阅读说明：本技术 传输功率控制 (Transmission power control ) 是由 L·维尔赫姆森 于 2018-03-06 设计创作，主要内容包括：公开了一种用于被配置为根据先听后说(LBT)过程进行操作的无线通信节点的方法。该方法包括：针对即将来临的传输,执行信道感测,以确定无线通信节点所经受的干扰水平；响应于所确定的干扰水平,确定用于即将来临的传输的最大传输功率水平；以及响应于所确定的最大传输功率水平,选择将被用于即将来临的传输的编码速率和调制中的至少一个。根据一些实施例,该方法还包括在执行信道感测之前准备多个传输分组变体,其中,每个传输分组变体与相应的传输功率水平相关联。进而,选择编码速率和调制中的至少一个可包括：响应于所确定的最大传输功率水平和多个传输分组变体的相应的传输功率水平,选择多个传输分组变体中的一个传输分组变体。还公开了对应的装置、无线通信节点以及计算机程序产品。(A method for a wireless communication node configured to operate in accordance with a Listen Before Talk (LBT) procedure is disclosed. The method comprises the following steps: performing channel sensing for an upcoming transmission to determine an interference level experienced by a wireless communication node; determining a maximum transmission power level for the upcoming transmission in response to the determined interference level; and selecting at least one of a coding rate and a modulation to be used for the upcoming transmission in response to the determined maximum transmission power level. According to some embodiments, the method further comprises preparing a plurality of transmission packet variants prior to performing channel sensing, wherein each transmission packet variant is associated with a respective transmission power level. Further, selecting at least one of a code rate and a modulation may include: selecting one of the plurality of transmission packet variants in response to the determined maximum transmission power level and the respective transmission power level of the plurality of transmission packet variants. Corresponding apparatus, wireless communication nodes and computer program products are also disclosed.)

1. A method for a wireless communication node configured to operate in accordance with a listen before talk, LBT, procedure, the method comprising: in connection with the forthcoming transmission,

performing (220) channel sensing to determine an interference level experienced by the wireless communication node;

determining (230) a maximum transmission power level for the upcoming transmission in response to the determined interference level; and

selecting (240) at least one of a coding rate and a modulation to be used for the upcoming transmission in response to the determined maximum transmission power level.

2. The method of claim 1, further comprising:

the forthcoming transmission is performed by transmitting (250) a transmission packet using the selected coding rate and/or the selected modulation.

3. The method of any of claims 1-2, wherein the channel sensing comprises measuring one or more of:

-a received signal power;

-receiving signal energy; and

-the received power of the predefined signature sequence.

4. The method of any of claims 1 to 3, further comprising:

preparing (210) a plurality of transmission packet variants (310, 320, 330, 340) prior to performing the channel sensing, wherein each transmission packet variant is associated with a respective transmission power level, and wherein selecting (240) at least one of the coding rate and the modulation comprises: selecting (245) one of the plurality of transmission packet variants in response to the determined maximum transmission power level and the respective transmission power levels of the plurality of transmission packet variants.

5. The method of claim 4, wherein the selected transmission packet variant belongs to a subset of the plurality of transmission packet variants, a respective transmission power level of each transmission packet variant in the subset being less than or equal to the determined maximum transmission power level.

6. The method of claim 5, wherein the respective transmission power level of the selected transmission packet variant is a maximum transmission power level of the respective transmission power levels of the subset.

7. The method of any of claims 5 to 6, wherein each transmission packet variant is configured to provide a respective data rate, and wherein the respective data rate of the selected transmission packet variant is the largest of the respective data rates of the subset.

8. The method of any of claims 4 to 7, wherein each of the plurality of transport packet variants is associated with a respective coding rate and a respective modulation.

9. The method of claim 8, wherein preparing the plurality of transport packet variants comprises: each transmission packet variant is prepared using a respective one of a plurality of predefined modulation and coding schemes, MCSs (310, 320).

10. The method of claim 8, wherein preparing the plurality of transport packet variants comprises: preparing a single transport packet (330) using a systematic code, and wherein selecting the one transport packet variant comprises selecting (334, 335, 336) a number of check bits of the systematic code.

11. The method of claim 8, wherein preparing the plurality of transmission packet variants comprises preparing a single transmission packet (340), and wherein selecting the one transmission packet variant comprises selecting a modulation order.

12. A computer program product comprising a non-transitory computer readable medium (500), having thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and configured to cause execution of the method according to any of claims 1 to 11 when the computer program is run by the data-processing unit.

13. An apparatus for a wireless communication node configured to operate according to a listen before talk, LBT, procedure, the apparatus comprising control circuitry (400), the control circuitry (400) being configured to, for an upcoming transmission, cause:

performing channel sensing to determine an interference level experienced by the wireless communication node;

determining a maximum transmission power level for the upcoming transmission in response to the determined interference level; and

selecting at least one of a coding rate and a modulation to be used for the upcoming transmission in response to the determined maximum transmission power level.

14. The apparatus of claim 13, wherein the control circuitry is further configured to: preparing a plurality of transmission packet variants prior to performing the channel sensing, wherein each transmission packet variant is associated with a respective transmission power level, and wherein selecting at least one of the coding rate and the modulation comprises: selecting one of the plurality of transmission packet variants in response to the determined maximum transmission power level and the corresponding transmission power levels of the plurality of transmission packet variants.

15. The apparatus of claim 14, wherein each of the plurality of transport packet variants is associated with a respective coding rate and a respective modulation.

16. The apparatus of claim 15, wherein the control circuitry is configured to prepare the plurality of transmission packet variants by preparing each transmission packet variant using a respective one of a plurality of predefined Modulation and Coding Schemes (MCSs).

17. The apparatus of claim 15, wherein the control circuitry is configured to prepare the plurality of transmission packet variants by preparing a single transmission packet using a systematic code, and wherein the control circuitry is configured to select the one transmission packet variant by selecting a number of check bits of the systematic code.

18. The apparatus of claim 15, wherein the control circuitry is configured to prepare the plurality of transmission packet variants by preparing a single transmission packet, and wherein the control circuitry is configured to select the one transmission packet variant by selecting a modulation order.

19. A wireless communication node comprising an apparatus according to any of claims 13 to 18.

Technical Field

The present disclosure relates generally to the field of wireless communications. More particularly, the present disclosure relates to control of transmission power in wireless communications.

Background

The coexistence approach may be necessary, or at least beneficial, when different devices are to share a wireless communication channel. This may be true when devices operate according to the same communication standard (e.g., IEEE 802.11) but without overall network coordination, and when devices operate according to a different communication standard. A particularly relevant example is when the communication channel is included in an unlicensed frequency band (e.g., one of the 2.45GHz ISM bands, or 5GHz bands).

A common coexistence approach is based on the principle of Listen Before Talk (LBT), also known as carrier sense multiple access with collision avoidance (CSMA/CA). According to this method, a device intending to transmit using a wireless communication channel senses the channel and determines whether the communication channel is busy (in use, or otherwise occupied) or free (unoccupied). If the communication channel is determined to be busy, the transfer is deferred. If the communication channel is determined to be idle, transmission is initiated. The method aims to avoid collisions by only initiating transmissions when the communication channel is not already in use.

The sensing process is typically based on a threshold (e.g., defined in terms of received signal power). A communication channel may be determined to be idle when a sensing metric (e.g., received signal power) is below a threshold and busy otherwise.

A typical consideration for selecting the threshold is that if the expected start of a transmission may result in a collision, the threshold should be low enough to detect an ongoing transmission from another device. Yet another typical consideration for selecting the threshold is that the threshold should be high enough so that an intended transmission is not deferred when it does not pose any harm in terms of collisions. If the threshold is decreased, the likelihood of deferring channel access is increased. If the threshold is increased, the probability of causing a collision is increased.

As an illustrative example, in IEEE802.11, the power threshold for announcing that the channel is idle is-82 dBm if an IEEE802.11 preamble is detected and-62 dBm if no preamble is detected but only energy is detected. This effectively means that when an IEEE802.11 device is sensing the channel, there is 20dB more aggressiveness for transmitting devices that do not use the IEEE802.11 preamble. The value chosen in IEEE802.11 may be considered as a compromise between the possibility of unnecessarily deferring channel access and the possibility of causing collisions.

Even if the threshold is carefully selected, a suitable threshold may often be extremely condition dependent. Thus, in some approaches (e.g., as applied in IEEE802.11 ax), there is an adaptive threshold that varies in response to the selected maximum transmission power. In this approach, the reduced maximum transmission power may allow for a higher threshold, since the probability of causing collisions is reduced when the maximum transmission power is reduced.

US 2013/0203458 a1 discloses selecting a transmit power configuration for communication within a shared frequency band, wherein the selection is between a low transmit power configuration applying a transmit power below a predetermined power threshold without a listen-before-talk method and a high transmit power configuration applying a transmit power of at least the predetermined power threshold.

US 2016/0309420 a1 discloses adjusting the transmission power based on interference information, adjusting the packet size when the measured error rate differs from a target error rate, and transmitting packets according to the transmission power.

However, the method according to the prior art still has drawbacks.

For example, if a maximum transmission power is determined and the channel is determined to be busy using sensing corresponding to a threshold, using an even lower transmission power may have proven the channel to be idle for sensing using a corresponding higher threshold. If even lower transmission power is already sufficient for successful transmission, the capacity of the channel is wasted in this scenario.

Furthermore, if a maximum transmission power is determined and the channel is determined to be idle using sensing corresponding to a threshold, the channel may also prove to be idle using an even higher transmission power for sensing using a corresponding lower threshold. Using even higher transmission power typically results in higher data rates. Thus, in this scenario, the capacity of the channel is also wasted.

Therefore, there is a need for alternative and preferably improved methods of transmission power control associated with Listen Before Talk (LBT) procedures. Preferably, the alternative method is more efficient in terms of the utilization of the channel capacity. This effectiveness may be measured in terms of one or more of the following: the amount of unnecessary deferral of the intended transmission, and the amount of collisions.

Disclosure of Invention

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It is an object of some embodiments to address or mitigate, alleviate, or eliminate at least some of the above or other disadvantages.

According to a first aspect, this is achieved by a method for a wireless communication node configured to operate according to a Listen Before Talk (LBT) procedure. The method comprises the following steps: performing channel sensing for an upcoming transmission to determine an interference level experienced by a wireless communication node; determining a maximum transmission power level for the upcoming transmission in response to the determined interference level; and selecting at least one of a coding rate and a modulation to be used for the upcoming transmission in response to the determined maximum transmission power level.

In some embodiments, the method further comprises: the forthcoming transmission is performed by transmitting the transmission packet using the selected coding rate and/or the selected modulation.

In some embodiments, channel sensing includes measuring one or more of: receiving signal power; receiving signal energy; and the received power of the predefined signature sequence.

In some embodiments, the method further comprises: preparing a plurality of transmission packet variants prior to performing channel sensing, wherein each transmission packet variant is associated with a respective transmission power level, and wherein selecting at least one of a coding rate and a modulation comprises: selecting one of the plurality of transmission packet variants in response to the determined maximum transmission power level and the respective transmission power level of the plurality of transmission packet variants.

In some embodiments, the selected transmission packet variant belongs to a subset of the plurality of transmission packet variants, the respective transmission power level of each transmission packet variant in the subset being less than or equal to the determined maximum transmission power level.

In some embodiments, the respective transmission power level of the selected transmission packet variant is the maximum transmission power level of the subset of the respective transmission power levels.

In some embodiments, each transmission packet variant is configured to provide a respective data rate, wherein the respective data rate of the selected transmission packet variant is the largest of the respective data rates of the subset.

In some embodiments, each of the plurality of transmission packet variants is associated with a respective coding rate and a respective modulation.

In some embodiments, preparing a plurality of transport packet variants comprises: each transmission packet variant is prepared using a respective one of a plurality of predefined Modulation and Coding Schemes (MCSs).

In some embodiments, preparing a plurality of transport packet variants comprises: a single transport packet is prepared using the systematic code. Further, selecting a transport packet variant includes selecting a number of check bits of the systematic code.

In some embodiments, preparing a plurality of transport packet variants comprises: a single transport packet is prepared. Further, selecting one transmission packet variant includes selecting a modulation order.

A second aspect is a computer program product comprising a non-transitory computer readable medium having thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit and configured to cause execution of the method according to the first aspect when the computer program is run by the data processing unit.

A third aspect is an apparatus for a wireless communication node configured to operate in accordance with a Listen Before Talk (LBT) procedure. The apparatus comprises control circuitry configured to, for an upcoming transmission, cause: performing channel sensing to determine an interference level experienced by the wireless communication node; determining a maximum transmission power level for the upcoming transmission in response to the determined interference level; and selecting at least one of a coding rate and a modulation to be used for the upcoming transmission in response to the determined maximum transmission power level.

A fourth aspect is a wireless communication node comprising the apparatus of the third aspect.

In some embodiments, any of the above aspects may additionally have features identical to or corresponding to any of the various features described above for any of the other aspects.

An advantage of some embodiments is that alternative methods of transmission power control associated with Listen Before Talk (LBT) procedures are provided.

Another advantage of some embodiments is to enable more efficient use of channel capacity.

Yet another advantage of some embodiments is that instantaneous channel variations may be taken into account for transmission power control.

Drawings

Other objects, features and advantages will become apparent from the following detailed description of embodiments, which proceeds with reference to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating exemplary embodiments.

FIG. 1 is a diagram illustrating an exemplary scenario in which some embodiments may be applied;

FIG. 2 is a flow diagram illustrating exemplary method steps according to some embodiments;

fig. 3 is a schematic diagram illustrating an example of a transport packet variation in accordance with some embodiments;

FIG. 4 is a schematic block diagram illustrating an exemplary apparatus according to some embodiments;

FIG. 5 is a schematic diagram illustrating an exemplary computer-readable medium, according to some embodiments;

FIG. 6 illustrates a telecommunications network connected to a host computer via an intermediate network, in accordance with some embodiments;

figure 7 illustrates a host computer in communication with user equipment via a base station over a partial wireless connection, in accordance with some embodiments;

fig. 8 is a flow diagram illustrating exemplary method steps implemented in a communication system including a host computer, a base station, and user equipment, in accordance with some embodiments;

fig. 9 is a flow diagram illustrating exemplary method steps implemented in a communication system including a host computer, a base station, and user equipment, in accordance with some embodiments;

fig. 10 is a flow diagram illustrating exemplary method steps implemented in a communication system including a host computer, a base station, and user equipment, in accordance with some embodiments;

fig. 11 is a flow diagram illustrating exemplary method steps implemented in a communication system including a host computer, a base station, and user equipment, in accordance with some embodiments.

Detailed Description

As has been mentioned above, it should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Hereinafter, embodiments of the present disclosure will be described and illustrated more fully with reference to the accompanying drawings. The solutions disclosed herein may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In a typical approach using the LBT principle (also referred to as CSMA/CA), a packet is (at least partially) ready for transmission once the maximum transmission power is set and before performing the actual sensing. This is because packet preparation typically takes too long to be complete after the channel has been determined to be idle. In a typical example, packet preparation prior to channel sensing may include: a Modulation and Coding Scheme (MCS) selected based on the maximum transmission power is used to generate a coded packet, and control information necessary for a receiver to decode the packet is generated and encoded.

If the channel is determined to be idle, the preparation of the packet may be completed and the packet may be transmitted. In a typical example, completing packet preparation after channel sensing may include modulating and upconverting to radio frequency. If the channel is determined to be busy, preparation of the packet is typically not complete and transmission of the packet may be deferred.

Even if it is beneficial to adaptively select the sensing threshold based on the maximum transmission power, there is no guarantee that the maximum transmission power is suitable for the condition at the time of sensing, so that there is a risk of wasting channel capacity as mentioned above. For example, the MCS may not be optimized for the instantaneous channel conditions.

In the following, embodiments will be described for a wireless communication node configured to operate according to a Listen Before Talk (LBT) procedure. The wireless communication node may be a wireless communication device (e.g. a station STA, or a user equipment UE) or a network node (e.g. an access point AP, or a base station BS). In embodiments described herein, channel sensing is performed prior to determining the maximum power level, and the maximum power level is determined based on the results of the channel sensing. Thereby, the maximum power level is adapted based on the actual channel conditions and the above mentioned waste of channel capacity may be at least partly mitigated.

Fig. 1 schematically shows an exemplary scenario in which some embodiments may be applied. A wireless communication device (STA1)100 is preparing an expected (upcoming) transmission 102 to a network node (AP1) 110. Another wireless communication device (STA2)120 is transmitting 122 to another network node (AP2) 130. When STA1 senses a channel prepared for an intended transmission 102, it may determine the interference level caused by STA 2's transmission 122, which is shown at 121. Alternatively or additionally, similar considerations may apply to other interference sources (e.g., other STAs and/or APs in addition to STA 2).

Fig. 2 illustrates a method 200 according to some embodiments. The method 200 may generally be performed by a wireless communication node. For example, the wireless communication node may be a wireless communication device (e.g., STA1 in fig. 1) or a network node (e.g., AP1 in fig. 1).

In step 220, channel sensing is performed for the forthcoming transmission to determine the interference level experienced by the wireless communication node. Channel sensing may be performed in any suitable manner and any suitable metric may be used to quantify the interference level. For example, channel sensing may include measuring received signal strength (e.g., preamble detection) in terms of received signal power, received signal energy, or received power of a predefined signature sequence.

It should be noted that channel sensing, in contrast to prior art methods, does not typically involve comparing the determined interference level to a threshold to determine whether the channel is free or busy. Instead, the method proceeds to step 230, wherein a maximum (allowable/permitted) transmission power level for the forthcoming transmission is determined in response to the determined interference level.

Typically, the maximum transmission power level is determined such that the determined interference level would cause the channel to be determined as idle in a sensing method according to the prior art if the maximum transmission power level would result in a corresponding threshold level for sensing. Further, the maximum transmission power level may be determined as the highest transmission power level that satisfies the condition.

In some embodiments, the maximum transmission power level is determined in step 230 by selecting a maximum transmission power level from a limited plurality of maximum transmission power levels.

In step 240, at least one of a coding rate and a modulation to be used for the forthcoming transmission is selected in response to the determined maximum transmission power level.

In some scenarios, the determined interference level may be too high to find (or not feasible) a maximum transmission power level that satisfies the above-described conditions (or any other suitable conditions) for enabling determination of an idle channel. One example is when the limited plurality of maximum transmission power levels does not include any maximum transmission power level that satisfies the condition. In such a scenario, step 230 may include determining that the maximum transmission power level is "zero" and deferring or avoiding the upcoming transmission.

However, in many scenarios, a maximum transmission power level may be (and may be) found that satisfies the above-described conditions (or any other suitable conditions) for enabling a determination of an idle channel. Then the method may proceed to step 250 wherein the forthcoming transmission is performed by transmitting the transmission packet using the selected coding rate and/or the selected modulation and at a transmission power not higher than the determined maximum transmission power level.

In some embodiments, the method 200 may include preparing multiple (e.g., two or more) transmission packet variants prior to performing channel sensing, as shown by optional step 210. Each transmission packet variant is then associated with a respective transmission power level, forming a finite plurality of maximum transmission power levels. The respective transmission power levels may be different for all of the plurality of transmission packet variants or may be uniform for some of the plurality of transmission packet variants.

Typically, all of the plurality of transmission packet variants have the same payload and are associated with respective coding rates and/or respective modulations resulting in respective transmission power levels. The respective coding rates and/or respective modulations may be different for all of the plurality of transmission packet variants or the respective coding rates and/or respective modulations may be the same for some of the plurality of transmission packet variants.

Accordingly, selecting at least one of a code rate and a modulation in step 240 may include: as shown in optional sub-step 245, one of the plurality of transmission packet variants is selected in response to the determined maximum transmission power level and the corresponding transmission power level of the plurality of transmission packet variants.

The selected transmission packet variant may belong to a subset of the plurality of transmission packet variants, the respective transmission power level of each transmission packet variant in the subset being less than or equal to the determined maximum transmission power level.

Typically, the selection conditions may be: the respective transmission power level of the selected transmission packet variant is the maximum transmission power level of the respective transmission power levels of the subset.

Alternatively or additionally, if each transport packet variant is configured to provide a respective data rate, the selection condition may be: the respective data rate of the selected transport packet variant is the maximum data rate of the respective data rates of the subset. The respective data rates may be different data rates for all of the plurality of transport packet variants or the respective data rates may be the same data rates for some of the plurality of transport packet variants.

In a typical example, a plurality of transmission packet variants are prepared in step 210, each prepared according to a respective coding rate and/or modulation resulting in a respective transmission power level of the transmission packet variant. Then the interference level determined in step 220 is used to select one of the transmission packet variants (and thus the code rate and/or modulation according to step 240). The selection is made by step 230; on the condition that the respective transmission power level of the selected one transmission packet variant should be lower than a maximum transmission power level, wherein the maximum transmission power level is associated with an idle determination of a channel having the determined interference level. Typically, the selected one of the transmission packet variants should have the highest corresponding transmission power level among the transmission packet variants that satisfy the condition.

Preparing multiple transport packet variants may include, for example, performing Forward Error Correction (FEC) coding, interleaving, and adding a preamble. Step 250 may include deriving the transport packet from the selected transport packet variant. Deriving the transport packet may include, for example, performing modulation and adding control information.

Fig. 3 is a schematic diagram illustrating three examples (a, b, c) of multiple transport packet variations in accordance with some embodiments.

Fig. 3(a) illustrates a method in which preparing a plurality of transmission packet variants includes preparing each transmission packet variant using a respective one of a plurality of predefined Modulation and Coding Schemes (MCSs). In the method, step 240 of fig. 2 may include selecting one of the prepared transmission packet variants. Typically, as shown in fig. 3(a), at least some of the plurality of transmission packet variants may have different lengths of time.

In the example of fig. 3(a), the plurality of transport packet variants comprises two transport packet variants 310, 320. The transport packet variant 310 has a Preamble (PA)311, a control part (CNTR)312, and a payload part 313, wherein the payload part comprises DATA (ENC DATA) encoded using a first modulation and coding scheme (MCS 1). The transport packet variant 320 has a Preamble (PA)321, a control part (CNTR)322, and a payload part 323, wherein the payload part comprises DATA (ENC DATA) encoded using a second modulation and coding scheme (MCS 2).

In another example, three different packets may be prepared using MCS0, MCS4, and MCS 7. Then the channel is sensed and the following rules are applied to select which packets should be sent based on the maximum transmission power level (maximum TX power):

-maximum TX power equal to or greater than 15dB ═ sending packets employing MCS7

-maximum TX power less than 15dBm but equal to or greater than 6dBm ═ sending packets employing MCS4

-maximum TX power less than 6dBm but equal to or greater than-6 dBm ═ sending packets employing MCS0

-deferring transmission with a maximum transmission power less than-6 dBm or more ═

As illustrated in fig. 3(a), a complete packet may generally include more than just encoded data 313, 323.

Typically, some kind of preamble 311, 321 is pre-appended to the data. For example, a preamble may be needed for time synchronization, frequency estimation, and channel estimation. Such a preamble can be generated very simply, in which case the generation can be done instantaneously, or the preamble can be generated in advance.

In addition, the packet typically also contains some control information 312, 322 necessary to properly receive the packet. Such control information may typically contain information about the MCS used and the size of the packet.

In general, the number of packets prepared before a channel is sensed may be a trade-off between performance and complexity. To optimize channel usage (which may be considered as an example of a performance metric), packets may even be prepared for each available MCS. On the other hand, the number of packets prepared may be limited due to complexity reasons.

Fig. 3(b) illustrates a method in which preparing a plurality of transmission packet variants includes preparing a single transmission packet using a systematic code. In the method, step 240 of fig. 2 may include selecting a number of check bits of the systematic code. Thus, a plurality of transport packet variants are formed by using different numbers of check bits of the single transport packet. Thereby, the transmission packet variants of the plurality of transmission packet variants inherently have different time lengths.

In the example of fig. 3(b), a single transport packet 330 has a Preamble (PA)331, a control portion (CNTR)332, and a payload portion 333, wherein the payload portion comprises DATA encoded using a systematic code (ENC DATA). Thus, the encoded data includes a first information bit portion 337 and a second parity bit portion 338. The selection of step 240 may include using the entire single transport packet 330, or using a portion of the single transport packet 330 with some of the parity bits removed (truncated at 335 or 336) or all of the parity bits removed (truncated at 334). Thus, in the example of fig. 3(b), the plurality of transport packet variants includes four transport packet variants. In this example, multiple transmission packet variants may typically, but not necessarily, use the same modulation.

Fig. 3(c) shows a method in which preparing a plurality of transmission packet variants includes preparing a single transmission packet. In this method, step 240 of fig. 2 may include selecting a modulation order. Thus, multiple transmission packet variants are formed by using different modulation orders for modulating a single transmission packet. Thus, the transport packet variants of the plurality of transport packet variants usually have the same length of time but different bandwidths. Thus, the method is particularly suitable for multiplexing users in frequency (e.g., in systems using orthogonal frequency division multiplexing, OFDM).

In the example of fig. 3(c), a single transport packet 340 has a Preamble (PA)341, a control portion (CNTR)342, and a payload portion 343, where the payload portion includes encoded DATA (ENC DATA). The selection of step 240 may include using the entire single transmission packet 340, the single transmission packet 340 being modulated using different modulation orders. Different modulation orders typically result in different bandwidths 344, 345, 346, 347 (e.g., corresponding to 256QAM (quadrature amplitude modulation), 16QAM, QPSK (quadrature phase shift keying), and BPSK (binary phase shift keying), respectively). Thus, in the example of fig. 3(c), the plurality of transport packet variants includes four transport packet variants.

In a particular example, the same code is used to encode the data packet and the modulation is selected based on the maximum transmission power level that can be used. The channel is sensed and the following rules are applied to select how the packet should be modulated before transmission based on the maximum transmission power level (maximum TX power):

-maximum TX power equal to or greater than 15dBm ═ 256-QAM

-maximum TX power less than 15dBm but equal to or greater than 10dBm >16-QAM

-maximum TX power less than 10dBm but equal to or greater than 5dBm > QPSK

-maximum TX power less than 5dBm or more ═ BPSK

Since 256-QAM carries 8 bits of information in one symbol, 16-QAM carries 4 bits of information in one symbol, QPSK carries 2 bits of information in one symbol, and BPSK carries 1 bit of information in one symbol, preferably, the bandwidth is selected correspondingly.

If Orthogonal Frequency Division Multiple Access (OFDMA) is used and the minimum bandwidth of Resource Units (RUs) is 2MHz, the number of allocated RUs for transmission of a packet may be based on a maximum transmission power level that may be used according to an interference level determined from channel sensing. Continuing with the numerical example above, this may be expressed as follows:

-maximum TX power equal to or greater than 15dBm ═ 1 RU

-maximum TX power less than 15dBm but equal to or greater than 10dBm ═ 2 RUs

-maximum TX power less than 10dBm but equal to or greater than 5dBm ═ 4 RUs

-maximum TX power less than 5dBm or more >8 RUs

Thus, according to these embodiments, when a higher maximum transmission power level can be used, a smaller bandwidth can be used, allowing more concurrent transmissions to other users via frequency reuse with OFDMA.

Fig. 4 schematically illustrates an example apparatus 420 according to some embodiments. The example apparatus may be included, for example, in a wireless communication node 410 configured to operate in accordance with a Listen Before Talk (LBT) procedure. The exemplary apparatus may be configured to perform a method as described in connection with fig. 2. For example, the exemplary apparatus may be configured to perform the method described in connection with fig. 2.

The apparatus comprises a control Circuit (CNTR)400, the control Circuit (CNTR)400 being configured to, for an upcoming transmission: performing channel sensing to determine the level of interference experienced by the wireless communication node (compare with step 220 of fig. 2); determining a maximum transmission power level for the upcoming transmission in response to the determined interference level (compare with step 230 of fig. 2); and selecting at least one of a code rate and a modulation to be used for the upcoming transmission in response to the determined maximum transmission power level (compare with step 240 of fig. 2).

To this end, the control circuit 400 may include or be associated with one or more of the following: a channel sensing Circuit (CS)401, a determination circuit (DET)402, and a selection circuit (SEL) 403. The channel sensing circuitry 401 may be configured to perform channel sensing to determine an interference level experienced by the wireless communication node. The determination circuit 402 may be configured to determine a maximum transmission power level for the upcoming transmission in response to the determined interference level. The selection circuit 403 may be configured to select at least one of a coding rate and a modulation to be used for the forthcoming transmission in response to the determined maximum transmission power level.

The control circuitry may be further configured to prepare a plurality of transport packet variants prior to performing channel sensing (compare with step 210 of fig. 2). To this end, the control circuit 400 may comprise or be associated with a preparation circuit (PREP)404, which preparation circuit (PREP)404 is configured to prepare a plurality of transport packet variants.

The control circuit may be further configured to send the transport packet (compare to step 250 of fig. 2). To this end, control circuitry 400 may be associated with transmit circuitry (e.g., a transmitter; shown in FIG. 4 as transceiver TX/RX)430 configured to transmit the transport packets.

Some embodiments provide methods and apparatuses for using optimal transmission power in an LBT system. The methods and apparatus are applicable to packet transmission in conditions where the conditions are unknown, when the packet is formatted, and what transmission power may be used. The following methods are provided: enabling efficient and immediate adjustment of the transmission packets to the appropriate transmission power level even when most, or even the entire, baseband processing may need to be performed before the appropriate transmission power level is known (i.e., before channel sensing). Embodiments enable postponing the selection of the packet form to be transmitted until after knowing the available transmission power level.

According to some embodiments, a listen-before-talk scheme may be applied, wherein the conventional trade-off between a low probability of accessing the channel at a high transmission power and a high probability of accessing the channel at a low transmission power is avoided. By using a method adapted to the instantaneous channel condition, the possibility of accessing the channel using a relatively large transmission power is increased, thereby improving the system performance.

When transmitting data over a wireless channel, it is generally desirable to transmit at as high a rate as possible while ensuring a high probability that the receiver can correctly decode the transmitted data. If an unnecessarily low data rate is used, the capacity of the channel is wasted; this may for example result in an unnecessarily large channel occupancy (and thus a waste of capacity). If too high a data rate is used, the packet cannot be decoded correctly and must be retransmitted (thus wasting capacity).

In systems operating in unlicensed bands and channel access is based on the listen before talk (LBT; also known as CSMA/CA) principle, the transmission of information is often challenging. The reasons for this include: it may take a considerable amount of time to gain access to the channel and interference conditions may vary greatly.

To access a channel under LBT, it must first be determined that the channel is idle. Once the channel is determined to be idle, devices with packets to transmit may begin contending for the channel. Contention for the channel is typically based on a mechanism that includes a random backoff, which is intended to reduce the likelihood that two or more devices having data to transmit initiate transmissions simultaneously, thereby causing collisions. If the channel is determined to be busy, the device waits for the channel to become free to perform the above-described process. In situations with multiple ongoing transmissions from several overlapping networks, the likelihood that the channel will often be determined to be busy is high, meaning that the device will have to wait a long time to begin contending for the channel.

In many practical situations, it may not be necessary to wait for a channel to be determined as idle. In particular, if the proper transmission power level is used, the channel may be accessed and packets successfully transmitted in many situations without corrupting the ongoing transmission that has been detected. To achieve high overall throughput when several cells overlap and interfere with each other, one approach may be to not transmit at a higher power than necessary; thereby reducing overall interference and enabling concurrent transmissions.

The inventors have realized that sensing the channel first and comparing the received signal power with a predetermined threshold may not be a good way to access the channel in an efficient way when the interfering signal power changes. Rather, the reverse order may be used. In particular, instead of selecting a sensing threshold based on the determined transmission power level, the maximum allowable transmission power level may be based on the experienced interference power level. Thus, channel access can (in principle) always be ensured by applying a sufficiently low transmission power level. In practice, however, there is a high probability of a lower limit for the transmission power below which channel access is meaningless. According to some embodiments, the channel may not be accessed at all when the interference level is too high such that the maximum allowable transmission power level is below the lower limit.

The described embodiments and their equivalents may be implemented in software or hardware or a combination thereof. Embodiments may be performed by general purpose circuitry. Examples of general purpose circuitry include a Digital Signal Processor (DSP), a Central Processing Unit (CPU), a co-processor unit, a Field Programmable Gate Array (FPGA), and other programmable hardware. Alternatively or additionally, embodiments may be performed by special purpose circuits such as Application Specific Integrated Circuits (ASICs). The general purpose circuitry and/or the specific purpose circuitry may be associated with or included in, for example, a device such as a wireless communication device or a network node (e.g., access point; base station).