WO2001035545A2 - Technique a diversite dans le temps permettant d'ameliorer le debit binaire d'une transmission dans un systeme a porteuses multiples et appareil correspondant - Google Patents

Technique a diversite dans le temps permettant d'ameliorer le debit binaire d'une transmission dans un systeme a porteuses multiples et appareil correspondant Download PDF

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Publication number
WO2001035545A2
WO2001035545A2 PCT/US2000/042063 US0042063W WO0135545A2 WO 2001035545 A2 WO2001035545 A2 WO 2001035545A2 US 0042063 W US0042063 W US 0042063W WO 0135545 A2 WO0135545 A2 WO 0135545A2
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WO
WIPO (PCT)
Prior art keywords
bit
rate
error rate
carrier signal
transmission
Prior art date
Application number
PCT/US2000/042063
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English (en)
Other versions
WO2001035545A3 (fr
Inventor
Marcos C. Tzannes
Original Assignee
Aware, Inc.
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 Aware, Inc. filed Critical Aware, Inc.
Priority to AU36432/01A priority Critical patent/AU3643201A/en
Priority to JP2001537177A priority patent/JP2003514430A/ja
Priority to EP00991952A priority patent/EP1228616A2/fr
Priority to KR1020027005831A priority patent/KR20020049026A/ko
Priority to CA002387814A priority patent/CA2387814A1/fr
Publication of WO2001035545A2 publication Critical patent/WO2001035545A2/fr
Publication of WO2001035545A3 publication Critical patent/WO2001035545A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/005—Control of transmission; Equalising
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/08—Arrangements for detecting or preventing errors in the information received by repeating transmission, e.g. Verdan system

Definitions

  • This invention relates to communication systems using multicarrier modulation. More particularly, the invention relates to a method and apparatus for improving the transmission bit rate in a multicarrier modulation system.
  • transceivers communicate over a communication channel using multicarrier modulation, such as discrete multitone modulation (DMT).
  • DMT discrete multitone modulation
  • a DMT transmitter such as a DMT modem, receives an input bit stream comprising information bits and modulates the information bits onto carrier signals (carriers) or sub-channels spaced within a usable frequency band of the communication channel. The modulation occurs at a symbol transmission rate of the system.
  • the DMT transmitter typically modulates the phase characteristic (or phase) and amplitude of the carrier signals using an Inverse Fast Fourier Transform (IFFT) to generate a time domain signal (or transmission signal) that is a linear combination of the carrier signals.
  • IFFT Inverse Fast Fourier Transform
  • the DMT transmitter transmits the transmission signal to a DMT receiver over the communication channel.
  • the receiver demodulates the received carrier signals using a Fast Fourier Transform.
  • the number of information bits that each carrier signal carries during a single DMT symbol depends on the signal-to-noise ratio (SNR) of that carrier signal and the associated bit-error rate
  • BER BER requirement of the communication channel.
  • DSL communication systems operate with a BER of 1 x 10 '7 (i.e., one bit in ten million is received in error on average).
  • Different carriers can have different SNR and therefore may carry a different number of bits at the same BER.
  • SNR SNR for a given BER that is less than a minimum SNR needed to modulate a complete information bit
  • DMT transmitter does not use that particular carrier signal. For example, to carry at least one complete information bit at a BER of 1 x 10 "7 , a carrier signals needs a minimum uncoded SNR of 11.34 dB. Any carrier signal with an SNR less than 11.34 dB is not used and consequently, in noisy multicarrier communication systems, many carrier signals can remain unused.
  • One objective of the invention is to increase the transmission bit rate of multicarrier modulation transceivers by using carrier signals with an signal-to-noise ratio (SNR) that precludes transmitting one information bit at a specified BER during a single DMT symbol period.
  • the invention features a method in a multicarrier modulation system including two transceivers in communication with each other using a transmission signal having a plurality of carrier signals for modulating an input bit stream.
  • One of the carrier signals has a signal-to-noise ratio (SNR) that precludes transmitting at a bit-error rate a complete information bit of the input bit stream on that one carrier signal during a single symbol period.
  • SNR signal-to-noise ratio
  • the same information bit of the input bit stream is modulated during multiple symbol periods on this carrier signal, to increase the effective SNR of that carrier signal and achieve the specified bit-error rate.
  • the multiple symbol periods can be successive in order.
  • At least one bit is allocated to the carrier signal having the SNR that precludes transmitting a complete information bit at the bit-error rate.
  • a transmission bit rate is determined, and the modulating of the same information bit occurs when the transmission bit rate is less than a minimum transmission bit rate.
  • the modulating of the same information bit occurs if the modulating will improve the transmission bit rate by at least a predefined threshold percentage.
  • the invention features a method for communicating over a communication channel.
  • one or more information bits of an input bit stream are transmitted on one or more carrier signals at a first bit-error rate.
  • a same information bit of the input bit stream is transmitted on one of the carrier signals at a second bit-error rate.
  • the second bit-error rate is higher than the first bit-error rate.
  • the successive symbol periods can include the symbol period during which one or more information bits of the input bit stream are transmitted on one or more carriers at the first bit-error rate. The number of bits transmitted per symbol period and the transmission bit rate at the first bit-error rate are thereby increased.
  • the invention features a method wherein a carrier signal having an SNR that precludes transmitting a complete information bit at a bit-error rate during a single symbol period is demodulated.
  • the carrier is demodulated for successive symbol periods to obtain partial information regarding an information bit during each of the successive symbol periods.
  • the partial information is combined to produce a complete information bit.
  • the invention features a method wherein a same information bit is received during successive symbol periods on a previously unusable carrier signal at a second bit-error rate.
  • the previously unusable carrier signal was unusable because the carrier signal was unable to carry bits at a first bit-error rate.
  • the second bit-error rate is higher than the first bit-error rate, thereby increasing the transmission bit rate at the first bit-error rate.
  • Fig. 1 is a block diagram of an embodiment of a digital subscriber line (DSL) communications system including a discrete multitone modulation (DMT) transceiver in communication with a remote transceiver; and
  • DSL digital subscriber line
  • DMT discrete multitone modulation
  • Fig. 2 is a flow diagram of an embodiment of a process for increasing the transmission bit rate of the communication system.
  • Fig. 1 shows a digital subscriber line (DSL) communication system 2 including a discrete multitone modulation (DMT) transceiver 10 in communication with a remote transceiver 14 over a communication channel 18 using a transmission signal 38 having a plurality of carrier signals.
  • the DMT transceiver 10 includes a DMT transmitter 22 and a DMT receiver 26 and the remote transceiver 14 includes a transmitter 30 and a receiver 34.
  • OFDM orthogonally multiplexed quadrature amplitude modulation
  • DWMT discrete wavelet multitone
  • OFDM orthogonal frequency division multiplexing
  • the communication channel 18 provides a downstream transmission path from the DMT transmitter 22 to the receiver 34, and an upstream transmission path from the transmitter 30 to the DMT receiver 26.
  • the communication channel 18 is a pair of twisted wires of a telephone subscriber line.
  • the communication channel 18 is a fiber optic wire, a quad cable, consisting of two pairs of twisted wires, or a quad cable that is one of a star quad cable, a Dieselhorst-Martin quad cable, and the like.
  • the communication channel 18 is the air through which the transmission signal 38 travels between the transceivers 10, 14.
  • the DMT transmitter 22 includes a QAM encoder 42, a bit allocation table (BAT) 44, and a modulator 46.
  • the transmitter 30 of the remote transceiver 14 comprises equivalent components as the DMT transmitter 22.
  • this embodiment specifies a detailed description of the DMT transmitter 22, the inventive concepts apply also to the receivers 34, 36, which have similar components to that of the DMT transmitter 22, but perform inverse functions in a reverse order.
  • the QAM encoder 42 maps an input serial data bit stream 54, which consists of information bits, into N parallel QAM symbols 58, where N represents the number of carrier signals generated by the modulator 46.
  • the modulator 46 uses an inverse fast Fourier transform (IFFT) to change the QAM symbols 58 into a transmission signal 38 comprised of a sequence of DMT symbols 70.
  • IFFT inverse fast Fourier transform
  • Each carrier signal of the transmission signal 38 is modulated with a different QAM symbol 58.
  • a pilot tone is included in the transmission signal 38 to provide a reference signal for coherent demodulation of the carrier signals at the receiver 34 during reception of the transmission signal 38.
  • the modulator 46 modulates information bits on carrier signals on a DMT symbol by DMT symbol basis.
  • Each DMT symbol period is approximately 250 ms, which corresponds to a 4 kHz DMT symbol rate.
  • the number of bits modulated on a particular carrier signal during a DMT symbol period depends on the signal-to-noise ratio (SNR) of that carrier signal at a specified BER.
  • the modulator 46 can modulate several information bits on each carrier signal when the communication channel 18 has low noise (i.e., a high SNR on each carrier signal) and thus achieves a high system transmission bit rate.
  • the SNR can be low and the number of information bits modulated on each carrier signal few, resulting in a low system transmission bit rate.
  • Table 1 below shows the required uncoded SNR at a 1 x 10 " BER for modulating one through eight information bits on a carrier signal during one DMT symbol period using QAM.
  • the SNR of one or more carrier signals is too low to carry a full information bit at the specified bit-error rate.
  • the SNR of a carrier signal is less than 11.34 dB, such a SNR precludes the transmission of a complete bit of information on that carrier signal at a BER of 1 x 10 '7 .
  • the transceivers 10, 14 make use of these carrier signals that might otherwise remain unused for conveying information over the communication channel 18.
  • carrier signals are referred to as recovered carrier signals.
  • the transmitter 22 transmits one or more information bits on the recovered carrier signal for successive DMT symbol periods at a higher BER than the specified BER. The effect of transmitting an information bit on a recovered carrier signal for successive DMT symbol periods at the higher BER, although that carrier signal cannot transmit a complete information bit at the specified BER, is to increase the effective SNR of the recovered carrier signal and achieve the specified BER.
  • the modulator 46 modulates one information bit over two successive DMT symbols 70.
  • Table 2 illustrates an embodiment of the required
  • the transmitter 22 transmits one or more information bits on the recovered carrier signal during non-successive DMT symbol periods at a higher BER than the specified BER.
  • the transmitter 22 can transmit the same information bit on a recovered carrier signal during every other DMT symbol period (e.g., during the first and third DMT symbol periods).
  • Other examples include transmitting the same information bit over every third, fourth, fifth DMT symbol period, and so on.
  • the transmitter 22 can transmit the complete information bit on a recovered carrier signal using non-successive DMT symbol periods as long as the receiver 34 knows which DMT symbol periods the transmitter 22 is using to transmit that information bit.
  • the transmitter 22 can transmit more than one bit on a recovered carrier signal during a single DMT symbol period.
  • the BER at which the multiple bits are transmitted is higher than if only one information bit was transmitted on that recovered canier signal.
  • the transmitter 22 transmits the same information bits on the recovered carrier signal for a greater number of successive DMT symbols than needed for transmitting one information bit. For example, if the SNR is 8.34 dB, the recovered carrier signal can carry two bits over four successive DMT symbols 70 to achieve a BER of 1 x 10 "7 .
  • the BAT 44 is in communication with the modulator 46 to specify the number of bits carried by each carrier signal.
  • the BAT 44 in one embodiment allocates one bit and specifies additional information that indicates the number of DMT symbol periods needed to convey the complete information bit.
  • the BATs 44, 44' identify which carrier signals are being used to convey information bits over more than one DMT symbol period and the number of DMT symbol periods required to transmit information bits on that carrier signal.
  • the BAT specifies fractions of bits to indicate the number of DMT symbol periods needed to convey the complete information bit.
  • Fig. 2 shows embodiments of a process used by the DMT transceiver 10 and the remote transceiver 14 for communicating over the communication channel 18.
  • the remote receiver 34 determines (step 204) the number of bits to be carried by each carrier signal.
  • the remote receiver 34 measures the SNR for a specified bit-error rate.
  • the measured SNR limits the number of bits that the carrier signal can carry and achieve the specified bit-error rate.
  • Table 1 described above shows the SNR required for a carrier signal to convey one through eight bits at a bit-error rate of 1 x 10 "7 .
  • the receiver 34 determines (step 206) from the measured SNR of the recovered carrier signal how many DMT symbol periods are needed to convey the information bit completely at the specified BER. For example, when the measured SNR is 8.34 dB, the receiver 34 determines that two DMT symbol periods are needed to carry the complete information bit at the specified bit-error rate of 1 x 10 "7 . Approximately one-half of the bit information can be conveyed during each of the two symbol periods; in effect, during each symbol period the carrier signal conveys partial information or a fraction of the information bit. If, for example, the measured SNR is instead 5.34 dB, then the receiver determines that four DMT symbol periods are needed to convey the complete information bit.
  • the remote receiver 34 then communicates (step 208) the number of bits allocated to each carrier signal to the transmitter 22.
  • the remote receiver 34 can specify the number of DMT symbol periods needed to convey the complete information bit or the fraction of the information bit conveyed during each DMT symbol period.
  • the transmitter 22 and remote receiver 34 each create (step 212) its copy of the bit allocation table 44, 44', which specify the number of bits allocated to each carrier signal, in accordance with the information determined by the receiver 34 and communicated to the transmitter 22.
  • the BAT 44 in one embodiment allocates one bit and specifies additional information that indicates the number of DMT symbol periods needed to convey the complete information bit. In another embodiment, the BAT specifies the fraction of the information bit conveyed during each DMT symbol period for recovered carrier signals.
  • the transmitter 22 can modulate information bits on recovered carrier signals if using of such recovered carrier signals will increase the transmission bit rate of the DSL communication system 2 by a predetermined amount. For example, if the increase in the transmission bit rate is equal to or exceeds a predefined threshold percentage (e.g., 10%), the transmitter 22 then uses recovered carrier signals for transmitting information bits.
  • a predefined threshold percentage e.g. 10%
  • the transmitter 22 modulates
  • one embodiment of the BAT 44 can allocate one bit to carrier signal #1, one bit to carrier signals #2 and #3, and three bits to carrier signals #4 and #5. Further, the BAT 44 can identify carrier signal #1 as a recovered carrier signal that carries the same information bit for two successive DMT symbols. Thus, carrier signals #2, #3, #4, and #5 carry new information bits during each of the two successive DMT symbols 70 at the first BER, while the recovered carrier signal #1 carries the same information bit over both of the two successive DMT symbols 70 at the second BER. In another embodiment, the second of the two successive DMT symbol periods can be used to carry only the information bits on the recovered carrier signals (e.g., carrier signals #2, #3, #4, and
  • the transmitter 22 transmits the information bits at the first BER during one DMT symbol 70, and subsequently transmits the information bits on the recovered carrier signals at the second BER during the two successive DMT symbol periods.
  • the DMT transmitter 22 then transmits (step 228) the transmission signal 38 to the receiver
  • the receiver 34 demodulates (step 230) the transmission signal 38 for successive DMT symbol periods to obtain partial information about the information bit during each of the successive DMT symbol periods.
  • the receiver 34 then linearly combines (step 232) the partial information of the information bit to generate the complete information bit.
  • the receiver 34 uses the first DMT symbol period in the series of successive DMT symbol periods to determine whether the same information bit is modulated over the successive DMT symbol periods. For example, if the receiver 34 determines that the phase of the carrier signal is approximately 90°, the receiver 34 anticipates that the information bit has a value that is equal to one. The receiver 34 therefore does not need to wait for the following DMT symbol(s) to bring additional partial bit information so that the receiver 34 can generate the complete information bit. Thus, in this embodiment receiving an information bit over multiple DMT symbols does not increase the delay of demodulating that information bit. If, however, the phase of the carrier signal is less than 90°, such as 45°, the receiver 34 may need additional information provided by subsequent DMT symbol(s) to determine the value of the information bit.
  • the 45° phase might correspond to a bit value of one or might be the result of noise.
  • the receiver 34 can still decide from this phase that the information bit has a value of 1 and then use error checking to determine later if the decision was erconeous.
  • the conditions of the communication change may change to affect the SNRs of one or more carrier signals.
  • the receiver 34 and the transmitter 22 dynamically exchange bit allocation information corresponding to the new communication channel 18 conditions.
  • such exchanged information may include the number of DMT symbol periods needed to transmit a complete information bit, as described above. The exchange of the information can occur at the boundary of complete information bit (e.g., after the second DMT symbol 70 conveying an information bit that is completely transmitted in two DMT symbols).

Abstract

Cette invention a trait à une technique permettant d'accroître le rapport signal/bruit effectif (SNR) d'un signal de porteuse dont le SNR empêche la transmission d'un bit d'information complet d'un train binaire en entrée à un certain taux d'erreur binaire lors d'une période de symbole unique. L'accroissement du SNR du signal de porteuse repose sur la modulation d'un même bit d'information du train binaire en entrée durant des périodes de symbole successives. Cette modulation durant des périodes de symbole successives permet d'atteindre le taux d'erreur binaire du signal de porteuse. Ce dernier est démodulé pour des périodes de symbole successives et ce, afin d'obtenir une information partielle relative au bit d'information. On combine cette information partielle pour produire un bit d'information complet.
PCT/US2000/042063 1999-11-10 2000-11-10 Technique a diversite dans le temps permettant d'ameliorer le debit binaire d'une transmission dans un systeme a porteuses multiples et appareil correspondant WO2001035545A2 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
AU36432/01A AU3643201A (en) 1999-11-10 2000-11-10 A time diversity method and apparatus for improving transmission bit rate in a multicarrier system
JP2001537177A JP2003514430A (ja) 1999-11-10 2000-11-10 時間ダイバーシテイー方法およびマルチキャリアシステムにおいて通信ビットレートを向上させる装置
EP00991952A EP1228616A2 (fr) 1999-11-10 2000-11-10 Technique a diversite dans le temps permettant d'ameliorer le debit binaire d'une transmission dans un systeme a porteuses multiples et appareil correspondant
KR1020027005831A KR20020049026A (ko) 1999-11-10 2000-11-10 다중 반송파 시스템에서 송신 비트 전송률을 개선하기위한 시간 다이버시티 방법 및 장치
CA002387814A CA2387814A1 (fr) 1999-11-10 2000-11-10 Technique a diversite dans le temps permettant d'ameliorer le debit binaire d'une transmission dans un systeme a porteuses multiples et appareil correspondant

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16454399P 1999-11-10 1999-11-10
US60/164,543 1999-11-10

Publications (2)

Publication Number Publication Date
WO2001035545A2 true WO2001035545A2 (fr) 2001-05-17
WO2001035545A3 WO2001035545A3 (fr) 2001-12-20

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PCT/US2000/042063 WO2001035545A2 (fr) 1999-11-10 2000-11-10 Technique a diversite dans le temps permettant d'ameliorer le debit binaire d'une transmission dans un systeme a porteuses multiples et appareil correspondant

Country Status (6)

Country Link
EP (1) EP1228616A2 (fr)
JP (1) JP2003514430A (fr)
KR (1) KR20020049026A (fr)
AU (1) AU3643201A (fr)
CA (1) CA2387814A1 (fr)
WO (1) WO2001035545A2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20030094914A (ko) * 2002-06-10 2003-12-18 삼성전자주식회사 오에프디엠신호의 전송률을 향상시킬 수 있는 오에프디엠송신기 및 그의 신호압축방법
US8675612B2 (en) 2001-05-14 2014-03-18 Interdigital Technology Corporation Channel quality measurements for downlink resource allocation

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100833649B1 (ko) 2006-12-07 2008-05-29 한국전자통신연구원 이동 통신 시스템의 그룹형 다중 간섭 잡음 제거 장치 및그 방법
US11916679B2 (en) * 2019-09-11 2024-02-27 Silicon Laboratories Inc. Apparatus and method to reduce spectral peaks in Bluetooth communications

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0869647A2 (fr) * 1997-04-01 1998-10-07 Lucent Technologies Inc. Système de modulation multiporteuse à paramètres de fonctionnement dynamiquement réglables
US5832030A (en) * 1996-06-12 1998-11-03 Aware, Inc. Multi-carrier transmission system utilizing channels with different error rates

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5832030A (en) * 1996-06-12 1998-11-03 Aware, Inc. Multi-carrier transmission system utilizing channels with different error rates
EP0869647A2 (fr) * 1997-04-01 1998-10-07 Lucent Technologies Inc. Système de modulation multiporteuse à paramètres de fonctionnement dynamiquement réglables

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8675612B2 (en) 2001-05-14 2014-03-18 Interdigital Technology Corporation Channel quality measurements for downlink resource allocation
US9456449B2 (en) 2001-05-14 2016-09-27 Interdigital Technology Corporation Channel quality measurements for downlink resource allocation
US10004080B2 (en) 2001-05-14 2018-06-19 Interdigital Technology Corporation Channel quality measurements for downlink resource allocation
KR20030094914A (ko) * 2002-06-10 2003-12-18 삼성전자주식회사 오에프디엠신호의 전송률을 향상시킬 수 있는 오에프디엠송신기 및 그의 신호압축방법

Also Published As

Publication number Publication date
JP2003514430A (ja) 2003-04-15
WO2001035545A3 (fr) 2001-12-20
CA2387814A1 (fr) 2001-05-17
AU3643201A (en) 2001-06-06
EP1228616A2 (fr) 2002-08-07
KR20020049026A (ko) 2002-06-24

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