# Patent

## Title
Method for transmitting an uplink channel sounding reference signal

## Abstract

A method wherein: a base station assigns resource to an uplink channel sounding reference signal (SRS) of a UE, sends the SRS configuration parameters to the UE, wherein the SRS configuration parameters include SRS bandwidth parameter BSRS and an SRS frequency domain position parameter nRRC; after receiving the SRS configuration parameters, the UE calculates the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters, and sends the SRS to the base station using the resource; wherein the frequency domain resource assigned to the SRS by the base station corresponds to a node of a tree structure configured by an SRS bandwidth, and the configured BSRS corresponds to the level on which the node is located, while the configured nRRC corresponds to the index of a branch node on the lowest level of the node in the tree structure.

## Background
RELATED APPLICATIONS
This is the U.S. national stage application which claims priority, under 35 U.S.C. §119, to International Patent Application No.: PCT/CN2009/072720, filed on Jul. 10, 2009, which claims priority to Chinese Patent Application No.: 200810144407.6, filed Jul. 29, 2008, the disclosures of which are incorporated by reference herein in its entirety.
TECHNICAL FIELD
The present invention relates to a technique for transmitting an uplink channel sounding reference signal, particularly to a method for transmitting an uplink channel sounding reference signal.
BACKGROUND
In the Long Term Evolution (LTE) system, an uplink channel sounding reference signal (SRS) is a signal sent to the base station by the user equipment (UE) side, i.e. the terminal and is mainly used by the base station to sound the quality of an uplink channel. According to the result of the sounding, the base station achieves the scheduling of the uplink data, e.g. the frequency resource occupied in uplink transmission, or the modulation coding mode used.
In existing LTE systems, multiple SRS bandwidths are supported. An SRS bandwidth configuration is based on a tree structure and every SRS bandwidth configuration corresponds to one tree structure, wherein, the SRS-Bandwidth of the highest level in the tree structure corresponds to the maximum bandwidth of the SRS bandwidth configuration. The total number of resource blocks (RBs) corresponding to the uplink bandwidth configuration is NRBUL. Tables 1-4 illustrate the SRS bandwidth configurations under different uplink bandwidth configurations. Table 1 corresponds to 6≦NRBUL≦40, Table 2 corresponds to 40<NRBUL≦60, Table 3 corresponds to 60<NRBUL≦80, and Table 4 corresponds to 80<NRBUL≦110.
In these tables, mSRS,b represents the number of RBs contained in every node on the bth level of the tree structure in the frequency domain; when b>0, Nb represents the number of branch nodes of a node on the (b−1)th level, which are located on the bth level of the tree structure; while b=0 corresponds to the highest level of the tree structure, where there must be Nb=1, and mSRS,0 is the maximum SRS bandwidth under the configuration.











TABLE 1








SRS-
SRS-
SRS-
SRS-


SRS-
Bandwidth
Bandwidth
Bandwidth
Bandwidth


Bandwidth
b = 0
b = 1
b = 2
b = 3















configuration
mSRS,0
N0
mSRS,1
N1
mSRS,2
N2
mSRS,3
N3


















0
36
1
12
3
4
3
4
1


1
32
1
16
2
8
2
4
2


2
24
1
4
6
4
1
4
1


3
20
1
4
5
4
1
4
1


4
16
1
4
4
4
1
4
1


5
12
1
4
3
4
1
4
1


6
8
1
4
2
4
1
4
1


7
4
1
4
1
4
1
4
1




















TABLE 2








SRS-
SRS-
SRS-
SRS-


SRS-
Bandwidth
Bandwidth
Bandwidth
Bandwidth


Bandwidth
b = 0
b = 1
b = 2
b = 3















configuration
mSRS,0
N0
mSRS,1
N1
mSRS,2
N2
mSRS,3
N3


















0
48
1
24
2
12
2
4
3


1
48
1
16
3
8
2
4
2


2
40
1
20
2
4
5
4
1


3
36
1
12
3
4
3
4
1


4
32
1
16
2
8
2
4
2


5
24
1
4
6
4
1
4
1


6
20
1
4
5
4
1
4
1


7
16
1
4
4
4
1
4
1




















TABLE 3








SRS-
SRS-
SRS-
SRS-


SRS-
Bandwidth
Bandwidth
Bandwidth
Bandwidth


Bandwidth
b = 0
b = 1
b = 2
b = 3















configuration
mSRS,0
N0
mSRS,1
N1
mSRS,2
N2
mSRS,3
N3


















0
72
1
24
3
12
2
4
3


1
64
1
32
2
16
2
4
4


2
60
1
20
3
4
5
4
1


3
48
1
24
2
12
2
4
3


4
48
1
16
3
8
2
4
2


5
40
1
20
2
4
5
4
1


6
36
1
12
3
4
3
4
1


7
32
1
16
2
8
2
4
2




















TABLE 4








SRS-
SRS-
SRS-
SRS-


SRS-
Bandwidth
Bandwidth
Bandwidth
Bandwidth


Bandwidth
b = 0
b = 1
b = 2
b = 3















configuration
mSRS,0
N0
mSRS,1
N1
mSRS,2
N2
mSRS,3
N3


















0
96
1
48
2
24
2
4
6


1
96
1
32
3
16
2
4
4


2
80
1
40
2
20
2
4
5


3
72
1
24
3
12
2
4
3


4
64
1
32
2
16
2
4
4


5
60
1
20
3
4
5
4
1


6
48
1
24
2
12
2
4
3


7
48
1
16
3
8
2
4
2









The frequency domain starting position of the SRS is determined by high layer configured cell-specific SRS bandwidth configuration, UE-specific SRS bandwidth BSRS and frequency domain position parameter nRRC, RRC refers to Radio Resource Control, wherein:
Cell-specific SRS bandwidth configuration parameter: the UE determines the tree structure of the SRS bandwidth, mSRS,b and Nb on every branch corresponding to the tree structure according to the uplink bandwidth and this parameter. This parameter is broadcast in the cell.
UE-specific SRS bandwidth parameter BSRS: it corresponds to one of the four values of b in the above-mentioned tables and is used for determining on which level of the tree structure the SRS is located.
UE-specific SRS frequency domain position parameter nRRC.
According to the tree structure of the SRS bandwidth and the three parameters above mentioned, the SRS frequency domain starting position is determined using the following formula.




  
    
      
        
          k
          0
        
        =
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              2
              ⁢
              
                
              
              ⁢
              
                M
                
                  sc
                  ,
                  b
                
                RS
              
              ⁢
              
                n
                b
              
            
          
        
      
    
    
      
        (
        1
        )
      
    
  




Wherein:
k0 represents the frequency domain starting position of the uplink channel SRS, namely the subcarrier index number.
k′0=(└NNBUL/2┘−mSRS,0/2)NSCRB+kTC, wherein (└NRBUL/2┘−mSRS,0/2)NSCRB ensures that the bandwidth allowed to send the SRS in the system is at the central position of the system bandwidth, └*┘ represents rounding down. NSCRB represents the number of subcarriers contained in an RB in the frequency domain. SC is the abbreviation for “subcarrier”, namely the subcarrier.
kTCε{0,1} is the offset of SRS “Transmission Comb”. The SRS is sent in every other subcarrier in the frequency domain, so it is like a comb in the frequency domain.
Msc,bRS=mSRS,bNscRB/2 represents the length of the SRS sequence at the branch of the bth level in the tree structure.
nb represents the index of a branch node of a node on the (b−1)th level, which is located on the bth level, hence there is nbε{0, 1, 2, . . . , Nb−1}.
nb is calculated according to the frequency domain position parameter nRRC, and the specific correlation between nb and nRRC is related to the way the nRRC is determined.
Currently, there is no specific solutions as to how to determine nRRC, and the frequency domain starting position obtained from the existing solutions is incorrect. Therefore, the SRS frequency domain starting position can not be determined correctly, which leads to the problem that the UE can not send an SRS to the base station at the correct frequency domain starting position, and thus it is difficult for the base station to perform the uplink channel sounding accurately.
SUMMARY
The technical problem to be solved in the present invention is to provide a method for transmitting an uplink channel sounding reference signal, which makes the base station to perform the uplink channel sounding accurately.
To solve the above-mentioned technical problem, the present invention provides a method for transmitting an uplink channel sounding reference signal, including:
a base station assigns resource to an uplink channel sounding reference signal (SRS) of a UE, and sends SRS configuration parameters to the UE, the SRS configuration parameters include an SRS bandwidth parameter BSRS and an SRS frequency domain position parameter nRRC:
after receiving the SRS configuration parameters, the UE calculates the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters, and then sends the SRS to the base station using the resource;
wherein, the frequency domain resource assigned to the SRS by the base station corresponds to a node in a tree structure of an SRS bandwidth configuration, and the configured BSRS corresponds to the level on which the node is located, while the configured nRRC corresponds to the index of the branch node on the lowest level of the node in the tree structure.
Further, the nRRC may be:




  
    
      n
      RRC
    
    =
    
      {
      
        0
        ,
        1
        ,
        ...
        ⁢
        
          
        
        ,
        
          
            (
            
              
                ∏
                
                  b
                  =
                  0
                
                3
              
              ⁢
              
                
              
              ⁢
              
                N
                b
              
            
            )
          
          -
          1
        
      
      }
    
  
  ,




wherein Nb may represent the number of branch nodes of a node on the (b−1)th level, which are located on the bth level of the tree structure, and when b=0, Nb=1.

Further, the calculation of the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters may be specifically as follows: the index nb of a branch node of a node on the (b−1)th level, which is located on the bth level, may be calculated according to the following formula; the frequency domain starting position of the SRS may be calculated according to the nb calculated: nb=└4nRRC/mSRS,b┘ mod Nb, wherein └*┘ may represent rounding down, mSRS,b may represent the number of resource blocks contained in every node on the bth level of the tree structure in the frequency domain, and b=0, 1, . . . , BSRS.
Preferably, the nRRC may correspond to the index of any branch node on the lowest level of the node in the tree structure, and the indexes of branch nodes on the lowest level of the tree structure may start from 0 and may be numbered 0, 1, 2, 3 . . . in sequence.
Preferably, after the SRS is sent to the base station using the resource, the method may also include:
the base station may receive the SRS sent by the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.
The present invention also provides a method for transmitting an uplink channel sounding reference signal, which includes:
a base station assigns resource to an uplink channel sounding reference signal (SRS) of a UE, and sends SRS configuration parameters to the UE, wherein the SRS configuration parameters including an SRS bandwidth parameter BSRS and an SRS frequency domain position parameter nRRC;
after receiving the SRS configuration parameters, the UE calculates the frequency domain starting position of the SRS of the resource used for sending the SRS, and then sends the SRS to the base station using the resource;
wherein the frequency domain resource assigned to the SRS by the base station corresponds to a node in a tree structure of the SRS bandwidth configuration, and the configured BSRS corresponds to the level on which the node is located, and the configured nRRC corresponds to the index of the node on the level determined by the BSRS in the tree structure.
Further, the nRRC may be:




  
    
      n
      RRC
    
    =
    
      {
      
        0
        ,
        1
        ,
        ...
        ⁢
        
          
        
        ,
        
          
            (
            
              
                ∏
                
                  b
                  =
                  0
                
                
                  B
                  SRS
                
              
              ⁢
              
                
              
              ⁢
              
                N
                b
              
            
            )
          
          -
          1
        
      
      }
    
  
  ,




wherein Nb may represent the number of branch nodes of a node on the (b−1)th level, which are located on the bth level of the tree structure, and when b=0, Nb=1.

Further, the calculation of the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters may be specifically as follows: the index nb of a branch node of a node on the (b−1)th level, which is located on the bth level, may be calculated according to the following formula; the frequency domain starting position of the SRS may be calculated according to the nb calculated: nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb, wherein └*┘ may represent rounding down, mSRS,b may represent the number of resource blocks contained in every node on the bth level of the tree structure in the frequency domain, and b=0, 1, . . . , BSRS.
Preferably, the indexes of nodes on every level of the tree structure may start from 0, and may be numbered 0, 1, 2, 3 . . . in sequence.
Further, after the SRS is sent to the base station using the resource, the method may also include: the base station may receive the SRS sent by the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.
With the method of the present invention, the correlation between nRRC and nb can be determined correctly, and the method can solve the existing problem that the frequency domain starting position of the SRS can not be determined, which makes it difficult to perform the uplink channel sounding accurately.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flow chart of a method illustrating that a base station sends SRS configuration information and a UE sends an SRS according to the configuration information; and
FIG. 2 is a diagram illustrating the calculation of the frequency domain starting position of the SRS for the configuration 0 in Table 2.



DETAILED DESCRIPTION
In the following description, the embodiments of the present invention are described in detail in combination with the accompanying drawings, so that those skilled in the art can sufficiently understand the realization process that how the present invention solves the technical problem using the technical means and achieves the technical effect, and can implement the present invention according to the realization process.
The First Embodiment
FIG. 1 illustrates a method for a base station sending SRS configuration information and a UE sending an SRS according to the configuration information. The method includes the following steps.
Step 110, when a base station needs to receive an SRS from a UE to perform the uplink channel sounding, it assigns resource to the SRS and sends SRS configuration parameters to the UE.
SRS configuration parameters are classified into three categories, wherein the first category is a parameter related to the time domain position of an SRS; the second category is a parameter related to the sequence used by an SRS; and the third category is a parameter related to the frequency domain position of an SRS. The first and second categories of parameters are outside the scope of the present invention. Some cell-specific parameters are broadcast in cells, while UE-specific parameters are configured through high layer signaling.
Parameters related to the frequency domain position of an SRS include an SRS bandwidth parameter BSRS and an SRS frequency domain position parameter nRRC. The frequency domain resource assigned to the SRS by the base station corresponds to a node in a tree structure of SRS bandwidth configuration; the SRS bandwidth parameter BSRS configured by the base station corresponds to the level on which the node is located; the configured SRS frequency domain position parameter nRRC, corresponds to the index of the branch node on the lowest level of the node in the tree structure, or corresponds to the index of the node on the level determined by the BSRS in the tree structure.
Step 120, according to the SRS configuration parameters received, the UE determines the parameters related to the time domain, frequency domain and sequence of the resource used for sending the SRS, and then sends the SRS to the base station using the resource;
the UE determines the transmission period of the SRS and the number of the subframe in which the SRS is located according to the received parameters related to the time domain position, determines the frequency domain position (including the frequency domain starting position) where the SRS is sent and the length of sequence according to the received parameters related to the frequency domain position, and determines the sequence used by the SRS according to the parameter related to the sequence.
Step 130, the base station receives the SRS sent by the UE side at the corresponding time frequency position according to the SRS parameters configured for the UE.
In the embodiment, a base station assigns the resource to the SRS and the resource assigned corresponds to a node in the tree structure in the frequency domain; the SRS bandwidth parameter BSRS is configured according to the level on which the node is located and the SRS frequency domain position parameter nRRC, is configured according to the index of a the branch node on the lowest level of the node in the tree structure, wherein the nRRC is:




  
    n
    RRC
  
  =
  
    
      {
      
        0
        ,
        1
        ,
        ...
        ⁢
        
          
        
        ,
        
          
            (
            
              
                ∏
                
                  b
                  =
                  0
                
                3
              
              ⁢
              
                
              
              ⁢
              
                N
                b
              
            
            )
          
          -
          1
        
      
      }
    
    .
  




In the embodiment, the value of nRRC for a branch node which is not on the lowest level is the index of any branch node on the lowest level of the branch node.
The UE calculates nb according to the above-mentioned nRRC wherein nb represents the index of a branch node of a node on the (b−1)th level, which are located on the bth level:

nb=└4nRRC/mSRS,b┘ mod Nb.

According to the parameter nb calculated, the UE can calculate a correct frequency domain starting position by the formula (1) and sends the SRS on the corresponding resource, so that the base station can receive the SRS correctly. Other parameters required in the calculation according to the formula (1) may be acquired through existing means, which are not repeated here.
Table 5, shown below, illustrates an SRS bandwidth configuration for the configuration 0 in Table 2. From Table 2, the following values which are N0=1,N1=2,N2=2 and N3=3 can be obtained, wherein the UE-specific SRS bandwidth parameter BSRS is configured by the base station, therefore, in this diagram:
when BSRS=0, there is only one node on the level, and nRRC={0, 1, 2, . . . , 11};
when BSRS=1, there are two nodes on the level: for the node #0, n={0, 1, . . . , 5}, and for the node #1, nRRC={6, 7, . . . , 11};
when BSRS=2, there are four nodes on the level: for the node #0, nRRC={0,1,2}; for the node #1, nRRC={3,4,5}; for the node #2, nRRC={6,7,8}; and for the node #3, nRRC={9,10,11};
when BSRS=3, the configuration corresponds to the lowest level of the tree structure, the values of all the nodes are {0, 1, 2, . . . , 11} respectively.
Here, the number of nodes on the level of the tree structure where the SRS is located is determined according to the tree structure. When configuring the SRS parameters for the UE, the base station configures the time-frequency-code parameters used to send the SRS by the UE according to the actual condition, e.g. coverage requirements, collisions with other UEs, the moving speed of UE, etc.
The Second Embodiment
The process of the second embodiment is the same as that of the first embodiment. In the following description, only the method for determining the frequency domain starting position is described.
In the embodiment, a base station assigns the resource to the SRS and the resource assigned corresponds to a node in the tree structure in the frequency domain; the SRS bandwidth parameter BSRS is configured according to the level on which the node is located and the SRS frequency domain position parameter nRRC is configured according to the index of the node on the level determined by BSRS (the indexes of nodes on every level start from 0 and are numbered 0, 1, 2, 3 . . . in sequence), hence the scope of the value of nRRC is




  
    n
    RRC
  
  =
  
    
      {
      
        0
        ,
        1
        ,
        ...
        ⁢
        
          
        
        ,
        
          
            (
            
              
                ∏
                
                  b
                  =
                  0
                
                
                  B
                  SRS
                
              
              ⁢
              
                
              
              ⁢
              
                N
                b
              
            
            )
          
          -
          1
        
      
      }
    
    .
  




The UE calculates nb according to the formula (I) and the meaning of nb in the formula (I), wherein nb represents the index of a branch node of a node on the (b−1)th level, which is located on the bth level:

nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb.

According to the parameter nb calculated, the UE can calculate a correct frequency domain starting position by the formula (1) and sends the SRS on the corresponding resource, so that the base station can receive the SRS correctly.
Table 6, shown below, illustrates an SRS bandwidth configuration for the configuration 0 in Table 2. From the configuration 0 in Table 2, the following values which are N0=1,N1=2,N2=2 and N3=3 can be obtained, so in the diagram:



  
    
      
        when
        ⁢
        
          
        
        ⁢
        
          B
          SRS
        
      
      =
      0
    
    ,
    
      
        
          n
          RRC
        
        =
        
          
            {
            
              0
              ,
              1
              ,
              ...
              ⁢
              
                
              
              ,
              
                
                  (
                  
                    
                      ∏
                      
                        b
                        =
                        1
                      
                      
                        B
                        SRS
                      
                    
                    ⁢
                    
                      
                    
                    ⁢
                    
                      N
                      b
                    
                  
                  )
                
                -
                1
              
            
            }
          
          =
          
            {
            0
            }
          
        
      
      ;
    
  




  
    
      
        when
        ⁢
        
          
        
        ⁢
        
          B
          SRS
        
      
      =
      1
    
    ,
    
      
        
          n
          RRC
        
        =
        
          
            {
            
              0
              ,
              1
              ,
              ...
              ⁢
              
                
              
              ,
              
                
                  (
                  
                    
                      ∏
                      
                        b
                        =
                        1
                      
                      
                        B
                        SRS
                      
                    
                    ⁢
                    
                      
                    
                    ⁢
                    
                      N
                      b
                    
                  
                  )
                
                -
                1
              
            
            }
          
          =
          
            
              {
              
                0
                ,
                1
                ,
                ...
                ⁢
                
                  
                
                ,
                
                  
                    N
                    1
                  
                  -
                  1
                
              
              }
            
            =
            
              {
              
                0
                ,
                1
              
              }
            
          
        
      
      ;
    
  




  
    
      
        when
        ⁢
        
          
        
        ⁢
        
          B
          SRS
        
      
      =
      2
    
    ,
    
      
        
          n
          RRC
        
        =
        
          
            {
            
              0
              ,
              1
              ,
              ...
              ⁢
              
                
              
              ,
              
                
                  (
                  
                    
                      ∏
                      
                        b
                        =
                        1
                      
                      
                        B
                        SRS
                      
                    
                    ⁢
                    
                      
                    
                    ⁢
                    
                      N
                      b
                    
                  
                  )
                
                -
                1
              
            
            }
          
          =
          
            
              {
              
                0
                ,
                1
                ,
                ...
                ⁢
                
                  
                
                ,
                
                  
                    
                      N
                      1
                    
                    ⁢
                    
                      N
                      2
                    
                  
                  -
                  1
                
              
              }
            
            =
            
              {
              
                0
                ,
                1
                ,
                2
                ,
                3
              
              }
            
          
        
      
      ;
    
  




  
    
      
        and
        ⁢
        
          
        
        ⁢
        when
        ⁢
        
          
        
        ⁢
        
          B
          SRS
        
      
      =
      3
    
    ,
    
      
        n
        RRC
      
      =
      
        
          {
          
            0
            ,
            1
            ,
            ...
            ⁢
            
              
            
            ,
            
              
                (
                
                  
                    ∏
                    
                      b
                      =
                      1
                    
                    
                      B
                      SRS
                    
                  
                  ⁢
                  
                    
                  
                  ⁢
                  
                    N
                    b
                  
                
                )
              
              -
              1
            
          
          }
        
        =
        
          
            {
            
              0
              ,
              1
              ,
              ...
              ⁢
              
                
              
              ,
              
                
                  
                    N
                    1
                  
                  ⁢
                  
                    N
                    2
                  
                  ⁢
                  
                    N
                    3
                  
                
                -
                1
              
            
            }
          
          =
          
            
              {
              
                0
                ,
                1
                ,
                2
                ,
                ...
                ⁢
                
                  
                
                ,
                11
              
              }
            
            .
          
        
      
    
  



In the following description, applied cases in which the frequency domain starting position of an uplink channel SRS is determined according to the SRS bandwidth configuration parameter, the SRS bandwidth BSRS and the frequency domain position parameter nRRC are presented in combination with FIG. 2.
Case 1
As shown in FIG. 2, for the configuration 0 in Table 2, if the base station adopts the method of the first embodiment, the UE-specific parameters configured are BSRS=1 and nRRC=6, and the corresponding frequency domain resource is the area represented by

    
    
        

of the level corresponding to BSRS=1 as shown in FIG. 2, wherein nRRC can be any one of {6,7,8,9,10,11}.

    
    


After the UE receives the above-mentioned parameters, the following can be obtained according to the configuration 0 in Table 2:
N0=1, N1=2, N2=2, N3=3
mSRS,0=48, mSRS,1=24, mSRS,2=12, mSRS,3=4
mSRS,BSRS=mSRS,1=24.
According to nb=└4nRRC/mSRS,b┘ mod Nb and b=0, 1, . . . , BSRS, the following can be obtained by calculation:

n0=└4nRRC/mSRS,0┘ mod N0=└24/48┘ mod 1=0

n1=└4nRRC/mSRS,1┘ mod N1=└24/24┘ mod 2=1

If the base station adopts the method of the second embodiment, the configured parameters are BSRS=1 and nRRC=1, so according to

nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb, the following can be obtained by calculation:

n0=└24nRRC/mSRS,0┘ mod N0=└24/48┘ mod 1=0

n1=└24nRRC/mSRS,1┘ mod N1=└24/24┘ mod 2=1.

For the same branch nodes, there are different scopes of values of nRRC in different embodiments, but the values of nb obtained from the corresponding correlation between nRRC and nb are the same, and so the frequency domain starting positions of the SRSs are also the same.
Assume NRBUL=60 and NSCRB=12, then k′0=(└NNBUL/2┘−mSRS,0/2)NSCRBkTC=6NSCRB.
According to




  
    
      k
      0
    
    =
    
      
        k
        0
        ′
      
      +
      
        
          ∑
          
            b
            =
            0
          
          
            B
            SRS
          
        
        ⁢
        
          
        
        ⁢
        
          2
          ⁢
          
            M
            
              sc
              ,
              b
            
            RS
          
          ⁢
          
            n
            b
          
        
      
    
  
  ,




the UE gets the frequency domain starting position of the SRS, namely the index of the frequency domain subcarrier by calculation:





  
    
      
        
          k
          0
        
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              2
              ⁢
              
                M
                
                  sc
                  ,
                  b
                
                RS
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              
                m
                
                  SRS
                  ,
                  b
                
              
              ⁢
              
                N
                sc
                RB
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              N
              sc
              RB
            
            ⁡
            
              (
              
                
                  
                    m
                    
                      SRS
                      ,
                      0
                    
                  
                  ⁢
                  
                    n
                    0
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      
                        
                      
                      ⁢
                      1
                    
                  
                  ⁢
                  
                    n
                    1
                  
                
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            6
            ⁢
            
              N
              SC
              RB
            
          
          +
          
            
              N
              SC
              RB
            
            ⁡
            
              (
              
                0
                +
                0
                +
                24
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          30
          ⁢
          
            
          
          ⁢
          
            N
            SC
            RB
          
        
      
    
  
  
    
      
        =
        
        ⁢
        360.
      
    
  




From the diagram illustrating the calculation of the frequency domain starting position of the SRS as shown in FIG. 2, it can be got that the frequency domain starting position of the SRS corresponding to the area  is 30NSCRB, namely, the frequency domain starting position calculated by the UE is consistent with the frequency domain starting position of the frequency domain resource assigned by the base station. Therefore, the base station can receive the SRS sent by the UE correctly and then perform the uplink channel sounding accurately.
Case 2
As shown in FIG. 2, for the configuration 0 in Table 2, if the base station adopts the method of the first embodiment, the UE-specific parameters configured are BSRS=2 and nRRC=3, namely corresponding to the area

    
    
        

of the level corresponding to BSRS=2 as shown in FIG. 2.

    
    


After the UE receives the relevant parameters, the following can be obtained according to the configuration 0 in Table 2:
N0=1, N1=2, N2=2, N3=3
mSRS,0=48, mSRS,1=24, mSRS,2=12, mSRS,3=4
mSRS,BSRS=mSRS,2=12.
According to nb=└4nRRC/mSRS,b┘ mod Nb and b=0, 1, . . . , BSRS, the following can be obtained by calculation:

n0=└4nRRC/mSRS,0┘ mod N0=└12/48┘ mod 1=0

n1=└4nRRC/mSRS,1┘ mod N1=└12/24┘ mod 2=0

n2=└4nRRC/mSRS,2┘ mod N2=└12/12┘ mod 2=1.

If the base station adopts the method of the second embodiment, the configured parameters are BSRS=2 and nRRC=1; here, according to:

nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb, the UE gets the following by calculation:

n0=└12nRRC/mSRS,0┘ mod N0=└12/48┘ mod 1=0

n1=└12nRRC/mSRS,1┘ mod N1=└12/24┘ mod 2=1

n2=└12nRRC/mSRS,2┘ mod N2=└12/12┘ mod 2=1.

From the above, the results obtained from the two methods are the same by calculation.
Assume NRBUL=60 and NSCRB=12, then k′0=(└NRBUL/2┘−mSRS,0/2)NSCRB+kTC=6NSCRB.
According to




  
    
      k
      0
    
    =
    
      
        k
        0
        ′
      
      +
      
        
          ∑
          
            b
            =
            0
          
          
            B
            SRS
          
        
        ⁢
        
          
        
        ⁢
        
          2
          ⁢
          
            M
            
              sc
              ,
              b
            
            RS
          
          ⁢
          
            n
            b
          
        
      
    
  
  ,




the UE gets the frequency domain starting position of the SRS by calculation, i.e., the index of the frequency domain subcarrier is:





  
    
      
        
          k
          0
        
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              2
              ⁢
              
                M
                
                  sc
                  ,
                  b
                
                RS
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              
                m
                
                  SRS
                  ,
                  b
                
              
              ⁢
              
                N
                sc
                RB
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              N
              sc
              RB
            
            ⁡
            
              (
              
                
                  
                    m
                    
                      SRS
                      ,
                      0
                    
                  
                  ⁢
                  
                    n
                    0
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      
                        
                      
                      ⁢
                      1
                    
                  
                  ⁢
                  
                    n
                    1
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      
                        
                      
                      ⁢
                      2
                    
                  
                  ⁢
                  
                    n
                    2
                  
                
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            6
            ⁢
            
              N
              SC
              RB
            
          
          +
          
            
              N
              SC
              RB
            
            ⁡
            
              (
              
                0
                +
                0
                +
                12
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          18
          ⁢
          
            
          
          ⁢
          
            N
            SC
            RB
          
        
      
    
  
  
    
      
        =
        
        ⁢
        216
      
    
  




From the diagram illustrating the calculation of the frequency domain starting position of the SRS as shown in FIG. 2, it also can be got that, the frequency domain starting position of the SRS corresponding to the area  is 18NSCRB, i.e. the frequency domain starting position calculated by the UE is consistent with the frequency domain starting position of the frequency domain resource assigned by the base station. Therefore, the base station can receive the SRS sent by the UE correctly and then performs the uplink channel sounding accurately.
Case 3
As shown in FIG. 2, for the configuration 0 in Table 2, if the base station adopts the method of the first embodiment, the UE-specific parameters configured are BSRS=2 and nRRC=9, namely corresponding to the area

    
    
        

of the level corresponding to BSRS=2 as shown in FIG. 2.

    
    


After the UE receives the relevant parameters, the following can be obtained according to the configuration 0 in Table 2:
N0=1, N1=2, N2=2, N3=3
mSRS,0=48, mSRS,1=24, mSRS,2=12, mSRS,3=4
mSRS,BSRS=mSRS,2=12.
According to nb=└4nRRC/mSRS,b┘ mod Nb and b=0, 1, . . . , BSRS, the following can be obtained by calculation:

n0=└4nRRC/mSRS,0┘ mod N0=└36/48┘ mod 1=0

n1=└4nRRC/mSRS,1┘ mod N1=└36/24┘ mod 2=1

n2=└4nRRC/mSRS,2┘ mod N2=└36/12┘ mod 2=1.

If the base station adopts the method of the second embodiment, the configured parameters are BSRS=2 and nRRC=3. According to, nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb, the following can be obtained by calculation:

n0=└12nRRC/mSRS,0┘ mod N0=└36/48┘ mod 1=0

n1=└12nRRC/mSRS,1┘ mod N1=└36/24┘ mod 2=1

n2=└12nRRC/mSRS,2┘ mod N2=└36/12┘ mod 2=1.

Assume NRBUL=60 and NSCRB=12, then k′0=(└NRBUL/2┘−mSRS,0/2)NSCRB+kTC=6NSCRB.
According to




  
    
      k
      0
    
    =
    
      
        k
        0
        ′
      
      +
      
        
          ∑
          
            b
            =
            0
          
          
            B
            SRS
          
        
        ⁢
        
          
        
        ⁢
        
          2
          ⁢
          
            M
            
              sc
              ,
              b
            
            RS
          
          ⁢
          
            n
            b
          
        
      
    
  
  ,




the UE gets the frequency domain starting position of the SRS by calculation, i.e. the index of the frequency domain subcarrier is:





  
    
      
        
          k
          0
        
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              2
              ⁢
              
                M
                
                  sc
                  ,
                  b
                
                RS
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              
                m
                
                  SRS
                  ,
                  b
                
              
              ⁢
              
                N
                sc
                RB
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              N
              sc
              RB
            
            ⁡
            
              (
              
                
                  
                    m
                    
                      SRS
                      ,
                      0
                    
                  
                  ⁢
                  
                    n
                    0
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      
                        
                      
                      ⁢
                      1
                    
                  
                  ⁢
                  
                    n
                    1
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      
                        
                      
                      ⁢
                      2
                    
                  
                  ⁢
                  
                    n
                    2
                  
                
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            6
            ⁢
            
              N
              SC
              RB
            
          
          +
          
            
              N
              SC
              RB
            
            ⁡
            
              (
              
                0
                +
                24
                +
                12
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          42
          ⁢
          
            N
            SC
            RB
          
        
      
    
  
  
    
      
        =
        
        ⁢
        504
      
    
  




From the diagram illustrating the calculation of the frequency domain starting position of the SRS as shown in FIG. 2, it can also be got that, the frequency domain starting position of the SRS corresponding to the area  is 42NSCRB, namely the frequency domain starting position calculated by the UE is consistent with the frequency domain starting position of the frequency domain resource assigned by the base station. Therefore, the base station can receive the SRS sent by the UE correctly and then perform the uplink channel sounding accurately.
Case 4
As shown in FIG. 2, for the configuration 0 in Table 2, if the base station adopts the method of the first embodiment, the UE-specific parameters configured are BSRS=3 and nRRC=7, namely corresponding to the area

    
    
        

of the level corresponding to BSRS=3 as shown in FIG. 2.

    
    


After the UE receives the relevant parameters, the following can be obtained according to the configuration 0 in Table 2:
N0=1, N1=2, N2=2, N3=3
mSRS,0=48, mSRS,1=24, mSRS,2=12, mSRS,3=4
mSRS,0=48, mSRS,1=24, mSRS,2=12, mSRS,3=4.
mSRS,BSRS=mSRS,3=4.
According to nb=└4nRRC/mSRS,b┘ mod Nb and b=0, 1, . . . , BSRS, the UE gets the following by calculation:

n0=└4nRRC/mSRS,0┘ mod N0=└28/48┘ mod 1=0

n1=└4nRRC/mSRS,1┘ mod N1=└28/24┘ mod 2=1

n2=└4nRRC/mSRS,2┘ mod N2=└28/12┘ mod 2=0

n3=└4nRRC/mSRS,3┘ mod N3=└28/4┘ mod 3=1.

If the base station adopts the method of the second embodiment, the configured parameters are BSRS=3 and nRRC=7, so according to nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb, the following can be obtained by calculation:

n0=└4nRRC/mSRS,0┘ mod N0=└28/48┘ mod 1=0

n1=└4nRRC/mSRS,1┘ mod N1=└28/24┘ mod 2=1

n2=└4nRRC/mSRS,2┘ mod N2=└28/12┘ mod 2=0

n3=└4nRRC/mSRS,3┘ mod N3=└28/4┘ mod 3=1.

It can be seen that, when the node assigned in the frequency domain is on the lowest level of the tree structure, the value of nRRC obtained from the method of the first embodiment is the same as that from the method of the second embodiment.
Assume NRBUL=60 and NSCRB=12, then k′0=(└NRBUL/2┘−mSRS,0/2)NSCRB+kTC=6NSCRB.
According to




  
    
      k
      0
    
    =
    
      
        k
        0
        ′
      
      +
      
        
          ∑
          
            b
            =
            0
          
          
            B
            SRS
          
        
        ⁢
        
          
        
        ⁢
        
          2
          ⁢
          
            M
            
              sc
              ,
              b
            
            RS
          
          ⁢
          
            n
            b
          
        
      
    
  
  ,




the base station gets the frequency domain starting position of the SRS by calculation, namely the index of the frequency domain subcarrier is





  
    
      
        
          k
          0
        
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              2
              ⁢
              
                M
                
                  sc
                  ,
                  b
                
                RS
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              ∑
              
                b
                =
                0
              
              
                B
                SRS
              
            
            ⁢
            
              
            
            ⁢
            
              
                m
                
                  SRS
                  ,
                  b
                
              
              ⁢
              
                N
                sc
                RB
              
              ⁢
              
                n
                b
              
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            k
            0
            ′
          
          +
          
            
              N
              sc
              RB
            
            ⁡
            
              (
              
                
                  
                    m
                    
                      SRS
                      ,
                      0
                    
                  
                  ⁢
                  
                    n
                    0
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      1
                    
                  
                  ⁢
                  
                    n
                    1
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      2
                    
                  
                  ⁢
                  
                    n
                    2
                  
                
                +
                
                  
                    m
                    
                      SRS
                      ,
                      2
                    
                  
                  ⁢
                  
                    n
                    2
                  
                
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          
            6
            ⁢
            
              N
              SC
              RB
            
          
          +
          
            
              N
              SC
              RB
            
            ⁡
            
              (
              
                0
                +
                24
                +
                0
                +
                4
              
              )
            
          
        
      
    
  
  
    
      
        =
        
        ⁢
        
          34
          ⁢
          
            
          
          ⁢
          
            N
            SC
            RB
          
        
      
    
  
  
    
      
        =
        
        ⁢
        408.
      
    
  




From the diagram illustrating the calculation of the frequency domain starting position of the SRS as shown in FIG. 2, it also can be got that, the frequency domain starting position of the SRS corresponding to the area  is 34NSCRB, i.e. the frequency domain starting position calculated by the UE is consistent with the frequency domain starting position of the frequency domain resource assigned by the base station. Therefore, the base station can correctly receive the SRS sent by the UE and then perform the uplink channel sounding accurately.
The above-mentioned descriptions are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. All modifications, equivalent substitutions and improvements etc, made within the spirit and principle of the present invention, shall be included in the appended claims of the present invention. For example, the system to which the present invention is applied is not limited to the LTE system.
INDUSTRIAL APPLICABILITY
The present invention can determine the correlation between nRRC and nb correctly and solve the existing problem that the frequency domain starting position of the SRS can not be determined, which makes it difficult to perform the uplink channel sounding accurately, thus has excellent industrial applicability.

## Claims

1. A method for transmitting an uplink channel sounding reference signal (SRS), including:
receiving, by a User Equipment (UE), SRS configuration parameters from a base station, wherein the SRS configuration parameters include an SRS bandwidth parameter BSRS and an SRS frequency domain position parameter nRRC, wherein RRC refers to Radio Resource Control;
calculating, by the UE, the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters after receiving the SRS configuration parameters, and then sending the SRS to the base station using the resource;
wherein the frequency domain resource assigned to the SRS by the base station corresponds to a node in a tree structure of an SRS bandwidth configuration, and the configured BSRS corresponds to the level on which the node is located, while the configured nRRC corresponds to the index of the branch node on the lowest level of the node in the tree structure;
wherein the calculation of the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters is specifically as follows: calculating index nb according to the following formula, wherein the index nb is the index of a branch node located on the bth level of a node on the (b−1)th level; and then the frequency domain starting position of the SRS is calculated according to the nb:


nb=└4nRRC/mSRS,b┘ mod Nb;


wherein └*┘ represents rounding down, mSRS,b represents the number of resource blocks contained in every node on the bth level of the tree structure in the frequency domain, and b=0, 1, . . . , BSRS; and
wherein Nb is the number of branch nodes located on the bth level of a node on the (b−1)th level of the tree structure, and when b=0, then Nb=1.

2. The method according to claim 1, wherein the nRRC is:




  
    n
    RRC
  
  =
  
    
      {
      
        0
        ,
        1
        ,
        ...
        ⁢
        
          
        
        ,
        
          
            (
            
              
                ∏
                
                  b
                  =
                  0
                
                3
              
              ⁢
              
                
              
              ⁢
              
                N
                b
              
            
            )
          
          -
          1
        
      
      }
    
    .

3. The method according to claim 2, wherein after the SRS is sent to the base station using the resource, the method also including:
receiving, by the base station, the SRS sent from the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.

4. The method according to claim 1, wherein
the nRRC corresponds to the index of any branch node on the lowest level of the node in the tree structure, and the indexes of branch nodes on the lowest level of the tree structure start from 0 and are numbered 0, 1, 2, 3 . . . in sequence.

5. The method according to claim 4, wherein after the SRS is sent to the base station using the resource, the method also including:
receiving, by the base station, the SRS sent from the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.

6. The method according to claim 1, wherein after the SRS is sent to the base station using the resource, the method also including:
receiving, by the base station, the SRS sent from the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.

7. A method for transmitting an uplink channel sounding reference signal (SRS), including:
receiving, by a User Equipment (UE), SRS configuration parameters from a base station, wherein the SRS configuration parameters include an SRS bandwidth parameter BSRS and an SRS frequency domain position parameter nRRC, wherein RRC refers to Radio Resource Control;
calculating, by the UE, the frequency domain starting position of the SRS of the resource used for sending the SRS after receiving the SRS configuration parameters, and then sending the SRS to the base station using the resource;
wherein the frequency domain resource assigned to the SRS by the base station corresponds to a node of a tree structure of an SRS bandwidth configuration, and the configured BSRS corresponds to the level on which the node is located, and the configured nRRC corresponds to the index of the node on the level determined by the BSRS in the tree structure; and
wherein the calculation of the frequency domain starting position of the SRS of the resource used for sending the SRS according to the SRS configuration parameters is specifically as follows: calculating index nb according to the following formula, wherein the index nb is the index of a branch node located on the bth level of a node on the (b−1)th level; and then the frequency domain starting position of the SRS is calculated according to the nb calculated:


nb=└mSRS,BSRSnRRC/mSRS,b┘ mod Nb,


wherein └*┘ represents rounding down, mSRS,b represents the number of resource blocks contained in every node on the bth level of the tree structure in the frequency domain, and b=0, 1, . . . , BSRS; and
wherein Nb represents the number of branch nodes of a node on the (b−1)th level, which are located on the bth level of the tree structure, and when b=0, Nb=1.

8. The method according to claim 7, wherein the nRRC is:




  
    n
    RRC
  
  =
  
    
      {
      
        0
        ,
        1
        ,
        ...
        ⁢
        
          
        
        ,
        
          
            (
            
              
                ∏
                
                  b
                  =
                  0
                
                
                  B
                  SRS
                
              
              ⁢
              
                
              
              ⁢
              
                N
                b
              
            
            )
          
          -
          1
        
      
      }
    
    .

9. The method according to claim 8, wherein after the SRS is sent to the base station using the resource, the method also including:
receiving, by the base station, the SRS sent from the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.

10. The method according to claim 7, wherein
the indexes of nodes on every level of the tree structure start from 0, and are numbered 0, 1, 2, 3 . . . in sequence.

11. The method according to claim 10, wherein after the SRS is sent to the base station using the resource, the method also including:
receiving, by the base station, the SRS sent from the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.

12. The method according to claim 7, wherein after the SRS is sent to the base station using the resource, the method also including:
receiving, by the base station, the SRS sent from the UE at the corresponding time-frequency position according to the SRS configuration parameters of the UE.