Low memory and low latency cyclic prefix addition
AssigneeCisco Technology, Inc.
InventorsSantosh Anikhindi, Vincent K. Jones, IV
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Abstract
Systems and methods for appending cyclic prefixes to OFDM bursts while employing minimal additional memory and adding minimal latency are provided. This facilitates lower cost implementations of OFDM communication systems including systems that carry real time traffic such as telephony and video conferencing. The phases of frequency domain symbols are rotated prior to application of the IFFT so that cyclic prefix addition may be implemented as cyclic postfix addition. Cyclic postfix addition requires much less memory and imposes much less latency then cyclic prefix addition.
Claims15
In a multitone transmitter, a method for developing a multitone signal, the method comprising:
- developing a frequency domain burst of N frequency domain symbols;
- phase rotating said frequency domain symbols to produce phase-rotated frequency domain symbols;
- transforming said phase-rotated frequency domain symbols into a time domain burst;
- and
- appending to an end of said time domain burst a cyclic postfix duplicating a first v time domain symbols of said time domain burst;
- wherein N and v are positive integers and
- wherein said phase rotating is performed so as to make a result of said appending equivalent to an expected result of:
- transforming said frequency domain symbols into a second time domain burst without phase rotating said frequency domain symbols;
- and
- appending to a beginning of said second time domain burst a cyclic prefix duplicating a last v time domain symbols of said second time domain burst.
In a multitone communication system, apparatus for developing a multitone signal, said apparatus comprising:
- a phase rotator that receives a frequency domain burst of N frequency domain symbols and applies a phase rotation to said frequency domain symbols to produce phase rotated frequency domain symbols;
- a transform block that converts said phase rotated frequency domain symbols to a time domain burst;
- and
- an appending block that appends to an end of said time domain burst a cyclic postfix duplicating a first v time domain symbols of said time domain burst;
- wherein N and v are positive integers and
- wherein said phase rotator rotates phase so as to make an output of said appending block equivalent to an expected result of:
- transforming said frequency domain symbols into a second time domain burst without phase rotating said frequency domain symbols;
- and
- appending to a beginning of said second time domain burst a cyclic prefix duplicating a last v time domain symbols of said second time domain burst.
A computer program product for developing a multitone signal in a multitone communication system, said product comprising:
- code that develops a frequency domain burst of N frequency domain symbols;
- code that phase rotates said frequency domain symbols to produce phase rotated frequency domain symbols;
- code that transforms said phase rotated frequency domain symbols into a time domain burst;
- code that appends to an end of said time domain burst a cyclic postfix duplicating a first v time domain symbols of said time domain burst;
- wherein N and v are positive integers and;
- a computer-readable storage medium storing the codes;
- and
- wherein said code that phase rotates is used so as to make a result of said code that appends equivalent to an expected result of:
- transforming said frequency domain symbols into a second time domain burst without phase rotating said frequency domain symbols;
- and
- appending to a beginning of said second time domain burst a cyclic prefix duplicating a last v time domain symbols of said time domain burst.
In a multitone transmitter, apparatus for developing a multitone signal, the apparatus comprising:
- means for developing a frequency domain burst of N frequency domain symbols;
- means for phase rotating said frequency domain symbols to produce phase-rotated frequency domain symbols;
- means for transforming said phase-rotated frequency domain symbols into a time domain burst;
- and
- means for appending to an end of said time domain burst a cyclic postfix duplicating a first v time domain symbols of said time domain burst;
- wherein N and v are positive integers and
- wherein said means for phase rotating is used so as to make a result of said means for appending equivalent to an expected result of:
- transforming said frequency domain symbols into a second time domain burst without phase rotating said frequency domain symbols;
- and
- appending to a beginning of said second time domain burst a cyclic prefix duplicating a last v time domain symbols of said second time domain burst.
Dependencies are inferred from the claim text.