WIRELESS COMMUNICATION SYSTEM

Field

The present application relates to a method, apparatus, and computer program.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations/access points and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided, for example, by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

Summary

According to an aspect, there is provided an apparatus in a network node, comprising means for: causing a configuration to be provided, to a user equipment, the configuration defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; acquiring a channel occupancy for transmission in a subset of the plurality of sub-bands, wherein the first time window is at least partially within the channel occupancy; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and causing a transmission of the first signal to the user equipment in the second sub-band at a time during the channel occupancy.

The configuration may define at least one further sub-band in the plurality of sub-bands where the user equipment is expected to receive the first signal, wherein the second sub-band is within the at least one further sub-band and the at least one further sub-band is different than the first sub-band.

The first time window may comprise a discovery reference signal time window. The means may be for determining the time during the channel occupancy for transmission of the first signal, wherein the time is within both the first time window and the channel occupancy time.

The means may be for causing a configuration to be provided, to the user equipment, of a bandwidth part split into the plurality of sub-bands.

The means may be for performing listen-before-talk per sub-band in the plurality of sub-bands in order to acquire the channel occupancy for transmission.

The second sub-band may be determined from the subset of the plurality of sub-bands according to a predetermined rule.

The predetermined rule may be at least one of: the lowest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band, or the largest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band.

The time may be determined relatively to the channel occupancy, or determined according to a predetermined location within the first time window, or a combination thereof.

The first signal may comprise a discovery reference signal.

According to another aspect, there is provided an apparatus in a user equipment, comprising means for: receiving a configuration, from a network node, defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; detecting a channel occupancy in a subset of the plurality of sub-bands which has been acquired by the network node for transmission; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and receiving the first signal from the network node in the second sub-band at a time during the channel occupancy.

The means for detecting may be for detecting a group common physical downlink control channel and/or a wideband demodulation reference signal on another sub-band other than the first sub-band of the plurality of sub-bands.

The detecting may be performed by detecting a preamble received from the network node.

The means may be for synchronising with the network node using the received first signal. The means may be for, when in idle mode or when performing radio resource management neighbour cell measurements, detecting the channel occupancy at at least one predefined time instance before the first time window.

The configuration may define at least one further sub-band in the plurality of sub-bands where the user equipment is expected to receive the first signal, wherein the second sub-band is within the at least one further sub-band and the at least one further sub-band is different than the first sub-band.

The first time window may comprise a discovery reference signal time window.

The means may be for determining the time during the channel occupancy for reception of the first signal, wherein the time is within both the first time window and the channel occupancy time.

The means may be for receiving a configuration, from the network node, of a bandwidth part split into the plurality of sub-bands.

The second sub-band may be determined from the subset of the plurality of sub-bands according to a predetermined rule.

The predetermined rule may be at least one of: the lowest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band, or the largest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band.

The time may be determined relatively to the channel occupancy, or determined according to a predetermined location within the first time window, or a combination thereof.

The first signal may comprise a discovery reference signal.

According to an aspect, there is provided method comprising: causing a configuration to be provided, to a user equipment, the configuration defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; acquiring a channel occupancy for transmission in a subset of the plurality of sub-bands, wherein the first time window is at least partially within the channel occupancy; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and causing a transmission of the first signal to the user equipment in the second sub-band at a time during the channel occupancy.

The configuration may define at least one further sub-band in the plurality of sub-bands where the user equipment is expected to receive the first signal, wherein the second sub-band is within the at least one further sub-band and the at least one further sub-band is different than the first sub-band.

The first time window may comprise a discovery reference signal time window.

The method may comprise determining the time during the channel occupancy for transmission of the first signal, wherein the time is within both the first time window and the channel occupancy time.

The method may comprise causing a configuration to be provided, to the user equipment, of a bandwidth part split into the plurality of sub-bands.

The method may comprise performing listen-before-talk per sub-band in the plurality of sub-bands in order to acquire the channel occupancy for transmission.

The second sub-band may be determined from the subset of the plurality of sub-bands according to a predetermined rule.

The predetermined rule may be at least one of: the lowest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band, or the largest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band.

The time may be determined relatively to the channel occupancy, or determined according to a predetermined location within the first time window, or a combination thereof.

The first signal may comprise a discovery reference signal.

According to another aspect, there is provided method comprising: receiving a configuration, from a network node, defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; detecting a channel occupancy in a subset of the plurality of sub-bands which has been acquired by the network node for transmission; determining that the first sub band is not within the subset of the plurality of sub-bands; determining a second sub band that is within the subset of the plurality of sub-bands; and receiving the first signal from the network node in the second sub-band at a time during the channel occupancy.

The method may comprise detecting may be for detecting a group common physical downlink control channel and/or a wideband demodulation reference signal on another sub-band other than the first sub-band of the plurality of sub-bands.

The detecting may be performed by detecting a preamble received from the network node. The method may comprise synchronising with the network node using the received first signal.

The method may comprise, when in idle mode or when performing radio resource management neighbour cell measurements, detecting the channel occupancy at at least one predefined time instance before the first time window.

The configuration may define at least one further sub-band in the plurality of sub-bands where the user equipment is expected to receive the first signal, wherein the second sub-band is within the at least one further sub-band and the at least one further sub-band is different than the first sub-band.

The first time window may comprise a discovery reference signal time window.

The method may comprise determining the time during the channel occupancy for reception of the first signal, wherein the time is within both the first time window and the channel occupancy time.

The method may comprise receiving a configuration, from the network node, of a bandwidth part split into the plurality of sub-bands.

The second sub-band may be determined from the subset of the plurality of sub-bands according to a predetermined rule.

The predetermined rule may be at least one of: the lowest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band, or the largest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band.

The time may be determined relatively to the channel occupancy, or determined according to a predetermined location within the first time window, or a combination thereof.

The first signal may comprise a discovery reference signal.

According to another aspect, there is provided an apparatus comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: causing a configuration to be provided, to a user equipment, the configuration defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; acquiring a channel occupancy for transmission in a subset of the plurality of sub-bands, wherein the first time window is at least partially within the channel occupancy; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and causing a transmission of the first signal to the user equipment in the second sub-band at a time during the channel occupancy.

The configuration may define at least one further sub-band in the plurality of sub-bands where the user equipment is expected to receive the first signal, wherein the second sub-band is within the at least one further sub-band and the at least one further sub-band is different than the first sub-band.

The first time window may comprise a discovery reference signal time window.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: determining the time during the channel occupancy for transmission of the first signal, wherein the time is within both the first time window and the channel occupancy time.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: causing a configuration to be provided, to the user equipment, of a bandwidth part split into the plurality of sub-bands.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: performing listen-before-talk per sub-band in the plurality of sub-bands in order to acquire the channel occupancy for transmission.

The second sub-band may be determined from the subset of the plurality of sub-bands according to a predetermined rule.

The predetermined rule may be at least one of: the lowest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band, or the largest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band.

The time may be determined relatively to the channel occupancy, or determined according to a predetermined location within the first time window, or a combination thereof.

The first signal may comprise a discovery reference signal.

According to another aspect, there is provided an apparatus comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: receiving a configuration, from a network node, defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; detecting a channel occupancy in a subset of the plurality of sub-bands which has been acquired by the network node for transmission; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and receiving the first signal from the network node in the second sub-band at a time during the channel occupancy.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: detecting may be for detecting a group common physical downlink control channel and/or a wideband demodulation reference signal on another sub-band other than the first sub band of the plurality of sub-bands.

The detecting may be performed by detecting a preamble received from the network node.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: synchronising with the network node using the received first signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: when in idle mode or when performing radio resource management neighbour cell measurements, detecting the channel occupancy at at least one predefined time instance before the first time window.

The configuration may define at least one further sub-band in the plurality of sub-bands where the user equipment is expected to receive the first signal, wherein the second sub-band is within the at least one further sub-band and the at least one further sub-band is different than the first sub-band.

The first time window may comprise a discovery reference signal time window.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: determining the time during the channel occupancy for reception of the first signal, wherein the time is within both the first time window and the channel occupancy time.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform: receiving a configuration, from the network node, of a bandwidth part split into the plurality of sub-bands.

The second sub-band may be determined from the subset of the plurality of sub-bands according to a predetermined rule.

The predetermined rule may be at least one of: the lowest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band, or the largest sub-band index of the subset of the plurality of sub-bands is selected as the second sub-band.

The time may be determined relatively to the channel occupancy, or determined according to a predetermined location within the first time window, or a combination thereof.

The first signal may comprise a discovery reference signal.

According to another aspect, there is provided a non-transitory computer readable medium comprising program instructions thereon for performing at least the following: causing a configuration to be provided, to a user equipment, the configuration defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; acquiring a channel occupancy for transmission in a subset of the plurality of sub-bands, wherein the first time window is at least partially within the channel occupancy; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and causing a transmission of the first signal to the user equipment in the second sub-band at a time during the channel occupancy.

According to another aspect, there is provided a non-transitory computer readable medium comprising program instructions thereon for performing at least the following: receiving a configuration, from a network node, defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal; detecting a channel occupancy in a subset of the plurality of sub-bands which has been acquired by the network node for transmission; determining that the first sub-band is not within the subset of the plurality of sub-bands; determining a second sub-band that is within the subset of the plurality of sub-bands; and receiving the first signal from the network node in the second sub-band at a time during the channel occupancy. A computer product stored on a medium may cause an apparatus to perform the methods as described herein.

An electronic device may comprise apparatus as described herein.

In the above, various aspects have been described. It should be appreciated that further aspects may be provided by the combination of any two or more of the various aspects described above.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims.

Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a plurality of base stations and a plurality of communication devices; Figure 2 shows a schematic diagram of an example communication device; Figure 3 shows a schematic diagram of an example network function;

Figure 4 schematically shows example discovery reference signal transmission windows;

Figure 5 schematically shows an example carrier with multiple synchronisation signal blocks;

Figure 6 schematically shows example sub-band configurations;

Figure 7 schematically shows an example operation of a communication system;

Figure 8 schematically shows another example operation of a communication system;

Figure 9 shows an example signalling diagram between network entities; Figure 10 shows an example method performed by a network node; and Figure 11 shows an example method performed by a user equipment.

Detailed description

Before explaining in detail some examples of the present disclosure, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples. In a wireless communication system 100, such as that shown in Figure 1, mobile communication devices or user apparatus or user equipment (UE) 102, 104 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be a user equipment (UE) or a machine type terminal or any other suitable device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station or access point, and transmit and/or receive communications on the carrier.

The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved.

A base station may be referred to more generally as simply a network apparatus or a network access point. Base stations are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatus. The controller apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller. In Figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 107. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.

In Figure 1, base stations 106 and 107 are shown as connected to a wider communications network 113 via a gateway 112. A further gateway function may be provided to connect to another network.

There may be smaller base stations or cells (not shown) in some networks. These may be pico or femto level base stations or the like.

A possible communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device may be a user equipment (UE) or terminal. An appropriate communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a smart phone, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine type device or any combinations of these or the like.

The device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the communication device.

A device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204.

The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. This may be optional in some embodiments.

A display 208, a speaker and a microphone can be also provided. One or more of these may be optional in some embodiments.

A communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto. One or more of these may be optional.

The communication devices may access the communication system based on various access techniques.

An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as 5G or New Radio (NR). The previous 3GPP based developments are often referred to as different generations for example 2G, 3G, 4G. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMAX (Worldwide Interoperability for Microwave Access). It should be appreciate that although some embodiments are described in the context of a 4G and/or 5G system, other embodiments may be provided in any other suitable system including but not limited to subsequent systems or similar protocols defined outside the 3GPP forum.

An example apparatus is shown in Figure 3. Figure 3 shows an apparatus that could be comprised within a network function. As an example, the network function could be a base station (gNB, eNB, etc.), a management function, a serving gateway, a packet data network gateway, an access and mobility management function or a session management function. The apparatus 300 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. For example the apparatus 300 can be configured to execute an appropriate software code to provide functions. The apparatus 300 may be included in a chipset apparatus.

Some of the example embodiments as shown below may be applicable to 3GPP 5G standards. However, some example embodiments may also be applicable to 4G, 3G and other 3GPP standards.

Some example embodiments relate to NR unlicensed (NR-U). Some examples aim to improve (gNB) channel access for the transmission of discovery reference signals (DRS) in conditions where DRS and the corresponding synchronisation signal blocks (SSB) are to be transmitted on a sub-band which is not one of the sub-bands the gNB has gained access to and is currently transmitting on. The DRS is a set of signals that may comprise at least a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a channel state information reference signal (CSI-RS). DRS transmission is utilized in licensed assisted access (LAA) for cell detection, synchronization, and radio resource management (RRM) measurement. Licensed-Assisted Access (LAA) enables operators to access unlicensed spectrum while adhering to Listen-Before-Talk (LBT) requirements. LBT is a technique in radio communications wherein radio transmitters first monitor or sense the radio environment before the radio transmitter starts a transmission. LBT can be used by a radio device to find a free radio channel to operate on.

It has been proposed to 3GPP to have different category channel access schemes for NR-based access of the unlicensed spectrum. The channel access schemes for NR-based access for unlicensed spectrum can be classified into the following categories:

• Category 1 : Immediate transmission after a short switching gap

- This is used for a transmitter to immediately transmit after a switching gap inside a channel occupancy time (COT).

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

• Category 2: LBT without random back-off

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

• Category 3: LBT with random back-off with a contention window of fixed size

- 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.

• Category 4: LBT with random back-off with a contention window of variable size

- 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.

For different transmissions in a COT and different channels/signals to be transmitted, different categories of channel access schemes can be used. Some proposals have been made to 3GPP regarding NR-U DRS which are shown in Figure 4. Figure 4 shows two back-to-back half-frame DRS transmission windows 401 , 403. The DRS transmission windows 401 , 403 may also be referred to as DRS time windows. In this example, the DRS transmission windows 401, 403 of 5ms comprises 20 SSB candidate positions 405, i.e. half-slots. The subcarrier spacing in this example is 30 kFIz, and the corresponding slot duration is 0.5 ms. Consequently, the duration if a DRS transmission window 401 is 20 ^* 0.25 ms = 5 ms, i.e. one half frame. In Figure 4, the two back-to-back half-frame DRS transmission windows 401, 403, are consecutive in time. Flowever, the half-frame DRS transmission windows may repeat with a periodicity of 20 ms or higher. For example, the half-frame DRS transmission windows 401 , 403, may be separated by at least 15 ms (see for example Figure 7). In some examples, the DRS transmission window 401, 403 may comprise a discovery measurement timing configuration (DMTC). In other examples, the DRS transmission window 401, 403 may comprise a synchronisation signal physical broadcast channels (SS/PBCFI) block measurement time configuration (SMTC). In other examples, the DRS transmission window 401, 403 may comprise a measurement timing configuration.

From the beginning of the DRS transmission windows 401, 403, a base station (gNB) attempts to transmit the SSBs. In the Figure 4, ‘X’ denotes that the channel was occupied in certain SSB candidate positions (i.e. LBT is not successful), hence, preventing SSB transmission. When the channel becomes free, the base station transmits Q=4 SSBs with different beams, where Q is the predetermined number of SSBs (the SSB corresponding to a beam) belonging to an SSB burst. In this example of Figure 4, the SSB candidate position before which the LBT is successful is different for the first DRS transmission window 401 (LBT successful before SSB candidate position 4) and the second DRS transmission window 403 (LBT successful before SSB candidate position 3). Correspondingly, in the first DRS transmission window 401, the SSB for beam # 0 is transmitted first 407, followed by beam #1, #2, and #3. In the second DRS transmission window 403, since the LBT is successful already one candidate position (slot) earlier, beam # 3 is transmitted first 409, followed by beam #0, #1, and #2. In this example, the transmission of 4 beams requires 1ms.

Figure 5 shows wideband operation in NR in an example where there are multiple SSBs within a network carrier. Figure 5 shows both cell defining SSBs (CD- SSBs) and non-cell defining SSBs (NCD-SSBs), in a wideband network carrier. There are two CD-SSBs, SSB1 501 and SSB4503 which identify two serving cells that have overlapping bandwidth-parts (BWP) in the frequency domain. In other examples, the BWPs may not be overlapping. Figure 5 shows a first UE 505 and a second UE 507. From the UE perspective, a serving cell is associated to a single SSB. There is also provided two NCD-SSBs, SSB2509 and SSB3511 , which are both also on the same carrier. The NCD-SSBs 509, 511 indicate (for initial access UE) where the UE 505, 507 may find the cell defining SSB. Radio resource management (RRM) measurements based on both CD-SSBs 501 , 503 and NCD-SSBs 509, 511 can be configured. NR-U supports wideband operation where the base station can configure a

BWP to span over a set of LBT sub-bands. For example, the base station could configure an 80MFIz BWP comprising 4 LBT sub-bands, such that an LBT sub-band is 20 MHz. Figure 6 labels these 4 sub-bands ‘a’, ‘b’, ‘c’ and ‘d’. Therefore, the base station could perform LBT per 20 MHz sub-band and then transmit a downlink burst on a sub-set of sub-bands given the LBT outcome. The example shown in Figure 6 assumes that transmission is allowed on contiguous sub-bands, and not non contiguous sub-bands. However, in other examples, transmission is allowed on non contiguous sub-bands as well. If the LBT outcome is positive in 1 sub-band, then a transmission may occur on the corresponding sub-band as shown by label 601. If the LBT outcome is positive in 2 sub-bands, then transmission may occur on the corresponding 2 sub-bands as shown by label 603. If the LBT outcome is positive in 3 sub-bands, then transmission may occur on the corresponding 3 sub-bands as shown by label 605. If the LBT outcome is positive on 4 sub-bands then transmission may occur in sub-bands ‘a’, ‘b’, ‘c’ and ‘d’ as shown by label 607. However, in some situations, periodic DRS (including SSB burst) transmission may be due on a sub-band (e.g. sub-band #X), while the base station has acquired a COT for a separate sub-band (e.g. sub-band #Y). Due to implementation constraints, a base station cannot perform LBT on one sub-band while transmitting on a separate sub-band. A base station may not be able to transmit and receive at the same time if there is not enough frequency separation between the sub-bands. Accordingly, in this situation, stopping a downlink (DL) transmission to perform a CAT2 channel access scheme for sub-band #X may not be desirable, because there is no guarantee that a CAT2 LBT on sub-band #X will be successful, and the base station may lose the right to transmit on sub-band #Y. It has been proposed in the past to address the above problem by introducing more than one CD-SSB per single serving cell. This would include transmitting SSBs in all sub-bands. However, transmitting SSBs in all sub-bands would significantly increase the DL overhead. Therefore, an efficient solution for DRS transmission, relying on one CD-SSB needs to be developed.

Some of the example embodiments as shown below may address the above mentioned problems among others.

Figure 7 shows an example of operation of a communication system. The UE in this example may be in RRC connected mode. Figure 7 shows a time period with 30 time slots, from slot #0 to slot #29. There are provided 4 sub-bands labelled, sub band #0, sub-band #1, sub-band #2 and sub-band #3. For example, a base station could have configured an 80MHz BWP comprising 4 LBT sub-bands, such that an LBT sub-band is 20 MHz. In other examples, there may be less than 4 sub-bands, or more than 4 sub-bands. Figure 7 shows two DRS time windows, a first DRS window 701 and a second DRS window 703. The DRS window represents a range in time where the UE may expect to receive a DRS/SSB. In this example, the DRS window 701 , 703 is 5 time slots wide. In other examples, the DRS window 701 , 702 may be less than 5 time slots, or more than 5 time slots. The first DRS window 701 is from slot #0 to slot #4. The second DRS window 703 is from slot #20 to slot #24. Therefore, the example of Figure 7 shows a DRS window periodicity of 20ms if a time slot represents 1 ms.

Figure 7 shows that in slot #1 of sub-band #3 the UE receives a first DRS 704. Slot #1 is the second time slot of the first DRS window 701. The channel access scheme, performed at the base station, for this transmission of the first DRS 705 may be CAT 2, as described earlier. The DRS transmission window 701,703 within sub- band #3 may be referred to as the primary SSB 705. The UE may be configured, by a base station, with the primary SSB 705. The primary SSB 705 indicates on which sub band and in which set of time slots making up the DRS window the UE may expect to receive a DRS from the base station. Therefore, for the second DRS window 703 the primary SSB 706 is one of the slots in slots #20 to #24 of sub-band #3. In some examples, the time slots in the DRS window will be selected if that time slot has a clear channel.

As shown in Figure 7, in slot #19, the base station acquires a COT 707 on sub bands #0 and #1. The channel access scheme for this COT transmission from the base station may be CAT 4, as described earlier. In Figure 7, the COT 707 spans sub- band #0 and sub-band #1 for time slots #19 to #25. However, all of the primary SSB 706 locations in slots #20 to #24 of the second DRS transmission window 703 remain located in sub-band #3 instead. The UE detects the COT 707 in slot #19. The UE may detect the COT 707 based on, for example, a group common physical downlink control channel (GC-PDCCH) and/or a wideband demodulation reference signal (WB-DMRS). In some examples, the GC-PDCCH may be scrambled by a known radio network temporary identifier (RNTI). In other examples, other suitable detection techniques are used by the UE. Once the UE has detected the COT 707, the UE knows that during the COT 707 the base station is transmitting on sub-bands #0 and #1. During the COT 707 the base station does not transmit on sub-band #3. Therefore, the UE receives a second DRS 709 in one of the sub-bands of the COT 707. In the example of Figure 7, the UE receives the second DRS 709 in the second time slot of the second DRS window 703 (i.e. slot #21 ). The UE may determine which of the sub-bands and which of the slots of the COT 707 the DRS will arrive according to a predetermined rule. The predetermine rule may be, for example, the largest sub-band index (i.e. sub-band #1 ) and the n-th valid time slot of the DRS window starting from m slots after the COT has been detected. Alternatively, it may be a predetermined slot of the DRS window, such as the last slot of the DRS window. It should be understood that these examples of predetermined rules are given as examples only and other suitable predetermined rules may be used by the UE. The steps performed by the UE of Figure 7 will now be described in more detail below.

The UE may first take part in an RRC connection procedure with a network. Once connected, the UE may be configured with at least two DRS/SSB locations in frequency and/or time within the DRS window 701, 703. The at least two DRS/SSB locations may comprise a primary SSB 705, 706, in frequency and a secondary SSB 709 in frequency. The time location candidates, valid time slots of the DRS transmission window, are the same for both the primary SSB 705, 706 and secondary SSB 709 in this example. The secondary SSB 709 may be made up of one or more suitable sub-bands with suitable time slots being the time slots of the second DRS transmission window 703. Therefore, one SSB is the primary SSB location 705, 706, while the remaining SSBs are the secondary SSB 709.

The RRC connected UE will expect to receive a DRS/SSB at a location within the primary SSB 705, 706, unless within a predetermined time ahead of the DRS window 701, 703 the UE detects WB-DMRS and/or GC-PDCCH on another sub- band(s) (i.e. other than the primary sub-band). The detection of WB-DMRS and/or GC- PDCCH on another sub-band indicates COT in time and frequency, such that the indicated channel occupancy time overlaps in time with the DRS window at the primary location Upon detection of such indication of an ongoing channel occupancy, the UE attempts to detect the DRS/SSB on one of the time slots and on one of the sub-bands within the secondary SSB 709, based on the COT and according to predetermined rules. The predetermined rule may be, for example, that the largest sub-band index of the COT is used as the secondary SSB location 709. In another example the predetermined rule may be that the lowest sub-band index of the COT is used the secondary SSB location 709. As an example only, the time location may be determined, for example, as the 1 ^st valid slot of the DRS window starting from 2 slots after the slot where COT start has been detected. The network may pre-configure the UE with the predetermined rule. As seen in the example of Figure 7, the UE receives a second DRS 711 within the secondary SSB 709. The second DRS 711 is found within the time and frequency of the COT 707. In this example, the second DRS 711 is in the second time slot of the second DRS window 703 (i.e. slot #21) and in sub-band #1. This should be appreciated as an example only, the second DRS 711 could be received by the UE in any time slot of the second DRS window 703, and any sub-band in which the COT has acquired access to.

The UE may not be required to read system information, for example physical broadcast channels (PBCH)/system information blocks (SIBs), from the secondary DRS upon receiving system update by paging in an RRC connected state, but may acquire synchronization. The UE may use the received DRS to remain synchronised with the base station. The UE may not be required to read system information if for example, the base station operates with multiple overlapping cells, and the secondary SSB of one cell overlaps with primary SSB of another cell with a different cell ID.

Figure 8 shows another example operation of a UE. The UE in this example may be in idle mode or performing RRM measurements. Figure 8 shows a time period with 22 time slots labelled slot #13 to slot #34. There are provided 4 sub-bands labelled, sub-band #0, sub-band #1, sub-band #3 and sub-band #3 of a BWP configured to a UE. In other examples, there may be less than 4 sub-bands, or more than 4 sub-bands. Figure 8 shows a DRS window 801. In this example, the DRS window 801 is 5 time slots wide. In other examples, the DRS window 801 may be less than 5 time slots, or more than 5 time slots. The DRS window 801 ranges from slot #25 to slot #29.

Figure 8 illustrates a UE camping on a cell. The UE camping on the cell/ performing RRM measurements does not typically perform physical downlink control channel (PDCCH) monitoring. However, as shown in Figure 8 the UE wakes up one time slot before the DRS window 801 period starts. This is represented by the rectangle 803 in slot #24 spanning sub-bands #0 to #3. In other examples, the UE may wake up more than one time slot before the DRS window 801 starts. The UE wakes up early to detect WB-DMRS and/or GC-PDCCH. The detection of WB-DMRS and/or GC-PDCCH indicates a COT 803 acquired by a base station in time and frequency. Therefore the detecting of the WB-DMRS and/or GC-PDCCH provides knowledge for the UE of the sub-bands acquired by the base station for transmission. Based on the outcome of the detection, the UE determines on which sub-band to attempt detection of the DRS transmission from the base station according to rules discussed above in relation to Figure 7. In Figure 8, the COT 707 spans sub-band #0 and sub-band #1 for time slots #23 to #29. The UE may be configured, by a base station, with a primary SSB 805. The primary SSB 805 indicates on which sub-band and which time slots the UE is expecting to receive the DRS 807 from the base station. In Figure 8, the primary SSB 805is one of the slots in slots #25 to #29 in sub-band #3. The time slot in the DRS window 801 may be selected by gNB if the slot has a clear channel. These numbers are given as an example only and any suitable slot or sub-band could be used as the primary SSB 805. However, as the UE has detected the COT 803, the UE will attempt to detect the DRS 807 from a time and frequency within the COT 803. In Figure 8, the UE attempts to detect the DRS 807 in sub-band #1 rather than sub-band #3, as sub band #1 is within the COT 803, which is known as the secondary SSB 807. The time slot where the UE attempts to detect the DRS 807 is determined according to predetermined rules discussed above. In this example, as the first valid slot is in the DRS window 801 , the UE receives the DRS 807 in slot #25. The UE may be configured with a subset of sub-bands which are eligible for secondary location of DRS detection. The UE may select one of the subset of sub-band based on a predetermined rule. The predetermined rule may be that the largest sub-band index of the COT is used as the secondary SSB location 807. In another example the predetermined rule may be that the lowest sub-band index of the COT is used the secondary SSB location 807. In an example, the secondary SSB position 807 (in time) within the sub-band would be the same as on the primary SSB 805. In other examples, the secondary SSB position 807 (in time) within the sub-band would be different compared to the primary SSB 805. In case of RRM measurements performed during the DRS SMTC or DMTC window, the RNTI of GC-PDCCH or sequence initialization of PDCCH wide-band DMRS may be configured by ‘MeasObjectNR’ information element of abstract syntax notation one (ASN.1 ) in TS 38.331.

Figure 9 shows an example signalling diagram between network entities. The communications of Figure 9 take place between a network node, such as for example, a base station 901 , and a user device, such as for example, a user equipment (UE) 903.

At step 1 , the base station 901 configures a bandwidth part (BWP) that has a plurality of sub-bands. For example, the base station 901 may configure an 80MFIz BWP comprising 4 LBT sub-bands, of 20MFIz per LBT sub-band. The base station 901 may configure the user equipment 903 with the BWP with the plurality of sub bands. It should be understood that these values are used as an example only to aid with the understanding of the disclosure and other suitable bandwidth and sub-band values may be used.

At step 2, the base station 901 transmits a configuration to the user equipment 903. The configuration may define a primary SSB location in time and/or frequency. The configuration may also define one or more secondary SSB locations in time and/or frequency. The primary SSB location and secondary SSB locations may be used by the UE 903 to know when to expect reception of a DRS. The primary SSB location and the one or more secondary SSB locations are found within a DRS window. The DRS window is a set of one or more time slots wherein DRS reception is expected by the UE 903. Once the UE 903 has been configured, the UE 903 will expect a DRS, transmitted by the base station 901 , at the primary SSB location unless the UE detects otherwise. This will be described in more detail in the below steps.

At step 3, the base station 901 acquires a channel occupancy time (COT) on a subset of sub-bands. The COT may represent a time and/or frequency whereby the base station 901 can perform transmission based on CAT4 LBT. The COT acquired may be similar to the COTs 707, 803 shown in Figures 7 and 8. At step 4, the base station 901 may determine that a DRS, due to be transmitted in the primary SSB, is due to be transmitted on a sub-band not part of the COT subset of sub-bands.

At step 5, the UE 903 may detect the COT of the base station. The UE may detect the COT based on GC-PDCCH and/or WB-DMRS. In other examples, the UE 903 may detect a preamble from the base station 901 which indicates the COT. In other examples, the UE may use other suitable methods to detect the COT. Once detected the UE may know the one or more time slots and the one or more sub-bands of the COT that the base station 901 has acquired. Using this information, the UE can determine whether or not the primary SSB is within the time and/or frequency of the COT.

At step 6, the base station 901 determines one of the one or more secondary SSB locations for DRS transmission based on the acquired COT. The selected secondary SSB will be within the time and/or frequency of the acquired COT. If there are more than one suitable locations for the secondary SSB based on the acquired COT then the selection may be made using a predetermined rule. The predetermined rule may be that the largest sub-band index of the COT is used as the secondary SSB location. In another example the predetermined rule may be that the lowest sub-band index of the COT is used the secondary SSB location. In time domain, the DRS may be expected by the UE 903 in the n-th valid DRS slot of DRS window starting from m slots after the COT has been detected. Alternatively, it may be a predetermined slot of the DRS window, such as the last slot for example. The base station may pre configure the UE 903 with the predetermined rule as part of the configuration of step 1. At step 7, the UE 903 determines one of the one or more secondary SSB locations for DRS reception based on the detected COT. As an example only, the COT may span a first sub-band and a second sub-band, however, the primary SSB was for a third sub-band. Once the UE determines that the sub-band of the primary SSB is not within the COT, the UE must determine whether the first or second sub-band should be used as the selected secondary SSB location for reception of the DRS from the base station. The selected secondary SSB will be within the time and/or frequency of the detected COT. If there are more than one suitable locations for the secondary SSB based on the acquired COT then the selection may be made using the predetermined rule as discussed above. At step 8, the base station 901 transmits the DRS in the selected secondary SSB time and/or frequency location. The UE 903 will receive the DRS in the determined secondary SSB time and/or frequency location. The UE 903 may use the received DRS to acquire synchronisation with the base station 901 /network. In some examples, the steps shown above may be performed in a different order. In some examples, one or more steps may be removed.

The above mentioned steps of Figure 9 are applicable to both RRC connected UEs and idle UEs. However, an idle UE or UE performing RRM measurements will have the additional step of waking up before step 5, and detecting the COT. An idle UE may wake up one or more slots ahead of a DRS window in order to attempt to detect a COT.

As a typical base station cannot perform LBT on one sub-band while transmitting on other sub-bands the present disclosure means that the DRS can still be transmitted to the UE using the same sub-band as is already being used to transmit in the COT. Thus, the UE may better maintain the synchronisation with the base station, resulting in a better performance of the system. Furthermore, an idle UE may be able to access system information more quickly by determining the location of a DRS on secondary SSBs.

Figure 10 shows an example method performed by a network node. Step 1001 comprises causing a configuration to be provided, to a user equipment, the configuration defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal.

Step 1003 comprises acquiring a channel occupancy for transmission in a subset of the plurality of sub-bands, wherein the first time window is at least partially within the channel occupancy.

Step 1005 comprises determining that the first sub-band is not within the subset of the plurality of sub-bands.

Step 1007 comprises determining a second sub-band that is within the subset of the plurality of sub-bands. Step 1009 comprises causing a transmission of the first signal to the user equipment in the second sub-band at a time during the channel occupancy.

The method steps may be performed by an apparatus. The apparatus may be comprised within a network node such as a base station, for example, a gNB or an eNB. In other examples, the network node may be within the apparatus. Each method step may be performed by a different part or component of the apparatus. The method steps may be performed by an apparatus, such as a chipset or 1C, within the base station. It must be understood that one or more steps may be omitted or take place in an alternate order. Figure 11 shows an example method performed by a user equipment.

Step 1101 comprises receiving a configuration, from a network node, defining a first sub-band in a plurality of sub-bands and a first time window, where the user equipment is expected to receive a first signal.

Step 1103 comprises detecting a channel occupancy in a subset of the plurality of sub-bands which has been acquired by the network node for transmission.

Step 1105 comprises determining that the first sub-band is not within the subset of the plurality of sub-bands.

Step 1107 comprises determining a second sub-band that is within the subset of the plurality of sub-bands.

Step 11109 comprises receiving the first signal from the network node in the second sub-band at a time during the channel occupancy.

The method steps may be performed by an apparatus. The apparatus may be comprised within a user device, such as a UE. In other examples, the UE may be within the apparatus. Each method step may be performed by a different part or component of the UE. The method steps may be performed by an apparatus, such as chipset or IC, within the UE. It must be understood that one or more steps may be omitted or take place in an alternate order.

It should be understood that each step in the signalling diagram of the Figures and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

It is noted that whilst embodiments have been described in relation to one example of a standalone 5G networks, similar principles maybe applied in relation to other examples of standalone 3G or LTE networks. It should be noted that other embodiments may be based on other cellular technology other than 5G or on variants of 5G. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

It should be understood that the apparatuses may comprise or be coupled to other units or modules. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The embodiments of this invention may be implemented by computer software executable by a data processor, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it. Further in this regard it should be noted that any steps in the signalling diagrams as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.