Reducing inter-carrier interference in ofdm and ofdma systems by time sample scaling based on cyclic prefix samples
OwnerAssaf Prihed, Eran Goldsteininventors
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Abstract
In described embodiments, an orthogonal frequency multiplexing (OFDM) system reduces inter-carrier interference (“ICI”) of a received signal. In general, the ICI is reduced, within software, hardware, or both, by scaling of receive samples according to scaling factors derived from cyclic prefix samples and correlated samples in a received OFDM symbol.
Claims14
A method of reducing inter-carrier interference in a signal received from a channel, the method comprising:
- detecting a cyclic prefix of an orthogonal frequency division multiplexing (“OFDM”) symbol having beginning portion and an ending portion, the cyclic prefix being within the end portion of the OFDM symbol;
- comparing the beginning portion of the OFDM symbol and the cyclic prefix at the ending portion of the OFDM symbol;
- deriving fading changing rate parameters for the comparison of the beginning and the cyclic prefix at the ending portion of the OFDM symbol;
- performing an interpolation using the derived parameters, thereby estimating an inverse fading scalar;
- multiplying the OFDM symbol by the inverse fading scalar;
- performing a frequency domain transform on the OFDM symbol to generate a constant fading;
- and
- removing the constant fading from the OFDM symbol.
A method of generating an OFDM symbol for user data, the method for reducing inter-carrier interference in a wireless electronic signal carrying the OFDM symbol through a channel, the method comprising:
- generating, by applying an inverse frequency domain transform to a block of data, an orthogonal frequency division multiplexing (“OFDM”) symbol having a beginning portion and an ending portion;
- generating a cyclic prefix for the OFDM symbol;
- and
- modifying the OFDM symbol in a transmission sequence such that the beginning portion of the modified OFDM symbol is substantially equivalent to the ending portion of the modified OFDM symbol with the cyclic prefix as the ending portion of the modified OFDM symbol;
- wherein the step of generating the cyclic prefix generates a relatively short cyclic prefix between approximately 10% and approximately 35% of a time of the OFDM symbol prior to modifying the OFDM symbol by the cyclic prefix.
A non-transitory machine-readable storage medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method for generating an orthogonal frequency division multiplexing (“OFDM”) symbol for user data, the method for reducing inter-carrier interference in a wireless electronic signal transferring the OFDM symbol through a channel, comprising the steps of:
- detecting a cyclic prefix of an OFDM symbol having beginning portion and an ending portion, the cyclic prefix within the end portion of the OFDM symbol;
- comparing the beginning portion of the OFDM symbol and the cyclic prefix at the ending portion of the OFDM symbol;
- deriving fading changing rate parameters for the comparison of the beginning and the cyclic prefix at the ending portion of the OFDM symbol;
- performing an interpolation using the derived parameters, thereby estimating an inverse fading scalar;
- multiplying the OFDM symbol by the inverse fading scalar;
- performing a frequency domain transform on the OFDM symbol to generate a constant fading;
- and
- removing the constant fading from the OFDM symbol.
Dependencies are inferred from the claim text.