Channel estimation for wireless systems with multiple transmit antennas
View Patent ↗In various embodiments, techniques are provided to determine channel characteristics of various communication systems such as OFDM systems or systems using a plurality of transmit antennas by using various sets of training symbols.
1. A method of characterizing one or more communication channels, comprising:
receiving a set of first symbols associated with a first communication channel;
receiving a set of second symbols associated with a second communication channel; and
characterizing at least a first communication channel based on at least the set of first symbols and the set of second symbols to produce a set of first channel characteristics;
wherein characterizing one or more communication channels is performed by selecting a plurality of training symbols disposed within said at least the set of first symbols and the set of second symbols, where a correlation between two different sets of said training symbols is zero.
2. The method of claim 1 , wherein the set of first symbols is received from a first transmit device and the set of second symbols is received from a second transmit device.
3. The method of claim 2 , wherein the set of first symbols and the set of second symbols are received using a common receive device.
4. The method of claim 3 , wherein at least the first communication channel is further based on an orthogonal frequency division multiplexing technique.
5. The method of claim 1 , wherein at least the first communication channel is based on a constant-modulus technique.
6. The method of claim 5 , wherein characterizing at least the first communication channel includes:
performing a first correlation to produce a set of first correlations; and
determining the set of first channel characteristics based on at least the set of first correlations.
7. The method of claim 6 , wherein determining the set of first channel characteristics includes determining at least a set of first pre-estimates h 1 [n].
8. The method of claim 7 , wherein the set of first pre-estimates h 1 [n] is determined based on the equation:
h
_
1
[
n
]
=
1
K
p
1
[
n
]
,
wherein h 1 [n] is the set of first correlations and K is a constant.
9. The method of claim 1 , wherein characterizing at least the first communication channel includes:
performing a first correlation to produce a set of first correlations;
performing a second correlation to produce a set of second correlations; and
determining a set of channel pre-estimates based on at least the first correlation product and the second correlation product.
10. The method of claim 9 , wherein determining the set of first channel characteristics includes determining at least a set of first preestimates h 1 [n].
11. An apparatus for communicating, comprising:
a receive device that receives at least a set of first training symbols transmitted by a first transmit device and a set of second training symbols transmitted by a second transmit device; and
an estimator that estimates at least a first channel related to the first transmit device based on at least the set of first training symbols;
wherein a cross-correlation between two different sets of the first set of training symbols and the second set of training symbols is zero.
12. The apparatus of claim 11 , wherein the estimator further estimates the first channel based on at least the set of second training symbols.
13. The apparatus of claim 12 , wherein the estimator estimates the first channel without using a matrix inversion.