Apparatus and method for transmitting data with conditional zero padding

The method of claim 3, wherein the zero tail comprises a minimum amount of zero tail so that a length of the zero tail in addition to the fixed length for cyclic prefixes is greater than or equal to the channel delay spread.

The method of claim 7, comprising, for a given OFDM symbol period:nprocessing N inputs with a Discrete Fourier Transform, DFT, where N is a fixed DFT size;performing subcarrier mapping on an output of the DFT;processing an output of the subcarrier mapping with an Inverse Fast Fourier Transform, IFFT;performing parallel to serial conversion on an output of the IFFT, and applying the cyclic prefix;wherein when it is determined that the cyclic prefix is long enough to avoid ISI, the N inputs are N data symbols, and when it is determined that the cyclic prefix is not long enough to avoid ISI, the N inputs include N-M data symbols and M zeros, where M represents an amount of zero padding.

The transmitter of claim 16, wherein the circuitry comprises:na padding component configured to pad a stream of data symbols with an amount of zero padding determined in accordance with an estimated channel delay spread to avoid ISI between consecutive OFDM symbols to be transmitted;a Discrete Fourier Transform, DFT, component configured to transform the data that has been padded from a time domain into a frequency domain;a subcarrier mapping component configured to map the data in the frequency domain to a frequency sub-band;an Inverse Fast Fourier Transform, IFFT, component configured to transform the data back from the frequency domain to the time domain; anda parallel to serial component configured to convert the data in the time domain into a serial signal and append the cyclic prefix therein prior to transmission;wherein the serial signal comprises OFDM symbols such that each OFDM symbol is preceded by a cyclic prefix and the OFDM symbol has enough zero padding to avoid ISI between consecutive OFDM symbols;wherein, for a given OFDM symbol period, the DFT component accepts N inputs, where N is a fixed DFT size;wherein when it is determined that the cyclic prefix is long enough to avoid ISI, the N inputs are N data symbols, and when it is determined that the cyclic prefix is not long enough to avoid ISI, the N inputs include N-M data symbols and M zeros, where M represents an amount of zero padding.

The transmitter of claim 19, wherein the zero tail comprises a minimum amount of zero tail so that a length of the zero tail in addition to the fixed length for cyclic prefixes is greater than or equal to the channel delay spread.

The method of claim 28 wherein the step of determining includes obtaining an estimate of the channel delay spread.

The method of claim 30 wherein the step of inserting zero padding further includes inserting zero head into the fixed length symbol.