Patent Description:
An example of a telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), 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 exists a need for further improvements in LTE technology.

For example, improvements are being proposed to further lower latency in LTE networks. As latency requirements are decreased, underlying frame structures presently supported in LTE may be incapable of effectively achieving the desired latency.

<CIT> discloses an apparatus including a User Equipment (UE) having a receiver and a decoder. The receiver is configured to receive, from an eNodeB (eNB), a signal indicating a configuration of a period to receive one or more Physical Downlink Control Channels (PDCCHs) in respective one or more Transmission Time Intervals (TTIs). Each of the one or more PDCCHs conveys a same Downlink Control Information (DCI) format. The DCI format includes at least one field indicating a first Time Division Duplexing (TDD) Uplink-Downlink (UL-DL) configuration in a first cell for DL data receptions or UL data transmissions. A TDD UL-DL configuration includes ten TTIs each having a respective serial index from <NUM> to <NUM>. The receiver is also configured to receive, from the eNB, at least one PDCCH of the one or more PDCCHs. The decoder is configured to decode the DCI format conveyed by the at least one PDCCH in a second cell. The period is a multiple of ten TTIs, and the one or more TTIs are in a last ten TTIs of the period.

<CIT> dis directed to methods and apparatus of a base station or a User Equipment (UE) in communication with each other. The UE is configured by the base station for operation with an adapted Time Division Duplex (TDD) Uplink-Downlink (UL-DL) configuration. A process enabling transmission of acknowledgement information from the UE for communication in two different sets of DL Transmission Time Intervals (TTIs) is provided.

Preferred embodiments are subject of the dependent claims.

These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements").

Accordingly, in one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. By way of example, and not limitation, such computer-readable media can comprise 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 in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), and floppy disk where disks usually reproduce data magnetically, while discs reproduce data optically with lasers.

Described herein are various aspects related to communicating in a wireless network according to a frame structure that allows dynamic switching between uplink (UL) and downlink (DL) communications. For example, the frame structure can include a plurality of transmission time intervals (TTI) (e.g., time division duplexing (TDD) symbols), which can be configured or used for uplink or downlink communications. The frame structure may also include at least some TTIs that are dedicated downlink or uplink TTIs. For example, the dedicated downlink and uplink TTIs can be provided to enable radio resource management (RRM) measurements, synchronization between communicating nodes, channel state information (CSI) feedback, random access channel (RACH) communications, scheduling requests (SR), etc. In the remaining configurable TTIs, one or more communicating nodes can switch between uplink and downlink communications, and can notify other nodes of the switch. This allows the node to set the downlink/uplink configuration (e.g., of a given carrier) to facilitate improved communication throughput based on parameters of the one or more communicating nodes.

Referring first to <FIG>, a diagram illustrates an example of a wireless communications system <NUM>, in accordance with aspects described herein. The wireless communications system <NUM> includes a plurality of access points (e.g., base stations, eNBs, or WLAN access points) <NUM>, a number of user equipment (UEs) <NUM>, and a core network <NUM>. Access points <NUM> may include a scheduling component <NUM> configured to communicate resource grants (e.g., for control and/or data uplink communications) to UEs <NUM> based on a frame structure, for example but not limited to frame structure <NUM> (<FIG>), configured for lower latency communications. Similarly, one or more of UEs <NUM> may include a communicating component <NUM> configured to receive, decode, transmit, and operate using the frame structure (e.g., based on resource grants or other indicators received from an access point <NUM>, as described herein).

Some of the access points <NUM> may communicate with the UEs <NUM> under the control of a base station controller (not shown), which may be part of the core network <NUM> or the certain access points <NUM> (e.g., base stations or eNBs) in various examples. Access points <NUM> may communicate control information and/or user data with the core network <NUM> through backhaul links <NUM>. In examples, the access points <NUM> may communicate, either directly or indirectly, with each other over backhaul links <NUM>, which may be wired or wireless communication links. The wireless communications system <NUM> may support operation on multiple carriers (waveform signals of different frequencies). Multi-carrier transmitters can transmit modulated signals simultaneously on the multiple carriers. For example, each communication link <NUM> may be a multi-carrier signal modulated according to the various radio technologies described above. Each modulated signal may be sent on a different carrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, data, etc..

In this regard, a UE <NUM> can be configured to communicate with one or more access points <NUM> over multiple carriers using carrier aggregation (CA) (e.g., with one access point <NUM>) and/or multiple connectivity (e.g., with multiple access points <NUM>). In either case, UE <NUM> can be configured with at least one primary cell (PCell) configured to support uplink and downlink communications between UE <NUM> and an access point <NUM>. It is to be appreciated that there can be a PCell for each communication link <NUM> between a UE <NUM> and a given access point <NUM>. In addition, each of the communication links <NUM> can have one or more secondary cells (SCell) that can support uplink and/or downlink communications as well. In some examples, the PCell can be used to communicate at least a control channel, and the SCell can be used to communicate a data channel. In one example, the PCell and/or SCell can configure one or more enhanced component carriers (eCC) that provide lower latency communications (e.g., using frame structure <NUM> in <FIG> or a similar frame structure with lower latency TTIs), as described further herein.

In some examples, at least a portion of the wireless communications system <NUM> may be configured to operate on multiple hierarchical layers in which one or more of the UEs <NUM> and one or more of the access points <NUM> may be configured to support transmissions on a hierarchical layer that has a reduced latency with respect to another hierarchical layer. In some examples a hybrid UE <NUM>-a may communicate with access point <NUM>-a on both a first hierarchical layer that supports first layer transmissions with a first subframe type and a second hierarchical layer that supports second layer transmissions with a second subframe type. For example, access point <NUM>-a may transmit subframes of the second subframe type that are time division duplexed with subframes of the first subframe type.

In some examples, hybrid UE <NUM>-a may acknowledge receipt of a transmission by providing acknowledgement (ACK)/non-acknowledgement (NACK) for the transmission through, for example, a HARQ scheme. Acknowledgments from hybrid UE <NUM>-a for transmissions in the first hierarchical layer may be provided, in some examples, after a predefined number of subframes following the subframe in which the transmission was received. The hybrid UE <NUM>-a, when operating in the second hierarchical layer may, in examples, acknowledge receipt in a same subframe as the subframe in which the transmission was received. The time required to transmit an ACK/NACK and receive a retransmission may be referred to as round trip time (RTT), and thus subframes of the second subframe type may have a second RTT that is shorter than a RTT for subframes of the first subframe type.

In other examples, a second layer UE <NUM>-b may communicate with access point <NUM>-b on the second hierarchical layer only. Thus, hybrid UE <NUM>-a and second layer UE <NUM>-b may belong to a second class of UEs <NUM> that may communicate on the second hierarchical layer, while legacy UEs <NUM> may belong to a first class of UEs <NUM> that may communicate on the first hierarchical layer only. Access point <NUM>-b and UE <NUM>-b may communicate on the second hierarchical layer through transmissions of subframes of the second subframe type. Access point <NUM>-b may transmit subframes of the second subframe type exclusively, or may transmit one or more subframes of the first subframe type on the first hierarchical layer that are time division multiplexed with subframes of the second subframe type. Second layer UE <NUM>-b, in the event that access point <NUM>-b transmits subframes of the first subframe type, may ignore such subframes of the first subframe type. Thus, second layer UE <NUM>-b may acknowledge receipt of transmissions in a same subframe as the subframe in which the transmissions are received. Thus, second layer UE <NUM>-b may operate with reduced latency compared to UEs <NUM> that operate on the first hierarchical layer.

The access points <NUM> may wirelessly communicate with the UEs <NUM> via one or more access point antennas. Each of the access points <NUM> sites may provide communication coverage for a respective coverage area <NUM>. In some examples, access points <NUM> may be referred to as a base transceiver station, a radio base station, a radio transceiver, a basic service set (BSS), an extended service set (ESS), a NodeB, eNodeB, Home NodeB, a Home eNodeB, or some other suitable terminology. The coverage area <NUM> for a base station may be divided into sectors making up only a portion of the coverage area (not shown). The wireless communications system <NUM> may include access points <NUM> of different types (e.g., macro, micro, and/or pico base stations). The access points <NUM> may also utilize different radio technologies, such as cellular and/or WLAN radio access technologies (RAT). The access points <NUM> may be associated with the same or different access networks or operator deployments. The coverage areas of different access points <NUM>, including the coverage areas of the same or different types of access points <NUM>, utilizing the same or different radio technologies, and/or belonging to the same or different access networks, may overlap.

In LTE/LTE-A network communication systems, the terms evolved Node B (eNodeB or eNB) may be generally used to describe the access points <NUM>. The wireless communications system <NUM> may be a Heterogeneous LTE/LTE-A network in which different types of access points provide coverage for various geographical regions. For example, each access point <NUM> may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. Small cells such as pico cells, femto cells, and/or other types of cells may include low power nodes or LPNs. A small cell would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs <NUM> with service subscriptions with the network provider, for example, and in addition to unrestricted access, may also provide restricted access by LTEs <NUM> having an association with the small cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like). An eNB for a small cell may be referred to as a small cell eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells.

The core network <NUM> may communicate with the eNBs or other access points <NUM> via one or more backhaul links <NUM> (e.g., S1 interface, etc.). The access points <NUM> may also communicate with one another, e.g., directly or indirectly via backhaul links <NUM> (e.g., X2 interface, etc.) and/or via backhaul links <NUM> (e.g., through core network <NUM>). The wireless communications system <NUM> may support synchronous or asynchronous operation. For synchronous operation, the access points <NUM> may have similar frame timing, and transmissions from different access points <NUM> may be approximately aligned in time. For asynchronous operation, the access points <NUM> may have different frame timing, and transmissions from different access points <NUM> may not be aligned in time. Furthermore, transmissions in the first hierarchical layer and second hierarchical layer may or may not be synchronized among access points <NUM>.

The UEs <NUM> are dispersed throughout the wireless communications system <NUM>, and each UE <NUM> may be stationary or mobile. A UE <NUM> may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE <NUM> may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a wearable item such as a watch or glasses, a wireless local loop (WLL) station, or the like. A UE <NUM> may be able to communicate with macro eNodeBs, small cell eNodeBs, relays, and the like. A UE <NUM> may also be able to communicate over different access networks, such as cellular or other WWAN access networks, or WLAN access networks.

The communication links <NUM> shown in wireless communications system <NUM> may include uplink (UL) transmissions from a UE <NUM> to an access point <NUM>, and/or downlink (DL) transmissions, from an access point <NUM> to a UE <NUM>. The downlink transmissions may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. The communication links <NUM> may carry transmissions of each hierarchical layer which, in some examples, may be multiplexed in the communication links <NUM>. The UEs <NUM> may be configured to collaboratively communicate with multiple access points <NUM> through, for example, Multiple Input Multiple Output (MIMO), carrier aggregation (CA), Coordinated Multi-Point (CoMP), multiple connectivity (e.g., CA with each of one or more access points <NUM>) or other schemes. MIMO techniques use multiple antennas on the access points <NUM> and/or multiple antennas on the UEs <NUM> to transmit multiple data streams. Carrier aggregation may utilize two or more component carriers on a same or different serving cell for data transmission. CoMP may include techniques for coordination of transmission and reception by a number of access points <NUM> to improve overall transmission quality for UEs <NUM> as well as increasing network and spectrum utilization.

As mentioned, in some examples, access points <NUM> and UEs <NUM> may utilize carrier aggregation to transmit on multiple carriers. In some examples, access points <NUM> and UEs <NUM> may concurrently transmit in a first hierarchical layer, within a frame, one or more subframes each having a first subframe type using two or more separate carriers. Each carrier may have a bandwidth of, for example, <NUM>, although other bandwidths may be utilized. Hybrid UE <NUM>-a, and/or second layer UE <NUM>-b may, in certain examples, receive and/or transmit one or more subframes in a second hierarchical layer utilizing a single carrier that has a bandwidth greater than a bandwidth of one or more of the separate carriers. For example, if four separate <NUM> carriers are used in a carrier aggregation scheme in the first hierarchical layer, a single <NUM> carrier may be used in the second hierarchical layer. The <NUM> carrier may occupy a portion of the radio frequency spectrum that at least partially overlaps the radio frequency spectrum used by one or more of the four <NUM> carriers. In some examples, scalable bandwidth for the second hierarchical layer type may be combined techniques to provide shorter RTTs such as described above, to provide further enhanced data rates.

Each of the different operating modes that may be employed by wireless communications system <NUM> may operate according to frequency division duplexing (FDD) or time division duplexing (TDD). In some examples, different hierarchical layers may operate according to different TDD or FDD modes. For example, a first hierarchical layer may operate according to FDD while a second hierarchical layer may operate according to TDD. In some examples, OFDMA communications signals may be used in the communication links <NUM> for LTE downlink transmissions for each hierarchical layer, while single carrier frequency division multiple access (SC-FDMA) communications signals may be used in the communication links <NUM> for LTE uplink transmissions in each hierarchical layer. Additional details regarding implementation of hierarchical layers in a system such as the wireless communications system <NUM>, as well as other features and functions related to communications in such systems, are provided below with reference to the following figures.

<FIG> is a diagram illustrating an example of an access network <NUM> in an LTE network architecture. In this example, the access network <NUM> is divided into a number of cellular regions (cells) <NUM>. One or more lower power class eNBs <NUM> may have cellular regions <NUM> that overlap with one or more of the cells <NUM>. The lower power class eNB <NUM> may be a femto cell (e.g., home eNB (HeNB)), pico cell, micro cell, or remote radio head (RRH). The macro eNBs <NUM> are each assigned to a respective cell <NUM> and are configured to provide an access point to the core network <NUM> for all the UEs <NUM> in the cells <NUM>. In an aspect, eNBs <NUM> may include a scheduling component <NUM> configured to communicate resource grants to UEs <NUM> based on a frame structure, for example but not limited to frame structure <NUM> (<FIG>), configured for lower latency communications. Similarly, one or more of UEs <NUM> may include a communicating component <NUM> configured to receive, decode, transmit, and operate using the frame structure (e.g., based on resource grants or other indicators received from an access point <NUM>, as described herein). There is no centralized controller shown in this example of an access network <NUM>, but a centralized controller may be used in alternative configurations. The eNBs <NUM> are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to a serving gateway.

The modulation and multiple access scheme employed by the access network <NUM> may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM may be used on the DL and SC-FDMA may be used on the UL to support both frequency division duplexing (FDD) and time division duplexing (TDD). As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project <NUM> (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.

The eNBs <NUM> may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNBs <NUM> to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data steams may be transmitted to a single UE <NUM> to increase the data rate or to multiple UEs <NUM> to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL. The spatially precoded data streams arrive at the UE(s) <NUM> with different spatial signatures, which enables each of the UE(s) <NUM> to recover the one or more data streams destined for that UE <NUM>. On the UL, each UE <NUM> transmits a spatially precoded data stream, which enables the eNB <NUM> to identify the source of each spatially precoded data stream.

Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.

In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides "orthogonality" that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR).

<FIG> is a block diagram of an eNB <NUM> in communication with a UE <NUM> in an access network. In the DL, upper layer packets from the core network are provided to a controller/processor <NUM>. The controller/processor <NUM> implements the functionality of a layer <NUM> (L2) (e.g., a media access control (MAC) layer). In the DL, the controller/processor <NUM> provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE <NUM> based on various priority metrics. The controller/processor <NUM> is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE <NUM>.

The transmit (TX) processor <NUM> implements various signal processing functions for the L1 layer (i.e., physical layer). The signal processing functions includes coding and interleaving to facilitate forward error correction (FEC) at the UE <NUM> and mapping to signal constellations 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 coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. Each spatial stream is then provided to a different antenna <NUM> via a separate transmitter 318TX. Each transmitter 318TX modulates an RF carrier with a respective spatial stream for transmission. In addition, eNB <NUM> may include a scheduling component <NUM> configured to communicate resource grants to UE <NUM> using a frame structure for lower latency communications over at least one CC, for example but not limited to frame structure <NUM> (<FIG>).

The RX processor <NUM> implements various signal processing functions of the L1 layer. The RX processor <NUM> performs spatial processing on the information to recover any spatial streams destined for the UE <NUM>. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB <NUM>. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB <NUM> on the physical channel. The data and control signals are then provided to the controller/processor <NUM>.

The controller/processor <NUM> implements the L2 layer. The controller/processor can be associated with a memory <NUM> that stores program codes and data. In the UL, the controller/processor <NUM> provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink <NUM>, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink <NUM> for layer <NUM> (L3) (e.g., radio link control (RLC) layer) processing. The controller/processor <NUM> is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations. In addition, UE <NUM> may include a communicating component <NUM> configured to receive, decode, transmit, and operate using the frame structure for lower latency (e.g., based on resources granted according to the frame structure by scheduling component <NUM> or other indictors received from eNB <NUM>), as described herein.

In the UL, a data source <NUM> is used to provide upper layer packets to the controller/processor <NUM>. The data source <NUM> represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission by the eNB <NUM>, the controller/processor <NUM> implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB <NUM>. The controller/processor <NUM> is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB <NUM>.

Channel estimates derived by a channel estimator <NUM> from a reference signal or feedback transmitted by the eNB <NUM> may be used by the TX processor <NUM> to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor <NUM> are provided to different antenna <NUM> via separate transmitters 354TX. Each transmitter 354TX modulates an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB <NUM> in a manner similar to that described in connection with the receiver function at the UE <NUM>. The RX processor <NUM> may implement the L1 layer.

The controller/processor <NUM> implements the L2 layer. In the UL, the controller/processor <NUM> provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE <NUM>. Upper layer packets from the controller/processor <NUM> may be provided to the core network.

<FIG> is a diagram illustrating a non-limiting example of a frame structure <NUM>. Frame structure <NUM> depicts a TDD frame structure having multiple frames of time (Tm) equal to x milliseconds (ms), where x is a positive integer. Each frame can include one or more TTIs configured to be a dedicated downlink TTI <NUM>, a configurable downlink or uplink TTI <NUM>, or a dedicated uplink TTI <NUM>. In an example, a TTI can correspond to a TDD symbol (e.g., an OFDM symbol, a SC-FDM symbol, etc.). For example, designating dedicated downlink TTIs <NUM> and dedicated uplink TTIs <NUM> can enable radio resource management (RRM) measurements, synchronization between UEs and eNBs, channel state information (CSI) feedback transmissions, random access channel (RACH) communications, SRs, etc. over the dedicated TTIs. In an example, the dedicated downlink TTIs <NUM> and dedicated uplink TTIs <NUM> can be radio resource control (RRC) configured between network nodes (e.g., between a UE and eNB) or otherwise known by the network nodes.

Moreover, for example, the remaining TTIs <NUM>, which are configurable for uplink or downlink communications, can be dynamically switched between uplink and downlink communications. These TTIs <NUM> are also referred to herein as "configurable TTIs," and may include substantially any TTI that is not dedicated as a downlink or uplink TTI. A serving network node, such as an eNB, can determine one or more parameters related to switching the TTIs <NUM> between uplink and downlink communications (e.g., a time period, such as a TTI, for which to perform switching, a duration for the switching, etc.) and can indicate the one or more parameters to other network nodes, such as a UE, for communicating with the serving network node, as described further herein. In this regard, a network node receiving a resource grant or other indicator of the one or more parameters from the serving network node can determine whether a given TTI is configured for receiving communications from the serving network node (downlink communications) or transmitting communications to the serving network node (uplink communications). In one example, indicating switching in this regard allows for multiple contiguous (configurable) TTIs to be configured for the same type of communications (downlink or uplink) and may thus allow for burst communications.

Thus, in one example, TTIs <NUM>, <NUM>, <NUM>, and <NUM> may be configured for downlink communications, and a switch can be indicated to uplink communications for TTIs <NUM> and <NUM>, as described herein. Similarly, a switch may be indicated back to downlink communications for a configurable TTI following TTI <NUM>. Utilizing configurable TTIs in this regard can allow for dynamic determination of a split between uplink and downlink resources in a given frame, which can be based on communication related parameters at the serving network node such to allow more uplink or downlink resources for improving uplink or downlink communications during the frame.

In one specific example, each TTI in the frame structure <NUM> can be defined by an OFDM or SC-FDM symbol and may be of a length shorter than that the <NUM> millisecond subframe TTIs of LTE, such to provide lower latency communications. Thus, in an example, a frame may correspond to a subframe that includes a plurality of TTIs, a frame that includes a plurality of subframes that each include a plurality of TTIs, etc. The dynamic switching between uplink and downlink TTIs may provide for an adaptable frame to handle a desired distribution of uplink and downlink communications, which can allow for achieving certain uplink/downlink latencies.

Referring to <FIG>, aspects are depicted with reference to one or more components and one or more methods that may perform the actions or functions described herein. In an aspect, the term "component" as used herein may be one of the parts that make up a system, may be hardware or software or some combination thereof, and may be divided into other components. Although the operations described below in <FIG> are presented in a particular order and/or as being performed by an example component, it should be understood that the ordering of the actions and the components performing the actions may be varied, depending on the implementation. Moreover, it should be understood that the following actions or functions may be performed by a specially-programmed processor, a processor executing specially-programmed software or computer-readable media, or by any other combination of a hardware component and/or a software component capable of performing the described actions or functions.

<FIG> illustrates an example system <NUM> for communicating between nodes in a wireless network based on a frame structure that facilitate dynamic switching of downlink/uplink TTIs. System <NUM> includes a UE <NUM> that communicates with an eNB <NUM> to access a wireless network, examples of which are described in <FIG>, above. In an aspect, eNB <NUM> and UE <NUM> may have established one or more downlink channels over which to communicate via downlink signals <NUM>, which can be transmitted by eNB <NUM> (e.g., via transceiver <NUM>) and received by UE <NUM> (e.g., via transceiver <NUM>) for communicating control and/or data messages (e.g., in signaling) from the eNB <NUM> to the UE <NUM> over configured communication resources. Moreover, for example, eNB <NUM> and UE <NUM> may have established one or more uplink channels over which to communicate via uplink signals <NUM>, which can be transmitted by UE <NUM> (e.g., via transceiver <NUM>) and received by eNB <NUM> (e.g., via transceiver <NUM>) for communicating control and/or data messages (e.g., in signaling) from the UE <NUM> to the eNB <NUM> over configured communication resources. As described further herein, for example, eNB <NUM> may communicate a resource grant or other indicator <NUM> that can indicate one or more parameters regarding switching from downlink to uplink communications (or vice versa) in a TTI.

In an aspect, UE <NUM> may include one or more processors <NUM> and/or a memory <NUM> that may be communicatively coupled, e.g., via one or more buses <NUM>, and may operate in conjunction with or otherwise implement a communicating component <NUM> for communicating with eNB <NUM> such to transmit uplink signals <NUM> thereto and/or receive downlink signals <NUM> therefrom according to a frame structure having TTIs configurable for uplink or downlink communications. For example, the various operations related to communicating component <NUM> may be implemented or otherwise executed by one or more processors <NUM> and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the operations may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors <NUM> may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or an application specific integrated circuit (ASIC), or a transmit processor, receive processor, or a transceiver processor associated with transceiver <NUM>. Further, for example, the memory <NUM> may be a non-transitory computer-readable medium that includes, but is not limited to, random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), a register, a removable disk, and any other suitable medium for storing software and/or computer-readable code or instructions that may be accessed and read by a computer or one or more processors <NUM>. Moreover, memory <NUM> or computer-readable storage medium may be resident in the one or more processors <NUM>, external to the one or more processors <NUM>, distributed across multiple entities including the one or more processors <NUM>, etc..

In particular, the one or more processors <NUM> and/or memory <NUM> may execute actions or operations defined by communicating component <NUM> or its subcomponents. For instance, the one or more processors <NUM> and/or memory <NUM> may execute actions or operations defined by a resource grant receiving component <NUM> for obtaining resource grants from eNB <NUM>, which may include or otherwise implicitly indicate one or more TTIs configured for uplink communications or downlink communications. In an aspect, for example, resource grant receiving component <NUM> may include hardware (e.g., one or more processor modules of the one or more processors <NUM>) and/or computer-readable code or instructions stored in memory <NUM> and executable by at least one of the one or more processors <NUM> to perform the specially configured resource grant receiving and/or processing operations described herein. Further, for instance, the one or more processors <NUM> and/or memory <NUM> may execute actions or operations defined by a downlink/uplink switch detecting component <NUM> for determining one or more configurable TTIs where communications with eNB <NUM> switch from downlink to uplink and/or vice versa. In an aspect, for example, downlink/uplink switch detecting component <NUM> may include hardware (e.g., one or more processor modules of the one or more processors <NUM>) and/or computer-readable code or instructions stored in memory <NUM> and executable by at least one of the one or more processors <NUM> to perform the specially configured downlink/uplink switch detecting operations described herein. Further, for instance, the one or more processors <NUM> and/or memory <NUM> may optionally execute actions or operations defined by a reference signal monitoring component <NUM> for monitoring communication resources for one or more reference signals, which may be used to determine whether communications in a configurable TTI were switched to downlink communications from uplink communications in a previous TTI and/or vice versa. In an aspect, for example, reference signal monitoring component <NUM> may include hardware (e.g., one or more processor modules of the one or more processors <NUM>) and/or computer-readable code or instructions stored in memory <NUM> and executable by at least one of the one or more processors <NUM> to perform the specially configured reference signal monitoring operations described herein.

Similarly, in an aspect, eNB <NUM> may include one or more processors <NUM> and/or a memory <NUM> that may be communicatively coupled, e.g., via one or more buses <NUM>, and may operate in conjunction with or otherwise implement a one or more of a scheduling component <NUM> for communicating one or more resource grants or other indicators <NUM> to a UE <NUM>, which may indicate one or more parameters regarding switching from downlink to uplink communications, and/or vice versa, in one or more TTIs. For example, the various functions related to scheduling component <NUM> may be implemented or otherwise executed by one or more processors <NUM> and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors, as described above. It is to be appreciated, in one example, that the one or more processors <NUM> and/or memory <NUM> may be configured as described in examples above with respect to the one or more processors <NUM> and/or memory <NUM> of UE <NUM>.

In an example, the one or more processors <NUM> and/or memory <NUM> may execute actions or operations defined by scheduling component <NUM> or its subcomponents. For instance, the one or more processors <NUM> and/or memory <NUM> may execute actions or operations defined by a resource grant generating component <NUM> for generating one or more resource grants and/or other indicators <NUM> for the UE <NUM>, where the resource grant and/or other indicator <NUM> may indicate one or more parameters regarding a TTI during which communications are switched from downlink to uplink, and/or vice versa. In an aspect, for example, resource grant generating component <NUM> may include hardware (e.g., one or more processor modules of the one or more processors <NUM>) and/or computer-readable code or instructions stored in memory <NUM> and executable by at least one of the one or more processors <NUM> to perform the specially configured resource grant generating operations described herein. Further, for instance, the one or more processors <NUM> and/or memory <NUM> may execute actions or operations defined by an optional downlink/uplink switch indicating component <NUM> for indicating, via the resource grant or other indicators <NUM>, one or more parameters regarding a TTI during which communications are switched from downlink to uplink, and/or vice versa. In an aspect, for example, downlink/uplink switch indicating component <NUM> may include hardware (e.g., one or more processor modules of the one or more processors <NUM>) and/or computer-readable code or instructions stored in memory <NUM> and executable by at least one of the one or more processors <NUM> to perform the specially configured downlink/uplink switch indicating operations described herein.

It is to be appreciated that transceivers <NUM>, <NUM> may be configured to transmit and receive wireless signals through one or more antennas, an RF front end, one or more transmitters, and one or more receivers. In an aspect, transceivers <NUM>, <NUM> may be tuned to operate at specified frequencies such that UE <NUM> and/or eNB <NUM> can communicate at a certain frequency. In an aspect, the one or more processors <NUM> may configure transceiver <NUM> and/or one or more processors <NUM> may configure transceiver <NUM> to operate at a specified frequency and power level based on a configuration, a communication protocol, etc. to communicate uplink signals <NUM> and/or downlink signals <NUM>, respectively, over related uplink or downlink communication channels.

In an aspect, transceivers <NUM>, <NUM> can operate in multiple bands (e.g., using a multiband-multimode modem, not shown) such to process digital data sent and received using transceivers <NUM>, <NUM>. In an aspect, transceivers <NUM>, <NUM> can be multiband and be configured to support multiple frequency bands for a specific communications protocol. In an aspect, transceivers <NUM>, <NUM> can be configured to support multiple operating networks and communications protocols. Thus, for example, transceivers <NUM>, <NUM> may enable transmission and/or reception of signals based on a specified modem configuration.

<FIG> illustrates an example method <NUM> for communicating with a network entity (e.g., by a UE) based on a frame structure that facilitates dynamic switching between TTIs configured for downlink and uplink communications. At Block <NUM>, a UE may optionally communicate with a network entity using a frame structure that allows dynamic switching of configurable TTIs between downlink and uplink communications within the frame. Communicating component <NUM> of UE <NUM> (<FIG>) can communicate with the network entity (e.g., eNB <NUM>) using a frame structure that allows dynamic switching of configurable TTIs between downlink and uplink communications within the frame. In one example, resource grant generating component <NUM> can configure UE <NUM> with resources designated based on the frame structure, and resource grant receiving component <NUM> can receive the resources for communicating with eNB <NUM> via communicating component <NUM>. In an example, the frame structure can be similar to frame structure <NUM> (<FIG>) including dedicated downlink TTIs, TTIs configurable for either uplink or downlink communications, and/or dedicated uplink TTIs. Thus, for example, resource grant generating component <NUM> may generate, and resource grant receiving component <NUM> may receive, a downlink resource grant indicating downlink resources in corresponding TTIs that are configurable as downlink or uplink resources or in TTIs that are dedicated downlink TTIs, an uplink resource grant indicating uplink resources in corresponding TTIs that are configurable as downlink or uplink resources or in TTIs that are dedicated uplink TTIs, etc..

For example, UE <NUM> and eNB <NUM> may communicate in downlink or uplink bursts such that the TTIs configurable for downlink or uplink communications are configured for downlink communications for one or more TTIs, and then for uplink communications for one or more TTIs, and then back to downlink, and so on. As described, in an example, eNB <NUM> can define switching between downlink and uplink communications in these TTIs such to achieve a desired uplink or downlink latency, which may include defining the switching based at least in part on a load on eNB <NUM>, a buffer status, quality-of-service, subscription level, etc. of UE <NUM>, and/or similar parameters that can indicate a demand for communication resources. In this regard, as described further herein, eNB <NUM> may indicate one or more parameters regarding a switch in the configurable TTIs from downlink to uplink and/or vice versa to UE <NUM> and/or one or more other UEs. It is to be appreciated, in one example however, that the UE <NUM> and/or one or more other UEs need not communicate with the network entity over granted resources to receive information regarding switching of configurable TTIs from downlink to uplink communications, and/or vice versa, as described herein.

Accordingly, at Block <NUM>, a UE may receive a notification from the network entity of switching a configurable TTI from downlink communications to uplink communications. Downlink/uplink switch detecting component <NUM> can receive the notification from the network entity of switching a configurable TTI from downlink communications to uplink communications. It is to be appreciated that various notifications of switching a configurable TTI from downlink to uplink communications can be employed in this regard. In one example, in receiving the notification at Block <NUM>, at Block <NUM> the UE may optionally receive the notification in an uplink resource grant that indicates the configurable TTI. Thus, for example, where UE <NUM> is scheduled resources by eNB <NUM>, resource grant generating component <NUM> can generate an uplink resource grant <NUM> for UE <NUM> related to a given TTI, and scheduling component <NUM> can transmit the uplink resource grant <NUM> (e.g., via transceiver <NUM>) to UE <NUM>. In this example, resource grant receiving component <NUM> can receive the notification in an uplink resource grant <NUM> received from eNB <NUM> (e.g., via transceiver <NUM>) that indicates the configurable TTI. For example, downlink/uplink switch detecting component <NUM> can determine the downlink to uplink switch in a given TTI based at least in part on a TTI or similar timing information indicated in the uplink resource grant. In one example, downlink/uplink switch detecting component <NUM> can determine the downlink to uplink switch to occur in the TTI corresponding to the granted uplink resources, a number of TTIs before the granted uplink resources, a number of TTIs after the TTI in which the uplink resource grant is received, a TTI indicated as the switching TTI in the resource grant, etc..

In another example (e.g., where UE <NUM> is not scheduled by eNB <NUM> or in any case), downlink/uplink switch indicating component <NUM> can indicate a switch from downlink to uplink communications in a configurable TTI using an indicator. Thus, for example, in receiving the notification at Block <NUM>, at Block <NUM>, the UE may optionally receive the notification as an indicator in a previous TTI configured for downlink communications. For example, downlink/uplink switch detecting component <NUM> may receive the notification as an indicator <NUM> in the previous TTI configured for downlink communications (e.g., a heads-up bit that can be transmitted in a downlink signal <NUM>, using a downlink channel, etc.), in which case downlink/uplink switch detecting component <NUM> can receive the bit or other indicator <NUM> (e.g., via transceiver <NUM>), and can determine the configurable TTI as an upcoming TTI where communications are switched to uplink communications. The indicator may indicate at least one of the switch occurring in the next TTI, a number of TTIs in advance where the switch will occur (e.g., a known or configured number of TTIs after a heads-up bit is received or an explicit number of TTIs specified in the indicator), an explicit TTI where the switch will occur where the TTIs can be identified (e.g., by frame number, subframe number, etc.), and/or the like. For example, downlink/uplink switch detecting component <NUM> can monitor communications from eNB <NUM> to detect the indicator.

For instance, where UE <NUM> is scheduled by eNB <NUM>, downlink/uplink switch detecting component <NUM> can monitor communications from eNB <NUM> following receipt of a downlink grant or other indication of a downlink grant duration. Otherwise, UE <NUM> can monitor communications from eNB <NUM> at substantially any configurable TTI (and/or a dedicated downlink TTI) until the indication of switching (e.g., an uplink resource grant or other indicator <NUM>) is received from eNB <NUM>.

In addition, for example, the resource grant or other indicator <NUM> may include one or more parameters indicating a duration of the uplink TTIs until the configurable TTIs are again switched to downlink communications. For example, the one or more parameters may correspond to a number of TTIs indicated in the resource grant or other indicator <NUM> that relate to a burst length of the uplink burst. In one example, a non-zero value for the number of TTIs may also be the parameter that indicates switching to uplink communications in a next TTI. In any case, downlink/uplink switch detecting component <NUM> can detect the switch to uplink communications for the duration, and at the end of the duration may determine a switch back to downlink communications, as described further herein.

In additional examples, the eNB <NUM> may not communicate an explicit notification of switching the TTIs between downlink and uplink communications, and/or vice versa, but rather communications from eNB <NUM> may implicitly notify of switching. Accordingly, downlink/uplink switch detecting component <NUM> may attempt to blindly detect whether a given TTI is configured for downlink or uplink communications. For example, in receiving the notification at Block <NUM>, at Block <NUM>, the UE may optionally detect one or more reference signals in previous configurable TTIs, and determining that the configurable TTI is configured for uplink communications based at least in part on detecting that the configurable TTI does not include the one or more reference signals. For example, reference signal monitoring component <NUM> can detect the one or more reference signals in the previous configurable TTIs, and downlink/uplink switch detecting component <NUM> can determine that the configurable TTI is configured for uplink communications based at least in part on detecting that the configurable TTI does not include the one or more reference signals.

In one example, in detecting that the configurable TTI does not include the one or more reference signals at Block <NUM>, at Block <NUM>, the UE may optionally detect that the configurable TTI does not include the one or more reference signals by detecting a pilot sequence corresponding to the one or more reference signals in the previous configurable TTIs and determining that the pilot sequence is not present in the configurable TTI. Reference signal monitoring component <NUM> can detect the pilot sequence corresponding to the one or more reference signals in the previous configurable TTIs, and can determine whether the pilot sequence is present in the configurable TTI.

In one example, eNB <NUM> can transmit reference signals, such as cell-specific reference signal (CRS), according to the pilot sequence. eNB <NUM> can transmit the reference signals using a dense pilot signal, which may include transmitting a reference signal with a dense pilot configuration (e.g., using substantially all available bandwidth, or at least more than a frequency subcarrier, to transmit the reference signal in a TTI). This can facilitate improved receipt and detection of the pilot signal by the UE <NUM>. In another example, eNB <NUM> may transmit the reference signal using a relatively sparse pilot configuration (e.g., a pilot configuration normally defined for a RAT, such as LTE, which may use less bandwidth than a dense pilot configuration). In either case, the reference signals transmitted as a pilot signal in this regard can be used for performing channel estimation to coherently detect subsequent transmissions of the reference signal or related pilot sequences. In this example, reference signal monitoring component <NUM> can monitor signals in the previous configurable TTIs, and can observe the reference signal transmitted as a pilot signal. Reference signal monitoring component <NUM> can accordingly use the reference signal to perform channel estimation, and the channel estimates obtained from the previous configurable TTIs may be used to aid the detection of reference signals in subsequent TTIs to determine that a subsequent TTI is a downlink TTI based on detecting a related (e.g., similar) pilot sequence in the subsequent TTI.

In this example, reference signal monitoring component <NUM> can monitor the channel for reference signals in the previous configurable TTIs configured for downlink communications (or in dedicated downlink TTIs), and can observe or otherwise determine the pilot sequence of reference signals (e.g., CRS) transmitted by eNB <NUM>. Reference signal monitoring component <NUM> can accordingly attempt to coherently detect the reference signal (e.g., CRS) in subsequent downlink TTIs, such as the configurable TTI, based on the detected pilot sequence. Where reference signal monitoring component <NUM> does not encounter reference signals having the determined pilot sequence in the configurable TTI, this may be a notification that the configurable TTIs have switched from downlink to uplink communications, and downlink/uplink switch detecting component <NUM> may determine that the communications have been switched from downlink to uplink communications in the configurable TTI (or before).

It is to be appreciated, in another example, that the reference signal monitoring component <NUM> may not rely on the channel estimates from the previous configurable TTIs but instead rely on the current TTI to determine the pilot sequence, thus non-coherently detecting reference signals received in downlink signals <NUM> from eNB <NUM>. For example, reference signal monitoring component <NUM> may non-coherently detect the reference signals where the previous configurable TTIs were not downlink TTIs, or otherwise where coherent detection is not used or supported (e.g., which can conserve memory that may be otherwise used to store information regarding the previously detected reference signals). In either case, as described, downlink/uplink switch detecting component <NUM> can detect that a TTI is configured for downlink communications based at least in part on detecting the reference signals in the TTI. Similarly, in an example, downlink/uplink switch detecting component <NUM> can detect that a TTI is not configured for downlink communications (e.g., is configured for uplink communications) based at least in part on not detecting the reference signals or related pilot sequence in the TTI. Thus, downlink/uplink switch detecting component <NUM> can receive the notification of switching the configurable TTI based on determining (non-coherently) whether the TTI includes one or more reference signals associated with downlink communications.

In addition, in an example, in receiving the notification at Block <NUM>, at Block <NUM>, the UE may optionally determine that the previous configurable TTIs are configured for downlink communications further based at least in part on decoding a physical layer channel from one or more signals received in the previous configurable TTI. Downlink/uplink switch detecting component <NUM> can determine that the previous configurable TTIs are configured for downlink communications further based at least in part on decoding a physical layer channel from one or more signals received in the previous configurable TTI. This can have occurred before detecting that the configurable TTI does not include the one or more reference signals at Block <NUM>, such to implicitly receive the notification that the configurable TTIs are switched from downlink to uplink communications. In another example, downlink/uplink switch detecting component <NUM> can additionally or alternatively attempt to decode a known physical layer channel in signals received from eNB <NUM> to confirm that the previous configurable TTIs were configured for downlink communications, as described further herein. In one example, downlink/uplink switch detecting component <NUM> can attempt to decode the physical layer channel, such as a physical control format indicator channel (PCFICH), based on the received CRS to confirm that the previous configurable TTIs corresponded to downlink communications.

In any case, based on receiving the explicit or implicit notification of switching the configurable TTIs from downlink to uplink communications, communicating component <NUM> can switch the transceiver <NUM> or related resources (e.g., an antenna, one or more processors <NUM> that can operate the antenna such as a modem processor, etc.) from a receive mode to a transmit mode. In another example, communicating component <NUM> can enter sleep mode, as described herein, which may include deactivating one or more components of the transceiver <NUM>, a related processor (e.g., a modem processor), an antenna, etc. for a period of time based on detecting the configurable TTI is configured for uplink communications. Where the UE <NUM> is not scheduled to communicate with eNB <NUM>, for example, this can conserve resources and lower power consumption of the UE <NUM>.

At Block <NUM>, the UE can transmit uplink communications to the network entity during the configurable TTI based at least in part on the notification. For example, with the transceiver <NUM> in transmit mode, as described, communicating component <NUM> can transmit uplink communications to the network entity (e.g., eNB <NUM>) during the configurable TTI based at least in part on the notification. For example, a first TTI in an uplink data burst (e.g., and/or dedicated uplink TTIs) can be used by scheduled and/or non-scheduled UEs <NUM> for transmitting uplink control information to eNB <NUM>, such as CSI reports, ACK/NACK feedback, SRs, etc. Accordingly, in this example, scheduling for transmitting at least some of the uplink control information may not be required of eNB <NUM>, as the UE <NUM> can detect the switch of the configurable TTI to uplink communications (e.g., based on a resource grant or other indicator <NUM>, as described above) and can accordingly transmit the control data in the configurable TTI. This can additionally conserve resources and reduce latency as explicit resource granting for control data communications may not be needed. In this example, however, it is to be appreciated that control channel resources may be semi-statically allocated to the UE <NUM> for communicating control data in the first uplink TTIs (e.g., in an initial resource grant from the eNB <NUM>, etc.), but may not be needed for each transmission of control data in a first uplink TTI of an uplink burst.

In addition, where the switch to uplink communications is part of a resource grant received by UE <NUM>, communicating component <NUM> can transmit additional uplink communications to UE <NUM> in the uplink data burst. For example, communicating component <NUM> can continue transmitting to the eNB <NUM> until the uplink data burst has ended (e.g., until the eNB <NUM> indicates switching configurable TTIs from uplink to downlink communications, whether by an explicit indication from the eNB <NUM>, an indication of a number of TTIs related to the uplink data burst until switching to downlink communications, detecting a switch based on receiving one or more downlink signals from the eNB <NUM>, etc., as described further herein).

<FIG> also illustrates an example method <NUM> for communicating with a network entity (e.g., by a UE) based on a frame structure that facilitates dynamic switching between TTIs configured for downlink and uplink communications. At Block <NUM>, the UE may optionally communicate with a network entity using a frame structure that allows dynamic switching of configurable TTIs between downlink and uplink communications within the frame, as described with respect to <FIG> above. At Block <NUM>, the UE may receive a notification from the network entity of switching a configurable TTI from downlink communications to uplink communications, as described with respect to <FIG> above. At Block <NUM>, the UE may transmit uplink communications to the network entity during the configurable TTI based at least in part on the notification, as described with respect to <FIG> above.

At Block <NUM>, the UE may optionally determine a first configurable TTI to be switched for downlink communications based at least in part on the notification. For example, downlink/uplink switch detecting component <NUM> can determine the first configurable TTI to be switched for downlink communications based at least in part on the notification. As described, downlink/uplink switch indicating component <NUM> may indicate a switch in the configurable TTIs from uplink to downlink using one or more indicators, which can be the same indicator as used to provide the notification of switching from downlink to uplink communications as received by communicating component <NUM> (e.g., at Block <NUM>). For example, resource grant generating component <NUM> can specify a burst length of the uplink resource grant provided to UE <NUM> (e.g., where the burst length can correspond to a number of TTIs), an index of the TTI during which communications will be switched back to downlink, etc. In another example, downlink/uplink switch indicating component <NUM> may generate the other indicator of the downlink to uplink switch (e.g., the TTI carrying the heads-up bit) to also include one or more parameters (e.g., in L1 signaling) indicating when a switch back to downlink communications will occur (e.g., a burst length of the uplink burst, an index of the TTI during which the communications will be switched back to downlink, etc.). Accordingly, in either case, downlink/uplink switch detecting component <NUM> can detect the switch in the configurable TTIs from uplink to downlink communications (e.g., for a downlink burst) based on one or more parameters received in the uplink resource grant or other indicator <NUM>.

In another example, scheduling component <NUM> may begin transmitting downlink signals <NUM> without necessarily indicating the switch to downlink to UE <NUM> or one or more other UEs. Thus, for example, downlink/uplink switch detecting component <NUM> can detect the switch based on receiving the one or more downlink signals, as described further herein. Accordingly, in an example, in determining the first configurable TTI to be switched for downlink communications at Block <NUM>, at Block <NUM>, the UE may monitor for signals from the network entity in one or more configurable TTIs following at least one TTI over which uplink communications are transmitted, and determining switching of the one or more configurable TTIs back to downlink communications based on detecting a reference signal or decoding a downlink control channel. For example, reference signal monitoring component <NUM> can monitor for signals from the network entity (e.g., reference signals from eNB <NUM>) in one or more configurable TTIs following the at least one TTI over which uplink communications are transmitted (e.g., by UE <NUM>), and can determine switching of the one or more configurable TTIs back to downlink communications based on detecting a reference signal or decoding a downlink control channel.

For example, where downlink reference signals are detected from eNB <NUM> following a determined switch from downlink to uplink communications, this may indicate a switch back from uplink to downlink communications in the configurable TTIs (e.g., where the downlink reference signal is received in a configurable TTI and/or not received in a dedicated downlink TTI). For example, where UE <NUM> is scheduled by eNB <NUM> but does not receive an indication of when the switch to downlink communications occurs, communicating component <NUM> can transmit its uplink data information over one or more uplink TTIs according to its uplink resource grant received from eNB <NUM>, and then reference signal monitoring component <NUM> can begin monitoring for downlink reference signals from eNB <NUM> to determine when the configurable TTIs are switched from uplink back to downlink communications. This may include communicating component <NUM> switching the transceiver <NUM> to a receive mode to monitor for the reference signals following transmitting the uplink data information. In another example, where UE <NUM> is not scheduled by eNB <NUM> at all, communicating component <NUM> can possibly transmit uplink control information over the first uplink TTI in the indicated uplink data burst, and then reference signal monitoring component <NUM> can begin monitoring for downlink reference signals from eNB <NUM> to determine when the configurable TTIs are switched from uplink back to downlink communications. Again, this may include communicating component <NUM> switching the transceiver <NUM> to a receive mode to monitor for the reference signals after transmitting uplink control information or otherwise.

In one example, monitoring for signals from the eNB <NUM> in this regard can facilitate blindly detecting whether a given TTI is downlink or uplink. As described above, eNB <NUM> can transmit reference signals, such as CRS, according to a pilot sequence. In this example, monitoring for signals at Block <NUM> may include monitoring for signals having a known or learned pilot sequence. In one example, reference signal monitoring component <NUM> can observe reference signals received from eNB <NUM> in previous downlink TTIs, and can detect the pilot sequence utilized (e.g., based on a channel estimate of the reference signals received from eNB <NUM>). Reference signal monitoring component <NUM> can accordingly attempt to detect the reference signals in subsequent downlink TTIs based on the detected pilot sequence. In addition, in an example, reference signal monitoring component <NUM> can attempt to decode a known physical layer channel in subsequent received signals based on the received reference signals (e.g., CRS), such as a downlink control channel (e.g., physical downlink control channel (PDCCH), physical control format indicator channel (PCFICH) or a similar channel) to confirm that the configurable TTI is switched for downlink communications.

In any case, where the first configurable TTI to be switched is determined at Block <NUM>, communicating component <NUM> can switch transceiver <NUM>, as described, to a receive mode to receive downlink signals <NUM> from eNB <NUM>. Thus, at Block <NUM>, the UE can optionally receive control data from the network entity in the first configurable TTI. Communicating component <NUM> can receive the control data from the network entity (e.g., eNB <NUM>) in the first configurable TTI. As described, this can include receiving downlink signals <NUM> from eNB <NUM>, which may include the control data from eNB <NUM>. In one example, the control data may indicate a resource grant for UE <NUM> and/or an indication of when the TTIs will be switched back for uplink communications. In any case, for example, communicating component <NUM> can continue to receive downlink signals <NUM> in one or more TTIs, and method <NUM> can accordingly continue to <NUM> to receive another notification of switching a configurable TTI from downlink communications to uplink communications, and so on. In other words, downlink/uplink switch detecting component <NUM> can continue to detect switching from downlink to uplink communications in the configurable TTIs and from uplink to downlink communications to synchronize communications with eNB <NUM> using the techniques described above.

<FIG> illustrates an example method <NUM> for determining (e.g., by a UE) whether a configurable TTI is configured for uplink or downlink communications. At Block <NUM>, the UE may monitor one or more configurable TTIs for one or more reference signals. Reference signal monitoring component <NUM> can monitor the one or more configurable TTIs for the one or more reference signals. As described, for example, reference signal monitoring component <NUM> can monitor for a pilot signal and/or one or more pilot sequences known to correspond to a reference signal. In one example, reference signal monitoring component <NUM> can receive a pilot signal (e.g., from eNB <NUM>) in a previous TTI (e.g., according to a dense or sparse pilot configuration), and can utilize the pilot signal to detect similar reference signals received in subsequent TTIs. Reference signal monitoring component <NUM> can thus determine a pilot sequence for one or more reference signals transmitted by eNB <NUM>, and can utilize the pilot sequence to attempt coherent detection of one or more reference signals in subsequent configurable TTIs. In another example, reference signal monitoring component <NUM> can non-coherently detect reference signals in a TTI without detecting similar reference signals in previous TTIs.

At Block <NUM>, the UE may determine whether one or more reference signals are detected in a TTI. Reference signal monitoring component <NUM> can determine whether one or more reference signals are detected in the TTI. As described, this can be based on verifying a pilot sequence of the reference signals, performing channel estimation to determine the signals are reference signals, etc..

Where one or more reference signals are detected in the TTI at Block <NUM>, at Block <NUM> the UE may determine that the configurable TTI is configured for downlink communications. Downlink/uplink switch detecting component <NUM> can determine that the TTI is configured for downlink communications where the one or more reference signals are detected in the TTI. The reference signals can correspond to downlink reference signals, such as CRS, as described above. Accordingly, at Block <NUM>, the UE may receive downlink communications during the configurable TTI. Communicating component <NUM> can receive the downlink communications (e.g., from eNB <NUM>) during the configurable TTI. It is to be appreciated that where the transceiver <NUM> is configured for uplink communications when the one or more reference signals are detected at <NUM>, receiving downlink communications at Block <NUM> may also include communicating component <NUM> switching the transceiver <NUM> and/or related resources (e.g., a modem processor, antenna, etc.) to receive downlink signals during the TTI.

Where one or more reference signals are not detected in the TTI at Block <NUM>, at Block <NUM> the UE may determine that the configurable TTI is configured for uplink communications. Downlink/uplink switch detecting component <NUM> can determine that the TTI is configured for uplink communications where the one or more reference signals are not detected in the TTI. Accordingly, at Block <NUM>, the UE may transmit uplink communications during the configurable TTI, or at Block <NUM>, may enter a sleep mode during one or more TTIs. Communicating component <NUM> can transmit the uplink communications during the configurable TTI and/or enter the sleep mode during one or more TTIs. For example, transmitting the uplink communications at Block <NUM> can include communicating component <NUM> transmitting uplink control communications (e.g., ACK/NACK, CSI, SR, etc., which may be transmitted over semi-statically assigned resources) at least in the first configurable TTI determined to be configure for uplink communications. In addition, in an example, entering the sleep mode at Block <NUM> may include suspending or deactivating one or more resources of the UE <NUM> (e.g., transceiver <NUM> or components thereof, a modem processor, an antenna, etc.) during one or more TTIs. For example, this may occur where a TTI is determined to be configured for uplink communications, and the UE <NUM> did not receive an uplink resource grant or is finished transmitting to the eNB <NUM>, etc. It is to be appreciated that where the transceiver <NUM> is configured for downlink communications when the one or more reference signals are not detected at <NUM>, transmitting downlink communications at Block <NUM> and/or entering the sleep mode at Block <NUM> may also include communicating component <NUM> switching the transceiver <NUM> and/or related resources (e.g., a modem processor, antenna, etc.) to transmit uplink signals during the TTI.

In either case, method <NUM> can proceed from Block <NUM> or <NUM>/<NUM> to Block <NUM> to continue monitoring the configurable TTIs for one or more reference signals to determine whether the configurable TTIs are configured for uplink or downlink communications.

<FIG> illustrates an example method <NUM> for indicating (e.g., by an eNB) a switch between downlink and uplink communications for one or more configurable TTIs. At Block <NUM>, the eNB may communicate with a UE using a frame structure that allows dynamic switching of configurable TTIs between uplink and downlink communications within the frame. Scheduling component <NUM> (<FIG>) can communicate with the UE (e.g., UE <NUM>) using the frame structure that allows dynamic switching of configurable TTIs between uplink and downlink communications within the frame. In one example, resource grant generating component <NUM> can configure UE <NUM> with resources designated based on the frame structure, as described, which scheduling component <NUM> can use to transmit and/or receive communications to/from UE <NUM>. In addition, for example, scheduling component <NUM> can transmit downlink reference signals or other signals over configurable TTIs configured for downlink communications, dedicated downlink TTIs, etc. In an example, the frame structure can be similar to frame structure <NUM> (<FIG>) including dedicated downlink TTIs, TTIs configurable for either uplink or downlink communications, and/or dedicated uplink TTIs.

At Block <NUM>, the eNB may determining to switch a configurable TTI from downlink to uplink communications. Scheduling component <NUM> can determine to switch the configurable TTI from downlink to uplink communications. As described, for example, scheduling component <NUM> can determine to switch configurable TTIs from downlink to uplink communications based at least in part on one or more parameters of the eNB <NUM>, such as parameters indicative of a load at the eNB <NUM>, delay requirements for packets at the eNB <NUM>, etc., one or more parameters of the UE <NUM>, such as parameters indicative of a buffer status, quality of service, subscription level, etc. of the UE <NUM>, one or more parameters regarding a time interval over which to switch between downlink and uplink communications, delay requirements for packets at the UE <NUM>, etc., and/or the like. Thus, for example, scheduling component <NUM> may determine to switch configurable TTIs from downlink to uplink communications and/or vice versa to attain a desired downlink or uplink latency. In another example, eNB <NUM> may receive instructions from one or more network components and/or a request (e.g., SR) from a UE, such as UE <NUM>, to switch from downlink to uplink communications.

At Block <NUM>, the UE may transmit an indication of the switch to the UE. Downlink/uplink switch indicating component <NUM> can transmit the indication of the switch to the UE (e.g., UE <NUM>). For example, the switch may include an explicit or implicit indicator, as described above (e.g., a resource grant or other indicator <NUM>, one or more reference signals, etc.). In one example, in transmitting the indication of the switch at Block <NUM>, at Block <NUM>, the eNB may optionally transmit the indication in an uplink resource grant to the UE. Resource grant generating component <NUM> can generate an uplink resource grant for UE <NUM> to include the indication, and thus scheduling component <NUM> can transmit the indication in the uplink resource grant to the UE <NUM>. Accordingly, for example, receipt of the uplink resource grant can indicate when the switch is to occur (e.g., an explicit indication of the TTI where then switch is to occur, an indicated or known a number of TTIs after receiving the grant, etc.). In another example, as described, transmitting the indication at Block <NUM> may include scheduling component <NUM> transmitting another indicator to the UE <NUM> (e.g., a heads-up indicator of the switch). In this regard, for example, the indicator can indicate a switch to uplink communications is to occur in a next configurable TTI, and/or can explicitly indicate a subsequent TTI at which the switch is to occur.

At Block <NUM>, the eNB may optionally determine to switch a configurable TTI from uplink to downlink communications. Scheduling component <NUM> can determine to switch the configurable TTI from uplink to downlink communications. As described, for example, scheduling component <NUM> can determine to switch configurable TTIs from downlink to uplink communications based at least in part on one or more parameters of the eNB <NUM> such to achieve a desired uplink and/or downlink latency, etc..

At Block <NUM>, the UE may transmit an indication of the switch to the UE. Scheduling component <NUM> can transmit the indication of the switch to the UE <NUM>. As described for example, the indication transmitted in the uplink resource grant or other indicator <NUM> may also include an indication of when the TTIs will be switched back to downlink communications. For example, the indication may include a size of the uplink resource grant, which can indicate a switch back to downlink communications is to occur after the uplink resource grant, or another indication of a switch back to downlink communications (e.g., an index of the TTI during which the switch is to occur, a number of TTIs after which the switch is to occur, etc.), as described. Similarly, for non-scheduled UEs (and/or scheduled UEs in another example), downlink uplink switch indicating component <NUM> can generate the other indicator (e.g., a heads-up indicator) identifying when a switch to uplink communications is to occur. Moreover, in an example, the indicator may also specify a burst length of an uplink data burst, an index of the TTI during which the switch is to occur, etc., so that a TTI at which a switch back to downlink communications is to occur can be identified.

In another example, as described, scheduling component <NUM> can transmit downlink reference signals and/or downlink grants (generated by resource grant generating component <NUM>) when scheduling component <NUM> determines to switch the configurable TTIs to downlink communications. This may occur without explicit notification to the UE <NUM> and/or other UEs. UE <NUM> can accordingly determine the switch by detecting receipt of the reference signals, decoding one or more control channels based on the reference signal, etc., as described above. Accordingly, in one example, in transmitting the indication of the switch to the UE at Block <NUM>, at Block <NUM>, the UE may transmit a dense pilot signal with CRS to indicate a downlink TTI. Scheduling component <NUM> can transmit the dense pilot signal with the CRS to indicating the downlink TTI. For example, scheduling component <NUM> can transmit the dense pilot signal using a plurality of subcarriers (e.g., all available subcarriers in a bandwidth utilized by the UE <NUM> to communicate with eNB <NUM>), which may occur in the first TTI of a downlink burst, to facilitate improved receipt and detection by the UE <NUM>. This can assist the UE <NUM> in performing an initial channel estimation of one or more CRSs based on the dense pilot signal to determine the pilot sequence of the CRS, as described above, for subsequently determining whether CRS is present in one or more configurable TTIs to detect a switch to downlink communications.

<FIG> illustrates an example of a communication timeline <NUM> having TTIs as configured for uplink or downlink communications in dynamic TDD frame structures (e.g., frame structure <NUM> in <FIG>), as described herein. Timeline <NUM> may be used for communication between a UE <NUM> and an eNB <NUM>, as described above. For example, in some cases, timeline <NUM> include signals such as uplink signals <NUM> and/or downlink signals <NUM>. The pilot transmissions shown on timeline <NUM> may be used by UE <NUM> (e.g., using reference signal monitoring component <NUM>) to determine whether a TTI is configured for uplink or downlink communications (e.g., and/or whether communications were switched from an uplink burst to a downlink burst, or vice versa, in the TTI), as described.

Timeline <NUM> may include downlink (DL) burst <NUM>-a over one or more TTIs, as described, which can be configured or dedicated for downlink communications. DL burst <NUM>-a can include preamble DL symbols <NUM>-a and regular DL symbols <NUM>-a. In some examples, regular DL symbols <NUM>-a may include regular pilot signals (e.g., CRS or other reference signals) and preamble DL symbol <NUM>-a may include a dense pilot signal (e.g., a plurality of embedded reference signal tones, such as CRS tones, in a usable bandwidth, as described). A dense pilot may be sent at the beginning of DL burst <NUM>-a to facilitate improved baseline channel estimation at the UE <NUM>, as described. Timeline <NUM> may also include a second DL burst <NUM>-b, which in some cases may be sent without prior signaling to the UE <NUM> (e.g., without an explicit indication that the configurable TTI is switched to downlink communications). DL burst <NUM>-b may include a preamble DL symbol <NUM>-b and regular pilot symbols <NUM>-b, similarly to DL burst <NUM>-a. Timeline <NUM> may also include UL burst <NUM>-a and UL burst <NUM>-b, which can relate to a UE (e.g., UE <NUM>) transmitting uplink signals <NUM> to eNB <NUM> based on an uplink resource grant provided to the UE. DL burst <NUM>-b may be received subsequent to an UL burst (e.g., UL burst <NUM>-a), or it may be received immediately following DL burst <NUM>-a (not shown).

Irrespective of the order of reception, a UE <NUM> (e.g., downlink/uplink switch detecting component <NUM>) may determine whether a TTI is configured for uplink or downlink communications based at least in part on a detection of a pilot signal (e.g., reference signal) whose pilot sequence is known (e.g., based on a previous configuration or observation of the reference signal). For example, preamble DL symbol <NUM>-a may include CRS, whose presence may indicate to a UE <NUM> that DL burst <NUM>-a is a DL burst. In some examples, a UE <NUM> (e.g., downlink/uplink switch detecting component <NUM>) may confirm a blind detection of DL burst <NUM>-a by decoding a known physical layer channel (e.g., PDCCH, PCFICH, etc.). UL burst <NUM>-a may not include a reference signal whose pilot sequence is known (e.g., CRS). Thus, the UE <NUM> may detect an absence of the reference signal (e.g., based on absence of the pilot sequence) and determine that UL burst <NUM>-a is an UL burst (and thus the related TTI is an uplink TTI).

<FIG> illustrates an example of DL burst pilot pattern <NUM> including an expanded view of regular DL symbols <NUM>-c for blind detection of whether a TTI is configured for uplink or downlink communications in dynamic TDD frame structures (e.g., frame structure <NUM> in <FIG>), as described herein. DL burst <NUM>-c may be used for communications between a UE <NUM> and an eNB <NUM>, as described above, and may be an aspect of DL burst <NUM>-a and DL burst <NUM>-b, as described with reference to <FIG>.

DL burst pilot pattern <NUM> may include an example of time and frequency resource elements of DL burst <NUM>-c representing example locations of pilot tones <NUM>. For example, pilot tones for the first antenna may be transmitted on regularly spaced tones (every <NUM> tone in this example) in each TTI (e.g., symbol), where the index (offset) of the pilot tone can be shifted by a certain amount (<NUM> tones in this example) every symbol. The pattern may be repeated every N symbols, where N is a positive integer (e.g., <NUM> symbols in this example). Pilots for different transmit antennas may be transmitted on different tone locations. DL burst pilot pattern <NUM> represents one possible pattern for pilot transmission in a DL burst <NUM>, but other pilot patterns may also be used.

In an example, a UE <NUM> may monitor a wireless channel from an eNB <NUM> for a pilot transmission (e.g., as part of DL burst pilot pattern <NUM>). In some cases, the UE <NUM> (e.g., reference signal monitoring component <NUM>) may detect a pilot sequence and may determine (e.g., by downlink/uplink switch detecting component <NUM>) that the transmission is a DL transmission (e.g., DL burst <NUM>-c), and thus that the corresponding TTI is configured for downlink communications. Downlink/uplink switch detecting component <NUM> may also verify that the TTI is configured for downlink communications by decoding a known physical layer DL channel in the TTI or in a subsequent TTI (e.g., based on the reference signal corresponding to the pilot sequence). In another example, downlink/uplink switch detecting component <NUM> may identify an absence of a pilot sequence on the wireless channel during the TTI and may determine that the TTI is not configured for downlink communications (e.g., that the TTI is configured for uplink communications).

It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

Claim 1:
A method (<NUM>) for communicating using dynamic uplink and downlink transmission time interval, TTI, switching in a wireless network, comprising:
receiving, in a TTI configured for downlink communications, an uplink resource grant from a network entity;
determining, based at least in part on receiving the uplink resource grant, switching of a configurable TTI from downlink communications to uplink communications, wherein the configurable TTI is subsequent in time to the TTI during which the uplink resource grant is received, and wherein the configurable TTI is one of a plurality of TTIs in a frame structure that allows dynamic switching of configurable TTIs between downlink and uplink communications within a frame;
transmitting, based at least in part on receiving the uplink resource grant, uplink communications to the network entity during the configurable TTI;
monitoring (<NUM>) for signals from the network entity in multiple configurable TTIs subsequent to the configurable TTI over which the uplink communications are transmitted, wherein at least a first one of the multiple configurable TTIs is configured for uplink communications; and determining switching of at least a second one of the multiple configurable TTIs back to being configured for downlink communications based at least in part on at least one of detecting a downlink reference signal in the second one of the multiple configurable TTIs or decoding a downlink control channel in the second one of the multiple configurable TTIs based at least in part on detecting the downlink reference signal.