" can be applied from the left to the matrix 5 ⁇ representing the reference signal 202 transmitted by the cell J, or the expansion matrix E can be applied from the right to the matrix s ⁇ , so that the N channel components of the transmitted signal are processed in the step 404 on the level of the L channel components.
  • v is the noise component.
  • the column vectors h r and h 2 are the channel estimates, each having length L, in the frequency domain for the primary and interfering channels, respectively.
  • the channel estimates of length L are representative of the channel estimates of length /v. At least under certain conditions, it can be shown that processing of the sequences on the level of L channel components is sufficient for reconstructing the processed channel estimates of length N (i.e., the output of the Channel Estimates Processing block 506).
  • n Lx2L and/or the application of the expansion matrix E may be attributed to the filtering step 406.
  • n Lx2L is a I x 2L matrix with ones along the main diagonal.
  • a variant of the first embodiment is described with reference to the block diagram 500 shown in Fig. 7.
  • the block diagram 500 in Fig. 7 schematically illustrates a signal flow according to the variant of the first embodiment.
  • the additional knowledge can be incorporated as a-priori information into the technique.
  • the a-priori information can be obtained by evaluating coarse channel estimates over a long period, e.g. multiple OFDM symbols, multiple slots or longer periods of time, e.g. by means of the
  • Parameter Estimation block 502 indicated in each of the Figs. 6 to 8.
  • a variety of existing statistical techniques for implementing long term channel parameter estimation in the block 502 is available.
  • the channel parameters are input for the long-term filtering in the Channel
  • Fig. 7 represents the signal flow for the variation of the first embodiment.
  • the Parameter Estimation block 502 corresponds to block 502 of the first
  • the block 502 gets as input the coarse channel estimates and h 2 as well as the filtered channel estimates t and h 2 .
  • the block 502 outputs an estimate of the noise variance power ⁇ adjuance matrices R X and R 2 , which is shown at reference sign 702.
  • the Parameter Processing block 504 includes the channel estimation filtering matrix.
  • the Parameter Processing block 504 is provided with the two reference sequences S 1 and S 2 (or, in a further variant, only the product S"S 2 ) and the channel parameter as derived by the Parameter Estimation block 502.
  • the channel estimation filtering matrix is calculated as
  • the full channel estimate having length N is obtained, as in the first embodiment, according to Eq. (7).
  • the full channel estimate having length N which is also referred to as the coarse channel estimate, are given by: h ⁇ EE ⁇ a ⁇ + a ⁇ y, (14)
  • the multiplication with EE" in the step 406 may be interpreted as an FFT after application of a rectangular window of length L on an IFFT result of S m y or equivalents, as low-pass filtering of S m y with an equivalent sine filter in the frequency domain.
  • Fig. 9 shows a diagram 900 with channel magnitude on the vertical axis and the subcarrier on the horizontal.
  • the diagram 900 illustrates the channel estimation technique for the second embodiment in a noiseless condition in detail.
  • the conventional Least Squares channel estimate 902 results from ignoring the
  • Fig. 10 shows that the first embodiment shown at reference sign 1004 and the second embodiment shown at reference sign 1006 are equivalent when noise dominates.
  • Both embodiments perform better than the conventional least squares technique shown at reference sign 1002 (also referred to as simple least square technique).
  • the technique allows reference symbol interference mitigation in the channel estimator, e.g., in the presence of known time and frequency synchronous
  • At least some implementations achieve a computationally efficient coarse channel estimation using a modified reference signal sequence based on both the primary and interfering sequences.
  • the modified signal is compatible with existing coarse channel estimators followed by filtering.
  • the embodiments may be implemented exclusively in the frequency domain.
  • the technique can mitigate the effects of a known intra-frequency time-synchronized interferer on reference symbols with no data interference. At least some
  • Heterogeneous Network thereby improving the receiver performance and data throughput.
  • HetNet Heterogeneous Network
  • At least some embodiments provide a low-complexity technique to extend the existing OFDM receivers to handle such interferers.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

L'invention concerne un procédé d'estimation de canal. Dans un aspect du procédé, un signal est reçu. Le signal comprend une superposition d'un signal de référence avec un ou plusieurs signaux brouilleurs. Le signal reçu est traité d'après à la fois le signal de référence et le ou les signaux brouilleurs. Un résultat du traitement est filtré pour estimer un canal sur lequel le signal de référence est reçu.
PCT/EP2014/075205 2014-11-20 2014-11-20 Procédé d'estimation de canal en présence d'interférence WO2016078724A1 (fr)

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Publication number Priority date Publication date Assignee Title
EP3609093A1 (fr) 2018-08-09 2020-02-12 FRAUNHOFER-GESELLSCHAFT zur Förderung der angewandten Forschung e.V. Relais et unité de réception
WO2024108534A1 (fr) * 2022-11-25 2024-05-30 Oppo广东移动通信有限公司 Procédé et dispositif de communication

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JENS BALTERSEE: "On the Capacity of Multiple-Input Multiple-Output Wireless Systems with Data-Aided Channel Estimation passage", ON THE CAPACITY OF MULTIPLE-INPUT MULTIPLE-OUTPUT WIRELESSSYSTEMS WITH DATA-AIDED CHANNEL ESTIMATION, SHAKER VERLAG, AACHEN, DE, 1 January 2002 (2002-01-01), pages 49 - 55, XP002418073 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3609093A1 (fr) 2018-08-09 2020-02-12 FRAUNHOFER-GESELLSCHAFT zur Förderung der angewandten Forschung e.V. Relais et unité de réception
WO2024108534A1 (fr) * 2022-11-25 2024-05-30 Oppo广东移动通信有限公司 Procédé et dispositif de communication

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