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. An apparatus, comprising:
a baseband processor coupled to transmit circuitry and at least one antenna, wherein the baseband processor is configured to:
transmit signaling to a transmitter for transform selection;
receive, based on the transmitted signaling, one of transformed or non-transformed orthogonal frequency division multiplexing (OFDM) uplink signals,
wherein the transformed OFDM uplink signals include a first plurality of symbols that have undergone coding and modulation, discrete Fourier transform (DFT) transformation, and an inverse Fast Fourier transform (IFFT),
wherein the non-transformed OFDM uplink signals include a second plurality of symbols that have undergone coding and modulation and the IFFT; wherein the second plurality of symbols have not undergone the DFT transform; wherein the non-transformed OFDM uplink signals include a plurality of clusters, wherein a cluster is a set of contiguous subcarriers.
2. The apparatus of claim 1 , wherein the non-transformed OFDM uplink signals support two modes: a first mode wherein the clusters of non-transformed OFDM uplink signals are contiguous and a second mode wherein the clusters of non-transformed OFDM uplink signals are non-contiguous.
3. The apparatus of claim 2 , wherein the transformed OFDM uplink signals support the first mode and the second mode.
4. The apparatus of claim 1 ,
wherein transformed OFDM uplink signals are selected based at least in part on the first plurality of symbols corresponding to an uplink control channel.
5. The apparatus of claim 1 ,
wherein the baseband processor is further configured to:
receive a plurality of pilot signals, wherein the pilot signals are time-division multiplexed with the transformed or non-transformed OFDM uplink signals.
6. The apparatus of claim 5 ,
wherein the plurality of pilot signals for each time-division slot are comprised within a plurality of contiguous sub carriers in frequency.
7. The apparatus of claim 1 ,
wherein the transformed OFDM uplink signals and the non-transformed OFDM uplink signals are time-division multiplexed.
8. A base station, comprising:
at least one antenna;
transmit circuitry coupled to the at least one antenna; and
a baseband processor coupled to the transmit circuitry and the at least one antenna, wherein the base station is configured to:
transmit signaling to a transmitter for transform selection;
receive, based on the transmitted signaling, one of transformed or non-transformed orthogonal frequency division multiplexing (OFDM) uplink signals,
wherein the transformed OFDM uplink signals include a first plurality of symbols that have undergone coding and modulation, discrete Fourier transform (DFT) transformation, and an inverse Fast Fourier transform (IFFT),
wherein the non-transformed OFDM uplink signals include a second plurality of symbols that have undergone coding and modulation and the IFFT; wherein the second plurality of symbols have not undergone the DFT transform; wherein the non-transformed OFDM uplink signals include a plurality of clusters, wherein a cluster is a set of contiguous subcarriers.
9. The base station of claim 8 , wherein the non-transformed OFDM uplink signals support two modes: a first mode wherein the clusters of non-transformed OFDM uplink signals are contiguous and a second mode wherein the clusters of non-transformed OFDM uplink signals are non-contiguous.
10. The base station of claim 9 , wherein the transformed OFDM uplink signals support the first mode and the second mode.
11. The base station of claim 8 ,
wherein transformed OFDM uplink signals are selected based at least in part on the first plurality of symbols corresponding to an uplink control channel.
12. The base station of claim 8 ,
wherein the baseband processor is further configured to:
receive a plurality of pilot signals, wherein the pilot signals are time-division multiplexed with the transformed or non-transformed OFDM uplink signals.
13. The base station of claim 12 ,
wherein the plurality of pilot signals for each time-division slot are comprised within a plurality of contiguous sub carriers in frequency.
14. The base station of claim 8 ,
wherein the transformed OFDM uplink signals and the non-transformed OFDM uplink signals are time-division multiplexed.
15. A method for operating a base station, the method comprising:
transmitting signaling to a transmitter for transform selection;
receiving, based on the transmitted signaling, one of transformed or non-transformed orthogonal frequency division multiplexing (OFDM) uplink signals,
wherein the transformed OFDM uplink signals include a first plurality of symbols that have undergone coding and modulation, discrete Fourier transform (DFT) transformation, and an inverse Fast Fourier transform (IFFT),
wherein the non-transformed OFDM uplink signals include a second plurality of symbols that have undergone coding and modulation and the IFFT; wherein the second plurality of symbols have not undergone the DFT transform; wherein the non-transformed OFDM uplink signals include a plurality of clusters, wherein a cluster is a set of contiguous subcarriers.
16. The method of claim 15 , wherein the non-transformed OFDM uplink signals support two modes: a first mode wherein the clusters of non-transformed OFDM uplink signals are contiguous and a second mode wherein the clusters of non-transformed OFDM uplink signals are non-contiguous.
17. The method of claim 15 ,
wherein transformed OFDM uplink signals are selected based at least in part on the first plurality of symbols corresponding to an uplink control channel.
18. The method of claim 15 , the method further comprising:
receiving a plurality of pilot signals, wherein the pilot signals are time-division multiplexed with the transformed or non-transformed OFDM uplink signals.
19. The method of claim 18 ,
wherein the plurality of pilot signals for each time-division slot are comprised within a plurality of contiguous sub carriers in frequency.
20. The method of claim 15 ,
wherein the transformed OFDM uplink signals and the non-transformed OFDM uplink signals are time-division multiplexed.