Backward-compatible long training sequences for wireless communication networks

Abstract

A network device for generating an expanded long training sequence with a minimal peak-to-average ratio. The network device includes a signal generating circuit for generating the expanded long training sequence. The network device also includes an Inverse Fourier Transform for processing the expanded long training sequence from the signal generating circuit and producing an optimal expanded long training sequence with a minimal peak-to-average ratio. The expanded long training sequence and the optimal expanded long training sequence are stored on more than 52 sub-carriers.

What is claimed: 
     
       1. A wireless communications device, comprising:
 a signal generator that generates an extended long training sequence; and 
 an Inverse Fourier Transformer operatively coupled to the signal generator, 
 wherein the Inverse Fourier Transformer processes the extended long training sequence from the signal generator and provides an optimal extended long training sequence with a minimal peak-to-average ratio, and 
 wherein at least the optimal extended long training sequence is carried by a greater number of subcarriers than a standard wireless networking configuration for an Orthogonal Frequency Division Multiplexing scheme, 
 wherein the optimal extended long training sequence is carried by exactly 56 active sub-carriers, and 
 wherein the optimal extended long training sequence is represented by encodings for indexed sub-carriers −28 to +28, excluding indexed sub-carrier 0 which is set to zero, as follows: 
 
       
         
           
                 
                 
                 
                 
                 
                 
                 
                 
               
                     
                 
                   Sub-carrier 
                   −28 
                   −27 
                   −26 
                   −25 
                   −24 
                   −23 
                   −22 
                 
                   Encoding 
                   +1 
                   +1 
                   +1 
                   +1 
                   −1 
                   −1 
                   +1 
                 
                   Sub-carrier 
                   −14 
                   −13 
                   −12 
                   −11 
                   −10 
                   −9 
                   −8 
                 
                   Encoding 
                   +1 
                   +1 
                   +1 
                   −1 
                   −1 
                   +1 
                   +1 
                 
                   Sub-carrier 
                   1 
                   2 
                   3 
                   4 
                   5 
                   6 
                   7 
                 
                   Encoding 
                   +1 
                   −1 
                   −1 
                   +1 
                   +1 
                   −1 
                   +1 
                 
                   Sub-carrier 
                   15 
                   16 
                   17 
                   18 
                   19 
                   20 
                   21 
                 
                   Encoding 
                   +1 
                   +1 
                   −1 
                   −1 
                   +1 
                   −1 
                   +1 
                 
                     
                 
                   Sub-carrier 
                   −21 
                   −20 
                   −19 
                   −18 
                   −17 
                   −16 
                   −15 
                 
                   Encoding 
                   +1 
                   −1 
                   +1 
                   −1 
                   +1 
                   +1 
                   +1 
                 
                   Sub-carrier 
                   −7 
                   −6 
                   −5 
                   −4 
                   −3 
                   −2 
                   −1 
                 
                   Encoding 
                   −1 
                   +1 
                   −1 
                   +1 
                   +1 
                   +1 
                   +1 
                 
                   Sub-carrier 
                   8 
                   9 
                   10 
                   11 
                   12 
                   13 
                   14 
                 
                   Encoding 
                   −1 
                   +1 
                   −1 
                   −1 
                   −1 
                   −1 
                   −1 
                 
                   Sub-carrier 
                   22 
                   23 
                   24 
                   25 
                   26 
                   27 
                   28 
                 
                   Encoding 
                   −1 
                   +1 
                   +1 
                   +1 
                   +1 
                   −1 
                   −1. 
                 
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       
        
       
     
     
       2. The wireless communications device according to  claim 1 , wherein at least the optimal extended long training sequence is carried by at least 56 active sub-carriers. 
     
     
       3. The wireless communications device according to  claim 2 , wherein the at least 56 active sub-carriers correspond to at least indexed sub-carriers −28 to +28.  
     
     
       4. The wireless communications device according to claim  2  1, wherein the optimal extended long training sequence has a minimum peak-to-average power ratio of 3.6 dB. 
     
     
       5. The wireless communications device according to  claim 1 , wherein at least the optimal extended long training sequence is carried by at least 63 active sub-carriers. 
     
     
       6. The wireless communications device according to  claim 5 , wherein the at least 63 active sub-carriers correspond to at least indexed sub-carriers −32 to +31. 
     
     
       7. The wireless communications device according to  claim 5 , wherein the optimal extended long training sequence has a minimum peak-to-average power ratio of 3.6 dB. 
     
     
       8. The wireless communications device according to  claim 1 , wherein a binary phase shift key encoding is used for each sub-carrier above the +26 indexed sub-carrier and below the −26 indexed sub-carrier. 
     
     
       9. The wireless communications device according to  claim 1 , wherein the Inverse Fourier Transformer comprises at least one of the following: an Inverse Fast Fourier Transformer and or an Inverse Discrete Fourier Transformer. 
     
     
       10. The wireless communications device according to  claim 1 , wherein the wireless communications device comprises one or more of the following: a personal digital assistant, a laptop computer, a personal computer, a processor, and a cellular phone. 
     
     
       11. The wireless communications device according to  claim 1 , wherein the wireless communications device comprises a wireless mobile communications device. 
     
     
       12. The wireless communications device according to  claim 1 , wherein the wireless communications device comprises one or more of the following: an access point and a base station. 
     
     
       13. The wireless communications device according to  claim 1 , wherein the wireless communications device is backwards compatible with legacy wireless local area network devices. 
     
     
       14. The wireless communications device according to  claim 1 , wherein the optimal extended long training sequence is longer than a long training sequence used by a legacy wireless local area network device in accordance with a legacy wireless networking protocol standard. 
     
     
       15. The wireless communications device according to  claim 14 , wherein the legacy wireless local area network device uses the optimal extended long training sequence to estimate a carrier frequency offset even though the optimal extended long training sequence is longer than the long training sequence that is specified by the legacy wireless networking protocol standard. 
     
     
       16. The wireless communications device according to  claim 15 , wherein the long training sequence that is specified by the legacy wireless networking protocol standard is maintained in the extended long training sequence or the optimal extended long training sequence. 
     
     
       17. The wireless communications device according to  claim 1 , wherein the wireless communications device decreases power back-off. 
     
     
       18. The wireless communications device according to  claim 1 , wherein the wireless communications device registers with one or more of the following: an access point and a base station. 
     
     
       19. The wireless communications device according to  claim 1 , wherein the extended long training sequence or the optimal extended long training sequence is encoded using binary phase shift key encoding on each of the 56 active subcarriers. 
     
     
       20. The wireless communications device according to  claim 1 , comprising:
 a symbol mapper operatively coupled to the signal generator, wherein the symbol mapper receives coded bits and generates symbols for each of 64 subcarriers of an Orthogonal Frequency Division Multiplexing sequence. 
 
     
     
       21. The wireless communications device according to claim 14, wherein the legacy wireless networking protocol standard for the Orthogonal Frequency Division Multiplexing scheme corresponds to exactly 52 active subcarriers. 
     
     
       22. The wireless communications device according to claim 21, wherein, for a long training sequence of the legacy wireless networking protocol standard, the indexed sub-carrier 0 is set to zero and encodings for the indexed sub-carriers −26 to +26 excluding the indexed sub-carrier 0 are: 
       
         
           
                 
                 
                 
                 
                 
                 
                 
                 
               
                     
                 
                   Sub-carrier 
                   −26 
                   −25 
                   −24 
                   −23 
                   −22 
                   −21 
                   −20 
                 
                   Encoding 
                   +1 
                   +1 
                   −1 
                   −1 
                   +1 
                   +1 
                   −1 
                 
                   Sub-carrier 
                   −13 
                   −12 
                   −11 
                   −10 
                   −9 
                   −8 
                   −7 
                 
                   Encoding 
                   +1 
                   +1 
                   −1 
                   −1 
                   +1 
                   +1 
                   −1 
                 
                   Sub-carrier 
                   1 
                   2 
                   3 
                   4 
                   5 
                   6 
                   7 
                 
                   Encoding 
                   +1 
                   −1 
                   −1 
                   +1 
                   +1 
                   −1 
                   +1 
                 
                   Sub-carrier 
                   14 
                   15 
                   16 
                   17 
                   18 
                   19 
                   20 
                 
                   Encoding 
                   −1 
                   +1 
                   +1 
                   −1 
                   −1 
                   +1 
                   −1 
                 
                     
                 
                 
                 
                 
                 
                 
                 
                 
                 
               
                     
                   Sub-carrier 
                   −19 
                   −18 
                   −17 
                   −16 
                   −15 
                   −14 
                 
                     
                   Encoding 
                   +1 
                   −1 
                   +1 
                   +1 
                   +1 
                   +1 
                 
                     
                   Sub-carrier 
                   −6 
                   −5 
                   −4 
                   −3 
                   −2 
                   −1 
                 
                     
                   Encoding 
                   +1 
                   −1 
                   +1 
                   +1 
                   +1 
                   +1 
                 
                     
                   Sub-carrier 
                   8 
                   9 
                   10 
                   11 
                   12 
                   13 
                 
                     
                   Encoding 
                   −1 
                   +1 
                   −1 
                   −1 
                   −1 
                   −1 
                 
                     
                   Sub-carrier 
                   21 
                   22 
                   23 
                   24 
                   25 
                   26 
                 
                     
                   Encoding 
                   +1 
                   −1 
                   +1 
                   +1 
                   +1 
                   +1. 
                 
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
               
            
             
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       
        
       
     
     
       23. The wireless communications device according to claim 22, wherein:
 the Inverse Fourier Transformer comprises an Inverse Fast Fourier Transformer or an Inverse Discrete Fourier Transformer;   the wireless communications device comprises one or more of the following: a personal digital assistant, a laptop computer, a personal computer, a cellular phone, an access point, a processor, and a base station;   the wireless communications device is backwards compatible with the legacy wireless local area network device;   the legacy wireless local area network device uses the optimal extended long training sequence to estimate a carrier frequency offset even though the optimal extended long training sequence is longer than the long training sequence that is specified by the legacy wireless networking protocol standard;   the wireless communications device decreases power back-off;   the extended long training sequence or the optimal extended long training sequence is encoded using binary phase shift key encoding on each of the 56 active subcarriers; and   the wireless communications device further comprises a symbol mapper operatively coupled to the signal generator, wherein the symbol mapper receives coded bits and generates symbols for each of 64 subcarriers of an Orthogonal Frequency Division Multiplexing sequence.   
     
     
       24. The wireless communications device according to claim 1, wherein at least one output of the Inverse Fourier Transformer is operatively coupled to at least one digital-to-analog converter. 
     
     
       25. The wireless communications device according to claim 1, wherein at least one output of the Inverse Fourier Transformer is operatively coupled to multiple digital-to-analog converters. 
     
     
       26. The wireless communications device according to claim 1, wherein an input of the signal generator is operatively coupled to a frequency-domain windower. 
     
     
       27. The wireless communications device according to claim 1, wherein an output of the Inverse Fourier Transformer is operatively coupled to a time-domain windower. 
     
     
       28. The wireless communications device according to claim 27, wherein an output of the time-domain windower is operatively coupled to at least one digital-to-analog converter. 
     
     
       29. The wireless communication device according to claim 1, wherein an output of the Inverse Fourier Transformer is operatively coupled to a digital transmit filter. 
     
     
       30. The wireless communications device according to claim 1, wherein an output of the Inverse Fourier Transformer is operatively coupled to a parallel-to-serial convertor.