Patent ID: 11902409
Assignee: CHENGDU CORESAT TECHNOLOGY CO., LTD
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 4:
5. A frequency offset estimation device, applicable to a signal receiving end, wherein the signal receiving end is in communication with a signal sending end, and the device comprises:
an acquisition module, configured to acquire a main peak and a secondary peak of a PRACH signal when detecting that an access signal is in the PRACH signal sent by the signal sending end, wherein the PRACH signal is composed of a preset number of identical leader sequences;
a first determination module, configured to calculate a ratio of a peak value of the main peak to a peak value of the secondary peak and determine a first frequency offset according to the ratio and a preset subcarrier interval;
a compensation module, configured to perform a frequency offset compensation on the PRACH signal according to the first frequency offset, to obtain a compensation sequence after the frequency offset compensation;
a second determination module, configured to calculate a frequency offset between the compensation sequence and the leader sequences, to obtain a second frequency offset, so as to estimate a time delay of the access signal according to the second frequency offset; and
an estimation module configured to acquire a position of the main peak, and estimate a time delay of the access signal according to the position of the main peak and the second frequency offset, wherein
according to a main peak point m′ and a number {circumflex over (l)} of folds in integral folds of the frequency offset, a time delay position k is derived by calculation using a following formula, the access signal is expressed as:, r
   ⁡
   (
   n
   )
  
  =
  
   
    
     e
     
      j
      ⁢
      
       
        2
        ⁢
        πΔε
        ⁢
        n
       
       N
      
     
    
    ×
    A
    ⁢
    
     e
     
      
       -
       j
      
      ⁢
      
       
        π
        ⁢
        
         n
         ⁡
         (
         
          1
          +
          
           μ
           ′
          
         
         )
        
       
       N
      
     
    
    ⁢
    z
    ⁢
    
     
      c
      
       μ
       ′
      
     
     (
     
      n
      -
      κ
     
     )
    
   
   +
   
    w
    ⁡
    (
    n
    )
   
  
 

a correlation peak is expressed as:, R
   ⁡
   (
   
    m
    ,
    
     Δ
     ⁢
     f
    
   
   )
  
  =
  
   
    ∑
    
     n
     =
     0
    
    
     N
     -
     1
    
   
   
    
     r
     ⁡
     (
     n
     )
    
    ⁢
    
     
      s
      *
     
     (
     
      n
      -
      m
     
     )
    
   
  
 

wherein if the number of folds of the frequency offset is not an integer, the peak point of the above formula m′=k, and the searched peak position m′ is a user time delay k; and if the number of folds of the frequency offset is an integer; the main peak point m′ and an actual time delay point k satisfy MOD(μ′{circumflex over (l)}+κ,N)=m′;
wherein r(n) is the access signal, Δε is a frequency offset of the signal, Δε=Δf/fs, fs is a sampling rate, Δf is a frequency offset,, A
   =
   
    
     1
     
      N
     
    
    [
    
     
      ∑
      
       k
       =
       0
      
      
       N
       -
       1
      
     
     
      
       ZC
       μ
      
      (
      k
      )
     
    
    ]
   
  
  ,, w(n) is noise with a mean value of 0 and a variance of σ2, μ is a root value, k represents an index value of a ZC sequence, N represents a length of a time domain sequence, n represents an index of the time domain sequence, and μ′ is dual to the root value μ.