WO2018089911A1

WO2018089911A1 - Interference coordination in unlicensed spectrum

Info

Publication number: WO2018089911A1
Application number: PCT/US2017/061345
Authority: WO
Inventors: Huaning Niu; Gang Xiong; Wenting CHANG; Qiaoyang Ye
Original assignee: Intel IP Corporation
Priority date: 2016-11-14
Filing date: 2017-11-13
Publication date: 2018-05-17

Abstract

Embodiments of an Evolved Node-B (eNB), User Equipment (UE) and methods for communication are generally described herein. The eNB may detect a downlink signal from an interferer eNB in an unlicensed channel. The eNB may determine a received power of the downlink signal. The eNB may determine, based at least partly on the received power, whether the interferer eNB is to refrain from downlink transmission during a period in which an uplink transmission from a User Equipment (UE) to the server eNB is scheduled. The eNB may transmit, in the unlicensed channel, a clear-to-send-to-self (CTS-to-self) message that indicates: a start time of the period, a duration of the period, and whether the interferer eNB is to refrain from downlink transmission during the period.

Description

INTERFERENCE COORDINATION IN UNLICENSED SPECTRUM

TECHNICAL FIELD

[0001] This application claims priority to United States Provisional

Patent Application Serial No. 62/421,819, filed November 14, and United States Provisional Patent Application Serial No. 62/436,282, filed December 19, 2016, and United States Provisional Patent Application Serial No. 62/437,377, filed December 21, 2016, all of which are incorporated herein by reference in their entirety, TECHNICAL FIELD

[0002] Embodiments pertain to wireless communications. Some embodiments relate to wireless networks including 3 GPP (Third Generation Partnership Project) networks, 3GPP LTE (Long Tenn Evolution) networks, and 3GPP LTE -A (LTE Advanced) networks, although the scope of the

embodiments is not limited in this respect. Some embodiments relate to MulteFire networks and/or protocols. Some embodiments relate to

communication in unlicensed spectrum. Some embodiments relate to interference coordination in unlicensed spectrum.

BACKGROUND

[0003] Base stations and mobile devices operating in a network may exchange data and related control messages. In some cases, such a network may operate in unlicensed spectrum, which may introduce a variety of challenges.

For instance, interference between base stations and/or mobile devices may occur. In some cases, a device may not be able to communicate as a result of occur. In some cases, a device may not be able to communicate as a result of such interference. Accordingly, there is a general need for methods to coordinate and/or mitigate such interference in these and other scenarios.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1 is a functional diagram of a 3GPP network in accordance with some embodiments;

[0005] FIG. 2 illustrates a block diagram of an example machine in accordance with some embodiments;

[0006] FIG. 3 is a block diagram of an Evolved Node-B (eNB) in accordance with some embodiments;

[0007] FIG. 4 is a block diagram of a User Equipment (UE) in accordance with some embodiments;

[0008] FIG. 5 illustrates the operation of a method of communication in accordance with some embodiments;

[0009] FIG. 6 illustrates the operation of another method of communication in accordance with some embodiments;

[0010] FIG. 7 illustrates an example scenario in accordance with some embodiments;

[0011] FIG. 8 illustrates examples of timing in accordance with some embodiments;

[0012] FIG. 9 illustrates an example of preamble generation in accordance with some embodiments;

[0013] FIG. 10 illustrates additional examples of timing in accordance with some embodiments;

[0014] FIG. 11 illustrates additional examples of timing in accordance with some embodiments;

[0015] FIG. 12 illustrates another example scenario in accordance with some embodiments;

[0016] FIG. 13 illustrates another example scenario in accordance with some embodiments; [0017] FIG. 14 illustrates another example scenario in accordance with some embodiments; and

[0018] FIG. 15 illustrates example power thresholds in accordance with some embodiments.

DETAILED DESCRIPTION

[0019] The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0020] FIG. 1 is a functional diagram of a 3GPP network in accordance with some embodiments. It should be noted that embodiments are not limited to the example 3GPP network shown in FIG. 1, as other networks may be used in some embodiments. As an example, a network configured to communicate in accordance with unlicensed spectrum may be used in some cases. As another example, a network configured to communicate in accordance with a MulteFire protocol and/or MulteFire technique may be used in some cases.

[0021] As another example, a Fifth Generation (5G) network may be used in some cases. As another example, a New Radio (NR) network may be used in some cases. As another example, a wireless local area network (WLAN) may be used in some cases. Embodiments are not limited to these example networks, however, as other networks may be used in some embodiments. In some embodiments, a network may include one or more components shown in FIG. 1. Some embodiments may not necessarily include all components shown in FIG. 1, and some embodiments may include additional components not shown in FIG. 1.

[0022] The network 100 may comprise a radio access network (RAN)

(e.g., as depicted, the E-UTRAN or evolved universal terrestrial radio access network) 101 and the core network 120 (e.g., shown as an evolved packet core (EPC)) coupled together through an SI interface 115. For convenience and brevity sake, only a portion of the core network 120, as well as the RAN 101, is shown.

[0023] The core network 120 includes a mobility management entity

(MME) 122, a serving gateway (serving GW) 124, and packet data network gateway (PDN GW) 126. The RAN 101 includes Evolved Node-B's (eNBs) 104 (which may operate as base stations) for communicating with User Equipment (UE) 102. The eNBs 104 may include macro eNBs and low power (LP) eNBs.

[0024] In some embodiments, the eNB 104 may transmit signals (data, control and/or other) to the UE 102, and may receive signals (data, control and/or other) from the UE 102. These embodiments will be described in more detail below.

[0025] The MME 122 is similar in function to the control plane of legacy Serving GPRS Support Nodes (SGSN). The MME 122 manages mobility aspects in access such as gateway selection and tracking area list management. The serving GW 124 terminates the interface toward the RAN 101, and routes data packets between the RAN 101 and the core network 120. In addition, it may be a local mobility anchor point for inter-eNB handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. The serving GW 124 and the MME 122 may be implemented in one physical node or separate physical nodes. The PDN GW 126 terminates an SGi interface toward the packet data network (PDN). The PDN GW 126 routes data packets between the EPC 120 and the external PDN, and may be a key node for policy enforcement and charging data collection. It may also provide an anchor point for mobility with non-LTE accesses. The external PDN can be any kind of IP network, as well as an IP Multimedia Subsystem (IMS) domain. The PDN GW 126 and the serving GW 124 may be implemented in one physical node or separated physical nodes.

[0026] The eNBs 104 (macro and micro) terminate the air interface protocol and may be the first point of contact for a UE 102. In some

embodiments, an eNB 104 may fulfill various logical functions for the RAN 101 including but not limited to RNC (radio network controller functions) such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. In accordance with embodiments, UEs 102 may be configured to communicate Orthogonal Frequency Division Multiplexing (OFDM) communication signals with an eNB 104 over a multicarrier communication channel in accordance with an Orthogonal Frequency Division Multiple Access (OFDMA) communication technique. The OFDM signals may comprise a plurality of orthogonal subcarriers.

[0027] The S I interface 115 is the interface that separates the RAN 101 and the EPC 120. It is split into two parts: the Sl-U, which carries traffic data between the eNBs 104 and the serving GW 124, and the SI -MME, which is a signaling interface between the eNBs 104 and the MME 122. The X2 interface is the interface between eNBs 104. The X2 interface comprises two parts, the X2-C and X2-U. The X2-C is the control plane interface between the eNBs 104, while the X2-U is the user plane interface between the eNBs 104.

[0028] With cellular networks, LP cells are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with very dense phone usage, such as train stations. As used herein, the term low power (LP) eNB refers to any suitable relatively low power eNB for implementing a narrower cell (narrower than a macro cell) such as a femtocell, a picocell, or a micro cell. Femtocell eNBs are typically provided by a mobile network operator to its residential or enterprise customers. A femtocell is typically the size of a residential gateway or smaller and generally connects to the user's broadband line. Once plugged in, the femtocell connects to the mobile operator's mobile network and provides extra coverage in a range of typically 30 to 50 meters for residential femtocells. Thus, a LP eNB might be a femtocell eNB since it is coupled through the PDN GW 126. Similarly, a picocell is a wireless communication system typically covering a small area, such as in-building (offices, shopping malls, train stations, etc.), or more recently in-aircraft. A picocell eNB can generally connect through the X2 link to another eNB such as a macro eNB through its base station controller (BSC)

functionality. Thus, LP eNB may be implemented with a picocell eNB since it is coupled to a macro eNB via an X2 interface. Picocell eNBs or other LP eNBs may incorporate some or all functionality of a macro eNB. In some cases, this may be referred to as an access point base station or enterprise femtocell.

[0029] In some embodiments, a downlink resource grid may be used for downlink transmissions from an eNB 104 to a UE 102, while uplink

transmission from the UE 102 to the eNB 104 may utilize similar techniques. The grid may be a time-frequency grid, called a resource grid or time -frequency resource grid, which is the physical resource in the downlink in each slot. Such a time -frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid correspond to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time-frequency unit in a resource grid is denoted as a resource element (RE). There are several different physical downlink channels that are conveyed using such resource blocks. With particular relevance to this disclosure, two of these physical downlink channels are the physical downlink shared channel and the physical down link control channel.

[0030] As used herein, the term "circuitry" may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some embodiments, the circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, circuitry may include logic, at least partially operable in hardware. Embodiments described herein may be implemented into a system using any suitably configured hardware and/or software.

[0031] FIG. 2 illustrates a block diagram of an example machine in accordance with some embodiments. The machine 200 is an example machine upon which any one or more of the techniques and/or methodologies discussed herein may be performed. In alternative embodiments, the machine 200 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 200 may operate in the capacity of a server machine, a client machine, or both in server-client network environments. In an example, the machine 200 may act as a peer machine in peer-to-peer (P2P) (or other distributed) network environment. The machine 200 may be a UE 102, eNB 104, access point (AP), station (STA), mobile device, base station, personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a smart phone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations.

[0032] Examples as described herein, may include, or may operate on, logic or a number of components, modules, or mechanisms. Modules are tangible entities (e.g., hardware) capable of performing specified operations and may be configured or arranged in a certain manner. In an example, circuits may be arranged (e.g., internally or with respect to external entities such as other circuits) in a specified manner as a module. In an example, the whole or part of one or more computer systems (e.g., a standalone, client or server computer system) or one or more hardware processors may be configured by firmware or software (e.g., instructions, an application portion, or an application) as a module that operates to perform specified operations. In an example, the software may reside on a machine readable medium. In an example, the software, when executed by the underlying hardware of the module, causes the hardware to perform the specified operations.

[0033] Accordingly, the term "module" is understood to encompass a tangible entity, be that an entity that is physically constructed, specifically configured (e.g., hardwired), or temporarily (e.g., transitorily) configured (e.g., programmed) to operate in a specified manner or to perform part or all of any operation described herein. Considering examples in which modules are temporarily configured, each of the modules need not be instantiated at any one moment in time. For example, where the modules comprise a general -purpose hardware processor configured using software, the general-purpose hardware processor may be configured as respective different modules at different times. Software may accordingly configure a hardware processor, for example, to constitute a particular module at one instance of time and to constitute a different module at a different instance of time.

[0034] The machine (e.g., computer system) 200 may include a hardware processor 202 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 204 and a static memory 206, some or all of which may communicate with each other via an interlink (e.g., bus) 208. The machine 200 may further include a display unit 210, an alphanumeric input device 212 (e.g., a keyboard), and a user interface (UI) navigation device 214 (e.g., a mouse). In an example, the display unit 210, input device 212 and UI navigation device 214 may be a touch screen display. The machine 200 may additionally include a storage device (e.g., drive unit) 216, a signal generation device 218 (e.g., a speaker), a network interface device 220, and one or more sensors 221, such as a global positioning system (GPS) sensor, compass, accelerometer, or other sensor. The machine 200 may include an output controller 228, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.).

[0035] The storage device 216 may include a machine readable medium

222 on which is stored one or more sets of data structures or instructions 224 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 224 may also reside, completely or at least partially, within the main memory 204, within static memory 206, or within the hardware processor 202 during execution thereof by the machine 200. In an example, one or any combination of the hardware processor 202, the main memory 204, the static memory 206, or the storage device 216 may constitute machine readable media. In some embodiments, the machine readable medium may be or may include a non-transitory computer-readable storage medium. [0036] While the machine readable medium 222 is illustrated as a single medium, the term "machine readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 224. The term "machine readable medium" may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 200 and that cause the machine 200 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting machine readable medium examples may include solid-state memories, and optical and magnetic media. Specific examples of machine readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable

Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; Random Access Memory (RAM); and CD-ROM and DVD-ROM disks. In some examples, machine readable media may include non-transitory machine readable media. In some examples, machine readable media may include machine readable media that is not a transitory propagating signal.

[0037] The instructions 224 may further be transmitted or received over a communications network 226 using a transmission medium via the network interface device 220 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, a Long Term Evolution (LTE) family of standards, a Universal Mobile Telecommunications System (UMTS) family of standards, peer-to-peer (P2P) networks, among others. In an example, the network interface device 220 may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 226. In an example, the network interface device 220 may include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. In some examples, the network interface device 220 may wirelessly communicate using Multiple User MIMO techniques. The term "transmission medium" shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the machine 200, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software.

[0038] FIG. 3 is a block diagram of an Evolved Node-B (eNB) in accordance with some embodiments. It should be noted that in some embodiments, the eNB 300 may be a stationary non-mobile device. The eNB 300 may be suitable for use as an eNB 104 as depicted in FIG. 1. The eNB 300 may include physical layer circuitry 302 and a transceiver 305, one or both of which may enable transmission and reception of signals to and from the UE 200, other eNBs, other UEs or other devices using one or more antennas 301. As an example, the physical layer circuitry 302 may perform various encoding and decoding functions that may include formation of baseband signals for transmission and decoding of received signals. As another example, the transceiver 305 may perform various transmission and reception functions such as conversion of signals between a baseband range and a Radio Frequency (RF) range. Accordingly, the physical layer circuitry 302 and the transceiver 305 may be separate components or may be part of a combined component. In addition, some of the described functionality related to transmission and reception of signals may be performed by a combination that may include one, any or all of the physical layer circuitry 302, the transceiver 305, and other components or layers. The eNB 300 may also include medium access control layer (MAC) circuitry 304 for controlling access to the wireless medium. The eNB 300 may also include processing circuitry 306 and memory 308 arranged to perform the operations described herein. The eNB 300 may also include one or more interfaces 310, which may enable communication with other components, including other eNBs 104 (FIG. 1), components in the EPC 120 (FIG. 1) or other network components. In addition, the interfaces 310 may enable communication with other components that may not be shown in FIG. 1, including components external to the network. The interfaces 310 may be wired or wireless or a combination thereof. It should be noted that in some embodiments, an eNB or other base station may include some or all of the components shown in either FIG. 2 or FIG. 3 or both.

[0039] FIG. 4 is a block diagram of a User Equipment (UE) in accordance with some embodiments. The UE 400 may be suitable for use as a UE 102 as depicted in FIG. 1. In some embodiments, the UE 400 may include application circuitry 402, baseband circuitry 404, Radio Frequency (RF) circuitry 406, front-end module (FEM) circuitry 408 and one or more antennas 410, coupled together at least as shown. In some embodiments, other circuitry or arrangements may include one or more elements and/or components of the application circuitry 402, the baseband circuitry 404, the RF circuitry 406 and/or the FEM circuitry 408, and may also include other elements and/or components in some cases. As an example, "processing circuitry" may include one or more elements and/or components, some or all of which may be included in the application circuitry 402 and/or the baseband circuitry 404. As another example, a "transceiver" and/or "transceiver circuitry" may include one or more elements and/or components, some or all of which may be included in the RF circuitry 406 and/or the FEM circuitry 408. These examples are not limiting, however, as the processing circuitry, transceiver and/or the transceiver circuitry may also include other elements and/or components in some cases. It should be noted that in some embodiments, a UE or other mobile device may include some or all of the components shown in either FIG. 2 or FIG. 4 or both.

[0040] The application circuitry 402 may include one or more application processors. For example, the application circuitry 402 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors,

application processors, etc.). The processors may be coupled with and/or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the system.

[0041] The baseband circuitry 404 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 404 may include one or more baseband processors and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 406 and to generate baseband signals for a transmit signal path of the RF circuitry 406. Baseband processing circuitry 404 may interface with the application circuitry 402 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 406. For example, in some embodiments, the baseband circuitry 404 may include a second generation (2G) baseband processor 404a, third generation (3G) baseband processor 404b, fourth generation (4G) baseband processor 404c, and/or other baseband processor(s) 404d for other existing generations, generations in development or to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 404 (e.g., one or more of baseband processors 404a-d) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 406. The radio control functions may include, but are not limited to, signal modulation/demodulation,

encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 404 may include Fast-Fourier Transform (FFT), precoding, and/or constellation

mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 404 may include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

[0042] In some embodiments, the baseband circuitry 404 may include elements of a protocol stack such as, for example, elements of an evolved universal terrestrial radio access network (EUTRAN) protocol including, for example, physical (PHY), media access control (MAC), radio link control

(RLC), packet data convergence protocol (PDCP), and/or radio resource control (RRC) elements. A central processing unit (CPU) 404e of the baseband circuitry 404 may be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRC layers. In some embodiments, the baseband circuitry may include one or more audio digital signal processor(s) (DSP) 404f. The audio DSP(s) 404f may be include elements for

compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 404 and the application circuitry 402 may be implemented together such as, for example, on a system on a chip (SOC).

[0043] In some embodiments, the baseband circuitry 404 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 404 may support communication with an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 404 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

[0044] RF circuitry 406 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 406 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 406 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 408 and provide baseband signals to the baseband circuitry 404. RF circuitry 406 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 404 and provide RF output signals to the FEM circuitry 408 for transmission.

[0045] In some embodiments, the RF circuitry 406 may include a receive signal path and a transmit signal path. The receive signal path of the RF circuitry 406 may include mixer circuitry 406a, amplifier circuitry 406b and filter circuitry 406c. The transmit signal path of the RF circuitry 406 may include filter circuitry 406c and mixer circuitry 406a. RF circuitry 406 may also include synthesizer circuitry 406d for synthesizing a frequency for use by the mixer circuitry 406a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 406a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 408 based on the synthesized frequency provided by synthesizer circuitry 406d. The amplifier circuitry 406b may be configured to amplify the down-converted signals and the filter circuitry 406c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 404 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 406a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect. In some embodiments, the mixer circuitry 406a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 406d to generate RF output signals for the FEM circuitry 408. The baseband signals may be provided by the baseband circuitry 404 and may be filtered by filter circuitry 406c. The filter circuitry 406c may include a low-pass filter (LPF), although the scope of the embodiments is not limited in this respect.

[0046] In some embodiments, the mixer circuitry 406a of the receive signal path and the mixer circuitry 406a of the transmit signal path may include two or more mixers and may be arranged for quadrature down-conversion and/or up-conversion respectively. In some embodiments, the mixer circuitry 406a of the receive signal path and the mixer circuitry 406a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g.,

Hartley image rejection). In some embodiments, the mixer circuitry 406a of the receive signal path and the mixer circuitry 406a may be arranged for direct down-conversion and/or direct up-conversion, respectively. In some embodiments, the mixer circuitry 406a of the receive signal path and the mixer circuitry 406a of the transmit signal path may be configured for superheterodyne operation.

[0047] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 406 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 404 may include a digital baseband interface to communicate with the RF circuitry 406. In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

[0048] In some embodiments, the synthesizer circuitry 406d may be a fractional -N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 406d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider. The synthesizer circuitry 406d may be configured to synthesize an output frequency for use by the mixer circuitry 406a of the RF circuitry 406 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 406d may be a fractional N/N+1 synthesizer. In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 404 or the applications processor 402 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a lookup table based on a channel indicated by the applications processor 402.

[0049] Synthesizer circuitry 406d of the RF circuitry 406 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A). In some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0050] In some embodiments, synthesizer circuitry 406d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fix>). In some embodiments, the RF circuitry 406 may include an IQ/polar converter.

[0051] FEM circuitry 408 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 410, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 406 for further processing. FEM circuitry 408 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 406 for transmission by one or more of the one or more antennas 410.

[0052] In some embodiments, the FEM circuitry 408 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include a low-noise amplifier (LNA) to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 406). The transmit signal path of the FEM circuitry 408 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 406), and one or more filters to generate

RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 410. In some embodiments, the UE 400 may include additional elements such as, for example, memory /storage, display, camera, sensor, and/or input/output (I/O) interface.

[0053] The antennas 230, 301, 410 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, micro-strip antennas or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, the antennas 230, 301, 410 may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result.

[0054] In some embodiments, the UE 400 and/or the eNB 300 and/or the machine 200 may be a mobile device and may be a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a wearable device such as a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other device that may receive and/or transmit information wirelessly. In some embodiments, the UE 400 and/or eNB 300 and/or the machine 200 may be configured to operate in accordance with 3GPP standards, although the scope of the embodiments is not limited in this respect. Mobile devices or other devices in some embodiments may be configured to operate according to other protocols or standards, including IEEE 802.11 or other IEEE standards. In some embodiments, the UE 400 and/or the eNB 300 and/or the machine 200 and/or other device may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

[0055] Although the UE 400, the eNB 300, and the machine 200 are each illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software -configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements.

[0056] Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include readonly memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

[0057] It should be noted that in some embodiments, an apparatus used by the UE 400 and/or eNB 300 and/or machine 200 may include various components of the UE 400 and/or the eNB 300 and/or the machine 200 as shown in FIGs. 2-4. Accordingly, techniques and operations described herein that refer to the UE 400 (or 102) may be applicable to an apparatus for a UE. In addition, techniques and operations described herein that refer to the eNB 300 (or 104) may be applicable to an apparatus for an eNB.

[0058] In accordance with some embodiments, the eNB 104 may detect a downlink signal from an interferer eNB 104 in an unlicensed channel. The eNB 104 may determine a received power of the downlink signal. The eNB 104 may determine, based at least partly on the received power, whether the interferer eNB 104 is to refrain from downlink transmission during a period in which an uplink transmission from a UE 102 to the server eNB 104 is scheduled. The eNB 104 may transmit, in the unlicensed channel, a clear-to-send-to-self (CTS- to-self) message that indicates: a start time of the period, a duration of the period, and whether the interferer eNB 104 is to refrain from downlink transmission during the period. These embodiments are described in more detail below.

[0059] FIG. 5 illustrates the operation of a method of communication in accordance with some embodiments. It is important to note that embodiments of the method 500 may include additional or even fewer operations or processes in comparison to what is illustrated in FIG. 5. In addition, embodiments of the method 500 are not limited to the chronological order that is shown in FIG. 5. In describing the method 500, reference may be made to FIGs. 1-4 and 6-15, although it is understood that the method 500 may be practiced with any other suitable systems, interfaces and components.

[0060] In some embodiments, an eNB 104 may perform one or more operations of the method 500, but embodiments are not limited to performance of the method 500 and/or operations of it by the eNB 104. In some

embodiments, the UE 102 may perform one or more operations of the method 500 (and/or similar operations). Accordingly, although references may be made to performance of one or more operations of the method 500 by the eNB 104 in descriptions herein, it is understood that the UE 102 may perform one or more of the same operations, one or more similar operations and/or one or more reciprocal operations, in some embodiments.

[0061] In addition, while the method 500 and other methods described herein may refer to eNBs 104 or UEs 102 operating in accordance with a MulteFire protocol, a protocol for unlicensed spectrum, 3GPP standards, 5G standards and/or other standards, embodiments of those methods are not limited to just those eNBs 104 or UEs 102 and may also be practiced on other devices, such as a Wi-Fi access point (AP) or user station (STA). In addition, the method 500 and other methods described herein may be practiced by wireless devices configured to operate in other suitable types of wireless communication systems, including systems configured to operate according to various IEEE standards such as IEEE 802.1 1. The method 500 may also refer to an apparatus for a UE 102 and/or eNB 104 and/or other device described above.

[0062] It should also be noted that embodiments are not limited by references herein (such as in descriptions of the methods 500, 600 and/or other descriptions herein) to transmission, reception and/or exchanging of elements such as frames, messages, requests, indicators, signals or other elements. In some embodiments, such an element may be generated, encoded or otherwise processed by processing circuitry (such as by a baseband processor included in the processing circuitry) for transmission. The transmission may be performed by a transceiver or other component, in some cases. In some embodiments, such an element may be decoded, detected or otherwise processed by the processing circuitry (such as by the baseband processor). The element may be received by a transceiver or other component, in some cases. In some embodiments, the processing circuitry and the transceiver may be included in a same apparatus. The scope of embodiments is not limited in this respect, however, as the transceiver may be separate from the apparatus that comprises the processing circuitry, in some embodiments.

[0063] It should be noted that references to a "server eNB" and

"interferer eNB" are not limiting. Such references may be used for clarity. In some embodiments, an eNB 104 may be configured to perform one or more operations of either a server eNB 104 and may also be configured to perform one or more operations of an interferer eNB 104. In some embodiments, an eNB 104 may be configured to operate as a server eNB 104, to perform one or more operations of a server eNB 104, to operate as an interferer eNB 104 and/or to perform one or more operations of an interferer eNB 104. In some

embodiments, an eNB 104 may perform one or more operations of a server eNB 104 in some cases, and may perform one or more operations of an interferer eNB 104 in some cases.

[0064] In some embodiments, the server eNB 104 may be arranged to operate as a general authorized access (GAA) device in accordance with a MulteFire protocol, although the scope of embodiments is not limited in this respect.

[0065] At operation 505, the server eNB 104 may detect a downlink signal from an interferer eNB 104 in an unlicensed channel. At operation 510, the server eNB 104 may determine a received power of the downlink signal. It should be noted that embodiments are not limited to usage of a received power, as other measurements may be used. Non-limiting examples include received signal strength indicator (RSSI), signal quality measurement, and a signal-to- noise ratio (SNR). It should be noted that operations 505 and 510 may be extended to cases of more than one interferer eNB 104. For instance, the server eNB 104 may detect downlink signals from multiple interferer eNBs 104, in some cases. In addition, the server eNB 104 may determine received powers for more than one of the downlink signals, in some cases.

[0066] At operation 515, the server eNB 104 may schedule one or more uplink transmissions during a period in the unlicensed channel. In some embodiments, the eNB 104 may schedule one or more uplink transmissions from one or more UEs 102 during the period in the unlicensed channel, although the scope of embodiments is not limited in this respect.

[0067] At operation 520, the server eNB 104 may schedule one or more downlink transmissions during a period. The period may be the same period described at operation 515, although the scope of embodiments is not limited in this respect. In some embodiments, the eNB 104 may schedule one or more downlink transmissions to one or more UEs 102 during the period, although the scope of embodiments is not limited in this respect.

[0068] At operation 525, the server eNB 104 may determine, based at least partly on the received power, whether the interferer eNB 104 is to refrain from downlink transmission in the unlicensed channel during a period in which an uplink transmission from a UE 102 to the server eNB 104 is scheduled. In a non-limiting example, the server eNB 104 may determine that the interferer eNB 104 is to refrain from the downlink transmission during the period if the received power is greater than a predetermined threshold.

[0069] At operation 530, the server eNB 104 may determine, based at least partly on the received power, whether the interferer eNB 104 is to refrain from scheduling of uplink transmissions in the unlicensed channel during the period in which the uplink transmission from a UE 102 to the server eNB 104 is scheduled. It should be noted that similar techniques may be used in operations 525 and 530, although the scope of embodiments is not limited in this respect. For instance, in a non-limiting example, the server eNB 104 may determine that the interferer eNB 104 is to refrain from scheduling uplink transmissions during the period if the received power is greater than a predetermined threshold (which may be the same threshold as the one used at operation 525 or a different threshold.

[0070] It should be noted that embodiments may not necessarily include all operations shown in FIG. 5. In a non-limiting example, some embodiments may not necessarily include operation 530. In another non-limiting example, some embodiments may not necessarily include operation 525. In another non- limiting example, some embodiments may include operations 525 and 530.

[0071] It should also be noted that embodiments are not limited to the chronological order shown in FIG. 5. In some embodiments, one or more operations may be performed multiple times. In a non-limiting example, the server eNB 104 may perform operation 525 for each of multiple interferer eNBs 104, in some embodiments. In another non-limiting example, the server eNB 104 may perform operation 530 for each of multiple interferer eNBs 104, in some embodiments.

[0072] In some embodiments, the server eNB 104 may determine a range between a UE 102 (for which an uplink transmission is scheduled during the period) and the server eNB 104. The server eNB 104 may determine the range based on one or more received signals from the UE 102, location information and/or other factors. The server eNB 104 may determine, based at least partly on the range, whether the interferer eNB 104 is permitted to perform downlink transmissions in the unlicensed channel during the period and/or schedule uplink transmissions in the unlicensed channel during the period. In a non-limiting example, the server eNB 104 may determine that the interferer eNB 104 is permitted to perform a downlink transmission in the unlicensed channel during the period if the range is below a predetermined threshold.

[0073] In some embodiments, the server eNB 104 may determine range(s) between one or more UEs 102 and the server eNB 104. The server eNB 104 may determine, on a per-subframe basis and based at least partly on the ranges corresponding to the sub-frames, whether the other devices (interferer eNBs 104 and/or other UEs 102) are to refrain from transmission.

[0074] One or more other criteria may be used, in some embodiments.

For instance, the server eNB 104 may determine that the interferer eNB 104 is permitted to perform a downlink transmission in the unlicensed channel during the period based at least partly on the received power (measured on the downlink signal from the interferer eNB 104). In some embodiments, multiple criteria may be used, such as a comparison between the received power and a first threshold and another comparison between the range and a second threshold. In a non-limiting example, the server eNB 104 may determine that the interferer eNB 104 is permitted to perform the downlink transmission in the unlicensed channel during the period if the received power from the interferer eNB 104 is below the first threshold and if the range is below the second threshold. In another non-limiting example, the server eNB 104 may determine that the interferer eNB 104 is permitted to perform the downlink transmission in the unlicensed channel during the period if the received power from the interferer eNB 104 is below the first threshold or if the range is below the second threshold.

[0075] The above examples are not limiting, as one or more

comparisons, including but not limited to those described above, may be used. The above examples may be applicable to determination of whether the interferer eNB 104 is to refrain from scheduling of uplink transmissions during the period in the unlicensed channel, in some embodiments. One or more of the same or similar comparisons may be used, including but not limited to comparisons similar to those described above. In addition, the above examples may be extended to cases in which multiple interferer eNBs 104 are considered.

[0076] It should be noted that in some operations (including but not limited to those describe herein) a comparison between two quantities (such as a and b) may not necessarily be a direct comparison. In a non-limiting example, one or both quantities may be scaled for the comparison (such as a comparison between a and b *c, a comparison between a*c and b, a comparison between a*c and b *d and/or other). In another non-limiting example, one or more additive terms may be used (such as a comparison between a and b+c, a comparison between a+c and b, a comparison between a+c and b+d and/or other). In another non-limiting example, a comparison between a and b may be performed.

[0077] In some embodiments, the range may be used to classify the UE

102 as "near" or "far" (or other classification) from the server eNB 104. In some cases, if the UE 102 is considered near to the server eNB 104, it may be determined that a downlink transmission from the interferer eNB 104 in the unlicensed channel may not necessarily interfere with the uplink transmission from the UE 102 (and may therefore be permitted).

[0078] It should be noted that techniques described herein in which an eNB 104 determines whether an interferer eNB 104 is to refrain from downlink transmission in the unlicensed channel and/or scheduling of uplink transmission in the unlicensed channel may be used in other cases. For instance, the eNB 104 may use such techniques to determine whether a UE 102 is to refrain from uplink transmission in the unlicensed channel, in some embodiments.

[0079] At operation 535, the server eNB 104 may transmit, in the unlicensed channel, a clear-to-send-to-self (CTS-to-self) message. In some embodiments, the CTS-to-self message may indicate one or more of: a start time of the period (during which the uplink transmission from the UE 102 to the server eNB 104 is scheduled), a duration of the period, whether the interferer eNB 104 is to refrain from downlink transmission in the unlicensed channel during the period and/or other information. In some embodiments, the CTS-to- self message may further indicate whether the interferer eNB 104 is to refrain from scheduling uplink transmissions in the unlicensed channel during the period.

[0080] In some embodiments, the CTS-to-self message may include a bitmap for a plurality of sub-frames, wherein values of the bitmap may indicate whether downlink transmission in the unlicensed channel is permissible, by the interferer eNB 104, in corresponding sub-frames.

[0081] In some embodiments, the CTS-to-self message may include one or more of: an interference threshold, a start time of a period during which an uplink transmission from a UE 102 to the server eNB 104 is scheduled, a duration of the period and/or other information.

[0082] In some embodiments, the CTS-to-self message may include a downlink control information (DCI) that includes the start time of the period and the duration of the period. The DCI may be scrambled in accordance with a scrambling sequence that is reserved for scrambling of the DCI. In a non- limiting example, the scrambling sequence may be reserved for scrambling of the DCI by a plurality of eNBs 104 that includes the server eNB and the interferer eNB 104.

[0083] In some embodiments, the interferer eNB 104 may use the scrambling sequence to descramble the DCI. The scope of embodiments is not limited in this respect, however, as other suitable techniques may be used to descramble the DCI.

[0084] In some embodiments, the CTS-to-self message may include a preamble and a payload. The pay load may include the start time of the period, the duration of the period, and whether the interferer eNB 104 is to refrain from downlink transmission in the unlicensed channel during the period. The preamble may be based on a Fourier Transform (FT) operation (including but not limited to an inverse FT) on a vector mapped to resource elements (REs) of the unlicensed channel. The vector may include: a predetermined sequence mapped to a plurality of the REs that are spaced apart by a predetermined number of REs; and zeros mapped to the REs between the REs to which the predetermined sequence is mapped.

[0085] In some embodiments, the CTS-to-self message may be included in a physical downlink control channel (PDCCH), which may be part of a 3GPP standard and/or other standard.

[0086] It should be noted that some or all of the descriptions herein of the CTS-to-self message may be applicable to cases in which multiple interferer eNBs 104 are present. In a non-limiting example, the interferer eNB 104 may be included in a plurality of interferer eNBs 104. The server eNB 104 may attempt to detect downlink signals from the plurality of interferer eNBs 104 in the unlicensed channel. In some embodiments, the server eNB 104 may determine, based on received powers of the downlink signals, one or more of the interferer eNBs 104 that are to refrain from downlink transmission in the unlicensed channel during the period. The server eNB 104 may encode the CTS-to-self message to indicate the one or more interferer eNBs 104 that are to refrain from downlink transmission in the unlicensed channel during the period. In some embodiments, the server eNB 104 may determine, based on received powers of the downlink signals, one or more of the interferer eNBs 104 that are to refrain from scheduling of uplink transmissions in the unlicensed channel during the period. The server eNB 104 may encode the CTS-to-self message to indicate the one or more interferer eNBs 104 that are to refrain from scheduling of uplink transmissions in the unlicensed channel during the period.

[0087] In some embodiments, the CTS-to-self message may include a muting pattern, which will be described below.

[0088] At operation 540, the server eNB 104 may receive one or more uplink signals in the unlicensed channel during the period (the period in which the uplink transmission to the server eNB 104 is scheduled). At operation 545, the server eNB 104 may transmit one or more downlink signals in the unlicensed channel during the period.

[0089] At operation 550, an eNB 104 may receive a CTS-to-self message from another eNB 104 in the unlicensed channel. At operation 555, the eNB 104 may determine, based on the received CTS-to-self message, whether to refrain from downlink transmissions in the unlicensed channel and/or refrain from scheduling of uplink transmissions in the unlicensed channel.

[0090] As described herein, references to an "interferer eNB" and/or

"server eNB" may be used for clarity, but such references are not limiting. In some cases, an interferer eNB 104 may receive the CTS-to-self message. In some cases, a server eNB 104 may receive the CTS-to-self message. For instance, the server eNB 104 may receive a second CTS-to-self message from another eNB 104 during a second period and may transmit a first CTS-to-self message during a first period.

[0091] In a non-limiting example, the CTS-to-self message may indicate one or more of: an interference threshold, a start time of a period during which an uplink transmission from a UE 102 to the server eNB 104 is scheduled, a duration of the period and/or other information. The interferer eNB 104 may determine a received power of the CTS-to-self message. In some embodiments, the interferer eNB 104 may determine whether to refrain from downlink transmission in the unlicensed channel during the period based on a comparison between the received power and the interference threshold. In a non-limiting example, the interferer eNB 104 may determine to refrain from downlink transmission in the unlicensed channel during the period if the received power is greater than the interference threshold. [0092] In some embodiments, the interferer eNB 104 may determine whether to refrain from scheduling of uplink transmissions in the unlicensed channel during the period based on a comparison between the received power and the interference threshold. In a non-limiting example, the interferer eNB 104 may determine to refrain from scheduling of uplink transmissions in the unlicensed channel during the period if the received power is greater than the interference threshold.

[0093] It should be noted that in some operations (including but not limited to those describe herein) a comparison between two quantities (such as a and b) may not necessarily be a direct comparison. In a non-limiting example, one or both quantities may be scaled for the comparison (such as a comparison between a and b *c, a comparison between a*c and b, a comparison between a*c and b *d and/or other). In another non-limiting example, one or more additive terms may be used (such as a comparison between a and b+c, a comparison between a+c and b, a comparison between a+c and b+d and/or other).

[0094] In some embodiments, a CTS-to-self message may include one or more of: a start time of a period in which an uplink transmission to the server eNB 104 in an unlicensed channel is scheduled or a downlink transmission by the server eNB 104 in the unlicensed channel is scheduled, a duration of the period and/or other information.

[0095] In some embodiments, a payload of a CTS-to-self message may include one or more of: a start time of a period in which an uplink transmission to the server eNB 104 in an unlicensed channel is scheduled or a downlink transmission by the server eNB 104 in the unlicensed channel is scheduled, a duration of the period and/or other information. In some embodiments, the server eNB 104 may encode the payload in accordance with a first RE spacing. The server eNB 104 may encode a preamble in accordance with a second RE spacing that is based on a product of the first RE spacing and a predetermined scale factor that is an integer greater than one. The server eNB 104 may encode, for transmission in the unlicensed channel, a CTS-to-self message that includes the preamble and the payload.

[0096] In some embodiments, the server eNB 104 may encode the preamble based on a predetermined sequence mapped to REs of the unlicensed channel in accordance with the second RE spacing (which may be based on a product of the first RE spacing and a predetermined scale factor that is an integer greater than one). Accordingly, an output of an inverse FT operation applied to the predetermined sequence may be repeated in the time domain. For instance, if the second RE spacing is equal to (or approximately) k multiplied by the first RE spacing, k repetitions of a time sequence may be output.

[0097] In some embodiments, the predetermined sequence may be based on one or more of: a virtual cell identifier (ID), a common cell ID, an index of a symbol, an index of a slot, an index of a sub-frame and an index of a frame. Embodiments are not limited to usage of these parameters, as the predetermined sequence may be based on one or more other parameters, in some embodiments.

[0098] In some embodiments, the predetermined sequence may be based on a Zadoff-Chu (ZC) sequence, an m-sequence or a Hadamard sequence.

Embodiments are not limited to these sequences, as the predetermined sequence may be based on one or more other sequences, in some embodiments.

[0099] In some embodiments, the server eNB 104 may monitor the unlicensed channel during a clear channel access (CCA) period. In a non- limiting example, the server eNB 104 may encode the CTS-to-self message to align with an end of the CCA period. In another non-limiting example, the server eNB 104 may encode the CTS-to-self message for transmission before the end of the CCA period.

[00100] In some embodiments, the server eNB 104 may schedule one or more uplink transmissions by one or more UEs 102 in an unlicensed channel. The server eNB 104 may transmit, in the unlicensed channel, a CTS-to-self message that indicates one or more of: a remaining duration of a current sub- frame, one or more subsequent sub-frames in which the uplink transmissions by the UEs 102 are scheduled and/or other information. The CTS-to-self message may include a muting pattern that indicates, on a per-subframe basis for the subsequent sub-frames, whether other devices (such as interferer eNBs 104 and/or UEs 102) are to refrain from transmission in the unlicensed channel. In some embodiments, the muting pattern may be included in predetermined candidate muting patterns, and the CTS-to-self message may include an index mapped to the predetermined candidate muting patterns to indicate the muting pattern. In some embodiments, the muting pattern may be semi-statically configured by a spectrum access system (SAS) controller that manages access to the unlicensed channel in accordance with a MulteFire protocol.

[00101] It should be noted that embodiments are not limited to usage of the CTS-to-self message to communicate information described herein. One or more other messages may be used to communicate such information. In a non- limiting example, a physical downlink control channel (PDCCH) and/or similar may be used, in some embodiments.

[00102] In some embodiments, the server eNB 104 may schedule one or more uplink transmissions by one or more UEs 102 in an unlicensed channel. The server eNB 104 may transmit, in the unlicensed channel, a PDCCH that indicates one or more of: a remaining duration of a current sub-frame, one or more subsequent sub-frames in which the uplink transmissions by the UEs 102 are scheduled and/or other information. The PDCCH may include a muting pattern that indicates, on a per-subframe basis for the subsequent sub-frames, whether other devices (such as interferer eNBs 104 and/or UEs 102) are to refrain from transmission in the unlicensed channel. In some embodiments, the muting pattern may be included in predetermined candidate muting patterns, and the PDCCH may include an index mapped to the predetermined candidate muting patterns to indicate the muting pattern. In some embodiments, the muting pattern may be semi-statically configured by a spectrum access system (SAS) controller that manages access to the unlicensed channel in accordance with a MulteFire protocol.

[00103] In some embodiments, an apparatus of an eNB 104 may comprise memory. The memory may be configurable to store a received power of an interferer eNB 104. The memory may store one or more other elements and the apparatus may use them for performance of one or more operations. In some embodiments, the apparatus of the eNB 104 may include a transceiver. The transceiver may be configured to transmit the CTS-to-self message. The transceiver may transmit and/or receive other frames, PPDUs, messages and/or other elements. In some embodiments, the apparatus may include processing circuitry, which may perform one or more operations (including but not limited to operation(s) of the method 500 and/or other methods described herein). The processing circuitry may include a baseband processor. The baseband circuitry and/or the processing circuitry may perform one or more operations described herein, including but not limited to determination of whether the interferer eNB 104 is to refrain from downlink transmission in an unlicensed channel during a period.

[00104] FIG. 6 illustrates the operation of another method of

communication in accordance with some embodiments. As mentioned previously regarding the method 500, embodiments of the method 600 may include additional or even fewer operations or processes in comparison to what is illustrated in FIG. 6 and embodiments of the method 600 are not limited to the chronological order that is shown in FIG. 6. In describing the method 600, reference may be made to FIGs. 1-5 and 7-15, although it is understood that the method 600 may be practiced with any other suitable systems, interfaces and components. In addition, embodiments of the method 600 may be applicable to UEs 102, eNBs 104, APs, STAs and/or other wireless or mobile devices. The method 600 may also be applicable to an apparatus for a UE 102, eNB 104 and/or other device described above.

[00105] In some embodiments, the UE 102 may perform one or more operations of the method 600, but embodiments are not limited to performance of the method 600 and/or operations of it by the UE 102. In some embodiments, the eNB 104 may perform one or more operations of the method 600 (and/or similar operations). Accordingly, although references may be made to performance of one or more operations of the method 600 by the UE 102 in descriptions herein, it is understood that the eNB 104 may perform one or more of the same operations, one or more similar operations and/or one or more reciprocal operations, in some embodiments.

[00106] It should be noted that the method 600 may be practiced by the

UE 102 and may include exchanging of elements, such as frames, signals, messages and/or other elements, with the eNB 104. Similarly, the method 500 may be practiced by an eNB 104 and may include exchanging of such elements with a UE 102. In some cases, operations and techniques described as part of the method 500 may be relevant to the method 600. In addition, embodiments of the method 600 may include one or more operations performed by the UE 102 that may be the same as, similar to or reciprocal to one or more operations described herein performed by the eNB 104 (including but not limited to operations of the method 500). As an example, an operation of the method 600 may be the same as or similar to an operation of the method 500. As another example, an operation of the method 500 may include a downlink transmission by the eNB that is similar to an uplink transmission by the UE 102 included in the method 600. As another example, an operation of the method 500 may include transmission of an element by the eNB and an operation of the method 600 may include reception of the same element and/or similar element by the UE 102.

[00107] In addition, previous discussion of various techniques and concepts may be applicable to the method 600 in some cases, including CTS-to- self message, PDCCH, transmission in an unlicensed channel, reception in an unlicensed channel, uplink transmission, downlink transmission, received power, server eNB 104, interferer eNB 104, and/or others.

[00108] At operation 605, the UE 102 may receive a CTS-to-self message in an unlicensed channel. At operation 610, the UE 102 may determine, based on the received CTS-to-self message, whether to refrain from uplink

transmissions in the unlicensed channel during a period. For instance, the CTS- to-self message may indicate such information, in some cases. Embodiments are not limited to CTS-to-self messages for operations 605-610. Other messages may be received by the UE 102 and may be used, by the UE 102, to determine whether to refrain from uplink transmissions in the unlicensed channel during the period. In some embodiments, the UE 102 may receive a PDCCH in the unlicensed channel. The UE 102 may determine, based on the PDCCH, whether to refrain from uplink transmissions in the unlicensed channel during the period.

[00109] At operation 615, the UE 102 may transmit one or more uplink signals in the unlicensed channel during the period. At operation 620, the UE 102 may receive one or more downlink signals in the unlicensed channel during the period.

[00110] FIG. 7 illustrates an example scenario in accordance with some embodiments. FIG. 8 illustrates examples of timing in accordance with some embodiments. FIG. 9 illustrates an example of preamble generation in accordance with some embodiments. FIG. 10 illustrates additional examples of timing in accordance with some embodiments. FIG. 11 illustrates additional examples of timing in accordance with some embodiments. FIG. 12 illustrates another example scenario in accordance with some embodiments. FIG. 13 illustrates another example scenario in accordance with some embodiments. FIG. 14 illustrates another example scenario in accordance with some embodiments. FIG. 15 illustrates example power thresholds in accordance with some embodiments.

[00111] It should be noted that the examples shown in FIGs. 7-15 may illustrate some or all of the concepts and techniques described herein in some cases, but embodiments are not limited by the examples. For instance, embodiments are not limited by the name, number, type, size, ordering, arrangement and/or other aspects of the frames, messages, sub-frames, time periods, UEs 102, eNBs 104, cells, cellular layout, operations and/or other elements as shown in FIGs. 7-15. Although some of the elements shown in the examples of FIGs. 7-15 may be included in a 3GPP LTE standard and/or other standard, embodiments are not limited to usage of such elements that are included in standards. In some embodiments, one or more of the elements shown in the examples of FIGs. 7-15 may be included in a MulteFire protocol and/or may be relevant to MulteFire techniques, although the scope of embodiments is not limited in this respect.

[00112] In some embodiments, techniques may be used in an attempt to solve co-existence issues, and to avoid interference from the eNB 104 for downlink and uplink transmission. As illustrated in the scenario 700 in FIG. 7, a CTS-to-Self may be transmitted by a serving eNB (eNBl indicated by 705) to mute the interferer eNBs (such as eNB2 indicated by 710), which might cause uplink or downlink interference. The CTS-to-Self may carry information such as: the cell ID of interferer eNBs, muting subframes configuration (including DL subframe and/or UL subframe). Some descriptions herein may refer to the eNBs 705, 710 shown in FIG. 7, but embodiments are not limited to the scenario shown in FIG. 7 and are also not limited to the number or arrangement of components (eNBs 705, 710 and/or other components) shown in FIG. 7.

[00113] In some embodiments, the CTS-to-Self physical layer structure may include a preamble and a CTS-to-Self control channel. The preamble may be utilized for timing/frequency synchronization, presence detection and/or other operation(s). The CTS-to-Self control channel may be utilized to carry interfering cell ID and subframe configuration and/or other operation(s).

[00114] In some embodiments, the preamble sequence may be repeated in the time domain by using either interleaved frequency division multiple access (IFDMA) or larger subcamer spacing. In case of IFDMA based structure, preamble symbols may be mapped in every K subcamer in the frequency domain, while the remaining subcarriers are set to zero. This IFDMA structure with a Repetition Factor (RPF) of K may create K repeated blocks in the time domain.

[00115] For instance, in cases in which a larger subcamer spacing is applied (with a subcamer spacing of Δί), then the sequence number of repetition for preamble transmission can be K within one OFDM symbol when a subcamer spacing of KAf is used for preamble transmission. Based on these two approaches, the repeated preamble sequence may be utilized for detection and synchronization if the interfering eNB 710 is asynchronous with the serving eNB 705.

[00116] Furthermore, the sequence for the preamble transmission may be generated based on Zadoff-Chu (ZC) sequence, M-sequence, Hadamard sequence or other sequence(s). It should be noted that the preamble sequence may be generated as a function of one or more following parameters: virtual cell ID or a common cell ID symbol/slot/subframe/frame index or an ID value. Such a technique may be used to reduce the blind detection complexity at MF eNB receiver, in some cases. In some embodiments, the virtual cell ID or the common cell ID may be predefined in the specification and/or configured by high layers (such as SAS and/or other).

[00117] In some embodiments, a preamble sequence may be generated as a function of an ID value. This may help to further randomize the inter-cell interference in cases when multiple MF eNBs 104 transmit the preamble at the same time.

[00118] In a non-limiting example, the ID value may be randomly selected from an ID pool. In some embodiments, the ID pool may be predefined in the specification or configured by higher layers (such as SAS and/or other). In some embodiments, the size of the ID pool may be limited. This may reduce a blind detection complexity, in some cases. Any suitable number of ID values may be used in the ID pool. For instance, 2 or 4 ID values may be used.

[00119] In some embodiments, a structure for preamble generation in the time domain may be either aligned or not aligned with an OFDM symbol boundary. As illustrated in the scenario 800 in FIG.8, the partial sequence 832 which overlaps with CCA/eCCA 810 may not be transmitted (as indicated by 834). The repetition labeled 830 may be partially transmitted in some cases. Additional repetitions 840 are shown. Embodiments are not limited to the number of repetitions shown in the scenario 800. As illustrated in the scenario 850 in FIG.8, the repetitions 880 do not overlap with CCA/eCCA 860.

Embodiments are not limited to the number of repetitions shown in the scenario 850.

[00120] In some embodiments, the preamble sequence may be generated based on a ZC sequence with different cyclic shift(s). In some cases, a technique similar to a technique used to generate DMRS or SRS may be used. In some embodiments, a base sequence for the preamble may be pre-defined. In some embodiments, a base sequence for the preamble may be randomly selected from multiple predefined sequences. In some embodiments, a base sequence for the preamble may be configured by SAS. It should be noted that the preamble sequence may be wideband, and may occupy the entire system bandwidth, in some cases. In a non-limiting example, each repetition may be roughly 9us to align with a slot time. In another non-limiting example, each repetition may be roughly 24us to align with a CCA time.

[00121] In some embodiments, the preamble sequence before repetition may be self cyclic-prefixed. An example scenario 900 is shown in FIG. 9. The ZC sequence 910 may include a first portion 912 and a second portion 914, and the cyclic prefix (CP) 916 may be the same as (and/or based on) 914. Then after repetition (which may be performed in accordance with IFDMA or a larger subcarrier spacing as indicated by 920, in some cases), each repetition 930 may include the CP. In some embodiments, the sequence may be generated without self CP. [00122] In some embodiments, the control channel may span one or more symbols. Furthermore, control payload symbol(s) may be transmitted following the detection preamble. It can be wideband, where resource elements (REs) of one or more OFDM symbols (excluding the REs for DMRS transmission if DMRS is transmitted) are used for the CTS-to-Self payload.

[00123] In some embodiments, multiple sub-band resources may be defined. Furthermore, the eNB 104 may select one sub-band (for instance, according to the cell ID or the ID which is randomly selected for the preamble generation), to transmit the control channel. Alternatively, the eNB 104 may randomly select one sub-band for control channel transmission based on the physical cell ID. It should be noted that the sub-band may be localized or distributed in the system bandwidth. In the latter, frequency diversity gain may be achieved, in some cases.

[00124] In some embodiments, information bits with fixed length may be processed with one or more of CRC attachment, channel coding, rate matching and/or other operation, and may be subsequently mapped to the available REs.

In some cases, a technique similar to a technique used for LTE PDCCH may be used, although the scope of embodiments is not limited in this respect.

[00125] In some embodiments, a control channel generation procedure may reuse (at least partly) a cPDCCH generation procedure. Here, the aggregation level of cPDCCH may be extended, so as to occupy all the available

REs.

[00126] It should be noted that, depending on a transmission scheme for control channel transmission, a preamble or dedicated DM-RS may be employed as the DM-RS for control channel transmission. In a non-limiting example, in cases in which space frequency block code is adopted for control channel transmission, it may be desirable to employ dedicated DM-RS. In such cases, a DM-RS pattern may follow the CRS pattern within the first OFDM symbol of a DL subframe. Similar to the preamble sequence generation, the DM-RS sequence may be generated as a function of one or more of the following parameters: a virtual cell ID, a physical cell ID, a common cell ID, an ID which is randomly selected for preamble generation, a symbol/slot/subframe/frame index and/or other parameter(s). [00127] In some embodiments, a scrambling sequence for a control channel may be generated as a function of one or more of the following parameters: a virtual cell ID, a physical cell ID, a common cell ID, an ID which is randomly selected for preamble generation, an ID configured by SAS, a symbol/slot/subframe/frame index and/or other parameter(s).

[00128] In some embodiments, the CTS-to-Self may be transmitted in a floating manner or fixed manner. After transmission of the CCA or eCCA, the eNB 104 may transmit the CTS-to-Self in one or more available OFDM symbols. Referring to scenario 1000 in FIG. 10, the CTS-to-Self (labeled as "pay load") 1025 may be transmitted after transmission of the CCA or eCCA 1010. An interferer eNB 104 may have sufficient processing time to detect the demodulation and prepare the scheduling for mute, in some cases. Referring to scenario 1030 in FIG 10, if there exists multiple OFDM symbol gap between ending of CCA or eCCA 1040 and the starting of the next subframe (Note, the subframe can be partial subframe or full subframe), the CTS-to-Self (labeled as "pay load") 1055 may be transmitted near the middle of the subframe. One or more preamble sequences (labeled as "detection sequence") 1050 may be inserted prior to CTS-to-Self transmission and may be utilized, in some cases, for more fine synchronization or accurate detection. Further, one or more preamble sequences 1057 may be inserted after the CTS-to-Self 1055 and may be utilized, in some cases, for reservation signal to reserve the channel.

Referring to scenario 1060 in FIG. 10, the CTS-to-Self (labeled as "payload") 1085 may be transmitted at or near the end of the sub-frame. Since the CTS-to- Self 1085 is transmitted in a fixed position, a complexity for CTS-to-Self detection by an interferer eNB 104 may be reduced in some cases. The gap between the ending of CCA or e-CCA 1070 and the CTS-to-Self 1085 may be reserved by random sequence(s) using any suitable technique. In some embodiments, the gap may be filled using a long CP of a following OFDM symbol.

[00129] In some cases, a short sequence generated by frequency domain down-sample may be repeated multiple times depending on when a CCA finishes. This may cause confusion on which sequence is the last one which marks the start of the OFDM symbol carrying payload. In one embodiment, a sign of the last repeated sequence may be reversed to allow an interferer eNB 104 to detect the OFDM symbol. Referring to FIG. 11, in the scenario 1100, the eNB 104 may transmit the repetitions 1110 and the repetition 1120. In some embodiments, a sign of the sequence of repetition 1120 may be reversed.

[00130] In some embodiments, the end of one OFDM symbol boundary with a fixed time guard may be reserved. A dedicated sequence may be transmitted to mark the end of the OFDM symbol boundary. In some embodiments, an ending sequence and a corresponding CP may be used. In a non-limiting example, the ending sequence may be the same sequence as the preamble sequence with reversed sign. In a non-limiting example, the ending sequence may be generated based on a different root sequence as that used for generation of the preamble sequence. In the example scenario 1130, the eNB 104 may transmit the ending sequence 1154 and corresponding CP 1152.

[00131] In some embodiments, a transmission of a preamble sequence may be aligned to a full or halved OFDM boundary. The gap between the ending of CCA or eCCA and the beginning of the preamble sequence may be covered by a random sequence or may be filled using a long CP of the following OFDM symbol.

[00132] In some embodiments, a CTS-to-self message may be transmitted by an eNB 104. In some cases, the CTS-to-self message may be transmitted to mute another eNB 104 for a duration of time. This may enable a UE 102 to perform an UL transmission with reduced interference, in some cases. In descriptions herein, the eNB 104 that transmits the CTS-to-Self message may be referred to as a "server eNB 104" and other eNBs 104 that may receive the CTS- to-Self message may be referred to as "interferer eNBs 104." Such references are not limiting. These references may be used for clarity in some cases.

[00133] In some embodiments, a CTS-to-Self message may include one or more of: an UL duration, a starting subframe of a UL transmission and/or other. An interferer eNB 104 that may potentially cause interference (such as a level of interference above a threshold) to the serving eNB 104 may refrain from scheduling DL transmission(s) during one or more subframes. In some cases, these operations may improve UL performance for an uplink communication between a UE 102 and the server eNB 104. [00134] In some embodiments, an interference threshold and/or default targeting receiving power (P0) used in UL power control may be determined by the SAS and may be sent to one or more GAA eNBs 104.

[00135] In some cases, interference may be reciprocal. This may be due to point to point transmission, in some cases. The interferer eNB 104 may determine one or more measurements based on the CTS signal (such as a long term average of the signal from the serving eNB 104 and/or other

measurement s)). The interferer eNB 104 may use the measurements to determine an interference level. In a non-limiting example, the interferer eNB 104 may compare a received power with a target UL received power in the UL power control.

[00136] In some embodiments, UL transmission scheduling may include determination of a start of the UL transmission, duration of the UL transmission and/or other, which may be signaled in a CTS-to-self message. In some embodiments, the CTS-to-Self may be based on a cPDCCH. The serving cell eNB 104 may start sending the cPDCCH at the beginning of the burst. For other eNBs 104 to receive the cPDCCH, the SAS may indicate (to one or more other eNBs 104) a CC-RNTI used to scramble the cPDCCH.

[00137] In some embodiments, the UL transmission scheduling information (which may include the start of the UL transmission, the duration of the UL transmission and/or other) may be sent using a DCI format in a common search space, with a scrambling common to all cells.

[00138] In some embodiments, the UL transmission scheduling information (which may include the start of the UL transmission, duration of the UL transmission and/or other) may be sent in a preamble before the burst. The preamble may be common to multiple eNBs 104, in some cases.

[00139] For an interferer eNB 104 that may cause interference to the serving eNB 104, the interferer eNB 104 may refrain from transmission during the duration of the UL transmission or may schedule UL transmissions to UEs 102 for which a DL interference level is below a threshold. For instance, a UE 102 that is relatively far from the eNB 104 sending the CTS may be scheduled. Referring to FIG. 12, the first eNB 1210 (labeled as "eNB l") may send CTS-to- self message 1215. The second eNB 1220 (labeled as "eNB2") may schedule an UL transmission from the UE 1225. As seen in the scenario 1200, the UE 1225 may be sufficiently far from eNB l 1210, and therefore its UL transmission may be scheduled.

[00140] In some embodiments, the server eNB 104 may transmit a CTS- to-Self message to mute DL subframes by other eNBs 104. The CTS-to-self message may include one or more of: a DL subframe number, an ID of an interferer eNB 104 that may cause relatively high interference (such as interference above a threshold) in the DL subframe, a UL duration and/or other information. In some cases, the server eNB 104 may schedule DL transmission in accordance with a time division multiplexing (TDM) technique, which may increase a reuse factor during a subframe. However, this may reduce the multiuser scheduling gain of OFDMA system, in some cases.

[00141] In a non-limiting example, the CTS-to-self message may include one or more of: a DL subframe index list, muting eNB 104 PCI information, a UL subframe offset, a UL subframe duration and/or other information. It should be noted that a complete DL subframe index may not be needed in the CTS-to- self message, in some cases. For example, if a subframe is scheduled to a cell center UE 102, it may not be necessary to mute nearby eNBs 104.

[00142] An example scenario 1300 is shown in FIG. 13. The server eNB 1310 (referred to as "eNBl") may transmit a CTS-to-self message 1315, which may be received by the interferer eNB 1320 (referred to as "eNB2"). The eNB2 1320 may attempt to schedule UL transmissions that cause reduced interference and/or no interference to eNB 1 1310. In a non-limiting example, as indicated by 1325, eNB l 1310 may schedule subframes of [ Dl Dl D2 D3 U U U U] during a burst, wherein the "D" may indicate a subframe in which DL transmission is scheduled and a "U" may indicate a subframe in which UL transmission is scheduled. As indicated by 1330, eNB2 1320 may refrain from transmission in subframes Dl, and may schedule downlink transmission subframes D2 and D3.

[00143] In some embodiments, the CTS-to-self may include, in addition to an interfering cell ID (ID of an interferer eNB 104), a bitmap. Then the interferer eNB 104 may schedule different UEs 102 accordingly. The CTS information content may include one or more of: a PCI of the interferer eNB 104

(such as cell_IDeNB2), a bitmap of DL subframes (such as [1 1 0 0] or other bitmap of any suitable length and values), a UL subframe offset, a UL transmission duration and/or other information.

[00144] In some embodiments, the CTS information may be included in a

PDCCH transmission in a common search space with an RNTI common to multiple eNBs 104. In some embodiments, the CTS information may be indicated in a preamble.

[00145] In a "MulteFire" protocol, little or no assistance from the licensed spectrum may be used by devices for communication in unlicensed spectrum. Although MulteFire is described herein, embodiments are not limited to communication in accordance with MulteFire protocol. It is understood that some or all of the methods, operations, techniques and/or concepts described herein may be applicable to communication in accordance with other protocols.

[00146] In a non-limiting example, MulteFire may be used in 3.5GHz spectrum. In another non-limiting example, a 3GPP protocol may employ new radio (NR) or LAA on 3.5 GHz Citizens Broadband Radio Service (CBRS) spectrum. In some embodiments, a three-tiered access model for 3.5 GHz CBRS band may be used: 1) Incumbent (such as Federal user, Fixed Satellite Service and/or other), 2) priority access licensees (PALs) (such as 100 MHz bands of spectrum, bands that may be auctioned for short-term licensing and/or other), and 3) general authorized access (GAA): 150 MHz open for anyone with an FCC-certified device. In some embodiments, according to the above order of priority, channel access by devices of a higher priority may be protected from channel access by devices of lower priorities. For instance, the channel access by PAL may be protected from GAA, whereas PAL may operate so as to not hinder the channel access by an incumbent.

[00147] In some embodiments, an entity (including but not limited to an entity/controller of a spectrum access system (SAS)) may authorize and/or manage usage of CBRS (PAL, GAA) spectrum. The SAS controller may maintain the prioritized channel access. As a frequency coordinator, the SAS controller may optimize frequency usage to facilitate coexistence. It is possible that SAS may have limited coexistence provisioning between GAAs by means of spectrum coordination, in some cases. [00148] In some embodiments, transmission equipment with specific and standardized capabilities may be employed by CBRS operators for use in the 3.5 GHz band. This equipment is called Citizens Broadband Service Device (CBSD). The CBDSs may be fixed stations or networks of stations. Two types of CBDSs are described herein: Category A (a lower power CBSD for indoor use) and Category B (a higher power CBSD for outdoor use). Embodiments are not limited to two types and are not limited to these two particular types. In some cases, permissible transmit powers between devices in the two categories may be quite different.

[00149] Referring to FIG. 14, a scenario 1400 illustrates a coexistence issue of outdoor high power eNB 1410 and indoor low power eNB 1420. Due to high transmission power, outdoor eNB 1410 may silence/block other transmitters in the wide range including those indoor eNBs 1420. On the other hand, the indoor eNB 1420 may not be able to symmetrically silence the outdoor eNB 1410 due to lower transmission power. Some or all of the methods, operations, techniques and/or concepts described herein may be applicable to a scenario like 1400, but embodiments are not limited to scenarios like 1400.

[00150] In some embodiments, an ED threshold may be adapted based on transmission power. In a non-limiting example, the ED threshold may be set according to the following equation or similar equation: ED threshold = -72 + (23 + 10*logl0(BW in MHz / 20 MHz) - Ptx) dBm. In another non-limiting example, the ED threshold may be set according to the following equation or similar equation: ED threshold = max(-82, -72 + (23 + 10*logl0(BW in MHz / 20 MHz) - Ptx)) dBm. In some embodiments, the ED threshold may be semi- statically indicated to the eNB 104. For instance, SAS signaling and/or other signaling may be used. In some embodiments, the ED threshold may be fixed. Non-limiting examples 1510 and 1520 are shown in FIG. 15.

[00151] In some embodiments, LPNs may transmit signals which indicate the time resources where nearby devices need to defer their transmissions. This may help LPNs to reserve the channel. Two approaches are described below, but embodiments are not limited to these two approaches.

[00152] In some embodiments, a preamble transmission before a burst may indicate a total burst duration. The LPN may transmit a preamble that indicates the duration of the burst and further indicates expected numbers of DL and/or UL subframes. The preamble may be transmitted before the start of the burst. The preamble may be effectively broadcast before the transmission of the burst. The receiver may perform blind detection of the preamble. Upon reception of the preamble, a nearby receiver that successfully received the preamble may refrain from transmission(s) during the burst duration indicated by the preamble. Upon reception of the preamble, the nearby receiver that successfully received the preamble may refrain from performance of LBT during the burst duration indicated by the preamble.

[00153] In some embodiments, the preamble may span one or more symbols. In some embodiments, the preamble may include a reference signal. Non-limiting example references signals include cell specific reference signal (CRS), demodulation reference signal (DMRS) and channel state information reference signal (CSI-RS). In some embodiments, the preamble may include one or more of CRS, DMRS or CSI-RS modified so that preamble is detectable by all nearby devices. This may enable demodulation of the burst information, in some cases. The generation/RE mapping of these RSs (CRS, DMRS or CSI-RS) may depend on a cell ID in legacy LTE, in some embodiments. In some cases, this may enable detection of the preamble by multiple devices. In some embodiments, the cell ID used in the RS generation/RE mapping may be set to a default value (such as 0 or other value) or may be set by SAS signaling.

[00154] The following provides a non-limiting example for CRS, while similar methods may be adopted for DMRS and CSI-RS as well. CRS may use gold sequences whose generation may be dependent on the Cell ID. In order to reduce blind decoding attempts at the eNB, Cell-ID (NID) used for CM may be set to a default value for CRS scrambling. A scrambling technique from a standard, such as a 3 GPP LTE standard, may be used, although the scope of embodiments is not limited in this respect. In some embodiments, a default value may be set to 0, or may be signaled by SAS. In some embodiments, the CRS mapping for the preamble may occur according to the default cell-ID.

[00155] In some embodiments, the preamble may include one or more synchronization signals. Non-limiting examples include primary

synchronization signal (PSS) and/or secondary synchronization signal (SSS). In some embodiments, the PSS may be present in the first symbol of the central 6 PRBs within the preamble. The SSS may be present in the second symbol of the central 6 PRBs within the preamble. Alternatively, the PSS may be in the second symbol while SSS may be in the first symbol.

[00156] In some embodiments, the preamble may include a payload. The payload may include burst duration information, in some embodiments. In a non-limiting example, the burst duration information may be encoded via TBCC at 1/3 rate and QPSK modulation.

[00157] In some embodiments, presence detection of the preamble may be performed with RS detection. In addition, the performance/blind detection of preamble detection may be improved with the synchronization signal (PSS/SSS) in the preamble, in some cases.

[00158] In some embodiments, a set of sequences may be adopted for CTS. The set may be irrelevant to the cell ID, in some cases. In some embodiments, different sequences in the set may be used to indicate different burst duration information. In a non-limiting example, sequence #1 and sequence #2 may denote the burst duration of 1 subframe and 2 subframes, respectively. Devices (such as nearby devices, in some cases) may perform hypothesis tests among the set of sequences, and may defer the LBT and transmission for a duration corresponding to the detected sequence.

[00159] In some embodiments, reserved PRACH sequences may be used, and the Cat B HPN may reuse the procedure of PRACH reception.

Embodiments are not limited to these sequences, however, as other sequences may be used. In some embodiments, a gap may exist between the preamble and the data burst, so as to leave processing time for HPN for detection.

[00160] In some cases, cPDCCH may be used to indicate the frame configuration. For instance, the cPDCCH may indicate the current/next subframe length, and the configuration (offset and duration) of following UL burst.

[00161] In some embodiments, LPNs may use the PDCCH to hold the medium. The PDCCH may include one or more of the following information: a length of current/next subframe, a duration of a remaining transmission burst and/or other information. [00162] In some embodiments, a plurality of subframes may be used for transmission. It should be noted that the subframes that are occupied may be restricted to the subframes which schedule UEs 102 at a cell edge (such as UE 1430 in FIG. 14). Subframes in which UEs 102 in a relatively good coverage may not necessarily be indicated, in some embodiments. It should be noted that UEs 102 may be categorized into categories that may be different from "at a cell edge" and "in relatively good coverage." For instance, it may be determined whether a distance between a UE 102 and an eNB 104 is below a threshold, and the UE 102 may be categorized accordingly. In addition, this classification (below or above the threshold) may be used, in some embodiments, to determine whether corresponding sub-frames are to be signaled as sub-frames in which other devices are to refrain from transmission and/or scheduling.

[00163] In some embodiments, a DCI format may be defined for the

PDCCH to carry the above information. Alternatively, a DCI format (such as a DCI format 1C or other) may be used. An RNTI (which may be different from CC-RNTI, in some embodiments) may be used to scramble the DCI.

[00164] In some embodiments, for reservation of the channel, the PDCCH may be modified to be detectable by nearby devices. Such devices may include UEs 102 associated with the eNB 102 that transmits the PDCCH, other UEs 102, other eNBs 104 and/or other devices.

[00165] In some embodiments, the PDCCH may be detected by receiving eNBs. If eNBs 104 of a same operator receive the PDCCH, the eNB(s) 104 may perform blind detection of PDCCH over NID and may perform different hypothesis over scrambling for CRS/cPDCCH. In some embodiments, scrambling used for PDCCH and CRS may use a default Cell-ID (such as a cell- ID value of 0, a cell -ID value signaled by SAS and/or other).

[00166] In some embodiments, after detection of the PDCCH, the receiving eNB 104 may not necessarily perform LBT and may defer its transmission in the duration indicated by the PDCCH which is used for transmission of the LPN who transmits the PDCCH. In some embodiments, the

PDCCH may be transmitted in every DL subframe, or in a subset of DL subframes. For instance, the PDCCH may be transmitted in the beginning NDL subframe (for instance, N=2 or 3 or other value), or every other subframe. [00167] In some embodiments, HPNs may broadcast a muting pattern.

Devices that receive the indication may use the muted subframes for LBT and transmission.

[00168] In some embodiments, the muting pattern may be indicated as a bitmap. In some embodiments, multiple muting patterns may be pre-defined or may be indicated via SAS. An associated index may be indicated by HPNs. The muting granularity may be a radio frame, a subframe or multiple consecutive subframes.

[00169] In some embodiments, the indication of the muting pattern may be transmitted in every DL subframe, or in a subset of DL subframes. For instance, the indication may be transmitted in the beginning N DL subframes (for instance, N=2 or 3 or other value), or every other subframe.

[00170] In some embodiments, a PDCCH may include the muting pattern of the HPNs (for instance, the set of subframes that the HPN will mute). The PDCCH may be common across cells. Devices that receive the PDCCH may use the muted subframes for LBT and transmission.

[00171] In some embodiments, a format of DCI may be defined for the PDCCH to carry the above information. Alternatively, another DCI format (such as DCI format 1C or other) may be reused. An RNTI (which may be different from CC-RNTI) may be used to scramble the DCI.

[00172] In some embodiments, the PDCCH may be detected by one or more receiving eNBs 104. For eNBs 104 of a same operator that receive the cPDCCH, the eNB(s) 104 may perform blind detection of cPDCCH over NID and may perform different hypothesis over scrambling for CRS/cPDCCH. In some embodiments, the scrambling used for PDCCH and CRS may use a default cell-ID (such as a cell-ID value of 0, a cell-ID value signaled by SAS and/or other). After detection of the cPDCCH, the receiving devices may perform transmission subject to LBT during the muted duration.

[00173] In some embodiments, a plurality of sequences may be used to indicate the muting pattern. The sequence may be common across cells.

Different sequences in the plurality may be used to indicate different muting patterns. For example, sequence #1 and sequence #2 may denote the muting pattern #1 and muting pattern #2, respectively. The muting pattern may be pre- defined or indicated by SAS. Other devices may perform hypothesis tests among the plurality of sequences, and may perform the LBT and transmission for a duration corresponding to the muted subframe indicated by the detected sequence.

[00174] In some embodiments, the sequence(s) may include one or more reference signals (such as cell specific reference signal (CRS), demodulation reference signal (DMRS), channel state information reference signal (CSI-RS) and/or other). In some embodiments, CRS or DMRS or CSI-RS may be modified so that a preamble is detectable by one or more other devices. The generation/RE mapping of these RSs may depend on a cell ID in legacy LTE. To make the preamble detectable by other devices, the cell ID used in the RS generation/RE mapping may be set to a default value. For example, the cell ID used for sequence generation may be configured by a set of values that are predefined or indicated by SAS. The RE mapping may be predefined or may be indicated by SAS. In some embodiments, the sequences may be defined for the purposes above. In some embodiments, reserved PRACH sequences may be used. These examples are not limiting, however, as any suitable set of sequences may be used.

[00175] In some embodiments, the muting pattern may be semi-statically configured. The SAS may signal the muting pattern, which may be based on a long-term estimation of interference, in some cases. In some embodiments, the SAS may configure the muting pattern by a bitmap based method. For instance, Nbits may be used (for instance, N=10 or other value) and HPNs may mute based on the N-bit indication, with the muting pattern repeating every Ν subframes. Alternatively, a set of muting pattern may be predefined, and the SAS may indicate an index of the pattern to be used.

[00176] In some embodiments, the eNB 104 may perform detection of

CTS message (for instance, a preamble or PDCCH that includes transmission burst/subframe information). In some embodiments, a UE 102 may also employ one or more techniques described above and herein. For instance, the UE 102 may perform ED adjustment based on the transmission similar to eNB 104. In another non-limiting example, the UE 102 may use CTS technique(s) (for instance, transmission of a preamble to hold the medium). In some embodiments, the UE 102 may detect the preamble and cPDCCH sent by other device(s), and may refrain from transmission for the burst interval indicated by transmitting devices. One or more techniques that are used by an eNB 104 (such as an interferer eNB 104 and/or other) in description herein may be used by a UE 102, in some embodiments. In some embodiments, the UE 102 may perform cPDCCH detection and may use the muted subframes for LBT and transmission and may refrain from transmission for the un-muted duration indicated by the transmitting device. In some cases, when the UE 102 receives a CTS message, the UE 102 may continue to monitor the PDCCH and may receive a PDSCH (if scheduled), even during the transmission time indicated by the CTS message. In some embodiments, the UE 102 may defer the LBT and UL transmission during the transmission time indicated by the CTS message.

[00177] In Example 1, an apparatus of an Evolved Node-B (eNB) may comprise memory. The eNB may be configurable to operate as a server eNB. The apparatus may further comprise processing circuitry. The processing circuitry may be configured to detect a downlink signal from an interferer eNB in an unlicensed channel. The processing circuitry may be further configured to determine a received power of the downlink signal. The processing circuitry may be further configured to store the received power in the memory. The processing circuitry may be further configured to determine, based at least partly on the received power, whether the interferer eNB is to refrain from downlink transmission during a period in which an uplink transmission from a User Equipment (UE) to the server eNB is scheduled. The processing circuitry may be further configured to encode, for transmission in the unlicensed channel, a clear-to-send-to-self (CTS-to-self) message that indicates: a start time of the period, a duration of the period, and whether the interferer eNB is to refrain from downlink transmission during the period.

[00178] In Example 2, the subject matter of Example 1, wherein the processing circuitry may be further configured to determine that the interferer eNB is to refrain from the downlink transmission during the period if the received power is greater than a predetermined threshold.

[00179] In Example 3, the subject matter of one or any combination of

Examples 1-2, wherein the processing circuitry may be further configured to encode the CTS-to-self message to further indicate whether the interferer eNB is to refrain from scheduling uplink transmissions during the period.

[00180] In Example 4, the subject matter of one or any combination of

Examples 1-3, wherein the processing circuitry may be further configured to encode the CTS-to-self message to include a bitmap for a plurality of sub- frames. Values of the bitmap may indicate whether downlink transmission is permissible, by the interferer eNB, in corresponding sub-frames.

[00181] In Example 5, the subject matter of one or any combination of

Examples 1-4, wherein the processing circuitry may be further configured to determine a range between the UE and the server eNB. The processing circuitry may be further configured to determine that the interferer eNB is permitted to perform the downlink transmission during the period if the range is below a predetermined threshold.

[00182] In Example 6, the subject matter of one or any combination of Examples 1-5, wherein the interferer eNB is included in a plurality of interferer eNBs. The processing circuitry may be further configured to attempt to detect downlink signals from the plurality of interferer eNBs in the unlicensed channel. The processing circuitry may be further configured to determine, based on received powers of the downlink signals, one or more of the interferer eNBs that are to refrain from downlink transmission during the period. The processing circuitry may be further configured to encode the CTS-to-self message to indicate the one or more interferer eNBs that are to refrain from downlink transmission during the period.

[00183] In Example 7, the subject matter of one or any combination of Examples 1-6, wherein the CTS-to-self message may include a preamble and a payload. The pay load may include the start time of the period, the duration of the period, and whether the interferer eNB is to refrain from downlink transmission during the period. The preamble may be based on an inverse

Fourier Transform (FT) operation on a vector mapped to resource elements (REs) of the unlicensed channel. The vector may include: a predetermined sequence mapped to a plurality of the REs that are spaced apart by a predetermined number of REs, and zeros mapped to the REs between the REs to which the predetermined sequence is mapped. [00184] In Example 8, the subject matter of one or any combination of

Examples 1-7, wherein the processing circuitry may be further configured to encode the CTS-to-self message in a physical downlink control channel (PDCCH).

[00185] In Example 9, the subject matter of one or any combination of

Examples 1-8, wherein the server eNB may be arranged to operate as a general authorized access (GAA) device in accordance with a MulteFire protocol.

[00186] In Example 10, the subject matter of one or any combination of

Examples 1-9, wherein the apparatus may further include a transceiver to transmit the CTS-to-self message.

[00187] In Example 11, the subject matter of one or any combination of

Examples 1-10, wherein the processing circuitry may include a baseband processor to determine whether the interferer eNB is to refrain from downlink transmission during the period and to encode the CTS-to-self message.

[00188] In Example 12, a computer-readable storage medium may store instructions for execution by one or more processors to perform operations for communication by an Evolved Node-B (eNB). The eNB may be configurable to operate as an interferer eNB. The operations may configure the one or more processors to decode, from a server eNB, a clear-to-send-to-self (CTS-to-self) message that indicates: an interference threshold, a start time of a period during which an uplink transmission from a User Equipment (UE) to the server eNB is scheduled, and a duration of the period. The operations may further configure the one or more processors to determine a received power of the CTS-to-self message. The operations may further configure the one or more processors to determine whether to refrain from downlink transmission during the period based on a comparison between the received power and the interference threshold.

[00189] In Example 13, the subject matter of Example 12, wherein the operations may further configure the one or more processors to determine to refrain from downlink transmission during the period if the received power is greater than the interference threshold.

[00190] In Example 14, the subject matter of one or any combination of

Examples 12-13, wherein the CTS-to-self message may include a downlink control information (DCI) that includes the start time of the period and the duration of the period. The operations may further configure the one or more processors to descramble the DCI in accordance with a scrambling sequence that is reserved for scrambling of the DCI by a plurality of eNBs that includes the server eNB and the interferer eNB.

[00191] In Example 15, an apparatus of an Evolved Node-B (eNB) may comprise memory. The apparatus may further comprise processing circuitry. The processing circuitry may be configured to encode a pay load in accordance with a first resource element (RE) spacing, wherein the pay load includes: a start time of a period in which an uplink transmission to the eNB in an unlicensed channel is scheduled or a downlink transmission by the eNB in the unlicensed channel is scheduled, and a duration of the period. The processing circuitry may be further configured to encode a preamble in accordance with a second RE spacing that is based on a product of the first RE spacing and a predetermined scale factor that is an integer greater than one. The processing circuitry may be further configured to encode, for transmission in the unlicensed channel, a clear- to-send-to-self (CTS-to-self) message that includes the preamble and the payload.

[00192] In Example 16, the subject matter of Example 15, wherein the processing circuitry may be further configured to encode the preamble based on a predetermined sequence mapped to REs of the unlicensed channel in accordance with the second RE spacing.

[00193] In Example 17, the subject matter of one or any combination of

Examples 15-16, wherein the predetermined sequence may be based on one or more of: a virtual cell identifier (ID), a common cell ID, an index of a symbol, an index of a slot, an index of a sub-frame and an index of a frame.

[00194] In Example 18, the subject matter of one or any combination of

Examples 15-17, wherein the predetermined sequence may be based on a Zadoff-Chu (ZC) sequence, an m-sequence or a Hadamard sequence.

[00195] In Example 19, the subject matter of one or any combination of

Examples 15-18, wherein the processing circuitry may be further configured to monitor the unlicensed channel during a clear channel access (CCA) period. The processing circuitry may be further configured to encode the CTS-to-self message to align with an end of the CCA period.

[00196] In Example 20, an apparatus of an Evolved Node-B (eNB) may comprise memory. The apparatus may further comprise processing circuitry. The processing circuitry may be configured to schedule one or more uplink transmissions by one or more User Equipments (UEs) in an unlicensed channel. The processing circuitry may be further configured to encode, for transmission in the unlicensed channel, a physical downlink control channel (PDCCH) that indicates: a remaining duration of a current sub-frame, and one or more subsequent sub-frames in which the uplink transmissions by the UEs are scheduled. The processing circuitry may be further configured to decode one or more uplink packets received from the UEs in the unlicensed channel.

[00197] In Example 21, the subject matter of Example 20, wherein the

PDCCH may further include a muting pattern that indicates, on a per-subframe basis for the subsequent sub-frames, whether other devices are to refrain from transmission.

[00198] In Example 22, the subject matter of one or any combination of

Examples 20-21, wherein the muting pattern may be included in predetermined candidate muting patterns. The PDCCH may include an index mapped to the predetermined candidate muting patterns to indicate the muting pattern.

[00199] In Example 23, the subject matter of one or any combination of

Examples 20-22, wherein the muting pattern may be semi-statically configured by a spectrum access system (SAS) controller that manages access to the unlicensed channel in accordance with a MulteFire protocol.

[00200] In Example 24, the subject matter of one or any combination of

Examples 20-23, wherein the processing circuitry may be further configured to determine ranges between the UEs and the eNB. The processing circuitry may be further configured to determine, on a per-subframe basis and based at least partly on the ranges corresponding to the sub-frames, whether the other devices are to refrain from transmission.

[00201] In Example 25, an apparatus of an Evolved Node-B (eNB), the eNB configurable to operate as an interferer eNB, may comprise means for decoding, from a server eNB, a clear-to-send-to-self (CTS-to-self) message that indicates: an interference threshold, a start time of a period during which an uplink transmission from a User Equipment (UE) to the server eNB is scheduled, and a duration of the period. The apparatus may further comprise means for determining a received power of the CTS-to-self message. The apparatus may further comprise means for determining whether to refrain from downlink transmission during the period based on a comparison between the received power and the interference threshold.

[00202] In Example 26, the subject matter of Example 25, wherein the apparatus may further comprise means for determining to refrain from downlink transmission during the period if the received power is greater than the interference threshold.

[00203] In Example 27, the subject matter of one or any combination of

Examples 25-26, wherein the CTS-to-self message may include a downlink control information (DCI) that includes the start time of the period and the duration of the period. The apparatus may further comprise means for descrambling the DCI in accordance with a scrambling sequence that is reserved for scrambling of the DCI by a plurality of eNBs that includes the server eNB and the interferer eNB.

[00204] The Abstract is provided to comply with 37 C.F.R. Section 1.72(b) requiring an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

CLAIMS What is claimed is:

1. An apparatus of an Evolved Node-B (eNB), the eNB configurable to operate as a server eNB, the apparatus comprising: memory; and processing circuitry, configured to:

detect a downlink signal from an interferer eNB in an unlicensed channel;

determine a received power of the downlink signal;

store the received power in the memory;

determine, based at least partly on the received power, whether the interferer eNB is to refrain from downlink transmission during a period in which an uplink transmission from a User Equipment (UE) to the server eNB is scheduled;

encode, for transmission in the unlicensed channel, a clear-to-send-to-self (CTS-to-self) message that indicates:

a start time of the period,

a duration of the period, and

whether the interferer eNB is to refrain from downlink transmission during the period.

2. The apparatus according to claim 1, the processing circuitry further configured to:

determine that the interferer eNB is to refrain from the downlink transmission during the period if the received power is greater than a predetermined threshold.

3. The apparatus according to claim 1 or 2, the processing circuitry further configured to:

encode the CTS-to-self message to further indicate whether the interferer eNB is to refrain from scheduling uplink transmissions during the period.

4. The apparatus according to claim 1, the processing circuitry further configured to:

encode the CTS-to-self message to include a bitmap for a plurality of sub-frames, wherein values of the bitmap indicate whether downlink transmission is permissible, by the interferer eNB, in corresponding sub-frames.

5. The apparatus according to claim 1, the processing circuitry further configured to:

determine a range between the UE and the server eNB, and

determine that the interferer eNB is permitted to perform the downlink transmission during the period if the range is below a predetermined threshold.

6. The apparatus according to claim 1, 4 or 5, wherein:

the interferer eNB is included in a plurality of interferer eNBs, the processing circuitry is further configured to:

attempt to detect downlink signals from the plurality of interferer eNBs in the unlicensed channel;

determine, based on received powers of the downlink signals, one or more of the interferer eNBs that are to refrain from downlink transmission during the period; and

encode the CTS-to-self message to indicate the one or more interferer eNBs that are to refrain from downlink transmission during the period.

7. The apparatus according to claim 1, wherein:

the CTS-to-self message includes a preamble and a payload, the payload includes the start time of the period, the duration of the period, and whether the interferer eNB is to refrain from downlink transmission during the period, and

the preamble is based on an inverse Fourier Transform (FT) operation on a vector mapped to resource elements (REs) of the unlicensed channel,

the vector includes:

a predetermined sequence mapped to a plurality of the REs that are spaced apart by a predetermined number of REs, and zeros mapped to the REs between the REs to which the predetermined sequence is mapped.

8. The apparatus according to claim 1 or 7, the processing circuitry further configured to encode the CTS-to-self message in a physical downlink control channel (PDCCH).

9. The apparatus according to claim 1, wherein the server eNB is arranged to operate as a general authorized access (GAA) device in accordance with a MulteFire protocol.

10. The apparatus according to claim 1, wherein the apparatus further includes a transceiver to transmit the CTS-to-self message.

11. The apparatus according to claim 1, wherein the processing circuitry includes a baseband processor to determine whether the interferer eNB is to refrain from downlink transmission during the period and to encode the CTS-to- self message.

12. A computer-readable storage medium that stores instructions for execution by one or more processors to perform operations for communication by an Evolved Node-B (eNB), the eNB configurable to operate as an interferer eNB, the operations to configure the one or more processors to:

decode, from a server eNB, a clear-to-send-to-self (CTS-to-self) message that indicates:

an interference threshold,

a start time of a period during which an uplink transmission from a User Equipment (UE) to the server eNB is scheduled, and

a duration of the period;

determine a received power of the CTS-to-self message;

determine whether to refrain from downlink transmission during the period based on a comparison between the received power and the interference threshold.

13. The computer-readable storage medium according to claim 12, the operations to further configure the one or more processors to:

determine to refrain from downlink transmission during the period if the received power is greater than the interference threshold.

14. The computer-readable storage medium according to claim 12 or 13, wherein:

the CTS-to-self message includes a downlink control information (DCI) that includes the start time of the period and the duration of the period,

the operations further configure the one or more processors to descramble the DCI in accordance with a scrambling sequence that is reserved for scrambling of the DCI by a plurality of eNBs that includes the server eNB and the interferer eNB.

15. An apparatus of an Evolved Node-B (eNB), the apparatus comprising: memory; and processing circuitry, configured to:

encode a payload in accordance with a first resource element (RE) spacing, wherein the payload includes:

a start time of a period in which an uplink transmission to the eNB in an unlicensed channel is scheduled or a downlink transmission by the eNB in the unlicensed channel is scheduled, and

a duration of the period;

encode a preamble in accordance with a second RE spacing that is based on a product of the first RE spacing and a predetermined scale factor that is an integer greater than one; and

encode, for transmission in the unlicensed channel, a clear-to-send-to-self (CTS-to-self) message that includes the preamble and the payload,

wherein the memory is configured to store the payload.

16. The apparatus according to claim 15, the processing circuitry further configured to encode the preamble based on a predetermined sequence mapped to REs of the unlicensed channel in accordance with the second RE spacing.

17. The apparatus according to claim 16, wherein the predetermined sequence is based on one or more of: a virtual cell identifier (ID), a common ID, an index of a symbol, an index of a slot, an index of a sub-frame and an index of a frame.

18. The apparatus according to claim 16, wherein the predetermined sequence is based on a Zadoff-Chu (ZC) sequence, an m-sequence or a Hadamard sequence.

19. The apparatus according to any of claims 15-18, the processing circuitry further configured to:

monitor the unlicensed channel during a clear channel access (CCA) period; and

encode the CTS-to-self message to align with an end of the CCA period.

20. An apparatus of an Evolved Node-B (eNB), the apparatus comprising: memory; and processing circuitry, configured to:

schedule one or more uplink transmissions by one or more User

Equipments (UEs) in an unlicensed channel;

encode, for transmission in the unlicensed channel, a physical downlink control channel (PDCCH) that indicates:

a remaining duration of a current sub-frame, and one or more subsequent sub-frames in which the uplink transmissions by the UEs are scheduled; and

decode one or more uplink packets received from the UEs in the unlicensed channel,

wherein the memory is configured to store the one or more uplink packets.

21. The apparatus according to claim 20, wherein the PDCCH further includes a muting pattern that indicates, on a per-subframe basis for the subsequent sub-frames, whether other devices are to refrain from transmission.

22. The apparatus according to claim 21, wherein:

the muting pattern is included in predetermined candidate muting patterns, and

the PDCCH includes an index mapped to the predetermined candidate muting patterns to indicate the muting pattern.

23. The apparatus according to claim 21, wherein the muting pattern is semi-statically configured by a spectrum access system (SAS) controller that manages access to the unlicensed channel in accordance with a MulteFire protocol.

24. The apparatus according to claim 21, the processing circuitry further configured to:

determine ranges between the UEs and the eNB, and

determine, on a per-subframe basis and based at least partly on the ranges corresponding to the sub-frames, whether the other devices are to refrain from transmission.