Abstract:
The present invention provides an enhanced uplink power control mechanism based on interference management and transmission quality control: the uplink power is controlled on the basis of simultaneously considering both the interference of neighboring cells and the system performance of the cell, that is, the transmit power of the mobile station is controlled. The mobile station controls its transmit power according to interference over thermal of the neighboring cells or sectors of the cell or sector which the mobile station is located in, transmission loss compensation and quality of signal received from the mobile station by the base station which serves the mobile station. The uplink power is controlled on the basis of simultaneously considering both the interference of neighboring cells and the system performance of the cell via using the method and device of the present invention, and thus the system performance is improved effectively.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to mobile station and base station in communication network, and more particularly relates to transmit power control mobile station. 
       BACKGROUND OF THE INVENTION 
       [0002]    Inter-cell interference (ICI) greatly impacts system performance in frequency reuse 1 (FR1) for WiMAX uplink. Therefore, is important that proper power control should be employed by the system to control the amount of ICI. ICI is often measured by interference over thermal (IoT), which is defined as total received power from all the mobile stations (MS) in neighboring cells plus thermal noise power divided by thermal noise power. IoT value can reflect the magnitude of inter-cell interference. 
         [0003]    Power control mechanism based on IoT control usually sets a target IoT value, and needs all the cells to exchange their measured IoT values. Each cell adjusts transmit power of all users within the cell according to reported IoT values from neighboring cells and fractional transmission loss compensation. However, the change of system performance, such as Hybrid Automatic Repeat reQuest (HARQ) acknowledgements, has not been considered in the process of power control. 
         [0004]    In current IEEE802.16e specification, the target receive Signal-to-Noise Ratio (SNR) of each mobile station (MS) is determined by specific modulation and coding scheme (MCS). Outer loop (OL) controller can further adjust transmit power of each MS according to system performance variation, such as HARQ ACK/NACK messages. The disadvantage of the method is that only system performance variation of the cell is considered, but the interference from other neighboring cells is not considered. 
         [0005]    IEEE802.16m specification is the further evolvement of IEEE802.16e specification and should have better system performance than IEEE802.16e. Therefore, a more advanced power control mechanism is needed to improve system performance. 
       SUMMARY OF THE INVENTION 
       [0006]    For the purpose of solving above-mentioned disadvantages in background of the invention, the present invention proposes an enhanced uplink power control mechanism based on interference management and transmission quality control: the uplink power is controlled, that is, the transmit power of mobile station is controlled, on the basis of simultaneously considering both the interference of neighboring cells and the system performance of the cell. 
         [0007]    According to the first aspect of the present there is provided a method controlling the transmit power, in a mobile station in wireless communication network, characterized in controlling the transmit power of the mobile station according to interference over thermal of the neighboring cells or sectors of the cell or sector which the mobile station is located in, transmission loss compensation and quality of the signal received from the mobile station by the base station which serves the mobile station. 
         [0008]    Preferably, the method comprises following steps: 
         [0009]    i. receiving a first indication message from the base station, the first indication message comprising a first adjustment amount of transmit power of the mobile station, wherein the first adjustment amount is determined by the base station according to magnitude relationship between the interference over thermal of the neighboring cells or sectors and predetermined target interference over thermal; 
         [0010]    ii. determining transmission loss compensation amount; 
         [0011]    iii. determining a second adjustment amount according to quality of the signal received from the mobile station by the base station; 
         [0012]    iv. controlling the transmit power of the mobile station according to the first adjustment amount, the transmission loss compensation amount and the second adjustment amount. 
         [0013]    According to the second aspect of the present invention, there is provided a method of indicating a mobile station to adjust its transmit power, in a base station of wireless communication network, comprising following steps: 
         [0014]    receiving measurement reports of interference over thermal sent by a plurality of neighboring base stations, each measurement report comprising interference over thermal of neighboring cell or sector corresponding to the base station;
       determining the average value of interference over thermal of a plurality of neighboring cells or sectors;   comparing the average value of the interference over thermal with predetermined target interference over thermal, and obtaining a comparison result;   determining a first adjustment amount of transmit power of the mobile station according to the comparison result;       
 
         [0018]    sending a first indication message comprising the first adjustment amount to the mobile station. 
         [0019]    According to the third aspect of the present invention, there is provided a control device for controlling the transmit power, in a mobile station in wireless communication network, characterized in controlling the transmit power of the mobile station according to interference over thermal of the neighboring cells or sectors of the cell or sector which the mobile station is located in, transmission loss compensation and quality of the signal received from the mobile station by the base station which serves the mobile station. 
         [0020]    Preferably, the control device comprises a first receiving means, a first determining means, a second determining means and a power control means; wherein, the first receiving means is used for receiving a first indication message from the base station, the first indication message comprising a first adjustment amount of transmit power of the mobile station, wherein the first adjustment amount is determined by the base station according to magnitude relationship between the interference over thermal of the neighboring cells or sectors and predetermined target interference over thermal; the first determining means is used for determining transmission loss compensation amount; the second determining means is used for determining a second adjustment amount according to quality of the signal received from the mobile station by the base station; the power control means is used for controlling the transmit power of the mobile station according to the first adjustment amount, the transmission loss compensation amount and the second adjustment amount. 
         [0021]    According to the fourth aspect of the present invention, there is provided an indicating device for indicating a mobile station to adjust its transmit power, in a base station of wireless communication network, the indicating device comprises a second receiving means, a third determining means, a comparing means, a fourth determining means and a sending means; the second receiving means is used for receiving measurement reports of interference over thermal transmitted by a plurality of neighboring base stations, each measurement report comprising interference over thermal of neighboring cell or sector corresponding to the base station; the third determining means is used for determining the average value of interference over thermal of a plurality of neighboring cells or sectors; the comparing means is used for comparing the average value of the interference over thermal with predetermined target interference over thermal, and obtaining a comparison result; the fourth determining means is used for determining a first adjustment amount of transmit power of the mobile station according to the comparison result; the sending means is used for sending a first indication message comprising the first adjustment amount to the mobile station. 
         [0022]    The uplink power is controlled on the basis of simultaneously considering both the interference of neighboring cells and the system performance of the cell via using the method and device of the present invention, and thus the system performance is improved effectively. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects and advantages of the present invention will become apparent. 
           [0024]      FIG. 1  is a simple schematic diagram of topological structure of network; 
           [0025]      FIG. 2  is a flow diagram of a method of controlling the transmit power, in a mobile station in wireless communication network, according to an embodiment of the present invention; 
           [0026]      FIG. 3  is a flow diagram of a method of indicating a mobile station served by a base station to adjust its transmit power, in the base station in wireless communication network, according to an embodiment of the present invention; 
           [0027]      FIG. 4  is a structural block diagram of a control device for controlling the transmit power, in a mobile station in wireless communication network, according to an embodiment of the present invention; 
           [0028]      FIG. 5  is a structural block diagram of an indicating device for indicating a mobile station served by a base station to adjust its transmit power, in the base station in wireless communication network, according to an embodiment of the present invention; 
       
    
    
       [0029]    In drawings, same or similar reference signs refer to the same or similar device or method step. 
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0030]    In the followings, embodiments of the present invention are described in detail with reference to the drawings. 
         [0031]      FIG. 1  shows a simple schematic diagram of topological structure of network. In  FIG. 1 , the mobile station MS 1  is located in the cell C 1  served by the base station BS# 1 , and the cell C 2  is served by the base station BS# 2 . The frequency reuse factor is 1, that is, each cell uses same frequency resource. The signal sent by MS 1  is useful signal for BS# 1 , but is interference for BS# 2  or other neighboring base stations (not shown in  FIG. 1  for the reason of briefness). Those ordinary skilled in the art can understand that  FIG. 1  only shows two cells for the reason of briefness. In fact, there are a plurality of neighboring cells around C 1 ; there are six neighboring cells around C 1  for classical hexagonal cellular structure. MS 1  controls its transmit power according to interference over thermal of the neighboring cells of the cell which MS 1  is located in, transmission loss compensation and quality of the uplink signal received from MS 1  by BS# 1 . 
         [0032]      FIG. 2  shows a flow diagram of a method of controlling the transmit power, in a mobile station in wireless communication network, according to an embodiment of present invention. 
         [0033]    In the following, the control process of the transmit power of MS 1  in  FIG. 2  is described in detail with reference to  FIG. 1 . 
         [0034]    Firstly, in step S 201 , MS 1  receives a first indication message from BS# 1 , the first indication message comprising a first adjustment amount of transmit power of MS 1 , wherein the first adjustment amount is determined by BS# 1  according to magnitude relationship between the interference over thermal of the neighboring cells or sectors and predetermined target interference over thermal. 
         [0035]    Secondly, in step S 202 , MS 1  determines transmission loss compensation 
         [0036]    Further, in step S 203 , MS 1  determines a second adjustment amount of transmit power according to quality of the signal received from the mobile station by BS# 1 . 
         [0037]    Finally, in step S 204 , MS 1  controls its transmit power according to the first adjustment amount, the transmission loss compensation amount and the second adjustment amount. 
         [0038]    In the following, the determining processes of the first adjustment amount, transmission loss compensation amount and the second adjustment amount are respectively described via examples. 
         [0039]    Firstly, the determining process of the first adjustment amount is described. 
         [0040]    BS# 1  determines the first adjustment amount of transmit power of MS 1  according to magnitude relationship between the interference over thermal of the neighboring cells or sectors and predetermined target interference over thermal; BS# 1  sends the first indication message comprising the first adjustment amount to MS 1 . 
         [0041]      FIG. 3  shows a flow diagram of a method in BS# 1  of indicating MS 1  to adjust its transmit power, that is, a flow diagram of BS# 1  of determining the first adjustment amount for MS 1 , according to an embodiment of the present invention, which is described in detail in the following. 
         [0042]    Firstly, in step S 301 , BS# 1  receives measurement reports of interference over thermal sent by a plurality of neighboring base stations, each measurement report comprising interference over thermal of neighboring cell or sector corresponding to the base station. Preferably, the interference over thermal which neighboring base station such as BS# 2  in  FIG. 1  sends to BS# 1  is an average value of interference over thermal in a plurality of frequency domains and/or time domains. 
         [0043]    Secondly, in step S 302 , BS# 1  determines the average value of interference over thermal of a plurality of neighboring cells or sectors. For the scenario that the cell C 1  which MS 1  is located in is divided into sectors, BS# 1  measures the interference over thermal of the sectors outside the sector which MS 1  is located in, which is averaged together with the interference over thermal of sectors in neighboring cells (also called “neighboring sectors”). 
         [0044]    Further, in step S 303 , BS# 1  compares the average the interference anal of neighboring cells or sectors With predetermined target interference over thermal, and obtains a comparison result. Target interference over thermal is a predetermined target value and is also a target which the system performance wants to achieve. The detailed value is determined according to the empirical value of actual system. 
         [0045]    Then, in step S 304 , BS# 1  determines a first adjustment amount of transmit power of MS 1  according to the comparison result. To be specific, the average value of the interference over thermal of neighboring cells is greater than the target interference over thermal, the first adjustment amount is determined as a negative value, that is, MS 1  is indicated to reduce its transmit power. If the average value of the interference over thermal of neighboring cells is smaller than the target interference over thermal, the first adjustment amount is determined as a positive value, that is, MS 1  is indicated to increase its transmit power. If the average value of the interference over thermal of neighboring cells is equal to the target interference over thermal, the first adjustment amount is determined as zero. 
         [0046]    Finally, in step S 305 , BS# 1  sends the first indication message comprising the first adjustment amount to MS 1 . 
         [0047]    In the following the determining process of the first adjustment amount is described by example. 
         [0048]    Taking  FIG. 1  as an example, 
         [0000]        Rx _power1 =Tx _power− TL 1  (1)
 
         [0000]        Rx _power2 =Tx _power− TL 2  (2)
 
         [0000]    Let equation (1) minus (2), the result is: 
         [0000]        Rx _power1 =Rx _power2−diff —   TL   (3)
 
         [0049]    Wherein, Tx_power is the transmit power of MS 1 ; Rx_power1 is the power of signal received from MS 1  by BS# 1 ; Rx_power2 is the power of signal received from MS 1  by BS# 2 ; TL 1  and TL 2  are transmission losses of signals, sent by MS 1 , from MS 1  to BS# 1  and BS# 2 , which comprise pathloss, shadowing, transmitting antenna gains and receiving antenna gains; diff_TL=TL 1 −TL 2 , diff_TL is the transmission loss difference between the signal transmission loss from MS 1  to BS# 1  and from MS 1  to BS# 2 . For the sake of convenience, the units of variables in the description are all in dB. 
         [0050]    If the interference caused by the MS 1  to neighboring cell BS#n is the strongest, which corresponds to the maximum transmission loss difference between MS 1  to BS# 1  and MS 1  to BS#n, that is, the transmission loss TL 1  from MS 1  to BS# 1  and the transmission loss TLn from MS 1  to BS#n are the closest. 
         [0051]    On the basis of equation (3), considering the impact of noise and supposed that the transmission loss difference is the maximum, the transmission loss compensation factor α is introduced and the equation (4) is obtained: 
         [0000]      Target —   SINR =min(Target —   INR −α×max(diff_TL),max —   SINR )  (4)
 
         [0052]    Wherein, 0≦α≦1, α=1 represents complete transmission compensation; max_SINR represents the predetermined maximum target signal to interference plus noise ratio of the signal received from MS 1  by BS# 1 ; Target_SINR is the signal to interference plus noise ratio of the signal received from MS 1  by BS# 1 . BS# 1  desires to achieve the Target_SINR; Target_INR represents the target value of the strongest interference caused by MS 1  to neighboring base stations, which is called et interference-to-noise ratio. 
         [0053]    Target interference-to-noise ratio (Target_INR) in equation (4) may be further adjusted based on interference over thermal information exchange among surrounding base stations, For example, BS# 1  receives respective interference over thermal(Measured_IoT) reported by neighboring base stations, and compares the average value of a plurality of interference over thermal with predetermined target IoT value (Target_IoT), and adjusts the target interference-to-noise ratio of MS 1  accordingly, which is listed by formula as follows: 
         [0000]    If mean(measured_IoT(j))&gt;Target_IoT(wherein j≠1) 
         [0000]      Target —   INR =Target —   INR −Down —   INR  
 
         [0000]    else if mean (measured_IoT (j))&gt;Target_IoT 
         [0000]      Taget —   INR =Target —   INR +Up —   INR    
         [0000]      else 
         [0000]      Target_INR=Target_INR  (5)
 
         [0054]    Wherein, measured_IoT (j) denotes interference over thermal measured by neighboring base stations of BS# 1 ; Down_INR is down adjustment step for target interference-to-noise ratio, Up_INR is up adjustment step for target interference-to-noise ratio. Up_INR and Down_INR may be constant or variable, which is determined according to actual system requirement. Usually, during system initialization, Taget_INR value is set according to empirical value, and then, with the running of system, Target_INR is adjusted gradually according to interference over thermal of neighboring cells. 
         [0055]    BS# 1  sends the first indication message comprising the adjustment value of target interference-to-noise ratio of MS 1 , namely the above-mentioned first adjustment amount, to MS 1 . After having received the first indication message, MS 1  updates its target signal to interference plus noise ratio Target_SINR according to equation (4), and adjusts its transmit power accordingly. To be specific, how MS 1  adjusts its transmit power Tx_power according to target signal to interference plus noise ratio Target_SINR will be described in detail in the following. 
         [0056]    Firstly, the determining of the transmission loss compensation amount is described in detail in the following. 
         [0057]    According to the approximate symmetry feature of uplink and down k signal in a large-scale area, MS 1  may use the transmission loss of downlink signal to approximate the transmission loss of uplink, For example, for MS 1 , the power of signal from BS# 1  is the greatest within all of signals received from each base station (each base station transmits broadcast signal with almost the same power), and the power of signal from BS#n is the second greatest, then the maximum transmission loss may be approximated as: 
         [0000]      max(diff —   TL )= Rx _powern_MS1 −Rx _powner1_MS1  (6)
 
         [0058]    The determining of the second adjustment amount is described in the following. 
         [0059]    MS 1  further adjusts the transmit power according to the quality of the signal received from MS 1  by BS# 1 , that is, determines the second adjustment amount, BS# 1  feeds the quality of the signal received from MS 1  by it back to MS 1 . Preferably, BS# 1  sends a second indication message to MS 1 , the second indication message being used for indicating whether the data packets received from MS 1  by BS# 1  are right or wrong. 
         [0060]    For example, in data transmission based on HARQ, if the data packets received from MS 1  by BS# 1  are wrong, BS# 1  will send a second indication message NACK indicating wrong receiving to MS 1 , if the data packets received from MS 1  by BS# 1  are right, BS# 1  will send a second indication message ACK indicating right receiving to MS 1 . Sometimes, for example, when the uplink and downlink are symmetric, MS 1  may further determine the second adjustment amount according to the quality of the signal received from BS# 1  by MS 1 . 
         [0061]    Taking the data transmission based on HARQ as an example, when MS 1  receives the indication message NACK from BS# 1 , MS 1  will adjust the transmit power an up adjustment step (Up_OL) higher. when MS 1  receives the indication message ACK from BS# 1 . MS 1  will adjust the transmit power a down adjustment step Down_OL( ) lower, shown in formula (7) as follows: 
         [0062]    if NACK
       Offset_OL=Offset_OL+Up_OL       
 
         [0064]    else if ACK
       Offset_OL=Offset_OL−Down_OL       
 
         [0066]    else 
         [0000]      Offset_OL=Offset_OL  (7)
 
         [0067]    Wherein, Offset_OL denotes the second adjustment amount, Up_OL denotes up adjustment step of the second adjustment amount, Down_OL denotes down adjustment step of the second adjustment amount. Up_OL and Down_OL may be constant or variable, which are determined according to actual system. 
         [0068]    Finally, transmit power of MS 1  can be determined by to interference plus noise ratio Target_SINR, the second adjustment transmission loss, noise power and interference over thermal of the eel which MS 1  is located in, as shown in equation (8): 
         [0000]        Tx _power=Target —   SINR +Offset_OL+ TL 1+Noise_power+measured_IoT  (1)
 
         [0069]    Wherein, TL 1  is the transmission loss from MS 1  to BS# 1 , and may either be estimated by MS 1  according to downlink signal or be sent to MS 1  after being measured by BS# 1 : Noise_power is the estimation value of noise power, and may either be the noise power estimated by MS 1  itself or be the noise power which is estimated by BS# 1  and sent to MS 1 ; measured_IoT (1) is the interference over thermal of the cell or sector which MS 1  is located in, which is usually measured by BS# 1  and sent to MS 1 . Preferably, measured_IoT (1) is also the statistical average in time domain and/or frequency domain. Certainly, BS# 1  may also send the physical quantities needed for measured_IoT (1) calculation to MS 1 , and then MS 1  calculates interference over thermal measured_IoT (1). For example, BS# 1  only sends interference and noise amount to MS 1 , and MS 1  calculates interference over thermal measured_IoT (1). 
         [0070]    Usually, during system initialization, firstly Offset_OL is set according to empirical value, and then, with the running of system, Offset_OL is adjusted gradually according to the quality of the signal received by BS# 1 . 
         [0071]    From equation (8) it can be seen that the transmit power control of MS 1  mainly comprises two parts: one is that MS 1  determines target signal to interference plus noise ratio according to the first adjustment amount and the transmission loss compensation amount (called “external adjustment” for short in the following), the other is the second adjustment amount (called “internal adjustment” for short in the following) determined according to the quality of the signal received from MS 1  by BS# 1 . Internal adjustment and external adjustment may have the same frequency or not. If internal adjustment and external adjustment have the same frequency, Offset_OL is the accumulated value of Up_OL and Down_OL. If internal adjustment frequency is greater than external adjustment frequency, when external adjustment is not executed, and only internal adjustment is executed, only adding Up_OL or reducing Down_OL on the basis of Tx_power is ok. 
         [0072]    Usually, the transmit power of MS 1  has predetermined maximum power value Max_power, and MS 1  needs to judge whether transmit power Tx_power determined according manor is greater than predetermined maximum power value Max_power; if transmit power Tx_power is greater than predetermined maximum power value Max_power, then Tx_power=Max_power. 
         [0073]    It should be noted that those ordinary skilled in the art can understand that determining modes of the above-mentioned first adjustment amount, the transmission loss compensation amount and the second adjustment amount are only exemplary. In practice, there are a plurality of detailed determining modes of the first adjustment amount, the transmission loss compensation amount and the second adjustment amount with respect to different system, which are not limited to above-mentioned embodiments. In addition, the physical meaning of the first adjustment amount and the second adjustment amount may be slightly different from the above-mentioned meaning. 
         [0074]      FIG. 4  shows a structural block diagram a control device  400  for controlling the transmit power of a mobile station, in the mobile station in wireless communication network, according to an embodiment of the present invention. The control device  400  comprises a first receiving means  401 , a first determining means  402 , a second determining means  403 , a power control means  404  and an obtaining means  405 . 
         [0075]    In the following, with reference the topological structure of network shown in  FIG. 1 , how the control device  400  in MS 1  controls the transmit power of MS 1  according to interference over thermal of neighboring cells of MS 1 , the transmission loss compensation and the quality of uplink signal received from MS 1  by BS#  1  is described in detail. 
         [0076]    Those ordinary skilled in the art can understand that the control device  400  shown in  FIG. 4  is only exemplary. The control device  400  of the present invention may have different structures according to different function implement and is not limited to that shown in  FIG. 4 . 
         [0077]    Firstly, the first receiving means  401  receives the first indication message from BS# 1 , the first indication message comprising a first adjustment amount of transmit power of MS 1 , wherein the first adjustment amount is determined by BS# 1  according to magnitude relationship between the interference over thermal of the neighboring cells or sectors and predetermined target interference over thermal. 
         [0078]    Secondly, the first determining means  402  determines transmission loss compensation amount. 
         [0079]    Further, the second determining means  403  determines the second adjustment amount of transmit power of MS 1  according to the quality of signal received from MS 1  by BS# 1 . 
         [0080]    Finally, the power control means  404  controls its transmit power according to the first adjustment amount, the transmission loss compensation amount and the second adjustment amount. 
         [0081]    The determining processes of the first adjustment amount, the transmission loss compensation amount and the second adjustment amount are respectively described in the following via examples. 
         [0082]    Firstly, the determining process of the first adjustment amount is described, 
         [0083]      FIG. 5  shows a structural block diagram of an indicating device  500 , for indicating MS 1  served by BS# 1  to adjust its transmit power, in BS# 1  in wireless communication network, according to an embodiment of the present invention. The indicating device  500  comprises a second receiving means  501 , a third determining means  502 , a comparing means  503 , a fourth determining means  504 , a sending means  505  and a measuring means  506 . 
         [0084]    The indicating device  500  in BS#  1  determines the first adjustment amount of transmit power of MS 1  according to the magnitude relationship between the interference over thermal of the neighboring cells or sectors and the predetermined target interference over thermal; and the indicating device  500  in BS# 1  sends the first indication message comprising the first adjustment amount to MS 1 . The process will be described in detail in the following.  FIG. 3  shows a flow diagram of a method in BS#  1  of indicating MS 1  to adjust its transmit power, that is, determining, in BS# 1 , the first adjustment amount for MS 1 , according to an embodiment of the present invention, which is described in detail in the following. 
         [0085]    Firstly, the second receiving means  501  receives measurement reports of interference over thermal sent by a plurality of neighboring base stations, each measurement report comprising interference over thermal of neighboring cell or sector corresponding to the base station. Preferably, interference over thermal which is sent to BS# 1  by neighboring base stations such as BS# 2  in  FIG. 1  is an average value of interference over thermal in a plurality of frequency domains and/or time domains. 
         [0086]    Secondly, the third determining means  502  determines the average value of interference over thermal of a plurality of neighboring cells or sectors. For the scenario that the cell C 1  which MS 1  is located in is divided into sectors, BS# 1  measures the interference over thermal of the sectors outside the sector which MS 1  is located in, which is averaged with the interference over thermal of sectors in neighboring cells (also called “neighboring sectors”) by the third determining means  502 . 
         [0087]    Further, the comparing means  503  compares the average value of the interference over thermal of neighboring cells or sectors with predetermined target interference over thermal, and obtains a comparison result. Target interference over thermal is a predetermined target value and is also a target which the system performance wants to achieve. The detailed value is determined according to the empirical value of actual system. 
         [0088]    Then, the fourth determining means  504  determines the first adjustment amount of transmit power of MS 1  according to the comparison result from the comparing means  503 . To be specific, if the average value of the interference over thermal of neighboring cells is greater than the target interference over thermal, the first adjustment amount is determined as negative value, that is, MS 1  is indicated to reduce its transmit power. If the average value of the interference over thermal of neighboring cells is smaller than the target interference over thermal, the adjustment amount is determined as positive value, that is, MS 1  is indicated to increase its transmit power. If the average value of the interference over thermal of neighboring cells is equal to the target interference over thermal, the first adjustment amount is determined as zero. 
         [0089]    Finally, the sending means  505  sends a first indication message comprising the first adjustment amount to MS 1 . 
         [0090]    The determining process of the first adjustment amount can refer to embodiment in above-mentioned method description. That is referring to equation (4), target interference-to-noise ratio (Target_INR) in  FIG. 4 ) may be further adjusted based on interference over thermal information exchange among surrounding base stations. For example, the second receiving means  501  receives respective interference over thermal (Measured_IoT) reported by neighboring base stations, and the comparing means  503  compares the average value of a plurality of interference over thermal determined by the third determining means  502  with target IoT value (Target_IoT), and the fourth determining means  504  determines the adjustment amount for adjusting the target interference-to-noise ratio of MS 1 , namely the first adjustment amount accordingly, which is shown in equation (5). 
         [0091]    The sending means  505  sends the first indication message to MS 1 , the first indication message comprising the adjustment value of target interference-to-noise ratio of MS 1 , namely the above-mentioned first adjustment amount. After the first receiving means  401  in MS 1  receives the first indication message, the power control means  404  updates target signal to interference plus noise ratio Target_SINR of MS 1  according to equation (4), and adjusts the transmit power accordingly. To be specific, how the power control means  404  adjusts its transmit power Tx_power according to target signal to interference plus noise ratio Target_SINR is described in detail in the following. 
         [0092]    Firstly, the process that the first determining means  402  determines the transmission loss compensation amount is described in detail in the following. 
         [0093]    According to the approximate symmetry feature of uplink and downlink signal in a large-scale area, the first determining means  402  may use the transmission loss of downlink signal to approximate the transmission loss of uplink. For example, for MS 1 , the power of signal from BSS# 1  is the greatest within all of signals received from each base station and the power of signal from BS#n is the second greatest, then the first determining means  402  determines the difference of signal power between BS# 1  and BS#n as the transmission loss compensation amount, as shown in equation (6). 
         [0094]    The process that the second determining means  403  determines the second adjustment amount is described in the following. 
         [0095]    The second determining means  403  further adjusts the transmit power according to the quality of signal received from MS 1  by BS# 1 , that is, determines the second adjustment amount. BS# 1  feeds the quality of signal received from MS 1  by BS# 1  hack to MS 1 . Preferably, BS# 1  sends a second indication message to MS 1 , the second indication message being used for indicating whether the data packets received from MS 1  by BS# 1  are right or wrong. 
         [0096]    For example, in data transmission based on HARQ, if the data packets received from MS 1  by BS# 1  are wrong, BS# 1  will send a second indication message NACK indicating wrong receiving to MS 1 ; if the data packets received from MS 1  by BS# 1  are right, BS# 1  will send a second indication message ACK indicating right receiving to MS 1 . Sometimes, for example, when the uplink and downlink are symmetric, the second determining means  403  may further determine the second adjustment amount according to the quality of signal received from BS# 1  by itself. 
         [0097]    Taking the data transmission based on HARQ as an example, when MS 1  receives the indication message NACK from BS# 1 , the second determining means  403  will adjust the transmit power an up adjustment step (Up_OL) higher; when MS 1  receives the indication message ACK from BS# 1 , the second determining means  403  will adjust the transmit power a down adjustment step (Down_OL) lower, as shown in above-mentioned formula (7). 
         [0098]    Finally, the power control means  404  determines transmit power of MS 1  according to the target signal to interference plus noise ratio Target_SINR, the second adjustment amount, transmission loss, noise power and interference over thermal of the cell or sector which MS 1  is located in, as shown in equation (8). Wherein, measured_IoT (1) is the interference over thermal of the cell or sector which MS 1  is located in, and is obtained by the obtaining means  405  from BS# 1 . Measured_IoT (1) is usually measured by the measuring means  506  in BS# 1 , and then is sent to MS 1  by the sending means  505 . Preferably, measured_IoT (1) is also the statistical average in time domain and/or frequency domain. Certainly, BS# 1  may also send the physical quantities needed for measured_IoT (1) calculation to MS 1 , and then MS 1  calculates the interference over thermal measured_IoT (1). For example, BS# 1  only sends interference and noise amount to MS 1 , and MS 1  calculates measured_IoT (1). 
         [0099]    From equation (8) it can be seen that the transmit power control of MS 1  mainly comprises two parts: one is that MS 1  determines target signal to interference plus noise ratio according to the first adjustment amount and the transmission loss compensation amount, that is, above-mentioned “external adjustment”; the other is the second adjustment amount, that is, above-mentioned “internal adjustment”, determined according to the quality of signal received from MS 1  by BS# 1 . Internal adjustment and external adjustment may have the same frequency or not. If internal adjustment and external adjustment have the same frequency, Offset_OL is the accumulated value of Up_OL and Down_OL. If internal adjustment frequency is greater than external adjustment frequency, when external adjustment is not executed, and only internal adjustment is executed, only adding Up_OL or reducing Down_OL on the basis of Tx_power is ok, 
         [0100]    Usually, the transmit power of MS 1  has predetermined maximum power value Max_power, and the power control means  404  needs to judge whether transmit power Tx_power determined according to equation (8) is greater than the predetermined maximum power value Max_power; if Tx_power is greater than the predetermined maximum power value Max_power, Tx_power=Max_power. 
         [0101]    It should be noted that those ordinary skilled in the art can understand that determining modes of the above-mentioned first adjustment amount, the transmission loss compensation amount and the second adjustment amount are only exemplary. In practice, there are a plurality of detailed determining modes of the first adjustment amount, the transmission loss compensation amount and the second adjustment amount according to system difference, which are not limited to above-mentioned embodiments. In addition, the physical meaning of the first adjustment amount and the second adjustment amount may be slightly different from the above-mentioned meaning. 
         [0102]    The embodiments of the present invention are described above. It should be understood that the present invention is not limited to the above-mentioned particular embodiments, and those skilled in the art may make all kinds of variation or modification within the scope of the appended claims. The technical solution of the present invention may be implemented with software or hardware.