JP4864286B2 - 搬送周波数オフセットを補償する方法およびシステム - Google Patents
搬送周波数オフセットを補償する方法およびシステム Download PDFInfo
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- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/07—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop using several loops, e.g. for redundant clock signal generation
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- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
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- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
- H03L7/093—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using special filtering or amplification characteristics in the loop
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- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
- H03L7/0991—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop the oscillator being a digital oscillator, e.g. composed of a fixed oscillator followed by a variable frequency divider
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- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
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- H04L27/2662—Symbol synchronisation
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2668—Details of algorithms
- H04L27/2673—Details of algorithms characterised by synchronisation parameters
- H04L27/2675—Pilot or known symbols
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- H—ELECTRICITY
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- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
- H04L2027/0063—Elements of loops
- H04L2027/0067—Phase error detectors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/261—Details of reference signals
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Description
多くの直交周波数分割多重化(OFDM)規格(standard:標準)では、パイロット(信号)(既知の値)をユーザ・データに組み込んで送信することを要求している。従来の直交周波数分割多重化システムでは、パイロットの位相情報を平均化して、ノイズの多い環境での閉ループ搬送周波数オフセット・トラッキング(追従性)を改善するのが一般的である。例えば、パイロットの位相の平均を使用して、搬送周波数オフセット推定値(offset estimation)を導出することができ、この推定値を使用して、搬送周波数オフセットの影響が軽減または除去されるように、等化器のタップ(tap)の位相回転を調節することができる。この技術の1つの欠点は、時間変化チャネルが存在する場合に、各パイロットの位相が独立して変化する可能性があることである。具体的には、全てのパイロットの位相は、上述のように、送信機側搬送周波数と受信機側搬送周波数の不一致により生じる搬送周波数オフセットを表す共通の位相回転を共有する。しかし、時間変化チャネルが存在する場合には、各パイロット(pilot)の位相が、その送信チャネルが時間と共に変化することにより引き起こされる独立した位相回転も含む場合がある。これら独立したパイロット位相回転は、場合により、パイロット位相の破壊的平均化(destructive averaging)につながる可能性があり、これにより搬送周波数オフセット推定値の導出に誤りが生じることがある。搬送周波数オフセット推定値が誤っていると、その推定値を使用して実際の搬送周波数オフセットを補償する任意の処理ユニット(例えば、等化器)の性能が低下する可能性がある。本発明は、この問題の解決に向けられる。
Claims (18)
- 直交周波数分割多重化(OFDM)方式の受信機において、直交周波数分割多重化信号を処理する方法であって、
直交周波数分割多重化信号を受信するステップと、
前記受信した直交周波数分割多重化信号から複数のパイロットを抽出するステップと、
抽出した前記複数のパイロットを処理して、時間変化チャネルにより引き起こされる独立したパイロットの位相回転を表す独立位相エラーを低減させる処理ステップと、
所定対の抽出パイロットの位相差を計算するステップと、
前記計算した位相差を、所定の高速フーリエ変換(FFT)ウインドウ・オフセットを表すしきい値と比較するステップと、
前記計算した位相差が前記しきい値を超える場合に、上流側FFTモジュールのFFTウインドウを調節するステップと、
独立位相エラーが所定値まで低減された後で、処理した前記複数のパイロットから搬送周波数オフセット推定値を導出するステップと、
を含む方法。 - 前記搬送周波数オフセット推定値を使用して搬送周波数オフセットを補正するステップを更に含む、請求項1に記載の方法。
- 前記処理ステップが、前記複数のパイロットの各パイロットを別々のフェーズ・ロック・ループに通すことを含む、請求項1に記載の方法。
- 前記処理ステップが、前記複数のパイロットの各パイロットを時分割フェーズ・ロック・ループに通すことを含む、請求項1に記載の方法。
- 前記搬送周波数オフセット推定値を導出するステップが、
搬送周波数オフセットにより引き起こされるパイロット位相回転の平均を表す前記複数のパイロットについての共通位相エラーを計算するステップと、
前記共通位相エラーを積分してノイズの影響を軽減するステップと、
前記積分した共通位相エラーから搬送周波数オフセット推定値を導出するステップと、
を含む、請求項1に記載の方法。 - 前記所定値がほぼゼロである、請求項1に記載の方法。
- 前記所定値が、前記導出する搬送周波数オフセット推定値がほぼ一定となるように選択される、請求項1に記載の方法。
- 前記搬送周波数オフセット推定値を導出するステップが、
前記計算した位相差の変化率をトラッキングするステップと、
前記導出した搬送周波数オフセット推定値を調節して、前記FFTウインドウ・オフセットによる位相回転を表すトラッキングした前記変化率を補償するステップと、
を更に含む、請求項1に記載の方法。 - 前記OFDM方式の受信機が、無線LANアダプタ、家庭用ネットワーク端末、携帯端末、およびデスクトップ端末のうちの1つとして実施される、請求項1に記載の方法。
- 直交周波数分割多重化(OFDM)信号を処理するシステムであって、
直交周波数分割多重化信号の複数のパイロットを受信し、時間変化チャネルにより引き起こされる独立したパイロット位相回転を表す各パイロットの独立位相エラーを低減する処理モジュールであって、ユーザ・データ・セグメント内の2つの所定のパイロットの間の位相差を計算する位相差計算機、及び、前記計算した位相差が所定値を超えている場合に上流側のFFTウインドウの位置を調節するFFTウインドウ同期ユニットを含む処理モジュールと、
前記各パイロットの独立位相エラーが所定値まで低減された後で、前記複数のパイロットから搬送周波数オフセット推定値を導出する、前記処理モジュールに結合された搬送周波数オフセット推定モジュールと、
を含むシステム。 - 直交周波数分割多重化(OFDM)方式の受信機が、無線LANアダプタ、家庭用ネットワーク端末、携帯端末およびデスクトップ端末のうちの1つとして実施される、請求項10に記載のシステム。
- 前記所定値がほぼゼロである、請求項10に記載のシステム。
- 前記所定値が、前記導出した搬送周波数オフセット推定値がほぼ一定となるように選択される、請求項10に記載のシステム。
- 前記処理モジュールが、それぞれがユーザ・データ・セグメント内の所定のパイロットの専用である複数のフェーズ・ロック・ループを含む、請求項10に記載のシステム。
- 前記処理モジュールが、ユーザ・データ・セグメント内の全てのパイロットを処理するようにクロック制御された時分割フェーズ・ロック・ループを含む、請求項10に記載のシステム。
- 前記搬送周波数オフセット推定モジュールが、
前記搬送周波数オフセットにより引き起こされるパイロット位相回転の平均を表す前記複数のパイロットの共通位相エラーを計算する平均化ユニットと、
前記共通位相エラーを積分してノイズの影響を低減する積分器ユニット)と、を含む、請求項10に記載のシステム。 - 前記搬送周波数オフセット推定モジュールが、
前記計算した位相差の変化を複数のユーザ・データ・セグメントにわたってトラッキングし、前記導出した搬送周波数オフセットに対してFFTウインドウのドリフトによる位相回転を補償する、前記位相差計算機に結合された位相差率推定器を更に含む、請求項10に記載のシステム。 - 直交周波数分割多重化(OFDM)信号を処理するシステムであって、
直交周波数分割多重化信号から複数のパイロットを抽出する手段と、
時間変化チャネルにより引き起こされる独立した位相回転を表す独立位相エラーを、前記抽出したパイロットから除去する手段と、
所定対の抽出パイロットの位相差を計算する手段と、
前記計算した位相差を、所定の高速フーリエ変換(FFT)ウインドウ・オフセットを表すしきい値と比較する手段と、
前記計算した位相差が前記しきい値を超える場合に、上流側FFTモジュールのFFTウインドウを調節する手段と、
前記各パイロットの独立位相エラーが所定レベルまで低減され、FFTウインドウのドリフトが補償された後で、前記複数のパイロットから搬送周波数オフセット推定値を導出する手段と、
を含むシステム。
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PCT/US2001/020054 WO2003001760A1 (en) | 2001-06-22 | 2001-06-22 | Method and system for compensation of a carrier frequency offset in an ofdm receiver |
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US (1) | US8184523B2 (ja) |
EP (1) | EP1400083B1 (ja) |
JP (1) | JP4864286B2 (ja) |
KR (1) | KR100802973B1 (ja) |
CN (1) | CN1520669A (ja) |
BR (1) | BRPI0117039B1 (ja) |
DE (1) | DE60142082D1 (ja) |
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US8184523B2 (en) | 2012-05-22 |
EP1400083B1 (en) | 2010-05-05 |
JP2004531168A (ja) | 2004-10-07 |
DE60142082D1 (de) | 2010-06-17 |
BRPI0117039B1 (pt) | 2015-12-08 |
EP1400083A1 (en) | 2004-03-24 |
US20040156349A1 (en) | 2004-08-12 |
BR0117039A (pt) | 2004-07-27 |
WO2003001760A1 (en) | 2003-01-03 |
KR100802973B1 (ko) | 2008-02-14 |
CN1520669A (zh) | 2004-08-11 |
MXPA03011643A (es) | 2004-04-02 |
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