CODEBOOK AND CODEBOOK SEARCH
Briefly, in accordance with one or more embodiments, a codebook used to provide a precoding matrix indicator and/or channel state information comprises one or more rank-1 codewords and at least one or more rank-2 codewords exhibiting a nesting property with the rank-1 codewords, and one or more rank-2 codewords not exhibiting a nesting property with the rank-1 codewords. Further, the rank-1 codewords may include at least some Discrete Fourier Transform (DFT) vectors, and at least some vectors that are optimized for a cross polarize array of antennas if the array of antennas is cross polarized. The codebook may be utilized for single-user multiple-input, multiple-output (SU-MIMO) or multi-user multiple-input, multiple-output (MU-MIMO).
1 . A user equipment (UE), comprising:
a wireless transceiver having an array of one or more antennas; and
a processor coupled to the wireless transceiver and a memory coupled to the processor, the memory having a codebook stored therein, wherein the codebook comprises:
one or more rank-1 codewords;
at least one or more rank-2 codewords exhibiting a nesting property with the rank-1 codewords; and
one or more rank-2 codewords not exhibiting a nesting property with the rank-1 codewords.
2 . A user equipment as claimed in claim 1 , wherein the rank-1 codewords include at least some Discrete Fourier Transform (DFT) vectors, and at least some vectors that are optimized for the array of antennas if the array of antennas is cross polarized.
3 . A user equipment as claimed in claim 1 , wherein the processor is configured to perform a search of the codebook for single-user multiple-input, multiple-output (SU-MIMO) by:
performing a channel state information (CSI) search to find a best precoding matrix indicator (PMI) for the rank-1 codewords and the rank-2 codewords to maximize channel capacity;
selecting a better rank; and
reporting the better rank and the best PMI and CQI for the better rank.
4 . A user equipment as claimed in claim 1 , wherein the processor is configured to perform a search of the codebook for multi-user multiple-input, multiple-output (MU-MIMO) by:
performing a channel state information (CSI) search to find a best precoding matrix indicator (PMI) for the rank-1 codewords and the rank-2 codewords using each column of each codeword as a rank-1 precoder;
selecting a better rank; and
reporting the better rank and the best PMI and CQI for the better rank to an enhanced Node B.
5 . A user equipment as claimed in claim 1 , further comprising a touch screen to receive a touch input to control the processor.
6 . A user equipment (UE), comprising:
a wireless transceiver having an array of one or more antennas; and
a processor coupled to the wireless transceiver and a memory coupled to the processor, the memory having a codebook stored therein, wherein the codebook comprises:
one or more rank-1 codewords; and
one or more rank-2 codewords;
wherein the rank-1 codewords include at least some Discrete Fourier Transform (DFT) vectors, and at least some vectors that are optimized for the array of antennas if the array of antennas is cross polarized.
7 . A user equipment as claimed in claim 6 , wherein at least one or more rank-2 codewords exhibit a nesting property with the rank-1 codewords; and
one or more rank-2 codewords do not exhibit a nesting property with the rank-1 codewords.
8 . A user equipment as claimed in claim 6 , wherein the processor is configured to perform a search of the codebook for single-user multiple-input, multiple-output (SU-MIMO) by:
performing a channel state information (CSI) search to find a best precoding matrix indicator (PMI) for the rank-1 codewords and the rank-2 codewords to maximize channel capacity;
selecting a better rank; and
reporting the better rank and the best PMI and CQI for the better rank.
9 . A user equipment as claimed in claim 6 , wherein the processor is configured to perform a search of the codebook for multi-user multiple-input, multiple-output (MU-MIMO) by:
performing a channel state information (CSI) search to find a best precoding matrix indicator (PMI) for the rank-1 codewords and the rank-2 codewords using each column of each codeword as a rank-1 precoder;
selecting a better rank; and
reporting the better rank and the best PMI and CQI for the better rank to an enhanced Node B.
10 . A user equipment as claimed in claim 6 , further comprising a touch screen to receive a touch input to control the processor.
11 . A method to perform a codebook search, comprising:
performing a channel state information (CSI) search to find a best precoding matrix indicator (PMI) for rank-1 codewords and rank-2 codewords of the codebook;
selecting a better rank; and
reporting the better rank and the best PMI and CQI for the better rank.
12 . A method as claimed in claim 11 , wherein said performing is implemented for single-user multiple-input, multiple-output (SU-MIMO).
13 . A method as claimed in claim 11 , wherein said performing is implemented for multi-user multiple-input, multiple-output (MU-MIMO) by using each column of each codeword as a rank-1 precoder.
14 . A method as claimed in claim 11 , wherein the codebook comprises:
one or more rank-1 codewords;
at least one or more rank-2 codewords exhibiting a nesting property with the rank-1 codewords; and
one or more rank-2 codewords not exhibiting a nesting property with the rank-1 codewords.
15 . A method as claimed in claim 11 , wherein the rank-1 codewords include at least some Discrete Fourier Transform (DFT) vectors, and at least some vectors that are optimized for the array of antennas if the array of antennas is cross polarized.
16 . An article of manufacture comprising a non-transitory medium having instructions thereon that, if executed, result in:
performing a channel state information (CSI) search to find a best precoding matrix indicator (PMI) for rank-1 codewords and rank-2 codewords of the codebook;
selecting a better rank; and
reporting the better rank and the best PMI and CQI for the better rank.
17 . An article as claimed in claim 16 , wherein said performing is implemented for single-user multiple-input, multiple-output (SU-MIMO).
18 . An article as claimed in claim 16 , wherein said performing is implemented for multi-user multiple-input, multiple-output (MU-MIMO) by using each column of each codeword as a rank-1 precoder.
19 . An article as claimed in claim 16 , wherein the codebook comprises:
one or more rank-1 codewords;
at least one or more rank-2 codewords exhibiting a nesting property with the rank-1 codewords; and
one or more rank-2 codewords not exhibiting a nesting property with the rank-1 codewords.
20 . An article as claimed in claim 16 , wherein the rank-1 codewords include at least some Discrete Fourier Transform (DFT) vectors, and at least some vectors that are optimized for the array of antennas if the array of antennas is cross polarized.