System and method for HARQ feedback in RRC inactive state
Systems and methods for transmitting uplink control information, for example ACK/NACK, while in RRC_inactive state, are provided. Uplink control information is transmitted while in RRC_INACTIVE state by transmitting a sequence from a set of possible sequences to convey the uplink control information, the transmitted sequence associated with a value of the uplink control information. The sequence is asynchronously transmitted. Signalling may be used to configure a transmission resource within which to transmit the sequence, wherein the transmission resource has a time duration that is longer than a time duration to transmit the sequence. This has the effect of introducing a gap following sequence transmission that can ensure the sequence transmission does not interfere with a data transmission.
1. A method comprising:
receiving, by a user equipment (UE), a control message that releases the UE from the RRC_CONNECTED state, the control message comprising configuration information for conveying acknowledgment/negative acknowledgment (ACK/NACK) feedback in an RRC_INACTIVE state;
entering, by the UE, into the RRC_INACTIVE state from RRC_CONNECTED state;
transmitting, by the UE, in accordance with said configuration information,
a symbol sequence from a set of possible symbol sequences to convey the ACK/NACK feedback.
2. The method of claim 1 further comprising:
receiving signalling to configure a transmission resource within which to transmit the symbol sequence, wherein the transmission resource has a time duration that is longer than a time duration to transmit the symbol sequence.
3. The method of claim 1 the method further comprising:
receiving, by the user equipment (UE) a downlink data transmission while in RRC_INACTIVE state;
wherein transmitting the symbol sequence from the set of possible sequences comprises:
transmitting a symbol sequence to indicate a NACK in respect of the downlink data transmission that is not correctly decoded; or
transmitting a symbol sequence to indicate an ACK in respect of the downlink data transmission that is correctly decoded; or
transmitting a first symbol sequence to indicate a NACK in respect of the downlink data transmission is not correctly decoded and transmitting a second symbol sequence to indicate an ACK in respect of the downlink data transmission is correctly decoded.
4. The method of claim 1 , wherein the configuration information is one of:
UE-specific;
Cell-specific; or
UE-group-specific.
5. The method of claim 1 wherein the ACK/NACK feedback consists of m bits, the method further comprising determining the symbol sequence by:
modulating the m bits to produce a modulated symbol;
multiplying the modulated symbol with a first sequence to obtain a first set of complex valued symbols; and
block-wise spreading the first set of complex valued symbols with a first spreading sequence.
6. The method of claim 5 , wherein the symbol sequence is a first symbol sequence, and the method further comprising:
transmitting, within a same slot of the first symbol sequence, a second symbol sequence determined from the ACK/NACK feedback, wherein the second symbol sequence is:
the same as the first symbol sequence; or
determined by multiplying the modulated symbol with a second sequence different from the first sequence to obtain a second set of complex valued symbols, and block- wise spreading the second set of complex valued symbols with said first spreading sequence; or
determined by block-wise spreading the first set of complex valued symbols with a second spreading sequence that is different from the first spreading sequence; or
determined by multiplying the modulated symbol with a second sequence different from the first sequence to obtain a second set of complex valued symbols, and block- wise spreading the second set of complex valued symbols with a second spreading sequence that is different from said first spreading sequence.
7. The method of claim 1 further comprising:
receiving signalling indicating a resource partition, the resource partition having an associated set of symbol sequences;
wherein transmitting the symbol sequence comprises transmitting a symbol sequence selected from the associated set of symbol sequences based on a UE identifier of the UE.
8. The method of claim 1 further comprising:
transmitting the symbol sequence with a subcarrier spacing different from other transmissions in a same resource grid, wherein the subcarrier spacing is a spacing between consecutive OFDM subcarriers.
9. An apparatus comprising:
a processor and a memory, wherein the apparatus is configured to:
receiving a control message that releases the UE from the RRC_CONNECTED state, the control message comprising configuration information for conveying acknowledgment/negative acknowledgment (ACK/NACK) feedback in an RRC_INACTIVE state;
entering into the RRC_INACTIVE state from RRC_CONNECTED state;
transmit, in accordance with said configuration, a symbol sequence from a set of possible symbol sequences to convey the ACK/NACK.
10. The apparatus of claim 9 further configured to receive signalling to configure a transmission resource within which to transmit the symbol sequence, wherein the transmission resource has a time duration that is longer than a time duration to transmit the symbol sequence.
11. The apparatus of claim 9 the apparatus further configured to receive a downlink data transmission while in RRC_INACTIVE state;
wherein the apparatus is configured to transmit the symbol sequence from the set of possible sequences, by:
transmitting a symbol sequence to indicate a NACK in respect of the downlink data transmission that is not correctly decoded; or
transmitting a symbol sequence to indicate an ACK in respect of the downlink data transmission that is correctly decoded; or
transmitting a first symbol sequence to indicate a NACK in respect of the downlink data transmission is not correctly decoded and transmitting a symbol second sequence to indicate an ACK in respect of the downlink data transmission is correctly decoded.
12. The apparatus of claim 9 , wherein the configuration information is one of:
UE-specific;
Cell specific;
UE-group specific.
13. The apparatus of claim 9 wherein said ACK/NACK feedback consists of m bits, the apparatus further configured to determine the symbol sequence by:
modulating the m bits to produce a modulated symbol;
multiplying the modulated symbol with a first sequence to obtain a first set of complex valued symbols; and
block-wise spreading the first set of complex valued symbols with a first spreading sequence.
14. The apparatus of claim 13 , wherein the symbol sequence is a first symbol sequence, and the method further configured to:
transmit, within a same slot of the first symbol sequence, a second symbol sequence determined from the ACK/NACK feedback, wherein the second symbol sequence is:
the same as the first symbol sequence; or
determined by multiplying the modulated symbol with a second sequence different from the first sequence to obtain a second set of complex valued symbols, and block-wise spreading the second set of complex valued symbols with said first spreading sequence; or
determined by block-wise spreading the first set of complex valued symbols with a second spreading sequence that is different from the first spreading sequence; or
determined by multiplying the modulated symbol with a second sequence different from the first sequence to obtain a second set of complex valued symbols, and block-wise spreading the second set of complex valued symbols with a second spreading sequence that is different from said first spreading sequence.
15. The apparatus of claim 9 further configured to receive signalling indicating a resource partition, the resourced partition having an associated set of symbol sequences;
wherein transmitting the symbol sequence comprises transmitting a symbol sequence from the associated set of symbol sequences based on a UE identifier of the UE.
16. The apparatus of claim 9 further configured to transmit the symbol sequence with a subcarrier spacing different from other transmissions in a same resource grid, wherein the subcarrier spacing is a spacing between consecutive OFDM subcarriers.
17. A method comprising:
receiving, by a user equipment (UE), a control message that releases the UE from the RRC_CONNECTED state, the control message comprising configuration information for conveying a scheduling request in an RRC_INACTIVE state;
entering, by the UE, into the RRC_INACTIVE state from RRC_CONNECTED state;
transmitting, by the UE, in accordance with said configuration information, a symbol sequence from a set of possible symbol sequences to convey the scheduling request.
18. The method of claim 13 , wherein the control message further comprises configuration information for conveying acknowledgment/negative acknowledgment (ACK/NACK) feedback in the RRC_INACTIVE state.
19. An apparatus comprising:
a processor and a memory, wherein the apparatus is configured to:
receive, by the apparatus, a control message that releases the apparatus from the RRC_CONNECTED state, the control message comprising configuration information for conveying a scheduling request in an RRC_INACTIVE state;
entering, by the apparatus, into the RRC_INACTIVE state from RRC_CONNECTED state;
transmitting, by the apparatus, in accordance with said configuration information, a symbol sequence from a set of possible symbol sequences to convey the scheduling request.
20. The apparatus of claim 19 , wherein the control message further comprises configuration information for conveying acknowledgment/negative acknowledgment (ACK/NACK) feedback in the RRC_INACTIVE state.