WO1999014865A1 - Systeme et procede de regulation du debit binaire dans les communications par modem - Google Patents

Systeme et procede de regulation du debit binaire dans les communications par modem Download PDF

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Publication number
WO1999014865A1
WO1999014865A1 PCT/US1998/019171 US9819171W WO9914865A1 WO 1999014865 A1 WO1999014865 A1 WO 1999014865A1 US 9819171 W US9819171 W US 9819171W WO 9914865 A1 WO9914865 A1 WO 9914865A1
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WO
WIPO (PCT)
Prior art keywords
data
data rate
modem
threshold value
good
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/US1998/019171
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English (en)
Inventor
Daniel L. Moore
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.)
Diamond Multimedia Systems Inc
Original Assignee
Diamond Multimedia Systems 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 Diamond Multimedia Systems Inc filed Critical Diamond Multimedia Systems Inc
Publication of WO1999014865A1 publication Critical patent/WO1999014865A1/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
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • 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
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1806—Go-back-N protocols
    • 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
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1809—Selective-repeat protocols

Definitions

  • the invention generally relates to the transmission of information between modems or other communication devices, and specifically the invention relates to determining the best data rate for a particular connection.
  • modems transmit information between one another at a data rate, typically measured in bits per second (bps). Often, however, it is desirable to change the data rate during a particular connection, particularly to reduce the bit error rate or to improve data throughput (the number of good bits received per unit time). Newer modulation protocols
  • modems e.g., ITU-T V.32 or V.34
  • modems e.g., ITU-T V.32 or V.34
  • QM Quality Measure
  • the received carrier signal is examined and a bit error rate is determined, often in the form of a "Quality Measure" (QM), a unitless indicator of the quality of a connection.
  • QM Quality Measure
  • the received carrier signal is examined and various mathematical functions are applied to determine a QM. For instance, some vendors utilize quadrature amplitude modulation, which includes examining the sine wave carrier, periodically phase shifting the sine wave, and plotting the amplitude at various times in a polar coordinate system. These calculations will generally yield a statistical approximation of the bit error rate of the signal.
  • the ultimate goal of producing a Quality Measure is to give a numerical representation of the quality of a particular connection. For instance, some vendors use a QM range of 0 (representing a perfect connection with no errors) to 127 (indicating a large number of bit errors and that the connection is about to be disconnected). Further, the modem vendor often provides a threshold QM value, e.g., a QM of 30. The threshold QM indicates that if a QM of higher than the threshold is measured for the connection, the data rate should be lowered to reduce bit errors. If a QM below the threshold is measured, the data rate for the connection should be increased or remain the same.
  • QM i.e., using the carrier to derive a statistical approximation of the bit error rate
  • QM does not allow for the selection of the most optimum data rate for the connection in terms of data throughput.
  • the optimum data throughput may occur when a data rate with a lower bit error rate is maintained, while with other connections the optimum throughput may occur at a higher data rate with a higher bit error rate.
  • the goal is ultimately to get the most good data received in any given time interval.
  • many modem vendors choose a fairly low threshold QM, e.g., 25-30. Nonetheless, the inventor of the present invention has discovered that often using a data rate yielding a QM well above the threshold QM results in a higher throughput that still has acceptable performance. Thus, Quality Measure is not a reliable indicator for achieving optimum data throughput rate.
  • calculating QM can consume a noticeable percentage of
  • a method in accordance with the invention takes advantage of the error correction protocol utilized by the modem to determine a measurement of the data bandwidth used for error correction and compares that measurement to a threshold value. The comparison results in an indication of whether data rate needs to be adjusted to maximize throughput.
  • one embodiment of the invention counts the number of good, or valid, frames received during a given time interval. During the same time interval, the number of frames that are ignored and/or are required to be retransmitted for error correction are also counted. A ratio of the number of good frames to the number of ignored/retransmitted frames serves as the measurement of data bandwidth used for error-correction.
  • the measurement is compared to a threshold value.
  • the threshold value is predetermined.
  • the threshold value is the difference between the present data rate and a possible new data rate. If the measurement exceeds the threshold value a change in data rate is indicated.
  • a system and method in accordance with the invention is advantageous in that it produces a more accurate and cost effective method of determining an optimum data rate for maximum data throughput than conventionally used methods.
  • Fig. 1 illustrates in a generalized representational block diagram of data transmission between a transmit and a receive modem, including a block diagram representation of a frame structure; and Fig. 2 illustrates the steps to be performed in accordance with one embodiment of the present invention.
  • a method in accordance with the invention allows the error-correcting protocol utilized by the modem to select the data rate that will maximize data throughput.
  • the receiving modem counts the number of valid data frames it receives during a given time interval, and the receiving modem also counts the number of data frames the modem, via the error-correcting protocol, requests to be retransmitted and/or frames that are ignored during the same time interval.
  • the ratio of the count of the good frames received to the count of those that were retransmitted and/or ignored provides a measurement of the data bandwidth being lost due to error correction.
  • the ratio is then compared to a threshold value and, if the ratio exceeds the threshold value, the data rate is adjusted accordingly. More specific details of the invention are discussed below.
  • FIG. 1 shows a transmit modem 102 and a receive modem 104.
  • each modem is capable of both receive and transmit functions, but for the convenience of this discussion are here referred to separately as a transmit and a receive modem.
  • Information is generally sent between the modems 102, 104 in accordance with a standardized protocol such as V.42, propounded by the ITU-T and incorporated by reference herein.
  • V.42 is an error-correcting protocol.
  • the error-correcting function of V.42 is also commonly referred to as Link Access Procedure for Modems or "LAPM'.
  • An alternative function to LAPM and also specified in V.42 is referred to herein as the "V.42 alternative protocol.”
  • Both LAPM and V.42 alternative protocol require data and other information to be transmitted in a structure called a frame.
  • Fig. 1 shows a generic V.42 frame 110.
  • a frame contains an opening flag field 112, an address field 114, a control field 116, an information field 118, a frame check sequence (FCS) field 120, and a closing flag field 122.
  • the flag fields, 112 and 122 delimit the frame by using a predetermined unique bit pattern, "01111110.”
  • the address field 114 generally identifies the error- correcting connection and the error-correcting entity associated with the connection.
  • the FCS field 120 is used to guard against bit errors in transmission and contains a Cyclic Redundancy Check (CRC) polynomial used to evaluate if an error has occurred.
  • the control field 116 is generally used to distinguish between different frame types (e.g. , information frames, supervisory frames, and unnumbered frames ' ).
  • the information field 118 is the field into which the data or command information is inserted.
  • V.42 different frame types are used to send different types of information.
  • Information frames are used to send data packets.
  • Supervisory frames are used to transmit control information.
  • Unnumbered frames are used to transmit additional information (data, control signals) but are not used for general data packet transmission.
  • frame (unless indicated otherwise by context) generally refers to sequentially numbered frames, and, in the context of the description, will most commonly be information frames.
  • sequence numbers that appear in control field 116.
  • the sequence numbers aid in keeping track of data transmitted and/or received. As defined in V.42, the sequence numbers range from 0-127. After receiving a frame numbered 127, the sequence numbers for the next frames are 0, 1, 2.... Such sequence numbers are thus sometimes referred to as "modulus" sequence numbers. Keeping track of such modulus sequence numbers is well understood in the art.
  • the number of transmitted and/or retransmitted frames is generally only known to the transmitting modem and not the receiving modem (i.e., the receiving modem has no way of determining if a frame is sent if the frame is not received). Further, if a frame does contain an error, the receiving modem can no more make sense of such a frame than if the receiving modem had received noise. Such erroneous frames are simply ignored by the receiving modem. Nonetheless, in accordance with the invention the receiving modem determines both how many frames received are good as well as how many frames had to be retransmitted and/or were ignored, and the receiving modem does so by taking advantage of a sequential numbering system such as that used by LAPM in one embodiment of the invention.
  • step 210 the frame is checked for errors by running a calculation on a CRC polynomial in the FCS field 120 of the frame 110 ( Figure 1) as is generally known in the art. If the frame contains an error, the frame is ignored, step 222 and the process returns to step 210 to receive the next frame. When a frame is ignored, the frame is simply discarded and no acknowledgment of the frame is sent to the transmitting modem as is done when good frames are received. If the received frame is good, step 220, the sequence number of the frame is verified, step 223. If the sequence number is the expected sequence number, then a counter 130, representing a "good count" increments by one, step 225.
  • the counter can be implemented in software, hardware, and/or firmware as is known in the art.
  • the modem 104 requests retransmission of the missing frame or frames, step 235, as is known in the art, e.g., in accordance with V.42.
  • Modem 104 performs a calculation on the CRC polynomial in the FCS field 120 of each frame 10-14 as each frame is received. If modem 104 determines that frames 10-13 are error-free, but that frame 14 contains a CRC error, the receive modem 104 will ignore frame 14. Upon receipt of frame 15, the receive modem will recognize that a frame is missing and request retransmission of frame 14 following procedures specified by V.42, step 230 ( Figure 2).
  • the number of frames retransmitted by the transmitting modem 102 depends on whether the modems are in selective reject (RET) mode or selective repeat (SREJ) mode, both of which are alternative optional modes of operation specified by V.42.
  • RET selective reject
  • SREJ selective repeat
  • retransmit N if frame 14 is requested to be retransmitted, the transmit modem retransmits frame 14 only.
  • the transmitting modem transmits the frame requested to be retransmitted, e.g., frame 14, plus all frames following frame 14 that were already transmitted, e.g., frames 15-17.
  • frame 14 the frame subsequent to the erroneous frame (frame 14) may have already been transmitted by the transmitting modem 102 by the time receiving modem 104 can request retransmission. If, for instance, frames 15-17 have been transmitted, and if the modems are operating in REJ mode, frames 14-17 will be retransmitted.
  • the receiving modem 104 counts the number of retransmitted frames, step 235 (Fig. 2), in a counter 132.
  • Counter 132 can be implemented in software, hardware, and/or firmware as is known by those of skill in the art. If the modems are operating in REJ mode, the receiving modem 104 counts in counter 132 the frame that caused the retransmission request and any other frames received until the desired frame, e.g., frame 14, is received. In the above example, counter 132 would have counted four retransmitted frames (frames 14-17). If the modem is operating in SREJ mode, then the receiving modem simply counts, in counter 132, the number of times it sends a retransmission request. Of course, similar methods of counting can be implemented using other error correcting protocols, such as V.42 alternative protocol, and the scope of the invention should not be construed to be limited to LAPM or even V.42.
  • step 240 the number of good frames received, as indicated by counter 130, and the number of retransmitted frames received, as indicated by the counter 132, are compared in the form of a ratio 136 to a threshold value 138.
  • the threshold 138 can be fixed or configurable in different embodiments of the invention.
  • the comparison in one embodiment of the invention is made by comparator 140. If the ratio 136 of good frames received to retransmitted frames exceeds the threshold 138, then the data rate is adjusted accordingly, step 260.
  • the ratio 136 exceeds a threshold (threshold 1) if the ratio is greater than the threshold, step 250, and the data rate is lowered accordingly, step 260. In other embodiments of the invention, the ratio exceeds a threshold (threshold 2) if the ratio is less than the threshold 260, and the data rate will be raised in step 260. Still other embodiments provide for both of the comparisons of steps 250 and 252. If the appropriate time interval has not passed, step 240, the process returns to step 210 to receive the next frame.
  • any of elements 134, 136, 138, and 140 can be implemented in hardware, software, and/or firmware as is known in the art.
  • step 260 The actual method of adjusting the data rate, step 260, will depend upon the modulation method being utilized for the connection. For instance, V.34 supports rate renegotiations, retrains, and seamless rate changes, each of which is known in the art.
  • a method in accordance with the invention also accounts for the situation where an erroneous frame is received, but no frames follow (i.e., no missing frames are identified in step 223).
  • a situation will be of no consequence: if frames are not being sent, there is generally no need to adjust the data rate. Nonetheless, as is known in the art, the transmitting modem contains a timer. If the transmitting modem does not receive an acknowledgment of the missing frame during a given time period, the transmitting modem will query the receive modem, ultimately prompting the retransmission of the frame. Thus, some embodiments of the invention will include "ignored" frames in the retransmission count by monitoring these queries.
  • An alternative embodiment of a method in accordance with the invention is to compare the data bandwidth being used for error correction to the change in the data rate that will occur if the data rate is lowered.
  • the change in data rate is used as a threshold value. If the bandwidth being used for error correction exceeds the change in data rate that will occur, then the data rate can be adjusted to increase data throughput.
  • a running average over several time intervals could be utilized to compare with the threshold.
  • several thresholds could be utilized, i.e., comparison to several thresholds could indicate an adjustment of data rates up or down by more than one data rate step.

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  • Engineering & Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)

Abstract

Le procédé de cette invention permet au protocole de correction d'erreurs, utilisé par le modem (104), de choisir le débit binaire qui porte au maximum la quantité de données transmises. A cet effet, le modem récepteur (104) compte le nombre des trames de données valables (130) qu'il reçoit pendant un laps de temps déterminé et compte également le nombre des trames de données dont le modem (104) demande la retransmission (132), au moyen du protocole de transmission d'erreurs, et/ou de celles ignorées pendant ce même laps de temps. Le rapport (136) du nombre des trames valables (130) reçues et de celles qui ont été ignorées ou retransmises (132) permet de mesurer la largeur de bande des données qui a été perdue suite à la correction d'erreurs. On compare (140) ensuite ce rapport à une valeur du seuil (138); si le taux (136) est supérieur à la valeur du seuil (138), on modifie le débit binaire en conséquence.
PCT/US1998/019171 1997-09-15 1998-09-14 Systeme et procede de regulation du debit binaire dans les communications par modem Ceased WO1999014865A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US92954297A 1997-09-15 1997-09-15
US08/929,542 1997-09-15

Publications (1)

Publication Number Publication Date
WO1999014865A1 true WO1999014865A1 (fr) 1999-03-25

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PCT/US1998/019171 Ceased WO1999014865A1 (fr) 1997-09-15 1998-09-14 Systeme et procede de regulation du debit binaire dans les communications par modem

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009506625A (ja) * 2005-08-26 2009-02-12 テレフオンアクチーボラゲット エル エム エリクソン（パブル） Ｕｍｔｓにおけるフロー制御
US20130138830A1 (en) * 2011-11-28 2013-05-30 Huawei Technologies Co., Ltd. Method and network device for controlling transmission rate of communication interface
EP2195980B1 (fr) * 2007-09-26 2014-11-05 International Business Machines Corporation Procédé, système et produit-programme informatique pour un contrôle de congestion adaptatif sur des voies virtuelles pour une architecture ethernet de centre de données
CN111780632B (zh) * 2020-06-28 2023-10-24 贵州全安密灵科技有限公司 一种电子雷管通信速率的调整方法和装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4788697A (en) * 1987-01-02 1988-11-29 American Telephone & Telegraph Company Method and apparatus for synchronizing a signal to a time base
US5365577A (en) * 1990-09-27 1994-11-15 Radish Communications Systems, Inc. Telecommunication display system
US5475711A (en) * 1992-10-30 1995-12-12 At&T Corp. System for channel capacity modulation
US5497383A (en) * 1993-01-22 1996-03-05 Motorola, Inc. Error detector circuit for receiver operative to receive discretely-encoded signals

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4788697A (en) * 1987-01-02 1988-11-29 American Telephone & Telegraph Company Method and apparatus for synchronizing a signal to a time base
US5365577A (en) * 1990-09-27 1994-11-15 Radish Communications Systems, Inc. Telecommunication display system
US5475711A (en) * 1992-10-30 1995-12-12 At&T Corp. System for channel capacity modulation
US5497383A (en) * 1993-01-22 1996-03-05 Motorola, Inc. Error detector circuit for receiver operative to receive discretely-encoded signals

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009506625A (ja) * 2005-08-26 2009-02-12 テレフオンアクチーボラゲット エル エム エリクソン（パブル） Ｕｍｔｓにおけるフロー制御
EP1917751A4 (fr) * 2005-08-26 2011-07-06 Ericsson Telefon Ab L M Controle de flux dans umts
EP2195980B1 (fr) * 2007-09-26 2014-11-05 International Business Machines Corporation Procédé, système et produit-programme informatique pour un contrôle de congestion adaptatif sur des voies virtuelles pour une architecture ethernet de centre de données
US20130138830A1 (en) * 2011-11-28 2013-05-30 Huawei Technologies Co., Ltd. Method and network device for controlling transmission rate of communication interface
US8667167B2 (en) * 2011-11-28 2014-03-04 Huawei Technologies Co., Ltd. Method and network device for controlling transmission rate of communication interface
CN111780632B (zh) * 2020-06-28 2023-10-24 贵州全安密灵科技有限公司 一种电子雷管通信速率的调整方法和装置

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