Channel usage indication and synchronization for LTE operation in unlicensed band

Abstract

The invention discloses channel usage indication and synchronization for LTE operation in an unlicensed band. Systems, methods, and instrumentalities are disclosed for LTE operation LTE-U in an unlicensed spectrum. A wireless transmit / receive unit (WTRU) may establish a connection with a first cell on a licensed frequency band. The WTRU may receive a first downlink transmission from a second cell operating on an unlicensed frequency band. The WTRU may determine that a synchronization signal from a third cell operating on an unlicensed frequency band is transmitted using one or more resource elements. The WTRU may perform frequency and / or timing estimation based on the synchronization signal transmission. The WTRU may perform rate matching around one or more resource elements corresponding to the synchronization signal transmission. The WTRU may perform rate matching around the one or more resource elements by de-mapping symbols of the downlink transmission.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202010530521.3, titled "Channel Usage Indication and Synchronization for LTE Operation in Unlicensed Bands", with a filing date of September 24, 2015, and this application is a divisional application of Chinese Patent Application No. 201580063144.4, titled "Channel Usage Indication and Synchronization for LTE Operation in Unlicensed Bands", filed on September 24, 2015.

[0002] Cross-reference to Related Applications

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 054,881, filed on September 24, 2014; U.S. Provisional Patent Application No. 62 / 075,720, filed on November 5, 2014; and U.S. Provisional Patent Application No. 62 / 203,734, filed on August 11, 2015, the contents of which are incorporated herein by reference. Background Art

[0004] Cellular systems, such as LTE systems, use licensed spectrum. For example, an operator can obtain the right to transmit and receive cellular signals in a certain portion of a frequency band in a geographical area through a government auction. The operator can exclusively use the licensed spectrum to provide services to its users without worrying about in-band interference from other communication systems. In contrast, unlicensed spectrum remains unclaimed and can be used by various users for various purposes using various radio access technologies (RATs). Summary of the Invention

[0005] Disclosed are systems, methods, and means for LTE operation in unlicensed spectrum (LTE-U), where the LTE operation can include carrier aggregation in licensed and unlicensed spectrum, such as licensed-assisted access (LAA). LTE-U operation can be supported through channel usage indication (such as a busy signal) and / or synchronization (sync) signaling.

[0006] For example, a wireless transmit / receive unit (WTRU) may establish a connection with a first cell on an authorized frequency band. The WTRU may receive a first downlink transmission. The first downlink transmission may be received from a second cell operating on an unlicensed frequency band. The WTRU may determine that a synchronization signal transmission from a third cell operating on an unlicensed frequency band is transmitted using one or more resource elements. The one or more resource elements may correspond to a portion of one or more resource blocks of a downlink transmission from the second cell. The synchronization signal transmission may include one or more of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS), and / or a demodulation reference signal (DMRS).

[0007] The WTRU may determine that a synchronization signal transmission from a third cell operating on an unlicensed frequency band is transmitted using one or more resource elements by receiving downlink control information (DCI) on a downlink physical channel. The downlink physical channel may indicate which resource elements are used for the synchronization signal transmission. The WTRU may perform frequency and / or timing estimation. The frequency / timing estimation may be based on the synchronization signal transmission. The WTRU may perform demodulation and / or resource symbol scaling. The demodulation and / or resource symbol scaling may be based on the synchronization signal transmission. The WTRU may determine a power offset. The power offset may be between the synchronization signal transmission and one or more other downlink transmissions. The WTRU may determine a power level of a second downlink transmission based on the power offset.

[0008] The WTRU may perform rate matching around one or more resource elements corresponding to the synchronization signal transmission. When receiving a downlink transmission from the second cell, the WTRU may perform rate matching around one or more resource elements. The WTRU may perform rate matching around one or more resource elements by demapping symbols of the downlink transmission. During the demapping process, the one or more resource elements corresponding to the synchronization signal transmission may be skipped. The WTRU may receive a configuration from the first cell on the authorized frequency band. The configuration may indicate which resource elements the third cell will use to transmit the synchronization signal transmission. The configuration may be received in a radio resource control (RRC) message. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A is a system diagram of an exemplary communication system in which one or more embodiments disclosed herein may be implemented;

[0010] Figure 1B is a system diagram of an exemplary wireless transmit / receive unit (WTRU) that may be used within the Figure 1A illustrated communication system;

[0011] Figure 1C is a system diagram of an exemplary radio access network and an exemplary core network that can be used within the Figure 1A illustrated communication system;

[0012] Figure 1D is a system diagram of another exemplary radio access network and another exemplary core network that can be used within the Figure 1A illustrated communication system;

[0013] Figure 1E is a system diagram of another exemplary radio access network and another exemplary core network that can be used within the Figure 1A illustrated communication system;

[0014] Figure 2 is a diagram illustrating an exemplary licensed-assisted access deployment;

[0015] Figure 3 is a diagram illustrating an exemplary eNB timeline including an initial busy signal;

[0016] Figure 4 is a diagram illustrating an example of 25 physical resource blocks (PRBs) shared between a busy signal and data transmission;

[0017] Figure 5 is a diagram illustrating an example of 25 physical resource blocks (PRBs) shared between a busy signal and data transmission;

[0018] Figure 6 is a diagram illustrating an example of an ongoing busy signal and data transmission. Detailed Description

[0019] The detailed description of the illustrative embodiments will now be described with reference to the different drawings. While this detailed description section provides specific examples of possible embodiments, it should be noted that these details are illustrative and do not limit the scope of the present application.

[0020] Figure 1AFIG. 0 is an illustration of an exemplary communication system 100 that can implement one or more of the disclosed embodiments. The communication system 100 can be a multi-access system that provides content such as voice, data, video, messaging, broadcast, etc. to a plurality of wireless users. The communication system 100 allows multiple wireless users to access such content by sharing system resources including wireless bandwidth. As an example, the communication system 100 can use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), and the like.

[0021] As Figure 1A shown, the communication system 100 can include wireless transmit / receive units (WTRUs) such as UE 102a, 102b, 102c, and / or 102d (which can generally be collectively referred to as WTRU 102), radio access networks (RANs) 103 / 104 / 105, core networks 106 / 107 / 109, public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each of the WTRUs 102a, 102b, 102c, 102d can be any type of device configured to operate and / or communicate in a wireless environment. For example, the WTRUs 102a, 102b, 102c, 102d can be configured to transmit and / or receive wireless signals and can include user equipment (UE), mobile stations, fixed or mobile subscriber units, pagers, cellular telephones, personal digital assistants (PDA), smart phones, laptop computers, netbooks, personal computers, wireless sensors, consumer electronic devices, and the like.

[0022] The communication system 100 can also include base stations 114a and 114b. Each of the base stations 114a, 114b can be any type of device configured to facilitate access to one or more communication networks by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d, and the networks can be, for example, core networks 106 / 107 / 109, the Internet 110, and / or networks 112. As an example, the base stations 114a, 114b can be base transceiver stations (BTSs), Node Bs, eNode Bs, home Node Bs, home eNode Bs, site controllers, access points (APs), wireless routers, and the like. Although each of the base stations 114a, 114b is described as a single component, it should be understood that the base stations 114a, 114b can include any number of interconnected base stations and / or network components.

[0023] Base station 114a may be part of RAN 103 / 104 / 105, and the RAN 103 / 104 / 105 may further include other base stations and / or network components (not shown), such as base station controllers (BSCs), radio network controllers (RNCs), relay nodes, and the like. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals within a specific geographical area called a cell (not shown). A cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Base station 114a may include multiple (e.g., three) transceivers, for example, each transceiver corresponding to one sector of the cell. Base station 114a may use multiple-input multiple-output (MIMO) technology, whereby multiple transceivers may be used for each sector of the cell.

[0024] Base stations 114a, 114b may communicate with one or more WTRUs 102a, 102b, 102c, 102d via air interfaces 115 / 116 / 117, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interfaces 115 / 116 / 117 may be established using any suitable radio access technology (RAT).

[0025] More specifically, as described above, the communication system 100 may be a multiple access system and may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, base station 114a in RAN103 / 104 / 105 and WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), and this technology may use Wideband CDMA (WCDMA) to establish the air interfaces 115 / 116 / 117. WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA) and / or High-Speed Uplink Packet Access (HSUPA).

[0026] Base station 114a and WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), and this technology may use Long-Term Evolution (LTE) and / or Advanced LTE (LTE-A) to establish the air interfaces 115 / 116 / 117.

[0027] The base station 114a and the WTRUs 102a, 102b, 102c can implement radio access technologies such as IEEE 802.16 (Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0028] As an example, Figure 1A the base station 114b in [ ] can be a wireless router, a home Node B, a home evolved Node B (eNB), or an access point, and can use any suitable RAT to facilitate wireless connections in a local area, such as a business premise, a residence, a vehicle, a campus, etc. The base station 114b and the WTRUs 102c, 102d can establish a Wireless Local Area Network (WLAN) by implementing radio technologies such as IEEE 802.11. The base station 114b and the WTRUs 102c, 102d can establish a Wireless Personal Area Network (WPAN) by implementing radio technologies such as IEEE 802.15. The base station 114b and the WTRUs 102c, 102d can establish a pico cell or a femto cell by using a cellular-based RAT (such as WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.). As Figure 1A shown, the base station 114b can be directly connected to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the core network 106 / 107 / 109.

[0029] The RANs 103 / 104 / 105 can communicate with the core networks 106 / 107 / 109, which can be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more WTRUs 102a, 102b, 102c, 102d. For example, the core networks 106 / 107 / 109 can provide call control, accounting services, location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions such as user authentication. Although in Figure 1AAlthough not shown, it should be understood that RANs 103 / 104 / 105 and / or core networks 106 / 107 / 109 may communicate directly or indirectly with other RANs that use the same or different radio access technologies (RATs) as RANs 103 / 104 / 105. For example, in addition to being connected to RANs 103 / 104 / 105 that use E-UTRA radio technology, core networks 106 / 107 / 109 may also communicate with other RANs (not shown) that use GSM radio technology.

[0030] Core networks 106 / 107 / 109 may also act as gateways for WTRUs 102a, 102b, 102c, 102d to access the public switched telephone network (PSTN) 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer network devices that use common communication protocols, which may be the Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet Protocol (IP) in the TCP / IP Internet protocol suite. Networks 112 may include wired or wireless communication networks that are owned and / or operated by other service providers. For example, network 112 may include another core network that is connected to one or more RANs, and the one or more RANs may use the same or different RATs as RANs 103 / 104 / 105.

[0031] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities. For example, WTRUs 102a, 102b, 102c, 102d may include multiple transceivers that communicate with different wireless networks on different wireless links. For example, Figure 1A the illustrated WTRU 102c may be configured to communicate with a base station 114a that uses a cellular-based radio technology and with a base station 114b that may use IEEE 802 radio technology.

[0032] Figure 1B is a system diagram illustrating a WTRU 102. As Figure 1BAs shown, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive component 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and other peripheral devices 138. It should be understood that while remaining compliant with the embodiments, the WTRU 102 may also include any sub-combination of the foregoing components. The base stations 114a and 114b and / or the nodes represented by the base stations 114a and 114b (such as, but not limited to, a Base Transceiver Station (BTS), a Node B, a Site Controller, an Access Point (AP), a Home Node B, an evolved Home Node B (eNodeB), a Home evolved Node B (HeNB or He Node B), a Home evolved Node B Gateway, and a Proxy Node) may include some or all of the components depicted in Figure 1B and described herein.

[0033] The processor 118 may be a general-purpose processor, a dedicated processor, a conventional processor, a Digital Signal Processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) circuit, any other type of Integrated Circuit (IC), a state machine, etc. The processor 118 may perform signal encoding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, and the transceiver 120 may be coupled to the transmit / receive component 122. Although Figure 1B the processor 118 and the transceiver 120 are described as separate components, it should be understood that the processor 118 and the transceiver 120 may be integrated in one electronic component or chip.

[0034] The transmit / receive component 122 may be configured to transmit or receive signals to or from a base station (such as base station 114a) via an air interface 115 / 116 / 117. For example, the transmit / receive component 122 may be (a) an antenna configured to transmit and / or receive RF signals, (b) a transmitter / detector configured to transmit and / or receive IR, UV, or visible light signals, (c) configured to transmit and receive RF and optical signals. It should be understood that the transmit / receive component 122 may be configured to transmit and / or receive any combination of wireless signals.

[0035] In addition, although in Figure 1BThe transmit / receive component 122 is described as a single component, but the WTRU 102 can include any number of transmit / receive components 122. More specifically, the WTRU 102 can utilize MIMO technology. The WTRU 102 can include two or more transmit / receive components 122 (e.g., multiple antennas) that transmit and receive radio signals via the air interface 115 / 116 / 117.

[0036] The transceiver 120 can be configured to modulate the signals to be transmitted by the transmit / receive component 122 and to demodulate the signals received by the transmit / receive component 122. As described above, the WTRU 102 can have multi-mode capabilities. Accordingly, the transceiver 120 can include multiple transceivers that allow the WTRU 102 to communicate via multiple RATs such as UTRA and IEEE 802.11.

[0037] The processor 118 of the WTRU 102 can be coupled to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and can receive user input data from these components. The processor 118 can also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. In addition, the processor 118 can access information from any suitable memory, such as the non-removable memory 130 and / or the removable memory 132, and can store information in these memories. The non-removable memory 130 can include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 can include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. The processor 118 can access information from, and store data in, memories that are not actually located within the WTRU 102, such as, for example, memories located in a server or a home computer (not shown).

[0038] The processor 118 can receive power from the power supply 134 and can be configured to distribute and / or control the power for the other components in the WTRU 102. The power supply 134 can be any suitable device for powering the WTRU 102. For example, the power supply 134 can include one or more dry battery packs (such as nickel cadmium (Ni-Cd), nickel zinc (Ni-Zn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0039] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) related to the current location of the WTRU 102. As a supplement or replacement to the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via the air interface 116, and / or determine its location based on the signal timing received from two or more nearby base stations. It should be understood that the WTRU 102 may obtain location information by means of any suitable positioning implementation.

[0040] The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connections. For example, the peripheral devices 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a video game console module, an Internet browser, and so on.

[0041] Figure 1C is an example of a system diagram of the RAN 103 and the core network 106. As described above, the RAN 103 may use E-UTRA radio technology and communicate with the WTRU 102a, 102b, 102c via the air interface 115. The RAN 103 may also communicate with the core network 106. As Figure 1C shown, the RAN 103 may include Node Bs 140a, 140b, 140c, each of which may include one or more transceivers that communicate with the WTRU 102a, 102b, 102c via the air interface 115. Each of the Node Bs 140a, 140b, 140c may be associated with a specific cell (not shown) within the RAN 103. The RAN 103 may also include RNCs 142a, 142b. It should be understood that the RAN 103 may include any number of Node Bs and RNCs.

[0042] As Figure 1CAs shown, Node Bs 140a, 140b can communicate with RNC 142a. In addition, Node B 140c can also communicate with RNC 142b. Node Bs 140a, 140b, 140c can communicate with the corresponding RNCs 142a, 142b via the Iub interface. RNCs 142a, 142b can communicate with each other via the Iur interface. Each of RNCs 142a, 142b can be configured to control the corresponding Node Bs 140a, 140b, 140c connected thereto. Additionally, each of RNCs 142a, 142b can be configured to perform or support other functions, such as outer loop power control, load control, admission control, packet scheduling, handover control, macro diversity, security functions, data encryption, and so on.

[0043] Figure 1C The core network 106 shown can include a media gateway (MGW) 144, a mobile switching center (MSC) 146, a serving GPRS support node (SGSN) 148, and / or a gateway GPRS support node (GGSN) 150. Although each of the foregoing components is described as being part of the core network 106, it should be understood that other entities outside of the core network operator may also own and / or operate any of these components.

[0044] The RNC 142a in the RAN 103 can be connected to the MSC 146 in the core network 106 via the IuCS interface. The MSC 146 can be connected to the MGW 144. The MSC 146 and the MGW 144 can provide access to a circuit-switched network such as the PSTN 108 for the WTRUs 102a, 102b, 102c to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices.

[0045] The RNC 142a in the RAN 103 can also be connected to the SGSN 148 in the core network 106 via the IuPS interface. The SGSN 148 can be connected to the GGSN 150. The SGSN 148 and the GGSN 150 can provide access to a packet-switched network such as the Internet 110 for the WTRUs 102a, 102b, 102c to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0046] As described above, the core network 106 can also be connected to a network 112, which can include other wired or wireless networks owned and / or operated by other service providers.

[0047] Figure 1DThis is an example of a system diagram of RAN 104 and core network 107. As described above, RAN 104 can use E-UTRA radio technology and communicate with WTRUs 102a, 102b, 102c via air interface 116. In addition, RAN 104 can also communicate with core network 107.

[0048] RAN 104 can include eNode Bs 160a, 160b, 160c, but it should be understood that RAN 104 can include any number of eNode Bs. Each eNode B 160a, 160b, 160c can include one or more transceivers for communicating with WTRUs 102a, 102b, 102c via air interface 116. eNode Bs 160a, 160b, 160c can implement MIMO technology. Thus, for example, eNode B 160a can use multiple antennas to transmit wireless signals to WTRU 102a and receive wireless signals from WTRU 102a.

[0049] Each eNode B 160a, 160b, 160c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in the uplink (UL) and / or downlink (DL), etc. As Figure 1D shown, eNode Bs 160a, 160b, 160c can communicate with each other via the X2 interface.

[0050] Figure 1D The core network 107 shown can include a Mobility Management Entity (MME) 162, a Serving Gateway 164, and a Packet Data Network (PDN) Gateway 166. Although each of the above components is described as part of core network 107, it should be understood that other entities outside of the core network operator can own and / or operate any of these components.

[0051] MME 162 can be connected to each eNode B 160a, 160b, 160c in RAN 104 via the S1 interface and can act as a control node. For example, MME 162 can be responsible for authenticating users of WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a specific serving gateway during the initial attachment process of WTRUs 102a, 102b, 102c, etc. The MME162 can also provide control plane functions for handover between RAN 104 and other RANs (not shown) using other radio technologies such as GSM or WCDMA.

[0052] The serving gateway 164 may be connected to each eNodeB 160a, 160b, 160c in the RAN 104 via the S1 interface. The serving gateway 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The serving gateway 164 may also perform other functions, such as anchoring the user plane during the handover process between eNodeBs, triggering paging when downlink data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and so on.

[0053] The serving gateway 164 may also be connected to the PDN gateway 166, which may provide the WTRUs 102a, 102b, 102c with access to a packet switched network such as the Internet 110 in order to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0054] The core network 107 may facilitate communication with other networks. For example, the core network 106 may provide the WTRUs 102a, 102b, 102c with access to a circuit switched network such as the PSTN 108 in order to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. As an example, the core network 107 may include or communicate with an IP gateway (such as an IP Multimedia Subsystem (IMS) server), where the IP gateway serves as an interface between the core network 107 and the PSTN 108. In addition, the core network 107 may also provide the WTRUs 102a, 102b, 102c with access to the network 112, which may include other wired or wireless networks owned and / or operated by other service providers.

[0055] Figure 1E is an example of a system diagram of the RAN 105 and the core network 109. The RAN 105 may be an access service network (ASN) that communicates with the WTRUs 102a, 102b, 102c over the air interface 117 by using IEEE802.16 radio technology. As will be discussed further below, communication links between different functional entities of the WTRUs 102a, 102b, 102c, the RAN 104, and the core network 109 may be defined as reference points.

[0056] As Figure 1EAs shown, the RAN 105 may include base stations 180a, 180b, 180c and an ASN gateway 182. However, it should be understood that the RAN 105 may include any number of base stations and ASN gateways. Each of the base stations 180a, 180b, 180c may be associated with a specific cell (not shown) in the RAN 105, and each base station may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c via the air interface 117. The base stations 180a, 180b, 180c may implement MIMO technology. Thus, for example, the base station 180a may use multiple antennas to transmit wireless signals to the WTRU 102a and receive wireless signals from the WTRU 102a. The base stations 180a, 180b, 180c may also provide mobility management functions such as handover triggering, tunnel establishment, radio resource management, traffic classification, quality of service (QoS) policy enforcement, and so on. The ASN gateway 182 may act as a traffic aggregation point and may be responsible for implementing paging, subscriber profile caching, routing to the core network 109, and so on.

[0057] The air interface 117 between the WTRUs 102a, 102b, 102c and the RAN 105 may be defined as the R1 reference point implementing the IEEE802.16 standard. Additionally, each of the WTRUs 102a, 102b, 102c may establish a logical interface (not shown) with the core network 109. The logical interface between the WTRUs 102a, 102b, 102c and the core network 109 may be defined as the R2 reference point, which may be used for authentication, authorization, IP host configuration management, and / or mobility management.

[0058] The communication link between each of the base stations 180a, 180b, 180c may be defined as the R8 reference point, which includes protocols for facilitating WTRU handover and data transfer between the base stations. The communication link between the base stations 180a, 180b, 180c and the ASN gateway 182 may be defined as the R6 reference point. The R6 reference point may include protocols for facilitating mobility management based on mobility events associated with each of the WTRUs 102a, 102b, 180c.

[0059] As Figure 1EAs shown, the RAN 105 can be connected to the core network 109. The communication link between the RAN 105 and the core network 109 can be defined as the R3 reference point. As an example, this reference point includes protocols for facilitating data transfer and mobility management capabilities. The core network 109 can include a Mobile IP Home Agent (MIP-HA) 184, an Authentication, Authorization, and Accounting (AAA) server 186, and a gateway 188. Although each of the foregoing components is described as part of the core network 109, it should be understood that entities other than the core network operator may own and / or operate any of these components.

[0060] The MIP-HA can be responsible for IP address management and can allow the WTRUs 102a, 102b, 102c to roam between different ASNs and / or different core networks. The MIP-HA 184 can provide the WTRUs 102a, 102b, 102c with access to a packet-switched network such as the Internet 110 to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The AAA server 186 can be responsible for user authentication and support of user services. The gateway 188 can facilitate interworking with other networks. For example, the gateway 188 can provide the WTRUs 102a, 102b, 102c with access to a circuit-switched network such as the PSTN 108 to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. Additionally, the gateway 188 can also provide the WTRUs 102a, 102b, 102c with access to the network 112, which can include other wired or wireless networks owned and / or operated by other service providers.

[0061] Although not shown in Figure 1E it should be understood that the RAN 105 can be connected to other ASNs, and the core network 109 can be connected to other core networks. The communication link between the RAN 105 and other ASNs can be defined as the R4 reference point, which can include protocols for coordinating the movement of the WTRUs 102a, 102b, 102c between the RAN 105 and other ASNs. The communication link between the core network 109 and other core networks can be defined as the R5 reference point, which can include protocols for facilitating interworking between the home core network and the visited core network.

[0062] The use of licensed spectrum can include one or more constraints and growing communication demands (e.g., for broadband data). Unlicensed spectrum can be used for non-cellular services and / or applications, such as Wi-Fi. A portion of the unlicensed spectrum can be used by cellular carriers (e.g., to overcome one or more constraints and / or meet communication requirements). The unlicensed spectrum (e.g., one or more bands of the unlicensed spectrum) can be used for one or more purposes. The unlicensed spectrum can be used by one or more users (e.g., cellular carriers). The one or more purposes and the one or more users can use multiple radio access technologies (RATs). If the unlicensed spectrum is used for one or more purposes and / or by one or more users, there is a possibility of conflicts occurring.

[0063] LTE operation in unlicensed spectrum can be referred to as LTE-unlicensed operation or LTE-U. LTE-U can be implemented alone (e.g., without support from an operator operating in a licensed band). LTE-U can be implemented in combination with LTE (e.g., LTE operation in licensed spectrum) and / or other technologies.

[0064] The process of extending LTE (or other licensed cellular technology) to unlicensed spectrum can be implemented in various deployment scenarios. For example, one deployment scenario can use carrier aggregation. As an example, carrier aggregation can be used to aggregate a primary (e.g., licensed) carrier and a secondary (e.g., unlicensed) carrier. The carrier aggregation deployment scenario can be referred to as "licensed-assisted access" (LAA) for unlicensed spectrum.

[0065] Figure 2 is a diagram illustrating an exemplary licensed-assisted access deployment. A WTRU 202 can establish connections with a primary component carrier 210 (e.g., a primary cell PCell) and one or more secondary component carriers 2121 (e.g., secondary cells SCell). The WTRU202 can receive one or more downlink transmissions 208 from one or more of the secondary component carriers 212. In LAA, the primary component carrier or serving cell 210 can be a licensed carrier. For example, the primary component carrier 210 can use licensed spectrum (e.g., a licensed band). One or more of the secondary component carriers 212 can include one or more unlicensed carriers. For example, one of the secondary component carriers among the one or more secondary component carriers 212 can use unlicensed spectrum (e.g., an unlicensed band). The PCell 210 and one or more SCell 212 can be aggregated. For example, one or more unlicensed Scells and zero or more licensed SCells can be aggregated together, and the PCell210 can either be aggregated or not. As another example, the PCell 210 and one or more Scell 212 can belong to one eNB.

[0066] AsFigure 2 As shown, the WTRU 204 may establish connections with a primary component carrier 218 (e.g., a primary cell, PCell) and one or more secondary component carriers 220 (e.g., secondary cells, SCell). The WTRU 204 may receive downlink and uplink transmissions 216 from one or more secondary component carriers 220. In LAA, the primary component carrier or serving cell 218 may be a licensed carrier. For example, the primary component carrier 218 may use licensed spectrum (e.g., a licensed frequency band). One or more secondary component carriers 220 may include one or more unlicensed carriers. For example, one of the one or more secondary component carriers 220 may use unlicensed spectrum (e.g., an unlicensed frequency band). The PCell 218 and SCell 220 may be aggregated. For example, one or more unlicensed SCell and zero or more licensed SCell may be aggregated together, and the PCell 218 may or may not be aggregated. As another example, the PCell 218 and one or more SCell 220 may belong to one eNB.

[0067] Deployment scenarios for LTE-U operation may include dual connectivity. As an example, dual connectivity may be used when one or more unlicensed SCell and a licensed Pcell belong to different eNBs.

[0068] Considering that unlicensed spectrum is a shared resource of the public, deploying LTE operations in unlicensed spectrum may address coexistence with other unlicensed technologies (e.g., Wi-Fi) and / or coexistence with one or more other LTE operators. For example, LTE deployment in unlicensed spectrum may attempt to minimize interference and / or provide fairness among multiple users of the unlicensed spectrum. LTE deployment in unlicensed spectrum may include one or more coexistence mechanisms (e.g., listen-before-talk (LBT) and coexistence gaps).

[0069] In the LBT coexistence mechanism, a system node may listen to a channel (e.g., a frequency band having a certain center frequency and bandwidth). The system node may include an access point (AP), an evolved Node B (eNB), a user equipment (UE), a wireless transmit / receive unit (WTRU), etc. The system node may determine whether the channel (e.g., a portion of the channel) is being used. The system node may determine whether the channel is being used before performing a transmission on the channel (e.g., a portion of the channel). The system node may perform a listening process to determine whether the channel is in use. The listening process may include performing one or more measurements. The one or more measurements may include measuring the amount of energy detected in the channel.

[0070] In a coexistence gap mechanism, a system node can provide one or more gaps in a transmission. The system node can transmit on a channel or a portion of a channel. One or more gaps in the transmission can allow other potential users to determine that the signal or a portion of the channel is available for use (e.g., in whole or in part).

[0071] LTE-U can be implemented with or without aggregation and / or dual connectivity. LTE-U can be implemented with or without being combined with LTE. LTE-U can be implemented using a coexistence mechanism.

[0072] When one or more coexistence mechanisms are implemented in an LTE-U deployment, one or more transmission, reception, and / or scenario issues can result. For example, one or more transmission gaps and / or air interface differences between LTE and other technologies (such as Wi-Fi) can result in one or more technical issues.

[0073] An unlicensed band (e.g., a channel) can be located between LTE licensed band boundaries. An unlicensed band or a portion of an unlicensed band can become idle (e.g., unused). When an unlicensed band or a portion of an unlicensed band is idle, the LTE system can use the unlicensed band or the portion of the unlicensed band. The LTE system can indicate the usage of the unlicensed band (e.g., to ensure that Wi-Fi detects LTE channel usage) (as an example, so that Wi-Fi does not transmit on the unlicensed band when the LTE system is using the unlicensed band).

[0074] The LTE system can be silent (e.g., when it has no channels for data). One or more WTRUs can perform synchronization using synchronization and / or reference signal transmissions. The synchronization and / or reference signal transmissions are available during certain periods and do not use synchronization and / or reference signal transmissions during other periods (for example, there may be no LTE transmissions / there may be silent periods).

[0075] Here, one or more terms and phrases are used interchangeably. For example, Wi-Fi, WiFi, and Wifi are used interchangeably; system and node are used interchangeably. eNB, cell, Scell, and Pcell are used interchangeably. Unlicensed, license-exempt (LE), LTE-U, and LAA are used interchangeably. Operating is used interchangeably with transmitting and / or receiving. Component carrier is used interchangeably with serving cell. The terms channel, frequency channel, radio channel, LE channel, and frequency band are used interchangeably. Access channel is used interchangeably with usage channel and transmitting and / or receiving on a channel. Channel and LTE channel are used interchangeably. Channel and signal are used interchangeably. The term data / control is used interchangeably with data and / or control signal and / or channel. Data / control is used interchangeably with LTE data / control, data / control, and data / control channel and / or signal. eNB and LTE-U eNB are used interchangeably. Examples described for a WTRU may be performed by an eNB or other node and / or applicable to an eNB or other node. Similarly, examples related to UL access or UL transmission are equally applicable to DL access and / or downlink transmission. Frequency band, bandwidth, and / or channel are used interchangeably.

[0076] An LAA cell or SCell may include a cell or SCell that can use or operate in unlicensed spectrum (such as a frequency band). An LAA cell or SCell may be associated with a corresponding PCell. For example, an LAA cell or SCell may be aggregated with a PCell. The PCell may use or operate in licensed spectrum. The LAA SCell may be configured for uplink and / or downlink operation. In some examples, the LAA SCell may operate in (e.g., only in) the downlink but not be used in the uplink.

[0077] An unlicensed channel or LAA channel may include a frequency band in unlicensed spectrum. A WTRU and / or an eNB may use the LAA channel for data, such as DL and / or UL data.

[0078] An LTE-U frequency band (such as a channel) may be used in a license-assisted manner. For example, an LTE-U frequency band may be used as or for an LAA SCell. The LAA SCell may support uplink transmission. In a licensed channel, the LTE-U frequency band may be used without assistance from the PCell. An LTE-U cell (such as an LTE-U PCell) may support UL and / or DL transmission.

[0079] The channel may include an LTE channel or signal (e.g., an uplink or downlink physical channel or signal). The downlink channel or signal may include PSS, SSS, PBCH, PDCCH, EPDCCH, and / or PDSCH. The uplink channel or signal may include PRACH, PUCCH, SRS, and / or PUSCH. The channel may include a frequency band. The channel may include a certain amount of spectrum. The certain amount of spectrum may include a center and / or carrier frequency and bandwidth. The licensed and / or unlicensed spectrum may include one or more channels that may overlap. The control may include synchronization with respect to the one or more channels.

[0080] An LTE-U (e.g., LAA) eNB may include an eNB or cell that can transmit and / or receive one or more LTE channels (e.g., physical channels) and / or signals. The LTE-U eNB may operate in an unlicensed (LE) frequency band (e.g., transmit and / or receive signals). The LTE-U eNB may transmit and / or receive one or more LTE channels and / or signals in a licensed frequency band and / or an LE frequency band. One or more other radio access technologies (RATs) (e.g., Wi-Fi) may operate in the LE frequency band. One or more other LTE-U eNBs and / or one or more WTRUs may operate in the LE frequency band.

[0081] Channel usage indication and / or synchronization (sync) signals may support LTE-U operation. The channel usage indication may include a busy signal.

[0082] The busy signal may be used to acquire (e.g., reserve and / or maintain) an unlicensed channel for LTE-U operation. The busy signal may initially be sent when unlicensed channel usage indicates that the channel will be used by the eNB and / or WTRU. A busy signal sent before or near the start of channel usage may be referred to as an initial busy signal. As an example, when an unlicensed channel is being used, the busy signal may be used to indicate that the channel is being used by transmitting the busy signal at a predetermined interval. A busy signal sent during channel usage and / or periodically during channel usage to indicate that channel usage will continue may be referred to as an ongoing busy signal. The busy signal may be used in a synchronous or asynchronous manner. An LTE-type signal may be transmitted as the busy signal.

[0083] The busy signal can be configured (e.g., adapted and / or deployed) based on one or more of the following: static conditions, dynamically variable conditions, use of resource allocation, use of concurrent resource (e.g., PRB) sharing, and / or causing one or more busy signal transmissions to be sent between different users. The static and / or dynamically variable conditions can include channel overlap between users. One or more resource allocations can include bandwidth allocation and / or one or more physical resource block (PRB) allocations. The busy signal can be sent together with one or more data and / or control signals. One or more resources (e.g., PRB) available for the busy signal, data and / or control signals can be dynamically changed. The busy signal can indicate channel usage information.

[0084] The synchronization signal can be used to acquire and / or maintain synchronization between a WTRU for LTE-U operation and an eNB. An LTE type signal can be transmitted as an LTE-U synchronization signal. The synchronization signal can be configured (e.g., adapted and / or deployed) based on one or more of the following: static conditions, dynamically variable conditions, use of resource allocation, and / or use of resource sharing in time and / or frequency. Synchronization signals from different eNBs can be provided (e.g., simultaneously) in a resource set. Synchronization signals from different eNBs can be provided in the same time slot and / or orthogonal frequency division multiplexing (OFDM) symbol. The synchronization signal can be spread in time and / or frequency (e.g., to reduce interference). The synchronization signal can be rate matched. The synchronization signal can include cell-specific and / or WTRU-specific configurations. The synchronization signal can be sent together with one or more data and / or control signals. One or more resources (e.g., PRB) available for the synchronization signal, busy signal, data and / or control signals can be dynamically changed. Synchronization signal transmission (e.g., indication) can be provided with blind detection and / or without blind detection. For example, the synchronization signal transmission can be sent with one or more patterns and / or implicit indications. A synchronization signal power offset can be provided. The synchronization signal power offset can indicate the power offset between the synchronization signal and one or more other signals (e.g., data signals).

[0085] Channel usage indication (e.g., busy signal) can implement LTE-U operation. For example, an eNB (e.g., LTE-U eNB) can use a certain frequency band during a certain period (e.g., transmit on it). The eNB can vacate the frequency band during other periods (e.g., stop using the frequency band or stop transmitting on the frequency band). During the period when the eNB uses or can use the channel, the eNB can attempt to prevent other devices (e.g., AP, other eNB, WTRU, etc.) from using the frequency band. The eNB can reduce interference by preventing other devices from using the frequency band. For example, other devices (e.g., AP, other eNB, WTRU, etc.) near the eNB may cause interference on the eNB's receiver.

[0086] LTE operation in unlicensed bandwidth may be inconsistent with the operation of other RATs. For example, before vacating the channel, the Wi-Fi system uses the entire frequency band (e.g., 20 or 22 MHz channel). A Wi-Fi system using coexistence technology (e.g., LBT) may expect other systems to operate like the Wi-Fi system (e.g., use part of, all of the channel, or not use the channel). A Wi-Fi system deploying LBT can perform energy detection in a small time window (e.g., 4 microseconds and / or 20 microseconds). A Wi-Fi system deploying LBT can determine whether the frequency band can be freely used. The Wi-Fi system can determine whether the frequency band can be freely used by performing energy detection in a small time window. When the Wi-Fi system determines that the frequency band can be freely used, the Wi-Fi system can determine to use the frequency band.

[0087] The LTE system can operate in the unlicensed frequency band using a time window larger than the RAT (e.g., Wi-Fi) LBT measurement window. For example, an LTE subframe can be 1 millisecond. As an example, the LTE system operating bandwidth (BW) can be 5, 10, or 20 MHz. The LTE system can use a part of the BW and / or can use different parts of the BW in different parts of the time window. For example, LTE transmission can be performed with dynamically variable time-frequency resources. As an example, PDSCH transmission can span one or more resource blocks (RBs), where the resource block can span the entire system bandwidth or a part of it. LTE transmission can be performed over the entire subframe, and / or can be performed using a subset of the symbols (e.g., OFDM symbols) of the subframe. One or more reference signals (e.g., cell-specific reference signal (CRS)) can span the BW (e.g., the entire BW). One or more reference signals can be present in a subset of the symbols of the subframe and / or a subset of the subcarriers on the system bandwidth.

[0088] LTE transmissions can leave one or more gaps and / or holes in frequency and / or time. Other users and / or systems (e.g., Wi-Fi systems) may interpret one or more gaps and / or holes as indicating that the frequency band being used by the LTE-U eNB is idle. The frequency band interpreted as idle may not actually be idle.

[0089] Channel use indication (e.g., busy signal) can be used to facilitate LTE-U operation by allowing nodes (e.g., WTR, eNB, etc.) to announce channel use. For example, an eNB (e.g., LTE-U eNB) and / or a WTRU can transmit a signal (e.g., channel use indicator or busy signal). The signal can be transmitted over the entire frequency band or a portion of the frequency band. The signal can be transmitted during a certain time period. The signal can indicate that the frequency band is busy. The signal can be received by one or more potential users of the frequency band. As an example, the signal can indicate that the frequency band is busy when the frequency band is in use (e.g., there is transmission and / or reception over the entire channel or a portion of the channel), when the frequency band is planned to be used (e.g., planned transmission and / or reception), and / or when the frequency band is reserved for use by the eNB and / or one or more WTRUs (e.g., reserved and / or pre - booked for current and / or future transmission and / or reception).

[0090] As an example, the busy signal can be received, measured, decoded, read, detected, and / or sensed by a user or potential user of the frequency band. Devices operating in the vicinity of the range of the device (e.g., eNB or WTRU) transmitting the busy signal in that frequency band can interpret the busy signal as an indication that the channel is being used for LTE-U transmission. When a device receives, measures, decodes, reads, detects, and / or senses the busy signal, the device can determine not to attempt to access the frequency band (e.g., transmit on it or use the frequency band). For example, an LTE-U device (e.g., LTE-U eNB or LTE-U WTRU) can access the channel concurrently with the device transmitting the busy signal.

[0091] The busy signal can have one or more of the characteristics described herein. The busy signal can include an initial busy signal and / or an in - progress busy signal. When a device accesses (e.g., initially uses) and / or reserves access to the frequency band, the device can send an initial busy signal. As an example, the initial busy signal can be sent after initially determining that the frequency band is idle. When a device uses the frequency band and / or reserves the frequency band, an in - progress busy signal can be sent at that time. One or more characteristics of the initial busy signal can correspond to one or more characteristics of the in - progress busy signal.

[0092] The busy signal sent by the first eNB may be transparent to the one or more WTRUs and / or the second eNB. The one or more WTRUs and / or the second eNB may not be aware of (eg, informed of) one or more of the content and / or characteristics of the busy signal.

[0093] When a device acquires and / or maintains a frequency band, the device may take action to prevent (e.g., with the intent to prevent) one or more other devices from using the frequency band. The process of acquiring and / or maintaining a frequency band may include sending an indication that the channel has and / or may have one or more of the following states: being used, scheduled to be used, or reserved for use. The process of acquiring and / or maintaining a frequency band may include using the frequency band or transmitting on the frequency band (e.g., a frequency channel). The device may acquire and / or maintain one or more frequency bands. The device may send one or more signals and / or one or more busy signals. The one or more frequency bands and / or signals may include one or more LTE channels and / or signals.

[0094] Active time for a frequency band (eg, frequency channel) may include time during which one or more signals (eg, busy signals) may be transmitted on and / or using the frequency band. The eNB may perform transmissions on the frequency band during the active time.

[0095] As an example, the WTRU may be indicated whether an LTE-U cell is active. For example, whether an LTE-U cell is active may be indicated by physical layer signaling on the LTE-U cell and / or associated or aggregated PCell and / or by the presence of a busy signal. The LTE-U cell may be active when the LTE-U cell has a frequency band and / or uses or is scheduled to use a frequency band. In one example, the indication may indicate (e.g., explicitly indicate) one or more aspects of the activity time. The one or more aspects of the activity time may include the start of the activity time, the ongoing activity time, and / or the end of the activity time. The busy signal may indicate whether the LTE-U cell is active.

[0096] The activity time may be replaced by another time (which may or may not be a specific time, as an example). For example, the LTE-U eNB may activate the LTE-U cell on demand (as an example, rather than specifying a specific activity time for the LTE-U cell). The LTE-U eNB may activate the LTE-U cell on demand based on one or more first trigger criteria. The LTE-U eNB may deactivate the LTE-U cell based on one or more second trigger criteria. The amount of time that the LTE-U cell is active may vary based on one or more criteria (e.g., an observed criterion). A busy signal during the period when the LTE-U cell is active may indicate the amount of time that the LTE-U cell is active.

[0097] The eNB may want to perform transmission and / or reception on an unlicensed band (e.g., a channel). The eNB may monitor the unlicensed band. The eNB may monitor the unlicensed channel before the unlicensed channel becomes available. One or more devices (e.g., other LTE-U eNBs, WTRUs, and / or users such as WiFi stations or APs) may contend for the use of the unlicensed band. The LTE-U eNB may determine (e.g., observe) that the unlicensed channel band is available (e.g., the unlicensed band appears to be idle). When the LTE-U eNB determines that the unlicensed band is available, the LTE-U eNB may (e.g., quickly) acquire the unlicensed band. The process of acquiring the unlicensed band may include using the unlicensed band and / or indicating that the unlicensed band is busy. The LTE-U eNB may indicate that the unlicensed band is busy by using an initial busy signal.

[0098] For example, the LTE-U eNB may send an initial busy signal with synchronous and / or asynchronous timing (e.g., DL timing) for operating on and / or in the unlicensed band. The eNB may acquire the band at a time corresponding to the LTE time structure and / or LTE time boundary (e.g., the beginning of an LTE symbol, time slot (TS), subframe (SF), and / or radio frame).

[0099] The busy signal timing may be based on (e.g., depend on) whether synchronous and / or asynchronous timing can be used. The eNB may use the DL timing for transmission and / or as a reference for transmission on the band. The eNB may use the DL timing for reception on the band. The DL timing may include synchronous timing and / or asynchronous timing relative to other transmissions and / or timings. For example, the other transmissions and / or timings may include one or more DL transmissions and / or timings of the PCell. The PCell may include an associated or aggregated PCell. As an example, the other transmissions and / or timings may include one or more DL transmissions and / or timings of the previous active time of the band.

[0100] In the case of using synchronous timing, the LTE time structure and / or boundary for the LTE-U band can correspond to the time structure and / or boundary of the associated or aggregated PCell. The LTE time structure and / or boundary for the LTE-U band can correspond to the time structure and / or boundary of the previous active time of the band (e.g., the previous and / or DL transmissions performed by the eNB on the band). In the case of using asynchronous timing, the LTE time structure and / or boundary for the LTE-U band may not correspond to the time structure and / or boundary of the associated or aggregated PCell. In the case of using asynchronous timing, the LTE time structure and / or boundary for the LTE-U band may not correspond to the time structure and / or boundary of the previous active time of the band.

[0101] The LTE-U eNB can use synchronous (Sync) DL timing. The synchronous DL timing can include a scenario where the DL timing of the current active time can be calibrated (e.g., corresponding to or synchronized with) the timing in the previous active time and / or the PCell timing. The eNB can wait for the start of the next symbol, TS, SF, and / or frame in order to transmit one or more LTE channels (e.g., synchronous, data, and / or control channels). The start of the next symbol, TS, SF, and / or frame can correspond to the previous active time and / or the PCell timing. The one or more LTE channels can be scheduled for reception by one or more WTRUs (e.g., sent to the WTRUs). During the waiting time, the eNB can transmit a busy signal (e.g., an initial busy signal). The busy signal can indicate to one or more users (e.g., potential users) that one or more LTE channels may not be idle.

[0102] Figure 3 An exemplary LAA eNB timeline is shown. The exemplary LAA eNB timeline can include the start of subframe n 302. The exemplary LAA eNB timeline can include the first time 304 when the LAA eNB first observes the channel to be idle. The exemplary LAA eNB timeline can include a second time when the LAA eNB observes the channel to be idle for a period. The period can include a channel clearance time frame (e.g., 34 milliseconds). The eNB can transmit an initial busy signal. The initial busy signal can hold the channel until the next subframe boundary. The exemplary LAA eNB timeline can include a third time 308 at the end of subframe n and the start of the next subframe. The next subframe can be denoted as subframe n+1. At 308, the LAA eNB can stop transmitting the initial busy signal and / or can start transmitting data and / or control signals.

[0103] The LTE-U eNB can use asynchronous (Async) DL timing. The asynchronous DL timing can correspond to a scenario where the DL timing in the current active time may not be calibrated (e.g., corresponding to or synchronized with) the timing in the previous active time and / or the PCell timing. The start time for LTE DL transmission can begin when the eNB determines that the channel is idle. The start time of the LTE DL transmission can include the beginning of the first subframe for DL LTE channel transmission. The start time of the LTE DL transmission can include a timing offset. The LTE-U eNB using asynchronous DL timing can transmit an initial busy signal. As an example, when the timing offset is small (e.g., zero and / or below the lowest WiFi Clear Channel Assessment (CCA) period), the LTE-U eNB may not use and / or transmit an initial busy signal. When the timing offset is small, one or more potential users do not see the channel as idle before the LTE-U eNB starts the DL transmission of one or more LTE channels.

[0104] The eNB and / or WTRU can use synchronous and / or asynchronous DL timing based on one or more eNB and / or WTRU capabilities. The use of synchronous and / or asynchronous DL timing can be configurable. The eNB can notify the WTRU (e.g., by means of signaling passed via the associated or aggregated PCell, such as Radio Resource Control (RRC) signaling) whether synchronous and / or asynchronous DL timing can be used and / or what reference timing can be used. The reference timing can include the PCell timing and / or the previous active time timing of the LTE-U cell.

[0105] The reference timing can include the previous active time timing of the LTE-U cell. The LTE-U cell can include a fixed timing schedule. The fixed timing schedule can exclude one or more effects of timing drift. If the reference timing is the previous active time timing of the LTE-U cell, then the LTE-U cell can include a fixed timing schedule. One or more signals can be sent (e.g., turned on) during the active time. One or more signals are not sent (e.g., turned off) during the inactive time. The fixed timing schedule can remain the same during the active time and the inactive time.

[0106] The eNB can send a busy signal (e.g., an initial busy signal) during a period. The period can include the time between determining that the frequency band is idle and the eNB transmitting one or more LTE channels and / or signals.

[0107] The eNB can determine whether the frequency band is idle. When the eNB determines that the frequency band is idle, the eNB can send a busy (e.g., initial busy) signal until the next LTE DL transmission opportunity. The next LTE DL transmission opportunity can include the next valid time unit (e.g., its start). The next valid time unit can be based on the synchronized DL timing. The next LTE DL transmission opportunity can include the earliest time unit (e.g., its start). The WTRU can receive an LTE DL transmission in or from the earliest time unit. The WTRU can receive an LTE DL transmission, e.g., when the WTRU determines that there is an LTE DL transmission. The WTRU can determine the existence of an LTE DL transmission based on blind detection and / or based on receiving an indication of its existence or upcoming existence.

[0108] The WTRU can receive an indication (e.g., be notified) of an upcoming LTE DL transmission on an unlicensed frequency band (e.g., before an actual transmission). As an example, an upcoming LTE DL transmission on an unlicensed frequency band can be indicated by the eNB or via a DL transmission indication. The DL transmission indication can be signaled on an associated or aggregated PCell. The DL transmission indication can be provided in and / or included in the physical layer signaling (e.g., included in or provided by the PDCCH, EPDCCH, and / or downlink control information (DCI) format).

[0109] The time unit can include one or more of a symbol, a time slot, a subframe, a frame (e.g., a radio frame), and / or an LTE time unit.

[0110] The LTE-U eNB can reserve and / or acquire a frequency band by sending or transmitting a busy signal (e.g., an initial busy signal). The WTRU can detect an LTE signal (e.g., a meaningful LTE signal) and / or a DL transmission. The LTE-U eNB can reserve the frequency band by sending a busy signal until the WTRU detects an LTE signal and / or a DL transmission.

[0111] The handover time can include the time between when the eNB senses an idle frequency band and the time of transmission (e.g., the initial busy signal transmission and / or the LTE DL transmission). The handover time can be minimized. A handover time longer than a threshold may cause a potential user to determine that the channel is idle. The potential user may attempt to acquire the channel. The potential user attempting to acquire the channel may conflict with the eNB that has acquired the channel. One or more collision avoidance techniques (e.g., for reducing the likelihood of a collision) can be provided here. The one or more collision avoidance techniques can include a backoff technique. The backoff technique can include a random waiting time before sensing the channel and / or a random amount of sensing time.

[0112] The busy signal can include one or more formats. The format of the busy signal can be transparent (e.g., unknown) to one or more WTRUs. The busy signal can be formatted as an LTE signal. For example, the eNB can transmit an LTE signal as the busy signal. One or more random samples and / or signals can be used for the busy signal.

[0113] The shortest duration of the LTE signal can include one OFDM period. When transmitting the busy signal as part of an OFDM symbol, one or more LTE-like time domain samples (e.g., similar to the CP) can be used at this time. When transmitting the busy signal in a part of an OFDM symbol and one or more complete OFDM symbols, one or more sampled level signals can be transmitted in the part of the OFDM symbol, and one or more LTE signals can be transmitted in the one or more complete OFDM symbols. When transmitting the busy signal in a part of an OFDM symbol and one or more complete OFDM symbols, one or more sampled level symbols can be transmitted in the part of the OFDM symbol and / or the one or more complete OFDM symbols.

[0114] One or more signals are available for the busy signal. The one or more signals can be sent in signal transmission. The one or more signals can be used for a part of the busy signal. The one or more signals can include PSS, SSS, PBCH, CRS, PDCCH, and EPDCCH. The channel and / or signal for the busy signal can be transmitted at a time and / or frequency position that is not typical for LTE. The time and / or frequency position can be repeated.

[0115] The time density of the busy signal can meet one or more LBT expectations of the RAT (e.g., WiFi). The busy signal can enable the detection of LTE-U transmissions. For example, the busy signal can generate energy in the time window (e.g., 20 microseconds) used for CCA, thereby enabling the detection of LTE-U transmissions (e.g., by neighboring Wifi nodes).

[0116] The busy signal can include one or more specific static and / or dynamic configurations of bandwidth (BW) and / or physical resource blocks (PRB). The one or more specific static and / or dynamic configurations of the BW and / or PRB can improve the deployment of the busy signal according to one or more prevailing conditions, resource allocations, and / or other dynamics.

[0117] The LTE-U eNB may send (e.g., transmit) a busy signal. The busy signal may include an initial and / or an in - progress busy signal. The busy signal may prevent one or more users (e.g., potential users) of a frequency band from acquiring and / or accessing the frequency band. One or more users of the frequency band may include one or more LTE-U eNBs, WTRUs, and / or Wi-Fi users. One or more users of the frequency band may receive the busy signal (e.g., an ongoing transmission) (e.g., sense its presence). After receiving the busy signal, one or more users of the frequency band may not use the channel. One or more users of the frequency band may use energy detection (e.g., measurement) to sense the presence of a transmission. As an example, the detected energy may correspond to interference in the BW of interest.

[0118] A user (e.g., a WiFi user) may receive (e.g., only view) a portion of an LTE-U transmission. The portion of the LTE-U transmission may include a portion of the energy of the LTE-U transmission. For example, the BW of interest to the user may overlap with a portion of the transmission BW of the LTE-U eNB. When the BW of interest to the user overlaps with a portion of the transmission BW of the LTE-U eNB, the user may determine that the BW of interest is free to access (as an example, even if it may not actually be free to access). The busy signal may be configured to prevent transmissions on the transmission BW of the LTE-U eNB when the BW of interest overlaps with a portion of the transmission BW of the LTE-U eNB.

[0119] The data BW may include the entire BW of the frequency band configured and / or used for LTE-U (e.g., for an LTE-U SCell). For example, the BW may be 1.4, 3, 5, 10, 20 MHz or other frequency ranges. The data BW may include the BW of the frequency band used for an LTE-U session. An LTE-U session may be a limited period of time for use by the eNB, reserved for use, or a reserved channel. For example, an LTE-U session may start when the eNB determines that the frequency band is idle. An LTE-U session may start when the eNB acquires the frequency band. The LTE-U session may end when the eNB vacates the frequency band. The eNB may use the BW (e.g., use the entire BW or a portion thereof) during an LTE-U session (e.g., in each subframe of the LTE-U session). The BW may be the data BW. The data BW may be less than the entire BW of the frequency band. The eNB may configure the data BW. The eNB may indicate the data BW to one or more WTRUs. The eNB may indicate the data BW by means of signaling (e.g., physical layer and / or higher layer signaling).

[0120] The BW of interest to the user may overlap (e.g., partially overlap) with the full BW and / or the data BW.

[0121] The LTE-U cell can transmit a busy signal within the operating BW. The operating BW can be the full data BW of the LTE-U band (e.g., the LTE-U channel in use). The LTE-U cell can send a busy signal on the BW, thereby occupying a part (e.g., some or all) of the operating BW of the LTE-U band. The LTE-U cell can transmit a busy signal on a BW whose coverage exceeds the operating BW of the LTE-U band. The BW whose coverage exceeds the operating BW of the LTE-U band can include the maximum BW.

[0122] One or more LTE-U eNBs and / or WTRUs and / or their transceivers can operate on the same frequency band. The one or more LTE-U eNBs and / or WTRUs and / or their transceivers can follow the same channel parameter configuration (numerology). The busy signal can be transmitted within the operating BW of the LTE-U band. The busy signal transmitted within the operating BW of the LTE-U band can allow determination (e.g., by one or another LTE-U eNB or WTRU) that the LTE-U band is being used. As an example, one or more busy signal energy samples can be received on the operating BW of the LTE-U channel (e.g., the calibrated operating BW).

[0123] The LTE-U cell can transmit a busy signal (e.g., a part of the busy signal) outside the configured or actual data / transmission BW (e.g., full or data BW) for the LTE-U cell. The busy signal transmission may coincide and / or overlap with all or a part of the primary channels (e.g., bands) of a WiFi system such as 802.11 and / or 802.11ac. The said part of the primary channel of the WiFi system may be outside the configured or actual data / transmission BW (e.g., full or data BW) for the LTE-U cell.

[0124] The WiFi receiver can measure and / or detect the busy signal. The WiFi receiver can decode one or more signals on the primary frequency band (e.g., 20 or 22 MHz WiFi). The primary frequency band does not coincide (e.g., overlap) with the transmission BW (e.g., full or data BW) of the LTE-U cell. The primary frequency band may overlap with the busy signal transmission outside the transmission BW of the LTE-U cell. Measuring the busy signal on the primary channel can provide higher reliability compared to measuring the busy signal on the secondary BW part of the 802.11n and / or 802.11ac system BW that may coincide with the LTE-U transmission BW.

[0125] The busy signal can be configured to be transmitted in a frequency band, a channel, and / or one or more BW parts that may coincide, overlap, and / or be inside the LTE-U band and / or inside the BW (e.g., the whole or data BW) of the LTE-U band (e.g., completely inside it).

[0126] The busy signal may be configured to be transmitted in one or more BW portions in a frequency band, a channel, and / or a BW that may coincide, overlap, and / or be within a BW that is larger than the operating BW of the LTE-U band or outside the operating BW of the LTE-U band.

[0127] The busy signal BW may include a set of contiguous physical resource blocks (PRBs). The busy signal may include non-contiguous PRBs (e.g., within the BW and / or distributed across the BW). The busy signal BW may include a fixed BW that may be independent of the data BW, such as 20 MHz or 22 MHz. The busy signal BW may include the entire BW of the frequency band. The busy signal BW may include the data BW. The busy signal BW may include a function of the full and / or data BW, such as a certain number of PRBs that are wider than the full or data BW. The busy signal BW may include a function of the cell ID and / or one or more other configuration parameters of the LTE-U cell. The busy signal BW may include a BW that partially or fully overlaps with the full and / or data BW portion of the LTE-U band. The busy signal BW may include a BW that is partially or fully outside the full or data BW of the LTE-U band.

[0128] The initial busy signal may correspond to a first BW. The ongoing busy signal may correspond to a second BW. The first BW may be equal to the second BW.

[0129] The busy signal may be transmitted on one or more PRBs. The one or more PRBs may be within the busy signal BW. The busy signal may be transmitted on one or more sets of PRBs. The one or more sets of PRBs may be within the busy signal BW. The one or more sets of PRBs may include a set of one or more contiguous and / or non-contiguous PRBs.

[0130] The one or more PRBs for use by the busy signal may include a function of the cell ID and / or one or more other parameters configured for the cell.

[0131] The one or more PRBs used by the eNB for the busy signal may be dynamically changeable, that is, it may change according to a subframe and / or a set of subframes. For example, the eNB may use one or more PRBs with the worst and / or best channel quality for busy signal transmission. The eNB may measure local interference. The eNB may receive one or more reported interference measurements from one or more WTRUs. The channel quality of the one or more PRBs may be determined based on the local interference measurement and / or the reported interference measurement.

[0132] The busy signal can be sent in one or more fixed or configured sets of PRBs. For example, one or more PRBs can be located at or near the edge of the full or data BW. For other users or potential users that can operate in a neighbor band that partially overlaps with the full and / or data BW, such as other LTE-U eNBs, WTRUs, and / or WiFi users, the user can receive (e.g., detect) one or more sets of busy signal PRBs.

[0133] Figure 4 Illustrative BW 400 shows 25 PRBs that can correspond to 5 MHz (e.g., according to the authorized LTE specification). In Figure 4 , the PRBs available for data transmission are shaded. The PRBs that can be allocated for busy signal transmission are not shaded. As shown, the first four and the last four PRBs can send busy signal transmissions. The 17 middle PRBs can be used for data transmission.

[0134] As an example, the busy signal can cover the frequency bandwidth by including frequency hopping. The bandwidth of the frequency band can correspond to one or more of the following: a fixed BW setting, a configured BW setting, and / or the data bandwidth. The frequency bandwidth can remain constant over a period of time and / or can change over a period of time (e.g., according to the transmission setting).

[0135] The frequency hopping BW, one or more BW portions, and / or PRBs for busy signal transmission can enable WiFi with partial channel overlap to detect that the LTE-U band is being used.

[0136] The frequency hopping pattern and / or signaling sequence for the busy signal can be announced by means of one or more transmission parameters. The frequency hopping pattern and / or signaling sequence for the busy signal can be derived from one or more transmission parameters.

[0137] As an example, one or more PRBs for the busy signal can be transmitted in a pattern within the full channel BW or data BW. The pattern can include one or more sets of consecutive and / or discrete PRBs. For example, a set of PRBs can include N1 consecutive PRBs and / or N2 consecutive PRBs. The N1 consecutive PRBs can be used for busy signal transmission. The N2 consecutive PRBs can be used for data and / or control transmission (e.g., in the case where the full frequency band can be occupied by repeating the same pattern).

[0138] The eNB can signal to the WTRU and / or another eNB about the pattern and / or PRB usage of one or more of its busy signals. One or more patterns and / or sets of PRBs can be used for the busy signal. Signaling the pattern and / or set of PRB usage can include signaling an indication of the pattern and / or set of PRB usage available for and / or reserved for use by the eNB.

[0139] Figure 5 Illustrates an exemplary BW 500 with 25 PRBs that can correspond to 5 MHz (e.g., in accordance with the authorized LTE specification). In Figure 5 , the PRBs available for data transmission are shaded. The PRBs that can be allocated for busy signal transmission are not shaded. As shown, one out of every 4 PRBs can transmit a busy signal. The busy signal pattern can be represented as "1000", where "1" can represent the PRB that can be allocated for the busy signal and "0" can represent the PRB that can transmit a data signal.

[0140] Signaling the pattern and / or the set of PRBs used can include signaling a bitmap. For example, the eNB can transmit and the WTRU can receive a bitmap indication of which PRBs are available for busy and which PRBs are available for data / control. As an example, for a BW with 25 PRBs, the bitmap indication can include 25 elements, where the first state of each bit (e.g., '1') can indicate that the corresponding PRB is available for the busy signal and the second state (e.g., '0') can indicate that the corresponding PRB is not available for the busy signal and / or the corresponding PRB is available for data and / or control transmission. As an example, the bitmap can be represented as 1100011000110001100011000. The bitmap can include a repeatable pattern, such as 11000.

[0141] For one or more parameters of the busy signal, such as BW, the number of available PRBs (e.g., minimum or maximum number), PRB location, etc., these parameters can depend on the frequency channel on which the busy signal is transmitted. For example, one or more parameters can depend on one or more of the channel BW, channel center frequency, and / or channel number or ID.

[0142] The ongoing busy signal can be used after the LTE-U eNB acquires a frequency band (e.g., a channel) and / or after it starts transmission. The LTE-U eNB may plan to hold the frequency band for a period of time. This period can include one or more LTE time units during which the frequency band cannot be fully used (e.g., sensed) by the LTE-U eNB and / or one or more WTRUs. One or more other users can detect (e.g., sense) that the frequency band is idle during this period. The one or more other users can transmit on the frequency band.

[0143] For example, when the eNB does not transmit on the frequency band in the DL for one or more symbols and / or subframes (e.g., because there is no data to transmit), there may be idle LTE time units on that frequency band. When there is no active UL transmission (e.g., PUSCH, PUCCH, and / or SRS transmission) on the frequency band in the UL for one or more symbols and / or subframes, the frequency band may have idle LTE time units. When TDD UL subframes are not used (e.g., in the case where LTE-U only supports DL), the frequency band may have idle LTE time units. During the TDD UL / DL subframe transition, the frequency band may have idle LTE time units.

[0144] When the strength of the transmitted signal is not sufficient to be detected by other users (e.g., as an active user of the frequency band), the LTE time unit can be perceived as idle. Other users may include other LTE-U eNBs, WTRUs, and / or WiFi users. One or more other users may perceive the frequency band as idle and / or may attempt to access and use the frequency band.

[0145] When the eNB has acquired the frequency band (e.g., channel) and / or is ready to transmit or has transmitted one or more LTE signals on that frequency band, the eNB can transmit an in - progress busy signal. Other users or potential users, such as other LTE-U eNBs, WTRUs, and / or WiFi users, can detect the in - progress busy signal. The other users or potential users will consider the frequency band as unavailable, and this will enable the eNB to transmit the in - progress busy signal to maintain the frequency band.

[0146] The in - progress busy signal can be transmitted at known time unit boundaries. The LTE-U eNB can send the in - progress busy signal in an LTE time unit. The LTE time unit can be idle or can be perceived as idle. As an example, the in - progress busy signal transmission can be followed by, for example, immediately followed by a period for the LTE-U eNB and / or one or more connected WTRUs to perform one or more UL and / or DL channel transmissions.

[0147] The in - progress busy signal can be used to reserve a frequency band (e.g., a channel) for UL transmission (i.e., tx). For example, the eNB can determine whether a frequency band is idle, e.g., using LBT (e.g., measurement) techniques to determine. The eNB can acquire the frequency band. For example, the eNB can send a DL signal with a busy signal and one or more of the LTE DL channels or signals. The eNB can provide a UL grant for UL resources in sub - frame n + k to the WTRU in sub - frame n, where for FDD, k can be 4 and can depend on the UL / DL configuration for TDD. As an example, the eNB can continue to transmit in the DL through all or part of sub - frame n + k - 1 in order to keep the frequency band by making the frequency band appear busy (e.g., continuously busy) until the WTRU acquires and / or uses the frequency band for UL transmission in sub - frame n + k. As an example, when the eNB does not keep the frequency band in other ways during this time, the eNB can transmit a busy signal for all or part of the time before sub - frame n + k. When the eNB does not have enough DL data to transmit to one or more WTRUs, the eNB may not be able to keep the frequency band.

[0148] The busy signal can be transmitted with one or more data and / or control signals. The eNB and / or WTRU can transmit a busy signal (e.g., an in - progress busy signal with one or more of LTE data, control, synchronization channels, and / or signals).

[0149] The busy signal transmission and the data / control signal transmission can be simultaneous. For example, when the LTE - U eNB and / or one or more connected WTRUs are not transmitting and / or receiving other signals on the frequency band, then the LTE - U eNB can transmit a busy signal (e.g., an in - progress busy signal) on the frequency band (e.g., an unlicensed frequency channel). The operations related to non - simultaneous in - progress busy signal transmission can be similar to the initial busy signal transmission when there is no data and / or control channel or signal being transmitted in the LTE - U cell or LTE - U frequency band.

[0150] The eNB can transmit a busy signal (e.g., an in - progress busy signal) on a frequency band (e.g., an unlicensed frequency channel), and at the same time, it can transmit and / or receive DL and / or UL LTE channels and / or signals on the same frequency band (e.g., in different PRBs of the frequency band).

[0151] One or more control channels and / or signals can include one or more synchronization channels and / or signals.

[0152] For example, the eNB may transmit a busy signal, such as an ongoing busy signal, in the PRBs (e.g., one or more or all PRBs) of the LTE-U band or cell, where the PRBs are not available for data and / or control channel or signal transmission within the full or data BW of the LTE-U band or cell.

[0153] Figure 6 Shows an example of ongoing busy signal transmission 600. For illustrative purposes, in Figure 6 , the data signal may be shaded, and the ongoing busy signal will not be shaded. The eNB may perform transmission in a band that uses a BW of N PRBs for transmission. As an example, six PRBs may be used in the example shown in Figure 6 . The eNB may transmit data (and / or control) signals through N PRBs in one or more subframes, such as subframes n-1 and n+1. The eNB does not use the entire BW for data (and / or control) in one subframe, such as subframe n. In this subframe, the eNB may transmit an ongoing busy signal in one or more PRBs where it does not transmit data (and / or control) signals, such as PRBs 3, 4, and 5 in subframe n of the figure. The ongoing busy signal enables other users to detect (e.g., better detect) the transmitted signal, and / or interpret the band as busy, and as an example, other users will thus not acquire the band.

[0154] Regardless of whether the eNB transmits any data and / or control signals, the eNB may send a busy signal, such as an ongoing busy signal, in one or more sets of PRBs. The eNB may transmit the busy signal in one or more sets of PRBs different from the set of PRBs for transmitting LTE data and / or control channels.

[0155] The eNB may (e.g., always may) perform transmission on a set of dynamically shared PRBs. The dynamically shared PRBs may be dynamically shared between the busy signal and one or more data / control signals. As an example, the transmission in the set of PRBs may include a busy signal and / or one or more data / control signals.

[0156] As an example, for different subframes, the ratio of the busy signal to the data / control signal on the set of PRBs may be different. For example, the ratio of the busy signal to the data / control signal on the set of PRBs may depend on the PRBs requested, used, and / or scheduled for data / control transmission. The set of PRBs and the set of busy signal PRBs may be the same.

[0157] As an example, for the set of PRBs designated or used for the busy signal, when no data / control signal is transmitted and / or not planned to be transmitted in a subframe, the eNB may transmit the busy signal in the set of PRBs of this subframe.

[0158] For a set of PRBs designated or used for the busy signal, the eNB does not transmit the busy signal in a subframe (e.g., when the number of PRBs that can be transmitted or scheduled to be transmitted in a subframe for data / control exceeds the number of PRBs in the set of PRBs). The eNB may allocate and / or transmit data / control signals on the subframes of the PRBs in the set of PRBs. The data / control may serve as the busy signal.

[0159] For a set of PRBs designated or used for the busy signal, as an example, when the non-zero number of PRBs that can be transmitted or scheduled to be transmitted in a subframe for data / control signals is less than the number of PRBs in the set of PRBs, the eNB may share the set of PRBs between the data / control signal and the busy signal in the subframe. The eNB may allocate and / or transmit data / control in the PRBs that include all or part of the PRBs in the set of PRBs. The eNB may transmit the busy signal in one or more remaining PRBs of the set of PRBs.

[0160] For a set of PRBs designated or used for the busy signal and another set that may include remaining PRBs (e.g., in the full or data BW), as an example, when the number of PRBs that can be transmitted or scheduled to be transmitted in a subframe for data / control exceeds the number of remaining PRBs, the eNB may share the set of PRBs between the busy signal and the data / control signal transmission. After allocating the PRBs in the subframe to data / control, the eNB may transmit the busy signal in one or more PRBs of the available set of PRBs. As an example, when there are no available PRBs after the allocation, the eNB does not transmit the busy signal.

[0161] For example, when the full channel (or data) BW can be N (e.g., 100) PRBs, multiple (e.g., the first X and / or the last Y) PRBs can be allocated or designated for the busy signal. For example, PRBs 0 - 19 and 80 - 99 can be allocated or designated for the busy signal. During the active time, as an example, when the eNB has a frequency band or can transmit or receive signals on that frequency band, the eNB can send signals in the multiple PRBs allocated or designated for the busy signal. The signals can be one or more of the busy signal and / or the data / control signal. As an example, Y can be 0.

[0162] For example, when the LTE-U eNB has one frequency band and has no data and / or control signals to transmit, the eNB can transmit a busy signal in the first X and / or last Y PRBs, such as PRBs 0 - 19 and 80 - 99. For example, when the LTE-U eNB has a frequency band and the eNB has the full (or data) BW of data / control signals to transmit (such as 100 PRBs), the eNB does not send a busy signal. As an example, the eNB can use all of the full (or data) BW for data / control signal transmission. The eNB can transmit a busy signal in one or more remaining PRBs not used for data / control. For example, when the LTE-U eNB has the frequency band and the BW it has is less than the full (or data) BW of data / control signals to transmit (such as 100 PRBs) and / or more than the BW of data / control signals to transmit minus (X + Y) PRBs, such as the value of 90 PRBs for data / control signals, the eNB can transmit a busy signal in PRBs 0 - 4 and 95 - 99 and transmit data / control in PRBs 5 - 94.

[0163] Having a frequency band can include using and / or planning to use the frequency band. During the active time of the frequency band for the eNB, the eNB can have or can consider having the frequency band.

[0164] The LTE-U cell can share one or more frequency resources (such as one or more sets of PRBs) with one or more other LTE-U cells and / or other users (such as WiFi users). The LTE-U eNB does not send signals on a set of PRBs that may be used by another LTE-U eNB.

[0165] For example, in one or more subframes, the LTE-U eNB does not use the entire BW, such as one or more or all available PRBs in the full or data BW. The LTE-U eNB can transmit LTE data, control channels, and / or signals on a first set of PRBs (such as one of the sets). The LTE-U eNB can send a busy signal on a second, for example, designated set of PRBs. As an example, when there is not enough data to occupy the full or data BW, then the LTE-U eNB does not use a third set of PRBs (such as the third set of PRBs or the set of remaining PRBs). The LTE-U eNB can share the frequency band with a second LTE-U eNB. The second LTE-U eNB can use one or more unused PRBs (such as the third set of PRBs) for communication, such as using them for LTE data and / or control channels (such as in the DL).

[0166] A band sharing arrangement may be configured by a network, e.g., via OA&M signaling. The band sharing may be arranged by one or more eNBs. A first eNB may inform a second eNB of the first eNB's intention to use a portion of an unlicensed band, such as during a time period and / or in one or more subframes. As an example, the first eNB may communicate this intention to the second eNB via X2. The first eNB may indicate band usage and / or a scheduled band usage in one or more of physical layer, MAC, and RRC signaling. The second eNB may determine the first eNB's intention by monitoring the physical layer, MAC, and RRC signaling.

[0167] An eNB may determine the usage of LTE-U eNBs and / or WTRUs by monitoring one or more portions of the LTE-U band. As an example, when the eNB determines that another LTE-U eNB or LTE-U WTRU may have the band, the eNB may determine the availability of PRBs by monitoring one or more subsets of PRBs of the band. In particular, for example, when the eNB determines that one or more PRBs are available for use and / or sharing, the eNB may use these PRBs for DL and / or UL transmissions. Available may include not being used. As an example, based on the properties of OFDM or based on an expected interference below a certain threshold, one or more unused PRBs may also be considered available for sharing.

[0168] For one or more LTE-U eNBs (and / or WTRUs) that may share, e.g., use an unlicensed band in a subframe simultaneously, they may transmit a busy signal in the subframe. Multiple users of the band (e.g., one or more eNBs and / or WTRUs) may transmit one or more busy signals simultaneously, e.g., in a particular subframe of the same or different PRB sets.

[0169] If one or more busy signals are transmitted simultaneously from different LTE-U users (e.g., eNBs and / or WTRUs) in the same PRB set, it may result in a stronger overall busy signal. Other users in the band, such as other LTE-U eNBs, WTRUs, and / or WiFi users, will detect the stronger overall busy signal. The stronger overall busy signal may protect the band from access by other users.

[0170] For example, the first eNB may acquire a 20 MHz frequency band (e.g., a channel) that may include 100 PRBs. The first eNB may transmit a first busy signal on this frequency band. The first eNB may transmit the first busy signal at the edge of this frequency band, e.g., on the first and last 10 PRBs. The first eNB may transmit the first busy signal on PRBs 1 to 10 and PRBs 91 to 100. The second eNB may detect and / or be informed of the presence of the first eNB. The second eNB may share one or more frequency band resources with the first eNB. The second eNB may transmit a second busy signal with the first eNB in the same set of PRBs, e.g., on PRBs 1 to 10 and PRBs 91 to 100. The second eNB may monitor the total received power level of each PRB on PRBs 11 to 90. The second eNB may identify one or more PRBs having the minimum total received power and / or interference level. The second eNB may transmit data on the identified PRBs, especially one or more PRBs such as those having the minimum total received power and / or interference. In one example, the second eNB may be provided with and / or may receive from the first eNB a priority PRB usage list. The priority PRB usage list may indicate the PRB usage priority for the first eNB for data transmission. The second eNB may (e.g., only may) transmit data on the PRBs used by the first eNB in the received priority PRB usage list and having a lower (e.g., the lowest) usage priority.

[0171] As an example, the eNB may use different power parameters for the busy signal in different subframes. One or more power parameters may depend on whether simultaneous transmission of the busy signal and / or data / control signals is supported in the subframe.

[0172] The center frequency of the LTE-U frequency band (e.g., a channel) may be different from the WiFi channel. The center frequency of the LTE-U frequency band may be determined based on the RAT of other users, e.g., WiFi, the channel center frequency.

[0173] As an example, information may be conveyed in the busy signal. For example, the busy signal transmitted by the LTE-U eNB may carry information beneficial to other users or potential users of the LTE-U frequency band (e.g., other LTE-U eNBs or WTRUs).

[0174] The busy signal may include a control channel, e.g., PDCCH or EPDCCH. Control channels such as PDCCH or EPDCCH may either be used as or replace the busy signal, or be part of the busy signal, and / or may provide a function of the busy signal. For example, the busy signal may be replaced by a control channel.

[0175] The busy signal may include or otherwise convey information. For example, the busy signal may convey or indicate one or more of the following. For example, the busy signal may indicate how long, e.g., in how many additional subframes and / or frames, the transmitter of the busy signal may plan to hold and / or use the frequency band before releasing and / or vacating the frequency band. The busy signal may indicate how long, e.g., in how many subframes and / or frames, the transmitter of the busy signal has held and / or used the frequency band before it acquired (e.g., first acquired) the frequency band. The busy signal may indicate when or how long ago the first transmission of the busy signal occurred. The busy signal may indicate how much gap time (e.g., minimum gap time) the transmitter of the busy signal may allow or plans to allow when it vacates the channel. For example, the gap time may correspond to one or more of a plurality of symbols, time slots, and / or frames. The busy signal may indicate one or more transmission parameters of the data that the transmitter of the busy signal may transmit and / or plans to transmit, such as frequency or BW information. The busy signal may convey one or more transmission parameters of the data transmitted by a WTRU controlled by the busy signal transmitter.

[0176] The busy signal, PDCCH, and / or EPDCCH may convey this information. Other mechanisms other than the busy signal may be used to convey this information.

[0177] The eNB that transmits the busy signal may provide information (e.g., configuration information) related to one or more parameters of the busy signal, such as time (e.g., one or more subframes and / or frames) and / or frequency location (e.g., PRB). The eNB may provide the information to one or more WTRUs and / or eNBs in broadcast signaling transmission and / or in dedicated signaling transmission. The broadcast signal transmission may be sent via a PCell associated with and / or aggregated with the LTE-U cell.

[0178] The eNB may signal information to the WTRU via a PCell that may be associated with or aggregated with the LTE-U cell, e.g., by using RRC signaling. The eNB may signal information to another eNB, e.g., by using X2 signaling on the X2 interface.

[0179] The eNB may obtain information related to another eNB, e.g., a neighbor eNB, by reading the broadcast information of other eNBs.

[0180] The eNB may provide an RNTI to the WTRU and / or eNB via, such as, broadcast or dedicated signaling. The RNTI enables the WTRU and / or eNB to receive and / or decode the content of the busy signal.

[0181] The eNB and / or WTRU may receive and / or decode one or more contents of the busy signal transmitted by another eNB.

[0182] The eNB and / or WTRU may use this information to determine when to acquire a frequency band. For example, when an LTE-U user has a frequency band and it is both permitted and / or feasible to use it simultaneously, the eNB and / or WTRU may determine to acquire the frequency band. When the current user will vacate the frequency band and the frequency band may be idle, and / or when sufficient gap time is allowed for other users or after that, etc., the eNB and / or WTRU may determine to acquire the frequency band.

[0183] The eNB and / or WTRU may use this information to determine when not to attempt to acquire the frequency band. For example, when an LTE-U user may have the frequency band and / or before the gap time for other users is exceeded, etc., the eNB and / or WTRU may determine not to acquire the channel.

[0184] LTE-U synchronization (sync) signals may support LTE-U operation. LTE-U synchronization signals may be transmitted in synchronization signal transmissions. In an LTE system, the eNB may transmit one or more reference signals, such as CRS, in one or more (e.g., all) DL subframes. The eNB may transmit one or more synchronization signals in one or more DL subframes of a radio frame. The eNB may transmit one or more reference signals and / or one or more synchronization signals in one or more (e.g., all) radio frames.

[0185] The WTRU may receive one or more reference signals and / or synchronization signals from the eNB in one or more DL subframes. The WTRU may use one or more of the reference signals and / or synchronization signals (e.g., for acquiring and / or maintaining frequency and / or time synchronization with the eNB).

[0186] The LTE-U eNB may use the unlicensed frequency band (e.g., channel) periodically and / or aperiodically. The LTE-U eNB may transmit on the unlicensed frequency band during a first period. The LTE-U eNB may vacate (e.g., not use) the unlicensed frequency band during a second period. The LTE-U eNB may alternate between transmitting on the unlicensed frequency band and vacating the unlicensed frequency band. As an example, due to this alternating operation, the LTE-U eNB does not transmit DL reference signals and / or synchronization signals in some subframes and / or frames. The intermittent availability of one or more DL references and / or synchronization signals may prevent the WTRU from achieving time and / or frequency synchronization with acceptable (e.g., reasonable or sufficient) performance.

[0187] A wireless transmit / receive unit (WTRU) may establish a connection with a first cell on an authorized frequency band. The WTRU may receive a first downlink transmission. The first downlink transmission may be received from a second cell operating on an unlicensed frequency band. The WTRU may determine a synchronization signal transmission from a third cell operating on an unlicensed frequency band using one or more resource elements. The one or more resource elements may correspond to a portion of one or more resource blocks of a downlink transmission from the second cell. The synchronization signal transmission may include one or more of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS), and / or a demodulation reference signal (DMRS).

[0188] The WTRU may determine that a synchronization signal transmission from a third cell operating on an unlicensed frequency band is transmitted using one or more resource elements by receiving downlink control information (DCI) on a downlink physical channel. The downlink physical channel may indicate which resource elements are used for the synchronization signal transmission.

[0189] An LTE-U eNB may provide and / or transmit a signal (or set of signals) for synchronization purposes (e.g., frequency and / or timing synchronization). The signal may be used by the WTRU. The WTRU may use the signal to acquire and / or maintain frequency and / or timing synchronization with the eNB. The signal may be referred to as an “LTE-U synchronization signal” or a synchronization signal. In one example, the LTE-U synchronization signal may be different from the PSS and / or SSS used in some LTE systems. In one example, the LTE-U synchronization signal may include one or more of the PSS and / or SSS.

[0190] The LTE synchronization signal and the busy signal may be implemented and / or presented by the same signal (or set of signals). The LTE synchronization signal and the busy signal may include one or more of the same signals.

[0191] The LTE-U synchronization signal may include a specific format. In one example, the time interval of the LTE-U synchronization signal may be based on one or more OFDM symbols, one or more subframes, and / or one or more frames.

[0192] For example, the LTE-U synchronization signal may occur and / or repeat in one or more OFDM symbols and / or time slots, such as in a subframe, at the beginning of a subframe, or before the beginning of a subframe. The LTE-U synchronization signal may occur and / or repeat in one or more subframes, such as in a frame.

[0193] The WTRU may receive LTE-U synchronization signals in one or more OFDM symbols and / or time slots, e.g., within a subframe, at the beginning of a subframe, or before the beginning of a subframe. The WTRU may receive LTE-U synchronization signals in one or more subframes, e.g., within a frame. In the OFDM symbols, time slots, and / or subframes, the LTE-U synchronization signals may be the same, e.g., may be repeated.

[0194] For example, the LTE-U synchronization signals may be transmitted on a set of PRBs, such as six PRBs in the center, and / or on multiple (e.g., two) OFDM symbols within multiple PRBs. The LTE-U synchronization signals transmitted on one or more specific OFDM symbols (e.g., the first OFDM symbol) may be similar to the PSS sequence. The LTE-U synchronization signals transmitted on one or more other OFDM symbols (e.g., the second OFDM symbol) may be similar to the SSS sequence. The LTE-U synchronization signals may include one or more of PSS, CSS, PBCH, CRS, CSI-RS, or DMRS.

[0195] As an example, before transmitting LTE data and / or control signals on an LTE-U band (e.g., a channel), the eNB may transmit a set of LTE-U synchronization signals on that channel in a continuous manner or a selected number of times in consecutive symbols.

[0196] On one or more different frequency resources in one or more different symbols and / or subframes, e.g., on different sets of PRBs, the eNB may transmit and / or the WTRU may receive LTE-U synchronization signals. By transmitting LTE-U synchronization signals on one or more different frequency resources, higher frequency diversity gain can be provided for LTE-U synchronization signal reception.

[0197] The LTE-U synchronization signals may include one or more LTE system signals, e.g., PSS, SSS, PBCH (e.g., MIB), CRS, CSI-RS, DMRS, etc. The transmission of one or more LTE system signals that are part of the LTE-U synchronization signals may be according to the symbols and / or symbol order of the signals in the LTE system.

[0198] The LTE-U synchronization signals and data may coexist. One or more LTE-U channel resources, e.g., PRBs, may be shared between one or more LTE-U synchronization signals and / or one or more DL channel signals (e.g., control and / or data signals). The WTRU may receive LTE-U synchronization signals and / or one or more DL channel signals on the same set of channel resources, e.g., on a set of PRBs.

[0199] For LTE synchronization signals and data / control time sharing, as an example, a WTRU may receive an LTE-U synchronization signal and one or more data / control signals in the same set of PRBs. The LTE-U synchronization signal and one or more data / control signals may be received in different time slots and / or OFDM symbols.

[0200] For example, in the case of using different time slots, the set of PRBs may be shared between the LTE-U synchronization signal and one or more data / control signals, where a first time slot may be allocated to the LTE-U synchronization signal and a second time slot may be allocated to one or more data / control signals. For example, as part of a DL grant, a WTRU may receive an indication specifying how to detect and / or decode one or more subframes. The sharing may apply to one or more subframes.

[0201] As an example, one or more different OFDM symbols may be used. The LTE-U synchronization signal may be transmitted in one or more OFDM symbols (e.g., each or more of, a time slot, a subframe, and / or a radio frame). In one example, one or more OFDM symbols or resource elements (REs) of one or more OFDM symbols may be used for LTE-U synchronization signal transmission. The one or more OFDM symbols and / or the REs of the one or more OFDM symbols may not be used for LTE data / control signals. For example, on a first OFDM symbol in a PDSCH region of one or more subframes, e.g., all subframes, the eNB may transmit and / or the WTRU may receive the LTE-U synchronization signal.

[0202] The WTRU may be configured by the eNB as to which subframes may include PRB sharing for the LTE-U synchronization signal and data / control signals. As an example, the configuration may be performed by means of higher layer signaling (e.g., RRC signaling).

[0203] As an example, in different PRBs, the eNB may transmit and / or the WTRU may receive the LTE-U synchronization signal and data / control signals. The different PRBs may be within the same subframe and / or time slot. The WTRU may receive the LTE-U synchronization signal in a first PRB group. The WTRU may receive (e.g., simultaneously receive) one or more data / control signals in a second PRB group. As an example, the WTRU may expect the LTE-U synchronization signal to be included in a subset of PRBs of the subframe.

[0204] As an example, one or more LTE-U synchronization signals can be separated by means of code division multiplexing (CDM). The first eNB and the second eNB can simultaneously transmit their respective LTE-U synchronization signals on the same resource set, e.g., on the same set of PRBs. One or more very neighboring eNBs may cause significant interference to the reception of one or more LTE-U synchronization signals by a WTRU. The interference generated to the reception of the LTE-U synchronization signals may affect the synchronization performance of one or more WTRUs. As an example, CDM can be used to reduce inter-cell LTE-U synchronization signal interference. Scrambling and / or orthogonal cover code (OCC) can be used.

[0205] For example, the LTE-U synchronization signals can be spread in time and / or frequency by using OCC. Time spreading can include repeating the signal in the time domain. Each repetition of the signal can be multiplied by the bits of the corresponding OCC. Spreading in frequency can include repeating the signal in one or more PRBs. Each repetition of the signal can be multiplied by the bits of the corresponding OCC. Spreading in time and / or frequency can increase the number of resources allocated to the LTE-U synchronization signals, which may depend on the length of the OCC. Each eNB can use the OCC for the LTE-U synchronization signals. The one or more OCCs of the one or more eNBs (e.g., eNBs close to each other) can be different.

[0206] The LTE-U synchronization signals can be scrambled with a predetermined sequence. For different eNBs, the predetermined sequence can be different. For example, the scrambling sequence can depend on the cell ID and / or reference sequence of a particular LTE-U cell and / or the associated or aggregated LTE PCell.

[0207] The LTE-U synchronization signals can be configured. The LTE-U synchronization signal configuration can be indicated. For example, a WTRU can be configured to have and / or can implicitly and / or explicitly receive one or more of the following: the identification of the configured frequency and / or time resources that can be allocated to and / or used for the LTE-U synchronization signals and other applicable repetition information; or an indication of the presence or upcoming presence of the LTE-U synchronization signals.

[0208] LTE-U synchronization signal configuration / indication can be used to represent resource allocation and / or presence indication for LTE-U synchronization signals. A WTRU may receive a configuration (e.g., LTE-U synchronization signal configuration / indication). This configuration may indicate that one or more resource elements will be used by the cell for transmitting asynchronous signal transmissions. Resource allocation may include repetition. The resource allocation and / or presence indication may be provided by the eNB and / or received by the WTRU (e.g., separately or jointly). The resource allocation and / or presence indication may use the same or different signaling. For example, the resource allocation may be provided by higher layer signaling. As an example, the presence indication may be provided by physical layer signaling. As an example, when the WTRU can determine the presence of the LTE-U synchronization signal by blind detection, then the presence indication may not be provided and / or used. And as an example, when the LTE-U synchronization signal can occur regularly, such as periodically or at known or configured intervals, then the presence indication may not be provided and / or used.

[0209] LTE-U synchronization signals may include cell-specific configuration and / or indication. LTE-U synchronization signal resource allocation may be cell-specific. Two or more WTRUs configured with an LTE-U cell may receive the same LTE-U synchronization signal resource allocation. Two or more WTRUs configured with an LTE-U cell may expect LTE-U synchronization signals at the same time and / or frequency resource positions.

[0210] The presence indication may be provided in a cell-specific manner (e.g., by means of a DCI format with a common RNTI). As an example, even without DL data for the WTRU, the cell-specific presence indication can enable the WTRU to synchronize to or remain synchronized with the LTE-U cell.

[0211] LTE-U synchronization signals may be WTRU-specific, e.g., on demand. Two or more WTRUs configured with an LTE-U cell may receive the same or different WTRU-specific LTE-U synchronization signal resource allocations. Two or more WTRUs with different resource allocations may expect LTE-U synchronization signals at different time and / or frequency positions.

[0212] WTRU-specific LTE-U synchronization signals can be used in one or more scenarios. For example, when the LTE-U synchronization signal is beamformed and / or precoded for one or more specific WTRUs, then WTRU-specific LTE-U synchronization signals can be used. WTRU-specific LTE-U synchronization signals can be used when a group of WTRUs receive LTE-U synchronization signals, whereby other WTRUs without scheduled data do not attempt to detect and / or decode the LTE-U synchronization signal.

[0213] The presence indication can be provided in a WTRU-specific manner, for example, by means of a DCI format with a WTRU-specific RNTI (such as a C-RNTI or other RNTI) or an RNTI for a WTRU group. The WTRU-specific presence indication can target one or more WTRUs for which the LTE-U synchronization signal appears or appears shortly thereafter in the DL data. By providing the WTRU-specific presence indication, one or more WTRUs can be enabled to perform one or more measurements, report one or more measurements, and / or synchronize or maintain synchronization with the LTE-U cell.

[0214] Two or more LTE-U synchronization signal configuration / indication mechanisms can be different. As an example, this depends on whether the WTRU supports blind detection of LTE-U synchronization signals and / or whether the LTE-U synchronization signals appear in a periodic manner or at known or configured intervals.

[0215] For example, in the case of LAA, the WTRU can receive the LTE-U synchronization signal configuration / indication from the eNB by means of an associated or aggregated PCell.

[0216] The WTRU can receive the LTE-U synchronization signal resource allocation and / or presence indication from the PCell by means of physical layer and / or higher layer signaling, such as by means of a PCell DL grant (such as by means of cross-carrier scheduling or a similar mechanism).

[0217] The LTE-U synchronization signal resource allocation and / or presence indication can be included in physical layer signaling such as a DCI format on the PCell. The WTRU can monitor the DCI format on the PCell. The DCI format can indicate the presence or impending presence of the LTE-U synchronization signal and / or the LTE-U data / control signal.

[0218] The WTRU can receive a DL grant for cross-carrier scheduling of an LTE-U SCell on the PCell. The cross-carrier scheduling DL grant can indicate to the WTRU the possible presence (or impending presence) of an LTE-U synchronization signal on the LTE-U frequency band. The cross-carrier scheduling DL grant can provide the WTRU with a grant for one or more DL resources on the LTE-U frequency band.

[0219] The WTRU can learn the timing relationship between the presence indicator and the presence of the LTE-U synchronization signal.

[0220] The LTE-U SCell may be time-shifted from the authorized PCell by multiple symbols or time slots (as an example, thereby allowing the WTRU time to be synchronized with the LTE-U cell before receiving the grant data).

[0221] When, after, or in response to receiving physical layer signaling, such as a DL grant, that may indicate the presence or impending presence of an LTE-U synchronization signal, the WTRU may use the LTE-U synchronization signal to achieve, maintain, or correct its synchronization with the LTE-U cell. The WTRU may attempt to receive DL data based on the DL grant. The attempted reception may occur concurrently with and / or after the synchronization process. The synchronization may use the LTE-U synchronization signal.

[0222] LTE-U synchronization signal resource allocation may be received in a DL grant (e.g., for indicating a predefined or preconfigured set of resource allocations to be used) or via other techniques, such as by means of semi-static RRC signaling from the eNB.

[0223] As an example, the WTRU may receive the LTE-U synchronization signal in accordance with a predefined and / or preconfigured pattern with respect to one or more of subframes, time slots, OFDM symbols, resource elements, and / or PRBs. The predefined and / or preconfigured pattern may be referred to as an LTE-U synchronization signal pattern.

[0224] The eNB may provide a configuration. The WTRU may receive the configuration via a higher layer signaling, such as RRC signaling. The eNB may define or may configure a set of patterns. The WTRU may receive the set of patterns via the higher layer signaling. Physical layer signaling (e.g., on the PCell) may indicate which pattern is applicable at a particular time.

[0225] During the active time of the LTE-U band, the WTRU may expect the presence of an LTE-U synchronization signal in the LTE-U band (e.g., channel) based on the LTE-U synchronization signal pattern.

[0226] Regardless of whether the LTE-U cell is active or inactive, the WTRU may expect the presence of an LTE-U synchronization signal in the LTE-U band based on the LTE-U synchronization signal pattern.

[0227] One or more indications may be implicit. For example, the eNB may transmit the LTE-U signal and / or synchronization signal once and / or more than once every XX + YY milliseconds. XX and / or YY may be configured values, e.g., signaled by the eNB to the WTRU. YY may be 0 or may not be used.

[0228] The WTRU can be configured to have a set of PRBs for the expected LTE-U synchronization signal. As an example, when the WTRU does not receive an LTE-U synchronization signal after XX milliseconds have elapsed since the most recent LTE-U synchronization signal and / or the start of the previous active period and / or the end of the previous active period, the WTRU can expect the LTE-U synchronization signal in subframe XX + YY since the most recent LTE-U synchronization signal and / or the start of the previous active period and / or the end of the previous active period.

[0229] The WTRU can determine (e.g., derive) one or more signal characteristics based on the most recent active period. For example, the multiple can be that the repetition of consecutive LTE-U synchronization signals is the same as the signal repetition for the most recent active period. The multiple can be that the repetition of consecutive LTE-U synchronization signals can depend on the time elapsed since the most recent active period. For example, when the elapsed time is less than a threshold (e.g., 20 milliseconds), the WTRU can expect an instance of the LTE-U synchronization signal, e.g., no repetition of the LTE-U synchronization signal. As an example, when the elapsed time is greater than another threshold (e.g., 100 milliseconds), the WTRU can expect multiple repetitions (e.g., 2 repetitions) of the LTE-U synchronization signal.

[0230] The WTRU can search and / or perform blind decoding for potential LTE-U synchronization signals periodically or continuously. The WTRU can search a set of possible LTE-U synchronization signals. The WTRU can derive some information from the indices of the LTE-U synchronization signals in the set. For example, considering that the complexity of the blind detection process increases with the number of detection scenarios, the blind detection process for LTE-U synchronization signals can accept a limited number of waveforms.

[0231] For example, the WTRU can determine (e.g., derive) the start of one or more of the OFDM symbols, time slots, subframes, and / or frames for the LTE-U band. As an example, the determination can depend on the timing detected for the LTE-U synchronization signal (e.g., the detected timing of the WTRU), e.g., asynchronous DL timing.

[0232] The LTE-U cell can share one or more frequency resources, such as one or more sets of PRBs, with one or more LTE-U cells and / or other users (e.g., WiFi users). Two or more eNBs can transmit LTE-U synchronization signals on the same set of PRBs (e.g., overlapping resources) and / or different sets of PRBs (e.g., non-overlapping resources).

[0233] For example, different LTE-U eNBs may transmit LTE-U synchronization signals in different PRB sets and / or different subframes. The use of different PRB sets and / or different subframes for two or more synchronization signals can ensure that there is no overlap in resource usage for synchronization signal transmission.

[0234] Signals for transmission and / or reception may be rate matched around one or more channel resources. For example, an LTE-U eNB may perform rate matching around the LTE-U synchronization signals of other eNBs. As an example, terms such as performing "rate matching" and / or performing rate matching around one or more channel resources may be used to refer to or include transmitting or receiving in a manner that skips or does not use one or more channel resources. As an example, one or more channel resources may include one or more REs, symbols (e.g., SC-FDMA or OFDM symbols), PRBs, subcarriers, carriers, time slots, subframes, and so on.

[0235] A transmitter (e.g., an eNB or a WTRU that may perform transmission or plans to perform transmission) may perform rate matching on signals (e.g., signals to be transmitted or planned to be transmitted) around one or more channel resources. For example, a WTRU may perform rate matching around one or more resource elements. When receiving a DL transmission, the WTRU may perform rate matching around one or more resource elements. In one example, performing rate matching on signals around one or more channel resources may refer to or include that the transmitter does not perform transmission and / or does not map DL (or UL) signals in one or more channel resources and / or map the signals to one or more channel resources.

[0236] The WTRU may perform rate matching around one or more resource elements corresponding to synchronization signal transmission. When receiving a downlink transmission from a second cell, the WTRU may perform rate matching around one or more resource elements. The WTRU may perform rate matching around one or more resource elements by demapping the symbols of the downlink transmission. One or more resource elements corresponding to synchronization signal transmission may be skipped during the demapping process. The WTRU may receive a configuration on an authorized frequency band from a first cell. The configuration may indicate which resource elements will be used by a third cell for synchronization signal transmission. The configuration may be received in a radio resource control (RRC) message.

[0237] A receiver (e.g., an eNB or a WTRU that can perform reception or attempt to perform reception) may perform rate matching on one or more channel resources when receiving or attempting to receive a signal. Rate matching around one or more channel resources may include a process in which its receiver does not expect, receive, and / or decode DL (or UL) signals in one or more channel resources. The receiver may skip signal reception (or attempt signal reception) in one or more channel resources and / or signal an unmapping from one or more channel resources.

[0238] The eNB may perform rate matching around one or more LTE-U synchronization signals of one or more other eNBs. For example, the eNB may perform rate matching on DL signals (e.g., data and / or control signals such as PDSCH and / or (E)PDCCH) on one or more (e.g., all) channel resources (e.g., REs) of DL signals of one or more other eNBs (e.g., synchronization and / or busy signals of neighboring eNBs). For example, the eNB does not transmit DL signals (e.g., in a subframe and / or frame schedulable for a neighboring eNB to transmit its synchronization signal) on one or more channel resources that may be used by the synchronization signal of a neighboring eNB. As an example, by avoiding transmission in the same resources as the neighboring synchronization signal, reception of the neighboring synchronization signal (e.g., by a WTRU receiving or attempting to receive the synchronization signal of the neighbor) may be improved. By avoiding transmission in channel resources used by other eNBs, interference from transmissions of other eNBs may also be avoided.

[0239] During the active time for an LTE-U band (e.g., a channel), the LTE-U eNB does not transmit (and / or does not expect to receive from, such as a WTRU) signals, such as data, control, and / or busy signals, on channel resources (e.g., a set of PRBs) that are available for one or more other LTE-U eNBs to transmit one or more signals, such as LTE-U synchronization signals. During the active time, a WTRU that can communicate with the eNB on the channel does not expect to receive (e.g., from the eNB) and / or does not transmit signals, such as data, control, and / or busy signals, on channel resources (e.g., a set of PRBs) that are available for one or more other LTE-U eNBs to transmit one or more signals, such as LTE-U synchronization signals. The eNB and / or the WTRU may perform rate matching around one or more channel resources (e.g., a set of PRBs).

[0240] The eNB may receive and / or determine synchronization and / or busy signal information related to one or more other eNBs (e.g., neighbor eNBs). The eNB may determine the time and / or frequency positions of one or more channel resources of the synchronization and / or busy signals of one or more other eNBs (e.g., one or more neighbor eNBs managed by the same operator). For example, the eNB may determine the synchronization and / or busy signal of another eNB based on one or more of the following factors. The eNB may determine the synchronization and / or busy signal of another eNB based on receiving synchronization and / or busy signal information from the network. The eNB may determine the synchronization and / or busy signal of another eNB based on receiving synchronization and / or busy signal information via the X2 interface (e.g., from another eNB). As an example, the signal information may be provided proactively or in response to a request from the eNB for synchronization and / or busy signal information. The eNB may determine the synchronization and / or blind signal of another eNB based on receiving, detecting, and / or decoding the air interface broadcast signal of another eNB. The eNB may determine the synchronization and / or busy signal of another eNB based on receiving synchronization and / or busy signal information from one or more connected WTRUs. As an example, the WTRU may determine the synchronization and / or busy signal information of the eNB, e.g., by receiving, detecting, and / or decoding the air interface broadcast signal of the eNB. The air interface broadcast signal may include the synchronization and / or busy signal.

[0241] The eNB may perform rate matching on one or more DL signals (e.g., all) at one or more determined time and / or frequency positions of the channel resources of its synchronization and / or busy signals around one or more other eNBs.

[0242] The eNB may send a request for the time and / or frequency positions of one or more channel resources of the synchronization and / or busy signal to another eNB. As an example, the request may be sent by the eNB via the X2 interface. The eNB may send the time and / or frequency positions of one or more channel resources of the synchronization and / or busy signal to another eNB, e.g., sent unsolicited or in response to a request from the other eNB. As an example, the time and / or frequency positions may be sent by the eNB via the X2 interface.

[0243] The eNB may send a request to the WTRU for the time and / or frequency location of one or more channel resources for the synchronization and / or busy signals of another eNB. As an example, the request may be sent by the eNB by means of a higher layer signaling such as RRC signaling. The WTRU may send the time and / or frequency location of one or more channel resources of the synchronization and / or busy signals of the first eNB to the second eNB, for example, sent without request or in response to a request from the second eNB. As an example, the information may be sent by the WTRU via a higher layer signaling such as RRC signaling.

[0244] As an example, as a replacement and / or supplement to the synchronization and / or busy signals, one or more other signals and / or channels may be used.

[0245] An eNB rate matching and symbol mapping process may be provided. For example, the eNB may perform rate matching on the DL signals around one or more REs that can be used by a neighboring eNB, for example, for synchronization and / or busy signals. In one example, during the rate matching process, the eNB does not map (e.g., any) data and / or control signal symbols to one or more REs around which the rate matching of the DL signal is being performed, for example, one or more REs that can be used by a neighboring eNB for its synchronization and / or busy signals. The eNB may skip one or more REs that can be used by a neighboring eNB for synchronization and / or busy signals during the symbol-to-RE mapping process. As an example, skipping one or more REs may be performed, for example, by placing the modulation symbols mapped to the REs if not skipped in the next available RE, for example, according to a RE mapping process or rule that may be fixed, pre-configured, known, or determined. One or more skipped REs may correspond to synchronization signal transmission.

[0246] The eNB may map data and / or control signal symbols to one or more available REs available for data and / or control signal mapping. The eNB may consider (e.g., any) REs that may overlap with the synchronization and / or busy signals of another eNB such as a neighboring eNB as unavailable REs, and / or may not use such REs in its symbol-to-RE mapping process. For example, the eNB may (e.g., only may) map blocks of potentially coded, complex-valued data and / or control symbols to resource elements (e.g., REs within one or more PRB sets) that are not available for transmitting the synchronization and / or busy signals of one or more other eNBs.

[0247] Different rate matching configurations (e.g., different arrangements of resources around which signals may or should be rate matched) may affect the total number of useful resource elements (REs) in different subframes. The transport block size may depend on the rate matching configuration. For example, the transport block size (TBS) may be determined based on a combination of the MCS index and the applied rate matching configuration. In another example, the TBS may be independent of the rate matching configuration. The coding scheme may depend on the TBS and the rate matching configuration.

[0248] WTRU reception may be based on the applied rate matching and / or symbol-to-RE mapping. The WTRU may determine which channel resources can and which channel resources cannot carry the complex-valued symbols (e.g., data and / or control symbols) intended to be received by the WTRU. As an example, this determination may be made as part of DL signal reception, where rate matching may be performed around one or more channel resources (e.g., REs) for the DL signal.

[0249] The WTRU may determine the resources (e.g., REs) of one or more channels around which rate matching can be performed (e.g., by the eNB during the symbol-RE mapping process). As an example, this determination may be performed as part of receiving a DL signal transmission, where rate matching may be performed around one or more channel resources (e.g., REs) for the DL transmission. For example, the WTRU may demap one or more symbols of the DL transmission. One or more REs corresponding to synchronization signal transmission may be skipped during the demapping process. This determination enables the WTRU to demap one or more symbols, e.g., reverse the symbol-to-RE mapping by the eNB. The WTRU may demap symbols in accordance with this determination. As an example, during the demapping process, the WTRU may skip one or more REs that have been determined to be skipped or around which rate matching is performed, e.g., in a DL transmission. By skipping one or more REs during rate matching, the WTRU can detect and / or decode the transmitted data and / or control DL signal.

[0250] An indication of the resources around which a DL transmission may be rate matched may be provided and / or used. The indication may be semi-static or dynamic.

[0251] As an example, the WTRU may determine one or more channel resources around which rate matching can be performed based on a configuration or information provided by the eNB via signaling, which may be, as an example, physical layer or RRC signaling.

[0252] The WTRU may be configured to have and / or be notified by the eNB or the network, either directly or via the PCell, of channel resources (e.g., sets of REs, PRBs, and / or subframes) that can be used to transmit LTE-U synchronization and / or busy signals for one or more other LTE-U eNBs. The WTRU may determine rate matching around the channel resources, for example, based on or according to the received configuration or information.

[0253] As an example, the configuration of the channel resources that can be used by the eNB for synchronization and / or busy signals and / or the identification of said channel resources may be the same as the configuration of the channel resources for which rate matching can be or should be performed and / or the identification of said channel resources.

[0254] For example, the WTRU may receive an indication from the (e.g., serving) eNB of one or more channel resources (e.g., rate matching around REs) available or already available for the DL channel to perform rate matching. The indication may include an indication of one or more channel resources for the synchronization and / or busy signals of another eNB.

[0255] The WTRU may be configured to have and / or may receive an indication that may include one or more time and / or frequency resources (e.g., REs) for the eNB to perform rate matching for DL signal transmission. The WTRU may be configured to have and / or may receive an indication, where the indication may include information from which the WTRU can determine one or more time and / or frequency resources (e.g., REs) that can be used by the eNB to perform rate matching for DL signal transmission. As an example, a configuration, such as a configuration related to rate matching, may be sent to the WTRU in higher layer signaling such as DCI and / or physical layer signaling.

[0256] A WTRU may receive an indication from an eNB for indicating a set of channel resources, where the eNB may perform rate matching around the set of channel resources when transmitting a DL signal transmission. The set of channel resources may be periodic. As an example, a configuration may include one or more time positions, one or more frequency positions, and / or one or more transmission characteristics of the channel resources. A configuration may include one or more of the following: a period of a frame or subframe, a frame offset, such as a frame offset for a starting frame, a subframe index or offset, and a slot or slot offset. A configuration may include one or more of the following: a subframe index within one or more radio frames, such as a slot index within a subframe, a PRB and / or a PRB and / or subcarrier that may be within a slot, and / or one or more OFDM or SC-OFDM symbols that may be within these PRBs and / or subcarriers. As an example, when receiving and / or demapping a DL signal from the eNB, the WTRU may (or may be understood or configured to) take into account rate matching around the indicated or determined time and / or frequency positions.

[0257] In one example, the WTRU may receive a subframe indication for xx subframes (e.g., from a serving eNB), such as a 40-bit bitmap for xx = 40 subframes. One (e.g., each) bit may indicate whether the corresponding subframe within the period of the 40 subframes may contain a synchronization and / or busy signal that may be transmitted by another eNB. The WTRU may receive an indication of REs that may be available for a synchronization and / or busy signal of another eNB within the indicated subframe, for example. As an example, when a subframe is indicated as likely to have a synchronization and / or busy signal transmitted by another eNB, such as when the 40-bit subframe bitmap provides an indication, the WTRU may determine (e.g., by means of configuration) that a DL signal (e.g., from the serving eNB) may be rate matched around one or more of the configured and / or indicated REs within the subframe.

[0258] The WTRU may receive in DCI, such as DL grant, an indication that may identify or be available to the WTRU to determine channel resources (e.g., PDSCH associated with the DL grant or a later or other DL signal) that can be wrapped to perform rate matching on the DL signal. For example, the WTRU may receive in subframe n an indication of DCI for rate matching on the channel resources in subframe n+m. The value of m may be a fixed value and / or known to the WTRU. The value of m may be indicated to the WTRU in the same DCI or may be configured via higher layer signaling. The indication may include a bitmap that indicates resources that will not be used for symbol-to-RE mapping and / or demapping. The WTRU may be configured (e.g., in a semi-static manner) with a set of possible RE mapping configurations. As an example, DCI such as DL grant may include an indication (e.g., a code point) to indicate which of the configured mappings the WTRU may adopt or use in, e.g., subframe n or n+m.

[0259] The WTRU may distinguish between two or more LTE-U synchronization signals from different eNBs, e.g., based on channel resources (e.g., REs, PRBs, and / or a set of subframes) that may be allocated to or available for two or more LTE-U synchronization signals.

[0260] One or more resources may be shared with different subframes. For example, the WTRU may be configured to have one or more channel resources (e.g., a set of REs or PRBs) that may be in different subframes, where the channel resources may be used for different LTE-U synchronization signal transmissions.

[0261] As an example, a single set of PRBs may be allocated to one or more LTE-U synchronization signals in one or more subframes, all subframes, or a set of subframes. Two or more LTE-U eNBs may use the same set of PRBs for their LTE-U synchronization signal transmissions. However, each LTE-U eNB may perform transmissions in different subsets of subframes. For example, during the active time of the LTE-U band, the LTE-U eNB may transmit an LTE-U synchronization signal every 4 subframes on the LTE-U band. The WTRU may expect an LTE-U synchronization signal from the LTE-U eNB in a subframe where the two LSB SFN bits in the subframe may be equal to mod(PCell_cell_ID,4) or mod(SCell_cell_ID,4).

[0262] One or more resources may be shared with different sets of PRBs. The WTRU may be configured to have one or more channel resources (e.g., a set of REs or PRBs) that may be used by different LTE-U eNBs to perform LTE-U synchronization signal transmissions within the same subframe.

[0263] For example, assume that N sets of PRBs (e.g., four sets of PRBs) can be allocated for LTE-U synchronization signal transmission in one or more subframes, all subframes, or a set of subframes. Two or more LTE-U eNBs may transmit LTE-U synchronization signals in the same subframe. The two or more LTE-U eNBs may transmit LTE-U synchronization signals on different sets of PRBs. Among the configured sets of PRBs, the WTRU may expect LTE-U synchronization signals from the LTE-U eNB on the set of PRBs where the index is equal to mod(PCell_cell_ID,4) or mod(SCell_cell_ID,4).

[0264] Although the examples herein may be described in terms of PRB resources, the methods and techniques described herein may also apply to other types of resource usage. For example, other resources that can be used for LTE-U synchronization signal transmission, busy signal transmission, data transmission, etc. may be identified or defined by resource elements (REs), virtual resource blocks (VRBs), subcarriers, subframes, codes, other time-frequency resources, etc. Thus, the examples of using PRBs as reference resources disclosed herein are equally applicable to scenarios where resources are defined based on REs or other types of resource definitions (and vice versa).

[0265] The first eNB may map data and / or control signal symbols to one or more channel resources (e.g., REs) that can be used by the second eNB to transmit its synchronization and / or busy signals. The first eNB may silence one or more (e.g., all) signal transmissions (e.g., perform signal silencing) on one or more of these channel resources (e.g., REs) used by the second eNB.

[0266] As an example, silencing transmissions on one or more channel resources (e.g., REs) may be performed by discarding (e.g., not transmitting or transmitting with zero power) one or more modulation symbols mapped to one or more channel resources (e.g., REs). One or more other REs of the same signal are not affected by the presence, location, and / or density of the silenced REs.

[0267] The WTRU may determine and / or be explicitly and / or implicitly informed of the location in time and / or frequency of one or more silenced channel resources (e.g., REs). One or more of the methods described herein for configuring, notifying, or determining rate matching around channel resources may be applied to one or more silenced channel resources.

[0268] For example, for a WTRU that can learn about silent channel resources (e.g., REs) such as time and frequency positions, before sampling the received signals corresponding to these channel resources (e.g., REs) for reception and / or decoding processing, e.g., before passing the signal samples to a receiver and / or decoding processing, the WTRU can cause (e.g., force) the signal samples to be zero. By forcing one or more received signal samples, the performance of the receiver can be improved. As an example, this improvement can be achieved by limiting the input interference and / or noise level when no meaningful information is being transmitted.

[0269] One or more LTE-U synchronization signals can be used in combination with resource overlap. The WTRU can receive two or more LTE-U synchronization signals from different LTE-U eNBs in the same set of PRBs and / or set of subframes. The two or more LTE-U synchronization signals can be configured taking into account orthogonal principles such as CDM, whereby the WTRU can still detect its LTE-U synchronization signal in the presence of LTE-U synchronization signals from other LTE-U eNBs that may cause interference. One or more techniques and / or design principles associated with CDM can be applied. For example, different OCCs and / or scrambling for signals from different eNBs can be applied.

[0270] An indication of the LTE-U synchronization signal power offset can be provided. For example, the eNB can transmit an LTE-U synchronization signal with a certain power level. This power level may be different (e.g., a higher or lower power level) compared to other DL signals. The eNB can transmit a first LTE-U synchronization signal with a first power level and a second LTE-U synchronization signal with a second power level. The LTE-U synchronization signal transmission power that is different (e.g., higher or lower) compared to other DL signals (e.g., other synchronization signals, PDSCH, (E)PDCCH, PHICH) can improve the synchronization, channel estimation, detection, and / or other mechanisms of the WTRU.

[0271] The power level of a signal such as a synchronization signal can correspond to the total power transmitted (and / or received) in a set of resources that are limited in time and / or frequency. As an example, a set of resources that are limited in time can include one or more resources indicated and / or included in a single (or a group or a certain number of) radio frames, sub-frames, time slots, OFDM symbols, etc. As an example, a set of resources that are limited in frequency can include one or more resources indicated and / or included in a single (or a group or a certain number of) radio channels, PRBs, sub-carriers, etc. A set of resources that are limited in time and frequency can include a set of REs of a signal carrying, for example, a synchronization signal. A set of resources that are limited in time and frequency can include a set of OFDM and / or SC-FDMA symbols that constitute a specific number of PRBs.

[0272] As an example, a WTRU can determine the power level of a signal by detecting the signal and / or measuring its received power level. A WTRU can determine the power level of a signal based on a power indication received from other entities in the network, such as from its eNB (e.g., serving eNB).

[0273] A WTRU can receive an indication of a power offset. The power offset can include a power offset (or potential power offset) between an LTE-U synchronization signal and one or more other DL signals. The eNB or the network can provide an indication to the WTRU. As an example, the indication can be provided by or via a PCell that can be associated or aggregated with the LTE-U cell. The indication can be provided to or received by the WTRU, which can be dynamically, e.g., via DL control signaling, or can be semi-statically, e.g., via higher layer signaling, such as RRC signaling.

[0274] A WTRU can determine a power offset. The power offset can be between a synchronization signal transmission and one or more other downlink transmissions. The WTRU can determine the power level of a second downlink transmission based on the power offset.

[0275] The WTRU can determine the received power offset to be the power level difference between two DL signal transmissions such as first_dl_signal and second_dl_signal, where, as an example, first_dl_signal can be received (or transmitted to the WTRU) by the WTRU before receiving (or transmitting second_dl_signal).

[0276] The WTRU may determine the first_dl_signal of the indicated power offset. For example, the WTRU may determine that the first_dl_signal corresponding to the received power offset may be the last received synchronization signal before receiving the power offset indication. As another example, as part of the power offset indication, the WTRU may receive an indication of the subframe, signal type, and / or allocated resources of the first_dl_signal.

[0277] The WTRU may determine the second_dl_signal of the indicated power offset. For example, after receiving the power offset indication, the WTRU may determine that the second_dl_signal corresponding to the received power offset includes the next received DL signal (e.g., PDSCH, (E)PDCCH). In another example, for example, as part of the power offset indication, the WTRU may receive an indication of the subframe, signal type, and / or allocated resources of the second_dl_signal.

[0278] For example, as part of the DL grant, the WTRU may receive an indication of the power offset (e.g., power offset). As an example, the power offset may be interpreted as the amount of power by which a data signal (or control or reference signal) may be reduced compared to the power of the LTE-U synchronization signal. As an example, the power offset may be determined as the difference in power levels (e.g., transmit power level per PRB) between corresponding signals such as the first_dl_signal and the second_dl_signal. The WTRU may determine (e.g., interpret) the first_dl_signal as the last received synchronization signal before receiving the power offset indication. The WTRU may determine the synchronization signal power level by means of measurement. The WTRU may interpret the second_dl_signal as the next PDSCH (or (E)PDCCH) signal. The WTRU may determine the power level of the second_dl_signal (e.g., the next PDSCH) as the sum of the power level of the measured first_dl_signal (e.g., the most recent synchronization signal) and the indicated power offset level. This sum may be scaled and / or adjusted by the number of resource blocks (e.g., PRBs) of the first_dl_signal and the second_dl_signal. The WTRU may use the indicated power offset, for example, using the power level of the LTE-U synchronization signal and / or the power level of the data (or control or reference) signal to determine the power of another signal.

[0279] After receiving a power offset indication, the WTRU may interpret the first_dl_signal as the next synchronization signal. The WTRU may measure the synchronization signal power level. The next synchronization signal may be before, temporally overlapping with, or in the same subframe as the second_dl_signal.

[0280] The WTRU may receive an indication of the power level of an LTE-U synchronization signal. The WTRU may receive an indication of the power level of one or more control and / or data signals.

[0281] The WTRU may perform frequency estimation, timing estimation, and / or synchronization (e.g., by using the synchronization signal). The WTRU may use the synchronization signal to perform channel estimation. The WTRU may use the synchronization signal to perform coherent demodulation and / or symbol scaling. For example, the WTRU may use the synchronization signal to perform channel estimation. The WTRU may use the estimated channel and / or the indicated power offset between the synchronization signal and the data / control signal (e.g., to appropriately scale the detected symbols before performing symbol demapping, before performing soft information calculation, before performing bit probability calculation, and / or before any other process before performing the channel decoding process).

[0282] The WTRU may perform frequency and / or timing estimation. The frequency and / or timing estimation may be based on synchronization signal transmission. The WTRU may perform demodulation and / or resource symbol scaling. The demodulation and / or resource symbol scaling may be based on synchronization signal transmission.

[0283] The use of LAA channels by different networks and / or operators may cause cell ID conflicts between cells (e.g., SCell) in the LAA channel. By determining the cell ID, cell ID conflicts can be avoided or reduced. For example, the cell ID of the LAA SCell may be determined based on one or more of the following: the identifier of the eNB, such as the cell ID, the cell ID of the eNB's PCell, the operator of the eNB, the center frequency of the authorized frequency band used by the eNB, the center frequency of the unlicensed frequency band used by the LAA SCell, or a random seed, etc.

[0284] The cell ID may be determined when the LAA SCell is deployed. The cell ID of the LAA SCell may be obtained when in use, planned to be used, or deployed. The eNB may autonomously select the cell ID of the LAA SCell.

[0285] For a WTRU that can be served by an LAA SCell, the WTRU can be informed via the PCell of the timing of actions to be taken relative to the LAA SCell. As an example, the information that can be provided by the PCell can include the cell ID of the LAA SCell and / or the timing when such a cell ID can be applied to or used by the LAA SCell. For example, the WTRU can be configured with an indication of when actions such as synchronization, measurement, and / or PDSCH transmission will occur. One or more WTRU actions that can be adopted for the LAA SCell can be pre-scheduled. The scheduling can be implicit or explicit. The WTRU can expect a signal from an LAA SCell using a certain cell ID after (e.g., only after) receiving an indication of the cell ID and / or after the time when the cell ID applies, where the time when the cell ID applies can be provided or configured by the eNB via the PCell. As for synchronization or measurement, the WTRU can (e.g., can only) use RS sampling during the valid time indicated by the PCell. If RS sampling is used at certain times indicated by the PCell, then it will enable multiple LAA SCells controlled by different eNBs in a single LAA channel to reuse the same cell ID. As an example, since signals transmitted by other LAA SCells using the same cell ID as the configured LAA SCell of the WTRU do not appear at times that the WTRU considers valid, there will be no cell ID confusion on the WTRU.

[0286] The cell ID can be configured in a distributed manner. When the eNB can use, intends to use, or deploy an LAA SCell, the eNB can select the cell ID. By selecting the cell ID, conflicts within the LAA channel can be avoided. For example, for an eNB that can configure an LAA SCell, the eNB may use the information exchange messages described herein to communicate or negotiate with other eNBs so that the eNB can select a cell ID that is not yet used within a geographical area and / or on the LAA channel. Such communication or negotiation can be performed via broadcasting. For example, the eNB can broadcast the cell ID selected for the LAA SCell. The broadcast message can be located on the LAA channel (possibly the LAA channel on which the cell operates) and / or on the licensed spectrum. One or more other (e.g., neighboring) eNBs can reply, thereby potentially indicating whether there will be a conflict with one of the LAA SCells they deploy.

[0287] Before using or deploying a LAASCell, the eNB can perform listening on the LAA channel. As an example, it can try to determine the cell ID of a cell that may be deployed on the LAA channel through a discovery process. The eNB can use another cell ID that will not conflict with the currently deployed LAA SCell. If the eNB can determine that the LAA SCell (or cell ID) will not be active on the LAA channel for a certain (e.g., pre-configured) amount of time, then the eNB can determine that the cell ID is no longer in use. The eNB can use the cell ID for the LAA SCell it uses or deploys.

[0288] The cell ID can be dynamically configured / indicated. For WTRU actions related to the LAA SCell, the PCell that can schedule such actions can indicate the cell ID to be used or adopted. A virtual cell ID can be used. As an example, the LAA SCell can change the cell ID between active times. The WTRU may or may not know whether the new cell ID represents the cell that previously used the old cell ID. As an example, quasi-co-location between the old cell ID and the new cell ID can be provided to or configured in the WTRU to enable faster synchronization. For example, measurements made at previous measurement occasions can be used in combination with current measurements. The cell ID (or virtual cell ID) hopping can be pre-configured, and the WTRU can know the cell ID (or virtual cell ID) hopping sequence and can operate correctly without being dynamically indicated a new (virtual) cell ID.

[0289] The LAASCell can use channel hopping. For example, the eNB can deploy the LAASCell on multiple channels. At a specific time, the LAA SCell can be active on (e.g., only on) a single channel. Except for the center frequency, the configuration of the LAASCell can remain consistent. For example, the cell ID of the LAA SCell can remain constant regardless of which LAA channel it is for each active time. The cell ID of the LAA SCell can be based on time and / or the LAA channel and can change per active time. The WTRU can know the relationship between the active time, the LAA channel, and the cell ID. The WTRU may or may not receive a dynamic indication. The cell ID of the LAA SCell related to the new active time can be indicated to the WTRU. The WTRU can use such information to determine the LAA channel where the LAA SCell is active.

[0290] One or more eNBs use and / or operate on one or more LAA channels. For an eNB that can use and / or operate on an LAA channel, the eNB can be considered to have, use, or operate an LAA cell, such as an LAA SCell. An LAA cell or SCell belonging to one eNB can compete with another LAA cell or SCell belonging to another eNB for the resources of the LAA channel. Such competition can be supplementary to or a replacement for the competition with other users of the channel, such as WiFi users or radars.

[0291] As an example, multiple eNBs can share information and / or LAA channels so as to use the LAA channels fairly and / or efficiently among themselves and with other users. The LAA channel can be shared and / or used by one or more eNBs, where the one or more eNBs can be associated with different operators. For example, the LAA channel can be shared and / or used by one or more eNBs in a TDM manner and / or an FDM manner simultaneously.

[0292] In some examples, the terms communication and negotiation can be used interchangeably.

[0293] The parameters of the LAA cell can be transferred. An eNB can deploy or operate one or more LAA cells or SCells on the same or different unlicensed channels. An eNB can obtain a list of unlicensed channels available for it to monitor the traffic. Such monitoring enables the eNB or one or more LAA cells or SCells to acquire one or more channels, such as channels for downlink transmission.

[0294] An eNB can use or wish or intend to use an LAA channel. For example, the eNB can obtain or determine one or more LAA cell parameters through communication and / or negotiation (such as with other eNBs that can or also can use or intend to use the channel). The one or more LAA cell parameters are available for the eNB or other eNBs to use for the cells associated with the channel (such as LAA SCells).

[0295] The LAA cell parameters can include one or more of the following: cell ID (such as the cell ID of the LAA cell), synchronization signal configuration or information, reference signal configuration or information, busy signal configuration or information, and / or active time configuration or information.

[0296] The synchronization signal configuration or information can include information related to the resources available for the cell to transmit synchronization signals.

[0297] Reference signal configuration or information may include information related to reference signals (such as CRS, CSI-RS, CSI-IM, DM-RS, PRS) that can be transmitted in a cell, such as which reference signals can be transmitted in the cell, and / or information related to resources available for the cell to transmit one or more (such as each) reference signals.

[0298] Busy signal configuration or information may include information related to resources that can be used by a cell to transmit a busy signal.

[0299] Information related to resources for transmission (such as transmission of synchronization signals, reference signals, and / or busy signals) may include, but is not limited to, one or more of the following: RE mapping, subframe configuration and / or offset, orthogonal cover code (OCC), cyclic shift, random sequence generator parameters, one or more associated PRBs, etc.

[0300] Active time configuration or information may include a timing or pattern (or multiple patterns), where the timing or pattern indicates the timing when a LAA cell (such as a SCell) may become or attempt to become active or start, or the timing when the eNB turns on or attempts to turn on (puts into an active state) the LAA cell (such as a SCell). For an eNB, for example, an eNB that can monitor the LAA channel, the eNB can determine or negotiate (with one or more other eNBs) the time instance (or timing) when it can attempt to acquire the channel and can put the LAA cell (such as a SCell) into an active state or start it.

[0301] An active or turned-on LAA cell can transmit one or more synchronization signals, can transmit one or more reference signals, can transmit one or more busy signals, and / or transmit DL data and / or control signals.

[0302] The eNB can determine or obtain information (such as active time configuration or information) related to when other eNBs can use or attempt to use the LAA channel. The eNB will not attempt to acquire the channel during all of that time or a portion of that time. As an example, it will not attempt to acquire the channel when the channel is likely to be busy, thereby saving power. This can reduce the probability of conflicting attempts to acquire the channel.

[0303] A WTRU may be configured to have a LAA SCell. This configuration may be consistent with activating an SCell (e.g., a LAA SCell) on the WTRU. Parameters may be configured on the WTRU. These parameters enable the WTRU to be served by the LAA SCell. The parameters may include one or more LAA cell parameters. As an example, the value of the LAA cell parameter may be (or may have been) negotiated, obtained, or determined by an eNB based on communication or information exchange with another eNB. The value of the LAA cell parameter may or may not be the same as the value provided to (e.g., by the eNB) or configured in the WTRU. For example, the eNB may obtain or determine certain or some resources for transmitting synchronization signals. The eNB may configure resources for the WTRU, where the resources may be the same as, different from (or partially different from), overlapping with, or may be a subset of the certain resources.

[0304] The eNB may configure the WTRU to have one or more quasi - co - location (QCL) assumptions or sets of assumptions between, for example, a LAA SCell and a PCell. The QCL assumptions may be for one or more of delay spread, average delay, Doppler spread, and Doppler shift. The WTRU may be configured to have a set consisting of multiple QCL assumptions. As an example, the configuration may be performed in a dynamic or semi - static manner.

[0305] The LAA cell is revocable. For example, when the eNB does not (e.g., no longer) use or does not plan to use the LAA channel, then the eNB may revoke the corresponding LAA SCell. For example, when the eNB can stop monitoring a certain LAA channel, the eNB may revoke the SCell configured by the eNB to use or operate in a certain LAA channel.

[0306] This revocation may mean that one or more (e.g., all) resources configured and / or reserved for the LAA SCell may be released. The LAA SCell or the eNB may indicate to one or more LAA SCells (e.g., adjacent LAA SCells) that may use or operate on the affected LAA channel that it is likely to release the LAA SCell and / or one or more (e.g., all) of its resources.

[0307] The eNB may withdraw the LAA SCell from the LAA channel based on one or more of the following: channel congestion, traffic load, number of failed attempts to acquire the channel, number of eNBs or cells competing for the LAA channel, interference measurement, and / or one or more of the typical, average, or peak delays in the process of acquiring the channel. The one or more criteria may be measured or determined by the eNB and / or the WTRU. The one or more criteria measured or determined by the WTRU may be signaled by the WTRU to the eNB. If the one or more criteria exceed or are below a certain threshold, then the eNB may withdraw the LAA SCell.

[0308] The eNB may determine the number of competing deployments and / or active LAA SCells that are likely to operate on the LAA channel. If the eNB determines that there is too much competition (e.g., too many other LAA SCells in the channel), then the eNB will not use the channel or may withdraw the LAA SCell from the channel.

[0309] For example, if the number of competing LAA SCells in the same LAA channel is less than x, then the LAA SCell may be deployed to operate on the LAA channel (e.g., only operate on it). When the first LAA SCell (e.g., the eNB of the first LAA SCell) determines that a new LAA SCell has entered the LAA channel (e.g., has been deployed on the channel and / or is active on the channel) and / or the total number of competing LAA SCells may (or now may) exceed a certain threshold, then the first LAA SCell may be withdrawn.

[0310] The first LAA SCell (e.g., the eNB of the first LAA SCell) may negotiate with the second LAA SCell (e.g., the eNB of the second LAA SCell) regarding resources (e.g., negotiate regarding critical or highly important uses of the LAA channel). Based on this negotiation, one or more of the LAA SCells or eNBs may determine that there are not enough resources to meet the scheduling requirements and may withdraw the LAA SCell from the LAA channel (e.g., the LAA SCell without enough LAA channel resources).

[0311] As an example, the LAA cell may be configured or deployed with the intention of using the cell in the channel. One or more of the examples described regarding withdrawal may apply to the process of configuring or deploying the cell, where the decision-making criteria for this process may be the same as or opposite to the criteria described (for example, exceeding the threshold may be replaced with being below the threshold, insufficient may be replaced with sufficient, etc.).

[0312] LAA channel information is exchangeable. For example, an eNB can share information related to one or more LAA channels it is currently or will use in the future. This information exchange can be used for resource negotiation or sharing between LAA SCells described herein.

[0313] The information exchange between eNBs can be facilitated by the X2 or an X2-like interface. This information exchange can be proactive (e.g., an eNB can transmit information to another (e.g., neighboring) eNB before a problem occurs due to the use of an LAA channel) or reactive (e.g., once a problem occurs due to the use of an LAA channel, the eNB can transmit information to another (e.g., neighboring) eNB).

[0314] The information exchange between eNBs can be facilitated by broadcast messages. The over-the-air broadcast of information can be used to transmit information related to the current or future use of one or more LAA channels by, for example, an eNB or an LAA cell. Such messages can be unidirectional.

[0315] The broadcast message can trigger neighboring cells affected by the contained information to respond to the broadcast information, and such response can be made through its own broadcast message or by any other means described herein.

[0316] The message can be broadcast from the PCell or a cell using licensed spectrum. The broadcast message can be related to the use of one or more LAA channels. The broadcast message can originate from an LAA SCell (or a cell using the unlicensed band). The information exchanged by means of the broadcast can be associated with (e.g., only associated with) the LAA SCell (or the LAA channels used by the LAA SCell).

[0317] The broadcast message can be included in the MIB and / or SIB. The LAA MIB and / or SIB transmission can be used to transmit these messages. For example, when the LAA SCell has acquired a channel, the MIB and / or SIB can be transmitted in a resource subset at this time. As an example, the MIB and / or SIB can be transmitted in certain subframes (e.g., a subset of subframes or all subframes), and can be transmitted in one or more RBs or subcarriers, where the RB may be a group of central RBs or subcarriers in the central RB.

[0318] MIB and / or SIB resources can be semi-statically assigned to the LAA SCell, and conflicts generated with simultaneously operating LAA SCells can be restricted. The MIB and / or SIB can be transmitted when the LAA SCell is (or is not) in an active state. The MIB and / or SIB can use repetition coding. For example, within the active time, the messages included in the MIB and / or SIB can be repeated once every x subframes.

[0319] Resources can be reserved on each LAA channel. The LAA SCells deployed on the channel can be allocated a set of such resources to broadcast information related to the current or future use of the LAA channel to neighboring LAA SCells. For example, one or more symbols / slots / subframes and subcarriers / PRBs / sub-bands can be reserved. The LAA SCell can control such resources, for example, by previously successfully acquiring the LAA channel or by negotiating semi-static ownership of such resources. The LAA SCell can broadcast the relevant information.

[0320] Broadcast messages can use reference signals dedicated to the LAA SCell, where the signals enable the WTRU or other LAA SCells to demodulate the messages. For example, the broadcast messages can be transmitted on one or more antenna ports, and / or pre-configured precoding and / or signals similar to CRS can be used to perform demodulation. As an example, scrambling and / or frequency hopping can be used on the broadcast messages to reduce interference to nearby LAA SCells and other RAT access points and the impact of interference from the LAA SCells and access points.

[0321] Specific resources may be associated with the time when the LAA SCell acquires or may acquire the LAA channel. The LAA SCell can transmit broadcast messages in such resources. For example, the LAA SCell can transmit the broadcast message in the xth symbol after acquiring the channel.

[0322] The L1 signaling or channel can be used for information exchange. Information about the current or future use of the LAA channel can be indicated by (or by using) one or more L1 signals or channels. Busy signals, one or more synchronization signals, and / or reference signals, etc. can indicate the relevant information. The parameters of the signals and / or channels can indicate information related to the current or future use of the LAA channel. For example, the transmission on the first set of REs can indicate the first information exchange message, the transmission on the second set of REs can indicate the second information exchange message, and the transmissions on both sets of REs can indicate the third information exchange message. For the signal parameters that can be used to indicate information related to the use of one or more LAA channels in the LAA SCell, the signal parameters can include but are not limited to: resources used in combination with subframes, (virtual) cell IDs that can be used to generate signal sequences, cyclic shifts of signals, orthogonal cover codes of signals, and / or antenna ports on which signals can be transmitted. As an example, the RB, symbol, or RE used to transmit a signal can indicate a specific signal.

[0323] For example, the reference signal (RS) can be configured to have a set of possible transmission resources (such as RE mapping, PRB set, pseudo-random sequence, OCC, etc.), and the use of the specific resource set for transmitting the RS can announce the relevant information to neighboring cells.

[0324] For example, for the RS that can be sent in a certain (e.g., the last) subframe before the LAA SCell releases the LAA channel and / or switches to the inactive state (or sleeps), the RS can use a resource set. While the same (or another) RS sent in another (e.g., any other) subframe will use another resource set. The eNB or cell can monitor the RS, and / or can use the position of the RS of another (e.g., neighboring) LAA cell to determine whether other LAA cells are using or plan to release the channel.

[0325] The resources used by the RS in the last subframe during the active time can indicate whether the LAA SCell remains deployed when transitioning to the sleep state, or whether it will discard the LAA channel. The resources of the synchronization signal used when the LAA SCell becomes active can indicate the length of time it remains active. The resources used to transmit the busy signal or synchronization signal at the beginning of the active time can indicate the resources that can be reserved and / or used during this active time or subsequent active times. This enables different LAA SCells to use LAA concurrently or simultaneously.

[0326] The L1 signal and / or channel can be used to exchange information related to the current or future use of the LAA channel. Such information can be explicitly indicated within the channel / signal (e.g., via coded information elements within the channel / signal). Such information can be indicated in a manner similar to that described above for certain signals. The channel can be scheduled by means of the (E)PDCCH, and it is possible to schedule it by using a new DCI format. For example, the channel parameters can be indicated by means of a DCI format that can be detected using an RNTI. The RNTI can be used by the LAA SCell on one or more LAA channels, or it can be specific to the LAA SCell. The RNTI can be configured at the time of LAA SCell deployment. The (E)PDCCH used to schedule message transmission on the channel can indicate information such as, but not limited to: resources (e.g., RBs) for message transmission on the new channel, message timing related to the (E)PDCCH transmission, modulation and coding scheme, and / or demodulation reference signal parameters (e.g., antenna port, orthogonal cover code, cyclic shift, quasi co-location assumption, precoder, transmit power ratio between the demodulation reference signal and other reference signals). As an example, the message timing related to the (E)PDCCH transmission can indicate that the message can be transmitted in the same subframe as the (E)PDCCH. The message timing related to the (E)PDCCH transmission can indicate that the message may be transmitted in a subframe that may have been indicated or preconfigured after the (E)PDCCH has been transmitted.

[0327] The channel can include a control region, where the control region indicates that the parameters of the scheduled information exchange message can be indicated. The parameters included in the control region of the channel can be any of the parameters described here for the (E)PDCCH. The LAA SCell can preconfigure a part of the channel (e.g., a set of RBs or REs) for control information.

[0328] The resources associated with the channel can be allocated based on sub-TTIs. For example, the channel can be transmitted in one of the two time slots within a TTI. The channel can be defined on a set of symbols within a time slot. The channel can be defined on a set of symbols spanning multiple time slots and / or subframes. The transmission power for the channel can be different from that for other channels. The control region of the channel can indicate the transmission power offset between the channel and perhaps one or more other signals and / or channels. The channel can include some REs dedicated to transmitting the demodulation reference signal.

[0329] The LAA SCell can transmit a beacon to convey information related to its current or future use of the LAA channel. Such beacons can be transmitted at pre-configured times. The beacon can be transmitted when the LAA SCell is not in the active mode. There may be a conflict between such beacons and other LAA SCells (or other RATs) using the LAA channel. Such beacons can be transmitted on resources previously negotiated between the deployed LAA SCells sharing the LAA channel. An LAA SCell that is active when another LAA SCell transmits its beacon can use the blank pattern on the resources used for the beacon. Doing so can limit the interference encountered by its WTRU.

[0330] For beacon transmissions performed by an active LAA SCell or any other LAA SCell, some resources of the LAA channel can be fixed. For example, the beacon can be transmitted by an active LAA SCell at pre-configured and possibly fixed or variable time instances (one or more OFDM symbols, one or more time slots, one or more sub-frames) and a set of sub-carriers. The beacon can contain an indication of the LAA SCell that transmits it (e.g., cell ID). Some resources can be reserved and used as beacons by other currently deployed but dormant LAA SCells. To avoid conflicts between multiple dormant LAA SCells, specific resources (e.g., RE or OCC) can be determined based on the cell ID of the LAA SCell. Regardless of whether the LAA SCell is active or dormant, the beacon can have resources determined based on the parameters of the LAA SCell (e.g., cell ID).

[0331] Information can be exchanged via one or more WTRUs. The WTRU can act as an intermediary for information exchange between multiple eNBs. The eNB can configure the LAA SCell for the WTRU, and through this configuration, the WTRU can be instructed to listen for possible information messages being transmitted by one or more LAA SCells sharing the same LAA channel. The messages listened to by the WTRU can use any of the above methods for information exchange. For example, the WTRU can listen to broadcast messages from adjacent LAA SCells, where the message provides information related to the use of the LAA channel. The WTRU can be provided with UL resources to report the information it has collected from the broadcast messages of one or more adjacent LAA SCells, where the UL resources can be in the form of UL grants for its PCell.

[0332] Information collected by a WTRU may be passively relayed by an adjacent LAA SCell. Passive relaying of information means that the adjacent LAA SCell does not actively attempt to exchange information with other LAA SCells, but its current behavior in the LAA channel enables the WTRU or other LAA SCells to make assumptions about its use of the LAA channel. For example, the WTRU may perform discovery and may measure the transmissions of adjacent LAA SCells. The WTRU may provide feedback on the measurements. Based on the measurements, the serving cell of the WTRU may use the LAA channel and / or the parameters by which the configured LAA SCells typically use the LAA channel to determine the parameters of a particular LAA SCell. For example, the WTRU may be configured with measurements regarding adjacent LAA SCells. As an example, the WTRU may be given a threshold and may determine the amount of time that an adjacent LAA SCell performs transmissions, where that amount of time results in a measurement greater than the threshold. This enables the WTRU and, by extension, the eNB to determine the activity level of the adjacent LAA SCell.

[0333] The WTRU may be given information from its serving cell for sharing with other eNBs. For example, the WTRU may be provided with information regarding the current or future use of LAA SCells by its PCell. In addition, the WTRU may be given resources to attempt to connect to an adjacent cell (in the licensed band and / or the unlicensed band, if UL transmissions are permitted in the unlicensed band). Such resources may include a cell ID, physical random access channel (PRACH) parameters (preamble and resources), timing reference, and possibly a UL grant. The WTRU may enable information exchange by connecting to an adjacent cell in the licensed band. The serving cell may know the cell ID of adjacent LAA SCells in the LAA channel. The serving cell may or may not know the appropriate licensed cell operated by the same eNB. The serving cell determines the appropriate licensed cell based on the relationship between the cell ID of the LAA SCell and its associated licensed band PCell. The WTRU may attempt to connect to one or more adjacent cells to transmit the information. The WTRU may use UL resources to convey information for its serving cell (or one or more LAA SCells of its serving eNB). The adjacent cell may determine if any relevant information is being exchanged by listening for such resources. The transmission of the WTRU may include an identifier of the LAA SCell (or eNB) from which the information originated and / or an identifier of the LAA SCell for which the information is intended.

[0334] The WTRU may start establishing a direct link between the serving eNB and an adjacent eNB by communicating with the adjacent eNB. For example, the WTRU may transmit relevant information (such as the serving cell ID) to the adjacent cell, and the adjacent cell may establish an interface to dock with the serving cell for information exchange.

[0335] Messages for exchanging information between two eNBs can effectively use one or more LAA channels. Here, the terms message and indication are used interchangeably and can refer to any information originating from an eNB (or a deployed LAASCell) and usable by another eNB (or another deployed LAA SCell). This message or indication can include any information related to the current or future use of one or more LAA channels, and these will be further described here.

[0336] Messages can be transmitted periodically between eNBs. For example, when deploying an LAA SCell, the eNB can start periodically transmitting its LAA channel usage via one or more interfaces described here. This periodic message transmission can be unidirectional. For example, the eNB does not expect any response from the adjacent eNB. The periodic message transmission can result in a periodic or aperiodic response from the adjacent eNB. As an example, the message can be aperiodic, such as a single message transmission. The eNB can transmit relevant information in the message and can expect or not expect a response (such as an acknowledgment) from the adjacent eNB.

[0337] The information exchange message can (e.g., can always) be transmitted when deploying the LAASCell (possibly regardless of whether the LAA SCell is active or dormant). The message can be transmitted only in one of the dormant state or the active state. Different resource or interface sets can be configured for information exchange in the active state and in the dormant state.

[0338] The message can be triggered by the eNB sending a message. For example, the eNB may wish to inform the adjacent eNB of its current use of the LAA channel via the LAA SCell and can transmit a message. The message can be prompted by another eNB. As an example, the first eNB may wish to know the status of the second eNB (such as the channel monitoring set). The first eNB can send a trigger message, which can prompt the other eNB to transmit a message indicating its status. The trigger message itself can be regarded as an information exchange message. The trigger message may result in a single transmission of a message response and / or may trigger the periodic transmission of the message.

[0339] Message parameters can depend on the active or inactive (e.g., dormant) state of the LAA SCell. For example, a dormant cell can transmit a message when prompted. An active cell can transmit messages periodically. The timing of the periodic messages can be relative to the PCell, and / or can be relative to the timing of the LAA SCell. For example, an LAA SCell that is asynchronous with the PCell (and whose timing during the active period can depend on the time when the LAA SCell acquires the LAA channel and becomes active) can transmit an information exchange message according to the time of acquiring the LAA channel.

[0340] The message can be used to convey information related to the current or future use of one or more LAA channels. The message can be transmitted by means of an interface or mechanism as described herein. The message can originate from one or more of the following: an eNB having one or more LAA SCells that have been deployed and are currently active in the LAA channel, an eNB having one or more LAA SCells that have been deployed and are currently dormant in the LAA channel, an eNB having no deployed LAA SCells in one or more LAA channels, an LAA cell or SCell, a cell in the authorized spectrum such as a PCell, etc.

[0341] For information contained in a message transmitted between two or more eNBs (or LAA SCells), the information can enable fair and efficient use of one (or more) LAA channels. The information in the message can be used for unidirectional transmission. For example, the message can indicate the current or future use of an LAA channel by an eNB. The information in the message can be used for bidirectional transmission. For example, the information can enable negotiation between multiple eNBs, thereby achieving fair and efficient use of one or more LAA channels.

[0342] The information exchange message can include an identifier of the source of the information exchange message (e.g., cell ID). For example, the cell ID of an eNB cell in the authorized spectrum or an LAA SCell. The message can or can also include a list of deployed LAA SCells that may be on multiple LAA channels. The list can include recently revoked LAA SCells (or LAA SCells about to be revoked). This enables neighboring eNBs or LAA SCells to track the traffic in the LAA channel.

[0343] The information exchange message can include an identifier of the intended destination of the message (e.g., cell ID). For example, the cell ID of the destination eNB cell in the authorized spectrum or the cell ID of one or more LAA SCells.

[0344] The information exchange message may include a set of channel monitoring. The eNB may indicate (e.g., to an adjacent eNB) its set of channel monitoring. As an example, the message may include a list of channels that the eNB may be monitoring and / or may be attempting to acquire. The monitored channels may be channels having one or more deployed LAAS Cells. The channels included in the set of channel monitoring may be one or more of the following: 1) not monitored, 2) monitored but without a deployed LAAS Cell, 3) monitored and with a deployed LAAS Cell. The eNB may indicate in the message a change in its set of channel monitoring (e.g., some or all of it). For example, the message may contain a complete list of the monitored channels, or may (e.g., only may) include an update with respect to the previous set (which may be in the form of channels to be added or removed from the set of channel monitoring or a change in the type of monitoring on each channel).

[0345] The information exchange message may include the timing of the current active time of the LAAS Cell. This information may indicate the start of the current active time, the end of the current active time, the length of the entire active time, the remaining duration of the current active time. For some systems, such as synchronous systems, the timing information may refer to the PCell of the source eNB. For some systems, such as asynchronous systems, the message may (or may also) indicate the time reference at the time of information exchange (or an indication of another timing reference). This enables the destination eNB or LAA SCell to understand the relative timing included in the information exchange message.

[0346] The information exchange message may indicate the timing of the expected future active time. This may include an indication of one or more of the start of the expected active time, the end of the expected active time, and the length of the entire expected active time.

[0347] The information exchange message may include an indication of the timing of the deployment / withdrawal of the LAAS Cell. The source eNB may indicate when it will deploy or withdraw one or more LAAS Cells.

[0348] The information exchange message may include the LAA channel access type. The message may indicate synchronous access (e.g., the LAAS Cell may be synchronized to the PCell) or asynchronous access (e.g., the timing of the LAA SCell may depend on the time when the LAA channel can be acquired). The LAA channel access type may be decoupled from the message timing. The LAA channel access type may be indicated in the message. For example, the transmission of the message may be scheduled according to the timing synchronized with the PCell. The data transmission on the LAA SCell may be asynchronous. The LAA SCell data transmission may use a blank pattern (e.g., zero-power transmission) on some REs to enable the message transmission.

[0349] An information exchange message may include LAA SCell transmission power. For RBs and / or subframes within the active time, the transmission power may be fixed. The transmission power may change over subframes and / or RBs of the active time. This allows multiple LAA SCells to concurrently or simultaneously use the LAA channel. The variable transmission power may be indicated by a transmission power pattern, where (e.g., each) subgroup of RBs and / or subframes of the active time may have an assigned value anywhere between 0 and a pre-configured maximum transmit power.

[0350] An information exchange message may indicate an interference level. The message may include an indication of the interference level in the LAA channel, e.g., the interference level encountered by the LAA SCell and / or the WTRU served by the LAA SCell. Such interference values may be explicit. As an example, the interference level may be quantified and / or may be represented as low, medium, and high. The interference level may represent the interference measured in the LAA channel and / or the interference acceptable to the source LAA SCell at the current or future active time.

[0351] An information exchange message may include resource priority information or a pattern. The source eNB may indicate different priority levels for the resources used for its active time transmission and, if possible, for the sleep time transmission. Such priority levels may be represented as a pattern of different priorities for one or more of the RBs and / or symbols / slots / subframes. The priority pattern may indicate how the eNB may and / or will prioritize usage. This allows adjacent LAA SCells to use lower priority resources. The information exchange message and / or the priority pattern may include or indicate a set of resources available for the busy or synchronization signal. This information may be used to enable the cooperation and / or joint transmission of busy signals performed by multiple LAA SCells in the LAA channel.

[0352] An information exchange message may include an indication (or request) of high priority resources. For example, the eNB (or LAA SCell) may indicate on the same or a different LAA channel that it may or may request to obtain the priority of the LAA channel. For example, for an LAA SCell, e.g., a sleeping LAA SCell, it may request or reserve the channel for high priority purposes, such as transmitting a synchronization signal to the WTRU it serves, so that the WTRU can remain synchronized. The transmission of high priority resources (as an example, or a request for the resources) triggers a fallback operation on another (e.g., adjacent) LAA SCell, e.g., enabling the LAA SCell to transmit a high priority indication indicating a higher likelihood of obtaining the LAA channel.

[0353] An information exchange message may include an indication of radar activity detection. The eNB (or LAA SCell) may indicate to another eNB (or LAA SCell) that radar has been detected on the LAA channel. Doing so can cause adjacent eNBs to stop attempting to acquire the LAA channel and / or potentially cause the eNB to deactivate the LAA SCell on the LAA channel.

[0354] The information exchange message may indicate long-term behavior. Doing so can indicate to the recipient of the message that such an LAA channel is expected to be used by the source LAA SCell for a relatively long period of time. For example, the source LAA SCell may indicate the amount or type of traffic expected for the WTRU served by the LAA SCell. As an example, the source LAA SCell may indicate whether the traffic is expected to continue for multiple active times and / or for how many active times. The message may include the rate at which the LAA SCell will attempt to acquire the LAA channel in the future. The amount of traffic may be indicated in a report similar to or via the buffer status report. The message may include the number of WTRUs that can be served by the LAA SCell.

[0355] The content of the message may be explicitly included within the message or may be implicitly included (e.g., determined based on one or more parameters or characteristics of the message or message transmission). For example, a parameter or characteristic of the information exchange message (e.g., the resource used to transmit the message, such as a subframe and / or PRB) may implicitly indicate one or more possible contents of the message as described herein (e.g., the remaining duration of the active time).

[0356] LAA channel resources may be shared between eNBs. The eNB may use the information exchange message to share the LAA channel.

[0357] The first eNB may deploy the first LAA SCell. For example, the eNB or LAA SCell may use one or more of the solutions described herein to indicate that it may be (or may become) active and / or may be active for a particular duration x (the duration may be measured in symbols, time slots, subframes, etc.). The second eNB or LAA SCell may share one or more channels by negotiating with the first eNB / LAA SCell. For example, the second eNB (or second LAA SCell) may indicate to the first eNB (or LAA SCell) via the information exchange message one or more of the following: the desire or request to use or share multiple RBs or a set of RBs, and / or the expected or requested amount of time for the RBs, where the amount of time may be less than the remaining active time of the first LAA SCell.

[0358] The first LAA SCell may grant the request, and as an example, it may or may not stop scheduling on the RBs indicated by the second LAA SCell during the requested amount of time. The first LAA SCell may indicate to the second LAA SCell a set of resources (RBs and / or subframes) or another set of resources on which the first LAA SCell does not transmit and / or the second LAA SCell transmits.

[0359] For a set of RBs that the second LAA SCell may wish or request and / or the first LAA SCell may release to enable the second LAA SCell to send data, the set may include part or all of the bandwidth of the LAA channel. During the time (e.g., a subset of subframes) when the second LAA SCell may have the channel, the first LAA SCell may remain active but not perform transmissions.

[0360] The second LAA SCell may request (and / or the first LAA SCell may provide) a set of RBs in which the first LAA SCell may reduce its transmission power so that the second LAA SCell can perform a simultaneous transmission on the same RBs.

[0361] As an example, the second eNB (or second LAA SCell) may indicate to the first eNB (or LAA SCell) via an information exchange message the willingness or request to acquire the LAA (e.g., full LAA) channel before the end of the previously indicated active time of the first LAA SCell.

[0362] If the first LAA SCell agrees, it may return to an inactive (or dormant) state before its initially indicated or expected time. The first LAA SCell may cooperate with the second LAA SCell to ensure that the channel remains (or appears to remain) busy during the handover time when the second LAA SCell can acquire the channel. Doing so can prevent other cells or access points from acquiring the channel before the second LAA SCell starts its transmission. As long as a cell is allowed to hold a channel (e.g., before this), the second LAA SCell can hold the channel (e.g., until), which is independent of the duration for which the first LAA SCell has the channel. As long as the first LAA SCell remains in its active period, the second LAA SCell can hold the channel. The remaining time may depend on the indication sent by the first LAA SCell or may depend on the maximum active period allowed by regulation for LAA channel acquisition.

[0363] As an example, the second eNB (or the second LAA SCell) may, by means of an information exchange message, indicate to the first eNB (or LAA SCell) a request for interference reporting from a WTRU connected to the first LAA SCell. As an example, the first LAA SCell may trigger an interference measurement report from its WTRU to determine whether the second LAA SCell can perform simultaneous transmission without significantly degrading the performance of the WTRU of the first LAA SCell. The measurement resources available for the WTRU may be negotiated between the first and the second LAA SCells. As an example, the second LAA SCell may transmit a pseudo interference signal to enable the WTRU of the first LAA SCell to measure (e.g., appropriately) the impact of a potential transmission from the second LAA SCell.

[0364] An interference request from the second LAA SCell may result in the first LAA SCell replying with an interference indication. For example, the first LAA SCell may indicate one of two interference levels: low (which, as an example, means that the second LAA SCell may perform simultaneous transmission) or high (which, as an example, means that the second LAA SCell should not perform simultaneous transmission). More than two interference levels may be used for this indication. The first LAA SCell may indicate to the second LAA SCell a set of precoding matrices that may or may not be used, e.g., to limit the interference that the WTRU of the first LAA SCell may encounter.

[0365] As an example, the second eNB (or the second LAA SCell) may, by means of an information exchange message, indicate to the first eNB (or LAA SCell) a set of interference measurements available for the WTRU of the second LAA SCell to take. As an example, doing so enables the first LAA SCell to modify its transmission power or precoding in order to limit the interference that the WTRU of the second LAA SCell may encounter. As an example, the second LAA SCell may provide a list of favorable (or unfavorable) precoding matrices that may (or may not) be used by the first LAA SCell in order to limit the interference to the WTRU of the second LAA SCell.

[0366] As an example, the second eNB (or the second LAA SCell) may, by means of an information exchange message, indicate to the first eNB (or LAA SCell) a request for the first LAA SCell to transmit a signal (such as a busy signal). Doing so may indicate to the second LAA SCell when (e.g., at an exact or near-exact moment) the first LAA SCell will relinquish the channel. Doing so enables the second LAA SCell to access the channel prior to other LAA SCells or other RATs. This process may (e.g., only may) be applied to or used for transmitting high-priority signals (such as reference signal transmissions that enable the WTRU to remain synchronized with the LAA SCell). The LAA SCell may (or only may) obtain (or be allowed to obtain) the channel in a manner for a certain transmission, such as a high-priority transmission, and may limit the duration for which it remains active after transmitting the high-priority signal.

[0367] As an example, the second eNB (or the second LAA SCell) may, by means of an information exchange message, indicate to the first eNB (or LAA SCell) a request to jointly transmit a busy (or synchronization) signal through the first and second LAA SCells. The transmission of such a signal may be done in the same resources and may thereby increase the power at which the signal is received by other nodes or may potentially improve the coverage of the signal. The transmission of such a signal may be performed on orthogonal resources. For example, the first LAA SCell may transmit a busy signal in the first set of subcarriers of a symbol. The second LAA SCell may transmit a busy signal in the second set of subcarriers of the same symbol.

[0368] As an example, the second eNB (or the second LAA SCell) may, by means of an information exchange message, indicate to the first eNB (or LAA SCell) a request for the first LAA SCell to transmit a synchronization signal that enables the second LAA SCell to synchronize. In response to the request, the first LAA SCell may transmit the synchronization signal. Doing so enables the two LAA SCells to share resources during their simultaneous active times and may be used when the LAA SCell is not synchronized with its corresponding PCell.

[0369] As an example, a second eNB (or a second LAA SCell) may indicate to a first eNB (or an LAA SCell) via an information exchange message the channel that the second LAA SCell will select during an upcoming active time. The second LAA SCell may request the first LAA SCell to indicate the channel that it may use during the next active time. These solutions enable these two LAA SCells to coordinate their operations when using dynamic frequency selection. Two or more LAA SCells may negotiate to reduce the likelihood of attempting to acquire the same channel. The LAA SCell may use dynamic frequency selection. The LAA SCell may indicate to another (e.g., neighboring) LAA SCell the hopping pattern that it may use. The LAA SCell may negotiate to share resources in the overlapping part of the channel.

[0370] For example, a first eNB or a first LAA SCell may indicate to a second eNB or a second LAA SCell that it has acquired an LAA channel. This indication may be sent in the form of a preamble. This indication enables multiple LAA SCells to share the active time of the first LAA SCell simultaneously, e.g., using the same resources. The preamble may indicate one or more timings of the LAA SCell (to enable other LAA SCells to synchronize to the cell that initially acquired the channel), the timing / length of the active time (to enable other LAA SCells to know how long they can remain active), the LAA SCell (virtual) cell ID, the transmission power of the LAA SCell, and / or the busy and / or synchronization signal configuration of the LAA SCell.

[0371] The methods and means described herein may be used alone or applied in any combination to other wireless technologies and other services.

[0372] A WTRU may refer to the identity of a physical device or to the identity of a user, e.g., a subscription-related identity such as an MSISDN, a SIP URI, etc. A WTRU may refer to an application-based identity, e.g., a user name used in accordance with an application.

[0373] The above process can be implemented in a computer program, software, and firmware combined with a computer-readable medium for operation by a computer and / or a processor. Examples of computer-readable media include, but are not limited to, electrical signals (transmitted via wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, buffer memories, semiconductor storage devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM discs and digital versatile discs (DVDs). A processor associated with the software can be used to implement a radio frequency transceiver used in a WTRU, UE, terminal, base station, RNC, and / or any host computer.

Claims

1. A first device associated with a wireless communication network, the first device comprising: a processor configured to: receive information from a second device associated with the wireless communication network, wherein the information indicates one or more of a time resource or a frequency resource associated with receiving a first indication regarding whether the second device has acquired a channel associated with an unlicensed band; receive the first indication from the second device using one or more of the time resource or the frequency resource, wherein the first indication is used to indicate that the second device has acquired the channel, and the first indication further indicates a time period during which the second device has acquired the channel; determine to use the acquired channel to perform a transmission based on the first indication from the second device and an additional indication regarding the use of the acquired channel; and perform the transmission using the acquired channel.

2. A method implemented by a first device associated with a wireless communication network, the method comprising: receive information from a second device associated with the wireless communication network, wherein the information indicates one or more of a time resource or a frequency resource associated with receiving a first indication regarding whether the second device has acquired a channel associated with an unlicensed band; receive the first indication from the second device using one or more of the time resource or the frequency resource, wherein the first indication is used to indicate that the second device has acquired the channel, and the first indication further indicates a time period during which the second device has acquired the channel; determine to use the acquired channel to perform a transmission based on the first indication from the second device and an additional indication regarding the use of the acquired channel; and perform the transmission using the acquired channel.

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