Patent Description:
Certain wireless communication networks require a carrier-sense mechanism to avoid or reduce interference between wireless devices utilizing similar spectrum. This is particularly the case with radio-access technologies using unlicensed spectrum, such as Wi-Fi. The carrier-sense mechanism usually involves a transmitting device sensing the wireless medium for a period of time prior to transmitting over that medium. If the medium is determined to be busy (e.g., another device is transmitting in the vicinity of the transmitting device), the transmission may be deferred; if the medium is determined to be idle, the transmission can take place.

The carrier sensing mechanism in <NUM> Wi-Fi is called <NUM>-persistent slotted carrier sense multiple access with random backoff time and with collision avoidance (CSMA/CA). This technique is well known in the art. Further detail on <NUM>-persistent slotted carrier sense multiple access can be found in a book by <NPL>). Further detail on random backoff and collision avoidance can be found in a book by <NPL>). In <NUM>, CSMA/CA is performed through two main carrier sense mechanisms: energy detect clear-channel assessment (CCA) and signal detect CCA.

For energy detect CCA, it is specified that if a wireless device (STA) detects signal power on the primary channel on any antenna, where the signal power is larger than a power threshold of Pe = -<NUM> dBm, under a sensing time of smaller than or equal to Te = <NUM>, it shall defer from transmitting.

For signal detect CCA, it is specified that if a STA detects an orthogonal frequency division multiplex (OFDM) signal on the primary channel on any antenna with a power threshold of Ps = -<NUM> dBm under a sensing time of Ts = <NUM>, the STA shall defer from transmitting. Signal-detect CCA may be achieved for example by detecting a signal using the short training field (STF) part of the transmitted signal, and by determining whether the power is stronger than or equal to the power threshold Ps = -<NUM> dBm. Note that the power threshold for signal-detect CCA is different (lower) than the power threshold for energy-detect CCA.

For secondary channels, different power thresholds are possible. Furthermore, with the introduction of high efficiency (HE) in <NUM>. 11ax, color bits and other mechanisms allow for various different power thresholds.

Wireless communication increasingly relies on beamforming techniques to increase signal gain at a receiver and to reduce interference between transmissions. To perform beamforming, the channel from the transmitter to the receiver is typically known at the transmitter. One way to obtain this knowledge is through channel sounding. Once the channel is known, it is fed back from the receiver to the transmitter for accurate beamforming. Beamforming in Wi-Fi is explained in more detail in the book by Perahia and Stacey. With the introduction of <NUM> ay, pre-defined beams were introduced, meaning that less time needs to be spent on training, at the cost of reduced beamforming gain.

Thus significant gains can be made through the use of beamforming techniques. One problem, however, is that a transmitting device is still required to perform a clear channel assessment prior to transmitting. Existing CCA mechanisms are omni-directional, and do not take into account the benefits of beamforming. A transmitting device may be able to use beamforming to transmit to a target receiving device without causing interference to other devices which are transmitting nearby. However, a traditional CCA is likely to fail due to the presence of those devices; thus the transmitting device would defer transmission, and back-off. The available radio resources are inefficiently utilized, and the transmitting device is subject to unnecessary delays.

<CIT> discloses a method and apparatus for performing loop power control and transmission power control (TPC) in a wireless network. <CIT> discloses a method of a transmit apparatus for a directional listen-before-talk (LBT) operation in a wireless communication system. <CIT> describes spatial reuse using directional clear channel assessment (CCA). A first device may establish a directional wireless communications link with a second device, and determine a potentially interfering signal from a third device.

A <NPL>) discloses a discussion of the potential enhancements for the LBT mechanism such as LBT type for different physical signals/channels, LBT type for shared COT with switching points(s), LBT for wider bandwidth operation (e.g., integer multiple of <NUM>), CWS adjustments, and LBT in TX/Rx beamforming scenarios.

A <NPL>) discloses a discussion of potential solutions and techniques for NR-U (NR-based access to Unlicensed Spectrum).

Embodiments of the present disclosure seek to address these and other problems. The present invention is defined by the claims appended hereto.

Methods, apparatus and device-readable mediums are disclosed relating to wireless access in a network requiring a carrier-sense mechanism. One aspect provides a method performed by a transmitting device for transmitting to a receiving device in a wireless communications network. The transmitting device comprises a plurality of antenna elements. The method comprises: performing a directional carrier-sense assessment for one or more sub-bands configured for transmissions between the transmitting device and the receiving device, wherein each sub-band comprises one or more subcarriers, the directional carrier-sense assessment utilizing beamforming to detect a respective level of wireless activity on each of the sub-bands in a particular direction for transmissions to the receiving device, wherein the level of wireless activity in each sub-band comprises one of: idle and busy; selecting a respective transmit power for each sub-band based on the determined level of wireless activity; and transmitting to the receiving device in the particular direction, using the respective selected transmit power for each sub-band, in response to a determination that a number of subcarriers belonging to idle sub-bands exceeds a threshold number of subcarriers.

Apparatus and non-transitory device-readable mediums comprising instructions for performing the method set out above are also disclosed. For example, in another aspect, there is provided a transmitting device comprising processing circuitry and a plurality of antenna elements. The processing circuitry is configured to: perform a directional carrier-sense assessment for one or more sub-bands configured for transmissions between the transmitting device and the receiving device, wherein each sub-band comprises one or more subcarriers, the directional carrier-sense assessment utilizing beamforming to detect a respective level of wireless activity on each of the sub-bands in a particular direction for transmissions to the receiving device, wherein the level of wireless activity in each sub-band comprises one of: idle and busy; select a respective transmit power for each sub-band based on the determined level of wireless activity; and transmit to the receiving device in the particular direction, using the respective selected transmit power for each sub-band, in response to a determination that a number of subcarriers belonging to idle sub-bands exceeds a threshold number of subcarriers.

<FIG> shows a wireless communication network <NUM> according to embodiments of the disclosure. The network <NUM> comprises a first access point <NUM>, a target wireless device <NUM>, an interfering wireless device <NUM> and a second access point <NUM>. The access points <NUM>, <NUM> and wireless devices <NUM>, <NUM> transmit to each other using a radio-access technology that requires performance of a carrier-sense assessment (e.g., a CCA) prior to each transmission. For example, the radio-access technology may utilize unlicensed spectrum, which is shared between multiple radio-access technologies. In one embodiment, the network <NUM> implements one or more IEEE <NUM> standards (known as "Wi-Fi") and comprises a wireless local area network (WLAN). For convenience, the terminology used herein may correspond to that used in the <NUM> standards (e.g., "access point", "STA"). However, the concepts described herein may also find use in other radio-access technologies.

The scenario depicted in <FIG> is as follows. The target wireless device <NUM> belongs to a basic service set (BSS) associated with the first access point <NUM>. The interfering wireless device <NUM> belongs to a BSS associated with the second access point <NUM>. The first access point <NUM> has data to transmit to the target wireless device <NUM>, and is therefore required to perform a carrier-sense assessment prior to transmitting. The interfering wireless device <NUM> is transmitting to the second access point <NUM> at the same time, and using the same wireless spectrum (e.g., the same channel) as that configured for transmissions between the first access point <NUM> and the target wireless device <NUM>.

The first access point <NUM> may therefore perform a carrier-sense assessment to determine if the channel is free or busy. A traditional carrier-sense assessment is omni-directional (i.e. equally sensitive in all directions), and illustrated by the dashed circle <NUM> in <FIG>. The interfering wireless device <NUM> is within the dashed circle <NUM>, illustrative of the transmissions by the interfering wireless device <NUM> exceeding a power threshold associated with the omni-directional carrier-sense assessment. Thus, in ordinary circumstances, the first access point <NUM> would defer transmission until a later time (when a further carrier-sense assessment is performed).

The first access point <NUM> comprises a plurality of antennas or antenna elements, and is therefore capable of using beamforming techniques to focus its transmissions into one or more beams. As will be understood by those skilled in the art, beamforming involves the application of a set of weights and/or phase shifts to signals provided to or received from each antenna or antenna element such that those signals are weighted and/or phase-shifted by respective amounts. By applying a set of weights and/or phase shifts to signals provided to the antennas for transmission, a transmission beam is formed; by applying a set of weights and/or phase shifts to signals received by the antennas, a reception beam is formed (i.e. the reception is more sensitive in one direction than other directions). The beams may be pre-defined (e.g., in a standard implemented by the first access point <NUM>, such as IEEE <NUM>. 11ay), or determined based on feedback from earlier transmissions by the receiving wireless device.

In particular, the first access point <NUM> is able to utilize one or more beams <NUM> to transmit to the target wireless device <NUM>. In the illustrated embodiment, five different beams are shown: a main beam 120c, pointed directly towards the target wireless device <NUM>; and four side beams (or side lobes) 120a, 120b, 120d and 120e. In this context, it will be understood by those skilled in the art that a beam need not necessarily be transmitted along a vector path directly towards a receiving device to provide effective transmission to that receiving device. A beam may be subjected to one or multiple reflections and attenuations from surfaces and objects in the vicinity of the transmitting device and the receiving device. This is particularly so where the beam is transmitted indoors, as is often the case for WLANs. Thus a side beam (e.g. 120a) may provide a transmission mechanism which is as or more effective than a main beam 120c.

Further, it will be understood by those skilled in the art that each beam may correspond to a particular transmission frequency (or subcarrier). For example, a set of weights and/or phase-shifts applied to signals for transmission by the plurality of antennas will generally produce multiple beams, including a main transmission beam at a first transmission frequency, and one or more secondary transmission beams (or side beams) at one or more second transmission frequencies.

In order to utilize available radio resources more efficiently, and to decrease the likelihood of deferring transmission owing to negative carrier-sense assessments, according to embodiments of the disclosure a transmitting device is configured to perform a directional carrier-sense assessment to detect a level of wireless activity in a particular direction, prior to transmitting to a receiving device in the particular direction. The transmitting device selects or determines a transmit power based on the detected level of wireless activity, and uses the transmit power in its subsequent transmission to the receiving device.

By performing a carrier-sense assessment in a particular direction, the transmitting device is able to determine whether a subsequent transmission in that direction is likely to cause interference to (i.e. to collide with) transmissions by other devices only in that direction. Transmissions by devices in other directions will not be adversely effected by a subsequent transmission using beamforming, and therefore those transmissions need not be taken into account when performing the carrier-sense assessment.

Further, embodiments of the disclosure divide the configured wireless spectrum (e.g., a channel configured for transmissions by the transmitting device) into one or more sub-bands, and determine the level of wireless activity in each sub-band. Respective transmit powers are selected for each sub-band, based on the level of activity detected in the directional carrier-sense assessment, and used in a subsequent transmission to the receiving device. For example, a relatively low or zero transmit power may be selected for a sub-band with a relatively high level of wireless activity (e.g., busy); a relatively high transmit power may be selected for a sub-band with a relatively low level of wireless activity (e.g., idle). Thus, not only is the direction of any transmission taken into account, but also the particular frequencies at which the transmission occurs.

Further detail regarding embodiments of the disclosure can be found below, in the description of <FIG>.

<FIG> is a flowchart of a method in a transmitting device according to embodiments of the disclosure. The transmitting device may be suitable device, such as an access point or a mobile device (STA). For example, the transmitting device may be the first access point <NUM> described above with respect to <FIG>. The transmitting device is configured with one or more channels over which wireless transmissions can take place with one or more receiving devices. The channel may correspond to a particular transmission frequency, or in practice a range of frequency centered around a particular transmission frequency.

Embodiments of the disclosure also refer to a "sub-band", which is a sub-division of the full bandwidth configured for transmissions by the transmitting device. In embodiments which utilize orthogonal frequency division multiplexing, a sub-band may correspond to one or more subcarriers.

The full frequency band, BW, under consideration may be divided into I sub-bands (where I is an integer equal to or greater than one). The full bandwidth BW may comprise one or more channels, within one or more different transmission bands. Therefore, the sub-bands may also be non-adjacent in the frequency domain. For example, one sub-band may reside in the <NUM> ISM band, while another sub-band resides in the <NUM> band, and/or the <NUM> band.

The bandwidth of each sub-band may be the same or different. For example, in the former case, the bandwidth S of each sub-band may correspond to one subcarrier i.e., <MAT>, where N_FFT is the fast Fourier transform length. Alternatively, the bandwidth of the (single) sub-band may correspond to the entire bandwidth BW. For the general case (applying to OFDM transmissions), the bandwidth S of each sub-band comprises K subcarriers (where K is an integer equal to or greater than one). The subcarriers may be adjacent in the frequency domain or not.

The method shown in <FIG> further assumes that the wireless channel between the transmitting device and the receiving device is known and calibrated. That is, the antenna weights and/or phase shifts to be applied for beamforming transmissions between the transmitting device and the receiving device are known. For example, the transmitting device may have previously communicated with the receiving device and determined the appropriate beamforming parameters to be used for transmissions to the receiving device. In this regard, it may be assumed that the transmitting device and the receiving device are sufficiently static that the beamforming parameters from a previous communication will apply to a current situation.

The method begins upon the transmitting device determining that data is available for transmission to the receiving device. In step <NUM>, the transmitting device optionally performs an omni-directional carrier-sense assessment, i.e. as known in the prior art and discussed above in the background section.

The omni-directional carrier-sense assessment detects the level of wireless (i.e., radio) activity over the entire bandwidth BW configured for transmissions by the transmitting device. For example, the bandwidth BW may correspond to one or more channels. The carrier-sense assessment in step <NUM> is omni-directional in the sense that it is equally sensitive in all directions and does not, for example, apply beamforming techniques to increase the sensitivity in a particular direction above that in other directions.

The omni-directional carrier-sense assessment may comprise a clear-channel assessment (CCA), and may utilize energy-detect or signal-detect mechanisms to determine the channel as busy or idle. In either case, the detected power is compared to a power threshold: Pe for energy detect; and Ps for signal detect. In signal detect, the transmitting device is synchronized with the interfering device and triggers the signal detect carrier-sense assessment upon detection of a short training field (STF) in a transmitted WiFi packet.

In step <NUM>, the transmitting device determines whether the channel (or carrier) is free or not, based on the detected power. If the channel is free, the method proceeds to step <NUM>, and the transmitting device transmits to the receiving device following conventional methods.

If the channel is not free, however, the method proceeds to step <NUM> in which the transmitting device performs a directional carrier-sense assessment over each of the I sub-bands. That is, the transmitting device applies a set of weights and/or phase-shifts to signals for each of its plurality of antennas or antenna elements, so as to increase the sensitivity of reception in a direction which is suitable for transmissions to the receiving device. As will be understood from the description above with respect to <FIG>, the direction need not correspond precisely to the line-of-sight between the transmitting device and the receiving device, but may instead account for reflections and attenuations on the path between the transmitting device and the receiving device. Further, each subcarrier may correspond to a slightly different direction.

<FIG> is a schematic diagram of a directional carrier sense mechanism <NUM> according to embodiments of the disclosure, which may be implemented in the transmitting device. The carrier-sense mechanism <NUM> is shown acting on a single sub-band.

As noted above, the transmitting device comprises a plurality of antennas <NUM>, of which three are shown in <FIG> (referenced as 302a, 302b and 302c respectively). Any number of antennas greater than two is contemplated by the present disclosure. The number of antennas is denoted N. The received signal from each antenna <NUM> is converted to the digital domain by respective analogue-to-digital converters 304a, 304b, 304c, before being passed to respective fast Fourier transform (FFT) modules 306a, 306b, 306c. The FFT modules <NUM> divide each signal into its frequency components. In the illustrated example, where a sub-band corresponds to K subcarriers, each FFT module <NUM> outputs K signals corresponding to the different subcarriers.

Each frequency component is provided to a respective multiplying element, where it is multiplied by a respective beamforming weight. Thus, the kth frequency component from the nth antenna is multiplied by a weight vn(k). The frequency components output from the FFT module 306a are provided to a set of multiplying elements 308a; the frequency components output from the FFT module 306b are provided to a set of multiplying elements 308b; and the frequency components output from the FFT module 306c are provided to a set of multiplying elements 308c.

The weighted frequency component outputs for each antenna are provided to respective summing elements <NUM>, such that the weighted outputs from all antennas for a particular frequency component are summed together. Thus, there are K summing elements <NUM>. The power in each frequency component is determined by squaring the summed outputs in respective squaring elements 312a, 312b, 312c, and the overall detected power Pr(i) for the ith sub-band is determined by summing the power outputs in a further summing element <NUM>.

In order to compare the detected received power Pr(i) for the ith sub-band to a power threshold, one or more compensating factors may be applied. For example, a first compensation factor Pcs may be applied to compensate for the fact that the detected received power is for a sub-band rather than the whole bandwidth BW. The first compensation power may for example be <MAT> (where S is the bandwidth of the ith sub-band, as noted above). Using our previous examples, if s = BW, Pcs(i) = <NUM>, and if <MAT>, Pcs(i) = -<NUM> log<NUM> N_FFT. Thus it will be seen that the first compensation factor is equal to zero if the sub-band comprises the entire bandwidth.

A second compensation factor Pc may be optionally applied to compensate for the antenna gain. For example, Pc may be set as the antenna gain in embodiment. As an example, the antenna gain may be constant such that Pc = <NUM> log<NUM> N [dB], where N is the number of antennas. Another way of measuring the amount of power in the direction of the maximal gain is through the equivalent isotropic radiated power (EIRP). Thus another choice of Pc is to set it as the EIRP. In yet a further example, the second compensation factor may be ignored entirely.

After compensation by the first and/or second compensation factors, the detected received power can be compared to the threshold values (Pe for energy detect; Ps for signal detect). Thus the compensated power Pr(i) - Pcs(i) - Pc may be compared with the energy detect threshold Pe or the signal detect threshold Ps. In the latter case, the signal detect mechanism may be altered compared to the omni-directional carrier-sense assessment, by waiting for an offset after detection of the short training field before measuring the power. That is, the omni-directional signal detect CCA is triggered upon detection of a short training field (where each WiFi packet comprises two STFs at the start, each <NUM> long). As the directional carrier-sense assessment is concerned only with active subcarriers, the power may be measured after the STFs have finished (e.g., during transmission of the long training fields, LTFs). For example, the directional sub-band carrier-sense assessment may be performed after <NUM> from the start of each packet, rather than <NUM> after the start of the packet as with omni-directional signal detect CCA.

Thus the output of step <NUM> is a binary determination for each of the one or more sub-bands as to whether the sub-band is idle (i.e., received power below the threshold) or busy (i.e., received power above the threshold). If a sub-band is determined to be idle, all of the subcarriers belonging to that sub-band are determined to be idle; if a sub-band is determined to be busy, all of the subcarriers belonging to that sub-band are determined to be busy.

In step <NUM>, it is determined whether there are sufficient idle subcarriers to reliably transmit to the receiving device (e.g., such that the receiving device has a good chance to receive and decode the transmission). For example, the number of idle subcarriers is compared to a threshold number of subcarriers. In one embodiment, the threshold number of subcarriers is determined based on the total number of subcarriers across the bandwidth BW and the coding rate. For example, the total number of subcarriers may be multiplied by the coding rate to give the threshold number, such that if there are <NUM> subcarriers and the coding rate is <NUM>, the threshold number is <NUM>. Alternative formulations are of course possible, and the present disclosure is not limited in that respect.

If there are insufficient idle subcarriers, the method proceeds to step <NUM> and, in the illustrated embodiment, the transmitting device defers from transmitting to the receiving device. For example, the transmitting device may back-off for a time before reattempting the carrier-sense assessment. Alternatively, the transmitting device may repeat the directional carrier-sense assessment, but using a different configuration of sub-bands, e.g., a different number of sub-bands, or differently arranged sub-bands. In one particular example, the transmitting device may repeat the directional carrier-sense assessment using a higher number of sub-bands, such that the total bandwidth is analyzed with higher granularity.

If there are sufficient idle subcarriers, the method proceeds to step <NUM>, in which the transmitting device selects transmit powers for each of the one or more sub-bands. Where the carrier-sense assessment is binary for each sub-band (i.e., idle or busy), the selection of transmit powers may comprise selecting a zero transmit power for busy sub-bands such that those sub-bands are punctured or muted; the transmit powers for idle sub-bands may be selected to be "full" or conventional, i.e. whatever transmit power is conventionally selected for transmitting to the receiving device. It will here be noted that various adaptive power control mechanisms may be utilized by the transmitting device (e.g., those as defined in <NUM>. 11ax), and the transmit power control described here may act in combination with such mechanisms.

In step <NUM>, the transmitting device transmits its data to the receiving device using the transmit powers selected in step <NUM>.

The description above has focused on an embodiment in which a binary determination is made as to whether a sub-band is busy or idle. In practice, however, different sub-bands may experience different degrees of interference. In an example not covered by the claims, instead of comparing the received power for each sub-band to a single threshold in step <NUM> and proceeding to step <NUM>, the received power for each sub-band in step <NUM> is used to select a transmit power for that sub-band, i.e., the method proceeds directly from step <NUM> to step <NUM>.

In such an example, the transmit power may be chosen as a function of the received power for a sub-band. The function may describe an inverse relationship between the received power for each sub-band and the transmit power for that sub-band, such that a relatively high received power in a sub-band results in a relatively low transmit power being selected; conversely, a relatively low received power in a sub-band results in a relatively high transmit power for that sub-band. The transmit power may be determined mathematically, based on the received power for each sub-band. Alternatively, a look-up table may be utilized, linking a plurality of ranges of received power to respective transmit power values. Thus the transmitting device may measure the received power for a sub-band and select the corresponding transmit power from the look-up table. Again, the present disclosure is not limited in that respect.

Thus embodiments of the disclosure provide methods in which spatial and frequency resources are re-used, making the usage of transmission resources more efficient and reducing the likelihood that a transmitting device will be subject to delays through carrier-sense failures.

<FIG> is a schematic diagram of a transmitting device <NUM> according to embodiments of the disclosure. The transmitting device <NUM> is operative to communicate in a wireless communications network requiring a carrier-sense mechanism, such a wireless local area network compliant with IEEE <NUM> specifications. The transmitting device <NUM> may be a wireless device such as a mobile station or user equipment, or a network node such as an access point or a base station.

The transmitting device <NUM> comprises processing circuitry <NUM>, a non-transitory device-readable medium (such as memory) <NUM> and one or more interfaces <NUM>. The processing circuitry <NUM> may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other components, such as device readable medium <NUM>, the transmitting device <NUM> with functionality. In some embodiments, processing circuitry <NUM> may include radio frequency (RF) transceiver circuitry and baseband processing circuitry.

In certain embodiments, some or all of the functionality described herein as being provided by a transmitting device may be performed by processing circuitry <NUM> executing instructions stored on device readable medium <NUM> or memory within processing circuitry <NUM>. alternative embodiments, some or all of the functionality may be provided by processing circuitry <NUM> without executing instructions stored on a separate or discrete device readable medium, such as in a hard-wired manner. For example, the processing circuitry <NUM> may be configured to perform the method described above with respect to <FIG>. The benefits provided by such functionality are not limited to processing circuitry <NUM> alone or to other components of the transmitting device <NUM>, but are enjoyed by the transmitting device <NUM> as a whole, and/or by end users and the wireless network generally.

Device readable medium <NUM> may store any suitable instructions, data or information, including a computer program, software, an application including one or more of logic, rules, code, tables, etc. and/or other instructions capable of being executed by processing circuitry <NUM> and, utilized by the transmitting device <NUM>.

Interface(s) <NUM> are used in the wireless communication of signalling and/or data between the transmitting device <NUM> and a receiving device. Interface(s) <NUM> may include radio front end circuitry that may be coupled to, or in certain embodiments a part of, a plurality of antenna elements. The radio front end circuitry may be configured to condition signals communicated between the antenna elements and processing circuitry <NUM>. The radio front end circuitry may receive digital data that is to be sent to a receiving device via a wireless connection. The radio front end circuitry may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters and/or amplifiers. The radio signal may then be transmitted via the antenna elements. Similarly, when receiving data, the antenna elements may collect radio signals which are then converted into digital data by the radio front end circuitry.

According to embodiments of the disclosure, the processing circuitry <NUM> is configured to perform a directional carrier-sense assessment for one or more sub-bands configured for transmissions between the transmitting device <NUM> and a receiving device. The directional carrier-sense assessment utilizes beamforming to detect a respective level of wireless activity on each of the sub-bands in a particular direction for transmissions to the receiving device. The processing circuitry <NUM> is further configured to select a respective transmit power for each sub-band based on the determined level of wireless activity, and to initiate a transmission to the receiving device in the particular direction, using the respective selected transmit power for each sub-band.

<FIG> is a schematic diagram of a transmitting device <NUM> according to further embodiments of the disclosure. The transmitting device <NUM> is operative to communicate in a wireless communications network requiring a carrier-sense mechanism, such a wireless local area network compliant with IEEE <NUM> specifications. The transmitting device <NUM> may be a wireless device such as a mobile station or user equipment, or a network node such as an access point or a base station. The transmitting device <NUM> may be configured to implement or perform the method described above with respect to <FIG>.

The transmitting device <NUM> comprises a carrier-sense module <NUM>, a transmit-power select module <NUM> and a transmit module <NUM>. According to embodiments of the disclosure, the carrier-sense module <NUM> is configured to perform a directional carrier-sense assessment for one or more sub-bands configured for transmissions between the transmitting device <NUM> and a receiving device. The directional carrier-sense assessment utilizes beamforming to detect a respective level of wireless activity on each of the sub-bands in a particular direction for transmissions to the receiving device. The transmit-power select module <NUM> is configured to select a respective transmit power for each sub-band based on the determined level of wireless activity. The transmit module <NUM> is configured to to initiate a transmission to the receiving device in the particular direction, using the respective selected transmit power for each sub-band.

It should be noted that the above-mentioned embodiments illustrate rather than limit the concepts disclosed herein, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended following claims. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claim 1:
A method performed by a transmitting device (<NUM>, <NUM>, <NUM>) for transmitting to a receiving device (<NUM>) in a wireless communications network, the transmitting device comprising a plurality of antenna elements, the method comprising:
performing (<NUM>) a directional carrier-sense assessment for one or more sub-bands configured for transmissions between the transmitting device and the receiving device, wherein each sub-band comprises one or more subcarriers, the directional carrier-sense assessment utilizing beamforming to detect a respective level of wireless activity on each of the sub-bands in a particular direction for transmissions to the receiving device wherein the level of wireless activity in each sub-band comprises one of: idle and busy;
selecting (<NUM>) a respective transmit power for each sub-band based on the determined level of wireless activity; and
transmitting (<NUM>) to the receiving device in the particular direction, using the respective selected transmit power for each sub-band, in response to a determination (<NUM>) that a number of subcarriers belonging to idle sub-bands exceeds a threshold number of subcarriers.