WO2009035381A1

WO2009035381A1 - Method and arrangement in a communication system

Info

Publication number: WO2009035381A1
Application number: PCT/SE2007/050636
Authority: WO
Inventors: Petter Ljung
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-09-11
Filing date: 2007-09-11
Publication date: 2009-03-19

Abstract

A method and arrangement is provided in a first node for restricting the noise rise within a cell in a wireless communication system and for adjusting the transmission power of radio signals. 5 The method and arrangement comprises estimating a noise rise and comparing the estimated noise rise with a predetermined noise rise threshold limit. Further, the method comprises estimating a SIR value and comparing the estimated SIR value with a SIR target value. The present method also comprises generating a power adjustment command in dependence of the outcome of the comparison between the estimated SIR 0 value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit. Further, the present method comprises sending the power adjustment command to the second node for adjusting the transmission power at the second node.

Description

METHOD AND ARRANGEMENT IN A COMMUNICATION SYSTEM

TECHNICAL FIELD

The present invention relates to a method and arrangement in a first node comprised in a wireless communication system. In particular it relates to adjusting the transmission power of radio signals sent over a radio link in the wireless communication system.

BACKGROUND Wireless communication systems such as Universal Mobile Telecommunication

Systems (UMTS), Code-Division-Multiple-Access (CDMA) networks, Wideband Code Division Multiple Access (WCDMA) and similar technologies, typically include a plurality of user equipments, such as mobile cellular radio telephones, having transceivers communicating with transceivers of serving base stations. Each user equipment transceiver includes a transmitter and a receiver which communicate with a corresponding base station receiver or transmitter via one or more radio links. A radio link typically comprises a plurality of communication channels such as e.g. signalling channels and traffic channels.

There is often a plurality of user equipments present simultaneously in the same cell. These simultaneously present user equipments could under certain circumstances interfere with each other, such that they implicitly trigger each other to increase the transmission power in an uncontrolled way. This unwanted behaviour is normally referred to as a power rush or a party effect within a cell and it creates a noise rise peak.

There are various reasons why a noise rise peak occurs, for instance that there are too many user equipments emitting signals simultaneously within a cell and therefore interfere with each other, or that the bit rate is too high for too many user equipments at a certain moment.

In most of the above mentioned communication systems where CDMA related technology are used, all user equipment transmits in the same frequency band. This unfortunately leads to that all user equipments within a cell also contribute to the interference level in the uplink. The load of a cell is directly related to the interference level or noise rise of the same cell. A high level of noise rise may lead to that many user equipments have insufficient transmission power to transmit data successfully at the allocated service data rate i.e. insufficient service coverage. Thus, in order to optimize the load of a cell, it is important to be able to restrict the so called uplink noise rise. The uplink noise rise is a term for the interference above the noise floor of a certain cell. The noise floor is a measurement of a signal created from the sum of all the noise sources and unwanted, background signals, comprising e.g. thermal noise, within a measurement system.

An excessive noise rise leads to reduced coverage, sometimes referred to as cell breathing, and could also lead to power rushes where different user equipments trigger each other to raise power in an uncontrolled way, something which has a severe impact on the network performance. Typically an operator wants to restrict the acceptable uplink load to a certain uplink noise rise level. Current methods used for avoiding excessive noise rise are based on either one of the two methodologies admission control or congestion control.

Before admitting an increased load in a cell, the system predicts the noise rise contribution from the new load. If the total noise rise exceeds an acceptable noise rise level, the requested increase is not admitted. This methodology is called admission control. The load increase refers to either a new user equipment in the cell or a rate increase for an existing user equipment. A method and device for uplink load estimation is revealed in document WO 2006/076969 A1. However, predicting the noise rise contribution of user equipment in an accurate way is difficult and could under certain circumstances be more or less impossible. One main obstacle to a correct prediction of the noise rise contribution is that it will change dynamically with the radio environment as the user moves around in the network.

According to the congestion control method, the system continuously measures the noise rise and, if an excessive noise rise is detected, actions are taken to decrease the load. An example of such action is to bar new users to enter the cell, or to reduce the rate for some or all users within the cell. Also this method suffers from some major drawbacks. The process for reducing load when an excessive noise rise is detected is rather slow. First of all the excessive noise rise must be detected and this must be signalled to the controlling node. The controlling node may be a Radio Network Controller or a Radio Base Station. Secondly, the controlling node must be decided on an appropriate action for reducing load. Such appropriate action is to select a user equipment to release or select which user equipment should reduce its rate. Thirdly, the controlling node must signal its decision to the user equipment. Fourthly, the user equipment must decode and implement the decision received from the controlled node. Only after this stage the noise rise in the cell is reduced.

The time for these four steps to be executed may vary depending on the situation; however an estimate is that the entire process takes at least 100 ms, and could take even some seconds. During this time, the noise floor limit is violated and as already mentioned, this leads to that coverage is violated and also that power rushes are triggered.

SUMMARY

It is therefore an object to obviate at least some of the above mentioned disadvantages and provide a mechanism that improves the performance and/or capacity in a wireless communication system.

The object is achieved by a method in a first node in a wireless communication system. The method aims at adjusting the transmission power of a radio signal sent over a radio link from a second node, also comprised in the wireless communication system. The radio signal is then received by the first node.

The method comprises the steps of obtaining an estimated noise rise and comparing the estimated noise rise with a predetermined noise rise threshold limit. Further, the method comprises the steps of obtaining an estimated SIR value and comparing the estimated SIR value with a SIR target value.

The present method also comprises the steps of generating a power adjustment command for adjusting the power at the second node in dependence of the outcome of the comparison between the estimated SIR value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit.

Further, the present method comprises the step of sending the generated power adjustment command to the second node. The generated power adjustment command will be used for adjusting the transmission power at the second node when sending the signal to the first node.

In accordance with the present invention, the object is also achieved by an arrangement in a first node in a wireless communication system. The arrangement is adapted to receive a radio signal over a radio link from a second node comprised in the wireless communication system. The arrangement comprises a first obtain unit adapted to obtain an estimated noise rise. Also, the arrangement according to the present invention comprises a first comparison unit adapted to compare the estimated noise rise with a predetermined noise rise threshold limit. The arrangement also comprises a second obtain unit which is adapted to obtain a SIR target value and an estimated SIR value. Also, the present arrangement comprises a second comparison unit adapted to compare the estimated SIR value with the SIR target value. Further, the arrangement comprises a command generator unit adapted to generate a power adjustment command to adjust the power at the second node in dependence of the outcome of the comparison between the estimated SIR value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit.

The arrangement also comprises a send unit adapted to send the generated power adjustment command to the second node. The generated power adjustment command will be used for adjustment of the transmission power at the second node when sending a signal to the first node.

Since the first node detects if the noise rise within the cell reaches the predetermined noise rise limit and reacts by generating and sending a power adjustment command to decrease the transmission power at the second node, a noise rise peak above the noise rise limit is avoided, as this is a fast process due to the integration of noise rise restriction into the power regulation. As the first node reacts on an emerging noise rise situation, it is possible to increase the capacity within a cell, compared with existent technology since no large back off in terms of load is required, which improves the capacity of a wireless communication system.

An advantage of the present method and arrangement according to some embodiments is that power rushes are limited or prevented, which improves the link quality.

An advantage of the present method and arrangement according to some embodiments is that it may be implemented in the first node and used for uplink power control of any arbitrary second node entering the cell. The second node may not have to be modified in any way, which reduces the amount of work, effort and cost involved when implementing the present method.

An advantage of the present method and arrangement according to some embodiments is that it may be implemented easily. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described more in detail in relation to the enclosed drawings, in which:

Figure 1 is a schematic block diagram over a wireless communication system according to the present method.

Figure 2 is a flow chart illustrating embodiments of method steps in a node for adjusting the transmission power of radio signals sent over a radio link.

Figure 3 is a block diagram illustrating an arrangement in a node for adjusting the transmission power of radio signals sent over a radio link.

DETAILED DESCRIPTION The invention is defined as a method and an arrangement which may be put into practice in the embodiments described below.

Figure 1 depicts a first node 120 communicating with a second node 110 in a wireless communication system 100. The communication between the first node 120 and the second node 110 is made over a radio link 140 in a cell 150 comprised in the wireless communication system 100. The wireless communication system 100 also comprises a radio network controller 130.

In some embodiments, the first node 120 may be a base station, a wireless communications station, a fixed station, a control station, a repeater or any similar arrangement for radio communication. The second node 110 may in some embodiments be a user equipment such as a mobile cellular radiotelephone, a Personal Digital Assistant (PDA), a laptop, a computer or any other kind of device capable of communicate radio resources.

However, in the example depicted in Figure 1 , the first node 120 is a base station and the second node 110 is a user equipment.

The wireless communication system 100 may be based on technologies such as e.g. Code division multiple access (CDMA), Wideband Code Division Multiple Access (WCDMA), CDMA 2000, High Speed Downlink Packet Data Access (HSDPA). High Speed Uplink Packet Data Access (HSUPA), High Data Rate (HDR) etc. A radio signal is sent from the second node 110 over a radio link 140 and is received by the first node 120. The power of the signal, which may be too high or too low to be suitable for the first node 120, is adjustable by the first node 120. Such adjustment of the power of a signal received from the second node 110 may in some embodiments be performed partly in the radio network controller 130 and partly in the base station 120. In some embodiments may such adjustment of the power of a signal received from the second node 110 be performed entirely in the radio network controller 130.

Figure 2 is a flow chart illustrating a method in the first node 120 in the wireless communication system 100, for adjusting the transmission power of a radio signal sent over the radio link 140 from the second node 110 comprised in the wireless communication system 100, to be received by the first node 120.

The radio link 140 may be a circuit switched or packet oriented uplink channel especially suited for high data rates and bursty transmissions. The method comprises a number of steps 201- 206 for appropriately adjust the transmission power of the second node 110. It is to be noted that the steps 201- 206 may be performed in any arbitrary order and that some steps e.g. step 201 and step 203, or even all steps may be performed simultaneously. According to some embodiments, the method steps however are performed sequentially.

The method for adjusting the transmission power of the second node 110 may according to some embodiments run every time slot of a radio frame and is typically less than 1 ms. In WCDMA, the method may typically run each 1/15 of the frame, e.g. 0.67 ms when the frame is 10 ms. Thus, according to some embodiments, about 1 500 power adjusting commands are sent each second. The method controls the transmission power of the second node 1 10 so that an appropriate power level is maintained in order to reach a predetermined quality target. It also ensures to compensate for the near-far problem, so that a signal received from users far out in the cell 150 are not swamped out by a stronger signal.

Step 201

An estimated noise rise in the cell 150 is obtained. Such estimation of the noise rise may be performed within the first node 120. However, according to some embodiments, the estimation of the noise rise may be performed in any other node. Further, the noise rise may be estimated by continuously measure the Received Total Wideband Power (RTWP) in the cell and compare with a previously determined noise floor of each cell.

Step 202 The estimated noise rise is compared with a predetermined noise rise threshold limit. The predetermined noise rise threshold limit may be set e.g. by the operator in dependence on the signal propagation conditions within a certain cell 150. Thus the predetermined noise rise threshold limit may be a different value in different cells in dependence of e.g. coverage. The noise rise threshold limit, which may be set differently in different cells, is the maximum tolerable noise rise in the cell 150. The noise rise threshold limit may also, according to some embodiments, be obtained from another node in the wireless communication system.

Step 203 An estimated Signal to Interference Ratio (SIR) value is obtained. The estimation of the SIR value may be performed within the first node 120. The estimation of the SIR value may according to some embodiments be performed in any other node in the wireless communication system.

The estimation of the SIR value is preferably made on signals sent from the second node 110 to the first node 120, i.e. uplink signals. In e.g. WCDMA, SIR may be measured on dedicated physical control channel (DPCCH), which DPCCH comprises pilots and TPC commands for uplink power control.

Step 204 In this step, the estimated SIR value is compared with a SIR target value. The SIR target value may e.g. be previously set by an outer loop power control in dependence on the error rate measured on a signal received from the second node 110 and a certain quality target. The SIR target value may be obtained from the first node 120 or from the control node 130. According to some embodiments, the SIR target value is set in dependence of a noise rise, e.g. according to the outcome of a comparison between an estimated noise rise value and a predetermined noise rise threshold limit.

The comparison between the estimated SIR value and the SIR target value is made in order to determine if the estimated SIR value is less than, equal to or more than the SIR target value. Step 205

A power adjustment command for adjusting the power at the second node 110 is made. The power adjustment command is generated in dependence of the outcome of the comparison between the estimated SIR value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit.

If the estimated noise rise value exceeds, according to some embodiments, or is equal to, the predetermined noise rise threshold limit or if the estimated SIR value exceeds, or is equal to, the SIR target value, a power adjustment command for decreasing the power at the second node 110 is generated. This may be illustrated by the following formula:

// SIR_n, ≥ SIR_x^_x or NR_esl ≥ NR_hmt => Power DOlVN Command

Wherein SIR^₁ Is the estimated SIR value, 5/Λ_target is the SIR target value, NR_est \s the estimated noise rise and NR_iamt is the predetermined noise rise threshold limit.

According to some embodiments, a power adjustment command for increasing the power at the second node 110 is generated if the estimated noise rise falls below the predetermined noise rise threshold limit and the estimated SIR value falls below the SIR target value. This may be illustrated by the formula: if SIR_n, < SIR_x^₁ and NR_esl < NR_hιmt => Power UP Command

Wherein SIR_al ^'\s the estimated SIR value, SJR_aige{ \s the SIR target value, NR_al \s the estimated noise rise and NR_hmt is the predetermined noise rise threshold limit.

In order to avoid or limit problems caused by violated SIR target, it may be an advantage, according to some embodiments of the present method, to provide the method step 205 with further partial steps. E.g. the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit may be disregarded as a criterion for generating the power adjustment command for adjusting the power at the second node 110, if the estimated SIR value falls below the SIR target value by a certain predetermined threshold value.

In that case, it is required to calculate the difference between the estimated SIR value and the SIR target value and compare that difference with the predetermined threshold value. This may be described: Maxdiff = SIR_arget - SlR_al

Where Maxdiff is the predetermined threshold value, SIR_esl \s the estimated SIR value and SIR^₁ is the SIR target value. The size of the predetermined threshold value

Maxdiff may vary in different cells depending on the radio signal propagation conditions and may be e.g. between 0.1dB and 10 dB. For example, maxdiff may be e.g. 3 dB.

If the difference between the SIR target value and the estimated SIR value exceeds a certain predetermined threshold value, the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit may be disregarded. The power adjustment command is calculated only in dependence of the outcome of the comparison between the estimated SIR value and the SIR target value.

This may be illustrated by the following formulas: // SIR_a,_m -SIR_al < Maxdiff and SIR_esl < SIR₁₃^ and NR_al < NR_limk => Power UP if SIR_tMm - SlR_al > Maxdiff and SIR_al < SIR^ =* Power UP

Where Maxdiff is the predetermined threshold value, SIR_esl \s the estimated SIR value, SIR_ars,_t is the SIR target value, NR_esl \s the estimated noise rise and NΛ_hmil is the predetermined noise rise threshold limit.

In some embodiments of the present method step 205, the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit may be disregarded as a criterion for generating the power adjustment command for adjusting the power at the second node 110. According to these embodiments, the outcome of said comparison may be disregarded if the radio link 140 between the first node 120 and the second node 110 belongs to a predetermined quality of service class. E.g. for radio links with a high quality of service ranking e.g. speech, video telephony data, and network control traffic, power adjustment command for adjusting the power at the second node 110 may be generated without considering the noise rise. Thus according to some embodiments of the present method, the method step 205 may be performed considering the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit only for radio links with a low quality of service ranking, e.g. best effort connection and /or data package traffic. Such embodiments have the advantage of not violating the SIR target for users with a high quality of service ranking. In some embodiments of step 205, the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit may be disregarded as a criteria for generating the power adjustment command for adjusting the power at the second node 110, if the estimated SIR value differs from SIR target value during a time period that exceeds a certain predetermined time limit.

This predetermined time limit may be set to an arbitrary value e.g. 10 ms. The time limit may also be different for different cells, depending on the radio propagation conditions in each cell 150. An advantage of those embodiments may be that they are easy and cheap to implement.

According to some embodiments of the present method, a noise rise control mechanism may be implemented by altering the SIR target value in dependence of the estimated noise rise. Thus the SIR target value may be reduced with a certain predetermined value if the estimated noise rise exceeds, or is equal to, the predetermined noise rise limit. This may be illustrated: if NR_eil > NR_lmn ^ SIR^ = SIR₁₃^ -H dB

Where NR_esl is the estimated noise rise and NR_Umt is the predetermined noise rise threshold limit and SIR^₁ is the SIR target value, n is an arbitrary value which may be any number, e.g. 1 dB.

The SIR target value may according to some embodiments be adjusted inter alia reduced or increased, in the base station 120. The SIR target value may then in turn be compared with an estimated SIR value and, in dependence of that comparison, a power adjustment command may be sent to the second node 110 as previously described.

Step 206

After the generation according to step 205, the generated power adjustment command is sent to the second node 110 for adjusting the transmission power at the second node 110. The power adjustment command thus may be a power DOWN command for decreasing the transmission power of the second node 110 or a power UP command for increasing the transmission power of the second node 110. The described method according to the method steps 201-206 allow for a fast and accurate control of the noise rise in order to prevent that the noise rise exceeds the noise rise limit.

In some embodiments of the present method, the first node 120 is represented by a base station. It may however, according to some embodiments as previously mentioned be represented by a wireless communications station, a fixed station, a control station, a repeater or any similar arrangement for radio communication. The first node 120 may also according to some embodiments be represented by a user equipment such as a mobile cellular radiotelephone, a Personal Digital Assistant (PDA), a laptop, a computer or any other kind of device capable of communicate radio resources.

In order to further improve the present method, especially in certain situations such as for instance at system overload when the noise rise may stay close to the predetermined noise rise limit, further steps may be taken. A high noise rise at or close to the predetermined noise rise limit is undesired since the SIR target will be violated for a longer period. Thus, if the noise rise persists to be at the level of the noise rise limit for some predefined time limit, maybe 10 ms or 50 ms, an overload indication may be sent to the controlling node 130 to take appropriate actions and reduce load. Such action may be to stop new users from entering the cell 150, select a user to release or select a user who should reduce its rate etc.

The present method may in some embodiments be implemented with a plurality of noise rise limits at different levels, such as by means of example a first noise rise limit NR1 and a second noise rise limit NR2. According to some embodiments of the invention, certain measures may be taken at the lower first noise rise limit NR1 , such as implementing the present method of power control only on best effort connections. At the second, higher noise rise limit NR2, the situation may be more critical and a more effective countermeasure may be appropriate to implement, such as implementing the present method of power control on all connections. Such embodiments have the advantage of being able of adapting a hierarchy of measures in order to control the noise rise within a cell, such that modest countermeasures may be used in non critical situations and more effective countermeasures may be saved for severely critical situations, which may improve the functionality of the wireless communication system 100. Thus the estimated noise rise may be compared with a plurality of predetermined noise rise threshold limits, such that each violated predetermined noise rise threshold limit trigger a different action. Such actions may be to implement the present method of power control only on certain connections, to block certain users from entering the cell, to reduce 5 the allowed load for some users, to implement the present method of power control on all connections, etc.

To perform the method steps 201-206 in the first node 120 for adjusting the transmission power of radio signals sent over the radio link 140 from the second node 10 110, the first node 120 comprises an arrangement 300 depicted in Figure 3. The arrangement 300 is adapted to use the SIR target value.

The present arrangement 300 also comprises a first obtain unit 301 adapted to obtain the estimated noise rise. The first obtain unit 301 may e.g. be a load estimator.

15 Further, the present arrangement 300 comprises a first comparison unit 302 adapted to compare the estimated noise rise with a predetermined noise rise threshold limit.

The arrangement 300 also comprises a second obtain unit 303 adapted to obtain an estimated SIR value. The second obtain unit 303 may in some embodiments be an 20 estimation unit, adapted to estimate the SIR value.

Also, the arrangement 300 further comprises a second comparison unit 304 which is adapted to compare the estimated SIR value with the SIR target value.

According to some embodiments, the SIR target value is set in dependence of the comparison between the estimated noise rise with a predetermined noise rise threshold 25 limit.

In some embodiments, the second comparison unit 304 may be adapted to determine if the difference between the estimated SIR value and the SIR target value falls below, or exceeds, a certain predetermined threshold value.

According to some embodiments of the present arrangement 300, the second 30 comparison unit 304 may be adapted to measure the time period for which the estimated SIR value differs from SIR target value e.g. by comprising a timer. In some embodiments, the second comparison unit 304 may be comprised within the first comparison unit 302.

Also, the present arrangement 300 comprises a command generator unit 305 adapted to generate a power adjustment command to adjust the power at the second

35 node 110. The power adjustment command is generated in dependence of the outcome of the comparison between the estimated SIR value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit.

According to some embodiments, the present arrangement 300 comprises a command generator unit 305 adapted to generate the power adjustment command in order to increase or decrease the power at the second node 110, depending on the result of the comparison made by the first comparison unit 302 and by the second comparison unit 304. According to some embodiments, the first comparison unit 302 and/ or the second comparison unit 304 and/ or the command generator unit 305 may be comprised within the same physical unit. According to some embodiments however, the first comparison unit 302 and/ or the second comparison unit 304 and/ or the command generator unit 305 are comprised within different physical units.

Further, the present arrangement 300 comprises a send unit 306 adapted to send the generated power adjustment command to the second node 110 for adjustment of the transmission power at the second node 110. The send unit 306 may in some embodiments be comprised within the same physical unit as the first comparison unit 302 and/ or the second comparison unit 304 and/ or the command generator unit 305.

According to some embodiments of the present arrangement 300 be an advantage if the arrangement 300 comprises a detection unit 307. The detection unit 307 may preferably be adapted to determine if the connection with the second node 110 belongs to a predetermined quality of service class. According to some embodiments, the detection unit 307 may be adapted to determine if the connection with the second node 110 is a best effort connection.

In some embodiments of the present arrangement, the first node 120 is represented by a base station. It may however, according to some embodiments as previously discussed be represented by a wireless communications station, a fixed station, a control station, a repeater or any similar arrangement for radio communication. The first node 120 may also according to some embodiments be represented by a user equipment such as a mobile cellular radiotelephone, a Personal Digital Assistant (PDA), a laptop, a computer or any other kind of device capable of communicate radio resources. The present method may with particular advantage be used for technologies such as an Enhanced Uplink (EUL) or High-Speed Uplink Packet Access (HSUPA) in the wireless communication system 100, as the present method and arrangement implements a fast and accurate mechanism to prevent uplink noise rise from exceeding specified noise rise limits.

The description of the present method and arrangement has focused mainly and by means of example only on the uplink power control in the base station 120. It may however also be performed e.g. partly in the base station controller or radio network controller 130.

By means of example and in order to simplify the comprehension, the term SIR has been consistently used in this text when describing a Signal to noise and Interference Ratio, which is the ratio between the level of a desired signal to the level of background noise and/or signal disturbance. The higher the ratio, the less obtrusive is the background noise. However, there exist several other acronyms which are sometimes used to describe the same or a similar ratio, like e.g. the Signal to Noise Ratio (SNR or S/N), Signal to Noise and Interference Ratio (SNIR), Signal to Interference and Noise Ratio (SINR) or an inversion of the ratio, like Interference to Signal Ratio, (ISR). Any of these or similar ratios may be used in the context of the present method and arrangement instead of the SIR.

The methods for adjusting the transmission power of radio signals sent over the radio link 140 from the first node 120 according to the present method may be implemented through one or more processors, such as the processor 306 in the first node arrangement 300 depicted in Figure 3 together with computer program code for performing the functions of the method. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the method according to the present invention when being loaded into the first node 120. The data carrier may be a CD ROM disc, a memory stick, or any other medium such as a disk or tape that can hold machine readable data. The computer program code may furthermore be provided as pure program code on a server and downloaded to the first node 120 remotely. While the method and arrangement described in this document are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that there is no intent to limit the present method and arrangement to the particular forms disclosed, but on the contrary, the present method and arrangement are to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the method and arrangement as defined by the claims.

Like reference numbers signify like elements throughout the description of the figures. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless expressly stated otherwise. It should be further understood that the terms "comprises" and/or "comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these methods and arrangements belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Claims

1. Method in a first node (120) in a wireless communication system (100), for adjusting the transmission power of a radio signal sent over a radio link (140) from a second node (110) comprised in the wireless communication system (100), to be received by the first node (120), the method comprises the steps of: obtaining (201 ) an estimated noise rise value, comparing (202) the estimated noise rise with a predetermined noise rise threshold limit, obtaining (203) an estimated Signal to Interference-and-noise Ratio (SIR) value of the radio link (140), comparing (204) the estimated SIR value with a Signal to Interference-and-noise Ratio target (SIR target) value, generating (205) a power adjustment command for adjusting the power at the second node (110) in dependence of the outcome of the comparison between the estimated SIR value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit. sending (206) the generated power adjustment command to the second node (110), which generated power adjustment command will be used for adjusting the transmission power at the second node (110) when sending a signal to the first node (120).

2. Method according to claim 1 , wherein a power adjustment command for decreasing the power at the second node (110) is generated if the estimated noise rise exceeds, or is equal to, the predetermined noise rise threshold limit or if the estimated SIR value exceeds, or is equal to, the SIR target value.

3. Method according to claim 1 , wherein a power adjustment command for increasing the power at the second node (110) is generated if the estimated noise rise falls below the predetermined noise rise threshold limit and the estimated SIR value falls below the SIR target value.

4. Method according to any of the claims 1-3, wherein the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit is disregarded as a criteria for generating the power adjustment command for adjusting the power at the second node (110), if the estimated SIR value falls below the SIR target value by a certain predetermined threshold value.

5. Method according to any of the claims 1-4, wherein the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit is disregarded as a criteria for generating the power adjustment command for adjusting the power at the second node (110), if the connection with the second node (110) is associated with a predetermined quality of service class.

6. Method according to any of the claims 1-5, wherein, the outcome of the comparison between the estimated noise rise value and the predetermined noise rise limit may be disregarded as a criteria for generating the power adjustment command for adjusting the power at the second node (110), if the estimated SIR value differs from SIR target value during a time period that exceeds a certain predetermined time limit.

7. Method according to any of the claims 1-6, wherein the SIR target value is set in dependence of the estimated noise rise.

8. Method according to claim 7, wherein the SIR target value is reduced with a certain predetermined value if the estimated noise rise exceeds, or is equal to, the predetermined noise rise limit.

9. Method according to any of the claims 1-8, wherein the estimated noise rise is compared with a plurality of predetermined noise rise threshold limits, such that each violated predetermined noise rise threshold limit trigger a different action.

10. Method according to any of the claims 1-9, wherein an overload indication is sent to a control node (130) if the noise rise persist to be at the level of the noise rise limit longer than a predetermined time.

11. Method according to any of the claims 1-10, wherein the first node (120) is represented by a base station.

12. Arrangement (300) in a first node (120) comprised in a wireless communication system (100), wherein the arrangement (300) is adapted to receive a radio signal over a radio link (140) from a second node (110) comprised in the wireless communication system (100), the first node arrangement (300) comprises: a first obtain unit (301 ) adapted to obtain an estimated noise rise, a first comparison unit (302) adapted to compare the estimated noise rise with a 5 predetermined noise rise threshold limit, a second obtain unit (303) adapted to obtain an estimated Signal to Interference- and-noise Ratio (SIR) value, a second comparison unit (304) adapted to compare the estimated SIR value with a SIR target value,

10 a command generator unit (305) adapted to generate a power adjustment command to adjust the power at the second node (110) in dependence of the outcome of the comparison between the estimated SIR value and SIR target value and/ or the outcome of the comparison between the estimated noise rise value and the predetermined noise rise threshold limit, and

15 a sender unit (306) adapted to send the generated power adjustment command to the second node (110), which generated power adjustment command is used for adjusting the transmission power at the second node (110) when sending the signal to the first node (120).

20 13. Arrangement (300) in a first node (120) according to claim 12, wherein the command generator unit (305) is adapted to generate a power adjustment command to increase the power at the second node (110) if the estimated noise rise falls below the predetermined noise rise threshold limit and the estimated SIR value falls below the SIR target value, or decrease the power at the second node (110) if the estimated noise rise

25 exceeds, or is equal to, the predetermined noise rise threshold limit or if the estimated SIR value exceeds, or is equal to, the SIR target value.

14. Arrangement (300) in a first node (120) according any of the claims 12-13, wherein the second comparison unit (304) is adapted to determine if the difference between the

30 estimated SIR value and the SIR target value falls below or exceeds a certain predetermined threshold value.

15. Arrangement (300) in a first node (120) according to any of the claims 12-14, wherein the second node arrangement (300) comprises a detection unit (307), adapted to determine if the connection with the second node (110) belongs to a predetermined quality of service class.

16. Arrangement (300) in a first node (120) according to any of the claims 12-15, wherein the first node (120) is represented by a base station.