Demodulation reference signals transmission in wireless systems
Systems, methods, and instrumentalities are disclosed herein associated with transmission of demodulation reference signals (DMRS) in wireless systems. DMRS symbols may be placed in a slot for channel estimation operations. For example, channel estimation performance may be enhanced based on using an increased number of DMRS symbols. Channel estimation enhancements may be performed by transmitting DMRS symbols in an extended slot, for example, to avoid data degradation (e.g., which may result from replacing data transmission symbols with DMRS symbols). An extended slot may be a slot that includes symbols spanning across multiple slots (e.g., two slots, consecutive slots), for example, such as a slot n and a slot n+1.
1 . A wireless transmit/receive unit (WTRU) comprising:
a memory; and
a processor in communication with the memory, the processor configured to:
receive downlink control information (DCI), wherein the DCI indicates an uplink grant for a physical uplink shared channel (PUSCH) transmission, a first number of symbols, a pattern of reference signals in an uplink slot, and an indication to use an extended slot associated with the PUSCH transmission, wherein the uplink grant for the PUSCH transmission is associated with the uplink slot, wherein the extended slot comprises symbols of the uplink slot and one or more symbols at an end of a previous slot, wherein the previous slot is contiguous with the uplink slot, and wherein the first number of symbols is a number of symbols to use in the uplink slot;
determine, based on one or more of a duration of the extended slot, the first number of symbols, or the pattern of reference signals in the uplink slot, a second number of symbols, wherein the second number of symbols comprises at least one of a reference signal symbol or a PUSCH transmission symbol, and wherein the second number of symbols is a number of symbols to use in a portion of the extended slot associated with the previous slot;
determine a first part of a transmission and a second part of the transmission, wherein the first part of the transmission is determined based at least on the second number of symbols, and wherein the second part of the transmission is determined based on the first number of symbols and the pattern of reference signals in the uplink slot;
transmit, in one or more symbols at the end of the previous slot, the first part of the transmission; and
transmit, in the uplink slot, the second part of the transmission;
wherein a power and phase continuity is maintained for the first part of the transmission and the second part of the transmission, if the WTRU receives an indication to control power and phase to maintain the power and phase continuity.
2 . The WTRU of claim 1 , wherein the processor is further configured to determine respective locations of respective symbols of the second number of symbols in the portion of the extended slot associated with the previous slot, and wherein determining the first part of the transmission is further based on the respective locations of respective symbols of the second number of symbols in the portion of the extended slot associated with the previous slot.
3 . The WTRU of claim 2 , wherein determining the respective locations of respective symbols of the second number of symbols in the portion of the extended slot associated with the previous slot is further based on one or more of the duration of the extended slot, the first number of symbols, or the pattern of reference signals in the uplink slot.
4 . The WTRU of claim 1 , wherein the second number of symbols comprises a number of reference signal symbols and a number of PUSCH transmission symbols.
5 . The WTRU of claim 1 , wherein the second number of symbols is zero reference signal symbols or more than zero reference signal symbols.
6 . The WTRU of claim 1 , wherein the pattern of reference signals in the uplink slot indicates zero reference signal symbols or more than zero reference signal symbols are in the uplink slot.
7 . The WTRU of claim 1 , wherein determining the second number of symbols is further based on the duration of the extended slot, the first number of symbols, and the pattern of reference signals in the uplink slot.
8 . The WTRU of claim 1 , wherein the DCI is received with an explicit or implicit bundling indication.
9 . The WTRU of claim 1 , wherein the processor is further configured to stop maintaining the phase or power continuity if one or more conditions are satisfied.
10 . The WTRU of claim 9 , wherein the one or more conditions include at least one of:
the WTRU receives the DCI without a bundle indication;
the WTRU receives a termination indication in the DCI;
the WTRU does not receive a bundle indication over a time;
the WTRU receives a stop indication; or
the WTRU observes a channel variation.
11 . A method implemented by a wireless transmit/receive unit (WTRU), the method comprising:
receiving downlink control information (DCI), wherein the DCI indicates an uplink grant for a physical uplink shared channel (PUSCH) transmission, a first number of symbols, a pattern of reference signals in an uplink slot, and an indication to use an extended slot associated with the PUSCH transmission, wherein the uplink grant for the PUSCH transmission is associated with the uplink slot, wherein the extended slot comprises symbols of the uplink slot and one or more symbols at an end of a previous slot, wherein the previous slot is contiguous with the uplink slot, and wherein the first number of symbols is a number of symbols to use in the uplink slot;
determining, based on one or more of a duration of the extended slot, the first number of symbols, or the pattern of reference signals in the uplink slot, a second number of symbols, wherein the second number of symbols comprises at least one of a reference signal symbol or a PUSCH transmission symbol, and wherein the second number of symbols is a number of symbols to use in a portion of the extended slot associated with the previous slot;
determining a first part of a transmission and a second part of the transmission, wherein the first part of the transmission is determined based at least on the second number of symbols, and wherein the second part of the transmission is determined based on the first number of symbols and the pattern of reference signals in the uplink slot;
transmitting, in one or more symbols at the end of the previous slot, the first part of the transmission; and
transmitting, in the uplink slot, the second part of the transmission;
wherein a power and phase continuity is maintained for the first part of the transmission and the second part of the transmission, if the WTRU receives an indication to control power and phase to maintain the power and phase continuity.
12 . The method of claim 11 , further comprising:
determining respective locations of respective symbols of the second number of symbols in the portion of the extended slot associated with the previous slot, and wherein determining the first part of the transmission is further based on the respective locations of respective symbols of the second number of symbols in the portion of the extended slot associated with the previous slot.
13 . The method of claim 12 , wherein determining the respective locations of respective symbols of the second number of symbols in the portion of the extended slot associated with the previous slot is further based on one or more of the duration of the extended slot, the first number of symbols, or the pattern of reference signals in the uplink slot.
14 . The method of claim 11 , wherein the second number of symbols comprises a number of reference signal symbols and a number of PUSCH transmission symbols.
15 . The method of claim 11 , wherein the second number of symbols is zero reference signal symbols or more than zero reference signal symbols.
16 . The method of claim 11 , wherein the pattern of reference signals in the uplink slot indicates zero reference signal symbols or more than zero reference signal symbols are in the uplink slot.
17 . The method of claim 11 , wherein determining the second number of symbols is further based on the duration of the extended slot, the first number of symbols, and the pattern of reference signals in the uplink slot.
18 . The method of claim 11 , wherein the DCI is received with an explicit or implicit bundling indication.
19 . The method of claim 11 , further comprising stopping maintaining the phase or power continuity if one or more conditions is satisfied.
20 . The method of claim 19 , wherein the one or more conditions include at least one of:
the WTRU receives the DCI without a bundle indication;
the WTRU receives a termination indication in the DCI;
the WTRU does not receive a bundle indication over a time;
the WTRU receives a stop indication; or
the WTRU observes a channel variation.