Uplink transmission gaps in eMTC

Aspects of the present disclosure provide techniques and apparatus for uplink transmission gaps in enhanced machine type communications (eMTC). In one aspect, a method is provided which may be performed by a wireless device such as a user equipment (UE), which can be a low cost eMTC UE. The method generally includes transmitting a random access preamble, receiving a random access response in response to the random access preamble, transmitting an uplink message containing an indication of a capability of the UE to transmit using uplink gaps, and receiving signaling of configuration information regarding uplink gaps.

BACKGROUND

Field of the Disclosure

Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to uplink transmission gaps in enhanced machine type communication(s) (eMTC).

Description of Related Art

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)/LTE-Advanced (LTE-A) systems and orthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations (BSs) via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the BSs to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the BSs. This communication link may be established via a single-input single-output, multiple-input single-output or a multiple-input multiple-output (MIMO) system.

A wireless communication network may include a number of BSs that can support communication for a number of wireless devices. Wireless devices may include user equipments (UEs). Machine type communications (MTC) may refer to communication involving at least one remote device on at least one end of the communication and may include forms of data communication which involve one or more entities that do not necessarily need human interaction. MTC UEs may include UEs that are capable of MTC communications with MTC servers and/or other MTC devices through Public Land Mobile Networks (PLMN), for example. Wireless devices may include Internet-of-Things (IoT) devices (e.g., narrowband IoT (NB-IoT) devices). IoT may refer to a network of physical objects, devices, or “things”. IoT devices may be embedded with, for example, electronics, software, or sensors and may have network connectivity, which enable these devices to collect and exchange data.

Some next generation, NR, or 5G networks may include a number of base stations, each simultaneously supporting communication for multiple communication devices, such as UEs. In LTE or LTE-A network, a set of one or more BSs may define an e NodeB (eNB). In other examples (e.g., in a next generation or 5G network), a wireless multiple access communication system may include a number of distributed units (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (e.g., CU, central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more distributed units (DUs), in communication with a CU, may define an access node (e.g., AN, a new radio base station (NR BS), a NR NB, a network node, a gNB, a 5G BS, an access point (AP), etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or to a UE) and uplink channels (e.g., for transmissions from a UE to a BS or DU).

These 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. NR (e.g., 5G radio access) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, MIMO antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE, MTC, IoT, and NR technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

Certain aspects of the present disclosure generally relate to uplink transmission gaps in enhanced/evolved machine type communication(s) (eMTC).

Certain aspects of the present disclosure provide a method, performed by a wireless device, such as a user equipment (UE). The method generally includes transmitting a random access preamble, receiving a random access response, in response to the random access preamble, transmitting an uplink message containing an indication of a capability of the UE to transmit using uplink gaps, and receiving signaling of configuration information regarding uplink gaps.

Certain aspects of the present disclosure provide a method, performed by a wireless device, such as a base station (BS). The method generally includes receiving a random access preamble from a UE, transmitting a random access response to the UE, in response to the random access preamble, receiving an uplink message from the UE containing an indication of a capability of the UE to transmit using uplink gaps, and transmitting, to the UE, signaling of configuration information regarding uplink gaps.

Certain aspects of the present disclosure provide an apparatus, such as a wireless device (e.g., a UE). The apparatus generally includes means for transmitting a random access preamble, means for receiving a random access response, in response to the random access preamble, means for transmitting an uplink message containing an indication of a capability of the UE to transmit using uplink gaps, and means for receiving signaling of configuration information regarding uplink gaps.

Certain aspects of the present disclosure provide an apparatus, such as a wireless device (e.g., a BS). The apparatus generally includes means for receiving a random access preamble from a UE, means for transmitting a random access response to the UE, in response to the random access preamble, means for receiving an uplink message from the UE containing an indication of a capability of the UE to transmit using uplink gaps, and means for transmitting, to the UE, signaling of configuration information regarding uplink gaps.

Certain aspects of the present disclosure provide an apparatus, such as a wireless device (e.g., a UE). The apparatus generally includes at least one processor configured to output for transmission a random access preamble, obtain a random access response, in response to the random access preamble, output for transmission an uplink message containing an indication of a capability of the UE to transmit using uplink gaps, and obtain signaling of configuration information regarding uplink gaps; and memory coupled with the at least one processor.

Certain aspects of the present disclosure provide an apparatus, such as a wireless device (e.g., a BS). The apparatus generally includes at least one processor configured to obtain a random access preamble from a UE, output for transmission a random access response to the UE, in response to the random access preamble, obtain an uplink message from the UE containing an indication of a capability of the UE to transmit using uplink gaps, and output for transmission, to the UE, signaling of configuration information regarding uplink gaps; and memory coupled with the at least one processor.

Certain aspects of the present disclosure provide a computer readable medium having computer executable code stored thereon for wireless communications by a wireless device, such as a UE. The computer executable code generally includes code for transmitting a random access preamble, code for receiving a random access response, in response to the random access preamble, code for transmitting an uplink message containing an indication of a capability of the UE to transmit using uplink gaps, and code for receiving signaling of configuration information regarding uplink gaps.

Certain aspects of the present disclosure provide a computer readable medium having computer executable code stored thereon for wireless communications by a wireless device, such as a BS. The computer executable code generally includes code for receiving a random access preamble from a UE, code for transmitting a random access response to the UE, in response to the random access preamble, code for receiving an uplink message from the UE containing an indication of a capability of the UE to transmit using uplink gaps, and code for transmitting, to the UE, signaling of configuration information regarding uplink gaps.

Numerous other aspects are provided including methods, apparatus, systems, computer program products, computer-readable medium, and processing systems. To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques for uplink transmission gaps in, for example, enhanced/evolved machine type communications (eMTC). According to certain aspects, a user equipment (UE), which may be a low cost (LC) eMTC UE may transmit a random access preamble and receive a random access response. The UE may transmit an uplink message containing an indication of capability of the UE regarding uplink gaps and receive signaling of configuration information regarding uplink gaps based, at least in part, on the indicated capability.

Example Wireless Communications Network

FIG. 1illustrates an example wireless communication network100, in which aspects of the present disclosure may be practiced. For example, techniques presented herein may be used for uplink transmissions gaps in enhanced/evolved machine type communications (eMTC). Wireless communication network100includes user equipment (UEs)120and base stations (BSs)110. UE120may be a low cost (LC) device, such as an eMTC UE. UE120may transmit a random access preamble to BS110. UE120may receive a random access response, in response to the preamble, from BS110. UE120may transmit an uplink message containing an indication of capability of the UE120regarding uplink gaps, to BS110. UE120can receive signaling of configuration information regarding uplink gaps from BS110.

Wireless communication network100may be an LTE network or some other wireless network, such as new radio (NR) or 5G network. Wireless communication network100may include a number of BSs110and other network entities. A BS is an entity that communicates with UEs and may also be referred to as a Node B (NB), a enhanced/evolved NB (eNB), a gNB, a 5G NB, an access point (AP), a NR BS, a transmission reception point (TRP), etc. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

Wireless communication network100may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS110or a UE120) and send a transmission of the data to a downstream station (e.g., a UE120or a BS110). A relay station may also be a UE that can relay transmissions for other UEs. In the example shown inFIG. 1, relay station110dmay communicate with macro BS110aand UE120din order to facilitate communication between BS110aand UE120d. A relay station may also be referred to as a relay eNB, a relay base station, a relay, etc.

UEs120(e.g.,120a,120b,120c) may be dispersed throughout wireless communication network100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, a Customer Premises Equipment (CPE), etc. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device, medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wristband, and/or smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), industrial manufacturing equipment, a global positioning system (GPS) device, or any other suitable device configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or enhanced/evolved MTC (eMTC) devices. MTC/eMTC UEs may be implemented as IoT UEs. IoT UEs include, for example, robots/robotic devices, drones, remote devices, sensors, meters, monitors, cameras, location tags, etc., that may communicate with a BS, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link.

One or more UEs120in the wireless communication network100may be a narrowband bandwidth UE. As used herein, devices with limited communication resources, e.g. smaller bandwidth, may be referred to generally as narrowband UEs. Similarly, legacy devices, such as legacy and/or advanced UEs (e.g., in LTE) may be referred to generally as wideband UEs. Generally, wideband UEs are capable of operating on a larger amount of bandwidth than narrowband UEs.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a BS110) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. For scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. BSs110are not the only entities that may function as a scheduling entity. In some examples, UE120may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs120). In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

FIG. 2shows a block diagram of a design of BS110and UE120, which may be one of the BSs and one of the UEs illustrated inFIG. 1. BS110may be equipped with T antennas234athrough234t, and UE120may be equipped with R antennas252athrough252r, where in general T≥1 and R≥1.

On the uplink, at UE120, transmit processor264may receive and process data from data source262and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, etc.) from controller/processor280. Processor264may also generate reference symbols for one or more reference signals. The symbols from transmit processor264may be precoded by TX MIMO processor266if applicable, further processed by modulators254athrough254r(e.g., for SC-FDM, OFDM, etc.), and transmitted to BS110. At BS110, the uplink signals from UE120and other UEs may be received by antennas234, processed by demodulators232, detected by MIMO detector236if applicable, and further processed by receive processor238to obtain decoded data and control information sent by UE120. Processor238may provide the decoded data to data sink239and the decoded control information to controller/processor240. BS110may include communication unit244and communicate to network controller130via communication unit244. Network controller130may include communication unit294, controller/processor290, and memory292.

Controllers/processors240and280may direct the operation at BS110and UE120, respectively, to perform techniques presented herein for power savings for control channel monitoring in enhanced machine type communications (eMTC). For example, processor240and/or other processors and modules at BS110, and processor280and/or other processors and modules at UE120, may perform or direct operations of BS110and UE120, respectively. For example, controller/processor280and/or other controllers/processors and modules at UE120, and/or controller/processor240and/or other controllers/processors and modules at BS110may perform or direct operations1100and1200shown inFIGS. 11 and 12, respectively. Memories242and282may store data and program codes for BS110and UE120, respectively. Scheduler246may schedule UEs for data transmission on the downlink and/or uplink.

FIG. 3shows an exemplary frame structure300for FDD in a wireless communication system (e.g., LTE). The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be partitioned into 10 subframes with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, for example, seven symbol periods for a normal cyclic prefix (as shown inFIG. 3) or six symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L−1.

In certain wireless communication systems (e.g., LTE), a BS may transmit a PSS and SSS on the downlink in the center of the system bandwidth for each cell supported by the BS. The PSS and SSS may be transmitted in symbol periods 6 and 5, respectively, in subframes 0 and 5 of each radio frame with the normal cyclic prefix, as shown inFIG. 3. The PSS and SSS may be used by UEs for cell search and acquisition. The BS may transmit a CRS across the system bandwidth for each cell supported by the BS. The CRS may be transmitted in certain symbol periods of each subframe and may be used by the UEs to perform channel estimation, channel quality measurement, and/or other functions. The BS may also transmit a physical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 of certain radio frames. The PBCH may carry some system information. The BS may transmit other system information such as system information blocks (SIBs) on a physical downlink shared channel (PDSCH) in certain subframes. The BS may transmit control information/data on a physical downlink control channel (PDCCH) in the first B symbol periods of a subframe, where B may be configurable for each subframe. The BS may transmit traffic data and/or other data on the PDSCH in the remaining symbol periods of each subframe.

In certain systems (e.g., such as NR or 5G systems), a BS may transmit these or other signals in these locations or in different locations of the subframe.

FIG. 4shows two exemplary subframe formats410and420with the normal cyclic prefix. The available time frequency resources may be partitioned into resource blocks (RBs). Each RB may cover 12 subcarriers in one slot and may include a number of resource elements (REs). Each RE may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.

Subframe format410may be used for two antennas. A CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11. A reference signal is a signal that is known a priori by a transmitter and a receiver and may also be referred to as pilot. A CRS is a reference signal that is specific for a cell, e.g., generated based on a cell identity (ID). InFIG. 4, for a given RE with label Ra, a modulation symbol may be transmitted on that RE from antenna a, and no modulation symbols may be transmitted on that RE from other antennas. Subframe format420may be used with four antennas. A CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11 and from antennas 2 and 3 in symbol periods 1 and 8. For both subframe formats410and420, a CRS may be transmitted on evenly spaced subcarriers, which may be determined based on cell ID. CRSs may be transmitted on the same or different subcarriers, depending on their cell IDs. For both subframe formats410and420, REs not used for the CRS may be used to transmit data (e.g., traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation,” which is publicly available.

The wireless network may support hybrid automatic retransmission request (HARQ) for data transmission on the downlink and uplink. For HARQ, a transmitter (e.g., a BS) may send one or more transmissions of a packet until the packet is decoded correctly by a receiver (e.g., a UE) or some other termination condition is encountered. For synchronous HARQ, all transmissions of the packet may be sent in subframes of a single interlace. For asynchronous HARQ, each transmission of the packet may be sent in any subframe.

A UE may be located within the coverage of multiple BSs. One of these BSs may be selected to serve the UE. The serving BS may be selected based on various criteria such as received signal strength, received signal quality, pathloss, etc. Received signal quality may be quantified by a signal-to-noise-and-interference ratio (SINR), or a RSRQ, or some other metric. The UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering BSs. The wireless communication network may support a 180 kHz deployment for narrowband operation (e.g., NB-IoT) with different deployment modes. In one example, narrowband operations may be deployed in-band, for example, using RBs within a wider system bandwidth. In one case, narrowband operations may use one RB within the wider system bandwidth of an existing network (e.g., such as an LTE network). In this case, the 180 kHz bandwidth for the RB may have to be aligned with a wideband RB. In one example, narrowband operations may be deployed in the unused RBs within a carrier guard-band (e.g., LTE). In this deployment, the 180 kHz RB within the guard band may be aligned with a 15 kHz tone grid of wideband LTE, for example, in order to use the same Fast Fourier Transform (FFT) and/or reduce interference in-band legacy LTE communications.

The focus of traditional LTE design (e.g., for legacy “non MTC” devices) is on the improvement of spectral efficiency, ubiquitous coverage, and enhanced quality of service (QoS) support. Current LTE system downlink (DL) and uplink (UL) link budgets are designed for coverage of high end devices, such as state-of-the-art smartphones and tablets, which may support a relatively large DL and UL link budget.

However, as described above, one or more UEs in the wireless communication network (e.g., wireless communication network100) may be devices that have limited communication resources, such as narrowband UEs, as compared to other (wideband) devices in the wireless communication network. For narrowband UEs, various requirements may be relaxed as only a limited amount of information may need to be exchanged. For example, maximum bandwidth may be reduced (relative to wideband UEs), a single receive radio frequency (RF) chain may be used, peak rate may be reduced (e.g., a maximum of 1000 bits for a transport block size), transmit power may be reduced, Rank 1 transmission may be used, and half duplex operation may be performed.

In some cases, if half-duplex operation is performed, MTC UEs may have a relaxed switching time to transition from transmitting to receiving (or receiving to transmitting). For example, the switching time may be relaxed from 20 μs for regular UEs to 1 ms for MTC UEs. Release 12 MTC UEs may still monitor downlink (DL) control channels in the same way as regular UEs, for example, monitoring for wideband control channels in the first few symbols (e.g., PDCCH) as well as narrowband control channels occupying a relatively narrowband, but spanning a length of a subframe (e.g., enhanced PDCCH or ePDCCH).

Certain standards (e.g., LTE Release 13) may introduce support for various additional MTC enhancements, referred to herein as enhanced MTC (or eMTC). For example, eMTC may provide MTC UEs with coverage enhancements up to 15 dB or better.

As illustrated in the subframe structure500ofFIG. 5, eMTC UEs can support narrowband operation while operating in a wider system bandwidth (e.g., 1.4/3/5/10/15/20 MHz). In the example illustrated inFIG. 5, a conventional legacy control region510may span system bandwidth of a first few symbols, while a narrowband region530of the system bandwidth (spanning a narrow portion of a data region520) may be reserved for an MTC physical downlink control channel (referred to herein as an M-PDCCH) and for an MTC physical downlink shared channel (referred to herein as an M-PDSCH). In some cases, an MTC UE monitoring the narrowband region may operate at 1.4 MHz or 6 resource blocks (RBs).

However, as noted above, eMTC UEs may be able to operate in a cell with a bandwidth larger than 6 RBs. Within this larger bandwidth, each eMTC UE may still operate (e.g., monitor/receive/transmit) while abiding by a 6-physical resource block (PRB) constraint. In some cases, different eMTC UEs may be served by different narrowband regions (e.g., with each spanning 6-PRB blocks). As the system bandwidth may span from 1.4 to 20 MHz, or from 6 to 100 RBs, multiple narrowband regions may exist within the larger bandwidth. An eMTC UE may also switch or hop between multiple narrowband regions in order to reduce interference.

The Internet-of-Things (IoT) may refer to a network of physical objects, devices, or “things”. IoT devices may be embedded with, for example, electronics, software, or sensors and may have network connectivity, which enable these devices to collect and exchange data. IoT devices may be sensed and controlled remotely across existing network infrastructure, creating opportunities for more direct integration between the physical world and computer-based systems and resulting in improved efficiency, accuracy, and economic benefit. Systems that include IoT devices augmented with sensors and actuators may be referred to cyber-physical systems. Cyber-physical systems may include technologies such as smart grids, smart homes, intelligent transportation, and/or smart cities. Each “thing” (e.g., IoT device) may be uniquely identifiable through its embedded computing system may be able to interoperate within existing infrastructure, such as Internet infrastructure.

NB-IoT may refer to a narrowband radio technology specially designed for the IoT. NB-IoT may focus on indoor coverage, low cost, long battery life, and large number of devices. To reduce the complexity of UEs, NB-IoT may allow for narrowband deployments utilizing one PRB (e.g., 180 kHz+20 kHz guard band). NB-IoT deployments may utilize higher layer components of certain systems (e.g., LTE) and hardware to allow for reduced fragmentation and cross compatibility with, for example, NB-LTE and/or eMTC.

FIG. 6illustrates an example deployment600of NB-IoT, according to certain aspects of the present disclosure. Three NB-IoT deployment configurations include in-band, guard-band, and standalone. For the in-band deployment configuration, NB-IoT may coexist with a legacy system (e.g., GSM, WCDMA, and/or LTE system(s)) deployed in the same frequency band. For example, the wideband LTE channel may be deployed in various bandwidths between 1.4 MHz to 20 MHz. As shown inFIG. 6, a dedicated RB602within that bandwidth may be available for use by NB-IoT and/or the RBs1204may be dynamically allocated for NB-IoT. As shown inFIG. 6, in an in-band deployment, one RB, or 200 kHz, of a wideband channel (e.g., LTE) may be used for NB-IoT.

Certain systems (e.g., LTE) may include unused portions of the radio spectrum between carriers to guard against interference between adjacent carriers. In some deployments, NB-IoT may be deployed in a guard band606of the wideband channel.

In other deployments, NB-IoT may be deployed standalone (not shown). In a standalone deployment, one 200 MHz carrier may be utilized to carry NB-IoT traffic and GSM spectrum may be reused.

Deployments of NB-IoT may include synchronization signals such as PSS for frequency and timing synchronization and SSS to convey system information. For NB-IoT operations, PSS/SSS timing boundaries may be extended as compared to the existing PSS/SSS frame boundaries in legacy systems (e.g., LTE), for example, from 10 ms to 40 ms. Based on the timing boundary, a UE is able to receive a PBCH transmission, which may be transmitted in subframe 0 of a radio frame.

Example NR/5G RAN Architecture

New radio (NR) may refer to radios configured to operate according to a new air interface (e.g., other than Orthogonal Frequency Divisional Multiple Access (OFDMA)-based air interfaces) or fixed transport layer (e.g., other than Internet Protocol (IP)). NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. NR may include Enhanced Mobile Broadband (eMBB) service targeting wide bandwidth (e.g. 80 MHz beyond), millimeter wave (mmW) targeting high carrier frequency (e.g. 60 GHz), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra reliable low latency communications (URLLC) service.

A single component carrier (CC) bandwidth of 100 MHZ may be supported. NR RBs may span 12 sub-carriers with a sub-carrier bandwidth of 75 kHz over a 0.1 ms duration. Each radio frame may consist of 50 subframes with a length of 10 ms. Consequently, each subframe may have a length of 0.2 ms. Each subframe may indicate a link direction (e.g., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include DL/UL data as well as DL/UL control data. UL and DL subframes for NR may be as described in more detail below with respect toFIGS. 9 and 10.

The NR RAN may include a CU and DUs. A NR BS (e.g., a NB, an eNB, a gNB, a 5G NB, a TRP, an AP, etc.) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells). For example, the RAN (e.g., a CU or DU) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases DCells may not transmit synchronization signals—in some case cases DCells may transmit synchronization signals.

FIG. 7illustrates an example logical architecture700of a distributed RAN, according to aspects of the present disclosure. 5G access node706may include access node controller (ANC)702. ANC702may be a CU of the distributed RAN. The backhaul interface to the next generation core network (NG-CN)704may terminate at ANC702. The backhaul interface to neighboring next generation access nodes (NG-ANs)710may terminate at ANC702. ANC702may include one or more TRPs708. As described above, TRP may be used interchangeably with “cell”, BS, NR BS, NB, eNB, 5G NB, gNB, AP, etc.

TRPs708may comprise a DU. TRPs708may be connected to one ANC (e.g., ANC702) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific AND deployments, TRP708may be connected to more than one ANC. TRP708may include one or more antenna ports. TRPs708may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

Logical architecture700may be used to illustrate fronthaul definition. The architecture may be defined that support fronthauling solutions across different deployment types. For example, logical architecture700may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter). Logical architecture700may share features and/or components with LTE. According to aspects, NG-AN710may support dual connectivity with NR. NG-AN710may share a common fronthaul for LTE and NR. Logical architecture700may enable cooperation between and among TRPs708. For example, cooperation may be preset within a TRP and/or across TRPs via ANC702. In some cases, no inter-TRP interface may be needed/present.

A dynamic configuration of split logical functions may be present within logical architecture700. The packet data convergence protocol (PDCP), radio link control (RLC), and medium access control (MAC) protocols may be adaptably placed at ANC702or TRP708.

FIG. 8illustrates an example physical architecture800of a distributed RAN, according to aspects of the present disclosure. Centralized core network unit (C-CU)802may host core network functions. C-CU802may be centrally deployed. C-CU802functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

Centralized RAN unit (C-RU)804may host one or more ANC functions. Optionally, C-RU804may host core network functions locally. C-RU804may have distributed deployment. C-RU804may be closer to the network edge.

DU806may host one or more TRPs. DU806may be located at edges of the network with radio frequency (RF) functionality.

FIG. 9is a diagram showing an example of a DL-centric subframe900. DL-centric subframe900may include control portion902. Control portion902may exist in the initial or beginning portion of DL-centric subframe900. Control portion902may include various scheduling information and/or control information corresponding to various portions of DL-centric subframe900. In some configurations, control portion902may be a physical DL control channel (PDCCH), as shown inFIG. 9. DL-centric subframe900may also include DL data portion904. DL data portion904may sometimes be referred to as the payload of DL-centric subframe900. DL data portion904may include the communication resources utilized to communicate DL data from the scheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE). In some configurations, DL data portion904may be a physical DL shared channel (PDSCH).

DL-centric subframe900may also include common UL portion906. Common UL portion906may sometimes be referred to as an UL burst, a common UL burst, and/or various other suitable terms. Common UL portion906may include feedback information corresponding to various other portions of DL-centric subframe900. For example, common UL portion906may include feedback information corresponding to control portion902. Non-limiting examples of feedback information may include an acknowledgment (ACK) signal, a negative acknowledgment (NACK) signal, a HARQ indicator, and/or various other suitable types of information. Common UL portion906may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests (SRs), and various other suitable types of information. As illustrated inFIG. 9, the end of DL data portion904may be separated in time from the beginning of common UL portion906. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the subordinate entity) to UL communication (e.g., transmission by the subordinate entity). One of ordinary skill in the art will understand that the foregoing is merely one example of a DL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

FIG. 10is a diagram showing an example of an UL-centric subframe1000. UL-centric subframe1000may include control portion1002. Control portion1002may exist in the initial or beginning portion of UL-centric subframe1000. Control portion1002inFIG. 10may be similar to control portion1002described above with reference toFIG. 9. UL-centric subframe1000may also include UL data portion1004. UL data portion1004may sometimes be referred to as the payload of UL-centric subframe1000. The UL portion may refer to the communication resources utilized to communicate UL data from the subordinate entity (e.g., UE) to the scheduling entity (e.g., UE or BS). In some configurations, control portion1002may be a PDCCH. In some configurations, the data portion may be a physical uplink shared channel (PUSCH).

As illustrated inFIG. 10, the end of control portion1002may be separated in time from the beginning of UL data portion1004. This time separation may sometimes be referred to as a gap, guard period, guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the scheduling entity) to UL communication (e.g., transmission by the scheduling entity). UL-centric subframe1000may also include common UL portion1006. Common UL portion1006inFIG. 10may be similar to common UL portion906described above with reference toFIG. 9. Common UL portion1006may additionally or alternatively include information pertaining to CQI, sounding reference signals (SRSs), and various other suitable types of information. One of ordinary skill in the art will understand that the foregoing is merely one example of an UL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

Example Uplink Transmission Gaps in eMTC

As mentioned above, certain systems (e.g., Release 13 enhanced machine type communication (eMTC) systems), may support narrowband operation (e.g., communications on a 6 resource block (RB) band) and half duplex transmissions/reception for up to, e.g., 15 dB coverage enhancements or better. These systems may reserve a portion of the system bandwidth for an MTC physical downlink control (MPDCCH). The MPDCCH may be transmitted in a narrowband, may use at least one subframe, and may rely on demodulation reference signal (DMRS) demodulation. Coverage may be increased by performing repetition/bundling of signals.

A user equipment (UE), which may be a low cost (LC) UE such as an eMTC UE may be configured for half-duplex operation. In half-duplex operation, the UE may only support transmission in one direction at a time. Thus, the UE may not monitor for downlink transmissions (such as for the MPDCCH) during the period that the UE transmits on the uplink. In some cases, the UE may transmit on the uplink for a long period (e.g., 2048 ms). Thus, the local oscillator (LO) of the UE may drift during this uplink period, for example, due to temperature change. Since the UE is not monitoring downlink during this period, the UE may not be able to correct for the frequency offset due to the LO drift.

Some UEs may use uplink gaps to correct for the frequency offset. For example, if the uplink transmission period is longer than a threshold duration (e.g., Y ms), the UE can stop uplink transmission for an uplink gap period (e.g., X ms). During the uplink gap period (e.g., referred to as a transmission gap or uplink gap), the UE can obtain the downlink frequency error estimation and correct the uplink frequency error (e.g., correct for the LO drift). However, some UEs may be configured with other mechanisms for correcting the frequency offset (e.g., such as temperature compensation) and, thus, may not need to use uplink gaps.

Therefore, it may be desirable for the uplink gaps to be enabled or disabled (e.g., configured or not configured) for UEs, for example, based on whether the UE needs/uses uplink gaps for frequency error correction. For example, it may be desirable for the UE to be able to signal that the UE requests (e.g., needs, uses, supports, has a capability for) uplink transmission gaps so that uplink gaps can be configured by the network. Techniques for the UE to use or not use uplink gaps (e.g., without receiving an explicit configuration from the network) are also desirable, for example, for initialization of the uplink transmission gaps, for example, in cases where the BS may not know whether the UE desires the uplink transmission gaps.

Accordingly, techniques for uplink transmission gaps in eMTC are desirable.

Techniques presented herein may be used for uplink transmission gaps in eMTC. In aspects, a UE (e.g., such as120) which may be a LC device such as an eMTC UE, can perform an uplink transmission gap capability negotiation with the BS (e.g., such as BS110).

Example Uplink Transmission Gap Negotiation

According to certain aspects, a two-step negotiation can be performed between the BS and UE.FIG. 11is a flow diagram illustrating example operations1100for uplink gap negotiation, in accordance with certain aspects of the present disclosure. Operations1100may be performed, for example, by a UE (e.g., UE120) which may be a low cost device such as an eMTC UE.

Operations1100may begin, at1102, by transmitting (e.g., using gaps or not using gaps) a random access preamble (e.g., a RACH Msg. 1). The random access preamble transmitted by the UE to the BS may be a physical random access channel (PRACH) message (e.g., a Msg1/preamble). Since the PRACH is an initial transmission, the BS may not know whether or not the UE desires, supports, or is capable of, using uplink transmission gaps. Thus, the UE may always transmit the PRACH using uplink gaps, regardless of capability. For non-contention based PRACH, the UE may transmit using uplink gaps or not using gaps, depending on received signaling.

According to certain aspects, repetitions for PRACH transmission may not be transmitted back to back. For example, for some PRACH configurations, the UE may only transmit a single preamble per radio frame. In such cases, the UE may not desire uplink transmission gaps. According to certain aspects, the use of gaps for PRACH transmission may depend on a total transmission time of the random access preamble, the maximum number of PRACH transmissions, and/or the separation between two repetitions of PRACH. For example, if there is a separation of 3 ms between two PRACH transmissions, then the UE may not need gaps (e.g., because it can retune to downlink, stay in downlink for 1 ms to get frequency error estimation, and retune to uplink again).

At1104, the UE receives a random access response (e.g., a RACH Msg. 2), in response to the random access preamble.

At1106, the UE transmits an uplink message (e.g., a RACH Msg3 and/or a Msg5) containing an indication of a capability of the UE to transmit using uplink gaps (e.g., a request to use uplink gaps between repeated uplink transmissions). For example, the UE may respond to RAR from the BS by sending the RACH procedure Msg3 transmission to the BS. According to certain aspects, the Msg3 transmission may include the indication (e.g., 1 bit) of the capability of the UE to transmit using uplink gaps. For example, the UE may send a request for uplink transmission gaps (e.g., a first step in the two-step negotiation). In aspects, the indication may be included only in frequency division duplexing (FDD) cells and, in this case, the bit may be reserved/unused in time division duplexing (TDD) cells. Alternatively, the indication/request may be provided in a different message, such as a Msg. 5 after the RACH procedure (e.g., an RRC message after the UE connects to the cell).

At1108, the UE receives signaling (e.g., via RRC signaling or higher layer/semi-static signaling) of configuration information regarding uplink gaps (e.g., RACH Msg. 4 or a different message). According to certain aspects, the UE may transmit a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and/or a physical random access channel (PRACH), in accordance with the configuration information regarding uplink gaps.

As mentioned above, the signaling of the configuration information regarding uplink gaps may be received in a Msg. 4 transmission (e.g., an RRC configuration/reconfiguration message or security activation message) from the BS. Alternatively, the configuration information regarding uplink gaps may be received in a different (e.g., later) message, for example, after the Msg.5sent by the UE.

The configuration information may configure the UE to use uplink transmission gaps. For example, if the uplink message from the UE (e.g., the Msg. 3 or Msg. 5) indicates that the UE desires (e.g., requests, supports as a capability, etc.) transmission gaps, the UE may expect to receive configuration information from the BS (e.g., the Msg. 4 RRC configuration or other message) configuring the UE for use of uplink transmission gaps (e.g., the second step in the two-step negotiation); however, if the uplink message from the UE indicates that the UE does not desire (request, support of a capability, etc.) uplink transmission gaps, the network may still decide to configure the UE with uplink transmission gaps or may not configure with the UE with uplink transmission gaps.

In some cases, the configuration information regarding the uplink gaps for the UE can be provided by the BS implicitly. For example, the UE may transmit an indication of whether or not the UE requests/supports uplink transmission gaps (e.g., 1 bit in message 3 or message 5), and the UE may start operating according to this indication after reception of a later message from the BS (e.g., after reception of Msg. 4 if the UE provided its indication in Msg. 3, or after reception of Msg. 6 (RRC reconfiguration and/or security activation), if the provided its indication in Msg. 5, etc.). In some cases, the reception of this later message can be detected by higher layers (e.g., RRC), and after reception of this message the higher layers may deliver a message to the physical layer indicating whether gaps are to be used or not. Uplink transmission gaps may be requested based on UE's capability to handle uplink transmission gaps. Similarly, the uplink gap configuration may be set based on UE's capability to handle uplink transmission gaps.

According to certain aspects, the UE may transmit PUSCH, PUCCH and/or PRACH transmissions with or without transmission gaps, for example, according to the configuration from the eNB.

As mentioned above, the uplink message from the UE may be provided as the Msg. 3 or Msg. 5. According to certain aspects, the UE may provide the indication of gap capability, request for gaps, in both the Msg. 3 and the later message (e.g., the Msg5). In this case, the indication in the later message may be consistent with the indication in the earlier message (e.g., in the Msg3).

FIG. 12is a flow diagram illustrating example operations1200for uplink transmission gap negotiation and configuring, in accordance with certain aspects of the present disclosure. Operations1200may be performed, for example, by a BS (e.g., BS110). Operations1200may be complementary operations by the BS to the operations1100performed by the UE. Operations1200may begin, at1202, by receiving a random access preamble from a UE. At1204, the BS transmits a random access response to the UE, in response to the random access preamble. At1206, the BS receives an uplink message from the UE containing an indication of a capability of the UE to transmit using uplink gaps. At1208, the BS transmits, to the UE, signaling of configuration information regarding uplink gaps.

FIG. 13is an example call flow diagram illustrating example operations for uplink transmission gap negotiation and configuration, in accordance with certain aspects of the present disclosure. As shown inFIG. 13, UE1302(e.g., UE120) can send a Msg. 1 random access preamble with or without using uplink gaps. BS1304(e.g., BS110) can respond with the Msg. 2 RAR. UE1302then sends the Msg. 3 RRC Connection Request which, in a first example, may include the indication of the UE's uplink gap capability (or request for uplink gaps). BS1304then sends the Msg. 4 RRC Connection Setup which, according to the first example, includes uplink gap configuration information for UE1302. After the RACH procedure, scheduled RRC transmissions can occur. In a second example, UE1302may send the uplink gap capability indication in a Msg. 5 and BS1304sends Msg. 6 with the uplink gap configuration information for UE1302. In some cases, UE1302may provide the indication in both the Msg. 3 and the Msg. 5. In some cases, uplink gap configuration information may be provided to the UE via higher layer signaling, without an explicit indication from BS1304.

Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase, for example, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, for example the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. As used herein, reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” For example, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form. Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). As used herein, including in the claims, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

As used herein, the term “identifying” encompasses a wide variety of actions. For example, “identifying” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “identifying” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “identifying” may include resolving, selecting, choosing, establishing and the like.

In some cases, rather than actually communicating a frame, a device may have an interface to communicate a frame for transmission or reception. For example, a processor may output a frame, via a bus interface, to an RF front end for transmission. Similarly, rather than actually receiving a frame, a device may have an interface to obtain a frame received from another device. For example, a processor may obtain (or receive) a frame, via a bus interface, from an RF front end for transmission.

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, firmware, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Generally, where there are operations illustrated in Figures, those operations may be performed by any suitable corresponding counterpart means-plus-function components.

For example, means for determining, means for performing, means for setting, means for processing, means for obtaining, means for transmitting, means for receiving, means for sending, means for signaling, and/or means for transmitting may include one or more processors, transmitters, receivers, antennas, and/or other elements of the user equipment120and/or the base station110illustrated inFIG. 2.