Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/30—Transmission power control [TPC] using constraints in the total amount of available transmission power
  • H04W52/32—TPC of broadcast or control channels
  • H04W52/325—Power control of control or pilot channels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/38—TPC being performed in particular situations
  • H04W52/40—TPC being performed in particular situations during macro-diversity or soft handoff
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/16—Performing reselection for specific purposes
  • H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/06—TPC algorithms
  • H04W52/14—Separate analysis of uplink or downlink
  • H04W52/146—Uplink power control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/18—TPC being performed according to specific parameters
  • H04W52/22—TPC being performed according to specific parameters taking into account previous information or commands
  • H04W52/221—TPC being performed according to specific parameters taking into account previous information or commands using past power control commands
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/54—Signalisation aspects of the TPC commands, e.g. frame structure
  • H04W52/58—Format of the TPC bits

Definitions

• the present invention relates to the control of radio links in a radiocommunication system. It relates more particularly to the power adaptation for certain radio links capable of modifying the transmission conditions for radio channels for high speed data transmission.
• Radiocommunication systems such as the GSM system ("Global System for Mobile communications") or the UMTS system (“Universal Mobile Telecommunication System”). They aim to improve the performance of reception of the transmitted information while limiting the risks of interference.
• GSM Global System for Mobile communications
• UMTS Universal Mobile Telecommunication System
• Power control is particularly sensitive when applied to data transmission channels allowing a high speed, because too low power on such channels can generate a high error rate in the transmission, detrimental to the speed offered. This is also the case for channels giving feedback on high speed channels, since transmission of such channels with too low power can lead to misinterpretation of feedback information. , which may affect the useful throughput on high-speed channels.
• HSDPA High Speed Downlink Packet Access
• the HSDPA provides for the use of shared downlink channels, called HS-PDSCH ("High Speed - Physical Downlink Shared CHannel”), allowing a base station to transmit data at high speed to terminals.
• the terminals send back to the base station feedback information, in particular acknowledgments and indications related to the quality of the downlink transmissions, on dedicated dedicated uplink channels, called HS-DPCCH ("High Speed - Dedicated Physical Control CHànnel ").
• HS-DPCCH High Speed - Dedicated Physical Control CHànnel
• Each DPCH has a data subchannel (DPDCH, "Dedicated Physical Data CHannel”) and a control subchannel (DPCCH, "Dedicated Physical Control CHannel”).
• the DPCCH notably carries information for controlling the transmit power in the opposite direction.
• each time interval of 666 ⁇ s on the DPCCH descending from a base station to the terminal (DL_DPCCH) carries bits TPC ("Transmit Power Control") for controlling the transmission power by the terminal on the DPCH amount.
• TPC Transmit Power Control
• the value of this TPC bit indicates to the terminal whether it must increase or decrease its transmission power during the next time interval of 666 ⁇ s on the rising DPCH.
• HS-DPCCH To secure the reception of the HS-DPCCH, it is known to use a higher power on an HS-DPCCH compared to the rising DPCCH (UL_DPCCH). This is conventionally achieved by the use of a power offset between the HS-DPCCH and the UL_DPCCH, on which a terminal communicates, in favor of the HS-DPCCH.
• DPCH is in macrodiversity mode, or "soft handover” (SHO).
• SHO soft handover
• This mode provided in particular in the UMTS system, allows the terminal to receive the same information on dedicated channels from several base stations simultaneously, in order to increase the reliability and the quality of reception.
• the base stations coming into play are then part of what is called an active set.
• the transmissions made by the terminal are received by the different base stations and then recombined to more reliably find the information transmitted.
• SHO mode is not available for channels
• HS-PDSCH and HS-DPCCH which relate to only one base station. If the communication is in SHO for the dedicated channel UL_DPCCH, the power adjustment on this channel generally takes account of the propagation conditions on all existing radio links with each base station of the active set.
• the terminal combines the TPC bits received from the different base stations to determine whether to decrease or increase its transmit power. The procedures are explained in section 5.1.2.2 of the technical specification TS 25.214, version 5.0.0, "Physical layer procedures (FDD)", published in March 2002 by the 3GPP organization. If the transmit power on the UL_DPCCH is set conventionally, obtaining the transmit power on the HS-DPCCH by applying an offset to that of the UL_DPCCH channel may adversely affect the quality of the transmission.
• a transmission power thus adapted for the UL_DPCCH, and therefore for the HS-DPCCH takes into account the reception quality of the UL_DPCCH by all the base stations of the active set, and not only by the station base carrying the HS-PDSCH downlink.
• the HS-DPCCH whose power is adjusted, thanks to an offset, relative to the UL_DPCCH, then sees its power further decrease, when it was already considered too low by the station concerned.
• the HS-DPCCH, and in particular the acknowledgments it carries, may be received with a high error rate, which degrades performance.
• the HS-DPCCH channel does not carry pilot bits, that is to say bits known to the receiving base station and from which the latter is capable of demodulating a transmitted signal.
• pilot bits carried by the UL_DPCCH channel allow the base station to demodulate the signal transmitted on the HS-DPCCH under good conditions.
• a too significant drop in power on the UL_DPCCH caused by good reception by other stations of the active set, can degrade the decoding of the HS-DPCCH by the base station for which it is intended.
• Having transmitting powers always high on the HS-DPCCH and UL_DPCCH channels would limit the problems mentioned, but would permanently degrade the overall performance of the system, notably by creating interference.
• the activity rate of the HS-DPCCH channel can be low in certain cases (the HS-DPCCH may only carry acknowledgment information and may not even be the subject of any transmission during the periods of silence of the HS- PDSCH), maintaining high power on the HS-DPCCH channels and especially UL_DPCCH would then be counterproductive.
• Another aspect of the invention in the context of HSDPA, is to increase the transmission power of the HS-DPCCH and ULJDPCCH channels by a value sufficient to allow the base station concerned to decode the HS-DPCCH with good reliability, while limiting this increase over time.
• the invention thus proposes a radiocommunication method, in which an active set of transceivers of a cellular network communicate with a terminal according to frame structures subdivided into successive time slots.
• the process comprising the following steps:
• the terminal performs the following steps for each time slot of the downlink dedicated channels during a period of non-transmission of the fourth radio signal:
• This way of adjusting the power of the fourth radio signal makes it possible to optimize the conditions for reception by the reference transceiver (the one that transmits for the terminal on the HS-PDSCH).
• the method advantageously takes into account the possible drift of the power control applied compared to what the reference transceiver claimed in the non-transmission period on the uplink signaling channel, drift due to the different commands that may have been send the other transceivers in the active set.
• the first radio signal carries pilot symbols to assist reception of the signals transmitted by the terminal on the uplink channels.
• the first radio signal then has its power controlled in a similar manner to the resumption of transmission on the uplink signaling channel, in order to allow good demodulation of the fourth signal.
• the detected differences are typically taken into account in the adjustment of the transmission power of the fourth radio signal in the first time slot following the non-transmission period and in the adjustment of the transmission power of the first radio signal in a slot corresponding time of the dedicated dedicated channel.
• This optimization of the power of the first signal is carried out on the uplink channel outside of the transmission periods on the signaling channel using the conventional power control procedure.
• the transmission power of the first and fourth radio signals after said first phase is preferably adjusted by applying the first power modification command received from the reference transceiver.
• the terminal stores, during the period of non-transmission of the fourth radio signal, the number of differences detected for the K most recent time slots of the dedicated downlink channels, K being a positive integer.
• the adjustment of the transmission power of the fourth radio signal in the first time slot following the non-transmission period then includes the application of a proportional correction, in dB, to the number of differences stored.
• node B in the case of a UMTS network.
• the first signal sent by the terminal is picked up by these transceivers, which produce flexible estimates of the information transmitted. A soft combination of these estimates is performed locally, which optimizes the reception of information.
• the transceivers of the active set forming part of the same unit in SerHO issue first orders for identical power modifications on their dedicated downlink channels. If the reference transceiver, transmitting for the terminal on the shared channel, is part of this unit, it may happen that it picks up the uplink channels rather weakly when it sends back commands to decrease power because that one or more other transceivers of the active set also forming part of the unit properly capture these uplink channels, giving rise to good combined reception. In such a circumstance, the terminal will not be able to realize that the reference transceiver actually wants an increase in power. This may result in poor reception of the uplink signaling channel associated with the shared downlink channel for the terminal. This risk is advantageously avoided by activating the reception of the fourth radio signal in each of the transceivers of the active set forming part of the unit, and by combining the estimates thus obtained, without the need to report to the supervisory body.
• the invention provides that the radio unit activates reception of the fourth radio signal in each of the group's transceivers and combines the versions of the fourth radio signal received respectively by the group's transceivers to retrieve the feedback information.
• the invention also provides a radio unit suitable for such an implementation of the method.
• This unit comprises several transceivers controllable to belong to an active set of transceivers relative to a terminal.
• Each transceiver of the unit belonging to the active set is arranged to receive a first radio signal transmitted by the terminal on a dedicated uplink channel and to transmit, on a dedicated downlink channel, a second radio signal carrying a modification command. of power in each time slot, the power modification command being determined jointly for the transceivers of the unit belonging to the active set by combining the versions of the first radio signal respectively received by said transceivers.
• One of the transceivers belonging to the active set is also controllable to transmit in isolation and intermittently a third radio signal to the terminal, on a downlink shared channel and to receive a fourth radio signal transmitted intermittently by the terminal on an uplink signaling channel associated with said downlink shared channel, the fourth radio signal providing feedback information for the transmission of the third radio signal.
• the radio unit further comprises means for activating the reception of the fourth radio signal in each of the transceivers of the unit belonging to the active set and means for combination of the versions of the fourth radio signal respectively received by the transceivers of the unit belonging to the active set, to recover the feedback information.
• Another aspect of the present invention relates to a radiocommunication terminal for communicating with a cellular network using frame structures subdivided into successive time slots for the transmission of radio signals, comprising:
• the second adjustment means being arranged to take account of the differences detected by the detection means during at least part of said period.
• FIGS. 1A and 1B are diagrams illustrating the frame structure used on dedicated traffic channels in the UMTS system in FDD mode;
• - Figure 2 is a diagram of a system implementing the invention
• - Figure 3 is a diagram illustrating the main radio channels involved in the invention
• - Figure 4 is a schematic representation of the operations performed by a terminal according to the invention when the transmissions on the HS-DPCCH channel are distant in time
• - Figure 5 is a schematic representation of the operations performed by the terminal when the transmissions on the HS-DPCCH channel are closer together in time
• FIG. 6 is a diagram of another system implementing the invention.
• the invention will be described more particularly in its nonlimiting application to third generation radiocommunication networks of the UMTS type in FDD mode. ("Frequency Division Duplex").
• UMTS is a radiocommunication system using multiple access with code distribution (CDMA, “Code-Division Multiple Access”), that is to say that the symbols transmitted are multiplied by spreading codes made up of samples called “chips” whose rate (3.84 Mchip / s in the case of UMTS) is higher than that of the symbols transmitted.
• CDMA Code-Division Multiple Access
• the spreading codes distinguish different physical channels PhCH (“Physical CHannel”) which are superimposed on the same transmission resource constituted by a carrier frequency.
• PhCH Physical CHannel
• the auto- and cross-correlation properties of the spreading codes allow the receiver to separate the PhCHs and extract the symbols intended for it.
• a scrambling code is allocated to each cell, and different physical channels used by that cell are distinguished by mutually orthogonal “channelization” codes.
• the global spreading code is the product of the “channelization” code and the cell jamming code.
• the spreading factor (equal to the ratio between the chip rate and the symbol rate) is a power of 2 between 4 and 512. This factor is chosen according to the symbol rate to be transmitted on the PhCH.
• the modulation used on dedicated physical channels of the DPCH type is a quadrature phase modulation (QPSK, “Quadrature Phase Shift Keying”).
• QPSK Quadrature Phase Shift Keying
• FIG. 1A illustrates the contribution of a descending DPCH (DL_DPCH) to a time slot in FDD mode, which comprises: - a number of PL pilot bits. Known a priori from the terminal, these bits PL allow it to estimate some of the parameters useful for demodulating the signal, in particular for power control;
• TPC Transmit Power Control
• the DL_DPCH can thus be seen as bringing together a dedicated channel for control, or DL_DPCCH, corresponding to the TFCI, TPC and PL fields, and a dedicated channel for data, or DLJDPDCH, corresponding to the DATAI and DATA2 fields, these data channels and control being time multiplexed.
• DL_DPCCH dedicated channel for control
• DLJDPDCH dedicated channel for data
• the complex baseband signal has a real part (channel I of the QPSK) carrying the data of the UL_DPDCH and an imaginary part (channel Q) carrying the information of the UL_DPCCH which includes the same type of information as the DL_DPCCH plus possibly feedback bits (FBI). This is illustrated in Figure 1B.
• each base station 1, 2, 3 transmits information to the terminal 4 via a downlink DL_DPCH 1 , DL_DPCH 2 , DL_DPCH 3 .
• Terminal 4 transmits information via an uplink channel UL_DPCH.
• the UL_DPCH transmitted by the terminal is received by each of the base stations with a view to recombining the signal transmitted in a radio network (not shown in the figure). Conversely, the channels DL_DPCH 1 , DL_DPCH 2 , DL_DPCH 3 transmit the same information
• the terminal recombines to decode the signal with increased reliability.
• the base stations 1, 2, 3 which communicate simultaneously with the terminal 4, thus form part of what is called an active set.
• Each base station 1, 2, 3 belonging to the active set estimates a signal / interference ratio SIR is ("Signal-to-lnterferer Ratio") for the uplink channel UL_DPCCH.
• SIR Signal / interference ratio
• Each base station compares the value of SIR it has estimated with a target value SIR target .
• each base station in the active set generates a TPC command and transmits it at the rate of one per time slot on the DL_DPCCH bound for terminal 4.
• the transmitted TPC command is equal to "0 "(or” - “according to a notation used later) if the value of SIR estimated by a base station of the active set is greater than the target value. Conversely, if the SIR value estimated by a base station in the active set is less than the target value, the base station considered transmits the TPC command "1" (or "+” according to a notation used later ) at terminal 4.
• the terminal 4 receives in the corresponding time slot the various TPC commands emanating from each base station 1, 2, 3 of the active set. It then determines a combined TPC command from the TPC commands received. According to a method provided by the standard, the result of this combination amounts to a logical AND operation: the combined command is equal to "0"("-") when at least one of the base stations 1, 2, 3 of l active set has transmitted a " ⁇ " command for the time slot corresponding, and "1"("+”) if all the base stations 1, 2, 3 of the active set have transmitted a TPC command "+".
• the adaptation of the transmission power of the terminal on its UL_DPCCH channel is then carried out taking into account the value of this step and the combined TPC command.
• the combined TPC command is "-"
• the transmission power is reduced by ⁇ .
• the combined TPC command is "+”
• the transmit power is increased by ⁇ .
• the standard provides for a different setting of the terminal transmit power on the UL_DPDCH and UL_DPCCH subchannels.
• Gain factors ⁇ d and ⁇ c calculated or signaled by the network, are respectively applied to these two subchannels (section 5.1.2.5 of the aforementioned specification TS 25.214).
• the HSDPA allows transmission by a high-speed database station for a set of terminals located in the coverage area of the base station. It is based on a shared high-speed downlink transport channel: the HS-DSCH (“High Speed - Downlink Shared CHannel”). In the FDD mode in which we are more particularly interested in this description, this channel has in particular the characteristics:
• the MAC-hs At the access network level, part of the medium access control protocol (MAC) layer, the MAC-hs, is located in the base station. Thus, we make sure to offer a high speed on this channel. For the same reason, the HS-PDSCH uses a factor relatively low spread, equal to 16. In a given cell and for a given scrambling code, up to 15 HS-PDSCH channels can be established using orthogonal "channelization" codes, a single HS-DSCH being able to be allocated to a user.
• the HS-DSCH transport channel is carried by a physical channel
• HS-PDSCH High Speed - Physical Downlink Shared CHannel
• This channel does not support SHO mode because the rapid transmission mechanisms assume communication with a single base station.
• the HS-PDSCH bringing information to the attention of the terminal 4, is transmitted by the base station 1.
• HS-SCCH High Speed - Shared Control CHannel
• the signaling information carried by the HS-SCCHs identifies the destination terminals of the blocks transmitted on the HS-DSCHs, and provides them with a certain number of useful indications for the reception of these blocks:
• Transport Format and Resource Indicator giving information concerning the format of the dynamic part of the HS-DSCH channel, in particular for the modulation scheme used, and the physical resources allocated
• An HS-SCCH channel uses a spreading factor of 128, with a sub-frame identical to that of the HS-DSCH (3 slices of 666 ⁇ s). All the HS-PDSCHs transmitted by a base station are aligned in time and the synchronization of the HS-SCCHs is advanced by two slices (1333 ⁇ s) compared to that of the associated HS-PDSCHs, as illustrated in FIG. 3. This allows the destination terminal of a data block transmitted on an HS-PDSCH in a 2 ms HSDPA subframe to know the information necessary for its reception.
• Some information contained in the TFRI namely the allocated codes as well as the modulation used, are essential for the terminals because they allow them to start to re-encode the HS-PDSCH (s) which concern them. This is why this information from the TFRI is included in the first section of each sub-frame on the HS-SCCH.
• a rapid decoding of the HS-SCCH allows a terminal to read the content of the HS-PDSCH in the next subframe without loss of information.
• a dedicated uplink channel is also defined in the HSDPA functionality: the HS-DPCCH (“High Speed-Dedicated Physical Control CHannel”). It allows the terminal involved in an HSDPA transmission to return feedback information to the base station carrying the HS-PDSCH channel. This feedback information includes in particular the acknowledgments of the HARQ protocol and measures useful for link adaptation.
• the HS-DPCCH uses a subframe structure whose duration is equivalent to that of a subframe, that is to say 2 ms, with a spreading factor equal to 256.
• Each HS-DPCCH subframe is composed of a first field of 2560 chips (10 symbols) containing the acknowledgments of the HARQ protocol (field noted "ACK" in FIG. 3).
• HS-DPCCH is not transmitted continuously. This is particularly the case in periods when no information is transmitted to the terminal on the HS-PDSCH shared channel.
• FIG. 3 gives a temporal representation of the main channels used between a base station 1 and a terminal 4 involved in an HSDPA communication. After despreading and decoding of the signal received on four HS-SCCH channels indicated at the terminal (only two of which are shown in FIG. 3), the latter identifies the HS-PDSCH channel on which the base station optionally sends it high-speed data with an offset of two time slots. This transmission is indicated on the appears in time slots # 0, # 1 and # 2.
• dedicated channels are also used: the downlink DL_DPCH shifted with respect to HS-S ⁇ CH by a time ⁇ 1 and the uplink channel UL_DPCH having a time offset T 0 , corresponding to approximately 1024 chips, with respect to DL_DPCH.
• T 0 time offset
• the first subframe or time slot # 0 by 2ms is offset from the end of time slot # 2 of the HS-PDSCH.
• This offset corresponds to 7.5 time slots (that is to say 5 ms), to which is added an adjustment in time ⁇ 2 so as to preserve the orthogonality between the codes of HS-DPCCH and UL_DPCCH, this adjustment consisting in making the offset between these two channels multiple of the duration of 256 chips.
• a second HSDPA transmission is indicated to the terminal by another HS-SCCH channel. It is noted with the time slice indexes # 3, # 4 and # 5. The transmission then takes place on an HS-PDSCH channel, which can be the same as for the first transmission, as is the case in FIG. 3, or else on one or more other HS-PDSCHs of the base station considered. .
• the second HSDPA transmission is the subject of an acknowledgment on a subframe of the HS-DPCCH, but that the CQI is not transmitted for this second transmission.
• the period of silence on the downward HSDPA channels between the two represented transmissions implies an absence of transmission by the terminal concerned on its dedicated HS-DPCCH channel, even if the terminal can take advantage of this silence to repeat indications of acquittal.
• reception by the base station supporting the HSDPA (base station 1 in the figure 2) must be reliable under penalty of repetition of the data transmitted on the HS-PDSCH channel leading to a drop in flow rate contrary to the objective, or more generally a degradation of the HSDPA service.
• the power control on the HS-DPCCH must therefore be taken care of in order to limit errors on reception by the base station 1.
• the HS-DPCCH does not carry pilot bits.
• the base station 1 uses the pilot bits transmitted by the terminal 4 on its dedicated channel UL_DPCCH to demodulate the signal transmitted on the HS-DPCCH insofar as the two channels meet the same propagation conditions, with at most a slight offset temporal.
• the pilot bits transmitted on a time slot of the UL_DPCCH allow the base station 1 to demodulate the signal corresponding to the sub-frame of the HS-DPCCH channel whose transmission started before the end of said time slot of the UL_DPCCH.
• the power control mode performed on the UL_DPCCH and HS-DPCCH channels is modified in the same way, so that an offset can be applied to the transmission power of a time slot of the UL_DPCCH for obtain that of the corresponding HS-DPCCH subframe.
• the UL_DPCCH channel is capable of transmitting permanently, even outside any HSDPA transmission, the transmission power on this channel cannot be systematically fixed at its maximum value, as one could have considered for the HS-DPCCH whose transmissions are not continuous, on pain of creating harmful interference to other communications.
• the transmit power on the UL_DPDCH can vary in the same way as on the UL_DPCCH, as provided in section 5.1.2.5 of the aforementioned specification TS 25.214.
• the HSDPA aims to offer a high downlink speed.
• the HSDPA channels are therefore established for a base station 1 whose signals are received with a good field level at the terminal 4.
• the base station 1 is that which receives the signals transmitted by the terminal 4 with the maximum field level.
• the line SB j designates the TPC commands sent by the base station i (1 ⁇ i ⁇ 3).
• the TPC commands are obtained following measurements made by the base stations on the dedicated uplink channel UL_DPCCH, as described above.
• the sub-frames of the HS-DPCCH were aligned with the TPC commands transmitted to each time slot of the UL_DPCCH whereas we have seen that these could be slightly shifted in time. This should be interpreted as meaning that a power change command for a time slot of the UL_DPCCH also applies to the corresponding HS-DPCCH subframe, i.e. the subframe which starts before the end of said time slot.
• SB 2 and SB 3 receive the signals transmitted by the terminal 4 with a level or more exactly a SIR is higher than that estimated by SB This can result in a command "-" for SB 2 and SB 3 , while SB 1 transmits a TPC "+” bit because the power it receives from terminal 4 on the UL_DPCCH is too low (SIR is ⁇ SIR target ) which risks preventing good reception of information from HS-DPCCH.
• SB 1 transmits a TPC "+” bit because the power it receives from terminal 4 on the UL_DPCCH is too low (SIR is ⁇ SIR target ) which risks preventing good reception of information from HS-DPCCH.
• SIR is ⁇ SIR target
• this imbalance is attenuated as soon as the transmission on the HS-DPCCH channel is resumed, that is to say as soon as a new acknowledgment is to be transmitted on the HS-DPCCH and as soon as the pilot bits allowing to demodulate the signal containing this acknowledgment are transmitted on the UL_DPCCH.
• terminal 4 when terminal 4 does not transmit on the HS-DPCCH, it is made to store, as and when they are received, and on a window of K values, with K integer, the values of TPC commands received from SB 1 as well as the combined TPC command values from the different base stations calculated by the terminal 4 ("COMB" in FIG. 4).
• the number K of stored values can be fixed, but can also be a variable depending for example on the memory size available in the terminal 4 or else on the number of time slots separating two successive transmissions on the HS-DPCCH.
• the stored values are circled in the example illustrated in FIG. 4, where K has been set to the value 6. They correspond to the last values of TPC, for SB 1 and COMB respectively, just before a new transmission on the channel HS- DPCCH, corresponding, in the example, to the subframe numbered N + 1 in FIG. 4.
• ⁇ conventional power control
• the 2 x ⁇ dB are linked to taking into account the detected differences and the ⁇ dB are linked to the current TPC command sent by SBi.
• the transmission power of the HS-DPCCH being adjusted in the same way as for the UL_DPCCH, except for an offset, the correction of 2 x ⁇ dB + ⁇ dB also applies to the ACK subframe of the HS -DPCCH.
• ⁇ 2 x ⁇ .
• the TPC commands of SB 1 are applied to the uplink channels. Indeed, the power deficit having been attenuated, even compensated for, on the first time slot (ACK) of the new transmission on the HS-DPCCH, it suffices for the terminal 4 to adapt the power according to the commands of SB 1 to transmit the following time slots (CQI) to comply with the transmission error rate desired by SB.,. This is what is illustrated at the end of the line RES of FIG. 4, on which we see that the power variations actually applied by the terminal 4 over the last two time slots (respectively "+” and "-”) are identical to those requested by SB 1 in its TPC commands.
• the combined TPC commands are conventionally applied to vary the power over the corresponding time slots of the UL_DPCCH.
• FIG. 4 there is indeed the sequence "- + - + + -" for the first three time slots represented on the line RES, as on the line COMB.
• FIG. 5 Another embodiment is illustrated in FIG. 5 where the transmissions on the HS-DPCCH channel (sub-frames N and N + 1) are closer together in time than in the previous case.
• the power was calibrated on the commands of SB 1 and it was only during the three following time slots, where the power is controlled by the combination (COMB) of the TPC commands that differences appeared between the commands COMB and SB ⁇
• the variations in power applied (RES) by the terminal 4 on its HS-DPCCH and UL_DPCCH channels only take account of the TPC commands from SB. ,, that is to say say of the base station supporting HSDPA channels.
• the HS-DPCCH # N + 1 subframe of the example illustrated in FIG. 5 is repeated. This is equivalent to having two consecutive transmissions on the HS-DPCCH channel. In this case, the power variations applied remain in accordance with SB TPC commands.,.
• the combined COMB commands are again implemented by the terminal 4 (see line RES) to modify the transmission power on the UL_DPCCH channel at the end of the last N + 1 transmission.
• the last three time slots shown in FIG. 5 include a sequence of "-" on both the COMB and RES lines.
• each base station 1, 2, 3 serves a cell of the network.
• the equipment called node B in a UMTS network can generally comprise one or more transceivers to serve respective cells which are distinguished by different sets of spreading codes.
• macrodiversity it is common for several cells of the active set to belong to the same base station or node B. This is the case of the SerHO mentioned previously.
• the reference cell that is to say the one which is responsible for transmitting on the shared channel (s) HS-PDSCH for the terminal, belongs to the same node B as one or more other cells of the active set.
• FIG. 6 This case is illustrated in FIG. 6, where the terminal 4 simultaneously receives identical information from the three cells 11, 12, 13 depending on the base station 10, respectively on the DL_DPCCH 11 channels,
• Terminal 4 combines the signals received from the three cells, which gives it a higher quality of reception than it would benefit from by receiving information only from one of the cells.
• the terminal 4 transmits information on a dedicated channel UL_DPCCH.
• the latter is received by the transceivers of the three cells 11, 12, 13.
• the channel UL_DPCCH contains pilot bits.
• the transmitted pilot bits are the subject of a joint measurement at the level of the base station 10.
• the TPC bits are evaluated globally by base station 10.
• TPC bits are transmitted to terminal 4 by each of cells 11, 12, 13 on its respective DL_DPCCH channel.
• Terminal 4 for its part, performs a joint estimation of the signals received and deduces therefrom the TPC command to be applied.
• the invention provides that in such a case, the communication on the HS-DPCCH is also in SerHO as regards the cells belonging to the same node B as that which transmits on the HS-PDSCH.
• This means that the HS-DPCCH will be received by each of the transceivers 11, 12, 13 and then recombined at the base station 10.
• the terminal 4 has the concept of "radio link set" (see section

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

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• 2002
  • 2002-07-02 FR FR0208249A patent/FR2842048B1/fr not_active Expired - Fee Related
• 2003
  • 2003-06-25 AU AU2003258825A patent/AU2003258825A1/en not_active Abandoned
  • 2003-06-25 EP EP03762708A patent/EP1518336A2/de not_active Withdrawn
  • 2003-06-25 WO PCT/FR2003/001961 patent/WO2004006466A2/fr not_active Ceased

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