Efficient employment of digital upsampling using IFFT in OFDM systems for simpler analog filtering
AssigneeQUALCOMM Incorporated
InventorsRaghuraman Krishnamoorthi, Fuyun Ling, Rajiv Vijayan
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Abstract
Systems and methods are provided for transmitting OFDM information via IFFT up-sampling components that transmit data at a higher sampling rate than conventional systems to simplify filter requirements and mitigate leakage between symbols. In one embodiment, an NL point IFFT is performed on a zero inserted set of frequency domain symbols. In another embodiment, the NL point IFFT is further optimized by exploiting the fact that (N−1) L of the frequency domain symbols are zero. This enables an embodiment that consists of a pre-processor that multiplies the input samples by complex phase factors, followed by L point IFFTs.
Claims29
A method for transmitting OFDM information, comprising:
- determining a set of sub-carriers to broadcast in an OFDM network;
- and
- performing a transform at N sample multiples over the sub-carriers to mitigate filter requirements or noise generation in the network, where N is an integer greater than or equal to 2.
A transmitter module for a wireless network system, comprising:
- a processor to generate a carrier subset for a transmitter;
- a clock adapted to operate at multiples of a Nyquist rate for the transmitter;
- and
- a transform component to generate samples according to at least twice the Nyquist rate in order to mitigate filter requirements for the transmitter.
A system for transmitting OFDM information in a network, comprising:
- means for transmitting a symbol stream;
- means for transforming the symbol stream according to at least two multiples of a Nyquist sampling rate;
- and
- means for receiving the symbol stream in the network.
A machine readable medium having machine executable instructions stored thereon, comprising:
- determining a carrier subset for a transmitter;
- applying zero padding to a frequency domain symbol set to produce at least twice the number of frequency domain symbols;
- and
- applying the extended set of symbols to an IFFT to generate samples for transmission in a network.
A machine readable medium having a data structure stored thereon, comprising:
- a plurality of data fields storing a transmitter symbol set;
- and
- a plurality of data fields to perform an IFFT on the symbol set, where the IFFT is divided into at least two data processing fields;
- and
- employing at least one of the data processing fields for zero padding operations.
A wireless communications transmitter, comprising:
- a memory that stores an IFFT to perform an up-sampling operation;
- and
- a processor to insert zeros that extend a number of frequency domain symbols that are submitted to the up-sampling operation.
A wireless communications network, comprising:
- a base station adapted to perform Inverse Fast Fourier Transforms (IFFT) of a symbol set at an increased sample multiple, where the sample multiple is at least two times over a Nyquist sampling criterion;
- and
- at least one wireless receiver to receive the symbol set across the wireless communications network.
Dependencies are inferred from the claim text.