EP2745563A1 - Transfert intercellulaire entre n uds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets - Google Patents

Transfert intercellulaire entre n uds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets

Info

Publication number
EP2745563A1
EP2745563A1 EP12737515.2A EP12737515A EP2745563A1 EP 2745563 A1 EP2745563 A1 EP 2745563A1 EP 12737515 A EP12737515 A EP 12737515A EP 2745563 A1 EP2745563 A1 EP 2745563A1
Authority
EP
European Patent Office
Prior art keywords
radio link
data
data transmission
pending data
pending
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.)
Withdrawn
Application number
EP12737515.2A
Other languages
German (de)
English (en)
Inventor
Alexander Sayenko
Jani Matti Johannes Moilanen
Hans Thomas Hoehne
Isman Bazar
Karri Markus Ranta-Aho
Jeroen Wigard
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.)
Nokia Solutions and Networks Oy
Original Assignee
Nokia Siemens Networks Oy
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 Nokia Siemens Networks Oy filed Critical Nokia Siemens Networks Oy
Priority to EP12737515.2A priority Critical patent/EP2745563A1/fr
Priority claimed from PCT/EP2012/063490 external-priority patent/WO2013023842A1/fr
Publication of EP2745563A1 publication Critical patent/EP2745563A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off

Definitions

  • the invention generally relates to data forwarding in multi-point transmission. More particularly, the invention relates to efficient data forwarding and re ⁇ transmission for data split multi-point wireless broadband systems during link removal.
  • Multi-flow One of the multi-point transmission schemes, which hence will be referred to as Multi-flow, is charac- terized by splitting the application level data into several flows and sending each flow from a particular base station.
  • a few technical chal ⁇ lenges arise when a mobile station or user equipment (UE) experiences mobility, thereby causing removal of one of the radio links from the participating set and possible loss of data as a result of this action.
  • UE user equipment
  • 3GPP HSPA 3GPP HSPA, but it is not limited only to that particular type of wireless communications network.
  • Multi-flow is a multi-point transmission scheme, which is characterized by splitting the application level data into several independent streams and send ⁇ ing them over different radio links, for example dif ⁇ ferent cells. Based on existing simulation results, higher gains are achieved at the cell edge, where signal strength from transmitting cells is comparably the same, thus allowing a UE to receive data simulta ⁇ neously from several cells.
  • the cell edge is characterized by the fact that one of the links may fade and/or experience a significant performance degradation, therefore caus ⁇ ing its removal by the network from the participating set of radio links in the multi-point transmission scheme. In turn, this may result in data loss in the base station buffers, leading to performance degrada ⁇ tion of higher layer protocols, such as TCP.
  • the invention seeks to solve at least some of the above-mentioned problems.
  • the invention provides a method, which includes determining that a first radio link is to be dropped, ending a pending data transmission on the first radio link, determining which data of the pend ⁇ ing data transmission needs to be transmitted, and forwarding the data of the pending data transmission on a second radio link.
  • the first and second radio links are data links to the same user equipment. Furthermore, it is not required to detect lost data packets or perform retransmission of lost data packets, thereby avoiding UE involvement and additional actions on the part of the network.
  • the step of forwarding may include sending an instruction from a control node to a network node that the network node should schedule said data of said pending data transmission over said second radio link .
  • a control node e.g. a radio network controller (RNC)
  • RNC radio network controller
  • a network access node e.g. a Node B
  • the network node may automatically schedule the data of the pending data transmission on the second radio link, without any instruction from the control node.
  • the step of ending the pending data transmission includes starting a timer and transmitting data of the pending data transmission on the first radio link until expiry of the timer.
  • the step of ending the pending data transmission may include clearing data of the pending data transmis ⁇ sion from a buffer of a network node used to establish the first radio link.
  • the method includes signalling a lowest transmission sequence number of data of said pending data transmission that was in the buffer upon clearing of the data.
  • the method may further include signalling that the pending data transmission on the first radio link has ended.
  • the signalling can include an indication of whether there is still data to be transmitted on the first radio link.
  • the invention also provides a control node, which in ⁇ cludes a processing unit configured to determine that a first radio link is to be dropped, configured to end a pending data transmission on the first radio link, and configured to determine which data of the pending data transmission needs to be transmitted.
  • a transmitter is configured to forward the data of the pending data transmission on a second radio link.
  • the transmitter is further configured to signal instructions to a network node to end the first radio link.
  • the invention further provides a network node.
  • the network node includes a transmitter configured to transmit data on a first radio link and a processing unit configured to end a pending data transmission on the first radio link upon removal of the first radio link .
  • a scheduler in the network node may automatically schedule data on a second radio link or it may re ⁇ ceive instructions from a control node to do so.
  • the network node further includes a receiver, which is configured to receive instruc ⁇ tions from a control node to end the first radio link .
  • the network node includes a timer. Data of the pending data transmission can be sent on the first radio link until expiry of the timer.
  • the timer can have a value, within which a scheduler in the network node should transmit pending data.
  • the network node includes a buffer so that ending the pending data transmission over the first radio link involves clearing data of the pend ⁇ ing data transmission from a buffer.
  • the network node can remove all data packets of the pending data transmission over the first radio link from its buffers, without further attempting to transmit those.
  • the transmitter may be further configured to signal that there are still data packets from the pending data transmission over the first radio link remaining in the buffer. This may include signalling a lowest transmission sequence number of data of the pending data transmission that was in the buffer upon clearing of the data.
  • the transmitter may be further configured to signal that the pending data transmission on said first radio link has ended.
  • This signalling may in ⁇ clude an indication of whether there is still data to be transmitted on the first radio link.
  • the invention also provides a computer program product including a program comprising software code portions being arranged, when run on a processor to perform determining that a first radio link is to be dropped, ending a pending data transmission on the first radio link, determining which data of the pend ⁇ ing data transmission needs to be transmitted, and forwarding the data of the pending data transmission on a second radio link.
  • the computer program product includes a computer-readable medium on which the software code portions are stored, and/or wherein the program is directly loadable into a memory of the processor.
  • Figure 1 is a simplified schematic block diagram of a communications network
  • Figure 2 is a simplified schematic block diagram of a network node for a communications network
  • Figure 3 is a simplified schematic block diagram of a control node for a communications network
  • Figure 4 is a flow chart illustrating a method ac ⁇ cording to an embodiment of the invention.
  • FIG. 5 is a message flow diagram illustrating a method according to an invention.
  • Figure 1 schematically shows a wireless communica ⁇ tions network.
  • a WCDMA radio access network is illustrated: however, the in ⁇ vention may also apply to any other kind of wireless network, for example an LTE network.
  • the network is a Multi-flow wireless system and uses a multi-point transmission scheme. That is, a mobile station or user equipment (UE) 1 may exchange data with the network over two radio links Rl and R2 (in reality more radio links may be used but just two are shown here for simplicity and ease of understanding) .
  • the first radio link Rl is via a cell CI of the net ⁇ work, which is accessed via a Node B NB1 and the sec ⁇ ond radio link R2 is via a cell C2, which is accessed via a Node B NB2.
  • the Node Bs NB1 and NB2 are both controlled by a ra ⁇ dio network controller (RNC) 2 over an Iub interface so that the radio links Rl and R2 terminate at the RNC 2.
  • RNC ra ⁇ dio network controller
  • Each Node B NB1, NB2 includes a transmitter Txl and a receiver Rxl for transmitting and receiving data.
  • a scheduler S is provided for scheduling data transmis ⁇ sions and a buffer B temporarily stores data packets for transmission to the UE 1.
  • the Node B NB1, NB2 further includes a timer T and a processor PI.
  • the RNC 2 includes a transmitter Tx2, a receiver Rx2 and a processor P2.
  • Step SI it is determined that the radio link Rl is about to fail or be dropped.
  • the RNC 2 determines that the radio link Rl is to be deleted, and in ⁇ structs the Node B NB1 to delete the radio link Rl by stopping or completing pending transmissions.
  • Step S2 the Node B NB1 ends pending data transmis ⁇ sions either in response to the instruction from the RNC 2, or automatically without instruction.
  • the Node B NB1 confirms deletion of the radio link Rl and in ⁇ dicates the last successful transmission or first pending data packet to the RNC 2.
  • Step S3 the RNC 2 determines which data packets need to be trans ⁇ mitted and in Step S4 starts efficiently forwarding the pending data packets originally directed to the deleted radio link Rl by expeditingthose packets com ⁇ pared to other data packets on the radio link R2 scheduled for first transmission via the Node B NB2.
  • Step S4 the RNC 2 determines which data packets need to be trans ⁇ mitted and in Step S4 starts efficiently forwarding the pending data packets originally directed to the deleted radio link Rl by expeditingthose packets com ⁇ pared to other data packets on the radio link R2 scheduled for first transmission via the Node B NB2.
  • Embodiments of the invention are illustrated in more detail in the message flow diagram shown in Figure 5.
  • the RNC 2 can instruct Node B NBl to schedule data from its output buffer B for the correspondent UE 1 as fast as possible. This may also be done automatically by the Node B NBl without an explicit indication from RNC 2. However, in cases when the RNC 2 is more interested in faster removal of the radio link Rl, rather than waiting for transmission of UE data, an explicit indication by the RNC 2 to the Node B NBl is more preferable.
  • the Node B NBl may also signal a discard operation, where the Node B NBl removes all data packets of the UE 1 from its buffer(s) B, without further attempting to transmit those data packets .
  • a timer value is provided in the timer T, within which the scheduler S of the Node B NBl should transmit pending data. If it is accompanied by the timer value, then the Node B NBl can either try to transmit the pending data within the given time interval and/or discard remaining data. For discarding data, the Node B NBl has several implementation options: either to discard RLC PDU buffers and stop ongoing HARQ processes, or
  • Hybrid Automatic Repeat Request HARQ is a combination of forward error correcting coding and an error detection mechanism improving the successful transmissions in poor signal conditions.
  • a HARQ process controls the successful transmission of a PDU.
  • the Node B NB1 can finish its ongoing HARQ processes and try to send some data from another buffer in the Node B NB1 containing a
  • a buffer e.g., a buffer
  • the MAC-d buffer for dedicated transmissions between the UE 1 and radio network/ for a transport channel dedicated to the UE 1 towards the radio network; the MAC-d buffer.
  • the Node B NB1 can indicate in the link removal confirmation message whether there are still data packets in the output buffer B intended for the UE 1. This serves as indication to the RNC 2 as to whether it should take some additional action regarding pro ⁇ active retransmission of buffered data that were flushed as a result of removal of the radio link Rl in the Node B NB1.
  • the Node B NB1 can additionally signal the lowest transmission sequence number SN of data that was in the buffer B upon its removal (or the highest RLC PDU sequence number SN delivered to the UE 1) . This assists the RNC 2 in deciding which data to retransmit.
  • the Node B NB1 can also signal the lowest transmission sequence number of data that was in the buffer B upon its removal in the case that the RNC 2 had signalled a discard operation to the Node B NB1.
  • the RNC 2 can retransmit pro-actively all the unacknowledged data packets previously sent to that link Rl . If there is explicit information on the lowest pending transmission sequence number that was in the buffer B, only the relevant data can be retransmitted .
  • the RNC For the purpose of retransmission over a different link radio link R2 , the RNC maintains a table with mapping between the PDCP service data unit SN and RLC PDU SN. Once the RNC 2 knows which RLC PDUs were dropped from the buffer B of the Node B NB1, it can schedule relevant PDCP service data units SDUs for retransmission .
  • the RNC 2 can use a priority mechanism to ensure that the Node B NB2 handles those data packets first, thus ensuring reduced delays at the re-ordering buffer of the UE 1.
  • the priority mechanisms can be based on using available fields in the Iub flow control signalling (frame protocol) . To avoid problems for protocol cross-over, the priority should be given in the radio link R2 to retransmission of data packets from pending data transmissions over the radio link Rl over new transmissions of data packets.
  • the RNC 2 can signal whether it should wait for all the pending transmissions over the radio link Rl to be finished or just send forward completed SDUs from its buffer.
  • An indication to the Node B NB 1 from the RNC 2 to either schedule data or flush the data from the buffer B is implementable as a simple 1-bit indicator.
  • the advantage of having this bit originates from the fact that the RNC 2 might be interested in removing the link as soon as possible instead of waiting for pending data to be sent. This could be the case when the RNC 2 knows that only a few RLC PDUs were sent to the removed link Rl or if the link conditions of the radio link Rl are already not good enough for the data to be scheduled fast enough.
  • An indication to the RNC 2 whether pending data from the output buffers were transmitted successfully or not is also implementable as a simple 1-bit indicator.
  • the 1-bit indicator can accompanied with the lowest sequence number of data that was in the buffer B of the Node B NB1 upon the buffer B being flushed .
  • the NodeB NB1 may flush or discard data in the buffer B relevant for the UE1 even if the RNC 2 asks for an explicit transmission of pending data. This is advantageous if the downlink channel performance becomes so bad that there is no way for the Node B NB1 to ensure a reliable data transmission .
  • the Node B NB1 does not have to inspect RLC PDU sequence numbers, whereas a need to report back to RNC 2 the sequence number of buffered packets puts an additional requirement to inspect the RLC PDU content. However, this operation must be performed only once for the head of queue RLC PDU.
  • the Node B NB1 can report back to the RNC 2 just the number of RLC PDUs in the buffer B. Based on this number the RNC 2 can determine which RLC PDUs were discarded in the buffer of the Node B NB1.
  • the RNC 2 keeps a mapping between the data sequence number known by the Node B NB1 (i.e. the MAC layer Transmission Sequence Number) with the data sequence number in the RNC 2 (i.e. the RLC Sequence Number) ) .
  • the RNC 2 can decide which data should be retransmitted . In case the lowest sequence number SN is missing, all sent but un-acknowledged PDUs can be immediately sent over the other link radio link R2.
  • the RNC 2 performs an additional step of analyzing which PDCP SDUs to be retransmitted. Since the PDCP split assumes two independent RLC processes, the RLC PDU SN from the RLC process on the removed link Rl must be mapped back to the PDCP SN numbering, from which the RNC 2 takes the relevant PDCP SDUs and sends them over the other radio link R2. In order to facilitate this mapping, the RNC 2 maintains the mapping between PDCP SDU SNs and the RLC process/SN.
  • the retransmissions can be prioritized by indicating a higher priority for them in a field of the frame protocol used over the lub interface.
  • the application level data is TCP, or its type is not known, a safer choice for the network is to ensure that pending packets from the removed link Rl are retransmitted to the UE 1, which in turn must wait for missing packets to be delivered by the network .
  • the network can decide not to retransmit packets, thus ensuring delays of the streaming content. In this case, to avoid data transmission stall,
  • the RNC 2 informs the UE 1 to ignore the missing PDUs and send forward all the complete PDCP SDUs to a higher layer (e.g. UDP) .
  • a higher layer e.g. UDP
  • Another way to accomplish this is to use an existent RLC mechanism by instructing the UE 1 to move forward its receiving window, which requires an explicit message from the RNC 2.
  • any method step is suitable to be implement ⁇ ed as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;
  • ASIC Applica ⁇ tion Specific IC (Integrated Circuit)
  • FPGA Field-programmable Gate Arrays
  • CPLD Computer ⁇ plex Programmable Logic Device
  • DSP Digi ⁇ tal Signal Processor
  • - devices, units or means e.g. the above-defined appa ⁇ ratuses and network devices, or any one of their respec- tive units/means
  • an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the pos ⁇ sibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer pro ⁇ gram or a computer program product comprising executable software code portions for execution/being run on a pro ⁇ cessor;
  • - a device may be regarded as an apparatus or as an as- sembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example .
  • respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts.
  • the mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.
  • any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention.
  • Devices and means can be imple ⁇ mented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.
  • UE user equipment
  • mobile station de ⁇ scribed herein may refer to any mobile or stationary device including a mobile telephone, a computer, a mobile broadband adapter, a USB stick for enabling a device to access to a mobile network, etc.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Cette invention se rapporte à la suppression de l'une des liaisons en HSPA multiflux, mais le procédé ci-décrit s'applique aussi au fonctionnement en HSDPA normal pendant le transfert intercellulaire. L'invention vise en particulier à réduire au minimum l'effet négatif d'une liaison radio supprimée, c'est-à-dire l'abandon de paquets et/ou les retards. Selon ledit procédé, où la liaison radio à supprimer passe par un premier nœud B (NB1) (demande de suppression de RL), le NB1 met fin à la transmission de données en attente et informe le RNC qui commande des données qui n'ont pas été transmises, en particulier sous la forme du plus petit numéro de sequence dans sa mémoire tampon. Par la suite, ledit RNC décide, en fonction de ce numéro de séquence, des paquets de données qui doivent être retransmis sur une seconde liaison radio par le biais d'un second nœud B (NB2), et donne au NB2 les ordres qui en découlent (envoi de données).
EP12737515.2A 2011-08-16 2012-07-10 Transfert intercellulaire entre n uds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets Withdrawn EP2745563A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP12737515.2A EP2745563A1 (fr) 2011-08-16 2012-07-10 Transfert intercellulaire entre n uds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP2011064094 2011-08-16
EP12737515.2A EP2745563A1 (fr) 2011-08-16 2012-07-10 Transfert intercellulaire entre n uds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets
PCT/EP2012/063490 WO2013023842A1 (fr) 2011-08-16 2012-07-10 Transfert intercellulaire entre nœuds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets

Publications (1)

Publication Number Publication Date
EP2745563A1 true EP2745563A1 (fr) 2014-06-25

Family

ID=50732662

Family Applications (1)

Application Number Title Priority Date Filing Date
EP12737515.2A Withdrawn EP2745563A1 (fr) 2011-08-16 2012-07-10 Transfert intercellulaire entre n uds b en hsdpa ou hspa multiflux comprenant la retransmission de paquets

Country Status (1)

Country Link
EP (1) EP2745563A1 (fr)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2013023842A1 *

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