Request to send (RTS)/clear to send (CTS) using a self-contained slot

Apparatuses, systems, and methods for a wireless device and base station transmitting and/or receiving request to send (RTS) and clear to send (CTS) messages in 5G New Radio. The RTS/CTS messages may be comprised within a single self-contained mini slot. The RTS/CTS message design may provide for link adaptation and/or beamforming.

FIELD

The present application relates to wireless devices, and more particularly to apparatus, systems, and methods for reducing interference between radio access technologies.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. There exist numerous different wireless communication technologies and standards. Some examples of wireless communication standards include GSM, UMTS (WCDMA), LTE, LTE Advanced (LTE-A), 3GPP2 CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), IEEE 802.11 (WLAN or WI-FI, and WIGIG), IEEE 802.16 (WIMAX), BLUETOOTH, and others. Further, wireless communication technology has evolved from voice-only communications to also include the transmission of data, such as Internet and multimedia content.

With the increasing number of wireless communication technologies in existence, it has become more common for wireless devices to include multiple antennas and/or multiple radios to implement various wireless communication technologies. Some standards (e.g., recent versions of IEEE 802.11ad and 802.11ay) use directional wireless techniques to improve system performance.

Further, interference and collisions between transmissions of one or multiple radio access technologies (RATs) are increasingly possible (e.g., in unlicensed spectrum). For example, collisions may be possible between transmissions, e.g., between 5G/cellular transmissions and wireless local area network (WLAN) transmissions. For example, collisions and interference may be due in part to the hidden node problem. Interference and collisions may degrade the wireless ecosystem and lead to negative impacts on users, e.g., of both RATs. Thus, improvements in the field are desired.

SUMMARY

Embodiments relate to apparatuses, systems, and methods to perform request to send (RTS) and clear to send (CTS) messaging, e.g., in a 5G environment. The RTS/CTS design may reduce or avoid collisions of transmissions (e.g., associated with a hidden node such as a WI-FI device) in unlicensed spectrum transmission mediums. The RTS and CTS messages may be transmitted in a single self-contained mini slot. The use of a self-contained mini slot may facilitate fast turn-around between the sender and receiver. The RTS/CTS design may provide for link adaptation and/or beamforming (e.g., including beam acquisition, tracking, management, direction, shape, etc.). For example, reference signals may be included in (or with) RTS/CTS. Multiple transmit and/or receive beams may be used to transmit/receive RTS/CTS in multiple symbols of the self-contained mini slot.

The techniques described herein may be implemented in and/or used with a number of different types of devices, including but not limited to base stations, cellular phones, tablet computers, wearable computing devices, portable media players, and any of various other computing devices.

DETAILED DESCRIPTION

Terms

IEEE 802.11—refers to technology based on IEEE 802.11 wireless standards such as 802.11a, 802.11.b, 802.11g, 802.11n, 802.11-2012, 802.11ac, 802.11ad, 802.11ay, and/or other IEEE 802.11 standards. IEEE 802.11 technology may also be referred to as “WI-FI” or “wireless local area network (WLAN)” technology.

FIG. 1illustrates a simplified example wireless communication system, according to some embodiments. It is noted that the system ofFIG. 1is merely one example of a possible system, and that features of this disclosure may be implemented in any of various systems, as desired.

As shown, the example wireless communication system includes a base station102A which communicates over a transmission medium with one or more user devices106A,106B, etc., through106N. Each of the user devices may be referred to herein as a “user equipment” (UE) or “new radio unit” (NRU). Thus, the user devices106are referred to as UEs, UE devices, or NRUs.

The base station (BS)102A may be a base transceiver station (BTS) or cell site (a “cellular base station”), and may include hardware that enables wireless communication with the UEs106A through106N.

As shown, the base station102A may also be equipped to communicate with a network100(e.g., a core network of a cellular service provider, a telecommunication network such as a public switched telephone network (PSTN), and/or the Internet, among various possibilities). Thus, the base station102A may facilitate communication between the user devices and/or between the user devices and the network100. In particular, the cellular base station102A may provide UEs106with various telecommunication capabilities, such as voice, SMS and/or data services.

In some embodiments, base station102A may be a next generation base station, e.g., a 5G New Radio (5G NR) base station, or “gNB”. In some embodiments, a gNB may be connected to a legacy evolved packet core (EPC) network and/or to a NR core (NRC) network. In addition, a gNB cell may include one or more transmission and reception points (TRPs). In addition, a UE capable of operating according to 5G NR may be connected to one or more TRPs within one or more gNBs.

In some embodiments, base station102A may be (or may include) an access point (AP). The base station102A may be capable of communicating using one or more wireless local area network (WLAN) communication standards. For example, the base station102A may be capable of communicating using IEEE 802.11 standards (e.g., WI-FI).

FIG. 2illustrates user equipment106(e.g., one of the devices106A through106N) in communication with a base station102and an access point104, according to some embodiments. The UE106may be a device with cellular communication capability such as a mobile phone, a hand-held device, a computer or a tablet, or virtually any type of wireless device.

The access point104may be an access point providing a wireless local area network (WLAN). The access point104may be equipped to communicate with a network100(e.g., a wide area network (WAN), such as the Internet, among various possibilities). Thus, the access point104may facilitate communication between the UEs106and/or between the UEs106and the network100. The access point104and the UEs106may be configured to communicate over the transmission medium using WI-FI, including any of various versions of IEEE 802.11 (e.g., a, b, g, n, ac, ad, ay, wake-up radio (WUR), etc.).

In some embodiments, the WLAN may be an ad hoc network, e.g., using Personal Basic Service Set (PBSS) architecture, e.g., as defined in IEEE 802.11 ad. In such cases, the role of access point104may be performed by a UE device (e.g., one of the UEs106) acting as a PBSS Control Point (PCP). For convenience, the terms “access point” and “AP/PCP” may be used herein to include an access point or PCP.

Any or all of UE106, AP104, and/or BS102may be configured to operate according to the techniques disclosed herein. In particular, these devices may transmit and/or receive request to send and/or clear to send messages. Further, these devices may perform link adaptation and/or beamforming (e.g., including beam acquisition, tracking, management, direction, shape, etc.) based at least in part on such messages.

FIG.3—Block Diagram of a UE

FIG. 3illustrates an example simplified block diagram of a communication device106, according to some embodiments. It is noted that the block diagram of the communication device ofFIG. 3is only one example of a possible communication device. According to embodiments, communication device106may be a user equipment (UE) device, a new radio unit (NRU), a mobile device or mobile station (STA), a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet and/or a combination of devices, among other devices. As shown, the communication device106may include a set of components300configured to perform core functions. For example, this set of components may be implemented as a system on chip (SOC), which may include portions for various purposes. Alternatively, this set of components300may be implemented as separate components or groups of components for the various purposes. The set of components300may be coupled (e.g., communicatively; directly or indirectly) to various other circuits of the communication device106.

For example, the communication device106may include various types of memory (e.g., including NAND flash310), an input/output interface such as connector I/F320(e.g., for connecting to a computer system; dock; charging station; input devices, such as a microphone, camera, keyboard; output devices, such as speakers; etc.), the display360, which may be integrated with or external to the communication device106, and cellular communication circuitry330such as for 5G NR, LTE, GSM, etc., and short to medium range wireless communication circuitry329(e.g., Bluetooth™ and WLAN circuitry (e.g., IEEE 802.11, WI-FI)). In some embodiments, communication device106may include wired communication circuitry (not shown), such as a network interface card, e.g., for Ethernet.

The cellular communication circuitry330may couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas335and336as shown. The antennas may be grouped into any number of antenna arrays, each containing any number of antennas. The short to medium range wireless communication circuitry329may also couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas337and338as shown, which may also be grouped into antenna arrays. Alternatively, the short to medium range wireless communication circuitry329may couple (e.g., communicatively; directly or indirectly) to the antennas335and336in addition to, or instead of, coupling (e.g., communicatively; directly or indirectly) to the antennas337and338. The short to medium range wireless communication circuitry329and/or cellular communication circuitry330may include multiple receive chains and/or multiple transmit chains for receiving and/or transmitting multiple spatial streams, such as in a multiple-input multiple output (MIMO) configuration.

The communication device106may further include one or more smart cards345that include SIM (Subscriber Identity Module) functionality, such as one or more UICC(s) (Universal Integrated Circuit Card(s)) cards345.

As shown, the SOC300may include processor(s)302, which may execute program instructions for the communication device106and display circuitry304, which may perform graphics processing and provide display signals to the display360. The processor(s)302may also be coupled to memory management unit (MMU)340, which may be configured to receive addresses from the processor(s)302and translate those addresses to locations in memory (e.g., memory306, read only memory (ROM)350, NAND flash memory310) and/or to other circuits or devices, such as the display circuitry304, short range wireless communication circuitry229, cellular communication circuitry330, connector I/F320, and/or display360. The MMU340may be configured to perform memory protection and page table translation or set up. In some embodiments, the MMU340may be included as a portion of the processor(s)302.

As noted above, the communication device106may be configured to communicate using wireless and/or wired communication circuitry. The communication device106may be configured to transmit a request to attach to a first network node operating according to the first RAT and transmit an indication that the wireless device is capable of maintaining substantially concurrent connections with the first network node and a second network node that operates according to the second RAT. The wireless device may also be configured transmit a request to attach to the second network node. The request may include an indication that the wireless device is capable of maintaining substantially concurrent connections with the first and second network nodes. Further, the wireless device may be configured to receive an indication that dual connectivity with the first and second network nodes has been established.

As described herein, the communication device106may include hardware and software components for implementing the above features for time division multiplexing UL data for NSA NR operations. The processor302of the communication device106may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor302may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor302of the communication device106, in conjunction with one or more of the other components300,304,306,310,320,329,330,340,345,350,360may be configured to implement part or all of the features described herein.

Further, as described herein, cellular communication circuitry330and short range wireless communication circuitry329may each include one or more processing elements. In other words, one or more processing elements may be included in cellular communication circuitry330and, similarly, one or more processing elements may be included in short range wireless communication circuitry329. Thus, cellular communication circuitry330may include one or more integrated circuits (ICs) that are configured to perform the functions of cellular communication circuitry330. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of cellular communication circuitry230. Similarly, the short range wireless communication circuitry329may include one or more ICs that are configured to perform the functions of short range wireless communication circuitry32. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of short range wireless communication circuitry329.

Any of the processing elements (e.g., processors)302and/or processors associated with cellular communication circuitry330and/or short range wireless communication circuitry329may be configured to cause the wireless device to perform any or all of the various method elements or features described herein.

FIG.4—Block Diagram of a Base Station/Access Point

FIG. 4illustrates an example block diagram of a base station102/access point104, according to some embodiments. For convenience, the term base station is used for the remainder of the description ofFIG. 4. It is noted that the base station ofFIG. 4is merely one example of a possible base station. As shown, the base station102may include processor(s)404which may execute program instructions for the base station102. The processor(s)404may also be coupled to memory management unit (MMU)440, which may be configured to receive addresses from the processor(s)404and translate those addresses to locations in memory (e.g., memory460and read only memory (ROM)450) or to other circuits or devices.

The base station102may include at least one network port470. The network port470may be configured to couple to a network (e.g., a telephone network and/or the internet) and provide a plurality of devices, such as UE devices106, access to the network as described above inFIGS. 1 and 2.

The base station102may include at least one antenna434, and possibly multiple antennas. The radio430and at least one antenna434may be configured to operate as a wireless transceiver and may be further configured to communicate with UE devices106. The antenna434may communicate with the radio430via communication chain432. Communication chain432may be a receive chain, a transmit chain or both. The radio430may be configured to communicate via various wireless communication standards, including, but not limited to, 5G NR, LTE, LTE-A, GSM, UMTS, CDMA2000, WI-FI, etc.

In addition, as described herein, processor(s)404may be comprised of one or more processing elements. In other words, one or more processing elements may be included in processor(s)404. Thus, processor(s)404may include one or more integrated circuits (ICs) that are configured to perform the functions of processor(s)404. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processor(s)404.

Further, as described herein, radio430may be comprised of one or more processing elements. In other words, one or more processing elements may be included in radio430. Thus, radio430may include one or more integrated circuits (ICs) that are configured to perform the functions of radio430. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of radio430. Further, any processing elements associated with430may be configured to implement or support implementation of part or all of the features described herein.

FIG.5: Block Diagram of Cellular Communication Circuitry

The cellular communication circuitry330may couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas335a-band336as shown (inFIG. 3). Any number of antennas may be included in each of one or more antenna arrays. An antenna switch block (not shown) may be included to switch between antennas and/or antenna arrays. Multiple antennas may be used for single or multiple spatial streams (e.g., directional streams or beams for transmitting or receiving, e.g., Tx or Rx beams). Thus, the wireless device may be able to communicate according to standards that include directional functionality (e.g., 5G). Similarly, the wireless device may also be able to implement directional multi-gigabit (DMG) or enhanced directional multi-gigabit (EDMG) functionality, such as IEEE 802.11 ad and ay. The device may use a plurality of different antenna patterns (e.g., within a single array or potentially multiple antenna arrays) to transmit/receive for different directional sectors/beams. The device may sweep through beams and attempt to select a preferred/best beam (e.g., that offers the best transmission/reception characteristics).

In some embodiments, cellular communication circuitry330may include dedicated receive chains (including and/or coupled to, e.g., communicatively; directly or indirectly, dedicated processors and/or radios) for multiple RATs (e.g., a first receive chain for LTE and a second receive chain for 5G NR). For example, as shown inFIG. 5, cellular communication circuitry330may include a modem510and a modem520. Modem510may be configured for communications according to a first RAT, e.g., such as LTE or LTE-A, and modem520may be configured for communications according to a second RAT, e.g., such as 5G NR.

In some embodiments, a switch570may couple transmit circuitry534to uplink (UL) front end572. In addition, switch570may couple transmit circuitry544to UL front end572. UL front end572may include circuitry for transmitting radio signals via antenna336. Thus, when cellular communication circuitry330receives instructions to transmit according to the first RAT (e.g., as supported via modem510), switch570may be switched to a first state that allows modem510to transmit signals according to the first RAT (e.g., via a transmit chain that includes transmit circuitry534and UL front end572). Similarly, when cellular communication circuitry330receives instructions to transmit according to the second RAT (e.g., as supported via modem520), switch570may be switched to a second state that allows modem520to transmit signals according to the second RAT (e.g., via a transmit chain that includes transmit circuitry544and UL front end572).

In some embodiments, the cellular communication circuitry330may be configured to establish a first wireless link with a first cell according to a first radio access technology (RAT), wherein the first cell operates in a first system bandwidth and establish a second wireless link with a second cell according to a second RAT, wherein the second cell operates in a second system bandwidth. The first and second system bandwidth may be the same, they may be separate, or they may overlap. Further, the cellular communication circuitry330may be configured to determine whether the cellular communication circuitry330has uplink activity scheduled according to both the first RAT and the second RAT and perform uplink activity for both the first RAT and the second RAT by time division multiplexing (TDM) uplink data for the first RAT and uplink data for the second RAT if uplink activity is scheduled according to both the first RAT and the second RAT. In some embodiments, to perform uplink activity for both the first RAT and the second RAT by time division multiplexing (TDM) uplink data for the first RAT and uplink data for the second RAT if uplink activity is scheduled according to both the first RAT and the second RAT, the cellular communication circuitry330may be configured to receive an allocation of a first UL subframe for transmissions according to the first RAT and an allocation of a second UL subframe for transmissions according to the second RAT. In some embodiments, the TDM of the uplink data may be performed at a physical layer of the cellular communication circuitry330. In some embodiments, the cellular communication circuitry330may be further configured to receive an allocation of a portion of each UL subframe for control signaling according to one of the first or second RATs.

As described herein, the modem510may include hardware and software components for implementing the above features or for time division multiplexing UL data for NSA NR operations, as well as the various other techniques described herein. The processors512may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor512may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor512, in conjunction with one or more of the other components530,532,534,550,570,572,335and336may be configured to implement part or all of the features described herein.

In addition, as described herein, processors512may include one or more processing elements. Thus, processors512may include one or more integrated circuits (ICs) that are configured to perform the functions of processors512. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processors512.

As described herein, the modem520may include hardware and software components for implementing the above features for time division multiplexing UL data for NSA NR operations, as well as the various other techniques described herein. The processors522may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor522may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor522, in conjunction with one or more of the other components540,542,544,550,570,572,335and336may be configured to implement part or all of the features described herein.

In addition, as described herein, processors522may include one or more processing elements. Thus, processors522may include one or more integrated circuits (ICs) that are configured to perform the functions of processors522. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processors522.

In some embodiments, processor(s)512,522, etc. may be configured to implement or support implementation of part or all of the methods described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively, the processor(s)512,522, etc. may be configured as a programmable hardware element, such as an FPGA, or as an ASIC, or a combination thereof. In addition, as described herein, processor(s)512,522, etc. may include one or more processing elements. Thus, processor(s)512,522, etc. may include one or more integrated circuits (ICs) that are configured to perform the functions of processor(s)512,522, etc. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processor(s)512,522, etc.

It will be appreciated that the illustrated circuitry is exemplary only. In some embodiments, (different numbers of modems, RF front ends, DL front ends, UL front ends, switches, and/or antennas are possible, and may be configured as desired.

In some implementations, fifth generation (5G) wireless communication will initially be deployed concurrently with current wireless communication standards (e.g., LTE). For example, dual connectivity between LTE and 5G new radio (5G NR or NR) has been specified as part of the initial deployment of NR. Thus, as illustrated inFIGS. 6A-B, evolved packet core (EPC) network600may continue to communicate with current LTE base stations (e.g., eNB602). In addition, eNB602may be in communication with a 5G NR base station (e.g., gNB604) and may pass data between the EPC network600and gNB604. Thus, EPC network600may be used (or reused) and gNB604may serve as extra capacity for UEs, e.g., for providing increased downlink throughput to UEs. In other words, LTE may be used for control plane signaling and NR may be used for user plane signaling. Thus, LTE may be used to establish connections to the network and NR may be used for data services.

FIG. 6Billustrates a proposed protocol stack for eNB602and gNB604. As shown, eNB602may include a medium access control (MAC) layer632that interfaces with radio link control (RLC) layers622a-b. RLC layer622amay also interface with packet data convergence protocol (PDCP) layer612aand RLC layer622bmay interface with PDCP layer612b. Similar to dual connectivity as specified in LTE-Advanced Release 12, PDCP layer612amay interface via a master cell group (MCG) bearer to EPC network600whereas PDCP layer612bmay interface via a split bearer with EPC network600.

Additionally, as shown, gNB604may include a MAC layer634that interfaces with RLC layers624a-b. RLC layer624amay interface with PDCP layer622bof eNB602via an X2interface for information exchange and/or coordination (e.g., scheduling of a UE) between eNB602and gNB604. In addition, RLC layer624bmay interface with PDCP layer614. Similar to dual connectivity as specified in LTE-Advanced Release 12, PDCP layer614may interface with EPC network600via a secondary cell group (SCG) bearer. Thus, eNB602may be considered a master node (MeNB) while gNB604may be considered a secondary node (SgNB). In some scenarios, a UE may be required to maintain a connection to both an MeNB and a SgNB. In such scenarios, the MeNB may be used to maintain a radio resource control (RRC) connection to an EPC while the SgNB may be used for capacity (e.g., additional downlink and/or uplink throughput).

In general, a non-stand alone (NSA) implementation employs dual connectivity in both uplink (UL) and downlink (DL). In other words, dual connectivity requires two active radio links in both UL and DL. In some implementations, depending on frequency band combinations, two (substantially) concurrent UL connections may cause receiver sensitivity degradation at the UE. For example, in some proposed implementations, a UE may be required to support 4 DL and 1 UL connection in LTE on bands 1 (UL: 1920-1980 MHz, DL: 2110-2170 MHz), 3 (UL: 1710-1785 MHz, DL: 1805-1880 MHz), 7 (UL: 2500-2570 MHz, DL: 2620-2690 MHz), and 20 (UL: 832-862 MHz, DL: 791-821 MHz) while (substantially) concurrently supporting 1 DL and 1 UL connection in NR at 3400-3800 MHz. In such implementations, a 5thorder intermodulation product (IM5) produced at a 5G NR transmitter of the UE from a 2ndharmonic of LTE UL band 3 and NR UL may fall into LTE DL band 7 frequencies during (substantially) simultaneous UL operation. Similarly, a 4thorder harmonic of LTE UL band 20 and NR UL transmission may create a 5thorder intermodulation product that may interfere with LTE DL band 7 reception and thus desensitize a receiving for LTE DL band 7.

In addition, future specifications NR NSA may require a UE to support co-existence of LTE UL and NR UL within the bandwidth of an LTE component carrier and co-existence of LTE DL and NR DL within the bandwidth of an LTE component carrier. Further, such an implementation may be further required to minimize impact to NR physical layer design to enable such co-existence and to not impact LTE legacy devices (e.g., devices that do not support NR) operating on an LTE carrier co-existing with NR.

Thus, in some implementations of NR NSA, a UE may be configured with multiple UL carriers on different frequencies (e.g., where there is at least one LTE carrier and at least one NR carrier of a different carrier frequency) but operate on either the LTE carrier or the NR carrier at a given time. In other words, the UE may be configured to operate on only one of the carriers at a given time among a pair of LTE and NR carriers. Note that such an implementation may also allow for (substantially) simultaneous operation on two or more UL carriers at a given time.

In some embodiments, a UE, such as communication device106, may support LTE and NR co-existence on specific bands and/or frequencies. In addition, a UE may determine that for a band combination, UL sharing in NSA mode may be required to avoid receiver sensitivity degradation. Thus, the UE may need to inform the network that UL sharing mode will be used for the LTE/NR band combination. In some embodiments, a conditional field may be added to a UE capability message. The conditional field may indicate whether UL sharing mode will be used for the allocated band combination. In addition, the conditional field may indicate which bands/frequencies that the UE supports NSA operations. Note further that in some embodiments, e.g., as further described below, the UE may be configured to perform NSA operations via time division multiplexing (TDM). However, in other embodiments, the UE may be configured to perform NSA operations via other mechanisms such as frequency division multiplexing (FDM) or MAC layer multiplexing.

In some embodiments, WLAN and 5G may use the same or overlapping frequency resources. As a result, traffic on one RAT may interfere with traffic on another, and may therefore increase congestion. For example, cellular transmissions colliding with WLAN transmissions may lead to retransmissions on the WLAN network and therefore may increase congestion, e.g., on the WLAN network. Such collisions may downgrade (e.g., negatively impact) the wireless ecosystem and may harm the experience of the end users of both cellular and WLAN networks (e.g., a lose-lose situation). For example, WLAN transmissions may be polluted by the cellular transmissions, and WLAN users may experience more congestion and retransmission, among various possibilities. Cellular users may experience worse radio link conditions (e.g., lower signal-noise ratio (SNR) and/or lower channel quality index (CQI)), smaller transport block size (TBS), and higher congestion (e.g., higher time and/or frequency resource occupancy), among various possibilities.

Listen-before-talk (LBT) techniques may reduce the interference of cellular transmissions on WLAN networks in unlicensed spectrum (e.g., mmWave bands), under some conditions. LBT is a contention-based protocol, according to which a transmitter may listen (e.g., determine whether another device is transmitting) prior to initiating a transmission (e.g., talking). Thus the transmitter may wait for the medium (e.g., wireless medium, transmission medium) to be clear (e.g., for no other device to be transmitting on the medium) before beginning its transmission. LBT techniques may be applied inter-RAT (e.g., WLAN and cellular) or intra-RAT (e.g., between devices within a WLAN network or within a cellular network). LBT mechanics may be widely adopted for unlicensed spectrum sharing. However, in some embodiments, LBT techniques may be ineffective for solving the hidden node problem. The hidden node problem may exist either between RATs or within a single RAT.

The benefits of LBT may be most significant for WLAN networks that are close to a 5G BS (e.g., sharing the same medium, e.g. unlicensed spectrum). However, in some embodiments, LBT may be ineffective (e.g., relatively or completely) for WLAN networks that are further from the BS. For example, if there are 5G users in the coverage area of a WLAN network for which the 5G BS cannot monitor traffic (e.g., which may be referred to as a hidden node or hidden WLAN network), the cellular transmissions may cause congestion on the hidden WLAN network that the BS cannot avoid through LBT (e.g., because when the BS listens it may not detect the WLAN traffic). The maximum transmission power from a BS (e.g., including/plus beamforming gain) may generally be larger than the transmission power of a WLAN AP. In some embodiments, hidden WLAN networks may share a service set identifier (SSID) with a WLAN network that the BS can monitor.

In some embodiments, for NRUs/UEs (e.g., UE106), base stations (e.g., BS102), and access points (e.g., AP104) that operate in sub-6 GHz spectrum, the hidden node problem may be similar to that of LTE licensed assisted access (LAA). However, for NRUs/UEs (e.g., UE106), base stations (e.g., BS102), and access points (e.g., AP104) that operate in higher frequency bands (e.g., mmWave or millimeter wave bands), the hidden node problem may be more severe, e.g., under directional transmission with narrow Tx/Rx beams for high frequency with high-gain beamforming (e.g., as in 5G, in some embodiments). For example, the channel availability sensed by a transmitter may not match that sensed by a receiver. Further, in the case that an omni-directional antenna is used during carrier sensing, while a directional antenna is used for data transmission, additional differences may include: 1) the coverage/range of sensing and coverage/range of data transmission may be different (e.g., the coverage of the sensing area may be smaller), and 2) the likelihood of an exposed or hidden node may be higher.

In WLAN (e.g., WI-FI), request to send (RTS) and clear to send (CTS) messaging techniques may reduce (e.g., or help solve) the hidden node problem. However, current LTE LAA does not include an RTS/CTS design.

FIG. 7illustrates an exemplary case of the hidden node problem. As illustrated a gNB (e.g., BS102) may be able to receive messages transmitted by UE106a. However, the gNB may not be able to receive messages transmitted by an AP (e.g., AP104) or UE106b. Thus, AP104may be a hidden node. BS102may not detect transmissions of AP104and may transmit to UE106a, e.g., using time/frequency resources also used by AP104. As a result, collisions may occur. Note that, such transmissions of AP104may be directed to any device(s), e.g., they may or may not be to UE106a.

Due to the beamforming gain of transmissions by BS102, the interference of the transmissions on the network (e.g., WLAN) of AP104may be significant. It will be appreciated thatFIG. 7is not a scale drawing and that the relative ranges of BS102and AP104may be different than shown. For example, the range of BS102may be larger than the range of AP104, or vice versa.

FIG.8—Request to Send (RTS) and Clear to Send (CTS) Messaging

FIG. 8illustrates an exemplary sequence of RTS and CTS messages, according to some embodiments. In some embodiments, two devices (e.g., a UE106and a BS102, two UEs, etc.) may exchange RTS and CTS messages. The devices may be capable of communication according to one or more 5G standards. For example, the devices may include an NRU and a gNB, among various possibilities. One device may be considered a sender (821) and the other may be considered a receiver (822), although it will be appreciated that such labels are illustrative only. For example, a device may perform the role of sender821at one time and perform the role of receiver822at another time. The RTS/CTS handshake messaging may avoid or reduce the occurrence of collisions or interference, e.g., related to the hidden node problem. The RTS and CTS messages may be cellular (e.g., 5G) transmissions. Referring to the illustrated case ofFIG. 7, for example, an RTS/CTS handshake may avoid/reduce collisions of transmissions by sender821(e.g., BS102) with transmissions of an AP (e.g., AP104) which may be in range of receiver822(e.g., UE106a).

Such messaging (e.g., RTS/CTS messaging) may also allow for link adaptation and/or beamforming in one or both directions (e.g., for transmissions from the sender821to the receiver822and/or from the receiver822to the sender821). For example, the RTS and/or CTS messages may include or be associated with information or reference symbols useful for link adaptation and/or beam acquisition/management. Similarly, RTS and/or CTS messages may be transmitted and received using a sweep of Tx and/or Rx beams and information about beam selection may be included (e.g., in CTS).

In some embodiments, both the RTS and the CTS messages may be transmitted during (e.g., within) the same self-contained mini slot. A self-contained mini slot may represent a set of time and frequency resources used in 5G communications, and may include resources for two-way communication (e.g., a message and a response, e.g., an RTS and CTS). For example, a first message (e.g., an RTS) may be transmitted from a sender in a first symbol or symbols of the self-contained mini slot, and a receiver may transmit a response (e.g., a CTS) in a second one or more symbols of the self-contained mini slot. The use of a self-contained mini slot may facilitate fast turn-around between the sender and receiver.

Following a successful RTS/CTS handshake, the devices may exchange data (e.g., uplink and/or downlink, transmissions from the sender821to the receiver822and/or from the receiver822to the sender821, etc.). Other users (e.g., other UE and/or network devices such as a neighbor BS or AP) which may detect or decode either the RTS or CTS may refrain from initiating transmissions in response to detecting the RTS/CTS.

RTS and CTS may be transmitted and described in terms of time and frequency resources. Such resources may or may not be scheduled by a gNB or other BS.

In time, the transmissions may be characterized as follows, in some embodiments. An RTS message and a responsive CTS message may be transmitted within a self-contained mini slot (e.g., both an RTS and corresponding CTS may be transmitted within the same mini slot). This sequence of messages in the same mini slot may facilitate fast turn-around times between the sender and receiver to check whether the communication link between them is available and may support proper communication. A small number of symbols (e.g., 2, for example, although other values are possible) within the self-contained mini slot may be used for RTS/CTS, which may allow the other symbols to be left empty and may thus minimize the potential interference addition to the existing wireless link(s). Multiple RTS/CTS may be spatially or frequency multiplexed on the same time axis to enable multiple communication pairs sensing (e.g., multiple pairs of devices concurrently performing RTS/CTS). In some embodiments, multiple (e.g., sequential) self-contained mini slots may be used for transmission of RTS and CTS. In some embodiments, other combinations or types of slots, frames, subframes, or symbols may be used.

In frequency, the transmissions may be characterized as follows, in some embodiments. RTS/CTS messages may use a small bandwidth part (BWP) (e.g., a subset of contiguous resource blocks on a carrier, the subset may be as small as possible/practical), which may limit the potential interference addition along the communication path(s). Large (e.g., or relatively larger) BWP may also be used in some embodiments. In some embodiments, RTS/CTS messages may use resource element (RE) rasters (e.g. one RE every N REs) to fulfill wideband transmission while limiting interference at the same time.

The RTS and/or CTS may include (e.g., or be transmitted with) additional information. Such information may be transmitted on various time and frequency resources. For example, RTS may include intended upcoming data transmission length (e.g. length of a transmit opportunity (TXOP)) and/or destination address. RTS may also contain downlink control information (DCI) and may specify (e.g., map) BWP information for upcoming data communication.

Further, channel state information reference signals (CSI-RS) may be inserted in or included together (e.g., piggybacked) with RTS and/or CTS messages in order to perform uni-directional or bi-directional link adaption. The RTS target (e.g., receiver822) may perform CSI-RS measurement and send back link adaption parameters (e.g. CQI, Rank etc.) in or with a CTS message. The receiver822may in turn include CSI-RS in or with the CTS to enable the sender821to perform link adaptation. In other words, the RTS sender821may perform link assessment based on CSI-RS, which may be piggybacked with CTS messages sent by CTS sender (e.g., receiver822). Thus, both sender821and receiver822may transmit CSI-RS to allow the other party to perform link adaptation, in some embodiments. Moreover, each party (e.g., sender821and receiver822) may transmit link adaptation parameters to the other party in response to measurements of the CSI-RS. In some embodiments, other types of reference signals may be used, e.g., for link adaptation.

In some embodiments, the RTS/CTS messaging design may include (e.g., embedded) beamforming (e.g., beam acquisition and/or tracking) capability. Beamforming may be important for directional communication techniques, e.g., for transmission in mmWave spectrum. A self-contained mini slot may have configuration with more than 2 symbols, e.g., 12 symbols, for example. If more than 1 symbol is scheduled in the mini slot configuration, different Tx beams, quasi-collocation (QCL), and/or CSI-RS may be used for different symbols to transmit RTS so that different Tx beams can be evaluated at the receiver822. In other words, sender821may transmit the same RTS multiple times using different Tx beams (e.g., possibly with different QCL indications and/or different CSI-RS). If more than one symbol is scheduled for RTS with the same Tx beam, the receiver822may also switch Rx beams (e.g., for the same Tx beam in different symbols) so that receiver822may evaluate/track different Rx beams. In some embodiments, Tx and Rx beam tracking may be limited to neighbor beams (e.g., beams that may be sufficiently similar for the devices to switch between beams in the time available). The transmission configuration indicator (TCI) offset of neighbor beams may be specified through RRC and/or MAC-CE messages. TCI may be included in/with RTS/CTS messages in order to identify the beam(s) used to transmit the RTS/CTS messages.

FIG. 8is a communication flow diagram illustrating one such method for two devices in communication, according to some embodiments. In various embodiments, some of the elements of the methods shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired.

Aspects of the method ofFIG. 8may be implemented by devices, such as a UE106and BS102illustrated in and described with respect toFIGS. 1-6, or more generally in conjunction with any of the computer circuitry, systems, devices, elements, or components shown in the Figures herein, among other devices, as desired. For example, a processing element (e.g.,302,404,512,522, any processing elements associated with wireless circuitry or a radio, etc.) may be configured to cause a UE, base station, network element, access point, etc. to perform any of the illustrated method elements, among various possibilities. Although aspects of the method ofFIG. 8are described with respect to communications using WLAN and cellular RATs, it will be appreciated that these RATs are exemplary only and that the methods may be applied to any combination of RATs. Further, the method may be applied to larger numbers of RATs (e.g., three or more RATs). Further, the method may be applied to larger numbers of devices (e.g., three or more devices). As shown, the method may operate as follows.

Sender821(e.g., and also Receiver822) may wait for a backoff/LBT period (801). The duration of the backoff/LBT period may be configured according to a wireless standard (e.g., a 5G standard) or may be configured as desired. Sender821may determine that the medium (e.g., one or more relevant frequency bands, such as mmWave bands) is clear for at least the duration of the backoff/LBT period. Sender821may use any form of sensing and/or any desired beam(s) to detect transmissions on the medium and to determine that the medium is clear. Sender821may use a timer or timers to determine that the medium remains clear for the duration of the backoff/LBT period. If sender821detects any transmissions on the medium, it may restart the backoff/LBT period (e.g., reset a backoff timer).

Receiver822may similarly use any sensing technique(s) and/or beam(s) to determine whether the medium (e.g., a first medium) is clear and may also use timers to determine that the medium remains clear for the duration of a backoff/LBT period. Receiver822may detect transmissions that sender821may not detect, e.g., receiver822may detect transmissions from a node that is hidden from sender821. Such transmissions may or may not be directed to or successfully decoded by receiver822. For example, such transmissions may be WLAN transmissions (e.g., on a network provided by AP104, as illustrated inFIG. 7, among various possibilities) or cellular transmissions, among other possibilities.

Either or both of sender821and receiver822may send, receive, and/or detect transmissions with another device during the backoff/LBT period. For example, such transmissions may be performed on a separate medium, a different RAT, and/or using different spatial resources (e.g., in a different direction). In some embodiments, such transmissions may not interfere with transmissions between sender821, receiver822, and/or other devices (e.g., AP104), e.g., on the first medium. Therefore, such transmissions may not lead to a determination that the first medium is not clear, according to some embodiments.

Sender821may transmit an RTS (802). The RTS may be transmitted after sender821has determined that the medium (e.g., the first medium) is clear for the LBT/backoff period. The RTS may be transmitted in one or more symbols of a self-contained mini slot.

The RTS may be designed to support link adaptation and/or beamforming. For example, the RTS may be transmitted one or more times (e.g., in multiple symbols of the self-contained mini slot) and may use one or more beams (e.g., sequentially, e.g., a different beam for each symbol or each group of multiple groups of symbols). The RTS may be transmitted with additional information, such as CSI-RS (e.g., such information may be included in the RTS or associated with the RTS).

The RTS may be transmitted with information about a requested transmission, such as bandwidth, location of bandwidth, BWP, duration, and/or destination.

Receiver822may receive and decode the RTS. Receiver822may take any number of measurements of, or related to, the RTS. For example, receiver822may measure or determine signal strength (e.g., reference signal strength indicator (RSSI)), channel quality indicator (CQI), beam direction (e.g. optimal beam pair for communication), signal quality (e.g., reference signal received quality (RSRQ)), signal-to-noise ratio (SNR), signal to interference and noise ratio (SINR), etc. of the RTS and/or any CSI-RS.

Receiver822may determine link adaptation information and/or beamforming information (804). For example, based on any CSI-RS that is transmitted with the RTS, the receiver822may determine link adaptation parameters, e.g., a preferred modulation and coding scheme, rank, PMI, or transmit power.

Similarly, if sender821used multiple Tx beams or QCL to transmit RTS (and/or CSI-RS), the receiver822may determine a preferred Tx beam of sender821(e.g., based on RSSI or other measurements taken by receiver822during each symbol that sender821transmitted the RTS). Further, receiver822may use multiple Rx beams to receive the RTS and associated information. If receiver822used multiple Rx beams or QCL to receive RTS and/or CSI-RS, receiver822may evaluate Rx beam tracking and may determine one or multiple preferred Rx beams (e.g., of receiver822).

Receiver822may transmit a CTS to sender821(806). The CTS may be transmitted in one or more symbols of the same self-contained mini slot as the RTS. Receiver822may determine that the medium is clear. Such a determination may be based on sensing/measurements performed during, prior to, and/or subsequent to the backoff/LBT period801. If the medium is not clear, receiver822may not transmit a CTS.

The CTS may be designed to support link adaptation and/or beamforming. For example, the CTS may be transmitted one or more times (e.g., in multiple symbols of the self-contained mini slot) and may use one or more beams (e.g., sequentially, e.g., a different beam for each symbol or each group of multiple groups of symbols). The CTS may be transmitted with additional information, such as CSI-RS.

The CTS may be transmitted with an indication (e.g., or indications) of any link adaptation and/or beamforming parameters determined by receiver822. For example, the CTS may include or be transmitted with indications of requested modulation and coding scheme, rank, precoding matrix indicator (PMI), requested transmit power, preferred Tx beam, and/or preferred Rx beam. In some embodiments, such indications may be transmitted separately.

Sender821may receive and decode the CTS. Sender821may take any number of measurements of, or related to, the CTS. For example, sender821may measure or determine signal strength (e.g., RSSI), CQI, signal quality (e.g., RSRQ), SNR, SINR, etc. of the CTS and/or any CSI-RS.

Sender821may determine link adaptation and/or beamforming (808). For example, based on any CSI-RS that is transmitted with the CTS, the sender821may determine link adaptation parameters, e.g., a preferred modulation and coding scheme, and/or rank, and/or PMI, and/or transmit power.

Similarly, if receiver822used multiple Tx beams or QCL to transmit CTS (and/or CSI-RS), the sender821may determine one or multiple preferred Tx beams (e.g., based on RSSI or other measurements). Further, if sender821used multiple Rx beams or QCL to receive CTS and/or CSI-RS, sender821may evaluate Rx beam tracking and may determine one or multiple preferred Rx beams.

Sender821and receiver822may exchange data (810). The period of time of the data exchange may be referred to as a data communication stage, and may include one or more slots (e.g., self-contained mini slots).

In some embodiments, during the data communication stage, sender821may (e.g., additionally or alternatively) transmit data to a different device (e.g., other than receiver822), e.g., as indicated by destination information sent with the RTS. For example, sender821may transmit data to another device on a network associated with or provided by receiver822.

Sender821and receiver822may use/implement any link adaptation and/or beamforming parameters or information determined previously. The exchange of data may also be performed using any additional information (e.g., TXOP, duration, BWP, etc.) indicated by (e.g., or with) the RTS and/or CTS. The exchange of data may include transmissions from the sender821to the receiver822. In some embodiments, data may also be transmitted from the receiver822to the sender821.

Sender821and receiver822may initiate a next data cycle, e.g., may start a new backoff/LBT period in response to one device having data to transmit to the other device. Any number of data cycles may occur between the devices. Either or both of the devices may also participate in any number of data cycles with other devices.

FIG. 9is a time/frequency diagram illustrating an exemplary sequence of RTS/CTS messages. Time is illustrated on the horizontal access and frequency on the vertical axis.

During a 1stdata cycle (901), the devices may first wait a back-off and LBT stage (901a).

During an RTS/CTS stage (901b), the sender (e.g.,821) may transmit an RTS (951) during a first symbol (901b1), the sender and receiver (e.g.,822) may wait two symbols (e.g., empty symbols), and the receiver may transmit a CTS (952) during a fourth symbol (901b4). The RTS/CTS stage (901b) may be a self-contained mini slot. The RTS and CTS may each be transmitted using small BWP (e.g., the same BWP as illustrated, or different BWPs). The RTS may contain information (e.g., BWP, duration, destination, etc.) for a data communication stage. CSI-RS (961a,961b) may be transmitted concurrently (e.g., using different frequency resource elements than the RTS/CTS) with either or both of the RTS/CTS (e.g., during symbols901b1or901b4, respectively). Note that both symbols901b1and901b4illustrate CSI-RS961(a and b, respectively) at five frequency locations; however any number of frequency locations may be used for CSI-RS. Either or both of the sender and/or receiver may determine link adaptation and/or beamforming based on the RTS, CTS, and/or CSI-RS.

Following the RTS/CTS stage, the devices may exchange data in a data communication stage (901c). The sender and receiver may implement any link adaptation and/or beamforming parameters determined based on the RTS, CTS, and/or CSI-RS. The data communication stage may include a TXOP. The sender may use a large BWP (953) to transmit data. At the conclusion of the data communication stage, the devices may switch back to small BWP for next CTS/RTS stage.

During a second data cycle (902), the devices may first wait a back-off and LBT stage. During an RTS/CTS stage, the sender may transmit an RTS during a first symbol, the sender and receiver may wait two symbols, and no CTS (954) may be received by the sender during a fourth symbol. For example, the receiver may not transmit a CTS because it may determine that the medium is not clear. Based on not receiving a CTS, the sender may determine that the medium is not clear for data communications (e.g., a failed RTS/CTS handshake). Thus, the devices may conclude the second data cycle, e.g., without a data communication stage. CSI-RS may or may not be transmitted by the receiver or received by the sender during the fourth symbol of the RTS/CTS stage.

During a third data cycle (903), the devices may again successfully perform an RTS/CTS handshake and may proceed to communicate data, e.g., as illustrated in and described with respect to the first cycle (901).

It will be appreciated that the sequence ofFIG. 9is exemplary only. Other numbers of data cycles and other patterns of successful vs. failed RTS/CTS handshakes are possible according to embodiments.

FIG. 10is a time/frequency diagram illustrating an exemplary sequence of RTS/CTS messages. Time is illustrated on the horizontal access and frequency on the vertical axis. Tx and Rx beams are illustrated.

A mini slot may be configured with 6 symbols (1001-1006) for downlink (e.g., RTS) and 2 symbols (1008-1009) for uplink (e.g., CTS). It will be appreciated that the directions may be reversed (e.g., downlink may correspond to CTS). Any number of symbols (e.g., zero or more) may occur between the RTS and CTS symbols (1007).

The RTS sender may sweep 3 Tx beams and the RTS receiver may sweep 2 Rx beams during the 6 RTS symbols. As shown, during the first two symbols (1001-1002), the sender may transmit RTS on a (e.g., small) BWP (1051), and may use a first Tx beam (1071). The sender may also transmit CSI-RS using one or more other BWPs (1061) at the same time. The receiver may use a first Rx beam (1081) during the first symbol (1001) and a second Rx beam (1082) during the second symbol (1082). During the next two symbols, the sender may continue to transmit RTS and CSI-RS (e.g., using the same or different BWPs), using a second Tx beam. During the next two symbols, the sender may use a third Tx beam. The receiver may continue alternating between the first and second Rx beams for the third to sixth symbols. The receiver may determine which of the two Rx beams and which of the three Tx beams provide the best directional communication link characteristics (e.g., beamforming). The receiver may also determine link adaptation based on measurements of the RTS and/or CSI-RS.

During the CTS symbols (1008-1009), the receiver may transmit the CTS (and possibly reference signals, e.g., sounding reference signals (SRS)) using a Tx beam (1091) that corresponds to the determined Rx beam with the best characteristics. The receiver may further send information (e.g., TCI) to the sender identifying the Tx beam (e.g., of the sender) that the receiver determined provided the best characteristics. The sender may sweep through two (e.g., or any number of) Rx beams (1092), and may thus gather additional beamforming information. It will be appreciated that both the sender and the receiver may perform beam sweeps using any number of beams during the CTS symbols (e.g., as illustrated for the RTS symbols1001-1006, among various possibilities). Additional CTS symbols may be used to support such beam sweeps, according to some embodiments. The additional beamforming information gathered during the CTS symbols may allow for better beamforming, e.g., in the case that beam reciprocity is not achieved. The sender may transmit the additional beamforming information gathered during the CTS symbols to the receiver.

In the following, exemplary embodiments are provided.

In one set of embodiments, a method for operating a wireless device may comprise: at the wireless device, during a self-contained mini slot: receiving a request to send (RTS) from a second device during a first one or more symbols of the self-contained mini slot; in response to receiving the RTS, determining that a wireless medium associated with the RTS is clear; determining at least one of link adaptation information and beamforming information, wherein said determining is based on the RTS; and in response to determining that the wireless medium associated with the RTS is clear, transmitting a clear to send (CTS) to the second device during a second one or more symbols of the self-contained mini slot, wherein the CTS comprises an indication of the at least one of link adaptation information and beamforming information.

In some embodiments, the RTS may comprise CSI-RS, wherein the at least one of link adaptation information and beamforming information comprises a modulation and coding scheme.

In some embodiments, the method may further comprise: measuring signal strength of the CSI-RS, wherein the modulation and coding scheme is based at least in part on the signal strength of the CSI-RS.

In some embodiments, said receiving the RTS, may comprise using multiple Rx beams to receive the RTS, wherein the at least one of link adaptation information and beamforming information comprises a preferred Rx beam.

In some embodiments, the method may further comprise: taking measurements during each of the first one or more symbols of the self-contained mini slot; wherein the at least one of link adaptation information and beamforming information comprises a preferred Tx beam, wherein the preferred Tx beam is based on the measurements.

In some embodiments, the method may further comprise: receiving data from the second device, using the at least one of link adaptation information and beamforming information.

In another set of embodiments, an apparatus may comprise a processing element and may be configured to cause a wireless device to: receive a request to send (RTS) from a second device during a first one or more symbols of a self-contained mini slot, wherein the RTS is received on a wireless medium; determine that the wireless medium is clear; transmit a clear to send (CTS) to the second device during a second one or more symbols of a self-contained mini slot, wherein transmitting the CTS is in response to receiving the RTS and determining that the wireless medium is clear.

In some embodiments, the RTS may be received in a first small bandwidth part, and the CTS may be transmitted in a second small bandwidth part.

In some embodiments, the second small bandwidth part may be the same as the first small bandwidth part.

In some embodiments, the CTS may support link adaptation.

In some embodiments, the CTS may support beamforming.

In another set of embodiments, a method for operating a wireless device may comprise: at the wireless device, during a self-contained mini slot: transmitting a request to send (RTS) and channel state information reference signals (CSI-RS) to a second device; and receiving a clear to send (CTS) from the second device, wherein the CTS comprises link adaptation information based on the CSI-RS; and after the self-contained mini slot, transmitting data to the second device, wherein said transmitting is in response to receiving the CTS and utilizes the link adaptation information.

In some embodiments, the transmission medium may comprise unlicensed spectrum.

In some embodiments, the RTS may be a 5G transmission and/or the CTS may be a 5G transmission.

In some embodiments, the method may further comprise: determining that a transmission medium is clear, wherein said transmitting the RTS is based on determining that the transmission medium is clear.

In some embodiments, the CSI-RS may be transmitted at the same time as the RTS and on a different frequency than the RTS.

In another set of embodiments, an apparatus may comprise a processing element and may be configured to cause a wireless device to: determine that a transmission medium is clear; transmit a request to send (RTS) to a second device during first symbols of a self-contained mini slot, wherein transmitting the RTS is based on the determination that the transmission medium is clear; receive a clear to send (CTS) from the second device during one or more second symbols of a self-contained mini slot; and transmit data to the second device using the beamforming information in response to the CTS.

In some embodiments, the RTS may comprise information about a requested transmission, wherein the data is transmitted to the second device according to the information about the requested transmission.

In some embodiments, the wireless device may transmit the RTS using multiple beams, wherein the wireless device sequentially transmits the RTS using each of the multiple beams for one or more of the first symbols, wherein the CTS comprises beamforming information.

In another set of embodiments, an apparatus may comprise a processing element and may be configured to cause a wireless device to: during a self-contained mini slot: transmit a request to send (RTS) to a second device during a first one or more symbols of the self-contained mini slot; receive a clear to send (CTS) from the second device during a second one or more symbols of the self-contained mini slot; and determine one or more of link adaptation and beamforming information; and after the self-contained mini slot, exchange data with the second device in response to the CTS and using the one or more of link adaptation and beamforming information.