WO2000074329A1 - Procedes d'estimation des retards de propagation pour un systeme de transmission - Google Patents
Procedes d'estimation des retards de propagation pour un systeme de transmission Download PDFInfo
- Publication number
- WO2000074329A1 WO2000074329A1 PCT/FR2000/001410 FR0001410W WO0074329A1 WO 2000074329 A1 WO2000074329 A1 WO 2000074329A1 FR 0001410 W FR0001410 W FR 0001410W WO 0074329 A1 WO0074329 A1 WO 0074329A1
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- WO
- WIPO (PCT)
- Prior art keywords
- matrix
- size
- vectors
- vector
- transmitter
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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
- H04L25/024—Channel estimation channel estimation algorithms
- H04L25/0242—Channel estimation channel estimation algorithms using matrix methods
- H04L25/0248—Eigen-space methods
-
- 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
Definitions
- the present invention relates to the field of digital radiocommunications, and more particularly to the techniques used to estimate the characteristics of propagation channels between a radio transmitter and an associated receiver.
- the propagation channel response between a digital radio transmitter and receiver is generally characterized by its impulse response h j (t) which can be expressed in the form
- the index j refers to different embodiments of the impulse response
- d denotes the number of significant propagation paths between the transmitter and the receiver, indexed by i, the complex coefficients s ,, are gains associated with echoes received along the different paths
- ⁇ denotes the propagation delay associated with the path i, assumed to be constant for the different embodiments of the impulse response
- a (t) denotes the time form of an elementary pulse which integrates the shapings spectral and the different filterings that the transmitter and the receiver and the receiver operate on the signal
- the estimation of the arrival times defined by the propagation delays ⁇ is used in the context of demodulation, in particular for synchronization purposes
- rake receivers used in CDMA receivers (“code d ivision multiple access ”), we need to know the propagation delays associated with a certain number of paths, in order to take advantage of the diversity provided by multiple paths
- the present invention aims to propose new methods for estimating characteristics of radio propagation channels, which are of good accuracy without need to know a priori the shape of the modulation / demodulation pulse, in order to provide good robustness to any vari ations of the form of this pulse
- the invention thus proposes a method for estimating at least one delay associated with a propagation path between a radio transmitter and a radio receiver, comprising the following steps
- I m- -1 designates the identity size matrix denote the matrices of size (m-1) ⁇ d respectively formed by the first m-1 lines and by the last m-1 lines of the matrix E, and
- E + denotes the pseudo-inverse matrix of size d ⁇ (m-1) of E
- the vector ⁇ is related to the frequency transform of the pulse a (t), so that the method can take advantage of the knowledge of the shape of this pulse after having deduced it from the measurements of the impulse response
- the method presents therefore the advantages of the methods exploiting this knowledge of the shape of the pulse, while being able to adapt to variations of this shape
- the vector ⁇ is moreover a by-product of the above process, which can be used independently in known methods of estimating arrival times based on knowledge of the shape of the pulse, or in any other application where this knowledge is of interest
- a second aspect of the invention thus relates to a method for estimating the shape of a pulse associated with at least one propagation path between a radio transmitter and a radio receiver, comprising the following steps
- E ⁇ denotes the pseudo-inverse matrix of size d ⁇ (m-1) of E
- v_ is2 ⁇ S 2 is2 / is2 ' ⁇ ⁇ 1 des ⁇ 9 ⁇ a ⁇ t the matrix version and ® the product term by term, and - obtain an estimate of a transform in the frequency domain of the form of the pulse based on the components of a vector
- FIG. 1 is a block diagram of a radio transmitter and receiver to which the invention can be applied
- FIG. 2 is a flow diagram of a delay estimation method implemented by the receiver of FIG. 1,
- FIG. 3 is a graph illustrating the precision of the estimation of the delays according to this method.
- the transmitter 1 represented in FIG. 1 comprises a source 2 of digital signal S n representing for example speech, signaling data,
- the baseband signal S n is subjected to a modulator 3 which performs spectral shaping and transposition around a carrier frequency
- the resulting radio signal is amplified and broadcast by I antenna 4 of the transmitter 1
- each of these paths has a gain s ,, and causes a propagation delay ⁇ , as explained previously with reference to the formula
- the radio signal received by the antenna 7 of the receiver 6 is the superposition of the signals received along the different paths, as expressed by the sum in formula (1).
- the demodulator 8 of the receiver 6, which processes the radio signal picked up by the antenna 7 and amplified, has three parts
- a module 9 ensures the baseband conversion of the signal as well as the filtering (analog and / or digital) required to optimize, in a manner known per se, the performance of the receiver,
- a module 10 estimates the impulse response of the propagation channel between the transmitter and the receiver, on the basis of the baseband signal delivered by the module 9,
- an equalization module 1 1 proceeds with the estimation of the symbols S n of the digital signal generated by the source 2 of the transmitter, this estimated digital signal S n constituting the output signal of the demodulator 8 Different conventional methods can be used by module
- the digital signal S n modulated by the transmitter contains synchronization sequences known a priori, which allow the receiver to evaluate the impulse response h (t) of the channel by correlation On can then obtain an estimate h j (t) of the impulse response of the channel for each signal section containing a synchronization sequence
- the index j referring to these sections, we obtain a certain number of successive observations h j (t) of the impulse response of the channel This response can vary over time
- the shape of the impulse a (t) is constant and that the delays ⁇ , are stable on a certain number of observations of the impulse response only the gains are subject to rapid channel changes (Rayleigh fading)
- the observation statistics of the channel are enriched by the diversity
- the impulse response can be estimated from each of the signals picked up by the antennas, which provides a spatial diversity which enriches the observation statistics of the impulse response.
- the module 1 1 can operate according to any known equalization method II can for example be a Viterbi equalizer
- the receiver 6 shown in FIG. 1 further comprises a module 12 for estimating the propagation delay ⁇ , caused by one or more of the multiple propagation paths F
- These delays ⁇ can for example be supplied to an external unit which proceeds to the location of a mobile terminal forming the transmitter 1 (or the receiver 6), this unit operating on the basis of the propagation delays estimated between this mobile terminal and several fixed stations, for example by a conventional triangulation method
- Each estimate - î j (t) produced by module 10 is a noisy measure of the real impulse response modeled by the formula (1)
- N [ri j (f ⁇ ), n j (f 2 ), A being the matrix of m rows and d columns
- J., A J 2 A ⁇ (7)
- J and J are the matrices (m-1) ⁇ m of selection of the first m-1 and
- the first step 20 consists in receiving an estimate h j (t) of the impulse response of the channel produced by the module 10, to calculate the Fou ⁇ er transform to form the column vector H., for example with a conventional algorithm of transform of
- the next step 21 is the estimation of the cova ⁇ ance matrix R of the observations of the impulse response in the frequency domain
- This cova ⁇ ance matrix is the mathematical expectation of the mat ⁇ ce H. H ⁇ , which can be estimated by an average calculation.
- T * can be the arithmetic mean of the matrices H. H. obtained from the last L estimates of the channel response, the number L being chosen so that the delay stability hypothesis ⁇ , over the calculation period of the cova ⁇ ance matrix is substantially verified
- ⁇ and ⁇ are the diagonal matrices respectively containing the e eigenvalues of larger modules and the md eigenvalues of smaller modules of the cova ⁇ ance matrix
- E and E are the matrices of sizes mxd and m ⁇ (md) whose columns are formed by the eigenvectors respectively associated with the eigenvalues contained in the matrices ⁇
- Module 12 determines the matrix E in step 22, which can use any conventional diagonalization method to extract the eigenvectors associated with d eigenvalues of larger modules of the matrix R
- Vmin [ V 1> v 2-> v m- ⁇ ] is ' e eigenvector associated with the eigenvalue of
- step 23 module 12 calculates the matrix ⁇ from the matrix
- step 24 He then extracts from it (step 24) the eigenvector ⁇ / min associated with the eigenvalue of minimum modulus, and he deduces the vector ⁇ according to the relations (16) in step 25. He can then obtain the terms of the matrix ⁇ according to the relation (14) in step 26.
- module 12 finds its eigenvalues ⁇ f (1 ⁇ i ⁇ d) which are the
- FIG. 3 illustrates the performance of the method for estimating the smallest of the delays ⁇ , - when the signal to noise ratio (SNR) varies.
- the ordinates represent the standard deviation ⁇ of the estimate of the smallest delay relative to the symbol time T b .
- Curve I represents the theoretical limit (Cramer Rao).
- Curve II shows the precision obtained with a subspace method using beforehand the correct information of the impulse a (t), and curve III that obtained with the same method based on an inexact knowledge of the form of l 'pulse a (t) (original pulse filtered bandpass).
- Curve IV shows the precision of the estimation of the arrival time obtained with the above process The fact that the shape of the pulse is estimated and not known a priori naturally increases the standard deviation ⁇ But the process provides good robustness to uncertainties about the shape of the pulse
- the module 12 can thus estimate the shape of the pulse a (t), except for a gain and a delay
- This estimated form can be used, for example, in another mode of estimating the delays ⁇ ,
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Physics & Mathematics (AREA)
- Mathematical Physics (AREA)
- Mobile Radio Communication Systems (AREA)
- Monitoring And Testing Of Transmission In General (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00935254A EP1181794A1 (fr) | 1999-05-28 | 2000-05-24 | Procedes d'estimation des retards de propagation pour un systeme de transmission |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR99/06788 | 1999-05-28 | ||
FR9906788A FR2794312B1 (fr) | 1999-05-28 | 1999-05-28 | Procedes d'estimation de caracteristiques de trajets de propagation entre un emetteur et un recepteur radio |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2000074329A1 true WO2000074329A1 (fr) | 2000-12-07 |
WO2000074329A8 WO2000074329A8 (fr) | 2001-04-12 |
Family
ID=9546136
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR2000/001410 WO2000074329A1 (fr) | 1999-05-28 | 2000-05-24 | Procedes d'estimation des retards de propagation pour un systeme de transmission |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1181794A1 (fr) |
FR (1) | FR2794312B1 (fr) |
WO (1) | WO2000074329A1 (fr) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1998002967A2 (fr) * | 1996-07-12 | 1998-01-22 | Nokia Mobile Phones Limited | Procede d'estimation d'un retard et recepteur |
US5841395A (en) * | 1997-09-12 | 1998-11-24 | Raytheon Corporation | Localized interference nulling preprocessor |
-
1999
- 1999-05-28 FR FR9906788A patent/FR2794312B1/fr not_active Expired - Fee Related
-
2000
- 2000-05-24 WO PCT/FR2000/001410 patent/WO2000074329A1/fr not_active Application Discontinuation
- 2000-05-24 EP EP00935254A patent/EP1181794A1/fr not_active Withdrawn
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1998002967A2 (fr) * | 1996-07-12 | 1998-01-22 | Nokia Mobile Phones Limited | Procede d'estimation d'un retard et recepteur |
US5841395A (en) * | 1997-09-12 | 1998-11-24 | Raytheon Corporation | Localized interference nulling preprocessor |
Non-Patent Citations (2)
Title |
---|
SCHELL S V ET AL: "PARTIALLY BLIND IDENTIFICATION OF FIR CHANNELS FOR QAM SIGNALS", PROCEEDINGS OF THE MILITARY COMMUNICATIONS CONFERENCE (MILCOM),US,NEW YORK, IEEE, PAGE(S) 592-596, ISBN: 0-7803-2490-0, XP000580891 * |
ZHI DING: "A BLIND CHANNEL IDENTIFICATION ALGORITHM BASED ON MATRIX OUTER- PRODUCT", IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC),US,NEW YORK, IEEE, PAGE(S) 852-856, ISBN: 0-7803-3251-2, XP000625895 * |
Also Published As
Publication number | Publication date |
---|---|
WO2000074329A8 (fr) | 2001-04-12 |
FR2794312A1 (fr) | 2000-12-01 |
FR2794312B1 (fr) | 2001-08-17 |
EP1181794A1 (fr) | 2002-02-27 |
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