Multi-carrier transmission system

Abstract

Multi-carrier transmission system comprises transmitter including acquisition unit configured to acquire 2 m (m: a natural number) modulated signals including no-information signals which are failed to be used for information transmission and 2 n (n: a natural number, n<m) signals, acquisition unit subjecting modulated signals to inverse discrete Fourier trans-form to obtain transformed signals, no-information signal included in L th modulated signal of modulated signals being used as first no-information signal of no-information signals, every K th modulated signal of modulated signals that is counted from first no-information signal being used as no-information signal (K: a natural number, L: an integer, K=2 m−n , 0≦L≦K−1), and transmission unit configured to transmit transformed signals, and receiver including receiving unit configured to receive the transformed signals, and detection unit configured to detect synchronization timing based on at least one no-information signal included in the transformed signals.

1 . A multi-carrier transmission method comprising:
 acquiring 2 m  (m: a natural number) modulated signals including 2 n  (n: a natural number; n<m) no-information signals which are failed to be used for information transmission;   subjecting the modulated signals to inverse discrete Fourier transform to obtain a plurality of transformed signals, an L th  modulated signal of the modulated signals being a first no-information signal of the no-information signals, every K th  modulated signal of the modulated signals that is counted from the first no-information signal being a subsequent no-information signal of the no-information signals (K: a natural number; L: an integer; K=2 m−n ; 0≦L≦K−1);   transmitting the transformed signals;   receiving the transformed signals; and   detecting synchronization timing by extracting a sequence of time-base signals of the received signals to establish a relation between the received signals, the relation being determined by positions of the no-information signals included in the transformed signals.   
   
   
       2 . The method according to  claim 1 , wherein detecting the synchronization timing detects the synchronization timing based on a constraint corresponding to a relational expression related to the transformed signals. 
   
   
       3 . The method according to  claim 1 , wherein subjecting the modulated signals to the inverse discrete Fourier transform transforms the M (=2 m ) modulated signals X k  (k: an integer; 0≦k≦M−1) into X k , X k  being defined to be
     x   k =(1 /M )( X   0   +W   M   −k   X   1   +W   M   −2k   X   2   + . . . +W   −(M−1)k   X   M−1) ),     ( W   M =exp(− j 2 π/M ); j 2 =1)   
   
   
       4 . The method according to  claim 1 , further comprising increasing the number of transmission bits of at least one of (2 m −2 n ) modulated signals which fail to include the no-information signals, the number of transmission bits of the (2 m −2 n ) modulated signals being higher than the number of transmission bits of the 2 m  modulated signals if the 2 m  modulated signals fail to include the no-information signals. 
   
   
       5 . The method according to  claim 4 , wherein increasing the number of the transmission bits increases a multi-value modulating number of at least one of the 2 m  modulated signals other than the modulated signals including the no-information signals. 
   
   
       6 . A multi-carrier transmission method comprising:
 acquiring 2 m  (m: a natural number) modulated signals including 2 n  (n: a natural number; n<m) no-information signals which are failed to be used for information transmission;   subjecting the 2 m  modulated signals to inverse discrete Fourier transform to obtain a plurality of transformed signals, an L th  modulated signal of the modulated signals being a first no-information signal of the no-information signals, every K th  modulated signal of the modulated signals that is counted from the first no-information signal being a subsequent no-information signal of the no-information signals (K: a natural number; L: an integer; K=2 m−n ; 0≦L≦K−1)   transmitting 2 m  transformed signals;   receiving the 2 m  transformed signals;   calculating, based on the 2 m  transformed signals received, a constraint given by a relational expression established between the 2 m  received signals determined by positions of the no-information signals included in the transformed signals; and   correcting at least one of the transformed signals to establish the constraint by extracting a sequence of time-base signals of the 2 m  received signals.   
   
   
       7 . The method according to  claim 6 , wherein transmitting the 2 m  transformed signals copies q (q: an integer; 1≦q≦2 m ) sequential latter ones of the 2 m  transformed signals, and transmits q copied modulated signals before the 2 m  modulated signals. 
   
   
       8 . The method according to  claim 6 , wherein assuming that the 2 m  transformed signals received are represented by y k  (k: an integer; 0≦k≦M−1; M=2 m ), correcting at least one of the transformed signals corrects at least one of the 2 m  modulated signals received y k , using a constraint given by following equations:
     y   p   +W   K   L   y   p+N   +W   K   2L   y   p+2N   + . . . +W   K   (K−1)L   y   p+(K−1)N =0     ( W   K =exp(− j 2 π/K ) j 2 =−1; N=2 n ; p: an integer; 0≦p≦N−1)   
   
   
       9 . The method according to  claim 6 , which further comprises determining, if a to-be-corrected received signal is predetermined, a level of noise based on a constraint established between received signals other than the to-be-corrected received signal,
 and wherein correcting at least one of the transformed signals fails to correct the to-be-corrected received signal if the level of the noise is higher than a value, correcting at least one of the transformed signals corrects the to-be-corrected received signal if the level of the noise is not higher than the value.   
   
   
       10 . The method according to  claim 6 , wherein subjecting the 2 m  modulated signals to the inverse discrete Fourier transform transforms the M (=2 m ) modulated signals X k  (k: an integer; 0≦k≦M−1) into a value given by the following formula:
     x   k =(1 /M )( X   0   +W   M   −k   X   1   +W   M   −2   X   2   + . . . +W   M   −(M−1)k   X   M−1 )     ( W   M =exp(−j2 π/M ); j 2 =−1)   
   
   
       11 . A multi-carrier transmission method comprising:
 acquiring 2 m  (m: a natural number) modulated signals including 2 n  (n: a natural number; n<m) no-information signals which are failed to be used for information transmission;   subjecting the 2 m  modulated signals to inverse discrete Fourier transform to obtain a plurality of transformed signals, an L th  modulated signal of the modulated signals being a first no-information signal of the no-information signals, every K th  modulated signal of the modulated signals that is counted from the first no-information signal being a subsequent no-information signal of the no-information signals (K: a natural number; L: an integer; K=2 m−n ; 0≦L≦K−1)   transmitting 2 m  transformed signals;   receiving 2 m  transmitted signals;   detecting 2 m  received signals which have distorted amplitudes;   correcting at least one of detected signals;   transforming, if the correction unit fails to correct at least one of the detected signals, both the at least one detected signal corrected and the at least one detected signal which are failed to be corrected; and   setting, to no-information signals, the received signals which correspond to the no-information signals, subjecting the no-information signals and a plurality of transformed signals to inverse discrete Fourier transform, and inputting, to the transforming unit, a plurality of inverse-discrete-Fourier-transformed signals which correspond to a plurality of amplitude-distorted signals, as corresponding input signals.   
   
   
       12 . The method according to  claim 11 , further comprising determining whether setting the received signals should operate, based on a constraint given by a relational expression established between the 2 m  transmitted signals and also based on the amplitude-distorted signals. 
   
   
       13 . The method according to  claim 11 , further comprising:
 counting number of operations of each of setting the received signals and transforming both the at least one detected signal corrected and the at least one detected signal which are failed to be corrected; and   outputting a stop signal for stopping setting the received signals if the number of operations exceeds a value.   
   
   
       14 . The method according to  claim 11 , further comprising:
 storing, in a storage unit, a plurality of amplitudes for a plurality of first output signals;   comparing respective amplitudes corresponding to the first output signals with a plurality of second output signals which are output after transforming both the at least one detected signal corrected and the at least one detected signal which are failed to be corrected receives a plurality of signals output and processes each of the signals; and   outputting a stop signal for stopping setting the received signals if a difference between the amplitudes corresponding to the first output signals and the second output signals is lower than a value.   
   
   
       15 . The method according to  claim 11 , wherein assuming that the 2 m  received signals are represented by y k  (k: an integer; 0≦k≦M−1; M=2 m ), correcting at least one of the detected signals corrects at least one of the 2 m  received signals y k , using a constraint given by the following equations:
     y   p   +W   K   L   y   p+N   +W   K   2L   y   p+2N   + . . . +W   K   (K−1)L   y   p+(K−1)N =0.     ( W   k =exp(− j 2 π/K ), j 2 =−1, N=2 n , p: an integer; 0≦p≦N−1)   
   
   
       16 . A multi-carrier transmission method comprising:
 acquiring 2 m  (m: a natural number) modulated signals including 2 n  (n: a natural number; n<m) no-information signals which are failed to be used for information transmission;   subjecting the 2 m  modulated signals to inverse discrete Fourier transform to obtain a plurality of transformed signals, an L th  modulated signal of the modulated signals being a first no-information signal of the no-information signals, every K th  modulated signal of the modulated signals that is counted from the first no-information signal being a subsequent no-information signal of the no-information signals (K: a natural number; L: an integer; K=2 m−n ; 0≦L≦K−1) and   transmitting 2 m  transformed signals of the transformed signals;   receiving the transmitted 2 m  transformed signals;   estimating a value of L based on the received 2 m  transformed signals.   
   
   
       17 . The method according to  claim 16 , wherein estimating the value estimates the value of L based on a constraint as a relational expression established between the 2 m  modulated signals. 
   
   
       18 . The method according to  claim 16 , wherein estimating the value includes:
 generating, from the 2 m  received signals, K calculation signals for calculating a constraint as a relational expression established between the 2 m  modulated signals; and   subjecting the K calculation signals to discrete Fourier transform.   
   
   
       19 . The method according to  claim 18 , wherein subjecting the K calculation signals to discrete Fourier transform subjects the K calculation signals to one of discrete Fourier transformer and fast Fourier transformer. 
   
   
       20 . The method according to  claim 16 , wherein assuming that the 2 m  received signals are represented by y k  (k: an integer; 0≦k≦M−1; M=2 m ), estimating the value acquires a power of
   ( y   p   +W   K   L   y   p+N   +W   K   2L   + . . . +W   K   (K−1)L′   y   p+(K−1)N )     ( W   k =exp(− j 2 π/K ), j 2 =−1, N=2 n , p: an integer; 0≦p≦N−1, 0≦L′≦K−1)   
     for each value of p, and estimates the value of L from a value of L′ which makes the power not higher than a value.