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WO2000072540A1 - Techniques de correction pour systemes de communications au moyen de signalement orthogonal - Google Patents

Techniques de correction pour systemes de communications au moyen de signalement orthogonal Download PDF

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Publication number
WO2000072540A1
WO2000072540A1 PCT/US2000/013560 US0013560W WO0072540A1 WO 2000072540 A1 WO2000072540 A1 WO 2000072540A1 US 0013560 W US0013560 W US 0013560W WO 0072540 A1 WO0072540 A1 WO 0072540A1
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WIPO (PCT)
Prior art keywords
output
soft decision
interference
signal
complementary code
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
PCT/US2000/013560
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English (en)
Inventor
Sirikiat L. Ariyavistakul
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Home Wireless Networks Inc
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Home Wireless Networks Inc
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Filing date
Publication date
Application filed by Home Wireless Networks Inc filed Critical Home Wireless Networks Inc
Priority to EP00932536A priority Critical patent/EP1188283A1/fr
Priority to AU50243/00A priority patent/AU5024300A/en
Publication of WO2000072540A1 publication Critical patent/WO2000072540A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H04L25/06—DC level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
    • H04L25/067—DC level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing soft decisions, i.e. decisions together with an estimate of reliability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L23/00—Apparatus or local circuits for systems other than those covered by groups H04L15/00 - H04L21/00
    • H04L23/02—Apparatus or local circuits for systems other than those covered by groups H04L15/00 - H04L21/00 adapted for orthogonal signalling
    • 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
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
    • H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
    • H04L25/03057—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a recursive structure
    • 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
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
    • H04L2025/03375—Passband transmission
    • 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
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L2025/03433—Arrangements for removing intersymbol interference characterised by equaliser structure
    • H04L2025/03439—Fixed structures
    • H04L2025/03445—Time domain
    • H04L2025/03471—Tapped delay lines
    • H04L2025/03484—Tapped delay lines time-recursive
    • H04L2025/0349—Tapped delay lines time-recursive as a feedback filter

Definitions

  • the present invention relates to systems and methods for improving performance of systems which use orthogonal signaling, including complementary code keying, and more particularly, for improving such performance through new equalization techniques.
  • Cordless and cellular phones, pagers, wireless capable palm computing devices and other similar wireless related data devices and equipment are becoming increasingly ubiquitous. These present a mass market opportunity for wireless data terminals as well as broadband wireless services.
  • First are enhanced cellular networks with increased bit rate capabilities which enable greater mobility and globalized communications possibilities for users because of (among other things) handoff and roaming functionality.
  • Second are non-centralized wireless local area networks (LAN's), which offer orders of magnitude higher data rates through coverage area restriction to provide substantially reduced signal attenuation and multipath delay spread. Both system approaches have been the focus of extensive research and standards activities.
  • an air interface or wireless technique to enable wireless data include the following considerations.
  • broadband services will increasingly require increased power for both RF radiation (to overcome the increased thermal noise bandwidth) and signal processing.
  • Advanced signal processing techniques will enable the receiver to operate at a low signal-to-noise ratio (SNR), thus reducing the RF power requirement.
  • SNR signal-to-noise ratio
  • High frequency reuse efficiency is preferred for several reasons. Greater frequency reuse translates into lower required bandwidth. This is important because, due to spectrum congestion, broadband services will face limits on the total amount of bandwidth available. High frequency reuse can be achieved with a number of cochannel interference management techniques, such as improved engineering, power control, frequency hopping, and dynamic channel assignment. In addition, receiver techniques such as interference cancellation and smart antennas will enable the receiver to operate at a low required signal-to-interference ratio (SIR).
  • SIR signal-to-interference ratio
  • Transmission overhead includes guard bands, guard times, coding redundancy, and all the bandwidth (frequency / time / code) dedicated for the purpose of receiver training and acquisition.
  • CMOS complementary code keying
  • DSSS direct sequence spread spectrum
  • CCK as proposed by the IEEE 802.11 standards committee is a form of orthogonal signaling in which the information data is mapped into nearly orthogonal sequences (or code symbols) to be transmitted.
  • the receiver correlates the received signal with all possible transmit waveforms to find the most likely code symbol, from which the information data is recovered through reverse mapping.
  • the absolute phase of the orthogonal waveform is also used to carry information.
  • the CCK specified by the IEEE 802.11 committee takes each 8 bits of information data and converts it into one of the 256 possible 8-chip-long CCK code symbols, where each chip is quaternary phase modulated.
  • CCK aims to deliver on four goals the IEEE 802.11 committee deemed critical — concerning speed, interoperability, bandwidth usage and worldwide compatibility. Addressing the speed issue, CCK can deliver very robust Ethernet-equivalent data rates of better than 10 Mb/s. Interoperability is enhanced because this approach allows downshifting that makes it interoperable with existing 1 and 2 Mb/s 802.11 networks. CCK operates within the existing DSSS 1 and 2 Mb/s channels of the 2.4 GHz ISM band. And, like the 1 and 2 Mb/s standard, this extension is truly compatible with worldwide standards developed by global regulatory bodies such as the FCC, ETSI, and the MKK.
  • CCK provides another important characteristic - strong multipath interference properties.
  • One of the main benefits of CCK is its ability to handle multipath interference.
  • CCK's absence of simultaneous orthogonal signals on the in-phase (I) and quadrature (Q) rails (which exist in other orthogonal signaling schemes) serves to minimize cross rail interference.
  • ISI intersymbol interference
  • the 11 Mb/s WLAN receiver be equipped with an equalizer capable of eliminating both ICI and ISI or at least reducing or minimizing these more efficiently and effectively, in a low cost, robust implementation compatible with the criteria discussed above.
  • Fig. 1 is a functional block diagram which shows a conventional decision feedback equalizer.
  • Fig. 2 is a functional block diagram which shows one system and technique for use of a decision feedback equalizer to equalize complementary code keyed or other orthogonal signals.
  • Fig. 3 is a diagram which schematically represents structure and format of a complementary code keyed symbols.
  • Fig. 4 is a functional block diagram which shows a preferred embodiment of a system and technique according to the present invention for equalizing complementary code keyed or other orthogonal signals.
  • Fig. 5 is a diagram which shows computer-predicted performance of various equalizing techniques.
  • Fig. 6 is a diagram which shows the multipath delay profile employed to generate the data shown in Fig. 5.
  • Fig. 7 is a diagram which shows effects of certain digital implementations of techniques according to the present invention.
  • Fig. 8 is a functional block diagram of a transceiver which incorporates devices and processes according to the present invention.
  • a decision feedback equalizer shown generally with numeral 10
  • Hard decision functionality or slicer 16 feeds hard decision information to the FBF.
  • the FBF uses already-detected data to cancel ISI from past data symbols so that the FFF only has to suppress ISI from future data symbols.
  • a DFE is suitable for high data rate applications because it is implementable with low complexity compared to other equalization techniques. See, for instance, S. L. Ariyavisitakul and G. M. Durant, "A Broadband Wireless Packet Technique Based On Coding Diversity And Equalization," IEEE Communications Magazine, 110 (July 1998) ("Ariyavisitakul and Durant”) which is incorporated herein by reference.
  • DFE In order to apply DFE to CCK (or any orthogonal signaling system), a straightforward approach is to use the DFE to equalize the signal before CCK symbol detection.
  • the DFE has the same structure as Fig. 1 , but it operates on each chip of the CCK symbol as if the chip was a quaternary phase shift keying (QPSK) symbol.
  • QPSK phase shift keying
  • the drawback of this approach is that, since the processing gain of CCK is not utilized, the decisions made by the DFE will have a relatively high error probability, and the decision errors will trigger improper ICI and ISI cancellation which affects the final CCK detection output.
  • a CCK system which uses a DFE as a predetection equalizer will perform only as well as a non-spreading QPSK system at high signal-to-noise ratio (SNR).
  • SNR signal-to-noise ratio
  • the processing gain of CCK can be utilized by feeding back the more reliable output of the CCK symbol detector to the DFE.
  • This requires a data to CCK symbol remapper (or, simply for convenience in this document, but in a non-limiting way, "remapper” or “remodulator”) which maps the decided data into necessary CCK chip waveforms for ISI cancellation by the FBF (see Fig. 2).
  • remapper or, simply for convenience in this document, but in a non-limiting way, "remapper” or “remodulator”
  • the receiver needs to feedback the chip waveform corresponding to that symbol to the equalizer.
  • the invention contemplates any way to map the proxy corresponding to the decided symbol into a CCK symbol waveform with 8 chips. These chip values may then be used in the feedback filter of the equalizer.
  • devices and processes according to the present invention are mapping information data into CCK symbol waveforms, and any such process for mapping is referred to herein as remodulation or remapping. Such remapping can be done using remodulation techniques, but other techniques may be used as well.
  • the demodulator 18 and remapper 20 are shown in Fig. 2, as are FFF 22 and FBF 24 and hard decision functionality 26 in equalizer 28.
  • the use of more reliable decisions improves the DFE performance as well as the error performance of the final CCK detection output.
  • the CCK decision is available only once every 8 chips, the sliced output of the DFE is still needed for the remaining ICI cancellation, depending on which chip is currently being equalized. For example, referring to Fig. 3, if chip #0 of the current CCK symbol is being equalized, past CCK decisions are sufficient to create all the waveforms necessary for ISI and ICI cancellation.
  • the present invention employs a DFE for equalization of CCK or any orthogonal signaling scheme.
  • a system according to the present invention which employs methods according to the present invention, is shown in Fig. 4.
  • Fig 4 shows an equalizer 30 which may use conventional demodulator 32, remapper 34, FFF 36, and FBF 38. Similar to what is shown in Fig. 2, both the DFE output and the CCK decisions are used as input to FBF 38. However, instead of using a hard decided DFE output, the output of the DFE is passed through soft decision functionality 40 in order to use the soft-decided chip value for ICI cancellation.
  • Functionality 40 as is the case with demodulator 32, remapper 34, FFF 36, FBF 38 and other circuits, need not be implemented in discrete components or devices, but may be implemented in any desirable fashion.
  • FFF 36 and FBF 38 may be implemented using a series of taps located in the same or proximate geographical area to each other, in a single integrated circuit.
  • CCK decisions reliable ISI cancellation can be achieved (similar to the method in Fig. 2).
  • soft chip feedback the ICI may not be completely canceled, but the impact of decision errors is minimized due to the fact that the soft-decided value is likely to be small when the chip is not reliable.
  • Soft decision functions may be employed.
  • one form of such a function is a hyperbolic tangent function. If the function is overly steep, the decision is overly hard and therefore less preferred for at least the reasons mentioned in the preceding paragraph. If too soft, residual noise may be excessive.
  • Soft decision functions, techniques and devices are disclosed in S. L. Ariyavisitakul and Y. Li, Joint Coding and Decision Feedback Equalization for Broadband Wireless Channels, 16 IEEE J. Selected Areas in Communications, 1670 (No. 9, December 1998) (“Ariyavisitakul and Li”), which is incorporated herein by this reference.
  • the soft decision originates a function of the present and past DFE output sequence ⁇ y y n . , y n -2 • • • y n -M) ⁇ ⁇ resort ⁇ ⁇ n p ( ⁇ n ,yford-. > y n - ⁇ • • • yford- M ) • all possible values of x.
  • ⁇ is a parameter which controls the softness of the function.
  • ⁇ should be set according to the measured signal-to-noise ratio (SNR) at the output of the equalizer.
  • SNR signal-to-noise ratio
  • MSE mean-square error
  • f(y) digitally is by using a look-up table approach.
  • a read only memory (ROM) or other memory as appropriate can be used to store all possible values of f(y) corresponding to a practical range of y.
  • ROM read only memory
  • y n is translated to the appropriate address to read f(y n ) from the ROM.
  • Fig. 8 is a functional block diagram showing one transceiver which can include equalization processes and devices according to the present invention.
  • Fig. 8 should not be interpreted or construed to limit the invention to any particular hardware and / or software implementation, as should not any description in this document.
  • Any form of radio apparatus which performs modulation and/or demodulation that is adapted or adaptable to devices and processes according to the present invention is appropriate to consider as a system within the scope of the invention.
  • Fig. 8 shows a transceiver 50 which includes an RF stage 52 which in turn can include conventional duplexing and amplification circuits, and which is coupled to one or more conversion stages 54 and 56.
  • the IF modulation / demodulation circuits 56 convert the signal into baseband (I) (Q) waveforms, and are coupled to circuits 58 according to the present invention, such as are described above, for performing processes according to the present invention.
  • Those circuits 58 may interface to appropriate conventional or unconventional media access control (MAC) circuits 60 for handling voice, data and other signals.
  • Transceiver 50 may form part of a wireless LAN, or one of the various pieces of equipment in networks such as are disclosed in U.S.S.N. 09/229,848, filed January 12, 1999, entitled "Wireless Communications Gateway For A Small Home Or Office," U.S.S.N.
  • a computer simulation was performed to evaluate the CCK radio link performance of systems and techniques according to the present invention under typical indoor wireless fading channels.
  • An example of the results is shown in Fig. 5.
  • the measure of performance is the packet error rate (PER), where each packet contains 400 payload bits.
  • the multipath delay profile employed is shown in Fig. 6; this delay profile is proposed by the Joint Technical Committee T1/E1 (JTC) to represent a severe multipath environment within a commercial building. Rayleigh fading is superimposed on each path.
  • the maximum path delay is 2.1 ⁇ s, i.e., about 29 chip periods.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

L'invention concerne des dispositifs, système et procédés permettant de corriger des signaux modulés de manière orthogonale et, plus précisément, des signaux modulés à code complémentaire. Une sortie de fonctionnalité à décision souple, fondée sur lesdits signaux, permet de produire des informations qui sont renvoyées auxdits signaux modulés à code complémentaire, le but étant de réduire les interférences et, surtout, les autobrouillages provoqués par des retards de propagation par trajets multiples, au niveau des signaux modulés à code complémentaire. En outre, les informations fondées sur lesdits signaux modulés à code complémentaire, informations qui peuvent être basées sur le remappage des signaux après leur démodulation afin de correspondre aux symboles modulant le code complémentaire, peuvent être renvoyées aux signaux modulés à code complémentaire afin, notamment, de réduire les interférences et de tirer parti du gain de traitement résultant de techniques de traitement de modulation de code complémentaire.
PCT/US2000/013560 1999-05-21 2000-05-17 Techniques de correction pour systemes de communications au moyen de signalement orthogonal Ceased WO2000072540A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP00932536A EP1188283A1 (fr) 1999-05-21 2000-05-17 Techniques de correction pour systemes de communications au moyen de signalement orthogonal
AU50243/00A AU5024300A (en) 1999-05-21 2000-05-17 Equalization techniques for communication systems using orthogonal signaling

Applications Claiming Priority (2)

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US31680099A 1999-05-21 1999-05-21
US09/316,800 1999-05-21

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003069863A1 (fr) 2002-02-14 2003-08-21 Koninklijke Philips Electronics N.V. Procede et systeme d'egalisation de retroaction par decision conjointe et decodage de cle de code complementaire utilisant un treillis
WO2003107534A1 (fr) 2002-06-12 2003-12-24 Bermai, Inc. Demodulation cck via egalisateur a decision retroactive de symboles
EP1467531A1 (fr) * 2003-04-07 2004-10-13 Harris Corporation Système d'égalisation de canal utilisant une remodulation d'une estimation du signal reçu
WO2004112339A1 (fr) * 2003-05-28 2004-12-23 Qualcomm Incorporated Egaliseur a decision retroactive a codage-decodage cck combines dans le filtrage avec retroaction
WO2005002163A3 (fr) * 2003-06-24 2005-03-24 Qualcomm Inc Contenu ameliore d'entree de circuit de decision et de filtre de retour pour les communications numeriques codees par blocs
US7130343B2 (en) 2002-02-27 2006-10-31 Advanced Micro Devices, Inc. Interference reduction in CCK modulated signals
US7263119B1 (en) 2001-11-29 2007-08-28 Marvell International Ltd. Decoding method and apparatus
US7324433B1 (en) 2001-11-29 2008-01-29 Marvell International Ltd. Method and apparatus for determining signal quality
US7339918B2 (en) 2000-06-26 2008-03-04 Nokia Corporation Method for improving the quality of data transmission

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CARL ANDREN,MARK WEBSTER: "CCK Modulation delivers 11 Mbps for high Rate IEEE 802.11 Extension", INTERNET, 14 March 2000 (2000-03-14), pages 1 - 8, XP002147321 *
WANG T ET AL: "IMPROVED ADAPTIVE DECISION-FEEDBACK EQUALIZATION WITH INTERLEAVING FOR CODED MODULATION SYSTEMS", PROCEEDINGS OF THE GLOBAL TELECOMMUNICATIONS CONFERENCE (GLOBECOM),US,NEW YORK, IEEE, 28 November 1994 (1994-11-28), pages 6 - 10, XP000488508, ISBN: 0-7803-1821-8 *

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7339918B2 (en) 2000-06-26 2008-03-04 Nokia Corporation Method for improving the quality of data transmission
US8059707B1 (en) 2001-11-29 2011-11-15 Marvell International Ltd. Decoding method and apparatus
US7746925B1 (en) 2001-11-29 2010-06-29 Marvell International Ltd. Decoding method and apparatus
US7701871B1 (en) 2001-11-29 2010-04-20 Marvell International Ltd. Method and apparatus for determining signal quality
US7263119B1 (en) 2001-11-29 2007-08-28 Marvell International Ltd. Decoding method and apparatus
US7324433B1 (en) 2001-11-29 2008-01-29 Marvell International Ltd. Method and apparatus for determining signal quality
US7606296B1 (en) 2001-11-29 2009-10-20 Marvell International Ltd. Decoding method and apparatus
CN1633792B (zh) * 2002-02-14 2010-07-14 皇家飞利浦电子股份有限公司 使用网格结合判定反馈均衡和补码键控解码的方法和系统
KR100957176B1 (ko) 2002-02-14 2010-05-11 코닌클리케 필립스 일렉트로닉스 엔.브이. 수신된 상보 코드 키(cck) 인코드된 심볼(칩)을 디코드하기 위한 시스템 및 방법과, 통신 채널을 통해 통신되는 심볼들을 수신하기 위한 수신기 디바이스
US7027538B2 (en) 2002-02-14 2006-04-11 Koninklijke Philips Electronics N.V. Method and system for joint decision feedback equalization and complementary code key decoding using a trellis
WO2003069863A1 (fr) 2002-02-14 2003-08-21 Koninklijke Philips Electronics N.V. Procede et systeme d'egalisation de retroaction par decision conjointe et decodage de cle de code complementaire utilisant un treillis
US7130343B2 (en) 2002-02-27 2006-10-31 Advanced Micro Devices, Inc. Interference reduction in CCK modulated signals
EP1540817A4 (fr) * 2002-06-12 2009-05-27 Dsp Group Inc Demodulation cck via egalisateur a decision retroactive de symboles
WO2003107534A1 (fr) 2002-06-12 2003-12-24 Bermai, Inc. Demodulation cck via egalisateur a decision retroactive de symboles
US7548598B2 (en) 2003-04-07 2009-06-16 Harris Corporation Method and apparatus for iteratively improving the performance of coded and interleaved communication systems
EP1467531A1 (fr) * 2003-04-07 2004-10-13 Harris Corporation Système d'égalisation de canal utilisant une remodulation d'une estimation du signal reçu
RU2343632C2 (ru) * 2003-05-28 2009-01-10 Квэлкомм Инкорпорейтед Корректор с решающей обратной связью с комбинированным кодированием-декодированием сск в фильтрации обратной связи
US7324590B2 (en) 2003-05-28 2008-01-29 Qualcomm Incoporated Equalizer with combined CCK encoding-decoding in feedback filtering of decision feedback equalizer
JP2007504788A (ja) * 2003-05-28 2007-03-01 クゥアルコム・インコーポレイテッド 帰還型フィルタリングにおいて、ｃｃｋ符号化と復号とを組み合わせた判定帰還型等化器
WO2004112339A1 (fr) * 2003-05-28 2004-12-23 Qualcomm Incorporated Egaliseur a decision retroactive a codage-decodage cck combines dans le filtrage avec retroaction
JP2011045095A (ja) * 2003-05-28 2011-03-03 Qualcomm Inc 帰還型フィルタリングにおいて、ｃｃｋ符号化と復号とを組み合わせた判定帰還型等化器
US7986728B2 (en) 2003-05-28 2011-07-26 Qualcomm Incorporated Equalizer with combined CCK encoding-decoding in feedback filtering of decision feedback equalizer
WO2005002163A3 (fr) * 2003-06-24 2005-03-24 Qualcomm Inc Contenu ameliore d'entree de circuit de decision et de filtre de retour pour les communications numeriques codees par blocs
US8290025B2 (en) 2003-06-24 2012-10-16 Qualcomm Incorporated Slicer input and feedback filter contents for block coded digital communications

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EP1188283A1 (fr) 2002-03-20
AU5024300A (en) 2000-12-12

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