Patent Description:
Wireless multiple-access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is designed to improve spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards. LTE may use orthogonal frequency division multiple access (OFDMA) on the downlink (DL), single-carrier frequency division multiple access (SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology.

In some examples, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs). In a LTE or LTE-Advanced (LTE-A) network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation new radio (NR) or <NUM> network), a wireless multiple access communication system may include a number of smart radio heads (RHs) in communication with a number of access node controllers (ANCs), where a set of one or more RHs, in communication with an ANC, defines a base station (e.g., an eNB or gNB). A base station may communicate with a set of UEs on DL channels (e.g., for transmissions from a base station to a UE) and UL channels (e.g., for transmissions from a UE to a base station).

A base station in some LTE or NR deployments may transmit to one or more UEs using a transmission time interval (TTI) that is reduced in length relative to legacy LTE TTIs. Such a TTI may be referred to as a shortened TTI (sTTI) and users communicating using sTTIs may be referred to as low latency users. An sTTI may be a subset of one or more subframes that correspond to legacy TTI subframes. A base station may allocate transmission resources for sTTIs to a UE that may include time and/or frequency resources. Efficient allocation of such resources for data, control information, and reference signal transmissions may help to increase the efficiency of a wireless communications system.

<NPL> discusses some issues related to PUCCH format for latency reduction, and also provides related suggestions to solve those issues.

<NPL> discusses the DL RS and UL RS for short TTI transmission and made some observations and proposals to solve the issues observed.

Improved methods, systems, devices, or apparatuses of various examples may be used to support dynamic reference signal configuration for shortened transmission time interval (sTTI) communications in low latency wireless communications systems. Resources allocated for low latency communication may be used for uplink and downlink communication using sTTIs that have a reduced length relative to TTIs of communications that may be relatively latency insensitive, such as enhanced mobile broadband (eMBB) transmissions that may use a <NUM> TTI duration. Communications using sTTIs may use, in some cases, a sTTI duration that corresponds to one slot of a wireless subframe, or a sTTI duration that corresponds to two or three orthogonal frequency division multiplexing (OFDM) symbols, for example. In some cases, sTTIs may be configured to have boundaries within or aligned with boundaries of a slot of a <NUM> TTI. In some examples, the sTTls may span two or three OFDM symbols, and each slot may have two two-symbol TTIs and one three-symbol TTI. In such a manner, all seven symbols of a slot using a normal cyclic prefix may be utilized and system resources may be more efficiently utilized relative to a case where three two-symbol sTTIs would be included in a seven-symbol slot.

Various techniques as disclosed herein may provide for dynamically configuring DMRS transmissions for sTTIs based on a location of a sTTI within a subframe, other uplink transmission resources that may be allocated to a user equipment (UE), pilot signals that may be transmitted using resources of a sTTI, other reference signals (e.g., sounding reference signal (SRS) transmissions), mobility of the UE, other processing timelines, or any combination thereof. A pattern of reference signal symbols, data symbols, and/or null symbols may be identified, and provided to the UE as a reference signal configuration along with an allocation of uplink resources for one or more sTTI. The UE may receive the reference signal configuration and allocation of uplink resources, and may transmit uplink communications using the allocated uplink resources. The reference signal configuration, such as a demodulation reference signal (DMRS) configuration, may be identified dynamically by a base station and signaled to the UE. Reference signals from two or more UEs may, in some cases, be multiplexed (e.g., by applying different cyclic shifts at each UE) and transmitted using reference signal resources for a sTTI.

Such low latency communications may be used in systems, for example, that may support multiple different services for data communications that may be selected depending upon the nature of the communications. For example, communications that require low latency and high reliability, sometimes referred to as mission critical (MiCr) communications, may be served through a lower-latency service (e.g., an ultra-reliable low-latency communication (URLLC) service) that uses sTTIs. Correspondingly, communications that are more delay-tolerant may be served through a service that provides relatively higher throughput with somewhat higher latency, such as a mobile broadband service (e.g., an eMBB service) that uses <NUM> TTIs. In other examples, communications may be with UEs that are incorporated into other devices (e.g., meters, vehicles, appliances, machinery, etc.), and a machine-type communication (MTC) service (e.g., massive MTC (mMTC)) may be used for such communications. In some cases, different services (e.g., eMBB, URLLC, mMTC) may have different TTIs, different sub-carrier (or tone) spacing and different cyclic prefixes.

The present disclosure describes various techniques with reference to next generation networks (e.g., <NUM> or NR networks) that are being designed to support features such as high bandwidth operations, more dynamic subframe/slot types, and self-contained subframe/slot types (in which HARQ feedback for a subframe/slot may be transmitted before the end of the subframe/slot). However, such techniques may be used for any system in which TTIs of different lengths may be transmitted in a wireless communications system.

Aspects of the disclosure are initially described in the context of a wireless communications system. Various examples of DMRS configurations for different sTTIs are then discussed. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to dynamic reference signal configuration for shortened transmission time interval wireless communications.

<FIG> illustrates an example of a wireless communications system <NUM> in accordance with various aspects of the present disclosure. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be a LTE (or LTE-Advanced) network, or a New Radio (NR) network. In some cases, wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, and communications with low-cost and low-complexity devices. Wireless communications system <NUM> may provide for dynamic configuration of reference signal transmissions, such as DMRS transmissions, when using sTTls.

Each base station <NUM> may provide communication coverage for a respective geographic coverage area <NUM>. Communication links <NUM> shown in wireless communications system <NUM> may include uplink (UL) transmissions from a UE <NUM> to a base station <NUM>, or downlink (DL) transmissions, from a base station <NUM> to a UE <NUM>. Control information and data may be multiplexed on an uplink channel or downlink according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information transmitted during a TTI of a downlink channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region and one or more UE-specific control regions).

A UE <NUM> may also be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE <NUM> may also be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of things (IoT) device, an Internet of Everything (loE) device, a machine type communication (MTC) device, an appliance, an automobile, a drone, or the like.

Some UEs <NUM>, such as MTC or loT devices, may be low cost or low complexity devices, and may provide for automated communication between machines, i.e., Machine-to-Machine (M2M) communication.

In some cases, an MTC device may operate using half-duplex (one-way) communications at a reduced peak rate. MTC devices may also be configured to enter a power saving "deep sleep" mode when not engaging in active communications. In some cases, MTC or loT devices may be designed to support mission critical functions and wireless communications system may be configured to provide ultra-reliable and low latency communications for these functions.

Base stations <NUM> may be an example of a LTE eNB, an eLTE eNB, an NR gNB, an NR Node-B, an NR access node, and may include an access node controller (ANC).

A base station <NUM> may interface with the core network <NUM> through backhaul links <NUM> (e.g., S1, S2, NG-<NUM>, NG-<NUM>, NG-<NUM>, NG-C, NG-U, etc.) and may perform radio configuration and scheduling for communication with the UEs <NUM> within an associated coverage area <NUM>. In various examples, the base stations <NUM> may communicate, either directly or indirectly (e.g., through core network <NUM>), with each other over backhaul links <NUM> (e.g., X1, X2, Xn, etc.), which may be wired or wireless communication links. Each base station <NUM> may also communicate with a number of UEs <NUM> through a number of other network devices, where a network device may be an example of a transmission reception point (TRP), a distributed unit (DU), a radio head (RH), a remote radio head (RRH), or a smart radio head.

Wireless communications system <NUM> may support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A carrier may also be referred to as a component carrier (CC), a layer, a channel, etc. The terms "carrier," "component carrier," "cell," and "channel" may be used interchangeably herein. A UE <NUM> may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation.

An eCC may be characterized by one or more features including: wider bandwidth, shorter symbol duration, and shorter transmission time interval (TTIs). An eCC may also be configured for use in unlicensed spectrum or shared spectrum (where more than one operator is allowed to use the spectrum). A shorter symbol duration is associated with increased subcarrier spacing. A device, such as a UE <NUM> or base station <NUM>, utilizing eCCs may transmit wideband signals (e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc.) at reduced symbol durations (e.g., <NUM> microseconds). A TTI in eCC may consist of one or multiple symbols. In some cases, the TTI duration (that is, the number of symbols in a TTI) may be variable. A <NUM> or NR carrier may be considered an eCC.

For example, wireless communications system <NUM> may employ LTE License Assisted Access (LTE-LAA) or LTE Unlicensed (LTE U) radio access technology or NR technology in an unlicensed band such as the <NUM> Industrial, Scientific, and Medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations <NUM> and UEs <NUM> may employ listen-before-talk (LBT) procedures to ensure the channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a CA configuration in conjunction with CCs operating in a licensed band. Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, or both. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD), time division duplexing (TDD) or a combination of both.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit (which may be a sampling period of Ts = <NUM>/<NUM>,<NUM>,<NUM> seconds). Time resources in LTE/LTE-A may be organized according to radio frames of length of <NUM> (Tf= 307200Ts), which may be identified by a system frame number (SFN) ranging from <NUM> to <NUM>. Each frame may include ten <NUM> subframes numbered from <NUM> to <NUM>. A subframe may be further divided into two <NUM> slots, each of which contains <NUM> or <NUM> modulation symbol periods (depending on the length of the cyclic prefix prepended to each symbol). Excluding the cyclic prefix, each symbol contains <NUM> sample periods. In some cases the subframe may be the smallest scheduling unit, also known as a TTI. In other cases, a TTI may be shorter than a subframe or may be dynamically selected (e.g., in sTTI bursts or in selected component carriers using sTTIs). Various examples discussed herein provide techniques for shortened TTIs, which may provide reference signal configuration for sTTIs that may be used to provide reliable DMRS transmissions that may be used when demodulating sTTI uplink transmissions from a UE <NUM>.

<FIG> illustrates an example of a wireless communications system <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications. Wireless communications system <NUM> includes base station <NUM>-a and UE <NUM>-a, which may be examples of aspects of a UE <NUM> as described above with reference to <FIG>. In the example of <FIG>, the wireless communications system <NUM> may operate according to a radio access technology (RAT) such as a <NUM> or NR RAT, although techniques described herein may be applied to any RAT and to systems that may concurrently use two or more different RATs.

Base station <NUM>-a may communicate with UE <NUM>-a over carrier <NUM>. In some examples, base station <NUM>-a may allocate resources for communication with UEs over carrier <NUM>. For example, base station <NUM>-a may allocate subframes <NUM> for communication with UE <NUM>-a, and one or more subframes <NUM> may correspond to a legacy LTE TTI of <NUM>. In this example, subframes <NUM> may include a first subframe <NUM>-a, a second subframe <NUM>-b, and a third subframe <NUM>-c. Each of the subframes <NUM> may include two slots, in which each slot may have seven symbols for a normal cyclic prefix. In this example, a first slot (slot <NUM>) <NUM> and a second slot (slot <NUM>) <NUM> may be included in the first subframe <NUM>-a.

As indicated above, in the uplink of a low latency system, different sTTI lengths may be used for transmissions over carrier <NUM>. For example, two-symbol sTTI and <NUM>-slot sTTI durations may be supported for physical uplink control channel (PUCCH) and physical uplink shared channel (PUSCH) transmissions (or shortened PUCCH (sPUCCH) and shortened PUSCH (sPUSCH) transmissions). Thus, within first slot <NUM> or second slot <NUM>, there may be multiple sTTIs, such as a first sTTI (TTI-<NUM>) <NUM>, a second sTTI (TTI-<NUM>) <NUM>, and a third sTTI (TTI-<NUM>) <NUM>, that may each have a two or three OFDM symbol duration. While various examples discussed herein are described with respect to uplink communications, such techniques may also apply to downlink communications in some examples. When two-symbol sTTI is used, in some cases it may be desirable to have a fixed sTTI structure in which sTTI boundaries lie within slot boundaries or are aligned with slot boundaries, such as the boundaries of the first slot <NUM> or second slot <NUM>, which may be referred to as slot-aligned sTTIs. As discussed above, when using a normal CP, seven symbols are included in each of the first slot <NUM> or second slot <NUM>, and thus each slot may include three sTTIs for slot-aligned sTTIs. In some cases, one of the sTTIs may be configured as a three-symbol TTI, so as to efficiently utilize each symbol of each slot. In such cases, different patterns can be considered, such as having the three-symbol TTI located at the end of the first slot <NUM> or second slot <NUM>, or at the beginning of the first slot <NUM> or second slot <NUM>.

As the TTI length gets shorter, it may not always possible to reuse the legacy DMRS pattern, as a particular sTTI may not include a legacy DMRS symbols (symbol <NUM> of each slot). For example, a <NUM>-symbol sPUSCH covering symbols <NUM> and <NUM> of a subframe does not include a legacy DMRS symbol. Various aspects of the present disclosure provide that DMRS configurations for sTTIs may be dynamically configured to provide efficient data transmissions with sufficient DMRS transmissions. Various configurations may be identified and one of the configurations selected for an sTTI based on various factors, that may allow DMRS sharing across multiple sTTIs and/or multiple UEs <NUM>. DMRS sharing may be beneficial to help reduce overhead for uplink transmissions, as of one symbol of each two-symbol sTTI being reserved for DMRS may incur an overhead that is relatively high.

<FIG> illustrates an example of slot-aligned sTTI patterns <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications. Slot-aligned sTTI patterns <NUM> may be used for low latency communications between a UE and a base station such as discussed above with respect to <FIG> and <FIG>. A subframe <NUM> may have resources allocated for uplink communication. Subframe <NUM> may include two slots: first slot (slot <NUM>) <NUM> and second slot (slot <NUM>) <NUM> that may correspond to legacy LTE slots. Each of the first slot <NUM> and the second slot <NUM> may include slot-aligned sTTIs allocated for low latency communication. Each of the first slot <NUM> and the second slot <NUM> may include three sTTIs, including a first TTI (TTI-<NUM>) <NUM>, a second TTI (TTI-<NUM>) and a third TTI (TTI-<NUM>) <NUM>. In some examples, the TTIs <NUM> through <NUM> may be aligned in a <NUM>-<NUM>-<NUM> slot alignment <NUM>, in which the first TTI <NUM> may include three symbols, the second TTI <NUM> may include two symbols, and the third TTI <NUM> may include two symbols.

In other examples, the TTIs <NUM> through <NUM> may be aligned in a <NUM>-<NUM>-<NUM> slot alignment <NUM>, in which the first TTI <NUM> may include two symbols, the second TTI <NUM> may include two symbols, and the third TTI <NUM> may include three symbols. In other examples, the TTIs <NUM> through <NUM> may be aligned in a <NUM>-<NUM>-<NUM> slot alignment <NUM>, in which the first TTI <NUM> may include two symbols, the second TTI <NUM> may include three symbols, and the third TTI <NUM> may include two symbols. Of course, other alignment patterns may be used for communications, and the illustrated slot alignment <NUM> through <NUM> are provided for purposes of illustration and discussion. Additionally, the first slot <NUM> may use a different slot alignment than the second slot <NUM>. For example, each of the first slot <NUM> and the second slot <NUM> may use the <NUM>-<NUM>-<NUM> slot alignment <NUM> or may use the <NUM>-<NUM>-<NUM> slot alignment <NUM>. Alternatively, the first slot <NUM> may use a <NUM>-<NUM>-<NUM> slot alignment <NUM> and the second slot may use the <NUM>-<NUM>-<NUM> slot alignment <NUM>. Other combinations may be used as well, including combinations with different slot alignments.

As can be seen from above, in order to make sure that the sTTIs do not cross the slot boundary within the <NUM> subframe, both <NUM>-symbol and <NUM>-symbol sTTIs may be used within a slot. In various examples, dynamic DMRS positioning may be used that is designed to cover various different sTTI durations and allow DMRS sharing between sTTIs and/or UEs. In some cases, a base station <NUM>-a may schedule multiple sTTIs in which a DMRS transmission of a first sTTI may be used for demodulation of the first sTTI and one or more other sTTIs. The base station <NUM>-a may dynamically schedule uplink DMRS positions via, for example, a sPDCCH uplink grant. Additionally, in some cases, different UEs may be configured to multiplex their DMRSs over a same DMRS symbol using different cyclic shifts. Thus, overhead associated with DMRS transmissions may be reduced compared to cases where TTIs and/or UEs do not share DMRS transmissions, and network efficiency can be increased.

<FIG> illustrates an example of two-symbol sTTI data and DMRS patterns <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with aspects of the present disclosure. DMRS patterns <NUM> may be used as DMRS configurations in uplink transmissions between UEs <NUM> and base stations <NUM> such as discussed above with reference to <FIG>.

In one example of <FIG>, a two-symbol sTTI may include a first symbol <NUM> configured for data transmissions and a second symbol <NUM> configured for data transmissions, illustrated as pattern <NUM>-a <NUM>. In another example, a two-symbol sTTI may include a first symbol <NUM> configured for data transmissions and a second symbol <NUM> configured for DMRS transmissions, illustrated as pattern <NUM>-b <NUM>. In a third example, a two-symbol sTTI may include a first symbol <NUM> configured for DMRS transmissions and a second symbol <NUM> configured for data transmissions, illustrated as pattern <NUM>-c <NUM>. In a fourth example, a two-symbol sTTI may include a first symbol <NUM> configured as a null symbol without any transmissions by a UE, and a second symbol <NUM> configured for DMRS transmissions, illustrated as pattern <NUM>-d <NUM>. Other patterns may also be used, and DMRS patterns <NUM> are provided for purposes of illustration and discussion with the understanding that other patterns may be desirable is some cases.

<FIG> illustrates an example of a three-symbol sTTI data and DMRS patterns <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications. DMRS patterns <NUM> may be used as DMRS configurations in uplink transmissions between UEs <NUM> and base stations <NUM> such as discussed above with reference to <FIG>.

In one example of <FIG>, a three-symbol sTTI may include a first symbol <NUM> configured for data transmissions, a second symbol <NUM> configured for data transmissions, and a third symbol <NUM> configured for data transmissions, as illustrated as pattern <NUM>-a <NUM>. In another example, a three-symbol sTTI may include a first symbol <NUM> configured for data transmissions, a second symbol <NUM> configured for data transmissions, and a third symbol <NUM> configured for DMRS transmissions, illustrated as pattern <NUM>-b <NUM>. In a third example, a three-symbol sTTI may include a first symbol <NUM> configured for data transmissions, a second symbol <NUM> configured for DMRS transmissions and a third symbol <NUM> configured for data transmissions, illustrated as pattern <NUM>-c <NUM>. In a fourth example, a three-symbol sTTI may include a first symbol <NUM> configured for DMRS transmissions, a second symbol <NUM> configured for data transmissions and a third symbol <NUM> configured for data transmissions, illustrated as pattern <NUM>-d <NUM>. In a fifth example, a three-symbol sTTI may include a first symbol <NUM> and a second symbol <NUM> both configured as null symbols without any transmissions by a UE, and a third <NUM> configured for DMRS transmissions, illustrated as pattern <NUM>-e <NUM>. Other patterns may also be used, and DMRS patterns <NUM> are provided for purposes of illustration and discussion with the understanding that other patterns may be desirable is some cases.

Using the patterns of <FIG> and <FIG>, a large variety of sPUSCH and DMRS sequences can be created via multiple sequential uplink grants. For example, a base station may configure a first sTTI as a two-symbol sTTI using pattern <NUM>-b <NUM> and a second sTTI as a two-symbol sTTI using pattern <NUM>-a <NUM>. In this example, the DMRS transmission provided in the first sTTI may be used for demodulation of both the first sTTI and the second sTTI. In some examples, null symbols may be configured according to pattern <NUM>-d <NUM> and pattern <NUM>-e <NUM>, and may be defined to trigger a DMRS transmission to be used in one or more subsequent sTTIs. In some examples, since no uplink data is transmitted when these two patterns are configured, the related bit fields within the uplink grant can either be considered as invalid or can be reinterpreted in some different ways.

In some examples, a second UE may be configured to transmit a DMRS using one of the null symbol patterns <NUM> or <NUM> concurrently with a first UE that is transmitting data in the non-DMRS symbols. The first and second UEs in such cases may use different cyclic shifts for their respective DMRS transmissions. In order to enable early DMRS transmission via a pattern that uses null symbols, two grants may be provided to a UE, a first grant for the sTTI with one or more null symbols, and a second grant for a sTTI with an uplink data transmission and which has a DMRS transmission (e.g., in order to provide enhanced DMRS-based demodulation in cases where the UE has high mobility). In some cases, such as pattern <NUM>-d <NUM>, since the data symbols are shifted to the right by one symbol, a processing timeline may be adjusted to provide processing of the shifted data symbols. For example, instead of a processing timeline of n + <NUM> for providing HARQ feedback, a processing timeline of n + <NUM> may be configured.

The configured pattern, as indicated above, is selected based on one or more different factors, such as other sTTI transmissions of a UE. A selected is based on the position of the sTTI within the <NUM> subframe. For example, if the sTTI is located at the end of slot <NUM> of a subframe that is not configured for a SRS transmission, the sTTI may be selected to be a three-symbol TTI with pattern <NUM>-a <NUM> or pattern <NUM>-d <NUM>. If such a subframe is configured for a SRS transmission, the three-symbol sTTI effectively becomes a two-symbol sTTI, and pattern <NUM>-a <NUM> or pattern <NUM>-c <NUM> may be configured, for example. As discussed above, the DMRS configuration for a sTTI may be indicated in downlink control information (DCI) provided by a base station, that may provide a sPDCCH uplink grant and an indication of a DMRS configuration.

In cases where a DMRS symbol is shared across multiple sTTIs, the future DMRSs may not be used for data demodulation in instances where this would increase a delay in processing of a sTTI. However, in various cases, a DMRSs over a current sTTI and/or a DMRS of a prior sTTI may be considered for data demodulation. For example, if a first sTTI uses pattern <NUM>-b <NUM>, and a second sTTI uses pattern <NUM>-b <NUM>, demodulation of the first sTTI, eNB may not wait to receive the DMRS symbol over the second sTTI, but demodulation of the second sTTI may use both the DMRS symbol of the first TTI and the DMRS symbol of the second sTTI. As a result, the performance of these two sTTIs may be uneven, and in such cases a base station may configure these sTTIs with different MCSs. For example, such a base station may choose a smaller MCS index over the first sTTI and a larger MCS index over the second sTTI.

<FIG> illustrates an example of cross-subframe scheduling <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications. Cross-subframe scheduling <NUM> may be used, in some examples, in uplink transmissions that span multiple subframes between UEs <NUM> and base stations <NUM> such as discussed above with reference to <FIG>.

In this example, a first subframe (subframe <NUM>) <NUM> and a second subframe (subframe <NUM>) <NUM> include allocated resources for uplink transmissions of a UE. The first subframe <NUM> may include a first slot (slot <NUM>) <NUM> and a second slot (slot <NUM>) <NUM>, and within the second slot <NUM>, TTI n <NUM> may be located at an end of the second slot <NUM>. Within the second subframe <NUM> may be a first slot (slot <NUM>) <NUM> and a second slot (slot <NUM>) <NUM>, and TTI n+<NUM> may be located at the beginning of the first slot <NUM>. In some cases, for the demodulation of the sTTIs sent in the second subframe <NUM>, such as TTI n+<NUM> <NUM>, one or more DMRSs sent in the first subframe <NUM>, such as in TTI n <NUM>, may be used. For example, TTI n <NUM> may be a three-symbol sTTI that is configured for pattern <NUM>-b <NUM> or pattern <NUM>-e <NUM>. TTI n+<NUM> <NUM> may also be a three-symbol sTTI and may be configured for pattern <NUM>-b <NUM>. For the demodulation of the second sTTI, both DMRSs can be used. In this case, the effective uplink pattern for the second sTTI is [DMRS; data; data; DMRS] which may be beneficial in high mobility scenarios.

<FIG> illustrates an example of a process flow <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications. Process flow <NUM> may include a base station <NUM>-b, and a UE <NUM>-b, which may be examples of the corresponding devices described with reference to <FIG>. The base station <NUM>-b and the UE <NUM>-b may establish a connection <NUM> according to established connection establishment techniques for the wireless communications system. The UE <NUM>-b may transmit, in some examples, a buffer status report (BSR) that may indicate the presence of uplink data for transmission, and may also indicate that a service for the data is a low-latency service or other service that may use sTTIs.

At block <NUM>, base station <NUM>-b may identify uplink transmissions to be transmitted by the UE <NUM>-a. For example, the base station <NUM>-b may identify that the uplink data indicated by the UE <NUM>-b may take a number of sTTIs to transmit, which may be determined based on various factors such as channel conditions between the base station <NUM>-b and the UE <NUM>-b, a MCS supported by the channel used for transmissions, a MIMO configuration, etc..

At block <NUM>, the base station may identify a DMRS configuration for the one or more sTTIs. Such a DMRS configuration may be identified to provide a sufficient number of DMRS transmissions for one or more sTTIs to support demodulation of each of the sTTIs. For example, if the base station <NUM>-b determines that two <NUM>-symbol sTTIs are to be used for uplink transmissions the first sTTI may be configured with a DMRS symbol and the second sTTI may be configured with only data symbols.

At block <NUM>, the base station <NUM>-b may allocate uplink resources for the identified sTTIs, which may include an allocation for at least a first sTTI and a sTTI in some examples. The allocation of resources may be determined based on a number of data symbols needed to service the UE <NUM>-b uplink data and a number of DMRS symbols needed for reliable demodulation of the uplink transmissions. For example, if the UE <NUM>-b is relatively close to the base station <NUM>-b and traveling at a relatively low speed (or not at all), the base station <NUM>-b may select a sequence of DMRS patterns that includes relatively few DMRS symbols. Alternatively, if the UE <NUM>-b is relatively far from the base station <NUM>-b (e.g., a cell-edge UE) and/or traveling at a relatively high rate of speed, the base station <NUM>-b may select a sequence of DMRS patterns for the sTTIs that may provide more DMRS transmissions, which may be used to more reliably demodulate the uplink transmissions and enhance the likelihood of successful reception of such signals.

The base station <NUM>-b may transmit DCI <NUM> to the UE <NUM>-b. The DCI <NUM> may include, for example, a sPDCCH uplink grant that indicates allocated uplink resources for a particular sTTI and the DMRS configuration for the sTTI. In some cases, where UE <NUM>-b is scheduled for multiple sTTIs, multiple uplink grants may be provided that dynamically schedule uplink DMRS positions for the different sTTIs. Also, as indicated above, in some cases the base station <NUM>-b may allocate resources to a second UE (not shown) to allow the second UE to transmit a DMRS concurrently with a DMRS of the UE <NUM>-b. In such cases, the second UE may use a different cyclic shift for the DMRS transmission than the UE <NUM>-b. In some cases, the second UE may be scheduled for the DMRS transmission using a DMRS pattern with null symbols, and the second UE may reinterpret the uplink grant with an indication of null symbols to indicate that a particular cyclic shift is to be used for the DMRS transmission. Such a cyclic shift may be preconfigured, provided using RRC signaling, or provided in the uplink grant.

At block <NUM>, the UE <NUM>-a may identify the DMRS configuration for the sTTI(s). For example, the UE <NUM>-a may receive the DCI <NUM> that includes an allocation of uplink resources for a first sTTI and an indication of the DMRS configuration for the first sTTI.

At block <NUM>, the UE <NUM>-b may generate the DMRS and/or data transmissions for the sTTI. The data transmissions and/or DMRS may be generated based on the allocated resources from an uplink grant provided in the DCI <NUM>, for example. In some cases, the UE <NUM>-a may apply a cyclic shift to the DMRS transmissions in order to multiplex the DMRS transmission with a second DMRS transmission of a second UE.

UE <NUM>-b may then transmit uplink transmission(s) <NUM> to the base station <NUM>-b, which may perform received signal processing at block <NUM>. Such processing may include demodulating the uplink transmissions <NUM> using a transmitted DMRS from a sTTI or from one or more previously received sTTIs. In some case, such processing may include acknowledgment feedback processing (e.g., HARQ feedback). In some examples, the DMRS pattern of the uplink transmissions <NUM> may include an initial DMRS symbol followed by two data symbols, and the base station <NUM>-b may modify a processing timeline for processing the two data symbols (e.g., from a n+<NUM> timeline to a n+<NUM> timeline) to provide acknowledgment feedback.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a base station <NUM> as described with reference to <FIG>. Wireless device <NUM> may include receiver <NUM>, base station communications manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

Receiver <NUM> may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to dynamic reference signal configuration for shortened transmission time interval wireless communications, etc.). Information may be passed on to other components of the device. The receiver <NUM> may be an example of aspects of the transceiver <NUM> described with reference to <FIG>.

Base station communications manager <NUM> may be an example of aspects of the base station communications manager <NUM> described with reference to <FIG>. Base station communications manager <NUM> may allocate uplink resources for a first UE in a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe, identify a DMRS configuration for the first TTI from a plurality of DMRS configurations, wherein the identified DMRS configuration comprises an OFDM symbol location within the first TTI that is to be used by the first UE for a DMRS transmission, and transmit an uplink grant for an uplink transmission to the first UE, the uplink grant including an indication of the allocated uplink resources for the first TTI and the DMRS configuration.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a wireless device <NUM> or a base station <NUM> as described with reference to <FIG> and <FIG>. Wireless device <NUM> may include receiver <NUM>, base station communications manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

Base station communications manager <NUM> may be an example of aspects of the base station communications manager <NUM> described with reference to <FIG>. Base station communications manager <NUM> may also include resource allocation component <NUM>, DMRS component <NUM>, and uplink grant component <NUM>.

Resource allocation component <NUM> may allocate uplink resources for a first UE in a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe.

DMRS component <NUM> may identify a DMRS configuration for the first TTI from a set of DMRS configurations, where the identified DMRS configuration includes an OFDM symbol location within the first TTI that is to be used by the first UE for a DMRS transmission. In some examples, DMRS component <NUM> may identify a second UE that is to be configured for a DMRS transmission in the first TTI. In some cases, the DMRS configuration for the first TTI provides a DMRS transmission for an uplink transmission by the first UE in a second TTI. In some cases, the first TTI is located within a first radio subframe and the second TTI is located within a second radio subframe.

Uplink grant component <NUM> may transmit an uplink grant for an uplink transmission to the first UE, the uplink grant including an indication of the allocated uplink resources for the first TTI and the DMRS configuration. In some cases, uplink grant component <NUM> may transmit the DMRS configuration and cyclic shift to be applied to the DMRS transmission to a second UE. In some cases, uplink grant component <NUM> may transmit a second uplink grant to the first UE that includes an indication of allocated uplink resources for the second TTI to be used for a second uplink transmission during the second TTI, and where a DMRS of the first TTI may be used for demodulation of the second TTI. In some cases, the uplink grant may further include an indication of a cyclic shift to be used by the first UE to transmit the DMRS.

<FIG> shows a block diagram <NUM> of a base station communications manager <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. The base station communications manager <NUM> may be an example of aspects of a base station communications manager <NUM>, a base station communications manager <NUM>, or a base station communications manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>. The base station communications manager <NUM> may include resource allocation component <NUM>, DMRS component <NUM>, uplink grant component <NUM>, DMRS pattern component <NUM>, cyclic shift component <NUM>, processing timeline component <NUM>, and MCS component <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

Uplink grant component <NUM> may transmit an uplink grant for an uplink transmission to the first UE, the uplink grant including an indication of the allocated uplink resources for the first TTI and the DMRS configuration. In some cases, uplink grant component <NUM> may transmit the DMRS configuration and cyclic shift to be applied to the DMRS transmission to a second UE. In some cases, uplink grant component <NUM> may transmit a second uplink grant to the first UE that includes an indication of allocated uplink resources for the second TTI to be used for a second uplink transmission during the second TTI, and where a DMRS of the first TTI may be used for demodulation of the second TTI. In some cases, the uplink grant may further include an indication of a cyclic shift to be used by the first UE to transmit the DMRS.

DMRS pattern component <NUM> may identify a first pattern of DMRS, data, or null symbols for a first TTI and a second pattern of DMRS, data, or null symbols for a second TTI, and where the first pattern and the second pattern are identified based on data to be transmitted in the first TTI or the second TTI, a location within a radio subframe of the first TTI or the second TTI, or any combination thereof. In some cases, the DMRS configuration indicates an OFDM symbol location within the first TTI that is to be used for a DMRS transmission. In some cases, the first TTI includes two OFDM symbols or three OFDM symbols, and where the DMRS configuration indicates a pattern of a DMRS symbol, one or more data symbols, or one or more null symbols for the first TTI. In some cases, the DMRS configuration may indicate a first pattern of DMRS, data, or null symbols for the first TTI. In some cases, the DMRS configuration may indicate a DMRS symbol and one or more null symbols to trigger a DMRS transmission from the first UE in the first TTI. In some cases, the identifying the DMRS configuration for the first TTI is further based on a position of the first TTI within a radio subframe, whether an SRS is to be transmitted during the first TTI, or any combination thereof.

Cyclic shift component <NUM> may identify, for each of the first UE and the second UE, different cyclic shifts that are to be applied to their respective DMRS transmission.

Processing timeline component <NUM> may, in some cases, modify a processing timeline for processing the two data symbols for the first TTI in cases where an initial DMRS symbol is followed by two data symbols for the first TTI. MCS component <NUM> may select a MCS for the first TTI and the second TTI based on the DMRS configuration of the first TTI.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. Device <NUM> may be an example of or include the components of wireless device <NUM>, wireless device <NUM>, or a base station <NUM> as described above, e.g., with reference to <FIG>, <FIG> and <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including base station communications manager <NUM>, processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, network communications manager <NUM>, and base station coordination manager <NUM>. These components may be in electronic communication via one or more busses (e.g., bus <NUM>). Device <NUM> may communicate wirelessly with one or more UEs <NUM>.

Base station communications manager <NUM> may be an example of aspects of a base station communications manager <NUM>, a base station communications manager <NUM>, or a base station communications manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a digital signal processor (DSP), a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), an field-programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting dynamic reference signal configuration for shortened transmission time interval wireless communications).

Software <NUM> may include code to implement aspects of the present disclosure, including code to support dynamic reference signal configuration for shortened transmission time interval wireless communications. Software <NUM> may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software <NUM> may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

Base station coordination manager <NUM> may manage communications with other base station <NUM>, and may include a controller or scheduler for controlling communications with UEs <NUM> in cooperation with other base stations <NUM>. For example, the base station coordination manager <NUM> may coordinate scheduling for transmissions to UEs <NUM> for various interference mitigation techniques such as beamforming or joint transmission. In some examples, base station coordination manager <NUM> may provide an X2 interface within a wireless communication network technology to provide communication between base stations <NUM>.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a UE <NUM> as described with reference to <FIG>. Wireless device <NUM> may include receiver <NUM>, UE communications manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

UE communications manager <NUM> may be an example of aspects of the UE communications manager <NUM> described with reference to <FIG>.

UE communications manager <NUM> may receive an allocation of uplink resources from a base station for a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe and identify a DMRS configuration for the first TTI.

Transmitter <NUM> also may transmit a DMRS to the base station using the allocated uplink resources based on the DMRS configuration.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a wireless device <NUM> or a UE <NUM> as described with reference to <FIG> and <FIG>. Wireless device <NUM> may include receiver <NUM>, UE communications manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

UE communications manager <NUM> may be an example of aspects of the UE communications manager <NUM> described with reference to <FIG>. UE communications manager <NUM> may also include resource allocation component <NUM> and DMRS component <NUM>.

Resource allocation component <NUM> may receive an allocation of uplink resources from a base station for a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe, receive a second allocation of uplink resources from the base station for a second TTI, the DMRS transmission during the first TTI to be used for demodulation of an uplink data transmission of the second TTI. In some cases, the resource allocation component <NUM> may reinterpret one or more bit fields associated with the one or more null symbols within the allocation of uplink resources.

DMRS component <NUM> may identify a DMRS configuration for the first TTI. In some cases, the first TTI is located within a first radio subframe and the DMRS component <NUM> may identify a DMRS configuration for a second TTI located within a second radio subframe, where a DMRS from the first TTI is to be used for demodulation of a data transmission of the second TTI.

<FIG> shows a block diagram <NUM> of a UE communications manager <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. The UE communications manager <NUM> may be an example of aspects of a UE communications manager <NUM>, a UE communications manager <NUM>, or a UE communications manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>. The UE communications manager <NUM> may include resource allocation component <NUM>, DMRS component <NUM>, DMRS pattern component <NUM>, and cyclic shift component <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

Resource allocation component <NUM> may receive an allocation of uplink resources from a base station for a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe. In some cases, resource allocation component <NUM> may receive a second allocation of uplink resources from the base station for a second TTI, the DMRS transmission during the first TTI to be used for demodulation of an uplink data transmission of the second TTI. In some cases, resource allocation component <NUM> may reinterpret one or more bit fields associated with the one or more null symbols within the allocation of uplink resources.

DMRS component <NUM> may identify a DMRS configuration for the first TTI and/or one or more other TTIs. In some cases, the first TTI is located within a first radio subframe and the DMRS component <NUM> may identify DMRS configuration for a second TTI located within a second radio subframe.

DMRS pattern component <NUM> may determine a DMRS pattern for one or more TTIs. In some cases, the DMRS configuration indicates an OFDM symbol location within the first TTI that is to be used for transmitting the DMRS. In some cases, the first TTI includes two OFDM symbols or three OFDM symbols, and where the DMRS configuration indicates a pattern of a DMRS symbol, one or more data symbols, or one or more null symbols for the first TTI. In some cases, the allocation of uplink resources indicates one or more null symbols and a DMRS symbol within the first TTI, which may trigger a DMRS transmission that may be used in a second TTI subsequent to the first TTI.

Cyclic shift component <NUM> may identify, based on the allocation of uplink resources, a cyclic shift that is to be applied to the DMRS transmission.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. Device <NUM> may be an example of or include the components of UE <NUM> as described above, e.g., with reference to <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE communications manager <NUM>, processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, and I/O controller <NUM>. These components may be in electronic communication via one or more busses (e.g., bus <NUM>). Device <NUM> may communicate wirelessly with one or more base stations <NUM>.

UE communications manager <NUM> may be an example of aspects of a UE communications manager <NUM>, a UE communications manager <NUM>, or a UE communications manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting dynamic reference signal configuration for shortened transmission time interval wireless communications).

<FIG> shows a flowchart illustrating a method <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a base station <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a base station communications manager as described with reference to <FIG>. In some examples, a base station <NUM> may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station <NUM> may perform aspects the functions described below using special-purpose hardware.

At block <NUM> the base station <NUM> may allocate uplink resources for a first UE in a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a resource allocation component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may identify a DMRS configuration for the first TTI from a set of DMRS configurations, where the identified DMRS configuration includes an OFDM symbol location within the first TTI that is to be used by the first UE for a DMRS transmission. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a DMRS component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may transmit an uplink grant for an uplink transmission to the first UE, the uplink grant including an indication of the allocated uplink resources for the first TTI and the DMRS configuration. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a uplink grant component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may identify a second UE that is to be configured for a DMRS transmission in the first TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a DMRS component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may identify, for each of the first UE and the second UE, different cyclic shifts that are to be applied to their respective DMRS transmission. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a cyclic shift component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may transmit the DMRS configuration and cyclic shift to be applied to the DMRS transmission to the second UE. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a uplink grant component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may transmit a second uplink grant to the first UE that includes an indication of allocated uplink resources for the second TTI to be used for a second uplink transmission during the second TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a uplink grant component as described with reference to <FIG>. In some cases, the first TTI includes two OFDM symbols or three OFDM symbols, and the DMRS configuration indicates a pattern of a DMRS symbol, one or more data symbols, or one or more null symbols for the first TTI, and a DMRS configuration identifying a first pattern of DMRS, data, or null symbols for the first TTI may indicate the DMRS symbol and one or more null symbols are to trigger a DMRS transmission from the first UE in the first TTI that is to be used to demodulate the second uplink transmission.

<FIG> shows a flowchart illustrating a method <NUM> for dynamic reference signal configuration for shortened transmission time interval wireless communications in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a UE communications manager as described with reference to <FIG>. In some examples, a UE <NUM> may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE <NUM> may perform aspects the functions described below using special-purpose hardware.

At block <NUM> the UE <NUM> may receive an allocation of uplink resources from a base station for a first TTI, the first TTI including two or more OFDM symbols within a slot of a radio subframe. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a resource allocation component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may identify a DMRS configuration for the first TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a DMRS component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may transmit a DMRS to the base station using the allocated uplink resources based at least in part on the DMRS configuration. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a transmitter as described with reference to <FIG>.

At block <NUM> the UE <NUM> may identify, based at least in part on the allocation of uplink resources, a cyclic shift that is to be applied to the DMRS transmission. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a cyclic shift component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may identify a DMRS configuration for the first TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a DMRS component as described with reference to <FIG>. In some cases, the first TTI includes two OFDM symbols or three OFDM symbols, and the DMRS configuration indicates a pattern of a DMRS symbol, one or more data symbols, or one or more null symbols for the first TTI.

At block <NUM> the UE <NUM> may determine that the allocation of uplink resources indicates one or more null symbols and a DMRS symbol within the first TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a DMRS pattern component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may receive a second allocation of uplink resources from the base station for a second TTI, the DMRS transmission during the first TTI to be used for demodulation of an uplink data transmission of the second TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a resource allocation component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may transmit a DMRS to the base station using the allocated uplink resources based at least in part on the DMRS configuration of the first TTI. Such a transmission may be followed by a transmission of uplink data using the uplink resources of the second TTI. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a transmitter as described with reference to <FIG>.

The terms "system" and "network" are often used interchangeably. A code division multiple access (CDMA) system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-<NUM>, IS-<NUM>, and IS-<NUM> standards. A time division multiple access (TDMA) system may implement a radio technology such as Global System for Mobile Communications (GSM).

An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications system (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of Universal Mobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and Global System for Mobile communications (GSM) are described in documents from the organization named "3rd Generation Partnership Project" (3GPP). While aspects an LTE or an NR system may be described for purposes of example, and LTE or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE or NR applications.

In LTE/LTE-A networks, including such networks described herein, the term evolved node B (eNB) may be generally used to describe the base stations. The wireless communications system or systems described herein may include a heterogeneous LTE/LTE-A or NR network in which different types of evolved node B (eNBs) provide coverage for various geographical regions. For example, each eNB, gNB or base station may provide communication coverage for a macro cell, a small cell, or other types of cell. The term "cell" may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, eNodeB (eNB), next generation NodeB (gNB), Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area for a base station may be divided into sectors making up only a portion of the coverage area. The wireless communications system or systems described herein may include base stations of different types (e.g., macro or small cell base stations). The UEs described herein may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like. There may be overlapping geographic coverage areas for different technologies.

Other examples and implementations are within the scope of the appended claims.

By way of example, and not limitation, non-transitory computer-readable media may comprise RAM, ROM, electrically erasable programmable read only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.

Claim 1:
A method for wireless communication, comprising:
receiving an uplink resource allocation for transmission of a transmission time interval, TTI, the TTI comprising two or more orthogonal frequency division multiplexing, OFDM, symbols within a slot,
the uplink resource allocation indicating a demodulation reference signal, DMRS, configuration for the TTI, a symbol location within the TTI of a DMRS being based on the DMRS configuration, the DMRS configuration being further based at least in part on a position of the TTI in the slot; and
transmitting the DMRS based at least in part on the DMRS configuration.