Method and system for combining DFT-transformed OFDM and non-transformed OFDM
Methods and systems are provided that enable an OFDM transmitter to be used for transmitting conventional OFDM or a form of transformed OFDM. A technique is provided for transforming a coded and modulated sequence of samples prior to an IFFT that enables the transformed sequence of samples to be transmitted using conventional OFDM or transformed OFDM. The selection of a transform function for transforming the coded and modulated sequence of samples may be based on optimizing the transform function for particular operating conditions between the transmitter and receiver. In some embodiments of the invention OFDM and time transformed OFDM are multiplexed in time and/or frequency in a transmission frame. In some embodiments of the invention a pilot pattern is provided in which the pilot are sent using OFDM and data is sent using OFDM and/or transformed OFDM.
1. A wireless communication system, comprising:
an antenna;
a baseband processor configured to apply a discrete Fourier transform (DFT) transformation to a first plurality of symbols conforming to a first traffic type to obtain an intermediate set of symbols, and perform an inverse Fast Fourier transform (IFFT) on a first mapped set of symbols corresponding to the intermediate set of symbols to produce a set of transformed orthogonal frequency-division multiplexing (OFDM) signals;
transmit circuitry coupled to the baseband processor and configured to receive the transformed OFDM signals and transmit a first signal using the transformed OFDM signals via the antenna;
wherein the baseband processor is further configured to perform an inverse Fast Fourier transform (IFFT) on a second mapped set of symbols corresponding to a second plurality of symbols conforming to a second traffic type to generate non-transformed OFDM signals, wherein, in generating the non-transformed OFDM signals, the baseband processor does not apply a DFT transformation; and
wherein the transmit circuitry is further configured to receive the non-transformed OFDM signals and transmit a second signal using the non-transformed OFDM signals via the antenna.
2. The wireless communication system of claim 1 , wherein the second traffic type corresponds to a control channel, wherein the first traffic type does not correspond to the control channel.
3. The wireless communication system of claim 1 , wherein the second traffic type corresponds to control information, wherein the first traffic type corresponds to non-control information.
4. The wireless communication system of claim 1 , wherein the first traffic type corresponds to data modulation symbols, wherein the second traffic type corresponds to pilot sequence symbols.
5. The wireless communication system of claim 1 , wherein the first plurality of symbols is transmitted at a first time, wherein the second plurality of symbols is transmitted at a second time.
6. The wireless communication system of claim 1 , wherein the wireless communication system is a mobile terminal.
7. The wireless communication system of claim 1 , wherein the wireless communication system is a base station.
8. The wireless communication system of claim 1 , wherein the each of first and second traffic types do not correspond to pilot sequence symbols.
9. A method for operating a wireless communication system, the method comprising:
applying, by the baseband processor, a discrete Fourier transform (DFT) transformation to a first plurality of symbols conforming to a first traffic type to obtain an intermediate set of symbols;
generating, by the baseband processor, a first mapped set of symbols corresponding to the intermediate set of symbols;
performing, by the baseband processor, an inverse Fast Fourier transform (IFFT) on the first mapped set of symbols to produce a set of transformed orthogonal frequency-division multiplexing (OFDM) signals;
transmitting, by the baseband processor via transmit circuitry of the wireless communication system, the transformed OFDM signals using one or more antennae;
generating, by the baseband processor, a second mapped set of symbols corresponding to a second plurality of symbols conforming to a second traffic type;
performing, by the baseband processor, an inverse Fast Fourier transform (IFFT) on the second mapped set of symbols to generate non-transformed OFDM signals, wherein, in generating the non-transformed OFDM signals, a DFT transformation is not applied to the second plurality of symbols; and
transmitting, by the base band processor via the transmit circuitry of the wireless communication system, the non-transformed OFDM signals using the one or more antennae.
10. The method of claim 9 , wherein the second traffic type corresponds to a control channel, wherein the first traffic type does not correspond to the control channel.
11. The method of claim 9 , wherein the second traffic type corresponds to control information, wherein the first traffic type corresponds to non-control information.
12. The method of claim 9 , wherein the first traffic type corresponds to data modulation symbols, wherein the second traffic type corresponds to pilot sequence symbols.
13. The method of claim 9 , wherein the first plurality of symbols is transmitted at a first time, wherein the second plurality of symbols is transmitted at a second time.
14. The method of claim 9 , wherein the wireless communication system is a mobile terminal.
15. The method of claim 9 , wherein the wireless communication system is a base station.
16. An apparatus, comprising:
a baseband processor configured to receive a first plurality of symbols conforming to a first traffic type, apply a discrete Fourier transform (DFT) transformation to the first plurality of symbols to obtain an intermediate set of symbols, and perform an inverse Fast Fourier transform (IFFT) on a first mapped set of symbols corresponding to the intermediate set of symbols to produce a set of transformed orthogonal frequency-division multiplexing (OFDM) signals;
wherein the baseband processor is further configured to output the transformed OFDM signals to transmit circuitry for transmission;
wherein the baseband processor is further configured to receive a second plurality of symbols conforming to a second traffic type and perform an inverse Fast Fourier transform (IFFT) on a second mapped set of symbols corresponding to the second plurality of symbols, wherein said non-transformed OFDM does not include the DFT transformation to produce non-transformed OFDM signals; and
wherein the baseband processor is further configured to output the non-transformed OFDM signals to transmit circuitry for transmission.
17. The apparatus of claim 16 , wherein the second traffic type corresponds to a control channel, wherein the first traffic type does not correspond to the control channel.
18. The apparatus of claim 16 , wherein the second traffic type corresponds to control information, wherein the first traffic type corresponds to non-control information.
19. The apparatus of claim 16 , wherein the first traffic type corresponds to data modulation symbols, wherein the second traffic type corresponds to pilot sequence symbols.
20. The apparatus of claim 16 , wherein the transformed OFDM signals are transmitted at a first time, wherein the non-transformed OFDM signals are transmitted at a second time.