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WO2009075548A1 - Procédé pour contrôler le réglage de puissance en liaison montante en tenant compte du rapport de multiplexage - Google Patents

Procédé pour contrôler le réglage de puissance en liaison montante en tenant compte du rapport de multiplexage Download PDF

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Publication number
WO2009075548A1
WO2009075548A1 PCT/KR2008/007380 KR2008007380W WO2009075548A1 WO 2009075548 A1 WO2009075548 A1 WO 2009075548A1 KR 2008007380 W KR2008007380 W KR 2008007380W WO 2009075548 A1 WO2009075548 A1 WO 2009075548A1
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WIPO (PCT)
Prior art keywords
transmission power
mobile stations
power
uplink
power control
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/KR2008/007380
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English (en)
Inventor
Dong Cheol Kim
Bin Chul Ihm
Jin Sam Kwak
Wook Bong Lee
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LG Electronics Inc
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LG Electronics Inc
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Priority claimed from KR1020080113261A external-priority patent/KR101572880B1/ko
Application filed by LG Electronics Inc filed Critical LG Electronics Inc
Priority to US12/746,710 priority Critical patent/US8830904B2/en
Priority to JP2010536859A priority patent/JP5081981B2/ja
Priority to CN2008801205406A priority patent/CN101897133A/zh
Publication of WO2009075548A1 publication Critical patent/WO2009075548A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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]
    • H04W52/06—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]
    • H04W52/06—TPC algorithms
    • H04W52/16—Deriving transmission power values from another channel
    • 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
    • H04W52/26—TPC being performed according to specific parameters using transmission rate or quality of service QoS [Quality of Service]
    • H04W52/267—TPC being performed according to specific parameters using transmission rate or quality of service QoS [Quality of Service] taking into account the information rate
    • 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
    • H04W52/42—TPC being performed in particular situations in systems with time, space, frequency or polarisation diversity

Definitions

  • the present invention relates to a broadband wireless mobile communication system, and more particularly, to transmission power control.
  • next-generation mobile communication and wireless transmission systems use a Multi-Input Multi-Output (MIMO) scheme in which data is transmitted using multiple antennas.
  • MIMO Multi-Input Multi-Output
  • Single-user MIMO forms a channel matrix H between one Mobile Station (MS) having two or more antennas and a Base Station (BS) having two or more antennas.
  • MS Mobile Station
  • BS Base Station
  • multi-user or collaborative MIMO forms a channel matrix H between two or more MSs, each having one antenna, and one BS having multiple antennas.
  • the concept of uplink collaborative MIMO is illustrated in FIG. 1.
  • This method has several advantages. First, each MS needs only one power amplifier since only one transmission path is necessary for the MS. In addition, even though each MS operates with other MSs in a MIMO scheme, it is not necessary to divide an output of the MS into respective signals for antennas since the MS transmits signals using one antenna, and thus the MS need not undergo a 3dB power loss that is common in general MIMO. Second, if two MSs are appropriately selected as described above, it is possible to obtain a much better channel matrix H than when two antennas are installed in one MS.
  • the first-generation MIMO scheme it is assumed that one BS and one user (MS) transmit a plurality of information simultaneously through multiple antennas.
  • one BS and multiple users (MSs) create a matrix for MIMO Spatial Multiplexing (SM) as can be seen from FIGs. 1 and 2.
  • SM Spatial Multiplexing
  • the BS should determine an MS with which the BS should form a 2x2 matrix at a specific time in order to achieve the highest transfer rate. It is possible to achieve a transfer rate of a total of 2.5Mbps (2.0+0.5) if the BS forms a MIMO channel with User-1, to achieve a transfer rate of a total of 2.0Mbps if the BS forms a MIMO channel with User-2, and to achieve a transfer rate of a total of 1.8Mbps if the BS forms a MIMO channel with User-3. Accordingly, the BS forms a single-user MIMO channel with User-1 at the given time.
  • a MIMO channel may be formed between the BS and a single user in the case where a transfer rate that can be achieved between the BS and the user at a specific time is the highest among all combinations of transfer rates.
  • the multi-user MIMO is conceptually broader than the single-user MIMO.
  • the conventional technologies use a single-user power control scheme in which it is assumed that only one user uses a specific resource, regardless of the number of users that transmit signals by simultaneously using the same resource. However, actually, a number of users may use the same resource as in the multi-user MIMO scheme.
  • An object of the present invention devised to solve the problem lies on maintaining the same level of interference as in the single user power control scheme, by taking into consideration the multi-user MIMO scheme, in which two or more users use one resource, when uplink power control is performed.
  • the objects of the present invention can be achieved by providing a method for controlling uplink transmission power in a wireless mobile communication system that uses a frequency division multiplexing scheme in multi-cell environments, the method including receiving information regarding a number of users who are allocated a resource region at a given time, and performing uplink power control based on the received number of users.
  • a method for controlling uplink transmission power in a wireless mobile communication system that uses a frequency division multiplexing scheme in multi-cell environments, the method including receiving information regarding a number of users who share an uplink time- frequency resource region from a base station, calculating a power adjustment value based on the received number of users, and determining the uplink transmission power by adding the calculated power adjustment value to a reference transmission power, wherein, when only one mobile station uses the uplink time-frequency resource region, the reference transmission power is equal to a transmission power of the mobile station.
  • the expression "two or more mobile stations (or users) share an uplink time- frequency resource region” indicates that two or more mobile stations transmit signals using the same frequency at the same time.
  • the addition of the calculated power adjustment value to the reference transmission power is performed under the assumption that both the values are represented in logarithmic scale. Either multiplication or division may be used when both the calculated power adjustment value and the reference transmission power are represented in linear scale.
  • the power adjustment value may be given by -
  • the power adjustment value may also be calculated by a joint function including the received number of mobile stations and a Modulation Coding Scheme (MCS) level as independent variables.
  • MCS Modulation Coding Scheme
  • joint function may indicate that the output of the function is determined based on input variables having a zero or nonzero correlation with each other.
  • a method for controlling uplink transmission power in a wireless mobile communication system that uses a frequency division multiplexing scheme in multi-cell environments, the method including receiving information regarding a number of mobile stations which share an uplink time-frequency resource region from a base station, and determining the uplink transmission power by a joint function including the received number of mobile stations and a reference transmission power as independent variables, wherein, when only one mobile station uses the uplink time-frequency resource region, the reference transmission power is equal to a transmission power of the mobile station.
  • a method for controlling uplink transmission power in a wireless mobile communication system that uses a frequency division multiplexing scheme in multi-cell environments, the method including determining a number of mobile stations which share an uplink time- frequency resource region, determining a transmission power of a mobile station based on at least one parameter including the determined number of mobile stations, and generating a transmission power command message including information regarding the determined transmission power and transmitting the generated transmission power command message to the mobile station.
  • the at least one parameter including the determined number of mobile stations may include a noise power level or an interference signal level at a base station. This method may be repeated at regular intervals or at irregular intervals.
  • the transmitting step may be performed at regular intervals.
  • the transmission power command message may also be a dedicated message for the mobile station.
  • the transmission power command message may be a broadcast message.
  • a number of mobile stations Ml at a time Tl and a number of mobile stations M2 at a time T2 may be calculated and a more recently calculated number of mobile stations among the two numbers of mobile stations Ml and M2 may be determined to be the number of mobile stations which share the uplink time-frequency resource region. That is, since the above method may be repeated a number of times, the transmission power command message may be transmitted a number of times.
  • the number of mobile stations which share the same resource can be repeatedly determined twice or more during the time interval between one transmission power command message and another transmission power command.
  • only the number of mobile stations determined immediately before the transmission power command message is transmitted can be used.
  • a method for controlling uplink transmission power in a wireless mobile communication system that uses a frequency division multiplexing scheme in multi-cell environments, the method including a base station determining a number of mobile stations which share an uplink time-frequency resource region and transmitting the determined number of mobile stations to a mobile station, the mobile station receiving the number of mobile stations and determining a power adjustment value based on the received number of mobile stations, and determining the uplink transmission power by adding the determined power adjustment value to a reference transmission power value.
  • the reference transmission power value may be a transmission power of a last frame among frames that have already been transmitted.
  • the reference transmission power value may be equal to a transmission power of the mobile station.
  • the power adjustment value may be given by -M(dB), where M is the received number of mobile stations.
  • the power adjustment value may also be calculated by a joint function including the received number of mobile stations and an MCS level as independent variables.
  • the present invention it is possible to reduce the level of system interference when two or more mobile stations use the same time-frequency resources in a broadband wireless mobile communication system in multi-cell environments.
  • FIG. 1 illustrates the concept of uplink collaborative MIMO.
  • FIG. 2 illustrates an example downlink multi-user MIMO system.
  • FIG. 3 illustrates changes of the output of an MS according to inner-loop power control in a stable radio condition.
  • FIG. 4 illustrates frame structures of uplink/downlink DCHs and the operation of uplink inner-loop power control.
  • FIG. 5 illustrates the operation of downlink inner-loop power control.
  • FIG. 6 illustrates the ratio of powers of a downlink DPDCH and a downlink DPCCH.
  • FIG. 7 illustrates an example of changes of the Eb/No value according to outer- loop power control.
  • FIG. 8 illustrates the correlation between inner-loop and outer-loop power control functions.
  • FIG. 9 illustrates control of a target SIR according to outer-loop power control.
  • FIG. 10 illustrates two methods for allocating power to an HSDPA physical channel HS-DPSCH.
  • FIG. 11 illustrates the correlation between power control functions.
  • FIG. 12 illustrates the configurations of power control functions.
  • FIGs. 13A and 13B illustrate an IoT level that can be obtained when simulation is performed according to an embodiment of the present invention.
  • FIG. 14 illustrates a relationship between reception of a transmission power control signal and uplink transmission according to an embodiment of the present invention.
  • FIGs. 15A and 15B illustrate a power control method according to an embodiment of the present invention.
  • a single user may be referred to as a "single mobile station (MS)".
  • Block Error Rate (BLER) is used as a criterion for quality in an asynchronous wireless mobile communication scheme and a Frame Error Rate (FER) is used as a criterion for quality in a synchronous wireless mobile communication scheme.
  • BLER Block Error Rate
  • FER Frame Error Rate
  • Power control is used to 1) maximize the capacity of communication of the serving BS, 2) extend MS battery life, 3) maximize the capacity of communication of each neighbor BS, and (4) maintain uniform communication quality.
  • Power control is mainly divided into open-loop power control and closed-loop power control.
  • open-loop power control when an MS attempts to perform communication in downlink and transmits a response to paging from a BS, the MS can derive the loss (or attenuation) of a path between the BS and the MS from a downlink signal received from the BS.
  • the BS determines uplink transmission power based on the path loss derived in this manner, the level of noise at the BS, and the level of interference at the BS. Using this method, the output (or power) of the MS is minimized as much as possible, thereby minimizing its effects on the capacity and quality of uplink communication.
  • an MS located near the BS transmits a signal at a low output level and an MS located distant from the BS transmits a signal at a high output level in both the cases of synchronous and asynchronous open-loop power control.
  • - cdma mobile_tx_power -RSSI + PowerOffset + NomPwr + IniPwr + Init_coorection - RSSI: Strength of signals that the MS receives from all BSs
  • IniPwer Compensation value that determines the weight of random access initial power
  • Init_correction Correct the output of the MS according to Ec/Io value measured at the MS.
  • PowerOffset is a constant defined according to the frequency and radio configuration and Init_correction is a parameter compensating for the output (or power) according to the Ec/Io value measured at the MS.
  • NomPwer and IniPwr are parameters indicating arbitrary compensation values set by the operator.
  • CDMA is determined solely by the strength of reception power according to the distance from the BS.
  • actual reception power at the MS may vary due to a variety of factors such as a change in the output of the BS which rises up to 64dB depending on the amount of communication or an increased deviation of the reception power at a region in which signals of multiple BSs overlap.
  • the MS may erroneously determine that the distance from the BS is decreased and then may perform open-loop power control.
  • the MS should increase the power of transmission accordingly.
  • the MS may fail to detect such a status change, thereby failing to correctly increase the transmission power. This may cause an increase in the number of access channel probe transmissions. That is, the method in which the MS derives the distance from the BS based only on the strength of reception power may exhibit numerous errors.
  • the asynchronous scheme utilizes the following two factors in order to perform a more accurate open-loop power control operation.
  • the BS broadcasts the output level of a common pilot channel (CPICH), which maintains a constant output regardless of the amount of communication, to all MSs and the MS measures the Received Signal Code Power (RSCP) of only the CPICH rather than the total reception power, thereby allowing the MS to calculate an accurate loss of the path from the BS to the MS.
  • CPICH common pilot channel
  • the CPICH output level is repeatedly broadcast through an SIB 5 message of a BCH (physically, a P-CCPCH).
  • the BS broadcasts the BS reception noise level through a BCH (P- CCPCH) SIB 7 message at regular intervals to notify the MS of by how much the MS should increase the output level of open-loop power control for transmission to overcome the BS reception noise.
  • a BCH P- CCPCH
  • the level of WCDMA open-loop power control is determined as follows.
  • Received Signal Code Power i.e., the reception strength of a CPICH received from the MS - UL interference: A noise level measured at the receiving end of the BS
  • Inner-loop power control serves to adjust the output of the MS to a minimum level that can be appropriately received by the BS during uplink communication, thereby maximizing the capacity of uplink communication while minimizing the effects of interference on other BSs. More specifically, inner-loop power control serves to reduce the output level of each MS which is currently in a channel condition far higher than that corresponding to the reference Eb/No or SIR value and to increase the output level of each MS, which is currently in a channel condition worse than that corresponding to an Eb/No or SIR value less than the reference Eb/No or SIR value, within a maximum allowable output level of the MS. Power control also extends the battery life of the MS.
  • Inner-loop power control is also referred to as "fast power control” since it is quickly performed between the Node-B (i.e., BS) and the MS.
  • Inner-loop power control optimizes the output of a dedicated channel (DCH) that is being used for downlink communication, thereby maximizing the capacity of downlink communication while minimizing the effects of interference on MSs located in the areas of other BSs.
  • DCH dedicated channel
  • a Signal to Interference/Noise Ratio (SINR) of an uplink physical downlink control channel (PDCCH) pilot symbol measured at the BS is higher than a target SINR
  • the BS instructs the MS to reduce the output of the MS using a transmission power command (TPC) of a dedicated physical control channel (DPCCH).
  • TPC transmission power command
  • the BS instructs the MS to increase the output of the MS using a transmission power command (TPC). More specifically, the control of the output of the MS indicates control of the uplink DPCCH power and the power of a DPDCH is adjusted in conjunction with that of the DPCCH according to a specified ratio (see FIG. 4).
  • a level setting parameter value of ⁇ d / ⁇ c of the dedicated physical data channel (DPDCH) and the DPCCH can specified by the BS or can be set through calculation by the MS.
  • HSDPA HSDPA
  • uplink inner-loop power control is performed at a frequency of 1500 times per second.
  • synchronous closed-loop power control is performed 800 times per second.
  • FIG. 3 illustrates changes of the output of an MS according to inner-loop power control in a stable radio condition.
  • Uplink power control is not performed in perfect real time but instead is performed according to a closed-loop response with a slight time delay. Accordingly, no matter how stable the radio condition is, the output of the MS is not completely uniform and may exhibit changes in triangular forms having a constant period and a constant change width as shown in FIG. 3. This change width can be considered a type of jitter caused by closed-loop delay.
  • the MS measures an SINR of a DPCCH pilot symbol and issues a command requesting that a downlink DPDCH power allocated to the MS be increased if the measured SINR level is less than a threshold and issues a command requesting that the downlink DPDCH power be reduced if the measured SINR level is higher than the threshold.
  • FIG. 4 illustrates frame structures of uplink/downlink DCHs and the operation of uplink inner-loop power control.
  • FIG. 5 illustrates the operation of downlink inner-loop power control.
  • FIG. 6 illustrates the ratio of powers of a downlink DPDCH and a downlink
  • Transport format combination information (TFCI) of the downlink DPCCH, the TPC, and the power ratio of the DPDCH of the pilot symbol are defined as parameters POl, P02, and P03 as shown in FIG. 6 and are specified by the operator.
  • the criterion for communication quality that the user actually experiences is the block error rate (BLER) or the frame error rate (FER) rather than the SINR.
  • BLER block error rate
  • FER frame error rate
  • the MS may exhibit characteristics of a BLER far below the target BLER, so that the quality of communication with other users and the capacity of communication are reduced due to excessive output of the MS.
  • a problem may be caused in maintaining the quality of communication of the MS of its own.
  • a process in which the reference SINR value of inner-loop power control is not fixed to a specific value but instead is changed on a 10msec basis according to radio wave environments to maintain the measured BLER value at the target BLER value is referred to as "outer-loop power control".
  • Outer-loop power control is applied to both downlink and uplink and is generally performed at a low frequency of several times per second.
  • FIG. 7 illustrates an example of changes of the Eb/No value according to outer- loop power control.
  • Table 1 illustrates SINR values required to maintain the quality of an adaptive multi-rate (AMR) voice service at a level corresponding to a BLER of 1% according to the radio condition of the communication user and FIG. 7 illustrates an example wherein a target E t ZN 0 value is changed using an outer-loop power control function in order to maintain the BLER of the AMR voice service at 1% in the ITU-R pedestrian A channel model.
  • the E t ,/N 0 value required to maintain the same communication quality varies depending on the radio environments of the MS.
  • the E b /N 0 value cannot be the ultimate target of power control.
  • FIG. 8 illustrates the operating principle of UL outer-loop power control.
  • FIG. 9 illustrates control of a target SIR according to outer-loop power control.
  • Target_BLER 1%, 99 good frames and 1 bad frame are present. Accordingly, the
  • SIR value is stepped down by 5dB during a duration of 99 frames and therefore the
  • Tables 2 and 3 describe the types and functions of parameters defined for uplink/downlink inner-loop power control and outer-loop power control. Since the final purpose of all power control is to maintain the same BLER value, the initial operation of the power control is to set a target BLER value through power control. Generally, the target BLER value is set to 1% or 2%.
  • the HS-PDSCH which is a physical channel of the HSDPA, is a channel to which AMC is applied. Accordingly, an effective channel coding gain or a modulation scheme used in the HS-PDSCH are controlled according to the radio condition of the receiving MS to achieve the highest data rate that the current radio condition permits. That is, since the bit energy reaching the receiver is kept constant through the AMC function although the level of the HS-PDSCH is kept constant (i.e., although power control is not applied), the AMC function cannot replace the DL power control function.
  • the HSDPA AMC has a dynamic range of 30 dB. Accordingly, AMC is preferentially applied in a link adaptive manner for a channel radio condition change of
  • FIG. 10 illustrates two methods for allocating power to an HSDPA physical channel HS-DPSCH.
  • power allocation for the HS-PDSCH is not clearly defined in the standard specification, two allocation methods can be used in actual implementations. As illustrated in FIG. 10, in the first method, constant RF power may be allocated to the HS-PDSCH, and, in the second method, all the remaining BS HPA power that is left after the existing WCHMA Release 99 service is provided may be allocated to the HS- PDSCH.
  • Setting of power control for the uplink HS-DPCCH which is a physical channel carrying control information of the HS-PDSCH, is statically performed according to a ratio specified for the uplink DPCCH.
  • the RF power level of various uplink/downlink physical channels varies according to the transfer rate and the static level set by the system operator or according to a dynamic power control function.
  • FIG. 11 illustrates the principle of implementing power control. The implementation principle of power control can be understood from the following processes.
  • Step 1) The purpose of power control is to achieve the same BLER (or FER). Accordingly, power control should be performed based on a target BLER.
  • Step 2 since the strength of a radio wave received during one block (frame) time of 10msec (20msec in the case of the synchronous scheme) very significantly and very rapidly varies due to multiple reflected waves, control of the output of the MS on a block (frame) basis may be meaningless.
  • the Node-B sets an SINR (or Eb/No) threshold, which is one of the values in which the target reception BLER is reflected, as a new target value for power control and performs inner-loop power control according to the new target value.
  • SINR or Eb/No
  • the SINR threshold which is the target value of power control in the Node-B
  • the target BLER which is the ultimate target value of power control.
  • power control of 3GPP WCDMA is implemented in the following manner.
  • the RNC measures the reception quality for a predetermined time and increases the target SINR value at the Node-B if the measured reception quality is lower than the target value (i.e., the target BLER) and decreases the target SINR value if the measured reception quality is excessively higher than the target value.
  • the Node-B performs inner-loop power control at a high speed.
  • FIG. 12 illustrates the correlation between different types of power control and the locations thereof.
  • the correlations and locations of power control functions of the synchronous and asynchronous schemes are basically identical.
  • the functions of downlink power control in synchronous CDMA IS-95A/B in which wireless data transmission has not been recognized as being important have slightly different locations and structures.
  • OFDM is a multi-carrier modulation scheme in which a frequency band is divided into multiple orthogonal subcarriers to transmit data in order to reduce inter-symbol interference effects.
  • serially received data symbols are converted into N parallel data symbols and the N parallel data symbols are carried over N separate subcarriers, respectively.
  • the subcarriers allow orthogonality to be maintained in the frequency dimension.
  • Each orthogonal channel undergoes independent frequency selective fading, and the interval between the transmitted symbols is increased, thereby minimizing inter-symbol interference.
  • OFDMA Orthogonal Frequency Division Multiple Access
  • a subcarrier is provided as a frequency resource to each user.
  • the frequency resources are individually provided to multiple users so that the frequency resources of the users do not overlap.
  • frequency resources are exclusively allocated to each user. Accordingly, in OFDMA, a total frequency range can be divided into a number of sub-bands to be processed, unlike CDMA.
  • the OFDMA system also uses a power control scheme as one method to reduce inter-cell interference caused by adjacent cells and path loss caused by the distance between the BS and the MS.
  • a power control scheme By using the power control scheme, it is possible to adjust transmission power so that data can be transmitted with the lowest power level while maintaining a certain quality of service (QoS) of the wireless communication system.
  • QoS quality of service
  • the embodiments described below can be applied to the OFDMA system.
  • the present invention can also be applied to a system that includes a plurality of MSs that commonly use the same frequency band at the same time in multi-cell environments.
  • uplink open-loop power control is performed according to an embodiment of the present invention in the case where one MS uses one time-frequency-domain resource and in the case where two or more MSs simultaneously use one time-frequency-domain resource.
  • the method for controlling power when two or more MSs use the same resource uses a power control scheme represented by a function of the number of simultaneous users M. Basically, this method does not reduce performance while maintaining a level of interference that can be obtained through the power control method in the case where one MS uses one time-frequency-domain resource.
  • the first scheme may also be referred to as an "SI_MO scheme".
  • the second scheme may be a Collaborative Spatial Multiplexing (CSM) or Virtual Spatial Multiplexing (VSM) scheme.
  • CSM Collaborative Spatial Multiplexing
  • VSM Virtual Spatial Multiplexing
  • transmission power control according to this scheme can be represented by the following Mathematical Expression 1. [MATHEMATICAL EXPRESSION 1]
  • Tx_power_level(dBm) Tx_Power_si_Mo + f(M) [dBm per subcarrier]
  • Mathematical Expression 1 “dBm per subcarrier” can be replaced with “dBm per Hz”.
  • Tx_Power_si_Mo” represents transmission power per MS set according to the first scheme.
  • f(M) represents an adjustment value of transmission power according to the number of MSs (M) that simultaneously transmit signals using the same resource.
  • Mathematical Expression 1 can also be associated with a Modulation and Coding Scheme (MCS) level used for transmission. If Mathematical Expression 1 is not associated with the MCS level, f(M) can be represented by Mathematical Expression 2 or Mathematical Expression 3.
  • the amount of interference caused to a neighboring cell or sector when two or more MSs simultaneously transmit signals using the same resource can be equal to the amount of interference caused to a neighboring cell or sector when one MS transmits signals.
  • Mathematical Expression 1 is associated with the MCS level, Mathematical Expression 1 can be modified to the following Mathematical Expression 4. [MATHEMATICAL EXPRESSION 4]
  • Tx_power_level(dBm) Tx_Power_ SLM o + f(M,MCS),
  • f(M, MCS) represents an adjustment value of transmission power according to the MCS level and the number of MSs (M) that simultaneously transmit signals using the same resource.
  • Mathematical Expression 2 or Mathematical Expression 4 can be generalized as the following Mathematical Expression 5.
  • Tx_power_level(dBm) f(Tx_Power_si_MO, M, MCS)
  • FIGs. 13A and 13B illustrate an IoT level that can be obtained when simulation is performed according to this embodiment.
  • FIGs. 13A and 13B illustrate a Cumulative Distribution Function (CDF) of the IoT level in each time zone of each sector when an MS transmits signals according to the scheme 1 and the scheme 2 described above in the OFDMA system.
  • FIG. 13A illustrates simulation results according to the scheme 1
  • FIG. 13B illustrates simulation results according to the scheme 2.
  • Closed-loop Power Control 1 Closed-loop Power control according to another embodiment of the present invention can be represented by Mathematical Expression 6 or Mathematical Expression 7.
  • Pi ast represents transmission power in a previous frame
  • ⁇ JPC represents the difference between the two transmission powers.
  • A represents a reference transmission power, which may be equal to that of the equation of closed-loop power control for one MS.
  • the BS can transmit " ⁇ TPC " to the MS at regular or irregular intervals.
  • the period at intervals of which the value is changed may be, without being limited to, a subframe(s), a frame(s), or a radio frame(s).
  • FIG. 14 illustrates a relationship between reception of a transmission power control signal and uplink transmission.
  • the BS can transmit a Transmission Power Command (TPC) message to MSs at intervals of a predetermined period or irregular intervals.
  • TPC Transmission Power Command
  • M the number of MSs which simultaneously use resources of one time-frequency region can be changed more frequently than the period at intervals of which the TPC message is received as shown in FIG. 14.
  • the number of MSs is changed four times while the TPC message is transmitted three times in the example of FIG. 14.
  • each MS can take into consideration the M value when determining transmission power to transmit data in uplink.
  • the BS may determine and transmit the M value to the MS.
  • the TPC message may indicate the amount of power change for one
  • the TPC message may indicate the amount of power change for each of two or more MSs that use resources of a specific time-frequency region in dB.
  • TPCs 1401, 1402, and 1403 shown in FIG. 14 each indicate the amount of power change for one MS in dB.
  • M MSs
  • the transmission power level can be adjusted according to the multiplexing ratio M of MSs that use time-frequency-domain resources.
  • the multiplexing ratio M can be determined by receiving a predetermined indicator/message from the BS.
  • FIGs. 15A and 15B illustrate a power control method according to an embodiment of the present invention.
  • FIG. 15A illustrates the power control method of FIG. 14 in a different fashion.
  • a BS determines the number of MSs (Ml) which simultaneously use the same resource.
  • the BS determines TPCl based on parameters including the determined number of MSs (Ml).
  • the parameters may include noise and interference levels at the BS.
  • the BS transmits the determined TPCl to each MS.
  • the MS adjusts transmission power according to the received TPCl.
  • FIG. 15B illustrates a modification of the method of FIG. 15A wherein each MS can calculate an amount of power adjustment and adjust transmission power according to the calculated amount.
  • Steps 1501B-1504B are identical to the above steps 1501A- 1504A of FIG. 15 A.
  • the BS recalculates the number of MSs (M2) which simultaneously use the same resource.
  • the BS transmits the value M2 to each MS.
  • the MS can adjust transmission power according to the received value M2.
  • the MS can adjust transmission power according to at least one of Mathematical Expressions 1 to 7.
  • the BS can transmit not only TPCl information but also
  • the MS can adjust transmission power using the difference between M2 and Ml .
  • control signal is illustrated as being transmitted to only one MS in FIGs. 15 A and 15B, the same signal can be transmitted as a dedicated signal or a broadcast signal to other MSs.
  • the above message can be constructed as a type of dedicated message. For example, let us assume that the total frequency band is divided into N subbands. Here, if the number of MSs multiplexed using subband #0 is Mi and the number of MSs multiplexed using subband #N-1 is M 2 , a dedicated message #0 can be transmitted to Mi MSs while a dedicated message #N-1 can be transmitted to M 2 MSs.
  • the above message can be constructed as a type of broadcast message.
  • the total frequency band is divided into N subbands.
  • the number of MSs multiplexed in each subband is M, it is only necessary to transmit the same message to all MSs. Accordingly, the message can be transmitted as a type of broadcast message. This can reduce the amount of control overhead.
  • the MS When the MS receives such a dedicated message or broadcast message, the MS can reflect the resulting value, which has been obtained taking the multiplexing ratio into consideration, in the power control equation for single user as in Mathematical Expressions 1 to 7 described above.
  • Tables 4 and 5 illustrate an example of the dedicated message described above.
  • the first column represents fields included in the dedicated message.
  • the second column represents the number of bits of each field.
  • Tables 4 and 5 represent the dedicated message type, each of the tables needs a UserID field indicating a user ID.
  • the multiplexing ratio M may be transmitted or alternatively the difference between the multiplexing ratio of the previous frame and the multiplexing ratio of the current frame may be transmitted.
  • the table may include a field indicating which function is used as in Table 5.
  • the table may also include a field indicating start and end times of a time zone for representing a time section to which the transmitted M value is to be applied.
  • Tables 6 and 7 represent an example of the broadcast message described above.
  • the table may include a field indicating which function is used as in Table 7.
  • CLPCnew(dBm) CLPC refere n ce (dBm) + h( ⁇ M)(dB)
  • CLPC new represents a transmission power of the current frame
  • ast represents a transmission power of an immediately previous frame
  • g(M) represents the difference between the two transmission powers.
  • the ⁇ jpc value which is the difference between the transmission powers of the two signals.
  • g(M) which is the difference between the transmission powers of the two signals is calculated using the M value.
  • ⁇ M rather than M may also be transmitted as in Mathematical Expression 9.
  • ⁇ M is the difference between the multiplexing ratio of the previous frame and the multiplexing ratio of the current frame.
  • the BS can transmit the value "M” or " ⁇ M” to the MS at regular or irregular intervals.
  • the period at intervals of which the value is changed may be, without being limited to, a subframe(s), a frame(s), or a radio frame(s).
  • the method of FIG. 14 may also be applied to the embodiment of Mathematical Expressions 8 to 11. The only difference is that the M value is transmitted instead of transmitting the TCP message as in the method of FIG. 14.
  • the present invention can be applied to a wireless mobile communication system which uses multiple carriers.
  • the present invention can be applied to an orthogonal frequency division multiplexing access (OFDMA) system, an orthogonal frequency division multiplexing (OFDM) system, a single carrier-frequency division multiplexing (SC-FDMA) system, etc.
  • OFDM orthogonal frequency division multiplexing access
  • SC-FDMA single carrier-frequency division multiplexing
  • FDM frequency division multiplexing
  • an embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or the like.
  • ASICs application specific integrated circuits
  • DSPs digital signal processors
  • DSPDs digital signal processing devices
  • PLDs programmable logic devices
  • FPGAs field programmable gate arrays
  • processors controllers, microcontrollers, microprocessors, or the like.
  • the embodiments of the present invention may be implemented in the form of modules, processes, functions, or the like which perform the features or operations described above.
  • Software code can be stored in a memory unit so as to be executed by a processor.
  • the memory unit may be located inside or outside the processor and can communicate data with the processor through a variety of known means.
  • the present invention can be used in a broadband wireless mobile communication system in multi-cell environments.

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Abstract

L'invention concerne un procédé pour maintenir les interférences systèmes à un faible niveau, lorsqu'au moins deux utilisateurs utilisent une région de ressources dans un système de communications sans fil. L'objectif de l'invention est de régler la puissance de transmission en liaison montante dans un système de communications mobile sans fil à large bande dans un environnement multicellulaire. A cet effet, les informations concernant le nombre d'utilisateurs qui partagent une région de ressources temps-fréquence en liaison montante sont reçues d'une station de base, une valeur de réglage de la puissance est calculée sur la base du nombre estimés d'utilisateurs, et la puissance de transmission en liaison montante est déterminée par réflexion de la valeur de réglage de puissance calculée dans une puissance de transmission référence. Lorsqu'une seule station mobile utilise la région de ressources temps-fréquence en liaison montante, la puissance de transmission référence est égale à la puissance de transmission de la station mobile.
PCT/KR2008/007380 2007-12-12 2008-12-12 Procédé pour contrôler le réglage de puissance en liaison montante en tenant compte du rapport de multiplexage Ceased WO2009075548A1 (fr)

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US12/746,710 US8830904B2 (en) 2007-12-12 2008-12-12 Method for controlling uplink power control considering multiplexing rate/ratio
JP2010536859A JP5081981B2 (ja) 2007-12-12 2008-12-12 多重化率を考慮したアップリンク電力制御方法
CN2008801205406A CN101897133A (zh) 2007-12-12 2008-12-12 考虑复用比例/比率地控制上行功率控制的方法

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US1293107P 2007-12-12 2007-12-12
US61/012,931 2007-12-12
KR1020080113261A KR101572880B1 (ko) 2007-12-12 2008-11-14 다중화율을 고려한 상향링크 전력제어 방법
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WO2012002660A3 (fr) * 2010-06-29 2012-02-23 Samsung Electronics Co., Ltd. Procédé et appareil adaptés pour réguler une puissance de transmission dans un réseau sans fil
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WO2011008023A3 (fr) * 2009-07-15 2011-03-31 Lg Electronics Inc. Procédé et appareil de commande de puissance de liaison montante dans un système de communication sans fil
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WO2012002660A3 (fr) * 2010-06-29 2012-02-23 Samsung Electronics Co., Ltd. Procédé et appareil adaptés pour réguler une puissance de transmission dans un réseau sans fil
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CN103458530B (zh) * 2013-09-05 2017-01-25 华为技术有限公司 随机接入方法和用户设备
WO2018136691A3 (fr) * 2017-01-20 2018-09-27 Qualcomm Incorporated Réglage de puissance pour transmission conjointe multipoint coordonnée
EP3571872A2 (fr) * 2017-01-20 2019-11-27 QUALCOMM Incorporated Réglage de puissance pour transmission conjointe multipoint coordonnée
US10638431B2 (en) 2017-01-20 2020-04-28 Qualcomm Incorporated Power control for coordinated multipoint joint transmission
EP3761724A4 (fr) * 2018-02-26 2021-04-21 Vivo Mobile Communication Co., Ltd. Procédé de configuration de puissance et terminal
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