WO2009088342A1 - Temporisateur de réordonnancement pour protocole de retransmission - Google Patents

Temporisateur de réordonnancement pour protocole de retransmission Download PDF

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Publication number
WO2009088342A1
WO2009088342A1 PCT/SE2008/051379 SE2008051379W WO2009088342A1 WO 2009088342 A1 WO2009088342 A1 WO 2009088342A1 SE 2008051379 W SE2008051379 W SE 2008051379W WO 2009088342 A1 WO2009088342 A1 WO 2009088342A1
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WO
WIPO (PCT)
Prior art keywords
reordering timer
data units
received
missing data
gap
Prior art date
Application number
PCT/SE2008/051379
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English (en)
Inventor
Johan Torsner
Michael Meyer
Anna Larmo
Original Assignee
Telefonaktiebolaget L M Ericsson (Publ)
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 Telefonaktiebolaget L M Ericsson (Publ) filed Critical Telefonaktiebolaget L M Ericsson (Publ)
Publication of WO2009088342A1 publication Critical patent/WO2009088342A1/fr

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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
    • H04L1/12—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
    • H04L1/1829—Arrangements specially adapted for the receiver end
    • H04L1/1848—Time-out mechanisms

Definitions

  • the present invention relates generally to retransmission protocols for wireless communication systems and, more particularly, to a reordering timer for a retransmission protocol to enable out of sequence delivery of data units
  • a retransmission protocol is implemented in both the Radio Link Control (RLC) layer and Medium Access Control (MAC) layer to make data transmission more reliable
  • RLC Radio Link Control
  • MAC Medium Access Control
  • a Hybrid ARQ (HARQ) protocol is implemented in the MAC layer to reduce the error rate to approximately 1 %
  • a second retransmission protocol is implemented at the RLC layer to correct residual errors and further reduce the error rate to a level acceptable for the service, which is typically in the range of 10 6
  • the HARQ protocol used in HSPA and LTE causes some RLC Protocol Data Units (PDUs) to be received out of order, i e , in another order than in which they were originally transmitted by the peer entity If data is delivered to RLC out of order, it may trigger unnecessary retransmissions because the RLC will interpret gaps in the sequence numbers as missing PDUs, even if they may still be under retransmission by the underlying HARQ protocol
  • HSDPA a reordering functionality is used to restore the order of the R
  • the LTE reordering functionality starts a reordering timer when a missing RLC PDU is detected, i e , when the first PDU following one or more missing PDUs is received If the missing PDU has not been received when the reordering timer expires, it triggers the transmission of an RLC status report, which will include a negative acknowledgement (NACK) for the missing PDU
  • NACK negative acknowledgement
  • the request for retransmission of the missing PDU may be delayed some configurable amount of time to allow for HARQ retransmissions of the PDU to be completed After this time has passed, it is assumed that HARQ has failed, and the PDU will be retransmitted by RLC If the missing PDU is received while the reordering timer is running the timer is stopped since the gap no longer exists
  • the specified reordering works well when there is a single gap in the sequence numbers i e , one or several consecutive PDUs are missing
  • this approach has some disadvantages in the case where several gaps exist in the received sequence numbers
  • any poll ( ⁇ e , request for transmitting a status report) received will be unnecessarily delayed until the missing PDUs are received
  • the expiry of the reordering timer may trigger a redundant request for retransmission of the missing PDUs, even if a retransmission request for the missing PDUs has already been sent.
  • a reordering timer is started when a first gap comprising one or more missing data packets is detected and the timer is not already running. The timer is stopped when all of the first missing data packets are received, even if one or more second missing data units corresponding to a second gap preceding said first gap are not yet received. The timer is continued when second missing data packets corresponding to a second gap preceding said first gap are received. When the timer expires, a request for retransmission of the first missing data packets is sent.
  • Fig. 1 illustrates an exemplary communication network.
  • Fig. 2 illustrates an exemplary protocol stack for a wireless communication device including a radio link control layer that implements a retransmission protocol.
  • Figs. 3-5 illustrate an exemplary method of operating a reordering timer to supervise a retransmission protocol.
  • Fig. 6 illustrates an exemplary user terminal.
  • Fig. 7 illustrates an exemplary processor for implementing a retransmission protocol.
  • Figs. 8A and 8B are flow diagrams illustrating exemplary methods for operating a reordering timer.
  • LTE Long Term Evolution
  • 3GPP Third Generation Partnership Project
  • the communication system 10, shown in Fig. 1 comprises a transmitting terminal 20 and a receiving terminal 30.
  • the transmitting terminal 20 transmits signals over a communication channel 40 to the receiving terminal 30.
  • the transmitting terminal 20 may comprise a base station in an LTE network, sometimes referred to as an Evolved Node B (eNodeB), and the receiving terminal 30 may comprise a user terminal (e.g., cellular telephone, PDA, laptop computer, etc.).
  • the transmitting terminal 20 may comprise a user terminal and the receiving terminal 30 may comprise a base station.
  • transmitting terminal 20 and receiving terminal 30 may each comprise a communication terminal 100 (Fig. 4) with a transceiver for two-way communications.
  • the terms "transmitting” and “receiving” are thus used herein to indicate the direction of communication between two communication terminals.
  • Fig. 2 provides a general overview of the LTE protocol architecture 200, for communications between a transmitting terminal 20 and a receiving terminal 30 in LTE systems.
  • the LTE protocol architecture 200 is a layered protocol stack. Each layer of the protocol stack 200 represents a set of protocols or functions needed to communicate over the communication channel 40.
  • the protocol stack 200 in LTE includes a physical (PHY) layer 240, the medium access control (MAC) layer 230, the radio link control (RLC) layer 220, and the packet data convergence protocol (PDCP) layer 210.
  • the protocol stack 200 is typically implemented by a specially programmed processor.
  • User plane data to be transmitted in the form of IP packets enters the PDCP layer 210, where the IP headers may be compressed to reduce the number of bits transmitted over the air interface.
  • PDCP layer 210 also performs ciphering and deciphering of the IP packets for security.
  • RLC layer 220 ensures almost error free, in sequence delivery of compressed IP packets to the PDCP layer 210 at the receiving terminal 30, which is needed for certain types of communication.
  • RLC layer 220 segments and/or concatenates compressed IP received from the PDCP layer 210 over radio bearers to create RLC protocol data units (PDUs).
  • PDUs RLC protocol data units
  • the RLC layer 220 implements a retransmission protocol described in more detail below to handle retransmission of missing or erroneously received RLC PDUs.
  • MAC layer 230 offers services to the RLC layer 220 in the form of logical channels.
  • the MAC layer 230 maps RLC PDUs received on various logical channels from RLC layer 220 to corresponding transport channels.
  • MAC layer 230 is responsible for uplink and downlink scheduling.
  • MAC PDUs are fed by the MAC layer 230 to the PHY layer 240.
  • PHY layer 240 handles coding/decoding, modulation/demodulation, interleaving, and spreading prior to transmission of one or more PHY layer PDUs.
  • a retransmission protocol is implemented in both the RLC layer 220 and MAC layer 230 to make data transmission more reliable.
  • a Hybrid ARQ (HARQ) protocol is implemented in the MAC layer 230 to reduce the error rate to approximately 1 %.
  • a second retransmission protocol is implemented at the RLC layer 220 to correct residual errors and further reduce the error rate to a level that is needed for the service, typically in the order of approximately 10 "6 . Because MAC layer 230 is not required to deliver RLC PDUs in sequence to RLC layer 220, the HARQ protocol implemented in the MAC layer 230 causes some RLC PDUs to be received out of order.
  • reordering of the RLC PDUs is performed in the RLC layer 220.
  • gaps in the sequence numbers of received RLC PDUs would result in RLC requesting retransmission of missing RLC PDUs or PDU segments.
  • the missing data units may still be subject to retransmission by the MAC HARQ process. Therefore, to prevent unnecessary retransmission requests, a reordering timer for RLC is introduced. When a missing RLC PDU is detected, the reordering timer is started and the retransmission request is delayed until the expiration of the reordering timer. If the missing RLC PDU is received before expiration of the timer, the reordering timer is stopped.
  • FIG. 3 illustrates operation of one exemplary reordering timer in the scenario where a later gap in the sequence number is filled before an earlier gap is filled.
  • PDU 3 has been received and the reordering timer is started, since PDU 2 is missing.
  • the timer expires at time t1 and a request for retransmission of PDU2 is sent.
  • PDUs 4 and 7 are received.
  • the reordering timer is restarted since a new gap comprising PDUs 5 and 6 is detected.
  • the PDUs 5 and 6 are received. If the reordering timer is continued at t3, any poll request (e.g., request for a status report) received in PDUs with sequence numbers 5 or above will be unnecessarily delayed. Further, the expiration of the reordering timer will trigger a redundant request for retransmission of PDU 2 even if a retransmission request for PDU 2 has already been sent.
  • any poll request e.g., request for a status report
  • the RLC layer 220 may in some embodiments of the invention remember the gap that triggered the reordering timer and stop the reordering timer when the corresponding RLC PDUs are received, even if other RLC PDUs with a lower sequence number are still missing.
  • This alternative method of operation is illustrated in Fig. 4.
  • PDU 3 has been received and the reordering timer is started, since PDU 2 is missing.
  • the timer expires at time t1 and a request for retransmission of PDU 2 is sent.
  • PDUs 4 and 7 are received and the reordering timer is restarted since a new gap comprising PDUs 5, and 6 is detected.
  • the RLC layer 220 remembers the gap that triggered the reordering timer.
  • the PDUs 5 and 6 are received and the reordering timer is stopped since the gap that triggered the timer is closed, even though RLC PDU 2 is still missing.
  • Fig. 5 illustrates operation of the exemplary reordering timer in the scenario where an earlier gap in the sequence number is filled before a later gap is filled.
  • PDU 3 has been received and the reordering timer is started, since PDU 2 is missing.
  • the timer expires at time t1 and a request for retransmission of PDU 2 is sent.
  • PDUs 4 and 7 are received and the reordering timer is restarted since a new gap comprising PDUs 5, and 6 is detected.
  • the RLC layer 220 remembers the gap that triggered the reordering timer.
  • the PDU 2 is received, closing the earlier gap. In this case, the reordering timer is continued since the gap that triggered the timer is still open.
  • Fig. 6 illustrates an exemplary communication device 100 that implements the retransmission protocol as previously described.
  • the communication device 100 may comprise a base station that implements the retransmission protocol for uplink transmissions, or a user terminal that implements the retransmission protocol for downlink transmissions.
  • the communication terminal 100 comprises a transceiver 1 10 connected to an antenna 1 12, a processor 120, and memory 130.
  • Transceiver 1 10 enables the communication terminal 100 to transmit signals to and receive signals from a remote terminal.
  • the communication terminal 100 may comprise, for example, a conventional cellular transceiver operating according to the LTE standard, WCDMA standard, or other communication standard now known or later developed.
  • the processor 120 processes the signals transmitted and received by the transceiver 1 10 and controls operation of the user terminal 100.
  • Processor 120 includes an RLC module 122 for implementing the RLC protocols as previously described.
  • Memory 130 stores programs and data needed for operation.
  • Fig. 7 illustrates the main functional elements of the RLC module 122.
  • RLC module 122 includes a retransmission controller 124, a reordering timer 126 under the control of the retransmission controller 124, and a buffer 128 for temporarily storing RLC PDUs while reordering is performed.
  • the retransmission controller 124 comprises the main control logic for implementing RLC layer protocols and is responsible for reordering RLC PDUs that are received out of sequence.
  • RLC controller 124 starts the reordering timer 126 when a gap is detected and stops the reordering timer 126 when a gap is filled.
  • retransmission controller 124 sends a retransmission request (e.g., NACK) for the missing RLC PDU to the transmitting terminal 20.
  • a retransmission request e.g., NACK
  • the reordering timer 126 delays a retransmission request when a missing packet is detected to give time for the HARQ protocols implemented in the MAC layer 230 to deliver the out of sequence RLC PDUs.
  • Fig. 8A illustrates an exemplary method 400 implemented by the retransmission controller 124 when a missing gap is detected in the sequence numbers of the received RLC PDUs.
  • the retransmission controller 124 determines whether the reordering timer is active (block 404). If the reordering timer 126 is already active, the retransmission controller terminates the procedure 400 (block 412). On the other hand, if the reordering timer 126 is not active, the retransmission controller 124 starts the reordering timer 126. If the missing RLC PDUs are not received when the timer expires (block 408), retransmission controller 124 sends a retransmission request to the peer RLC layer at the transmitting terminal 20 (block 410) and the procedure ends (block 412).
  • missing RLC PDUs may be received by the RLC layer 220.
  • Fig. 8B illustrates exemplary method 450 performed by the retransmission controller 124 to process a missing RLC PDU received by the RLC layer 220 while the reordering timer 126 is active. The procedure is triggered by receipt of a missing RLC PDU (block 452). As previously noted, the sequence numbers of the received RLC PDUs may have multiple gaps. A received RLC PDU may belong to any one of the unfilled gaps.
  • the retransmission controller 124 After sending the received RLC PDU to the reordering buffer 128 (block 454), the retransmission controller 124 determines whether the received RLC PDU belongs to the gap that triggered the reordering timer 126 (block 456). The gap triggering the reordering timer 126 is referred to herein as the current gap. If the received RLC PDU belongs to an earlier gap (e.g., a gap preceding the current gap), the retransmission controller 124 continues the reordering timer 126 (block 458). If the received RLC PDU belongs to the current gap, the retransmission controller 124 next determines whether all RLC PDUs in the current gap have been received (block 460).
  • the retransmission controller 124 continues the reordering timer (block 458). If all RLC PDUs in the current gap have been received, the retransmission controller 124 stops the reordering timer (block 462) and terminates the procedure (block 464).

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

Abstract

L'invention porte sur un contrôleur de retransmission pour dispositif de communication. Le contrôleur utilise un temporisateur de réordonnancement pour superviser un protocole de retransmission. Le contrôleur de retransmission démarre le temporisateur de réordonnancement, lorsqu'un premier intervalle comprenant au moins une unité de données manquante est détecté et que le temporisateur est inactif. Le contrôleur de retransmission arrête le temporisateur de réordonnancement, lorsque l'ensemble des premières unités de données manquantes sont reçues, même si de secondes unités de données manquantes correspondant à un second intervalle précédent le premier intervalle sont manquantes. Si le temporisateur de réordonnancement expire avant réception de toutes les premières unités de données manquantes, le contrôleur de retransmission envoie une demande de retransmission à l'émetteur.
PCT/SE2008/051379 2008-01-07 2008-12-01 Temporisateur de réordonnancement pour protocole de retransmission WO2009088342A1 (fr)

Applications Claiming Priority (2)

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US1941008P 2008-01-07 2008-01-07
US61/019,410 2008-01-07

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015020507A1 (fr) * 2013-08-09 2015-02-12 주식회사 팬택 Procédé et appareil de réordonnancement de pdcp dans un système à double connectivité
KR20150018248A (ko) * 2013-08-09 2015-02-23 주식회사 팬택 이중연결 시스템에서 멀티 플로우를 고려한 ｐｄｃｐ 재배열 방법 및 장치
KR20150018249A (ko) * 2013-08-09 2015-02-23 주식회사 팬택 이중연결 시스템에서 멀티 플로우를 고려한 ｐｄｃｐ 재배열 방법 및 장치
CN105264830A (zh) * 2014-05-09 2016-01-20 华为技术有限公司 数据包的处理方法、终端、基站及系统
WO2017039912A1 (fr) * 2015-08-31 2017-03-09 Qualcomm Incorporated Procédé permettant d'éviter des transmissions inutiles d'unités de données de protocole

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WO2002091659A2 (fr) * 2001-04-27 2002-11-14 Telefonaktiebolaget Lm Ericsson (Publ) Procedure de reordonnancement de paquets de donnees dans un systeme de communications
EP1326388A2 (fr) * 2002-01-05 2003-07-09 Lg Electronics Inc. Système et procédé pour éviter des blocages utilisant une temporisation, dans un système d'accès pour paquets descendant à grande vitesse

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US5754754A (en) * 1995-07-26 1998-05-19 International Business Machines Corporation Transmission order based selective repeat data transmission error recovery system and method
WO2002091659A2 (fr) * 2001-04-27 2002-11-14 Telefonaktiebolaget Lm Ericsson (Publ) Procedure de reordonnancement de paquets de donnees dans un systeme de communications
EP1326388A2 (fr) * 2002-01-05 2003-07-09 Lg Electronics Inc. Système et procédé pour éviter des blocages utilisant une temporisation, dans un système d'accès pour paquets descendant à grande vitesse

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015020507A1 (fr) * 2013-08-09 2015-02-12 주식회사 팬택 Procédé et appareil de réordonnancement de pdcp dans un système à double connectivité
KR20150018248A (ko) * 2013-08-09 2015-02-23 주식회사 팬택 이중연결 시스템에서 멀티 플로우를 고려한 ｐｄｃｐ 재배열 방법 및 장치
KR20150018249A (ko) * 2013-08-09 2015-02-23 주식회사 팬택 이중연결 시스템에서 멀티 플로우를 고려한 ｐｄｃｐ 재배열 방법 및 장치
KR102156191B1 (ko) 2013-08-09 2020-09-15 팬텍 주식회사 이중연결 시스템에서 멀티 플로우를 고려한 ｐｄｃｐ 재배열 방법 및 장치
KR102156192B1 (ko) 2013-08-09 2020-09-15 팬텍 주식회사 이중연결 시스템에서 멀티 플로우를 고려한 ｐｄｃｐ 재배열 방법 및 장치
CN105264830A (zh) * 2014-05-09 2016-01-20 华为技术有限公司 数据包的处理方法、终端、基站及系统
WO2017039912A1 (fr) * 2015-08-31 2017-03-09 Qualcomm Incorporated Procédé permettant d'éviter des transmissions inutiles d'unités de données de protocole
CN107925665A (zh) * 2015-08-31 2018-04-17 高通股份有限公司 避免不必要的协议数据单元(pdu)传输
US9999049B2 (en) 2015-08-31 2018-06-12 Qualcomm Incorporated Avoiding unnecessary protocol data unit (PDU) transmissions
JP2018526913A (ja) * 2015-08-31 2018-09-13 クゥアルコム・インコーポレイテッドＱｕａｌｃｏｍｍ Ｉｎｃｏｒｐｏｒａｔｅｄ 不要なプロトコルデータユニット（ｐｄｕ）送信を回避すること
CN107925665B (zh) * 2015-08-31 2019-05-14 高通股份有限公司 避免不必要的协议数据单元(pdu)传输

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