WO2023237202A1

WO2023237202A1 - Devices and methods for enhanced probing in a wireless communication network with adjustment of probing rate based on noise level

Info

Publication number: WO2023237202A1
Application number: PCT/EP2022/065726
Authority: WO
Inventors: Shahar PATURY; Avi WEITZMAN; Doron Ezri
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2022-06-09
Filing date: 2022-06-09
Publication date: 2023-12-14

Abstract

A station (110) for a wireless communication network (100). The station (110) comprises a processing circuitry (111) configured to implement a rate control algorithm configured to adapt a current transmission rate for communicating with a further station (120) of the wireless communication network (100). The station (110) further comprises a communication interface (113) configured to transmit a plurality of probing frames at a plurality of candidate transmission rates with a probing rate. The processing circuitry (111) is further configured to estimate an interference noise level at the further station (120) and to adjust the probing rate based on the estimated interference noise level.

Description

DEVICES AND METHODS FOR ENHANCED PROBING IN A WIRELESS COMMUNICATION NETWORK WITH ADJUSTMENT OF PROBING RATE BASED ON NOISE LEVEL

TECHNICAL FIELD

The present invention relates to wireless communications. More specifically, the present invention relates to devices and methods for enhanced probing in a wireless communication network.

BACKGROUND

Wireless communication networks, such as IEEE 802.11 based WLANs, have become popular at an unprecedented rate. Besides conventional Internet applications such as email, file transfer, and browsing, wireless communication networks such as WLANs support real time applications, so that the demand for high bandwidth increases rapidly, due to the proliferation of mobile devices such as laptops, smart phones, and smart TV. Wireless channels are extremely variable and can be affected by a number of different factors, such as interference from other wireless devices, multi-path fading and signal attenuation. Therefore, one of the key components of a wireless communication system, in particular an 802.11 system, is a transmission rate adaptation mechanism, which adjusts the transmission rate of the transmitting wireless device to the channel conditions. However, both the adjustment speed of the transmission rate and an overhead of the wireless communication network may depends on a probing rate used for probing the channel conditions.

SUMMARY

It is an objective of the present disclosure to provide devices and methods for a more efficient probing of the channel conditions in a wireless communication network.

The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect a transmitter station for a wireless communication network, in particular a local area network, WLAN, is provided. The station comprises a processing circuitry configured to implement a rate control algorithm, RCA, configured to adapt a current optimal transmission rate for communicating with a further receiver station of the wireless communication network due to dynamic channel conditions. The station further comprises a communication interface configured to transmit a plurality of probing frames at a plurality of candidate transmission rates with a probing rate. The processing circuitry is further configured to estimate an interference noise level at the further station and to adjust the probing rate based on the estimated interference noise level.

The rate control algorithms may adapt the transmission rate dynamically to the changing channel conditions, so that the performance of a radio link established between the transmitter station and the further receiver station can be maximized.

In a further possible implementation form of the first aspect, the processing circuitry is configured to determine an interference noise level at a location of the station for estimating the interference noise level at a location of the further station.

In a further possible implementation form of the first aspect, the processing circuitry is configured to determine the interference noise level at the station as a time-averaged interference noise level.

In a further possible implementation form of the first aspect, the current transmission rate is defined by a current modulation and coding scheme, MCS, of a plurality of MCSs. For adapting the transmission rate, the processing circuitry is configured to select a different MCS of the plurality of MCSs. For selecting a different MCS the processing circuitry may be configured to increase or decrease a MCS index of the current MCS.

In a further possible implementation form of the first aspect, the RCA is an open loop based RCA.

In a further possible implementation form of the first aspect, the plurality of probing frames comprises one or more data frames.

In a further possible implementation form of the first aspect, the processing circuitry is further configured to adapt the current transmission rate to one, i.e. the optimal of the plurality of candidate transmission rates.

In a further possible implementation form of the first aspect, the processing circuitry is configured to estimate a temporal behavior of the interference noise level at the further station and to adjust the probing rate based on the estimated temporal behavior of the interference noise level. In a further possible implementation form of the first aspect, the processing circuitry is configured to decrease the probing rate (being larger than a minimal probing rate) for a candidate transmission rate being larger than the current transmission rate, if the interference noise level is substantially constant.

In a further possible implementation form of the first aspect, the processing circuitry is configured to increase the probing rate (being smaller than a maximal probing rate) for a candidate transmission rate being larger than the current transmission rate, if the interference noise level increases or decreases substantially.

In a further possible implementation form of the first aspect, the processing circuitry is configured to select the plurality of candidate transmission rates in such a way that more of the candidate transmission rates are larger (as long as the rate is smaller than a maximal MCS) than the current transmission rate, if the interference noise level is substantially constant or decreasing.

In a further possible implementation form of the first aspect, the processing circuitry is configured to select the plurality of candidate transmission rates in such a way that more of the candidate transmission rates are smaller (as long as the rate is larger than a minimal MCS) than the current transmission rate, if the interference noise level is increasing. The processing circuitry may be further configured to increase the probing rate.

According to a second aspect a method is provided of operating a transmitter station in a wireless communication network, in particular a local area network, WLAN.

The method comprises a step of implementing a rate control algorithm, RCA, configured to adapt a current optimal transmission rate for communicating with a further receiver station of the WLAN due to dynamic channel conditions.

The method further comprises a step of transmitting a plurality of probing frames at a plurality of candidate transmission rates with a probing rate.

The method further comprises a step of estimating an interference noise level at the further station. The method further comprises a step of adjusting the probing rate based on the estimated interference noise level.

The method according to the second aspect of the present disclosure can be performed by the transmitter station according to the first aspect of the present disclosure. Thus, further features of the method, according to the second aspect of the present disclosure, result directly from the functionality of the transmitter station according to the first aspect of the present disclosure as well as its different implementation forms described above and below.

According to a third aspect a computer program product is provided, comprising program code which causes a computer or a processor to perform the method according to the second aspect, when the program code is executed by the computer or the processor.

Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

Fig. 1 shows a schematic diagram illustrating an exemplary wireless communication network; Fig. 2 shows a diagram illustrating different RCA probe decisions of traditional RCA;

Fig. 3 shows a flow diagram illustrating processing steps implemented by a processing circuitry of a transmitter station according to an embodiment;

Fig. 4 shows a diagram illustrating different RCA probe decisions of traditional RCA in comparison with an RCA implemented by a processing circuitry of a transmitter station according to an embodiment; and

Fig. 5 shows a flow diagram illustrating steps of a method of operating a transmitter station according to an embodiment in a wireless communication network.

In the following, identical reference signs refer to identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

Figure 1 shows an exemplary wireless communication network 100, in particular local area network, WLAN 100, comprising a transmitter station 110 (or short station 110) and a further receiver station 120 (or short further station 120). The transmitter station 110 may be an access point, AP, 110 or any similar device configured to wirelessly transmit information to the further receiver station 120. The further receiver station 120 may be a further AP 120 or a non-AP station 120, for example a smartphone. The further receiver station 120 may be connected to the transmitter station 110 by a radio link 130. The radio link 130 may be under control of the transmitter station 110, for example by controlling a transmission rate or a channel frequency of the radio link 130. Although not illustrated in figure 1 , the wireless communication network 100 may comprise additionally to the transmitter station 110 and the further receiver station 120 a plurality of third stations. Further radio links established to the plurality of third stations may influence the radio link 130, in particular by inducing an interference noise level. Moreover, the radio link 130, in particular the interference noise level, may be influenced by a number of further factors, such as multi-path fading and signal attenuation. As illustrated in figure 1 , the transmitter station 110 comprises a processing circuitry 111 and a communication interface 113, in particular a wireless communication interface 113, for example in accordance with the IEEE 802.11 framework of standards. The processing circuitry 111 may be implemented in hardware and/or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The transmitter station 110 may further comprise a memory 115 configured to store executable program code which, when executed by the processing circuitry 111 , causes the transmitter station 110 to perform the functions and methods described herein.

Before describing different embodiments of the transmitter station 110 in more detail, in the following some technical background as well as terminology will be introduced making use of one or more of the following abbreviations:

ACK Acknowledge AP Access Point BW Bandwidth IEEE Institute of Electrical and Electronics Engineers MCS Modulation and Coding Scheme NACK Negative Acknowledge PER Packet Error Ratio I Packet Error Rate PHY Physical Layer RCA Rate Control Algorithm RSSI Receive Signal Strength Indicator SINR Signal to Interference plus Noise Ratio SNR Signal-To-Noise Ratio TX Transmit or Transmitter

WLAN Wireless local area network based on IEEE 802.11 and related standards

Most wireless systems contain rate control algorithms, RCA, designed to adapt the transmission rate between several available rates in response to changes of the channel and client location, i.e. location of the further receiver station 120. Rate adaptation varies the transmission rate of a wireless sender, i.e. the transmitter station 110, to match the wireless channel conditions, i.e. the properties of the radio link 130, in order to achieve the best possible performance. High transmission rate enables the transmission of larger data information blocks during define Tx times, however high data rates are more sensitive to channel conditions than lower data rates, so a full Tx success probability is lower in high rates. In contrast low data rates transfer smaller data blocks require longer transmit time; however, those packets are more resilient to errors. For example, a WLAN frame that failed to be ACKed, i.e. fails to be decode at the receiver end, needs to be re-transmit until ACKed.

Most RCA use probability statistics of Packet Error Rate, PER, measured by trial and error to select the “optimal” PHY rate for configuring the channel condition. However, using this trial- and-error approach for all Tx modes, such as for each BW permutation, spatial streams and MCS, may require huge overhead and data base almost linear to the increasing of the number of Tx modes. Moreover, using too high rates cause a high PER that will lead to retransmissions (those reduce the efficiency) and using too low rates causes the network to be inefficient. For example, the PER statistics are updated according to the received ACK I NACK indication of the entire Bandwidth. To allow the RCA to find the best rate to use, a probe frame such as a null data or real data frame with a different transmission rate than a current transmission rate can be sent. The probe frame allows the RCA to “sniff’ different transmission rates and update the transmission rate statistics.

Figure 2 shows a diagram illustrating different RCA probe decisions of traditional RCA. The diagram of figure 2 shows a first curve 11 of a transmission rate corresponding to an aggressive-probing based RCA, a second curve 13 of a transmission rate corresponding to a passive-probing based RCA and a third curve 15 of a theoretically optimal transmission rate. The theoretically optimal transmission rate is exemplary represented in figure 2 by the MCS index 5, for example after a condition change of the radio link 130. The initial situation before the condition change is exemplary represented in figure 2 by the MCS index 1.

Both the aggressive-probing based RCA and the passive-probing based RCA are configured to drop one transmission rate, i.e. MCS index, at failure, and stay on the last transmission rate of successful transmission. As exemplary shown in figure 2, a probe will be sent to one higher transmission rate, i.e. MCS index, than the last one after three successful transmissions for the aggressive-probing based RCA and after six successful transmissions for the aggressive- probing based RCA.

As illustrated in figure 2, the aggressive-probing based RCA can, relative to the passiveprobing based RCA, reduce the time between probes and allows a faster finding of the optimal transmission rate, but will induce much more overhead. Moreover, the passive-probing based RCA is, relative to the aggressive-probing based RCA, slower to achieve the optimal transmission rate, but can induce less overhead.

Figure 3 shows a flow diagram illustrating processing steps implemented by the processing circuitry 111 of the transmitter station 110. The processing circuitry 111 is configured to implement a rate control algorithm, RCA, configured to adapt a current optimal transmission rate for communicating with the further receiver station 120 of the wireless communication network 100 due to dynamic channel conditions, i.e. the condition of the radio link 130. The current transmission rate may be defined by a current modulation and coding scheme, MCS, of a plurality of MCSs. For adapting the transmission rate, the processing circuitry 111 may be configured to select a different MCS of the plurality of MCSs. For selecting a different MCS, the processing circuitry 111 may be configured to increase or decrease a MCS index of the current MCS.

The communication interface 113 is configured to transmit a plurality of probing frames at a plurality of candidate transmission rates with a probing rate. The probing rate may be a time difference between probing frames. The probing rate may be a PHY probing rate. The plurality of probing frames may comprise one or more data frames.

As illustrated by step 301 to 315 of figure 3, the RCA may be an open loop based RCA. In step 301 of figure 3, the processing circuitry 111 may be configured to periodically trigger a loop of the RCA and execute at least some of the steps 303 to 315 described below in more detail. The periodic execution may depend on the probing rate.

In step 303 of figure 3, the processing circuitry 111 is configured to estimate an interference noise level at the further station 120. The processing circuitry 111 may be configured to determine an interference noise level at a location of the transmitter station 110 for estimating the interference noise level at a location of the further station 120. The processing circuitry 111 may be configured to determine the interference noise level at the transmitter station 110 as a time-averaged interference noise level. The processing circuitry 111 may be configured to estimate a temporal behavior of the interference noise level at the further station 120. For example, the processing circuitry 111 may consider a SNR, SI NR and/or RSSI quality indicator of the radio link 130.

In steps 305a, 305b of figure 3, the processing circuitry 111 may be configured to compare the interference noise level determined in step 303 with a time average interference noise level. If a sum of the interference noise level determined in step 303 and a tolerance term x is smaller than the average noise level, the processing circuitry 111 may be configured to increase the MCS index in step 306a and proceed to step 309. If, on the other hand, a difference between the interference noise level determined in step 303 and the tolerance term x is larger than the average noise level, the processing circuitry 111 may be configured to decrease the MCS index in step 306b and proceed to step 309.

In case in step 305b the difference between the interference noise level determined in step 303 and the tolerance term x is not larger than the average noise level, the processing circuitry 111 in step 307 of figure 3 is configured to adjust the probing rate based on the estimated interference noise level. The RCA implemented by the processing circuitry 111 may adapt the transmission rate dynamically to the changing channel conditions, so that the performance of the radio link 130 can be maximized. The processing circuitry 111 may be further configured to adapt the current transmission rate to one, i.e. the optimal, of the plurality of candidate transmission rates. The processing circuitry 111 may be configured to adjust the probing rate based on the estimated temporal behavior of the interference noise level. The processing circuitry 111 may be configured to select the plurality of candidate transmission rates in such a way that more of the candidate transmission rates are larger than the current transmission rate, if the interference noise level is substantially constant or decreasing. The processing circuitry 111 may be configured to select the plurality of candidate transmission rates in such a way that more of the candidate transmission rates are smaller than the current transmission rate, if the interference noise level is increasing. Step 307 may trigger the execution of step 315 described below.

In step 309 of figure 3, the processing circuitry 111 may be configured to determine if the noise change determined in steps 305a, 305b is the first noise change within a time interval. If true, then the processing circuitry 111 may be configured to execute the step 311 described below. If false, then the processing circuitry 111 may be configured to execute the step 313 described below.

In step 311 of figure 3, the processing circuitry 111 may be configured to change, e.g. increase the MCS index, i.e. the transmission rate, for one try. Step 311 may trigger the execution of step 315 described below.

In step 313 of figure 3, the processing circuitry 111 may be configured to increase the probing rate for a candidate transmission rate being larger than the current transmission rate, if the interference noise level decreases. Step 313 may trigger the execution of step 307 described above. In step 315 of figure 3, the processing circuitry 111 may be configured to decrease the probing rate for a candidate transmission rate being larger than the current transmission rate, if the interference noise level is substantially constant. The processing circuitry 111 may be further configured to increase the probing rate if the interference noise level is increasing. In order to avoid a precipitately increase of the probing rating upon a massive change in the interference noise level, the processing circuitry 111 may be configured to merely send one probe probing an MCS index above the current before changing the probing rating.

Figure 4 shows a diagram illustrating different RCA probe decisions of traditional RCA in comparison with the RCA implemented by the processing circuitry 111 of the transmitter station 110 according to an embodiment. The diagram of figure 4 shows the first curve 11 of the transmission rate corresponding to the aggressive-probing based RCA, the second curve 13 of the transmission rate corresponding to the passive-probing based RCA and the third curve 15 of the theoretically optimal transmission rate. Figure 4 further shows a fourth curve 401 of the transmission rate implemented by the processing circuitry 111 of the transmitter station 100 according to an embodiment.

As illustrated in figure 4, the third curve 15 of the theoretically optimal transmission rate exemplary increases at a first event 407 from the MCS index 5 to the MCS 7 in response to a decrease, for example by 10dB, of a fifth curve 403 indicating a time average noise level and a decrease of a sixth curve 405 indicating a current noise level.

At a second event 409, the RCA implemented by the processing circuitry 115 may in response to the decrease of the noise level start a high probe interval, i.e. an interval with an increased probing rate.

At a third event 411 , the RCA implemented by the processing circuitry 115 may for example in response to a flattening of the fifth curve 403 stop the high probe interval, i.e. decrease the increased probing rate.

The RCA implemented by the processing circuitry 111 provides a smart and dynamic probing rate. In an initial state, the processing circuitry 111 may be configured to use a very high interference level as the reference for comparison. In other words, at the beginning the number of probes can be increased. As long as the interference level is relatively un-changed, the processing circuitry 111 may use a random PHY rate to MCS, i.e. around the used PHY rate, with higher probability to higher PHY rates. When the interference level decreases, the processing circuitry 111 may use more probes for higher PHY rates than the current. When the interference level increases, the processing circuitry 111 may use more probes for lower PHY rates than the current.

As illustrated in figure 4, the RCA implemented by the processing circuitry 111 of the transmitter station 110 according to an embodiment can overcome disadvantages of fix probing rate strategy selection used by traditional RCA by implementing a dynamic probing rate approach that changes the probing rate according to the interference level, i.e. dynamically selects to use an aggressive or a passive probing time and PHY rate. By dynamically selecting the probing rate a fast rate alignment is provided while reducing overhead.

Figure 5 shows a flow diagram illustrating steps of a method 500 of operating the transmitter station 110 according to an embodiment in the wireless communication network 100, in particular a local area network, WLAN 100.

The method 500 comprises a step 501 of implementing the rate control algorithm, RCA, configured to adapt a current optimal transmission rate for communicating with the further receiver station 120 of the wireless communication network 100 due to dynamic channel conditions.

The method 500 further comprises a step 503 of transmitting a plurality of probing frames at a plurality of candidate transmission rates with a probing rate.

The method 500 further comprises a step 505 of estimating an interference noise level at the further station 120. In an embodiment, the step 505 of estimating the interference noise level at the further station 120 may comprise estimating a change of the interference noise level at the further station 120, i.e. a difference between a current interference noise level and a previous noise level at the further station 120.

The method 500 further comprises a step 507 adjusting the probing rate based on the estimated interference noise level.

As the method 500 can be implemented by the transmitter station 110, further features of the method 500 result directly from the functionality of the transmitter station 110 and its different embodiments described above and below. The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, functional units in the embodiments of the invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.

Claims

1. A station (110) for a wireless communication network (100), wherein the station (110) comprises: a processing circuitry (111) configured to implement a rate control algorithm configured to adapt a current transmission rate for communicating with a further station (120) of the wireless communication network (100); and a communication interface (113) configured to transmit a plurality of probing frames at a plurality of candidate transmission rates with a probing rate; wherein the processing circuitry (111) is further configured to estimate an interference noise level at the further station (120) and to adjust the probing rate based on the estimated interference noise level.

2. The station (110) of claim 1 , wherein the processing circuitry (111) is configured to determine an interference noise level at a location of the station (110) for estimating the interference noise level at a location of the further station (120).

3. The station (110) of claim 2, wherein the processing circuitry (111) is configured to determine the interference noise level at the station (110) as a time-averaged interference noise level.

4. The station (110) of any one of the preceding claims, wherein the current transmission rate is defined by a current modulation and coding scheme, MCS, of a plurality of MCSs and wherein for adapting the transmission rate the processing circuitry (111) is configured to select a different MCS of the plurality of MCSs.

5. The station (110) of claim 4, wherein for selecting a different MCS the processing circuitry (111) is configured to increase or decrease a MCS index of the current MCS.

6. The station (110) of any one of the preceding claims, wherein the RCA is an open loop based RCA.

7. The station (110) of any one of the preceding claims, wherein the plurality of probing frames comprises one or more data frames.

8. The station (110) of any one of the preceding claims, wherein the processing circuitry (111) is further configured to adapt the current transmission rate to one of the plurality of candidate transmission rates.

9. The station (110) of any one of the preceding claims, wherein the processing circuitry (111) is configured to estimate a temporal behavior of the interference noise level at the further station (120) and to adjust the probing rate based on the estimated temporal behavior of the interference noise level.

10. The station (110) of claim 9, wherein the processing circuitry (111) is configured to decrease the probing rate for a candidate transmission rate being larger than the current transmission rate, if the interference noise level is substantially constant.

11. The station (110) of claim 9 or 10, wherein the processing circuitry (111) is configured to increase the probing rate for a candidate transmission rate being larger than the current transmission rate, if the interference noise level decreases.

12. The station (110) of any one of claims 9 to 11 , wherein the processing circuitry (111) is configured to select the plurality of candidate transmission rates in such a way that more of the candidate transmission rates are larger than the current transmission rate, if the interference noise level is substantially constant or decreasing.

13. The station (110) of any one of claims 9 to 11 , wherein the processing circuitry (111) is configured to select the plurality of candidate transmission rates in such a way that more of the candidate transmission rates are smaller than the current transmission rate, if the interference noise level is increasing.

14. The station (110) of claim 13, wherein the processing circuitry (111) is further configured to increase the probing rate.

15. A method (500) of operating a station (110) in a wireless communication network (100), wherein the method (500) comprises: implementing (501) a rate control algorithm configured to adapt a current transmission rate for communicating with a further station (120) of the wireless communication network (100); transmitting (503) a plurality of probing frames at a plurality of candidate transmission rates with a probing rate; estimating (505) an interference noise level at the further station (120); and adjusting (507) the probing rate based on the estimated interference noise level.

16. A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (500) of claim 15, when the program code is executed by the computer or the processor.