Patent Description:
Wireless communication, such as cellular wireless communication, may take place at the direction of an access node, comprised in a cellular communication network, for example. An access node may provide transmission permissions, grants, to user terminals in cells controlled by the access node, for example via a physical downlink control channel, PDCCH, or a corresponding channel.

When user terminals are to transmit on an unlicensed spectrum, which is an example of a shared spectrum as the spectrum may be shared by other users and even other systems, the cellular network may configure the user terminals for grant free operation, which may be known as "configured grants". In grant free operation, user terminals may employ the listen-before-talk, LBT, principle to assess if a radio resource they intend to use is free for use.

<CIT> discloses, for example that a base station may configure a UE to transmit a plurality of RA preambles. For example, as a UE moves toward a cell edge area (away from a base station), a transmit power for a RA preamble becomes larger. If a UE transmits a plurality of RA preambles at a cell edge area, a required transmit power of each of the plurality of RA preambles may be larger, and a required transmit power of the plurality of RA preambles may exceed a threshold (e.g., the threshold may be a maximum allowable transmit power for a cell).

<CIT> discloses a method including receiving, by the terminal, system information from a base station, the system information including transmit power information for transmitting a random access preamble; calculating a transmit power using the transmit power information; and transmitting the random access preamble using the calculated transmit power.

<CIT> discloses methods for adjusting the transmit power used by a mobile terminal for one or more RACH procedures. The invention suggests introducing a power scaling for uplink PRACH transmissions performing RACH procedures on an uplink component carrier. The power scaling is proposed on the basis of a prioritization among multiple uplink transmissions or on the basis of the uplink component carriers on which RACH procedures are performed.

<NPL>, discloses power control aspects in LAA with LBT.

According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims.

According to an aspect of the present disclosure, there is provided a method comprising receiving, by a user terminal, configuration for a grant-free transmission on a shared radio resource, the grant-free transmission comprising at least one collision avoidance transmission and at least one data transmission, wherein the at least one collision avoidance transmission precedes the at least one data transmission, determining a first transmission power for the at least one data transmission, determining a second transmission power for the at least one collision avoidance transmission based on information indicative to a location of the user terminal proportionate to a location of an access node providing a radio cell, and transmitting the at least one collision avoidance transmission at the second determined power and the at least one data transmission at the determined first transmission power.

According to another aspect of the present disclosure, there is provided an apparatus comprising means for carrying out the method in accordance with the second aspect.

<FIG> illustrates an example system in accordance with at least some embodiments. Access node (such as a gNB) <NUM> may be comprised in a cellular communication system, such as fifth generation, <NUM>, also known as New Radio, NR, or long-term evolution, LTE, for example.

In this example, wireless link <NUM> connects access node <NUM> with user terminal (user equipment, UE, user device) <NUM>. Likewise, wireless link <NUM> connects access node <NUM> with user terminal <NUM>. The wireless link may comprise a downlink for communicating from an access node towards a user terminal, and an uplink for communicating from the user terminal to the access node. A user terminal typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user terminal may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. The user terminal may also be a device having capability to operate in Internet of Things (IoT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. The user terminal may also utilise cloud: in some applications, the user terminal may comprise a small portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud.

An access node may, in general, be configured to control user terminal transmissions by assigning grants to the user terminals. A grant may be seen as a permission to send using radio resources specified in the grant, implicitly or explicitly. In some systems, the radio channel the access node uses to assign grants to user terminal is called a physical downlink control channel, PDCCH. On the other hand, where it is desired to use radio resources which the access node does not have exclusive control over, such as an unlicensed spectrum or other shared radio resource, for example, grant free operation may be performed. In NR, grant free operation is referred to as "configured grants", or Autonomous Uplink. In configured grant operation, instead of transmitting separate grant for each transmission of a user terminal, and access node may grant radio resources on a long-term basis, and the user terminals may then use those resources when necessary, without a further indication.

As the access node does not have exclusive control over the shared resources, it cannot directly allow the user terminal to transmit on these resources, for example, to transmit information to the access node <NUM> itself. Rather, multisystem coexistence methods may be employed, one of which is listen-before-talk, LBT. When using LBT, a user terminal planning to perform a transmission may first perform a test reception on the radio resources it plans to use, and then it will perform the transmission in case it does not receive energy during the test reception which would indicate another node is presently using the radio resources in question. By not receiving energy it is meant, that a received energy is less than an energy detection threshold in the user terminal. The test reception may be referred to as a listening period.

To interoperate with other user terminals using LBT, a user terminal initiating a transmission may transmit a collision avoidance signal before transmitting data in a data portion. We may designate a collision avoidance signal transmission also as a collision avoidance transmission. The collision avoidance transmission functions to reserve radio resources to the use of the transmitting user terminal, as other user terminal s intending to use the same resources will detect the collision avoidance transmission in their LBT respective listening periods, and responsively abstain from trying to use the resources.

To enable a user terminal to use shared radio resources, such as unlicensed resources or licensed radio resources shared with another system, an access node may provide to the user terminal information defining a permission for the user terminal to transmit on the shared resources. This information may comprise, for example, an assignment of specific radio resources the user terminal may use provided they appear to be free. The specific radio resources may comprise, depending on the technology used, a frequency, a spreading code, a physical resource block (PRB), an interlace, or a combination thereof. The information may further comprise a time offset from a reference point, which the user terminal must wait before beginning to transmit a collision avoidance signal.

<FIG> illustrates an example transmission in accordance with at least some embodiments. An example of time offset is illustrated in <FIG> illustrates collision avoidance signal <NUM>, followed by data transmission or portion <NUM>. Similarly, collision avoidance signal <NUM> precedes data portion or transmission <NUM>. A collision avoidance transmission or signal may be e.g. an extension of a cyclic prefix of the next OFDM symbol containing PUSCH data or reference signals. These transmissions may take place using the same specific radio resources, which have been assigned to two different user terminals. These resources are thus shared between user terminals.

A plurality of time offsets <NUM> may be assigned, to user terminals, for example in a one-to-one assignment such that each user terminal is allocated one offset, and each offset is provided to one user terminal only. Alternatively, more than one user terminal may be given the same time offset, in case the user terminals are expected to only fairly rarely try to use the shared resources. Yet another option is that each user terminal is given a set of possible offset values, and the user terminal chooses to use one of them is a (pseudo-) random fashion. The selection is done before each grant-free transmission. For example, collision avoidance transmission or signal <NUM> and data portion <NUM> may relate to user terminal <NUM>, and collision avoidance transmission or signal <NUM> and data portion or transmission may relate to user terminal <NUM>. Time offsets can be used as a mechanism to enable "overbooking" the specific radio resources allocated to the user terminals for grant-free transmission, by allocating the same specific radio resources to a plurality of user terminals, giving each of the plurality of user terminals a time offset with regard to the resources. The user terminal with the smallest offset may effectively have highest-priority access to the resources, since this user terminal may start a collision avoidance signal transmission first, to pre-empt the other potential users of the shared resources. In the example of <FIG>, a higher-priority user terminal <NUM>, with a smaller time offset, may be relatively near the access node and a lower-priority user terminal <NUM>, with a larger time offset, may be further away. Normal power control methods cause a transmission power of user terminal <NUM> to be relatively low, as it only needs to enable the nearby access node <NUM> to receive its transmissions. Thus, collision avoidance signal <NUM> could be transmitted at such a low power, that it does not trigger a detection of power during a LBT listening period at user terminal <NUM>. Thus, user terminal <NUM> might start using the specific radio resources user terminal <NUM> is already using, resulting in an interfering collision. Some embodiments provide an option to lower the likelihood of such a collision.

It should be appreciated that the coding of software for carrying out the embodiments shown and described below is well within the scope of a person of ordinary skill in the art.

One embodiment starts in block <NUM> of <FIG>. This embodiment is suitable for being carried out by a user device. Terms "receive" and "transmit" may comprise reception or transmission via a radio path. These terms may also mean preparation of a message to the radio path for an actual transmission or processing a message received from the radio path, for example, or controlling or causing a transmission or reception, when embodiments are implemented by software.

In block <NUM>, configuration for a grant-free transmission on a shared radio resource is received. The grant-free transmission comprises at least one collision avoidance transmission, such as a preamble or extension of a cyclic prefix of a data symbol, and at least one data transmission, wherein the at least one collision avoidance transmission precedes the at least one data transmission. We may designate the contents of the collision avoidance transmission as collision avoidance signal. The configuration may be received once in an initialization phase, periodically or when an access node carries out a reconfiguration or when the user device requests it, for example. When the at least one collision avoidance transmission comprises a preamble, it may immediately precede a first one of the at least one data transmission.

In block <NUM>, a first transmission power for the at least one data transmission is determined. The first transmission power may be determined in a corresponding manner to a normal power control procedure in the system, for example a closed-loop or open-loop power control procedure, or any combination thereof. In block <NUM>, a second transmission power is determined for the at least one collision avoidance transmission based on information indicative to the location of the user terminal proportionate to the location of an access node providing a radio cell.

The power or power level may be determined for the collision avoidance transmission being receivable in the area of the radio cell or in the example situation of <FIG>. The collision avoidance transmission or signal may be a preamble, or an extension of a cyclic prefix of a data symbol, a (control) signal or a part of a suitable signal, or any form of transmission named collision avoidance transmission, for example.

It should be understood that transmitting also the data transmission or portion at a higher power would cause more interference in the system, whereby transmitting only the collision avoidance transmission at an increased power provides enhanced coexistence on the shared resources, while controlling interference. A plurality of alternatives for the determining will be laid out.

A first example alternative comprises selecting a predetermined constant power level for the collision avoidance transmission. The power level may be either fixed in specifications or standards, such as a maximum power allowed by regulations, or the maximum power supported by a user terminal (UE, user device), such as <NUM> dBm, for example. Alternatively, the power level may be signaled to a user terminal from an access node, for example as part of the information defining the permission for the user terminal to transmit on the shared radio resources. However, the power level for collision avoidance transmission should always larger than or equal to the power level of the data transmission. If the required power for the data transmission is higher than the configured power of the collision avoidance transmission, the user terminal should set the same power to the collision avoidance transmission and data transmission transmissions as follows: <MAT> wherein PALU,data is a value given by power control equation such as: <MAT> wherein.

In other words, in the first example alternative the transmit power of the collision avoidance transmission is the larger of: the predetermined constant power level and the transmit power level of the data transmission.

A second example alternative comprises selecting a power level for the collision avoidance transmission which is the transmission power level for the data transmission in question or transmission incremented by a predetermined power offset. The size of the power offset, for example 3dB or an offset expressed in Watts, may be signalled to the user terminal by the access node, for example via radio resource control (RRC) signalling. This alternative may correspond to adding a power offset on top of a target received power at the access node, for example, i.e. P<NUM>_AUL term in the power control formulas, for example: <MAT> wherein.

In other words, the transmit power of the collision avoidance transmission is the smaller of: a maximum power the terminal device supports and the data transmission transmit power incremented by the power offset.

A third example alternative comprises selecting a power level for the collision avoidance transmission based on a pathloss between a user terminal and an access node such that the lower the pathloss, the higher the transmission power for the collision avoidance transmission. The pathloss is the difference between a transmitted power and a received power. For example, the power level for the collision avoidance transmission may be inversely proportional to the pathloss, or the power level for the collision avoidance transmission may increase linearly with decreasing pathloss. This may be equivalent to adding into power control formulas a second "alpha" parameter, which may have a negative value. However, the collision avoidance transmission transmit power should here also always be at least the data portion or data transmission transmit power, for example: <MAT> wherein.

As another example, transmission power for the collision avoidance transmission may be determined: <MAT> wherein.

Pathloss may be obtained from receiving from an access node a report concerning a power level at which a signal from a user terminal was received, or, alternatively or additionally, the user terminal may determine an estimate of the pathloss from a power control value in use with the access node, since the access node will, in general, instruct the user terminal to increase transmit power in general as a response to higher pathloss. Moreover, the user terminal may also estimate the pathloss by itself based on the power level at which it receives transmissions, such as synchronization signals or reference signals, from the access node.

A fourth example alternative comprises selecting a power level for the collision avoidance transmission based on a timing advance value between a user terminal and an access node, such that the smaller the timing advance value is, the higher the transmission power for the collision avoidance transmission. It should be understood that timing advance and user device's distance from the access node are usually correlated, but not necessarily one-to-one. Transmission power for the collision avoidance transmission may be determined as follows: <MAT>.

An access node may set a small timing advance value for user terminals close to it, and larger timing advance values for user terminals located further from it, and hence timing advance value can be indicative of the user terminal's distance from the access node. Thus, this resembles the third alternative, since the pathloss is expected to be smaller, when the user terminal is closer to the access node. User terminals close to the access node will use high transmission powers for their collision avoidance transmission transmissions, while cell-edge user terminals would use lower collision avoidance transmission transmit powers. The collision avoidance transmission transmit power should here also always be at least the data transmission transmit power also in this case. Cell-edge user terminals will have data transmission transmit powers that are fairly high to begin with. The timing advance value, in general, is used to allow time for radio signal propagation from further-away user terminals and is thus an indication of the physical distance between the user terminal and the access node. The user terminal will have the timing advance value, since it needs it to perform normal transmissions with the access node.

A fifth example alternative comprises selecting a power level for the collision avoidance transmission based on an outcome of an earlier transmission, such that in case the earlier transmission is unsuccessful, the transmission power for the collision avoidance transmission is increased. If a user terminal close to an access node does not get an acknowledgment for its grant-free transmission, it may assume that there is a possibility that the resources were overbooked, that it was not heard by another transmitting user terminal farther away, and that a collision occurred on the specific resources reserved and used for the earlier transmission. Consequently, the user terminal may for the next grant-free transmission increase the power of its collision avoidance transmission by, for example, a predefined amount in decibels or Watts. The predefined amount may be configurable by the access node, for example with RRC signaling comprising configuration information.

Additionally, user terminals or an access node may be able to determine transmission powers for a plurality of user terminals using the pathloss differences between the terminals. The pathloss differences between terminals can be for instance known in systems where device-to-device communication is enabled, or where the user terminals are able to listen to collision avoidance signals of each other, or where the access node is aware of locations of the user terminals and a pathloss map. In those cases, the collision avoidance transmission power may be scaled with a user terminal to user terminal pathloss and the data transmission may be scaled according to a user terminal to an access node pathloss.

When narrow antenna beams are used, the pathloss between user terminals may be derived from the pathloss of at least one user terminal to an access node: PL (UE1 - UE2) = PL(UE2 - gNB) - PL(UE1 - gNB), where PL(x-y) denotes the pathloss between two terminals x and y.

If it is assumable that an access node does not need to hear a collision avoidance transmission (such as an extension of a cyclic prefix of a data symbol, but only the regular cyclic prefix), the collision avoidance signal power can be scaled to be lower than the data part of the UL transmission. It may be scaled such that only another nearby terminal can hear it.

The first procedure to select the power level for the collision avoidance transmission may also be a combination of two or more of the alternatives described above. For example, a power offset relative to the data transmission (alternative <NUM>) may be increased in case the transmission is initially not successful (alternative <NUM>). The alternatives described above are graphically laid out in <FIG>. In general, configuration information received in the user terminal from the access node may define the power offset and/or mathematical function(s) enabling selection of the collision avoidance signal transmit power based on the pathloss, timing advance and/or an outcome of an earlier transmission.

<FIG> illustrates some embodiments of power control or setting for collision avoidance transmission. At the top left, denoted "A)", is the first alternative laid out above. For any data transmission transmit power P_data, the collision avoidance transmission transmit power, P_collision avoidance transmission, is the maximum allowed, either in the cell, a network, or for a user terminal. In other variants of the first alternative, the constant P_collision avoidance transmission may be other than the maximum allowed, as long as it is always at least P_data and not less.

At the top right, denoted "B)", is the second example alternative laid out above. The collision avoidance transmission transmit power is the data transmission transmit power incremented by a power offset. In other words, the collision avoidance transmission power is always higher than the data transmission transmit power by a constant offset, which may be expressed in decibels or Watts, for example. The size of the offset may be communicated from the access node to the user terminal via signalling, such as RRC signalling, for example. Of course, the collision avoidance transmission transmit power may not exceed a maximum transmit power allowed or possible for the user terminal, also in this case.

In the middle, left, denoted "C)" is the third example alternative laid out above. The collision avoidance transmission power is boosted relative to the data transmission transmit power when the user terminal is close to the access node, that is, when the transmission power of the data transmission, and pathloss, is low. Normal power control will cause the transmission power of the data transmission to be low when the user terminal is close to the access node, since communication can successfully be performed to the access node with low power, which also reduced unwanted interference in the system. For user terminals further away, the collision avoidance transmission is transmitted with the same power as the data transmission, in this example. In another example of the third alternative, a small power offset is allowed to remain also for user terminals further away from the access node. The fourth alternative may look similar in graphical terms as the "C)" illustration of <FIG>, as the timing advance is used instead of pathloss.

In the lowest part of <FIG>, denoted "D)", is the fifth example alternative laid out above. On the left, a user terminal close to the access node transmits a grant-free collision avoidance transmission and data transmission, which collides with a similar transmission from another user terminal, also depicted in <FIG>. The circle around the first-mentioned user terminal illustrates schematically the range of the collision avoidance transmission. Responsive to the failed transmission, the user terminal will re-transmit, now increasing the transmit power of the collision avoidance transmission, which is illustrated on the lower right. The other user terminal can now perceive the collision avoidance transmission during its LBT listening period, and it will responsively abstain from transmitting, thus avoiding a repeat of the collision. The transmission of the user terminal close to the access node may then succeed.

<FIG> illustrates an example apparatus capable of supporting at least some embodiments. Illustrated is device <NUM>, which may comprise, for example, a user terminal <NUM> of <FIG>. In applicable parts, the illustrated device may also correspond to an access node <NUM>, or an access point. Comprised in device <NUM> is processor <NUM>, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor <NUM> may comprise, in general, a control device. Processor <NUM> may comprise more than one processor. Processor <NUM> may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core designed by Advanced Micro Devices Corporation. Processor <NUM> may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor <NUM> may comprise at least one application-specific integrated circuit, ASIC. Processor <NUM> may comprise at least one field-programmable gate array, FPGA. Processor <NUM> may be means for performing method steps in device <NUM>. Processor <NUM> may be configured, at least in part by computer instructions, to perform actions.

A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. The circuitry or circuits may also be a system-on-chip type of an integrated circuit.

An apparatus or device may also comprise means for receiving (<NUM>), by a user terminal, configuration for a grant-free transmission on a shared radio resource, the grant-free transmission comprising at least one collision avoidance transmission and at least one data transmission, wherein the at least one collision avoidance transmission precedes the at least one data transmission, means for determining (<NUM>) a first transmission power for the at least one data transmission, means for determining (<NUM>) a second transmission power for the at least one collision avoidance transmission based on information indicative to the location of the user terminal proportionate to the location of an access node providing a radio cell, and means for transmitting (<NUM>) the at least one collision avoidance transmission at the second determined power and the at least one data transmission at the determined first transmission power.

Device or apparatus may be, include or be associated with at least one software application, module, unit or entity configured as arithmetic operation, or as a program (including an added or updated software routine), executed by at least one operation processor. Programs, also called program products or computer programs, including software routines, applets and macros, may be stored in any apparatus-readable data storage medium and they include program instructions to perform particular tasks. The data storage medium may be a non-transitory medium. The computer program or computer program product may also be downloaded to the apparatus. A computer program product may comprise one or more computer-executable components which, when the program is run, for example by one or more processors possibly also utilizing an internal or external memory, are configured to carry out any of the embodiments or combinations thereof described above. The one or more computer-executable components may be at least one software code or portions thereof. Computer programs may be coded by a programming language or a low-level programming language.

Embodiments provide computer programs comprising instructions which, when the program is executed by an apparatus, cause the apparatus to carry out embodiments described by means of <FIG>.

Device <NUM> may comprise a transmitter <NUM>. Device <NUM> may comprise a receiver <NUM>. Transmitter <NUM> and receiver <NUM> may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter <NUM> may comprise more than one transmitter. Receiver <NUM> may comprise more than one receiver. Transmitter <NUM> and/or receiver <NUM> may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, <NUM>, long term evolution, LTE, IS-<NUM>, wireless local area network, WLAN, Ethernet and/or worldwide interoperability for microwave access, WiMAX, standards, for example.

Device <NUM> may comprise user interface, UI, <NUM>. UI <NUM> may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device <NUM> to vibrate, a speaker and a microphone. A user may be able to operate device <NUM> via UI <NUM>, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory <NUM> or on a cloud accessible via transmitter <NUM> and receiver <NUM>, or via NFC transceiver <NUM>, and/or to play games.

Device <NUM> may comprise or be arranged to accept a user identity module <NUM>. User identity module <NUM> may comprise, for example, a subscriber identity module, SIM, card installable in device <NUM>. A user identity module <NUM> may comprise information identifying a subscription of a user of device <NUM>. A user identity module <NUM> may comprise cryptographic information usable to verify the identity of a user of device <NUM> and/or to facilitate encryption of communicated information and billing of the user of device <NUM> for communication effected via device <NUM>.

As an alternative to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise, processor <NUM> may comprise a receiver arranged to receive information in processor <NUM>, via electrical leads internal to device <NUM>, from other devices comprised in device <NUM>. As alternative to a serial bus, the receiver may comprise a parallel bus receiver.

Device <NUM> may comprise further devices not illustrated in <FIG>. For example, where device <NUM> comprises a smartphone, it may comprise at least one digital camera. Some devices <NUM> may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the front-facing camera for video telephony. Device <NUM> may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device <NUM>. In some embodiments, device <NUM> lacks at least one device described above. For example, some devices <NUM> may lack a NFC transceiver <NUM> and/or user identity module <NUM>.

Processor <NUM>, memory <NUM>, transmitter <NUM>, receiver <NUM>, NFC transceiver <NUM>, UI <NUM> and/or user identity module <NUM> may be interconnected by electrical leads internal to device <NUM> in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device <NUM>, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

<FIG> illustrates signalling in accordance with at least some embodiments. On the vertical axes are disposed, from the left, user terminal <NUM> of <FIG>, user terminal <NUM> of <FIG>, and the access node <NUM> of <FIG>. Time advances from the top toward the bottom.

In phases <NUM> and <NUM>, access node <NUM> provides to the user terminal <NUM> and <NUM>, respectively, information defining permissions for the respective user terminals to transmit on shared radio resources. The contents of this information have been described herein above. The specific resources allocated to user terminal <NUM> and <NUM> are, in this example, the same.

In phase <NUM>, user terminal <NUM> resolves to attempt a transmission on the shared radio resources. Phase <NUM> is an LBT listening period phase to determine, if the specific resources allocated to user terminal <NUM> are free. In this example they are free, and phase <NUM> follows, that being a collision avoidance transmission t, wherein the collision avoidance transmission power is selected using a different process than the selection of the data transmission t power. The data transmission is transmitted to access node <NUM> in phase <NUM>.

In phase <NUM>, user terminal <NUM> resolves to attempt a transmission on the shared radio resources. Phase <NUM> is an LBT listening period phase to determine, if the specific resources allocated to user terminal <NUM> are free. In this example they are not free, as the boosted collision avoidance transmission t (phase <NUM>) from user terminal <NUM> takes place during phase <NUM> and is detected by user terminal <NUM>. The boosted collision avoidance transmission power facilitates the detection of the collision avoidance transmission Responsive to the detection, user terminal <NUM> abstains from the transmission, instead waiting and then performing a new LBT listening period phase, phase <NUM> of <FIG>. By this time the resources are free, and user terminal <NUM> proceeds to transmit a collision avoidance transmission, phase <NUM>, and the data transmission, phase <NUM>, to access node <NUM>.

Claim 1:
An apparatus comprising:
means (<NUM>) for receiving, by a user terminal, configuration for a grant-free transmission on a shared radio resource, the grant-free transmission comprising at least one collision avoidance transmission and at least one data transmission, wherein the at least one collision avoidance transmission precedes the at least one data transmission;
means (<NUM>) for determining a first transmission power for the at least one data transmission;
means (<NUM>) for determining a second transmission power for the at least one collision avoidance transmission based on information indicative to a location of the user terminal proportionate to a location of an access node providing a radio cell, and
means (<NUM>) for transmitting the at least one collision avoidance transmission at the second determined power and the at least one data transmission at the determined first transmission power.