Channel state information feedback device, method thereof, and base station
View Patent ↗An embodiment of the present invention relates to a wireless communication system, wherein said wireless communication system uses multiple input and multiple output antenna (MIMO) on both transmission and receiving ends.
1. A base station in a wireless communication system, the base station comprising:
a layer mapper to perform mapping of a codeword to a layer;
at least two precoders to perform precoding of mapped symbols sequentially, using a precoding matrix; and
two or more antennas to transmit a wireless signal comprising the precoded symbol,
wherein the most internal precoder from among the precoders performs precoding using a precoding matrix satisfying P in P in H =I (P in denotes the most internal precoding matrix, H denotes an operator of the Hermitian matrix, and I denotes a unit matrix),
wherein the precoding matrix includes the most internal precoding matrix and an external precoding matrix, and the most internal precoding matrix is selected from an internal codeword codebook including codewords satisfying c in n (c in n ) H =I (c in n denotes a codeword written by an index n) and the external precoding matrix is selected from an external codeword codebook including codewords satisfying
min
n
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m
V
t
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i
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(V t denotes an eigen vector of a channel or a covariance matrix at t and c out m denotes a codeword written by an index m).
2. The base station of claim 1 , wherein the two precoding matrices are selected respectively from the internal codeword codebook and the external codeword codebook through use corresponding channel feedback information of a user equipment.
3. The base station of claim 2 , wherein the channel feedback information corresponds to a precoding matrix indicator.
4. The base station of claim 1 , wherein the internal codeword codebook and the external codeword codebook are identical to or different from each other.
5. The base station of claim 1 , wherein the internal codeword codebook and the external codeword codebook are an independent unitary codebook or not.
6. A channel state information feedback device in a wireless communication system, the device comprising:
a reference signal receiving unit to receive a reference signal from a base station;
a channel estimation unit to estimate a channel using the received reference signal;
a channel state information generating unit to generate, based on a channel estimation result of the channel estimation unit, channel state information including internal channel feedback information designating an internal codeword that is selected from an internal codeword codebook including codewords satisfying c in n (c in n ) H =I (c in n denotes a codeword written by an index n) and external channel feedback information designating an external codeword that is selected from an external codeword codebook including codewords satisfying
min
n
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t
-
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×
c
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(V t denotes an eigen vector of a channel or a channel covariance matrix at t and c out m denotes a codeword written by an index m); and
a feedback unit to feed back the generated channel state information.
7. The device of claim 6 , wherein the internal channel feedback information and the external channel feedback information correspond to an internal precoding matrix indicator (PMI in ) and an external precoding matrix indicator (PMI out ), respectively.
8. The device of claim 7 , wherein the internal precoding matrix indicator (PMI in ) and the external precoding matrix (PMI out ) satisfy the following equation:
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wherein V denotes an eigen vector of a channel H.
9. A channel state information feedback method, the method comprising:
a reference signal receiving step that receives a reference signal from a base station;
a channel estimation step that estimates a channel using the received reference signal;
a channel state information generating step that generates, based on a channel estimation result of the channel estimation step, channel state information including internal channel feedback information designating an internal codeword that is selected from an internal codeword codebook including codewords satisfying c in n (c in n ) H =I (c in n denotes a codeword written by an index n) and external channel feedback information designating an external codeword that is selected from an external codeword codebook including codewords satisfying
min
n
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m
V
t
-
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n
×
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(V t denotes an eigen vector of a channel or a channel covariance matrix at t and c out m denotes a codeword written by an index m); and
a feedback step that feeds back the generated channel state information.
10. The method of claim 9 , wherein the internal channel feedback information and the external channel feedback information correspond to an internal precoding matrix indicator (PMI in ) and an external precoding matrix indicator (PMI out ), respectively.
11. The method of claim 10 , wherein the internal precoding matrix indicator (PMI in ) and the external precoding matrix (PMI out ) satisfy the following equation:
(
PMI
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n
,
PMI
out
)
=
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n
,
m
(
c
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n
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)
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V
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c
out
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wherein V denotes an eigen vector of a channel H.