WO2013164024A1

WO2013164024A1 - Method for power control of sounding reference signals

Info

Publication number: WO2013164024A1
Application number: PCT/EP2012/058096
Authority: WO
Inventors: Pablo SOLDATI
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2012-05-03
Filing date: 2012-05-03
Publication date: 2013-11-07
Anticipated expiration: 2014-11-03

Description

METHOD FOR POWER CONTROL OF SOUNDING REFERENCE SIGNALS Technical Field

The present invention relates to a method in a wireless communication system for power control of sounding reference signals. Furthermore, the invention also relates to a method in a network control node, a method in a mobile station, a network control node device and a mobile station device, a computer program, and a computer program product thereof.

Background of the Invention

Sounding reference signals (SRS) are transmitted by a mobile terminal to estimate the uplink (UL) channel-state information (CSI) at different frequencies. The channel-state estimate can then be used to support uplink transmission, e.g. for dynamic channel-dependent scheduling, as well as to estimate the downlink (DL) channel condition assuming downlink/uplink channel reciprocity. Both periodic and aperiodic SRS can be configured by a serving cell controlling the mobile terminal.

The 3 GPP Long Term Evolution (LTE) employs a dedicated SRS power control procedure to reduce the interference created by SRS signals and ensure good channel-state estimates. The

is tightly tied to the physical uplink shared channel (PUSCH) power control, as it shares with the latter several parameters: the target power per resource block P₀ PUSCH,_C ^')■ '_> ^me P^am l°^ss estimate PL_C and compensation factor _c(J) ; and the closed-loop power adjustment f_c(i) . The remaining parameters denote: the maximum configured transmit power, -P_{CMAX c}( ; the bandwidth of the SRS transmission in subframe i for serving cell c expressed in number of resource blocks, _SRS ; and a 4-bit power offset i¾_{RS 0}FFSET,_CO) semi-statically configured by higher layers for m=0 and m=l.

Reusing the PUSCH power control parameters for SRS transmission is sound when the mobile terminal communicates in uplink and downlink with the same network control node device, e.g. the serving cell controlling the mobile station. However, issues can occur in more advanced systems where the downlink transmission points and the uplink reception points are geographically separated network control node devices, as in the case of heterogeneous networks or so called CoMP systems. Coordinated multi-point (CoMP) operation was agreed as part of the 3GPP LTE Rel-11 for downlink and uplink, 3GPP TR 36.819, implying coordinated downlink transmission and/or uplink reception from/at multiple geographically separated points, forming a so called CoMP cooperating set. To fully capitalize the potential of this technology, the existing LTE uplink power control procedures need to be enhanced. For instance, the existence of multiple reception points of the same signal transmitted from a UE (mobile station) causes the problem of determining a single basic metric that encompasses the total attenuation when a signal is jointly received at multiple reception points.

In heterogeneous networks, where the transmission power of a macro point is normally much higher than the transmission power of a pico-point, it is common for a mobile terminal to be associated to a macro point for DL operation and to a pico point for UL operation, as shown in Figure 1. It has been argued that this can happen for about 30 % of the mobile stations, with a path loss difference between downlink and uplink ranging up to 16dB. Hence, estimating the uplink path loss by reusing LTE Rel-10 procedures based on measuring the signal strength of downlink common reference signals (CRS) can be rather inaccurate. Any such inaccuracy due to the PUSCH power control results in an inaccuracy of the SRS power control.

The situation is further aggravated with CoMP operation. While the PUSCH closed-loop power control can compensate the path loss inaccuracy for the PUSCH channel, the same closed-loop transmit power control commands (TPC) cannot guarantee the correct operation of SRS, particularly when the sounding reference signals are used in support of downlink transmission.

The transmit power control procedure for sounding reference signals in the 3 GPP LTE Rel- 8/9/10 is tied to the open-loop and closed-loop power control parameters used for the transmission of the PUSCH channel as described in equation (1). It has been argued that for CoMP operation the power control procedure for sounding reference signals needs to be enhanced due to an imbalanced uplink/downlink propagation loss and due to the existence of multiple geographically separated network devices that are intended to receive the same sounding signals. In particular, several 3GPP papers, pointed out that sounding signals targeting network devices used for uplink reception from a mobile terminal, and sounding signals targeting network control devices used for downlink transmission to the same mobile terminal, may need two different transmit power settings. Two prior art solution approaches have been proposed to address this problem.

The first prior art solution approach consists of a SRS power control linked to the PUSCH power control (as in the LTE Rel-10 eq. (1)) with an increased range of the power offset ^SRS OFFSET, (^ot) - The increased range of the power offset is meant to compensate for the propagation loss difference between the mobile terminal and the network devices used for uplink reception and downlink transmission, so that to guarantee a higher transmission power for sounding reference signals targeting network devices associated to the downlink transmission. The drawback of this approach is twofold: firstly, the power offset i¾Rs oFFSET,c(^OT) i^s semi-statically configured by higher layer signalling from the serving cell controlling the mobile terminal. Therefore it cannot dynamically adjust the transmit power of the sounding reference signals on a sufficiently fast time-scale. Secondly, by enforcing a higher power offset through a semi-static higher layer signalling, the sounding reference signals targeting network devices associated with the uplink reception from the mobile terminal will be transmitted with unnecessary higher power, thus creating higher interference in the system. On other hand, if the power offset cannot be adjusted fast enough, sounding reference signals targeting network devices associated with the downlink transmission to the mobile terminal may use too low transmit power. The second prior art solution approach consists of introducing a separate SRS power control process to support the downlink operation in CoMP systems in addition to the power control for uplink CoMP reception, where the additional power control process is not tied to the power control of PUSCH. Although this approach allows a wider flexibility, keeping the SRS power control targeting downlink CoMP transmission points completely decoupled from the SRS power control targeting uplink CoMP reception points requires additional complexity at the mobile terminal as well as higher control signalling overhead. Hence, there is a need in the art for an improved method for power control of SRS. Summary of the Invention

An object of the present invention is to provide a solution which mitigates or solves the drawbacks and problems of prior art solutions.

According to a first aspect of the invention, the above mentioned objects are achieved by a method for power control of sounding reference signals (SRS) in a wireless communication system comprising one or more network control nodes and one or more mobile stations, wherein mobile stations are arranged for transmitting sounding reference signals (SRS) in the uplink for estimation of radio channel states; said method comprising the steps of:

- calculating, by at least one network control node, a power control parameter g when a downlink transmission to a mobile station is scheduled relating to a previous uplink transmission of sounding reference signals (SRS) from said mobile station;

- transmitting, by a network control node, said power control parameter g to said mobile station;

- receiving, by said mobile station, said power control parameter g;

- calculating, by said mobile station, a transmit power P for transmission of sounding reference signals (SRS) by using said power control parameter g; and

- transmitting, by said mobile station, sounding reference signals (SRS) with said calculated transmit power P.

According to a second aspect of the invention, the above mentioned objects are achieved by a method in a network control node of a wireless communication system comprising one or more network control nodes and one or more mobile stations, wherein mobile stations are arranged for transmitting sounding reference signals (SRS) in the uplink for estimation of radio channel states; said method comprising the steps of:

- calculating a power control parameter g when a downlink transmission to a mobile station is scheduled relating to a previous uplink transmission of sounding reference signals (SRS) from said mobile station; and

- transmitting said power control parameter g to said mobile station. According to a third aspect of the invention, the above mentioned objects are achieved by a method in a mobile station of a wireless communication system comprising one or more network control nodes and one or more mobile stations, wherein mobile stations are arranged for transmitting sounding reference signals (SRS) in the uplink for estimation of radio channel states; said method comprising the steps of:

- receiving a power control parameter g transmitted according to the method above;

- calculating a transmit power P for transmission of sounding reference signals (SRS) by using said power control parameter g; and

- transmitting sounding reference signals (SRS) with said calculated transmit power P.

According to a fourth aspect of the invention, the above mentioned objects are achieved with a network control node device of a wireless communication system, said wireless communication system comprising one or more network control node devices and one or more mobile station devices, wherein mobile station devices are arranged for transmitting sounding reference signals (SRS) in the uplink for estimation of radio channel states; said network control node device being arranged to:

- calculate a power control parameter g when a downlink transmission to a mobile station device is scheduled relating to a previous uplink transmission of sounding reference signals (SRS) from said mobile station device; and

- transmit said power control parameter g to said mobile station device.

According to a fifth aspect of the invention, the above mentioned objects are achieved with a mobile station device of a wireless communication system, said wireless communication system comprising one or more network control node devices and one or more mobile station devices, wherein mobile station devices are arranged for transmitting sounding reference signals (SRS) in the uplink for estimation of radio channel states; said mobile station device being arranged to:

- receive a power control parameter g transmitted by the network control node device above;

- calculate a transmit power P for transmission of sounding reference signals (SRS) by using said power control parameter g; and

- transmit sounding reference signals (SRS) with said calculated transmit power P. Different embodiments of the different aspects of the invention are defined and disclosed in the appended dependent claims and in the detailed description.

The invention also relates to a computer program and a computer program product.

The present invention provides a solution that enhances the power control of sounding reference signals of conventional radio cellular systems for the case of a wireless communication system with coordinated multi-point transmission and reception. The power control of sounding reference signals is enhanced by introducing a new parameter. The new parameter provides a power adjustment for sounding reference signals used to estimate the downlink radio channel.

Further, the present invention provides a solution for power control of sounding reference signals that, by introducing a new parameter within a current power control procedure of sounding reference signals used to estimate the uplink radio channel, can dynamically switch from a power control of sounding reference signals used to estimate the uplink radio channel to a power control of sounding reference signals used o estimate the downlink radio channel.

The present invention also enables to adjust the transmit power of sounding reference signals on a millisecond time-scale with minimal network signalling overhead and implementation complexity , when said sounding reference signals are used to estimate the downlink radio channel.

Further applications and advantages of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the present invention in which:

- Fig. 1 illustrates a CoMP configuration with unbalanced uplink and downlink propagation loss; and

Fig. 2 illustrates an embodiment of the present invention. Detailed Description of the Invention

To achieve the aforementioned and further objects, the present invention relates to a method for power control of SRSs transmitted in the uplink in a wireless communication system. The method comprises the steps of: calculating, by at least one network control node, a power control parameter g when a downlink transmission to a mobile station is scheduled relating to a previous uplink transmission of SRSs from the mobile station; transmitting, by a network control node, the power control parameter g to the mobile station; receiving, by the mobile station, the power control parameter g; calculating, by the mobile station, a transmit power P for transmission of SRSs by using the power control parameter g; and transmitting, by the mobile station, SRSs with the calculated transmit power P. The invention also relates to corresponding methods in a network control node and a mobile station.

Compared to the power control procedure for SRSs with a single transmission/reception point for both downlink and uplink operation, SRSs transmitted within a CoMP system are used to target geographically separated points to support either downlink transmission or uplink reception. Therefore, e.g. the LTE-A Rel-10 SRS power control procedure, which reuses parameters chosen for PUSCH power control, is not sufficient to allocate the correct SRS transmit power when SRS signals are supposed to target downlink transmission points. Hence, the present method embeds an additional closed-loop mechanism within an existing SRS power control procedure with the objective of correcting the SRS transmit power when the SRSs shall reach downlink transmission points. Thereby, by embedding a new parameter as an additional closed-loop mechanism within an existing SRS power control procedure with the objective of correcting the SRS transmit power when the sounding signals shall reach downlink transmission points a power control method with the above mentioned advantages is provided.

Fig. 2 illustrates the present method - when a downlink transmission to a mobile station is scheduled relating to a previous uplink transmission of SRSs from the mobile station, the network control node computes a power control parameter g that shall be used for power control of the SRSs. The network control node computes the parameter g in an earlier subframe where a transmission of SRSs from the mobile station were scheduled. According to an embodiment of the invention the network control node calculating the power control parameter g is the network control node (with associated serving cell) that controls the mobile station. Preferably, the power control parameter g is expressed in dB, and may be signalled to the mobile station in a transmit power command (TPC) comprised in downlink control information, e.g. in a suitable control channel such as the physical downlink control channel (PDCCH) or the enhanced physical downlink control channel (ePDCCH) in LTE systems. The power control parameter g is also preferably mobile station (UE) specific.

According to yet another embodiment, the transmit power command (TPC) is represented by N number of bits, these N bits indicating different values for the power control parameter g. For example, the N bits specifying a mapping between a transmit power adjustment (expressed in dB) calculated at a serving cell controlling the mobile station and a finite set of possible transmit power adjustments. An N-bit bitmap can be is used at the serving cell to map the calculated power adjustment g into a finite set of valued to be conveyed to the mobile station as the state of N information bits forming a transmit power control command. The bitmap used by the serving cell to create the transmit power control command shall be known at the mobile station.

An example of a simple 2-bit bitmap is, but not limited to, given in Table 1 below. In Table 1, the difference between a target received power in the uplink and the actual received power in the uplink for a previous transmission of SRSs is mapped into four values of g. The mapping described in Table 1 is arbitrary and not limiting for the invention. Each value of g is then associated with a combination of two binary bits ^₂) which shall be conveyed to the mobile station. For instance, if the received power difference is 6 dBm, a power control command consisting of the bits configuration &i&₂) ⁼ (01) is transmitted to the mobile station to enforce a power adjustment of 5 dBm.

Received power diff (dBm) Power adjustment g (dBm) Information bits (&i-¾)

>10dBm 10 dBm 00

>5dBm and <10dBm 5 dBm 01

>2dBm and <5dBm 2 dBm 10

<2dBm 1 dBm 11 Table 1. Example of 2-bit bitmap used at a receive device of the network to generate power control commands.

Furthermore, according to yet another embodiment, the calculated transmit power P is a minimum of: maximum allowed transmit power, and a sum of a value for the power control parameter g and a transmit power for the previous transmission of SRSs. The maximum allowed power is the maximum transmit power the mobile station can use for transmission of SRS. The present embodiment enables to dynamically adjust the transmit power of SRS by implicitly distinguishing whether the SRSs are used to estimate the uplink radio channel or the downlink radio channel.

Moreover, the calculated transmit power P may be derived from the equation:

where P(i) is a function defined according to any 3 GPP standard. Regarding the new parameter, g i) is either the value of g received from the network control node as e.g. TPC for the transmission of SRS in subframe i, or zero if no TPC was issued for the transmission of SRS in subframe i according to an embodiment

For use with existing LTE systems, P(i) and P_MAX are defined according to 3GPP TS 36.213 Release 10, i.e. :

P( = PsRs_oFFSET,c (^m^ + ^{l ol}°9io (.M_SRS>C) + P₀_PUSCH,C(J +^Kc 0)^■ PL_C + fc( , and PMAX ⁼ PcMAx.c, where:

P_CMAX (i) is the maximum uplink configured transmit power;

^ SRS OFFSET (^m) is ^a 4-bit parameter semi-statically configured by higher layers for m=0 and m=l;

S_RS is the bandwidth of the SRS transmission in subframe i expressed in number of resource blocks;

P_{0 PUSCH} (J) denoted the desired received power level per resource block set by higher layers by the serving cell controlling the mobile terminal;

PL_c is the path loss estimate calculated in the mobile terminal in decibels;

ccc(j) is a parameter provided by higher layers from the serving cell controlling the mobile terminal; f_c (i) is the current power control adjustment state sent to the mobile terminal from the for serving cell controlling the mobile terminal for uplink data channel power control. However, a modified version of the 3GPP TS 36.213 Release 10 can also be useful, i.e.

P( = P_SRS OFFSET, d™ + ^{l ol}°9io (M_SRSiC) + P₀__PUscH,c(j) +^Kc 0) · PLc, and P_MAX =

PcMAX Hence, as mentioned above, it should be realized that the present invention embeds an additional closed-loop mechanism within the existing SRS power control procedure with the objective of correcting the SRS transmit power when the SRSs shall reach downlink transmission points. Regarding different values for the power control parameter g the following two main approaches may be used depending on where in the system the parameter is calculated.

Calculated by the mobile station:

• the power control parameter g is set to zero if the mobile station does not receive any power control parameters related to the transmission of the SRSs.

Calculated by the network control node:

• the power control parameter g is calculated as a difference between a target received power in the uplink and an actual received power in the uplink for an earlier subframe where a SRS transmission from the mobile station is scheduled

• power control parameter g is set to a predefined maximum transmission power value by a network control node controlling the mobile station if the SRSs are not received by any network control nodes of the system.

It should be noted the three above embodiments may be used alone or in combination.

In another scenario it might be the case that a plurality of network control nodes is associated with the downlink transmission to the mobile station. In this case each of them may calculate a power control parameter gj for the mobile station. Therefore, one power control parameter g has to be selected among a plural of power control parameters calculated by the different network control nodes. This scenario is typical with coordinated multi-point operation, such as CoMP LTE, where a plurality of network control nodes is associated with the downlink transmission to a mobile station. It has been realized that one preferable selection criteria is to select the power control parameter g having a largest value among the plural power control parameters gj. Since each of the power control parameters gj represents the required power adjustment for SRS to be correctly received at the network control node computing the power control parameter, selecting the power control parameter g as the largest value among the plural power control parameters gj ensures that the SRS are correctly received at the network control node with the worst channel conditions. However, other selection criteria are possible.

Furthermore, as understood by the person skilled in the art, any method according to the present invention may also be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprises of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, the present invention also relates to a network control node device and a mobile station device. It should also be realised that the network control node device and the mobile station device may be modified, mutatis mutandis, according to the different embodiments of the corresponding methods. The term mobile station is used generically for all suitable mobile device such as mobile terminals, user equipment, etc. The network control node device is a network device which has the necessary functions to calculate the new parameter. The network control node device may also preferably also have the means to control the mobile station in the system.

Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. Method for power control of sounding reference signals (SRSs) in a wireless communication system comprising one or more network control nodes and one or more mobile stations, wherein mobile stations are arranged for transmitting sounding reference signals (SRSs) in the uplink for estimation of radio channel states; said method comprising the steps of:

- calculating, by at least one network control node, a power control parameter g when a downlink transmission to a mobile station is scheduled relating to a previous uplink transmission of sounding reference signals (SRSs) from said mobile station;

- receiving, by said mobile station, said power control parameter g;

- calculating, by said mobile station, a transmit power P for transmission of sounding reference signals (SRSs) by using said power control parameter g; and

- transmitting, by said mobile station, sounding reference signals (SRSs) with said calculated transmit power P.

2. Method according to claim 1, wherein said power control parameter g is expressed in dB.

3. Method according to claim 1, wherein said power control parameter g is transmitted in a form of a transmit power command (TPC) comprised in downlink control information.

4. Method according to claim 3, wherein said transmit power command (TPC) is represented by N number of bits, wherein said N number of bits indicates different values for said power control parameter g.

5. Method according to claim 1, wherein said at least one network control node calculating said power control parameter g controls said mobile station.

6. Method according to claim 1, wherein said calculated transmit power P is a minimum of: maximum allowed transmit power, and a sum of a value for said power control parameter g and a transmit power for said previous transmission of sounding reference signals (SRSs).

7. Method according to claim 6, wherein said calculated transmit power P is derived from the equation:

P_srs(I) = min {_{p ( + g (i} , where P(i) is a function preferably defined according to any 3 GPP standard.

8. Method according to claim 7, wherein P(i) and P_MAX are defined according to 3GPP TS 36.213 Release 10, i.e.

P(0 = PsR_S_OFFSET (m) + 1 log₁₀ (M_{SRS c}) + Po_PUSCH 0) +«c 0) - PLc + fdi), and

¾L4X ⁼ PcMAX

9. Method according to claim 7, wherein P(i) and P_MAX are defined according to a modified version of the 3GPP TS 36.213 Release 10, i.e.

P(0— PsRS_OFFSET Po_PUSCH 0) +^Kc 0) · PLc, and

¾L4X ⁼ PcMAX

10. Method according to claim 1, wherein said power control parameter g is set to zero if said mobile station does not receive any power control parameters related to said transmission of said sounding reference signals (SRSs).

11. Method according to claim 1, wherein said power control parameter g is calculated as a difference between a target received power in the uplink and an actual received power in the uplink for an earlier transmission of sounding reference signals (SRSs).

12. Method according to claim 11, wherein a plurality of network control nodes each calculates a power control parameter gj for said mobile station, and said method further comprises the step of: - selecting, by a network control node controlling said mobile station, one power control parameter g among a plural of power control parameters calculated by said plurality of network control nodes.

13. Method according to claim 12, wherein said step of selecting involves:

- selecting a power control parameter g having a largest value among said plural of power control parameters.

14. Method according to claim 1, wherein said power control parameter g is set to a predefined maximum transmission power value by a network control node controlling said mobile station if said sounding reference signals (SRSs) transmitted with said calculated transmit power P is not received by any network control nodes.

15. Method according to claim 1, wherein

- said sounding reference signals are periodically or aperiodically transmitted; and/or

- said power control parameter g is mobile station specific; and/or

- said at least one network control node is a base station, such as a eNodeB; and/or

- said mobile station is a user equipment (UE).

16. Method in a network control node of a wireless communication system comprising one or more network control nodes and one or more mobile stations, wherein mobile stations are arranged for transmitting sounding reference signals (SRSs) in the uplink for estimation of radio channel states; said method comprising the steps of:

- calculating a power control parameter g when a downlink transmission to a mobile station is scheduled relating to a previous uplink transmission of sounding reference signals (SRSs) from said mobile station; and

- transmitting said power control parameter g to said mobile station.

17. Method according to claim 16, wherein said power control parameter g is expressed in dB.

18. Method according to claim 16, wherein said power control parameter g is transmitted in a form of a transmit power command (TPC) comprised in downlink control information.

19. Method according to claim 18, wherein said transmit power command (TPC) is represented by N number of bits, wherein said N number of bits indicates different values for said power control parameter g.

20. Method according to claim 16, wherein said at least one network control node calculating said power control parameter g controls said mobile station.

21. Method according to claim 16, wherein said power control parameter g is calculated as a difference between a target received power in the uplink and an actual received power in the uplink for an earlier transmission of sounding reference signals (SRSs).

22. Method according to claim 16, wherein said power control parameter g is set to a predefined maximum transmission power value by a network control node controlling said mobile station if said sounding reference signals (SRSs) is not received by any network control nodes.

23. Method in a mobile station of a wireless communication system comprising one or more network control nodes and one or more mobile stations, wherein mobile stations are arranged for transmitting sounding reference signals (SRSs) in the uplink for estimation of radio channel states; said method comprising the steps of:

- receiving a power control parameter g transmitted according to any of claims 15-21 ;

- calculating a transmit power P for transmission of sounding reference signals (SRSs) by using said power control parameter g; and

- transmitting sounding reference signals (SRSs) with said calculated transmit power P.

24. Method according to claim 23, wherein said calculated transmit power P is derived from the equation:

P_srs(I) = min {_{p( + g(i} , where P(i) is a function preferably defined according to any 3 GPP standard.

25. Method according to claim 24, wherein P(i) is defined according to 3GPP TS 36.213 Release 10, i.e.

P (i) = PsRs_oFFSET,c (^m^ + ^{l ol}°9io (.M_SRS>C) + P₀_PUSCH,C (J +^Kc 0) · PLc + fc( , and

PMAX ⁼ PcMAX,C -

26. Method according to claim 24, wherein P(i) and P_MAX are defined according to a modified version of the 3GPP TS 36.213 Release 10, i.e.

P (i) = PSRS OFFSETA™) + ^{l oio}5io (WsRs,c) + PO_PUSCH,C (J) +^Kc 0) · ^c, ^and

¾L4X ⁼ PcMAX.C -

27. Method according to claim 23, wherein said power control parameter g is set to zero if said mobile station does not receive any power control parameters.

28. Computer program, characterised in code means, which when run by processing means causes said processing means to execute said method according to any of claims 1 -27.

29. Computer program product comprising a computer readable medium and a computer program according to claim 28, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

30. Network control node device of a wireless communication system, said wireless communication system comprising one or more network control node devices and one or more mobile station devices, wherein mobile station devices are arranged for transmitting sounding reference signals (SRSs) in the uplink for estimation of radio channel states; said network control node device being arranged to:

- calculate a power control parameter g when a downlink transmission to a mobile station device is scheduled relating to a previous uplink transmission of sounding reference signals (SRSs) from said mobile station device; and - transmit said power control parameter g to said mobile station device.

31. Mobile station device of a wireless communication system, said wireless communication system comprising one or more network control node devices and one or more mobile station devices, wherein mobile station devices are arranged for transmitting sounding reference signals (SRSs) in the uplink for estimation of radio channel states; said mobile station device being arranged to:

- receive a power control parameter g transmitted by the network control node device according to claim 30;

- calculate a transmit power P for transmission of sounding reference signals (SRSs) by using said power control parameter g; and

- transmit sounding reference signals (SRS) with said calculated transmit power P.