Patent Description:
A wireless communication network may include a number of eNBs that can support communication for a number of user equipments (UEs). A UE may communicate with an eNB via the downlink and uplink. The downlink (or forward link) refers to the communication link from the eNB to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the eNB.

An example of an emerging 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.

<NPL>), discusses alternatives how to transmit SRS in extended UpPTS regions. <NPL>), considers SRS enhancement to reduce the number of DL repetitions needed in TDD, especially for VoLTE.

A method performed by a user equipment, UE, a computer-program and UE apparatus are defined by the appended independent claims <NUM>, <NUM>, <NUM> respectively. Preferred embodiments of the invention are stipulated in the dependent claims. While several embodiments and/or examples have been disclosed in the description, the subject matter for which protection is sought is limited to those examples and/or embodiments which are encompassed by the scope of the appended claims. Embodiments and/or examples that do not fall under the scope of the claims are useful for understanding the invention.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer-readable medium for performing sounding operations. For example, certain aspects provide techniques for assigning symbols in an uplink pilot time slot (UpPTS) for sounding reference signal (SRS) transmission when communicating using a special subframe configuration that sets a fixed symbol length (e.g., <NUM>-symbols) for the UpPTS.

Aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting and the scope of the disclosure is being defined by the appended claims and equivalents thereof.

The techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below.

<FIG> illustrates an example wireless network <NUM> in which aspects of the present disclosure may be performed.

The system illustrated in <FIG> may be, for example, a long term evolution (LTE) network. The wireless network <NUM> may include a number of evolved Node Bs (eNBs) <NUM> and other network entities. An eNB may be a station that communicates with the UEs and may also be referred to as a base station, an access point, etc. A Node B is another example of a station that communicates with the UEs.

Each eNB <NUM> may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to a coverage area of an eNB and/or an eNB subsystem serving this coverage area, depending on the context in which the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. An eNB for a pico cell may be referred to as a pico eNB. An eNB for a femto cell may be referred to as a femto eNB or a home eNB. In the example shown in <FIG>, the eNBs 110a, 110b and 110c may be macro eNBs for the macro cells 102a, 102b and 102c, respectively. The eNB 110x may be a pico eNB for a pico cell 102x. The eNBs 110y and 110z may be femto eNBs for the femto cells 102y and 102z, respectively. An eNB may support one or multiple (e.g., three) cells.

A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., an eNB or a UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or an eNB). In the example shown in <FIG>, a relay station 110r may communicate with the eNB 110a and a UE 120r in order to facilitate communication between the eNB 110a and the UE 120r. A relay station may also be referred to as a relay eNB, a relay, etc..

The wireless network <NUM> may be a heterogeneous network that includes eNBs of different types, e.g., macro eNBs, pico eNBs, femto eNBs, relays, transmission reception points (TRPs), etc. These different types of eNBs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network <NUM>. For example, macro eNBs may have a high transmit power level (e.g., <NUM> Watts) whereas pico eNBs, femto eNBs and relays may have a lower transmit power level (e.g., <NUM> Watt).

For synchronous operation, the eNBs may have similar frame timing, and transmissions from different eNBs may be approximately aligned in time. For asynchronous operation, the eNBs may have different frame timing, and transmissions from different eNBs may not be aligned in time.

A network controller <NUM> may couple to a set of eNBs and provide coordination and control for these eNBs. The network controller <NUM> may communicate with the eNBs <NUM> via a backhaul. The eNBs <NUM> may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

A UE may also be referred to as a terminal, a mobile station, a subscriber unit, a station, etc. A UE may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a netbook, a smart book, etc. A UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays, etc. In <FIG>, a solid line with double arrows indicates desired transmissions between a UE and a serving eNB, which is an eNB designated to serve the UE on the downlink and/or uplink. A dashed line with double arrows indicates interfering transmissions between a UE and an eNB.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. For example, the spacing of the subcarriers may be <NUM> and the minimum resource allocation (called a 'resource block') may be <NUM> subcarriers (or <NUM>). Consequently, the nominal FFT size may be equal to <NUM>, <NUM>, <NUM>, <NUM> or <NUM> for system bandwidth of <NUM>, <NUM>, <NUM>, <NUM> or <NUM> megahertz (MHz), respectively. For example, a subband may cover <NUM> (i.e., <NUM> resource blocks), and there may be <NUM>, <NUM>, <NUM>, <NUM> or <NUM> subbands for system bandwidth of <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, respectively. New radio (NR) may use a different air interface, other than OFDM-based.

<FIG> shows a down link (DL) frame structure used in a telecommunication systems (e.g., LTE). The transmission timeline for the downlink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., <NUM> milliseconds (ms)) and may be partitioned into <NUM> sub-frames with indices of <NUM> through <NUM>. Each sub-frame may include two slots. Each radio frame may thus include <NUM> slots with indices of <NUM> through <NUM>. Each slot may include L symbol periods, e.g., <NUM> symbol periods for a normal cyclic prefix (as shown in <FIG>) or <NUM> symbol periods for an extended cyclic prefix. The <NUM> symbol periods in each sub-frame may be assigned indices of <NUM> through <NUM>-<NUM>. Each resource block may cover N subcarriers (e.g., <NUM> subcarriers) in one slot.

In LTE, an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB. The primary and secondary synchronization signals may be sent in symbol periods <NUM> and <NUM>, respectively, in each of sub-frames <NUM> and <NUM> of each radio frame with the normal cyclic prefix, as shown in <FIG>. The synchronization signals may be used by UEs for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in symbol periods <NUM> to <NUM> in slot <NUM> of sub-frame <NUM>. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) in only a portion of the first symbol period of each sub-frame, although depicted in the entire first symbol period in <FIG>. The PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to <NUM>, <NUM> or <NUM> and may change from sub-frame to sub-frame. M may also be equal to <NUM> for a small system bandwidth, e.g., with less than <NUM> resource blocks. In the example shown in <FIG>, M=<NUM>. The eNB may send a Physical Hybrid Automatic Retransmission (HARQ) Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each sub-frame (M=<NUM> in <FIG>). The PHICH may carry information to support HARQ. The PDCCH may carry information on uplink and downlink resource allocation for UEs and power control information for uplink channels. Although not shown in the first symbol period in <FIG>, it is understood that the PDCCH and PHICH are also included in the first symbol period. Similarly, the PHICH and PDCCH are also both in the second and third symbol periods, although not shown that way in <FIG>. The eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each sub-frame. The PDSCH may carry data for UEs scheduled for data transmission on the downlink. The various signals and channels in LTE are described in <NPL>" which is publicly available.

The eNB may send the PSS, SSS and PBCH in the center <NUM> of the system bandwidth used by the eNB. The eNB may send the PCFICH and PHICH across the entire system bandwidth in each symbol period in which these channels are sent. The eNB may send the PDCCH to groups of UEs in certain portions of the system bandwidth. The eNB may send the PDSCH to specific UEs in specific portions of the system bandwidth. The eNB may send the PSS, SSS, PBCH, PCFICH and PHICH in a broadcast manner to all UEs, may send the PDCCH in a unicast manner to specific UEs, and may also send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs). Each REG may include four resource elements in one symbol period. The PCFICH may occupy four REGs, which may be spaced approximately equally across frequency, in symbol period <NUM>. The PHICH may occupy three REGs, which may be spread across frequency, in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong in symbol period <NUM> or may be spread in symbol periods <NUM>, <NUM> and <NUM>. The PDCCH may occupy <NUM>, <NUM>, <NUM> or <NUM> REGs, which may be selected from the available REGs, in the first M symbol periods. Only certain combinations of REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. The UE may search different combinations of REGs for the PDCCH. The number of combinations to search is typically less than the number of allowed combinations for the PDCCH. An eNB may send the PDCCH to the UE in any of the combinations that the UE will search.

A UE may be within the coverage of multiple eNBs. One of these eNBs may be selected to serve the UE. The serving eNB may be selected based on various criteria such as received power, path loss, signal-to-noise ratio (SNR), etc..

<FIG> is a diagram <NUM> illustrating an example of an uplink (UL) frame structure in a telecommunications system (e.g., LTE). The available resource blocks for the UL may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.

A UE may be assigned resource blocks 310a, 310b in the control section to transmit control information to an eNB. The UE may also be assigned resource blocks 320a, 320b in the data section to transmit data to the eNB. The UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may span both slots of a subframe and may hop across frequency.

A set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH) <NUM>. The PRACH <NUM> carries a random sequence and cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (<NUM>) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (<NUM>).

<FIG> illustrates example components of the base station/eNB <NUM> and UE <NUM> illustrated in <FIG>, which may be used to implement aspects of the present disclosure. One or more components of the AP <NUM> and UE <NUM> may be used to practice aspects of the present disclosure. For example, antennas <NUM>, Tx/Rx <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM> and/or antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the eNB <NUM> may be used to perform the operations described herein.

<FIG> shows a block diagram <NUM> of a design of a base station/eNB <NUM> and a UE <NUM>, which may be one of the base stations/eNBs and one of the UEs in <FIG>. For a restricted association scenario, the base station <NUM> may be the macro eNB 110c in <FIG>, and the UE <NUM> may be the UE 120y.

At the base station <NUM>, a transmit processor <NUM> may receive data from a data source <NUM> and control information from a controller/processor <NUM>. The control information may be for the PBCH, PCFICH, PHICH, PDCCH, etc. The data may be for the PDSCH, etc. The processor <NUM> may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor <NUM> may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal.

On the uplink, at the UE <NUM>, a transmit processor <NUM> may receive and process data (e.g., for the PUSCH) from a data source <NUM> and control information (e.g., for the PUCCH) from the controller/processor <NUM>. At the base station <NUM>, the uplink signals from the UE <NUM> may be received by the antennas <NUM>, processed by the modulators <NUM>, detected by a MIMO detector <NUM> if applicable, and further processed by a receive processor <NUM> to obtain decoded data and control information sent by the UE <NUM>.

The processor <NUM> and/or other processors and modules at the base station <NUM> may perform or direct, e.g., the execution of various processes for the techniques described herein. The processor <NUM> and/or other processors and modules at the UE <NUM> may also perform or direct, e.g., the execution of the functional blocks illustrated herein, and/or other processes for the techniques described herein. The memories <NUM> and <NUM> may store data and program codes for the base station <NUM> and the UE <NUM>, respectively.

<FIG> is a diagram <NUM> illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer <NUM>, Layer <NUM>, and Layer <NUM>. Layer <NUM> (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer <NUM>. Layer <NUM> (L2 layer) <NUM> is above the physical layer <NUM> and is responsible for the link between the UE and eNB over the physical layer <NUM>.

In the user plane, the L2 layer <NUM> includes a media access control (MAC) sublayer <NUM>, a radio link control (RLC) sublayer <NUM>, and a packet data convergence protocol (PDCP) <NUM> sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer <NUM> including a network layer (e.g., IP layer) that is terminated at the packet data network (PDN) gateway <NUM> on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer <NUM> provides multiplexing between different radio bearers and logical channels. The PDCP sublayer <NUM> also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer <NUM> provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ). The MAC sublayer <NUM> provides multiplexing between logical and transport channels. The MAC sublayer <NUM> is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer <NUM> is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer <NUM> and the L2 layer <NUM> with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer <NUM> in Layer <NUM> (L3 layer). The RRC sublayer <NUM> is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE.

<FIG> shows two exemplary subframe formats <NUM> and <NUM> for the downlink with the normal cyclic prefix. The available time frequency resources for the downlink may be partitioned into resource blocks. Each resource block may cover <NUM> subcarriers in one slot and may include a number of resource elements. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.

Subframe format <NUM> may be used for an eNB equipped with two antennas. A CRS may be transmitted from antennas <NUM> and <NUM> in symbol periods <NUM>, <NUM>, <NUM> and <NUM>. A reference signal is a signal that is known a priori by a transmitter and a receiver and may also be referred to as a pilot. A CRS is a reference signal that is specific for a cell, e.g., generated based on a cell identity (ID). In <FIG>, for a given resource element with label Ra, a modulation symbol may be transmitted on that resource element from antenna a, and no modulation symbols may be transmitted on that resource element from other antennas. Subframe format <NUM> may be used for an eNB equipped with four antennas. A CRS may be transmitted from antennas <NUM> and <NUM> in symbol periods <NUM>, <NUM>, <NUM> and <NUM> and from antennas <NUM> and <NUM> in symbol periods <NUM> and <NUM>. For both subframe formats <NUM> and <NUM>, a CRS may be transmitted on evenly spaced subcarriers, which may be determined based on cell ID. Different eNBs may transmit their CRSs on the same or different subcarriers, depending on their cell IDs. For both subframe formats <NUM> and <NUM>, resource elements not used for the CRS may be used to transmit data (e.g., traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in <NPL>" which is publicly available.

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

A UE may be located within the coverage area of multiple eNBs. One of these eNBs may be selected to serve the UE. The serving eNB may be selected based on various criteria such as received signal strength, received signal quality, pathloss, etc. Received signal quality may be quantified by a signal-to-noise-and-interference ratio (SINR), or a reference signal received quality (RSRQ), or some other metric. The UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering eNBs.

Certain UEs may use spectrum of up to <NUM> bandwidths allocated in a carrier aggregation of up to a total of <NUM> (<NUM> component carriers) used for transmission in each direction. For some mobile systems, two types of carrier aggregation (CA) methods have been proposed, continuous CA and non-continuous CA. They are illustrated in <FIG>. Continuous CA occurs when multiple available component carriers are adjacent to each other (<FIG>). On the other hand, non-continuous CA occurs when multiple available component carriers are separated along the frequency band (<FIG>). Both non-continuous and continuous CA aggregates multiple component carriers to serve a single UE.

According to various aspects, the UE operating in a multicarrier system (also referred to as carrier aggregation) is configured to aggregate certain functions of multiple carriers, such as control and feedback functions, on the same carrier, which may be referred to as a "primary carrier. " The remaining carriers that depend on the primary carrier for support are referred to as associated secondary carriers. For example, the UE may aggregate control functions such as those provided by the optional dedicated channel (DCH), the nonscheduled grants, a physical uplink control channel (PUCCH), and/or a physical downlink control channel (PDCCH).

A sounding reference signal (SRS) is a reference signal transmitted by a UE in the uplink direction. The SRS may be used by the base station (e.g., gNB or eNB <NUM>) to estimate the uplink channel quality. For example, as illustrated in <FIG>, a UE <NUM> may transmit SRS to an eNB <NUM>. The eNB <NUM> may use this information to schedule uplink frequency resources for the UE. A special subframe generally refers to a subframe that serves as a switching point between downlink (DL) and uplink (UL) transmission, and may contain a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). The UpPTS may be used to transmit one or more SRSs.

Release-<NUM> of the 3GPP standard introduced configuration for UpPTS having a fixed number of symbols (e.g., <NUM> symbols) corresponding to UpPTS for physical uplink shared channel (PUSCH) transmission with special subframe configuration <NUM>. Release-<NUM> of the 3GPP standard previously introduced additional SRS transmissions for UpPTS. For releases of 3GPP prior to release-<NUM> (e.g., release-<NUM>), the length of UpPTS was not fixed, and depended on a special subframe configuration indicated to the UE via broadcast transmission and possibly additional parameters indicated to the UE via unicast transmission, as described in more detail herein. Therefore, the length of the UpPTS could vary to be <NUM> or <NUM> symbols based on a baseline indication via broadcast, or two or to four symbols based on an indication to the UE via unicast transmission.

<FIG> is a table <NUM> indicating information regarding SRS transmissions for a UpPTS. As illustrated, for subframe configurations <NUM>-<NUM>, a baseline value of one symbol is indicated, and for configurations <NUM>-<NUM>, a baseline value of two symbols is indicated. The baseline values may be used to determine assignment of symbols for SRS transmission. The baseline values may be indicated via a broadcast transmission in a system information block (SIB) broadcasted by an eNB (e.g., eNB <NUM>). Moreover, for configurations <NUM>-<NUM>, the variable "X" indicates additional symbols for SRS transmissions. For example, the configuration corresponding to variable X may be indicated to UEs via unicast transmission and indicate to use two or four additional symbols for SRS transmissions. In other words, the framework for SRS relies on two parts for UpPTS, a baseline UpPTS which may be determined based on the special subframe configuration being used, and an extended UpPTS corresponding to the X value in table <NUM>. As illustrated, for the special configuration <NUM>, the additional (extended) symbol indication is not present. The length of DwPTS and UpPTS given by table <NUM> is subject to the total length of DwPTS, GP and UpPTS being equal to <NUM> x Ts = <NUM>, where Ts is a basic time unit, and where X is the number of additional single-carrier frequency-division multiple access scheme (SC-FDMA) symbols in UpPTS provided by a higher layer parameter (e.g., srs-UpPtsAdd parameter) if configured, otherwise X being equal to <NUM>. As illustrated, the length of UpPTS with a normal cyclic prefix is <NUM> Ts, which corresponds to <NUM> symbols.

<FIG> are tables <NUM>, <NUM> used by UEs for the determination of SRS transmission. The table <NUM> is used for SRS not configured with additional SRS symbols in UpPTS, and table <NUM> is used for SRS configured with additional SRS symbols in UpPTS. The table <NUM> indicates a subframe index KSRS, which indicates the one or more symbols in the UpPTS to be assigned to one or more SRSs.

An eNB may signal which of the special subframe configurations described with respect to table <NUM> are to be used by a UE. For example, when an eNB signals a special subframe configuration <NUM>, the eNB also signals one of two legacy special subframe configurations (e.g., configuration <NUM> or configuration <NUM>). Therefore, UEs (e.g., legacy UEs) that may not understand the release-<NUM> signaling of special subframe configuration <NUM>, and thus need a fallback or legacy special subframe configuration, can use the signaling of the legacy special subframe configuration (e.g., one of configurations <NUM>-<NUM>) for SRS transmission.

As described herein, the framework for SRS transmission relies on two parts for UpPTS, a baseline UpPTS and an extended UpPTS. However, with the inclusion of release-<NUM> special subframe configuration <NUM>, this framework is broken since special subframe configuration <NUM> corresponds to a fixed number of symbols for UpPTS. Different UEs may have different understanding of the special subframe configuration (legacy UEs will read configurations <NUM>/<NUM> and new UEs will read configuration <NUM>), complicating the SRS scheduling. Moreover, a UE may be unable to determine the SRS resources from the tables <NUM> and <NUM> described with respect to <FIG>, since special subframe configuration <NUM> is a special subframe configuration that has no baseline and extended UpPTS, or may be considered to have only a baseline UpPTS with a length of <NUM> symbols which is not supported by table <NUM>. Certain aspects of the present disclosure provide techniques for performing SRS transmission by non-legacy UEs (e.g., UEs supporting release-<NUM>) in response to signaling from the eNB indicating special subframe configuration <NUM>.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, by a UE (e.g., a non-legacy UE) such as the UE <NUM>.

The operations <NUM> begin, at block <NUM>, by receiving signaling indicating a first subframe configuration (e.g., special subframe configuration <NUM>), the first subframe configuration corresponding to a subframe with a first number of symbols (e.g., <NUM> symbols) in a UpPTS, and at block <NUM>, receiving signaling indicating a second configuration (e.g., special subframe configuration <NUM> or <NUM>), the second configuration indicating a second number of symbols in the UpPTS (e.g., to be used for determining a configuration for SRS transmission). At block <NUM>, the operations <NUM> continue by generating a frame comprising the UpPTS having the first number of symbols corresponding to the first subframe configuration, the UpPTS including one or more SRSs corresponding to the second configuration, and at block <NUM>, transmitting the frame comprising the UpPTS.

For example, for SRS transmission, a UE that receives signaling from the eNB indicating special subframe configuration <NUM> (e.g., the first subframe configuration described with respect to <FIG>) may fall back to the legacy signaled special subframe configuration (e.g., the second configuration described with respect to <FIG>) such special subframe configuration <NUM>. In other words, for SRS purposes, the UE follows legacy fields (e.g., for configurations <NUM> and <NUM>), but for PUSCH purposes, the UE follows fields specific to configuration <NUM>. For example, if the eNB signals special subframe configuration <NUM> (e.g., for legacy UEs), the non-legacy UE may assume <NUM> symbol for SRS transmission in a UpPTS having <NUM> symbols. For instance, if a non-legacy UE receives signaling indicating to use special subframe configuration <NUM>, the UE may generate the UpPTS with <NUM> symbols corresponding to special subframe configuration <NUM>, but assign two symbols of the UpPTS for SRS transmission. Thus, the UE may determine where to transmit SRS in the UpPTS based on whether eNB has signaled to use special subframe configuration <NUM> or special subframe configuration <NUM>. For additional symbols in UpPTS, the UE will follow the unicast configuration (e.g., a unicast transmission from the eNB indicating extended SRS transmissions). For example, when the eNB signals fallback special subframe configuration <NUM> in a SIB, and signals two additional symbols for UpPTS via unicast for SRS purposes, the UpPTS length is <NUM> symbols (<NUM> baseline symbol + <NUM> additional symbols), but the UpPTS length may be <NUM> symbols in accordance with the special subframe configuration <NUM>.

In other words, if a higher layer parameter (e.g., referred to as "specialSubframePatterns-v1430") indicates ssp10 (e.g., indicating to use special subframe configuration <NUM>), or if the higher layer parameter (e.g., specialSubframePatterns-v1450) indicates ssp10-CRS-LessDwPTS (e.g., indicating to use special subframe configuration <NUM> without common reference signal (CRS) transmission on the 5th symbol of DwPTS), the UE may assume, for the purpose of transmitting SRS (e.g., determine subframe index kSRS), that the special subframe configuration is that signaled by specialSubframePatterns (without suffix) (e.g., special subframe configuration <NUM> or <NUM> signaled for legacy UEs).

<FIG> are tables <NUM>, <NUM> representing parameters indicated for special subframe configuration <NUM> which may be added to explicitly indicate information regarding SRS transmission, in accordance with certain aspects of the present disclosure. For example, table <NUM> is similar to table <NUM> described with respect to <FIG>, but corresponding to special subframe configuration <NUM>. The subframe index kSRS for the special subframe configuration <NUM> may indicate that the SRS is to be transmitted in the last two symbols of the UpPTS. Table <NUM> is similar to table <NUM> described with respect to <FIG>, but corresponding to special subframe configuration <NUM> and indicating that the SRS is to be transmitted in the last two or four symbols of the UpPTS.

In certain aspects, the indication of the symbols for SRS transmission may be implied by the UE. For example, the UE may refer to the legacy parameters described with respect to <FIG> and offset the assignment of the SRS symbols in the UpPTS such that the SRSs are transmitted in the last symbols of the UpPTS. For example, when table <NUM> indicates an SRS to be transmitted in the beginning two symbols, the UE may transmit SRS in the fifth and sixth symbols of the UpPTS instead, or start counting symbols from the third symbol of the UpPTS and assign the SRS transmissions accordingly.

In certain aspects, only additional SRS symbols may be supported. For example, when two or four additional SRS symbols are indicated by the unicast transmission (e.g., corresponding to table <NUM>), the UE may start counting from (e.g., assign the SRS transmissions to) the beginning of UpPTS. For example, the extra two symbols may use the beginning <NUM> symbols of the UpPTS, and extra four symbols may use the beginning four symbols of the UpPTS.

In certain aspects, SRS transmission may not be supported for the special subframe configuration <NUM>. In certain aspects, an additional configuration (e.g., indicated via unicast or broadcast transmission) may be indicated by the eNB to the UE used to determine what special subframe configuration baseline (e.g., one or two symbols) to use for SRS, instead of following the legacy fallback parameter.

Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more. " For example, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from the context to be directed to a singular form. Unless specifically stated otherwise, the term "some" refers to one or more. " That is, unless specified otherwise, or clear from the context, the phrase, for example, "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, for example the phrase "X employs A or B" is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. §<NUM>, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for.

In the case of a UE <NUM> (see <FIG>), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus.

Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory), flash memory, phase change memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof.

For example, instructions for performing the operations described herein and illustrated in the appended figures.

Claim 1:
A method for wireless communication, the method performed by a user-equipment, UE, the method comprising:
receiving (<NUM>) signaling indicating a first subframe configuration, the first subframe configuration corresponding to a subframe with a first number of symbols in an uplink pilot time slot, UpPTS;
receiving (<NUM>) signaling indicating a second configuration, the second configuration indicating a second number of symbols in the UpPTS;
wherein the first subframe configuration and the second configuration are signaled via different transmissions, wherein the first subframe configuration is signaled via a broadcast transmission and the second configuration is signaled via a unicast transmission to the UE;
generating (<NUM>) a frame comprising the UpPTS having the first number of symbols corresponding to the first subframe configuration, the UpPTS including one or more sounding reference signals, SRSs, corresponding to the second configuration; and
transmitting (<NUM>) the frame comprising the UpPTS.