EP2497306A1

EP2497306A1 - Power control setting in a low power network node

Info

Publication number: EP2497306A1
Application number: EP09749089A
Authority: EP
Inventors: Jürgen MICHEL; Ingo Viering
Original assignee: Nokia Siemens Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2009-11-03
Filing date: 2009-11-03
Publication date: 2012-09-12
Also published as: WO2011054374A1

Abstract

There is proposed a mechanism for setting power control settings for uplink power control in a network element controlling a communication connection to and from a user equipment, such as a base station or an eNodeB controlling a so-called femto cell (HeNB). The power control parameters of a HeNB are adjusted according to the position of the femto cell with respect to the served area of the "umbrella" Macro eNB. The HeNB may adjust the parameters autonomously, e.g. based on own measurements of the surrounding macro eNB, wherein path loss measurements, power control parameters and further parameters, such as a power margin and/or a worst case path-loss, provided by the network are considered. The HeNB adjusts the power control related parameters such that no UE connected to it transmits with more than a predetermined maximum power.

Description

DESCRIPTION

TITLE

POWER CONTROL SETTING IN A LOW POWER NETWORK NODE BACKGROUND OF THE INVENTION Field of the invention

The present invention relates to an apparatus, method and computer program product related to power control setting in a low power network node. In particular, the present invention is related to a mechanism for setting power control setting for uplink power control in a network element controlling a communication connection to and from a user equipment, such as a base station or an eNodeB controlling a small cell, e.g. a so-called femto cell (also referred to Local eNB (LeNB) or Home eNB (HeNB) ) .

Related background Art

The following meanings for the abbreviations used in this specification apply:

3GPP - 3^rd generation partnership proj ect

CSG - Closed Subscriber Group

DL - Downlink

eNB - eNode B (LTE base station)

HeNB - Home eNode B

LeNB - Local eNode B

LTE - Long term evolution

LTE-A - LTE-Advanced

OAM - Operation, administration and maintenance SINR - Signal-to-Interference-Noise-Ratio

UE - User equipment

UL - Uplink

WA - Wide area

LA - Local area

Related prior art

In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), or wire^¬ less communication networks, such as the cdma2000 (code di^¬ vision multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Tele- communications System (UMTS) , cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM) , the General Packet Radio System

(GPRS) , the Enhanced Data Rates for Global Evolutions

(EDGE) , or other wireless communication system, such as the Wireless Local Area Network (WLAN) or Worldwide Interopera^¬ bility for Microwave Access (WiMax) , took place all over the world. Various organizations, such as the 3^rd Genera^¬ tion Partnership Project (3GPP) , Telecoms & Internet con^¬ verged Services & Protocols for Advanced Networks (TISPAN) , the International Telecommunication Union (ITU), 3^rd Gen^¬ eration Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers) , the WiMax Forum and the like are working on standards for telecommunication network and ac- cess environments. Generally, for properly establishing and handling a communication connection between network elements such as a user equipment and another communication equipment or user equipment, a database, a server, etc., one or more interme- diate network elements such as control network elements, support nodes, service nodes and interworking elements are involved which may belong to different communication net^¬ works .

In mobile wireless communication networks, such as 3GPP Long-Term Evolution (LTE and LTE-A) , the implementation of cells of different sizes is contemplated. Cells implemented in such communication networks can be designed, for example, as so-called macro cells which represent a normal cell design with a full set of network properties and element, and so-called femto cells having a significant smaller cov^¬ erage area and also limited properties. In such cases, how^¬ ever, it is necessary to consider specific issues related to network optimization, configuration and interference reduction, in particular when the femto cells (i.e. HeNB) uses co-channel deployment. It is to be noted that not only femto cells using HeNBs are to be considered, but also gen^¬ eral low power (local) nodes (LeNB) deployed in an uncoordinated manner being under an overlay wide area macro net^¬ work operated on the same frequency layer.

Femto cells are controlled by comparable small base sta^¬ tions with lower maximum transmit power with relation, for example, to a typical macro LTE eNB and are typically de- signed for indoor deployments - in private residences or public areas (e.g. office). Base stations for femto-cells are also referred to as "Home eNode B" (HeNB) , for example, for LTE(-A) environments. As the femto cells are intended to be deployed and maintained individually by customers, their geographical location can not be assumed as known to the operator. Moreover, as the number of femto cells within macro cell area can eventually be large, the configuration of HeNB parameters from a centralized OAM may be difficult.

The implementations of femto cells provide significant benefits that help operators considering the investment. The most common benefits result in an off-loading of macro radio network traffic to femto nodes, improving coverage and/or capacity locally in a cost-effective manner, and im^¬ plementing home-zone services to increase revenue.

In many cases customers would also like to secure for them- selves a sufficient amount of resources at their HeNBs and protect it from unwanted access. To do so they will use the Closed Subscriber Group (CSG) configuration in which they will be able to define the list of authorized subscribers who will have access to their femto-cells . Because UEs will not always be allowed to connect to the base station that provides the best radio conditions, the CSG scheme can pose a serious threat to the functionality of the network from the interference point of view. To utilize the spectrum as efficiently as possible, co- channel deployment of low power (local) nodes (e.g. HeNBs) and the wide area eNBs is seen as an important use case in 3GPP standardization. This means that HeNBs use the same spectrum as the wide area (macro) eNBs, rather than an in- dependent second spectrum area (for example two blocks of

20MHz each one for macro eNBs and one for HeNBs) . The rea^¬ son for co-channel deployment is that operators may not have too much spectrum available, so sacrificing one channel for HeNBs would take away too much capacity from the Wide area Network. In LTE/LTE-A all the transmissions within one cell are planned to be orthogonal. It means that in the ideal case there is no interference between users connected to the same eNB . However, an interference that has to be taken into account may come from transmission of users connected to neighbouring eNBs that are scheduled to use the same frequency resources.

In case of low power nodes, with a co-channel wide area network overlay, the interference coordination and mitiga^¬ tion is a serious issue. In case of the uplink connection both the local and wide area users can be threatened.

With the CSG configuration a case is highly possible that a user not allowed connecting to HeNB has to connect with a high transmission power to a far wide area eNB and though generates a lot of interference at the nearby HeNB. On the other hand if the uplink power setting for the HeNB users is too high, the wide area users are the ones suffering.

Hence, there is a need to avoid or suppress interference in a network, in particular when there are small cells having low power overlaid by a macro cell network.

SUMMARY OF THE INVENTION

Thus, it is an object of the invention to provide an appa^¬ ratus, method and computer program product by means of which an improved mechanism for power control setting in a low power network node and user equipment connected thereto is achievable so that interference with communications in another cell is avoided. In particular, it is an object of the present invention to provide a mechanism allowing determining and setting of power control related parameters for uplink power control at a base station or eNodeB controlling a small cell, like femto cell controlled by a LeNB or HeNB.

These objects are achieved by the measures defined in the attached claims. According to an example of the proposed solution, there is provided, for example, a method comprising obtaining a re^¬ lational parameter based on a relationship between a network node of a first cell and a network node of a second cell, and calculating an uplink transmission power related parameter used for determining an uplink transmission power for the first cell based on the relational parameter.

Furthermore, according to an example of the proposed solu^¬ tion, there is provided an apparatus comprising an obtainer configured to obtain a relational parameter based on a re^¬ lationship between a network node of a first cell and a network node of a second cell, and a processor configured to calculate an uplink transmission power related parameter used for determining an uplink transmission power for the first cell based on the relational parameter.

According to further refinements, there may be comprised one or more of the following features:

- the relationship may be a relative position of the network node of the first cell and the network node of the second cell;

- a downlink path-loss parameter may be measured in the network node of the first cell relative to the network node in the second cell to determine the relational parame^¬ ter, and a theoretical transmission power value of a trans^¬ mission in the second cell for the network node located in the first cell may be calculated on the basis of power con- trol parameters of the second cell, wherein the power con^¬ trol parameters of the second cell may comprise at least a parameter indicating an averaged target signal-to- interference-noise ratio and a parameter indicating a frac^¬ tional path-loss compensation factor of the second cell;

- a margin parameter may be obtained, and a maximum uplink transmission power in the first cell may be determined on the basis of the margin parameter and the theo^¬ retical transmit power value;

- a second path loss parameter indicating an estimated worst case path loss in the first cell may be received, and the uplink transmission power related parameter for the first cell may be calculated on the basis of the second path loss parameter and the maximum uplink transmission power;

- transmission power related parameters may be deter^¬ mined in the network node of the second cell for obtaining the relational parameter, and/or information from may be received an external network node indicating the relational parameter;

- the first cell may be a small area cell served by a local network control node, and the second cell may be a macro cell served by another network control node using a higher transmission power than the local network control node ;

- the second cell may be identified as a macro cell on the basis of information provided by the another network control node;

- information concerning the uplink transmission power related parameter may be transmitted to a user equipment located in the first cell, the information further compris^¬ ing a path loss parameter indicating an estimated worst case path loss in the first cell, and/or a path loss pa^¬ rameter indicating a path loss between the first cell and the second cell, and/or an adjustable parameter;

- an indication may be received from a user equipment connected to the first cell that a path loss between the user equipment and the network node of the first cell is higher than a predetermined value, wherein the predeter- mined value may be related to an estimated worst case path loss in the first cell, and in reaction to the indication, a connection of the user equipment to the first cell may be inhibited or a handover of the user equipment from the first cell may be initiated;

- the processing may be executed or located in a local network control node controlling the first cell, or in an external network node connected to the local network con^¬ trol node and controlling the local network control node. In addition, according to an example of the proposed solu^¬ tion, there is provided a method comprising receiving an uplink transmission power related parameter from a network node controlling a communication in a first cell, the transmission power related parameter is based on a rela- tional parameter based on a relationship between the network node of the first cell and a network node of a second cell, receiving a path loss parameter indicating an path loss relative to the network node in the first cell, and calculating an uplink transmission power for a transmission in the first cell based on the transmission related parame^¬ ter and the path loss parameter.

Furthermore, according to an example of the proposed solu^¬ tion, there is provided an apparatus comprising a receiver configured to receive an uplink transmission power related parameter from a network control node controlling a communication in a first cell, the transmission power related parameter is based on a relational parameter based on a re- lationship between a network node of the first cell and a network node of a second cell, and to receive a path loss parameter indicating a path loss relative to the network node in the first cell, and a processor configured to cal^¬ culate an uplink transmission power for a transmission in the first cell based on the transmission related parameter and the path loss parameter.

- the received path loss parameter may indicate an es^¬ timated worst case path loss in the first cell;

- a path loss parameter indicating a path loss relative to the network node in the first cell may be deter^¬ mined, the determined path loss parameter may be compared with the estimated worst case path loss path loss parame^¬ ter, and if the determined path loss parameter is greater than the estimated worst case path loss parameter, a commu^¬ nication connection in the first cell may be terminated, and/or an indication may be sent to the network control element of the first cell that the determined path loss pa^¬ rameter is greater than the estimated worst case path loss parameter;

- an initial transmission power value may be obtained, and the initial transmission power value may be used as the uplink transmission power until a path loss parameter indicating a path loss for a communication in the first cell is determined; - a path loss parameter indicating a path loss relative to the network node in the second cell may be deter^¬ mined, wherein the received path loss parameter may indi^¬ cate a path loss between the network node in the first cell and the network node in the second cell, and the uplink transmission power for a transmission in the first cell may be calculated based on the transmission related parameter, the determined path loss parameter and the received path loss parameter;

- in the calculation of the uplink transmission power an adjustable parameter may be used, wherein the adjustable parameter may be set on the basis of information related to the determined path loss parameter and/or the received path loss parameter;

- the processing may be executed in a user equipment located in the first cell.

Moreover, according to another example of the proposed so^¬ lution, there is provided, for example, a computer program product for a computer, comprising software code portions for performing the steps of the above defined method, when said product is run on the computer. The computer program product may comprise a computer-readable medium on which said software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of the computer and/or transmittable via a network by means of at least one of upload, download and push procedures . By virtue of the proposed solutions, it is possible to find an optimum compromise between performance of a local net^¬ work control element, such as a HeNB, and the performance of a wide area network control element, such as a eNB, with regard to uplink transmission power setting and interference. In particular, by means of the proposed solution, it is possible to configure the HeNB such that is can autono^¬ mously set or adjust the power control parameters in a man^¬ ner that interference is minimized. Furthermore, by consid^¬ ering specific parameters related, for example, to a path loss, in the transmission power control calculation, it is possible to avoid interference or unsuitable connection of a UE to a femto cell, for example, by suitably controlling a handover of the UE trying to communicate in the femto cell to another (e.g. the macro) cell.

The above and still further objects, features and advan^¬ tages of the invention will become more apparent upon re^¬ ferring to the description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a diagram illustrating an example of an interference situation in a communication network having macro and femto cells.

Fig. 2 shows a diagram illustrating a further example of an interference situation in a communication network having macro and femto cells.

Fig. 3 shows a flow chart illustrating a procedure for set^¬ ting power control parameters according to an example of embodiments of the invention. Fig. 4 shows a flow chart illustrating a procedure for set^¬ ting power control parameters according to a further example of embodiments of the invention.

Fig. 5 shows a flow chart illustrating a procedure for set^¬ ting power control parameters according to another example of embodiments of the invention.

Fig. 6 shows a flow chart illustrating a procedure for set ting power control parameters according to another example of embodiments of the invention.

Fig. 7 shows a flow chart illustrating a procedure for set ting power control parameters according to another example of embodiments of the invention.

Fig. 8 shows a block circuit diagram illustrating a structure of an apparatus configured to execute a power control parameter setting according to an example of embodiments of the invention.

Fig. 9 shows a block circuit diagram illustrating a structure of an apparatus configured to execute a power control parameter setting according to a further example of embodi ments of the invention.

Fig. 10 shows a block circuit diagram illustrating a struc ture of an apparatus configured to execute a power control parameter setting according to another example of embodiments of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, examples and embodiments of the present invention are described with reference to the drawings. For illustrating the present invention, the examples and em^¬ bodiments will be described in connection with a communica^¬ tion system which may be based on a 3GPP LTE system where a base station functionality is provided by an eNB for a wide area cell and by an HeNB (as an example for an LeNB) for a femto cell. However, it is to be noted that the present in^¬ vention is not limited to an application in such a system or environment but is also applicable in other communica^¬ tion systems, connection types and the like.

A basic system architecture of a communication network may comprise a commonly known architecture of a wired or wire^¬ less access network subsystem. Such an architecture comprises one or more access network control units, radio ac^¬ cess network elements, access service network gateways or base transceiver stations, with which a user equipment is capable to communicate via one or more channels for trans^¬ mitting several types of data. The general functions and interconnections of these elements are known to those skilled in the art and described in corresponding specifi^¬ cations so that a detailed description thereof is omitted herein. However, it is to be noted that there are provided several additional network elements and signaling links used for a communication connection or a call between user terminals and/or servers than those described in detail herein below. Furthermore, the network elements, such as the HeNB, UE, OAM entity and the like, and their functions described herein may be implemented by software, e.g. by a computer program product for a computer, or by hardware. In any case, for executing their respective functions, correspond^¬ ingly used devices, such as an eNB, HeNB, network element like OAM entity etc., UE and the like, comprise several means and components (not shown) which are required for control, processing and communication/signaling functionality. Such means may comprise, for example, a processor unit for executing instructions, programs and for processing data, memory means for storing instructions, programs and data, for serving as a work area of the processor and the like (e.g. ROM, RAM, EEPROM, and the like), input means for inputting data and instructions by software (e.g. floppy diskette, CD-ROM, EEPROM, and the like) , user interface means for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like), inter^¬ face means for establishing links and/or connections under the control of the processor unit (e.g. wired and wireless interface means, an antenna, etc.) and the like.

As described above, several embodiments of the present in^¬ vention are directed to the problem of reducing interference in case of overlaid femto cells and wide area network cell, in particular in case of using co-channel deployment.

In order to guarantee proper radio conditions for all wide area and femto users in all locations, an adaptive uplink power control scheme may be used. For example, in an 3GPP LTE environment, an LTE uplink power control mechanism as described in 3GPP TS 36.213 v.8.8.0 may be used as the ba^¬ sis for power control, for example. For example, the uplink power control controls the transmit power of different uplink physical channels. For instance, for a physical uplink shared channel (PUSCH) , the setting of the UE transmit power for sub-frame number i may be de^¬ fined by: (0 = ^min{ cMAx .101og₁₀ (M_PUSCH (/)) +CC- PL + K(i)} ( 1 ) where,

• PcMAxi-^s the configured UE transmitted maximum power

(') is the bandwidth of the PUSCH resource assign^¬ ment expressed in number of resource blocks valid for subframe i.

• Po puscH i^{s a} parameter for setting an UL average tar^¬ get SINR and composed of the sum of a cell specific nominal component provided from higher layers and a UE specific component provided by higher layers

• a is a cell specific parameter provided by higher

layers also called fractional path-loss compensation factor

• PL is the downlink path loss estimate calculated in the UE in dB

• κ(ϊ) is an offset value calculated by UE from parame^¬ ters configured by higher layers

Further, for a physical uplink control channel (PUCCH) , the setting of the UE transmit power for a sub-frame number i may be defined by: (0^— ^ⁿ rCMAX ' ⁺ ^{ⁿCQI ' HARQ )+ K(i)} (2) where

• ^CMAX^-^S the configured UE transmitted maximum power

• -PcLPuccH is ^a parameter for setting an UL average target SINR and composed of the sum of a cell specific pa- rameter ^NOMINAL PUCCH provided by higher layers and a UE specific component P_{0 UE PUCCH} provided by higher layers.

• PL is the downlink path loss estimate calculated in the UE in dB

• h(n) is a PUCCH format dependent value which depends on the number information bits for the channel quality information used and the number of HARQ (Hybrid Auto^¬ matic Repeat Request) bits

• κ{ί) is an offset value calculated by UE from parame^¬ ters configured by higher layers

As indicated above, interference represents a significant issue in particular for HeNB deployment. The reason is that initial operator deployments may use the same frequency for both the HeNB and the macro networks .

In case of downlink transmissions, femto cells on the cell edge have been identified to be the critical ones. In Fig. 1, an example for a corresponding scenario is shown. According to Fig. 1, a user (i.e. a UE) 1 which is connected to a macro cell 4 (controlled by a corresponding network control node like an eNB 3) , but which is close to a femto cell 5 (controlled by a corresponding local network control node like a HeNB) which is located relatively far away from its serving (macro) eNB 3 may face a weak signal component from the macro cell, but a strong interference component from the femto cell 5 (from the HeNB thereof) .

It is to be noted that there may be the case that the UE 1 is not allowed to connect to the femto cell 5 (i.e. its HeNB) even if the HeNB signal is much stronger than that of the macro eNB 3, for example due to (commonly implemented) HeNB access restrictions (HeNB with CSG) .

On the other hand, a UE 2 being connected to the macro cell 4 and located close to a femto cell 6 (controlled by a cor^¬ responding local network control node like a HeNB) which is located relatively close to its serving (macro) eNB 3 may face a strong signal component from the macro cell. Thus, even in case a strong interference component from the femto cell 6 is received by the UE 2, the interference is not deemed to be critical.

On the other hand, in case of an uplink transmission scenario, the situation is different. In Fig. 2, an example for a corresponding scenario is shown.

In contrast to the downlink scenario described in Fig. 1, the critical femto cells to be considered for interference issues are those in the close vicinity of the Macro eNB 3.

While a UE 7 connected to a femto cell 5 located relatively far away from the macro eNB 3 in the macro cell 4 causes only a weak interference component to the eNB 3, UEs and HeNBs located close to the eNB 3 may be more problematic. For example, depending on the power control settings in the HeNB of the femto cell 5 and the deployment case in the home area (for example, the HeNB device may be located in the 2nd floor of a building while the user i.e. the UE 8 is in ground floor where the path loss between the HeNB and the UE 8 is increased for example by 2 times the ceiling loss) , the UE 8 connected to the HeNB may transmit with a relatively high transmit power. However, a neighboring us- ers like UE 9 connected to the macro eNB 3 may use a rela^¬ tively small transmit power, for example due to the low distance to the eNB 3 and the used (LTE) power control for^¬ mula ensuring that the dynamic range capabilities of the eNB receiver are satisfied (eNB has to detect far users with high path-loss at the same time) . Thus, the interfer^¬ ence component caused by the UE 8 with regard to the UE 9 may be significantly strong.

It is to be noted that in contrast to a downlink transmis^¬ sion case where only users (UEs) in the close proximity of the femto cells suffer interference problems (mainly at the cell edge where the macro signal is low) , in the uplink transmission case all macro cell users (UEs connected to the eNB 3, for example) are affected by interference issues as the interference is induced at the macro eNB antenna, mainly by HeNBs close to the macro eNB. It is to be noted that a HeNB located farther away from the macro eNB repre^¬ sents a weaker interference source since interference from their users have to cover a large path-loss before they in^¬ duce the interference.

It is to be further noted that also the number of HeNBs lo^¬ cated in the macro cell coverage area is to be considered. In case this number is high, the management of HeNBs may be difficult. For example, in case no interface between macro eNBs and the HeNBs, such as an X2 interface in 3GPP LTE), there exists no coordination capability. Therefore, accord^¬ ing to examples of embodiments of the invention, a high de- gree of self-configuration for the local network control nodes like the HeNB is provided.

There are several approaches conceivable which may be used for solving interference issues in scenarios as depicted in Figs. 1 and 2. For example, in the downlink transmission case, the problem of wide area (macro) cell performance re^¬ duction due to an interference from HeNBs may be solved by adjusting the transmission (TX) power of the HeNBs such that HeNBs in large distance to the Macro eNB reduce their power. In principle, this can be done by the HeNB autono^¬ mously, provided that it has the capability of measuring the signal strength of downlink reference signals, e.g. be^¬ fore switching on the HeNB (also referred to as "neighbor listening mode") . Another approach may be to use UE measurements of users connected to the macro eNB, which however requires a communication between the macro eNB and the re^¬ spective HeNB and is thus rather complex.

In case of uplink transmission scenarios, the approaches usable for the downlink scenario may not be feasible due to the different starting issues, as indicated above.

Presently, there are few considerations made as it is com^¬ monly assumed that as a basic problem coverage issues at the cell edge of the wide area cell can be expected so that there a deployment of HeNBs is deemed to be more likely. Hence, downlink transmission interference issues have been discussed so far due to the general common view, that in this scenario the macro cell is more sensitive for HeNB in^¬ terference. In this connection it is to be noted that the implementation of CSGs may increase the problem since there might be even macro users within a house covered by a femto cell . With regard to the uplink transmission interference sce^¬ nario, one solution may be to adjust the HeNB power control parameters such that its users (UEs connected to the femto cell) transmit always with a very small power. Based on the above described power control formulas (1) and (2), this means that small P0 values (such as P₀ PUCCH and/or P_{0 PUS}CH settings) are to be used. From a purely signal strength perspective this solution may be justified by the typically very small cell area of a HeNB. However, the interference level at HeNBs may be rather high, since interfering macro UEs may be located closely. This is in particular an issue for HeNB (femto) cells located close to the cell edge.

Those cells have to use high P0 values so that it is possi- ble that the connected UEs can transmit with a sufficient power to drown the high interference level generated from wide area UEs in uplink.

Thus, basically, from the above consideration it can be seen that for uplink transmission scenarios a femto cell being at the (macro) cell edge (i.e. far away from the macro eNB) could use very high POs, while it is noted that such a femto cell is less critical to the uplink transmis^¬ sion of the macro cells (in other words, the users con- nected to far HeNBs represent only a small interference risk for the macro eNB) . On the other hand, a femto cell located close to the macro eNB may be critical for the macro cell with regard to interference, while it is noted that such a femto cell may use a small P0 value.

In order to overcome the interference issue in case a first cell, such as a femto cell controlled by a HeNB or LeNB, is located within a second cell, such as a macro cell con^¬ trolled by a normal eNB, in uplink transmission scenarios, according to an example of embodiments of the invention, power control parameters of a HeNB are set or adjusted ac^¬ cording to the position of the femto cell (i.e. the HeNB) with respect to the served area of the "umbrella" macro eNB . According to examples of embodiments of the invention, the power control parameters may be set/adjusted autono^¬ mously by the HeNB.

Thus, according to an example of embodiments of the inven^¬ tion as shown in a flow chart in Fig. 3, a relational pa^¬ rameter based on a relationship between the first cell and the second cell, i.e. between a network node of the first cell (such as the HeNB) and a network node of the second cell (such as the macro eNB) is obtained (step SI), for ex^¬ ample by measurements in the HeNB or in another network node connected to the HeNB. Based on the relational parame^¬ ter, one or more transmission power related parameters used for determining an uplink transmission power for the first cell, i.e. for a UE or the like communicating in the first cell towards the HeNB, is calculated (step S2) . The rela^¬ tionship between the first cell and the second cell is, ac^¬ cording to examples of embodiments of the invention, a relative position of the first cell (i.e. of the LeNB or HeNB thereof) in the second cell, i.e. with regard to the eNB of the macro cell.

As indicated above, as a direct communication for control parameters between the network control nodes of the first and second cells, such as between the HeNB and the macro eNB, may be limited, for example due to the lack of a X2 interface, adj ustment/setting of power control parameters according to examples of embodiments of the invention is conducted with limited knowledge of the HeNB due to the limited interfaces of the HeNB (e.g. there is no X2 connec^¬ tion available for HeNBs) .

Thus, according to an example of embodiments of the inven- tion, the HeNB is configured to obtain information related to surrounding macro eNBs, for example by performing suit^¬ able measurements. For example, those measurements may be executed during specific idle or MBSFN (multicast broadcast single frequency network) subframes. For example, in an LTE based communication system, those measurements are called

Reference Signal Received Power (RSRP) . Based on those measurements, the HeNB may approximate the path loss from the (strongest) macro eNB (e.g. from which signalling with the strongest power level is received) to the HeNB. This means, for example, that the HeNB may identify the macro eNB of a possible plurality of (neighbour) macro eNBs

(macro cells) which is assumed to be the nearest eNB which has to be considered with regard to interference issues, as described above. It is to be noted that due to the rela- tively small area covered by the femto cell (HeNB) , the po^¬ sition of the HeNB may be assumed as being representative also for the proximity of the HeNB, i.e. basically for the entire femto cell. However, also more sophisticated proce^¬ dures may be executed where the position (s) of a sending UE in the femto cell is considered. For the measurements, the

HeNB may act as an UE (also referred to as UE mode), i.e. as if the HeNB is a UE of the macro cell, in case of LTE FDD (Frequency Division Duplex) . According to further examples of embodiments of the inven^¬ tion, the HeNB may be configured to detect the power con^¬ trol parameters of the macro eNB from reading broadcast in^¬ formation from the macro eNB, by getting neighbour cell in- formation or by obtaining corresponding information from an Operation and Maintenance Entity (OAM) .

As indicated above, according to examples of embodiments of the invention, the network control element of the first cell, such as the HeNB, is configured to set or adjust its power control parameters autonomously. This adjustment or setting may be executed, for example, as a function consid^¬ ering one or more of the following:

- path loss between the HeNB and the macro eNB, e.g. with respect to the strongest macro eNB, which may be derived for example on the basis of the RSRP measurements and the broadcasted TX power of the macro eNB,

- detected or obtained power control settings of the macro eNB, such as PO and a values in the macro cell (according to formulas (1) and (2), for example) ;

further parameters provided by the network, for ex- ample a margin value, an estimated worst case path loss value, parameters for a power control formula or the like.

Thus, according to examples of embodiments of the inven- tion, a downlink path-loss parameter is measured in the network node of the first cell (such as the HeNB) relative to the network node in the second cell (such as the macro eNB) to determine the relational parameter. Then, a theo^¬ retical transmission power value of a transmission in the second cell for a network node located in the first cell

(i.e. a theoretical transmission power the HeNB would use if it was a UE connected to the eNB of the macro cell) is determined on the basis of power control parameters of the second cell, such as a parameter indicating an averaged target SINR and a parameter indicating a fractional path- loss compensation factor of the second cell (i.e. Po, a). For the power control, also a parameter related to the sec^¬ ond cell and indicating the path loss value related to the path loss between the first cell and the second cell for the network node in the second cell, i.e. a path loss be^¬ tween the HeNB and the macro eNB is considered. Further^¬ more, according to examples of embodiments of the inven^¬ tion, a margin parameter like a margin power value is obtained from the network. The margin parameter may be a predetermined value stored in a network element, such as an OAM entity or the like, and represents a parameter for lim^¬ iting a transmission power in the first (the femto) cell, for example. Correspondingly, a maximum uplink transmission power in the first cell may be determined on the basis of the margin parameter and the theoretical transmit power value, for example by performing a calculation using the values .

According to examples of embodiments of the invention, as a further parameter, a second path loss parameter may be received, which parameter indicates an estimated worst case path loss in the first cell. The transmission power related parameters for the first cell are then calculated also on the basis of the estimated worst case path loss value wherein the maximum uplink transmission power calculated on the basis of the theoretical transmission power and the margin parameter is still considered.

Furthermore, according to examples of embodiments of the invention, transmission power related parameters for the macro cell (in particular the path loss parameter) may be obtained by a corresponding measurement in the HeNB. Fur^¬ thermore, necessary information, such as the parameter in- dicating an averaged target SINR and the parameter indicat^¬ ing a fractional path-loss compensation factor of the sec^¬ ond cell (i.e. Po, a), may be received from an external network element, such as an OAM entity, or both obtaining ways may be used (mixture of measurement and receiving in^¬ formation) , depending on the abilities of the HeNB and/or operator settings.

As indicated above, since the interference issue related to the macro cell (the macro eNB) is considered, it is also required to identify, in case more than one neighbor cells are present (i.e. signaling from more than one cell can be identified at the HeNB side) , the (strongest) macro cell (i.e. to distinguish the macro cell eNB(s) from possible other femto cells (other HeNBs) and to determine which macro cell is the strongest cell (i.e. the macro HeNB to be considered most for interference issues), for example.

Identification of the second cell as a macro cell to be considered may be based, for example, on information pro^¬ vided by the eNB of the macro cell, for example by the transmission power and bandwidth value setting of the macro eNB which is read by the HeNB from macro eNB broadcast can- nel, and/or determining that the scanned macro eNB utilizes open subscriber group type scrambling code (as a femto cell (the HeNB thereof) is likely to use CSG) .

According to examples of embodiments of the invention, in^¬ formation concerning the uplink transmission power related parameter is transmitted from the HeNB to a UE located and communicating in the first cell. This information may further comprise, in addition to power control related parame^¬ ters like PO and a in the femto cell, a path loss parameter indicating the estimated worst case path loss in the first cell. Further or alternatively, a path loss parameter indi- eating a path loss between the HeNB and the macro eNB may be transmitted to the UE . Also an adjustable parameter β usable for the transmission power control may be transmit^¬ ted towards the UE .

An example of an embodiment of the invention is illustrated in the flow chart according to Fig. 4, for example, which shows a procedure for setting power control parameters ac^¬ cording to a further example of embodiments of the inven- tion. Specifically, Fig. 4 shows a procedure executed in the HeNB operating autonomously.

In step S10, a theoretical transmit power value (or trans^¬ mission power value) P_TX is determined on the basis of power control parameters of the macro cell (the macro eNB) . Specifically, the HeNB evaluates, being in a UE mode, the transmit power P_TX which it would be using if it were scheduled by the macro eNB (i.e. if it were a UE operating in the macro cell) . The evaluation may be based, for exam^¬ ple, on the above power control equation (1) for the physi^¬ cal uplink control channel or the power control equation (2) for the physical uplink shared channel. Which of these equations (1) and (2) is used may be preconfigured or pa^¬ rameterized by OAM. Thus, according to an example of an em^¬ bodiment of the invention, the (theoretical) transmit power may be calculated in a simplified form like

¹ P TX = ¹P ΰ, macro +^τ a" macro T macro , HeNB i l l ' where Po,macro and _maCro are power control parameters re^¬ trieved in the macro cell (e.g. by signaling from the macro eNB) and L_macro,HeNB is the path loss between the HeNB and the macro eNB which may be determined as indicated above. In step S20, a margin parameter, such as a margin power Pmargin is obtained. The margin parameter is used to ensure that the HeNB adjusts its power control parameters in such a manner that none of the UEs connected to it transmits with a power increasing a specific value. In other words, a maximum transmission power is determined in step S30 on the basis of the theoretical transmit power P_TX and the margin value. For example, the maximum transmission power allowed for the UEs may be limited to a value being equal to or less than P_TX - Pmargin-

The margin parameter, like Pmargin, may be obtained in step S20 by being signalled by the network via OAM, or may be a preconfigured value stored in the HeNB. By means of the de^¬ termination in step S30, it is guaranteed that the inter^¬ ference produced by any user served by the HeNB is at least Pmargin below the desired received signal of a potential macro user located near the femto cell. According to an example of an embodiment of the invention, in the procedure according to Fig. 4, in step S40, a path loss parameter may be obtained, for example from the net^¬ work (e.g. the OAM) which indicates a "worst case path loss" for the home cell (L_worst,home) , i.e. a potential path loss between a UE operating in the home cell (the femto cell controlled by the HeNB) and the serving HeNB.

On the basis of the determined parameters and optionally on the additional path loss parameter, the HeNB is configured to calculate/adjust the transmission power control parame^¬ ters for an uplink transmission in the femto cell (home cell) . For example, the HeNB may set power control parame^¬ ters P₀,home and Xhome for the UEs connected to the HeNB such that a power control open-loop operating point for a path loss L_{worst/ home} fulfils

Tx m argin 0,hom<? hom e worst , hom e oL,max ^ ' where P₀L,max represents the maximum allowable transmission power for the UE .

In step S60, power control parameters for the (uplink) com munication in the femto cell are sent to UEs to connected to the HeNB, for example by broadcast or dedicated signal^¬ ing .

By means of the power control parameters thus set /adj usted, a UE connected to the femto cell is able to calculate/set the transmission power used, for example, in the uplink direction .

In Fig. 5, a flow chart illustrating a further example of an embodiment of the invention is depicted. Specifically, Fig. 5 shows a procedure executed on the UE side for set^¬ ting the transmission power according to the power control parameters retrieved at the HeNB side, for example. According to Fig. 5, in step S3, one or more uplink trans^¬ mission power related parameters are received from a net^¬ work control node controlling a communication in a first cell, e.g. from the HeNB controlling the femto cell to which the UE is connected or tries to be connected. The up- link transmission power related parameter (s) may correspond to those determined in a procedure according to Fig. 4, for example, i.e. ^~P₀,home and ot_home, which in turn are based on a relational parameter based on a relationship between a network node of the first cell (such as the HeNB) and a net- work node of a second cell (the macro cell) (such as the macro eNB) .

In step S4, also a path loss parameter indicating a path loss relative to the network node in the first cell is re^¬ ceived. According to one example of embodiments of the in^¬ vention, the received path loss parameter corresponds to L_WOrst,home, while in another example of embodiments of the invention the path loss parameter may correspond to the path loss between the HeNB and the macro eNB, i.e.

Lmacro , HeNB ·

Then, in step S5, an uplink transmission power for a transmission in the first cell is calculated based on the trans^¬ mission related parameter (s) and the path loss parameter.

According to an example of an embodiment of the invention, a procedure as illustrated in Fig. 6 may be executed. Spe^¬ cifically, Fig. 6 shows a processing when the UE considers also a parameter indicating the worst case path loss in the femto cell, i.e. „_orst,home ·

In step S100, the path loss parameter L_worst,home is received from the HeNB by suitable signalling. Then, in step S110, the UE determines the path loss L_home which it has in the communication to the HeNB. This path loss L_home may be influenced, for example, by obstacles like walls or the like.

Then, in step S120, the parameters L_home and L_worst,home are compared. An UE experiencing a path loss _home less or equal Lworst , home to the serving HeNB (i.e. the determination in step S120 is NO) , the power-control open-loop operating point may be set on the basis of the received power control parameters derived from signalling of the HeNB, for example according to oL ^•'O.home ^{+ U}homc ^' iom e ·* oL.max ^{\ 3} '

Thus, in step S 1 3 0 , the UE may start or continue a connec^¬ tion to the femto cell with an uplink transmission power based on the power-control open-loop operating point ac^¬ cording to equation ( 5 ) .

On the other hand, in case the determination in step S 1 2 0 is YE S ( Lhome is greater than L_worst,home) , i.e. the UE experi^¬ ences a path loss to a HeNB exceeding L_{wors t} , ii_0me , in view of the then necessary transmission power which would exceed the maximum allowed power (see Fig. 4 ) , it is not allowed for the UE to connect to or camp on the respective home cell controlled by this HeNB. Thus, in step S 1 4 0 , depending on the connection state of the UE (already connected or trying to connect to the HeNB) , the connection to the femto cell (the HeNB in question) is inhibited or terminated.

Specifically, in case the UE is already connected to this femto cell or camps on this cell, the power control open- loop operating point is set to the maximum allowed trans- mission power P₀L, max for this UE . Furthermore, a handover of the UE to a neighboring cell, probably to the macro cell, is to be prepared. On the other hand, in case the UE is not already connected to the femto cell or does not camp on the femto cell, the UE ignores the femto cell (the HeNB) and searches for an alternative connection point.

Additionally, in step S 1 5 0 , the UE reports the determined path loss parameter L_home to the serving HeNB so as to ini- tiate the handover procedure by indicating that the path loss to the HeNB exceeds L_worst,_home .

According to a further example of an embodiment of the in- vention, related to the steps S120 and S130 in Fig. 6, also the following processing may be executed. In the case that the UE is not capable to determine the path loss L_home from the UE to the HeNB prior to connection or handover to this HeNB, the UE may use immediately after handover to this HeNB a predefined power control open-loop operating point

PoL,init- This predefined power control open-loop operating point P₀L,init may be preset in the UE or transmitted from a network node, such as the HeNB. Then, the UE may adjust this operating point after information on the path loss be- tween the UE and the HeNB gets available. Depending on the result of a comparison between the (later) determined L_home and L„_orst, home, similar to the procedure in Fig. 6, in case the effective path loss exceeds the value of L_worst,home, the power control open-loop operating point is set to P₀L,max for this UE and the HeNB shall prepare a handover to a neighbouring cell, which will typically be the macro cell. Thus, basically a check based on the following relation (6) is executed: P oLAnit <P 0,hom <? + a home L worst om e =P oL,max ( ^6) '

According to a further example of an embodiment of the in^¬ vention, a procedure as illustrated in Fig. 7 may be exe- cuted. Specifically, Fig. 7 shows a processing when the UE considers also parameters indicating path losses between the home (femto) cell and the macro cell, i.e. between the HeNB and the macro eNB as well as between the UE and the macro eNB. Specifically, in the present example of an embodiment of the invention, the UL power control procedure exploits available information on the path loss L_macr0,uE between the UE in a home cell and neighbouring macro eNBs as well as information on the path loss L_macro,HeNB between the serving HeNB and neighbouring macro eNBs.

Thus, in step S200, similar to step S110 in Fig. 6, the UE determines the path loss L_home which it has in the femto cell in a communication to the HeNB (i.e. the path loss be^¬ tween the HeNB and the UE, L_HeNB UE) ·

In step S205, information on the path loss between the serving HeNB and neighbouring macro eNBs (L_macro,_HeNB) which may be derived as described in Fig. 4 by the HeNB, are re- ceived in the UE .

Then, in step S210, path loss information for the UE related to the macro cell (L_macr0iUE) are determined or ob^¬ tained. For example, this path loss information from a UE to a neighbouring macro eNB may be obtained through meas^¬ urement reports from the UE . The UE may determine the path loss to the neighboring macro eNB autonomously when it is capable to read the broadcast information of the macro eNB. This is likely to be the case when the path loss L_home to the HeNB is high, i.e. the critical cases when the power control open-loop operating point obtained for the HeNB may not be valid for the UE . According to examples of an em^¬ bodiment of the invention, the (serving) HeNB may support the path loss measurements of the UE for a certain macro eNB by forwarding broadcast information detected for that macro eNB. Another option would be to store available broadcast information of neighbouring cells in the UE which could be used later when the UE is no longer capable to detect this information.

In step S220, an adjustable parameter referred to as home is provided which is to be used with regard to the path loss information L_macro,HeNB and L_macr0,uE in the calculation of the transmission power. For example, an uplink transmission power, i.e. an appropriate power control open-loop operating point, may be calculated in step S230 on the basis of the following equation (7), considering a certain macro eNB (to which the path loss parameters are related) :

P ,HeNB) ⁽ 7 ⁾ It is to be noted that in the case that more than one macro cell (eNB) are receivable, there may be also path loss information available for a corresponding number of macro eNBs . Then, the processing results, based on equation (7), on several possible power control open-loop operating points, and the applied power control-open loop operating point P_0L is to be set to the minimum value P_0L obtained for the various macro eNBs.

Furthermore, according to an example of an embodiment of the invention, in the case that no information on the path loss to a neighbouring macro eNB is available, the adjustable parameter i_mme in equation (7) may be set to 0, so that the path loss information related to the macro cell are ignored.

Concerning the parameter β¾₀ια_θ/ according to a further example of an embodiment of the invention, the value thereof may depend on a relation between the path loss parameters related to the macro cell, i.e. L_macr0,uE and L_macr0,HeNB, for example a difference value according to L_macr0iUE - L_macr0iHeNB- For example, in the case Lmacro,uE L_macr0r HeNB r s maximum value for β¾ο_Γαε close to 1 may be set in order to rule out UL in^¬ terference from the home cell to the macro cell. On the other hand, the set value of home may decrease with the difference L_macr0,uE - L_macr0,_HeNB in the case that L_macr0,uE >

Lmacro,HeNB · Moreover, it may be considered that P_0L may not exceed a predefined maximum value. It is to be noted that the procedure described above in connection with Fig. 7 may be combined with a procedure ac^¬ cording to Fig. 6 by defining a maximum path loss L_{wo r s}t , home ·

Thus, basically, according to examples of embodiments of the invention, there is described a mechanism where the power control parameters of a HeNB are adjusted according to the position of the femto cell with respect to the served area of the "umbrella" Macro eNB. A macro eNB cell may be identified, if necessary, by its transmission power and bandwidth value setting which may be read by the HeNB from macro eNB broadcast cannel and/or by the fact that macro eNB utilizes open subscriber group type scrambling code. The HeNB may adjust the parameters autonomously e.g. based on own measurements of the surrounding Macro eNB. In this connection, the HeNB may consider path loss measurements (derived from RSRP and Tx power), and/or power control parameters, and/or further parameters provided by the network. The network may also signal a power margin and/or a worst case path-loss. The HeNB is required to adjust the power control parameters such that no user connected to it transmits with more than P_Tx - P_margin, where P_Tx is a poten^¬ tial transmit power given by standard power control formu^¬ las and where P0 and a have to be adjusted to fulfil the equation . In the case that information on path loss to macro eNBs is considered, the maximum allowed transmit power for a UE may be increased beyond the value of P_Tx - P_margin if the path loss of a UE to the macro NB exceeds the path loss for the HeNB to the macro NB .

In Fig. 8, a block circuit diagram of a network element 10 like a HeNB is shown which is configured to implement the power control parameter setting according to examples of embodiments of the invention. It is to be noted that the network element 10 may comprise several further elements or functions besides those described in connection with Fig. 8 which are omitted herein for the sake of simplicity as they are not essential for understanding the invention.

The network element 10 may be configured, for example, to execute a power control parameter setting according to Fig. 3 or Fig. 4 and may comprise a processing function or processor 11, such as a CPU or the like, which executes in^¬ structions given by programs or the like related to the power control. The processor 11 may comprise further portions dedicated to specific processings described below. Portions for executing such specific processings may be also provided as discrete elements or within one or more further processors, for example. Reference signs 12 and 13 denote transceivers or input/output (I/O) units connected to the processor 11 (or corresponding other elements comprising the functions of the further portions) . The I/O unit 12 may be used for communicating with UEs connected to the HeNB (the femto cell) . The I/O unit 13 may be used for communicating with other network elements, for example the eNB of the macro cell, an OAM entity and the like. The I/O units 12 and 13 may also be combined in one member, such as a transceiver unit or the like, or may comprise a distrib^¬ uted structure with a plurality of different interfaces. Reference sign 14 denotes a memory usable, for example, for storing data and programs to be executed by the processor 11 and/or as a working storage of the processor 11.

The processor 11 is configured to execute processings re^¬ lated to the power control parameter setting described in examples of embodiments of the invention. For example, the relational parameter may be obtained, transmission power related parameters may be calculated, path loss related pa^¬ rameters may be determined and/or received and/or sent, pa^¬ rameters for the power control are measured and/or re^¬ ceived, macro cell (s) may be identified, and the like.

In Fig. 9, a block circuit diagram of a network element 20 like a UE is shown which is configured to implement the power control parameter setting according to examples of embodiments of the invention. It is to be noted that the network element 20 may comprise several further elements or functions besides those described in connection with Fig. 9 which are omitted herein for the sake of simplicity as they are not essential for understanding the invention.

The network element 20 may be configured, for example, to execute a power control parameter setting according to Fig 5, Fig. 6 or Fig. 7 and may comprise a processing function or processor 21, such as a CPU or the like, which executes instructions given by programs or the like related to the power control. The processor 21 may comprise further por- tions dedicated to specific processings described below. Portions for executing such specific processings may be also provided as discrete elements or within one or more further processors, for example. Reference sign 22 denote a transceiver or input/output (I/O) unit connected to the processor 21 (or corresponding other elements comprising the functions of the further portions) . The I/O unit 22 may be used for communicating with the network, in particular the HeNB and the macro eNB (if required) to which the UE may be connected (the femto cell or the macro cell) . The

I/O unit 12 may also comprise a distributed structure with a plurality of different interfaces. Reference sign 23 de^¬ notes a memory usable, for example, for storing data and programs to be executed by the processor 21 and/or as a working storage of the processor 21.

The processor 21 is configured to execute processings re^¬ lated to the power control parameter setting described in examples of embodiments of the invention. For example, transmission power related parameters may be received and processed, uplink transmission power values may be calcu^¬ lated, path loss related parameters may be determined and/or received and/or sent, parameters for the power con^¬ trol may be measured and/or received, initial power set- tings may be determined and used, and the like.

In the above description of examples of embodiments of the invention, the local (low power) network control element (i.e. the HeNB) is configured to executed the power control parameter setting/adjustment autonomously. However, accord^¬ ing to another example of embodiments of the invention, the power control parameter setting for the femto cell (the HeNB) is not done by the HeNB itself, but under control of one or more external entities.

The setting processing in such examples of embodiments of the invention may follow the same principles as those de^¬ scribed in connection with Figs. 3 and 4, for example. In other words, the external entities may especially provide parameters for the power control procedure of the HeNB. As examples for those entities, the macro eNB, the operation and management entity (OAM) , a neighbor home eNB, a HeNB gateway element, or any combination of these entities may be used. It is to be noted that the HeNB may deliver spe^¬ cific information to the external entity, for example meas^¬ urements related to the macro cell ( L_macr0iHeNB or the like) and/or other information to the said network node, such as

Lmacro , UE or Lhome ·

In Fig. 10, a block circuit diagram of a network element 30 such as an OAM entity, a (macro) eNB, another HeNB, a HeNB gateway element or the like, is shown which is configured to implement the power control parameter setting according to further examples of embodiments of the invention. It is to be noted that the network element 30 may comprise sev^¬ eral further elements or functions besides those described in connection with Fig. 10 which are omitted herein for the sake of simplicity as they are not essential for under^¬ standing the invention.

The network element 30 may be configured, for example, to execute a (modified) power control parameter setting ac^¬ cording to Fig. 3 or Fig. 4 and may comprise a processing function or processor 31, such as a CPU or the like, which executes instructions given by programs or the like related to the power control. The processor 31 may comprise further portions dedicated to specific processings described below. Portions for executing such specific processings may be also provided as discrete elements or within one or more further processors, for example. Reference signs 32 and 33 denote transceivers or input/output (I/O) units connected to the processor 31 (or corresponding other elements comprising the functions of the further portions) . The I/O unit 32 may be used for communicating with the HeNB (the femto cell) to be controlled. The I/O unit 33 may be used for communicating with other network elements, for example an eNB of a macro cell where the controlled HeNB is lo^¬ cated, an OAM entity and the like. The I/O units 32 and 33 may also be combined in one member, such as a transceiver unit or the like, or may comprise a distributed structure with a plurality of different interfaces. Reference sign 14 denotes a memory usable, for example, for storing data and programs to be executed by the processor 31 and/or as a working storage of the processor 31.

The processor 31 is configured to execute processings re^¬ lated to the power control parameter setting described in examples of embodiments of the invention, i.e. to deter^¬ mined corresponding control commands for a HeNB or the like. For example, the relational parameter may be ob^¬ tained, transmission power related parameters may be calcu^¬ lated, path loss related parameters may be determined and/or received and/or sent, parameters for the power con^¬ trol may be measured and/or received, macro cell (s) may be identified, commands to the controlled HeNB may be prepared and sent for adjusting the power control parameter setting, and the like. For the purpose of the present invention as described herein above, it should be noted that

- an access technology via which signaling is transferred to and from a network element or node may be any technology by means of which a node can access an access network (e.g. via a base station or generally an access node) . Any pre^¬ sent or future technology, such as WLAN (Wireless Local Ac^¬ cess Network) , WiMAX (Worldwide Interoperability for Micro- wave Access) , BlueTooth, Infrared, and the like may be used; although the above technologies are mostly wireless access technologies, e.g. in different radio spectra, ac^¬ cess technology in the sense of the present invention im^¬ plies also wirebound technologies, e.g. IP based access technologies like cable networks or fixed lines but also circuit switched access technologies; access technologies may be distinguishable in at least two categories or access domains such as packet switched and circuit switched, but the existence of more than two access domains does not im- pede the invention being applied thereto,

- usable access networks may be any device, apparatus, unit or means by which a station, entity or other user equipment may connect to and/or utilize services offered by the access network; such services include, among others, data and/or (audio-) visual communication, data download etc . ;

- a user equipment may be any device, apparatus, unit or means by which a system user or subscriber may experience services from an access network, such as a mobile phone, personal digital assistant PDA, or computer;

- method steps likely to be implemented as software code portions and being run using a processor at a network element or terminal (as examples of devices, apparatuses and/or modules thereof, or as examples of entities includ- ing apparatuses and/or modules therefor), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the invention in terms of the functionality implemented;

- method steps and/or devices, apparatuses, units or means likely to be implemented as hardware components at a termi- nal or network element, or any module (s) thereof, are hard^¬ ware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor) , CMOS (Com^¬ plementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar

CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-

Transistor Logic), etc., using for example ASIC (Applica^¬ tion Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Sig- nal Processor) components; in addition, any method steps and/or devices, units or means likely to be implemented as software components may for example be based on any secu^¬ rity architecture capable e.g. of authentication, authori^¬ zation, keying and/or traffic protection;

- devices, apparatuses, units or means can be implemented as individual devices, apparatuses, units or means, but this does not exclude that they are implemented in a dis^¬ tributed fashion throughout the system, as long as the functionality of the device, apparatus, unit or means is preserved,

- an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code por^¬ tions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assem^¬ bly of more than one apparatus, whether functionally in co^¬ operation with each other or functionally independently of each other but in a same device housing, for example. As described above, there is proposed a mechanism for set^¬ ting power control settings for uplink power control in a network element controlling a communication connection to and from a user equipment, such as a base station or an eNodeB controlling a so-called femto cell (HeNB) . The power control parameters of a HeNB are adjusted according to the position of the femto cell with respect to the served area of the "umbrella" Macro eNB . The HeNB may adjust the pa^¬ rameters autonomously, e.g. based on own measurements of the surrounding macro eNB, wherein path loss measurements, power control parameters and further parameters, such as a power margin and/or a worst case path-loss, provided by the network are considered. The HeNB adjusts the power control related parameters such that no UE connected to it trans^¬ mits with more than a predetermined maximum power.

According to further examples of embodiments, there is pro^¬ vided an apparatus comprising obtaining means configured to obtain a relational parameter based on a relationship between a network node of a first cell and a network node of a second cell, and processing means configured to calculate an uplink transmission power related parameter used for determining an uplink transmission power for the first cell based on the relational parameter. Moreover, according to further examples of embodiments, there is provided an apparatus comprising receiving means configured to receive an uplink transmission power related parameter from a network control node controlling a communication in a first cell, the transmission power related parameter is based on a relational parameter based on a re^¬ lationship between a network node of the first cell and a network node of a second cell, and to receive a path loss parameter indicating a path loss relative to the network node in the first cell, and processing means configured to calculate an uplink transmission power for a transmission in the first cell based on the transmission related parame^¬ ter and the path loss parameter.

Although the present invention has been described herein before with reference to particular embodiments thereof, the present invention is not limited thereto and various modifications can be made thereto.

Claims

1. Method comprising:

obtaining a relational parameter based on a relationship between a network node of a first cell and a network node of a second cell, and

calculating an uplink transmission power related parameter used for determining an uplink transmission power for the first cell based on the relational parameter.

2. The method according to claim 1, wherein the relationship is a relative position of the network node of the first cell and the network node of the second cell.

3. The method according to claim 1 or 2, further comprising measuring a downlink path-loss parameter in the network node of the first cell relative to the network node in the second cell to determine the relational parameter, and determining a theoretical transmission power value of a transmission in the second cell for the network node lo^¬ cated in the first cell on the basis of power control pa^¬ rameters of the second cell, wherein the power control pa^¬ rameters of the second cell comprise at least a parameter indicating an averaged target signal-to-interference-noise ratio and a parameter indicating a fractional path-loss compensation factor of the second cell.

4. The method according to claim 3, further comprising

obtaining a margin parameter, and

determining a maximum uplink transmission power in the first cell on the basis of the margin parameter and the theoretical transmit power value.

5. The method according to claim 4, further comprising receiving a second path loss parameter indicating an estimated worst case path loss in the first cell,

calculating the uplink transmission power related pa- rameter for the first cell on the basis of the second path loss parameter and the maximum uplink transmission power.

6. The method according to any of claims 1 to 5, further comprising

determining transmission power related parameters in the network node of the second cell for obtaining the rela^¬ tional parameter, and/or

receiving information from an external network node indicating the relational parameter.

7. The method according to any of claims 1 to 6, wherein the first cell is a small area cell served by a local net^¬ work control node, and the second cell is a macro cell served by another network control node using a higher transmission power than the local network control node.

8. The method according to claim 7, further comprising

identifying the second cell as a macro cell on the ba^¬ sis of information provided by the another network control node.

9. The method according to any of claims 1 to 8, further comprising

transmitting information concerning the uplink trans- mission power related parameter to a user equipment located in the first cell, the information further comprising a path loss parameter indicating an estimated worst case path loss in the first cell, and/or a path loss parameter indi- eating a path loss between the first cell and the second cell, and/or an adjustable parameter.

10. The method according to any of claims 1 to 9, further comprising,

receiving an indication from a user equipment connected to the first cell that a path loss between the user equipment and the network node of the first cell is higher than a predetermined value, wherein the predetermined value is related to an estimated worst case path loss in the first cell, and

in reaction to the indication, inhibiting a connection of the user equipment to the first cell or initiating a handover of the user equipment from the first cell.

11. The method according to any of claims 1 to 10, wherein the method is executed in a local network control node con^¬ trolling the first cell, or in an external network node connected to the local network control node and controlling the local network control node.

12. Apparatus comprising:

an obtainer configured to obtain a relational parame^¬ ter based on a relationship between a network node of a first cell and a network node of a second cell, and

a processor configured to calculate an uplink trans^¬ mission power related parameter used for determining an uplink transmission power for the first cell based on the relational parameter.

13. The apparatus according to claim 12, wherein the rela^¬ tionship is a relative position of the network node of the first cell and the network node of the second cell.

14. The apparatus according to claim 12 or 13, further comprising

a processor configured to measure a downlink path-loss parameter in the network node of the first cell relative to the network node in the second cell to determine the rela^¬ tional parameter, and to determine a theoretical transmis^¬ sion power value of a transmission in the second cell for a network node located in the first cell on the basis of power control parameters of the second cell, wherein the power control parameters of the second cell comprise at least a parameter indicating an averaged target signal-to- interference-noise ratio and a parameter indicating a frac^¬ tional path-loss compensation factor of the second cell.

15. The apparatus according to claim 14, further comprising a processor configured to obtain a margin parameter, and

a processor configured to determine a maximum uplink transmission power in the first cell on the basis of the margin parameter and the theoretical transmit power value.

16. The apparatus according to claim 15, further comprising a receiver configured to receive a second path loss parameter indicating an estimated worst case path loss in the first cell, and

a processor configured to calculate the uplink trans^¬ mission power related parameter for the first cell on the basis of the second path loss parameter and the maximum up^¬ link transmission power.

17. The apparatus according to any of claims 12 to 16, fur^¬ ther comprising a processor configured to determine transmission power related parameters in the network node of the second cell for obtaining the relational parameter, and/or

a receiver configured to receive information from an external network node indicating the relational parameter.

18. The apparatus according to any of claims 12 to 17, wherein the first cell is a small area cell served by a lo^¬ cal network control node, and the second cell is a macro cell served by another network control node using a higher transmission power than the local network control node.

19. The apparatus according to claim 18, further comprising a processor configured to identify the second cell as a macro cell on the basis of information provided by the another network control node.

20. The apparatus according to any of claims 12 to 19, fur^¬ ther comprising

a transmitter configured to transmit information concerning the uplink transmission power related parameter to a user equipment located in the first cell, the information further comprising a path loss parameter indicating an estimated worst case path loss in the first cell, and/or a path loss parameter indicating a path loss between the first cell and the second cell, and/or an adjustable pa^¬ rameter .

21. The apparatus according to any of claims 12 to 20, fur^¬ ther comprising,

a receiver configured to receive an indication from a user equipment connected to the first cell that a path loss between the user equipment and the network node of the first cell is higher than a predetermined value, wherein the predetermined value is related to an estimated worst case path loss in the first cell, and

a processor configured to, in reaction to the indica^¬ tion, inhibit a connection of the user equipment to the first cell or initiate a handover of the user equipment from the first cell.

22. The apparatus according to any of claims 12 to 21, wherein the apparatus is comprised in a local network con^¬ trol node controlling the first cell, or in an external network node connected to the local network control node and controlling the local network control node.

23. Method comprising

receiving an uplink transmission power related parameter from a network node controlling a communication in a first cell, the transmission power related parameter is based on a relational parameter based on a relationship be^¬ tween the network node of the first cell and a network node of a second cell,

receiving a path loss parameter indicating an path loss relative to the network node in the first cell,

calculating an uplink transmission power for a transmission in the first cell based on the transmission related parameter and the path loss parameter.

24. The method according to claim 23, wherein the received path loss parameter indicates an estimated worst case path loss in the first cell.

25. The method according to claim 24, further comprising determining a path loss parameter indicating a path loss relative to the network node in the first cell, comparing the determined path loss parameter with the estimated worst case path loss path loss parameter, and

if the determined path loss parameter is greater than the estimated worst case path loss parameter,

terminating a communication connection in the first cell, and/or

sending an indication to the network control element of the first cell that the determined path loss parameter is greater than the estimated worst case path loss parame- ter.

26. The method according to claim 24 or 25, further comprising

obtaining an initial transmission power value, and using the initial transmission power value as the up^¬ link transmission power until a path loss parameter indicating a path loss for a communication in the first cell is determined .

27. The method according to claim 23, further comprising determining a path loss parameter indicating a path loss relative to the network node in the second cell,

wherein the received path loss parameter indicates a path loss between the network node in the first cell and the network node in the second cell, and

calculating the uplink transmission power for a transmission in the first cell based on the transmission related parameter, the determined path loss parameter and the re^¬ ceived path loss parameter.

28. The method according to claim 27, wherein in the calculation of the uplink transmission power an adjustable parameter is used, wherein the adjustable parameter is set on the basis of information related to the determined path loss parameter and/or the received path loss parameter.

29. The method according to any of claims 23 to 28, wherein the first cell is a small area cell served by a local net^¬ work control node, and the second cell is a macro cell served by another network control node using a higher transmission power than the local network control node.

30. The method according to any of claims 23 to 29, wherein the method is executed in a user equipment located in the first cell.

31. Apparatus comprising

a receiver configured to receive an uplink transmis^¬ sion power related parameter from a network control node controlling a communication in a first cell, the transmission power related parameter is based on a relational pa^¬ rameter based on a relationship between a network node of the first cell and a network node of a second cell, and to receive a path loss parameter indicating a path loss relative to the network node in the first cell, and

a processor configured to calculate an uplink trans^¬ mission power for a transmission in the first cell based on the transmission related parameter and the path loss parameter .

32. The apparatus according to claim 31, wherein the received path loss parameter indicates an estimated worst case path loss in the first cell.

33. The apparatus according to claim 32, further comprising a processor configured to determine a path loss pa^¬ rameter indicating a path loss relative to the network node in the first cell,

a processor configured to compare the determined path loss parameter with the estimated worst case path loss path loss parameter, and

a processor configured to, if the determined path loss parameter is greater than the estimated worst case path loss parameter, terminate a communication connection in the first cell, and/or to send an indication to the network control element of the first cell that the determined path loss parameter is greater than the estimated worst case path loss parameter.

34. The apparatus according to claim 32 or 33, further comprising

a processor configured to obtain an initial transmis^¬ sion power value, and to use the initial transmission power value as the uplink transmission power until a path loss parameter indicating a path loss for a communication in the first cell is determined.

35. The apparatus according to claim 31, further comprising a processor configured to determine a path loss pa^¬ rameter indicating a path loss relative to the network node in the second cell,

a processor configured to calculate the uplink trans^¬ mission power for a transmission in the first cell based on the transmission related parameter, the determined path loss parameter and the received path loss parameter.

36. The apparatus according to claim 35, wherein the proc^¬ essor configured to calculate the uplink transmission power is configured to use an adjustable parameter, wherein the adjustable parameter is set on the basis of information re- lated to the determined path loss parameter and/or the re^¬ ceived path loss parameter.

37. The apparatus according to any of claims 31 to 36, wherein the first cell is a small area cell served by a lo cal network control node, and the second cell is a macro cell served by another network control node using a higher transmission power than the local network control node.

38. The apparatus according to any of claims 31 to 37, wherein the apparatus is comprised in a user equipment cated in the first cell.

39. A computer program product for a computer, comprising software code portions for performing the steps of any of claims 1 to 11 or 23 to 30 when said product is run on the computer .

40. A computer program product according to claim 39, wherein said computer program product comprises a compute readable medium on which said software code portions are stored .

41. A computer program product according to claim 39, wherein said computer program product is directly loadable into the internal memory of the computer.