WO2019125126A1 - Système de communication multiporteuse pour canaux doublement sélectifs utilisant l'étalement en fréquence et l'annulation non linéaire d'interférence - Google Patents

Système de communication multiporteuse pour canaux doublement sélectifs utilisant l'étalement en fréquence et l'annulation non linéaire d'interférence Download PDF

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Publication number
WO2019125126A1
WO2019125126A1 PCT/MX2018/000151 MX2018000151W WO2019125126A1 WO 2019125126 A1 WO2019125126 A1 WO 2019125126A1 MX 2018000151 W MX2018000151 W MX 2018000151W WO 2019125126 A1 WO2019125126 A1 WO 2019125126A1
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Prior art keywords
matrix
data
channel
detection
decomposition
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PCT/MX2018/000151
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English (en)
Spanish (es)
Inventor
Fernando PEÑA CAMPOS
Joaquín CORTEZ GONZÁLEZ
Ramón PARRA MICHEL
José Alberto DEL PUERTO FLORES
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Centro De Investigación Y De Estudios Avanzados Del Instituto Politécnico Nacional
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Publication of WO2019125126A1 publication Critical patent/WO2019125126A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26

Definitions

  • Multi-carrier communication system for doubly selective channels using frequency dispersion and non-linear interference cancellation.
  • the present invention is related to the field of telecommunications, specifically to the implementation of a muiti-carrier communication system using orthogonal frequency modulation (OFDM: orthogonal frequency multiplexing division) that allows establishing broadband wireless links in environments with high mobilities such as vehicle-to-vehicle connections (V2V: vehicle ⁇ o vehicie).
  • OFDM orthogonal frequency modulation
  • V2V vehicle ⁇ o vehicie
  • V2V wireless communications links has had a great boom in recent years, this due to its main applications in terms of control and road safety as it is: avoid congestion of main roads, crash prevention, autonomous vehicles, remote tracking of vehicles, etc.
  • Different campaigns of measurements and sounding of the channel in V2V environments verify the existence of high frequencies of Doppier dispersion (greater than 600 Hz) and non-stationary statistics of the channel, which causes that the interference between subpor ⁇ adoras ( ⁇ CI: in ⁇ ercarrier interference) is one of the main problems that affect the performance of the various stages in the receiver.
  • the 802.11p standard retains a frame structure equal to that of the 802.11a / g / n standard, that is, it was not specifically designed to support the V2V channel conditions, which causes the received signal to experience high levels of ICI that eventually impact significantly reducing the performance of the system.
  • US20100098146 and US9621389 present systems with data estimators that include the iCI and offer better performance than conventional receivers. However, they strictly require the modification of! standard 802.1 1 p to be able to introduce extra training sequences, which decreases the spectral efficiency of! system and represents a compatibility problem. A) Yes same, they use cane estimators! with an observation window that covers a large number of GFDM symbols, which greatly impacted the memory required for its implementation, as well as the system's presence.
  • MI maximum likelihood detector
  • EP0521744A3 has the best performance, but its complexity increases abruptly with the constellation size and the number of subcarriers of data, so its implementation in a system that operates In real time it is not viable.
  • MIMO multiple input multiple output
  • DFE decision feedback equalizer
  • Figure 1 shows a diagram generated! of a vehicle-to-vehicle communication link.
  • Figure 2 shows the structure of the transmitter! communication system proposed for V2V communication incorporating a frequency dispersion scheme.
  • Figure 3 shows the structure of! receiver of the low complexity communications system proposed for V2V communication using frequency dispersion and non-linear interference cancellation.
  • Figure 4 shows a diagram exemplifying the search tree used by the algorithm M to perform the detection of the data.
  • Figure 5 shows the performance of a V2V link using the system proposed in this invention compared to the performance obtained using other reception techniques for existing V2V systems.
  • FIG. 1 shows the vehicle-to-vehicle transmitter (101) that incorporates data modulation along with digital baseband processing and analog conversion for transmitting the signal on the transmitting antenna (103), the signal The carrier travels through the V2V channel Wirelessly by electromagnetic waves to the receiving antenna (104).
  • the V2V receiver (102) the signal is demodulated and the analog / digital processing is performed to detect the sent data.
  • x '- n ⁇ is the transmitted OFDM block, is the received signal, is the answer of the cane! in the "-th", for an impulse as input into the ⁇ -th previous sample;
  • ⁇ ' N denotes the operation of modulus N, it is the additive circular Gaussian white noise and symmetric, with zero mean and variance cr, - circular convocation between the response to! channel impulse (R! G) and x M can be rewritten in terms of matrices and vectors such as:
  • H is a dimension matrix x ⁇ composed of the elements of the RiC in the form:
  • u Gs -fz, (VI!)
  • TDF discrete Fourier transform
  • MFC matrix channel response in the frequency domain
  • G takes the form of a diagonal matrix involving an ICI free system for which data defection is simple, however, in V2V environments due to the high mobility both of the transmitter and the receiver, the Doppler spread is significant, causing the matrix G to have energy in the components outside the main diagonal, causing ICI.
  • the receiver described in the following section of this invention combines the time-variant channel estimator iteratively coupled to the non-linear detection of data and a precoding scheme that allows obtaining ICI-free pilots in a single iteration, exploitation of the channel diversity and rapid convergence in the data detection stage.
  • DPSS discrete prolate spheroidai sequences
  • band system is the maximum dispersion of! delay time and D is the maximum frequency of Doppler scattering.
  • the subscript p denotes the sub-sampling of the vectors and matrices in the rows and columns corresponding to the position of the pilots.
  • index variable i q + M r) (r- ⁇ ⁇ 0 £ r £ M T 0 £ q £ M n - ⁇ la
  • any of the representations such as the impulse response and the channel transfer function can be calculated directly by performing the weighted sum of the functions of the base.
  • the estimated MFC can be calculated using the expression: Dispersion DF T.
  • the selectivity of the cane! V2V renders detection errors susceptible to OFDM systems because the local power of some subcarriers may be low due to deep fading, which makes it impossible to detect the transmitted data.
  • DFTS frequency spreading pre-coding technique
  • FFT fast Fourier transform
  • the elements transmitted in frequency in the positions of the data are constructed by applying to the data symbols in the vector ⁇ the Fourier matrix whose elements are determined by:
  • D and D are the vector of the received signal and the noise vector respectively, each in the
  • the matrix D is obtained by taking the columns and rows of t G " at the positions of the data carriers
  • the term ⁇ 3 ⁇ 4 pSp represents the interference in the carriers with data from the carriers with pilots.
  • the main point of innovation in the present invention is the efficient integration of DFTS precoding into e! process of the detection of the data in the receiver.
  • One of the problems of using DFTS in the receiver is reflected in the difficulty to apply non-linear detection algorithms while maintaining low computational complexity since the channel equivalent matrix It does not conserve structure in band, A solution to this disadvantage is to find an operator such that, when applied to the received signal, it reestablishes the band structure of the equivalent channel matrix.
  • the inverse Fourier transform D tai is used that the Cramer-Loéve operator in the channel matrix is completed.
  • the vector received at the position of the data is obtained as:
  • the detection of data using the maximum likelihood criterion can be obtained by finding the values that optimize the following expression; where is the set with all the possible combinations of transmitted symbols and% is the vector with the estimated data symbols.
  • This method of data detection is of great computational complexity due to the exhaustive calculation of all Euclidean distances.
  • the following describes two different methods of data detection that exploit the particular structure of the K matrix in the form of a band to obtain the defection of data in a suboptimal way with reduced computational complexity.
  • the non-line detection method! of low complexity proposed in the present invention consists of two main steps:
  • the QR decomposition is used to obtain the matrices Q and R from the channel matrix with precoding K such that the relation is fulfilled:
  • P is a permutation matrix with reordering as a function of the signal to interference ratio.
  • This decomposition can be carried out using different methods, however, in this invention a variant of the Gram-Schmidt algorithm is used.
  • permutations are made in the position of the columns with the objective that the lines resulting in matrix R are arranged according to their signal-to-noise ratio.
  • the quasibanda structure of the K-matrix is exploited to reduce the computational complexity to the maximum in the calculation of the QR decomposition.
  • K [K
  • the extended matrix is constructed in such a way that it includes noise statistics in the form: rxxxn
  • the advantage of using unit rotations in the orthogonalization process for obtaining the QR decomposition is that it conserves the original energy of all the elements of the original matrix K maintaining the dynamic range of all the variables used in the process. This feature facilitates the implementation of this method in devices for real-time execution using fixed-point arithmetic.
  • the resulting matrix after Ions can be expressed as:
  • the extended matrix is constructed according to the criterion to be used, either LS or MMSE.
  • the matrix is initialized , in which the permutations used for ordering the data elements. 4, The matrix is initialized
  • the band structure of the K matrix implies that one can do without the calculations relating to the large number of elements that are equal to zero. OSiC data detection.
  • the QR decomposition serves as the preprocessing stage in data detection.
  • An effective method to subsequently perform the interference cancellation is the OSiC algorithm which, in combination with the QR decomposition described above, allows the suboptimal detection of data with very low computational complexity.
  • the performance of these two techniques together in V2V systems with DFTS gives very low erroneous bit rates.
  • the QR decomposition of - provides an upper triangular matrix R, an orthogonal matrix of unitary norm Q as well as a. permutation vector P, such that . Ai replace this decomposition in equation (XXVII), you get:
  • the elements of! vector v can be expressed individually as: where! to notation they indicate the ⁇ -th element of the vector and the b - th element of the a - th row of a matrix according to e! case. In this way the detection of each of the data can be done in an iterative manner using the following expression;
  • the operator is used to specify quantization towards the closest symbol of the constellation used by the transmitter W, assuming that in each iteration the previous decisions are correct, the interference of previously detected symbols can be subtracted prior to the detection of the symbol.
  • the decoded symbols are reordered according to the permutation matrix R ,
  • ⁇ "" D as its ancestor nodes.
  • the distance between each node of a ⁇ -th level and the root is defined as the accumulated metric value, which represents the addition of all the metrics of branches from the root to the indicated node.
  • the accumulated metric is obtained from:
  • the optimal vector es is the one whose path minimizes (XLI).
  • the design of the NML detector for the V2V multi-carrier system is based on the incorporation of! algorithm
  • an iterative method of ICi cancellation is used; the main ideal is to use the G- channel matrix estimated in a first iteration to calculate the ICI that contaminates the pilot subcarriers and eliminate it. These pilots with lower ICI are used again to perform channel estimation and data detection. This process can be repeated iteratively for GFDM providing the same symbol in each of the iterations best performance 'in estimating the cana! and the detection of the data.
  • the structure of the transmitter is shown in Figure 2, the bits (201) of data that are input to a convolutional encoder (202) in order to add redundancy to the data. Subsequently the encoded data (203) are scattered using an interleaving block (204), then the interleaved data is modulated in phase and quadrature by means of the modulator (206) which delivers symbols belonging to a certain constellation. The modulated symbols (207) are grouped in blocks by means of the serial to parallel converter (208) to construct a block or vector (209) that is processed by the DFTS precoder (210).
  • the precoded data is input to a carrier dispatcher (212) which assigns the elements to data carriers or piiots as the case may be, likewise assigns the guardians in the corresponding indexes.
  • the output of (212) is then modulated in a conventional orthogonal frequency multiplexing scheme (GFDM) with the help of the IFFT (213), after which the cyclic prefix in (215) is appended to it.
  • GFDM orthogonal frequency multiplexing scheme
  • the converter block parallel to series takes each of the samples of! GFDM block to be delivered as output from the baseband digital processing stage of the receiver.
  • the received signal (301) is converted into blocks with the help of the serial to parallel converter (302), then the prefix cycle is eliminated in the block (303).
  • the received signal is demodulated in a conventional orthogonal frequency multiplexing scheme (GFDM) with the help of the fast Fourier transform block (304).
  • GFDM orthogonal frequency multiplexing scheme
  • the GFDM block in the frequency domain is introduced to a demapping device (308) for extracting the pilot symbols therefrom.
  • the pilots vector (307) is used to perform the estimation of the channel matrices in the domain of time (309) and in the frequency domain (310).
  • the time channel matrix (309) is truncated into major diagonal bands in truncation block (311).
  • the interference from the pilot carriers (312) to the OFDM vector in the frequency domain is subtracted, in order to subsequently perform the inverse operation of DFTS in the e! block called IDFT (314).
  • the proposed GRM block (315) performs the GR decomposition of the temporal channel matrix according to the selected method: LS (ZF) or MMSE, then the detection of data symbols is executed in the proposed Near-lvILD detector (316). (317) by the proposed signal model.
  • deinterlacing (318) and decoding (319) are performed to obtain the vector with the received data.
  • figure 5 is included with the comparison between the performance of the invention described here (NML tag) using only one iteration against the proposed system in EP20100450186 and ER2383985 ⁇ 1 (LMMSE tag) using several iterations. It also shows the maximum performance that a system can achieve in the exact knowledge of the response of! channel (ideal channel label).
  • the evaluation metric is the erroneous bit rate (BER) while the evaluation parameter is the signal-to-noise ratio in the receiver.
  • BER bit rate
  • the proposed invention achieves better performance while requiring a lower number of iterations

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

Abstract

La présente invention concerne un système et un procédé de communication pour parvenir à dépasser les distorsions et les affectations introduites par les canaux de communication V2V. A la différence d'une quelconque invention existante qui fonctionne dans les mêmes conditions, l'appareil décrit utilise une technique de réception complètement nouvelle basée sur le concept de la détection non linéaire de signaux à étalement en fréquence. Le récepteur de cet appareil parvient à atteindre de bonnes performances lors de l'exploitation de manière efficace de la diversité de fréquence conjointement à la structure en bande de la matrice de canal équivalente. Les performances en termes d'immunité de bruit sont bien meilleures que celles obtenues avec n'importe quelle technique connue à ce jour et en outre est nécessaire une quantité bien inférieure de calculs au niveau du récepteur.
PCT/MX2018/000151 2017-12-20 2018-12-14 Système de communication multiporteuse pour canaux doublement sélectifs utilisant l'étalement en fréquence et l'annulation non linéaire d'interférence WO2019125126A1 (fr)

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MX2017016960A MX2017016960A (es) 2017-12-20 2017-12-20 Sistema de comunicación multiplicadora para canales doblemente selectivos utilizando dispersión en frecuencia y cancelación no lineal de interferencia.
MXMX/A/2017/016960 2017-12-20

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CN115426223B (zh) * 2022-08-10 2024-04-23 华中科技大学 一种低轨卫星信道估计和符号检测方法及系统
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US20090116590A1 (en) * 2007-11-06 2009-05-07 Samsung Electronics Co. Ltd. Apparatus and method for detecting signal in multi-antenna system

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US20090116590A1 (en) * 2007-11-06 2009-05-07 Samsung Electronics Co. Ltd. Apparatus and method for detecting signal in multi-antenna system

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