Detection of directional channel access

Abstract

Methods are provided for using unlicensed transmission spectrum in a cellular communication network. UEs are allowed to transmit, e.g., on a random access channel (RACH), for a short period of time without performing a listen-before-transmit procedure. Base stations perform a listen-before-transmit procedure and schedule UE transmissions on available transmission spectrum. UEs can perform a listen-before-transmit procedure and use power differences between interlaces to determine whether to allow the UE to transmit.

Description

Technical Field

[0001] This disclosure relates to channel access detection, and in particular, such detection is performed prior to directed transmission. Background Technology

[0002] Wireless communication systems such as third-generation (3G) mobile phone standards and technologies are well-known. The 3G Partnership (3GPP) has developed such 3G standards and technologies. Generally speaking, third-generation wireless communication has been developed to the point of supporting macro cell mobile phone communication, and communication systems and networks have evolved towards broadband and mobile systems.

[0003] In a cellular wireless communication system, User Equipment (UE) connects to a Radio Access Network (RAN) via a radio link. The RAN includes a set of base stations that provide radio links to UEs located in cells covered by those base stations, and includes an interface connecting to the Core Network (CN), which has the function of controlling the overall network. It is understood that the RAN and CN each perform corresponding functions related to the overall network. For convenience, the term "cellular network" will be used to represent the combination of the RAN and CN, but it is understood that the term is also used to represent the individual systems performing the disclosed functions.

[0004] The 3rd Generation Partnership Project (3GPP) has developed the so-called Long Term Evolution (LTE) system, namely the Evolved Universal Mobile Communications System Territorial Radio Access Network (E-UTRAN), for mobile access networks supported by one or more macro cells called eNodeBs or eNBs (evolved NodeBs). More recently, LTE has further evolved into the so-called 5G or New Radio (NR) system, in which one or more cells are supported by base stations called gNBs. When NR was first proposed, it utilized the Orthogonal Frequency Division Multiplexing (OFDM) physical transmission format.

[0005] The NR protocol aims to provide the option of operating in unlicensed radio bands (known as NR-U). When operating in unlicensed radio bands, the gNB and UE must compete with other devices for physical media / resource access. For example, Wi-Fi, NR-U, and LAA may use the same physical resources.

[0006] In 3GPP design, unlicensed spectrum operation employs "Listen-before-talk (LBT)" as a channel access procedure. Therefore, radio transmitters are required to perform a clear channel assessment (CCA) check before transmitting. CCA involves energy detection (ED) over a specified period, referencing a threshold (ED threshold), to determine if the channel is occupied or idle. If the channel is occupied, a random back-off is applied within the contention window to minimize the duration of channel idle time before the transmitter can transmit. This introduces randomness among competing devices, thus avoiding collisions. To protect the transmission of Wi-Fi acknowledgment (ACK) messages, a delay period (e.g., 43 microseconds) is applied after each occupied CCA slot before another back-off to maximize traffic. Once a transmitter gains access to the channel, it is only allowed to transmit for a limited period, known as the maximum channel occupancy time (MCOT). To differentiate channel access priorities based on the type of traffic served (e.g., VoIP, video, all-in-the-way transmission, or background transmission), four LBT priority categories are defined, each with a different contention window size (CWS) and MCOT, as described in Section 4.1.2 of TS 37.213. Parameter m p The delay period is used to calculate the delay period when the channel is found to be occupied; the delay period is longer for lower priority categories.

[0007] For the 6 GHz unlicensed spectrum, the standards-setting organization has defined a single detection slot or CCA slot as having a duration of 9 microseconds, while for the 60 GHz unlicensed spectrum, it is defined as having a duration of 5 microseconds. Furthermore, the duration for energy detection within a detection slot has also been specified.

[0008] The base station (eNB / gNB) executes a Type 1 downlink channel access procedure, where the time span of the detection slots that are detected as idle before downlink transmission begins is randomized. Furthermore, whenever a channel is found to be occupied, the base station will back off with a delay period corresponding to the channel access priority used. The Type 1 procedure is primarily used for initial channel access to facilitate the majority of data transmission.

[0009] The base station (eNB / gNB) executes a Type 2 downlink channel access procedure, where the time span of the detection slots detected as idle before downlink transmission begins is deterministic. This is primarily used for data transmission when the same base station or UE has previously established channel access. This type of channel access is also permitted for the transmission of short-duration control signaling, such as discovery bursts.

[0010] Similar to downlink type 1 and type 2 channel access, uplink type 1 and type 2 channel access procedures have also been defined, in which the UE will perform channel access with random time periods or fixed time periods, respectively.

[0011] The NR protocol has introduced beam-based operation, allowing base stations to transmit in up to 64 beams in different directions. Beamforming technology is particularly important when operating at higher transmission frequencies due to higher path loss. For example, there is a significant amount of unlicensed spectrum available in the 60 GHz band.

[0012] The following disclosure relates to various improvements to cellular wireless communication systems. Summary of the Invention

[0013] This "Summary" is provided to introduce, in a simplified form, some selections of concepts that will be further described in the following "Detailed Description". This "Summary" is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0014] A method for performing a channel access procedure is provided, the method being performed by a user equipment (UE) using an unlicensed transmission spectrum, the method comprising the steps of: a pre-transmission listening detection operation, wherein power on multiple interleavings is detected; a total received power is compared with a first threshold; if the detected total power is lower than the threshold, transmission is permitted; otherwise, if the detected total power is higher than the threshold; a power difference detected between the highest and lowest power interleavings is calculated; and if the difference is higher than a second threshold, transmission is permitted; otherwise, if the difference is lower than the second threshold, transmission is not permitted.

[0015] The detection operation that listens before transmission can be an omnidirectional operation or a directional operation.

[0016] The UE can apply an offset to the first threshold.

[0017] The offset can be selected to compensate for beamforming imbalance between the UE and the associated base station.

[0018] The offset can be received from the base station.

[0019] The offset can be semi-static or dynamic.

[0020] The offset may be received in Radio Resource Control (RRC) signaling or in Downlink Control Information (DCI) messages.

[0021] The offset can be UE-specific or cell-specific.

[0022] A UE is provided that is configured to perform the methods described herein.

[0023] A method is provided for communication between a base station and a user equipment (UE) in a cellular network using unlicensed transmission spectrum. The method includes: allowing the UE to transmit to the base station for a maximum of a first maximum channel occupancy time without performing a pre-transmission listening procedure; and at the base station, executing a pre-transmission directional listening procedure and scheduling the UE to perform a transmission for a maximum of a second maximum channel occupancy time, wherein the first maximum channel occupancy time is less than the second maximum channel occupancy time.

[0024] The first maximum channel occupancy time can be valid for a single packet transmission.

[0025] The first maximum channel occupancy time can be valid for a single random access channel (RACH) transmission.

[0026] A cellular communication system is provided, which is configured to perform the methods described herein.

[0027] The present invention will now be described in detail with reference to the accompanying drawings. Attached Figure Description

[0028] The present invention will be described below by way of example only, in conjunction with the accompanying drawings, to provide further details, aspects, and embodiments. For simplicity and clarity, elements in the drawings are shown, and these elements are not necessarily drawn to scale. The same reference numerals are used throughout the various drawings for ease of understanding.

[0029] Figure 1 Selected components in a cellular wireless communication network are illustrated;

[0030] Figure 2 The limitations of pre-transmission directional listening are illustrated; and

[0031] Figure 3 The diagram illustrates the interference cone-shaped regions caused by different directional beams; and

[0032] Figure 4 The method of listening before transmitting is illustrated. Detailed Implementation

[0033] Those skilled in the art will recognize and understand that the specific details of the described examples are merely illustrative of some embodiments, and that the teachings set forth herein apply to various alternative configurations.

[0034] Figure 1 This diagram illustrates three base stations (e.g., eNB or gNB, depending on the specific cellular network standard and terminology) forming a cellular network. Typically, each base station is deployed by the cellular network operator to provide geographical coverage for UEs in that area. These base stations form a Radio Area Network (RAN). Each base station provides radio signal coverage for UEs in its area or cell. These base stations are interconnected via an X2 interface and connected to the core network via an S1 interface. As will be understood, only some basic details are shown here to illustrate the key characteristics of a cellular network. A PC5 interface is provided between multiple UEs for sidelink (SL) communication. Figure 1 The related interface and component names are for illustrative purposes only, and different systems operating on the same principles may use different naming conventions.

[0035] Each base station includes the hardware and software for implementing RAN functions, including communication with the core network and other base stations, the transmission of control and data signals between the core network and the UE, and maintaining or sustaining wireless communications for the UE associated with each base station. The core network includes the hardware and software for implementing network functions, such as overall network management and control, and the routing of calls and data.

[0036] The combination of unlicensed spectrum channel access procedures and beamforming transmission presents a series of new challenges for system design. The Listen Before Transmit (LBT) process in channel access procedures can employ omnidirectional or directional detection, but each may have limitations.

[0037] Figure 2 An example is shown where a base station uses beam 200 to communicate with two UEs, UE1 and UE2. UE1 uses beam 201, and UE2 uses beam 202. If UE1 and UE2 perform directional LBT on beams 201 and 202, they will not detect each other's transmissions, even if these transmissions would collide at the base station. If omnidirectional LBT is used, UE1 can detect UE2, but UE2 may not detect UE1 because the transmission is directed to the base station, not to UE2.

[0038] In systems where beamforming is used in both directions of the UE / base station link, the receiving beams of the UE and the base station are quasi-orthogonal. Therefore, interference energy detected at the base station's receiver will not affect the UE's receiver (and vice versa). Thus, directional LBT can only be used to avoid transmission / reception conflicts between the base station and the UE.

[0039] like Figure 3 As shown, the number of antennas used for beamforming at a base station is typically much greater than that at a UE (e.g., 128 elements per plane at a base station, compared to only 4 to 8 elements per plane at a UE). Therefore, the base station's beam is much narrower than the UE's beam. Consequently, a UE performing LBT will detect interference signals from a wider area than the area actually detected by the base station, thus overestimating the impact of the interference.

[0040] LBT (omnidirectional and directional) at the UE may not predict and avoid intra-cell interference that may occur at the base station receiver. However, the need for LBT may be reduced in beamforming systems, especially those employing very narrow beams with high angular sensitivity that reduce collision variations. Since each UE typically points towards the base station, the chance of interference between UE transmissions and other UE receptions is reduced, but this does not include interference from non-cellular systems (e.g., WiFi / WiGig) where LBT might be helpful. Therefore, there is a need for an LBT system for efficient channel access procedures while simultaneously supporting beamforming transmissions in unlicensed spectrum.

[0041] The following discloses three examples of LBT procedures that improve upon the shortcomings of existing technologies. In the first approach, the UE is allowed access to transmission resources for short-term directional transmissions without performing an LBT procedure. The allowed MCOT can be reduced compared to the MCOT obtained by performing an LBT procedure, but is sufficient for the UE to initiate uplink transmission. In the second approach, the UE uses directional LBT before transmission. The UE distinguishes detected energy based on its source to determine whether transmission should be considered. In the third approach, omnidirectional LBT is used before transmission, and interference discrimination is applied to determine whether detected energy affects transmission capability.

[0042] In the first procedure, the UE is allowed to perform short-term transmissions without performing LBT, even if these short-term transmissions are not scheduled by the base station. For example, the duration of the MCOT may be shortened, including the transmission of a single data packet. This allows the UE to perform RACH transmissions to establish a connection with the base station. The standard MCOT is obtained by performing a directed LBT procedure and scheduling the UE to transmit within that MCOT by the base station. Directed LBT performed by the base station effectively avoids intrasystem collisions. Therefore, a combination of directed LBT at the base station and no LBT at the UE is employed.

[0043] As mentioned above, directional LBT at the UE is unlikely to help avoid intra-system conflicts, but it may be helpful for inter-system coexistence. The directional LBT procedure can thus be improved by enabling the UE to distinguish between interference received from intra-system sources and interference received from other systems (e.g., WiFi / WiGig). The following discloses techniques for performing such "interference-aware LBT".

[0044] In the first example, intra-system transmissions (specifically NR-U) can be identified by energy detection across different interlaces available for transmission. The UE can compare the energy levels detected across different interlaces, and if the difference between two or more interlaces is greater than a threshold (e.g., 3dB or 6dB), it can be inferred that the energy originates from an intra-system UE transmission (NR-U) on an interlace. Conversely, if the total energy exceeds the threshold, but the difference between interlaces is small, it can be inferred that the signal originates from a different system (e.g., WiFi, WiGig, or a base station not using interlace-based transmissions). If non-intra-system transmissions are detected, consideration should be given to ensuring fair access to transmission resources.

[0045] In summary, the UE performs LBT with interleaving-based energy detection. Energy variations detected for each interleaving are used to distinguish intra-system (NR-U UL) transmissions from other transmissions. Interleaving-based energy detection does not add complexity because energy detection is performed on all Physical Resource Blocks (PRBs). Efficiency would be reduced if the base station allocated all interleavings to a single PUSCH channel, as this would reduce (or eliminate) variations between interleavings, even for intra-system UE transmissions.

[0046] If the UE detects an intra-system UL transmission on a certain interleaving, the UE can select one or more different interleavings for transmission, on which low energy is detected. Since the interleavings are orthogonal, the transmission at the base station can be detected and decoded. This approach may be particularly suitable for configured-grant transmissions, where the interleavings are predetermined and relatively static.

[0047] In another example, the UE can execute the LBT procedure on a bandwidth wider than both the standard NR-U operating bandwidth and the NR-U bandwidth. If additional energy is detected in this wider bandwidth, it can be inferred that the transmission originates from a different system, such as WiGig operating on a 2 GHz bandwidth.

[0048] Figure 4 A flowchart illustrating the method for differentiation during the LBT procedure is shown. In step 400, the UE performs energy detection on at least the interleavings in the LBT procedure to determine the power in each interleaving. In step 401, the total detected power (across all interleavings) is compared to a threshold. If the total power is below the threshold, the UE is allowed to proceed with the transmission in step 403 because no conflicting transmissions were detected. If the detected power exceeds the threshold, the UE continues to calculate the largest difference between the interleaving power in step 402. If this difference exceeds the threshold, it can be inferred that the detected transmission is within the UE's system on a certain interleaving, allowing the UE to proceed with the transmission in step 403 (or the transmission on the interleaving used by the base station to differentiate directionality, or the transmission using a different interleaving). However, if the difference is below the threshold, it is inferred that the transmission originates from a different system, and the transmission is not permitted. Figure 4 This method can be combined with other LBT procedures at the base station, which can acquire channels and schedule UEs for transmission.

[0049] based on Figure 4 The principles described can be used for directional or omnidirectional energy detection and LBT procedures.

[0050] As described above, the LBT performed by the UE may be affected by beamforming imbalance between the base station and the UE due to differences in beamwidth and associated gain. This can lead to overly pessimistic interference estimates at the UE (because the UE is detecting on a beam wider than the beam the base station will use to receive transmissions). This imbalance can be compensated for by applying an offset to the energy detection threshold at the UE where the beam imbalance difference is estimated. The base station can send this offset to each UE for application, either semi-statically (e.g., in RRC signaling) or dynamically (e.g., in DCI transmissions). This offset may depend on a range of factors, such as the beamforming capabilities of each device, the beams used, and the beam topology (distance between the UE and the base station, the angle between beams, and the beamwidth).

[0051] The offset can be defined based on individual characteristics of each UE or on a cell basis. These techniques can also be combined; for example, a cell-specific offset can be defined, and if some UEs require it due to their characteristics, the cell-specific offset can be modified with individual UE values. For example, a UE may have high beamforming capabilities and therefore require less offset. This cell-specific value can be indicated in the System Information Block (SIB) so that the UE can use it immediately, such as using UplinkConfigCommonSIB / BWP-UplinkCommon / rach-ConfigCommon, pucch-ConfigCommon, and pusch-ConfigCommon, and the UE-specific value can be provided in the BWP-UplinkDedicated IE.

[0052] As mentioned earlier, these techniques can be applied to both directional and omnidirectional LBT procedures.

[0053] Although not shown in detail, any device or apparatus forming part of the network may include at least a processor, a storage unit, and a communication interface, wherein the processor unit, storage unit, and communication interface are configured to perform the methods of any aspect of the present invention. Further options and choices are described below.

[0054] The signal processing functions of embodiments of the present invention, particularly the gNB and UE, can be implemented using computing systems or architectures known to those skilled in the art. Computing systems such as desktop, laptop, or notebook computers, handheld computing devices (PDAs, cellular phones, PDAs, etc.), mainframes, servers, clients, or any other type of dedicated or general-purpose computing device that may be desired or suitable for a given application or environment can be used. The computing system may include one or more processors, which can be implemented using general-purpose or dedicated processing engines (e.g., microprocessors, microcontrollers, or other control modules).

[0055] The computing system may also include main memory, such as random access memory (RAM) or other dynamic memory, for storing instructions and information to be executed by the processor. Such main memory may also be used to store temporary variables and other intermediate information to be executed by the processor during instruction execution. Similarly, the computing system may include read-only memory (ROM) or other static storage devices for storing static information and instructions for the processor.

[0056] The computing system may further include an information storage system, which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, floppy disk drive, magnetic tape drive, optical disc drive, compact disc (CD) or digital video drive (DVD) read or write drive (R or RW), or other removable or fixed media drive. The storage medium may include, for example, a hard disk, floppy disk, magnetic tape, optical disc, CD or DVD, or other fixed or removable media read or written by a media drive. The storage medium may include a computer-readable storage medium having specific computer software or data stored therein.

[0057] In alternative embodiments, the information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. Such components may include, for example, removable storage units and interfaces, such as program boxes and box interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, as well as other removable storage units and interfaces that allow software and data to be transferred from the removable storage units to the computing system.

[0058] The computing system may also include a communication interface. Such a communication interface can be used to allow software and data to be transferred between the computing system and external devices. Examples of communication interfaces may include modems, network interfaces (such as Ethernet or other NIC cards), communication ports (such as, for example, Universal Serial Bus (USB) ports), PCMCIA slots and cards, and so on. Software and data transmitted via the communication interface are in the form of signals, which may be electrical, electromagnetic, and optical signals, or other signals that can be received by the communication interface medium.

[0059] In this document, the terms "computer program product," "computer-readable medium," etc., can generally be used to refer to tangible media, such as memory, storage devices, or storage units. These and other forms of computer-readable media can store one or more instructions for use by a processor, including a computer system, to cause the processor to perform specified operations. Such instructions, generally referred to as "computer program code" (which may be grouped as computer programs or otherwise), when executed, enable a computing system to perform the functions of embodiments of the present invention. Note that the code may directly cause the processor to perform specified operations, be compiled to do so, and / or be combined with other software, hardware, and / or firmware elements (e.g., libraries for performing standard functions) to do so.

[0060] The non-transitory computer-readable medium may include at least one of the group consisting of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, and flash memory. In embodiments where the elements are implemented using software, the software may be stored in the computer-readable medium and loaded into the computing system, for example, using a removable storage drive. The control module (in this example, software instructions or executable computer program code), when executed by a processor in the computer system, causes the processor to perform the functions of the invention as described herein.

[0061] Furthermore, the concepts of this invention can be applied to any circuit used to perform signal processing functions within a network element. It is further foreseeable that, for example, semiconductor manufacturers can utilize these concepts when designing stand-alone devices and / or any other subsystem elements such as application-specific integrated circuits (ASICs) or digital signal processors (DSPs).

[0062] It will be appreciated that, for clarity, the above description has referred to embodiments of the invention with reference to a single processing logic. However, the inventive concept can also be implemented by a number of different functional units and processors to provide signal processing functionality. Therefore, references to specific functional units should be considered merely as references to appropriate means for providing the described functionality, and not as indications of a strict logical or physical structure or organization.

[0063] Various aspects of the invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The invention can optionally be implemented, at least in part, as computer software running on one or more data processors and / or digital signal processors, or as configurable modular components such as FPGA devices.

[0064] Therefore, the elements and components of embodiments of the present invention can be implemented physically, functionally, and logically in any suitable manner. In fact, the functionality can be implemented in a single unit, in multiple units, or as part of other functional units. Although the invention has been described in conjunction with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is defined only by the appended claims. Furthermore, although certain features have been described in conjunction with specific embodiments, those skilled in the art will recognize that different features of the described embodiments can be combined according to the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0065] Furthermore, although listed individually, multiple means, elements, or method steps may be implemented by a single unit or processor. Additionally, while a single feature may be included in different claims, these may also be advantageously combined, and including a feature in different claims does not imply that such a combination is not feasible and / or advantageous. Moreover, including a feature in a claim of one class does not imply limitation to that class, but rather indicates that the feature is equally applicable to other claim classes where appropriate.

[0066] Furthermore, the order of features in the claims does not imply a specific order in which any feature must be performed, and in particular, the order of individual steps in a method claim does not imply that the steps must be performed in that order. Rather, the steps can be performed in any suitable order. Moreover, singular references do not exclude plurals. Therefore, references to “a,” “first,” “second,” etc., do not exclude plurals.

[0067] Although the invention has been described in conjunction with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is defined only by the appended claims. Furthermore, although certain features have been described in conjunction with specific embodiments, those skilled in the art will recognize that different features of the described embodiments can be combined according to the invention. In the claims, the term "comprising" does not exclude the presence of other elements.

Claims

1. A method for performing a channel access procedure, the method being performed by a user equipment (UE) using an unlicensed transmission spectrum, characterized in that, The method includes the following steps: A pre-transmission monitoring operation is performed, during which the power of multiple interleaved components is detected. The total received power is compared with a first threshold. If the detected total power is lower than the threshold, transmission is allowed; otherwise, If the total detected power is higher than the threshold, the difference in power detected between the highest and lowest power interleaving is calculated, and if the difference is higher than the second threshold, transmission is allowed; otherwise, if the difference is lower than the second threshold, transmission is not allowed.

2. The method according to claim 1, characterized in that, The pre-transmission monitoring detection operation is an omnidirectional operation.

3. The method according to claim 1, characterized in that, The pre-transmission monitoring detection operation is a type of directional operation.

4. The method according to any of the preceding claims, characterized in that, The UE applies an offset to the first threshold.

5. The method according to claim 4, characterized in that, The offset is selected to compensate for beamforming imbalance between the UE and the associated base station.

6. The method according to claim 4, characterized in that, The offset is received from the base station.

7. The method according to claim 4, characterized in that, The offset can be semi-static or dynamic.

8. The method according to claim 6, characterized in that, The offset is received in Radio Resource Control (RRC) signaling or in Downlink Control Information (DCI) messages.

9. The method according to claim 4, characterized in that, The offset is UE-specific.

10. The method according to claim 4, characterized in that, The offset is cell-specific.

11. A user equipment (UE), characterized in that, The UE includes a module for performing the method according to any one of claims 1 to 10.

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