1. A method in a first wireless communication transceiver of controlling precoder selection feedback sent to a second wireless communication transceiver that precodes transmissions to the first wireless communication transceiver, wherein said precoder selection feedback indicates precoder selections by said first wireless communication transceiver, said method comprising:
receiving restriction signaling from the second wireless communication transceiver that identifies:
one or more permitted subsets within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or,
one or more permitted subsets of precoders within the defined sets of said conversion precoders and tuning precoders; and

generating said precoder selection feedback for sending to the second wireless communication transceiver based on restricting precoder selections by said first wireless communication transceiver according to said restriction signaling.', 'receiving restriction signaling from the second wireless communication transceiver that identifies:
one or more permitted subsets within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or,
one or more permitted subsets of precoders within the defined sets of said conversion precoders and tuning precoders; and', 'one or more permitted subsets within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or,', 'one or more permitted subsets of precoders within the defined sets of said conversion precoders and tuning precoders; and', 'generating said precoder selection feedback for sending to the second wireless communication transceiver based on restricting precoder selections by said first wireless communication transceiver according to said restriction signaling.

2. The method of claim 1, wherein a conversion precoder codebook contains said defined set of conversion precoders and a tuning precoder codebook contains said defined set of tuning precoders, and wherein said restriction signaling indicates at least one of:
a permitted subset of conversion precoders in said conversion precoder codebook; and
a permitted subset of tuning precoders in said tuning precoder codebook.', 'a permitted subset of conversion precoders in said conversion precoder codebook; and', 'a permitted subset of tuning precoders in said tuning precoder codebook.

3. The method of claim 2, wherein said precoder selection feedback comprises indications of a selected conversion precoder as selected by said first wireless communication transceiver from said permitted subset of conversion precoders in said conversion precoder codebook, and a selected tuning precoder as selected by said first wireless communication transceiver from said permitted subset of tuning precoders in said tuning precoder codebook.

4. The method of claim 2, wherein said precoder selection feedback comprises index values identifying codebook entries within said conversion and tuning precoder codebooks, as selected by said first wireless communication transceiver.

5. The method of claim 1, further comprising at least one of:
two or more predefined subsets of conversion precoders and two or more predefined subsets of tuning precoders; and
wherein said restriction signaling indicates at least one of: the permitted subset of conversion precoders among said two or more predefined subsets of conversion precoders, and the permitted subset of tuning precoders among said two or more predefined subsets of tuning precoders.', 'two or more predefined subsets of conversion precoders and two or more predefined subsets of tuning precoders; and', 'wherein said restriction signaling indicates at least one of: the permitted subset of conversion precoders among said two or more predefined subsets of conversion precoders, and the permitted subset of tuning precoders among said two or more predefined subsets of tuning precoders.

6. The method of claim 5, wherein at least one of the predefined subsets contains only precoders such that corresponding overall precoders fulfill a full PA utilization property, while at least one other one of the predefined subsets contains precoders such that corresponding overall precoders do not fulfill the full PA utilization property;
wherein the rows of an overall precoder matrix obeying the full PA utilization property all have the same I2-norm, where I2-norm of a row x with elements xk is defined as', 'wherein the rows of an overall precoder matrix obeying the full PA utilization property all have the same I2-norm, where I2-norm of a row x with elements xk is defined as', 'âx88x91
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.

7. The method of claim 5, wherein one or more of the predefined subsets are associated with a first operating mode of said first wireless communication transceiver or said second wireless communication transceiver, while one or more other ones of the predefined subsets are associated with a second operating mode of said first wireless communication transceiver or said second wireless communication transceiver, and wherein said restriction signaling identifies the one or more permitted subsets of precoders by indicating which operating mode applies.

8. The method of claim 1, wherein said defined set of conversion precoders or said defined set of tuning precoders are divided into one or more first subsets of precoders associated with Single-User Multiple-Input-Multiple-Output, SU-MIMO, operation of the second wireless communication transceiver and one or more second subsets of precoders associated with Multiple-User MIMO, MU-MIMO, operation of the second wireless communication transceiver, and wherein said restriction signaling identifies the one or more permitted subsets of precoders by indicating whether SU-MIMO or MU-MIMO operation applies.

9. The method of claim 1, wherein said defined set of conversion precoders includes NT Q different conversion precoders and said defined set of tuning precoders includes a number of corresponding tuning precoders, and wherein each said conversion precoder comprises a block diagonal matrix in which each block comprises a DFT-based precoder that defines NT Q different DFT based beams for a subgroup in a group of NT transmit antenna ports at the second wireless communication transceiver, where Q is an integer value and where the NT Q different conversion precoders, together with one or more of the tuning precoders, correspond to a set of NT Q different overall precoders, each overall precoder thus representing a size-NT DFT-based beam over the group of NT transmit antennas ports

10. The method of claim 1, wherein the second wireless communication transceiver comprises a base station in a wireless communication network and said first wireless communication transceiver comprises a user equipment, and wherein the method further comprises receiving said restriction signaling at least in part as Radio Resource Control (RRC) layer signaling

11. A first wireless communication transceiver configured to control precoder selection feedback sent to a second wireless communication wireless communication transceiver that precodes transmissions to the first wireless communication transceiver, wherein said precoder selection feedback indicates precoder selections by said first wireless communication transceiver, said first wireless communication transceiver comprising:
a receiver configured to receive restriction signaling from the second wireless communication transceiver that identifies:
one or more permitted subsets within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or,
one or more permitted subsets of precoders within the defined sets of said conversion precoders and said tuning precoders; and
a precoding feedback generator configured to generate said precoder selection feedback for sending to the second wireless communication transceiver, based on restricting precoder sections by said first wireless communication transceiver according to the restriction signaling.', 'a receiver configured to receive restriction signaling from the second wireless communication transceiver that identifies:', 'one or more permitted subsets within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or,', 'one or more permitted subsets of precoders within the defined sets of said conversion precoders and said tuning precoders; and', 'a precoding feedback generator configured to generate said precoder selection feedback for sending to the second wireless communication transceiver, based on restricting precoder sections by said first wireless communication transceiver according to the restriction signaling.12. The first wireless communication transceiver of claim 11, wherein said first wireless communication transceiver stores a representation of a conversion precoder codebook containing said defined set of conversion precoders and a representation of a tuning precoder codebook containing said defined set of tuning precoders, and wherein said restriction signaling indicates at least one of:
a permitted subset of conversion precoders in said conversion precoder codebook; and
a permitted subset of tuning precoders in said tuning precoder codebook.', 'a permitted subset of conversion precoders in said conversion precoder codebook; and', 'a permitted subset of tuning precoders in said tuning precoder codebook.13. The first wireless communication transceiver of claim 12, wherein said precoder selection feedback comprises indications of a selected conversion precoder as selected by said first wireless communication transceiver from said permitted subset of conversion precoders in said conversion precoder codebook, and a selected tuning precoder as selected by said first wireless communication transceiver from said permitted subset of tuning precoders in said tuning precoder codebook.14. The first wireless communication transceiver of claim 12, wherein said precoding feedback generator is configured to generate the precoder selection feedback as index values identifying codebook entries within said conversion and tuning precoder codebooks, as selected by said first wireless communication transceiver.15. The first wireless communication transceiver of claim 11, further comprising at least one of:
said first wireless communication transceiver storing two or more representations of predefined subsets of conversion precoders and two or more representations of predefined subsets of tuning precoders; and
wherein said restriction signaling indicates at least one of: the permitted subset of conversion precoders among said two or more predefined subsets of conversion precoders, and the permitted subset of tuning precoders among said two or more predefined subsets of tuning precoders.', 'said first wireless communication transceiver storing two or more representations of predefined subsets of conversion precoders and two or more representations of predefined subsets of tuning precoders; and', 'wherein said restriction signaling indicates at least one of: the permitted subset of conversion precoders among said two or more predefined subsets of conversion precoders, and the permitted subset of tuning precoders among said two or more predefined subsets of tuning precoders.16. The first wireless communication transceiver of claim 15, wherein at least one of the predefined subsets contains only precoders such that corresponding overall precoders fulfill a full PA utilization property for the second wireless communication transceiver, while at least one other one of the predefined subsets contains precoders such that corresponding overall precoders do not fulfill the full PA utilization property;
wherein the rows of an overall precoder matrix obeying the full PA utilization property all have the same I2-norm, where I2-norm of a row x with elements xk is defined as', 'wherein the rows of an overall precoder matrix obeying the full PA utilization property all have the same I2-norm, where I2-norm of a row x with elements xk is defined as', 'âx88x91
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.17. The first wireless communication transceiver of claim 15, wherein one or more of said predefined subsets are associated with a first operating mode of said first wireless communication transceiver or the second wireless communication transceiver, while one or more other ones of the predefined subsets are associated with a second operating mode of said first wireless communication transceiver or the second wireless communication transceiver, and wherein said restriction signaling identifies the one or more permitted subsets of precoders by indicating which operating mode applies.18. The first wireless communication transceiver of claim 11, wherein said defined set of conversion precoders or said defined set of tuning precoders are divided into one or more first subsets of precoders associated with Single-User Multiple-Input-Multiple-Output, SU-MIMO, operation of the second wireless communication transceiver and one or more second subsets of precoders associated with Multiple-User MIMO, MU-MIMO, operation of the etlaeF second wireless communication transceiver, and wherein said restriction signaling identifies the one or more permitted subsets of precoders by indicating whether SU-MIMO or MU-MIMO operation applies.19. The first wireless communication transceiver of claim 11, wherein said defined set of conversion precoders includes NT Q different conversion precoders and said defined set of tuning precoders includes a number of corresponding tuning precoders, and wherein each said conversion precoder comprises a block diagonal matrix in which each block comprises a DFT-based precoder that defines NT Q different DFT based beams for a subgroup in a group of NT transmit antenna ports at the second wireless communication transceiver, where Q is an integer value and where the NT Q different conversion precoders, together with one or more of the tuning precoders, correspond to a set of NT Q different overall precoders, each overall precoder thus representing a size- NT DFT-based beam over the group of NT transmit antennas ports.

20. The first wireless communication transceiver of claim 11, wherein the second wireless communication transceiver comprises a base station in a wireless communication network and said first wireless communication transceiver comprises a user equipment, and wherein said first wireless communication transceiver is configured to receive said restriction signaling at least in part as Radio Resource Control (RRC) layer signaling.

21. A second wireless communication transceiver configured to precode transmissions to a first wireless communication transceiver based at least in part on receiving precoder selection feedback from the first wireless communication transceiver that indicates an overall precoder for consideration by said second wireless communication transceiver in precoding to the first wireless communication transceiver, said second wireless communication transceiver including a receiver for receiving said precoder selection feedback from the first wireless communication transceiver and comprising:
a precoding controller configured to determine a restriction that limits precoder selection by the first wireless communication transceiver to:
one or more permitted subsets of overall precoders within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or
one or more permitted subsets of precoders within said defined sets of conversion precoders and tuning precoders; and
a transmitter cooperatively associated with said precoding controller and configured for transmitting said restriction signaling to the first wireless communication transceiver', 'a precoding controller configured to determine a restriction that limits precoder selection by the first wireless communication transceiver to:', 'one or more permitted subsets of overall precoders within a defined set of overall precoders, each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or', 'one or more permitted subsets of precoders within said defined sets of conversion precoders and tuning precoders; and', 'a transmitter cooperatively associated with said precoding controller and configured for transmitting said restriction signaling to the first wireless communication transceiver

22. The second wireless communication transceiver of claim 21, wherein said first wireless communication transceiver stores a representation of a conversion precoder codebook containing said defined set of conversion precoders and a representation of a tuning precoder codebook containing said defined set of tuning precoders, and wherein the second wireless communication transceiver is further configured to generate the restriction signaling to indicate at least one of:
a permitted subset of conversion precoders in said conversion precoder codebook; and
a permitted subset of tuning precoders in said tuning precoder codebook.', 'a permitted subset of conversion precoders in said conversion precoder codebook; and', 'a permitted subset of tuning precoders in said tuning precoder codebook.

23. The second wireless communication transceiver of claim 21, wherein said precoder selection feedback comprises indications of a selected conversion precoder as selected by said first wireless communication transceiver from said permitted subset of conversion precoders in said conversion precoder codebook, and a selected tuning precoder as selected by said first wireless communication transceiver from said permitted subset of tuning precoders in said tuning precoder codebook, and wherein said second wireless communication transceiver is configured to determine the overall precoder from the defined set of overall precoders corresponding to said indications in said precoder selection feedback.

24. The second wireless communication transceiver of claims 21, wherein the transceiver maintains a codebook representation of said defined set of overall precoders and uses indications of selected conversion and tuning precoders conveyed by said precoder selection feedback to identify the overall precoder selected by the first wireless communication transceiver.

25. The second wireless communication transceiver of claim 21, wherein said restriction signaling comprises a mode indicator that identifies one of a first and a second transmission mode, and wherein said precoding controller sets the mode indicator in dependence on whether the second wireless communication transceiver is operating in the first or the second transmission mode, and wherein one or more subsets among said defined sets of conversion precoders and tuning precoders at the first wireless communication transceiver are permitted for said first transmission mode, and one or more other ones of the subsets among said defined sets of conversion precoders and tuning precoders at said first wireless communication transceiver are permitted for said second transmission mode.

26. The second wireless communication transceiver of claim 21, wherein said second wireless communication transceiver comprises a base station in a wireless communication network.

27. A method in a second wireless communication transceiver that is configured to precode transmissions to a first wireless communication transceiver based at least in part on receiving precoder selection feedback from said first wireless communication transceiver that indicates an overall precoder for consideration by said second wireless communication transceiver in precoding to the first wireless communication transceiver, said method comprising:
determining a restriction that limits precoder selection by the first wireless communication transceiver to:
one or more permitted subsets of overall precoders within a defined set of overall precoders,each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or
one or more permitted subsets of precoders within defined sets of conversion precoders and tuning precoders
generating restriction signaling for indicating the one or more permitted subsets to said first wireless communication transceiver; and
sending the restriction signaling to the first wireless communication transceiver, to restrict precoder selection by the first wireless communication transceiver to the one or more permitted subsets.', 'determining a restriction that limits precoder selection by the first wireless communication transceiver to:', 'one or more permitted subsets of overall precoders within a defined set of overall precoders,each of which comprises a combination of a conversion precoder from a defined set of conversion precoders and a tuning precoder from a defined set of tuning precoders, or', 'one or more permitted subsets of precoders within defined sets of conversion precoders and tuning precoders', 'generating restriction signaling for indicating the one or more permitted subsets to said first wireless communication transceiver; and', 'sending the restriction signaling to the first wireless communication transceiver, to restrict precoder selection by the first wireless communication transceiver to the one or more permitted subsets.

28. The method of claim 27, wherein said first wireless communication transceiver stores a representation of a conversion precoder codebook containing said defined set of conversion precoders and a representation of a tuning precoder codebook containing said defined set of tuning precoders, and wherein the method further comprises said second wireless communication transceiver generating the restriction signaling to indicate at least one of:
a permitted subset of conversion precoders in said conversion precoder codebook; and
a permitted subset of tuning precoders in said tuning precoder codebook.', 'a permitted subset of conversion precoders in said conversion precoder codebook; and', 'a permitted subset of tuning precoders in said tuning precoder codebook.

29. The method of claim 27, wherein said precoder selection feedback comprises indications of a selected conversion precoder as selected by said first wireless communication transceiver from said permitted subset of conversion precoders in said conversion precoder codebook, and a selected tuning precoder as selected by said first wireless communication transceiver from said permitted subset of tuning precoders in said tuning precoder codebook, and said second wireless communication transceiver determining the overall precoder from the defined set of overall precoders corresponding to said indications in said precoder selection feedback.

30. The method of claim 27, wherein said second wireless communication transceiver maintains a codebook representation of the defined set of overall precoders and said method further comprises using indications of selected conversion and tuning precoders conveyed by said precoder selection feedback to identify the overall precoder selected by the first wireless communication transceiver.

31. The method of claim 27, wherein said restriction signaling comprises a mode indicator that identifies one of a first and a second transmission mode, and wherein said method further comprises setting the mode indicator in dependence on whether the transceiver is operating in the first or the second transmission mode, and wherein one or more subsets among said defined sets of conversion precoders and tuning precoders at the first wireless communication transceiver are permitted for said first transmission mode, and one or more other ones of the subsets among said defined sets of conversion precoders and tuning precoders at the first wireless communication transceiver are permitted for said second transmission mode.

32. The method of claim 27, wherein said second wireless communication transceiver comprises a base station in a wireless communication network.']