Mechanisms for multi-tier distributed co-operative multi-point technology

1. A method in a network node, the method comprising:

transmitting a pilot pattern; and

transmitting control information associating one or more first downlink transmit layers with the pilot pattern, each of the one or more first downlink transmit layers having a predefined modulation and coding scheme (MCS) without dynamic MCS adaptation and being multiplexed in a time-frequency resource space in at least one of: a time domain, a frequency domain, a code domain, a power domain, or a space domain, wherein the first downlink transmit layers are multiplexed in a first transmission tier: receiving, from a user equipment (UE), feedback information comprising at least one of:

information identifying first downlink transmit layers jointly detectable by the UE in the first transmission tier; AND

information identifying channel quality indicators (COIs) for second downlink transmit layers having adaptive modulation and coding and being multiplexed in a second transmission tier, the first and second transmission tiers being in respective time-frequency resource spaces that at least partially overlap; and scheduling downlink data transmission for the UE based on the feedback information.

2. The method of claim 1 , wherein, for each of the one or more first transmit layers, the control information comprises information indicating:

the pilot pattern that is associated with the downlink transmit layer; and

the predefined MCS associated with the downlink transmit layer.

3. The method of claim 2 , wherein:

the one or more first downlink transmit layers are transmitted using sparse code multiple access (SCMA) or low density signature orthogonal frequency division multiplexing (LDS-OFDM) waveforms; and

the control information further comprises information indicating codebooks or signatures associated with the one or more first downlink transmit layers.

4. The method of claim 2 , wherein the control information further comprises information indicating a transmit power associated with the downlink transmit layer.

5. The method of claim 1 , further comprising:

adjusting the feedback information received from the UE based on an average number of downlink transmit layers the UE has received at each of a number of scheduling intervals; and

scheduling downlink data transmission for the UE based on the adjusted feedback information.

6. The method of claim 1 , further comprising:

receiving, from a central coordinator, a feedback adjustment instruction regarding adjustment of the feedback information from the UE;

adjusting the feedback information from the UE in accordance with the feedback adjustment instruction; and

scheduling downlink data transmission for the UE based on the adjusted feedback information.

7. The method of claim 1 , further comprising:

triggering a hybrid automatic repeat request (HARQ) mechanism and/or an outer loop link adaptation (OLLA) mechanism in the second transmission tier based on receipt of an acknowledgement (ACK) or negative acknowledgement (NACK) from the UE regarding a data packet transmitted in the second transmission tier; and

in response to receiving a NACK from the UE regarding a data packet transmitted in the second transmission tier, rescheduling the downlink data transmission in the first transmission tier if a resend rate in the second transmission tier is below a threshold.

8. A network device comprising: a wireless interface;

a processor operatively coupled to the wireless interface; and

a computer readable storage medium operatively coupled to the processor, the computer readable storage medium storing programming for execution by the processor, the programming comprising instructions to:

transmit, via the wireless interface, a pilot pattern; and

transmit, via the wireless interface, control information associating one or more first downlink transmit layers with the pilot pattern, each of the one or more first downlink transmit layers having a predefined modulation and coding scheme (MCS) without dynamic MCS adaptation and being multiplexed in a time-frequency resource space in at least one of: a time domain, a frequency domain, a code domain, a power domain, or a space domain, wherein the first downlink transmit layers are multiplexed in a first transmission tier:

receive, via the wireless interface, feedback information from a user equipment (UE), the feedback information comprising at least one of:

information identifying first downlink transmit layers jointly detectable by the UE in the first transmission tier; AND

information identifying channel quality indicators (CQIs) for second downlink transmit layers having adaptive modulation and coding and being multiplexed in a second transmission tier, the first and second transmission tiers being in respective time-frequency resource spaces that at least partially overlap; and schedule downlink data transmission for the UE based on the feedback information.

9. The network device of claim 8 , wherein, for each of the one or more first downlink transmit layers, the control information comprises information indicating:

the pilot pattern that is associated with the downlink transmit layer; and

the predefined MCS associated with the transmit layer.

10. The network device of claim 9 , wherein the control information further comprises information indicating a transmit power associated with the downlink transmit layer.

11. The network device of claim 8 , wherein the instructions further comprise instructions to:

adjust the feedback information received from the UE based on an average number of downlink transmit layers the UE has received at each of a number of scheduling intervals; and

schedule downlink data transmission for the UE based on the adjusted feedback information.