Method and apparatus for latency reduction in LTE transmissions in unlicensed spectrum

Abstract

Aspects described herein relate to reducing transmission latency in unlicensed spectrum including listen - before - talk access. A dedicated ultra - low latency (ULL) data bearer with LBT access rules is established, the access rules allowing channel access with an access priority faster than that of control and signaling traffic. The ULL data is mapped to the dedicated ULL data bearer based on the LBT access rules, and channel selection is performed in a portion of the unlicensed spectrum using the LBT access rules. These latency reduction techniques include enabling ULL traffic to obtain fast channel access. These latency reduction techniques also include updating the size of the contention window for channel access. Additionally, these latency reduction techniques include enhancing CPDCCH - based signaling to accommodate the ULL frame structure. Further, these latency reduction techniques include providing robust operation against bursty interference for ULL transmissions. Additionally, these techniques include managing DRX for ULL. Additionally, these latency reduction techniques include joint scheduling of different TTI durations. These latency reduction techniques further include updating the SRS transmission timing. Additionally, these latency reduction techniques include reducing the latency associated with PRACH transmission. Further, these latency reduction techniques include reducing ULL transmission delay by ignoring or canceling scheduled uplink (e.g., LTE) transmissions.

Description

[0001] This application is a divisional application of the same-named patent application with application number 201780045711.2, filed on January 23, 2019.

[0002] Cross-reference to related applications

[0003] This patent application claims the benefit of priority to U.S. Non-Provisional Application No. 15 / 630,689, titled "LATENCY REDUCTION TECHNIQUES FOR LTE TRANSMISSION IN UNLICENSED SPECTRUM," filed on June 22, 2017, and Provisional Application No. 62 / 366,488, titled "LATENCY REDUCTION TECHNIQUES FOR LTE TRANSMISSION IN UNLICENSED SPECTRUM," filed on July 25, 2016. The above applications have been assigned to the assignee of this application and are hereby incorporated by reference in their entirety for all purposes. Technical field

[0004] Broadly speaking, the present disclosure relates to wireless communication systems, and more particularly, to techniques for reducing transmission latency in unlicensed spectrum. Background art

[0005] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. A typical wireless communication system may employ multiple access techniques that are capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple access techniques include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems.

[0006] These multiple access techniques have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at the urban, national, regional, and even global levels. An example of a telecommunication standard is Long Term Evolution (LTE). LTE is an enhanced set of the Universal Mobile Telecommunications System (UMTS) mobile standard released by the 3rd Generation Partnership Project (3GPP). LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, enhancing services, leveraging new spectrum, and better integrating with other open standards that 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. However, as the demand for mobile broadband access continues to increase, there is a need to further improve LTE technology. Preferably, these improvements should be applicable to other multiple access techniques and telecommunication standards that employ these techniques.

[0007] While newer multiple access systems such as LTE provide faster data throughput compared to older technologies, this increased downlink rate has triggered a greater demand for higher - bandwidth content such as high - resolution images and videos for use on or with mobile devices. As UE capabilities increase and the demand for bandwidth grows, lower latency in communication can be expected. SUMMARY OF THE INVENTION

[0008] A brief summary of one or more aspects is presented below in order to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all contemplated aspects and is neither intended to identify key or critical elements of all aspects nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0009] According to one aspect, the present disclosure provides a wireless communication method in a wireless communication system including listen-before-talk (LBT) access for transmission. The method includes establishing, by a wireless communication device, a dedicated ultra-low latency (ULL) data bearer having LBT access rules for accessing at least a portion of an unlicensed spectrum served by the wireless communication system, wherein the LBT access rules allow channel access with an access priority faster than control and signaling traffic. The method further includes receiving, at the wireless communication device, ULL data for transmission. The method further includes mapping, by the wireless communication device, the ULL data for transmission to the dedicated ULL data bearer based at least on the LBT access rules. The method further includes performing, by the wireless communication device, channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission. Additionally, the method includes transmitting, by the wireless communication device, the ULL data on the dedicated ULL data bearer via the channel.

[0010] According to another aspect, the present disclosure provides an apparatus for wireless communication using LBT access for transmission. The apparatus may include: a transceiver configured to transmit one or more wireless signals via one or more antennas; a memory configured to store instructions; and one or more processors communicatively coupled to the transceiver and the memory. The one or more processors may be configured to execute the instructions to establish a dedicated ULL data bearer having LBT access rules for accessing at least a portion of an unlicensed spectrum served by the wireless communication system, wherein the LBT access rules allow channel access with a priority faster than control and signaling traffic. The one or more processors may also be configured to execute the instructions to receive ULL data for transmission. The one or more processors may also be configured to map the ULL data for transmission to the dedicated ULL data bearer based at least on the LBT access rules. The one or more processors may also be configured to execute the instructions to perform channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission. Additionally, the one or more processors may also be configured to execute the instructions to transmit the ULL data on the dedicated ULL data bearer via the channel.

[0011] According to another aspect, the present disclosure provides an apparatus for wireless communication for transmission using LBT access. The apparatus may include a unit for establishing a dedicated ULL data bearer having LBT access rules for accessing at least a portion of the unlicensed spectrum served by a wireless communication system, wherein the LBT access rules allow channel access with an access priority faster than control and signaling traffic. The apparatus may further include a unit for receiving ULL data for transmission. The apparatus may further include a unit for mapping the ULL data for transmission to the dedicated ULL data bearer based at least on the LBT access rules. The apparatus may further include a unit for performing channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission. Additionally, the apparatus may further include a unit for transmitting the ULL data on the dedicated ULL data bearer through the channel.

[0012] According to another aspect, the present disclosure provides a non-transitory computer-readable medium storing computer-executable code for wireless communication at a wireless communication device for transmission using LBT access. The non-transitory computer-readable medium may further include code for establishing a dedicated ULL data bearer having LBT access rules for accessing at least a portion of the unlicensed spectrum served by a wireless communication system, wherein the LBT access rules allow channel access with an access priority faster than control and signaling traffic. The non-transitory computer-readable medium may further include code for receiving ULL data for transmission. The non-transitory computer-readable medium may further include code for mapping the ULL data for transmission to the dedicated ULL data bearer based at least on the LBT access rules. The non-transitory computer-readable medium may further include code for performing channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission. Additionally, the non-transitory computer-readable medium may further include code for transmitting the ULL data on the dedicated ULL data bearer through the channel.

[0013] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system that includes listen-before-talk (LBT) access for transmission. The method includes establishing, by a wireless communication device, a dedicated data bearer having LBT access rules for accessing at least a portion of an unlicensed spectrum served by the wireless communication system, wherein the listen-before-talk access rules allow for channel access during a time period corresponding to an ultra-low latency transmission time interval (TTI) based on a single deferral period, and wherein the LBT access rules further define an additional deferral period to be used after a transmission associated with the channel access during the time period. The method further includes performing, by the wireless communication device, channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission. Additionally, the method includes transmitting, by the wireless communication device, the dedicated data bearer over a channel in a portion of the unlicensed spectrum using the LBT access rules, wherein the transmission corresponds to the channel access during the time period. Further, the method includes waiting for the additional deferral period after using the channel access to transmit the dedicated data bearer during the time period before performing subsequent channel selection to access a corresponding channel in a portion of the unlicensed spectrum to be used in a subsequent transmission.

[0014] According to another aspect, the present disclosure provides an apparatus for wireless communication using LBT access for transmission. The apparatus may include: a transceiver configured to transmit one or more wireless signals via one or more antennas; a memory configured to store instructions; and one or more processors communicatively coupled to the transceiver and the memory. The one or more processors may be configured to execute the instructions to establish a dedicated data bearer having LBT access rules for accessing at least a portion of an unlicensed spectrum served by the wireless communication system, wherein the listen-before-talk access rules allow for channel access during a time period corresponding to an ultra-low latency TTI based on a single deferral period, and wherein the LBT access rules further define an additional deferral period to be used after a transmission associated with the channel access during the time period. The one or more processors may also be configured to perform channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission. The one or more processors may also be configured to transmit the dedicated data bearer over a channel in a portion of the unlicensed spectrum using the LBT access rules, wherein the transmission corresponds to the channel access during the time period. Additionally, the one or more processors may also be configured to wait for the additional deferral period after using the channel access to transmit the dedicated data bearer during the time period before performing subsequent channel selection to access a corresponding channel in a portion of the unlicensed spectrum to be used in a subsequent transmission.

[0015] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes transmitting a downlink subframe including ULL data and regular data by a wireless communication device, where the ULL data corresponds to a first transmission time interval shorter than a transmission time interval for control and signaling services (e.g., less than 1 ms), and where the regular data corresponds to a second transmission time interval for at least control and signaling services (e.g., at least 1 ms). The method further includes receiving, in the downlink subframe, one or more acknowledgment-related messages corresponding to at least a portion of the ULL data or at least a portion of the regular data. Additionally, the method includes updating, based on the one or more acknowledgment-related messages, a size of a contention window for channel access in a portion of an unlicensed spectrum served by a wireless communication system having LBT access rules.

[0016] According to yet another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes transmitting a first downlink subframe having a first set of resource elements assigned to a physical downlink control channel, where the first set of resource elements includes a configuration indication that identifies a structure of a second downlink subframe to be transmitted after the first downlink subframe. The method further includes transmitting a second downlink subframe having a second set of resource elements assigned to the physical downlink control channel, where the second set of resource elements includes a ULL indicator that identifies which symbols carry ULL data having a first transmission time interval shorter than a transmission time interval for control and signaling services (e.g., less than 1 ms), and where the second set of resource elements includes a new configuration indication that identifies the second downlink subframe as having a structure different from the structure identified by the configuration indication provided in the first downlink subframe.

[0017] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes identifying a set of data resource elements for transmission in a downlink subframe. The method further includes identifying a set of reference signal resource elements for transmission in the downlink subframe. Additionally, the method includes mapping both a first portion of the set of data resource elements and a first portion of the set of reference signal resource elements to one symbol of the downlink subframe. Further, the method includes mapping a second portion of the set of data resource elements and a second portion of the set of reference signal resource elements to a subsequent symbol of the downlink subframe, where the subsequent symbol is different from the one symbol of the downlink subframe. Furthermore, the method includes transmitting the downlink subframe.

[0018] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes receiving, by a wireless communication device, a first time slot of a downlink subframe, the downlink subframe including ULL data having a first transmission time interval (e.g., less than 1 ms) that is shorter than a transmission time interval for control and signaling traffic. The method further includes, at the end of the first time slot, initiating a discontinuous reception (DRX) on-duration having a period of less than or equal to one time slot.

[0019] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes scheduling a plurality of uplink transmissions, each uplink transmission having one of a plurality of TTI lengths, wherein the plurality of TTI lengths includes at least two different TTI lengths. The method further includes generating a downlink subframe having a set of resource elements assigned to a physical downlink control channel, wherein the set of resource elements includes downlink control information that identifies one or more uplink grants and a corresponding one of the plurality of TTI lengths for each of the plurality of uplink transmissions. Additionally, the method includes transmitting the downlink subframe.

[0020] According to yet another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes receiving a downlink subframe having a set of resource elements assigned to a physical downlink control channel, wherein the set of resource elements includes downlink control information that identifies a scheduling grant and a TTI length associated with the scheduling grant, and wherein the TTI length includes 1 symbol, 2 symbols, or 1 time slot. The method further includes generating a sounding reference signal (SRS) when triggered by the downlink control information. Additionally, the method includes mapping the SRS to a specific symbol of an uplink subframe based on the TTI length. Additionally, the method includes transmitting the uplink subframe.

[0021] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes transmitting, by a wireless communication device, a first uplink subframe including a random access preamble, wherein the random access preamble corresponds to a first TTI of 2 symbols. The method further includes monitoring a physical downlink control channel (PDCCH) for a first downlink subframe including a random access response, wherein the random access response corresponds to a second TTI of 2 symbols, 1 time slot, or 1 ms.

[0022] According to another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes scheduling one or more uplink transmissions for a duration of up to 16 ms. The method further includes identifying ULL data for transmission on a channel in at least a portion of the unlicensed spectrum served by the wireless communication system. Additionally, the method includes performing one or more LBT procedures during the scheduled duration to compete for access to the channel. Further, the method includes determining whether the competition for the channel is won based on the one or more LBT procedures. Additionally, the method includes transmitting a downlink subframe including the ULL data on the channel when it is determined that the competition is won.

[0023] According to yet another aspect, the present disclosure provides a wireless communication method in a wireless communication system including LBT access for transmission. The method includes scheduling one or more uplink transmissions for a duration of up to 16 ms. The method further includes identifying ULL data for transmission on a channel in at least a portion of the unlicensed spectrum served by the wireless communication system. Additionally, the method includes generating a first downlink subframe having a set of resource elements allocated to a physical downlink control channel, wherein the set of resource elements includes an indication identifying that at least a portion of the one or more scheduled uplink transmissions is cancelled. Further, the method includes transmitting the first downlink subframe on the channel. Additionally, the method includes transmitting a second downlink subframe including the ULL data on the channel.

[0024] To achieve the foregoing and related purposes, one or more aspects include the features that are fully described hereinafter and particularly pointed out in the claims. The following description and the drawings set forth in detail certain illustrative features of one or more aspects. However, these features are only indicative of some of the various ways in which the principles of the various aspects may be employed, and the description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network.

[0026] Figure 2A is a diagram illustrating an example of a DL frame structure in LTE.

[0027] Figure 2B is a diagram illustrating an example of channels within a DL frame structure in LTE.

[0028] Figure 2C is a diagram illustrating an example of a UL frame structure in LTE.

[0029] Figure 2D is a diagram illustrating an example of channels within a UL frame structure in LTE.

[0030] Figure 3 is a diagram showing an example of an evolved Node B (eNB) and a User Equipment (UE) in an access network.

[0031] Figure 4 is a diagram showing an example timeline for managing ULL communication in a wireless communication system.

[0032] Figure 5 is a diagram showing an example system for communicating using ULL radio access technology according to aspects described herein.

[0033] Figure 6 is a diagram showing an example of providing robust operation against burst interference for ULL transmission.

[0034] Figure 7 is a diagram showing an example frame structure for managing DRX for ULL transmission.

[0035] Figure 8 is a diagram showing an example of a method for achieving fast channel access by mapping ULL traffic to dedicated bearers in unlicensed spectrum according to aspects described herein.

[0036] Figure 9 is a diagram showing an example of a method for waiting to access a channel in unlicensed spectrum after transmitting ULL data on a channel in unlicensed spectrum according to aspects described herein.

[0037] Figure 10 is a diagram showing an example of a method for updating the contention window size according to aspects described herein.

[0038] Figure 11 is a diagram showing an example of a method for enhancing CPDCCH-based signaling to adapt to the ULL frame structure according to aspects described herein.

[0039] Figure 12 is a diagram showing an example of a method for providing robust operation against burst interference for ULL transmission according to aspects described herein.

[0040] Figure 13 is a diagram showing an example of a method for managing DRX for ULL traffic according to aspects described herein.

[0041] Figure 14 is a diagram showing an example of a method for jointly scheduling TTIs for ULL traffic according to aspects described herein.

[0042] Figure 15Is a diagram showing an example of a method for updating SRS transmission timing according to aspects described herein.

[0043] Figure 16 Is a diagram showing an example of a method for reducing the delay associated with PRACH transmission according to aspects described herein.

[0044] Figure 17 Is a diagram showing an example of a method for reducing downlink ULL transmission delay by ignoring scheduled uplink transmissions according to aspects described herein.

[0045] Figure 18 Is a diagram showing an example of a method for reducing downlink ULL transmission delay by canceling scheduled uplink transmissions according to aspects described herein. Detailed Description

[0046] The present disclosure generally relates to latency reduction techniques for LTE transmissions in unlicensed spectrum.

[0047] In one high-level aspect, the latency reduction techniques described herein include enabling ULL traffic to obtain fast channel access (compared to traditional channel access times), where the channel access is faster than the access priority for control and signaling traffic. For example, the present disclosure includes apparatuses and methods for defining dedicated bearers for ULL traffic mapping. For example, the apparatuses and methods may map ULL traffic to the highest LBT priority level, such as LBT priority level 1. Additionally or alternatively, the apparatuses and methods may delay channel access or use a larger contention window size during subsequent channel access after transmitting ULL traffic.

[0048] In another high-level aspect, the latency reduction techniques described herein include updating the size of the contention window for channel access. For example, the present disclosure includes apparatuses and methods for updating the size of the contention window for channel access based on acknowledgment-related messages corresponding to ULL data and / or LTE data.

[0049] In another high-level aspect, the latency reduction techniques described herein include enhancing CPDCCH-based signaling to accommodate the ULL frame structure. For example, the present disclosure includes apparatuses and methods for operating to send an indication that the structure of a downlink subframe (e.g., a ULL frame) has changed.

[0050] In another high-level aspect, the latency reduction techniques described herein include providing robust operation against bursty interference for ULL transmissions. For example, the present disclosure includes apparatuses and methods for mapping a portion of a data resource element set and a portion of a reference signal resource element set to one symbol of a downlink subframe.

[0051] In another high-level aspect, the latency reduction techniques described herein include managing DRX for ULL. For example, the present disclosure includes apparatus and methods for operating to initiate a DRX on-duration based on a transmission time interval of a first time slot of a downlink subframe including ULL data.

[0052] In another high-level aspect, the latency reduction techniques described herein include joint scheduling of different TTI durations. For example, the present disclosure includes apparatus and methods for operating to transmit a downlink subframe including downlink control information that identifies one or more uplink grants and a respective one of a plurality of TTI lengths associated with a plurality of scheduled uplink transmissions (e.g., ULL data transmissions).

[0053] In another high-level aspect, the latency reduction techniques described herein include updating SRS transmission opportunities. For example, the present disclosure includes apparatus and methods for operating to map SRS to multiple possible symbols of an uplink subframe based on a TTI length of 1 symbol, 2 symbols, or 1 time slot.

[0054] In another high-level aspect, the latency reduction techniques described herein include reducing latency associated with PRACH transmission. For example, the present disclosure includes apparatus and methods for operating to support both contention-based and contention-free PRACH procedures, where one or more messages associated with each PRACH procedure can correspond to a TTI length less than 1 ms and / or a TTI length less than the TTI length for control and signaling traffic.

[0055] In yet another high-level aspect, the latency reduction techniques described herein include reducing ULL transmission latency. For example, the present disclosure includes apparatus and methods operable to reduce downlink ULL transmission latency by ignoring or canceling a scheduled uplink (e.g., LTE) transmission such that downlink ULL data can be transmitted during the scheduled uplink duration.

[0056] The following detailed description, presented in conjunction with the accompanying drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. For the purpose of providing a thorough understanding of the various concepts, the detailed description includes specific details. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring the concepts.

[0057] Aspects of a telecommunications system will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether these elements are implemented as hardware or software depends on the particular application and the design constraints imposed on the overall system.

[0058] By way of example, an element, or any part of an element, or any combination of elements, can be implemented with a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors in the processing system can execute software. Software should be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, processes, functions, etc., regardless of whether it is referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0059] Thus, in one or more aspects, the described functions can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media can be any available medium that can be accessed by a computer. By way of example and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), and floppy disk, where disks usually magnetically reproduce data, while discs optically reproduce data with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0060] Figure 1FIG. 0 is a diagram illustrating an example of a wireless communication system 100 that includes one or more access networks 101 and one or more UEs 104 that communicate with one or more base stations 102. In accordance with this aspect, one or more UEs 104 may include a communication component 180, and one or more base stations 102 may include a communication component 190, where each of the communication component 180 and the communication component 190 is configured to receive, decode, transmit, and / or otherwise operate using the ULL frame structure as described herein. In one aspect, the ULL frame structure may include a TTI that is shorter than the TTI used for control and signaling traffic (e.g., less than 1 millisecond (ms), e.g., one symbol, two symbols, one time slot, etc.). The communication component 180 of the corresponding UE 104 and the communication component 190 of the corresponding base station 102 may include one or more components to reduce latency in ULL communication, e.g., for fast channel access, for contention window update, for CPDCCH-based signaling for a new frame structure, for interference handling, for discontinuous reception (DRX) management, for joint scheduling for different TTI durations, for controlling SRS transmission timing, for controlling PRACH transmission, and for UL grant cancellation, as discussed in more detail below.

[0061] Additionally, the wireless communication system 100 (also referred to as a wireless wide area network (WWAN)) may include an evolved packet core (EPC) 160 that communicatively couples one or more access networks 101 with other devices and / or networks, including IP services 176. The base stations 102 may include macro cells (high-power cellular base stations) and / or small cells (low-power cellular base stations). Macro cells include eNBs. Small cells include femto cells, pico cells, and micro cells, any of which may be referred to as a home eNB or simply an eNB.

[0062] The base station 102 (collectively referred to as the evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN)) interfaces with the EPC 160 via a backhaul link 132 (e.g., the S1 interface). In addition to other functions, the base station 102 may also perform one or more of the following functions: transmission of user data, encryption and decryption of radio channels, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, non-access stratum (NAS) message distribution, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and device tracking, radio access network information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., via the EPC 160) with each other over a backhaul link 134 (e.g., the X2 interface). The backhaul link 134 may be wired or wireless.

[0063] The base station 102 may communicate wirelessly with the UE 104. Each base station 102 may provide communication coverage for a corresponding geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102' may have a coverage area 110' that overlaps with the coverage area 110 of one or more macro base stations 102. A network including both small cells and macro cells may be referred to as a heterogeneous network. The heterogeneous network may also include a home evolved Node B (eNB) (HeNB) that may provide service to a restricted group called a closed subscriber group (CSG). The communication link 120 between the base station 102 and the UE 104 may include an uplink (UL) (also referred to as a reverse link) transmission from the UE 104 to the base station 102 and / or a downlink (DL) (also referred to as a forward link) transmission from the base station 102 to the UE 104. The communication link 120 may use MIMO antenna technology, which includes spatial multiplexing, beamforming, and / or transmit diversity. The communication link may be by virtue of one or more carriers. The base station 102 / UE 104 may use a bandwidth of up to Y MHz per carrier allocated in carrier aggregation of up to a total of Yx MHz (e.g., where Y = 5, 10, 15, or 20 MHz) (x = the number of component carriers) for transmission in each direction. The carriers may be adjacent or non-adjacent to each other. The allocation of carriers may be asymmetric with respect to the DL and UL (e.g., more or fewer carriers may be allocated for the DL than for the UL). The component carriers may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as the primary cell (PCell), while the secondary component carriers may be referred to as secondary cells (SCells).

[0064] The wireless communication system 100 may also include a Wi-Fi access point (AP) 150 that communicates with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a Clear Channel Assessment (CCA) or Listen Before Talk (LBT) function before communication to determine whether the channel is available (e.g., generally, to avoid transmitting on a channel where another transmission is occurring that would cause interference).

[0065] The small cell 102' may operate in licensed and / or unlicensed spectrum. When operating in the unlicensed spectrum, the small cell 102' may use LTE and use the same 5 GHz unlicensed spectrum as that used by the Wi-Fi AP 150. The small cell 102' using LTE in the unlicensed spectrum may improve the coverage of the access network and / or increase the capacity of the access network. LTE in the unlicensed spectrum may be referred to as Licensed-Assisted Access (LAA), Unlicensed LTE (LTE-U), or MuLTEfire (when operating in independent unlicensed spectrum operation). The unlicensed spectrum may also be referred to as shared unlicensed spectrum.

[0066] The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may communicate with a Home Subscriber Server (HSS) 174. The MME 162 is a control node that processes the signaling between the UE 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are passed through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides IP address allocation to the UE and other functions. The PDN Gateway 172 and the BM-SC 170 are connected to an IP service 176. The IP service 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a Packet Switched Streaming Service (PSS), and / or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and may be used to schedule MBMS transmissions. The MBMS Gateway 168 may be used to distribute MBMS traffic to base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area for broadcasting a specific service, and may be responsible for session management (start / stop) and for collecting eMBMS-related charging information.

[0067] A base station may also be referred to as Node B, evolved Node B (eNB), access point, base transceiver station, radio base station, radio transceiver, transceiver function, basic service set (BSS), extended service set (ESS), or some other appropriate term. Base station 102 provides an access point to the EPC 160 for the UE 104. Examples of the UE 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop computer, a personal digital assistant (PDA), a satellite radio device, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., an MP3 player), a camera, a gaming console, a tablet computer, a smart device, a wearable device, or any other device with similar functionality. The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a radio unit, a remote unit, a mobile device, a radio device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handheld device, a user agent, a mobile client, a client, or some other appropriate term.

[0068] Figure 2A FIG. 200 is a diagram showing an example of the DL frame structure in LTE, which can be used for Figure 1 ULL LTE (and / or LTE) communication between wireless communication devices, for example, carried out by one or more of the base stations 102 or 102', the UE 104, the AP 150, and / or the STA 152. Figure 2B FIG. 230 is a diagram showing an example of channels within the DL frame structure in LTE, which can be used for Figure 1 ULL LTE (and / or LTE) communication between wireless communication devices. Figure 2C FIG. 250 is a diagram showing an example of the UL frame structure in LTE, which can be used for Figure 1 ULL LTE (and / or LTE) communication between wireless communication devices. Figure 2D FIG. 280 is a diagram showing an example of channels within the UL frame structure in LTE, which can be used for Figure 1ULL LTE (and / or LTE) communication between wireless communication devices. Other wireless communication technologies may have different frame structures and / or different channels. In LTE, a frame (10 ms) can be divided into 10 equal-sized subframes. Each subframe can include two consecutive time slots. A resource grid can be used to represent the two time slots, and each time slot includes one or more time-concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs)). The resource grid can be divided into multiple resource elements (REs). In LTE, for a normal cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols in the time domain (for DL, OFDM symbols; for UL, SC-FDMA symbols), for a total of 84 REs. For an extended cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

[0069] As Figure 2A shown, some REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. DL-RS can include cell-specific reference signals (CRS) (sometimes also referred to as common RS), UE-specific reference signals (UE-RS), and channel state information reference signals (CSI-RS). Figure 2A illustrates the CRS for antenna ports 0, 1, 2, and 3 (denoted as R0, R1, R2, and R3 respectively), the UE-RS for antenna port 5 (denoted as R5), and the CSI-RS for antenna port 15 (denoted as R).

[0070] Figure 2B The diagram 230 in shows an example of various channels within the DL subframe of a frame. The physical control format indicator channel (PCFICH) can be within symbol 0 of time slot 0 and can carry a control format indicator (CFI) indicating whether the physical downlink control channel (PDCCH) occupies 1, 2, or 3 symbols ( Figure 2B illustrates a PDCCH occupying 3 symbols). The PDCCH can carry downlink control information (DCI) within one or more control channel elements (CCEs), and each CCE can include nine resource element groups (REGs), and each REG can include four consecutive REs in an OFDM symbol. A UE can be configured with a UE-specific enhanced PDCCH (ePDCCH), and the UE-specific enhanced PDCCH can also carry DCI. The ePDCCH can have 2, 4, or 8 RB pairs ( Figure 2BTwo resource block (RB) pairs are shown, with each subset including one RB pair). The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) can be within symbol 0 of slot 0 and can carry a HARQ indicator (HI) based on the physical uplink shared channel (PUSCH) that indicates HARQ acknowledgement (ACK) / negative ACK (NACK) feedback. The primary synchronization channel (PSCH) can be within symbol 6 of slot 0 in subframes 0 and 5 of a frame and can carry a primary synchronization signal (PSS) that can be used by the UE to determine subframe timing and the physical layer identity. The secondary synchronization channel (SSCH) can be within symbol 5 of slot 0 in subframes 0 and 5 of a frame and can carry a secondary synchronization signal (SSS) that can be used by the UE to determine the physical layer cell identity group number. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine the physical cell identifier (PCI). Based on the PCI, the UE can determine the location of the above-mentioned DL-RS. The physical broadcast channel (PBCH) can be within symbols 0, 1, 2, 3 of slot 1 in subframe 0 of a frame and can carry the master information block (MIB). The MIB can provide the number of RBs in the DL system bandwidth, the PHICH configuration, and the system frame number (SFN). The physical downlink shared channel (PDSCH) can carry user data, broadcast system information not sent via the PBCH, such as system information blocks (SIBs) and paging messages.

[0071] As Figure 2C shown, some resource elements (REs) can carry demodulation reference signals (DM-RS) for channel estimation at the eNB. The UE can also transmit sounding reference signals (SRS) in the last symbol of a subframe. The SRS can have a comb structure and the UE can transmit the SRS on one of the comb structures. The eNB can use the SRS for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0072] Figure 2D The illustration 280 in shows an example of various channels within the UL subframe of a frame. Based on the physical random access channel (PRACH) configuration, the PRACH can be within one or more subframes in a frame. The PRACH can include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. The physical uplink control channel (PUCCH) can be located at the edge of the UL system bandwidth. The PUCCH can carry uplink control information (UCI), such as a scheduling request, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and HARQ ACK / NACK feedback. The PUSCH can carry data and can additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and / or UCI.

[0073] The ULL can be based on multi-symbol level, symbol level, or time slot level durations (e.g., durations less than that of a 1 ms subframe). The frame structure for the ULL can be defined within the frequency bands of LTE and / or within the data portion of the resources in LTE (e.g., excluding a portion of the resources allocated for control data communication). Further, in this regard, at least a portion of the data portion of the resources can be divided for control and data communication for the ULL, which can be further divided into one or more RB groups, each RB group including a plurality of RBs. Thus, the control and data regions for ULL communication can also be defined on the RB groups. The control channel for the ULL can be referred to herein as the ULL PUCCH (uPUCCH), and the data channel for the ULL can be referred to herein as the ULL PUSCH (uPUSCH). Additionally, a region for transmitting the ULL reference signal (uRS) can be defined within the data region of LTE.

[0074] Figure 3 A block diagram of an eNB 310 that communicates with a UE 350 in an access network, where the eNB 310 can be Figure 1 an example of the base stations 102 or 102' and / or the AP 150, and the UE 350 can be Figure 1Examples of the UE 104 and / or STA 152. In one aspect, the communication component 190 can be part of the eNB 310, which is implemented, for example, within the controller / processor 375 and / or the memory 376. Similarly, in one aspect, the communication component 180 can be part of the UE 350, which is implemented, for example, within the controller / processor 359 and / or the memory 360. In the DL, IP packets from the EPC 160 can be provided to the controller / processor 375. The controller / processor 375 implements layer 3 and layer 2 functions. Layer 3 includes the radio resource control (RRC) layer, and layer 2 includes the packet data convergence protocol (PDCP) layer, the radio link control (RLC) layer, and the media access control (MAC) layer. The controller / processor 375 provides: RRC layer functions associated with broadcast system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functions associated with header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with the transmission of upper layer packet data units (PDUs), error correction via ARQ, concatenation, segmentation, and the reassembly of RLC service data units (SDUs), the re-segmentation of RLC data PDUs, and the re-ordering of RLC data PDUs; and MAC layer functions associated with the mapping between logical channels and transport channels, the multiplexing of MAC service data units (MAC SDUs) into transport blocks (TBs), the demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and prioritizing the logical channel arrangement.

[0075] The transmit (TX) processor 316 and the receive (RX) processor 370 implement the layer 1 functions associated with various signal processing functions. The layer 1, which includes the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) encoding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The encoded and modulated symbols can then be split into parallel streams. Each stream can then be mapped to OFDM subcarriers, multiplexed with reference signals (e.g., pilots) in the time and / or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to generate a physical channel carrying a stream of time-domain OFDM symbols. The OFDM stream can be space precoded to generate multiple spatial streams. Channel estimates from the channel estimator 374 can be used to determine the encoding and modulation schemes, as well as for spatial processing. The channel estimates can be derived from reference signals transmitted by the UE 350 and / or channel condition feedback. Each spatial stream can then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX can modulate an RF carrier with the corresponding spatial stream for transmission.

[0076] At the UE 350, each receiver 354RX receives signals via the corresponding antenna 352 of the UE 350. Each receiver 354RX recovers the information modulated onto the RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement the layer 1 functions associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, the RX processor 356 can combine them into a single OFDM symbol stream. The RX processor 356 then uses a fast Fourier transform (FFT) to convert the OFDM symbol stream from the time domain to the frequency domain. The frequency-domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols and reference signals on each subcarrier are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 310. These soft decisions can be based on the channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally transmitted by the eNB 310 on the physical channel. The data and control signals are then provided to the controller / processor 359, which implements the layer 3 and layer 2 functions.

[0077] The controller / processor 359 may be associated with a memory 360 that stores program code and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the EPC 160. The IP packets are then provided to a data sink 362, which represents all protocol layers above the L2 layer. Various control signals may also be provided to the data sink 362 for L3 processing. The controller / processor 359 is also responsible for error detection using the ACK and / or NACK protocols to support HARQ operations.

[0078] Similar to the functions described in connection with the DL transmission of the eNB 310, the controller / processor 359 provides: RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with the transmission of upper layer PDUs, error correction via ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; MAC layer functions associated with the mapping between logical and transport channels, multiplexing of MAC SDUs into TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and prioritization of logical channels.

[0079] In the UL, a data source 367 is used to provide upper layer packets to the controller / processor 359. The data source 367 represents all protocol layers above the L2 layer. Similar to the functions described in connection with the DL transmission of the eNB 310, the controller / processor 359 implements the L2 layer for the user plane and the control plane by providing header compression, encryption, packet segmentation and re-ordering, and multiplexing between logical and transport channels based on the radio resource allocation performed by the eNB 310. The controller / processor 359 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 310.

[0080] Channel estimates derived by the channel estimator 358 from reference signals or feedback sent by the eNB 310 may be used by the TX processor 368 to select an appropriate coding and modulation scheme and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a corresponding spatial stream for transmission.

[0081] UL transmissions are processed at the eNB 310 in a manner similar to that described for the receiver function at the associated UE 350. Each receiver 318RX receives signals via its respective antenna 320. Each receiver 318RX recovers the information modulated onto the RF carrier and provides the information to the RX processor 370.

[0082] The controller / processor 375 can be associated with a memory 376 that stores program code and data. The memory 376 can be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover IP packets from the UE 350. The IP packets from the controller / processor 375 can be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using the ACK and / or NACK protocols to support HARQ operations.

[0083] Figure 4FIG. is a diagram showing non - limiting examples of ULL timelines 400, 402 for managing ULL communication in a wireless communication system, where time extends from left to right in the figure. In this example, timelines 400, 402 include ULL frames of symbol durations in each symbol of a sub - frame. Both timelines 400, 402 depict symbols representing the TTI for the ULL physical downlink control channel (uPDCCH) and / or ULL physical downlink shared channel (uPDSCH) and symbols representing the TTI for the TTI including uPUCCH and / or uPDSCH. In timeline 400, 14 symbols 410, 411, etc. (e.g., for normal CP) are shown within a given sub - frame 412, and in timeline 402, 12 symbols 420, 421, etc. (e.g., for extended CP) are shown within a given sub - frame 422. In either case, by using a symbol - based TTI (e.g., a TTI less than the TTI for control and signaling traffic, e.g., less than 1 ms or less than a sub - frame, as opposed to the sub - frame - based TTI in LTE), lower latency is achieved in ULL. In other examples, the TTI can be two or more symbols, a time slot of a sub - frame (where a sub - frame includes two time slots), etc. Additionally, based on the duration of the TTI for ULL communication, the HARQ process response time can be approximately several symbols (e.g., 3 symbols, 4 symbols, etc.), several sets of symbols (e.g., 3 double - symbols, 4 double - symbols, etc.), several time slots (e.g., 3 time slots, 4 time slots, etc.). In the depicted example, the duration of ULL communication is 1 symbol, the uPDCCH / uPDSCH is sent in symbol 0 of the sub - frame, and the HARQ is processed and sent in symbol 7, etc. of the sub - frame. Thus, based on the shortened TTI duration, the amount of time associated with HARQ latency in ULL communication is also less than the corresponding HARQ latency in LTE communication.

[0084] Referring to Figure 5 , in an example of a wireless communication system 500 similar to system 100, more detailed examples of UE 104 and eNB 102 can include additional system components in one example implementation for reducing the latency of LTE transmissions in unlicensed spectrum.

[0085] Specifically, wireless communication system 500 includes a UE 104 that communicates with eNB 102 to access the wireless network, examples of which are in Figure 1 , 3described in etc. In particular, the UE 104 can communicate with a wireless network (e.g., EPC 160 and / or IP service 176) via the eNB 102. In one aspect, the eNB 102 and the UE 104 may have established one or more downlink channels 509 through which downlink signals can be sent by the eNB 102 (e.g., via transceiver 556) and received by the UE 104 (e.g., via transceiver 506) to send control and / or data messages (e.g., signaling) from the eNB 102 to the UE 104 on the configured communication resources. Additionally, for example, the eNB 102 and the UE 104 may have established one or more uplink channels through which uplink signals 508 can be sent by the UE 104 (e.g., via transceiver 506) and received by the eNB 102 (e.g., via transceiver 556) to transmit control and / or data messages (e.g., signaling) from the UE 104 to the eNB 102 on the configured communication resources. According to this aspect, one or more downlink channels 509 and one or more uplink channels 508 can be used to transmit ULL data and control signaling, LTE data and control signaling, or a combination of ULL and LTE data as well as control signaling.

[0086] According to the present disclosure, the UE 104 may include at least one memory 505 and one or more processors 503, which may be communicatively coupled, for example, via one or more buses 507, and may operate in conjunction with the communication component 180 to implement or otherwise effectuate the communication component 180 to reduce latency associated with receiving and transmitting ULL (and / or LTE) communications with one or more eNBs or other network nodes, as described herein. For example, various operations associated with the communication component 180 or sub-components of the communication component 180 may be implemented or otherwise performed by one or more processors 503, and in one aspect, may be performed by a single processor, while in other aspects, different operations may be performed by a combination of two or more different processors. For example, one or more processors 503 may include any one or any combination of the following: a modem processor, or a baseband processor, or a digital signal processor, or an application specific integrated circuit (ASIC), or a transmit processor, a receive processor, or a transceiver processor associated with the transceiver 506. The memory 505 may be a non-transitory computer-readable medium, which includes but is not limited to random access memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical disks (e.g., compact disks (CDs), digital versatile disks (DVDs)), smart cards, flash memory devices (e.g., cards, sticks, key drives), registers, removable disks, and any other suitable medium for storing software and / or computer-readable code or instructions that can be accessed and read by a computer or one or more processors 503. Additionally, the memory 505 or computer-readable storage medium may reside within one or more processors 503, external to one or more processors 503, or be distributed across multiple entities including one or more processors 503 and the like.

[0087] Similarly, in one aspect, eNB 102 can include one or more processors 553 and / or a memory 555, which can be communicatively coupled, for example, via one or more buses 557, and can operate in conjunction with the communication component 190 to implement or otherwise enable the communication component 190 to reduce latency associated with receiving and transmitting ULL (and / or LTE) communications with UE 104, as described herein. For example, various functions related to the communication component 190 or sub-components of the communication component 190 can be implemented or otherwise performed by one or more processors 553, and in one aspect, can be performed by a single processor, while in other aspects, different functions can be performed by a combination of two or more different processors, as described above. In one example, one or more processors 553 and / or the memory 555 can be configured as described in the examples above regarding one or more processors 503 and / or the memory 505 of UE 104.

[0088] Transceivers 506, 556 can be configured to transmit and receive wireless signals via one or more antennas, RF front-ends, one or more transmitters, and one or more receivers. In one aspect, the transceivers 506, 556 can be tuned to operate at a specified frequency such that UE 104 and / or eNB 102 can communicate at a particular frequency. In one aspect, one or more processors 503 can configure the transceiver 506 and / or one or more processors 553 can configure the transceiver 556 to operate at a specified frequency and power level based on a configuration, communication protocol, etc., to transmit an uplink communication signal 508 and / or a downlink signal 509 on a relevant uplink or downlink communication channel, respectively.

[0089] Transceivers 506, 556 can operate in multiple frequency bands (e.g., using a multi-band - multi-mode modem, not shown) to process digital data transmitted and received using the transceivers 506, 556. The transceivers 506, 556 can be multi-band and configured to support multiple frequency bands for a particular communication protocol. The transceivers 506, 556 can be configured to support multiple operating networks and communication protocols. Thus, for example, the transceivers 506, 556 can implement signal transmission and / or reception based on a specified modem configuration.

[0090] According to this aspect, the communication component 180 of the UE 104 may include one or more of a fast channel access component 510, a contention window update component 512, a CPDCCH signaling receiving (RX) component 514, an interference handling component 516, a DRX management component 518, a multi-TTI scheduling receiving (RX) component 520, an SRS controller component 522, a PRACH transmission component 524, and / or an uplink grant receiving (RX) component 526 to reduce the latency of ULL (and / or LTE) transmissions in unlicensed spectrum. The communication component 190 of the eNB 102 may include one or more of a fast channel access component 528, a contention window update component 530, a CPDCCH signaling transmitting (TX) component 532, an interference handling component 534, a DRX management component 536, a multi-TTI scheduling transmitting (TX) component 538, an SRS controller component 540, a PRACH transmission component 542, and / or an uplink grant transmitting (TX) component 544 to reduce the latency of ULL (and / or LTE) transmissions in unlicensed spectrum.

[0091] Fast Channel Access Scheme

[0092] More specifically, the fast channel access component 510 and / or the fast channel access component 528 may be configured to enable ULL traffic to obtain fast access to a channel. For example, the fast channel access component 510 and / or the fast channel access component 528 may be configured to: define a dedicated bearer for mapping ULL traffic onto unlicensed spectrum and transmit the dedicated bearer on a channel in unlicensed spectrum. Additionally or alternatively, the fast channel access component 510 and / or the fast channel access component 528 may be configured to wait after transmitting a dedicated data bearer on a channel in unlicensed spectrum before re-accessing the channel in unlicensed spectrum for a subsequent transmission.

[0093] Currently, in LAA, the LBT function supports four LBT priority levels (e.g., LBT priority level 1, LBT priority level 2, LBT priority level 3, LBT priority level 4), where the smaller the LBT priority level number, the higher the priority. In LAA, all high-priority services are mapped to LBT priority level 1. Each LBT priority level is defined by a parameter set, which at least includes: a number of CCA time slots in the deferral period, a minimum contention window size (CWmin), and a maximum contention window size (CWmax). For different LBT priority levels, each of these parameters is set differently. For example, LBT priority level 1 supports a deferral period of 1 time slot (e.g., 25 microseconds) at the eNB, a CWmin of three time slots, and a CWmax of seven time slots. LBT priority level 1 also supports a deferral period of 2 time slots (e.g., 34 microseconds) at the UE, a CWmin of three time slots, and a CWmax of seven time slots. These parameters allow services using LBT priority level 1 to access the channel for a period of up to 2 milliseconds at the eNB and UE. ULL services are based on a transmission time interval (TTI) that is smaller than the duration of traditional wireless communication technologies, so two milliseconds is greater than the sufficient amount of time for ULL services to access the channel. A bearer can carry ULL services, and each bearer can be mapped to a different LBT priority. For different frequency bands that can have different channel bandwidths, for example, the duration of the period during which ULL services can access the channel using LBT priority level 1 can be different. ULL services can use an LBT priority that is faster than the access priority for control and signaling services to access the channel.

[0094] This aspect includes a scheme for defining a dedicated bearer for mapping ULL services onto unlicensed spectrum. If a ULL service can be mapped onto a dedicated bearer or onto one of the high-priority bearers in a high-priority bearer class, the ULL service can be mapped onto the highest-priority bearer class (e.g., LBT priority class 1), thereby reducing the amount of time required for the ULL service to obtain access to the channel. It should be understood that in some aspects, a ULL service (e.g., due to a shortened TTI such as but not limited to a 1-slot TTI) can access the channel faster than an LBT priority class 1 service, e.g., faster than the access priority for control and signaling services. For example, a ULL service can access the channel using only the deferral period. Thus, to compensate, in additional or alternative aspects, the eNB 102 or the UE 104 can avoid accessing the channel for "X" milliseconds (where "X" is a configurable value) after transmitting only the ULL service on the channel (e.g., using LBT priority class 1). Alternatively, the eNB 102 or the UE 104 can use a larger (e.g., doubled) contention window size during a subsequent time period when the eNB accesses the channel. After transmitting the ULL service (e.g., only the ULL service), the eNB 102 or the UE 104 can avoid accessing the channel (e.g., the dedicated ULL data bearer) for a longer time period before the eNB 102 or the UE 104 accesses the channel for a subsequent transmission. This longer time period can compensate for the faster access for the previous transmission. For example, in response to transmitting a previous transmission using faster access, the eNB 102 or the UE 104 can double the contention window for a subsequent transmission.

[0095] CW Update

[0096] Further, and more specifically, the contention window update component 512 and / or the contention window update component 530 can be configured to update the contention window size of the UE 104 and / or the eNB 102, respectively.

[0097] In the traditional implementation of LAA, the contention window size is updated based on the latest available Hybrid Automatic Repeat reQuest (HARQ)-ACK feedback (e.g., ACK / NACK) of the first downlink subframe. In the traditional implementation of LAA, downlink transmissions may not start and / or end at subframe boundaries. The HARQ feedback can take values from, for example, ACK and NACK, where ACK refers to the case of correct reception, while NACK refers to the case where the control information (e.g., PDCCH) is correctly decoded but there is an error in the reception of the data (e.g., PDSCH). To efficiently utilize radio resources, partial subframes have been introduced in LAA, where downlink transmissions other than the reserved signals can start at the first or second slot boundary of a subframe (e.g., the initial partial subframe). Depending on the starting position of the DL transmission and due to the Maximum Channel Occupancy Time (MCOT) limit, the DL transmission may not end at the subframe boundary. Further, in traditional LAA, if the initial partial subframe is used, the contention window size is updated based on the latest available Hybrid Automatic Repeat reQuest (HARQ)-ACK feedback of both the initial partial subframe and the first subframe that can be used subsequently.

[0098] This aspect may include techniques for updating the contention window size. For example, in one aspect, if the HARQ-ACK feedback for ULL traffic on LAA is mapped to the licensed carrier, the UE 104 and / or the eNB 102 may have available HARQ-ACK feedback with a much earlier timeline than conventional (e.g., LTE) transmissions. Thus, the HARQ-ACK feedback for the ULL traffic transmitted by the UE 104 and / or the eNB 102 in the first subframe may be available at the eNB 102 and / or the UE 104, respectively, at an earlier time. Therefore, in one aspect, the contention window size of the UE 104 and / or the eNB 102 may be updated based on all available HARQ-ACK feedback from ULL and / or LTE transmissions in the previous "X" milliseconds (where "X" is a configurable value) at the UE 104 and / or the eNB 102. In additional or alternative aspects, different weights may be utilized to treat the HARQ-ACK reports for ULL traffic when determining whether to update (e.g., increase or decrease) the size of the contention window. For example, ULL traffic is coded towards lower latency and thus may not need to be retransmitted as many times as, for example, LTE traffic. Therefore, in one aspect, the contention window update component 512 of the UE 104 and / or the contention window update component 530 of the eNB 102 may assign weight factors to ULL traffic and / or conventional (e.g., LTE) traffic, which are, for example but not limited to, weighted by type of group. For example, in one aspect, one weight may be applied to the ACKs received for ULL traffic and another weight may be applied to the ACKs received for conventional traffic. For example, the eNB 102 and / or the UE 104 may receive four ACKs and two NACKs for ULL traffic and may also receive two ACKs for conventional traffic. In this example, the contention window update component 512 and / or the contention window update component 530 may apply a first weight to each ACK received for conventional traffic and may apply a second weight equal to half of the first weight to each ACK received for ULL traffic. Alternatively, in one aspect, the contention window update component 512 of the UE 104 and / or the contention window update component 530 of the eNB 102 may assign a weight of zero to each ACK received for ULL traffic.

[0099] CPDCCH - based Signaling for New Frame Structure

[0100] Additionally, more specifically, the CPDCCH signaling receive (RX) component 514 and / or the CPDCCH signaling transmit (TX) component 532 can be configured to enhance CPDCCH-based signaling to accommodate updates such as for the ULL frame structure for the current subframe. For example, in one aspect, both the CPDCCH signaling RX component 514 and the CPDCCH signaling TX component 532 can be configured to transmit and receive CPDCCH-based signaling. Alternatively, one of the CPDCCH signaling TX component 532 or the CPDCCH signaling RX component 514 can be configured to transmit CPDCCH-based signaling, while the other component can be configured to receive and decode CPDCCH-based signaling and act accordingly based on the received CPDCCH-based signaling.

[0101] In 3GPP Release 13 LAA, the common PDCCH (CPDCCH) is used to indicate the configuration of the current subframe and the next subframe for downlink transmission. For example, in LAA, the CPDCCH is used to indicate the number of OFDM symbols of the current subframe "n-1" and the next subframe "n" for downlink transmission. Information for subframe "n" can be carried in both subframe "n-1" and subframe "n".

[0102] This aspect can include techniques for enhancing CPDCCH-based signaling to accommodate the ULL frame structure. For example, in one aspect, if ULL traffic is carried in subframe "n", the configuration of subframe "n" can be changed on the fly. The eNB 102 can indicate in the CPDCCH of subframe "n" that the structure of subframe "n" has changed. Then, the UE 104 can follow the updated configuration indicated in the CPDCCH sent by the eNB 102. For example, several bits in the CPDCCH can indicate the configuration of the current subframe, including which symbols of the current subframe carry ULL traffic, and so on. The CPDCCH can also indicate several different subframe types as part of this CPDCCH-based signaling. For example, the CPDCCH can indicate subframe types such as but not limited to DL subframes, UL subframes, flexible frame structure 1, and / or flexible frame structure 2. In one aspect, the flexible frame structure can include a downlink (D) part and an uplink (U) part. For example, flexible frame structure 1 can include D D U U U D D U U U D U, etc. The flexible frame structure can be preconfigured by the eNB 102 according to, for example, the standardization in 3GPP Release 13 or by RRC configuration. For example, the D and U parts of the flexible frame structure can be arranged such that the UE 104 can decode the transmission at an earlier time.

[0103] In addition, the eNB 102 may impose certain restrictions on changing the flexible frame structure from one type to another (e.g., from flexible frame structure 1 to flexible frame structure 2, or vice versa). For example, a downlink subframe cannot be changed to an uplink subframe, but can be changed to, for example, flexible frame type 1.

[0104] Handling of Interference

[0105] In addition, and more specifically, the interference handling component 516 and / or the interference handling component 534 may be configured to provide more robust operation against burst interference for ULL transmissions.

[0106] In a conventional implementation of LAA, ULL transmissions may experience burst interference from, for example, small WiFi packets and / or other ULL transmissions, especially burst interference from hidden nodes. A hidden node may be a first UE (e.g., the first STA 152) that is hidden from a second UE (e.g., the second STA 152). For example, the first UE may transmit on the same access node (e.g., the AP 150 in Figure 1 as the second UE, but the first UE may be outside the range of the second UE. Thus, the second UE may not be hidden from (e.g., unable to listen to) the first UE.

[0107] This aspect includes techniques for providing more robust operation against burst interference for ULL transmissions, such as but not limited to 2-symbol TTI and / or 1-slot TTI ULL transmissions.

[0108] Referring to Figure 6 , Figure 6 shows aspects of providing robust operation against burst interference for ULL transmissions. For example, Figure 6A conventional 2-symbol TTI ULL frame 610 is shown. For example, the 2-symbol TTI ULL frame portion 610 may include a reference signal (RS) mapped to resource elements (REs) of a first OFDM symbol 612 and data mapped to the REs of a second OFDM symbol 614. In contrast, according to this aspect, the RS and data symbols may be mixed such that if one of the symbols experiences overwhelming interference, the other symbol may allow for the decoding of the ULL frame. For example, in one aspect, the 2-symbol TTI ULL frame portion 620 may include RS and data symbols mixed within the symbol period such that both the first OFDM symbol 622 and the second OFDM symbol 624 include a combination of RS REs and data REs. In one aspect, the first symbol 622 may include more RS REs than the second symbol 624 for front-loaded demodulation. By mixing the RS and data symbols, even if the transmission of the TTI ULL frame 620 experiences bursty interference from, for example, other ULL transmissions, the TTI ULL frame portion 620 may still be decoded.

[0109] DRX Management for ULL

[0110] The DRX management component 518 and / or the DRX management component 536 may be configured to manage DRX for ULL traffic.

[0111] In a conventional implementation of LAA / eLAA, the UE is required to monitor for possible DL transmissions starting from the subframe boundary or the second time slot of the subframe. That is, the DL transmission from the eNB is the entire subframe or a partial subframe that includes the entire second time slot. However, the ULL frame may have a duration of one time slot or a 2-symbol TTI.

[0112] This aspect may include a method for managing discontinuous reception (DRX) for ULL traffic.

[0113] Refer to Figure 7, An example of the frame structure 700 illustrates aspects of managing DRX for ULL. In this aspect, the DRX for ULL can be aligned with a reference signal or a configured boundary (such as but not limited to subframe and / or slot boundaries) (e.g., see "Possible DRX start points"). For example, the configuration of the DRX period can be based on the slot duration for a 1-slot and 2-symbol TTI. Additionally, the DRX period can be based on a 1 ms TTI. Regarding the configured DRX, inactivity timer, and control channel monitoring, they can all be based on the TTI duration of the ULL frame (e.g., 2 symbols or 1 slot). Thus, the design of the DRX for ULL can be simplified such that 1 ms, 1 slot, and 2-symbol TTIs share the same potential starting transmission opportunities. Additionally, the UE may not consume too much power (e.g., for monitoring in more scenarios).

[0114] Joint Scheduling with Different TTI Durations

[0115] The multi-TTI scheduling TX component 538 can be configured to jointly schedule multiple TTIs of different durations. Additionally, the multi-TTI scheduling RX component 520 can be configured to receive the jointly scheduled TTIs from the multi-TTI scheduling TX component 538.

[0116] In 3GPP Release 14 eLAA, DCI formats 0B and 4B can be used to enable uplink multi-TTI scheduling. In LTE, all scheduled TTIs have the same duration, and up to four different uplink authorizations can be received in a subframe. However, ULL can be based on multi-symbol level, symbol level, or slot level durations (e.g., less than the duration of a 1 ms subframe). That is, the scheduled TTIs for ULL services can all have different durations.

[0117] This aspect may include techniques for jointly scheduling TTIs for ULL services. In one aspect, for example, eNB 102 may send multiple TTI grants, each grant addressing a different TTI length in a subframe. For example, eNB 102 may send two grants in a subframe, where the first grant may schedule a TTI duration of 2 symbols and the second grant may schedule a TTI duration of 1 time slot. Alternatively, eNB 102 may use a single grant to schedule different durations for each of multiple TTIs. The order and duration of the TTI lengths may be derived from the DCI format used (e.g., format 0B and / or format 4B DCI), or explicitly indicated as using bits in the DCI. Additionally, eNB 102 may indicate multiple HARQ IDs, where each HARQ ID corresponds to a different TTI duration. For example, the first HARQ ID may correspond to the first TTI length and the second HARQ ID may correspond to the second TTI length.

[0118] SRS Transmission Opportunity

[0119] The SRS controller component 522 may be configured to update the SRS transmission occasion (e.g., location). Additionally, the SRS controller component 540 may be configured to send, for example, RRC configuration to update the SRS transmission occasion to the SRS controller component 522.

[0120] In 3GPP Release 14 eLAA, SRS can only be sent in the same transmission occasion as in the licensed spectrum. For example, SRS is always sent in the last OFDM symbol of the uplink subframe (e.g., the uplink pilot time slot (UpPTS) of a special subframe). For SRS triggered from a downlink grant, a timing indication is provided in the subframe. For SRS triggered from an uplink grant, SRS is always multiplexed with PUSCH. In 3GPP Release 14, the conversion based on the SRS carrier can bring more SRS transmission occasions in the licensed spectrum (e.g., multiple possible SRS transmission symbols in the uplink subframe).

[0121] In one aspect, the ULL subframe structure can be considered to update the SRS transmission position by using, for example, RRC configuration. If the ULL subframe structure is the flexible frame structure type 1, the SRS can be transmitted, for example, in the second symbol of the uplink subframe. Alternatively, if the ULL subframe structure is the flexible frame structure type 2, the SRS can be transmitted, for example, in the third symbol of the uplink subframe. Additionally, for the SRS triggered from a UL subframe, the SRS can be multiplexed with a short PUSCH (sPUSCH). Additionally, compared to the position of the SRS in a multi-TTI grant with a smaller slot TTI (e.g., 1-slot or 2-symbol TTI), the position of the SRS in a multi-TTI grant with a 1-subframe TTI can be configured differently.

[0122] PRACH Transmission

[0123] The PRACH transmission component 524 and / or the PRACH transmission component 542 can be configured to reduce the latency associated with the PRACH transmission.

[0124] In one aspect, two-step and four-step PRACH procedures can be supported for ULL transmission. The eNB 102 can implement the two-step or four-step PRACH procedure depending on the situation. For example, the eNB 102 can implement the two-step PRACH procedure to request uplink resources more quickly. In this case, the eNB 102 assumes that the UE is in the connected state. Further, the two-step PRACH procedure can conceptually be similar to the contention-based PUSCH, but can be used only for RACH purposes. Additionally or alternatively, the eNB 102 can implement the four-step PRACH procedure to achieve connection establishment, handover, etc.

[0125] In another or alternative aspect, a new TTI-based PRACH procedure can be supported for ULL transmission. The new TTI-based PRACH procedure can include a response window size based on a new TTI. For example, messages 2, 3 (if supported), and 4 (if supported) can be based on a 2-symbol TTI, 1-slot TTI, or 1-ms TTI. Message 1 can still be based on the traditional 2-symbol PRACH (format 4) or other formats. The differentiation of different TTIs can be based on the resource partitioning in the PRACH, an indicator in the PRACH (if the PRACH carries a payload), the resource partitioning in message 2, or an indicator in the PDCCH DCI for non-contention-based PRACH.

[0126] UL Grant Cancellation

[0127] The uplink grant RX component 526 and / or the uplink grant TX component 544 may be configured to reduce the ULL transmission latency caused by scheduled uplink (e.g., LTE) transmissions. For example, the uplink grant TX component 544 may be configured to send an indication that one or more uplink grants are cancelled. The uplink grant RX component 526 may be configured to receive from the uplink grant TX component 544 an indication that one or more uplink grants are cancelled.

[0128] In a conventional implementation of LAA, uplink transmissions can be scheduled within up to 16 ms from a single subframe. If the eNB needs to wait for the entire scheduled uplink duration before transmitting ULL traffic, there may be significant latency in the ULL traffic. This aspect includes several techniques to mitigate this problem. For example, in one aspect, the eNB 102 may ignore the uplink grant and start competing for access to the downlink channel. If the eNB 102 wins the competition, the eNB 102 may start transmitting. All other UEs (e.g., UE 104), other than the scheduled UE, always listen to the channel, and thus the UE can receive the eNB transmission. In another aspect, the eNB 102 may indicate on a licensed carrier enabling ULL that an uplink grant is cancelled. The eNB 102 may indicate the start subframe and the end subframe for which the grant is cancelled.

[0129] Fast Channel Access Scheme

[0130] Referring Figure 8 , an example of a method 800 for wireless communication includes reducing the transmission latency in unlicensed spectrum. For example, the method 800 relates to the implementation of defining a dedicated ULL data bearer for mapping ULL traffic onto unlicensed spectrum as discussed above, and may be performed by the fast channel access component 510 and / or the fast channel access component 528. In one aspect, the method 800 may be performed by the fast channel access component 510, for example, in conjunction with the processor 180, the memory 505, and / or the UE transceiver 506. In one aspect, the method 800 may be performed by the fast channel access component 528, for example, in conjunction with the processor 190, the memory 555, and / or the eNB transceiver 556.

[0131] At block 802, method 800 includes establishing a dedicated data bearer having LBT access rules for accessing at least a portion of the unlicensed spectrum served by a wireless communication system, where the LBT access rules permit channel access with an access priority faster than control and signaling traffic (e.g., in less than 1 millisecond). In one aspect, the established dedicated data bearer can be, for example, a dedicated ULL data bearer. Additionally, the established dedicated data bearer can have LBT access rules that permit channel access, for example, in less than or equal to 2 ms per time slot.

[0132] At block 804, method 800 includes receiving data for transmission. For example, the received data for transmission can be associated with a transmission time interval (TTI) shorter than that for control and signaling traffic, e.g., less than 1 ms. In one aspect, for example, the received data can be ULL data.

[0133] At block 806, method 800 includes mapping the data for transmission to the dedicated data bearer. In one aspect, in the case where method 800 includes establishing a dedicated ULL data bearer, mapping the data for transmission to the dedicated data bearer can include mapping the dedicated ULL data bearer to an LBT priority level 1 data bearer.

[0134] At block 808, method 800 includes performing channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission.

[0135] At block 810, method 800 includes transmitting the data over the channel on the dedicated data bearer. For example, transmitting ULL data over the selected channel on the dedicated ULL data bearer.

[0136] Fast Channel Access Scheme

[0137] Referring Figure 9 , example aspects of a method 900 for wireless communication include reducing transmission latency in the unlicensed spectrum. For example, method 900 relates to the manner of waiting to access a channel in the unlicensed spectrum after transmitting ULL data over a channel in the unlicensed spectrum as discussed above, and can be performed by the fast channel access component 510 and / or the fast channel access component 528. In one aspect, method 900 can be performed by the fast channel access component 510, for example, in conjunction with the processor 180, the memory 505, and / or the UE transceiver 506. In one aspect, method 900 can be performed by the fast channel access component 528, for example, in conjunction with the processor 190, the memory 555, and / or the eNB transceiver 556.

[0138] At block 902, method 900 includes establishing a dedicated data bearer having LBT access rules for accessing at least a portion of the unlicensed spectrum served by a wireless communication system, where the listen-before-talk access rules may permit channel access in less than 2 ms based on a single deferral period, and where the LBT access rules further define an additional deferral period to be used after a transmission associated with channel access in less than 2 ms. In one aspect, the additional deferral period may have a time value greater than the single deferral period. Additionally, the additional deferral period may include a contention window size larger than the LBT contention window size for LBT priority level 1 data bearers.

[0139] At block 904, method 900 includes performing channel selection in a portion of the unlicensed spectrum using the LBT access rules to identify a channel for transmission.

[0140] At block 906, method 900 includes transmitting the dedicated data bearer on a channel in a portion of the unlicensed spectrum using the LBT access rules, where transmitting corresponds to channel access in less than 2 ms.

[0141] At block 908, method 900 includes: waiting for the additional deferral period after transmitting the dedicated data bearer using channel access in less than 2 ms before performing subsequent channel selection to access a corresponding channel in a portion of the unlicensed spectrum to be used in a subsequent transmission.

[0142] CW Update

[0143] Referring Figure 10 , example aspects of method 1000 for wireless communication include reducing transmission latency in the unlicensed spectrum. For example, method 1000 relates to the implementation of updating the contention window size discussed above and may be performed by contention window update component 512 and / or contention window update component 530. In one aspect, method 1000 may be performed by contention window update component 512 in conjunction with, for example, processor 180, memory 505, and / or UE transceiver 506. In one aspect, method 1000 may be performed by contention window update component 530 in conjunction with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0144] At block 1002, method 1000 includes transmitting a downlink subframe including ULL data and regular (e.g., LTE) data, where the ULL data corresponds to a first TTI (e.g., less than 1 ms) shorter than the transmission time interval for control and signaling traffic, and where the regular data corresponds to a second transmission time interval (e.g., at least 1 ms) for control and signaling traffic.

[0145] At block 1004, method 1000 includes receiving, in a downlink subframe, one or more acknowledgment-related messages corresponding to at least a portion of the ULL data or at least a portion of the regular data. In one aspect, the one or more received acknowledgment-related messages (e.g., HARQ-ACK feedback) may be transmitted within an initial time period of the total time period used for transmitting the downlink subframe.

[0146] At block 1006, method 1000 includes updating a size of a contention window based on the one or more acknowledgment-related messages, the contention window being for channel access in a portion of the unlicensed spectrum served by a wireless communication system having LBT access rules. In one aspect, the size of the contention window may be updated by applying a first weight factor to each received acknowledgment-related message for the ULL data and by applying a second weight factor to each received acknowledgment-related message for the regular data. Additionally, in one aspect, the first weight factor may have a value different from that of the second weight factor.

[0147] CPDCCH - based Signaling for New Frame Structure

[0148] Referring Figure 11 , example aspects of method 1100 for wireless communication include reducing transmission latency in the unlicensed spectrum. For example, method 1100 involves enhancing CPDCCH-based signaling as discussed above to accommodate the implementation of the ULL frame structure, and may be performed by contention window update component 512 and / or contention window update component 530. In one aspect, method 1100 may be performed by contention window update component 512 in conjunction with, for example, processor 180, memory 505, and / or UE transceiver 506. In one aspect, method 1100 may be performed by contention window update component 530 in conjunction with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0149] At block 1102, method 1100 includes transmitting a first downlink subframe having a first set of resource elements assigned to a physical downlink control channel, wherein the first set of resource elements includes a configuration indication that identifies a structure for a second downlink subframe to be transmitted after the first downlink subframe.

[0150] At block 1104, method 1100 includes transmitting a second downlink subframe having a second set of resource elements assigned to a physical downlink control channel, where the second set of resource elements includes a ULL indicator that identifies which symbols carry ULL data having a first TTI (e.g., less than 1 ms) that is shorter than the transmission time interval for control and signaling traffic, and where the second set of resource elements includes a new configuration indicator that identifies the second downlink subframe as having a different structure than the structure identified by the configuration indicator provided in the first downlink subframe. In one aspect, the new configuration indicator identifies a new subframe type selected from a plurality of subframe types including any two or more of the following: a downlink subframe, an uplink subframe, a first flexible subframe, and a second flexible subframe having a flexible structure different from that of the first flexible subframe. Additionally, in one aspect, the second downlink subframe may be transmitted according to a structure restriction rule that restricts the format of the different structure of the second downlink subframe based on the structure identified by the configuration indicator provided in the first downlink subframe.

[0151] Interference Handling

[0152] Reference Figure 12 , example aspects of method 1200 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1200 relates to the implementation for providing robust operation against bursty interference for ULL transmissions discussed above, and may be performed by interference handling component 516 and / or interference handling component 534. In one aspect, method 1200 may be performed by interference handling component 516 in combination with, for example, processor 180, memory 505, and / or UE transceiver 506. In one aspect, method 1200 may be performed by interference handling component 534 in combination with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0153] At block 1202, method 1200 includes identifying a set of data resource elements for transmission in a downlink subframe.

[0154] At block 1204, method 1200 includes identifying a set of reference signal resource elements for transmission in a downlink subframe.

[0155] At block 1206, method 1200 includes mapping both a first portion of the set of data resource elements and a first portion of the set of reference signal resource elements to one symbol of the downlink subframe.

[0156] At block 1208, method 1200 includes mapping a second portion of a data resource element set and a second portion of a reference signal resource element set to subsequent symbols of a downlink subframe, where the subsequent symbols are different from the one symbol of the downlink subframe. In one aspect, mapping the first portion of the reference signal resource element set and mapping the second portion of the reference signal resource element set may further include: allocating a greater number of reference signal resource element sets to the one symbol as compared to the number of reference signal resource element sets allocated to subsequent symbols.

[0157] At block 1210, method 1200 includes transmitting the downlink subframe.

[0158] DRX Management for ULL

[0159] Referring Figure 13 , example aspects of method 1300 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1300 pertains to the implementation of managing discontinuous reception (DRX) for ULL services discussed above, and may be performed by DRX management component 518 and / or DRX management component 536. In one aspect, method 1300 may be performed by DRX management component 518 in conjunction with, for example, processor 180, memory 505, and / or UE transceiver 506. In one aspect, method 1300 may be performed by DRX management component 536 in conjunction with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0160] At block 1302, method 1300 includes: receiving a first time slot of a downlink subframe, the downlink subframe including ULL data having a first transmission time interval (e.g., less than 1 ms) that is shorter than the TTI for control and signaling traffic.

[0161] At block 1304, method 1300 includes: at the end of the first time slot, initiating a discontinuous reception (DRX) on period having a period of less than or equal to one time slot. In one aspect, a DRX on period may be initiated with a period of 1 symbol, 2 symbols, or 1 time slot.

[0162] Joint Scheduling with Different TTI Durations

[0163] Referring Figure 14 , example aspects of method 1400 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1400 pertains to the implementation of joint scheduling TTI for ULL services discussed above, and may be performed by multi-TTI scheduling TX component 538 in conjunction with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0164] At block 1402, method 1400 includes scheduling a plurality of uplink transmissions, each uplink transmission having one of a plurality of transmission time interval (TTI) lengths, where the plurality of TTI lengths includes at least two different TTI lengths.

[0165] At block 1404, method 1400 includes generating a downlink subframe having a set of resource elements assigned to a physical downlink control channel, where the set of resource elements includes downlink control information that identifies one or more uplink grants and a respective one of the plurality of TTI lengths for each of the plurality of uplink transmissions.

[0166] At block 1406, method 1400 includes transmitting the downlink subframe. For example, in one aspect, the multi-TTI scheduling TX component 538 may transmit the downlink subframe to the multi-TTI scheduling RX component 520.

[0167] SRS Transmission Opportunity

[0168] Referring Figure 15 , example aspects of method 1500 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1500 relates to the implementation of updating the SRS transmission timing discussed above and may be performed by the SRS controller component 522, e.g., in conjunction with the processor 180, the memory 505, and / or the UE transceiver 506.

[0169] At block 1502, method 1500 includes receiving a downlink subframe having a set of resource elements assigned to a physical downlink control channel, where the set of resource elements includes downlink control information that identifies a scheduling grant and a transmission time interval (TTI) length associated with the scheduling grant, and where the TTI length includes 1 symbol, 2 symbols, or 1 time slot. In one aspect, the SRS controller component 522 may receive the downlink subframe from, e.g., the SRS controller component 540.

[0170] At block 1504, method 1500 includes generating a sounding reference signal (SRS) when triggered by the downlink control information.

[0171] At block 1506, method 1500 includes mapping the SRS to a specific symbol of an uplink subframe based on the TTI length.

[0172] At block 1508, method 1500 includes transmitting the uplink subframe. For example, in one aspect, the uplink subframe may be transmitted to the SRS controller component 540.

[0173] PRACH Transmission

[0174] Refer to Figure 16 Figure 16 , example aspects of method 1600 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1600 relates to the implementation of reducing the latency associated with PRACH transmission discussed above, and can be executed by PRACH transmission component 524 and / or PRACH transmission component 542. In one aspect, method 1600 can be executed by PRACH transmission component 524 in combination with, for example, processor 180, memory 505, and / or UE transceiver 506. In one aspect, method 1600 can be executed by PRACH transmission component 542 in combination with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0175] At block 1602, method 1600 includes: transmitting a first uplink subframe including a random access preamble, where the random access preamble corresponds to a first transmission time interval (TTI) of 2 symbols.

[0176] At block 1604, method 1600 includes: monitoring a physical downlink control channel (PDCCH) for a first downlink subframe including a random access response, where the random access response corresponds to a second TTI of 2 symbols, 1 time slot, or 1 ms. Additionally, in one aspect, monitoring the PDCCH can include monitoring the PDCCH during the duration of a response window, where the duration of the response window can be less than 1 ms.

[0177] At block 1606, method 1600 optionally includes: transmitting a second uplink subframe including an RRC connection request, where the RRC connection request corresponds to a third TTI of 2 symbols, 1 time slot, or 1 ms.

[0178] At block 1608, method 1600 optionally includes: receiving a second downlink subframe including a contention resolution message, where the contention resolution message corresponds to a fourth TTI of 2 symbols, 1 time slot, or 1 ms.

[0179] UL Grant Cancellation

[0180] Refer to Figure 17 Figure 17 , example aspects of method 1700 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1700 relates to the implementation of reducing ULL transmission delay by ignoring scheduled uplink (e.g., LTE) transmissions discussed above, and can be executed by uplink grant TX component 544 in combination with, for example, processor 190, memory 555, and / or eNB transceiver 556.

[0181] At block 1702, method 1700 includes scheduling one or more uplink transmissions for a duration of up to 16 ms. In one aspect, an uplink grant TX component 544 may send a scheduling grant to, for example, an uplink grant RX component 526.

[0182] At block 1704, method 1700 includes: identifying ultra-low latency (ULL) data for transmission over a channel in at least a portion of the unlicensed spectrum served by a wireless communication system.

[0183] At block 1706, method 1700 includes performing one or more LBT procedures during the scheduled duration to compete for access to the channel.

[0184] At block 1708, method 1700 includes determining whether the competition for the channel has been won based on one or more LBT procedures.

[0185] At block 1710, method 1700 includes, upon determining that the competition has been won, transmitting a downlink subframe including the ULL data over the channel. For example, in one aspect, an uplink grant TX component 544 may send a downlink subframe to an uplink grant RX component 526.

[0186] UL Grant Cancellation

[0187] Referring Figure 18 , example aspects of a method 1800 for wireless communication include reducing transmission latency in unlicensed spectrum. For example, method 1800 relates to the implementation of reducing ULL transmission latency by canceling scheduled uplink (e.g., LTE) transmissions as discussed above, and may be performed by an uplink grant TX component 544, for example, in conjunction with a processor 190, a memory 555, and / or an eNB transceiver 556.

[0188] At block 1802, method 1800 includes scheduling one or more uplink transmissions for a duration of up to 16 ms. In one aspect, an uplink grant TX component 544 may send a scheduling grant to, for example, an uplink grant RX component 526.

[0189] At block 1804, method 1800 includes: identifying ULL data for transmission over a channel in at least a portion of the unlicensed spectrum served by a wireless communication system.

[0190] At block 1806, method 1800 includes generating a first downlink subframe having a set of resource elements assigned to a physical downlink control channel, where the set of resource elements includes an indication that at least a portion of the one or more scheduled uplink transmissions has been canceled.

[0191] At block 1808, method 1800 includes: transmitting a first downlink subframe on a channel. For example, in one aspect, the uplink grant TX component 544 may transmit the first downlink subframe to the uplink grant RX component 526.

[0192] At block 1810, method 1800 includes: transmitting a second downlink subframe including ULL data on a channel. For example, in one aspect, the uplink grant TX component 544 may transmit the second downlink subframe to the uplink grant RX component 526.

[0193] It should be understood that the specific order or hierarchy of steps in the disclosed processes is an illustration of exemplary methods. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the processes may be rearranged. Additionally, some steps may be combined or omitted. The appended method claims present the elements of the various steps in a sample order, but are not meant to be limited to the specific order or hierarchy presented.

[0194] The specific embodiments described above in conjunction with the accompanying drawings describe examples and do not represent the only examples that can be implemented or that are within the scope of the claims. When used in this specification, the word "example" means "serving as an example, instance, or illustration" and does not mean "preferred" or "superior to other examples." For the purpose of providing an understanding of the technologies described, the specific embodiments include specific details. However, the technologies may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0195] Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, computer-executable code or instructions stored on a computer-readable medium, or any combination thereof.

[0196] The various illustrative blocks and components described in connection with the present disclosure can be implemented or performed with a specially programmed device designed to perform the functions described herein, the specially programmed device such as, but not limited to, a processor, a digital signal processor (DSP), an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, or any combination thereof. The specially programmed processor can be a microprocessor, or, alternatively, the processor can be any conventional processor, controller, microcontroller, or state machine. The specially programmed processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such architecture.

[0197] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored on or transmitted via a non-transitory computer-readable medium as one or more instructions or code. Other examples and implementations are within the scope and spirit of the present disclosure and the appended claims. For example, due to the nature of software, the functions described above can be implemented using software, hardware, firmware, hardwired, or any combination of these, executed by a specially programmed processor. Features for implementing the functions can also be physically located at different positions, including being distributed such that portions of the functions are implemented at different physical locations. Additionally, as used herein (including in the claims), the "or" in a list of items that ends with "at least one of" indicates a discrete list, such that, for example, "at least one of A, B, or C" means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[0198] Computer-readable media includes computer storage media and communication media, where communication media includes any medium that facilitates the transfer of a computer program from one place to another. Storage media can be any available medium that can be accessed by a general-purpose or special-purpose computer. By way of example and not limitation, computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code units 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. In addition, any connection can be properly termed a computer-readable media. For example, if software is transmitted using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, wireless, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, wireless, and microwave are included in the definition of the medium. As used herein, disk and optical disk include compact disk (CD), laser disk, optical disk, digital versatile disk (DVD), floppy disk, and Blu-ray disk, where disks typically reproduce data magnetically, while optical disks optically reproduce data with lasers. Combinations of the above should also be included within the scope of protection of computer-readable media.

[0199] A previous description of the present disclosure is provided to enable those skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the spirit or scope of the present disclosure. In addition, although elements of the aspects and / or embodiments described herein may be described or claimed in the singular, the plural form is also contemplated unless expressly stated to be limited to the singular. Additionally, unless otherwise stated, all or part of any aspect and / or embodiment can be used in conjunction with all or part of any other aspect and / or embodiment. Therefore, the present disclosure is not intended to be limited to the examples and designs described herein, but rather to embrace the broadest scope consistent with the principles and novel features disclosed herein.

[0200] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the broadest scope consistent with the claim language, wherein the 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." The term "some," unless specifically stated otherwise, means one or more. All structural and functional equivalents of the elements of the various aspects described herein (known or later to be known to those of ordinary skill in the art) are expressly incorporated herein by reference and are intended to be encompassed by the claims. Additionally, all disclosures herein are not dedicated to the public, whether or not such disclosure is explicitly recited in the claims. No element of a claim should be construed as a functional limitation unless the element is expressly recited using the phrase "means for."

Claims

1. A wireless communication method in a wireless communication system including listen - before - talk (LBT) access for transmission, comprising: Scheduling one or more uplink transmissions; Identifying ultra - low - latency (ULL) data for transmission on a channel in at least a portion of the unlicensed spectrum served by the wireless communication system; Generating a first downlink sub - frame having a set of resource elements assigned to a physical downlink control channel, wherein the set of resource elements includes an indication identifying that at least a portion of one or more scheduled uplink transmissions is cancelled; Performing one or more LBT procedures to compete for access to the channel; Determining whether a competition for the channel is won based on the one or more LBT procedures; and When it is determined that the competition is won, transmitting the first downlink sub - frame on the channel and transmitting a second downlink sub - frame including the ULL data on the channel.

2. The method according to claim 1, wherein transmitting the first downlink sub - frame on the channel and transmitting the second downlink sub - frame on the channel are in at least the portion of the unlicensed spectrum served by the wireless communication system.

3. The method according to claim 2, wherein, The one or more uplink transmissions are scheduled for a duration of up to 16 milliseconds (ms).

4. The method according to claim 2, further comprising ignoring scheduled uplink transmissions.

5. The method according to claim 2, further comprising ignoring scheduled uplink long - term evolution (LTE) transmissions.

6. A wireless communication device for transmission using listen - before - talk (LBT) access, comprising: A transceiver for transmitting one or more wireless signals via one or more antennas; A memory configured to store instructions; And One or more processors communicatively coupled to the transceiver and the memory, wherein the one or more processors are configured to: Schedule one or more uplink transmissions; Identify ultra - low - latency (ULL) data for transmission on a channel in at least a portion of the unlicensed spectrum served by a wireless communication system; Generate a first downlink sub - frame having a set of resource elements assigned to a physical downlink control channel, wherein the set of resource elements includes an indication identifying that at least a portion of one or more scheduled uplink transmissions is cancelled; Perform one or more LBT procedures to compete for access to the channel; Determine whether a competition for the channel is won based on the one or more LBT procedures; and When it is determined that the competition is won, transmit the first downlink sub - frame on the channel and transmit a second downlink sub - frame including the ULL data on the channel.

7. The device according to claim 6, wherein transmitting the first downlink sub - frame on the channel and transmitting the second downlink sub - frame on the channel are in at least the portion of the unlicensed spectrum served by the wireless communication system.

8. The apparatus according to claim 7, wherein, The one or more uplink transmissions are scheduled for a duration of up to 16 milliseconds (ms).

9. The device according to claim 7, wherein, The one or more processors are configured to ignore scheduled uplink transmissions.

10. The apparatus according to claim 7, wherein, The one or more processors are configured to ignore a scheduled uplink Long Term Evolution (LTE) transmission.

11. A non-transitory computer-readable medium storing computer code executable by a processor for wireless communication using Listen Before Talk (LBT) access, the computer code including code for: Scheduling one or more uplink transmissions; Identifying Ultra-Low Latency (ULL) data for transmission on a channel in at least a portion of unlicensed spectrum served by a wireless communication system; Generating a first downlink subframe having a set of resource elements assigned to a physical downlink control channel, wherein the set of resource elements includes an indication identifying that at least a portion of one or more scheduled uplink transmissions is cancelled; Performing one or more LBT procedures to contend for access to the channel; Determining, based on the one or more LBT procedures, whether contention for the channel is won; and When determining that contention is won, transmitting the first downlink subframe on the channel and transmitting a second downlink subframe including the ULL data on the channel.

12. The non-transitory computer-readable medium according to claim 11, wherein, Transmitting the first downlink subframe on the channel and transmitting the second downlink subframe on the channel is in at least the portion of the unlicensed spectrum served by the wireless communication system.

13. The non-transitory computer-readable medium according to claim 12, wherein, The one or more uplink transmissions are scheduled for a duration of up to 16 milliseconds (ms).

14. The non-transitory computer-readable medium according to claim 12, further including code for ignoring a scheduled uplink transmission.

15. The non-transitory computer-readable medium according to claim 12, further including code for ignoring a scheduled uplink Long Term Evolution (LTE) transmission.

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