Patent Description:
Wireless data usage is growing exponentially and operators are facing capacity constraint in the networks. As licensed communication resources are limited (and can be very costly to obtain) and there is an ever increasing demand for the resources, one possible approach is to apply unlicensed frequency bands for the communication.

<CIT> discloses a dynamic configuration method for the guard period, GP, of TDD subframes. <CIT> discloses transmission opportunities for a WLAN system and deals with "coexistence gaps", which are used for different reasons, namely for transmissions of other users of coexisting radio technologies.

Embodiments described may be implemented in a radio system, such as in at least one of the following: Worldwide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, <NUM>), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, <NUM>) based on basic wideband-code division multiple access (W-CDMA), highspeed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced (LTE-A), and/or <NUM> system.

<FIG> shows a network to which the embodiments may be applicable. Radio communication networks, such as the Long Term Evolution (LTE) or the LTE-Advanced (LTE-A) of the <NUM>rd Generation Partnership Project (3GPP), are typically composed of at least one base station <NUM> providing coverage to a cell <NUM>. Each cell <NUM> may be, e.g., a macro cell, a micro cell, or a pico-cell, for example. The base station <NUM> may be evolved node B (eNB) as in the LTE and LTE-A, a radio network controller (RNC) as in the UMTS, a base station controller (BSC) as in the GSM/GERAN, or any other apparatus capable of controlling radio communication and managing radio resources within a cell. In the case of multiple eNBs in the communication network, the eNBs may be connected to each other with an X2 interface as specified in the LTE. The eNB <NUM> may be further connected via an S1 interface to an evolved packet core (EPC) <NUM>, more specifically to a mobility management entity (MME) and to a system architecture evolution gateway (SAE-GW).

The network may serve at least one terminal device <NUM>, located within the cell <NUM>. The terminal devices <NUM>, <NUM> may communicate with each other via the base station <NUM>. The terminal device <NUM>,<NUM> may be a terminal device of a cellular communication system, e.g. a computer (PC), a laptop, a palm computer, a mobile phone, a smart phone or any other user terminal or user equipment capable of communicating with the cellular communication network.

Typically the network uses licensed bands for communication. However, at times there exists a need to apply more resources. This may be accomplished by performing communications on unlicensed bands, such as LTE-Unlicensed (LTE-U). An example frequency band for such unlicensed LTE-operation may be the <NUM> industrial, scientific and medical (ISM) band. Although the licensed band LTE may have better service quality than the unlicensed spectrum and the LTE-U does not remove the need to have more licensed band, the LTE-U may be advantageous to meet the user demands in some situations. One solution may also be WiFi offloading, but the LTE can perform better than WiFi when the system becomes heavily loaded.

Before being permitted to transmit on a given unlicensed radio band, a user or an access point (such as an evolved node B (eNB) of the LTE-A) may, depending on the regulatory requirements, may need to monitor the given radio frequency for a short period of time to ensure the spectrum is not already occupied by some other transmission. This requirement is referred to as List-before-talk (LBT) -procedure.

In an embodiment, the proposed approach is applicable to frame based equipment. Such frame based equipment are equipment where the transmit/receive structure is not directly demand-driven but has fixed timing. For the frame based equipment, the LBT operation may be defined as follows. Before starting transmissions on an operating channel, the equipment may be required to perform a Clear Channel Assessment (CCA). The equipment may observe the operating channel(s) for the duration of the CCA observation time. This may be at least <NUM> microseconds. The energy detection threshold for the CCA may be proportional to the maximum transmission power of the transmitter.

The operating channel is considered occupied if the energy level in the channel exceeds a pre-set energy detection threshold. If the equipment finds the operating channel occupied, the equipment may not transmit on that channel during a next, predefined, fixed frame period. However, if the equipment finds the operating channel(s) to be clear, the equipment may transmit on the channel.

The total time during which the equipment may have transmissions on a given channel without re-evaluating the availability of that channel, is defined as a channel occupancy time. The channel occupancy time may be in the range <NUM> to <NUM> and the minimum idle period may be at least <NUM> % of the channel occupancy time used by the equipment for the current fixed frame period. Depending on the regulatory requirements, channel occupancy times outside the given range (from <NUM> to <NUM>) may also be considered.

Although these rules may partly define some boundary conditions for the system operating on the respective spectrum, these regulations do not provide for a detailed solution on how to define and operate the system. For example, one problem related to the LBT in connection of LTE-U is how to support LBT on top of the current LTE radio frame structure such that commonality with current the LTE radio frame structure is maximized and system overhead due to the LBT is minimized.

Therefore, there is proposed a channel reservation window arrangement which is suitable at least for the LTE-U operation. Thus, the proposed channel reservation window may support the LBT-procedure (such as the CCA). The channel reservation window may be used for subframe transmissions. Thus, the subframe is accommodated into the proposed channel reservation window. The proposed channel reservation window may comply with a maximum number of DL resources that can be supported without violating the LBT requirements.

As shown in <FIG>, <FIG>, in order to define at least one channel reservation window (CRW) <NUM>, the eNB <NUM> may, in step <NUM>, set a length for each of the at least one channel reservation window <NUM> such that each channel reservation window comprises a plurality of subframes <NUM>. Thus, in an embodiment, the length of a given channel reservation window <NUM> may be a multiple of a subframe length. In the example of <FIG>, the channel reservation window comprises <NUM> sub-frames. In the LTE, each subframe is set to last for <NUM> and, therefore, the length of the channel reservation window <NUM> of <FIG> may be <NUM>. It may also be recalled that, in the LTE, each subframe comprises two slots in time domain and each slot comprises either <NUM> symbols in case of an extended cyclic prefix (CP), or <NUM> symbols in case of normal CP.

In an embodiment, the length of the channel reservation window <NUM> varies between <NUM> and <NUM>. If we denote the number of subframes <NUM> as N, then N ∈ [<NUM>,<NUM>,. As known, ten consecutive subframes <NUM> form a frame of the LTE. Thus, using N ∈ [<NUM>,<NUM>,. ,<NUM>] may be advantageous in order to provide backwards compatibility, for example. In another embodiment, and depending on the regulatory rules, N=<NUM> is also an option.

In step <NUM>, the length of each channel reservation window is divided into a transmission part <NUM> and an idle part <NUM>. The transmission part <NUM> may correspond to the fixed frame period mentioned earlier. The idle part <NUM> may correspond to a discontinuous transmission (DTX) part which may not contain any transmission. The idle part <NUM> consists of one or more symbols in one sub-frame. As further shown in <FIG> with bricked blocks, the idle part <NUM> may comprise the LBT-procedure <NUM>, such as the CCA observation time (as explained above). The CCA process <NUM> may be performed during at least part of the idle part <NUM>. In an embodiment, the CCA <NUM> is performed at the end of the idle part <NUM>.

One problem related to the division performed in step <NUM> is how to dimension these parts <NUM> and <NUM> in a way which enables efficient data transmission and reliable CCA process <NUM>. In order to solve this, the base station <NUM> in step <NUM> maximizes, at a symbol level accuracy, the length of the transmission part <NUM> such that a ratio between the length of the idle part <NUM> and the length of the transmission part <NUM> fulfils a predetermined criterion. Thus, maximizing the length of the transmission part <NUM> comprises maximizing the number of symbols of the transmission part <NUM> such that the predetermined criterion is fulfilled. In a typical scenario, symbol length is assumed to be fixed when maximizing the number of symbols of the transmission part <NUM>. However, in some embodiments, it is also possible to consider symbols having different length options (e.g. T, T/<NUM>, T/<NUM>, etc.).

In an embodiment, the symbols are orthogonal frequency-division multiple access (OFDMA) symbols. Assuming each subframe <NUM> has Y OFDMA symbols, the channel reservation window <NUM> may comprises altogether N times Y symbols. Now the maximization of the length of the transmission part <NUM> may denote finding/determining the maximum number of OFDMA symbols for the transmission part <NUM> so that the idle part <NUM> still lasts at least the minimum length. There may be a presser requirement for length of the idle part <NUM>, which needs to be fulfilled. In an embodiment, the predetermined criterion requires that the length of the idle part is at least certain percentage of the length of the transmission part. In an embodiment, the certain percentage is five percent. Thus, the required length of the idle part <NUM> may depend on the size of the channel reservation window <NUM>. Therefore, setting the length for the idle part <NUM> may not be a straight-forward task, but requires consideration of the size of the channel reservation window <NUM>, for example.

Then, in step <NUM>, the base station <NUM> may concatenate the transmission part <NUM> and the idle part <NUM> so as to form the channel reservation window <NUM>. In an embodiment, the transmission part <NUM> precedes the idle part <NUM>. In this embodiment, the idle part <NUM> (and the CCA process <NUM> of the idle part <NUM>) of a previous channel reservation window precedes the transmission part <NUM> of the following channel reservation window. In another embodiment, the idle part <NUM> precedes the transmission part <NUM> in the channel reservation window <NUM>.

Thereafter, the base station <NUM> proceeds to radio frame transmission according to the channel reservation window <NUM>.

Let us look at closer on some embodiments on how the maximization problem may be solved. In an embodiment, as shown also in <FIG>, the transmission part <NUM> is further divided into two sub-blocks, namely into a first sub-block <NUM> and into a second sub-block <NUM>. In an embodiment, the length of the first sub-block <NUM> corresponds to the length of the channel reservation window <NUM> minus one subframe, i.e., to N-<NUM> sub-frames. As a result, the idle part <NUM> and the second sub-block <NUM> together form the one remaining sub-frame of the channel reservation window <NUM>. This remaining subframe comprising the idle part <NUM> and the second sub-block <NUM> is shown in <FIG> with a dotted block <NUM>. The length of the second sub-block <NUM> corresponds to the length of one sub-frame <NUM> minus the length of the idle part <NUM>.

In an embodiment, the idle part <NUM> and the second sub-block <NUM> are comprised in the last sub-frame <NUM> of the channel reservation window <NUM>. This may provide ease of configuration.

<FIG> opens up this subframe <NUM> in more details. As earlier implied, each subframe <NUM> comprises a predetermined number of symbols. In case of the normal CP, there are altogether <NUM> symbols (<NUM> times <NUM> symbols) in one LTE subframe. In case of the extended CP, there are altogether <NUM> symbols (<NUM> times <NUM> symbols) in one LTE subframe. The example Figure of 3B represents the case with the extended CP, so there are <NUM> symbols <NUM> in the LTE subframe <NUM>. In an embodiment, these symbols <NUM> are orthogonal frequency-division multiple access (OFDMA) symbols.

The base station <NUM> may then maximize, at the symbol level accuracy (at a symbol granularity), the length of the second sub-block <NUM> within the subframe <NUM> such that the ratio between the length of the idle part <NUM> and the length of the transmission part <NUM> fulfils the predetermined criterion. It may be noted that the second sub-block <NUM> is a part of the transmission part <NUM>. As the maximization is done at the symbol level accuracy (e.g. at an accuracy of one OFDMA symbol), maximizing the length of the second sub-block <NUM> comprises maximizing the number of symbols <NUM> of the second sub-block <NUM> such that the predetermined criterion is fulfilled. Thereafter, the length of the second sub-block <NUM> within the subframe <NUM> is an integer multiple of the length of the symbol <NUM>. This provides ease of implementation.

The predetermined criterion requires that the length of the idle part <NUM> is at least five percent of the length of the transmission part <NUM>. This may ensure that the CCA process <NUM> has enough resources to reliably detect any ongoing transmissions. However, other percentage values may be applied, depending on the current regulations, for example. Let us denote this predefined percentage value as X from here on. As an example, if the percentage value is five percent, then X = <NUM>,<NUM>.

In an embodiment, the number M of symbols <NUM> in the second sub-block <NUM> may be given as follows: <MAT> where <MAT> is the floor operation of A and Y corresponds to the number of (e.g. OFDMA) symbols per each subframe <NUM>. Parameter N is the length of the channel reservation window <NUM> in milliseconds, (N ∈ [<NUM>,<NUM>,. ,<NUM>]), that is the number of subframes <NUM> in the channel reservation window <NUM>. Following the Equation (<NUM>), M ∈ [<NUM>, <NUM>,.

When applying this equation and the steps provided above, the length of the idle part <NUM> increases in proportion to the length of the transmission part <NUM>. This is shown in <FIG>, where nine different LBT-enabling channel reservation window formats are given, each marked as LBT #. The upper part of the Figure shows, for the sake of comparison, a normal LTE radio frame having ten subframes (<NUM>, <NUM>, <NUM> ,. As shown, each LBT window #<NUM> - #<NUM>, comprises at least <NUM> subframes and one of the subframes includes the second sub-block <NUM> (marked with dotted blocks) and the idle part <NUM> (marked with blocks having right-leaning diagonal lines). As may be seen, the size of the idle part <NUM> becomes larger and the size of the second sub-block <NUM> becomes smaller as the channel reservation window <NUM> increases in size.

As said, the size/length of the CP may affect the number of symbols in a given subframe. Thus, in an embodiment, the size of the cyclic prefix is taken into account when maximizing the length (i.e. the number of symbols) of the transmission part <NUM>. In an embodiment, the length of the CP is assumed equal for all symbols. However, in an embodiment, if the cyclic prefix length/size is not equal for all symbols, the varying cyclic prefix length is taken into account when defining the channel reservation window <NUM> so that it is ensured that the predetermined criterion is met.

It may be noted that the equation (<NUM>) may ignore the fact that the CP length may be larger at the beginning of a subframe. Thus, in an embodiment, the "equal to" sign (=) may be changed to "equal to or smaller than" sign (≤).

Tables <NUM> and <NUM> show different LBT enabling channel reservation windows. Table <NUM> is for a case with the normal CP (<NUM> symbols in one sub-frame <NUM>, Y=<NUM>), whereas Table <NUM> is for a case with the extended CP (<NUM> symbols in one sub-frame <NUM>, Y=<NUM>). In both cases, the parameter X is set to be <NUM> %, as an example value. These channel reservation window formats enable the maximum utilization of LTE-U downlink resources in any given LBT scenario. The lengths are given in milliseconds in the Tables.

In an embodiment, the second sub-block <NUM> may be considered as a specific downlink pilot time slot (DwPTS) size-variant defined for the LTE-U. The DwPTS is a part of special subframe of a time-division (TD) LTE frame structure.

Let us then look at further embodiments. In an embodiment, the transmission part <NUM> may be time positioned with respect to a predetermined reference <NUM>, as shown in <FIG>. For example, the time positioning may define that the transmission on the channel reservation window <NUM> starts at the same time as a transmission of the reference <NUM>. This is shown in <FIG>. In another embodiment, there may be an offset parameter <NUM>, which may define the start of the transmission part <NUM> with respect to the reference <NUM>. The time offset may be valid for a predefined radio frame number. As the transmission part <NUM> and the idle part <NUM> are consecutive, time positioning the transmission part <NUM> simultaneously defines a time position for the idle part <NUM>. Similarly, time positioning the idle part <NUM> may define the start timing of the transmission part <NUM>.

In an embodiment, the reference <NUM> comprises a transmission of one of the following: a primary synchronization signal (PSS), a secondary synchronization signal (SSS). Use of PSS/SSS ,may be advantageous also from the point of view that typically other reference signals are more spread over the radio frame duration. It may be noted also that the PSS/SSS may be used to determine radio frame timing also in the normal LTE. The reference <NUM> may be the transmission of the PSS/SSS on a predetermined radio frame, such as radio frame #<NUM>.

In an embodiment, the bases station participates in carrier aggregation (CA) and the defined channel reservation window <NUM> is applied for transmissions on a secondary cell. Thus, there may be CA applied in the network for enhancing the communication efficiency and resources.

In an embodiment, the LTE-U may be developed so that it relies on the licensed band LTE operations. For example, in the CA, the primary cell (PCell) may operate on the licensed band whereas the unlicensed band may provide resources for the secondary cell (SCell) for transmitting a secondary component carrier (SCC). That is, the SCell may operate on the unlicensed band, whereas the PCell may operate on the licensed band. In an example, transmissions on SCell comprise only downlink transmissions while PCell is at least partly used for necessary uplink transmissions. Such SCell may be termed as supplementary downlink cell (SDL). Thus, in an embodiment, the channel reservation window <NUM> is applicable to the SDL operation. In an embodiment, the PCell is served by another base station than the eNB <NUM> providing the SCell and the SCC.

In an embodiment, the reference <NUM> comprises a radio frame transmitted on a primary component carrier (PCC). The PCC may be transmitted in the PCell. Thus, there may be a fixed timing relationship between the Pcell DL and the LTE-U operation (e.g. comprising the transmission on the channel reservation window <NUM>). For example, the beginning of a radio frame transmitted on the PCC and the beginning of a radio frame transmitted according to the channel reservation window on the SCC may be time aligned.

In an embodiment, radio frame and channel reservation window have different lengths. In such case, the timing relationship between the radio frame and channel reservation window depend on the radio frame or the subframe number. Radio frame may be used to determine e.g. time positions of certain signals on SCell, such as the PSS/SSS, while channel reservation window may be used to meet the regulatory requirements on the fixed frame period. For example, the position of the idle part <NUM> may be determined at least partly based on the channel reservation window, whereas the position of specific signals (e.g. the PSS/SSS) may be at least partly determined based on the radio frame.

In an embodiment, the radio frames on SCell and PCell may be time aligned. This may provide ease of specification, configuration and implementation.

In an embodiment, the subframes of the radio frame transmitted on the PCC and the subframes of the radio frame transmitted on the SCC according to the channel reservation window <NUM> are time aligned. Time aligning the subframes may provide efficiency. In another embodiment, there is a full time alignment between the PCell and LTE-U operation. This may mean that the symbols are fully time aligned as well.

In yet one embodiment, as shown in <FIG>, the offset parameter <NUM> may determine the beginning of the transmission part <NUM> (i.e. the beginning of the radio frame transmission on the channel reservation window <NUM>) with respect to the beginning of a radio frame transmitted on the PCC (or the beginning of the PSS/SSS in a predefined radio frame, as one non-limiting alternative). In an embodiment, the applied timing offset <NUM> in the cell <NUM> is different than a corresponding timing offset applied in a neighbouring cell. Having configurable offset <NUM> may be used to ensure that the CCAs <NUM> are not time aligned in neighbouring non-coordinated LTE-U cells. This may be useful for the LTE-U coexistence with multiple LTE-U deployments by different operators, all served by PCells that are time-synchronized (e.g. time division duplex (TDD) -cells where different operators are synchronized).

In an embodiment, the subframe <NUM> of the channel reservation window <NUM> (containing the second sub-block <NUM> and the idle part <NUM>) may be aligned with a TDD special subframe by using LBT-<NUM> or LBT-<NUM> channel reservation windows with an appropriate offset value <NUM>. The TDD frame format has a periodicity of <NUM>, so the use of LBT #<NUM> or LBT #<NUM> may be efficient.

As shown in <FIG>, in one embodiment, the base station <NUM> may apply, during the transmission of the PCC on the PCell, an integral number of channel reservation windows <NUM>, each having the same length. That is, the usage of the LTE-U channel reservation window formats may be static or semi-static. For instance, in <FIG>, there are two LBT- enabling channel reservation windows, each having five subframes. This may provide ease of complexity. The eNB <NUM> may configure the LTE-U channel reservation window format usage and timing with respect to the PCell via higher layer signalling. In an embodiment, the usage of the channel reservation window format usage and timing is pre-coded to the eNB <NUM>.

In another embodiment, a varying LTE-U channel reservation window format from channel reservation window to channel reservation window may be applied. That is, each cell/eNB may select one of the available LTE-U channel reservation window formats at a time. This is shown in <FIG>. In <FIG>, there are three different LBT- enabling channel reservation window formats applied, LBT #<NUM>, LBT #<NUM>, and LBT #<NUM>. The dotted vertical lines show that the beginnings of the LBT-enabling channel reservation window may be time aligned.

In this embodiment, the eNB <NUM> may define a plurality channel reservation windows with different lengths. It may be noted, that in an embodiment, the available LTE-U channel reservation window formats for the SDL may be tabulated in the specification and pre-coded to the eNB <NUM>. Moreover, the set of LTE-U channel reservation window formats are configured to the UEs <NUM>, <NUM> (e.g. via higher layers). UE uses the configured channel reservation window format for determining the position the transmission part <NUM> and for adjusting PDSCH reception accordingly, in particular in the subframe containing the idle part <NUM>.

The eNB <NUM> (or e.g. a user equipment) may, after detecting that the channel is free for transmission (e.g. after the CCA energy detection), select one of the plurality of channel reservation windows for a data transmission to a target device (such as to a user terminal or to an eNB, for example).

From the point of view of the eNB <NUM>, the eNB <NUM> may then indicate the selected channel reservation window <NUM> to a target user terminal (e.g. the UE <NUM>). For example, the eNB <NUM> may include the LTE-U channel reservation window format indicator in layer <NUM> (L1) signalling. As one non-limiting option, the indication may be made by including <NUM>-<NUM> bits in a scheduling assignment on the Physical Downlink Control Channel (PDCCH) or on the enhanced PDCCH. The eNB <NUM> may then perform the data transmission in the selected channel reservation window <NUM> to the user terminal <NUM>.

In an embodiment, the data transmission from the eNB <NUM> to the target user terminal is performed on the SCell and acknowledgement feedback for the data transmission is obtained on the PCell. Thus, the channel reservation window <NUM> is used for the transmissions on the SDL, while the uplink signaling from the UE is received on the PCell which may operate on a licensed band and thus may not need to use the LBT/CCA process.

In an embodiment, the applied channel reservation window format, varying from channel reservation window to channel reservation window, may be determined according to a pseudo-random pattern determined at least partially based on SCell physical cell identity. An outcome of a pseudo-random number generator depending for example on a channel reservation window number or on a subframe number and initialised at least partially with SCell physical cell identity may be used to determine the applied channel reservation window format. This embodiment may support fair LBT-procedure and access to the radio channel between neighbouring cells.

In one embodiment, as shown in <FIG>, the eNB <NUM> may exchange channel reservation window usage information with at least one neighbouring network node, such as with eNBs <NUM> and <NUM>. This embodiment may support coordination of the LTB channel reservation window format usage among neighbouring cells (marked with dashed circles in <FIG>). This may enable different interference coordination schemes for the CCA, e.g. synchronizing the idle periods <NUM> between neighbouring cells (e.g. in reuse <NUM> scenario) or de-synchronization of the idle periods <NUM> between the neighbouring cells (CCA operation within coordinated cells). As one option, this may ensure that neighbouring eNBs do not use the same timing for the CCA process. The coordination may be made via the X2 signalling <NUM>, <NUM>, for example. The information elements coordinated to the neighbouring cells may include, e.g., the usage of LTE-U channel reservation window formats and the timing of the LTE-U operation. The timing may include the information on how the channel reservation windows <NUM> are timed in different cells.

In an embodiment, the base station <NUM> may decide to apply the formed channel reservation window <NUM> instead of any predefined other channel reservation window. In an embodiment, this mandatory selection applies only in case the base station <NUM> provides the SCell in the CA and uses the generated channel reservation window <NUM> on the SCC.

Although the description has been written so that the base station <NUM> performs the method of <FIG>, the method may be performed by any radio device performing radio communication according to the CCA requirements, such as a user equipment.

As OFDMA symbols are used in the description as an example, it may be noted that a block-processing based approach is valid. This may mean that the proposed embodiments are equally valid for any waveform based on block-processing, including e.g. the Discrete Fourier Transform Spread OFDMA (DFT-S-OFDMA).

In an embodiment, the proposed method is applicable to downlink (DL) communication. In an embodiment the proposed method is applicable to communication taking place on a supplementary downlink cell (SDL).

In an embodiment, the proposed solution may have maximum commonality with the current LTE frame structures. This may be enable backward compatibility and straight-forward implementation. In an embodiment, overhead due to the CCA may be minimized. In an embodiment, the proposed channel reservation window <NUM> facilitates good interworking with the PCell in case of using the LBT (and, thus, the generated channel reservation window <NUM>) on the SCell. In an embodiment, the proposed channel reservation windows provide flexibility to match requirements in different bands and/or regions, while at the same time providing maximization of the LTE-U channel utilization and respecting regulatory requirements.

An embodiment, as shown in <FIG>, provides an apparatus <NUM> comprising a control circuitry (CTRL) <NUM>, such as at least one processor, and at least one memory <NUM> including a computer program code (PROG), wherein the at least one memory and the computer program code (PROG), are configured, with the at least one processor, to cause the apparatus to carry out any one of the described processes. The memory may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

In an embodiment, the apparatus <NUM> may be or be comprised in a base station (also called a base transceiver station, a Node B, a radio network controller, or an evolved Node B, for example). In an embodiment the apparatus <NUM> is or is comprised in the eNB <NUM>.

In another embodiment, the apparatus <NUM> may comprise the terminal device of a cellular communication system, e.g. a user equipment (UE), a user terminal (UT), a computer (PC), a laptop, a tabloid computer, a cellular phone, a mobile phone, a communicator, a smart phone, a palm computer, or any other communication apparatus. Alternatively, the apparatus <NUM> is comprised in such a terminal device. Further, the apparatus <NUM> may be or comprise a module (to be attached to the UE) providing connectivity, such as a plug-in unit, an "USB dongle", or any other kind of unit. The unit may be installed either inside the UE or attached to the UE with a connector or even wirelessly.

The apparatus <NUM> may further comprise communication interface (TRX) <NUM> comprising hardware and/or software for realizing communication connectivity according to one or more communication protocols. The TRX may provide the apparatus with communication capabilities to access the radio access network, for example.

The apparatus <NUM> may also comprise a user interface <NUM> comprising, for example, at least one keypad, a microphone, a touch display, a display, a speaker, etc. The user interface <NUM> may be used to control the apparatus by the user.

The control circuitry <NUM> may comprise <NUM> a channel reservation window generation circuitry <NUM> for generation of at least one channel reservation window <NUM>, according to any of the embodiments. A listen-before-talk (LBT) control circuitry <NUM> may be responsible of executing the LBT process, such as the CCA process. A carrier aggregation (CA) control circuitry <NUM> may be for handling CA operations, such as configuring the apparatus <NUM> to serve the SCell and transmitting frames in the channel reservation window <NUM> on the SCC.

As used in this application, the term 'circuitry' refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and soft-ware (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the apparatus(es) of embodiments may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chip set (e.g. procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit and executed by processors. The memory unit may be implemented within the processor or externally to the processor. In the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additionally, the components of the systems described herein may be rearranged and/or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

Embodiments as described may also be carried out in the form of a computer process defined by a computer program. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. For example, the computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example. Coding of software for carrying out the embodiments as shown and described is well within the scope of a person of ordinary skill in the art.

Claim 1:
An apparatus, comprising means (<NUM>, <NUM>, <NUM>) for performing:
receiving configuration of a channel reservation window format;
determining a position of a transmission part of at least one channel reservation window using the configured channel reservation window format,
wherein the at least one channel reservation window is divided into the transmission part and an idle part comprising one or more symbols in one sub-frame,
wherein the length of the transmission part is maximized, at a symbol level accuracy, such that a ratio between the length of the idle part and the length of the transmission part fulfils a predetermined criterion; and
receiving, based on the at least one channel reservation window, a data transmission.