초록 ▼

Multipoint broadcasting requires that the downlink-channel information be available at collaborating base stations. Methods and apparatus for wideband analog channel feedback are described that provide downlink-channel information feedback from mobile users to base stations via uplink channels, and

Multipoint broadcasting requires that the downlink-channel information be available at collaborating base stations. Methods and apparatus for wideband analog channel feedback are described that provide downlink-channel information feedback from mobile users to base stations via uplink channels, and that use very few or no resources of the RAT of the wireless cellular network. Also described are methods and apparatus that perform channel-feedback signal cancellation at base stations to reduce its interference on the uplink-traffic signal. Wideband analog channel feedback is adaptable to the feedback bandwidth in uplink, and it offers frequency diversity to combat the deep fading in feedback channels. Wideband analog channel feedback is also applicable to uplink channel-information feedback. Applications of the described methods and apparatus include multipoint broadcasting in a wireless cellular network, and more generally, channel feedback between two communicating devices in a communications network.

대표청구항 ▼

1. A method for channel-information feedback in a communications network, having at least one channel-acquiring device, at least one channel-feedback device, at least one forward channel from said channel-acquiring device to channel-feedback device, and, at least one reverse channel from said channe

1. A method for channel-information feedback in a communications network, having at least one channel-acquiring device, at least one channel-feedback device, at least one forward channel from said channel-acquiring device to channel-feedback device, and, at least one reverse channel from said channel feedback device to channel-acquiring device, comprising: (a) sending a forward-channel signal over said forward channel from said channel-acquiring device,(b) generating a first forward-channel estimate from said forward-channel signal at said channel-feedback device,(c) generating a feedback-information sequence that is a function of said first forward-channel estimate at said channel-feedback device,(d) generating a channel-feedback signal at said channel-feedback device by convolving said feedback-information sequence with a predetermined feedback-pilot sequence,(e) combining said channel-feedback signal with a reverse-channel traffic signal to form a combined reverse-channel signal at said channel-feedback device,(f) sending said combined reverse-channel signal over said reverse channel to said channel-acquiring device,(g) correlating said combined reverse-channel signal received at said channel-acquiring device with said feedback-pilot sequence to generate a pilot-correlation output,(h) generating a reverse-channel estimate from said combined reverse-channel signal received at said channel-acquiring device, and(i) generating a second forward-channel estimate at said channel-acquiring device from said pilot-correlation output and said reverse-channel estimate,whereby said channel-acquiring device acquires said second forward-channel estimate as the forward-channel estimate. 2. The method of claim 1, wherein said feedback-pilot sequence is a pseudo-random noise (PN) sequence. 3. The method of claim 1, wherein said feedback-pilot sequence is from a family of orthogonal sequences. 4. The method of claim 1, wherein said feedback-information sequence is said first forward-channel estimate, and said first forward-channel estimate is the estimate of the forward-channel impulse response sequence. 5. The method of claim 1, wherein said communications network is a wireless cellular network with a radio access technology (RAT). 6. The method of claim 5, wherein said RAT is code-division multiple access (CDMA), and said feedback-pilot sequence is a scrambling/spreading sequence of the CDMA. 7. The method of claim 5, wherein said channel-feedback signal is made to be independent of said RAT, whereby said channel-feedback signal uses no resources of said RAT. 8. The method of claim 5, wherein said channel-acquiring device is a base station, said channel-feedback device is a mobile user, said forward channel is a downlink channel, and said reverse channel is an uplink channel. 9. The method of claim 5, wherein said channel-acquiring device is a mobile user, said channel-feedback device is a base station, said forward channel is an uplink channel, and said reverse channel is a downlink channel. 10. The method of claim 1, wherein generating said second forward-channel estimate uses the method of zero-forcing (ZF) to generate said second forward-channel estimate from said pilot-correlation output and said reverse-channel estimate. 11. The method of claim 1, wherein generating said second forward-channel estimate uses the method of minimum mean-square error (MMSE) to generate said second forward-channel estimate from said pilot-correlation output and said reverse-channel estimate. 12. The method of claim 1, wherein said channel-acquiring device applies channel-feedback signal cancellation to decoding said reverse-channel traffic, further comprising: (a) generating a reconstructed channel-feedback signal with said pilot-correlation out-put and said feedback-pilot sequence, and(b) generating an updated reverse-channel traffic signal by subtracting said reconstructed channel-feedback signal from said combined reverse-channel signal received at said channel-acquiring device,whereby said channel-acquiring device uses said updated reverse-channel traffic for decoding. 13. The method of claim 12, wherein said channel-acquiring device applies said channel-feedback signal cancellation multiple times to cancel multiple channel-feedback signals. 14. The method of claim 12, wherein said channel-acquiring device applies said channel-feedback signal cancellation to cancel the channel-feedback signals from other channel-feedback devices to other channel-acquiring devices. 15. The method of claim 12, wherein said channel-acquiring device applies said channel-feedback signal cancellation iteratively, further comprising: (a) decoding said reverse-channel traffic,(b) generating a reconstructed reverse-channel traffic signal, and(c) generating an updated channel-feedback signal by subtracting said reconstructed reverse-channel traffic signal from said combined reverse-channel signal received at said channel-acquiring device,whereby said channel-acquiring device uses said updated channel-feedback signal for generating said reconstructed channel-feedback signal and said second forward-channel estimate. 16. The method of claim 1, wherein generating said channel-feedback signal further comprises frequency-scaling said channel-feedback signal to fit the bandwidth of said reverse channel if it is different from the bandwidth of said forward channel. 17. The method of claim 1, wherein generating said channel-feedback signal further comprises manipulating said channel-feedback signal to fit the allowable frequency region for channel feedback within said bandwidth of said reverse channel. 18. The method of claim 17, wherein manipulating said channel-feedback signal further comprises at least one of: (a) frequency-scaling,(b) frequency-shifting,(c) frequency-splitting,and any combination thereof. 19. The method of claim 1, wherein generating said channel-feedback signal further comprises frequency-blocking said channel-feedback signal so that said channel-feedback signal at certain blockable frequencies is not transmitted to said channel-acquiring device. 20. The method of claim 1, wherein generating said channel-feedback signal further comprises incorporating the frequency diversity into said channel-feedback signal. 21. The method of claim 20, wherein said frequency diversity is shift-and-overlap. 22. The method of claim 20, wherein said frequency diversity is scale-and-duplicate. 23. The method of claim 22, wherein said scale-and-duplicate frequency diversity is implemented by oversampling said feedback-information sequence. 24. The method of claim 22, wherein said scale-and-duplicate frequency diversity further comprises frequency-shifting.