WO2021156796A1

WO2021156796A1 - Methods for controlling channel access mode in unlicensed spectrum

Info

Publication number: WO2021156796A1
Application number: PCT/IB2021/050927
Authority: WO
Inventors: Min Wang; Mai-Anh Phan
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2020-02-06
Filing date: 2021-02-04
Publication date: 2021-08-12

Abstract

There is provided a method in a wireless device, operating in unlicensed or shared spectrum. The method comprises: obtaining an indication of a channel access mode of one or more cells; and selecting a cell from the one or more cells, based on the indication of the channel access mode. A wireless device is also provided for implementing this method. There is further provided method in a network node. The method comprises: receiving a mobility indication from a wireless device; and sending an indication of a channel access mode of one or more neighboring cells operating in unlicensed or shared spectrum, to the wireless device. A network node is also provided for implementing this method.

Description

METHODS FOR CONTROLLING CHANNEL ACCESS MODE IN UNLICENSED

SPECTRUM

RELATED APPLICATIONS

[0001] This application claims the benefits of priority of U.S. Provisional Patent Application No. 62/970,868, entitled “ Controlling channel access mode in unlicensed spectrum’ ’ and filed at the United States Patent and Trademark Office on February 6, 2020, the content of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present description generally relates to wireless communication systems and more specifically to controlling/handling channel access mode in a network node with unlicensed spectrum.

BACKGROUND

[0003] Next generation systems are expected to support a wide range of use cases with varying requirements ranging from fully mobile devices to stationary Internet of Things (IoT) or fixed wireless broadband devices. The traffic pattern associated with many use cases is expected to consist of short or long bursts of data traffic with varying length of waiting period in between (here called inactive state). In New Radio (NR), both Licensed Assisted Access (LAA) and standalone unlicensed (U) operation are to be supported in Third Generation Partnership Project (3GPP). Hence, the procedure of Physical Random Access Channel (PRACH) transmission and/or Scheduling Request (SR) transmission in unlicensed spectrum shall be investigated in 3GPP. [0004] In the following, channel sensing scheme based on Listen Before Talk (LBT), random access procedure and LBT scheme for PRACH and short Physical Uplink Control Channel (sPUCCH) are introduced.

[0005] Channel access procedure in NR unlicensed spectrum

[0006] Listen-before-talk (LBT) is designed for unlicensed spectrum co-existence with other RATs. In this mechanism, a radio device applies a clear channel assessment (CCA) check before any transmission. The transmitter involves energy detection (ED) over a time period compared to a certain threshold (e.g. ED threshold) in order to determine if a channel is idle. In case the channel is determined to be occupied, the transmitter performs a random back-off within a contention window before next CCA attempt. In order to protect the acknowledgement (ACK) transmissions, the transmitter must defer a period after each busy CCA slot prior to resuming back-off As soon as the transmitter has grasped access to a channel, the transmitter is only allowed to perform l transmission up to a maximum time duration (namely, the maximum channel occupancy time (MCOT)). For Quality of Service (QoS) differentiation, a channel access priority based on the service type has been defined. For example, there are four LBT priority classes defined for differentiation of contention window sizes (CWS) and MCOT between services.

[0007] The channel access schemes for NR-based access for unlicensed spectrum can be classified into the following categories:

[0008] Category 1 (Cat 1): Immediate transmission after a short switching gap:

1) This is used for a transmitter to immediately transmit after a Uplink (UL)/Downlink (DL) switching gap inside a Channel Occupancy Time (COT).

2) The switching gap from reception to transmission is to accommodate the transceiver turnaround time and is no longer than 16 ps.

[0009] Category 2 (Cat 2): LBT without random back-off:

1) The duration of time that the channel is sensed to be idle before the transmitting entity transmits is deterministic.

[0010] Category 3 (Cat 3): LBT with random back-off with a contention window of fixed size:

1) The LBT procedure has the following procedure as one of its components. The transmitting entity draws a random number N within a contention window. The size of the contention window is specified by the minimum and maximum value of N. The size of the contention window is fixed. The random number N is used in the LBT procedure to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel.

[0011] Category 4 (Cat 4): LBT with random back-off with a contention window of variable size:

1) The LBT procedure has the following as one of its components. The transmitting entity draws a random number N within a contention window. The size of contention window is specified by the minimum and maximum value of N. The transmitting entity can vary the size of the contention window when drawing the random number N. The random number N is used in the LBT procedure to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel. [0012] For different transmissions in a COT and different channel s/signals to be transmitted, different categories of channel access schemes can be used.

[0013] As described in 3GPP TR 38.889, if absence of Wi-Fi cannot be guaranteed (e.g. by regulation) in the band (sub-7 GHz) where NR-U is operating, the baseline assumption is, the NR- U operating bandwidth is an integer multiple of 20MHz. [0014] Channel access mechanisms need to comply with regulations and may therefore need to be adapted for particular frequency ranges.

[0015] For channel access mechanism, LTE-LAA LBT mechanism is adopted as baseline for 5GHz band and adopted as the starting point of the design for 6GHz band. At least for bands where absence of Wi-Fi cannot be guaranteed (e.g. by regulation), LBT can be performed in bandwidth units of 20 MHz.

[0016] For initiation of a COT by the gNB (operating as a Load Based Equipment (LBE) device), the channel access schemes in Table 1 (see below) are used.

[0017] Table 1: Channel access schemes for initiating a COT by gNB as LBE device

Note: Applicability of an LBT scheme other than Cat 4 LBT for control messages related to initial/random access, mobility, paging, reference signals only, and PDCCH-only transmissions, e.g. "RACH message 4", handover command, Group Common- Physical Downlink Control Channel (GC-PDCCH), or short message paging transmitted either alone or when multiplexed with DRS have been discussed. Further details related to exceptions in this note can be determined when specifications are developed.

[0018] At least for the case where a DL burst follows a UL burst within a gNB-initiated COT and there is no gap larger than 25 ps between any two transmissions in the COT, the channel access schemes in Table 2 (see below) apply for the DL burst following a UL burst.

[0019] Table 2: Channel access schemes for a DL burst follows a UL burst within a gNB-initiated COT as LBE device

Note: a DL burst is defined as a set of transmissions from a given gNB having no gaps or gaps of no more than 16 ps. Transmissions from a gNB having a gap of more than 16 ps are considered as separate DL bursts. [0020] Within a gNB-initiated COT, an UL burst for a UE consisting of one or more of Physical Uplink Shared Channel (PUSCH), PUCCH, PRACH, and Sounding Reference Signal (SRS) follows the channel access schemes in Table 3 (see below).

[0021] Table 3: Channel access schemes for a UL burst within a gNB-initiated COT as LBE device

Note: An UL burst is defined as a set of transmissions from a given UE having no gaps or gaps of no more than 16 ps. Transmissions from a UE having a gap of more than 16 ps are considered as separate UL bursts. The number of LBT attempts within a COT should be determined when specifications are developed.

[0022] For initiation of a COT by the UE, the channel access schemes in Table 4 are used (see below).

[0023] Table 4: Channel access schemes for initiating a COT by UE as LBE device

Note 1: If the COT includes multiple signals/channels with different channel access categories/ priority classes, the highest channel access priority class value and highest channel access category among the channel access priority classes and channel access categories corresponding to the multiple signals/channels applies. Note 2: Applicability of a channel access scheme other than Cat 4 for the following signals/channels have been discussed and details are to be determined when the specifications are developed:

UL control information including Uplink Control Information (UCI) only on PUSCH, e.g. HARQ-ACK, Scheduling Request, and Channel State Information;

Random Access.

[0024] For the Frame Based Equipment (FBE) mode of operation, a gNB acquires COT with Cat 2 immediately prior to the fixed frame period. Within the gNB acquired COT, if a gap is <= 16 ps, Cat 1 channel access scheme can be used by the gNB and associated UEs. Within the gNB acquired COT, if a gap is > 16 ps, Cat 2 channel access scheme should be used by the gNB and associated UEs. Note that these channel access mechanisms are intended to be aligned with any regulations for the FBE operation.

[0025] Handover procedure

[0026] A UE performs RRM measurements according to the configurations provided from the serving gNB, and the gNB is typically responsible for finding a good target cell. Once the handover criteria are met, the gNB sends a handover request to the target cell typically including the UE’s service requirements and capabilities. Based on such information, the target cell may accept or reject the UE. When the UE is accepted, it is provided with new RRC configurations which are suitable for operation in the target cell. The source and target cell may e.g. be configured with different channel access modes.

SUMMARY

[0027] Currently there exist some challenges. For channel access and transmissions in NR-U, the mechanisms and associated signaling adopted by LTE LAA (e.g. standardized QoS Class Identifier (QCI) to access priority mapping for DL and UL, how access priority per logical channel is determined for scheduled UL and autonomous uplink (AUL) transmissions, etc.) are used as the baseline.

[0028] However, it has been agreed in 3 GPP to study necessary changes on channel access mechanisms for NR-U due to the support of two modes of operations, i.e., Load Based Equipment (LBE) and Frame Based Equipment (FBE). For FBE, a device performs a clear channel assessment per fixed frame period for a duration of single 9us observation slot. If the channel is found to be busy after CCA operation, the equipment shall not transmit during this fixed frame period. The fixed frame period can be set to a value between 1 and 10 ms and can be adjusted once every 200ms. If the channel is found to be idle, the equipment/device can transmit immediately up to a duration referred to as channel occupancy time, after which the equipment shall remain silent for at least 5% of said channel occupancy time. At the end of the required idle period, the equipment can resume CCA for channel access.

[0029] For LBE, before a data transmission, a device must sense the medium to be idle for a defer period and a random backoff phase comprising of N9 ps observation slots (Tsl). The defer period depends on the Channel Access Priority Class of the data and consists of (16+m_p*Tsl), m_p as defined in Table 1, such that classes with higher priority have to defer for a shorter period and thus, increasing the probability for successful channel access and transmission. A is a counter drawn randomly within a dynamic contention window [0, CW] This procedure, commonly known as exponential backoff or category 4 (CAT4) LBT, is designed to randomize the start of transmissions from different nodes that want to access the channel at the same time. N can be decremented after each idle Tsl. If the energy received in a Tsl is sensed to be above the ED threshold, then the backoff process is suspended and the counter is frozen. The backoff process is resumed and the counter can be decremented once the medium has been idle for the duration of a defer period. Once the counter reaches zero, the node is allowed to initiate a channel occupancy (txOP) and transmit for a maximum transmit duration (MOOT).

Table 1: Channel access priority class for hot 1 DL and UL [0030] As described earlier, in LBE mode, a UE or gNB may choose a LBT option among Categories 1, 2, 3 and 4 to sense a channel, while in FBE mode, a UE or gNB may choose LBT option among Categories 1 and 2 to sense a channel. The two modes, FBE and LBE, are applicable exclusively from each other.

[0031] In RAN1#99, the following agreements have been made for the FBE operation: 1) Fixed Frame Period (FFP) configuration is included in System Information block (SIB)-l; 2) FFP configuration can be signaled for a UE with UE-specific Radio Resource Control (RRC) signaling. [0032] From the agreements, the FBE configuration is typically a cell specific setting, which means that a cell is configured with either FBE or LBE channel access type at a time. This makes sense since both channel access modes operate exclusively from each other. However, it is expected that a cell may change from one mode to another mode.

[0033] Given the above, for a cell configured with an access mode which is not aligned with a UE’s capability (in terms of supported access mode), there may be several issues regarding cell access control.

[0034] Issue 1: for cell selection/reselection, how does the UE handle it in case there is a cell which is configured with a different channel access mode from the UE?

[0035] Issue 2: for a UE that has triggered a handover, how does the UE select the target cell which supports the right channel access mode?

[0036] Issue 3: for a UE that has triggered RRC connection reestablishment, how does the UE select the cell supporting the right channel access mode to re-establish the RRC connection? [0037] The embodiments herein address the above issues. For example, mechanisms for an NR- U cell/system to perform access control for a UE according to supported and/or configured channel access mode (i.e., FBE or LBE) are proposed. The proposed mechanisms cover UEs in RRC IDLE, and RRC CONNECTED states. Furthermore, a mechanism on how to achieve a switch of channel access mode is also proposed.

[0038] According to one aspect, some embodiments include methods performed by a wireless device. For example, a method can comprise: obtaining an indication of a channel access mode of one or more cells; and selecting a cell based on the indication of the channel access mode.

[0039] According to another aspect, some embodiments include a wireless device configured, or operable, to perform one or more functionalities (e.g. actions, operations, steps, etc.) as described herein.

[0040] In some embodiments, the wireless device may comprise one or more communication interfaces configured to communicate with one or more other radio nodes and/or with one or more network nodes, and processing circuitry operatively connected to the communication interface, the processing circuitry being configured to perform one or more functionalities as described herein. In some embodiments, the processing circuitry may comprise at least one processor and at least one memory storing instructions which, upon being executed by the processor, configure the at least one processor to perform one or more functionalities as described herein.

[0041] In some embodiments, the wireless device may comprise one or more functional modules configured to perform one or more functionalities as described herein.

[0042] According to another aspect, some embodiments include a non-transitory computer- readable medium storing a computer program product comprising instructions which, upon being executed by processing circuitry (e.g., at least one processor) of the wireless device, configure the processing circuitry to perform one or more functionalities as described herein.

[0043] According to another aspect, some embodiments include methods performed by a network node. For example, a method can comprise: receiving a mobility indication from a wireless device; and sending an indication of a channel access mode of neighboring cells operating in unlicensed or shared spectrum, to the wireless device.

[0044] According to yet another aspect, some embodiments include a network node configured, or operable, to perform one or more functionalities (e.g. actions, operations, steps, etc.) as described herein.

[0045] In some embodiments, the network node may comprise one or more communication interfaces configured to communicate with one or more other radio nodes and/or with one or more network nodes, and processing circuitry operatively connected to the communication interface, the processing circuitry being configured to perform one or more functionalities as described herein. In some embodiments, the processing circuitry may comprise at least one processor and at least one memory storing instructions which, upon being executed by the processor, configure the at least one processor to perform one or more functionalities as described herein.

[0046] In some embodiments, the network node may comprise one or more functional modules configured to perform one or more functionalities as described herein.

[0047] According to yet another aspect, some embodiments include a non-transitory computer- readable medium storing a computer program product comprising instructions which, upon being executed by processing circuitry (e.g., at least one processor) of the network node, configure the processing circuitry to perform one or more functionalities as described herein.

[0048] The advantages/technical benefits of the embodiments are as follows: [0049] - With the proposed mechanisms, a cell or UE operating in unlicensed/shared spectrum is able to select the most suitable channel access mode.

[0050] This summary is not an extensive overview of all contemplated embodiments and is not intended to identify key or critical aspects or features of any or all embodiments or to delineate the scope of any or all embodiments. In that sense, other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Exemplary embodiments will be described in more detail with reference to the following figures, in which:

[0052] Figure 1 is a signalling flow between a User Equipment (UE) and a network node, for handling channel access mode, according to an embodiment.

[0053] Figure 2 is another signalling flow between a UE and a network node, for handling channel access mode, according to an embodiment.

[0054] Figure 3 illustrates a flow chart of a method in a wireless device, in accordance with an embodiment.

[0055] Figure 4 illustrates a flow chart of a method in a network node, in accordance with an embodiment.

[0056] Figure 5 illustrates one example of a wireless communications system in which embodiments of the present disclosure may be implemented.

[0057] Figures 6 and 7 are block diagrams that illustrate a wireless device according to some embodiments of the present disclosure.

[0058] Figures 8 and 9 are block diagrams that illustrate a network node according to some embodiments of the present disclosure.

[0059] Figure 10 illustrates a virtualized environment of a network node, according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

[0060] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments. Upon reading the following description in light of the accompanying figures, those skilled in the art will understand the concepts of the description and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the description. [0061] In the following description, numerous specific details are set forth. However, it is understood that embodiments may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of the description. Those of ordinary skill in the art, with the included description, will be able to implement appropriate functionality without undue experimentation. [0062] References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0063] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0064] Embodiments in this disclosure are described in the context of NR in unlicensed/shared spectrum (NR-U). However, they are not limited to NR-U scenarios only. They are also applicable to other unlicensed operation scenarios such as LTE LAA/eLAA/feLAA. Furthermore, the terms “channel access mode” or “LBT mode” are used to mean/describe that a gNB/UE operates as either “an FBE device” or “a LBE device”.

[0065] Example 1: Reducing handover latency exploiting knowledge on channel access modes used by neighboring cells

[0066] Figure 1 illustrates a first example. In step 110, a UE triggers a handover event (such as a serving cell change, Primary Cell (PCell) or Primary Secondary Cell (PSCell) change in a DC scenario). This handover event is signaled to the gNB (step 120). The serving gNB selects a target cell (step 140) based on measurement results reported by the UE (step 130). To select the target cell which is configured with the suitable channel access mode for the UE, the serving gNB may have two options:

[0067] Option 1: this option follows the legacy handover procedure. [0068] Option 2: the serving cell has already exchanged information on the channel access mode with its neighbor cells. For example, the information can be exchanged between cells via signaling such as Radio Resource Control (RRC) or other signaling alternative (e.g., other signaling messages via interfaces X2 or Xn). Alternatively, the information may be signaled to a cell by a core network entity via the Radio Access Network (RAN) and Core Network (CN) interface. Such information may be useful for the serving cell so that the serving cell may apply a coordinated channel access mechanism to avoid inter-cell blocking. In an example, FBE can be applied in all neighboring cells so that the neighboring gNBs can occupy the channel in a synchronized fashion to avoid a cell from blocking another cell. In this case, the serving cell already knows which channel access mode is configured for those neighbor cells. The serving cell can select a target cell based on the following conditions: 1) whether the cell has the strongest radio connections; 2) whether the cell supports the suitable channel access mode for the UE (i.e. FBE or LBE). As a note, the term “cell” in this disclosure may mean a base station location in the cell, which supports the different access modes and allows a UE to access the cell or not.

[0069] After selecting a suitable target cell, the serving cell sends a Handover (HO) Request to the target cell (step 150). The target cell can further reply with the Handover Request Ack message if the requested handover for the UE is accepted by the target cell.

[0070] For either of the 2 options, the serving cell may carry the information of the channel access mode for the selected target cell in the Handover command message (i.e. RRCReconfigureWithSync in NR). Upon reception of the Handover Command message (step 160), the UE can access the target cell according to the indicated channel access mode (step 170). The channel access mode information of the target cell could be also useful for the UE in case the UE supports both FBE and LBE modes.

[0071] Compared to Option 1, Option 2 may yield a shorter latency for the UE to complete the handover, since the serving cell doesn’t need to send the HO request to multiple target cells sequentially. The serving cell can select the target cell supporting the channel access mode fitting the UE from the start. As such, the UE may be prevented from being rejected for its HO request.

[0072] Example 2: UE-based handover decision using channel access mode information from candidate target cells

[0073] Figure 2 illustrates a second example. In step 210, a UE triggers a mobility procedure (such as RRC connection reestablishment or conditional handover), the gNB may provide assistance information to help the UE find a suitable target cell, i.e., the cell with suitable channel access mode for the UE. The gNB may obtain the channel access mode of its neighbor cells (step 220) by receiving/exchanging information from/between the neighbor cells, via X2 or Xn, for example. The assistance information may be provided by the gNB in at least one of the options below. [0074] In a first case, the serving gNB may signal the configured channel access mode of neighbor cells to UEs (step 230). The signaling may be sent by the gNB via System Information Block (SIB) or dedicated RRC signaling or Medium Access Control (MAC) Control Element (CE). Thus, a UE in RRC connected state would know what channel access mode is configured for every target cell prior to the trigger of RRC re-establishment. In case the UE has to perform RRC reestablishment upon occurrence of Radio Link Failure (RLF), the UE can immediately select the cell configured with a channel access mode which is suitable to the UE, to perform RRC reestablishment.

[0075] In a second case, for a conditional handover, the serving gNB may include the channel access mode for every configured candidate target cell to a UE. Such information is useful to the UE especially when the UE is configured with both FBE and LBE.

[0076] For a UE configured with a single channel access mode (either FBE or LBE), it may be unnecessary to include the channel access mode in the candidate target cell configuration, since the UE would assume all configured target cells shall support the same channel access mode as the UE.

[0077] Example 3: Quality of Service (QoS) based channel access mode selection [0078] As a third example, a UE supports both FBE and LBE modes. In this case, the channel access mode may be associated with the QoS configuration for different services. For services with critical QoS requirements such as latency, FBE may be beneficial to be applied. The UE and/or the gNB selects a target cellBWP/LBT subband/channel according to the QoS requirements of the services. As a result, a channel access mode (FBE or LBE) will be prioritized over another mode (LBE or FBE).

[0079] Example 4: event-triggered service switch

[0080] As a fourth example, a UE detecting another cell access mode, e.g. FBE instead of LBE, may start a specific service, e.g. industrial service, which is only supported in a certain channel access mode, and prioritize this channel access mode over the other. The FBE access mode is possible to be detected by the UE, since the FBE-based channel access is only performed at frame boundary. During other periods, the channel is shared between the gNB and UEs.

[0081] Example 5: time-limited cell barring if the cell’s channel access mode is not supported [0082] As a fifth example, for a UE performing cell selection/reselection, via reading signaling such as System Information Block (SIB) signaling, the UE determines if a monitoring cell allows the UE to access the cell based on whether the channel access mode configured in the cell is the same as the one the UE is capable of. In case the UE is not allowed to access the cell, the cell is considered to be barred for the UE for a configured time period. In case the UE is allowed to access the cell, the UE selects the cell and performs further access establishment to the cell. [0083] A cell may be configured with only a single channel access mode (i.e., FBE or LBE). The cell may change to operate with a different channel access mode. In this case, the UE is not allowed to access the cell if the channel access mode of the UE is different from that of the cell. The cell is barred for a configured time period, the UE may try to access the cell again after this period. If the cell has been changed to support the suitable channel access mode for the UE, the UE can access the cell and establish a connection with the cell. Also, the UE could access another suitable cell supporting the UE’s channel access mode.

[0084] A cell may be configured with both FBE and LBE. In one case, FBE is configured in a Bandwidth Part (BWP)/LBT subband/channel, while LBE is configured in another BWP/LBT subband/channel. A UE selects a BWP/LBT subband/channel supporting the channel access mode configured for the UE. In another case, FBE and LBE are enabled for the cell in different time periods. If the cell is barred for a UE within a time period because the enabled channel access mode in the time period is not supported by the UE, the UE can wait for a next period and try to access the cell again. In another case, the channel access mode setting for a BWP/LBT subband/channel may be updated from time to time. The UE accesses/switches to a BWP/LBT subband/channel according to its latest configured channel access mode.

[0085] Example 6: configuration of a default mode

[0086] As a sixth example, for a scenario in any of the examples above, in case a UE can access a cell without knowing the channel access mode configured for the cell (i.e., the cell may miss the configuration for channel access mode, or a UE, being in RRC connected or RRC inactive state, is not required to read the SIB signaling), the UE may assume a default channel access mode (either FBE or LBE) based on which the UE accesses the cell. The default channel access mode may be configured by the serving gNB or hard coded to the UE or hard coded in the specification of the 3GPP standard. The UE will first try to access the channel/LBT subband/BWP/cell/carrier using the default channel access mode. If the access doesn’t succeed after a couple of attempts (e.g., a threshold for the maximum channel access attempts may be configured for the UE), the UE can switch to a different channel access mode. In an example, a timer may be also configured for the UE. In case the UE cannot obtain the channel using the default or a configured channel access mode within the timer period, the UE can switch to another channel access mode upon expiry of the timer.

[0087] Now, turning to Figure 3, a flow chart of a method 300 for handling channel access mode in a communication network operating with unlicensed/shared spectrum will be described. Method 300 can be implemented in a wireless device. Method 300 comprises:

[0088] Step 310: Obtaining an indication of a channel access mode of one or more cells; and [0089] Step 320: selecting a cell from the one or more cells, based on the indication of the channel access mode.

[0090] In some examples, the wireless device may obtain the indication by receiving a message from a network node, the message comprising the indication.

[0091] In some examples, the message is received in a System Information Block (SIB), Medium Access Control (MAC) Control Element (CE) or Radio Resource Control (RRC) message.

[0092] In some examples, the wireless device may obtain the indication by detecting a channel access mode of the one or more cells and selecting a cell based on the detected channel access mode.

[0093] In some examples, the method (or the wireless device) may start a service supported by the detected channel access mode of the selected cell.

[0094] In some examples, selecting a cell may comprise selecting a cell whose indicated channel access mode is compatible with a channel access mode of the wireless device.

[0095] In some examples, selecting a cell may comprise receiving an indication of a cell selected by the network node, the selected cell having a channel access mode compatible with a channel access mode of the wireless device.

[0096] In some examples, the UE may further access the cell using the compatible channel access mode.

[0097] In some examples, the channel access mode may be associated with a Quality of Service (QoS) configuration of a service. In this case, the wireless device may select the cell based on the QoS of a service.

[0098] In some examples, the method may further comprise selecting a service based on the obtained indication of the channel access mode.

[0099] In some examples, selecting the service based on the obtained indication of the channel access mode may comprise selecting a service that is supported by the channel access mode of a selected cell. [0100] In some examples, the wireless device may prioritize the selected service over other services.

[0101] In some examples, the wireless device may further select several services simultaneously based on the obtained indication of the channel access mode.

[0102] In some examples, the wireless device may select the cell by determining if the wireless device is allowed to access the cell. If the wireless device is not allowed to access the cell, the wireless device can wait after the expiry of a time period or timer to access the cell again. Alternatively, the wireless device can select/use a different BWP or LBT sub-band or channel to access the cell.

[0103] In some examples, the wireless device may obtain the indication by assuming a default configuration of the channel access mode of the one or more cells.

[0104] In some examples, the channel access mode can be Frame Based Equipment (FBE) or Load Based Equipment (LBE).

[0105] In some examples, the wireless device may send a mobility indication to the network node. The mobility indication can be a handover request, measurement reports, etc.

[0106] Figure 4 illustrates a flow chart of a method 400 for handing channel access mode in a communication network operating with unlicensed/shared spectrum. Method 400 can be implemented in a network node, such as the serving network node. Method 400 comprises:

[0107] Step 410: Receiving a mobility indication from a wireless device; and

[0108] Step 420: Sending an indication of a channel access mode of one or more neighboring cells operating in unlicensed or shared spectrum, to the wireless device.

[0109] In some examples, method 400 (or the network node) may further comprise obtaining the channel access mode of the one or more neighboring cells.

[0110] In some examples, method 400 may further comprise selecting a cell whose channel access mode is compatible with a channel access mode of the wireless device.

[0111] In some examples, method 400 may further comprise sending an indication of the selected cell to the wireless device.

[0112] In some examples, sending the indication may comprise sending a System Information Block (SIB), Medium Access Control (MAC) Control Element (CE) or Radio Resource Control (RRC) message, which comprises the indication.

[0113] In some examples, the channel access mode may be associated with a QoS of a service. [0114] In some examples, method 400 may select a cell based on the QoS of a service. [0115] In some examples, the channel access mode may be Frame Based Equipment (FBE) or Load Based Equipment (LBE).

[0116] Figure 5 illustrates an example of a wireless network 500 that may be used for wireless communications. Wireless network 500 includes UEs 510 and a plurality of radio network nodes 520 (e.g., Node Bs (NBs) Radio Network Controllers (RNCs), evolved NBs (eNBs), next generation NB (gNBs), etc.) directly or indirectly connected to a core network 530 which may comprise various core network nodes. The network 500 may use any suitable radio access network (RAN) deployment scenarios, including Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (UTRAN), and Evolved UMTS Terrestrial Radio Access Network (EUTRAN). UEs 510 may be capable of communicating directly with radio network nodes 520 over a wireless interface. In certain embodiments, UEs may also be capable of communicating with each other via device-to-device (D2D) communication. In certain embodiments, network nodes 520 may also be capable of communicating with each other, e.g. via an interface (e.g. X2 in LTE or other suitable interface).

[0117] As an example, UE 510 may communicate with radio network node 520 over a wireless interface. That is, UE 510 may transmit wireless signals to and/or receive wireless signals from radio network node 520. The wireless signals may contain voice traffic, data traffic, control signals, and/or any other suitable information. In some embodiments, an area of wireless signal coverage associated with a radio network node 520 may be referred to as a cell.

[0118] It should be noted that a UE may be a wireless device, a radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), a sensor equipped with UE, iPAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), Universal Serial Bus (USB) dongles, Customer Premises Equipment (CPE) etc.

[0119] In some embodiments, the “network node” can be any kind of network node which may comprise of a radio network node such as a radio access node (which can include a base station, radio base station, base transceiver station, base station controller, network controller, gNB, NR BS, evolved Node B (eNB), Node B, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU), Remote Radio Head (RRH), a multi standard BS (also known as MSR BS), etc.), a core network node (e.g., MME, SON node, a coordinating node, positioning node, MDT node, etc.), or even an external node (e.g., 3rd party node, a node external to the current network), etc. The network node may also comprise a test equipment. [0120] In certain embodiments, network nodes 520 may interface with a radio network controller (not shown). The radio network controller may control network nodes 520 and may provide certain radio resource management functions, mobility management functions, and/or other suitable functions. In certain embodiments, the functions of the radio network controller may be included in the network node 520. The radio network controller may interface with the core network node 540. In certain embodiments, the radio network controller may interface with the core network node 540 via the interconnecting network 530.

[0121] The interconnecting network 530 may refer to any interconnecting system capable of transmitting audio, video, signals, data, messages, or any combination of the preceding. The interconnecting network 530 may include all or a portion of a public switched telephone network (PSTN), a public or private data network, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a local, regional, or global communication or computer network such as the Internet, a wireline or wireless network, an enterprise intranet, or any other suitable communication link, including combinations thereof.

[0122] In some embodiments, the core network node 540 may manage the establishment of communication sessions and various other functionalities for wireless devices 510. Examples of core network node 540 may include MSC, MME, SGW, PGW, O&M, OSS, SON, positioning node (e.g. E-SMLC), MDT node, etc. Wireless devices 110 may exchange certain signals with the core network node 540 using the non-access stratum layer. In non-access stratum signaling, signals between wireless devices 510 and the core network node 540 may be transparently passed through the radio access network. In certain embodiments, network nodes 520 may interface with one or more other network nodes over an internode interface. For example, network nodes 520 may interface each other over an X2 interface.

[0123] Although Figure 5 illustrates a particular arrangement of network 500, the present disclosure contemplates that the various embodiments described herein may be applied to a variety of networks having any suitable configuration. For example, network 500 may include any suitable number of wireless devices 510 and network nodes 520, as well as any additional elements suitable to support communication between wireless devices or between a wireless device and another communication device (such as a landline telephone). The embodiments may be implemented in any appropriate type of telecommunication system supporting any suitable communication standards and using any suitable components and are applicable to any radio access technology (RAT) or multi-RAT systems in which the wireless device receives and/or transmits signals (e.g., data). While certain embodiments are described for NR and/or LTE, the embodiments may be applicable to any RAT, such as UTRA, E-UTRA, narrow band internet of things (NB-IoT), WiFi, Bluetooth, next generation RAT (NR, NX), 4G, 5G, LTE FDD/TDD, etc. Furthermore, the communication system 500 may itself be connected to a host computer (not shown). The network 500 (with the wireless devices 510 and network nodes 520) may be able to operate in LAA or unlicensed spectrum.

[0124] Figure 6 is a schematic block diagram of the wireless device 510 according to some embodiments of the present disclosure. As illustrated, the wireless device 510 includes circuitry 600 comprising one or more processors 610 (e.g., Central Processing Einits (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like) and memory 620. The wireless device 510 also includes one or more transceivers 630 each including one or more transmitters 640 and one or more receivers 650 coupled to one or more antennas 660. Furthermore, the processing circuitry 600 may be connected to an input interface 680 and an output interface 685. The input interface 680 and the output interface 685 may be referred to as communication interfaces. The wireless device 510 may further comprise power source 690.

[0125] In some embodiments, the functionality of the wireless device 510 described above may be fully or partially implemented in software that is, e.g., stored in the memory 620 and executed by the processor(s) 610. For example, the processor 610 is configured to perform method 300 of Figure 3.

[0126] In some embodiments, a computer program including instructions which, when executed by the at least one processor 610, causes the at least one processor 610 to carry out the functionality of the wireless device 510 according to any of the embodiments described herein is provided (e.g. method 300 of Figure 3). In some embodiments, a carrier containing the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0127] Figure 7 is a schematic block diagram of the wireless device 510 according to some other embodiments of the present disclosure. The wireless device 510 includes one or more modules 700, each of which is implemented in software. The module(s) 700 provide the functionality of the wireless device 510 described herein. The module(s) 700 may comprise, for example, an obtaining module operable to perform step 310 of Figure 3. The module(s) 700 may further comprise a selecting module operable to perform step 320 of Figure 3. [0128] Figure 8 is a schematic block diagram of a network node 520 according to some embodiments of the present disclosure. As illustrated, the network node 520 includes a processing circuitry 800 comprising one or more processors 810 (e.g., CPUs, ASICs, FPGAs, and/or the like) and memory 820. The network node also comprises a network interface 830. The network node 520 also includes one or more transceivers 840 that each include one or more transmitters 850 and one or more receivers 860 coupled to one or more antennas 870. In some embodiments, the functionality of the network node 520 described above may be fully or partially implemented in software that is, e.g., stored in the memory 820 and executed by the processor(s) 810. For example, the processor 810 can be configured to perform any steps of the method 400 of Figure 4.

[0129] Figure 9 is a schematic block diagram of the network node 520 according to some other embodiments of the present disclosure. The network node 520 includes one or more modules 900, each of which is implemented in software. The module(s) 900 provide the functionality of the network node 520 described herein. The module(s) 900 may comprise, for example, a receiving module operable to perform step 410 of Figure 4, and a sending module operable to perform step 420 of Figure 4.

[0130] Figure 10 is a schematic block diagram that illustrates a virtualized embodiment of the wireless device 510 or network node 520, according to some embodiments of the present disclosure. As used herein, a “virtualized” node 1100 is a network node 520 or wireless device 510 in which at least a portion of the functionality of the network node 520 or wireless device 510 is implemented as a virtual component (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). For example, in Figure 11, there is provided an instance or a virtual appliance 1120 implementing the methods or parts of the methods of some embodiments. The one or more instance(s) runs in a cloud computing environment 1100. The cloud computing environment provides processing circuits 1130 and memory 1190-1 for the one or more instance(s) or virtual applications 1120. The memory 1190-1 contains instructions 1195 executable by the processing circuit 1160 whereby the instance 1120 is operative to execute the methods or part of the methods described herein in relation to some embodiments.

[0131] The cloud computing environment 1100 comprises one or more general-purpose network devices including hardware 1130 comprising a set of one or more processor(s) or processing circuits 1160, which may be commercial off-the-shelf (COTS) processors, dedicated Application Specific Integrated Circuits (ASICs), or any other type of processing circuit including digital or analog hardware components or special purpose processors, and network interface controlled s) (NICs) 1170, also known as network interface cards, which include physical Network Interface 1180. The general-purpose network device also includes non-transitory machine readable storage media 1190-2 having stored therein software and/or instructions 1195 executable by the processor 1160. During operation, the processor(s)/processing circuits 1160 execute the software/instructions 1195 to instantiate a hypervisor 1150, sometimes referred to as a virtual machine monitor (VMM), and one or more virtual machines 1140 that are run by the hypervisor 1150.

[0132] A virtual machine 1140 is a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine; and applications generally do not know they are running on a virtual machine as opposed to running on a “bare metal” host electronic device, though some systems provide para-virtualization which allows an operating system or application to be aware of the presence of virtualization for optimization purposes. Each of the virtual machines 1140, and that part of the hardware 1130 that executes that virtual machine 1140, be it hardware 1130 dedicated to that virtual machine 1140 and/or time slices of hardware 1130 temporally shared by that virtual machine 1140 with others of the virtual machine(s) 1140, forms a separate virtual network element(s) (VNE).

[0133] The hypervisor 1150 may present a virtual operating platform that appears like networking hardware to virtual machine 1140, and the virtual machine 1140 may be used to implement functionality such as control communication and configuration module(s) and forwarding table(s), this virtualization of the hardware is sometimes referred to as network function virtualization (NFV). Thus, NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in Data centers, and customer premise equipment (CPE). Different embodiments of the instance or virtual application 1120 may be implemented on one or more of the virtual machine(s) 1140, and the implementations may be made differently.

[0134] In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0135] Some embodiments may be represented as a non-transitory software product stored in a machine-readable medium (also referred to as a computer-readable medium, a processor-readable medium, or a computer usable medium having a computer readable program code embodied therein). The machine-readable medium may be any suitable tangible medium including a magnetic, optical, or electrical storage medium including a diskette, compact disk read only memory (CD-ROM), digital versatile disc read only memory (DVD-ROM) memory device (volatile or non-volatile), or similar storage mechanism. The machine-readable medium may contain various sets of instructions, code sequences, configuration information, or other data, which, when executed, cause a processor to perform steps in a method according to one or more of the described embodiments. Those of ordinary skill in the art will appreciate that other instructions and operations necessary to implement the described embodiments may also be stored on the machine-readable medium. Software running from the machine-readable medium may interface with circuitry to perform the described tasks.

[0136] The above-described embodiments are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the description, which is defined solely by the appended claims.

Claims

Claims: What is claimed is:

1. A method in a wireless device, operating in unlicensed or shared spectrum, the method comprising: obtaining an indication of a channel access mode of one or more cells; and selecting a cell from the one or more cells, based on the indication of the channel access mode.

2. The method of claim 1, wherein obtaining the indication comprises receiving a message from a network node, the message comprising the indication.

3. The method of claim 2, wherein receiving the message comprises receiving one of a System Information Block (SIB), Medium Access Control (MAC) Control Element (CE) and Radio Resource Control (RRC) message.

4. The method of claim 1, wherein obtaining the indication comprises detecting a channel access mode of the one or more cells and selecting a cell is based on the detected channel access mode.

5. The method of claim 4, further comprising starting a service supported by the detected channel access mode of the selected cell.

6. The method of any one of claims 1 to 5, wherein selecting a cell comprises selecting a cell whose indicated channel access mode is compatible with a channel access mode of the wireless device.

7. The method of any one of claims 1 to 5, wherein selecting a cell comprises receiving an indication of a cell selected by the network node, the selected cell having a channel access mode compatible with a channel access mode of the wireless device.

8. The method of claim 6 or 7, further comprising accessing the cell using the compatible channel access mode.

9. The method of any one of claims 1 to 5, wherein the channel access mode is associated with a Quality of Service (QoS) configuration of a service.

10. The method of claim 9, wherein selecting the cell is further based on the QoS of a service.

11. The method of claim 1, further comprising selecting a service based on the obtained indication of a channel access mode.

12. The method of claim 11, wherein selecting a service based on the obtained indication of a channel access mode comprises selecting a service that is supported by the channel access mode of the selected cell.

13. The method of claim 11 or 12, further comprising prioritizing the selected service over other services.

14. The method of claim 1, further comprising selecting several services simultaneously based on the obtained indication of the channel access mode.

15. The method of claim 1, wherein selecting the cell comprises determining if the wireless device is allowed to access the cell.

16. The method of claim 15, further comprising, if the wireless device is not allowed to access the cell, accessing the cell after expiry of a time period or using a different Bandwidth Part (BWP) or a different LBT subband or a different channel.

17. The method of claim 1, wherein obtaining the indication comprises assuming a default configuration of the channel access mode of the one or more cells.

18. The method of any one of claims 1 to 17, wherein the channel access mode is one of Frame Based Equipment (FBE) and Load Based Equipment (LBE).

19. The method of any one of claims 1 to 18, further comprising sending a mobility indication to the network node.

20. A wireless device comprising a communication interface and processing circuitry connected thereto and configured to perform the method of any one of claims 1 to 19.

21. A computer program product comprising a non-transitory computer readable storage medium having computer readable program code embodied in the medium, the computer readable program code comprising computer readable program code to operate according to the method of any one of claims 1 to 19.

22. A user equipment (UE) configured to communicate with a base station, the UE comprising a radio interface and processing circuitry configured to perform any of the steps of the method of any one of claims 1 to 19.

23. A method in a network node, the method comprising: receiving a mobility indication from a wireless device; and sending an indication of a channel access mode of one or more neighboring cells operating in unlicensed or shared spectrum, to the wireless device.

24. The method of claim 23, further comprising obtaining the channel access mode of the one or more neighboring cells.

25. The method of claim 23 or 24, further comprising selecting a cell whose channel access mode is compatible with a channel access mode of the wireless device.

26. The method of claim 25, further comprising sending an indication of the selected cell to the wireless device.

27. The method of any one of claims 23 to 26, wherein sending the indication comprising sending one of a System Information Block (SIB), Medium Access Control (MAC) Control Element (CE) and Radio Resource Control (RRC) message, which comprises the indication.

28. The method of any one of claims 23 to 27, wherein the channel access mode is associated with a Quality of Service (QoS) of a service.

29. The method of claim 28, further comprising selecting a cell based on the QoS of a service.

30. The method of any one of claims 23 to 29, wherein the channel access mode is one of Frame Based Equipment (FBE) and Load Based Equipment (LBE).

31. A network node comprising a communication interface and processing circuitry connected thereto and configured to perform the method of any one of claims 23 to 30.

32. A computer program product comprising a non-transitory computer readable storage medium having computer readable program code embodied in the medium, the computer readable program code comprising computer readable program code to operate according to the method of any one of claims 23 to 30.