Abstract:
A method for extracting an information sequence from transmitted data, includes receiving the transmitted data, rearranging the order of the received data, extracting a block coding sequence from the rearranged received data, detecting whether an error exists in the extracted block coding sequence, and decoding the extracted block coding sequence using block decoding to obtain the information sequence if no error is detected in the extracted block coding sequence.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates, in general, to an error correcting device and a method thereof and, more particularly, to a turbo decoding device and a method thereof. 
   This is a counterpart of and claims priority to Japanese patent application Ser. No. 172707/2002, filed on Jun. 13, 2002, the subject matter of which is incorporated herein by reference. 
   2. Description of the Related Art 
   In a wireless communication system, a transmitter side adds a cyclic redundancy check (CRC) to an information data to be sent, causing a block code data to be generated (CRC coding). The block code data is coded with a turbo code to generate a turbo code data (turbo coding). Then, an order of the turbo code data is arranged for dispersing an error (interleave), and the arranged turbo code data is transmitted. 
   On the other hand, a conventional receiver side rearranges the order of the transmitted arranged turbo code data (hereinafter “received data”) to have the previous order (deinterleave). The rearranged received data is decoded to generate the block code data (turbo decoding). Then, the conventional receiver side detects an error in the decoded block code data with CRC. 
   However, in the conventional receiver side the rearranged received data is always turbo-decoded. Although an ability of error correcting of turbo decoding is high, it necessitates lots of calculation. As a result, much more time and electric power is required. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, there is provided a method for extracting an information sequence from transmitted data, which includes receiving the transmitted data, rearranging the order of the received data, extracting a block coding sequence from the rearranged received data, detecting whether an error exists in the extracted block coding sequence, and decoding the extracted block coding sequence using block decoding to obtain the information sequence if no error is detected in the extracted block coding sequence. 
   The novel features of the invention will more fully appear from the following detailed description, appended claims and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing data constructions used in the present invention. 
       FIG. 2  is a block diagram showing a turbo coder used in the present invention. 
       FIG. 3  is a block diagram showing an apparatus of the present invention. 
       FIG. 4  is a flow chart showing an operation of the apparatus of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The preferred embodiments of the present invention will be described. However, the invention is not limited to the specific embodiments. Moreover, not all the combinations of the characteristics of the present invention described in the embodiments are essential to the present invention. 
   The data constructions used in the present invention will be described with reference to  FIGS. 1-2 .  FIG. 1  is a block diagram showing data constructions used in the present invention.  FIG. 2  is a block diagram showing a turbo coder used in the present invention. The turbo coder is described in “Turbo Coding”, Haruo Hagihara et al., Electro Information Communication, vol. 84 No.3,  FIG. 3 . 
   As shown in  FIG. 1 , an information sequence Xk (k: integer) comprises four bits (X 1 , X 2 , X 3 , X 4 ) as an example. The information sequence is coded with a block code to generate the block coding sequence Bn (n: integer) which comprises seven bits (X 1 , X 2 , X 3 , X 4 , α 1 , α 2 , α 3 ) as an example. The first four bits are the information sequence Xk, and the last three bits are redundancy bits Pj (J: integer). The block code to generate this block coding sequence Bn is called a systematic code. 
   As shown in  FIG. 2 , the turbo coder comprises an interleaver  200 , element coders  210  and  220 , a switch  230  and a parallel/serial converter  240 . The block coding sequence Bn is coded by the element coder  210 , and a coded data Y 1   n  (n: integer) is generated. On the other hand, an order of the block coding sequence Bn is arranged by the interleaver  200 . The arranged block coding sequence Bn is coded by the element coder  220 , and a coded data Y 2   m  (m: integer) is generated. The parallel/serial converter  240  outputs the block coding sequence Bn, the coded data Y 1   n  and the coded data Y 2   m  in serial (time division multiple). As shown in  FIG. 1 , the turbo coding sequence Zp (p: integer) is 21 bits (X 1 ,Y 11 ,Y 21 , X 2 ,Y 12 ,Y 22 , X 3 , . . . , α 3 ,Y 17 ,Y 27 ). As mentioned above, both the block code and the turbo code are the systematic codes. 
   First, the apparatus for extracting an information sequence from transmitted data in a wireless communication system of the present invention will be described with reference to  FIG. 3 . 
   The apparatus comprises a deinterleaver  300  and a decoding circuit  310 . The apparatus receives a transmitted data. As mentioned above, the transmitted data is the turbo coding sequence Zp an order of which is arranged. The turbo coding sequence Zp is generated by coding the block coding sequence Bn with the turbo code as noted above. Also, the block coding sequence Bn is generated by coding the information sequence Xk with the block code. 
   The deinterleaver  300  arranges the order of the received data to be in the previous order as it was at the transmitter side, and generates an arranged received data  300   a.    
   The decoding circuit  310  is coupled with the deinterleaver  300 . The decoding circuit  310  comprises a storing circuit  311 , an information sequence extracting circuit  312 , a turbo decoder  313 , a switch  314 , a cyclic redundancy check (CRC) decoder  315  and a block decoder  316 . The storing circuit  311  is coupled with the deinterleaver  300 . The storing circuit  311  comprises a memory  3111  and a control circuit  3112 . The memory  3111  is DRAM or RAM or the like. The memory  3111  must have the capacity to store at least one unit of received data at a time. The memory  3111  stores the arranged received data  300   a . The control circuit  3112  instructs the memory  3111  to output the stored received data  311   a  according to a control signal  315   a.    
   The information sequence extracting circuit  312  is coupled with the storing circuit  311 . The information sequence extracting circuit  312  comprises an AND circuit  3121  and a D-type flip-flop  3122 . The AND circuit  3121  is coupled with the storing circuit  311 . The AND circuit  3121  extracts the block coding sequence from the stored received data  311   a  according to a control signal  317 . The control signal  317  is generated in a main control circuit. As shown in  FIG. 1 , the control signal  317  is a pulse signal having a high voltage level for a short time every cycle. The AND circuit  3121  extracts the data from the stored received data  311   a  when the control signal  317  has a high voltage level. The extracted data  3121   a  is (X 1 , X 2 , X 3 , . . . , α 3 ). If there is no error in the transmitted data, the extracted data  3121   a  is the same as the block coding sequence Bn. The D-type flip-flop  3122  is coupled with the AND circuit  3121 . The D-type flip-flop  3122  latches the extracted data  3121   a  according to a clock signal  318  which is generated by a central control portion, and outputs the latched data  312   a . The information sequence extracting circuit  312  extracts the block coding sequence from the arranged received signal (turbo coding sequence) without turbo decoding. Because, the turbo code is the systematic code, and comprises the block coding sequence Bn and the redundancy bits Yij which is attached after the block coding sequence Bn. Therefore, only if the information sequence extracting circuit  312  extracts the redundancy bits Yij from the stored received data  311   a , the block coding sequence Bn is extracted. 
   The turbo decoder  313  is coupled with the storing circuit  311 . The turbo decoder  313  decodes the stored received data  311   a  according to the control signal  315   a , and generates a turbo-decoded data (new block coding sequence)  313   a . The switch  314  is coupled with the information sequence extracting circuit  312  and the turbo decoder  313 . The switch  314  outputs either the latched data  312   a  or the turbo-decoded data  313   a  according to the control signal  315   a . The CRC detector  315  detects whether an error exists in the latched data  312   a  or the turbo-decoded data  313   a , and outputs the control signal  315   a , the latched data  312   a  or the turbo-decoded data  313   a  and a detection result  315   b  which shows whether an error is detected or not. The block decoder  316  decodes the latched data  312   a  or the turbo-decoded data  313   a.    
   Next, an operation of the apparatus for extracting an information sequence from transmitted data in a wireless communication system of the present invention will be described reference to  FIG. 4 .  FIG. 4  is a flow chart showing an operation of the apparatus of the present invention. 
   The deinterleaver  300  arranges an order of the received data to be in the previous order as it was at the transmitter side (S 401 ). The memory  3111  of the storing circuit  311  stores the arranged received data  300   a  (S 402 ). The control circuit  3112  of the storing circuit  311  instructs the memory  3111  to output the stored received data  311   a , according to the control signal  315   a . The AND circuit  3121  extracts the data from the stored received data  311   a  according to the control signal  317 . The D-type flip-flop  3122  of the information sequence extracting circuit  312  latches the extracted data  3121   a  according to the clock signal  318 , and outputs the latched data  312   a  (S 403 ). The switch  314  electrically connects the information sequence extracting circuit  312  and the CRC detector  315 . The CRC detector  315  detects whether an error exists in the latched data  312   a  (S 404 ). If no error is detected in the latched data  312   a , the latched data  312   a  and a CRC detection result  315   b  are output to the block decoder  316 . The block decoder  316  decodes the latched data  312   a  (S 407 ). 
   On the other hand, if error is detected in the latched data  312   a  (S 407 ), the CRC detector  315  outputs the control signal  315   a  having a high voltage level. The turbo decoder  313  decodes the stored received data  311   a  according to the control signal  315   a , and generates the turbo-decoded data  313   a  (S 405 ). The switch  314  electrically connects the turbo decoder  313  and the CRC detector  315 . The CRC detector  315  detects whether an error exists in the turbo-decoded data  313   a  (S 406 ). If no error is detected in the turbo-decoded data  313   a , the turbo-decoded data  313   a  and a CRC detection result  315   b  are output to the block decoder  316 . The block decoder  316  decodes the turbo-decoded data  313   a  (S 407 ). If error is detected in the turbo-decoded data  313   a , the control circuit  3112  instructs the memory  3111  to output next arranged transmitted data  300   a.    
   According to the apparatus for extracting an information sequence from received data in a wireless communication system and the method thereof, first, the received data is detected using CRC. Then, if no error is detected in the received data, the apparatus and method of the present invention does not turbo-decode. On the other hand, if error is detected in the received data, the apparatus and method of the present invention turbo-decodes the received data. Therefore, the apparatus and method of the present invention prevent electric power consumption from increasing. 
   While the preferred form of the present invention has been described, it is to be understood that modifications will be apparent to those skilled in the art without departing from the spirit of the invention. 
   The scope of the invention, therefore, is to be determined solely by the following claims.