Patent Description:
The present application generally relates to wireless communications.

In wireless communication systems, a central node may serve one or more wireless transmit/receive units (WTRUs). When a central node serves one or more WTRUs, the opportunity to send transport blocks (TB) to the central node may be administered by the central node. For example, the central node may schedule a WTRU uplink (UL) transmission.

<NPL>", discusses different design aspect of grant-free transmission. <NPL>relates to a prioritization of UCI and grant free PUSCH transmission when there is an overlap in time domain resources (simultaneous transmission).

A wireless transmit receive unit (WTRU) may be configured to send grant free transmissions on grant free resources. The WTRU may send a first grant free transmission that comprises a first part and a second part. The first part and the second part may each be associated with a priority. The priority associated with the first part may be a higher priority than the priority associated with the second part. For example, the first part may include acknowledgement information (e.g., hybrid automatic repeat request (HARQ)) and the second part may include channel quality information (CQI). The WTRU may select a first back off value for the first grant free transmission from a first range of back off values. The WTRU may determine whether the first grant free transmission was successful. If the first grant free transmission was not successful, the WTRU may send a retransmission of the first grant free transmission. The retransmission may include the first part and may not include the second part. The WTRU may select a second back off value for the retransmission from a second range of back off values. The second range of back off values may be a larger range than the first range of back off values. The second range of back off values may indicate the number of grant free resource to skip prior to sending the retransmission.

Multiplexing may be used on the first grant free transmission and/or the retransmission of the first grant free transmission. The first grant free transmission may be multiplexed on a transport block using a first redundancy version. The retransmission may be multiplexed on another transport block using a second redundancy version. The second redundancy version may be associated with a higher redundancy than the first redundancy version.

A more detailed understanding may be had from the following description, given by way of examples in conjunction with the accompanying drawings wherein:.

A detailed description, which may include illustrative embodiments, will now be described with reference to the various Figures. Although this detailed description may provide detailed examples of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

The base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface <NUM> using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/or LTE-Advanced Pro (LTE-A Pro).

The CN <NUM> shown in <FIG> may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b.

Although the features and elements described herein consider LTE, LTE-A, New Radio (NR), and/or <NUM> specific protocols, it should be understood that the features and elements described herein are not restricted to LTE, LTE-A, New Radio (NR), and/or <NUM> specific protocols and may be applicable to other wireless systems.

In wireless communication systems, a central node (e.g., a gNodeB) may serve one or more WTRUs. When a central node serves one or more WTRUs, the opportunity to send transport blocks (TBs) to the central node may be administered by the central node. For example, a gNodeB (gNB) may schedule a WTRU uplink (UL) transmission by assigning time-frequency resources (e.g., separate time-frequency resources) to one or more WTRUs (e.g., each WTRU) and/or granting one or more resources (e.g., each resource) to a WTRU. Such arrangement for UL transmission may be referred to as grant-based UL transmission.

A gNB may broadcast the presence of one or more time-frequency resources and/or allow one or more WTRUs (e.g., a set of WTRUs) to compete for the resources (e.g., each resource), and/or allow access to the resources without an UL grant (e.g., a specific UL grant). Such arrangement (e.g., in New Radio (NR)) for UL transmission may be referred to as grant-free (GF) UL transmission, or an UL transmission without grant. The application of GF UL transmission may be in ultra-reliable low-latency communication (URLLC), massive machine-type communication (mMTC or MMTC), and/or enhanced mobile broadband (eMBB or EMBB) communication. MMTC may enable communication between a large number of low-cost and power-constrained (e.g., battery-driven) devices intended to support applications (e.g., smart metering, logistics, and/or field and body sensors). URLLC may enable devices and/or machines to reliably (e.g., ultra-reliably) communicate with very low latency and/or high availability. Enabling devices and/or machines to communicate with ultra-reliability, very low latency, and/or high availability may enable URLLC to provide vehicular communication, industrial control, factory automation, remote surgery, smart grids, and/or public safety applications. EMBB may provide enhancements to one or more (e.g., a variety) of parameters (e.g., data rate, delay, and coverage) of mobile broadband access.

GF UL transmission may be performed. One or more of the following may apply. A gNB may specify GF resources (e.g., via radio resource control (RRC) signaling). The GF resources may be WTRU-specific or may be WTRU-independent. A WTRU may pick a GF resource and/or send a TB on the GF resource. If the WTRU does not receive (e.g., after a period of time) a hybrid automatic repeat request acknowledgment (HARQ-ACK) (e.g., the corresponding HARQ-ACK for a TB), the WTRU may retransmit the TB (e.g., may plan to retransmit the TB). The WTRU may retransmit the TB on another GF resource and/or on a granted resource (e.g., if the gNB grants a resource). The WTRU may retransmit using GF resources, for example, until a max number of retries is reached.

In a GF UL transmission, a TB may be transmitted (e.g., transmitted K times) across consecutive resources (e.g., K consecutive GF resources). Such transmissions may be referred to as GF transmissions with K repetitions. For a GF UL transmission (e.g., for a TB transmission with K repetitions), the repetitions may follow a redundancy-version (RV) sequence that may be configured by WTRU-specific RRC signaling (e.g., to be a previously known sequence). An RV sequence may include a sequence of redundancy version values used by a WTRU. In examples, a RV sequence may include a sequence of one or more repeated redundancy versions (e.g., four repetitions of a redundancy version of <NUM>, such as, [<NUM>,<NUM>,<NUM>,<NUM>]). In examples, a RV sequence may include a sequence of one or more redundancy versions where the first and third redundancy version values are <NUM> and the second and fourth are with redundancy version values are <NUM> (e.g., [<NUM>,<NUM>,<NUM>,<NUM>]).

There may be an inefficiency in a (e.g., each) GF UL transmission, for example. The inefficiency may be due to the nature of GF transmission and/or may depend on the number of WTRUs attempting to use a (e.g., each) GF resource.

Depending on the application (e.g., URLLC or mMTC) for which the GF operation is used, there may be a chance (e.g., a low chance or a high chance) of a collision among the WTRUs attempting to access a GF resource. The higher the number of attempting WTRUs, the higher the chance of collision and/or the lower the overall efficiency. The chance of a collision among the attempting WTRUs may be lowered.

A WTRU may multiplex Uplink Control Information (UCI) with the TB (e.g., the TB that the WTRU attempts to send using a GF resource). The behavior of a WTRU, for example, after performing the GF operation, may be used to determine whether the gNB received (e.g., successfully received) the UCI.

One or more types of GF transmissions (e.g., in NR) may be performed. A gNB may specify GF resources using one or more of the following. A gNB may specify a GF resource via a Radio Resource Control (RRC) configuration (e.g., reconfiguration) without L1 signaling (e.g., Type <NUM>). A gNB may specify a GF resource via RRC configuration with L1 signaling (e.g., Type <NUM>). A gNB may specify a GF resource via RRC configuration with L1 signaling (e.g., that may modify one or more RRC-configured parameters) (e.g., Type <NUM>).

A grant-free (GF) resource may be selected by one or more WTRUs. For example, a WTRU selecting a GF resource from one or more (e.g., a set of) GF resources may perform an UL GF transmission. One or more of the following may apply. A WTRU may receive a HARQ-NACK for a TB that has been sent (e.g., previously sent) via a GF operation. The WTRU may not receive a HARQ-ACK or a HARQ-NACK for a TB transmission that has been sent. The WTRU may attempt to send the same TB (e.g., resend the same TB) or another TB (e.g., if the WTRU receives a HARQ-NACK, or the WTRU does not receive a HARQ-NACK or HARQ-ACK). The WTRU may choose the next resource for the UL GF transmission. A WTRU may attempt) to send the UL GF transmission on a GF resources that other WTRUs are also attempting to transmit on, such as in mMTC applications, which may increase the chance of a collision among the WTRUs.

The WTRU may retransmit a pending TB on a GF resource (e.g., the next immediately available GF resource). For example, the WTRU may retransmit the pending TB on the next immediately available GF resource (e.g., because doing so may lower the potential delay). If two or more WTRUs (e.g., all WTRUs) that have collided during the previous GF resource (e.g., which may lead to HARQ-NACK or DRX) retransmit their pending TB on the next (e.g., immediately next) GF resource(s), the chance of another collision may increase.

An opportunistic resource selection for a GF retransmission may be performed. An example of an opportunistic resource selection for GF retransmission is shown in <FIG>. For example, as shown in <FIG>, if a GF transmission by a WTRU is unsuccessful, the WTRU may choose an upcoming GF resource to retransmit its pending TB. One or more (e.g., two) WTRUs may attempt to send their pending TB on GF resource <NUM> in <FIG>. A gNB may be unsuccessful in decoding the TBs (e.g., any of the TBs), for example, due to a collision. The gNB may be unable to identify which WTRUs have used the GF resource <NUM>. The gNB may be unable to send HARQ feedback to the WTRUs. A WTRU may determine to retransmit the pending TB on the next available (e.g., next immediately available) GF resource (e.g., GF resource <NUM>), for example, because doing so would lower the delay (e.g., potential delay). If a WTRU determines to retransmit the pending TB on the next available (e.g., next immediately available) GF resource, there may be a low (e.g., no) chance of a collision. If two or more (e.g., all) WTRUs that have collided during the previous GF resource <NUM> retransmit their pending TB on the same resource, there may be an increase in the chance of a collision.

The WTRU may not retransmit on one or more subsequent GF resources (e.g., one or more immediately subsequent GF resources) and/or may retransmit the pending TB in an opportunistic manner (e.g., to lower the chance of collision). The WTRU may back off from retransmission, for example, by skipping a random number of GF resources (e.g., a back off value) before initiating a retransmission. Backing off for a random number of GF resources may lead to distributing the attempting WTRUs over a longer period, for example, because the random number may be chosen from a pre-defined range (e.g., range of back off values) and/or may be derived (e.g., drawn) according to a probability (e.g., non-deterministically) such that the chance of two or more WTRUs deriving (e.g., drawing) the same random number (e.g., the same back off value) is minimal. For example, the back off counter (e.g., back off value) may be derived (e.g., drawn) uniformly from a pre-defined range (e.g., <NUM> to T<NUM>). As T<NUM> becomes larger (e.g., as the back off range becomes larger), the chance of a collision (e.g., another collision) may be lowered, for example, among the contending WTRUs. For example, if T<NUM>=<NUM>, two WTRUs (e.g., two WTRUs that have collided in a previous attempt to transmit during a given GF resource) may be more likely (e.g., more likely than if T<NUM>=<NUM>) to derive (e.g., draw) different back off values from a range (e.g., a range of back off values that includes <NUM>, <NUM>, <NUM>, <NUM>) and/or may be more likely to send on separate GF resources. The two WTRUs may derive (e.g., draw) the same number (e.g., back off value) from the range (e.g., a range of back off values that includes <NUM>, <NUM>, <NUM>, <NUM>). If the derived (e.g., drawn) numbers are the same (e.g., the back off values are the same), the two WTRUs may transmit (e.g., retransmit) on the same GF resource, for example, which may lead to a (e.g., another) collision. If the transmission (e.g., retransmission) fails (e.g., also fails), a next GF resource for transmission may be chosen (e.g., chosen again). The next GF resource for transmission may be chosen randomly from a range (e.g., <NUM> to T<NUM>) that may be wider (e.g., larger) than the previous range (e.g., T<NUM> may be <NUM>×T<NUM>+<NUM>). For example, if Ti=<NUM>, then T<NUM>=<NUM>, where a WTRU (e.g., each WTRU) of the two or more WTRUs that have collided in the previous GF UL transmission may derive (e.g., draw) a back off value randomly with a uniform distribution from a range (e.g., a range of back off values that includes <NUM>, <NUM> ,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>). The range of the back off values may increase. As the range of back off values increases, the likelihood that different back off counters are derived (e.g., drawn) by contending WTRUs and/or the likelihood that separate GF resources are used by the contending WTRUs to send a transmission (e.g., subsequently send a transmission) may increase. As described herein, a backoff range may be referred to as contention window size (CWS).

A WTRU may initiate GF transmission or retransmission, for example, by deriving (e.g., drawing) a back off value (e.g., denoted by t) from a range of back off values (e.g., from T<NUM>to Ti), skipping resources (e.g., skipping the next t-<NUM> GF resources), and/or transmitting/retransmitting on a resource (e.g., the tth GF resource). T<NUM> may be equal to <NUM> (e.g., the first transmission may have a zero back off counter), T<NUM> may be equal to <NUM>, and Ti may be equal to <NUM>×Ti-<NUM>+<NUM> (e.g., leading to T<NUM>=<NUM>, T<NUM>=<NUM>, etc.). A non-zero back off counter may be used for T<NUM>, for example, for the first transmission (e.g., T<NUM>=<NUM>, and Ti=<NUM>×Ti-<NUM>+<NUM>, which may lead to T<NUM>=<NUM>, T<NUM>=<NUM>, T<NUM>=<NUM>, etc.). An example may include a coefficient, which may double the back off value range (e.g., after a collision). The increase may be performed with a different coefficient (e.g., <NUM>, which may triple the back off value range), for example, such that Ti=<NUM>×(Ti-<NUM>+<NUM>)-<NUM>). The back off value range may increase, for example, to lower the chance of another collision among two or more contending WTRUs. The sequence of Ti values may be pre-defined for WTRUs (e.g., some or all WTRUs), or may be communicated via RRC signaling, etc. A WTRU (e.g., each WTRU) may pick (e.g., may randomly pick) the Ti value according to whether it is transmitting for the first time, retransmitting for the first time, retransmitting for the second time, etc. (e.g., such that the backoff range may be different for first transmission, first retransmission, second retransmission, etc.). The sequence of Ti values may be provided to each WTRU via WTRU-specific RRC signaling and the sequence of one WTRU may be different from another WTRU, e.g., depending on the priority given to each WTRU (e.g., WTRUs running low-latency applications may be prioritized over WTRUs running MMTC applications).

The values of T<NUM>, T<NUM>, T<NUM>, etc., and/or the probability that a value is derived (e.g., drawn) from may be predefined (e.g., predefined in the specification) and/or may be signaled (e.g., signaled by RRC). The gNB may customize the parameters (e.g., the parameters that indicate the values of T<NUM>, T<NUM>, T<NUM>, etc. and/or the probability that a value is derived), for example, according to the deployment and/or application.

A WTRU (e.g., each WTRU) may priori select (e.g., or be granted) a random sub-set of the grant free resources available for transmission that may be unique to the WTRU (e.g., each WTRU). A grant free resource may be selected for transmission by a WTRU. The WTRU may select the grant free resource without receiving a unique and/or explicit grant from a gNB. For example, rather than the gNB allocating a set of resources to WTRUs (e.g., all the grant free WTRUs), a WTRU (e.g., each WTRU) may priori select (e.g., or be granted) a random sub-set of the grant free resources available for transmission. The sub-set of grant free resources may be unique to the WTRU (e.g., each WTRU). Upon failure of an initial transmission, the WTRU may send a retransmission on a resource (e.g., the next uniquely available grant free resource from the sub-set of grant free resources). The randomization of the WTRU specific grant free resource (e.g., the sub-set of grant free resources unique to the WTRU) may reduce the probability that a collision occurs between subsequent transmissions of the transmitting WTRUs.

It may be determined whether a GF transmission is successful or unsuccessful. When a WTRU sends a TB to a gNB (e.g., the WTRU's gNB), the WTRU may receive an HARQ-ACK or HARQ-NACK, for example, after the transmission (e.g., in response to the transmission). The timing between an UL transmission and the corresponding HARQ feedback (e.g., expected to be sent by the gNB to the WTRU) may be expressed by a parameter that may be obtained from one or more fields in the DCI, or may be configured by an RRC parameter.

In GF UL transmission, the WTRU may not receive or may not detect a HARQ-ACK or a HARQ-NACK (e.g., due to the collision of two or more transmissions by WTRUs transmitting on the same GF resource). After a certain time (e.g., an acknowledgment time), the WTRU may determine that a previously sent TB was not received by the gNB and/or may attempt to retransmit the TB using a GF resource (e.g., the next available GF resource). For GF UL transmission, the timing between a GF UL transmission and the expected HARQ feedback may be expressed by a parameter (e.g., an acknowledgement time) that may be carried in one or more fields in the DCI or may be specified by RRC.

One or more WTRUs may attempt to use GF resources (e.g., available GF resources) in one or more (e.g., a few) consecutive slots. If WTRUs (e.g., all WTRUs) wait for the same duration of time before determining that the previous GF transmission was unsuccessful, the WTRUs (e.g., all the WTRUs) may target the same GF resource for transmission (e.g., the next immediately available GF resource), for example, to perform a retransmission. A fixed time duration for WTRUs (e.g., all WTRUs) to determine whether a previous GF transmission is unsuccessful may lead to a higher chance of a collision on the next GF resource used for transmission. A WTRU may use a corresponding time duration (e.g., waiting time) that is different from another WTRU. Such a varying waiting time may distribute the retransmission attempts by the WTRUs, for example, over a range of two or more (e.g., several) GF resources and/or over two or more (e.g., several) slots. In a GF UL transmission, the timing between a GF UL transmission and a time (e.g., a maximum time) that the corresponding HARQ feedback is to be received (e.g., is expected to be received) may be expressed by a parameter (e.g., that may be carried in one or more fields in the DCI and/or specified by a WTRU-specific RRC). Such time interval may be different from a WTRU and another WTRU. The gNB may define the time interval. For example, the gNB may assign a time duration to one or more WTRU (e.g., each WTRU). This may be a gNB directed method. The gNB may specify a range of time from which the WTRU may pick (e.g., may randomly pick) a value and/or may choose the value to be the timing between a GF UL transmission and maximum time that the corresponding HARQ feedback is to be received (e.g., is expected to be received). The gNB specifying the range of time and/or choosing the value may be WTRU autonomous (e.g., more WTRU autonomous). The WTRU may provide feedback of (e.g., may need to provide feedback of) the value to the gNB. Feeding back the value to the gNB may reduce the amount of grant free blind decoding, for example, when the gNB is able to identify the WTRU and not decode the payload.

The range of time intervals may be determined by parameters (e.g., the traffic class). For example, low latency traffic may have a smaller range and/or latency tolerant traffic may have a larger range. A WTRU may have a range (e.g., a single range) that may be determined based on the WTRU application type (e.g., the range for URLLC application type < the range of a eMBB application type < the range for a mMTC application type). A WTRU may have two or more (e.g., multiple) ranges that may be selected based on the type of traffic to be sent.

One or more GF resources may be sensed, for example, to reduce collisions. In GF UL transmissions, one or more WTRUs may attempt to send their pending TB on the same GF resource. For example, one or more WTRUs may attempt to send their pending TB on the same GF resource because the GF resources may be up for grabs by one or more WTRUs (e.g., any WTRU) that is configured to perform GF UL transmission. An attempt by multiple WTRUs to use the same GF resources may cause a collision among the WTRUs (e.g., unsuccessful transmissions), for example, which may lead to none of the TB of the WTRUs being decoded (e.g., being decoded successfully). WTRUs may avoid such collisions, for example, by sensing the resource (e.g., the GF resource) to find out whether another WTRU is using the resource, for example, before attempting to send their pending TB during the same GF resource.

One or more time-domain GF resources may be sensed. A WTRU (e.g., each WTRU) that attempts to use a GF resource may choose a beginning portion of the resource to perform resource sensing, for example, to find out an availability of the resource. If no use of the resource is detected (e.g., if the WTRU determines that no other WTRU is using the resource), the WTRU may decide to send its pending TB on the remaining portion of the GF resource (e.g., after processing). Sensing the medium may include performing energy detection (ED), for example, during the sensing portion. <FIG> shows an example where the attempting WTRU senses the first symbols of the GF resource (e.g., the first three symbols of the GF resource). In order to benefit from such behavior, an attempting WTRU (e.g., each attempting WTRU) may choose a sensing interval that may be different from the sensing interval of another attempting WTRU. For example, a WTRU may determine to sense the availability of the grant-free resource during the WTRU's first few OFDM symbols (e.g., first three symbols as in <FIG>) and/or throughout the bandwidth of the grant-free resource. If it is detected that no other WTRU is using the resource (e.g., using energy-detection), the WTRU may determine to send the WTRU's pending TB on the remaining portion of the GF resource, for example, after processing.

A WTRU (e.g., each WTRU) may choose a number (e.g., a random number) of symbols, for example, that may be derived (e.g., drawn) using a priori known probability distribution. For example, WTRUs (e.g., all attempting WTRUs) may derive (e.g., draw) a number (e.g., a random number) uniformly from a range (e.g., <NUM>,<NUM>,<NUM>,<NUM>,<NUM>) and/or may perform the resource sensing during the derived number of symbols and/or throughout the bandwidth of the GF resource. <FIG> shows an example where three WTRUs attempt to use a grant-free resource and the WTRUs (e.g., each WTRU) uniformly derive (e.g., draws) a value (e.g., a single value) from a priori-known range (e.g., <NUM>,<NUM>,<NUM>,<NUM>,<NUM>). Referring to <FIG> one or more of the following may apply. A sensing interval for WTRU1 may be <NUM> symbols, a sensing interval for WTRU2 may be <NUM> symbols, and/or a sensing interval for WTRU3 may be <NUM> symbol. The three WTRUs may pseudo-randomly (e.g., according to a distribution) derive (e.g., draw) a number n from a priori-known range (e.g., <NUM>,<NUM>,<NUM>,<NUM>,<NUM>) and/or may sense the availability of the resource during the first n symbols and throughout the bandwidth of the grant-free resource. WTRU1 may sense the medium during the first four OFDM symbols of the GF resource. WTRU2 may sense the medium during the first three OFDM symbols of the GF resource. WTRU3 may sense the medium during the first OFDM symbol of the GF resource. WTRU3 may be the first WTRU that finds the medium is available and/or may attempt to send the WTRU's pending TB, for example, on the remaining portion of the GF resource (e.g., after processing). WTRU1 and WTRU2 (e.g., after sensing the medium for the duration that is expected) may determine that the GF resource is in use and/or may refrain from using the GF resource. Two or more WTRUs may derive (e.g., draw) the same number and/or may sense the resource for the same duration, which may lead to collision among the WTRUs. The chance for such outcome decreases as the resource sensing range increases.

Two or more WTRUs may attempt to use a GF resource (e.g., the same GF resource). WTRU3 may not attempt to use the GF resource (e.g., may not perform the resource sensing). WTRU2 and WTRU1 may sense the medium. For example, WTRU2 may be the first WTRU that determines that the medium is available and/or may send (e.g., attempt to send) the WTRU's pending TB at the remaining portion of the resource (e.g., after processing). WTRU1 (e.g., after sensing the medium for the duration (e.g., the expected duration)) may determine that the GF resource is in use and/or may refrain from using the GF resource. If neither WTRU3 nor WTRU2 attempt to use the GF resource (e.g., do not perform the resource sensing), the WTRU1 (e.g., after completion of its sensing period) may determine that the GF resource is not in use and/or may transmit its pending TB.

Depending on the sensing performed (e.g., energy detection) and/or the accuracy of sensing performed by a WTRU (e.g., each WTRU), the WTRU may determine earlier (e.g., earlier than the end of its sensing interval) that the GF resource is in use and/or may stop sensing the resource. For example, depending on the sensing and/or the accuracy of the sensing performed by a WTRU, the WTRU may fail to sense the medium is in use and/or may attempt to use the resource, which may cause a collision.

One or more frequency-domain GF resources may be sensed. A WTRU may perform (e.g., may consistently perform) resource sensing for the same number of OFDM symbols (e.g., one OFDM symbol and/or a priori known few OFDM symbols) and/or for a variable number of resource blocks (RB). <FIG> shows an example where three WTRUs attempt to use a given grant-free resource and/or a WTRU (e.g., each WTRU) uniformly derives (e.g., draws) a value (e.g., a single value) from a priori-known range. As illustrated in <FIG>, WTRU1, WTRU2, and WTRU3 may perform resource sensing on the same number of OFDM symbols but for a different number of RBs. Referring to <FIG>, one or more of the following may apply. A sensing interval for WTRU1 may be <NUM> RBs (e.g., before a GF transmission). A sensing interval for WTRU2 may be <NUM> RBs (e.g., before a GF transmission). A sensing interval for WTRU3 may be <NUM> RBs (e.g., before a GF transmission). The three WTRUs may pseudo-randomly derive (e.g., draw) (e.g., per a distribution) a number n from a priori-known range and/or may sense the availability of the resource during the top n RBs of the first OFDM symbol (e.g., or a priori-known first few OFDM symbols). WTRU1 may sense the medium during the top <NUM> RBs of the GF resource. WTRU2 may sense the medium during the top <NUM> RBs of the GF resource WTRU3 may sense the medium during the top <NUM> RBs of the GF resource. WTRU3 may be the first WTRU that finds the medium is available and/or may attempt to send the WTRU's pending TB on the remaining portion of the resource, for example, after processing. WTRU1 and WTRU2 (e.g., after sensing the medium for the duration that is respectively expected) may determine that the GF resource is in use and/or may refrain from using the GF resource. The range that a WTRU (e.g., each WTRU) derives (e.g., draws) the WTRU's sensing period from may be a priori known (e.g., communicated via a parameter by RRC or DCI). The range may be obtained (e.g., may implicitly be obtained) by a WTRU (e.g., each WTRU) as a function of the bandwidth of the GF resource. For example, the range may be the bandwidth of the GF resource represented by the number of RBs associated with the GF resource. <FIG> shows an example in which the range includes (<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>). The range may be implicitly obtained from the bandwidth of the GF resource which is <NUM> RBs.

Two or more WTRUs may attempt to use a GF resource (e.g., the same GF resource). WTRU3 may not attempt to use the GF resource (e.g., may not be performing the resource sensing). WTRU2 and WTRU1 may be sensing the medium. WTRU2 may be the first WTRU that determines that the medium is available and/or may attempt to send the WTRU's pending TB at the remaining portion of the resource (e.g., after processing). WTRU1 (e.g., after sensing the medium for the duration (e.g., the expected duration)) may determine that the GF resource is in use and/or may refrain from using the GF resource. If neither WTRU3 nor WTRU2 attempt to use the GF resource (e.g., do not perform the resource sensing), the WTRU1 (e.g., after completion of its sensing period) may determine that the GF resource is not in use and/or may transmit its pending TB.

A two-dimensional time-frequency GF resource may be sensed. A WTRU may perform the resource sensing for a variable number (e.g., derived pseudo-randomly from a priori known time-interval) of OFDM symbols (e.g., first OFDM symbols) of the GF resource and/or for a variable number (e.g., derived pseudo-randomly from a priori known RB-interval) of top resource blocks. For example, a time-interval may be (<NUM>,<NUM>,<NUM>) and/or a RB-interval may be (<NUM>,<NUM>,<NUM>,<NUM>,<NUM>). The WTRU may derive (e.g., draw) a number pseudo-randomly from the time-interval, which may be the time duration of the sensing interval. The WTRU may derive (e.g., draw) a number pseudo-randomly from the RB-interval, which may be the frequency bandwidth of the sensing interval. If the WTRU determines the resource is not in use (e.g., using energy-detection) during the sensing interval, the WTRU may send the WTRU's pending TB, for example, at the remaining portion of the GF resource after processing. A set of resource sensing areas may be priori known by one or more WTRU(s) (e.g., all WTRUs) and/or a WTRU may pseudo-randomly select an area to perform resource sensing. A resource sensing area may include rectangular time and frequency interval, such as (t, f) where t may be in units of OFDM symbol and/or f may be in units of RBs.

The resource sensing areas in <FIG> may include one or more of the following. t may be pseudo-randomly derived (e.g., drawn) by a WTRU from a priori distribution. t may be different for two or more WTRUs. For example, a WTRU attempting to use the GF resource may have a t that may be different from another WTRU. f may be fixed for one or more (e.g., all) WTRUs attempting to use the GF resource (e.g., f may be equal to the bandwidth of the GF resource, for example, all the RBs of the GF resource).

The resource sensing areas in <FIG> may include one or more of the following. f may be pseudo-randomly derived (e.g., drawn) by a WTRU from a priori distribution and/or f may be one or more RBs. f may be different in two or more WTRUs. For example, a WTRU attempting to use the GF resource may have an f that may be different from an f in another WTRU. t may be fixed for WTRUs (e.g., all WTRUs) attempting to use the GF resource (e.g., t may be equal to one or more OFDM symbols).

The sensing areas may be <NUM>-D time-frequency areas, for example, where the sensing area for a WTRU may differ from another WTRU in time and/or frequency domain. A set of sensing areas may be a priori known by one or more WTRU(s) (e.g., all WTRUs (e.g., (ti, fi) for one or more (e.g., all) the sensing areas is a priori identified by gNB and/or known to one or more (e.g., all) WTRUs). The WTRU may select a sensing area from the set. The set of sensing areas may be designed and/or may be nested. A smallest sensing area may be a subset of one or more sensing areas (e.g., all other sensing areas). A second smallest sensing area may be a subset of one or more other sensing areas (e.g., all other sensing areas besides the smallest sensing area), etc. The structure (e.g., the nested structure) of the sensing areas may allow for the determination (e.g., an unambiguous inference) of whether the resource is in use. For example, a fixed payload size carrying the sensing areas in the format of a bitmap may be used to indicate sensing areas within the GF resource. The two-dimensional bitmap may indicate one or more frequency-time areas/partitions within the GF resource.

The resource sensing may be performed in time-domain and/or RB-domain, for example, according to a sensing interval, which may be pseudo-randomly derived (e.g., drawn) from a priori-known distribution. One or more WTRUs may be prioritized to use a minimum sensing interval (e.g., performing no resource sensing). For example, a WTRU that is configured for low-latency applications may be configured by RRC to perform no sensing (e.g., as if the WTRU's sensing interval is zero) and/or the WTRU may attempt to use a GF resource without sensing. WTRUs (e.g., WTRUs that perform latency-tolerant applications, such as mMTC) may be configured to perform resource sensing. A WTRU with a certain application (e.g., a low-latency application) may get a higher priority, for example, compared to other WTRUs. The priori range that WTRU's derive (e.g., draw) a number from (e.g., pseudo-randomly derive a number from) may start from a non-zero number, for example, to prioritize the high-priority WTRUs. Prioritization may be performed based on or more criteria. In examples, the prioritization may be based on applications performed by a WTRU (e.g., low-latency vs mMTC applications).

For resource sensing, the number of resource elements (REs) from the GF resource that a WTRU uses for transmission of a TB may be variable and/or may not be known in advance (e.g., due to the sensing interval). The sensing interval may be a number that is pseudo-randomly derived. One or more of the following may apply (e.g., which may address the lack of knowledge).

The WTRU may prepare the TB, for example, as if there is no resource sensing. If the WTRU determines that the GF resource is not in use (e.g., after performing the resource sensing), the WTRU may rate match the prepared TB and/or send the rate-matched TB.

Where the outcome of the sensing interval is a few symbols (e.g., a sensing interval that leads to a few medium sensing interval), the WTRU may prepare the pending TB with various rate-matching assumptions. The various rate-matching assumptions of the TB may be based on an outcome. For example, a sensing range may be (<NUM>,<NUM>,<NUM>) and a WTRU may pseudo-randomly derive (e.g., draw) <NUM>, <NUM>, or <NUM>. Before using the GF resource, the WTRU may rate-match WTRU's pending TB, e.g., for possible sensing interval outcomes. One or more of the following may apply. The WTRU may prepare a rate-matched TB as if there is no sensing (e.g., corresponding to an outcome of <NUM> derived for the sensing interval). The WTRU may prepare a rate-matched TB with the remaining REs as if the sensing interval is <NUM>. The WTRU may prepare a rate-matched TB with the remaining REs as if the sensing interval is <NUM>. When the WTRU approaches the GF resource and/or pseudo-randomly derives (e.g., draws) from the range (<NUM>, <NUM>, <NUM>), the WTRU may have the rate-matched TB for an outcome ready.

The gNB may determine (e.g., uniquely determine) the rate-matching value, for example, because the gNB may know what portion of the GF resource has not been used (e.g., what was not used by the WTRU for resource sensing). The gNB may obtain (e.g., implicitly obtain or determine) the size of the resource sensing area (e.g., the number of OFDM symbols for the whole bandwidth of the GF resource, the number of RBs for a number (e.g., fixed number) of OFDM symbols, and/or the number of OFDM symbols and number of RBs). The gNB may obtain (e.g., subsequently obtain or determine) the portion of the resource that was used for transmission of the WTRU's TB and/or obtain (e.g., subsequently obtain or determine) the associated rate-matching ratio.

The WTRU may be configured with one or more of offset values by RRC signaling wherein a (e.g., each) offset value may be used by the WTRU to compute the amount of REs for the corresponding sensing range. The WTRU may consider the UL waveforms (e.g., OFDM vs. DFT-s-OFDM) and/or different UCI multiplexing mechanisms, for example, for determining the offset values.

The WTRU may be configured to perform resource sensing on the first few symbols of a slot, e.g. on the first OFDM symbol, or the first two OFDM symbols. If the WTRU is configured to perform resource sensing on the first few symbols of a slot, the WTRU may determine (e.g., implicitly determine) the first OFDM symbol within the slot available for UL GF transmission (e.g., the remaining portion of the GF resource -PUSCH- by the WTRU). For example, if the WTRU is performing the resource sensing during the first M OFDM symbols, the WTRU may determine that the GF PUSCH may be transmitted in the next K symbols (M+<NUM>, M+<NUM>,. , M+K) OFDM symbol. K may be a parameter, for example, in terms of the number of OFDM symbol(s), which may depend on the WTRU capability. For example, for a WTRU with high capability K=<NUM> (e.g., which may indicate the WTRU may transmit the UL GF PUSCH in the very next OFDM symbol after performing resource sensing). The WTRU may follow the slot-format configuration indicated in the slot format indicator (SFI) for the remaining symbols of the slot.

UCI multiplexing may be performed during GF transmission. A WTRU may take advantage of a grant-based resource and/or may multiplex UCI, for example, including Channel State Information (CSI), Channel Quality Indicator (CQI), Rank Indicator (RI), and/or the HARQ ACK/NACK information along the TB. The behavior of a WTRU may change during a GF transmission, for example, when the WTRU attempts to multiplex UCI information on the PUSCH.

An adaptive coding rate may be performed for UCI multiplexing. The processing performed by the WTRU (e.g., required to be performed by the WTRU) during UCI multiplexing may be agnostic of whether the UL transmission is grant-based or grant-free. The processing used for UCI multiplexing may be used during GF UL transmission. For GF transmission, the GF resource may be subject to interference and/or a collision. To address higher interference during the GF UL transmission, the redundancy-version (RV) may be adjusted and/or the TB may be rate-matched, for example, so that the multiplexed UCI may be encoded with a lower-rate coding. In GF UL transmission with K repetitions (e.g., where a UCI is multiplexed with a TB), the UCI info may be multiplexed using a lower rate code (e.g., compared to the previous transmission in the sequence of K transmissions). A lower rate code may be associated with a higher amount of redundancy. In a GF transmission with K repetitions, the UCI may be encoded with a lower-rate code in the second repetition, for example, compared to the first repetition. The UCI may be encoded with a lower-rate code in the third repetition, for example, compared to the second repetition, etc. To ensure that the gNB is aware of the coding rate used by the WTRU, a set of predefined rate matching/coding rate parameters may be specified, for example, wherein the WTRU may use the set of predefined rate matching/coding rate parameters sequentially during the TB (re)transmission with K repetitions. For example, the WTRU may follow a coding rate sequence, which may be configured by WTRU-specific RRC signaling to be {<NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>}. The WTRU may use a different beta-offset value for a (re)transmission (e.g., each (re)transmission), for example, to compute the amount of REs for a (e.g., each) respective UCI to be multiplexed during GF UL (re)transmissions. For example, the WTRU may follow a beta-offset sequence which may be configured by WTRU-specific RRC signaling to be <MAT>, <MAT>. The beta-offset for the first transmission may be smaller than the beta-offset for the second transmission, etc..

The WTRU may wait for the HARQ feedback of the WTRU's GF UL transmission (e.g., for a waiting time). While the WTRU is waiting for the HARQ feedback of its GF UL transmission, if a PUCCH resource is assigned to the WTRU, the WTRU may retransmit the UCI (e.g., regardless of whether the prior GF UL transmission was successful). If a collision happens during the GF transmission of the TB with multiplexed UCI, the WTRU may receive a HARQ-NACK or may not receive HARQ feedback. The multiplexed-UCI may not be received by the gNB and/or may be retransmitted (e.g., in an upcoming PUCCH opportunity, if any; multiplexed by a grant-based PUSCH resource; and/or retransmitted in another GF transmission).

Priority based UCI multiplexing may be performed. If the transmission of a UCI (e.g., HARQ ACK) by the WTRU has a higher priority than the GF transmission (e.g., for a given slot), the WTRU may drop the GF transmission (e.g., CSI or CQI) on PUSCH and/or may send the HARQ-ACK (e.g., only the HARQ-ACK) in the PUCCH. The WTRU may initiate (e.g., immediately initiate) the GF transmission on the grant free resource on PUSCH in the following slot. If the transmission of a UCI (e.g., periodic/semi-persistent CSI reports) by the WTRU has a lower priority than the GF data transmission (e.g., for a given slot), the WTRU may drop the periodic/semi-persistent CSI reports and/or proceed with the GF transmission of data on PUSCH and/or multiplex the periodic/semi-persistent CSI reports with the data and transmit on the GF resource on PUSCH. If the WTRU has dropped the UCI, the WTRU may continue with the transmission of the periodic /semi-persistent CSI reports in the next allocated PUCCH resource. The gNB may determine (e.g., blindly determine) the WTRU behavior, for example, by detecting (e.g., simultaneously detecting) PUCCH and/or the GF PUSCH resources. If the gNB detects PUSCH (e.g., while expecting UCI transmission by the WTRU on the PUCCH) the gNB may determine that the WTRU is multiplexing the UCI with the data and/or transmitting the UCI and the data on the GF resources on PUSCH.

The priority of the UCI transmissions may be configured by RRC. For example, the WTRU may determine that the WTRU is to (e.g., needs to) multiplex the HARQ-ACK with the data, for example, on a GF resource and/or not drop the HARQ-ACK if a predefined parameter (e.g., simultaneousAckNackAndData) provided by higher layers is set TRUE. The WTRU may determine that the WRTU is to drop (e.g., needs to drop) periodic/semi-persistent CSI report(s) and/or not multiplex CSI report(s) with the data on the GF resource, for example, if a predefined parameter (e.g., simultaneousCSIAndData) provided by higher layers is not set TRUE.

UCI multiplexing may be conditioned on the HARQ feedback. If for the initial transmission, the WTRU has multiplexed the UCI with data and/or transmitted on the GF UL resource and/or receives NACK from the gNB, the WTRU may not have a good coverage and/or neither the UCI nor the TB may have successfully been detected at the gNB. The WTRU may determine (e.g., autonomously determine) to drop the UCI and/or data for the GF retransmissions/repetitions, for example, according to the priority of the UCI contents. If the WTRU drops the UCI, the code rate for the GF TB retransmissions may be lowered, for example, which may result in a higher chance of successful detection of the TB at the gNB. If the WTRU drops the data, the UCI transmission by the WTRU may be on the PUCCH, for example, which may have a higher probability of detection at the gNB.

If for the initial transmission, the WTRU multiplexed the UCI with data and/or transmitted on the GF UL resource and/or receives ACK from the gNB, the WTRU may have a good coverage and UCI and/or TB may have been detected (e.g., successfully been detected) at the gNB. The WTRU may determine (e.g., autonomously determine) to multiplex the UCI, for example, with data for the GF retransmissions/repetitions (e.g., regardless of the priority of the UCI contents). The WTRU may not drop a UCI and/or may multiplex (e.g., always multiplex) UCI with data in the consequent GF retransmissions/repetitions.

Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claim 1:
A method implemented by a wireless transmit/receive unit, WTRU, the method comprising:
receiving a radio resource control, RRC, message, wherein the RRC message comprises information indicating physical uplink shared channel, PUSCH, resources for the WTRU;
determining that uplink control information is to be transmitted during a time period that at least partially overlaps with a transmission opportunity associated with the PUSCH resources in a first slot, wherein a transport block associated with the PUSCH resources is to be transmitted in the transmission opportunity;
determining that the uplink control information has a higher priority than the transmission opportunity associated with the PUSCH resources in the first slot;
transmitting the uplink control information via a physical uplink control channel, PUCCH, transmission during the time period in the first slot; and
transmitting the transport block associated with the PUSCH resources in a second slot, wherein the second slot is immediately subsequent to the first slot.