EP1325564A2 - Procede et systeme d'evaluation de la correction du decalage de frequence et de la rotation de phase dans des systemes cdma - Google Patents

Procede et systeme d'evaluation de la correction du decalage de frequence et de la rotation de phase dans des systemes cdma

Info

Publication number
EP1325564A2
EP1325564A2 EP01966908A EP01966908A EP1325564A2 EP 1325564 A2 EP1325564 A2 EP 1325564A2 EP 01966908 A EP01966908 A EP 01966908A EP 01966908 A EP01966908 A EP 01966908A EP 1325564 A2 EP1325564 A2 EP 1325564A2
Authority
EP
European Patent Office
Prior art keywords
frequency offset
output
phase rotation
finger
correlation
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.)
Withdrawn
Application number
EP01966908A
Other languages
German (de)
English (en)
Inventor
Xixian Chen
Xin Jin
Mohamed El-Tarhuni
Runbo Fu
Jeffrey Stanier
Neil Mcgowan
Wen Zhao
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.)
Nortel Networks Ltd
Original Assignee
Nortel Networks Ltd
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 Nortel Networks Ltd filed Critical Nortel Networks Ltd
Publication of EP1325564A2 publication Critical patent/EP1325564A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7087—Carrier synchronisation aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/711—Interference-related aspects the interference being multi-path interference
    • H04B1/7115—Constructive combining of multi-path signals, i.e. RAKE receivers
    • H04B1/7117—Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/711—Interference-related aspects the interference being multi-path interference
    • H04B1/7115—Constructive combining of multi-path signals, i.e. RAKE receivers
    • H04B1/712—Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop

Definitions

  • this motion introduces a time varying Doppler shift on the signals received over the channel which may be observed as a change in the frequency of signals received over the channel.
  • the change in frequency, or Doppler shift is related to the velocity of the mobile terminal and the angle between the direction of motion of the mobile terminal and the direction of arrival of the signal at the receiver.
  • the change in frequency hereinafter frequency offset
  • frequency offset may be as high as 1.6 kHz for a mobile terminal moving at 900 km/h and communicating in the 1.9 GHz band. It is an established fact that this frequency shift, if not compensated for, will greatly degrade the overall system performance.
  • Embodiments of the invention provide methods and apparatus which estimate frequency offset correction in a manner which is suitable in environments which may involve high speeds .
  • Decimation/summation can be performed at various points throughout the frequency offset determination, before or after application of the frequency offset correction. In most circumstances, the frequency offset correction will be estimated from a plurality of despread finger output sequences.
  • the entities which track and process resolvable ultipath components are commonly known as "Rake fingers" or simply “fingers".
  • a plurality of correlation functions each adapted to perform a respective correlation on respective input signals each of which is a function of a respective one of the plurality of despread finger output sequences to produce a corresponding plurality of correlation outputs, the correlation being performed between the respective input signal and a delayed version of the respective input signal.
  • a combiner combines the plurality of autocorrelation outputs to produce a combined correlation output, and an instantaneous frequency offset determining function determines an instantaneous frequency offset as a function of the combined correlation output.
  • the apparatus may further include a low-pass filter adapted to perform low-pass filtering on the instantaneous frequency offset to produce a filtered frequency offset.
  • the instantaneous frequency offset determining function is a function substantially mathematically equivalent to a scalar multiplied by an arctangent of the imaginary part of the correlation output over the real part of the correlation output.
  • the frequency offset correction is converted to a phase correction output with a numerically controlled oscillator.
  • a closed loop arrangement is provided wherein the frequency offset correction is fed back and applied prior to the correlation function.
  • the input signal is based upon a component which has known content, for example a pilot channel signal. In other embodiments, the input signal is based upon an input with unknown content which must therefore be estimated prior to correlation.
  • pilot channel phase rotation correction circuit adapted to apply the phase rotation correction to the pilot channel and/or a DLL (delay locked loop) phase rotation correction circuit adapted to apply the phase rotation correction to a DLL, and/or a finger ' sample phase rotation correction circuit adapted to apply a phase rotation correction circuit to finger data samples, and/or a searcher phase rotation correction circuit adapted to apply a phase rotation correction to a searcher.
  • DLL delay locked loop
  • Another embodiment of the invention provides a' CDMA receiver adapted to include any of the above summarized functionality.
  • Figure 1 is a block diagram of a frequency offset correction circuit according to a first embodiment of the invention
  • Figure 2 is a block diagram of a frequency offset correction circuit according to a second embodiment of the invention
  • Figure 3 is a schematic of circuitry using the phase rotation correction output produced by the circuitry of Figure 1 or 2 to apply correction to a pilot channel;
  • Figure 4 is a schematic of circuitry using the phase rotation correction output produced by the circuitry of Figures 1 or 2 in adjusting timing in a delay lock loop;
  • Figure 5 is a schematic of circuitry which applies the phase rotation correction output produced by the circuitry of Figure 1 or Figure 2 to correct data symbols;
  • Figure 8 is a schematic diagram of modifications to the circuitry of Figure 1 to accommodate CDMA signals which do not have a pilot channel .
  • the invention provides systems and methods adapted to compensate for the frequency offset between a mobile terminal and a base station, as well as to compensate for the Doppler frequency shift introduced by high-speed moving airplanes .
  • the two parts may be implemented separately or together, and in any suitable fashion with appropriate combinations of hardware, software, DSP, ASICs, FPGA, processors etc .
  • the invention is' applied in the context of receivers for
  • an assumption which is made is that all the finger paths of the same user undergo approximately the same frequency shift and that this frequency shift changes relatively slowly with the time.
  • the estimation period might be selected for example to equal the duration of a CDMA frame which is 20 ms in some systems.
  • the frequency offset algorithm works on pilot signals output by fingers after PN despreading in CDMA receivers.
  • the pilot signal is a component of the received signal which for the most part has known contents at . the receiver. More generally any component with known content could be used.
  • the signal may also contain unknown content such as is the case with the pilot channel which also includes power control information which should be removed.
  • the pilot signal x(n) from one finger can be expressed as follows:
  • An intermediate signal s (n) is produced by a multiplier 16 which multiplies x(n) by c (n) * (the complex conjugate of the nth known PN code chip) as follows :
  • the output rt 0 t(k) of combiner 30 is fed to an arctan functional block 32 which computes an estimate of the frequency offset according to:
  • arctan functional block 32 can be implemented in any suitable way, including but not limited to table look-up, DSP etc.
  • u(n) is a noise component which can be approximated by:
  • F(m + 1) (1- ⁇ ) F(m) + ⁇ f(m) ⁇
  • / (m) is the estimated frequency offset during the mth estimation period
  • ⁇ is a parameter of the first order IIR 34.
  • F(m+1) is the filter output which will be used to correct the frequency offset in the next frame.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

L'invention concerne des procédés et des appareils évaluant l'évaluation et la correction du décalage de fréquence d'une manière qui est appropriée pour des milieux mettant en oeuvre des vitesses élevées. L'invention concerne également un appareil et un procédé de correction du décalage de fréquence permettant d'évaluer une correction du décalage de fréquence à partir d'une séquence désétalée de sortie de doigts. L'appareil comprend une fonction de corrélation conçue pour effectuer une corrélation entre une séquence d'entrée qui est une fonction de la séquence désétalée de sortie de doigts et une version retardée de la séquence d'entrée pendant une période de mise à jour, en vue de produire une sortie de corrélation. L'appareil comprend également une fonction de détermination du décalage de fréquence instantané permettant de déterminer un décalage de fréquence instantané en tant que fonction de la sortie de corrélation. Dans la plupart des cas, la correction du décalage de fréquence est évaluée à partir d'une pluralité de séquences désétalées de sortie de doigts. Dans un tel contexte, une pluralité de fonctions de corrélation est prévue, chacune des fonctions étant conçue pour effectuer une corrélation respective sur des signaux d'entrée respectif, chaque signal étant une fonction d'une séquence désétalée de sortie de doigts respective, de manière à obtenir une pluralité correspondante de sorties de corrélation, la corrélation étant effectuée entre le signal d'entrée respectif et une version retardée du signal d'entrée respectif. Un combineur combine la pluralité de sorties d'autocorrélation, en vue de produire une sortie de corrélation combinée, et une fonction de détermination du décalage de fréquence instantané détermine un décalage de fréquence instantané en tant que fonction de la sortie de corrélation combinée. De manière à éliminer une variabilité à court terme dans l'évaluation, l'appareil peut également comprendre un filtre passe-bas conçu pour effectuer un filtrage passe-bas sur le décalage de fréquence instantané, en vue d'obtenir un décalage de fréquence filtré.
EP01966908A 2000-09-28 2001-09-07 Procede et systeme d'evaluation de la correction du decalage de frequence et de la rotation de phase dans des systemes cdma Withdrawn EP1325564A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US67125400A 2000-09-28 2000-09-28
US671254 2000-09-28
PCT/CA2001/001247 WO2002027956A2 (fr) 2000-09-28 2001-09-07 Procede et systeme d'evaluation de la correction du decalage de frequence et de la rotation de phase dans des systemes cdma

Publications (1)

Publication Number Publication Date
EP1325564A2 true EP1325564A2 (fr) 2003-07-09

Family

ID=24693747

Family Applications (1)

Application Number Title Priority Date Filing Date
EP01966908A Withdrawn EP1325564A2 (fr) 2000-09-28 2001-09-07 Procede et systeme d'evaluation de la correction du decalage de frequence et de la rotation de phase dans des systemes cdma

Country Status (3)

Country Link
EP (1) EP1325564A2 (fr)
AU (1) AU2001287452A1 (fr)
WO (1) WO2002027956A2 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8331492B2 (en) * 2002-07-04 2012-12-11 Intel Mobile Communications GmbH Device and method for determining the deviation of the carrier frequency of a mobile radio device from the carrier frequency of a base station
US8457178B2 (en) * 2007-03-26 2013-06-04 Qualcomm Incorporated Frequency offset estimator
CN111935050B (zh) * 2020-06-17 2022-07-05 中国船舶重工集团公司第七一五研究所 一种基于相位搜索的单载波频域均衡水声通信系统残余相偏修正方法

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5361276A (en) * 1993-09-13 1994-11-01 At&T Bell Laboratories All digital maximum likelihood based spread spectrum receiver
US5659573A (en) * 1994-10-04 1997-08-19 Motorola, Inc. Method and apparatus for coherent reception in a spread-spectrum receiver

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0227956A3 *

Also Published As

Publication number Publication date
AU2001287452A1 (en) 2002-04-08
WO2002027956A3 (fr) 2002-10-03
WO2002027956A2 (fr) 2002-04-04

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