EP1023784A2 - Procede et dispositif de reception pour l'estimation de canaux dans des systemes de telecommunication - Google Patents

Procede et dispositif de reception pour l'estimation de canaux dans des systemes de telecommunication

Info

Publication number
EP1023784A2
EP1023784A2 EP98954234A EP98954234A EP1023784A2 EP 1023784 A2 EP1023784 A2 EP 1023784A2 EP 98954234 A EP98954234 A EP 98954234A EP 98954234 A EP98954234 A EP 98954234A EP 1023784 A2 EP1023784 A2 EP 1023784A2
Authority
EP
European Patent Office
Prior art keywords
channel
data symbols
channel coefficients
coefficients
receiving device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP98954234A
Other languages
German (de)
English (en)
Inventor
Leo Rademacher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP1023784A2 publication Critical patent/EP1023784A2/fr
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • H04L25/0212—Channel estimation of impulse response

Definitions

  • the invention relates to a method and a receiving device for channel estimation in communication systems with transmission channels between radio stations, at least one of which is movable.
  • messages for example voice, image information or other data
  • radio communication systems this is done with the aid of electromagnetic waves via a radio interface.
  • the electromagnetic waves are emitted at carrier frequencies that lie in the frequency band provided for the respective system.
  • GSM Global System for Mobile Communication
  • the carrier frequencies are in the range of 900 MHz.
  • UMTS Universal Mobile Telecommunication System
  • 3rd generation systems frequencies in the frequency band of approx. 2000 MHz are provided.
  • the emitted electromagnetic waves are attenuated due to losses due to reflection, diffraction and radiation due to the curvature of the earth and the like. As a result, the reception power that is available at the receiving radio station decreases. This damping is location-dependent and also time-dependent for moving radio stations. If the mobile station moves very quickly, the channel conditions of a transmission channel change considerably even over a short period of time. In the case of multipath propagation, several signal components arrive at the receiving radio station with different delays. The influences described describe the connection-specific transmission channel.
  • a radio communication system is known from DE 195 49 148, which uses CDMA subscriber separation (CDMA Code Division Multiple Access), the radio interface additionally lending a time-division multiplex subscriber separation (TDMA Time
  • a JD method joint detection
  • JD method joint detection
  • at the receiving end in order to carry out improved detection of the transmitted data with knowledge of CDMA codes of several participants. It is known that at least two data channels can be assigned to a connection via the radio interface, each data channel being distinguishable by an individual spreading code.
  • transmitted data are transmitted as radio blocks (bursts) within time slots, mid-ambiences with symbols known in the receiving radio station being transmitted within a radio block.
  • These midambles can be used in the sense of training sequences for tuning the radio station on the reception side.
  • the receiving radio station uses the midambles to perform a channel estimate, i.e. an estimate of the channel impulse responses for different transmission channels.
  • channels designated by different CDMA codes can be set up in parallel for training sequences and user data.
  • the channel impulse response of a transmission channel also changes within a transmitted radio block, so that only parts of a radio block are used for channel estimation. Regardless of the channel conditions, a fixed number of equidistant channel coefficients is determined. However, this channel estimate is inaccurate.
  • the invention has for its object to provide a method and a receiving device for channel estimation, which is reliable despite the fast movement of the mobile station Allow determination of channel coefficients.
  • the object is achieved by the method with the features of claim 1 and the receiving device with the features of claim 11.
  • a receiving station in the method for channel estimation in communication systems with transmission channels between radio stations, at least one of which is movable, a receiving station consists of a data symbol
  • the data symbols are modified by a transmission method, e.g. through spreading, modulation and channel distortion.
  • the reception signal is broken down into individual samples on the reception side and compared with known data symbols to determine channel coefficients, with individual known data symbols of the reception signal being stored in the reception station.
  • the fact that a reduced number of channel coefficients is determined for fast-moving mobile stations improves the estimation accuracy for these channel coefficients.
  • the disproportion of short sub-blocks of the received signal to the long desired channel impulse responses is eliminated and the accuracy of the estimated channel impulse response is improved. With mobile stations moving more slowly, a larger number of channel coefficients is determined.
  • This type of channel estimation can also be used to shift limits for the speed of a radio station and the permissible channel conditions without simultaneously having to lengthen the training sequences or reduce the data rate.
  • the invention is applicable both to a transmission between a base station and a mobile station, and to a transmission between mobile stations.
  • the known data symbols are compared with samples of data symbols in the transmitted training sequence or the known data symbols are stored after data detection and then compared with the originally received samples. In this way, it is possible either to use undistorted known data symbols which allow a more precise channel estimation at the expense of a lower user data rate.
  • an accurate data estimate is a prerequisite for the subsequent comparison of the channel coefficients. However, this can be used to improve the channel estimation during the evaluation of parts of a radio block that do not contain any training sequences.
  • a further embodiment of the invention provides that when determining the channel coefficients a reduced number of values of the known data symbols, i.e. the training sequence or the estimated data symbols. In this way, accurate and current estimates for the channel coefficients are obtained even with a shortened period of time for sample values to be evaluated.
  • the channel coefficients to be determined are selected in such a way that on average they are more powerful than unselected values. This ensures that even a reduced number of channel coefficients describe the transmission channel with sufficient accuracy and forms a good basis for a subsequent data estimation using the channel coefficients.
  • the selected values can be taken from a previously determined larger number of channel coefficients. Consequently, according to the invention, only the significant channel coefficients are repeatedly calculated from a preceding channel estimate. The selection of the channel coefficients to be determined is repeated at larger intervals in order to take into account the development of the meaning of individual channel coefficients which are not constantly calculated. > ) IV ) 'y-> no Cn O Cn o Cn
  • FIG. 1 shows a block diagram of a mobile radio network
  • FIG. 5 shows a block diagram of a digital signal processing cleaning agent
  • FIG 7 a flowchart of channel estimation.
  • the structure of the radio communication system shown in FIG. 1 corresponds to a known GSM mobile radio network which consists of a multiplicity of mobile switching centers MSC which are networked with one another or which provide access to a fixed network PSTN. Furthermore, these mobile Switching centers MSC each connected to at least one base station controller BSC. Each base station con
  • the successive time slots ts divided by a frame structural ⁇ structure. Eight time slots ts are thus combined into a frame, a specific time slot of the frame forming a frequency channel for the transmission of useful data and being used repeatedly by a group of connections. Additional frequency channels, for example for frequency or time synchronization of the mobile stations MS, are not introduced in every frame, but at predetermined times within a multi-frame.
  • the parameters of the radio interface are e.g. as follows:
  • the parameters can also be set differently in the upward (MS -> BS) and downward direction (BS -> MS).
  • the receiver according to FIG. 4 relates to radio stations, which can be either a base station BS or a mobile station MS.
  • the receiving device according to the invention is used in the receiver for channel estimation.
  • a possible implementation of the corresponding transmitter can be found, for example, in German patent DE 197 34 936.
  • the reception path of the device is shown in detail in FIG.
  • the received signals rx are converted from the transmit frequency band into the low-pass range and split into a real and an imaginary component.
  • An analog low-pass filter takes place in submodule E2. and finally in the submodule E3 a double oversampling of the received signal with 13/3 MHz and a word length of 12 bits.
  • sub-module E4 digital low-pass filtering is carried out using a filter with a bandwidth of 13/6 MHz with the highest possible slope for channel separation. This is followed by a 2: 1 decimation of the double oversampled signal in sub-module E4.
  • the received signal e obtained in this way essentially consists of two parts, namely a part em for channel estimation (training sequence tseq with known data symbols t) and parts el and e2 for data estimation. in the
  • the channel coefficients h of the channel impulse responses are estimated using a known midamble basic code m of all transmitted in the respective time slot
  • sub-module E6 parameters b (k) for matched filters are determined for each data channel using the CDMA codes c (k).
  • the sub-module E7 eliminates the interference originating from the midambles m (k) in the reception blocks el / 2 used for data estimation. This is possible by knowing h (k) and m (k).
  • the data symbols d are determined using a pseudo-inverse of the combined channel matrix A.
  • An alternative solution method is a singular value decomposition of the combined channel matrix A.
  • Further solution methods relate to another optimization criterion, e.g. the minimum ean square error criterion (MMSE) instead of the zero forcing (ZF) criterion.
  • MMSE minimum ean square error criterion
  • ZF zero forcing
  • These solution methods can also be combined with one another.
  • the cross-correlation matrix A A is calculated. Since AA has a Töplitz structure, only a small part of the matrix has to be calculated, which can then be used to expand to the full size.
  • this matrix A * ⁇ A is large because large sub-blocks are selected. Only a small part of this matrix A * ⁇ A is then calculated. When moving quickly, the matrix A * ⁇ A shrinks, so that a complete calculation may be selected to achieve a lower-noise solution.
  • a Cholesky decomposition of A takes place H, where H is an upper triangular matrix. Due to the töplitz structure of AA, H also approximately has a töplitz structure and does not have to be fully calculated. A vector s represents the reciprocal of the diagonal elements of H, which can be used advantageously for solving equations.
  • Sub-module E13 the estimated data dl / 2 are demodulated, descrambled and finally fold-decoded using a Viterbi decoder.
  • the decoded data blocks ⁇ E (k 1 ) 3 are optionally fed to a first data sink D1 or via the source decoder E14 to a second data sink D2.
  • the decoded data blocks ⁇ E (k l ) 3 are fed back to the sub-module E5, which uses them to track the estimated channel coefficients h.
  • At the receiving end takes place by an analog processing, instead ie amplification, filtering, conversion to the baseband in the RF section, a digital low-pass filtering the Empfangss' ignale rx in a digital low pass filter.
  • the data estimation in the joint detection data estimator is carried out jointly for all connections, and a detailed description of the German patent DE 197 34 936 can be found.
  • the channel estimation that is carried out in submodule E5 is explained in more detail below.
  • the sub-module E5 contains a channel estimator KS, a memory device 1 SP and a control device SE, between which an information exchange is possible.
  • Data symbols t of the known training sequences tseq from the middle area 1 m, as well as already detected data symbols d for tracking the estimate, are stored in the memory device SP.
  • the control device SE can switch subscriber-individually between different modes of channel estimation, the channel estimation being carried out in the channel estimator KS.
  • the channel coefficients h are determined from the sample values el..el6 of the received signal e.
  • Transmitted data symbols d are modified by the transmission method, represented by the combined channel matrix A and are available to the receiving radio station as samples e.
  • the receiving radio station tries to determine estimated values d for the transmitted data symbols d by determining an estimated combined channel matrix A during the channel estimation.
  • the optimization criterion is, for example, the minimization of the quadratic error of the TL deviation of sample values e to the estimated received signal e.
  • the channel estimate in the mobile radio system must take into account the movement of the mobile stations MS.
  • the movement leads to a Doppler shift, which is caused by an amplitude and LO co to K) P "cn o Cn o cn o Cn
  • the combined channel matrix A being the influence of the spread by the CDMA codes c and the modulation by the rtra un scanal mi n
  • the delays (positions) of these significant channel coefficients h are determined in a step 4 (see FIG. 7). In the following, only this reduced number of channel coefficients h is then determined when evaluating the sub-blocks.
  • This procedure can also be used to increase the signal delays that can be represented by the channel impulse responses.
  • the number of channel coefficients h remains the same, but their spacing is increased.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

Conformément à l'invention, un signal de réception constitué par des symboles de données est reçu par une station de réception. Le signal de réception est séparé, côté réception, en des valeurs échantillonnées individuelles, et est comparé, pour la détermination des coefficients de canaux, avec des symboles de données connus, des symboles de données connus individuels du signal de réception étant mémorisés dans la station de réception. Le fait qu'un nombre réduit de coefficients de canaux soit déterminé pour des stations qui, en soi, se déplacent rapidement, permet d'améliorer la précision d'évaluation desdits coefficients de canaux.
EP98954234A 1997-10-14 1998-09-29 Procede et dispositif de reception pour l'estimation de canaux dans des systemes de telecommunication Ceased EP1023784A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19745367 1997-10-14
DE19745367 1997-10-14
PCT/DE1998/002873 WO1999020061A2 (fr) 1997-10-14 1998-09-29 Procede et dispositif de reception pour l'estimation de canaux dans des systemes de telecommunication

Publications (1)

Publication Number Publication Date
EP1023784A2 true EP1023784A2 (fr) 2000-08-02

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP98954234A Ceased EP1023784A2 (fr) 1997-10-14 1998-09-29 Procede et dispositif de reception pour l'estimation de canaux dans des systemes de telecommunication

Country Status (5)

Country Link
EP (1) EP1023784A2 (fr)
JP (1) JP2001520492A (fr)
CN (1) CN1281602A (fr)
AU (1) AU1143599A (fr)
WO (1) WO1999020061A2 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19935480A1 (de) 1999-07-28 2001-02-22 Infineon Technologies Ag Verfahren zur Schätzung der Kanalimpulsantworten eines Mobilfunkkanals
DE19938747A1 (de) * 1999-08-16 2001-03-22 Siemens Ag Verfahren zur Kanalschätzung in einem Funk-Kommunikationssystem
EP1091533B1 (fr) * 1999-10-07 2006-10-04 Robert Bosch Gmbh Procédé et dispositif d'estimation de canal dans un système de communication mobile
TW540200B (en) 2000-11-09 2003-07-01 Interdigital Tech Corp Single user detection
US7593357B2 (en) 2002-03-28 2009-09-22 Interdigital Technology Corporation Transmit processing using receiver functions
US20050232340A1 (en) * 2004-04-16 2005-10-20 Lucent Technologies, Inc. Intelligent antenna receiver architecture
WO2006106474A2 (fr) * 2005-04-08 2006-10-12 Koninklijke Philips Electronics N.V. Procede et appareil d'estimation de canal dans un systeme de communication mobile
CN101346955A (zh) * 2005-12-20 2009-01-14 皇家飞利浦电子股份有限公司 Ofdm系统中的用于信号接收的方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2953132B2 (ja) * 1991-09-12 1999-09-27 松下電器産業株式会社 データ受信装置の等化器
JP2770626B2 (ja) * 1991-11-29 1998-07-02 日本電気株式会社 適応受信機
FR2698226B1 (fr) * 1992-11-18 1995-01-13 Alcatel Radiotelephone Séquence d'apprentissage pour l'estimation d'un canal de transmission et dispositif d'estimation correspondant.
FI98018C (fi) * 1994-08-18 1997-03-25 Nokia Mobile Phones Ltd Menetelmä ja laite radiokanavan impulssivasteen mittaamiseksi

Non-Patent Citations (1)

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Title
See references of WO9920061A3 *

Also Published As

Publication number Publication date
WO1999020061A2 (fr) 1999-04-22
AU1143599A (en) 1999-05-03
JP2001520492A (ja) 2001-10-30
WO1999020061A3 (fr) 1999-06-24
CN1281602A (zh) 2001-01-24

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