Channel state information reporting enhancement for network assisted interference cancellation and suppression

1. An apparatus for receiving data from a network node, comprising

a receiver, which, in operation, receives a reference signal from the network node;

circuitry, which, in operation, determines a first channel quality according to the reference signal received by the receiver and processed in accordance with a first interference hypothesis, and determines a second channel quality according to the reference signal received by the receiver and processed in accordance with a second interference hypothesis, wherein

one of the first and second channel qualities has a greater size than the other one, and

a number of bits corresponding to a positive difference between sizes of the first and second qualities is used for an interference hypothesis indicator for indicating an interference hypothesis for which a lower-size channel quality is provided; and

a transmitter, which, in operation, transmits the first channel quality and the second channel quality in a channel quality message to the network node.

2. The apparatus according to claim 1 , wherein the first interference hypothesis corresponds to an absence of interference, the second interference hypothesis corresponds to a presence of interference, and the circuitry, in operation, processes the reference signal by interference cancellation or suppression in accordance with the second interference hypothesis.

3. The apparatus according to claim 1 , wherein the circuitry, in operation, determines a third channel quality according to the reference signals for multiple spatial layers, and generates a channel state information message which includes:

either the first and the second channel quality,

or the third channel quality.

4. The apparatus according to claim 3 , wherein the channel state information message has the following format:

when signaling the third channel quality: a rank indicator indicating a number of layers transmitted by multiple antennas, the third channel quality including channel quality for a plurality of codewords in accordance with the number of layers indicated by the rank indicator and a pre-coding matrix indicator indicating a pre-coding matrix for multi-layer transmission, and

when signaling the first and the second channel quality: a hypotheses indicator, the first channel quality or the second channel quality, and a pre-coding matrix indicator indicating a pre-coding matrix for single-layer transmission.

5. The apparatus according to claim 4 , wherein:

the channel state information message has the same length when signaling first and second channel quality as when signaling the third channel quality;

the pre-coding matrix indicator has the same length when indicating pre-coding matrix for multiple-layer transmission as well as single-layer transmission; and

the rank indicator and the hypothesis indicator have the same length.

6. The apparatus according to claim 5 , wherein for a first number of antenna ports, channel quality information for one interference hypothesis has shorter length than channel quality information for another interference hypothesis and at least its part is coded differentially with respect to the another interference hypothesis.

7. The apparatus according to claim 5 , wherein, for a first number of antenna ports, channel quality information for one codeword has the same length as channel quality information for one interference hypothesis.

8. The apparatus according to claim 7 , wherein the size of the channel state information message has the same size for single-layer transmission and for multiple-layer transmission.

9. The apparatus according to claim 4 , wherein:

the channel state information message has the greater length when signaling first and second channel quality than when signaling the third channel quality;

the first, the second, and the third quality have the same length;

the pre-coding matrix indicator has the same length when indicating pre-coding matrix for multiple-layer transmission as well as single-layer transmission; and

the rank indicator and the hypothesis indicator have the same length.

10. The apparatus according to claim 9 , wherein:

a common wideband channel quality indicator is transmitted, or

each of the first channel quality and the second channel quality includes a wideband channel quality indicator and N subband channel quality indicators which are coded differentially with respect to the wideband channel quality indicator, wherein

N is a positive integer,

first and second subband channel quality indicators have the same length, and

the wideband channel quality indicators for the first channel quality and the second channel quality have different non-zero lengths and are encoded differentially from each other.

11. The apparatus according to claim 3 , wherein:

the channel state information message includes a first-hypothesis precoding matrix indicator indicating precoding matrix for the first interference hypothesis, and a second-hypothesis precoding matrix indicator indicating precoding matrix for the second interference hypothesis;

the size of a second channel quality indicator is smaller than the size of a first channel quality indicator; and

the size of the channel state information message is equal when the first and second channel quality is signaled and when the third channel quality is signaled.

12. The apparatus according to claim 11 , wherein:

each of the first-hypothesis pre-coding matrix indicator and the second-hypothesis pre-coding matrix indicator consists of two components, which together specify a pre-coding to be applied for transmission; and

the channel state information message includes one common first component which is common for the first-hypothesis pre-coding matrix indicator and the second-hypothesis pre-coding matrix indicator, and separate respective second components for the first-hypothesis pre-coding matrix indicator and the second-hypothesis pre-coding matrix indicator.

13. The apparatus according to claim 1 , wherein the circuitry, in operation, generates a channel state information message, and the channel state information message includes a rank indicator, of which:

a first value indicates that the channel state information message further includes a pre-coding matrix indicator for a single spatial layer and the first channel quality;

a second value indicates that the channel state information message further includes a pre-coding matrix indicator for a single spatial layer, the first channel quality, and the second channel quality; and

a third value indicates that the channel state information message further includes a pre-coding matrix indicator for multiple spatial layers, the first channel quality, and the second channel quality.

14. The apparatus according to claim 3 , the circuitry, in operation, sets interpretation of the channel state information message to either a message transmitting the first channel quality and the second channel quality, or a message transmitting the third channel quality on the basis of at least one of:

semi-static higher-layer signaling,

dynamic signaling in a request to transmit the channel state information message request transmitted to the apparatus, or

dynamic signaling in the channel state information message, within a reporting type indicator.

15. An apparatus for transmitting data, comprising:

a receiver, which, in operation, receives a first channel quality and a second channel quality in a channel state information message received from a data receiving apparatus, the first channel quality being determined in accordance with a first interference hypothesis, the second channel quality being determined in accordance with a second interference hypothesis, wherein

one of the first and second channel qualities has a greater size than the other one, and

a number of bits corresponding to a positive difference between sizes of the first and second qualities is used for an interference hypothesis indicator for indicating an interference hypothesis for which a lower-size channel quality is provided;

circuitry, which, in operation, determines link configuration based on the first channel quality and the second channel quality; and

a transmitter, which, in operation, transmits to the data receiving apparatus the data according to the determined link configuration.

16. A method for receiving data from a network node, comprising:

receiving a reference signal from the network node;

determining a first channel quality according to the reference signal received by the receiver and processed in accordance with a first interference hypothesis;

determining a second channel quality according to the reference signal received by the receiver and processed in accordance with a second interference hypothesis, wherein

one of the first and second channel qualities has a greater size than the other one, and

a number of bits corresponding to a positive difference between sizes of the first and second qualities is used for an interference hypothesis indicator for indicating an interference hypothesis for which a lower-size channel quality is provided; and

transmitting the first channel quality and the second channel quality in a channel quality message to the network node.

17. A method for transmitting data to be executed in a network node, comprising:

receiving a first channel quality and a second channel quality in a channel state information message received from a data receiving apparatus, the first channel quality being determined in accordance with a first interference hypothesis, the second channel quality being determined in accordance with a second interference hypothesis, wherein

one of the first and second channel qualities has a greater size than the other one, and

a number of bits corresponding to a positive difference between sizes of the first and second qualities is used for an interference hypothesis indicator for indicating an interference hypothesis for which a lower-size channel quality is provided;

determining link configuration based on the first channel quality and the second channel quality; and

transmitting to the data receiving apparatus the data according to the determined link configuration.