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    • 专利摘要:
    METHOD FOR CONTROLLING UP-LINK TRANSMISSION DIVERSITY OPERATION AND USER EQUIPMENT. Method and devices are provided in which a user equipment transmits using at least two uplink transmit antennas and receives a set of control signals in the downlink direction of a cellular network. The user equipment estimates a received signal quality for each control signal in said set of control signals and determines, based on said received signal quality, which control signals were reliably received. The user equipment derives one or more parameters related to uplink transmission diversity operation using a subset of control signals from the set of control signals, said subset only including control signals determined to be reliably received; and transmits in the uplink direction by applying the derivative or more parameters to control the uplink transmit diversity operation. The accuracy of the transmit diversity parameter values derived/set by the UE can be improved. This will enhance the performance of uplink transmission diversity and also interference to neighboring cells.
    公开号:BR112012007967B1
    申请号:R112012007967-0
    申请日:2010-10-04
    公开日:2021-05-04
    发明作者:Muhammad Kazmi；Oskar Drugge；Johan Bergman
    申请人:Telefonaktiebolaget Lm Ericsson (Publ)；
    IPC主号:
    专利说明:

    TECHNICAL FIELD
    [001] The present invention relates to methods and devices to control uplink diversity transmission in a radio system. FUNDAMENTALS
    [002] A study paper called "Uplink transmit diversity for HSPA", see RP-090987, was recently completed on 3GPP. The purpose of the study article was to perform the feasibility study to assess the system gain of uplink transmission diversity schemes for High Speed Packet Access (HSPA) as well as to analyze the impact on User Equipment (UE) and implementation and base station complexity in a cellular radio system.
    [003] The basic and typical UE implementation includes a single uplink transmit antenna used for all types of uplink transmission, However, high end UEs can have and use multiple uplink transmit antennas for uplink transmission. This is commonly called uplink broadcast diversity. The goal of transmit diversity transmission is to achieve higher uplink data rate and/or lower UE transmit power due to spatial, angular and/or temporal diversities.
    [004] A commonly used uplink transmit diversity consists of two uplink transmit antennas. Signals from two or more uplink transmit diversity antennas may be transmitted differently in terms of their phases, amplitude, power, etc. This gives rise to different uplink transmission diversity schemes. Some well-known schemes are: - Open-loop transmission beamforming; - Closed loop transmission beamforming; - Switched antenna uplink transmission diversity open loop; - Switched antenna uplink transmit diversity closed-loop; - Space-time transmission diversity.
    [005] Typically, in any transmission diversity scheme, a set of parameters related to uplink transmission diversity is regularly adjusted by the UE. The objective is to ensure that the uplink transmission incorporates the desired spatial, temporal or angular diversities. This in turn improves uplink coverage, reduces interference, increases uplink bit rate and enables the UE to lower its transmitted power.
    [006] The transmit diversity parameters may include one or many of: relative phase, relative amplitude, relative power, relative frequency, timing, absolute or total power of transmitted signals in transmit diversity branches, etc.
    [007] The adjustment of all or a subset of these parameters is fundamental for the transmission beamforming scheme. The purpose of beamforming is to direct the uplink transmission or beam to the desired base station, which is usually the service base station. This allows the serving base station to decode the received signal more easily. Furthermore, high beam directivity to the desired base station reduces interference to neighboring base stations.
    [008] Similarly in the case of switched antenna transmit diversity, transmit diversity parameter implies selecting the most appropriate transmit antenna (for example, in terms of radio condition) among the available transmit diversity branches. By virtue of using the most suitable antenna for uplink transmission, the UE can either reduce its power while maintaining a given uplink information rate, or increase the information rate while maintaining a given output power.
    [009] In open-loop transmit diversity schemes, the UE autonomously adjusts the uplink transmit diversity parameters without using any signaling or network control commands. These schemes are simpler, although they may not show significant gain in all scenarios.
    [0010] On the other hand, in closed-loop transmission diversity schemes, the UE adjusts the uplink transmission diversity parameters by making use of a satisfactory network transmitted signaling or control commands. These commands or control signals reflect the uplink quality, for example, the quality measured at the base station. These commands (control signals) are signaled to the UE via the downlink. Furthermore, commands can be sent exclusively to the UE to enable it to adjust the uplink transmit diversity parameters. Alternatively, the UE may use any existing commands or signaling, which are originally intended for other purposes, to derive the uplink transmission diversity parameters. Examples of such implicit signaling or commands are Transmit Power Control (TPC) and Hybrid Automatic Repeat Request Acknowledgment (HARQ)/Negative Acknowledgment (ACK/NACK), etc., which are sent to the UE by the base station to uplink power control and uplink HARQ retransmission scheme, respectively. Closed-loop schemes have the potential to lead to better performance gain due to the use of network controlled signaling to adjust the uplink transmission diversity parameters.
    [0011] In addition, broadcast diversity schemes can be used in any cellular radio system technology including Long Term Evolution (LTE), Broadband Code Division Multiple Access (WCDMA) or Global System for Mobile Communication ( GSM). For example in LTE, switched antenna uplink transmit diversity is standardized in LTE release 8.
    [0012] Reliability is particularly important in transmissions where an entire decision relies on one or more simple commands such as on/off signaling, ACK and NACK responses, power up and down control commands, etc. Uncertain commands can cause actions to occur in the reverse direction and, in some cases, can lead to unstable behavior.
    [0013] Insecurity usually occurs due to bad radio conditions, low transmitted power level, poor coverage, high system load, etc., whereby the receiver cannot correctly interpret the correct meaning of the command.
    [0014] To ensure reliable operation, four sets of functionality can be specified: - Reliability check; - Behavior or action of UE and/or base station; - Indication or information of insecurity events for the network; - Prevention of insecurity.
    [0015] The reliability check can be based either on some signal strength or quality such as signal to interference ratio (SIR). It may also be based on some target bit error rate (BER) value. This means that a received command is considered uncertain in case the received signal quality or strength falls between the thresholds or if the BER is higher than the target.
    [0016] The behavior of UE or base station in response to detection of uncertain command depends on a particular functionality governed by the on/off command.
    [0017] Several uplink transmit diversity schemes exist that use signaling or network control commands to derive uplink transmit diversity parameters. For example, certain schemes such as uplink transmit beamforming could make use of TPC or HARQ ACK/NACK commands sent by the base station to derive the uplink transmit diversity parameters. Similarly, the switched antenna uplink transmit diversity scheme could make use of TPC or HARQ ACK/NACK commands for antenna selection. Both of these regimens have been studied within the scope of the recently completed study article on 3GPP, see RP-090987.
    [0018] Previous signaling (TPC or HARQ ACK/NACK or similar), which is transmitted on the downlink, is used to characterize the uplink quality. However, due to poor downlink quality, commands or network signaling such as TPC may be erroneously received by the UE. For example, due to error, the TPC that is either 0 (eg DOWN) or 1 (eg UP), if transmitted as 1 can be interpreted as 0 or vice versa. This will lead to erroneous adjustment of transmit diversity parameters in the case that TPC (or similar commands or signaling) is used for this purpose. Incorrect parameter adjustment can lead to incorrect beamforming or antenna switching. For example, the beam can be directed to the neighboring base station instead of the serving one. Uplink performance (ie UE with erroneous parameter setting due to incorrect received command) will deteriorate and neighboring cells will receive excessive and unnecessary interference.
    [0019] Furthermore, US Patent Application No. 2008/123768 describes a system where TPC and HARQ (ACK/NACK) indicator to adjust weighting of signals between the 2 transmit antennas. HARQ quality indicator is not used when NACK is received.
    [0020] The downlink quality varies with radio conditions and particularly deteriorates for UEs that are close to the cell edge or when the downlink load is high. Especially when being close to the cell edge, the UE is generally closer to the neighboring base stations and away from the serving one. Consequently, erroneously received commands (control signals), which cause incorrect adjustment of the uplink diversity parameters for transmitting uplink transmit diversity, will lead to even more significant interference and lower performance.
    [0021] It is, therefore, important to develop methods and arrangements that can ensure that the values of the uplink transmission diversity parameters are derived correctly. SUMMARY
    [0022] It is an object of the present invention to provide an improved method and device for treating the problems as outlined above.
    [0023] This object and others are achieved by the methods and devices as shown in the appended claims.
    [0024] As an embodiment, a method in a user equipment to control uplink transmit diversity operation is provided. User equipment transmits using at least two uplink transmit antennas and receives a set of control signals in the downlink direction of a cellular network. User equipment estimates a received signal quality for each control signal in said set of control signals and determines, based on said received signal quality, which control signals have been reliably received. The user equipment derives one or more parameters related to uplink transmission diversity operation using a subset of control signals from the set of control signals, said subset only including control signals determined to be reliably received; and transmits in the uplink direction by applying the derivative or more parameters to control the uplink transmit diversity operation. The accuracy of the transmit diversity parameter values derived/set by the UE can be improved. This will increase uplink transmit diversity performance and also reduce interference to neighboring cells.
    [0025] According to one embodiment, control signals include one or more types of the following control signals: transmit power control commands sent to user equipment to control user equipment uplink transmit power; Hybrid Automatic Repeat Request, HARQ, Negative Acknowledgment/Acknowledgement, ACK/NACK, signals sent to user equipment to control HARQ retransmissions by user equipment; control signals for explicit control of user equipment transmission diversity parameters.
    [0026] As an embodiment, the received signal quality is estimated based on one or more of: Signal to interference ratio, SIR; Signal-to-interference plus noise ratio, SINR; bit error rate; block error rate; service data unit (SDU) error rate; frame error rate; Symbol error rate.
    [0027] According to an embodiment, the set of control signals is all received on a single radio link.
    [0028] As an embodiment, the set of control signals is received on multiple radio links.
    [0029] According to an embodiment, the one or more parameters include one or more of the following: relative phase; relative power; relative frequency; timing; relative amplitude; absolute power; of signals transmitted in transmit diversity branches.
    [0030] As an embodiment, the uplink transmit diversity operation is transmit diversity beamforming and the one or more parameters include relative phase and amplitude of transmitted signals in transmit diversity branches.
    [0031] According to one embodiment, the uplink transmit diversity operation is switched antenna uplink transmit diversity and the one or more parameters include amplitude or power of transmitted signals in transmit diversity branches.
    [0032] According to one embodiment, if no control signal in said set of control signals is determined to be reliably received, the user equipment performs uplink transmissions using less than all transmit antennas in said set of at least two uplink transmit antennas.
    [0033] According to one embodiment, if no control signal in said set of control signals is determined to be reliably received, the user equipment switches to a transmission single antenna transmission mode in which uplink transmissions are performed using a single antenna in said set of at least two uplink transmit antennas.
    [0034] According to one embodiment, if the set of control signals consists of a number of N control signals among which less than a number of M control signals are determined to be reliably received, M < N, the user performs uplink transmissions using less than all transmit antennas in said set of at least two uplink antennas.
    [0035] According to one embodiment, if the set of control signals consists of a number of N control signals among which less than a number of M control signals are determined to be reliably received, M < N, the user switches a single transmit antenna transmission mode in which uplink transmissions are performed using a single antenna in said set of at least two uplink transmit antennas.
    [0036] According to an embodiment, a method in a user equipment (UE) is provided to control the operation of uplink transmit diversity according to which the UE transmits using at least two uplink transmit antennas. A set of control signals is received in the downlink direction by the UE of a cellular network. The UE estimates received signal quality for each control signal in said set of control signals and determines, based on said received signal quality, which control signals have been reliably received. The UE derives one or more parameters related to uplink transmission diversity operation using a subset of control signals from said set of control signals, said subset only including control signals determined to be reliably received. The UE transmits in the uplink direction while applying the derivative or more parameters to control the uplink transmit diversity operation.
    [0037] According to an embodiment, a method in a cellular network is provided to interact with a UE performing uplink transmission using an uplink transmission diversity operation scheme. The cellular network transmits a command signal to the UE, said command signal ordering the UE to inform the network when the UE for a defined period of time has failed to appropriately derive one or more parameters related to uplink transmission diversity operation from control signals received by the UE in the network downlink direction. The failure to properly derive said parameters being due to the low signal quality of said control signals as received by the UE. The cellular network further receives a report from the UE that it failed to appropriately derive one or more parameters related to uplink transmit diversity operation for the defined period of time.
    [0038] According to an embodiment, a method in a cellular network is provided to interact with a UE performing uplink transmission using an uplink transmission diversity operation scheme. The cellular network (and in particular one or more base stations) monitors the UE's uplink transmissions to detect events indicating that the UE has potentially failed to appropriately derive one or more parameters related to the operation of uplink transmission diversity from received control signals by the UE in the network downlink direction.
    [0039] Embodiments may include different methods in UE and network as well as respective apparatuses (UE and network nodes such as radio base stations) configured to, i.e. including adapted means, implement these different methods.
    [0040] The invention also extends to User Equipment arranged to control uplink transmission as per the previous methods. To enable the User Equipment to perform uplink transmission as per the above methods, the User Equipment can be provided with a controller (or several controllers) having circuitry arranged to perform the above processes. Controllers can be implemented using suitable hardware and/or software. Hardware can include one or many processors that can be arranged to run software stored on a readable storage medium. Processors can be implemented by a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which may be shared or distributed. In addition, a processor may include, without limitation, digital signal processor (DSP) hardware, ASIC hardware, read-only memory (ROM), random access memory (RAM), and/or other storage media. BRIEF DESCRIPTION OF THE DRAWINGS
    [0041] The present invention will now be described in more detail by means of non-limiting examples and with reference to the accompanying drawing, in which: Figure 1 is an overview of a cellular radio system; Figure 2 is a view of a user equipment; Figure 3 illustrates the relationship between symbol error rate of TPC SIR and TPC; Figure 4 is a flowchart illustrating some procedural steps performed when controlling uplink transmission in a user equipment. DETAILED DESCRIPTION
    [0042] The invention is applicable to a UE, alternatively called a mobile station, which is capable of transmitting any type of signal such as data control information, higher or lower layer signaling, etc., using more than one antenna of transmission. This capability is commonly called uplink transmit diversity. A typical uplink transmit diversity implementation might include two transmit antennas. However, the implementation is not limited to two antennas; it can include more than two antennas. One of the antennas can be considered as the primary antenna, which corresponds to the basic configuration, which typically includes a single transmit antenna. The remaining transmit antennas can be considered as the secondary antennas corresponding to the more advanced antenna configurations.
    [0043] In Figure 1, an overview of a cellular radio system 100 is described. The system 100 depicted in Figure 1 is a WCDMA system and uses terminology associated with the WCDMA system. It is, however, understood that the invention is applicable to any type of cellular radio system such as GSM, LTE and other similar systems. System 100 15 includes several base stations 101, only one of which is shown for the sake of simplicity. Base station 101 can connect to user equipments in the figure represented by UE 103 located in the area served by base station 101. System 100 is arranged to allow the use of uplink transmission diversity schemes. The base station and user equipment further include controllers or controller circuitry 105 and 107 to provide functionality associated with the respective entities. Controllers 105 and 107 may, for example, include suitable hardware and/or software. Hardware can include one or many processors that can be arranged to run software stored on a readable storage medium. Processors can be implemented by a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which may be shared or distributed. In addition, a processor may include, without limitation, digital signal processor (DSP) hardware, ASIC hardware, read-only memory (ROM), random access memory (RAM), and/or other storage media.
    [0044] In Figure 2, a user equipment 103 adapted to transmit on the uplink using a diversity transmission scheme. User equipment 103 includes a number of transmit antennas 111 of which two are shown for the sake of simplicity. It is understood that user equipment may include any number of transmit antennas. Antennas are shown to illustrate that user equipment is capable of uplink transmit diversity. As described above, the user equipment 103 further includes one or many controllers or controller circuitry 107 to enable the user equipment to implement the uplink diversity transmission methods as described herein.
    [0045] As an embodiment, the UE adjusts one or more parameters related to uplink transmit diversity in order to properly transmit on the uplink using transmit diversity. The transmit diversity parameter may include one or more of the following: relative phase, relative amplitude, relative power, relative frequency, timing, absolute or total power of transmitted signals in transmit diversity branches, etc. Relative phase can include the phase difference between the phase of the transmitted signal from the first transmit antenna and the phase of the transmitted signal from the second antenna or vice versa. Relative power in dB scale may include the power difference between the transmitted signal power of the first transmit antenna and the transmitted signal power of the second antenna or vice versa. Relative amplitude in dB may include amplitude difference between the amplitude of the signal transmitted from the first transmit antenna and the amplitude of the signal transmitted from the second antenna or vice versa. Relative frequency can include the frequency difference between the frequency of the transmitted signal from the first transmit antenna and the frequency of the transmitted signal from the second antenna or vice versa. Timing means adjusting proper transmission timing of signals transmitted in the diversity branches. Ideally, the signal transmission timing for all antennas should be the same. Consequently, the relative time should be as small as possible. Relative timing may include the time difference between the transmitted timing of the transmitted signal from the first transmit antenna and the transmitted timing of the transmitted signal from the second antenna or vice versa. Therefore, similar absolute timings are to be used in all branches of transmit diversity. Herein, absolute or total power is the total transmitted power of all transmit antennas.
    [0046] Relative power and relative amplitude can also be expressed in linear scale, in which case they will be power ratios or signals from the transmit antennas.
    [0047] Different types of uplink broadcast diversity schemes or variants can be employed using an appropriate algorithm for adjusting broadcast diversity parameters. For example, transmit diversity parameters such as relative phase and amplitude can be adjusted to create transmit diversity beamforming. Similarly in the case of switched antenna uplink transmit diversity, the output of the modulator is switched between the two transmit antennas by the UE, such that the UE transmits using one antenna at a time. This corresponds to the fact that the diversity parameter such as amplitude or power of the other antennas is zero. The invention is therefore applicable to any uplink transmit diversity scheme, in particular those using some type of control signals transmitted over the network in the downlink direction, which can be used to adjust transmit diversity parameters.
    [0048] Thus, an adjustment of the transmission diversity parameters can be based on one or more types of signals received by the UE from radio network nodes. Examples of signals are: transmit power control (TPC) commands sent by the base station to the UE to control the uplink transmitted power of the UE, HARQ ACK/NACK sent by the base station to the UE to control HARQ retransmissions by the UE as also any other explicit signaling to control or adjust the UE transmit diversity parameters, etc.
    [0049] The following features are elaborated below: - Reliability Detection; - UE Behavior for Reliability Operation.
    [0050] Yet another functionality that can be used is for the UE to indicate to the network that uncertain commands received repeatedly result or may result in an improper uplink transmission diversity parameter derivation: - Network event and action report.
    [0051] It should be noted that in subsequent sections, embodiments are described for the uplink transmit diversity and in particular for the transmit beamforming and switched antenna uplink transmit diversity schemes. However, the embodiments are applicable to any type of uplink transmit diversity scheme, which uses some type of downlink network control signaling to derive parameter values related to uplink transmit diversity. Similarly, the different methods that are described can be applied to any access technology notably GSM, WCDMA, cdma2000, LTE Frequency Division Duplex (FDD), LTE Time Division Duplex (TDD) or Radio Access Network Universal Mobile Telecommunications System (UTRAN) TDD, etc.
    [0052] With respect to reliability detection, downlink signals such as transmit power control (TPC), HARQ ACK/NACK, etc., received by the UE are used by the UE to derive the values of the diversity parameters from uplink transmission. Therefore, these downlink control signals (or commands), which are sent over the network, reflect the uplink signal quality. However, these signals as received by the UE on the downlink can be erroneous due to poor downlink quality. For example, due to poor downlink quality, the TPC UP command (eg l) sent over the network can be interpreted as DOWN (eg 0). Consequently, on/off type signals without strong protection, for example, in the form of channel coding can be either '0' or 'l' such as TPC, HARQ ACK/NACK, etc., are highly prone to errors of Front desk.
    [0053] A UE determines the reliability of the received signals before using them to derive or adjust the transmit diversity parameters or use them for any action or decision related to transmit diversity.
    [0054] In order to determine the reliability of a set of received signals, the UE can perform the steps of: - Receive a set of downlink signals, which can be, for example, TPC commands or HARQ ACK/NACKs or signals similar transmitted by network nodes; - Measure, estimate or derive the downlink quality of received signals, wherein said downlink quality of received signals or commands is based on any of the following: signal strength, SIR, SINR, bit error rate (BER) or symbol error rate of said received downlink signal or any satisfactory common or dedicated pilot signal, which can be mapped to downlink quality. Examples of common pilot signals are common pilot channel (CPICH) and synchronization channel (SCH) in UTRAN or reference signal and SCH in LTE. Examples of dedicated pilots are pilot symbols sent on dedicated physical control channel (DPCCH) in WCDMA or dedicated reference signal (DRS) in LTE. - Compare the received signal quality of the signals or commands with a threshold to determine if the received downlision signals are reliable or not. A received signal is reliable if its quality is above a threshold, otherwise it is uncertain. The threshold can be determined by the UE, predefined in the pattern or signaled by the network to the UE.
    [0055] As an example, Figure 3 illustrates the relationship between TPC SIR and TPC symbol error rate. The UE measures the SIR of the received TPC bits and compares this with the threshold (y) to check whether the received TPC bits are uncertain or not. For example, in WCDMA, the UE may first measure the SIR in TPC commands sent over Fractional Dedicated Physical Channel (F-DPCH) and use a mapping function to derive the TPC command error rate. The target TPC error rate can be fixed at a satisfactory threshold level, eg 30%, beyond which the command can be considered uncertain.
    [0056] Regarding UE behavior for reliability operation, the UE can be adapted to use only the reliably received downlink signals to derive the uplink transmit diversity parameter for any uplink transmit diversity decision such as antenna selection for uplink transmission.
    [0057] In Figure 4, a flowchart illustrating some steps performed when controlling uplink transmit diversity operation in a UE is described. The UE can be using at least two uplink transmit antennas. First, in a step 401, the UE receives a set of control signals in the downlink direction of a cellular network. The UE estimates a received signal quality for each control signal in said set of control signals in a step 403. Next, in a step 405, it then determines which control signals were reliably received based on the signal quality. Received. Thereafter, the UE derives one or more parameters related to the uplink transmit diversity operation using a subset of control signals from said set of control signals, said subset only including control signals determined to be reliably received in one step. 407. The UE then in a step 409 transmits in the uplink direction while applying the derivative or more parameters to control the uplink transmit diversity operation.
    [0058] The UE behavior of operating the uncertain commands, most notably the TPC commands, to derive uplink transmission diversity parameters or for antenna selection can be specified in the applicable standard, i.e., predetermined rules governing the behavior of EU. Different criteria for UE behavior of operating uncertain commands or control signals can be specified ie predetermined rules.
    [0059] For example, for any uplink transmit diversity type, the criteria can be specified as: - The UE shall use only reliably received commands (eg TPC or any explicit signaling for UL transmit diversity) to derive or adjust the uplink transmit diversity parameters used for uplink transmit diversity.
    [0060] In the case of transmission beam forming, the criteria can be specified as:
    [0061] The UE shall use only reliable received commands (e.g. TPC or any explicit signaling) to derive or adjust the uplink transmit diversity parameters used for uplink transmit beamforming.
    [0062] In the case of switched antenna transmission diversity, the criteria can be specified as:
    [0063] The UE shall use only reliably received commands (eg TPC or any explicit signaling) to select uplink antenna for uplink transmission in case of switched antenna transmission diversity.
    [0064] Yet another criterion can be specified as:
    [0065] The UE shall use only a single transmit antenna or not use uplink transmit diversity in the case that all received commands are received unreliably over a certain period.
    [0066] UE behavior depends on whether it receives signals or commands from a single radio link or multiple radio links. A radio link is a wireless link between the UE and a radio base station through which control information and/or data is exchanged between the UE and the radio base station. The radio base station may, for example, be a Node B in UTRAN, an eNode B in E-UTRAN, an access point or the like. Within the same location or location there may be more than one radio base station. Typically, transmission and reception of data/control takes place using a single radio link. However, in some cases such as in smooth pass transfer, multiple radio links are used for receiving and transmitting data and control information.
    [0067] In the case of a single radio link, when the UE receives downlink signals or commands from only one radio link. The UE may perform a step of: - Using only reliable downlink signals/commands such as TPC or HARQ ACK/NACK (i.e. whose quality is above threshold) to derive or adjust one or more transmission diversity parameters from uplink such as relative phase, relative amplitude, relative power, relative frequency, timing, absolute or total power of transmitted signals in transmit diversity branches or for uplink transmit antenna selection.
    [0068] According to an embodiment, when the UE uses a window (W) including several N commands received last to derive said uplink transmission diversity parameters, the UE can perform an additional step of: - Use all M , M being a number equal to or less than the number N (M <N) reliably total received signals/commands among the last N received signals/commands for deriving uplink transmit diversity parameters or for transmit antenna selection of uplink.
    [0069] In the case that all N commands received last are uncertain, then the UE can perform an additional step of: - Use only a single transmit antenna for uplink transmission until expiration of time period (T0), which it can either be determined by the UE or be a predefined value or be signaled by the network; or - At least one command received among the last N commands received becomes trusted.
    [0070] According to another embodiment, if all N commands received last are uncertain, then the UE can perform the steps of: - Extending the window size (W) of last received commands to a number L, where L is greater than the N number (L > N) to derive the uplink transmit diversity parameters. - Reducing the size of said window to the predefined or prefixed value when at least K number of commands out of L commands is reliably received.
    [0071] In case of multiple radio links, the UE receives downlink signals or commands from more than one radio link. Each radio link connects the UE to a different cell, which may or may not belong to the same base station location. This is the case for smooth pass-through on CDMA systems, eg WCDMA or cdma2000. Another example is that of coordinated multipoint transmission and reception (CoMP), which allows the UE to receive and transmit data over multiple radio links. CoMP can be employed in a variety of technologies including WCDMA and LTE.
    [0072] In such a case with multiple radio links, the UE can perform a step of: - Use only reliable downlink commands such as TPC or ACK/NACK (that is, whose quality is above threshold) of each radio link radio (or in other words use only reliable radio links) to derive or adjust one or more uplink transmission diversity parameters such as relative phase, relative amplitude, relative power, relative frequency, timing, absolute or total signal power transmitted in broadcast diversity branches or for uplink broadcast antenna selection.
    [0073] According to an embodiment, when the UE uses a window (W) including N commands received last from each radio link to derive said uplink transmission diversity parameters, the UE can perform a step of: - Use all M (M <N) commands received reliably from each radio link out of the total last N commands received from each radio link for deriving uplink transmit diversity parameters or for uplink transmit antenna selection.
    [0074] In the case that all N commands received last from all radio links are determined to be uncertain, then the UE can perform a step of: - Use only a single transmit antenna for uplink transmission until period expiration time (T0), which can either be determined by the UE or be a predefined or signaled value by the network; or - At least one command received among the last N commands received from at least one radio link becomes trusted.
    [0075] According to an embodiment, if all N commands received last from all radio links are determined to be uncertain, then the UE can perform the additional steps of: - Extending the window size (W) of last commands received for L (L > N) from all radio links to derive uplink transmit diversity parameters; - Reduce the size of said window to the predefined or prefixed value when at least K commands out of L commands for at least one radio link are reliably received.
    [0076] The UE can be adapted to ignore uncertain commands to prevent errors in adjusting the transmit diversity parameters. If the received commands are often unreliable, then this can lower the uplink transmit diversity performance. The network should preferably be informed (or otherwise detect) when this happens and take appropriate action to remedy the situation.
    [0077] Consequently, according to an embodiment, the UE can be adapted to explicitly inform the network when over a certain period of time the UE is unable to properly derive transmission diversity parameters due to uncertain downlink, which causes commands received unreliably. This error condition can be reported by the UE to the network in the form of events configured per network. Event parameters such as duration (T1) by which certain broadcast diversity (P) parameters cannot be set correctly can be configured by the network or can also be preset.
    [0078] In response to the event information, the network may take appropriate action. Such actions include increasing the transmission power level, congestion control to reduce interference or in the worst case cell switching, etc. This information can also be used for operational and maintenance purposes, ie for long term network planning to fix correct transmission power levels, cell size sizing, etc.
    [0079] Furthermore, the network can be adapted to also use the UE reported event (or any pertinent error condition relating to parameter setting due to poor downlink quality) to turn off transmit diversity completely by asking the UE to go to reverse mode, i.e. single transmit antenna transmission mode.
    [0080] Event information as described above explicitly notifies the network about the status of improper setting of parameters for uplink transmit diversity due to uncertain received commands. But this involves some extra signaling due to event information in the uplink. As another alternative, the network can itself deduce that the uplink transmit diversity parameters are not set correctly without any explicit UE reporting or any event reporting.
    [0081] As an example in the case of beamforming, if the beam direction of the beam received at the base station diverges by a certain threshold, then the network can increase the transmit power of the transmitted downlink signals or commands. Another possibility is that the network turns off broadcast diversity. Yet another possibility is for the network to perform pass-through transfer. Handover transfer to another cell can ensure better downlink quality, which in turn will improve the reliability of the received downlink command in the UE.
    [0082] Similarly, due to improper beam directivity, the neighboring base station may receive higher interference. Based on uplink cell load (eg users served) and knowledge of network planning (eg interference statistics), the base station can identify whether the interference is normal or due to specific cause such as improper beam formation. Such a base station can also inform neighboring base stations about expected interference from their served users.
    [0083] As an embodiment, a method in a cellular network to interact with a UE capable of performing uplink transmission using an uplink transmission diversity operation scheme is provided. According to the method, a command signal is transmitted to the UE, said command signal ordering the UE to inform the network when the UE for a defined period of time has failed to appropriately derive one or more parameters related to the uplink transmit diversity operation of control signals received by the UE in the network downlink direction, the failure to properly derive said parameters due to the low quality of received signal from said control signals as received by the UE. The network receives a report from the UE that it failed to appropriately derive one or more parameters related to the uplink transmit diversity operation for the defined period of time.
    [0084] As an embodiment, receipt of the UE report activates the network to perform at least one of: - increase non-downlink transmission power; - adapt congestion control to reduce downlink interference; - order the UE to change cell, eg performing pass-through; - order the UE to use single antenna uplink transmission.
    [0085] As an embodiment, the command signal from the network to the UE and the report from the UE to the network is transmitted using a radio resource control protocol.
    [0086] Furthermore, as per another embodiment, a method in a cellular network to interact with a UE performing uplink transmission using an uplink transmission diversity operation scheme is provided. According to the method, the network monitors uplink transmissions from the UE to detect events indicative of the UE having potentially failed to appropriately derive one or more parameters related to the operation of uplink transmission diversity from control signals received by the UE in the network downlink direction. .
    [0087] According to one embodiment, the uplink transmission diversity operating scheme is beamforming and in which the events include at least one of: - received beam direction diverging from an expected direction by more than a certain threshold; - higher than expected interference received from a neighboring base station.
    [0088] User methods and equipment as described here will improve the accuracy of the transmit diversity parameter values derived/set by the UE. This will increase uplink transmit diversity performance and also reduce interference to neighboring cells. Also, UE event reporting or independent detection in the network of the uncertain reception of downlink signals in the UE, will enable the network to take appropriate action (eg adjust transmit power, etc.). As a consequence of the network coming in with actions to improve the downlink, the accuracy of the transmit diversity parameter values set by the UE can be improved. This will increase uplink transmit diversity performance and also reduce interference to neighboring cells.
    权利要求:
    Claims (22)
    [0001]
    1. Method for controlling uplink transmit diversity operation in a user equipment, where the user equipment transmits using at least two uplink transmit antennas, the method comprising: receiving (401) a set of control signals in the downlink direction of a cellular network; estimating (403) a received signal quality for each control signal in said set of control signals; determine (405), based on said received signal quality, which control signals were reliably received; characterized in that it further comprises: deriving (407) one or more parameters related to the operation of uplink transmission diversity using a subset of control signals from said set of control signals, said subset only including control signals determined to be received from reliably; and, transmit (409) in the uplink direction while applying the derived parameter or more parameters to control the uplink transmit diversity operation.
    [0002]
    2. Method according to claim 1, characterized in that the control signals include control signals for explicit control of user equipment transmission diversity parameters.
    [0003]
    3. Method according to claim 1 or 2, characterized in that the received signal quality is calculated based on one or more of: Signal to interference ratio, SIR, Signal to interference ratio plus noise, SINR; bit error rate; block error rate; SDU error rate; frame error rate; Symbol error rate.
    [0004]
    4. Method according to any one of claims 1 to 3, characterized in that the one or more parameters include one or more of the following: relative phase; relative power; relative frequency; timing; relative amplitude; absolute power; of signals transmitted in transmit diversity branches.
    [0005]
    5. Method according to any one of claims 1 to 4, characterized in that if no control signal in said set of control signals is determined to be reliably received, the user equipment performs uplink transmissions using less that all transmit antennas in said set of at least two uplink transmit antennas.
    [0006]
    6. Method according to any one of claims 1 to 4, characterized in that if no control signal in said set of control signals is determined to be reliably received, the user equipment switches to a transmission mode of single transmit antenna in which uplink transmissions are performed using a single antenna in said set of at least two uplink transmit antennas.
    [0007]
    7. Method according to any one of claims 1 to 4, characterized in that, if the set of control signals consists of a number of N control signals among which less than a number of M control signals are determined to be reliably received, M < N, the user equipment performs uplink transmissions using less than all transmit antennas in said set of at least two uplink antennas.
    [0008]
    8. Method according to any one of claims 1 to 4, characterized in that if the set of control signals consists of a number of N control signals among which less than a number of M control signals are determined to be reliably received, M < N, the user equipment switches to a single transmit antenna transmission mode in which uplink transmissions are performed using a single antenna in said set of at least two uplink transmit antennas.
    [0009]
    9. Method according to any one of claims 1 to 8, characterized in that the user equipment is connected with multiple radio links and where the user equipment receives downlink signals or commands from more than one radio link, the method includes the step of: using only downlink commands whose quality is above the threshold of each radio link to derive or adjust one or more uplink transmit diversity parameters.
    [0010]
    10. Method according to any one of claims 1 to 9, characterized in that the user equipment explicitly notifies the network about the status of improper setting of parameters for uplink transmission diversity due to unreliable received commands.
    [0011]
    11. User equipment (103) arranged to control uplink transmit diversity operation, the user equipment including at least two uplink transmit antennas (111), the user equipment comprising configured controller circuitry (107) to: receive a set of control signals in the downlink direction of a cellular network; estimating a received signal quality for each control signal in said set of control signals; determine, based on said received signal quality, which control signals were reliably received; characterized in that the controller circuitry (107) is further configured to: derive one or more parameters related to uplink transmit diversity operation using a subset of control signals from said set of control signals, said subset only including control signals determined to be reliably received; and, transmitting in the uplink direction while applying the derived parameter or more parameters to control the uplink transmit diversity operation.
    [0012]
    12. User equipment according to claim 11, characterized in that the control signals include control signals for explicit control of user equipment transmission diversity parameters.
    [0013]
    13. User equipment according to claim 11 or 12, characterized in that controller circuitry (107) for estimating a received signal quality is arranged to estimate the received signal quality based on one or more of: Ratio from signal to interference, SIR; Signal-to-interference plus noise ratio, SINR; bit error rate; block error rate; SDU error rate; frame error rate; Symbol error rate.
    [0014]
    14. User equipment according to any one of claims 11 to 13, characterized in that the one or more parameters include one or more of the following: relative phase; relative power; relative frequency; timing; relative amplitude; absolute power; of signals transmitted in transmit diversity branches.
    [0015]
    15. User equipment according to claim 14, characterized in that the uplink transmit diversity operation is transmit diversity beamforming and the one or more parameters include relative phase and amplitude of transmitted signals in diversity branches of transmission.
    [0016]
    16. User equipment according to claim 14, characterized in that the uplink transmit diversity operation is switched antenna uplink transmit diversity and the one or more parameters include amplitude or power of transmitted signals in diversity branches of transmission.
    [0017]
    17. User equipment according to any one of claims 11 to 16, characterized in that the user equipment is arranged to perform uplink transmissions using less than all transmit antennas in said set of at least two transmit antennas of uplink if no control signal in that set of control signals is determined to be reliably received.
    [0018]
    18. User equipment according to any one of claims 11 to 16, characterized in that the user equipment is arranged to switch to a single transmit antenna transmission mode in which uplink transmissions are performed using a single antenna in said set of at least two uplink transmit antennas if no control signal in said set of control signals is determined to be reliably received.
    [0019]
    19. User equipment according to any one of claims 11 to 16, characterized in that the user equipment is arranged to perform uplink transmissions using less than all transmit antennas in said set of at least two uplink antennas if the set of control signals consists of a number of N control signals among which less than a number of M control signals are determined to be reliably received, M < N.
    [0020]
    20. User equipment according to any one of claims 11 to 16, characterized in that the user equipment is arranged to switch to a single transmit antenna transmission mode in which uplink transmissions are performed using a single antenna in said set of at least two uplink transmit antennas if the set of control signals consists of a number of N control signals among which less than a number of M control signals are determined to be reliably received, M < No.
    [0021]
    21. User equipment according to any one of claims 11 to 20, characterized in that the user equipment is connectable with multiple radio links and where the user equipment is adapted to receive downlink signals or commands of more than In a radio link, controller circuitry (107) is further arranged to use only downlink commands whose quality is above threshold of each radio link to derive or adjust one or more uplink transmit diversity parameters.
    [0022]
    22. User equipment according to any one of claims 11 to 21, characterized in that the user equipment is configured to explicitly notify the network of the status of improper parameter setting for uplink transmission diversity due to commands received unreliably.
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    IL218297D0|2012-04-30|
    BR112012007967A2|2016-03-29|
    PL2486673T3|2018-01-31|
    TW201141108A|2011-11-16|
    EP2486673B1|2017-08-09|
    US9407341B2|2016-08-02|
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    EP2486673A4|2015-12-23|
    JP6132830B2|2017-05-24|
    RU2532248C2|2014-11-10|
    NZ597953A|2014-06-27|
    RU2012118623A|2013-11-20|
    EP2486673A1|2012-08-15|
    CA2777215A1|2011-04-14|
    JP2013507824A|2013-03-04|
    TWI492560B|2015-07-11|
    WO2011043720A1|2011-04-14|
    ZA201201120B|2015-10-28|
    IL218297A|2015-07-30|
    CN102648588B|2014-11-26|
    CA2777215C|2017-10-31|
    CN102648588A|2012-08-22|
    MX2012002049A|2012-04-10|
    ES2642394T3|2017-11-16|
    JP2015092698A|2015-05-14|
    AU2010303993A1|2012-04-26|
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    法律状态:
    2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2020-01-14| B15K| Others concerning applications: alteration of classification|Free format text: A CLASSIFICACAO ANTERIOR ERA: H04B 7/06 Ipc: H04B 7/06 (1968.09), H04B 7/0404 (2017.01), H04W 5 |
    2020-01-14| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2021-04-06| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-05-04| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 10 (DEZ) ANOS CONTADOS A PARTIR DE 04/05/2021, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
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    US25006309P| true| 2009-10-09|2009-10-09|
    US61/250,063|2009-10-09|
    PCT/SE2010/051067|WO2011043720A1|2009-10-09|2010-10-04|Methods and devices for uplink diversity transmission|
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