Method and apparatus for data transmission in a multiuser downlink cellular system

1. A transmitter device, comprising:

a processor configured to:

determine a downlink channel quality of downlink channels between the transmitter device and a plurality of receiver devices;

compute a scheduler weight for each of the plurality of receiver devices;

for each modulation of a set of modulations, determine weighted bit-level capacities of all label bits based on the scheduler weights and based on the downlink channel qualities;

determine, for each modulation of the set of modulations, a highest weighted sum rate based on the weighted bit-level capacities;

select a modulation from the set of modulations according to a maximum weighted sum rate among the highest weighted sum rates, select a set of receiver devices from the plurality of receiver devices according to the selected modulation, and select a label bit-to-user equipment (bit-to-UE) allocation for receiver devices in the selected set of receiver devices according to the selected modulation, wherein all label bits having the same weighted bit-level capacity are allocated to a same receiver device in the selected set of receiver devices;

obtain a multiplexing matrix using the selected label bit-to-UE allocation and a number of resource elements, which are for transmitting a downlink signal S;

compute a code rate using the selected label bit-to-UE allocation and the determined bit-level capacity for each receiver device in the selected set; and

transmit, using the resource elements, the downlink signal S based on the obtained multiplexing matrix and computed code rates, to the receiver devices in the selected set.

2. The transmitter device according to claim 1 , wherein the processor is further configured to determine weighted bit-level capacities of all label bits for each modulation based on the determined channel quality of the downlink channels between the transmitter and the plurality of receiver devices by using a channel quality information (CQI) to bit level capacity table stored in a memory.

3. The transmitter device according to claim 1 , wherein the processor is further configured to:

receive the downlink channel qualities for the plurality of receiver devices; or

estimate the downlink channel qualities by measuring corresponding uplink channels for the plurality of receiver devices.

4. The transmitter device of claim 3 , wherein the downlink channel qualities are based one or more of a signal-to-noise ratio or a signal-to-interference plus noise ratio.

5. The transmitter device according to claim 1 , wherein the processor is further configured to:

encode, for the receiver devices in the selected set of receiver devices, an information word to obtain a code word;

use the obtained multiplexing matrix to multiplex the code words into a label vector of G elements l=(l(l), . . . , l(G)) according to the selected label bit-to-UE allocation; and

use each label of the label vector l=(l(l), . . . , l(G)) to select a modulation symbol from the selected modulation to obtain a symbol vector x=(x(l), . . . , x(G)) for the multiplexed code words;

wherein the downlink signal S comprises the symbol vector x=(x(1), . . . , x(G)).

6. The transmitter device according to claim 1 , wherein the processor is further configured to signal to the receiver devices in the selected set of receiver devices an index of the multiplexing matrix stored in a pre-computed library of multiplexing matrices.

7. The transmitter device according to claim 1 , wherein the multiplexing matrix is associated with at least two receiver devices from the selected set of receiver devices.

8. The transmitter device according to claim 1 , wherein the processor is further configured to transmit the downlink signal S with at least G number of time-frequency resource elements (RE).

9. The transmitter device according to claim 1 , wherein the processor is further configured to transmit to the receiver devices in the selected set of receiver devices a downlink control information comprising at least one of:

a field indicating time-frequency resource allocation common to all receiver devices in the selected set;

a field indicating a receiver device-specific code rate;

a field indicating a selected multiplexing matrix common to all receiver devices in the selected set; or

a field indicating a value in the selected multiplexing matrix to which a current receiver device from the selected set corresponds.

10. The transmitter device according to claim 1 , wherein the processor is further configured to transmit to the receiver devices in the selected set a downlink control information comprising at least one of:

a field indicating a time-frequency resource allocation common to all receiver devices in the selected set;

a field indicating a receiver device-specific code rate;

a field indicating a selected modulation common to all receiver devices in the selected set; or

a field indicating a receiver device-specific allocation of label bits.

11. A signaling method for concurrent transmission of non-orthogonal independent downlink data streams to receiver devices in a wireless communication system, the method comprising:

determining, by a transmitter device, a downlink channel quality of downlink channels between the transmitter device and a plurality of receiver devices;

computing, by the transmitter device, a scheduler weight for each of the plurality of receiver devices;

for each modulation of a set of modulations, determining, by the transmitter device, weighted bit-level capacities of all label bits based on the scheduler weights and based on the downlink channel qualities;

determining, for each modulation of the set of modulations, by the transmitter device, a highest weighted sum rate based on the weighted bit-level capacities;

selecting, by the transmitter device, a modulation from the set of modulations according to a maximum weighted sum rate among the highest weighted sum rates, select a set of receiver devices from the plurality of receiver devices according to the selected modulation, and select a label bit-to-user equipment (bit-to-UE) allocation for receiver devices in the selected set of receiver devices according to the selected modulation wherein all label bits having the same weighted bit-level capacity are allocated to a same receiver device in the selected set of receiver devices;

obtaining, by the transmitter device, a multiplexing matrix using the selected label bit-to-UE allocation and a number of resource elements, which are for transmitting a downlink signal S;

computing, by the transmitter device, a code rate using the selected label bit-to-UE allocation and the determined bit-level capacity for each receiver device in the selected set;

transmitting, by the transmitter device, using the resource elements, the downlink signal S based on the obtained multiplexing matrix and computed code rates, to the receiver devices in the selected set; and

sending, by the transmitter device, to the receiver devices control information comprising one or more of:

identities of the receiver devices selected for transmission;

code rates of the selected receiver devices;

a label bit-to-receiver device allocation for the selected receiver devices;

an index of an expanded constellation; or

the number of resource elements used for downlink transmission.

12. The signaling method of claim 11 , wherein the control information comprises:

a field indicating a time-frequency resource allocation common to all selected receiver devices;

a field indicating a receiver device-specific code rate;

a field indicating a selected multiplexing matrix common to all selected receiver devices; and

a field indicating a value in the selected multiplexing matrix to which a current receiver device from the selected receiver devices corresponds.

13. The signaling method of claim 11 , wherein the control information comprises:

a field indicating time-frequency resource allocation common to all selected receiver devices;

a field indicating a receiver device-specific code rate;

a field indicating a modulation common to all selected receiver devices; and

a field indicating a receiver device-specific allocation of label bits.

14. A transmitter device, comprising:

a processor configured to:

determine a downlink channel quality of downlink channels between the transmitter device and a plurality of receiver devices;

compute a scheduler weight for each of the plurality of receiver devices;

for each modulation of a set of modulations, determine weighted bit-level capacities of all label bits based on the scheduler weights and based on the downlink channel qualities;

determine, for each modulation of the set of modulations, a highest weighted sum rate based on the weighted bit-level capacities;

select a modulation from the set of modulations according to a maximum weighted sum rate among the highest weighted sum rates, select a set of receiver devices from the plurality of receiver devices according to the selected modulation, and select a label bit-to-user equipment (bit-to-UE) allocation for receiver devices in the selected set of receiver devices according to the selected modulation;

obtain a multiplexing matrix using the selected label bit-to-UE allocation and a number of resource elements, which are for transmitting a downlink signal S;

compute a code rate using the selected label bit-to-UE allocation and the determined bit-level capacity for each receiver device in the selected set; and

transmit, using the resource elements, the downlink signal S based on the obtained multiplexing matrix and computed code rates, to the receiver devices in the selected set;

encode, for the receiver devices in the selected set of receiver devices, an information word to obtain a code word;

use the obtained multiplexing matrix to multiplex the code words into a label vector of G elements l=(l(l), . . . , l(G)) according to the selected label bit-to-UE allocation; and

use each label of the label vector l=(l(l), . . . , l(G)) to select a modulation symbol from the selected modulation to obtain a symbol vector x=(x(1), . . . , x(G)) for the multiplexed code words;

wherein the downlink signal S comprises the symbol vector x=(x(1), . . . , x(G)).