Patent Publication Number: US-2021168865-A1

Title: Apparatus, system and method of communication based on clear channel assessment (cca) in one or more directions

Description:
CROSS REFERENCE 
     This application claims the benefit of and priority from U.S. Provisional Patent Application No. 62/246,178 entitled “APPARATUS, SYSTEM AND METHOD OF COMMUNICATING BASED ON DIRECTIONAL CLEAR CHANNEL ASSESSMENT (CCA)”, filed Oct. 26, 2015, the entire disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments described herein generally relate to communication based on Clear Channel Assessment (CCA) in one or more directions. 
     BACKGROUND 
     A wireless communication network in a millimeter-wave band may provide high-speed data access for users of wireless communication devices. 
     A wireless station may be configured to check if a Clear Channel Assessment (CCA) over a wireless channel is idle prior to accessing the wireless channel for a transmission. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity of presentation. Furthermore, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. The figures are listed below. 
         FIG. 1  is a schematic block diagram illustration of a system, in accordance with some demonstrative embodiments. 
         FIG. 2  is a schematic illustration of first and second Clear Channel Assessment (CCA) schemes for a Multi-User (MU) Multi-Input-Multi-Output (MIMO) (MU-MIMO) transmission, in accordance with some demonstrative embodiments. 
         FIG. 3  is a schematic illustration of a CCA scheme for a MU-MIMO transmission, in accordance with some demonstrative embodiments. 
         FIG. 4  is a schematic illustration of a CCA scheme for a Single-User (SU) MIMO (SU-MIMO) transmission, in accordance with some demonstrative embodiments. 
         FIG. 5  is a schematic illustration of first and second SU-MIMO transmission sequences from a first station to a second station, in accordance with some demonstrative embodiments. 
         FIG. 6  is a schematic illustration of a MU-MIMO transmission sequence from a first station to second and third stations, in accordance with some demonstrative embodiments. 
         FIG. 7  is a schematic flow-chart illustration of a method of communication based on CCA in one or more directions, in accordance with some demonstrative embodiments. 
         FIG. 8  is a schematic illustration of a product of manufacture, in accordance with some demonstrative embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of some embodiments. However, it will be understood by persons of ordinary skill in the art that some embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, units and/or circuits have not been described in detail so as not to obscure the discussion. 
     Discussions herein utilizing terms such as, for example, “processing”, “computing”, “calculating”, “determining”, “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulate and/or transform data represented as physical (e.g., electronic) quantities within the computer&#39;s registers and/or memories into other data similarly represented as physical quantities within the computer&#39;s registers and/or memories or other information storage medium that may store instructions to perform operations and/or processes. 
     The terms “plurality” and “a plurality”, as used herein, include, for example, “multiple” or “two or more”. For example, “a plurality of items” includes two or more items. 
     References to “one embodiment”, “an embodiment”, “demonstrative embodiment”, “various embodiments” etc., indicate that the embodiment(s) so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. 
     As used herein, unless otherwise specified the use of the ordinal adjectives “first”, “second”, “third” etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. 
     Some embodiments may be used in conjunction with various devices and systems, for example, a User Equipment (UE), a Mobile Device (MD), a wireless station (STA), a Personal Computer (PC), a sensor device, an Internet of Things (IoT) device, a desktop computer, a mobile computer, a laptop computer, a notebook computer, a tablet computer, a server computer, a handheld computer, a handheld device, a wearable device, a Personal Digital Assistant (PDA) device, a handheld PDA device, an on-board device, an off-board device, a hybrid device, a vehicular device, a non-vehicular device, a mobile or portable device, a consumer device, a non-mobile or non-portable device, a wireless communication station, a wireless communication device, a wireless Access Point (AP), a wired or wireless router, a wired or wireless modem, a video device, an audio device, an audio-video (A/V) device, a wired or wireless network, a wireless area network, a Wireless Video Area Network (WVAN), a Local Area Network (LAN), a Wireless LAN (WLAN), a Personal Area Network (PAN), a Wireless PAN (WPAN), and the like. 
     Some embodiments may be used in conjunction with devices and/or networks operating in accordance with existing Wireless-Gigabit-Alliance (WGA) specifications (Wireless Gigabit Alliance, Inc WiGig MAC and PHY Specification Version 1.1, April 2011, Final specification) and/or future versions and/or derivatives thereof, devices and/or networks operating in accordance with existing IEEE 802.11 standards (IEEE 802.11-2012, IEEE Standard for Information technology—Telecommunications and information exchange between systems Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Mar. 29, 2012; IEEE802.11ac-2013 (“IEEE P802.11ac-2013, IEEE Standard for Information Technology—Telecommunications and Information Exchange Between Systems—Local and Metropolitan Area Networks—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications—Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz”, December, 2013); IEEE 802.11ad (“IEEE P802.11ad-2012, IEEE Standard for Information Technology—Telecommunications and Information Exchange Between Systems—Local and Metropolitan Area Networks—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications—Amendment 3: Enhancements for Very High Throughput in the 60 GHz Band”, 28 December, 2012); IEEE-802.11REVmc (“IEEE 802.11-REVmc™/D3.0, June 2014 draft standard for Information technology—Telecommunications and information exchange between systems Local and metropolitan area networks Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification”); IEEE802.11-ay (IEEE 802.11 ay Standard for Information Technology—Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks—Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications—Amendment: Enhanced Throughput for Operation in License-Exempt Bands Above 45 GHz)) and/or future versions and/or derivatives thereof, devices and/or networks operating in accordance with existing WiFi Alliance (WFA) Peer-to-Peer (P2P) specifications (WiFi P2P technical specification, version 1.5, Aug. 4, 2014) and/or future versions and/or derivatives thereof, devices and/or networks operating in accordance with existing cellular specifications and/or protocols, e.g., 3rd Generation Partnership Project (3GPP), 3GPP Long Term Evolution (LTE) and/or future versions and/or derivatives thereof, units and/or devices which are part of the above networks, and the like. 
     Some embodiments may be used in conjunction with one way and/or two-way radio communication systems, cellular radio-telephone communication systems, a mobile phone, a cellular telephone, a wireless telephone, a Personal Communication Systems (PCS) device, a PDA device which incorporates a wireless communication device, a mobile or portable Global Positioning System (GPS) device, a device which incorporates a GPS receiver or transceiver or chip, a device which incorporates an RFID element or chip, a Multiple Input Multiple Output (MIMO) transceiver or device, a Single Input Multiple Output (SIMO) transceiver or device, a Multiple Input Single Output (MISO) transceiver or device, a device having one or more internal antennas and/or external antennas, Digital Video Broadcast (DVB) devices or systems, multi-standard radio devices or systems, a wired or wireless handheld device, e.g., a Smartphone, a Wireless Application Protocol (WAP) device, or the like. 
     Some embodiments may be used in conjunction with one or more types of wireless communication signals and/or systems, for example, Radio Frequency (RF), Infra Red (IR), Frequency-Division Multiplexing (FDM), Orthogonal FDM (OFDM), Orthogonal Frequency-Division Multiple Access (OFDMA), FDM Time-Division Multiplexing (TDM), Time-Division Multiple Access (TDMA), Multi-User MIMO (MU-MIMO), Spatial Division Multiple Access (SDMA), Extended TDMA (E-TDMA), General Packet Radio Service (GPRS), extended GPRS, Code-Division Multiple Access (CDMA), Wideband CDMA (WCDMA), CDMA 2000, single-carrier CDMA, multi-carrier CDMA, Multi-Carrier Modulation (MDM), Discrete Multi-Tone (DMT), Bluetooth®, Global Positioning System (GPS), Wi-Fi, Wi-Max, ZigBee™, Ultra-Wideband (UWB), Global System for Mobile communication (GSM), 2G, 2.5G, 3G, 3.5G, 4G, Fifth Generation (5G), or Sixth Generation (6G) mobile networks, 3GPP, Long Term Evolution (LTE), LTE advanced, Enhanced Data rates for GSM Evolution (EDGE), or the like. Other embodiments may be used in various other devices, systems and/or networks. 
     The term “wireless device”, as used herein, includes, for example, a device capable of wireless communication, a communication device capable of wireless communication, a communication station capable of wireless communication, a portable or non-portable device capable of wireless communication, or the like. In some demonstrative embodiments, a wireless device may be or may include a peripheral that is integrated with a computer, or a peripheral that is attached to a computer. In some demonstrative embodiments, the term “wireless device” may optionally include a wireless service. 
     The term “communicating” as used herein with respect to a communication signal includes transmitting the communication signal and/or receiving the communication signal. For example, a communication unit, which is capable of communicating a communication signal, may include a transmitter to transmit the communication signal to at least one other communication unit, and/or a communication receiver to receive the communication signal from at least one other communication unit. The verb communicating may be used to refer to the action of transmitting or the action of receiving. In one example, the phrase “communicating a signal” may refer to the action of transmitting the signal by a first device, and may not necessarily include the action of receiving the signal by a second device. In another example, the phrase “communicating a signal” may refer to the action of receiving the signal by a first device, and may not necessarily include the action of transmitting the signal by a second device. 
     As used herein, the term “circuitry” may refer to, be part of, or include, an Application Specific Integrated Circuit (ASIC), an integrated circuit, an electronic circuit, a processor (shared, dedicated, or group), and/or memory (shared, dedicated, group or), 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. 
     The term “logic” may refer, for example, to computing logic embedded in circuitry of a computing apparatus and/or computing logic stored in a memory of a computing apparatus. For example, the logic may be accessible by a processor of the computing apparatus to execute the computing logic to perform computing functions and/or operations. In one example, logic may be embedded in various types of memory and/or firmware, e.g., silicon blocks of various chips and/or processors. Logic may be included in, and/or implemented as part of, various circuitry, e.g. radio circuitry, receiver circuitry, control circuitry, transmitter circuitry, transceiver circuitry, processor circuitry, and/or the like. In one example, logic may be embedded in volatile memory and/or non-volatile memory, including random access memory, read only memory, programmable memory, magnetic memory, flash memory, persistent memory, and the like. Logic may be executed by one or more processors using memory, e.g., registers, stuck, buffers, and/or the like, coupled to the one or more processors, e.g., as necessary to execute the logic. 
     Some demonstrative embodiments may be used in conjunction with a WLAN, e.g., a WiFi network. Other embodiments may be used in conjunction with any other suitable wireless communication network, for example, a wireless area network, a “piconet”, a WPAN, a WVAN and the like. 
     Some demonstrative embodiments may be used in conjunction with a wireless communication network communicating over a frequency band of 60 GHz. However, other embodiments may be implemented utilizing any other suitable wireless communication frequency bands, for example, an Extremely High Frequency (EHF) band (the millimeter wave (mmWave) frequency band), e.g., a frequency band within the frequency band of between 20 Ghz and 300 GHZ, a frequency band above 45 GHZ, a frequency band below 20 GHZ, e.g., a Sub 1 GHZ (S1G) band, a 2.4 GHz band, a 5 GHZ band, a WLAN frequency band, a WPAN frequency band, a frequency band according to the WGA specification, and the like. 
     The term “antenna”, as used herein, may include any suitable configuration, structure and/or arrangement of one or more antenna elements, components, units, assemblies and/or arrays. In some embodiments, the antenna may implement transmit and receive functionalities using separate transmit and receive antenna elements. In some embodiments, the antenna may implement transmit and receive functionalities using common and/or integrated transmit/receive elements. The antenna may include, for example, a phased array antenna, a single element antenna, a set of switched beam antennas, and/or the like. 
     The phrases “directional multi-gigabit (DMG)” and “directional band” (DBand), as used herein, may relate to a frequency band wherein the Channel starting frequency is above 45 GHz. In one example, DMG communications may involve one or more directional links to communicate at a rate of multiple gigabits per second, for example, at least 1 Gigabit per second, e.g., 7 Gigabit per second, or any other rate. 
     Some demonstrative embodiments may be implemented by a DMG STA (also referred to as a “mmWave STA (mSTA)”), which may include for example, a STA having a radio transmitter, which is capable of operating on a channel that is within the DMG band. The DMG STA may perform other additional or alternative functionality. Other embodiments may be implemented by any other apparatus, device and/or station. 
     Reference is made to  FIG. 1 , which schematically illustrates a system  100 , in accordance with some demonstrative embodiments. 
     As shown in  FIG. 1 , in some demonstrative embodiments, system  100  may include one or more wireless communication devices. For example, system  100  may include a first wireless communication device  102 , and/or a second wireless communication device  140 . 
     In some demonstrative embodiments, devices  102  and/or  140  may include a mobile device or a non-mobile, e.g., a static, device. 
     For example, devices  102  and/or  140  may include, for example, a UE, an MD, a STA, an AP, a PC, a desktop computer, a mobile computer, a laptop computer, an Ultrabook™ computer, a notebook computer, a tablet computer, a server computer, a handheld computer, an Internet of Things (IoT) device, a sensor device, a handheld device, a wearable device, a PDA device, a handheld PDA device, an on-board device, an off-board device, a hybrid device (e.g., combining cellular phone functionalities with PDA device functionalities), a consumer device, a vehicular device, a non-vehicular device, a mobile or portable device, a non-mobile or non-portable device, a mobile phone, a cellular telephone, a PCS device, a PDA device which incorporates a wireless communication device, a mobile or portable GPS device, a DVB device, a relatively small computing device, a non-desktop computer, a “Carry Small Live Large” (CSLL) device, an Ultra Mobile Device (UMD), an Ultra Mobile PC (UMPC), a Mobile Internet Device (MID), an “Origami” device or computing device, a device that supports Dynamically Composable Computing (DCC), a context-aware device, a video device, an audio device, an A/V device, a Set-Top-Box (STB), a Blu-ray disc (BD) player, a BD recorder, a Digital Video Disc (DVD) player, a High Definition (HD) DVD player, a DVD recorder, a HD DVD recorder, a Personal Video Recorder (PVR), a broadcast HD receiver, a video source, an audio source, a video sink, an audio sink, a stereo tuner, a broadcast radio receiver, a flat panel display, a Personal Media Player (PMP), a digital video camera (DVC), a digital audio player, a speaker, an audio receiver, an audio amplifier, a gaming device, a data source, a data sink, a Digital Still camera (DSC), a media player, a Smartphone, a television, a music player, or the like. 
     In some demonstrative embodiments, device  102  may include, for example, one or more of a processor  191 , an input unit  192 , an output unit  193 , a memory unit  194 , and/or a storage unit  195 ; and/or device  140  may include, for example, one or more of a processor  181 , an input unit  182 , an output unit  183 , a memory unit  184 , and/or a storage unit  185 . Devices  102  and/or  140  may optionally include other suitable hardware components and/or software components. In some demonstrative embodiments, some or all of the components of one or more of devices  102  and/or  140  may be enclosed in a common housing or packaging, and may be interconnected or operably associated using one or more wired or wireless links. In other embodiments, components of one or more of devices  102  and/or  140  may be distributed among multiple or separate devices. 
     In some demonstrative embodiments, processor  191  and/or processor  181  may include, for example, a Central Processing Unit (CPU), a Digital Signal Processor (DSP), one or more processor cores, a single-core processor, a dual-core processor, a multiple-core processor, a microprocessor, a host processor, a controller, a plurality of processors or controllers, a chip, a microchip, one or more circuits, circuitry, a logic unit, an Integrated Circuit (IC), an Application-Specific IC (ASIC), or any other suitable multi-purpose or specific processor or controller. Processor  191  may execute instructions, for example, of an Operating System (OS) of device  102  and/or of one or more suitable applications. Processor  181  may execute instructions, for example, of an Operating System (OS) of device  140  and/or of one or more suitable applications. 
     In some demonstrative embodiments, input unit  192  and/or input unit  182  may include, for example, a keyboard, a keypad, a mouse, a touch-screen, a touch-pad, a track-ball, a stylus, a microphone, or other suitable pointing device or input device. Output unit  193  and/or output unit  183  may include, for example, a monitor, a screen, a touch-screen, a flat panel display, a Light Emitting Diode (LED) display unit, a Liquid Crystal Display (LCD) display unit, a plasma display unit, one or more audio speakers or earphones, or other suitable output devices. 
     In some demonstrative embodiments, memory unit  194  and/or memory unit  184  includes, for example, a Random Access Memory (RAM), a Read Only Memory (ROM), a Dynamic RAM (DRAM), a Synchronous DRAM (SD-RAM), a flash memory, a volatile memory, a non-volatile memory, a cache memory, a buffer, a short term memory unit, a long term memory unit, or other suitable memory units. Storage unit  195  and/or storage unit  185  may include, for example, a hard disk drive, a floppy disk drive, a Compact Disk (CD) drive, a CD-ROM drive, a DVD drive, or other suitable removable or non-removable storage units. Memory unit  194  and/or storage unit  195 , for example, may store data processed by device  102 . Memory unit  184  and/or storage unit  185 , for example, may store data processed by device  140 . 
     In some demonstrative embodiments, device  102  and/or device  140  may include and/or perform the functionality of one or more STAs. For example, device  102  may include at least one STA, and/or device  140  may include at least one STA. 
     In some demonstrative embodiments, device  102  and/or device  140  may include, operate as, and/or perform the functionality of one or more DMG STAs. For example, device  102  may include, operate as, and/or perform the functionality of, at least one DMG STA, and/or device  140  may include, operate as, and/or perform the functionality of, at least one DMG STA. 
     In other embodiments, devices  102  and/or  140  may perform the functionality of any other wireless device and/or station, e.g., a WLAN STA, a WiFi STA, and the like. 
     In some demonstrative embodiments, device  102  and/or device  140  may be configured to operate as, and/or perform the functionality of, an access point (AP), e.g., a DMG AP, and/or a personal basic service set (PBSS) control point (PCP), e.g., a DMG PCP, for example, an AP/PCP STA, e.g., a DMG AP/PCP STA. 
     In some demonstrative embodiments, device  102  and/or device  140  may be configured to operate as, and/or perform the functionality of, a non-AP STA, e.g., a DMG non-AP STA, and/or a non-PCP STA, e.g., a DMG non-PCP STA, for example, a non-AP/PCP STA, e.g., a DMG non-AP/PCP STA. 
     In other embodiments, device  102  and/or device  140  may perform the functionality of any other additional or alternative device and/or station. 
     In one example, a station (STA) may include a logical entity that is a singly addressable instance of a medium access control (MAC) and physical layer (PHY) interface to the wireless medium (WM). The STA may perform any other additional or alternative functionality. 
     In one example, an AP may include an entity that contains a station (STA), e.g., one STA, and provides access to distribution services, via the wireless medium (WM) for associated STAs. The AP may perform any other additional or alternative functionality. 
     In one example, a personal basic service set (PBSS) control point (PCP) may include an entity that contains a STA, e.g., one station (STA), and coordinates access to the wireless medium (WM) by STAs that are members of a PBSS. The PCP may perform any other additional or alternative functionality. 
     In one example, a PBSS may include a directional multi-gigabit (DMG) basic service set (BSS) that includes, for example, one PBSS control point (PCP). For example, access to a distribution system (DS) may not be present, but, for example, an intra-PBSS forwarding service may optionally be present. 
     In one example, a PCP/AP STA may include a station (STA) that is at least one of a PCP or an AP. The PCP/AP STA may perform any other additional or alternative functionality. 
     In one example, a non-AP STA may include a STA that is not contained within an AP. The non-AP STA may perform any other additional or alternative functionality. 
     In one example, a non-PCP STA may include a STA that is not a PCP. The non-PCP STA may perform any other additional or alternative functionality. 
     In one example, a non PCP/AP STA may include a STA that is not a PCP and that is not an AP. The non-PCP/AP STA may perform any other additional or alternative functionality. 
     In some demonstrative embodiments, wireless communication device  102  and/or device  140  may be capable of communicating content, data, information and/or signals via a wireless medium (WM)  103 . In some demonstrative embodiments, wireless medium  103  may include, for example, a radio channel, a cellular channel, an RF channel, a WiFi channel, an IR channel, a Bluetooth (BT) channel, a Global Navigation Satellite System (GNSS) Channel, and the like. 
     In some demonstrative embodiments, WM  103  may include one or more directional bands and/or channels. For example, WM  103  may include one or more millimeter-wave (mmWave) wireless communication bands and/or channels. 
     In some demonstrative embodiments, WM  103  may include one or more DMG bands and/or channels. In other embodiments WM  103  may include any other directional channels. 
     In some demonstrative embodiments, device  102  and/or device  140  may include one or more radios including circuitry and/or logic to perform wireless communication between devices  102 ,  140  and/or one or more other wireless communication devices. For example, device  102  may include at least one radio  114 , and/or device  140  may include at least one radio  144 . 
     In some demonstrative embodiments, radio  114  and/or radio  144  may include one or more wireless receivers (Rx) including circuitry and/or logic to receive wireless communication signals, RF signals, frames, blocks, transmission streams, packets, messages, data items, and/or data. For example, radio  114  may include at least one receiver  116 , and/or radio  144  may include at least one receiver  146 . 
     In some demonstrative embodiments, radio  114  and/or radio  144  may include one or more wireless transmitters (Tx) including circuitry and/or logic to transmit wireless communication signals, RF signals, frames, blocks, transmission streams, packets, messages, data items, and/or data. For example, radio  114  may include at least one transmitter  118 , and/or radio  144  may include at least one transmitter  148 . 
     In some demonstrative embodiments, radio  114  and/or radio  144 , transmitters  118  and/or  148 , and/or receivers  116  and/or  148  may include circuitry; logic; Radio Frequency (RF) elements, circuitry and/or logic; baseband elements, circuitry and/or logic; modulation elements, circuitry and/or logic; demodulation elements, circuitry and/or logic; amplifiers; analog to digital and/or digital to analog converters; filters; and/or the like. For example, radio  114  and/or radio  144  may include or may be implemented as part of a wireless Network Interface Card (NIC), and the like. 
     In some demonstrative embodiments, radios  114  and/or  144  may be configured to communicate over a directional band, for example, a mmWave band, and/or any other band, for example, a 2.4 GHz band, a 5 GHz band, an S1G band, and/or any other band. 
     In some demonstrative embodiments, radio  114  and/or radio  144  may include, or may be associated with, one or more antennas  107  and/or  147 , respectively. 
     In one example, device  102  may include a single antenna  107 . In another example, device  102  may include two or more antennas  107 . 
     In one example, device  140  may include a single antenna  147 . In another example, device  140  may include two or more antennas  147 . 
     Antennas  107  and/or  147  may include any type of antennas suitable for transmitting and/or receiving wireless communication signals, blocks, frames, transmission streams, packets, messages and/or data. For example, antennas  107  and/or  147  may include any suitable configuration, structure and/or arrangement of one or more antenna elements, components, units, assemblies and/or arrays. Antennas  107  and/or  147  may include, for example, antennas suitable for directional communication, e.g., using beamforming techniques. For example, antennas  107  and/or  147  may include a phased array antenna, a multiple element antenna, a set of switched beam antennas, and/or the like. In some embodiments, antennas  107  and/or  147  may implement transmit and receive functionalities using separate transmit and receive antenna elements. In some embodiments, antennas  107  and/or  147  may implement transmit and receive functionalities using common and/or integrated transmit/receive elements. 
     In some demonstrative embodiments, antennas  107  and/or  147  may include a directional antenna, which may be steered to a plurality of beam directions. For example, antenna  107  may be steered to a plurality of beam directions  135 , and/or antenna  147  may be steered to a plurality of beam directions  145 . For example, device  102  may transmit a directional transmission  139  to device  140 , and/or device  140  may transmit a directional transmission  149  to device  102 . 
     In some demonstrative embodiments, device  102  may include a controller  124 , and/or device  140  may include a controller  154 . Controller  124  may be configured to perform and/or to trigger, cause, instruct and/or control device  102  to perform, one or more communications, to generate and/or communicate one or more messages and/or transmissions, and/or to perform one or more functionalities, operations and/or procedures between devices  102 ,  140  and/or one or more other devices; and/or controller  154  may be configured to perform, and/or to trigger, cause, instruct and/or control device  140  to perform, one or more communications, to generate and/or communicate one or more messages and/or transmissions, and/or to perform one or more functionalities, operations and/or procedures between devices  102 ,  140  and/or one or more other devices, e.g., as described below. 
     In some demonstrative embodiments, controllers  124  and/or  154  may include circuitry and/or logic, e.g., one or more processors including circuitry and/or logic, memory circuitry and/or logic, Media-Access Control (MAC) circuitry and/or logic, Physical Layer (PHY) circuitry and/or logic, and/or any other circuitry and/or logic, configured to perform the functionality of controllers  124  and/or  154 , respectively. Additionally or alternatively, one or more functionalities of controllers  124  and/or  154  may be implemented by logic, which may be executed by a machine and/or one or more processors, e.g., as described below. 
     In one example, controller  124  may include circuitry and/or logic, for example, one or more processors including circuitry and/or logic, to cause, trigger and/or control a wireless device, e.g., device  102 , and/or a wireless station, e.g., a wireless STA implemented by device  102 , to perform one or more operations, communications and/or functionalities, e.g., as described herein. 
     In one example, controller  154  may include circuitry and/or logic, for example, one or more processors including circuitry and/or logic, to cause, trigger and/or control a wireless device, e.g., device  140 , and/or a wireless station, e.g., a wireless STA implemented by device  140 , to perform one or more operations, communications and/or functionalities, e.g., as described herein. 
     In some demonstrative embodiments, device  102  may include a message processor  128  configured to generate, process and/or access one or messages communicated by device  102 . 
     In one example, message processor  128  may be configured to generate one or more messages to be transmitted by device  102 , and/or message processor  128  may be configured to access and/or to process one or more messages received by device  102 , e.g., as described below. 
     In some demonstrative embodiments, device  140  may include a message processor  158  configured to generate, process and/or access one or messages communicated by device  140 . 
     In one example, message processor  158  may be configured to generate one or more messages to be transmitted by device  140 , and/or message processor  158  may be configured to access and/or to process one or more messages received by device  140 , e.g., as described below. 
     In some demonstrative embodiments, message processors  128  and/or  158  may include circuitry and/or logic, e.g., one or more processors including circuitry and/or logic, memory circuitry and/or logic, Media-Access Control (MAC) circuitry and/or logic, Physical Layer (PHY) circuitry and/or logic, and/or any other circuitry and/or logic, configured to perform the functionality of message processors  128  and/or  158 , respectively. Additionally or alternatively, one or more functionalities of message processors  128  and/or  158  may be implemented by logic, which may be executed by a machine and/or one or more processors, e.g., as described below. 
     In some demonstrative embodiments, at least part of the functionality of message processor  128  may be implemented as part of radio  114 , and/or at least part of the functionality of message processor  158  may be implemented as part of radio  144 . 
     In some demonstrative embodiments, at least part of the functionality of message processor  128  may be implemented as part of controller  124 , and/or at least part of the functionality of message processor  158  may be implemented as part of controller  154 . 
     In other embodiments, the functionality of message processor  128  may be implemented as part of any other element of device  102 , and/or the functionality of message processor  158  may be implemented as part of any other element of device  140 . 
     In some demonstrative embodiments, at least part of the functionality of controller  124  and/or message processor  128  may be implemented by an integrated circuit, for example, a chip, e.g., a System on Chip (SoC). In one example, the chip or SoC may be configured to perform one or more functionalities of radio  114 . For example, the chip or SoC may include one or more elements of controller  124 , one or more elements of message processor  128 , and/or one or more elements of radio  114 . In one example, controller  124 , message processor  128 , and radio  114  may be implemented as part of the chip or SoC. 
     In other embodiments, controller  124 , message processor  128  and/or radio  114  may be implemented by one or more additional or alternative elements of device  102 . 
     In some demonstrative embodiments, at least part of the functionality of controller  154  and/or message processor  158  may be implemented by an integrated circuit, for example, a chip, e.g., a System on Chip (SoC). In one example, the chip or SoC may be configured to perform one or more functionalities of radio  144 . For example, the chip or SoC may include one or more elements of controller  154 , one or more elements of message processor  158 , and/or one or more elements of radio  144 . In one example, controller  154 , message processor  158 , and radio  144  may be implemented as part of the chip or SoC. 
     In other embodiments, controller  154 , message processor  158  and/or radio  144  may be implemented by one or more additional or alternative elements of device  140 . 
     Some Specifications, e.g., an IEEE 802.11ad Specification, may be configured to support a Single User (SU) system, in which a Station (STA) cannot transmit frames to more than a single STA at a time. Such Specifications may not be able, for example, to support a STA transmitting to multiple STAs simultaneously, for example, using a multi-user MIMO (MU-MIMO) scheme, e.g., a downlink (DL) MU-MIMO, or any other MU scheme. 
     In some demonstrative embodiments, devices  102  and/or  140  may be configured to implement one or more Multi-User (MU) mechanisms. For example, devices  102  and/or  140  may be configured to implement one or more MU mechanisms, which may be configured to enable MU communication of Downlink (DL) frames using a Multiple-Input-Multiple-Output (MIMO) scheme, for example, between a device, e.g., device  102 , and a plurality of devices, e.g., including device  140  and/or one or more other devices. 
     In some demonstrative embodiments, devices  102  and/or  140  may be configured to communicate over a Next Generation 60 GHz (NG60) network, an Extended DMG (EDMG) network, and/or any other network. For example, devices  102  and/or  140  may be configured to support communication of SU-MIMO and/or MU-MIMO transmissions, for example, for communicating over the NG60 and/or EDMG networks. 
     In some demonstrative embodiments, a STA, e.g., device  102  and/or device  140 , may be configured to perform a MIMO transmission, e.g., a SU-MIMO transmission or a MU-MIMO transmission, which may include transmissions performed in a plurality of different directions. For example, device  102  may be configured to perform the SU-MIMO transmission or the MU-MIMO transmission including transmissions performed in a plurality of different directions of beam directions  135 ; and/or device  140  may be configured to perform the SU-MIMO transmission or the MU-MIMO transmission including transmissions performed in a plurality of different directions of beam directions  145 . 
     In some demonstrative embodiments, a STA, e.g., device  102  and/or device  140 , may be configured to perform a Clear Channel Assessment (CCA) with respect to a plurality of different directions, e.g., before transmitting a MIMO transmission via the plurality of directions. 
     In some demonstrative embodiments, in some cases, a CCA state may be idle in one or more directions of the plurality of directions to be used for the MIMO transmission, while the CCA state may be busy in one or more other directions of the plurality of directions to be used for the MIMO transmission. 
     In some demonstrative embodiments, it may be advantageous to enable a transmitter of a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU), e.g., device  102 , to transmit the PPDU in one or more directions where the CCA is idle, for example, in cases where the CCA is busy only in a subset of intended directions of the PPDU, e.g., as described below. 
     In some demonstrative embodiments, devices  102  and/or  140  may be configured to enable a dynamic adaptation of a transmission, for example, in cases, in which the CCA state is idle only in a subset of directions of the directions to be used for the MIMO transmission, e.g., as described below. 
     In some demonstrative embodiments, enabling the dynamic adaptation of MIMO transmissions, e.g., SU-MIMO and/or MU-MIMO transmissions, may enable to highly improve performance, e.g., especially in dense environments. 
     In some demonstrative embodiments, devices  102  and/or  140  may be configured to perform transmission in the one or more directions with the idle CCA, e.g. as described below. 
     In some demonstrative embodiments devices  102  and/or  140  may be configured to perform the dynamic adaptation, e.g., with a Request to Send (RTS) and/or a Clear to Send (CTS) exchange, e.g., as described below. 
     In some demonstrative embodiments devices  102  and/or  140  may be configured to perform the dynamic adaptation, e.g., even without an RTS/CTS exchange, e.g., as described below. 
     In some demonstrative embodiments, device  102  may be configured to perform a MIMO transmission to one or more devices, e.g., device  140  and/or one or more other devices. 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger device  102  to determine a plurality of directions, e.g., from the plurality of beam directions  135 , to transmit a plurality of respective data streams of the MIMO transmission. 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger device  102  to detect a plurality of CCA states corresponding to the plurality of directions, respectively. 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger device  102  to transmit one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions, for example, based on the plurality of CCA states. 
     In some demonstrative embodiments, controller  124  may select the one or more selected directions, e.g., to transmit the MIMO transmission to device  140 , to include directions having a detected CCA idle state. 
     In some demonstrative embodiments, the one or more selected directions may include, for example, only directions having a detected CCA idle state. 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger device  102  to construct a PPDU including the plurality of data streams, and to reconstruct the PPDU including the one or more selected data streams, for example, to be transmitted in the one or more respective selected directions. 
     In some demonstrative embodiments, device  102  may include one or more CCA modules  126 , configured to detect the plurality of CCA idle states. 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger one or more CCA modules  126  to detect the plurality of CCA idle states, sequentially, e.g., one by one, for example, if a number of CCA modules is less than a number of the plurality of directions to detect the CCA. 
     In one example, device  102  may include a single CCA module  126  to sequentially detect the CCA in the plurality of directions. 
     In another example, device  102  may include two CCA modules  126  to simultaneously detect the CCA in two directions. 
     In another example, device  102  may include any other number of CCA modules  126  to simultaneously detect the CCA in a plurality of directions. 
     In some demonstrative embodiments, controller  124  may be configured to detect the plurality of CCA idle states, sequentially, e.g., one by one, for example, if device  102  includes a single CCA module. 
     In some demonstrative embodiments, device  140  may include one or more CCA modules  156 , configured to detect the plurality of CCA idle states. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger one or more CCA modules  156  to detect the plurality of CCA idle states, sequentially, e.g., one by one, for example, if a number of CCA modules is less than a number of the plurality of directions to detect the CCA. 
     In one example, device  140  may include a single CCA module  156  to sequentially detect the CCA in the plurality of directions. 
     In another example, device  140  may include two CCA modules  156  to simultaneously detect the CCA in two directions. 
     In another example, device  140  may include any other number of CCA modules  156  to simultaneously detect the CCA in a plurality of directions. 
     In some demonstrative embodiments, controller  154  may be configured to detect the plurality of CCA idle states, sequentially, e.g., one by one, for example, if device  140  includes a single CCA module. 
     Reference is made to  FIG. 2 , which schematically illustrates a first CCA scheme  200  and a second CCA scheme  220  for an MU-MIMO transmission  210 , in accordance with some demonstrative embodiments. 
     In some demonstrative embodiments, schemes  200  and/or  220  may be implemented for a dynamic adaptation of the MU-MIMO transmission  210 , for example, even without performing an RTS and/or CTS exchange, e.g., as described below. 
     In some demonstrative embodiments, a station  202 , denoted AP, may be configured to transmit the MU-MIMO transmission  210  towards two stations  240 , denoted STA A and STA B. For example, STA  202  may perform the functionality of device  102  ( FIG. 1 ), and/or a STA  240  may perform the functionality of device  140  ( FIG. 1 ). 
     In some demonstrative embodiments, the station  202  may include a single CCA module. In other embodiments, the station  202  may include a plurality of CCA modules. 
     In one example, station  202  may prepare to perform the MU-MIMO transmission  210 , for example, after beamforming between station  202  and each of the stations  240  has already been performed. 
     In some demonstrative embodiments, station  202  may be configured to construct a PPDU configured to be transmitted to stations  240 , for example, as part of the MU-MIMO transmission  210 . 
     In some demonstrative embodiments, according to scheme  200 , station  202  may transmit the MU-MIMO transmission  210  via two separate antennas, e.g., via an antenna  207  in a first direction  212 , and via an antenna  209  in a second direction  214 . 
     In some demonstrative embodiments, according to scheme  220 , station  202  may transmit the MU-MIMO transmission  210  in the two different directions, e.g., directions  212  and  214 , via a single antenna  217 . 
     In some demonstrative embodiments, station  202  may be configured to check the CCA in the first direction  212 , e.g., a direction of STA A, and the second direction  214 , e.g., a direction of STA B, for example, before performing the MU-MIMO transmission  210  of the PPDU to stations  240 . 
     In some demonstrative embodiments, station  202  may check the CCA in first direction  212  and second direction  214 , sequentially, e.g., one by one or one after another, for example, if station  202  includes a single CCA module. In some demonstrative embodiments, station  202  may simultaneously check the CCA in first direction  212  and second direction  214 , for example, if station  202  includes two or more CCA modules, e.g., as described below in  FIG. 3 . 
     In some demonstrative embodiments, for example, if a CCA state is idle only in a direction of one of stations  240 , e.g., in the direction  212 , station  202  may be able to reconstruct the to be transmitted PPDU on the fly, e.g., in real-time, for example, in order to transmit only a single stream in the direction where the CCA state is idle, e.g., direction  212  to the STA A. 
     Referring back to  FIG. 1 , in some demonstrative embodiments, devices  102  and/or  140  may be configured to be able to check the CCA, e.g., independently, in each of a plurality of directions, for example, before transmitting a SU-MIMO or MU-MIMO transmission in the plurality of directions. 
     In one example, the independent checking of the CCA in the plurality of directions may be performed, for example, instead of checking one CCA with respect to the energy received from all of the plurality of different directions. 
     In some demonstrative embodiments, device  102  may be configured to independently check the CCA, e.g., sequentially or simultaneously, in each of a plurality of directions. 
     In some demonstrative embodiments, the one or more CCA modules  126  may include a plurality of CCA modules, e.g., two CCA modules or more than two CCA modules. 
     In some demonstrative embodiments, the two CCA modules  126  may be configured to simultaneously check the CCA in a plurality of respective directions. For example, the STA may be configured to have at least as many independent CCA capabilities as a number of simultaneous directions/spatial streams supported by the STA. 
     In one example, the two CCA modules  126  may be configured to perform an independent CCA over two directions, e.g., simultaneously, for example, to support an MU-MIMO transmission in two directions, e.g., as described below with reference to  FIG. 3 . 
     Reference is made to  FIG. 3 , which schematically illustrates a CCA scheme  300  for an MU-MIMO transmission  310 , in accordance with some demonstrative embodiments. 
     In some demonstrative embodiments, scheme  300  may be configured for a dynamic adaptation of the MU-MIMO transmission  310 , for example, even without performing an RTS and/or CTS exchange. 
     In some demonstrative embodiments, a station  302 , for example, an AP, denoted AP, may be configured to transmit the MU-MIMO transmission  310  towards two stations  340 , denoted STA A and STA B. For example, STA  302  may perform the functionality of device  102  ( FIG. 1 ), and/or a STA  340  may perform the functionality of device  140  ( FIG. 1 ). 
     In some demonstrative embodiments, the station  302  may include two CCA modules, e.g., a first CCA module  306 , denoted CCA  1 , and a second CCA module  308 , denoted CCA  2 . 
     In some demonstrative embodiments, CCA modules  306  and/or  308  may be configured to independently perform the CCA in two directions, e.g., simultaneously. For example, the two directions may include directions, which are planned to be used by station  302 , for example, for the MU-MIMO transmission  310 . 
     In some demonstrative embodiments, station  302  may perform a multi-CCA to check the CCA in a plurality of directions. 
     For example, as shown in  FIG. 3 , station  302  may perform a 2-CCA to independently check the CCA in a direction  312  towards STA A, and in a direction  314  towards STA B, e.g., simultaneously. 
     In some demonstrative embodiments, station  302  may be configured to generate, construct and/or re-construct a MU-MIMO PPDU, for example, based on the results of the multi-CCA, e.g., as described below. 
     In some demonstrative embodiments, station  302  may be configured to select to transmit the PPDU towards the STA A and the STA B, for example, if the CCA is idle in both directions  312  and  314 . 
     In some demonstrative embodiments, station  302  may be configured to select to defer transmission of the PPDU to a later time, or to cancel transmission of the PPDU, for example, if the CCA is busy in both directions  312  and  314 . 
     In some demonstrative embodiments, station  302  may be configured to select to transmit the PPDU only towards at least one STA for which the CCA is idle, for example, if CCA is idle in either the direction of STA A or the direction of STA B, but not both. 
     In some demonstrative embodiments, station  302  may be configured to implement this solution, for example, if station  302  may be able to reconstruct the PPDU on the fly. 
     For example, if station  302  is planning for a MU-MIMO PPDU transmission to STA A and STA B, e.g., as described above, then station  302  may be configured to reconstruct the transmission as a SISO transmission to either STA B or STA A, e.g., based on the CCA in the directions  312  and  314 . 
     In some demonstrative embodiments, station  302  may be configured to keep the frame format the same, e.g., the MU-MIMO format, for example, instead of reconstructing the frame in SISO format in the example above, e.g., to simplify implementation. 
     Referring back to  FIG. 1 , in some demonstrative embodiments, devices  102  and  140  may be configured communicate a MIMO transmission, for example, using dynamic adaptation with an RTS/CTS exchange, e.g., as described below. 
     In some demonstrative embodiments, device  102  may be configured to transmit the MIMO transmission, and/or device  140  may be configured to receive the MIMO transmission, for example, using dynamic MIMO/MU-MIMO transmission with the RTS/CTS exchange, e.g., as described below. 
     In some demonstrative embodiments, device  102  may be configured to implement a dynamic mechanism to adapt a MIMO transmission, e.g., using RTS and CTS exchanges, for example, in order to leave more time to adapt to a new transmission, e.g., from two streams directed to two stations into a single stream for a single station, for example, if it is too constraining to reconstruct the PPDU on the fly, e.g., as described below. 
     In some demonstrative embodiments, the dynamic mechanism utilizing the RTS/CTS exchange may, for example, allow a receiver of the transmission, e.g., device  140 , to check a CCA state before sending the CTS back to a transmitter of the transmission, e.g., device  102 . 
     In some demonstrative embodiments, devices  102  and/or  140  may be configured to implement a dynamic bandwidth mechanism configured to be applied to the spatial domain, e.g., instead of, or in addition to, a frequency domain, e.g., as described below. 
     In some demonstrative embodiments, device  102  may be configured to transmit, e.g., to device  140 , one or more RTS frames in one or more respective directions, e.g., of beam directions  135 , having the CCA idle state, for example, before transmission of the selected data streams in the directions having the CCA idle state (“the Tx directions”). 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger device  102  to transmit the one or more RTS frames in the one or more respective Tx directions having the CCA idle state. 
     In some demonstrative embodiments, device  102  may be configured to transmit an RTS frame only in one or more directions where the CCA is idle. 
     In some demonstrative embodiments, sending the RTS frame in two or more directions simultaneously may potentially cause an unintended beamforming effect. Accordingly, device  102  may be configured to apply a specific delay in some of the antennas, e.g., to cause a delay between transmissions of the RTS frame in different directions. 
     In some demonstrative embodiments, device  140  may receive from device  102  one or more RTS frames from one or more respective directions of beam directions  145 . 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to detect one or more CCA states corresponding to the one or more directions (“Rx directions”) of beam directions  145 , e.g., via which the one or more RTS frames were received. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to transmit to device  102  one or more CTS frames in one or more respective selected Rx directions of the one or more directions of beam directions  145 , for example, based on the one or more detected CCA states. 
     In some demonstrative embodiments, controller  154  may select the one or more selected Rx directions, e.g., to transmit the CTS frames to device  140 , to include only Rx directions having a detected CCA idle state. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to transmit to device  102  the one or more CTS frames, for example, in response to a poll frame from device  102 . 
     In some demonstrative embodiments, device  102  may receive the one or more CTS frames from device  140 . 
     In some demonstrative embodiments, controller  124  may be configured to control, cause and/or trigger device  102  to determine the one or more selected directions, e.g., over which the selected data streams are to be transmitted, for example, to include directions from which a CTS frame is received. 
     In some demonstrative embodiments, devices  102  and  140  may communicate a plurality of RTS frames and a plurality of CTS frames between devices  102  and  140 , for example, instead of one or more RTS frames and/or one or more CTS frames, for example, if each one of controllers  124  and/or  154  detects two or more directions between devices  102  and  140  having the CCA idle state, e.g., as described below. 
     In some demonstrative embodiments, device  102  may transmit a plurality of RTS frames to device  140 , in a plurality of respective directions, e.g., of beam directions  135 , having the CCA idle state, for example, if device  102  detects a plurality of CCA idle states in the plurality of respective Tx directions. 
     In some demonstrative embodiments, device  140  may receive the plurality of RTS frames from a plurality of different directions of beam directions  145 . 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to detect a plurality of CCA states corresponding to the plurality of the different Rx directions of beam directions  145 , respectively. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to select a plurality of selected Rx directions from the plurality of different Rx directions, for example, based on the plurality of CCA states corresponding to the plurality of the different Rx directions, from which the plurality of RTS frames are received. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to transmit a plurality of CTS frames in the plurality of selected Rx directions of the different Rx directions, from which the plurality of RTS frames are received. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to sequentially transmit to device  102  two or more CTS frames of the plurality of CTS frames. 
     In one example, device  140  may sequentially transmit the two or more CTS frames, for example, if device  140  does not support simultaneous uplink transmission. 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to simultaneously transmit to device  102  the two or more CTS frames of the plurality of CTS frames, e.g., if device  140  supports simultaneous uplink transmission. 
     In some demonstrative embodiments, device  102  may receive from device  140  the two or more CTS frames via two or more directions of beam directions  135 . 
     In some demonstrative embodiments, device  102  may transmit to device  140  the MIMO transmission over the two or more directions, from which the two or more CTS frames are received. 
     In some demonstrative embodiments, device  140  may receive the MIMO transmission from device  102 . 
     In some demonstrative embodiments, controller  154  may be configured to control, cause and/or trigger device  140  to process the MIMO transmission received from device  102  via the two or more directions of beam directions  145 . 
     Reference is made to  FIG. 4 , which schematically illustrates a CCA scheme  400  for a SU-MIMO transmission, in accordance with some demonstrative embodiments. 
     In some demonstrative embodiments, CCA scheme  400  may be configured to communicate an SU-MIMO transmission, e.g., including a first spatial stream  412  and a second spatial stream  414 , between a first station  420 , denoted STA 1 , and a second station  440 , denoted STA 2 . For example, STA  402  may perform the functionality of device  102  ( FIG. 1 ), and/or a STA  440  may perform the functionality of device  140  ( FIG. 1 ). 
     In some demonstrative embodiments, station  402  may independently check a first CCA in a direction  413  to be used for transmission of the first spatial stream  412 , and a second CCA in a direction  415  to be used for transmission of the second spatial stream  414 , e.g., simultaneously, for example, using two CCA modules  426 , e.g., as described above. 
     In some demonstrative embodiments, if the CCA is idle in both directions  413  and  415 , station  402  may send a first RTS in the direction  413 , e.g., using a first antenna  407 , and may send a second RTS in the direction  415 , e.g., using a second antenna  417 , for example, while applying a specific delay to antenna  417 , e.g., with respect to antenna  407 . 
     In some demonstrative embodiments, as shown in  FIG. 4 , station  440  may receive the first and second RTS frames, may detect that station  440  is the intended receiver of the RTS frames, and may determine the initiator of the transmission, e.g., station  402 . 
     In some demonstrative embodiments, station  440  may know the sectors that need to be used for the reception of spatial streams  412  and  414 , e.g., if station  440  is MIMO capable having two spatial streams, e.g., spatial streams  412  and  414 , and that station  440  has performed beamforming training with station  402 . 
     In some demonstrative embodiments, station  440  may receive the first and second RTS frames via two different directions, e.g., a direction  441  and a direction  442 . 
     In some demonstrative embodiments, station  440  may check the CCA in the two directions, e.g., the direction  441  and the direction  442 , for example, during a time between an end of the RTS transmission and a beginning of a CTS transmission. 
     In some demonstrative embodiments, for example, if the CCA is idle in all directions, e.g., directions  441  and  442 , station  440  may select to send CTS frames in both directions  441  and  442 , e.g., with a specific delay applied to some antennas of station  440 . 
     In some demonstrative embodiments, for example, if the CCA is busy on both directions  441  and  442 , station  440  may select not to send anything, and station  402  may defer or cancel the MIMO transmission, e.g., if station  402  does not receive an CTS frame from station  440 . 
     In some demonstrative embodiments, for example, if the CCA is busy only in one direction, e.g., direction  441 , station  440  may send the CTS on the direction where the CCA was idle, e.g., direction  442 . 
     In some demonstrative embodiments, station  402  may receive the one or more CTS frames via the one or more different directions, and may determine if a MIMO transmission is possible with all spatial streams, or if only some of the spatial streams can be used, e.g., based on the directions over which the CTS frames are received. 
     For example, station  402  may receive a CTS frame via direction  415 , for example, if station  440  sends the CTS via the direction  442 , e.g., where the CCA was determined by station  440  to be idle. 
     In some demonstrative embodiments, the RTS and/or CTS frames may be configured to carry additional information, e.g., information relating to the spatial streams where the CCA was idle, and/or any other information. 
     In some demonstrative embodiments, in case of a MU-MIMO transmission, and in case that uplink MU-MIMO is not supported, the RTS/CTS dynamic mechanism may include sending the CTS frames sequentially in time, e.g., not simultaneously. Accordingly, an initiator of the MU-MIMO transmission, e.g., station  402 , may receive the CTS frames from a plurality of STAs, e.g., all STAs, separately, e.g., as described below. 
     Reference is made to  FIG. 5 , which schematically illustrates SU-MIMO transmission sequences  510  and  520  from a first station  502 , denoted STA  1 , to a second station  540 , denoted STA  2 , in accordance with some demonstrative embodiments. 
     For example, STA  502  may perform the functionality of device  102  ( FIG. 1 ), and/or a STA  540  may perform the functionality of device  140  ( FIG. 1 ). 
     In some demonstrative embodiments, SU-MIMO transmission sequences  510  and/or  520  may include exchanging CTS and RTS frames. 
     In some demonstrative embodiments, as shown in  FIG. 5 , MIMO transmission sequence  510  may include transmission of two RTS frames  512  to station  540 , e.g., via two respective directions of two respective antennas of station  502 . 
     In some demonstrative embodiments, station  540  may receive the two RTS frames  512 , and may check for the CCA state in two directions, from which the two RTS frames  512  are received. 
     In some demonstrative embodiments, as shown in  FIG. 5 , station  540  may transmit two CTS frames  514  to station  502 , for example, if the CCA state is detected to be idle in each of the two directions, from which the two RTS frames  512  received. 
     In some demonstrative embodiments, as shown in  FIG. 5 , station  502  may receive the two CTS frames  514 , and may be aware that station  502  is allowed to transmit a MIMO transmission via the two respective directions of the two respective antennas of station  502 . 
     In some demonstrative embodiments, as shown in  FIG. 5 , station  502  may transmit a MIMO transmission including two data streams  516  to station  540 , for example, via the two respective directions of the two respective antennas of station  502 . 
     In some demonstrative embodiments, as shown in  FIG. 5 , MIMO transmission sequence  520  may include transmission of two RTS frames  532  to station  540 , e.g., via two respective directions of two respective antennas of station  502 . 
     In some demonstrative embodiments, station  540  may receive the two RTS frames  532 , and may check for the CCA state in the two directions, from which the two RTS frames  532  are received. 
     In some demonstrative embodiments, as shown in  FIG. 5 , station  540  may transmit a CTS frame  534  to station  502 , for example, if the CCA state is idle only in one selected direction, from the two directions from which the two RTS frames  532  are received. 
     In some demonstrative embodiments, as shown in  FIG. 5 , station  502  may receive the CTS frame  534 , and may be aware that station  502  is allowed to transmit a transmission only via the direction, from which the CTS frame  534  was received. 
     In some demonstrative embodiments, as shown in  FIG. 5 , station  502  may transmit a data stream  536  to station  540 , for example, via the direction from which CTS frame  534  was received. 
     Reference is made to  FIG. 6 , which schematically illustrates a MU-MIMO transmission sequence  610  between a first station  602 , denoted STA  1 , a second station  640 , denoted STA  2 , and a third station  660 , denoted STA  3 , in accordance with some demonstrative embodiments. 
     For example, STA  602  may perform the functionality of device  102  ( FIG. 1 ), and/or STA  640  and/or STA  660  may perform the functionality of device  140  ( FIG. 1 ). 
     In some demonstrative embodiments, MU-MIMO transmission sequence  610  may include exchanging of CTS frames, and RTS frames. 
     In some demonstrative embodiments, as shown in  FIG. 6 , MIMO transmission sequence  610  may include transmission of a first RTS frame  612  to station  640  and a second RTS frame  614  to station  660 , e.g., via first and second respective directions. 
     In some demonstrative embodiments, station  640  may receive the RTS frame  612 , and may check for the CCA state in a direction, from which the RTS frame  612  is received. 
     In some demonstrative embodiments, station  660  may receive the RTS frame  614 , and may check for the CCA state in a direction, from which the RTS frame  614  is received. 
     In some demonstrative embodiments, as shown in  FIG. 6 , station  640  may transmit a CTS frame  616  to station  602 , for example, if the CCA state is idle in the direction, from which the RTS frame  612  is received. 
     In some demonstrative embodiments, as shown in  FIG. 6 , station  602  may transmit a poll frame  618  to station  660 , for example, to poll for a CTS frame from station  660 . 
     In some demonstrative embodiments, as shown in  FIG. 6 , station  660  may select not to transmit the CTS frame to station  602 , for example, if the CCA state  624  is busy in the direction, from which the RTS frame  614  is received. 
     In some demonstrative embodiments, as shown in  FIG. 6 , station  602  may receive CTS frames  616  from station  640 , and may not receive a CTS frame from station  660 . Accordingly, the station  602  may be aware that the CCA state is idle only in the direction towards station  640 . 
     In some demonstrative embodiments, as shown in  FIG. 6 , station  602  may transmit a data stream  622  to station  640 , for example, via the first direction, for example, the direction from which station  602  receives CTS frame  616  from station  640 . 
     In some demonstrative embodiments, as shown in  FIG. 6 , station  602  may select not to transmit a data stream to station  660 , for example, via the second direction, for example, the direction from which station  602  did not receive a CTS frame from station  660 . 
     Referring back to  FIG. 1 , in some demonstrative embodiments, a station, e.g., device  102  and/or device  140 , may be configured to advertise its capabilities of dynamic spatial domain transmission. 
     In some demonstrative embodiments, a capability of a STA may include an indication of whether or not the STA is able to reconstruct a PPDU, e.g., on the fly, for example, in case one or more directions are busy, for example, for SU-MIMO, and/or MU-MIMO, e.g., as described above 
     In some demonstrative embodiments, a capability of a STA may include an indication of whether or not the STA is able to perform multi-directional CCA, for example, by a plurality of CCA modules. 
     In some demonstrative embodiments, a capability of a STA may include an indication of how many directions of a multi-directional CCA are supported by the STA. 
     In some demonstrative embodiments, a capability of a STA may include an indication of whether or not the STA is able to perform multi-directional CCA in a time between reception of one or more RTS frames and transmission of one or more CTS frames. 
     Reference is made to  FIG. 7 , which schematically illustrates a method of communication based on CCA in one or more directions, in accordance with some demonstrative embodiments. For example, one or more of the operations of the method of  FIG. 7  may be performed by one or more elements of a system, e.g., system  100  ( FIG. 1 ), for example, one or more wireless devices, e.g., device  102  ( FIG. 1 ), and/or device  140  ( FIG. 1 ); a controller, e.g., controller  154  ( FIG. 1 ), and/or controller  124  ( FIG. 1 ); a CCA module, e.g., CCA modules  126  ( FIG. 1 ) and/or CCA modules  156  ( FIG. 1 ); a radio, e.g., radio  114  ( FIG. 1 ), and/or radio  144  ( FIG. 1 ); a transmitter, e.g., transmitter  118  ( FIG. 1 ), and/or transmitter  148  ( FIG. 1 ); a receiver e.g., receiver  116  ( FIG. 1 ), and/or receiver  146  ( FIG. 1 ); and/or a message processor, e.g., message processor  128  ( FIG. 1 ), and/or message processor  158  ( FIG. 1 ). 
     As indicated at block  702 , the method may include determining a plurality of directions to transmit a plurality of respective data streams of MIMO transmission. For example, controller  124  ( FIG. 1 ) may be configured to control, cause and/or trigger device  102  ( FIG. 1 ) to determine the plurality of directions to transmit the plurality of respective data streams of the MIMO transmission, e.g., as described above. 
     As indicated at block  704 , the method may include detecting a plurality of CCA states corresponding to the plurality of directions, respectively. For example, controller  124  ( FIG. 1 ) may be configured to control, cause and/or trigger device  102  ( FIG. 1 ) to detect the plurality of CCA states corresponding to the plurality of directions, e.g., as described above. 
     As indicated at block  706 , the method may include transmitting one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions, based on the plurality of CCA states. For example, controller  124  ( FIG. 1 ) may be configured to control, cause and/or trigger device  102  ( FIG. 1 ) to transmit the one or more selected data streams of the plurality of data streams in the one or more respective selected directions of beam directions  135  ( FIG. 1 ), for example, based on the plurality of CCA states, e.g., as described above. 
     As indicated at block  708 , transmitting the one or more selected data streams in the one or more respective selected directions may include transmitting the one or more selected data streams only in directions including a detected CCA idle state. For example, controller  124  ( FIG. 1 ) may be configured to control, cause and/or trigger device  102  ( FIG. 1 ) to transmit the one or more selected data streams of the plurality of data streams only in directions including a detected CCA idle state, e.g., as described above. 
     As indicated at block  705 , the method may include transmitting one or more RTS frames in one or more respective directions having a CCA idle state. For example, controller  124  ( FIG. 1 ) may be configured to control, cause and/or trigger device  102  ( FIG. 1 ) to transmit the one or more RTS frames in the one or more respective directions having the CCA idle state, e.g., as described above. 
     As indicated at block  710 , transmitting the one or more selected data streams in the one or more respective selected directions may include transmitting the one or more selected data streams only in directions including directions from which a CTS frame is received, e.g., in response to the RTS frames. For example, controller  124  ( FIG. 1 ) may be configured to control, cause and/or trigger device  102  ( FIG. 1 ) to transmit the one or more selected data streams of the plurality of data streams only in the directions from which the CTS frame is received, e.g., as described above. 
     Reference is made to  FIG. 8 , which schematically illustrates a product of manufacture  800 , in accordance with some demonstrative embodiments. Product  800  may include one or more tangible computer-readable non-transitory storage media  802 , which may include computer-executable instructions, e.g., implemented by logic  804 , operable to, when executed by at least one computer processor, enable the at least one computer processor to implement one or more operations at device  102  ( FIG. 1 ), device  140  ( FIG. 1 ), radio  114  ( FIG. 1 ), radio  144  ( FIG. 1 ), transmitter  118  ( FIG. 1 ), transmitter  148  ( FIG. 1 ), receiver  116  ( FIG. 1 ), receiver  146  ( FIG. 1 ), controller  124  ( FIG. 1 ), controller  154  ( FIG. 1 ), message processor  128  ( FIG. 1 ), message processor  158  ( FIG. 1 ), and/or CCA modules  126  ( FIG. 1 ), CCA modules  156  ( FIG. 1 ), and/or to perform, trigger and/or implement one or more operations, communications and/or functionalities according to  FIGS. 1, 2, 3, 4, 5, 6 , and/or  7 , and/or one or more operations described herein. The phrase “non-transitory machine-readable medium” is directed to include all computer-readable media, with the sole exception being a transitory propagating signal. 
     In some demonstrative embodiments, product  800  and/or machine-readable storage medium  802  may include one or more types of computer-readable storage media capable of storing data, including volatile memory, non-volatile memory, removable or non-removable memory, erasable or non-erasable memory, writeable or re-writeable memory, and the like. For example, machine-readable storage medium  802  may include, RAM, DRAM, Double-Data-Rate DRAM (DDR-DRAM), SDRAM, static RAM (SRAM), ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), Compact Disk ROM (CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), flash memory (e.g., NOR or NAND flash memory), content addressable memory (CAM), polymer memory, phase-change memory, ferroelectric memory, silicon-oxide-nitride-oxide-silicon (SONOS) memory, a disk, a floppy disk, a hard drive, an optical disk, a magnetic disk, a card, a magnetic card, an optical card, a tape, a cassette, and the like. The computer-readable storage media may include any suitable media involved with downloading or transferring a computer program from a remote computer to a requesting computer carried by data signals embodied in a carrier wave or other propagation medium through a communication link, e.g., a modem, radio or network connection. 
     In some demonstrative embodiments, logic  804  may include instructions, data, and/or code, which, if executed by a machine, may cause the machine to perform a method, process and/or operations as described herein. The machine may include, for example, any suitable processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware, software, firmware, and the like. 
     In some demonstrative embodiments, logic  804  may include, or may be implemented as, software, firmware, a software module, an application, a program, a subroutine, instructions, an instruction set, computing code, words, values, symbols, and the like. The instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like. The instructions may be implemented according to a predefined computer language, manner or syntax, for instructing a processor to perform a certain function. The instructions may be implemented using any suitable high-level, low-level, object-oriented, visual, compiled and/or interpreted programming language, such as C, C++, Java, BASIC, Matlab, Pascal, Visual BASIC, assembly language, machine code, and the like. 
     Examples 
     The following examples pertain to further embodiments. 
     Example 1 includes an apparatus comprising logic and circuitry configured to cause a wireless station to determine a plurality of directions to transmit a plurality of respective data streams of a Multi-Input-Multi-Output (MIMO) transmission; detect a plurality of Clear Channel Assessment (CCA) states corresponding to the plurality of directions, respectively; and based on the plurality of CCA states, transmit one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions. 
     Example 2 includes the subject matter of Example 1, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 3 includes the subject matter of Example 1 or 2, and optionally, wherein the apparatus is configured to cause the wireless station to construct a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) comprising the plurality of data streams, and to reconstruct the PPDU comprising the one or more selected data streams. 
     Example 4 includes the subject matter of any one of Examples 1-3, and optionally, wherein the apparatus is configured to cause the wireless station to transmit one or more Request to Send (RTS) frames in one or more respective directions having a CCA idle state. 
     Example 5 includes the subject matter of Example 4, and optionally, wherein the apparatus is configured to cause the wireless station to transmit a plurality of RTS frames in a plurality of respective directions having the CCA idle state. 
     Example 6 includes the subject matter of Example 4 or 5, and optionally, wherein the apparatus is configured to cause the wireless station to determine the one or more selected directions to comprise directions from which a Clear to Send (CTS) frame is received. 
     Example 7 includes the subject matter of any one of Examples 1-6, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 8 includes the subject matter of any one of Examples 1-6, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 9 includes the subject matter of any one of Examples 1-8, and optionally, wherein the wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 10 includes the subject matter of any one of Examples 1-9, and optionally, comprising one or more directional antennas, a memory, and a processor. 
     Example 11 includes a system of wireless communication comprising a wireless station, the wireless station comprising one or more directional antennas; a memory; a processor; and a controller configured to cause the wireless station to determine a plurality of directions to transmit a plurality of respective data streams of a Multi-Input-Multi-Output (MIMO) transmission; detect a plurality of Clear Channel Assessment (CCA) states corresponding to the plurality of directions, respectively; and based on the plurality of CCA states, transmit one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions. 
     Example 12 includes the subject matter of Example 11, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 13 includes the subject matter of Example 11 or 12, and optionally, wherein the wireless station is to construct a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) comprising the plurality of data streams, and to reconstruct the PPDU comprising the one or more selected data streams. 
     Example 14 includes the subject matter of any one of Examples 11-13, and optionally, wherein the wireless station is to transmit one or more Request to Send (RTS) frames in one or more respective directions having a CCA idle state. 
     Example 15 includes the subject matter of Example 14, and optionally, wherein the wireless station is to transmit a plurality of RTS frames in a plurality of respective directions having the CCA idle state. 
     Example 16 includes the subject matter of Example 14 or 15, and optionally, wherein the wireless station is to determine the one or more selected directions to comprise directions from which a Clear to Send (CTS) frame is received. 
     Example 17 includes the subject matter of any one of Examples 11-16, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 18 includes the subject matter of any one of Examples 11-16, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 19 includes the subject matter of any one of Examples 11-18, and optionally, wherein the wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 20 includes a method to be performed at a wireless station, the method comprising determining a plurality of directions to transmit a plurality of respective data streams of a Multi-Input-Multi-Output (MIMO) transmission; detecting a plurality of Clear Channel Assessment (CCA) states corresponding to the plurality of directions, respectively; and based on the plurality of CCA states, transmitting one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions. 
     Example 21 includes the subject matter of Example 20, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 22 includes the subject matter of Example 20 or 21, and optionally, comprising constructing a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) comprising the plurality of data streams, and reconstructing the PPDU comprising the one or more selected data streams. 
     Example 23 includes the subject matter of any one of Examples 20-22, and optionally, comprising transmitting one or more Request to Send (RTS) frames in one or more respective directions having a CCA idle state. 
     Example 24 includes the subject matter of Example 23, and optionally, comprising transmitting a plurality of RTS frames in a plurality of respective directions having the CCA idle state. 
     Example 25 includes the subject matter of Example 23 or 24, and optionally, comprising determining the one or more selected directions to comprise directions from which a Clear to Send (CTS) frame is received. 
     Example 26 includes the subject matter of any one of Examples 20-25, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 27 includes the subject matter of any one of Examples 20-25, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 28 includes the subject matter of any one of Examples 20-27, and optionally, wherein the wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 29 includes a product comprising one or more tangible computer-readable non-transitory storage media comprising computer-executable instructions operable to, when executed by at least one computer processor, enable the at least one computer processor to implement operations at a wireless station, the operations comprising determining a plurality of directions to transmit a plurality of respective data streams of a Multi-Input-Multi-Output (MIMO) transmission; detecting a plurality of Clear Channel Assessment (CCA) states corresponding to the plurality of directions, respectively; and based on the plurality of CCA states, transmitting one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions. 
     Example 30 includes the subject matter of Example 29, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 31 includes the subject matter of Example 29 or 30, and optionally, wherein the operations comprise constructing a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) comprising the plurality of data streams, and reconstructing the PPDU comprising the one or more selected data streams. 
     Example 32 includes the subject matter of any one of Examples 29-31, and optionally, wherein the operations comprise transmitting one or more Request to Send (RTS) frames in one or more respective directions having a CCA idle state. 
     Example 33 includes the subject matter of Example 32, and optionally, wherein the operations comprise transmitting a plurality of RTS frames in a plurality of respective directions having the CCA idle state. 
     Example 34 includes the subject matter of Example 32 or 33, and optionally, wherein the operations comprise determining the one or more selected directions to comprise directions from which a Clear to Send (CTS) frame is received. 
     Example 35 includes the subject matter of any one of Examples 29-34, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 36 includes the subject matter of any one of Examples 29-34, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 37 includes the subject matter of any one of Examples 29-36, and optionally, wherein the wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 38 includes an apparatus of wireless communication by a wireless station, the apparatus comprising means for determining a plurality of directions to transmit a plurality of respective data streams of a Multi-Input-Multi-Output (MIMO) transmission; means for detecting a plurality of Clear Channel Assessment (CCA) states corresponding to the plurality of directions, respectively; and means for, based on the plurality of CCA states, transmitting one or more selected data streams of the plurality of data streams in one or more respective selected directions of the plurality of directions. 
     Example 39 includes the subject matter of Example 38, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 40 includes the subject matter of Example 38 or 39, and optionally, comprising means for constructing a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) comprising the plurality of data streams, and reconstructing the PPDU comprising the one or more selected data streams. 
     Example 41 includes the subject matter of any one of Examples 38-40, and optionally, comprising means for transmitting one or more Request to Send (RTS) frames in one or more respective directions having a CCA idle state. 
     Example 42 includes the subject matter of Example 41, and optionally, comprising means for transmitting a plurality of RTS frames in a plurality of respective directions having the CCA idle state. 
     Example 43 includes the subject matter of Example 41 or 42, and optionally, comprising means for determining the one or more selected directions to comprise directions from which a Clear to Send (CTS) frame is received. 
     Example 44 includes the subject matter of any one of Examples 38-43, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 45 includes the subject matter of any one of Examples 38-43, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 46 includes the subject matter of any one of Examples 38-45, and optionally, wherein the wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 47 includes an apparatus comprising logic and circuitry configured to cause a first wireless station to receive from a second wireless station one or more Request to Send (RTS) frames from one or more respective directions; detect one or more Clear Channel Assessment (CCA) states corresponding to the one or more directions, respectively; and transmit to the second wireless station one or more Clear to Send (CTS) frames in one or more respective selected directions of the one or more directions, based on the one or more CCA states. 
     Example 48 includes the subject matter of Example 47, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 49 includes the subject matter of Example 47 or 48, and optionally, wherein the apparatus is configured to cause the first wireless station to receive from the second wireless station a plurality of Request to Send (RTS) frames from a plurality of different directions, and to detect a plurality of CCA states corresponding to the plurality of different directions, respectively. 
     Example 50 includes the subject matter of any one of Examples 47-49, and optionally, wherein the one or more RTS frames comprise a plurality of RTS frames received from a plurality of different directions. 
     Example 51 includes the subject matter of Example 50, and optionally, wherein the apparatus is configured to cause the first wireless station to select a plurality of selected directions from the plurality of different directions, based on a plurality of CCA states corresponding to the plurality of different directions, and to transmit a plurality of CTS frames in the plurality of selected directions. 
     Example 52 includes the subject matter of Example 51, and optionally, wherein the apparatus is configured to cause the first wireless station to sequentially transmit two or more CTS frames of the plurality of CTS frames. 
     Example 53 includes the subject matter of Example 51, and optionally, wherein the apparatus is configured to cause the first wireless station to simultaneously transmit two or more CTS frames of the plurality of CTS frames. 
     Example 54 includes the subject matter of any one of Examples 47-53, and optionally, wherein the apparatus is configured to cause the first wireless station to transmit the one or more CTS frames in response to a poll frame from the second wireless station. 
     Example 55 includes the subject matter of any one of Examples 47-54, and optionally, wherein the apparatus is configured to cause the first wireless station to process a Multi-Input-Multi-Output (MIMO) transmission received from the second wireless device via the one or more selected directions. 
     Example 56 includes the subject matter of Example 55, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 57 includes the subject matter of Example 55, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 58 includes the subject matter of any one of Examples 47-57, and optionally, wherein the first wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 59 includes the subject matter of any one of Examples 47-58, and optionally, comprising one or more directional antennas, a memory, and a processor. 
     Example 60 includes a system of wireless communication comprising a first wireless station, the wireless station comprising one or more directional antennas; a memory; a processor; and a controller configured to cause the first wireless station to receive from a second wireless station one or more Request to Send (RTS) frames from one or more respective directions; detect one or more Clear Channel Assessment (CCA) states corresponding to the one or more directions, respectively; and transmit to the second wireless station one or more Clear to Send (CTS) frames in one or more respective selected directions of the one or more directions, based on the one or more CCA states. 
     Example 61 includes the subject matter of Example 60, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 62 includes the subject matter of Example 60 or 61, and optionally, wherein the first wireless station is to receive from the second wireless station a plurality of Request to Send (RTS) frames from a plurality of different directions, and to detect a plurality of CCA states corresponding to the plurality of different directions, respectively. 
     Example 63 includes the subject matter of any one of Examples 60-62, and optionally, wherein the one or more RTS frames comprise a plurality of RTS frames received from a plurality of different directions. 
     Example 64 includes the subject matter of Example 63, and optionally, wherein the first wireless station is to select a plurality of selected directions from the plurality of different directions, based on a plurality of CCA states corresponding to the plurality of different directions, and to transmit a plurality of CTS frames in the plurality of selected directions. 
     Example 65 includes the subject matter of Example 64, and optionally, wherein the first wireless station is to sequentially transmit two or more CTS frames of the plurality of CTS frames. 
     Example 66 includes the subject matter of Example 64, and optionally, wherein the first wireless station is to simultaneously transmit two or more CTS frames of the plurality of CTS frames. 
     Example 67 includes the subject matter of any one of Examples 60-66, and optionally, wherein the first wireless station is to transmit the one or more CTS frames in response to a poll frame from the second wireless station. 
     Example 68 includes the subject matter of any one of Examples 60-67, and optionally, wherein the first wireless station is to process a Multi-Input-Multi-Output (MIMO) transmission received from the second wireless device via the one or more selected directions. 
     Example 69 includes the subject matter of Example 68, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 70 includes the subject matter of Example 68, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 71 includes the subject matter of any one of Examples 60-70, and optionally, wherein the first wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 72 includes a method to be performed at a first wireless station, the method comprising receiving from a second wireless station one or more Request to Send (RTS) frames from one or more respective directions; detecting one or more Clear Channel Assessment (CCA) states corresponding to the one or more directions, respectively; and transmitting to the second wireless one or more Clear to Send (CTS) frames in one or more respective selected directions of the one or more directions, based on the one or more CCA states. 
     Example 73 includes the subject matter of Example 72, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 74 includes the subject matter of Example 72 or 73, and optionally, comprising receiving from the second wireless station a plurality of Request to Send (RTS) frames from a plurality of different directions, and detecting a plurality of CCA states corresponding to the plurality of different directions, respectively. 
     Example 75 includes the subject matter of any one of Examples 72-74, and optionally, wherein the one or more RTS frames comprise a plurality of RTS frames received from a plurality of different directions. 
     Example 76 includes the subject matter of Example 75, and optionally, comprising selecting a plurality of selected directions from the plurality of different directions, based on a plurality of CCA states corresponding to the plurality of different directions, and transmitting a plurality of CTS frames in the plurality of selected directions. 
     Example 77 includes the subject matter of Example 76, and optionally, comprising sequentially transmitting two or more CTS frames of the plurality of CTS frames. 
     Example 78 includes the subject matter of Example 76, and optionally, comprising simultaneously transmitting two or more CTS frames of the plurality of CTS frames. 
     Example 79 includes the subject matter of any one of Examples 72-78, and optionally, comprising transmitting the one or more CTS frames in response to a poll frame from the second wireless station. 
     Example 80 includes the subject matter of any one of Examples 72-79, and optionally, comprising processing a Multi-Input-Multi-Output (MIMO) transmission received from the second wireless device via the one or more selected directions. 
     Example 81 includes the subject matter of Example 80, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 82 includes the subject matter of Example 80, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 83 includes the subject matter of any one of Examples 72-82, and optionally, wherein the first wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 84 includes a product comprising one or more tangible computer-readable non-transitory storage media comprising computer-executable instructions operable to, when executed by at least one computer processor, enable the at least one computer processor to implement operations at a first wireless station, the operations comprising receiving from a second wireless station one or more Request to Send (RTS) frames from one or more respective directions; detecting one or more Clear Channel Assessment (CCA) states corresponding to the one or more directions, respectively; and transmitting to the second wireless one or more Clear to Send (CTS) frames in one or more respective selected directions of the one or more directions, based on the one or more CCA states. 
     Example 85 includes the subject matter of Example 84, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 86 includes the subject matter of Example 84 or 85, and optionally, wherein the operations comprise receiving from the second wireless station a plurality of Request to Send (RTS) frames from a plurality of different directions, and detecting a plurality of CCA states corresponding to the plurality of different directions, respectively. 
     Example 87 includes the subject matter of any one of Examples 84-86, and optionally, wherein the one or more RTS frames comprise a plurality of RTS frames received from a plurality of different directions. 
     Example 88 includes the subject matter of Example 87, and optionally, wherein the operations comprise selecting a plurality of selected directions from the plurality of different directions, based on a plurality of CCA states corresponding to the plurality of different directions, and transmitting a plurality of CTS frames in the plurality of selected directions. 
     Example 89 includes the subject matter of Example 88, and optionally, wherein the operations comprise sequentially transmitting two or more CTS frames of the plurality of CTS frames. 
     Example 90 includes the subject matter of Example 88, and optionally, wherein the operations comprise simultaneously transmitting two or more CTS frames of the plurality of CTS frames. 
     Example 91 includes the subject matter of any one of Examples 84-90, and optionally, wherein the operations comprise transmitting the one or more CTS frames in response to a poll frame from the second wireless station. 
     Example 92 includes the subject matter of any one of Examples 84-91, and optionally, wherein the operations comprise processing a Multi-Input-Multi-Output (MIMO) transmission received from the second wireless device via the one or more selected directions. 
     Example 93 includes the subject matter of Example 92, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 94 includes the subject matter of Example 92, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 95 includes the subject matter of any one of Examples 84-94, and optionally, wherein the first wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Example 96 includes an apparatus of wireless communication by a first wireless station, the apparatus comprising means for receiving from a second wireless station one or more Request to Send (RTS) frames from one or more respective directions; means for detecting one or more Clear Channel Assessment (CCA) states corresponding to the one or more directions, respectively; and means for transmitting to the second wireless one or more Clear to Send (CTS) frames in one or more respective selected directions of the one or more directions, based on the one or more CCA states. 
     Example 97 includes the subject matter of Example 96, and optionally, wherein the one or more selected directions comprise only directions having a detected CCA idle state. 
     Example 98 includes the subject matter of Example 96 or 97, and optionally, comprising means for receiving from the second wireless station a plurality of Request to Send (RTS) frames from a plurality of different directions, and detecting a plurality of CCA states corresponding to the plurality of different directions, respectively. 
     Example 99 includes the subject matter of any one of Examples 96-98, and optionally, wherein the one or more RTS frames comprise a plurality of RTS frames received from a plurality of different directions. 
     Example 100 includes the subject matter of Example 99, and optionally, comprising means for selecting a plurality of selected directions from the plurality of different directions, based on a plurality of CCA states corresponding to the plurality of different directions, and transmitting a plurality of CTS frames in the plurality of selected directions. 
     Example 101 includes the subject matter of Example 100, and optionally, comprising means for sequentially transmitting two or more CTS frames of the plurality of CTS frames. 
     Example 102 includes the subject matter of Example 100, and optionally, comprising means for simultaneously transmitting two or more CTS frames of the plurality of CTS frames. 
     Example 103 includes the subject matter of any one of Examples 96-102, and optionally, comprising means for transmitting the one or more CTS frames in response to a poll frame from the second wireless station. 
     Example 104 includes the subject matter of any one of Examples 96-103, and optionally, comprising means for processing a Multi-Input-Multi-Output (MIMO) transmission received from the second wireless device via the one or more selected directions. 
     Example 105 includes the subject matter of Example 104, and optionally, wherein the MIMO transmission is a Single-User (SU) MIMO transmission. 
     Example 106 includes the subject matter of Example 104, and optionally, wherein the MIMO transmission is a Multi-User (MU) MIMO transmission. 
     Example 107 includes the subject matter of any one of Examples 96-106, and optionally, wherein the first wireless station is a Directional Multi-Gigabit (DMG) Station (STA). 
     Functions, operations, components and/or features described herein with reference to one or more embodiments, may be combined with, or may be utilized in combination with, one or more other functions, operations, components and/or features described herein with reference to one or more other embodiments, or vice versa. 
     While certain features have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.