Transmission security for wireless communications

A transmission level security system for communications systems comprising:

• means for forming a plurality of digital signals representing a symbol to be transmitted over a communication medium, wherein respective ones of the plurality of digital signals are modulated onto respective ones of a plurality of subcarriers according to a multiple carrier modulation scheme;
• and
• means for introducing at a transmitter a predetermined group delay distortion in one or more of the plurality of subcarriers, such that portions of the one or more of the plurality of carriers will be received outside of a time window corresponding to the symbol at a receiver.

A method of transmission level security in a communication system comprising:

• forming a plurality of digital signals representing a symbol to be transmitted over a communication medium, wherein respective ones of the plurality of digital signals are modulated onto respective ones of a plurality of subcarriers according to a multiple carrier modulation scheme;
• and
• introducing at a transmitter a group delay distortion in one or more of the plurality of subcarriers but less than all of the plurality of subcarriers, such that portions of the one or more of the plurality of subcarriers will be received outside of a time window corresponding to the symbol at a receiver.

A method of transmission level security in a communication system comprising:

• forming a signal to be transmitted over a communication medium;
• and
• introducing at a transmitter a predetermined group delay distortion in the signal, such that portions of the signal will be received outside of a time window corresponding to the signal at a receiver.

A method of transmission level security for time windowed communication systems comprising:

• receiving a signal, wherein the signal has undergone a predetermined group delay distortion at a transmitter, wherein the predetermined group delay distortion is such that portions of the signal will be received outside of a nominal window of time corresponding to the signal at a receiver;
• and
• substantially removing the predetermined group delay distortion from the signal such that the signal fits within the nominal window of time.

A transmitter implementing transmission level security for wireless communications comprising:

• a baseband modulator producing a signal to be transmitted to a receiver;
• and
• an encryptor coupled to the baseband modulator for introducing a predetermined group delay distortion in the signal such that portions of the signal will be received outside of a nominal window of time corresponding to the signal at the receiver.