Spectral shaping for multiband OFDM transmitters with time spreading

Abstract

A method of shaping an orthogonal frequency division multiplexing (OFDM) signal spectrum of a transmitted signal is disclosed. An input signal including an input component is received and a first instance of the input component is generated. The method also includes determining that a second instance of the input component is to be different than the first instance. The second instance of the input component that is different from the first instance is generated. An output signal to be transmitted is generated and includes the first instance and the second instance of the input component.

1 . A method of shaping an orthogonal frequency division multiplexing (OFDM) signal spectrum of a transmitted signal, comprising:
 receiving an input signal including an input component;   generating a first instance of the input component;   determining that a second instance of the input component is to be different than the first instance;   generating the second instance of the input component that is different from the first instance; and   generating an output signal to be transmitted, wherein the output signal includes the first instance and the second instance.   
   
   
       2 . A method as recited in  claim 1 , wherein the input component is an OFDM symbol. 
   
   
       3 . A method as recited in  claim 1 , wherein the first instance and the second instance is are transmitted on a same transmission band. 
   
   
       4 . A method as recited in  claim 1  further comprising transmitting the output signal using frequency band hopping. 
   
   
       5 . A method as recited in  claim 1 , wherein the input signal includes a plurality of input components and all second instances of the plurality of input components are determined to be different than their corresponding first instance. 
   
   
       6 . A method as recited in  claim 1 , wherein generating the second instance of the input component includes inversion. 
   
   
       7 . A method as recited in  claim 1 , wherein generating the second instance of the input component includes swapping I and Q elements. 
   
   
       8 . A method as recited in  claim 1 , wherein generating the second instance of the input component includes complex conjugation. 
   
   
       9 . A method as recited in  claim 1 , wherein generating the second instance of the input component includes phase shifting. 
   
   
       10 . A method as recited in  claim 1 , wherein generating the second instance of the input component includes using a time domain representation. 
   
   
       11 . A method as recited in  claim 1  further comprising generating a pseudo random number, wherein the pseudo random number is used in determining that the second instance of the input component is to be different than the first instance. 
   
   
       12 . A method as recited in  claim 1 , wherein:
 the input signal includes a plurality of input components; and   a pseudo random sequence is used in determining which of the second instances of the plurality of input components are to be different than their corresponding first instance.   
   
   
       13 . A method as recited in  claim 1 , wherein:
 the input signal includes a plurality of input components;   a pseudo random sequence is used in determining which of the second instances of the plurality of input components are to be different than their corresponding first instance; and   in the event there are more input components than elements in the pseudo random sequence, the pseudo random sequence is reused.   
   
   
       14 . A method as recited in  claim 1 , wherein:
 the input signal includes a plurality of input components; and   a sequence used in the generation of pilots is used in determining which of the second instances of the plurality of input components are to be different than their corresponding first instance.   
   
   
       15 . A system for shaping an orthogonal frequency division multiplexing (OFDM) signal spectrum of a transmitted signal, comprising:
 an interface configured to receive an input signal including an input component; and   a signal processor configured to:
 generate a first instance of the input component; 
 determine that a second instance of the input component is to be different than the first instance; 
 generate the second instance of the input component that is different from the first instance; and 
 generate an output signal to be transmitted, wherein the output signal includes the first instance and the second instance. 
   
   
   
       16 . A system as recited in  claim 15 , wherein the first instance and the second instance are transmitted on a same transmission band. 
   
   
       17 . A system as recited in  claim 15 , wherein generating the second instance of the input component includes inversion. 
   
   
       18 . A system as recited in  claim 15 , wherein:
 the input signal includes a plurality of input components; and   a pseudo random sequence is used in determining which of the second instances of the plurality of input components are to be different than their corresponding first instance.   
   
   
       19 . A computer program product for shaping an orthogonal frequency division multiplexing (OFDM) signal spectrum of a transmitted signal, the computer program product being embodied in a computer readable medium and comprising computer instructions for:
 receiving an input signal including an input component;   generating a first instance of the input component;   determining that a second instance of the input component is to be different than the first instance;   generating the second instance of the input component that is different from the first instance; and   generating an output signal to be transmitted, wherein the output signal includes the first instance and the second instance.   
   
   
       20 . A computer program product as recited in  claim 19 , wherein the first instance and the second instance are transmitted on a same transmission band. 
   
   
       21 . A computer program product as recited in  claim 19 , wherein generating the second instance of the input component includes inversion. 
   
   
       22 . A computer program product as recited in  claim 19 , wherein:
 the input signal includes a plurality of input components; and   a pseudo random sequence is used in determining which of the second instances of the plurality of input components are to be different than their corresponding first instance.