WO2010151196A1

WO2010151196A1 - Method and arrangement in a wireless communications network for adaptation of power control setting

Info

Publication number: WO2010151196A1
Application number: PCT/SE2009/051038
Authority: WO
Inventors: David Astely; Magnus Lundevall; Jessica ÖSTERGAARD
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2009-06-26
Filing date: 2009-09-17
Publication date: 2010-12-29

Abstract

A method in a base station, for adapting Sounding Reference Signals (SRS) power control setting in a user equipment is provided. An SRS specific fractional pathloss compensation factor "α_sounding" value is decided based on a specific purpose for using SRS received from the user equipment. The α_sounding value is decided independent of a value of a data specific fractional pathloss compensation factor "α_data" to be used for data transmission to the base station. The user equipment is informed to use the decided α_sounding value for adapting the SRS power control setting in the user equipment. This enables the user equipment to send SRS, using power according to the adapted power control setting.

Description

METHOD AND ARRANGEMENT IN A WIRELESS COMMUNICATIONS NETWORK FOR ADAPTATION OF POWER CONTROL SETTING

TECHNICAL FIELD

The present invention relates to a method and an arrangement in a radio network node, a method and an arrangement in signalling device, and a method and an arrangement in a wireless communications network. In particular, it relates to adapting the Sounding Reference Signal "SRS" power control setting in the user equipment.

BACKGROUND

In a typical cellular system, also referred to as a wireless communications network, wireless terminals, also known as mobile stations and/or User Equipment units (UEs) communicate via a Radio Access Network (RAN) to one or more core networks. The wireless terminals can be mobile stations or user equipment units such as mobile telephones also known as "cellular" telephones, and laptops with wireless capability, e.g., mobile termination, and thus can be, for example, portable, pocket, hand-held, computer- included, or car-mounted mobile devices which communicate voice and/or data with radio access network.

The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a Radio Base Station (RBS)₁ which in some networks is also called "NodeB" or "B node" and which in this document also is referred to as a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units within range of the base stations.

In some versions of the radio access network, several base stations are typically connected. Radio network controllers are typically connected to one or more core networks. The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. In 3GPP this work regarding the 3G Long Term Evolution (LTE) system is ongoing

Sounding reference signals (SRS) are known signals that are transmitted in the uplink from user equipments, so that the base station can estimate the uplink channels. The channel estimates may be used for uplink Radio Resource Management (RRM) such as scheduling, link adaptation and power control, but also for downlink multiple antenna transmission and RRM₁ especially in case of Time Division Duplex (TDD) where the uplink and downlink use the same frequencies. SRS may also be used to derive timing-control commands for uplink time alignment. In Long Term Evolution (LTE)₁ the sounding reference signals have a duration of a single Orthogonal Frequency Division Multiplexing (OFDM) symbol. UEs are configured by higher layers to transmit sounding reference signals in the last symbol of one or several Up Link (UL) subframes, or in case of TDD, in Uplink Part of Time Slot (UpPTS), which is a short uplink time slot with configurable length of one or two OFDM symbols positioned right after the guard period at a switch from downlink to uplink. By means of time division multiplexing (TDM) different UEs may be separated in the sense that different UL subframes or different symbols in UpPTS are used. In addition to TDM₁ frequency domain multiplexing of UEs may be done, and to be able to multiplex UEs with different UL sounding bandwidth, SRS are transmitted using a repetition factor of two meaning that every second subcarrier is used. In addition to TDM and FDM, code division multiplexing (CDM) may also be used within a set of subcarriers in the same OFDM symbol. More specifically, different cyclic shifts of a Zhadoff-Chu sequence are used for this purpose.

SRS transmissions are configured with * a certain bandwidth, indicating how many resource blocks (in the frequency domain) the sounding reference signal will cover and the starting position in the frequency domain

• a certain period, indicating the distance, in time, between consecutive SRS transmissions • parameters related to frequency hopping, i.e. which subcarriers that will be used in which subframes

• parameters related to UE transmit antenna hopping in case the UE has two transmit antennas. • a certain duration, indicating either SRS transmission until stopped or a one shot

SRS transmission.

Just like other transmissions in the uplink, SRS transmissions are power controlled. The SRS power control formula resembles the power control used for the data channel, the Physical Uplink Shared Channel (PUSCH). The SRS power control involves e.g. compensation for the bandwidth used for sounding, e.g. using more power when the SRS uses larger bandwidth to keep the received power spectral density independent of the sounding bandwidth, compensation for the long-term estimate of noise and interference in the cell, and compensation for the UE's pathloss. The goal of the power control is to make sure that uplink transmission of data on PUSCH and control on Physical Uplink Control Channel (PUCCH) is received at a desired quality level. For uplink data transmissions on PUSCH, parameters in the UE are configurable. When the main purpose of SRS is to estimate uplink channel quality for scheduling and data transmission, parameters such as pathloss compensation are the same as for the PUSCH transmission so that the quality estimated from SRS are applicable to uplink data transmissions on PUSCH.

In the existing power control formula for SRS, fractional pathloss compensation is possible by setting the parameter α<1 and it is the same for both SRS transmissions as well as uplink data transmissions on PUSCH. With α<1 , UEs with large pathloss are received at the eNodeB with a lower Power Spectral Density (PSD) than UEs with small pathloss. Since CDM is used, there is a possible near-far problem where the SRS from the UE with low received PSD drowns in the SRS from one or several UEs with high received PSD in the same cell. There is of course a processing gain, which depends on the bandwidth used, but in the presence of imperfections in the transmitted signals and power settings, there can still be problems when it comes to obtaining accurate enough channel estimates. Another aspect is intercell interference, where there may be a fundamental multicell capacity limit.

As mentioned above, it is also stated that the parameter α used for SRS matches the α used for the PUSCH. SUMMARY

To be able to increase the cellular system capacity in terms of how many users in each cell that can perform sounding simultaneously, it is of importance to limit the interference generated to other cells and hence keep the received PSD as low as possible.

It is therefore an object of the invention to provide a mechanism that increases the performance in the wireless communications network when sending SRS.

According to a first aspect of the invention, the object is achieved by a method in a base station, for adapting the SRS power control setting in a user equipment. The base station decides an SRS specific fractional pathloss compensation factor " Os_0Uπdmg value based on a specific purpose for using SRS received from the user equipment. The or_sou/1d,_n9 value is decided independent of a value of a data specific fractional pathloss compensation factor "oc_da_ta to be used for data transmission to the base station. The base station then informs the user equipment to use the decided α_∞υndi_ng value for adapting the SRS power control setting in the user equipment. This enables the user equipment to send SRS, using power according to the adapted power control setting.

According to a second aspect of the invention, the object is achieved by a method in a user equipment, for adapting the SRS power control setting in the user equipment. The user equipment receives from the base station, information to use a decided SRS specific fractional pathloss compensation factor ^uα_sαunding'' value for adapting the SRS power control setting in the user equipment. The a_ddi_ng value has been decided by the base station based on a specific purpose for using SRS received from the user equipment, and is independent of a value of a data specific fractional pathloss compensation factor α^_/a value to be used for data transmission to the base station. The user equipment adapts the SRS power control setting according to the a sou_ndi_ng value comprised in the received information.

According to a third aspect of the invention, the object is achieved by a method in a wireless communications network, for adapting the SRS power control setting in a user equipment. An SRS specific fractional pathloss compensation factor "o_sou_nd_mg value is decided based on a specific purpose for using SRS received from the user equipment. The a_sound,_ng value is decided independent of the value of a data specific fractional pathloss compensation factor oaa_ta to be used for data transmission to a base station comprised in the wireless communications network. The SRS power control setting is adapted in the user equipment according to the decided α_sounύmg value, enabling the user equipment to send SRS₁ using power according to the adapted power control setting.

According to a forth aspect of the invention, the object is achieved by a base station for adapting the Sounding Reference Signal "SRS" power control setting in a user equipment. The base station comprises a deciding unit configured to decide an SRS specific fractional pathloss compensation factor α_sounύmg value, based on a specific purpose for using SRS received from the user equipment. The ihou_nd_mg value is decided independent of a value of a data specific fractional pathloss compensation factor α^r_a to be used for data transmission to the base station. The base station further comprises an informing unit configured to inform the user equipment to use the decided α_sound,_ng value for adapting the SRS power control setting in the user equipment. This enables the user equipment to send SRS, using power according to the adapted power control setting.

According to a fifth aspect of the invention, the object is achieved by a user equipment, for adapting the SRS power control setting in the user equipment. The user equipment comprises a receiving unit configured to receive from the base station, information to use a decided SRS specific fractional pathloss compensation factor "αsoυndmg" value, for adapting the SRS power control setting in the user equipment. The α sounding value has been decided by the base station based on a specific purpose for using SRS received from the user equipment, and is independent of a value of a data specific fractional pathloss compensation factor c^_ara value to be used for data transmission to the base station. The user equipment further comprises an adapting unit configured to adapt the SRS power control setting according to the α_soυndιπg value comprised in the received information.

According to a sixth aspect of the invention, the object is achieved by a wireless communications network, for adapting the SRS power control setting in a user equipment. The wireless communications network comprises a deciding unit configured to decide a SRS specific fractional pathloss compensation factor "α_S01/πd/ng" value, based on a specific purpose for using SRS received from the user equipment. The α_sounrtΛ9 value is decided independent of the value of a data specific fractional pathloss compensation factor "Odaia" to be used for data transmission to a base station comprised in the wireless communications network. The wireless communications network further comprises an adapting unit configured to adapt the SRS power control setting in the user equipment according to the decided α_sounφng value. This enables the user equipment to send SRS, using power according to the adapted power control setting.

An advantage with the present solution is that it provides enhanced flexibility in the use of sounding, for example for downlink or uplink. A further advantage with the present solution is that it provides enhanced sounding quality and/or capacity.

A yet further advantage with the present solution is that it provides a possibility to adapt sounding for several areas of applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail with reference to attached drawings illustrating exemplary embodiments of the invention and in which:

Figure 1 is a schematic block diagram illustrating embodiments of a wireless communication network.

Figure 2 is a combined schematic block diagram and flowchart depicting embodiments of a method.

Figure 3 is a schematic block diagram illustrating embodiments of a base station.

Figure 4 is a schematic block diagram illustrating embodiments of a user equipment.

Figure 5 is a flowchart depicting embodiments of a method in a wireless communications network.

Figure 6 is a schematic block diagram illustrating embodiments of a wireless communications network. Figure 7 is a flowchart depicting embodiments of a method in a base station.

Figure 8 is a flowchart depicting embodiments of a method in a user equipment.

DETAILED DESCRIPTION

As part of the present solution a problem will first be identified and discussed. Transmitter power control typically aims at maximizing the received signal power of desired signals, while limiting the generated interference. In the uplink, the amount of interference generated to neighbour cells depends, among other things, on the path gain from the mobile-terminal to these cells. Terminals close to neighbour cells generate more interference than terminals far away. For a given interference level in a neighbour cell, terminals far away may hence transmit with a higher power than terminals near the cell. This may be accomplished by power control mechanisms including a fractional pathloss compensation factor α. The terminal transmission power P, in dB, is set according to

P = X + a - PL where X is a parameter used to control the target received power, α the fractional pathloss compensation factor and PL the estimated pathloss. Setting α<1 allow low- pathloss terminals, likely to generate little interference, to be received at a higher power level. Contrary, α=1 gives full pathloss compensation meaning that the signals from all terminals are received at the same power level. Thus, α can be used to control the tradeoff between cell-edge quality and cell capacity. Different physical transmissions, e.g. data, control and sounding may be power controlled depending on which physical channel the transmissions are made or depending on the type of transmission on a certain physical channel. In the case of data and sounding channels this looks like

¹ p sounding — ~ ^Λ y sounding A ™- ™ . * P ^I¹ and where state of the art solutions use the same value for α for both channels. One such example the power control for 3GPP LTE:

The setting for SRS in the power control for 3GPP LTE is specified as follows: The setting of the UE transmit power for the Sounding Reference Symbol transmitted on subframe / is defined by: P_SRS (/) = min{P_CMAX , /^_OFFSET + 10 log₁₀ (M_SRS ) + P₀J_WOi U) + cc(j) ^• PL + /(/)} _[dBm] p Where ^CMAX is the configured UE transmitted power. For ^Ks ^{= 125} , ^PSRS_^OFFSE^T j_{s a} 4__{bit UE} specific parameter semi-statically configured by higher layers with 1dB step size in the range [-3, 12] dB.

For κ_s = o , /⁵ _{SR5 OFFSCT} ^{is a 4}"^{bit UE} specific parameter semi-statically configured by higher layers with 1.5 dB step size in the range [-10.5,12] dB.

^MsRS is the bandwidth of the SRS transmission in subframe i expressed in number of resource blocks.

^■^ is the current power control adjustment state for the PUSCH. O.PU^SCH O) _and a(j) _are p_aramet_{ers as} defined in Section 5.1.1.1, where J ⁼ K

The setting for the PUSCH in the power control for 3GPP LTE is specified as follows:

WH (0 = min{/^> _c^_x,101og₁₀(Λ/_PUSCH(0) + P_O._PUSCH O) + </) ' ^pL + Δ_π(0 + /(O) IdBm]

P where, ^CMAX is the configured UE transmitted power.

^^PUSCHCO j_s the bandwidth of the PUSCH resource assignment expressed in number of resource blocks valid for subframe /. P₀ pusc_H O) is a parameter composed of the sum of a cell specific nominal component ^po _{NOMINAL, PUSCH} O) provided from higher layers for;=0 and 1 and a UE specific component /*_O__UE__PUSCH (y) provided by higher layers for j=0 and 1. For PUSCH (re)transmissions corresponding to a semi-persistent grant theny=O , for PUSCH (re)transmissions corresponding to a dynamic scheduled grant theny=7 and for PUSCH (re)transmissions corresponding to the random access response grant then y=2.

^O_.UE_.PUSCH C²) = ° ^and ^O_NOMINAL_PUSCH (²) = ^o_.pRE + ^Δ PREAMBLE _Ms_gi < ^ere the parameter PREAIVIBLEJNITIAL-RECEIVED-TARGET-POWER P_{0 PRE} and Δ_{PΛEMttUι Mφ} are signalled from higher layers.

Fory =0 or 1, a e {o, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, l} is a 3-bit cell specific parameter provided by higher layers. For j=2, a(j) = 1. As is seen, for SRS the α term becomes α(l) and for PUSCH α is also α(l) except for (re)transmissions corresponding to a random access response grant, hence the α factor is the same and changing a changes a both for SRS. This may be appropriate when the SRS are used mainly for uplink RRM. In such a case, the number of users using a certain frequency in each cell may be one and the power control parameters may be chosen to increase cell throughput and user throughput for users in the cell centre or close to the base station at the expense of cell edge data rates.

However, for SRS transmissions used for downlink transmission (in for example TDD), it may instead be of important to maximize the system capacity for sounding. This is to increase the number of users that can perform sounding in different cells simultaneously so that the eNodeB can maintain up-to date channel estimates for downlink transmission. In such a case, it is not of importance to increase the quality of the SRS reception for users close to the base station but rather to ensure that there is enough quality for all users in the cell. For example, if the sounding is used for beam forming with multiple antennas, the benefit of such techniques may be the greatest at the cell edge, but this then requires that accurate channel estimates can be obtained also from cell edge users.

Figure 1 depicts a wireless communications network 100. The wireless communications network 100 may use technologies such as LTE or the IEEE 802.16 family of standards, notably "Mobile WiMAX". The wireless communications network 100 comprises a base station 110 serving a cell 115. The base station 110 may be a base station such as a NodeB, an eNodeB, or any other network unit capable of communicating over a radio carrier with a user equipment being present in the within its reach. A user equipment 120 is present within the first cell 115 and served by the first network node 110, and is in this case capable of communicating with the first network node 110 over a radio carrier. The user equipment 120 may be a mobile phone, a Personal Digital Assistant (PDA), or any other radio communications network unit capable to communicate with a base station over a radio channel. The user equipment 120 is referred to as UE in some of the figures. The user equipment 120 transmits Sounding Reference Signals SRS 125 or sounding reference symbols. In this text the term SRS also may be interpreted as sounding reference symbols, to e.g. be used by the base station 110 for e.g. estimating the uplink channels. The channel estimates may be used for uplink RRM such as scheduling, link adaptation and power control, but also for downlink multiple antenna transmission and RRM, especially in case of Time Division Duplex (TDD) where the uplink and downlink use the same frequencies. SRS may also be used to derive timing-control commands for uplink time alignment.

Power control

The SRS transmissions from the user equipment 120 are power controlled. To adapt the power control for SRS, the present solution provides a SRS specific fractional pathloss compensation factor, a_soundiπg that is independent of the value of a^_ate and that is decided based on what the SRS is used for. The user equipment 120 behaviour when transmitting SRS may then be configured by the network, signalling to the user equipment 120 using higher layer RRC signalling.

The SRS power control is adapted to what the SRS is used for, such as best information for an application, which e.g. may be for uplink RRM or for downlink RRM including beam forming. The SRS power control is further adapted to optimum, i.e. best possible, received SRS quality as mentioned above by providing the SRS specific fractional pathloss compensation factor, Osoun_Λns-

Some embodiments provides the possibility of having different SRS power control settings in different types uplink subframes and transmission slots such a Uplink Part of Time Slot (UpPTS), as well as different settings over time in the same type of slot so that sounding resources for both uplink RRM and downlink RRM can be appropriately configured.

Some embodiments provide reducing the signalling for configuring the SRS. In a specific embodiment wherein no signalling is required, the pathloss compensation is set to 1 for sending SRS in UpPTS which is then intended for downlink RRM including beam forming whereas the pathloss compensation in other ordinary uplink subframes is the same as for PUSCH since such sounding is then intended for uplink RRM.

The present solution method for adapting the SRS power control setting in a user equipment 120, according to some embodiments will no be described with reference to the combined signalling diagram and flowchart depicted in Figure 2 and with reference to Figure 3 depicting the base station 110 and Figure 4 depicting the user equipment 120. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below:

Step 201 The base station 110 decides the SRS specific fractional pathloss compensation factor "dsoun_dmg value, based on a specific purpose for using SRS received from the user equipment 120. The a_S0Un_dmg value is decided independent of a value of a data specific fractional pathloss compensation factor "αW to be used for data transmission to the base station 110. This step may be performed in a deciding unit 310 within the base station 110 as depicted in Figure 3.

Step 202

The base station informs the user equipment 120 to use the decided a_souπdmg value for adapting the SRS power control setting in the user equipment (120). The information may be sent to the user equipment e.g. by signalling the information to the user equipment 120, or may be implicit (hardcoded), fixed value in the standard.

In some embodiments a_soundιng = 1 such that it is never signalled but hardcoded in the user equipment 120. This step may be performed in an informing unit 320 within the base station 110 as depicted in Figure 3.The user equipment 120 receives the information from the base station 110. The information may be received by a receiving unit 410 within the user equipment 120 as depicted in Figure 4. Note that a_soundιng may be a constant 1 , eliminating the need for sending it. Alternatively, a_S0Und_mg may have a default value of 1, such that the base station does not send a new value unless it is not satisfied with a_soundιng = 1.

Therefore a_soanϋmg is not necessarily sent explicitly to the user equipment 120 with order to use it. Instead some other parameter may be signalled, such as e.g. the transmission mode used for downlink data transmission, which triggers the user equipment 120 to use the a∞unφng that it received in a previous time instance.

Step 203

The user equipment 120 adapts the SRS power control setting according to the ccsounϋing value comprised in the received information. This step may be performed by an adapting unit 420 within the user equipment 120 as depicted in Figure 4.

Step 204

The user equipment 120 sends SRS using a power according to the adapted SRS power control setting. This step may be performed by a sending unit 430 within the user equipment 120 as depicted in Figure 4. The present solution method for adapting the SRS power control setting in a user equipment 120, according to a specific embodiment will no be described with reference to the flowchart depicted in Figure 5 and with reference to Figure 6 depicting the wireless communications network 100. This embodiment relates to the case wherein a node within the radio communications network 100, or the base station 110, decides the a∞_undi_ng value, and the user equipment 120 is configured e.g. at factory and not receives the alpha from the base station 110.The method comprises the following steps, which steps may as well be carried out in another suitable order than described below:

Step 501

The wireless communications network 100 decides the SRS specific fractional pathloss compensation factor "ocsou_nd_mg" value, based on a specific purpose for using SRS received from the user equipment 120 in the base station 110. The a_∞undiπg value is decided independent of the value of a data specific fractional pathloss compensation factor "ocdata" to be used for data transmission to a base station 110 comprised in the wireless communications network 100. This step may be performed in a deciding unit 610 within the wireless communications network 100 depicted in Figure 6.

Step 502 The user equipment 120 adapts the SRS power control setting in the user equipment 120 according to the decided α sounding value. This step may be performed by an adapting unit 620 within the user equipment 120 depicted in Figure 6. It may be performed such that the user equipment 120 output power when transmitting SRS is set according to the α_souπdi_ng value. In some embodiments, the α_sou_nd_mg value is hardcoded in the user equipment.

Step 503

The user equipment 120 may then send SRS, using a power according to the adapted SRS power control setting. This step may be performed by a sending unit 630 within the user equipment 120 depicted in Figure 6.

Regarding the present solution according to the examples described above with reference to Figures 2-6, when it comes to signalling the information, there are several embodiments where one embodiment, namely using

in UpPTS does not require any additional signalling at all. This may be hardcoded for all time instance or only in e.g. UpPTS whereas a_∞undlng < 1 in other uplink subframes.

All embodiments of the present solution mentioned above may comprise:

- using a_soυndmg =1 to receive SRSs from different UEs at the same power level, which is desired in some applications of sounding such as sounding for DL RRM. This setting eliminates near-far effects and maximizes the received SRS quality and system capacity for SRS. The benefit of this embodiment is that no RRC signalling is needed and that hence overhead is saved.

- using aso_undmg = a_<i_a,_a in order to make the received SRS best reflect the quality on the data channel when sounding for UL RRM.

- being able to configure the terminals whether Osounomg^ or α_SOundmg - ccdata should be used for all sounding either by means of user equipment specific higher layer signalling or being broadcasted as part of system information to all users in a cell.

- using

in order to receive SRS from different user equipments at different power levels, giving information about for example the pathloss differences between user equipments

- using alternating α_sounϋmg in different instants of time to suit several purposes

- using different α_S0Uπ_Λπg in different of type of transmission slots to suit several purposes - using specific a_soundmg in the UpPTS field of the special subframe in 3GPP LTE

TDD.

- using αsoun_Λn^i in UpPTS and α∞i/ndwig = Odata in other uplink subframes. By regular uplink subframes is meant "all non-special uplink subframes" where special subframe is the subframe that has the switching point between DL and UL transmission.

The wireless communications network 100 performing the method steps above for adapting the SRS power control setting in the user equipment 120, will now be further described with reference to Figure 6.

The wireless communications network 100 comprises the deciding unit 610 configured to decide a SRS specific fractional pathloss compensation factor "oso_uncW" value, based on a specific purpose for using SRS received from the user equipment 120.

The α soundmg value is decided independent of the value of a data specific fractional pathloss compensation factor "αtøa" to be used for data transmission to a base station

110 comprised in the wireless communications network 100. In some embodiments the deciding unit 610 is configured to decide that the CCS_RS value is to be alternated between different values in different instants of time.

In some embodiments the deciding unit 610 is configured to decide the a_SRS value is to be different in different types of transmission slots. In some embodiments the deciding unit 610 further is configured to decide that the a soundmg value = 1. In these embodiments the specific purpose for using the SRS from the user equipment 120, may be for downlink Radio Resource Management "RRM".

In some embodiments the deciding unit 610 is configured to decide that the a _soundmg value = a_data. In these embodiments, the specific purpose for using the SRS from the user equipment 120 may be for uplink RRM.

In some embodiments the deciding unit 610 further is configured to decide that the ^so_un_dmg value < 1. In these embodiments the deciding unit 610 may be configured to decide the α sou_nd_mg value specifically for the user equipment 120. This enables the base station 110 to receive SRS from the user equipment 120 on a power level that differs from the power level of SRS received from other user equipments.

In some embodiments the GPP LTE TDD technology is used. In these embodiments the deciding unit 610 may be configured to decide that the α soundmg value is one specific α soun_dm_g value in a Uplink Part of Time Slot "UpPTS" field of the special subframe in 3GPP LTE TDD, which special subframe comprises the switch point between downlink and uplink transmission.

In some embodiments the deciding unit 610 further is configured to decide that the α _soundmg value =1 in the UpPTS field of the special subframe, and decide that the α_soundιng value = O_da_ta in other uplink subframes, or deciding that the αso_Unύmg value = adata in the UpPTS field of the special subframe and decide that the ocs_ound_mg value = 1 in other uplink subframes.

As mentioned above, the wireless communications network 100 comprises the user equipment 120. The user equipment 120 comprises the adapting unit 620 configured to adapt the SRS power control setting in the user equipment 120 according to the decided α _soundmg value. This enables the user equipment 120 to send SRS, using power according to the adapted power control setting.

The method steps performed in the base station 110 for adapting the SRS power control setting in a user equipment 120 according to some embodiments will now be described with reference to a flowchart depicted in Figure 7. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below:

Step 701

The base station 110 decides an SRS specific fractional pathloss compensation factor "ccsoυn_dm_g" value. The decision is based on a specific purpose for using SRS received from the user equipment 120. The a_souπdirg value is decided independent of a value of a data specific fractional pathloss compensation factor "oc_da_ta" to be used for data transmission to the base station 110.

In some embodiments this step of deciding comprises deciding that the a_sound,_πg value is to be alternated between different values in different instants of time.

In some further embodiments this step of deciding comprises deciding the a sou_ndi_ng value is to be different in different types of transmission slots. This step of deciding may comprise to decide that the a_S0Un_ϋmg value = 1. This may be decided when the specific purpose for using the SRS received from the user equipment 120 is for downlink Radio Resource Management "RRM".

This step of deciding may in some embodiments comprise to decide that the a sou_ndi_ng value = aa_ata. This may be decided when the specific purpose for using the SRS received from the user equipment 120, is for uplink RRM.

This step of deciding may in some embodiments comprise to decide that the α sounding value < 1. In these embodiments this step of deciding may comprise that the α sou_ndi_ng value is decided specifically for the user equipment 120. This enables the base station 110 to receive SRS from the user equipment 120 on a power level that differs from power level of SRS received from other user equipments.

In some embodiments the GPP LTE TDD technology is used. In these embodiments this step of deciding comprises, deciding that the α_SOuπdi_πg value is one specific α_sounding value in a Uplink Part of Time Slot "UpPTS" field of the special subframe in 3GPP LTE TDD. The special subframe comprises the switch point between downlink and uplink transmission.

In some embodiments this step of deciding comprises deciding that the

value =1 in the UpPTS field of the special subframe and deciding that the a_S0Undmg value = ocdata in other uplink subframes, or deciding that the α_soundiπg value = O₀^₃ in the UpPTS field of the special subframe and deciding that the a_souπdmg value = 1 in other uplink subframes.

Step 702 The base station 110 informs the user equipment 120 to use the decided a_souπdιng value for adapting the SRS power control setting in the user equipment 120. This enables the user equipment 120 to send SRS, using power according to the adapted power control setting.

In some embodiments, this step is performed by signalling, using user equipment specific higher layer signalling or by broadcasting.

The base station 110 performing the method steps above for adapting the SRS power control setting in the user equipment 120, will now be further described with reference to Figure 3. The base station 110, comprises the deciding unit 310 configured to decide an

SRS specific fractional pathloss compensation factor "a_soundmg" value based on a specific purpose for using SRS received from the user equipment 120. The αwi_dmg value is decided independent of a value of a data specific fractional pathloss compensation factor "Odata" to be used for data transmission to the base station 110. In some embodiments, the deciding unit 310 is configured to decide that the α_soun<ι_mg value is to be alternated between different values in different instants of time.

In some other embodiments the deciding unit 310 is configured to decide that the α souπdmg value is different in different types of transmission slots. in some embodiments, the deciding unit 310 is configured to decide that the α_sound,_ng value = 1. This may be decided when the specific purpose for using the SRS received from the user equipment 120 is for downlink Radio Resource Management "RRM".

In some embodiments the deciding unit 310 is configured to decide that the α en_ding value = O_data, e.g. when the specific purpose for using the SRS received from the user equipment 120, is for uplink RRM. In some embodiments the deciding unit 310 is configured to decide that the a_sounding value < 1. In these embodiments the deciding unit 310 may be configured to decide the a _sou_nd_mg value specifically for the user equipment 120. This enables the base station 110 to receive SRS from the user equipment 120 on a power level that differs from power level of SRS received from other user equipments. In some embodiments the GPP LTE TDD technology is used. In these embodiments the deciding unit 310 may be configured to decide that the a_∞uπζ}mg value is one specific a_∞mύmg value in a Uplink Part of Time Slot "UpPTS" field of the special subframe in 3GPP LTE TDD. The special subframe comprises the switch point between downlink and uplink transmission.

In some embodiments the deciding unit 310 may be configured to decide that the a so_una_mg value =1 in the UpPTS field of the special subframe, and decide that the a_So_Un*_ng value = Ω_da_fa in other uplink subframes, or deciding that the ctsoun_dmg value = aa_ata in the UpPTS field of the special subframe and deciding that the a_Sou_n*_ng value = 1 in other uplink subframes.

The base station 110, further comprises the informing unit 320 configured to inform 202 the user equipment 120 to use the decided α_soundmg value for adapting the SRS power control setting in the user equipment 120. This enables the user equipment 120 to send SRS, using power according to the adapted power control setting. In some embodiments the informing unit 320 is configured to inform the user equipment 120 by signalling, using user equipment specific higher layer signalling or by broadcasting.

The method steps in the user equipment 120 for adapting the SRS power control setting in the user equipment 120 according to some embodiments will now be described with reference to a flowchart depicted in Figure 8. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below:

Step 801

The user equipment 120 receives from the base station 110, information to use a decided SRS specific fractional pathloss compensation factor ^uα_SOundιng" value, for adapting the SRS power control setting in the user equipment 120. The α_sounϋmg value has been decided by the base station 110 based on a specific purpose for using SRS received from the user equipment 120 and is independent of a value of a data specific fractional pathloss compensation factor ctøa/a value to be used for data transmission to the base station 110.

In some embodiments the α_soundιπg value comprised in the received information is to be alternated between different values in different instants of time. In some embodiments the a sounding value comprised in the received information is different in different types of transmission slots.

In some embodiments the αso_UnΛπg value comprised in the received information = 1.

In some embodiments the a_sounfJmg value comprised in the received information = O₀₃₁₃.

In some embodiments, the a_soundmg value comprised in the received information < 1.

In some embodiments 3GPP LTE TDD technology is used. In these embodiments the a_S0Undmg value comprised in the received information may be a specific a_sounόmg value to be used when sending SRS in an Uplink Part of Time Slot "UpPTS" field of the special subframe. The special subframe comprises the switch point between downlink and uplink transmission.

In some embodiments the a_SOunώng value =1 , to be used when sending SRS in the UpPTS field of the special subframe, and the a_souπdιng value = α^_atø to be used when sending SRS in other uplink subframes, or the a_sounctmg value = α^_a(8 to be used when sending SRS in the UpPTS field of the special subframe and the a sou_ndi_ng value = 1 to be used when sending SRS in the in other uplink subframes.

This step of receiving the information from the base station 110 may be received via user equipment specific higher layer signalling or via broadcasting.

Step 802

The user equipment 120 adapts the SRS power control setting according to the a soundmg value comprised in the received information.

Step 803 The user equipment 120 sends SRS using a power according to the adapted SRS power control setting.

The user equipment 120 performing the method steps above for adapting the SRS power control setting in the user equipment 120, will now be further described with reference to Figure 4.

The user equipment 120 comprises the receiving unit 410 configured to receive from the base station 110, information to use a decided SRS specific fractional pathloss compensation factor "αso_Urtr_f,_ng ⁿ value, for adapting the SRS power control setting in the user equipment 120. the a_S0Undmg value has been decided by the base station 110 based on a specific purpose for using SRS received from the user equipment 120 and is independent of a value of a data specific fractional pathloss compensation factor a<t_a,_a value to be used for data transmission to the base station 110.

The αso_υn_dm_g value comprised in the received information may be adapted to be alternated between different values in different instants of time.

The α_SOundmg value comprised in the received information may be adapted to be different in different types of transmission slots.

In some embodiments the α_S0Un_dmg value comprised in the received information may be = 1. In some embodiments the αsoυn_dmg value comprised in the received information =

Odata-

In some embodiments the α_soυπdmg value comprised in the received information < 1.

In some embodiments 3GPP LTE TDD technology is used. In these embodiments the ccsou_nd_mg value comprised in the received information may be a specific α_souπdmg value to be used when sending SRS in an Uplink Part of Time Slot "UpPTS" field of the special subframe, which special subframe comprises the switch point between downlink and uplink transmission.

In some embodiments the α_sounϋmg value comprised in the received information =1 to be used when sending SRS in the UpPTS field of the special subframe, and the α_soundmg value comprised in the received information = a^ to be used when sending SRS in other uplink subframes, or wherein the α_soun(ι_ιng value comprised in the received information = ccdata to be used when sending SRS in the UpPTS field of the special subframe and the α soυndmg value = 1 to be used when sending SRS in the in other uplink subframes.

In some embodiments the receiving unit 410 further is configured to receive the information from the base station 110 via user equipment specific higher layer signalling or via broadcasting.

The user equipment 120 further comprises the adapting unit 420 configured to adapt the SRS power control setting according to the α_soundmg value comprised in the received information. The user equipment 120 further comprises the sending unit 430 configured to send

SRS using a power according to the adapted SRS power control setting.

The present mechanism for adapting the Sounding Reference Signal "SRS" power control setting in the user equipment 120, may be implemented through one or more processors, such as a processor 330 in the base station depicted in Figure 3, a processor 440 in the user equipment depicted in Figure 4, a processor 640 in the wireless communications network 100 and a processor 650 in the user equipment 120 within the wireless communications network 100 depicted in Figure 6, together with computer program code for performing the functions of the present solution. 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 present solution when being loaded into the wireless communications network 100, and the user equipment 120. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code can furthermore be provided as pure program code on a server and downloaded to the base station 110, the wireless communications network 100 and the user equipment 120 remotely.

When using the word "comprise" or "comprising" it shall be interpreted as non- limiting, i.e. meaning "consist at least of.

The present invention is not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1. A method in a base station (110), for adapting the Sounding Reference Signal "SRS" power control setting in a user equipment (120), the method comprising: deciding (201 ,701) an SRS specific fractional pathloss compensation factor

"ctsou_ndmg" value, based on a specific purpose for using SRS received from the user equipment (120), said a_sounding value being decided independent of a value of a data specific fractional pathloss compensation factor "c^ata to be used for data transmission to the base station (110), informing (202,702) the user equipment (120) to use the decided ccsoυnΦng value for adapting the SRS power control setting in the user equipment (120), enabling the user equipment (120) to send SRS, using power according to the adapted power control setting.

2. Method according to claim 1 , wherein the step of deciding (201 ,701) comprises deciding that the α_sounα,_ng value is to be alternated between different values in different instants of time.

3. Method according to claim 1 , wherein the step of deciding (201 ,701) comprises deciding the α_SOυn_dmg value is to be different in different types of transmission slots.

4. Method according to any of the claims 1-3, wherein the step of deciding (201,701) comprises deciding that the α_sotindmg value = 1.

5. Method according to the claim above, wherein the specific purpose for using the SRS received from the user equipment (120) is for downlink Radio Resource Management "RRM".

6. Method according to any of the claims 1-3, wherein the step of deciding (201 ,701) comprises deciding that the α_sounΛng value = α^_a(a.

7. Method according to the claim above, wherein the specific purpose for using the SRS received from the user equipment (120) is for uplink RRM.

8. Method according to any of the claims 4-7, wherein the step of informing (202,702) the user equipment (120) is performed by signalling, using user equipment specific higher layer signalling or by broadcasting.

9. Method according to any of the claims 1-3, wherein the step of deciding (201 ,701 ) comprises deciding that the a_sounύmg value < 1.

10. Method according to the claim above, wherein the step of deciding (201,701) comprises deciding the a_souπdiπg value specifically for the user equipment (120), enabling the base station (110) to receive SRS from the user equipment (120) on a power level that differs from power level of SRS received from other user equipments.

11. Method according to any of the claims 1-3, wherein Third Generation Partnership Project Long Term Evolution Time Division Duplex "GPP LTE TDD" technology is used, and wherein the step of deciding (201,701) comprises deciding that the ccsou_ndi_ng value is one specific aswnang value in a Uplink Part of Time Slot "UpPTS" field of the special subframe in 3GPP LTE TDD, which special subframe comprises the switch point between downlink and uplink transmission.

12. Method according to any of the claims 1-3, wherein the step of deciding (201,701) comprises deciding that the a_soundms value =1 in the UpPTS field of the special subframe and deciding that the ccso_uπd_mg value = o^m in other uplink subframes, or deciding that the Qr_Sou_/w_/mg value = a^_ta in the UpPTS field of the special subframe and deciding that the α_sounύmg value = 1 in other uplink subframes.

13. A method in a user equipment (120), for adapting the Sounding Reference Signal "SRS" power control setting in the user equipment (120), the method comprising: receiving (202,801) from the base station (110), information to use a decided SRS specific fractional pathloss compensation factor ^uα_Soun_dm9" value, for adapting the SRS power control setting in the user equipment (120), which α_sounαing value has been decided by the base station (110) based on a specific purpose for using SRS received from the user equipment (120) and being independent of a value of a data specific fractional pathloss compensation factor c^a_ta value to be used for data transmission to the base station (110), adapting (203,802) the SRS power control setting according to the α_∞unύmg value comprised in the received information.

14. Method according to claim 13, further comprising: sending (204,803) SRS using a power according to the adapted SRS power control setting.

15. Method according to any of the claims 13-14, wherein the a_Sou_n*_ng value comprised in the received information is to be alternated between different values in different instants of time.

16. Method according to any of the claims 13-15, wherein the α_sotmφπg value comprised in the received information is different in different types of transmission slots.

17. Method according to any of the claims 13-15, wherein the aso_un(iing value comprised in the received information = 1.

18. Method according to any of the claims 13-15, wherein the a_soundmg va\ue comprised in the received information = ccn_ata-

19. Method according to any of the claims 13-18, wherein the step of receiving (202,801) the information from the base station (110) is received via user equipment specific higher layer signalling or via broadcasting.

20. Method according to any of the claims 13-15, wherein the α_SOϋm/,_πg value comprised in the received information < 1.

21. Method according to any of the claims 13-15, wherein 3GPP LTE TDD technology is used and wherein the α_souπdιπg value comprised in the received information is a specific α_∞unώπg value to be used when sending SRS in an Uplink Part of Time Slot

"UpPTS" field of the special subframe, which special subframe comprises the switch point between downlink and uplink transmission.

22. Method according to any of the claims 13-15, and wherein the αso_undmg value comprised in the received information =1 to be used when sending SRS in the UpPTS field of the special subframe and wherein the aso_Uπ(img value comprised in the received information = α_<,_βte to be used when sending SRS in other uplink subframes, or wherein the a_sounύmg value comprised in the received information = cttata to be used when sending SRS in the UpPTS field of the special subframe and the ccsouπding value = 1 to be used when sending SRS in the in other uplink subframes.

23. A method in a wireless communications network (100), for adapting the Sounding Reference Signal "SRS" power control setting in a user equipment (120), the method comprising: deciding (501) a SRS specific fractional pathloss compensation factor "ocsoundmg" value, based on a specific purpose for using SRS received from the user equipment (120), said αsou_nύmg value being decided independent of the value of a data specific fractional pathloss compensation factor "tW to be used for data transmission to a base station (110) comprised in the wireless communications network (100), adapting (502) the SRS power control setting in the user equipment (120) according to the decided a_souna,_ng value, enabling the user equipment (120) to send (503) SRS, using power according to the adapted power control setting.

24. Method according to claim 23, wherein the step of deciding (501) comprises deciding that the CC_SR_S value is to be alternated between different values in different instants of time.

25. Method according to claim 23, wherein the step of deciding (501) comprises deciding the a_SRs value is to be different in different types of transmission slots.

26. Method according to any of the claims 23-25, wherein the step of deciding (501) comprises deciding that the a_S0Und,n₅ value = 1.

27. Method according to claim26, wherein the specific purpose for using the SRS from the user equipment (120), is for downlink Radio Resource Management "RRM".

28. Method according to any of the claims 23-25, wherein the step of deciding (501) comprises deciding that the a_sounΛπg value = α^a-

29. Method according to claim 28, wherein the specific purpose for using the SRS from the user equipment (120), is for uplink RRM.

30. Method according to any of the claims 23-25, wherein the step of deciding (501) comprises deciding that the a_sountimg value < 1.

31. Method according to claim 30, wherein the step of deciding (501) comprises deciding the a_SOUn(_tmg value specifically for the user equipment (120), enabling the base station (110) to receive SRS from the user equipment (120) on a power level that differs from the power level of SRS received from other user equipments.

32. Method according to any of the claims 23-25, wherein Third Generation Partnership Project Long Term Evolution Time Division Duplex "GPP LTE TDD" technology is used, and wherein the step of deciding (501) comprises deciding that the a_iOunφng value is one specific a_sounύmg value in a Uplink Part of Time Slot "UpPTS" field of the special subframe in 3GPP LTE TDD₁ which special subframe comprises the switch point between downlink and uplink transmission.

33. Method according to any of the claims 23-25, wherein the step of deciding (501) comprises deciding that the a_sounΛπg value =1 in the UpPTS field of the special subframe, and deciding that the a_SOu_mfo_>g value = O_03I3 in other uplink subframes, or deciding that the a_∞un_dmg value = an_ata in the UpPTS field of the special subframe and deciding that the O_s0Un^_n9 value = 1 in other uplink subframes.

34. A base station (110) for adapting the Sounding Reference Signal "SRS" power control setting in a user equipment (120), the base station (110) comprising: a deciding unit (310) configured to decide an SRS specific fractional pathloss compensation factor ^uα_sounding" value based on a specific purpose for using SRS received from the user equipment (120), said α_S0Und_mg value being decided independent of a value of a data specific fractional pathloss compensation factor "ocdata" to be used for data transmission to the base station (110), an informing unit (320) configured to inform the user equipment (120) to use the decided a_S0Un_dmg value for adapting the SRS power control setting in the user equipment (120), enabling the user equipment (120) to send SRS, using power according to the adapted power control setting.

35. A user equipment (120), for adapting the Sounding Reference Signal "SRS" power control setting in the user equipment (120), the user equipment (120) comprising: a receiving unit (410) configured to receive from the base station (110), information to use a decided SRS specific fractional pathloss compensation factor "ccsound_mg value, for adapting the SRS power control setting in the user equipment

(120), which a sou_nd_mg value has been decided by the base station (110) based on a specific purpose for using SRS received from the user equipment (120) and being independent of a value of a data specific fractional pathloss compensation factor ct_tte_ta value to be used for data transmission to the base station (110), an adapting unit (420) configured to adapt the SRS power control setting according to the α_sound_mg value comprised in the received information.

36. A wireless communications network (100), for adapting the Sounding Reference Signal "SRS" power control setting in a user equipment (120), the wireless communications network (100) comprising a user equipment (120): the wireless communications network (100) comprises a deciding unit (610) configured to decide a SRS specific fractional pathloss compensation factor

"ccso_undmg" value, based on a specific purpose for using SRS received from the user equipment (120), said α s_ou_nd_mg value being decided independent of the value of a data specific fractional pathloss compensation factor "αW to be used for data transmission to a base station (110) comprised in the wireless communications network (100), the user equipment (120) comprising an adapting unit (620) configured to adapt the SRS power control setting in the user equipment (120) according to the decided α so_undmg value, enabling the user equipment (120) to send SRS, using power according to the adapted power control setting.