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WO2007030308A2 - Procede et appareil de demappage d'un symbole module par une modulation d'amplitude en quadrature d'ordre superieur - Google Patents

Procede et appareil de demappage d'un symbole module par une modulation d'amplitude en quadrature d'ordre superieur Download PDF

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Publication number
WO2007030308A2
WO2007030308A2 PCT/US2006/032643 US2006032643W WO2007030308A2 WO 2007030308 A2 WO2007030308 A2 WO 2007030308A2 US 2006032643 W US2006032643 W US 2006032643W WO 2007030308 A2 WO2007030308 A2 WO 2007030308A2
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WO
WIPO (PCT)
Prior art keywords
soft bit
wtru
msb
threshold
qam
Prior art date
Application number
PCT/US2006/032643
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English (en)
Other versions
WO2007030308A3 (fr
Inventor
Qingyuan Dai
Robert Lind Olesen
Chang-Soo Koo
Nirav Shah
Original Assignee
Interdigital Technology Corporation
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 Interdigital Technology Corporation filed Critical Interdigital Technology Corporation
Publication of WO2007030308A2 publication Critical patent/WO2007030308A2/fr
Publication of WO2007030308A3 publication Critical patent/WO2007030308A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits
    • H04L27/3809—Amplitude regulation arrangements
    • 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

Definitions

  • the present invention is related a wireless communication system.
  • the present invention is related to a method and apparatus for de-mapping a symbol modulated by a high order quadrature amplitude modulation (QAM).
  • QAM quadrature amplitude modulation
  • FIG. 1 is a block diagram of a conventional wireless transmit/receive unit (WTRU) 100 on a transmit side.
  • the WTRU 100 includes a symbol mapper 102 and a transmitter 104.
  • the symbol mapper 102 maps a predetermined number of input bits 101 to a symbol 103 in accordance with a modulation scheme.
  • the symbol 103 is then transmitted by the transmitter 104 over a wireless channel.
  • Equation (2) where k denotes a k-th symbol index, X(Jc) is a transmitted symbol, subscript r denotes a real symbol, (i.e., an I channel symbol), subscript i denotes an imaginary symbol, (i.e., a Q channel symbol), and bo and b4 are the most significant bits (MSBs).
  • MSBs most significant bits
  • Viterbi decoding requires symbol-to-bit de-mapping of received samples.
  • the conventional maximum likelihood de-mapping schemes have a computational complexity proportional to the order of QAM. This becomes practically impossible when dealing with a high order QAM, such as 256-QAM for an IEEE 802. Hn multiple-input multiple-output (MIMO) system.
  • MIMO multiple-input multiple-output
  • a low complexity de-mapping scheme has been developed for binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 16 QAM or 64 QAM.
  • BPSK binary phase shift keying
  • QPSK quadrature phase shift keying
  • 16 QAM 16 QAM
  • 64 QAM 64 QAM.
  • the present invention extends a conventional symbol de-mapping method and apparatus for high order QAM, such as 256-QAM.
  • the present invention is related to a method and apparatus for de- mapping a symbol modulated by a high order QAM.
  • a transmitting WTRU maps N input bits to one of 2 N symbols in a 2 N -QAM constellation.
  • a receiving WTRU receives a signal and generates a sample of the received signal.
  • a soft bit value of the most significant bit (MSB) is calculated based on a value of the sample.
  • a magnitude of the soft bit value of the MSB is subtracted from a threshold. The threshold is initially set with respect to the QAM order, N.
  • a soft bit value of the next MSB is calculated based on the subtraction results.
  • the calculation and subtraction steps are repeated for the next MSB until soft bit values of all the remaining bits are obtained while dividing the initial threshold, (e.g., 4, 8, 16 for 64, 256, 512 QAM, respectively), by 2 each iteration for the next MSB.
  • the initial threshold e.g. 4, 8, 16 for 64, 256, 512 QAM, respectively
  • Figure 1 is a block diagram of a conventional WTRU on a transmit side.
  • Figure 2 shows a conventional constellation for 256-QAM.
  • Figure 3 is a block diagram of a WTRU on a receive side configured in accordance with the present invention.
  • Figure 4 shows a bit error rate (BER) versus a signal-to-noise ratio
  • the present invention provides low complexity symbol de-mapping method and apparatus for QAM, such as 256-QAM.
  • the present invention may be implemented in a WTRU.
  • WTRU includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a Node-B, a base station, a site controller, an access point (AP), or any other type of device capable of operating in a wireless environment.
  • the present invention may be implemented in any wireless communication network including, but not limited to, wideband code division multiple access (WCDMA), WCDMA long term evolution (LTE), IEEE 8O2.xx, orthogonal frequency division multiplexing (OFDM), or any other wireless communication system.
  • WCDMA wideband code division multiple access
  • LTE long term evolution
  • IEEE 8O2.xx orthogonal frequency division multiplexing
  • the present invention is also applicable to a system using a smart antenna, (e.g., switched beam antenna, phased array antenna, diversity and multiple-input multiple-output (MIMO) antenna, or the like).
  • a smart antenna e.g., switched beam antenna, phased array antenna, diversity and multiple-input multiple-output (MIMO) antenna, or the like.
  • MIMO multiple-input multiple-output
  • the present invention will be explained with reference to 256 QAM. However, it should be noted that the present invention is applicable to any modulation scheme lower or higher than 256-QAM for the Gray coded constellation. It is assumed that the 256 QAM symbols are transmitted at an average power of 170. Therefore, a proper scaling must be taken into account when the transmit signal is normalized to the average power of 1.
  • Figure 3 is a block diagram of a WTRU 300 on a receive side configured in accordance with the present invention.
  • the WTRU 300 includes a receiver 302, a first no ⁇ nalizer 304, a symbol de-mapper 306 and a second normalizer 308.
  • the receiver 302 receives transmitted signals 301 over a wireless channel and outputs samples 303 of the received signals to the first normalizer 304.
  • a frequency domain received sample for OFDM systems, R(k) , at a given time instant is expressed as follows: Equation (3) where G(A;) is a channel response and is an additive noise.
  • the first normalizer 304 performs normalization on the samples 303 using a minimum mean square error (MMSE) solution for generating a normalized sample value 305.
  • MMSE minimum mean square error
  • Equation (4) W(k) is a noise sample after normalization, ⁇ ; is a noise variance and * denotes a complex conjugate.
  • Equation (5) is used for the symbol de-mapping in the symbol de-mapper 306 in accordance with the present invention.
  • the symbol de-mapper 306 de-maps the normalized sample value to bits
  • the soft- decision values are determined based on the received sample value Z r (k) and Z 1 (k) , respectively, as follows:
  • the soft bits 307 are sent to the second no ⁇ nalizer 308 for normalization with an average transmit power. Since it is assumed that the average power is 170, the soft-decision values need to be normalized by to be mapped to [-1 1] as follows: Equation (19)
  • Figure 4 shows a BER versus an SNR, (i.e., Es/No), in simulation results for comparing the low complexity de-mapping scheme of the present invention with a conventional maximum likelihood de-mapping scheme.
  • SNR i.e., Es/No
  • AWGN additive white Gaussian noise
  • a method for symbol-to-bit de-mapping in a receiving WTRU in a wireless communication system including a plurality of WTRUs, wherein a transmitting WTRU maps N input bits to one of 2 N symbols in a 2 N -QAM constellation.
  • a WTRU for symbol-to-bit de-mapping in a wireless communication system including a plurality of WTRUs, wherein a transmitting
  • WTRU maps N input bits to one of 2 N symbols in a 2 N -QAM constellation.
  • the WTRU of embodiment 10 comprising a receiver for receiving a signal and generating a sample of the received signal.
  • the WTRU of embodiment 11 comprising a symbol-to-bit de- mapper for calculating a soft bit value of an MSB based on a value of the sample, subtracting a magnitude of the soft bit value of the MSB from a threshold, the threshold being set to N, calculating a soft bit value of a next MSB based on the subtraction results, and repeating subtraction and calculation of the soft bit value for the next MSB until soft bit values of all of the remaining bits are obtained while dividing the threshold by 2 for each iteration for the next MSB.
  • N is equal to 8.
  • the WTRU as in any of the embodiments 10-13, further comprising a normalizer for normalizing the soft bit values with a square root of an average power of the transmitted symbols.
  • WTRU is a mobile station.
  • WTRU is a base station.
  • An IC for symbol de-mapping in a wireless communication system including a plurality of WTRUs, wherein a transmitting WTRU maps N input bits to one of 2 N symbols in a 2 N -QAM constellation.
  • the IC of embodiment 18 comprising a receiver for receiving a signal and generating a sample of the received signal.
  • the IC of embodiment 19 comprising a symbol-to-bit de- mapper for calculating a soft bit value of an MSB based on a value of the sample, subtracting a magnitude of the soft bit value of the MSB from a threshold, the threshold being set to N, calculating a soft bit value of a next MSB based on the subtraction results, and repeating subtraction and calculation of the soft bit value for the next MSB until soft bit values of all of the remaining bits are obtained while dividing the threshold by 2 for each iteration for the next MSB.

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

Abstract

L'invention concerne un procédé et un appareil de démappage d'un symbole modulé par une modulation d'amplitude en quadrature d'ordre supérieur (QAM). Une unité d'émission/réception sans fil (WTRU) émettrice mappe N bits d'entrée sur un des 2N symboles dans une constellation 2N-QAM. Une WTRU réceptrice reçoit un signal et un échantillon du signal reçu. Une valeur binaire pondérée du bit le plus significatif (MSB) est calculée en fonction d'une valeur de l'échantillon. Une amplitude de la valeur binaire pondérée du MSB est soustraite d'un seuil. Le seuil est initialement défini par rapport à l'ordre QAM, N. Une valeur binaire pondérée du MSB suivant est calculée en fonction des résultats de soustraction. Les étapes de calcul et de soustraction sont répétées pour le MSB suivant jusqu'à ce que des valeurs binaires pondérées de l'ensemble des bits restants soient obtenues tout en divisant le seuil par 2 à chaque itération.
PCT/US2006/032643 2005-09-08 2006-08-22 Procede et appareil de demappage d'un symbole module par une modulation d'amplitude en quadrature d'ordre superieur WO2007030308A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US71523505P 2005-09-08 2005-09-08
US60/715,235 2005-09-08

Publications (2)

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WO2007030308A2 true WO2007030308A2 (fr) 2007-03-15
WO2007030308A3 WO2007030308A3 (fr) 2007-05-18

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114422317A (zh) * 2022-03-29 2022-04-29 中山大学 一种多载波qam映射/解映射电路的方法

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6952458B1 (en) * 2000-10-02 2005-10-04 Globespanvirata, Inc. Demapping system and method
US7529323B2 (en) * 2005-06-06 2009-05-05 The Aerospace Corporation Quaternary precoded continuous phase modulation soft bit metric demodulator

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114422317A (zh) * 2022-03-29 2022-04-29 中山大学 一种多载波qam映射/解映射电路的方法
CN114422317B (zh) * 2022-03-29 2022-07-05 中山大学 一种多载波qam映射/解映射电路的方法

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