WO2010006909A1

WO2010006909A1 - Method and apparatus for setting an uplink transmit power level for a wireless communication unit

Info

Publication number: WO2010006909A1
Application number: PCT/EP2009/057921
Authority: WO
Inventors: Akhilesh Pokhariyal; Seshaiah Ponnekanti
Original assignee: Ip.Access Limited
Priority date: 2008-07-15
Filing date: 2009-06-24
Publication date: 2010-01-21
Also published as: GB2462063A; TW201010490A; GB0812883D0; GB2462063B

Abstract

An access point for supporting communication in a femto cell of a cellular communication network. The access point comprises transceiver circuitry arranged to enable communication with one or more wireless communication units located within the femto cell, and signal processing logic arranged to determine at least one macro cellular interference criterion; and set the femto cell uplink transmit power level based on the at least one determined macro cellular interference criterion.

Description

METHOD AND APPARATUS FOR SETTING AN UPLINK TRANSMIT POWER LEVEL FOR A

WIRELESS COMMUNICATION UNIT

Field of the invention The field of the invention relates to a method and apparatus for setting an uplink transmit power level for a wireless communication unit. More particularly, the field of the invention relates to a method and apparatus for setting an uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network.

Background of the Invention

Wireless communication systems, such as the 3^rd Generation (3G) of mobile telephone standards and technology, are well known. An example of such 3G standards and technology is the Universal Mobile Telecommunications System (UMTS™), developed by the 3^rd Generation Partnership Project (3GPP) (www.3qpp.org). Typically, wireless communication units, or User Equipment (UE) as they are often referred to in 3G parlance, communicate with a Core Network (CN) of the 3G wireless communication system via a Radio Network Subsystem (RNS). A wireless communication system typically comprises a plurality of radio network subsystems, each radio network subsystem comprising one or more cells to which UEs may attach, and thereby connect to the network. The 3^rd generation of wireless communications has been developed for macro-cell mobile phone communications. Such macro cells utilise high power base stations (NodeBs in 3GPP parlance) to communicate with UEs within a relatively large coverage area.

Lower power (and therefore smaller coverage area) femto cells or pico-cells are a recent development within the field of wireless cellular communication systems. Femto cells or pico-cells (with the term femto cells being used hereafter to encompass pico-cells or similar) are effectively communication coverage areas supported by low power base stations (otherwise referred to as Access Points (APs)). These femto cells are intended to be able to be piggy-backed onto the more widely used macro-cellular network and support communications to UEs in a restricted, for example 'in-building', environment. In this regard, a femto cell that is intended to support communications according to the

3GPP standard will hereinafter be referred to as a 3G femto cell. Similarly, an access controller intended to support communications with a low power base station in a femto cell according to the 3GPP standard will hereinafter be referred to as a 3^rd generation access controller (3G AC). Similarly, an Access Point intended to support communications in a femto cell according to the 3GPP standard will hereinafter be referred to as a 3^rd Generation Access Point (3G AP).

Typical applications for such femto cell APs include, by way of example, residential and commercial (e.g. office) locations, 'hotspots', etc, whereby an AP can be connected to a core network via, for example, the Internet using a broadband connection or the like. In this manner, femto cells can be provided in a simple, scalable deployment in specific in-building locations where, for example, network congestion at the macro-cell level may be problematic.

As will be appreciated by a skilled artisan, in a large scale deployment, it is envisaged that there can be as many as a few million femto cells interspersed within the macro cellular layer. In a co-channel deployment, uplink interference from UEs connected to femto cells (femto-UEs) will become a major problem for macro cell receivers. Noise experienced by the macro cell receivers, caused by interference from femto-UEs, leads to a reduction in the effective coverage area for that macro cell.

Thus, there exists a need for an apparatus and a method for setting an uplink transmit power level for a wireless communication unit that substantially alleviates at least some of the deficiencies with current techniques and methods therefor.

Summary of the Invention

Accordingly, the invention seeks to mitigate, alleviate or eliminate one or more of the abovementioned disadvantages singly or in any combination.

According to a first aspect of the invention, there is provided an access point for supporting communication in a femto cell of a cellular communication network. The access point comprises transceiver circuitry arranged to enable communication with one or more wireless communication units located within the femto cell, and a signal processing logic module arranged to set a femto cell uplink transmit power level for a wireless communication unit connected to the access point based at least on a macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion. In this manner, the access point is able to take into account interference that may be experienced at a macro cell receiver, due to the uplink transmission of the wireless communication unit. Furthermore, the access point is able to set and/or modify the uplink transmit power level for the wireless communication unit accordingly. Thus, the uplink transmit power level for the wireless communication unit, when transmitting in the femto cell, may be appropriately limited, as necessary, in order to substantially limit any interference that would result from the uplink transmissions of the wireless communication unit as experienced by at least one neighbouring macro cell receiver(s).

In one optional embodiment of the invention, the signal processing logic module may comprise a path loss request logic module arranged to request the wireless communication unit to perform the at least one macro cell path loss measurement and report the at least one macro cell path loss measurement back to the access point. In this manner, the access point may instigate the power control of the wireless communication unit based on potential interference caused to a neighbouring macro cell, namely a cell of a different type to the femto cell. In one optional embodiment of the invention, the path loss request logic module may be arranged to request the wireless communication unit to perform the at least one macro cell path loss measurement periodically and/or in response to an event trigger.

In one optional embodiment of the invention, the estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion is calculated based on a difference between: a maximum allowed increment in uplink interference at the at least one neighbouring macro cell receiver from the wireless communication unit; and the path loss measurement at the at least one neighbouring macro cell receiver for the wireless communication unit.

In one optional embodiment of the invention, the signal processing logic module may be further arranged to set the femto cell uplink transmit power level for the wireless communication unit based at least on a lower value of: the estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion; and an uplink power value required to meet a coverage criterion.

In one optional embodiment of the invention, the femto cell uplink transmit power level required to meet a coverage criterion may be determined based at least on one or more of the following:

(i) a target quality for a given service in the uplink, (ii) a processing gain, (iii)a thermal noise level measurement, (iv)a noise rise margin,

(v) a maximum allowed path loss.

According to a second aspect of the invention, there is provided a method for setting a femto cell uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network, the method comprising, at an access point: determining at least one macro cellular interference criterion; and setting the femto cell uplink transmit power level based on the at least one determined at least one macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion. According to a third aspect of the invention, there is provided a wireless communication unit for communicating with an access point in a femto cell of a cellular communication network. The wireless communication unit comprises transceiver circuitry arranged to receive a request from the access point to perform an interference measurement, such as a path loss measurement, on a macro cell transmission. The wireless communication unit further comprises a signal processing logic module arranged to perform an interference measurement, such as a path loss measurement, on the macro cell transmission in response to the request, wherein the transceiver circuitry is arranged to transmit the interference measurement on the macro cell transmission and receive in response thereto receive a femto cell uplink transmit power level for use when communicating with the access point based at least on the macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

According to a fourth aspect of the invention, there is provided a method for setting a femto cell uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network. The method comprises, at the wireless communication unit: receiving a request from a femto cell access point to perform an interference measurement on a macro cell transmission; and performing an interference measurement on the macro cell transmission in response to the request. The method further comprises transmitting the interference measurement on the macro cell transmission to the access point; and receiving in response thereto a femto cell uplink transmit power level based at least on the macro cellular interference criterion for use when communicating with the access point, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

According to a fifth aspect of the invention, there is provided a wireless communication system adapted to support either of the aforementioned methods for setting an uplink transmit power value for a wireless communication unit connected to a femto cell.

According to a sixth aspect of the invention, there is provided a computer-readable storage element having computer-readable code stored thereon for programming a signal processing logic module to perform the aforementioned method for setting an uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network. The code is operable for, at an access point: determining at least one macro cellular interference criterion; and setting the femto cell uplink transmit power level based on the at least one determined macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

According to a seventh aspect of the invention, there is provided a computer-readable storage element having computer-readable code stored thereon for programming a signal processing logic module to perform the aforementioned method for setting an uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network. The code is operable for, at the wireless communication unit: receiving a request from a femto cell access point to perform an interference measurement on a macro cell transmission; and performing an interference measurement on the macro cell transmission in response to the request. The code is further operable for transmitting the interference measurement on the macro cell transmission to the access point; and receiving in response thereto a femto cell uplink transmit power level based at least on the macro cellular interference criterion for use when communicating with the access point, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

These and other aspects, features and advantages of the invention will be apparent from, and elucidated with reference to, the embodiments described hereinafter.

Brief Description of the Drawings

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 illustrates an example of part of a cellular communication network adapted in accordance with an embodiment of the invention.

FIG. 2 illustrates an example of a simplified flowchart of a method for setting an uplink transmit power level of a wireless communication unit, as determined by an access point in accordance with some embodiments of the invention. FIG. 3 illustrates an example of a simplified flowchart of a method for setting an uplink transmit power level of a wireless communication unit, as performed by the wireless communication unit in accordance with some embodiments of the invention.

FIG. 4 illustrates a typical computing system that may be employed to implement signal processing functionality in embodiments of the invention.

Detailed Description of Embodiments of the Invention

As mentioned previously, it is envisaged that uplink transmissions from femto UEs may create significant levels of interference to macro cell receivers, thereby leading to a reduction in the effective coverage area for that macro cell. Such interference is due, in particular, to the fact that there is no interaction at the Radio

Resource Management (RRM) level between macro cell base stations (e.g. NodeBs) and the femto cell access points. As a result, current access points for femto cells, which determine the uplink transmit power levels for femto-UEs connected thereto, have no means by which to take into account interference at the macro cell receiver, and to modify accordingly the uplink power transmission levels for the femto-UEs.

Referring now to the drawings, and in particular FIG. 1 , an example of part of a 3GPP network, adapted in accordance with an embodiment of the invention, is illustrated and indicated generally at 100. In FIG. 1 , there is illustrated an example of a communication system 100 that comprises a combination of a macro cell 185 and a plurality of 3G femto cells 150 adapted in accordance with one embodiment of the invention. For the embodiment illustrated in FIG. 1 , the radio network sub-system (RNS) comprises two distinct architectures arranged to handle the respective macro cell and femto cell communications. In the macro cell scenario, the RNS comprises a controller in the form of a Radio Network Controller (RNC) 136 having, inter alia, signal processing logic module 138. The RNC 136 is operably coupled to a Node B 124 for supporting communications within the macro cell 185. The RNC 136 is further operably coupled to a core network element 142, such as a serving General Packet Radio System (GPRS) support node (SGSN )/mobile switching centre (MSC), as known.

In a femto cell scenario, an RNS 110 comprises a network element, in a form of a 3G Access Point (3G AP) 130, performing a number of functions generally associated with a base station, and a controller in a form of a 3G Access controller (3G AC) 140. As will be appreciated by a skilled artisan, a 3G Access Point is a communication element that supports communications within a communication cell, such as a 3G femto cell 150, and as such provides access to a cellular communication network via the 3G femto cell 150. One envisaged application is that a 3G AP 130 may be purchased by a member of the public and installed in their home. The 3G AP 130 may then be connected to a 3G AC 140 over the owner's broadband internet connection 160.

Thus, a 3G AP 130 may be considered as encompassing a scalable, multi-channel, two- way communication device that may be provided within, say, residential and commercial (e.g. office) locations, 'hotspots' etc, to extend or improve upon network coverage within those locations. Although there are no standard criteria for the functional components of a 3G AP, an example of a typical 3G AP for use within a 3GPP system may comprise some Node-B functionality and some aspects of radio network controller (RNC) 136 functionality. The 3G AP 130 further comprises transceiver circuitry 155 arranged to enable communication with one or more wireless communication units located within the general vicinity of the communication cell, and in particular within the communication cell 150, such as User Equipment (UE) 114, via a wireless interface (Uu).

The 3G Access Controller 140 may be coupled to the core network (CN) 142 via an Iu interface, as shown. In this manner, the 3G AP 130 is able to provide both voice and data services to a cellular handset, such as UE 1 14, in a femto cell, in the same way as a conventional Node-B does in a macro cell, but with the deployment simplicity of, for example, a Wireless Local Area Network (WLAN) access point.

The UE 114 may be a wireless communication unit comprising a transceiver 116 arranged to transmit and receive signals, and signal processing logic module 118. As would be appreciated by a skilled person, UE 114 comprises numerous other functional and logical elements to support wireless communications and functionality and which will not be described further herein. As previously mentioned, in a large scale deployment, there can be as many as a few million femto cells interspersed within the macro cellular layer. In a co-channel deployment, uplink interference from UEs connected to femto cells (femto-UEs) becomes a major problem for macro cell receivers. For clarity, the term 'co-channel deployment' relates to the situation where two or more overlapping or neighbouring cells are configured to utilise the same frequency channel(s). Noise experienced by the macro cell receivers, caused by interference from femto-UE transmissions, would typically lead to a reduction in the effective coverage area for that macro cell. Accordingly for the embodiment illustrated in FIG. 1 , the access point 130 has been adapted to comprise a signal processing logic module 165 arranged to determine an uplink transmit power level for a wireless communication unit, such as UE 114, connected to the femto cell 150 based at least on a macro cellular interference criterion.

In this manner, the access point 130, or more particularly for the illustrated embodiment signal processing logic module 165, is able to take into account interference that may be experienced at one or more macro cell receiver(s), for example at Node-B 124, due to the femto cell uplink transmission of the UE 114, and to set and/or modify the uplink power level for the UE 114 accordingly. Thus, the uplink power transmission level for the UE 114 may be appropriately limited, as required, in order to sufficiently reduce potential interference that may result from the femto cell uplink power transmission of the UE 1 14, as would potentially experienced by at least one neighbouring macro cell receiver, such as Node-B 124.

In accordance with one example of an embodiment of the invention, the signal processing logic module 165 may be arranged to determine a suitable femto cell uplink transmit power level for the wireless communication unit, from at least one neighbouring macro cell, based on at least one macro cell path loss measurement criterion observed at a receiver of the wireless communication unit (UE 114).

As will be appreciated by a skilled artisan, a path loss measurement may typically be determined at the network element (in this case a Node-B), or at the wireless communication unit, based on the difference (the path loss) between the transmit power and the power level of the received signal. For example, in the case where the transmit power level of, say, the Node-B wireless communication unit is set to, say, +4OdBm the transmitted signal may be received at the wireless communication unit at, for example, a received signal level of -9OdBm. Thus, the wireless communication unit may measure the received signal power from the Node-B, and subtract this from an identified transmit power level (of +4OdBm) contained within the received signal, and determine the path loss calculation as 13OdB. In accordance with some embodiments of the present invention, the signal processing logic module 165 of the access point 130 may be operably coupled to a request logic module arranged to request the path loss measurement from the UE 1 14.

The macro cell transmission has an indication of the Transmit power level of the transmission, to assist the UE to perform the path loss measurement. For example, in a 3GPP transmission, the Primary CPICH transmit power level of the macro cell is indicated in system information broadcast, i.e., 'SIB 5'.

Equation 1 below illustrates an example of an algorithm that may be implemented by the signal processing logic module 165 for determining a maximum allowed femto cell uplink transmit power level P_UL for the UE 114, according to some embodiments of the present invention. PUL = min(P_UL,max, max(P_UL,new, PUL,,™)) [Equation 1]

where:

PuL.new = min(PuL,maxιncr, PuL.coverage) [Equation 2] and where:

Pu_L._maxi_ncr denotes an estimated maximum uplink transmit power level that is allowable to meet an uplink interference criterion of the macro cell, and

Puu_coverage denotes the uplink transmit power level required to meet a femto cell coverage criterion.

Equation 1 will maintain the calculated value of the femto cell uplink transmit power within the bounds of maximum and minimum allowed transmit power. In this manner, the signal processing logic module 165 is arranged to determine the uplink transmit power level P_UL for UE 114, based at least partly on the estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion Puu_maxmcr- As a result, the uplink power transmission level for the UE 114, as controlled by the transmit power control logic module (not shown) of the access point, may be limited (set) by the signal processing logic module 165 of the access point 130, such that interference experienced by the macro cell Node-B 124, as a result of femto cell uplink transmissions for the UE 114, may be sufficiently reduced. Furthermore, by calculating at least the lower of the estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion Puu_maxmcr, and the uplink power value required to meet a coverage criterion Puu_coverage, the uplink transmit power level may be set such that the coverage criterion is satisfied, as long as the uplink transmit power level remains within that required by the macro cellular interference criterion. However, when the uplink transmission level exceeds that required by the macro cellular interference criterion, the uplink transmission level may be limited in order to remain within the requirements of the macro cellular interference criterion. As a result, interference experienced by the Node-B 124 as a result of uplink power transmission levels by the UE 114 may be substantially limited when interference caused thereby is considered too high. Equation 3 below illustrates an example of an algorithm for calculating the estimated maximum uplink transmit power that is allowable to meet the macro cellular interference criterion r UL.maxincr-

PuL, maxinc ⁼ RSSIuL.maxincr — PI-UL, macro [Equation 3]

where:

RSSIu_L,_maxi_ncr denotes a maximum allowed increment in uplink interference, as perceived at the macro cell receiver of the Node-B 124 from the UE 114, and

PLu_L._macro denotes a path loss measurement received at the UE 114. In this manner, the maximum allowed increment in uplink interference measured at a macro cell receiver RSSIuu_maxi_ncr may be used to set a macro cellular interference criterion measure, whereby the amount of influence that interference experienced by the macro cell receiver has over the transmit power levels of the UE 1 14 may be varied depending on the value given to the maximum allowed increment in uplink interference at the macro cell receiver RSSIuu_maxi_ncr- Furthermore, the path loss measurement PLu_L._macro performed at the UE 114 provides a dynamic indication of the level of interference experienced by the macro cell receiver due to transmissions by the UE 114. In particular, the macro cell path loss measurement at the receiver of the UE 1 14 provides a means by which the femto cell access point 130 is able to take into account interference at the macro cell receiver, and to modify the femto cell uplink transmit power levels for the UEs accordingly.

Referring back to Equation 2, and as previously mentioned, Puu_coverage denotes the femto cell uplink transmit power level required to meet a femto cell coverage criterion. Equation 4 below illustrates an example of a calculation that may be used to determine a femto cell uplink transmit power level Puu_coverage required to meet a coverage criterion.

E, PUL coverage = — - PG + N₀ + NR_M - MAPL [Equation 4]

Where:

E,

— - represents a target signal-to-noise quality for a given service on the uplink, and in

particular represents a target signal to noise measurement that is required for a given service.

PG represents a processing gain, which is related to the multiple access technique and in a CDMA system is a result of de-spreading,

N₀ represents a thermal noise level measured at, say, the access point 130, NR_M represents a noise rise margin at, say, the access point 130, and MAPL represents a maximum allowed path loss, which translates into a target coverage range for the uplink.

The femto cell is configured for a target coverage area by the Operator using the MAPL parameter. The value can be changed by, for example, an Operations and Management (O&M) entity. Thus, equation 2 states that the femto cell uplink transmit power level should be a minimum of what is required to meet the femto cell coverage needs and minimum interference caused to the target cell. The Operator is able to limit the maximum interference caused by a UE connected to the femto cell on the macro cell. The minimum UL transmit power is determined by specs, and in 3GPP it is -50 dBm. The UL transmit power for coverage is determined by MAPL and service requirements. Thus, a new femto cell uplink transmit power level (Puι__,new) may be determined based on the smaller value of a macro cellular interference criterion (P_{UL, maxmc}) and the femto cell uplink transmit power level that is required to meet a femto cell coverage criterion (P_{UL, coverage})-

Referring back to Equation 1 , the signal processing logic module 165 for the illustrated embodiment, may be further arranged to determine the femto cell uplink transmit power level for the UE 114 based on a maximum possible femto cell uplink transmit power level Pu_L._max, and a minimum possible femto cell uplink transmit power level Pu_L._mm- More particularly, the signal processing logic module 165 may be arranged to set the femto cell uplink transmit power value (P_UL) to the new femto cell uplink transmit power level (Puι__,new), within the limits of the maximum possible femto cell uplink transmit power level (Puι__,max) and the minimum possible femto cell uplink transmit power level (Pu__,mιn)- For example, the maximum and minimum possible femto cell uplink transmit power levels for the UE 114 may be set according to 3GPP specifications, such as, 3GPP TS25.101 , or according to an Operator defined criterion.

In, one embodiment of the invention, it is envisaged that the signal processing logic module 165 is arranged to determine an uplink transmit power value for the UE 114 based on macro cellular interference criterion for a neighbouring co-channel, or adjacent channel, macro cell, for example substantially the closest neighbouring co-channel macro cell or adjacent channel macro cell.

Referring now to FIG. 2 there is illustrated an example of a simplified flowchart 200 of a method for setting an uplink transmit power value for a wireless communication unit connected to a femto cell of a cellular communication network, as determined by an access point and adapted according to some embodiments of the invention. The flowchart starts in step 205 with a switch on of the femto cell access point (AP). A mobile originated (MO)/ mobile terminated (MT) call request is received, and accepted by an Admission Control logic module in the AP, as shown in step 210. In response thereto, the AP commands the UE to measure a selected one or more macro cell path loss, as shown in step 215.

Next, in step 220, the AP receives the macro cell path loss measurement from the UE and calculates a maximum uplink transmit power allowable by the UE to meet a macro cellular interference criterion (Pu_L,maxmc)- This calculation is based on a difference between a maximum allowed increment in uplink interference as may be perceived at the at least one neighbouring macro cell receiver, and the macro cell path loss measured by the UE/ wireless communication unit receiver. Based thereon, the AP transmits an indication of a maximum allowed femto cell uplink transmit power level to the UE, for example using radio resource control (RRC) signalling, as shown in step 225. Thereafter, and optionally, periodically and/or in response to an event trigger the AP receives one or more path loss measurements related to selected macro cell(s) from the UE, as in step 230. For example, periodicity may be considered to be in the order of minutes, as the AP normally supports low speed UEs. Here, a sudden change in path loss would be considered to be a rare event. Furthermore, for example, an event triggered adjustment may be initiated when the path loss to the macro cell decreases beyond a threshold value, e.g., the UE moves outside the building.

The AP may then re-calculate the maximum allowed uplink transmit power level for the UE, as shown in step 235, for example by employing equations [2, 3, 4] above. The new uplink transmit power value (Puι__,new) is determined based on the smaller of macro cellular interference criterion (PuL,maxmc) and the uplink power value required to meet a coverage criterion (PuL._∞verage)-

Next, in step 240, a determination is made by the AP as to whether the maximum UE transmit power has changed. If it is determined that the maximum UE transmit power has not changed in step 240, the flowchart loops back to step 230. If it is determined that the maximum UE transmit power has changed in step 240, the AP transmits the new value of the maximum allowed femto cell uplink transmit power to the UE using, for example, RRC signalling, as shown in step 245. The flowchart then loops back to step 230. The uplink transmit power value (P_UL) is then set to the new uplink transmit power value

(Pu_L._new), within the limits of a maximum possible uplink transmit power level (Puι__,max) and a minimum possible uplink transmit power level (Pu_L._mm)-

Referring now to FIG. 3, an example of a simplified flowchart 300 of a method for setting an uplink transmit power level of a wireless communication unit, as performed by the wireless communication unit in accordance with some embodiments of the invention, is illustrated. The flowchart commences with the UE making a mobile originated (MO)/ mobile terminated (MT) call request, which is received, and accepted by an Admission Control logic module in the AP, as shown in step 305. In response thereto, the UE receives an AP command to measure a selected one or more macro cell path loss, as shown in step 310. The UE then measures the path loss on the selected one or more macro cells and transmits the macro cell PL measurements to the AP, as shown in step 315.

The UE then receives the maximum allowed femto cell uplink transmit power indication from the AP, for example in RRC signalling, as shown in step 320. The UE then applies the value of the maximum allowed femto cell uplink transmit power to its inner loop power control, as in step

325. Thereafter, the UE may receive and apply one or more updated values of the maximum allowed uplink transmit power from the AP, during for example a call, as shown in step 330 and step 335.

Although embodiments of the invention have been described with reference to performing a path loss measurement as an interference criterion, it is envisaged that other interference measurements may be used. For example, it is envisaged that interference values or equations or calculations may be used in accordance with embodiments of the invention that do not specifically calculate path loss, but may be associated with, say, aspects of a path loss calculation.

Referring now to FIG. 4, there is illustrated a typical computing system 400 that may be employed to implement signal processing functionality in embodiments of the invention. Computing systems of this type may be used in access points and wireless communication units. Those skilled in the relevant art will also recognize how to implement the invention using other computer systems or architectures. Computing system 400 may represent, for example, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment. Computing system 400 can include one or more processors, such as a processor 404. Processor 404 can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control logic module. In this example, processor 404 is connected to a bus 402 or other communications medium.

Computing system 400 can also include a main memory 408, such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by processor 404. Main memory 408 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 404. Computing system 400 may likewise include a read only memory (ROM) or other static storage device coupled to bus 402 for storing static information and instructions for processor 404.

The computing system 400 may also include information storage system 410, which may include, for example, a media drive 412 and a removable storage interface 420. The media drive

412 may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW), or other removable or fixed media drive. Storage media 418 may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive

412. As these examples illustrate, the storage media 418 may include a computer-readable storage medium having particular computer software or data stored therein.

In alternative embodiments, information storage system 410 may include other similar components for allowing computer programs or other instructions or data to be loaded into computing system 400. Such components may include, for example, a removable storage unit 422 and an interface 420, such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units 422 and interfaces 420 that allow software and data to be transferred from the removable storage unit 422 to computing system 400. Computing system 400 can also include a communications interface 424. Communications interface 424 can be used to allow software and data to be transferred between computing system 400 and external devices. Examples of communications interface 424 can include a modem, a network interface (such as an Ethernet or other NIC card), a communications port (such as for example, a universal serial bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via communications interface 424 are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by communications interface 424. These signals are provided to communications interface 424 via a channel 428. This channel 428 may carry signals and may be implemented using a wireless medium, wire or cable, fiber optics, or other communications medium. Some examples of a channel include a phone line, a cellular phone link, an RF link, a network interface, a local or wide area network, and other communications channels.

In this document, the terms 'computer program product' 'computer-readable medium' and the like may be used generally to refer to media such as, for example, memory 408, storage device 418, or storage unit 422. These and other forms of computer-readable media may store one or more instructions for use by processor 404, to cause the processor to perform specified operations. Such instructions, generally referred to as 'computer program code' (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system 400 to perform functions of embodiments of the present invention. Note that the code may directly cause the processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.

In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system 400 using, for example, removable storage unit 422, drive 412 or communications interface 424. The control logic module (in this example, software instructions or computer program code), when executed by the processor 404, causes the processor 404 to perform the functions of the invention as described herein.

It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to different functional elements and processors.

However, it will be apparent that any suitable distribution of functionality between different functional elements or processors, for example with respect to the base station or controller, may be used without detracting from the invention. For example, it is envisaged that functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors. Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

Although one embodiment of the invention describes an AP for UMTS™ network, it is envisaged that the inventive concept is not restricted to this embodiment.

Although the invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term 'comprising' does not exclude the presence of other elements or steps.

Moreover, an embodiment can be implemented as a computer-readable storage element having computer readable code stored thereon for programming a computer (e.g., comprising a signal processing device) to perform a method as described and claimed herein. Examples of such computer-readable storage elements include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, ROM, a Programmable Read Only Memory, PROM, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory, EEPROM, and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to 'a', 'an', 'first', 'second' etc. do not preclude a plurality.

Thus, a method and apparatus for setting an uplink transmit power value for a wireless communication unit connected to a femto cell of a cellular communication network have been described, which substantially addresses at least some of the shortcomings of past and present techniques and/or mechanisms for setting an uplink transmit power value for a wireless communication unit.

Claims

1. An access point for supporting communication in a femto cell of a cellular communication network, the access point comprising: transceiver circuitry arranged to enable communication with one or more wireless communication units located within the femto cell, and a signal processing logic module arranged to set a femto cell uplink transmit power level for a wireless communication unit connected to the access point based at least on a macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

2. The access point of Claim 1 wherein the signal processing logic module comprises a path loss request logic module arranged to request the wireless communication unit to perform the at least one macro cell path loss measurement and report the at least one macro cell path loss measurement back to the access point.

3. The access point of Claim 1 or Claim 2 wherein the path loss request logic module is arranged to request the wireless communication unit to perform the at least one macro cell path loss measurement periodically and/or in response to an event trigger.

4. The access point of Claim 1 wherein the estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion is calculated based on a difference between: a maximum allowed increment in uplink interference at the at least one neighbouring macro cell receiver from the wireless communication unit; and the path loss measurement at the at least one neighbouring macro cell receiver for the wireless communication unit.

5. The access point of any preceding Claim wherein the signal processing logic module is further arranged to set the femto cell uplink transmit power level for the wireless communication unit based at least on a lower value of: the estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion; and an uplink power value required to meet a coverage criterion.

6. The access point of Claim 5 wherein the femto cell uplink transmit power level required to meet a coverage criterion is determined based at least on one or more of the following: (i) a target quality for a given service in the uplink,

(ii) a processing gain,

(iii) a received thermal noise power level,

(iv) a noise rise margin, (v) a maximum allowed path loss.

7. The access point of any preceding Claim wherein the at least one macro cell comprises a co-channel macro cell or adjacent channel macro cell.

8. The access point of Claim 7 wherein the at least one macro cell is the geographically closest neighbouring co-channel macro cell or adjacent channel macro cell.

9. The access point of any preceding Claim wherein the signal processing logic module is further arranged to determine the femto cell uplink transmit power level for the wireless communication unit based on at least one of:

(i) a maximum possible femto cell uplink transmit power level, (ii) a minimum possible femto cell uplink transmit power level.

10. The access point of any preceding Claim further characterised in that the access point is a 3^rd Generation (3G) access point, and the cellular communication network comprises a

Universal Mobile Telecommunications System network.

11. A method for setting a femto cell uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network, the method comprising, at an access point: determining at least one macro cellular interference criterion; and setting the femto cell uplink transmit power level based on the at least one determined macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

12. A wireless communication unit for communicating with an access point in a femto cell of a cellular communication network, the wireless communication unit comprising: transceiver circuitry arranged to receive a request from the access point to perform an interference measurement on a macro cell transmission; and a signal processing logic module arranged to perform an interference measurement on the macro cell transmission in response to the request, wherein the transceiver circuitry is arranged to transmit the interference measurement on the macro cell transmission and receive in response thereto receive a femto cell uplink transmit power level for use when communicating with the access point based at least on the macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

13. A method for setting a femto cell uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network, the method comprising, at the wireless communication unit: receiving a request from a femto cell access point to perform an interference measurement on a macro cell transmission; performing an interference measurement on the macro cell transmission in response to the request; transmitting the interference measurement on the macro cell transmission to the access point; and receiving in response thereto a femto cell uplink transmit power level based at least on the macro cellular interference criterion for use when communicating with the access point, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

14. A wireless communication system adapted to support the method for setting an uplink transmit power value for a wireless communication unit connected to a femto cell of Claim 11 or

Claim 13.

15. A computer-readable storage element having computer-readable code stored thereon for programming a signal processing logic module to perform a method for setting an uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network, the code operable for: determining at least one macro cellular interference criterion; and setting the femto cell uplink transmit power level based on the at least one determined macro cellular interference criterion, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

16. A computer-readable storage element having computer-readable code stored thereon for programming signal processing logic module to perform a method for setting an uplink transmit power level for a wireless communication unit connected to a femto cell of a cellular communication network, the code operable for, at the wireless communication unit: receiving a request from a femto cell access point to perform an interference measurement on a macro cell transmission; performing an interference measurement on the macro cell transmission in response to the request; transmitting the interference measurement on the macro cell transmission to the access point; and receiving in response thereto a femto cell uplink transmit power level based at least on the macro cellular interference criterion for use when communicating with the access point, wherein the macro cellular interference criterion comprises at least one macro cellular path loss measurement performed by a receiver of the wireless communication unit and an estimated maximum uplink transmit power allowable to meet the macro cellular interference criterion.

17. The computer-readable storage element of Claim 15 or Claim 16, wherein the computer readable storage medium comprises at least one of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, ROM, a Programmable Read Only Memory, PROM, an Erasable Programmable Read Only Memory, EPROM, an Electrically

Erasable Programmable Read Only Memory, EEPROM, and a Flash memory.