WO2009040747A2 - Modification d'un motif de symboles pilotes - Google Patents

Modification d'un motif de symboles pilotes Download PDF

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Publication number
WO2009040747A2
WO2009040747A2 PCT/IB2008/053887 IB2008053887W WO2009040747A2 WO 2009040747 A2 WO2009040747 A2 WO 2009040747A2 IB 2008053887 W IB2008053887 W IB 2008053887W WO 2009040747 A2 WO2009040747 A2 WO 2009040747A2
Authority
WO
WIPO (PCT)
Prior art keywords
pilot symbol
symbol pattern
terminal
radio transmission
change request
Prior art date
Application number
PCT/IB2008/053887
Other languages
English (en)
Other versions
WO2009040747A3 (fr
Inventor
Matthew P.J. Baker
Timothy J. Moulsley
Filippo Tosato
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2009040747A2 publication Critical patent/WO2009040747A2/fr
Publication of WO2009040747A3 publication Critical patent/WO2009040747A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H04L5/0051—Allocation of pilot signals, i.e. of signals known to the receiver of dedicated pilots, i.e. pilots destined for a single user or terminal
    • 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
    • H04L1/0015—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the adaptation strategy
    • 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
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0027—Scheduling of signalling, e.g. occurrence thereof
    • 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
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0028—Formatting
    • H04L1/003—Adaptive formatting arrangements particular to signalling, e.g. variable amount of bits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0091—Signaling for the administration of the divided path
    • H04L5/0096—Indication of changes in allocation
    • 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
    • H04L2001/0092—Error control systems characterised by the topology of the transmission link
    • H04L2001/0093—Point-to-multipoint
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/006—Quality of the received signal, e.g. BER, SNR, water filling

Definitions

  • the invention relates generally to radio communication networks, and more particularly, it relates to such networks whereinpilot symbols are used, like a UMTS LTE network ('Universal Mobile Telecommunication System Long Term Evolution') for instance.
  • UMTS LTE Universal Mobile Telecommunication System Long Term Evolution'
  • Such a radio communication network comprises network entities and mobile terminals which are able to exchange information via radio channels.
  • an access scheme like OFDMA (Orthogonal Frequency Division Multiple Access') or like SC-FDMA ('Single Carrier Frequency Division Multiple Access') for instance.
  • An access scheme of this type is a digital multi-carrier modulation scheme, which uses a number of closely-spaced orthogonal sub-carriers.
  • a signal is transmitted in successive signal frames comprising symbols at respective locations along an axis of time and an axis of frequency in a time- frequency reference frame.
  • a received signal can differ from the corresponding transmitted signal due to several effects linked to the radio transmission medium, such as thermal noise or multi path fading caused by the interaction of the signal with reflections or echoes of itself, or interference from other signals passing through the same medium. All these effects cause distortions of the transmitted signal.
  • thermal noise or multi path fading caused by the interaction of the signal with reflections or echoes of itself, or interference from other signals passing through the same medium. All these effects cause distortions of the transmitted signal.
  • it can be useful to use pilot symbols in the radio transmission.
  • a pilot symbol is one or more predetermined symbols that may be transmitted from the transmitter to the receiver.
  • the transmitter and the receiver are able to know locations of pilot symbols in a transmitted signal frame and, on the basis of them, it is possible to control, to synchronize or to supervise the radio transmission, to carry out measurements on radio channels or to estimate radio channels.
  • a base station determines a pattern of pilot symbols associated to a mobile terminal for using in its signal transmission to this terminal.
  • the pilot symbol pattern is set at the network level.
  • Such a characteristic can be effective and relevant when, at the base station level, it is possible to predict an optimal usage of pilot symbols.
  • MBMS Multimedia Broadcast Multicast Service
  • SFN Single- Frequency Network
  • the network may configure a pilot symbol pattern with appropriately placed pilot symbols without needing additional information. In these conditions, the network can be an appropriate level to set the pilot symbol pattern.
  • Figures 1 and 2 illustrate two different pilot symbols patterns respectively used in two different radio transmission types.
  • Figure 1 illustrates a pilot symbol pattern 11 which is set at the base station level when the handled radio transmission corresponds to a non Multimedia Broadcast Single Frequency Network transmission.
  • Figure 2 illustrates a pilot symbol pattern 21 which is set at the base station level effectively to handle a radio transmission corresponding to a Multimedia Broadcast Single Frequency Network transmission.
  • pilot symbol patterns are illustrated in a time-frequency reference frame according to which the horizontal axis is the time axis t and the vertical axis is the frequency axis f.
  • the pilot symbol pattern 11 comprises more pilot symbols on the time axis and on the frequency axis than the pilot symbol pattern 21 .
  • the network may not have sufficient information to determine an effective and relevant pilot symbol pattern for transmission to a mobile terminal.
  • Typical feedback from the mobile terminal such as channel quality indicators (CQI) or Hybrid ARQ (HARQ) acknowledgements do not provide sufficient information for the pilot symbol pattern to be adapted appropriately.
  • CQI channel quality indicators
  • HARQ Hybrid ARQ
  • pilot symbol pattern comprises not enough pilot symbols, the quality level of transmission can be insufficient.
  • the used pilot symbol pattern comprises more pilot symbols than are required, the resources available for transmitting useful data symbols are reduced.
  • a first aspect of the present invention is a method for adapting a pilot symbol pattern used in a radio transmission through a radio channel from a network entity to a terminal in a radio communication network; the pilot symbol pattern comprising a set of pilot symbol locations in a time- frequency reference frame, wherein pilot symbols are transmitted in said pilot symbol locations in the radio transmission; and a current pilot symbol pattern being used in the radio transmission, this method comprising the following steps at the network entity :
  • a terminal in a radio communication network has information about the quality of a transmission from the base station, since it is adapted to determine at least some of the following indications:
  • the terminal is able to determine whether decoding failure occurs because of poor data reception (insufficient data symbol energy) or because of poor channel estimation (insufficient pilot symbol energy or insufficient pilot symbol density). Consequently, the terminal can detect if the radio transmission can be carried out with a better quality level if the pilot symbol pattern is changed.
  • the pilot symbol pattern used for a radio transmission between the base station and the terminal can be adapted in an effective, reliable and relevant way.
  • One embodiment of the present invention can be applied to a mobile radio communication network, and in this case the terminal is a mobile terminal.
  • the radio transmission may comprise a continuous signal in the time domain occupying substantially the same bandwidth, or a sequence of signals of limited duration having different bandwidths and occupying different parts of the radio spectrum.
  • no limitation is attached to this aspect regarding the present invention. Indeed, it can be applied to a non mobile radio communication network.
  • the different pilot symbol pattern is determined at the terminal.
  • the network entity can handle a plurality of pilot symbol patterns to be used for the radio transmission, and the change request indicates which pilot symbol pattern among the plurality of pilot symbol patterns is required.
  • the different pilot symbol pattern can be determined at the network entity based on information received from the terminal.
  • the change request on which the network entity bases the determination of the next pilot symbol pattern can be either explicit or implicit.
  • Implicit information received from terminal and used to determine the different pilot symbol pattern at the network entity can comprise an indication of the reason for a failed decoding of a data packet.
  • the change request may be explicit.
  • the network entity can use for instance the following feedback indications: - indication relative to Doppler spread; and/or
  • Such information comprised in the change request can indicate, for instance, if more or less pilot symbols are required in the next pilot symbol pattern.
  • the network entity is able to modify the current pilot symbol pattern in order to obtain a different pilot symbol pattern which is better adapted to the radio transmission.
  • Such information comprised in the change request can indicate time and/or frequency characteristics relative to the radio transmission.
  • knowing such characteristics relative to the radio transmission the network entity is itself able to adapt correctly the pilot symbol pattern.
  • an initial pilot symbol pattern is used for the radio transmission initially, the initial pilot symbol pattern being known by the terminal and the network entity. This can be predetermined as a default pilot symbol pattern which is always available for use by the terminal(s).
  • the different pilot symbol patterns only insert additional pilot symbols relative to the default pilot symbol pattern, and do not remove pilot symbols contained in the default pilot symbol pattern. In such a case, the default pilot symbol pattern represents the minimum density of pilot symbols.
  • a second aspect of the present invention is a network entity being appropriate to adapt a pilot symbol pattern for a radio transmission to a terminal in a radio communication network; the pilot symbol pattern indicating, in a time-frequency reference frame, pilot symbols transmitted in a signal frame in the radio transmission; a current pilot symbol pattern being used in the radio transmission; the network entity comprising means adapted to use a next pilot symbol pattern in said radio transmission after reception of a change request of pilot symbol pattern sent from said terminal.
  • the network entity further comprises means adapted to determine the different pilot symbol pattern based on information received from the terminal. This information received from the terminal can correspond to feedback indication relative to a quality level of the radio transmission.
  • this information received from the terminal can correspond to information comprised in the change request.
  • a third aspect of the present invention is a terminal being appropriate to adapt a pilot symbol pattern for a radio transmission received from a network entity in a radio communication network; the pilot symbol pattern indicating, in a time-frequency reference frame, pilot symbols transmitted in a signal frame in the radio transmission; a current pilot symbol pattern being used in the radio transmission; the terminal comprising means adapted to send a change request of pilot symbol pattern to the network entity and to use a different pilot symbol pattern in the radio transmission.
  • a fourth aspect of the present invention is a radio communication system comprising at least a network entity according to the second aspect of the present invention and a terminal according to the third aspect of the present invention.
  • a fifth aspect of the present invention is a computer program product comprising instructions for implementing a sending change request of pilot symbol pattern according to method according to the first aspect of the present invention when loaded and run on computer means of a terminal according to the third aspect of the present invention.
  • a sixth aspect of the present invention is a computer program product comprising instructions for implementing a method according to the first aspect of the present invention when loaded and run on computer means of a network entity according to the second aspect of the present invention.
  • figure 1 and 2 illustrate two different pilot symbols pattern respectively associated to two different transmission types which are used according to the art
  • - figure 3 illustrates a radio communication network according to one embodiment of the present invention
  • figure 4 illustrates the main steps of a method for adapting a pilot symbol pattern according to one embodiment of the present invention
  • figure 5 illustrates the main steps of a method for adapting a pilot symbol pattern according to another embodiment of the present invention.
  • Figure 3 illustrates a radio communication network according to one embodiment of the present invention.
  • Such a network comprises at least one network entity 31 and terminals 32-35, which can be mobile terminals.
  • Such a radio communication network can be based on any transmission protocol including the transmission of pilot symbols.
  • this network can be an UMTS LTE network.
  • the considered network is an UMTS network and the network entity corresponds to a base station.
  • the terminal is in charge of requesting a change of pilot symbol pattern, and the determination of the new pilot symbol pattern to be used can be determined either at the terminal or at the base station level.
  • Figure 4 illustrates the main steps of a method for adapting a pilot symbol pattern according to one embodiment of the present invention wherein the determination of the new pilot symbol pattern to be used for the considered radio transmission with the terminal is carried out on the terminal side.
  • the base station 31 performs a radio transmission 41 towards the terminal 32 by using a current pilot symbol pattern.
  • the current pilot symbol pattern can be an initial pilot symbol pattern which is known by the terminal and by the base station beforehand.
  • the terminal detects that this current pilot symbol pattern is not adapted to this radio transmission from the base station 31. Consequently, it decides to request the base station to change the pilot symbol pattern for this radio transmission.
  • the terminal determines itself the next pilot symbol pattern to be used and indicates it to the base station by sending a message 43 comprising a change request.
  • the base station can know a list of several different pilot symbol patterns and different indexes corresponding respectively to these different pilot symbol patterns, and on the other hand, the terminal can know the list of these indexes.
  • the terminal is able to indicate to the base station which pilot symbol pattern is required for the radio transmission by sending in the change request message 43 the corresponding index. This has the advantage of limiting the signalling overhead for sending the message 43.
  • the base station Upon reception of the change request message 43, the base station is able to retrieve the required pilot symbol pattern and, then, to use it for the radio transmission towards the terminal 32.
  • the determination of a next pilot symbol pattern to be used by the base station 31 for the radio transmission towards the terminal can be carried out at the base station itself.
  • Figure 4 illustrates this case.
  • a radio transmission 41 from the base station 31 to the terminal 32 is currently carried out, on the basis of a current pilot symbol pattern, which can be, at the beginning of the radio transmission, an initial pilot symbol pattern which is known beforehand on both sides, on the terminal side and on the base station side.
  • the terminal 32 detects that this current pilot symbol pattern seems to be no more adapted to this radio transmission. Consequently, it decides to request a change of pilot symbol pattern by sending a change request message 43 to the base station.
  • the next pilot symbol pattern is determined on the base station side, on the basis of information comprised in this change request message 43.
  • the base station 31 exploits information comprised in this message 43 to determine the next pilot symbol pattern to be used in this radio transmission.
  • Such information comprised in the change request message 43 can be an indication on the fact that more or less pilot symbols are required in the next pilot symbol pattern. It is possible to specify that more or less pilot symbols are required on the time axis and/or on the frequency axis.
  • This change request message 43 can also indicate time and/or frequency characteristics relative to the radio channel used for this radio transmission. Such characteristics may for example comprise one or more of a Doppler spread, a channel impulse response, a coherence time and a coherence bandwidth.
  • the change request message 43 sent by the terminal contains information specifying for instance if more or less pilot symbols are required in the next pilot symbol pattern, or indicating time and/or frequency characteristics relative to the used radio channel as described above.
  • the terminal In a general way, as the terminal is in charge of requesting a change of pilot symbol pattern, it is also in charge of detecting the need to carry out such a change. No limitation is attached to the way of such detection on the terminal side. Thus, the terminal can take into account any information useful to make it able to decide that a change of pilot symbol pattern is needed to enhance the considered radio transmission.
  • the terminal can take into account one of the following indications: - relative to Doppler spread; or
  • this is the terminal which takes the decision to request a change of pilot symbol pattern
  • the current pilot symbol pattern is closely adapted to the radio transmission which is considered.
  • the terminal has more relevant information to carry out such a decision than a network entity in a radio communication network.
  • the invention has been largely described in relation to pilot symbol patterns transmitted by a network entity to a mobile terminal, but it will be understood that the invention applies equally to opposite or other allocations of roles to nodes.

Abstract

L'invention concerne un motif de symboles pilotes comprenant un ensemble d'emplacements τ de symboles pilotes situés dans une trame de référence temps/fréquence. Selon l'invention, les symboles pilotes sont transmis dans lesdits emplacements de symboles pilotes lors d'une radiotransmission (41). Un motif actuel de symboles pilotes est utilisé pour une radiotransmission s'effectuant dans un réseau de radiocommunication, d'une entité de réseau (31) à un terminal (32). Puis, une demande de modification (43) du motif de symboles pilotes est envoyée du terminal à l'entité de réseau; et un motif de symboles pilotes suivant est utilisé dans ladite radiotransmission.
PCT/IB2008/053887 2007-09-28 2008-09-24 Modification d'un motif de symboles pilotes WO2009040747A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP07301417 2007-09-28
EP07301417.7 2007-09-28

Publications (2)

Publication Number Publication Date
WO2009040747A2 true WO2009040747A2 (fr) 2009-04-02
WO2009040747A3 WO2009040747A3 (fr) 2009-05-22

Family

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PCT/IB2008/053887 WO2009040747A2 (fr) 2007-09-28 2008-09-24 Modification d'un motif de symboles pilotes

Country Status (2)

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TW (1) TW200931903A (fr)
WO (1) WO2009040747A2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012045448A1 (fr) * 2010-10-07 2012-04-12 Lantiq Deutschland Gmbh Placement de pilote dynamique
US20130343477A9 (en) * 2011-11-04 2013-12-26 Research In Motion Limited PUSCH Reference Signal Design for High Doppler Frequency

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1643669A1 (fr) * 2003-08-12 2006-04-05 Matsushita Electric Industrial Co., Ltd. Dispositif de radiocommunication et procede de transmission de symboles pilotes
EP1804451A2 (fr) * 2005-12-29 2007-07-04 Samsung Electronics Co., Ltd. Appareil et procédé de détermination de trame pilote dans un système de communication par accès sans fil large bande

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1643669A1 (fr) * 2003-08-12 2006-04-05 Matsushita Electric Industrial Co., Ltd. Dispositif de radiocommunication et procede de transmission de symboles pilotes
EP1804451A2 (fr) * 2005-12-29 2007-07-04 Samsung Electronics Co., Ltd. Appareil et procédé de détermination de trame pilote dans un système de communication par accès sans fil large bande

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012045448A1 (fr) * 2010-10-07 2012-04-12 Lantiq Deutschland Gmbh Placement de pilote dynamique
US20130343477A9 (en) * 2011-11-04 2013-12-26 Research In Motion Limited PUSCH Reference Signal Design for High Doppler Frequency

Also Published As

Publication number Publication date
TW200931903A (en) 2009-07-16
WO2009040747A3 (fr) 2009-05-22

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