Method of a receiver estimating a plurality of channels
View Patent ↗A method and apparatus of a receiver estimating a plurality of channels is disclosed. The method includes the receiver receiving a composite signal. The composite signal includes a signal from each of a plurality of transmission antennas, wherein the signal of each transmission antenna includes a delay relative to other signals of other antennas. The receiver estimates channels between the receiver and the plurality of transmission antennas based on amplitude and a phase of a received composite signal, at a plurality of frequencies.
1. A method for estimating a plurality of channels at a receiver, comprising:
receiving a composite signal comprising a signal sent from each of a plurality of transmission antennas, the signal sent from each of the plurality of transmission antennas comprising a cyclic delay relative to the signal sent from other ones of the plurality of transmission antennas; and
estimating channels between the receiver and the plurality of transmission antennas based on an amplitude and a phase of the composite signal at a plurality of frequencies,
wherein the signal sent from each of the plurality of transmission antennas comprises the cyclic delay during an entirety of a preamble of a downlink frame, an entirety of a MAP of the downlink frame, and only a portion of a data part of the downlink frame.
2. The method of claim 1 , wherein the cyclic delay comprises at least one of Cyclic Delay Diversity (CDD) and Cyclic Shift Transmit Diversity CSTD.
3. The method of claim 1 , wherein the signal sent from each of the plurality of transmission antennas additionally comprises an amplitude variation relative to the signal sent from the other ones of the plurality of transmission antennas.
4. The method of claim 1 , wherein the signal sent from each of the plurality of transmission antennas is an OFDM signal.
5. The method of claim 1 , wherein estimating the channels between the receiver and the plurality of transmission antennas further comprise:
using channel tap delays to estimate the channels.
6. The method of claim 5 , further comprising:
estimating the channel tap delays by recognizing repetition of power delay profiles associated with the channels.
7. The method of claim 1 , further comprising:
receiving information regarding the cyclic delay of the signal sent from each of the plurality of transmission antennas relative to the signal sent from the other ones of the plurality of transmission antennas.
8. The method of claim 7 , wherein the information further comprises amplitude variation of the signal sent from each of the plurality of transmission antennas.
9. The method of claim 1 , further comprising:
using the channel estimates to improve signal reception of signals sent from the plurality of transmission antennas received outside of the preamble of the downlink frame, the MAP of the downlink frame, and the portion of the data part of the downlink frame.
10. The method of claim 1 , further comprising:
transmitting uplink beamformed signals, wherein characteristics of the uplink beamformed signals are selected based upon the estimated channels.
11. The method of claim 4 , wherein the channels are estimated by assuming a flat channel response, and solving equations for the channel response based on knowledge of cyclic delay using pilot measurements at a plurality of sub-carriers of the OFDM signals.
12. The method of claim 11 , wherein the channel response is assumed flat if a detected amplitude variation between consecutive pilots of an OFDM symbol is less than a threshold.
13. A method for estimating tap delay profiles of a plurality of channels, comprising:
receiving a composite signal comprising a signal sent from each of a plurality of transmission antennas, the signal sent from each of the plurality of transmission antennas comprising a cyclic delay relative to the signal sent from other ones of the plurality of transmission antennas; and
estimating channel tap delays between the receiver and the plurality of transmission antennas based on an amplitude and a phase of the composite signal at a plurality of frequencies,
wherein the signal sent from each of the plurality of transmission antennas comprises the cyclic delay during an entirety of a preamble of a downlink frame, an entirety of a MAP of the downlink frame, and only a portion of a data part of the downlink frame.
14. The method of claim 13 , further comprising:
estimating the channel tap delays by recognizing repetition of power delay profiles associated with the channels.
15. The method of claim 13 , further comprising:
using the channel tap delays to improve signal reception of signals sent from the plurality of transmission antennas received outside the preamble of the downlink frame, the MAP of the downlink frame, and the portion of the data part of the downlink frame.