Techniques for transmitting positioning reference signals in an unlicensed radio frequency spectrum band

Techniques are described for wireless communication. In one method, a positioning reference signal (PRS) may be generated. The PRS may be configured in at least one downlink subframe among a plurality of downlink subframes. The PRS may be transmitted in the at least one downlink subframe using an unlicensed radio frequency spectrum band.

FIELD OF THE DISCLOSURE

The present disclosure, for example, relates to wireless communication systems, and more particularly to techniques for transmitting positioning reference signals in an unlicensed radio frequency spectrum band.

BACKGROUND

By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple user equipments (UEs; e.g., mobile devices). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).

Some modes of communication may enable communication with a UE over different radio frequency spectrum bands (e.g., a licensed radio frequency spectrum band and/or an unlicensed radio frequency spectrum band). With increasing data traffic in cellular networks, the offloading of at least some data traffic from a licensed radio frequency spectrum band to an unlicensed radio frequency spectrum band may provide a cellular operator with opportunities for enhanced data transmission capacity. In other examples, an unlicensed radio frequency spectrum band may be used in a standalone mode where access to a licensed radio frequency spectrum band is not available.

Prior to transmitting data over an unlicensed radio frequency spectrum band, a transmitting apparatus may, in some examples, perform a clear channel assessment (CCA) procedure to gain access to the unlicensed radio frequency spectrum band. A CCA procedure may determine whether a particular channel of the unlicensed radio frequency spectrum band is available. When it is determined that the channel of the unlicensed radio frequency spectrum band is not available (e.g., because another device is already using the channel of the unlicensed radio frequency spectrum band), a CCA may be performed for the channel of the unlicensed radio frequency spectrum band again at a later time.

Because a base station may contend for access to an unlicensed radio frequency spectrum band, there is a chance that the base station may be unable to transmit a periodic signal such as a positioning reference signal (PRS) at a predetermined time period interval. When one or more base stations fail to transmit a PRS, a UE loses one or more opportunities to make PRS measurements, and it may not be possible to determine an accurate position of the UE from its PRS measurements.

SUMMARY

The present disclosure, for example, relates to one or more techniques for transmitting positioning reference signals in an unlicensed radio frequency spectrum band. A base station may, in some examples, periodically transmit a PRS adjacent a CCA exempt transmission (CET) and leverage the CCA exempt property of the CET. To leverage the CCA exempt property of the CET, the base station may transmit the PRS adjacent the CET such that a combined duration of the PRS and the CET is less than a maximum allowed duration of the CET. For example, the base station may transmit the PRS contiguously with the CET. In other examples, a base station may contend for access to an unlicensed radio frequency spectrum band and may transmit a PRS when winning contention for access to the unlicensed radio frequency spectrum band. When a base station does not win contention for access to an unlicensed radio frequency spectrum band for a period of time (e.g., a plurality of gating intervals), the base station may determine statistics (e.g., CCA clearance statistics) to improve the likelihood that a receiver (e.g., a UE) receives enough PRS transmissions to determine an accurate position of the UE. The base station may also receive statistics (e.g., CCA clearance statistics) from one or more UEs and/or other base stations. The base station may configure parameters of subsequent PRS transmissions and/or PRS measurements based on the statistics.

In a first set of illustrative examples, a method for wireless communication is described. In one example, the method may include generating a PRS; configuring the PRS in at least one downlink subframe among a plurality of downlink subframes; and transmitting the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band.

In some examples, the configuring the PRS in the at least one downlink subframe may include configuring the PRS to be adjacent a CET. In some examples, a combined duration of the PRS and the CET is less than a maximum allowed duration of the CET. In some examples, the transmitting the PRS may include periodically transmitting the PRS adjacent the CET. In some examples, the periodically transmitting the PRS adjacent the CET may include transmitting the PRS adjacent the CET according to a first periodicity and a first phase offset. In some examples, the first periodicity may differ from a second periodicity at which the CET is transmitted. In some examples, the first periodicity may be a variable periodicity.

In some examples in which the configuring the PRS in the at least one downlink subframe may include configuring the PRS to be adjacent a CET, the method may further include signaling a receiver of a timing of the transmitting the PRS adjacent the CET. In some examples, the transmitting the PRS may include transmitting the PRS contiguously with the CET. In some examples, the transmitting the PRS may include time synchronizing the transmitting the PRS, by a first transmitter, with a transmission of at least a second PRS by at least a second transmitter. In some examples, the transmitting the PRS may include transmitting the PRS, by a first transmitter, with a same periodicity as, and different phase offset than, a transmission of at least a second PRS by at least a second transmitter. In some examples, the transmitting the PRS may include transmitting the PRS, by a first transmitter, with a different periodicity than a transmission of at least a second PRS by at least a second transmitter. In some examples, the transmitting the PRS may include transmitting the PRS before the CET. In some examples, the transmitting the PRS may include transmitting the PRS after the CET. In some examples, the method may further include associating the PRS with a muting parameter. In some examples, the method may further include associating the PRS with a variable cell-specific frequency shift parameter.

In some examples, the transmitting the PRS may include transmitting the PRS to occupy a portion of the unlicensed radio frequency spectrum band less than all of the unlicensed radio frequency spectrum band. In some examples, the transmitting the PRS may include transmitting the PRS across a plurality of frequencies of the unlicensed radio frequency spectrum band.

In some examples, the configuring the PRS in the at least one downlink subframe may include configuring the PRS in at least one downlink subframe of a CCA frame. In some examples, the method may further include determining whether a CCA procedure failed, and gating off a transmission of the PRS based at least in part on the determining the CCA procedure failed. In some examples, the method may further include receiving at least one CCA clearance statistic related to at least one PRS measurement, and determining whether at least one additional PRS measurement may be needed based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement. In some examples, the at least one CCA clearance statistic related to the at least one PRS measurement may be received from at least one UE. In some examples, the at least one CCA clearance statistic related to the at least one PRS measurement may be received from at least one evolved NodeB (eNB). In some examples, the method may further include configuring the transmitting the PRS based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement, to increase a number of PRS transmissions within a measurement period. In some examples, the method may further include configuring the at least one additional PRS measurement based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement. In some examples, the method may include transmitting an indication to a receiver to use prior reference signal time difference (RSTD) measurements based at least in part on a prior PRS transmission.

In some examples, the method may further include receiving a set of RSTD measurements collected for each of a plurality of known locations, and transmitting the received set of RSTD measurements to be stored in a database. In some examples, the method may include receiving at least one RSTD measurement and at least one reference signal strength indicator (RSSI) associated with an unknown location, and estimating a position of the unknown location based at least in part on the at least one RSTD measurement and the at least one RSSI associated with the unknown location, and the set of RSTD measurements stored in the database.

In a second set of illustrative examples, an apparatus for wireless communication is described. In one example, the apparatus may include means for generating a PRS; means for configuring the PRS in at least one downlink subframe among a plurality of downlink subframes; and means for transmitting the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band. In some examples, the apparatus may further include means for implementing one or more aspects of the method for wireless communication described above with respect to the first set of illustrative examples.

In a third set of illustrative examples, another apparatus for wireless communication is described. In one example, the apparatus for wireless communication may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to generate a PRS, configure the PRS in at least one downlink subframe among a plurality of downlink subframes, and transmit the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band. In some examples, the instructions may also be executable by the processor to implement one or more aspects of the method for wireless communication described above with respect to the first set of illustrative examples.

In a fourth set of illustrative examples, a computer program product for communication by a wireless communication apparatus in a wireless communication system is described. In one example, the computer program product may include a non-transitory computer-readable medium storing computer-executable code executable by a processor to cause the wireless communication apparatus to generate a PRS, configure the PRS in at least one downlink subframe among a plurality of downlink subframes, and transmit the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band. In some examples, the instructions may also be executable by the processor to cause the wireless communication apparatus to implement one or more aspects of the method for wireless communication described above with respect to the first set of illustrative examples.

DETAILED DESCRIPTION

Techniques are described in which positioning reference signals are transmitted in an unlicensed radio frequency spectrum band. In some examples, a base station may contend for access to an unlicensed radio frequency spectrum band, and at times may not gain access to the unlicensed radio frequency spectrum band when access is needed to transmit a PRS. As a result, a base station may, in some examples, periodically transmit a PRS adjacent a CCA exempt transmission (CET) and leverage the CCA exempt property of the CET. To leverage the CCA exempt property of the CET, the base station may transmit the PRS adjacent the CET such that a combined duration of the PRS and the CET is less than a maximum allowed duration of the CET. For example, the base station may transmit the PRS contiguously with the CET. In other examples, a base station may contend for access to an unlicensed radio frequency spectrum band and may transmit a PRS when winning contention for access to the unlicensed radio frequency spectrum band. When a base station does not win contention for access to an unlicensed radio frequency spectrum band for a period of time (e.g., a plurality of gating intervals), the base station may determine statistics (e.g., CCA clearance statistics) to improve the likelihood that a receiver (e.g., a UE) receives enough PRS transmissions to determine an accurate position of the UE. The base station may also receive statistics (e.g., CCA clearance statistics) from one or more UEs and/or other base stations. The base station may configure parameters of subsequent PRS transmissions and/or PRS measurements based on the statistics.

Techniques are also described in which a base station or other apparatus may receive a set of reference signal time difference (RSTD) measurements collected for each of a plurality of known locations and store the received set of measurements in a database. The set of measurements may in some cases be collected by one or more receivers (e.g., one or more test UEs) that receive PRS transmissions, determine a set of RSTD measurements, and transmit the set of RSTD measurements along with location information to the base station or other apparatus. The set of measurements stored in a base station or other apparatus may be used to determine locations of one or more receivers (e.g., one or more UEs). For example, the base station or other apparatus may receive at least one RSTD measurement and at least one reference signal strength indicator (RSSI) associated with an unknown location (e.g., from a UE in an unknown location) and estimate a position of the unknown location based at least in part on the at least one RSTD measurement and the at least one RSSI associated with the unknown location, and the set of measurements (for the known locations) stored in the database. In an example, the base station may determine one or more RSTD measurements from the set of measurements (for the known location) that may be similar to the at least one RSTD measurements and the at least one RSSI associated with the unknown location to estimate the position of the unknown location. The use of RSTD measurements in this manner may provide more accurate position information than RSSI alone.

FIG. 1shows a diagram of an example of a wireless communication system100, in accordance with various aspects of the present disclosure. The wireless communication system100may include base stations (or cells)105, UEs115, and a core network130. The base stations105may communicate with the UEs115under the control of a base station controller (not shown), which may be part of the core network130or the base stations105in various examples. The base stations105may communicate control information and/or user data with the core network130through backhaul links132. Backhaul links132may be wired backhaul links (e.g., copper, fiber, etc.) and/or wireless backhaul links (e.g., microwave, etc.). In some examples, the base stations105may communicate, either directly or indirectly, with each other over backhaul links134, which may be wired or wireless communication links. The wireless communication system100may 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 link125may 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.

The base stations105may wirelessly communicate with the UEs115via one or more base station antennas. Each of the base stations105may provide communication coverage for a respective coverage area110. In some examples, a base station105may be referred to as an access point, a base transceiver station (BTS), a radio base station, a radio transceiver, a basic service set (BSS), an extended service set (ESS), a NodeB, an evolved NodeB (eNB), a Home NodeB, a Home eNodeB, a WLAN access point, a Wi-Fi node or some other suitable terminology. The coverage area110for a base station105may be divided into sectors making up only a portion of the coverage area. The wireless communication system100may include base stations105of different types (e.g., macro, micro, and/or pico base stations). The base stations105may also utilize different radio technologies, such as cellular and/or WLAN radio access technologies. The base stations105may be associated with the same or different access networks or operator deployments. The coverage areas of different base stations105, including the coverage areas of the same or different types of base stations105, utilizing the same or different radio technologies, and/or belonging to the same or different access networks, may overlap.

The UEs115may be dispersed throughout the wireless communication system100. A UE115may also be referred to by those skilled in the art as a mobile device, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a wireless device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE115may 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 UE115may be able to communicate with macro base stations, pico base stations, femto base stations, relay base stations, and the like. A UE115may also be able to communicate over different types of access networks, such as cellular or other WWAN access networks, or WLAN access networks. In some modes of communication with a UE115, communication may be conducted over a plurality of communication links125or channels, with each channel using a component carrier between the UE115and one of a number of cells (e.g., serving cells, which cells may in some cases be operated by the same or different base stations105).

Each component carrier may be provided over a licensed radio frequency spectrum band or an unlicensed radio frequency spectrum band, and a set of component carriers used in a mode of communication may all be received (e.g., at a UE115) over a licensed radio frequency spectrum band, all be received (e.g., at a UE115) over an unlicensed radio frequency spectrum band, or be received (e.g., at a UE115) over a combination of a licensed radio frequency spectrum band and an unlicensed radio frequency spectrum band.

The communication links125shown in wireless communication system100may include uplink channels (using component carriers) for carrying uplink (UL) communications (e.g., transmissions from a UE115to a base station105) and/or downlink channels (using component carriers) for carrying downlink (DL) communications (e.g., transmissions from a base station105to a UE115). The UL communications or transmissions may also be called reverse link communications or transmissions, while the DL communications or transmissions may also be called forward link communications or transmissions. The downlink communications and/or uplink communications may be made using a licensed radio frequency spectrum band, an unlicensed radio frequency spectrum band, or both.

In some examples, the wireless communication system100may be or include an LTE/LTE-A network. In LTE/LTE-A networks, the terms evolved Node B (eNB) may be generally used to describe individual ones or groups of the base stations105. The wireless communication system100may be a Heterogeneous LTE/LTE-A network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other type of cell. A macro cell may generally cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs115having service subscriptions with the network provider. A pico cell may generally cover a relatively smaller geographic area and may allow unrestricted access by UEs115with service subscriptions with the network provider. A femto cell may also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs115having an association with the femto cell (e.g., UEs115in a closed subscriber group (CSG), UEs115for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a pico cell may be referred to as a pico eNB. And, an eNB for a femto cell may be referred to as a femto eNB or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells.

The wireless communication system100according to an LTE/LTE-A network architecture may be referred to as an Evolved Packet System (EPS). An EPS may include one or more UEs115, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), an Evolved Packet Core (EPC) (e.g., core network130), a Home Subscriber Server (HSS), and an Operator's IP Services. The EPS may interconnect with other access networks using other Radio Access Technologies. For example, the EPS may interconnect with a UTRAN-based network and/or a CDMA-based network via one or more Serving GPRS Support Nodes (SGSNs). To support mobility of UEs115and/or load balancing, the EPS may support handover of UEs115between a source eNB (or base station105) and a target eNB (or base station105). The EPS may support intra-RAT handover between eNBs and/or base stations105of the same RAT (e.g., other E-UTRAN networks), and inter-RAT handovers between eNBs and/or base stations105of different RATs (e.g., E-UTRAN to CDMA, etc.). The EPS may provide packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.

The E-UTRAN may include eNBs and may provide user plane and control plane protocol terminations toward the UEs115. The eNBs and/or base stations105may be connected to other eNBs and/or base stations105via backhaul link134(e.g., an X2 interface and/or the like). The eNBs and/or base stations105may provide access points to the EPC (e.g., the core network130) for the UEs115. The eNBs and/or base stations105may be connected by backhaul link132(e.g., an S1 interface and/or the like) to the EPC. Logical nodes within the EPC may include one or more Mobility Management Entities (MMEs), one or more Serving Gateways, and one or more Packet Data Network (PDN) Gateways (not shown). Generally, the MME may provide bearer and connection management. All user IP packets may be transferred through the Serving Gateway, which itself may be connected to the PDN Gateway. The PDN Gateway may provide UE IP address allocation as well as other functions. The PDN Gateway may be connected to IP networks and/or the Operator's IP Services. These logical nodes may be implemented in separate physical nodes or one or more logical nodes may be combined in a single physical node. The IP Networks/Operator's IP Services may include the Internet, an Intranet, an IP Multimedia Subsystem (IMS), and/or a Packet-Switched (PS) Streaming Service (PSS).

UEs115and eNBs or base stations105may be configured to collaboratively communicate through, for example, Multiple Input Multiple Output (MIMO), Coordinated Multi-Point (CoMP), or other schemes. MIMO techniques use multiple antennas on a base station105and/or multiple antennas on a UE115to take advantage of multipath environments to transmit multiple data streams. CoMP includes techniques for dynamic coordination of transmission and reception by a number of eNBs and/or base stations105to improve overall transmission quality for UEs115, as well as to increase network and spectrum utilization. Generally, CoMP techniques may utilize backhaul links132and/or134for communication between base stations105to coordinate control plane and user plane communications for the UEs115.

The communication networks that may accommodate some of the various disclosed techniques may be packet-based networks that operate according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) techniques to provide retransmission at the MAC layer to ensure reliable data transmission. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between the UE and the network used for the user plane data. At the Physical layer, the transport channels may be mapped to physical channels.

The downlink physical channels may include at least one of a physical downlink control channel (PDCCH), a physical HARQ indicator channel (PHICH), and a physical downlink shared channel (PDSCH). The uplink physical channels may include at least one of a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH). The PDCCH may carry downlink control information (DCI), which may indicate data transmissions for UEs on the PDSCH as well as provide UL resource grants to UEs for the PUSCH. The UE may transmit control information in the PUCCH on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in the PUSCH on the assigned resource blocks in the data section.

LTE/LTE-A utilizes orthogonal frequency division multiple-access (OFDMA) on the downlink and single-carrier frequency division multiple-access (SC-FDMA) on the uplink. An OFDMA and/or SC-FDMA carrier may be partitioned into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, or the like. Each subcarrier may be modulated with data. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, K may be equal to 72, 180, 300, 600, 900, or 1200 with a subcarrier spacing of 15 kilohertz (KHz) for a corresponding system bandwidth (with guard band) of 1.4, 3, 5, 10, 15, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into sub-bands. For example, a sub-band may cover 1.08 MHz, and there may be 1, 2, 4, 8 or 16 sub-bands.

In some examples of the wireless communication system100, LTE/LTE-A may be deployed under different scenarios using an unlicensed radio frequency spectrum band. The deployment scenarios may include a supplemental downlink mode in which LTE/LTE-A downlink communications in a licensed radio frequency spectrum band may be offloaded to an unlicensed radio frequency spectrum band, a carrier aggregation mode in which both LTE/LTE-A downlink and uplink communications may be offloaded from a licensed radio frequency spectrum band to an unlicensed radio frequency spectrum band, and a standalone mode in which LTE/LTE-A downlink and uplink communications between an eNB and/or base station and a UE may take place in an unlicensed radio frequency spectrum band. Base stations105as well as UEs115may support one or more of these or similar modes of operation. OFDMA waveforms may be used in the communication links125for LTE/LTE-A downlink communications in the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band, while OFDMA, SC-FDMA and/or resource block interleaved FDMA waveforms may be used in the communication links125for LTE/LTE-A uplink communications in the licensed radio frequency spectrum band and/or unlicensed radio frequency spectrum band.

FIG. 2Ashows a downlink channel resource block200in which a positioning reference signal (PRS)205may be transmitted in a downlink channel, in accordance with various aspects of the present disclosure. By way of example, the downlink channel resource block200may be transmitted by one of the base stations105described with reference toFIG. 1. By way of further example, the PRS205shown inFIG. 2Amay be a PRS205mapped to antenna port6of the LTE/LTE-A New Carrier Type (NCT). The PRS205may be transmitted on one or two PBCH antenna ports.

The downlink channel resource block200includes a plurality of resource elements210. Each resource element210may correspond to one of a number of symbol periods (e.g., OFDM symbol positions215) and one of a number of frequency sub-carriers220. By way of example, the downlink channel resource block200includes resource elements spanning fourteen OFDM symbol positions (or two slots, labeled Slot0and Slot1; or one Subframe) and twelve frequency sub-carriers.

By way of further example, the PRS205may be transmitted in a set of one or more resource elements210of the downlink channel resource block200, such as, in the resource elements labeled R6.

The PRS205may have a number of configurable parameters. For example, the PRS205may have a configuration index, IPRS, mapped to the parameters TPRSand ΔPRS, where TPRSis a periodicity (e.g., 160, 320, 640, or 1280 ms) of transmissions of the PRS205, and where ΔPRSis a subframe offset (e.g., a subframe offset of 0 to 1120). The PRS205may also have configuration parameters such as a duration, NPRS; a number, M, of consecutive transmissions defining a measurement period; muting information (e.g., a muting parameter); a variable cell-specific frequency shift parameter, Vshift; a PRS bandwidth; and a number, n, of cells to measure. The duration, NPRS, may define a number of consecutive downlink subframes included in a PRS transmission (e.g., 1, 2, 4, or 6). The number of consecutive PRS transmissions defining a measurement period may depend on an intra-frequency or inter-frequency configuration of the PRS, and may in some cases be 8, 16, or 32. The muting information may mask PRS transmissions with a periodicity of 2, 4, 8, or 16. The variable cell-specific frequency shift parameter, Vshift, may in some examples be a value between 1 and 6, enabling a reuse factor of 6. The PRS bandwidth may in some examples be configured as 6, 15, 25, 50, 75, or 100 resource blocks. The number of cells to measure, n, may be any number of cells for which PRS measurements may be made.

A UE such as one of the UEs115described with reference toFIG. 1may receive a PRS such as the PRS205from one or a plurality of base stations105and/or eNBs. The UE may also receive signaling from the base stations and/or eNBs. The signaling may indicate configuration parameters for an observed time difference of arrival (OTDOA) reference cell and one or more OTDOA neighboring cells. In some examples, an OTDOA-ReferenceCell Info message may indicate configuration parameters for the OTDOA reference cell, and one or more OTDOA-NeighborCell Info messages may indicate configuration parameters for one or more OTDOA neighboring cells. The OTDOA-NeighborCell Info messages may include a slot timing offset and a PRS subframe offset between the reference cell and neighboring cells. The slot timing offset and the PRS subframe offset may be used for inter-frequency PRS transmissions, where base station and/or eNB transmission timing differences may exceed one subframe. An OTDOA-NeighborCell Info message also enables the use of PRS transmissions in inter-frequency and carrier aggregation mode scenarios.

A UE may make multiple PRS measurements and report a reference signal time difference (RSTD) for n−1 neighboring cells within a measurement period, TRSTD, from the start of an initial PRS transmission. A UE may be required to make a particular number of suitable PRS measurements (e.g., M/2 suitable measurements) within the measurement period, TRSTD, before its PRS measurements are deemed useful.

The PRS transmissions of multiple base stations and/or eNBs of a single operator may be synchronized across a same frequency to reduce interference. However, in dense deployments of base stations and/or eNBs, a base station and/or eNB may mute its PRS transmission in accordance with a muting pattern.

FIG. 2Bshows a downlink channel resource block250in which a PRS255may be transmitted in a downlink channel, in accordance with various aspects of the present disclosure. By way of example, the PRS255shown inFIG. 2Bmay be a PRS255mapped to antenna port6of the LTE/LTE-A New Carrier Type (NCT). The PRS255may be transmitted on four PBCH antenna ports.

The downlink channel resource block250includes a plurality of resource elements260. Each resource element260may correspond to one of a number of symbol periods (e.g., OFDM symbol positions265) and one of a number of frequency sub-carriers220. By way of example, the downlink channel resource block250includes resource elements spanning fourteen OFDM symbol positions (or two slots, labeled Slot0and Slot1; or one Subframe) and twelve frequency sub-carriers.

By way of further example, the PRS255may be transmitted in a set of one or more resource elements260of the downlink channel resource block250, such as, in the resource elements labeled R6. But for the locations of the resource elements260defining the PRS255, the downlink channel resource block250and PRS255may be configured similarly to the downlink channel resource block200and PRS205.

FIG. 3shows a wireless communication system300in which LTE/LTE-A is deployed under different scenarios using an unlicensed radio frequency spectrum band, in accordance with various aspects of the present disclosure. More specifically,FIG. 3illustrates examples of a supplemental downlink mode, a carrier aggregation mode, and a standalone mode in which LTE/LTE-A is deployed using an unlicensed radio frequency spectrum band. The wireless communication system300may be an example of portions of the wireless communication system100described with reference toFIG. 1. Moreover, a first base station305and a second base station305-amay be examples of aspects of one or more of the base stations105described with reference toFIG. 1, while a first UE315, a second UE315-a, a third UE315-b, and a fourth UE315-cmay be examples of aspects of one or more of the UEs115described with reference toFIG. 1.

In the example of a supplemental downlink mode in the wireless communication system300, the first base station305may transmit OFDMA waveforms to the first UE315using a downlink channel320. The downlink channel320may be associated with a frequency F1in an unlicensed radio frequency spectrum band. The first base station305may transmit OFDMA waveforms to the first UE315using a first bidirectional link325and may receive SC-FDMA waveforms from the first UE315using the first bidirectional link325. The first bidirectional link325may be associated with a frequency F4in a licensed radio frequency spectrum band. The downlink channel320in the unlicensed radio frequency spectrum band and the first bidirectional link325in the licensed radio frequency spectrum band may operate concurrently. The downlink channel320may provide a downlink capacity offload for the first base station305. In some examples, the downlink channel320may be used for unicast services (e.g., addressed to one UE) or for multicast services (e.g., addressed to several UEs). This scenario may occur with any service provider (e.g., an MNO) that uses a licensed radio frequency spectrum band and needs to relieve some of the traffic and/or signaling congestion.

In one example of a carrier aggregation mode in the wireless communication system300, the first base station305may transmit OFDMA waveforms to the second UE315-ausing a second bidirectional link330and may receive OFDMA waveforms, SC-FDMA waveforms, and/or resource block interleaved FDMA waveforms from the second UE315-ausing the second bidirectional link330. The second bidirectional link330may be associated with the frequency F1in the unlicensed radio frequency spectrum band. The first base station305may also transmit OFDMA waveforms to the second UE315-ausing a third bidirectional link335and may receive SC-FDMA waveforms from the second UE315-ausing the third bidirectional link335. The third bidirectional link335may be associated with a frequency F2in a licensed radio frequency spectrum band. The second bidirectional link330may provide a downlink and uplink capacity offload for the first base station305. Like the supplemental downlink described above, this scenario may occur with any service provider (e.g., MNO) that uses a licensed radio frequency spectrum and needs to relieve some of the traffic and/or signaling congestion.

In another example of a carrier aggregation mode in the wireless communication system300, the first base station305may transmit OFDMA waveforms to the third UE315-busing a fourth bidirectional link340and may receive OFDMA waveforms, SC-FDMA waveforms, and/or resource block interleaved waveforms from the third UE315-busing the fourth bidirectional link340. The fourth bidirectional link340may be associated with a frequency F3in the unlicensed radio frequency spectrum band. The first base station305may also transmit OFDMA waveforms to the third UE315-busing a fifth bidirectional link345and may receive SC-FDMA waveforms from the third UE315-busing the fifth bidirectional link345. The fifth bidirectional link345may be associated with the frequency F2in the licensed radio frequency spectrum band. The fourth bidirectional link340may provide a downlink and uplink capacity offload for the first base station305. This example and those provided above are presented for illustrative purposes and there may be other similar modes of operation or deployment scenarios that combine LTE/LTE-A in a licensed radio frequency spectrum band and an unlicensed radio frequency spectrum band for capacity offload.

As described above, one type of service provider that may benefit from the capacity offload offered by using LTE/LTE-A in an unlicensed radio frequency spectrum band is a traditional MNO having access rights to an LTE/LTE-A licensed radio frequency spectrum band. For these service providers, an operational example may include a bootstrapped mode (e.g., supplemental downlink, carrier aggregation) that uses the LTE/LTE-A primary component carrier (PCC) on the licensed radio frequency spectrum band and at least one secondary component carrier (SCC) on the unlicensed radio frequency spectrum band.

In the carrier aggregation mode, data and control may, for example, be communicated in the licensed radio frequency spectrum band (e.g., via first bidirectional link325, third bidirectional link335, and fifth bidirectional link345) while data may, for example, be communicated in the unlicensed radio frequency spectrum band (e.g., via second bidirectional link330and fourth bidirectional link340). The carrier aggregation mechanisms supported when using an unlicensed radio frequency spectrum band may fall under a hybrid frequency division duplexing-time division duplexing (FDD-TDD) carrier aggregation or a TDD-TDD carrier aggregation with different symmetry across component carriers.

In one example of a standalone mode in the wireless communication system300, the second base station305-amay transmit OFDMA waveforms to the fourth UE315-cusing a bidirectional link350and may receive OFDMA waveforms, SC-FDMA waveforms, and/or resource block interleaved FDMA waveforms from the fourth UE315-cusing the bidirectional link350. The bidirectional link350may be associated with the frequency F3in an unlicensed radio frequency spectrum band. The standalone mode may be used in non-traditional wireless access scenarios, such as in-stadium access (e.g., unicast, multicast). An example of a type of service provider for this mode of operation may be a stadium owner, cable company, event host, hotel, enterprise, or large corporation that does not have access to a licensed radio frequency spectrum band.

In some examples, a transmitting apparatus such as one of the base stations105and/or305described with reference toFIG. 1 and/or 3, and/or one of the UEs115and/or315described with reference toFIG. 1 and/or 3, may use a gating interval to gain access to a channel of an unlicensed radio frequency spectrum band (e.g., to a physical channel of the unlicensed radio frequency spectrum band). The gating interval may define the application of a contention-based protocol, such as an LBT protocol based on the LBT protocol specified in ETSI (EN 301 893). When using a gating interval that defines the application of an LBT protocol, the gating interval may indicate when a transmitting apparatus needs to perform a CCA. The outcome of the CCA may indicate to the transmitting device whether a channel of an unlicensed radio frequency spectrum band is available or in use for the gating interval (also referred to as an LBT frame, a CCA frame, or simply a frame). When a CCA indicates that the channel is available (e.g., “clear” for use) for a corresponding LBT frame, the transmitting apparatus may reserve and/or use the channel of the unlicensed radio frequency spectrum band during part or all of the LBT frame. When the CCA indicates that the channel is not available (e.g., that the channel is in use or reserved by another apparatus), the transmitting apparatus may be prevented from using the channel during the LBT frame.

In some cases, it may be useful for a transmitting apparatus to generate a gating interval on a periodic basis and synchronize at least one boundary of the gating interval with at least one boundary of a periodic frame structure. For example, it may be useful to generate a periodic gating interval for a cellular downlink in an unlicensed radio frequency spectrum band, and to synchronize at least one boundary of the periodic gating interval with at least one boundary of a periodic frame structure (e.g., a periodic LTE/LTE-A radio frame structure) associated with the cellular downlink. Examples of such synchronization are shown inFIG. 4.

FIG. 4shows an example400of a wireless communication410over an unlicensed radio frequency spectrum band, in accordance with various aspects of the present disclosure. By way of example, a CCA frame415, which may correspond to a periodic gating interval, may have a duration of 10 milliseconds and include a number of downlink subframes420, a number of uplink subframes425, and two types of special subframes, an S subframe430and an S′ subframe435. The S subframe430may provide a transition between downlink subframes420and uplink subframes425, while the S′ subframe435may provide a transition between uplink subframes425and downlink subframes420. During the S′ subframe435, a downlink clear channel assessment (DCCA)440may be performed by one or more base stations, such as one or more of the base stations105and/or305described with reference toFIG. 1 and/or 3, to contend for access to an unlicensed radio frequency spectrum band, for a period of time, the channel over which the wireless communication410occurs. Following a successful DCCA440by a base station, a base station may transmit a signal (e.g., a channel usage beacon signal (CUBS)445) to provide an indication to other base stations and/or apparatuses that the base station has reserved the channel.

The S′ subframe435may include 14 OFDM symbols, numbered0through13inFIG. 4. A first portion of the S′ subframe435, symbols0through5in this example, may be used by base stations as a silent DL period, which may be required for compatibility with LTE/LTE-A communication standards. Thus, a base station may not transmit data during the silent DL period, although a UE may transmit some amount of uplink data during the silent DL period. A second portion of the S′ subframe435may be used for a DCCA440. In the example400, the S′ subframe435includes seven DCCA slots, included in symbols6through12. Use of the DCCA slots by different network operators may be coordinated to provide more efficient system operation. In some examples, in order to determine which of the seven possible DCCA slots to use to perform a DCCA procedure, a base station105may evaluate a mapping-function of the form:
FD(GroupID,t)ε{1,2,3,4,5,6,7}
where GroupID is a “deployment group-id” assigned to the base station105, and t is the LBT frame number corresponding to a gating interval or frame for which DCCA is performed.

The CCA frame415described with reference toFIG. 4is configured as a time division duplexing (TDD) frame having both downlink subframes and uplink subframes. The techniques described herein may be employed with any number of variations of TDD frame (e.g., TDD frames having different numbers and/or arrangements of downlink subframes and uplink subframes), as well as downlink-only frame configurations.

FIG. 5shows an example500of CCA Exempt Transmissions (CETs)505, in accordance with various aspects of the present disclosure. As shown, an allocation of resources for CETs may be made, for example, once every eighty milliseconds (80 ms) or once every CET period, where the CET period may have a configurable periodicity. Each of a number of operators in the unlicensed radio frequency spectrum band (e.g., different PLMNs) may be provided a separate subframe (shown) or subframes (not shown) for transmitting CETs. By way of example,FIG. 5shows adjacent CET subframes for seven different operators (e.g., operators PLMN1, PLMN2, . . . , PLMN7). Such a structure may be applicable to both downlink and uplink subframes.

FIG. 6shows an example600of how a PRS may be configured for transmission adjacent a CET605, in accordance with various aspects of the present disclosure. More particularly,FIG. 6shows a sequence of subframes (e.g., subframe SF0to subframe SF9) transmitted by a first base station and a sequence of subframes (e.g., subframe SF0-ato subframe SF9-a) transmitted by a second base station.

The first base station and the second base station may in some examples be synchronized with respect to transmission of a CET605(e.g., a CET605-aof the first base station may be synchronized with a CET605-bof the second base station). The first base station may transmit a PRS adjacent the CET605-a. In one example, a PRS may be transmitted before the CET605-aas PRS_A610, transmitted in subframe SF5. In another example, a PRS may be transmitted after the CET605-aas PRS_B615, transmitted in subframe SF7. In other examples, one or more PRS may be transmitted before and after the CET605-aas PRS_A610, transmitted in subframe SF5, and as PRS_B615, transmitted in subframe SF7. Similarly, the second base station may transmit a PRS adjacent the CET605-b. In one example, a PRS may be transmitted before the CET605-bas PRS_C620, transmitted in subframe SF5-a. In another example, a PRS may be transmitted after the CET605-bas PRS_D625, transmitted in subframe SF7-a. In other examples, one or more PRS may be transmitted before and after the CET605-bas PRS_C620, transmitted in subframe SF5-a, and as PRS_D625, transmitted in subframe SF7-a.

In an example, the first base station and the second base station may be configured to transmit PRS at a same time and/or a same location (e.g., relative to the CETs605-aand605-b). In a first mode of operation, the first base station may transmit a PRS as PRS_A610and the second base station may transmit a PRS as PRS_C620, thereby time synchronizing and/or location synchronizing (e.g., before the CETs605-aand605-b) the PRS transmissions of the first base station and the second base station. In a second mode of operation, the first base station may transmit a PRS as PRS_B615and the second base station may transmit a PRS as PRS_D625, thereby time synchronizing and/or location synchronizing (e.g., after the CETs605-aand605-b) the PRS transmissions of the first base station and the second base station. In another example, the first base station and the second base station may be configured to transmit PRS at different times and/or different locations (e.g., relative to the CETs605-aand605-b). In a third mode of operation, the first base station may transmit a PRS as PRS_A610and the second base station may transmit a PRS as PRS_D625, thereby varying times and/or varying locations of the PRS transmissions of the first base station and the second base station. In a fourth mode of operation, the first base station may transmit a PRS as PRS_B615and the second base station may transmit a PRS as PRS_C620, thereby varying times and/or varying locations of the PRS transmissions of the first base station and the second base station. In the third and fourth modes of operation, the PRS transmissions of the first base station and the second base station are offset by a known offset (e.g., the length of the CET605). In other modes of operation, the PRS transmission of the first base station and/or the second base station may be transmitted in more than one subframe (e.g., in one to K subframes). In all of the modes of operation described in this paragraph, a PRS may be transmitted adjacent a CET. Transmitting a PRS contiguous with a CET may ensure that the PRS transmission is able to leverage the CCA exemption of the CET, particularly when the combined duration of the PRS and the CET do not exceed a maximum duration of the CET (e.g., five percent of the transmission time every fifty milliseconds).

The first base station and/or the second base station may be configured to transmit at a same or different periodicities. In some examples, a first periodicity of a PRS transmission by the first base station may be the same as a second periodicity of a PRS transmission by the second base station. When the first periodicity of the PRS transmission by the first base station is the same as the second periodicity of the PRS transmission by the second base station, the first base station and the second base station may be configured to transmit their respective PRS transmissions with a periodicity that is a multiple, J, of a CET transmission periodicity. When J=1, the periodicity at which the first base station and the second base station transmit their respective PRS transmissions may be the same as the CET transmission periodicity. When J>1, the periodicity at which the first base station and the second base station transmit their respective PRS transmissions may differ from the CET transmission periodicity. In some examples, J may be an integer from one to sixteen. In some examples, J may be configurable (e.g., changed) over time. When the first periodicity of the PRS transmission by the first base station is the same as the second periodicity of the PRS transmission by the second base station, and when J>1, the first base station and the second base station may be configured to transmit their respective PRS transmissions at a same or different phase. Thus, in one example, a first phase of the PRS transmission by the first base station may be the same as (e.g., time-synchronized with) a second phase of the PRS transmission by the second base station. In another example, the first phase of the PRS transmission by the first base station may be different (e.g., offset) from the second phase of the PRS transmission by the second base station. When the first base station and the second base station are configured to use different values of J, the first periodicity of the PRS transmission by the first base station may differ from the second periodicity of the PRS transmission by the second base station.

Turning now to the transmission of a PRS in an unlicensed radio frequency spectrum band for which there is a requirement that certain communications (e.g., LTE/LTE-A communications in the unlicensed radio frequency spectrum band) occupy at least a certain percentage of the available frequency bandwidth (e.g., at least 80% of the available frequency bandwidth),FIG. 7shows an example700of how a PRS may be transmitted using a plurality of interleaved resource blocks, such as a first resource block705, a second resource block710, a third resource block715, and a fourth resource block720, in accordance with various aspects of the present disclosure. The first resource block705, the second resource block710, the third resource block715, and the fourth resource block720may span at least a certain percentage of the available frequency bandwidth725of a subframe730, so that transmissions using the first resource block705, the second resource block710, the third resource block715, and the fourth resource block720occupy at least a required percentage of the frequency bandwidth.

In some examples, a PRS may be transmitted such that the PRS occupies each of the first resource block705, the second resource block710, the third resource block715, and the fourth resource block720, thereby satisfying the requirement that at least a certain percentage of the available frequency bandwidth be occupied. In other examples, a PRS may be transmitted such that the PRS occupies a portion of the unlicensed radio frequency spectrum band, which portion is less than all of the unlicensed radio frequency spectrum band. In the event that a PRS may occupy a portion (e.g., less than all) of the unlicensed radio frequency spectrum band, other signals may be transmitted with the PRS to satisfy the requirement that at least a certain percentage of the available frequency bandwidth be occupied. For example, the PRS may occupy the second resource block710and the third resource block715, and other downlink signals may be transmitted in the first resource block705and the fourth resource block720, in conjunction with the PRS.

FIG. 8shows an example800of how a PRS850may be configured for transmission in at least one downlink (D) subframe of a CCA frame815, in accordance with various aspects of the present disclosure. More particularly,FIG. 8shows a wireless communication810over an unlicensed radio frequency spectrum band, in which a CCA frame815corresponding to a periodic gating interval may have a duration of 10 milliseconds and include a number of downlink (D) subframes820and a special (S′) subframe835. During the S′ subframe835, a downlink clear channel assessment (DCCA)840may be performed by one or more base stations, such as one or more of the base stations105and/or305described with reference toFIG. 1 and/or 3, to reserve, for a period of time, the channel over which the wireless communication810occurs. Following a successful DCCA840by a base station, a base station may transmit a channel usage beacon signal (CUBS)845to provide an indication to other base stations and/or apparatuses that the base station has won contention to access the channel of the unlicensed radio frequency spectrum band.

In some examples, the PRS850may be configured for transmission in one or more of the downlink (D) subframes820, such as, in subframes SF2and SF3. However, when the DCCA840performed by a base station is not successful, the base station may not gain access to the CCA frame815, and the PRS850may not be transmitted. Thus, in the case of DCCA failure, the PRS850would not be transmitted, and a receiver (e.g., a UE) would not be able to perform a PRS measurement based at least partly on the PRS850.

FIG. 9shows a block diagram900of an apparatus905for use in wireless communication, in accordance with various aspects of the present disclosure. In some examples, the apparatus905may be an example of aspects of one or more of the base stations105,305, and/or305-adescribed with reference toFIG. 1 and/or 3. The apparatus905may also be a processor. The apparatus905may include a receiver module910, a wireless communication management module920, and/or a transmitter module930. Each of these components may be in communication with each other.

In some examples, the receiver module910may include at least one radio frequency (RF) receiver, such as at least one RF receiver operable to receive transmissions over a licensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses do not contend for access because the radio frequency spectrum band is licensed to particular users for particular uses) and/or an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use). In some examples, the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band may be used for LTE/LTE-A communications, as described, for example, with reference toFIG. 1 and/or 3. The receiver module910may be used to receive various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the transmitter module930may include at least one RF transmitter, such as at least one RF transmitter operable to transmit over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band. The transmitter module930may be used to transmit various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the wireless communication management module920may be used to manage one or more aspects of wireless communication for the apparatus905. In some examples, the wireless communication management module920may include a PRS generation module, a PRS configuration module940, and/or a PRS transmission module945.

In some examples, the PRS generation module935may be used to generate a PRS. The PRS may in some examples include a number of tones.

In some examples, the PRS configuration module940may be used to configure the PRS in at least one downlink subframe among a plurality of downlink subframes.

In some examples, the PRS transmission module945may be used to transmit the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band.

FIG. 10shows a block diagram1000of an apparatus1005for use in wireless communication, in accordance with various aspects of the present disclosure. In some examples, the apparatus1005may be an example of aspects of one or more of the base stations105,305, and/or305-adescribed with reference toFIG. 1 and/or 3, and/or an example of aspects of the apparatus905described with reference toFIG. 9. The apparatus1005may also be a processor. The apparatus1005may include a receiver module1010, a wireless communication management module1020, and/or a transmitter module1030. Each of these components may be in communication with each other.

In some examples, the receiver module1010may include at least one RF receiver, such as at least one RF receiver operable to receive transmissions over licensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses do not contend for access because the radio frequency spectrum band is licensed to particular users for particular uses) and/or an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use). In some examples, the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band may be used for LTE/LTE-A communications, as described, for example, with reference toFIG. 1 and/or 3. The receiver module1010may in some cases include separate receivers for the licensed radio frequency spectrum band and the unlicensed radio frequency spectrum band. The separate receivers may, in some examples, take the form of a licensed RF spectrum band LTE/LTE-A receiver module1012for communicating over the licensed radio frequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-A receiver module1014for communicating over the unlicensed radio frequency spectrum band. The receiver module1010, including the licensed RF spectrum band LTE/LTE-A receiver module1012and/or the unlicensed RF spectrum band LTE/LTE-A receiver module1014, may be used to receive various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the transmitter module1030may include at least one RF transmitter, such as at least one RF transmitter operable to transmit over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band. The transmitter module1030may in some cases include separate transmitters for the licensed radio frequency spectrum band and the unlicensed radio frequency spectrum band. The separate transmitters may, in some examples, take the form of a licensed RF spectrum band LTE/LTE-A transmitter module1032for communicating over the licensed radio frequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-A transmitter module1034for communicating over the unlicensed radio frequency spectrum band. The transmitter module1030, including the licensed RF spectrum band LTE/LTE-A transmitter module1032and/or the unlicensed RF spectrum band LTE/LTE-A transmitter module1034, may be used to transmit various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the wireless communication management module1020may be an example of one or more aspects of the wireless communication management module920described with reference toFIG. 9. The wireless communication management module1020may include a PRS generation module1035, a PRS configuration module1040, a PRS configuration signaling module1055, and/or a PRS transmission module1060. Each of these components may be in communication with each other.

In some examples, the PRS generation module1035may be used to generate a PRS. The PRS may in some examples include a number of tones.

In some examples, the PRS configuration module1040may be an example of the PRS configuration module940described with reference toFIG. 9and may include a PRS duration configuration module1045and/or a PRS periodicity configuration module1050. The PRS configuration module1040may be used to configure the PRS in at least one downlink subframe among a plurality of downlink subframes. The configuring may include configuring the PRS to be adjacent a CET. In another example, the configuring may include configuring the PRS to be a portion of a signal (e.g., a portion of a CCA frame).

In some examples, the PRS duration configuration module1045may be used to configure a duration of the PRS. In some examples, the PRS may be configured in units of downlink subframes and be configured to have a duration of one to K downlink subframes. In some examples, the PRS duration configuration module1045may configure a combined duration of the PRS and the CET to be less than a maximum allowed duration of the CET. In some examples, the maximum allowed duration of the CET may be a percentage of the Transmit On (Tx-ON) during a defined period of time.

In some examples, the PRS periodicity configuration module1050may be used to configure a periodicity and/or phase offset for transmitting the PRS adjacent the CET. In some examples, the PRS periodicity configuration module1050may configure a first periodicity of transmitting the PRS adjacent the CET to be the same as a second periodicity at which the CET is transmitted (e.g., the PRS may be transmitted every time the CET is transmitted). In other examples, the PRS periodicity configuration module1050may configure a first periodicity of transmitting the PRS adjacent the CET to differ from a second periodicity at which the CET is transmitted (e.g., the PRS may not be transmitted every time the CET is transmitted, but may be transmitted every J CETs, where the value of J is configurable). In these latter examples, the PRS periodicity configuration module1050may also configure a phase offset for transmitting the PRS adjacent the CET. In some cases, a first phase offset used by a first transmitter (e.g., a first base station) to transmit the PRS adjacent the CET may differ from a second phase offset used by a second transmitter (e.g., a second base station) to transmit the PRS adjacent the CET. The first periodicity may be a variable periodicity and the first phase offset may be a variable phase offset, such that the first transmitter may configure a periodicity and phase offset that are useful to the first transmitter and/or its receivers, and/or configure a periodicity and/or phase offset that are the same or different from a periodicity and/or phase offset used by another transmitter (e.g., the second transmitter). Other configurations of periodicity and/or phase offset that may be made by the PRS periodicity configuration module1050are described with reference toFIG. 6.

In some examples, the PRS periodicity configuration module1050may also or alternately be used to configure a muting parameter and/or a variable cell-specific frequency shift parameter associated with a PRS transmission.

In some examples, the PRS configuration signaling module1055may be used to signal to a receiver (e.g., a UE) various parameters associated with PRS transmissions. For example, the PRS configuration signaling module1055may be used to signal to a receiver a timing of transmitting the PRS adjacent the CET (e.g., a timing of transmitting an impending transmission of the PRS adjacent the CET).

In some examples, the PRS transmission module1060may be an example of the PRS transmission module945described with reference toFIG. 9and may be used to transmit the PRS adjacent the CET in the at least one downlink subframe using the unlicensed RF spectrum band LTE/LTE-A transmitter module1034and the unlicensed radio frequency spectrum band. In some examples, the PRS may be transmitted contiguously with the CET (e.g., with no transmission gaps between at least one downlink subframe in which the PRS is transmitted and at least one downlink subframe in which the CET is transmitted). In some examples, the PRS transmission module1060may periodically transmit the PRS adjacent the CET by periodically transmitting the PRS adjacent the CET according to the first periodicity and the first phase offset configured by the PRS periodicity configuration module1050.

Configuring the PRS to be adjacent a CET may enable the PRS to leverage the CET property of guaranteed transmission over the unlicensed radio frequency spectrum band. In some examples, the PRS transmission module1060may transmit the PRS before the CET. In other examples, the PRS transmission module1060may transmit the PRS after the CET.

In some examples, PRS transmission module1060may be used to transmit the PRS such that the PRS occupies a portion of the unlicensed radio frequency spectrum band, which portion is less than all of the unlicensed radio frequency spectrum band. In these examples, other downlink signals may be transmitted in conjunction with the PRS. The other downlink signals may in some cases be transmitted to meet unlicensed spectrum bandwidth usage requirements, as described with reference toFIG. 7.

In some examples, the PRS transmission module1060may transmit the PRS across a plurality of frequencies of the unlicensed radio frequency spectrum band, as may be useful in an inter-frequency and/or carrier aggregation transmission scenario. When the relative PRS transmission timing across the plurality of frequencies may be unknown, the PRS configuration signaling module1055may be used to signal, to a receiver (e.g., a UE), a timing offset indicating the relative PRS transmission timing across the plurality of frequencies.

In some examples, a plurality of apparatus1005may transmit a PRS. In such examples, various PRS transmission scenarios are possible. In a first example, the transmission of a PRS by the apparatus1005may be time synchronized with a transmission of at least a second PRS by at least a second apparatus (e.g., at least two apparatuses may transmit a PRS at the same time, in a same one or more downlink subframes). In a second example, a PRS transmitted by the apparatus1005may be transmitted before a CET, while at least a second PRS may be transmitted by a second apparatus after a CET. Alternately, a PRS transmitted by the apparatus1005may be transmitted after a CET, while at least a second PRS may be transmitted by a second apparatus before a CET. In either alternative, each PRS may be transmitted adjacent a CET. In a third example, a PRS transmitted by the apparatus1005may be transmitted with a same periodicity as, and a different phase offset than, a transmission of at least a second PRS transmitted by at least a second apparatus. In a fourth example, a PRS transmitted by the apparatus1005may be transmitted with a different periodicity than a transmission of at least a second PRS transmitted by at least a second apparatus. In a fifth example, a PRS transmitted by the apparatus1005may be associated with a muting parameter and/or a variable cell-specific frequency shift parameter, which muting parameter and/or variable cell-specific frequency shift parameter may be the same as, or different from, a muting parameter and/or a variable cell-specific frequency shift parameter associated with a transmission of at least a second PRS by at least a second apparatus. In a sixth example, a PRS may be transmitted by the apparatus1005in accordance with a combination of two or more of the preceding examples.

FIG. 11shows a block diagram1100of an apparatus1105for use in wireless communication, in accordance with various aspects of the present disclosure. In some examples, the apparatus1105may be an example of aspects of one or more of the base stations105,305, and/or305-adescribed with reference toFIG. 1 and/or 3, and/or an example of aspects of the apparatus905described with reference toFIG. 9. The apparatus1105may also be a processor. The apparatus1105may include a receiver module1110, a wireless communication management module1120, and/or a transmitter module1130. Each of these components may be in communication with each other.

In some examples, the receiver module1110may include at least one RF receiver, such as at least one RF receiver operable to receive transmissions over licensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses do not contend for access because the radio frequency spectrum band is licensed to particular users for particular uses) and/or an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use). In some examples, the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band may be used for LTE/LTE-A communications, as described, for example, with reference toFIG. 1 and/or 3. The receiver module1110may in some cases include separate receivers for the licensed radio frequency spectrum band and the unlicensed radio frequency spectrum band. The separate receivers may, in some examples, take the form of a licensed RF spectrum band LTE/LTE-A receiver module1112for communicating over the licensed radio frequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-A receiver module1114for communicating over the unlicensed radio frequency spectrum band. The receiver module1110, including the licensed RF spectrum band LTE/LTE-A receiver module1112and/or the unlicensed RF spectrum band LTE/LTE-A receiver module1114, may be used to receive various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the transmitter module1130may include at least one RF transmitter, such as at least one RF transmitter operable to transmit over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band. The transmitter module1130may in some cases include separate transmitters for the licensed radio frequency spectrum band and the unlicensed radio frequency spectrum band. The separate transmitters may, in some examples, take the form of a licensed RF spectrum band LTE/LTE-A transmitter module1132for communicating over the licensed radio frequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-A transmitter module1134for communicating over the unlicensed radio frequency spectrum band. The transmitter module1130, including the licensed RF spectrum band LTE/LTE-A transmitter module1132and/or the unlicensed RF spectrum band LTE/LTE-A transmitter module1134, may be used to transmit various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the wireless communication management module1120may be an example of one or more aspects of the wireless communication management module920described with reference toFIG. 9. The wireless communication management module1120may include a PRS generation module1135, a PRS configuration module1140, a CCA module1155, a PRS transmission module1160, a CCA clearance statistics analysis module1165, and/or a PRS measurement configuration module1170. Each of these components may be in communication with each other.

In some examples, the PRS generation module1135may be used to generate a PRS. The PRS may in some examples include a number of tones.

In some examples, the PRS configuration module1140may be an example of the PRS configuration module940described with reference toFIG. 9and may include a PRS duration configuration module1145and/or a PRS periodicity configuration module1150. The PRS configuration module1140may be used to configure the PRS in at least one downlink subframe among a plurality of downlink subframes of a CCA frame. The PRS configuration module1140may also configure PRS configuration parameters such as those that are currently used to configure a PRS in at least one downlink subframe of a licensed radio frequency spectrum band (e.g., duration, periodicity, number of consecutive transmissions defining a measurement period, etc., as described, for example, with reference toFIG. 2A and/or 2B). However, as discussed below, CCA failures may interfere with a strict implementation of some PRS configuration parameters.

In some examples, the PRS duration configuration module1145may be used to configure a duration of the PRS. In some examples, the PRS may be configured in units of downlink subframes and be configured to have a duration of one to K downlink subframes.

In some examples, the PRS periodicity configuration module1150may be used to configure a periodicity and/or phase offset for transmitting the PRS. In some cases, the PRS periodicity configuration module1150may be used to configure a first phase offset used by the apparatus1105to transmit the PRS, which first phase offset may differ from a second phase offset used by a second apparatus (e.g., a second base station) to transmit the PRS. The first periodicity may be a variable periodicity and the first phase offset may be a variable phase offset, such that the first transmitter may configure a periodicity and phase offset that are useful to the first transmitter and/or its receivers, and/or configure a periodicity and/or phase offset that are the same or different from a periodicity and/or phase offset used by another transmitter (e.g., the second transmitter).

In some examples, the CCA module1155may be used to perform a CCA procedure to contend for access to an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use) for a period of time (e.g., a frame).

In some examples, the PRS transmission module1160may be an example of the PRS transmission module945described with reference toFIG. 9and may be used to transmit the PRS in at least one downlink subframe of a frame for which a CCA was successfully performed by the CCA module1155. However, for a frame of the unlicensed radio frequency spectrum band for which a CCA procedure performed by the CCA module1155failed, the PRS transmission module1160may gate off a transmission of the PRS.

In some examples, the PRS transmission module1160may be used to transmit the PRS such that the PRS occupies a portion of the unlicensed radio frequency spectrum band, which portion is less than all of the unlicensed radio frequency spectrum band. In these examples, other downlink signals may be transmitted in conjunction with the PRS. The other downlink signals may in some cases be transmitted to meet unlicensed spectrum bandwidth usage requirements, as described with reference toFIG. 7.

In some examples, the PRS transmission module1160may be used to transmit the PRS across a plurality of frequencies of the unlicensed radio frequency spectrum band, as may be useful in an inter-frequency and/or carrier aggregation transmission scenario. When the relative PRS transmission timing across the plurality of frequencies may be unknown, the wireless communication management module1120may be used to signal, to a receiver (e.g., a UE), a timing offset indicating the relative PRS transmission timing across the plurality of frequencies.

In some examples, the CCA clearance statistics analysis module1165may be used to receive at least one CCA clearance statistic related to at least one PRS measurement. The at least one CCA clearance statistic may be received, in some examples, from at least one receiver (e.g., at least one UE) and/or at least one transmitter (e.g., at least one base station and/or eNB).

In some examples, a receiver of PRS transmissions may perform a number of suitable PRS measurements (e.g., M/2 suitable measurements) within a measurement period before its PRS measurements are deemed useful. This suitable PRS measurement requirement may be met by a receiver performing PRS measurements on the PRS transmissions of one or more transmitters (e.g., one or more base stations and/or eNBs). However, when one or more transmitters fail one or more CCA procedures for frames in which PRS transmissions are to be transmitted, the PRS transmissions are not transmitted and, therefore, a receiver (e.g., a UE) cannot make a suitable PRS measurement for that frame. There may also be instances in which signal interference renders a PRS transmission unusable for measurement purposes. As a result, a PRS transmission in a frame for which a CCA procedure needs to be performed increases the likelihood that a receiver will fail the M/2 suitable PRS measurements requirement. To increase the probability that a receiver will pass the M/2 suitable PRS measurements requirement, a receiver may identify frames for which a CCA procedure failed and determine CCA clearance statistics for reporting back to the network (e.g., to a serving cell of a base station and/or eNB). The CCA clearance statistics may be reported, for example, via RSTD measurement results and/or error reporting results. Transmitters (e.g., base stations and/or eNBs) may also identify frames for which a CCA procedure failed and determine CCA clearance statistics for reporting to other transmitters. Any or all of these CCA clearance statistics may be analyzed, in some examples, by the CCA clearance statistics analysis module1165.

In some examples, the PRS measurement configuration module1170may be used to determine whether an attempt to transmit at least M PRS signals during a measurement period has been made. If not, the PRS measurement configuration module1170may cause the CCA module1155to perform a CCA procedure for a next frame of the unlicensed radio frequency spectrum band in which a PRS is to be transmitted. An attempt to transmit a PRS may in some cases correspond to performing a CCA procedure for a frame of the unlicensed radio frequency spectrum band in which a PRS is to be transmitted (regardless of whether the CCA procedure fails).

In some examples, the PRS measurement configuration module1170may be used to determine whether at least one additional PRS measurement is needed, based at least in part on at least one CCA clearance statistic related to at least one PRS measurement. The PRS measurement configuration module1170may also be used, when needed, to configure transmissions of a PRS based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement (e.g., to increase a number of PRS transmissions within a measurement period), and/or to configure the at least one additional PRS measurement based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement.

Various parameters may be configured based at least in part on the at least one CCA clearance statistic. In some examples, the number of PRS transmissions may be increased while maintaining, for example, an M/2 suitable measurements requirement for PRS measurements to be deemed useful. In these examples, the greater number of PRS transmissions may increase the likelihood that a receiver will be able to meet the M/2 suitable measurements requirement. Changes in other configuration parameters (e.g., PRS duration) may also be made to increase the likelihood that a receiver will be able to meet the M/2 suitable measurements requirement.

After the PRS measurement configuration module1170changes one or more configuration parameters associated with PRS transmissions, a receiver may be requested (e.g., via the apparatus1105) to redo its PRS measurements and/or make additional PRS measurements. In the latter case, and by way of example, the PRS measurement configuration module1170may schedule additional PRS measurements for a receiver, but indicate to the receiver that prior PRS measurements may be used (or are to be used) in a cumulative manner in formulating an RSTD result.

FIG. 12shows a block diagram1200of an apparatus1205for use in wireless communication, in accordance with various aspects of the present disclosure. In some examples, the apparatus1205may be an example of aspects of one or more of the base stations105,305, and/or305-adescribed with reference toFIG. 1 and/or 3, and/or an example of aspects of the apparatus905described with reference toFIG. 9. The apparatus1205may also be a processor. The apparatus1205may include a receiver module1210, a wireless communication management module1220, and/or a transmitter module1230. Each of these components may be in communication with each other.

In environments where the locations of PRS transmitters are not known, PRS measurements may not be usable to determine the position of a receiver by conventional triangulation. The apparatus1205may be used to determine the position of a receiver in such environments. The apparatus1205may be useful in environments in which a receiver operates in a standalone mode with respect to an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use).

In some examples, the receiver module1210may include at least one RF receiver, such as at least one RF receiver operable to receive transmissions over licensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses do not contend for access because the radio frequency spectrum band is licensed to particular users for particular uses) and/or an unlicensed radio frequency spectrum band. In some examples, the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band may be used for LTE/LTE-A communications, as described, for example, with reference toFIG. 1 and/or 3. The receiver module1210may in some cases include separate receivers for the licensed radio frequency spectrum band and the unlicensed radio frequency spectrum band. The separate receivers may, in some examples, take the form of a licensed RF spectrum band LTE/LTE-A receiver module1212for communicating over the licensed radio frequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-A receiver module1214for communicating over the unlicensed radio frequency spectrum band. The receiver module1210, including the licensed RF spectrum band LTE/LTE-A receiver module1212and/or the unlicensed RF spectrum band LTE/LTE-A receiver module1214, may be used to receive various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the transmitter module1230may include at least one RF transmitter, such as at least one RF transmitter operable to transmit over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band. The transmitter module1230may in some cases include separate transmitters for the licensed radio frequency spectrum band and the unlicensed radio frequency spectrum band. The separate transmitters may, in some examples, take the form of a licensed RF spectrum band LTE/LTE-A transmitter module1232for communicating over the licensed radio frequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-A transmitter module1234for communicating over the unlicensed radio frequency spectrum band. The transmitter module1230, including the licensed RF spectrum band LTE/LTE-A transmitter module1232and/or the unlicensed RF spectrum band LTE/LTE-A transmitter module1234, may be used to transmit various types of data and/or control signals (i.e., transmissions) over one or more communication links of a wireless communication system, such as one or more communication links of the wireless communication system100and/or300described with reference toFIG. 1 and/or 3. The communication links may be established over the licensed radio frequency spectrum band and/or the unlicensed radio frequency spectrum band.

In some examples, the wireless communication management module1220may be an example of one or more aspects of the wireless communication management module920described with reference toFIG. 9. The wireless communication management module1220may include a PRS generation module1235, a PRS configuration module1240, a PRS transmission module1245, a known location measurement collection module1250, a measurement storing/indexing module1255, a measurement analysis module1260, and/or a position estimation module1265. Each of these components may be in communication with each other.

In some examples, the PRS generation module1235may be used to generate a PRS. The PRS may in some examples include a number of tones.

In some examples, the PRS configuration module1240may be used to configure the PRS in at least one downlink subframe among a plurality of downlink subframes.

In some examples, the PRS transmission module1245may be used to transmit the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band.

In some examples, the known location measurement collection module1250may be used to receive a set of RSTD measurements collected for each of a plurality of known locations. The RSTD measurements may be based at least in part on measurements of the PRS transmitted by the PRS transmission module1245, and may be received from one or more UEs (e.g., one or more test UEs). In some examples, the known location measurement collection module1250may also receive a set of RSSIs for each of the plurality of known locations

In some examples, the measurement storing/indexing module1255may be used to transmit the received set of measurements (e.g., the set of RSTD measurements and/or RSSIs) to be stored in a database. The measurement storing/indexing module1255may also be used to retrieve the measurements for use by the position estimation module1265.

In some examples, the measurement analysis module1260may be used to receive (e.g., from a UE) at least one RSTD measurement and at least one RSSI associated with an unknown location.

In some examples, the position estimation module1265may be used to estimate a position of the unknown location based at least in part on the at least one RSTD measurement, the at least one RSSI associated with the unknown location, and the set of measurements stored in the database. In some examples, the position estimation module1265may estimate the position using a two-step prediction and tracking process. First, based on previous position estimates, a current position probability may be obtained. This incorporates prediction based on movement. Then, given the current position probability, and the probability of RSTD measurements and RSSIs as a function of position, a probability of the current position given RSTD measurements and RSSI may be determined. The two steps may be described mathematically as:

p⁡(Lt)=∑Lt-1⁢⁢p⁡(Lt|Lt-1)⁢p⁡(Lt-1)p⁡(Lt|RSTD,RSSI)=p⁡(RSTD,RSSI|Lt)⁢p⁡(Lt)
The use of RSTD measurements provides better accuracy and less variability over the use of RSSI measurements alone.

FIG. 13shows a block diagram1300of a base station1305(e.g., a base station forming part or all of an eNB) for use in wireless communication, in accordance with various aspects of the present disclosure. In some examples, the base station1305may be an example of one or more aspects of the base station105,305, and/or305-adescribed with reference toFIG. 1 and/or 3, and/or one or more aspects of the apparatus905,1005,1105, and/or1205described with reference toFIG. 9, 10, 11, and/or12(e.g., when configured as a base station). The base station1305may be configured to implement or facilitate at least some of the base station and/or apparatus features and functions described with reference toFIG. 1, 2, 3, 4, 5, 6, 7, and/or8.

The base station1305may include a base station processor module1310, a base station memory module1320, at least one base station transceiver module (represented by base station transceiver module(s)1350), at least one base station antenna (represented by base station antenna(s)1355), and/or a base station wireless communication management module1360. The base station1305may also include one or more of a base station communications module1330and/or a network communications module1340. Each of these components may be in communication with each other, directly or indirectly, over one or more buses1335.

The base station memory module1320may include random access memory (RAM) and/or read-only memory (ROM). The base station memory module1320may store computer-readable, computer-executable code1325containing instructions that are configured to, when executed, cause the base station processor module1310to perform various functions described herein related to wireless communication and/or PRS transmission. Alternatively, the code1325may not be directly executable by the base station processor module1310but be configured to cause the base station1305(e.g., when compiled and executed) to perform various of the functions described herein.

The base station processor module1310may include an intelligent hardware device, e.g., a central processing unit (CPU), a microcontroller, an ASIC, etc. The base station processor module1310may process information received through the base station transceiver module(s)1350, the base station communications module1330, and/or the network communications module1340. The base station processor module1310may also process information to be sent to the transceiver module(s)1350for transmission through the antenna(s)1355, to the base station communications module1330, for transmission to one or more other base stations1305-aand1305-b, and/or to the network communications module1340for transmission to a core network1345, which may be an example of one or more aspects of the core network130described with reference toFIG. 1. The base station processor module1310may handle, alone or in connection with the base station wireless communication management module1360, various aspects of communicating over (or managing communications over) a first radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses do not contend for access because the radio frequency spectrum band is licensed to particular users for particular uses, such as a licensed radio frequency spectrum band usable for LTE/LTE-A communications) and/or a second radio frequency spectrum band (e.g., a radio frequency spectrum band, such as Wi-Fi radio frequency spectrum band, for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as an unlicensed radio frequency spectrum band usable for LTE/LTE-A communications).

The base station transceiver module(s)1350may include a modem configured to modulate packets and provide the modulated packets to the base station antenna(s)1355for transmission, and to demodulate packets received from the base station antenna(s)1355. The base station transceiver module(s)1350may, in some examples, be implemented as one or more base station transmitter modules and one or more separate base station receiver modules. The base station transceiver module(s)1350may support communications in the first radio frequency spectrum band and/or the second radio frequency spectrum band. The base station transceiver module(s)1350may be configured to communicate bi-directionally, via the antenna(s)1355, with one or more mobile stations or apparatuses, such as one or more of the UEs115and/or315described with reference toFIG. 1 and/or 3. The base station1305may, for example, include multiple base station antennas1355(e.g., an antenna array). The base station1305may communicate with the core network1345through the network communications module1340. The base station1305may also communicate with other base stations, such as the base stations1305-aand1305-b, using the base station communications module1330.

The base station wireless communication management module1360may be configured to perform and/or control some or all of the features and/or functions described with reference toFIG. 1, 2, 3, 5, 6, 7, and/or8related to wireless communication over the first radio frequency spectrum band and/or the second radio frequency spectrum band. For example, the base station wireless communication management module1360may be configured to support a supplemental downlink mode, carrier aggregation mode, and/or standalone mode using the first radio frequency spectrum band and/or the second radio frequency spectrum band. The base station wireless communication management module1360may also be configured to transmit a PRS over the first radio frequency spectrum band and/or the second radio frequency spectrum band. The base station wireless communication management module1360may include a base station LTE/LTE-A module for licensed spectrum1365configured to handle LTE/LTE-A communications in the first radio frequency spectrum band, and a base station LTE/LTE-A module for unlicensed spectrum1370configured to handle LTE/LTE-A communications in the second radio frequency spectrum band. The base station wireless communication management module1360, or portions of it, may include a processor, and/or some or all of the functions of the base station wireless communication management module1360may be performed by the base station processor module1310and/or in connection with the base station processor module1310. In some examples, the base station wireless communication management module1360may be an example of the wireless communication management module920,1020,1120, and/or1220described with reference toFIG. 9, 10, 11, and/or12.

FIG. 14shows a block diagram1400of a UE1415for use in wireless communication, in accordance with various aspects of the present disclosure. The UE1415may have various configurations and may be included or be part of a personal computer (e.g., a laptop computer, a netbook computer, a tablet computer, etc.), a cellular telephone, a PDA, a digital video recorder (DVR), an internet appliance, a gaming console, an e-reader, etc. The UE1415may, in some examples, have an internal power supply (not shown), such as a small battery, to facilitate mobile operation. In some examples, the UE1415may be an example of one or more aspects of the UE115,315,315-a,315-b, and/or315-cdescribed with reference toFIG. 1 and/or 3. The UE1415may be configured to implement at least some of the UE and/or apparatus features and functions described with reference toFIG. 1, 2, and/or3.

The UE1415may include a UE processor module1410, a UE memory module1420, at least one UE transceiver module (represented by UE transceiver module(s)1430), at least one UE antenna (represented by UE antenna(s)1440), and/or a UE wireless communication management module1460. Each of these components may be in communication with each other, directly or indirectly, over one or more buses1435.

The UE memory module1420may include RAM and/or ROM. The UE memory module1420may store computer-readable, computer-executable code1425containing instructions that are configured to, when executed, cause the UE processor module1410to perform various functions described herein related to wireless communication and/or PRS reception and measurement. Alternatively, the code1425may not be directly executable by the UE processor module1410but be configured to cause the UE1415(e.g., when compiled and executed) to perform various of the functions described herein.

The UE processor module1410may include an intelligent hardware device, e.g., a CPU, a microcontroller, an ASIC, etc. The UE processor module1410may process information received through the UE transceiver module(s)1430and/or information to be sent to the UE transceiver module(s)1430for transmission through the UE antenna(s)1440. The UE processor module1410may handle, alone or in connection with the UE wireless communication management module1460, various aspects of communicating over (or managing communications over) a first radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses do not contend for access because the radio frequency spectrum band is licensed to particular users for particular uses, such as a licensed radio frequency spectrum band usable for LTE/LTE-A communications) and/or a second radio frequency spectrum band (e.g., a radio frequency spectrum band, such as Wi-Fi radio frequency spectrum band, for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as an unlicensed radio frequency spectrum band usable for LTE/LTE-A communications).

The UE transceiver module(s)1430may include a modem configured to modulate packets and provide the modulated packets to the UE antenna(s)1440for transmission, and to demodulate packets received from the UE antenna(s)1440. The UE transceiver module(s)1430may, in some examples, be implemented as one or more UE transmitter modules and one or more separate UE receiver modules. The UE transceiver module(s)1430may support communications in the first radio frequency spectrum band and/or the second radio frequency spectrum band. The UE transceiver module(s)1430may be configured to communicate bi-directionally, via the UE antenna(s)1440, with one or more of the base stations105and/or305described with reference toFIG. 1 and/or 3, and/or the apparatus905,1005,1105, and/or1205described with reference toFIG. 9, 10, 11, and/or12. While the UE1415may include a single UE antenna, there may be examples in which the UE1415may include multiple UE antennas1440.

The UE state module1450may be used, for example, to manage transitions of the UE1415between an RRC idle state and an RRC connected state, and may be in communication with other components of the UE1415, directly or indirectly, over the one or more buses1435. The UE state module1450, or portions of it, may include a processor, and/or some or all of the functions of the UE state module1450may be performed by the UE processor module1410and/or in connection with the UE processor module1410.

The UE wireless communication management module1460may be configured to perform and/or control some or all of the features and/or functions described with reference toFIG. 1, 2, and/or3related to wireless communication and/or PRS transmission over the first radio frequency spectrum band and/or the second radio frequency spectrum band. For example, the UE wireless communication management module1460may be configured to support a supplemental downlink mode, carrier aggregation mode, and/or standalone mode using the first radio frequency spectrum band and/or the second radio frequency spectrum band. The UE wireless communication management module1460may also be configured to receive a PRS over the first radio frequency spectrum band and/or the second radio frequency spectrum band, perform PRS measurements, and generate and transmit a RSTD report. The UE wireless communication management module1460may include a UE LTE/LTE-A module for licensed spectrum1465configured to handle LTE/LTE-A communications in the first radio frequency spectrum band, and a UE LTE/LTE-A module for unlicensed spectrum1470configured to handle LTE/LTE-A communications in the second radio frequency spectrum. The UE wireless communication management module1460, or portions of it, may include a processor, and/or some or all of the functions of the UE wireless communication management module1460may be performed by the UE processor module1410and/or in connection with the UE processor module1410.

FIG. 15is a flow chart illustrating an example of a method1500for wireless communication, in accordance with various aspects of the present disclosure. For clarity, the method1500is described below with reference to aspects of one or more of the base stations105,305,305-a, and/or1305described with reference toFIG. 1, 3, and/or13, and/or aspects of one or more of the apparatuses905,1005,1105, and/or1205described with reference toFIG. 9, 10, 11, and/or12. In some examples, a base station and/or apparatus may execute one or more sets of codes to control the functional elements of the base station and/or apparatus to perform the functions described below.

At block1505, the method1500may include generating a PRS. The PRS may in some examples include a number of tones. The operation(s) at block1505may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS generation module935and/or1035described with reference toFIG. 9 and/or 10.

At block1510, the method1500may include configuring the PRS to at least one downlink subframe among a plurality of downlink subframes. The operation(s) at block1510may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS configuration module940and/or1040described with reference toFIG. 9 and/or 10.

At block1515, the method1500may include transmitting the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use). The operation(s) at block1515may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS transmission module945and/or1060described with reference toFIG. 9 and/or 10.

Thus, the method1500may provide for wireless communication. It should be noted that the method1500is just one implementation and that the operations of the method1500may be rearranged or otherwise modified such that other implementations are possible.

FIG. 16is a flow chart illustrating an example of a method1600for wireless communication, in accordance with various aspects of the present disclosure. For clarity, the method1600is described below with reference to aspects of one or more of the base stations105,305,305-a, and/or1305described with reference toFIG. 1, 3, and/or13, and/or aspects of one or more of the apparatuses905and/or1005described with reference toFIG. 9 and/or 10. In some examples, a base station and/or apparatus may execute one or more sets of codes to control the functional elements of the base station and/or apparatus to perform the functions described below.

At block1605, the method1600may include generating a PRS. The PRS may in some examples include a number of tones. The operation(s) at block1605may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS generation module935and/or1035described with reference toFIG. 9 and/or 10.

At block1610, the method1600may include configuring the PRS in at least one downlink subframe among a plurality of downlink subframes. The configuring may include configuring the PRS to be adjacent a CET. In some examples, the PRS may be configured in units of downlink subframes, and may be configured to have a duration of one to K downlink subframes. In some examples, a combined duration of the PRS and the CET may be less than a maximum allowed duration of the CET. In some examples, the maximum allowed duration of the CET may be a percentage of the Transmit On (Tx-ON) during a defined period of time. The operation(s) at block1610may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, the PRS configuration module940and/or1040described with reference toFIG. 9 and/or 10, and/or the PRS duration configuration module1045described with reference toFIG. 10.

At block1615, the method1600may include configuring a periodicity and/or phase offset for transmitting the PRS adjacent the CET. In some examples, a first periodicity of transmitting the PRS adjacent the CET may be the same as a second periodicity at which the CET is transmitted (e.g., the PRS may be transmitted every time the CET is transmitted). In other examples, a first periodicity of transmitting the PRS adjacent the CET may differ from a second periodicity at which the CET is transmitted (e.g., the PRS may not be transmitted every time the CET is transmitted, but may be transmitted every J CETs, where the value of J is configurable). In these latter examples, a phase offset for transmitting the PRS adjacent the CET may also be configured. In some cases, a first phase offset used by a first transmitter (e.g., a first base station) to transmit the PRS adjacent the CET may differ from a second phase offset used by a second transmitter (e.g., a second base station) to transmit the PRS adjacent the CET. The first periodicity may be a variable periodicity and the first phase offset may be a variable phase offset, such that the first transmitter may configure a periodicity and phase offset that are useful to the first transmitter and/or its receivers, and/or configure a periodicity and/or phase offset that are the same or different from a periodicity and/or phase offset used by another transmitter (e.g., the second transmitter). Other configurations of periodicity and/or phase offset that may be made by the PRS periodicity configuration module1050are described with reference toFIG. 10. The operation(s) at block1615may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS periodicity configuration module1050described with reference toFIG. 10.

At block1620, the method1600may include signaling a receiver (e.g., a UE) of a timing of transmitting the PRS adjacent the CET (e.g., a timing of transmitting an impending transmission of the PRS adjacent the CET). The operation(s) at block1620may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS configuration signaling module1055described with reference toFIG. 10.

At block1625, the method1600may include periodically transmitting the PRS adjacent the CET in the at least one downlink subframe using an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use). In some examples, the PRS may be transmitted contiguously with the CET (e.g., with no transmission gaps between at least one downlink subframe in which the PRS is transmitted and at least one downlink subframe in which the CET is transmitted). In some examples, periodically transmitting the PRS adjacent the CET may include periodically transmitting the PRS adjacent the CET according to the first periodicity and the first phase offset configured at block1615. The operation(s) at block1625may be performed using the wireless communication management module920,1020, and/or1360described with reference toFIG. 9, 10, and/or13, and/or the PRS transmission module945and/or1060described with reference toFIG. 9 and/or 10.

Configuring the PRS to be adjacent a CET may enable the PRS to leverage the CET property of guaranteed transmission over the unlicensed radio frequency spectrum band. In some examples, the transmitting the PRS may include transmitting the PRS before the CET. In other examples, the transmitting the PRS may include transmitting the PRS after the CET.

In some examples, the transmitting the PRS may include transmitting the PRS to occupy a portion of the unlicensed radio frequency spectrum band, which portion is less than all of the unlicensed radio frequency spectrum band. In these examples, other downlink signals may be transmitted in conjunction with the PRS. The other downlink signals may in some cases be transmitted to meet unlicensed spectrum bandwidth usage requirements, as described with reference toFIG. 7.

In some examples, the transmitting the PRS may include transmitting the PRS across a plurality of frequencies of the unlicensed radio frequency spectrum band, as may be useful in an inter-frequency and/or carrier aggregation transmission scenario. When the relative PRS transmission timing across the plurality of frequencies may be unknown, a timing offset indicating the relative PRS transmission timing across the plurality of frequencies may be signaled to a receiver (e.g., a UE). In some examples, the timing offset may be signaled by the PRS configuration signaling module1055described with reference toFIG. 10.

In some examples, the method1600may be performed in parallel by a configurable number of transmitters (e.g., by a configurable number of base stations, or by a configurable number of eNBs) as specified by signaling. When a plurality of transmitters are transmitting a PRS, various PRS transmission scenarios are possible. In a first example, the transmitting the PRS (at block1625) may include time synchronizing the transmitting the PRS, by a first transmitter, with a transmission of at least a second PRS by at least a second transmitter (e.g., at least two transmitters may transmit a PRS at the same time, in a same one or more downlink subframes). In a second example, the transmitting the PRS may include transmitting the PRS before the CET, by the first transmitter, while at least the second transmitter transmits at least a second PRS after a CET. Alternately, the transmitting the PRS may include transmitting the PRS after the CET, by the first transmitter, while at least the second transmitter transmits at least the second PRS before a CET. In either alternative, each PRS may be transmitted adjacent a CET. In a third example, the transmitting the PRS may include transmitting the PRS, by the first transmitter, with a same periodicity as, and a different phase offset than, a transmission of at least the second PRS by at least the second transmitter. In a fourth example, the transmitting the PRS may include transmitting the PRS, by the first transmitter, with a different periodicity than a transmission of at least the second PRS by at least the second transmitter. In a fifth example, the PRS may be associated with a muting parameter and/or a variable cell-specific frequency shift parameter, which muting parameter and/or variable cell-specific frequency shift parameter may be the same as, or different than, a second muting parameter and/or a second variable cell-specific frequency shift parameter associated with at least the second PRS transmitted by at least the second transmitter. In a sixth example, the transmitting the PRS may include transmitting the PRS in accordance with a combination of two or more of the preceding examples.

Thus, the method1600may provide for wireless communication. It should be noted that the method1600is just one implementation and that the operations of the method1600may be rearranged or otherwise modified such that other implementations are possible.

FIG. 17is a flow chart illustrating an example of a method1700for wireless communication, in accordance with various aspects of the present disclosure. For clarity, the method1700is described below with reference to aspects of one or more of the base stations105,305,305-a, and/or1305described with reference toFIG. 1, 3, and/or13, and/or aspects of one or more of the apparatuses905and/or1105described with reference toFIG. 9 and/or 11. In some examples, a base station and/or apparatus may execute one or more sets of codes to control the functional elements of the base station and/or apparatus to perform the functions described below.

At block1705, the method1700may include generating a PRS. The PRS may in some examples include a number of tones. The operation(s) at block1705may be performed using the wireless communication management module920,1120, and/or1360described with reference toFIG. 9, 11, and/or13, and/or the PRS generation module935and/or1135described with reference toFIG. 9 and/or 11.

At block1710, the method1700may include configuring the PRS in at least one downlink subframe among a plurality of downlink subframes of a CCA frame. PRS configuration parameters that are currently used to configure a PRS in at least one downlink subframe of a licensed radio frequency spectrum band (e.g., duration, periodicity, number of PRS attempts, etc.) may, in some examples, be used to configure a PRS in at least one downlink subframe of an unlicensed radio frequency spectrum band. However, as discussed below, CCA failures may interfere with a strict implementation of some PRS configuration parameters. In some examples, the PRS may be configured in units of downlink subframes, and may be configured to have a duration of one to K downlink subframes. The operation(s) at block1710may be performed using the wireless communication management module920,1120, and/or1360described with reference toFIG. 9, 11, and/or13, the PRS configuration module940and/or1140described with reference toFIG. 9 and/or 11, and/or the PRS duration configuration module1145described with reference toFIG. 11.

At block1715, the method1700may include configuring a periodicity and/or phase offset for transmitting the PRS. In some cases, a first phase offset used by a first transmitter (e.g., a first base station) to transmit the PRS may differ from a second phase offset used by a second transmitter (e.g., a second base station) to transmit the PRS. The first periodicity may be a variable periodicity and the first phase offset may be a variable phase offset, such that the first transmitter may configure a periodicity and phase offset that are useful to the first transmitter and/or its receivers, and/or configure a periodicity and/or phase offset that are the same or different from a periodicity and/or phase offset used by another transmitter (e.g., the second transmitter). The operation(s) at block1715may be performed using the wireless communication management module920,1120, and/or1360described with reference to FIG.9,11, and/or13, and/or the PRS periodicity configuration module1150described with reference toFIG. 11.

At block1720, the method1700may include performing a CCA procedure for a frame of an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use). At block1725, it may be determined whether a CCA procedure performed at block1720failed. When it is determined that the CCA procedure did not fail, the method1700may proceed to block1730. When it is determined that the CCA procedure failed, the method1700may proceed to block1735. The operation(s) at block1720and/or block1725may be performed using the wireless communication management module920,1120, and/or1360described with reference to FIG.9,11, and/or13, and/or the CCA module1155described with reference toFIG. 11.

At block1730, the method1700may include transmitting the PRS in the at least one downlink subframe of the frame of the unlicensed radio frequency spectrum band. At block1735, the method1700may include gating off a transmission of the PRS based at least in part on determining the CCA procedure failed. The operation(s) at block1730and/or block1735may be performed using the wireless communication management module920,1120, and/or1360described with reference toFIG. 9, 11, and/or13, and/or the PRS transmission module945and/or1160described with reference toFIG. 9 and/or 11.

In some examples, the transmitting the PRS may include transmitting the PRS to occupy a portion of the unlicensed radio frequency spectrum band, which portion is less than all of the unlicensed radio frequency spectrum band. In these examples, other downlink signals may be transmitted in conjunction with the PRS. The other downlink signals may in some cases be transmitted to meet unlicensed spectrum bandwidth usage requirements, as described with reference toFIG. 7.

In some examples, the transmitting the PRS may include transmitting the PRS across a plurality of frequencies of the unlicensed radio frequency spectrum band, as may be useful in an inter-frequency and/or carrier aggregation transmission scenario. When the relative PRS transmission timing across the plurality of frequencies may be unknown, a timing offset indicating the relative PRS transmission timing across the plurality of frequencies may be signaled to a receiver (e.g., a UE).

At block1740, the method1700may include determining whether an attempt to transmit at least M PRS signals during a measurement period has been made. If not, the method1700may return to block1720, where a CCA procedure may be performed for a next frame of the unlicensed radio frequency spectrum band in which a PRS is to be transmitted. Otherwise, the method1700may proceed to block1745. An attempt to transmit a PRS may in some cases correspond to performing a CCA procedure for a frame of the unlicensed radio frequency spectrum band in which a PRS is to be transmitted (regardless of whether the CCA procedure fails). The operation(s) at block1740may be performed using the wireless communication management module920,1120, and/or1360described with reference to FIG.9,11, and/or13, and/or the PRS measurement configuration module1170described with reference toFIG. 11.

At block1745, the method1700may include receiving at least one CCA clearance statistic related to at least one PRS measurement. The at least one CCA clearance statistic may be received, in some examples, from at least one receiver (e.g., at least one UE) and/or at least one transmitter (e.g., at least one base station and/or eNB).

In some examples, a receiver of PRS transmissions may be required to perform a particular number of suitable PRS measurements (e.g., M/2 suitable measurements) within a measurement period before its PRS measurements are deemed useful. This suitable PRS measurement requirement may be met by a receiver performing PRS measurements on the PRS transmissions of one or more transmitters (e.g., one or more base stations and/or eNBs). However, when one or more transmitters fail one or more CCA procedures for frames in which PRS transmissions are to be transmitted, the PRS transmissions are not transmitted and, therefore, a receiver (e.g., a UE) cannot make a suitable PRS measurement for that frame. There may also be instances in which signal interference renders a PRS transmission unusable for measurement purposes. As a result, the transmission of a PRS in a frame for which a CCA procedure needs to be performed increases the likelihood that a receiver will fail the M/2 suitable PRS measurements requirement. To increase the probability that a receiver will pass the M/2 suitable PRS measurements requirement, a receiver may identify frames for which a CCA procedure failed and determine CCA clearance statistics for reporting back to the network (e.g., to a serving cell of a base station and/or eNB). The CCA clearance statistics may be reported, for example, via RSTD measurement results and/or error reporting results. Transmitters (e.g., base stations and/or eNBs) may also identify frames for which a CCA procedure failed and determine CCA clearance statistics for reporting to other transmitters.

The operation(s) at block1745may be performed using the wireless communication management module920,1120, and/or1360described with reference toFIG. 9, 11, and/or13, and/or the CCA clearance statistics analysis module1165described with reference toFIG. 11.

At block1750, the method1700may include determining whether at least one additional PRS measurement is needed based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement. The operation(s) at block1750may be performed using the wireless communication management module920,1120, and/or1360described with reference toFIG. 9, 11, and/or13, and/or the PRS measurement configuration module1170described with reference toFIG. 11.

At block1755, the method1700may include, when needed, configuring the transmitting the PRS based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement (e.g., to increase a number of PRS transmissions within a measurement period), and/or configuring the at least one additional PRS measurement based at least in part on the at least one CCA clearance statistic related to the at least one PRS measurement.

In some examples, the number of PRS transmissions may be increased while maintaining, for example, an M/2 suitable measurements requirement for PRS measurements to be deemed useful. In these examples, the greater number of PRS transmissions may increase the likelihood that a receiver will be able to meet the M/2 suitable measurements requirement. Changes in other configuration parameters (e.g., PRS duration) may also be made to increase the likelihood that a receiver will be able to meet the M/2 suitable measurements requirement.

After changing one or more configuration parameters associated with PRS transmissions, a receiver may be requested (e.g., via a network, eNB, and/or base station) to redo its PRS measurements and/or make additional PRS measurements. In the latter case, and by way of example, a network may schedule additional PRS measurements for a receiver, but indicate to the receiver that prior PRS measurements may be used (or are to be used) in a cumulative manner in formulating an RSTD result.

The operation(s) at block1755may be performed using the wireless communication management module920,1120, and/or1360described with reference toFIG. 9, 11, and/or13, and/or the PRS measurement configuration module1170described with reference toFIG. 11.

Thus, the method1700may provide for wireless communication. It should be noted that the method1700is just one implementation and that the operations of the method1700may be rearranged or otherwise modified such that other implementations are possible.

FIG. 18is a flow chart illustrating an example of a method1800for wireless communication, in accordance with various aspects of the present disclosure. For clarity, the method1800is described below with reference to aspects of one or more of the base stations105,305,305-a, and/or1305described with reference toFIG. 1, 3, and/or13, and/or aspects of one or more of the apparatuses905and/or1205described with reference toFIG. 9 and/or 12. In some examples, a base station and/or apparatus may execute one or more sets of codes to control the functional elements of the base station and/or apparatus to perform the functions described below.

In environments where the locations of PRS transmitters are not known, PRS measurements may not be usable to determine the position of a receiver by conventional triangulation. The method1800may be used to determine the position of a receiver in such environments. The method1800may be particularly useful in environments in which a receiver operates in a standalone mode with respect to an unlicensed radio frequency spectrum band (e.g., a radio frequency spectrum band for which apparatuses may need to contend for access because the radio frequency spectrum band is available for unlicensed use, such as Wi-Fi use).

At block1805, the method1800may include generating a PRS. The PRS may in some examples include a number of tones. The operation(s) at block1805may be performed using the wireless communication management module920,1220, and/or1360described with reference toFIG. 9, 12, and/or13, and/or the PRS generation module935and/or1235described with reference toFIG. 9 and/or 12.

At block1810, the method1800may include configuring the PRS to at least one downlink subframe among a plurality of downlink subframes. The operation(s) at block1810may be performed using the wireless communication management module920,1220, and/or1360described with reference toFIG. 9, 12, and/or13, and/or the PRS configuration module940and/or1240described with reference toFIG. 9 and/or 12.

At block1815, the method1800may include transmitting the PRS in the at least one downlink subframe using an unlicensed radio frequency spectrum band. The operation(s) at block1815may be performed using the wireless communication management module920,1220, and/or1360described with reference toFIG. 9, 12, and/or13, and/or the PRS transmission module945and/or1245described with reference toFIG. 9 and/or 12.

At block1820, the method1800may include receiving a set of RSTD measurements collected for each of a plurality of known locations. The RSTD measurements may be based at least in part on measurements of the PRS transmitted at block1815, and may be received from one or more UEs (e.g., one or more test UEs). In some examples, block1820of the method1800may also include receiving a set of RSSIs for each of the plurality of known locations. The operation(s) at block1820may be performed using the wireless communication management module920,1220, and/or1360described with reference to FIG.9,12, and/or13, and/or the known location measurement collection module1250described with reference toFIG. 12.

At block1825, the method1800may include transmitting the received set of measurements (e.g., the set of RSTD measurements and/or RSSIs) to be stored in a database. The operation(s) at block1825may be performed using the wireless communication management module920,1220, and/or1360described with reference toFIG. 9, 12, and/or13, and/or the measurement storing/indexing module1255described with reference toFIG. 12.

At block1830, the method1800may include receiving (e.g., from a UE) at least one RSTD measurement and at least one RSSI associated with an unknown location. The operation(s) at block1830may be performed using the wireless communication management module920,1220, and/or1360described with reference toFIG. 9, 12, and/or13, and/or the measurement analysis module1260described with reference toFIG. 12.

At block1835, the method1800may include estimating a position of the unknown location based at least in part on the at least one RSTD measurement, the at least one RSSI associated with the unknown location, and the set of measurements stored in the database. In some examples, the position may be estimated using a two-step prediction and tracking process. First, based on previous position estimates, a current position probability may be obtained. This incorporates prediction based on movement. Then, given the current position probability, and the probability of RSTD measurements and RSSIs as a function of position, a probability of the current position given RSTD measurements and RSSI may be determined. The two steps may be described mathematically as:

p⁡(Lt)=∑Lt-1⁢⁢p⁡(Lt|Lt-1)⁢p⁡(Lt-1)p⁡(Lt|RSTD,RSSI)=p⁡(RSTD,RSSI|Lt)⁢p⁡(Lt)
The use of RSTD measurements provides better accuracy and less variability over the use of RSSI measurements alone.

The operation(s) at block1835may be performed using the wireless communication management module920,1220, and/or1360described with reference toFIG. 9, 12, and/or13, and/or the position estimation module1265described with reference toFIG. 12.

Thus, the method1800may provide for wireless communication. It should be noted that the method1800is just one implementation and that the operations of the method1800may be rearranged or otherwise modified such that other implementations are possible.

In some examples, aspects of one or more of the methods1500,1600,1700, and/or1800may be combined.