WO2013143142A1 - A method of special uplink power control using selectively averaged interference in heterogeneous networks - Google Patents

A method of special uplink power control using selectively averaged interference in heterogeneous networks Download PDF

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Publication number
WO2013143142A1
WO2013143142A1 PCT/CN2012/073405 CN2012073405W WO2013143142A1 WO 2013143142 A1 WO2013143142 A1 WO 2013143142A1 CN 2012073405 W CN2012073405 W CN 2012073405W WO 2013143142 A1 WO2013143142 A1 WO 2013143142A1
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WO
WIPO (PCT)
Prior art keywords
access node
mobile device
parameter
measured values
power value
Prior art date
Application number
PCT/CN2012/073405
Other languages
French (fr)
Inventor
Lili Xie
Wenjun Wu
Zhenning Shi
Original Assignee
France Telecom Research & Development Beijing Company Limited
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Application filed by France Telecom Research & Development Beijing Company Limited filed Critical France Telecom Research & Development Beijing Company Limited
Priority to PCT/CN2012/073405 priority Critical patent/WO2013143142A1/en
Publication of WO2013143142A1 publication Critical patent/WO2013143142A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/243—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account interferences
    • H04W52/244—Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/06—TPC algorithms
    • H04W52/14—Separate analysis of uplink or downlink
    • H04W52/146—Uplink power control

Definitions

  • the present invention generally relates to mitigating interference in a heterogeneous network.
  • a mobile network mobile devices, typically mobile phones or Smartphone, access the network by connecting to an access node, this connection is wireless and a transmission channel is established between the mobile device and the access node.
  • BTS Global System for Mobile communications
  • NB NodeB
  • eNB evolved NodeB or eNodeB
  • LTE Long Term Evolution
  • 4G 4G technology.
  • the radio signal emitted by such an access node covers a geographic area called a Macrocell: mobile devices within the area of such Macrocell may connect to the access node, also designed as Macrocell access node.
  • Network Coverage is obtained by deploying access nodes within a given geographic area, and mobile devices are connecting from one access node to another via roaming process.
  • Network Operators may deploy access nodes with limited emission range, typically on the order of 10 meters, such access nodes serve areas called Femtocells and are called, in a 3G/LTE context HNB (Home NodeB) or HeNB (Home eNodeB), or more generally Femtocell access node.
  • HNB Home NodeB
  • HeNB Home eNodeB
  • Femtocell access nodes are deployed to improve coverage in places where Macrocell coverage is poor.
  • the access to a Femtocell access node may be restricted to a limited group of mobile devices, this is the case for example when a mobile network operator which is also an ISP (Internet Service Provider) is integrating HeNB to the gateways provided to the customers to connect their local area network to Internet. In this case, the access to the HeNB is restricted to mobile devices registered by the customers on their gateway. It's also the case when a Femtocell access node is deployed at a company's request, to improve the coverage inside its premises; access is restricted to employee's mobile devices.
  • ISP Internet Service Provider
  • Femtocell access node has no access restriction, for example
  • Femtocell access nodes deployed within shops, subway or in tunnels Femtocell access nodes with limited access are defined as Closed Subscriber Group (CSG) Femtocell access nodes and Femtocell access nodes without access restriction are defined in this document as public Femtocell access nodes, even if in reality the access to a public Femtocell access node may be restricted to mobile devices of one network operator's customers.
  • CSG Closed Subscriber Group
  • CSG Femtocell is the area covered by a CSG Femtocell access node and a public Femtocell is the area covered by a public Femtocell access node.
  • This transmission channel comprises two transmission paths:
  • downlink path to convey information from the access node to the mobile device
  • uplink path a transmission path called "uplink path" to convey information from the mobile device to the access node.
  • a Macrocell access node emits and receives radio signals in a given frequency band to convey information to mobile devices within the area covered by the access node.
  • Macrocell access nodes placed next to the others are ideally using non overlapping frequency bands.
  • a Femtocell access node within a Macrocell may emit and receive radio signals using the same frequency band as the Macrocell access nodes, thus creating interferences between transmission channels established between mobile devices and the Macrocell access node and mobile devices and a Femtocell access node.
  • the low range of emission of the Femtocell access node prevents the Femtocell access node to interfere with the transmission channels established between mobile devices and their serving access node.
  • the quality of the transmission channel established between the mobile device and the Macrocell access node is usually decreasing as the Femtocell access node serving the Femtocell are often installed where the coverage of the Macrocell access node is poor; meanwhile the power of the interference generated by a mobile device connected to the Femtocell access node on the transmission channel established between the mobile device and the Macrocell access node is increasing. This situation results in a deterioration of the transmission channel established between the mobile device and the Macrocell access node, deterioration that may lead to a transmission cut, i.e. the communication between the mobile device and the Macrocell access node is terminated.
  • the mobile device attached to the Macrocell access node is authorized to connect to the Femtocell access node, the mobile device, using roaming process, establishes a transmission channel with the Femtocell access node.
  • This is the "raison d'etre" of a Femtocell as the transmission channel established between the mobile device and the Femtocell access node should be of better quality than the transmission channel established between the mobile device and the Macrocell access node when the mobile device is within the range the Femtocell.
  • the quality of the transmission channel established between the mobile device and the Macrocell access node is bound to decrease. Indeed, as the mobile device is getting closer to the Femtocell access node, the power of the interference generated by the mobile devices connected to the Femtocell access node on the transmission channel established between the mobile device and the Macrocell access node is getting higher, until the transmission channel established between the mobile device and the Macrocell access node is so deteriorated that it cuts, causing an outage of the mobile device connection with the Macrocell access node.
  • the estimated average interference power value calculated by this Femtocell access node gets extremely high .
  • the Femtocell access node informs the Macrocell access node to reduce transmission power of the interfering mobile device.
  • the Femtocell access node increases the transmission power of the mobile devices it serves. Since the uplink transmission power of mobile devices connected to the Femtocell access node increases, the interference on the established transmission channel between the Macrocell access node and the connected mobile device does not crease. As a result, the outage probability of the mobile device connected to the Macrocell access node increases. Moreover, the battery life of mobile devices connected to Femtocell access node is reduced since their transmission power is higher.
  • the present invention relates to a method for mitigating interference generated by at least a first mobile device connected to a first access node on a transmission channel established between a second mobile device and a second access node, said method being executed by the first access node and comprising the steps of: - Receiving a message emitted by the second access node indicating that a first parameter representing a power of a radio signal received by the second mobile device is greater than or equal to a first predetermined threshold, said radio signal being emitted by the first mobile device;
  • This method is applied for example when the first access node is a Closed Subscriber Group Femtocell access node and the second access node is a Macrocell access node. Furthermore, as Femtocell access node may have limited capacities in term of maximum connected mobile devices at a time, this method may also apply when a mobile device connected to a Macrocell access node, is approaching a public Femtocell access node already at full capacity, thus unable to accept the establishment of a new transmission channel with the mobile device.
  • the first access node uses the estimated average interference power value obtained to calculate a transmission power value for the first device and provides the first device with this information in order for the first mobile device to adapt its transmission power.
  • the first access node may either provide the first mobile device with calculated transmission power or may provide instruction on how much the first mobile device should increase or decrease its transmission power in order to reach the transmission power value calculated by the first access node.
  • the method of the invention allows a reduction of the transmission power of the first mobile devices connected to the first access node. As the transmission power of the first mobile devices is reduced, the interference caused on the transmission channel established between the second mobile device and the second access node is also reduced, thus decreasing the outage probability of the second mobile device. By reducing transmission power of the first mobile device, this method enables reducing power consumption of the first mobile devices as well.
  • the estimated average interference power value is estimated by discarding a predetermined number of values of the second parameter.
  • the different measured values of the second parameter are sorted from the largest value to the smallest value and then a predetermined number of values are discarded, beginning by the highest values.
  • the estimated average interference power value is calculated by discarding measured values of the second parameter higher than or equal to a third predetermined threshold.
  • measured values of the second parameter higher than a third predetermined threshold are removed from the set of measured values.
  • This third predetermined threshold can be fixed or calculated dynamically, for example by taking a multiple of previous estimations of average interference power. Discarding measured values of second parameter higher than a threshold before proceeding to the estimation of interference power is leading to decreasing the estimated average interference value.
  • the estimated average interference power value is calculated by determining a median value of the measured values of the second parameter.
  • the method further comprises the steps of:
  • the first reference value and the second reference value are equals; the values for first threshold and fourth threshold are equals and the values for the second threshold and the fifth threshold are equals. In others implementations of the invention, these values can be different. By choosing some reference or threshold values to be equals, the system implementation is simplified and device power consumption is limited.
  • This step allows the first access node to be informed that the second mobile device considers that the first access node is not interfering on the transmission channel established with second access node as the first parameter is lower than or equal to a fourth threshold.
  • the first access node is then checking that interferences caused by the second mobile device are low, this is done by determining the number of measured values of the second parameter higher than or equal to a second reference value and then comparing the number of said determined number of measured values to a fifth threshold; if the number of said determined number of values is lower or equal to the fifth threshold, then the first access node is calculating the estimated average interference according to the prior art.
  • the present invention also discloses an access node capable of mitigating interference generated by at least a first mobile device connected to said access node on a transmission channel established between another access node and a second mobile device, said access node comprising:
  • Another object of the invention concerns a computer program, in particular computer programs on or in an information medium or memory, suitable for implementing the method for mitigating interference object of the invention.
  • These programs can use any programming language, and be in the form of source code, binary code, or of code intermediate between source code and object code such as in a partially compiled form, or in any other desirable form for implementing the methods according to the invention.
  • the information medium may be any entity or device capable of storing the program.
  • the medium can comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or else a magnetic recording means, for example a diskette (floppy disk) or a hard disk.
  • the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means.
  • the program according to the invention may in particular be downloaded from a network of Internet type.
  • FIGURES are a diagrammatic representation of FIGURES.
  • Figure 1 represents a mobile network comprising a Macrocell overlapping a Femtocell in which the method for mitigating interference object of the invention is implemented;
  • Figure 2 shows a flow diagram illustrating the method for mitigating interference object of the invention
  • FIG. 3 shows a system in accordance with an embodiment of present invention.
  • Figure 1 represents a mobile network comprising a Femtocell 100 overlapped by a Macrocell 110.
  • Mobiles devices 102, 103 and 104 are connected to a Femtocell access node 101 covering the Femtocell 100, which means there is an established transmission channel between each mobile device 102, 103, 104 and the Femtocell access node 101 .
  • Only three mobile devices have been represented on Figure 1 , but more mobile devices could be connected to the Femtocell access node 101 .
  • Mobile devices 112, 113 and 114 are connected to the Macrocell access node 111 , which means there is an established transmission channel between each mobile device 112, 113, 114 and the Macrocell access node 111 .
  • the Mobile device 114 attached to the Macrocell access node 111 is within range of the Femtocell 100 but is unable to connect to the Femtocell access node 101 because, for example, the Femtocell access node 101 is a Closed Subscriber Group Femtocell access node and the mobile device 114 is not part of the Subscriber Group; or the Femtocell access node 101 has reached its full connection capacity.
  • the mobile device 114 is not allowed to perform roaming from the Macrocell access node 111 to the Femtocell access node 101 and is keeping its connectivity via an established transmission channel with the Macrocell access node 111 .
  • the interferences caused by the radio signals emitted by the mobile devices 102, 103, and 104 when transmitting data to the Femtocell access node 101 and the Femtocell access node 101 on the transmission channel established between the mobile device 114 and the Macrocell access node 111 are increasing.
  • the mobile device 114 is measuring a first parameter representing the level of interference. When the first parameter is higher than or equal to a first threshold T1 , the mobile device 114 is sending an aggression notification message to the Macrocell access node 111 , said aggression notification message comprising an identifier of the Femtocell access node 101 .
  • the Macrocell access node 111 is sending to the Femtocell access node 101 this aggression notification message, informing the Femtocell access node 101 that the mobile device 114 is receiving a level of interference higher than or equal to the first threshold T1 .
  • the Femtocell access node 101 measures the interference power it receives : to do that, the Femtocell access node 101 measures several instantaneous received interference power values during some time intervals, for example during 20 or 30 ms and determines a number of instantaneous received interference power values that are higher than or equal to a first reference value.
  • the Femtocell access node 101 When the number of instantaneous received interference power values that are higher than or equal to a first reference value is higher than or equal to a second threshold the Femtocell access node 101 is proceeding to the calculation of the estimated average interference value with a proposed method, called hereafter "special uplink power control procedure", method that takes into account the fact that the mobile device 114 is also interfering on established transmission channels between the Femtocell access node 101 and the connected mobile devices 102, 103 and 104.
  • the Femtocell access node 101 calculates transmission power for mobile devices 102, 103 and 104 using estimated average interference power value, and transmits to the mobile devices 102, 103 and 104 the transmission power value calculated or an instruction requesting in increase or a decrease in transmission power in order to reach the calculated transmission power value.
  • the present invention is reducing the outage probability of the mobile device 114 by detecting such a situation and adapting the uplink power control method executed by the Femtocell access node 101 , as described in Figure 2.
  • Figure 2 represents an implementation of the present invention in which the mobile device 114 is approaching a Femtocell 100, said mobile device 114 being unauthorized to connect to the Femtocell access node 101 .
  • the mobile device 114 informs the Macrocell access node 111 that interferences caused by at least one mobile device, 102 for example, attached to the Femtocell access node 101 , on the transmission channel established between the mobile device 114 and the Macrocell access node 111 is higher than a first threshold T1 .
  • This detection can be performed by measuring the power of the radio signal emitted by the Femtocell access node 101 and comparing it to the first threshold T1 . More generally, when the mobile device 114 receives a radio signal from a non-serving access node, meaning a different access node than the one it is connected to, i.e. the Macrocell access node 111 , the mobile device 114 is sending a message, called aggression notification, to the Macrocell access node 111 .
  • the aggression notification comprises an identification of the interfering Femtocell access node 101 .
  • the Macrocell access node 111 receiving the aggression notification sent by the mobile device 114 is then sending, during a step 21 1 , the notification message to the interfering Femtocell access node 101 .
  • the Femtocell access node 101 is receiving a message emitted by the Macrocell access node 111 indicating that a first parameter representing a power of a radio signal received by the mobile device 114 is greater than or equal to a first predetermined threshold T1 , said radio signal being emitted by the first mobile device - 102.
  • the Femtocell access nodes 101 Upon reception of the aggression notification during step 222, the Femtocell access nodes 101 is informed that a mobile device 114 is within range and that the transmission channel established between the mobile device 114 and the Macrocell access node 111 is interfered by the radio signal emitted by the Femtocell access node 101 . As the transmission channel established between the mobile device 114 and the Macrocell access node 111 is interfered by the radio signal emitted by the Femtocell access node 101 , channel reciprocity teaches that the transmission channel established between the mobile device 114 and the Macrocell access node 111 is also interfered by the radio signals emitted by mobile devices connected to the Femtocell access node 101 .
  • the Femtocell access node 101 is measuring the interference power value received from all the mobile devices located in the vicinity of the Femtocell 100, knowing that the most dominant interfering mobile device is probably the second mobile device 114. In a 3G context, this is done by measuring a second parameter representing the received interference power (RIP) during several timeslots. The Femtocell access node 101 is determining the number of measured values of the second parameter higher than or equal to a first reference R1 value determined according to the measured values of the second parameter.
  • RIP received interference power
  • the Femtocell access node 101 triggers a special uplink power control procedure an estimation of an average interference power value according to selected values of the second parameter.
  • the reference value R1 used in step 223 is either predetermined or dynamically defined according to, for example, an average value of RIP. In one implementation of the invention, the reference value R1 used in step 223 can be chosen as a multiple of previous average values of RIP.
  • the special uplink power control procedure 224 comprises the steps of:
  • - Measuring a plurality of values of a second parameter representing an interference power received by the first access node for example this is done by measuring instantaneous received interference power values during several time intervals, e.g. 20 ms or 30 ms;
  • Femtocell access node 101 the transmission power value calculated or an instruction requesting an increase or a decrease in transmission power in order to reach the calculated transmission power.
  • the estimated average interference power value is estimated by discarding a predetermined number of values of the second parameter, i.e. the highest values of the measured instantaneous received interference power are discarded. This is implemented by, for example, ordering the measured instantaneous received interference power values from the highest value to the lowest value, and then discarding a predetermined number of said values, beginning by the highest values of the measured instantaneous received interference power. Then, the Femtocell access node 101 is proceeding to the calculation of estimated average interference power based only on remaining values of the measured instantaneous received interference power.
  • the estimated average interference power value is calculated by discarding measured values of the second parameter higher than or equal to a third predetermined threshold T3.
  • the values of the measured instantaneous received interference power that are higher than or equal to the threshold T3 are discarded.
  • the threshold T3 is predetermined, either by defining the threshold T3 as a fixed parameter or it could be determined dynamically, according to previous values of estimated average interference power or a combination of past values of estimated average interference power and past values of the threshold T3 itself. Once the values of measured instantaneous received interference power higher than or equal to the thresholds T3 are discarded, the Femtocell access node 101 is proceeding to the calculation of estimated average interference power based only on remaining values of measured instantaneous received interference power.
  • the estimated average interference power value is calculated by determining a median value of the measured values of the second parameter.
  • all measured values of instantaneous received interference power are kept, but instead of proceeding to the calculation of the estimated average interference power by calculating an average value of measured values of instantaneous received interference power, the Femtocell access node 101 is proceeding by calculating a median value of instantaneous received interference power. This is particularly advantageous when there is a small number of much larger values, said larger values of measured received interference being caused by the mobile device 114.
  • calculation method is possible by, for example, combining previous methods, like discarding some values higher than or equals to a threshold and then determining an estimated average interference power by calculating the median value instead of the average value of remaining values.
  • step 203 the mobile device 114 is detecting that the interference created by Femtocell access node 101 is lower than or equal to a threshold T4, typically when the mobile device 114 is moving away from the Femtocell. Then in step 204 the mobile device 114 informs the Macrocell access node 111 by sending a retreat notification.
  • Threshold used in step 203 could be the same as the threshold used in step 201 , allowing an easier implementation of the present invention. It is also advantageous to choose the threshold used in step 203 lower than the threshold used in step 201 as to prevent or limit any flapping phenomena when interference caused by the Femtocell access node is varying around one of the threshold values.
  • step 212 the Macrocell access node 111 is relaying the retreat notification to the Femtocell access node 101 .
  • Macrocell access node 111 is receiving and sending notification between the mobile device 114 and the Femtocell access node 101 .
  • steps 21 1 or 212 may be as simple as forwarding the notification from the mobile device 114 to the Femtocell access node, but others implementations may include a system of management of the notification by, for example, implementing system of timers preventing the Macrocell access node 111 to send multiple aggression notification and retreat notification to the Femtocell access node.
  • the Macrocell access node 111 may also filter the notification as it may not be necessary to send an aggression notification received from a mobile device 114 if the Macrocell access node received and sent previously to the same Femtocell access node 101 another aggression notification received from another mobile device than mobile device 114. In this case, the Macrocell access node needs to keep in memory the received aggression notification and retreat notification in order to be able to send a retreat notification to the Femtocell access node 101 when all mobile devices which previously sent an aggression notification have also sent a retreat notification.
  • the Femtocell access node 101 When the Femtocell access node 101 receives a retreat notification in step 225, the Femtocell access node 101 proceeds to step 226 where it determines the number of measured values of the second parameter higher than or equal to a second reference value R2, R2 being determined according to the measured values of the second parameter.
  • the second reference value R2 can be chosen equal to the first reference value R1 , or predetermined or dynamically defined according to, for example, an average value of the second parameter. If the determined number of the measured values of the second parameter is lower than or equal to a fifth threshold T5, determined according to the total number of measured values, the Femtocell access node proceeds to step 221 , estimating an average interference power value by calculating an arithmetic mean of measured values of the second parameter.
  • FIG. 3 shows an example of hardware structure of the Femtocell access node 101 .
  • Such a Femtocell access node 101 comprises means 300 for emitting and receiving a radio signal.
  • Means 300 are capable of receiving a message emitted by another access node indicating that a first parameter representing a power of a radio signal received by the mobile device 114 is greater than or equal to a first predetermined threshold or lower than or equal to a fourth predetermined threshold.
  • Said means for receiving 300 are connected to an input of means 301 for measuring a plurality of values of a second parameter representing an interference power received by the Femtocell access node 101 .
  • Means 301 are connected to an input of means 302 for determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter or higher than or equal to a second reference value determined according to the measured values of the second parameter.
  • the means 302 are connected to an input of means 303 for determining when the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values or lower than or equal to a fifth threshold determined according to the total number of measured values.
  • the Femtocell access node 101 comprises also, connected to the means for determining 303, means 304 for estimating an average interference power value according to selected values of the second parameter.
  • means 304 are capable of discarding a predetermined number of values of the second parameter, in an additional embodiment, means 304 are capable of discarding measured values of the second parameter higher than or equal to a third predetermined threshold and in a further embodiment, means 304 are capable of determining a median value of the measured values of the second parameter.
  • Means 304 are also capable of calculating an arithmetic mean of measured values of the second parameter.
  • the means 304 for estimating the estimated average interference power value are connected to means 305 for calculating a transmission power value using the estimated average interference power value.
  • the means for calculating the transmission power value 305 are connected to the means 300 for emitting and receiving a radio signal.
  • the means 300 are capable of transmitting to a mobile device the calculated transmission power value.

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Abstract

The present invention concerns a method for mitigating interference generated by at least a first mobile device connected to a first access node on a transmission channel established between a second mobile device and a second access node, said method being executed by the first access node and comprising the steps of: - Receiving a message emitted by the second access node indicating that a first parameter representing a power of a radio signal received by the second mobile device is greater than or equal to a first predetermined threshold, said radio signal being emitted by the first mobile device; - Measuring a plurality of values of a second parameter representing an interference power received by the first access node; - Determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter; - When the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values, estimating an average interference power value according to selected values of the second parameter; - Calculating a transmission power value for the first mobile device using the estimated average interference power value, - Transmitting to the first mobile device the calculated transmission power value.

Description

A METHOD OF SPECIAL UPLINK POWER CONTROL USING SELECTIVELY AVERAGED INTERFERENCE IN HETEROGENEOUS NETWORKS
FIELD OF INVENTION :
The present invention generally relates to mitigating interference in a heterogeneous network.
BACKGROUND:
In a mobile network, mobile devices, typically mobile phones or Smartphone, access the network by connecting to an access node, this connection is wireless and a transmission channel is established between the mobile device and the access node. In GSM (Global System for Mobile communications) technology, an access node is called BTS (Base Transceiver Station), in 3G technology; an access node is called NB (NodeB) and eNB (evolved NodeB or eNodeB) for LTE (Long Term Evolution) or 4G technology. The radio signal emitted by such an access node covers a geographic area called a Macrocell: mobile devices within the area of such Macrocell may connect to the access node, also designed as Macrocell access node.
Network Coverage is obtained by deploying access nodes within a given geographic area, and mobile devices are connecting from one access node to another via roaming process. To improve coverage in places where the reception of the radio signals emitted by the access nodes is poor, like for example indoor, in the subway, in tunnels, etc. Network Operators may deploy access nodes with limited emission range, typically on the order of 10 meters, such access nodes serve areas called Femtocells and are called, in a 3G/LTE context HNB (Home NodeB) or HeNB (Home eNodeB), or more generally Femtocell access node. Thus, Femtocell access nodes are deployed to improve coverage in places where Macrocell coverage is poor.
The access to a Femtocell access node may be restricted to a limited group of mobile devices, this is the case for example when a mobile network operator which is also an ISP (Internet Service Provider) is integrating HeNB to the gateways provided to the customers to connect their local area network to Internet. In this case, the access to the HeNB is restricted to mobile devices registered by the customers on their gateway. It's also the case when a Femtocell access node is deployed at a company's request, to improve the coverage inside its premises; access is restricted to employee's mobile devices.
Another kind of Femtocell access node has no access restriction, for example
Femtocell access nodes deployed within shops, subway or in tunnels. Femtocell access nodes with limited access are defined as Closed Subscriber Group (CSG) Femtocell access nodes and Femtocell access nodes without access restriction are defined in this document as public Femtocell access nodes, even if in reality the access to a public Femtocell access node may be restricted to mobile devices of one network operator's customers.
Thus, CSG Femtocell is the area covered by a CSG Femtocell access node and a public Femtocell is the area covered by a public Femtocell access node.
When a mobile device is connected to the network via either a Macrocell access node or a Femtocell access node, at least one transmission channel is established between the mobile device and the access node. This transmission channel comprises two transmission paths:
a transmission path called "downlink path" to convey information from the access node to the mobile device;
a transmission path called "uplink path" to convey information from the mobile device to the access node.
A Macrocell access node emits and receives radio signals in a given frequency band to convey information to mobile devices within the area covered by the access node. To prevent interferences, Macrocell access nodes placed next to the others are ideally using non overlapping frequency bands.
For various reasons, one being the scarcity of frequency bands, a Femtocell access node within a Macrocell may emit and receive radio signals using the same frequency band as the Macrocell access nodes, thus creating interferences between transmission channels established between mobile devices and the Macrocell access node and mobile devices and a Femtocell access node.
When a mobile device attached to a Macrocell access node is not in the area covered by a Femtocell access node using the same frequency band as the Macrocell access node, the low range of emission of the Femtocell access node prevents the Femtocell access node to interfere with the transmission channels established between mobile devices and their serving access node.
When the mobile device served by the Macrocell access node is entering a
Femtocell the quality of the transmission channel established between the mobile device and the Macrocell access node is usually decreasing as the Femtocell access node serving the Femtocell are often installed where the coverage of the Macrocell access node is poor; meanwhile the power of the interference generated by a mobile device connected to the Femtocell access node on the transmission channel established between the mobile device and the Macrocell access node is increasing. This situation results in a deterioration of the transmission channel established between the mobile device and the Macrocell access node, deterioration that may lead to a transmission cut, i.e. the communication between the mobile device and the Macrocell access node is terminated.
In such a situation, if the mobile device attached to the Macrocell access node is authorized to connect to the Femtocell access node, the mobile device, using roaming process, establishes a transmission channel with the Femtocell access node. This is the "raison d'etre" of a Femtocell as the transmission channel established between the mobile device and the Femtocell access node should be of better quality than the transmission channel established between the mobile device and the Macrocell access node when the mobile device is within the range the Femtocell.
However, if the mobile device attached to the Macrocell access node is not authorized to connect to the Femtocell access node, the quality of the transmission channel established between the mobile device and the Macrocell access node is bound to decrease. Indeed, as the mobile device is getting closer to the Femtocell access node, the power of the interference generated by the mobile devices connected to the Femtocell access node on the transmission channel established between the mobile device and the Macrocell access node is getting higher, until the transmission channel established between the mobile device and the Macrocell access node is so deteriorated that it cuts, causing an outage of the mobile device connection with the Macrocell access node.
When a non authorized mobile device connected to a Macrocell access node approaches a CSG Femtocell access node, the estimated average interference power value calculated by this Femtocell access node gets extremely high . As a result, the Femtocell access node informs the Macrocell access node to reduce transmission power of the interfering mobile device. In the meantime, the Femtocell access node increases the transmission power of the mobile devices it serves. Since the uplink transmission power of mobile devices connected to the Femtocell access node increases, the interference on the established transmission channel between the Macrocell access node and the connected mobile device does not crease. As a result, the outage probability of the mobile device connected to the Macrocell access node increases. Moreover, the battery life of mobile devices connected to Femtocell access node is reduced since their transmission power is higher.
SUMMARY OF THE PRESENT INVENTION :
It is an object of the present system, processor and method to overcome disadvantages and/or make improvements in the prior art.
To that extend, the present invention relates to a method for mitigating interference generated by at least a first mobile device connected to a first access node on a transmission channel established between a second mobile device and a second access node, said method being executed by the first access node and comprising the steps of: - Receiving a message emitted by the second access node indicating that a first parameter representing a power of a radio signal received by the second mobile device is greater than or equal to a first predetermined threshold, said radio signal being emitted by the first mobile device;
- Measuring a plurality of values of a second parameter representing an interference power received by the first access node;
- Determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter;
- When the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values, estimating an average interference power value according to selected values of the second parameter;
- Calculating a transmission power value for the first mobile device using the estimated average interference power value;
- Transmitting to the first mobile device the calculated transmission power value.
This method is applied for example when the first access node is a Closed Subscriber Group Femtocell access node and the second access node is a Macrocell access node. Furthermore, as Femtocell access node may have limited capacities in term of maximum connected mobile devices at a time, this method may also apply when a mobile device connected to a Macrocell access node, is approaching a public Femtocell access node already at full capacity, thus unable to accept the establishment of a new transmission channel with the mobile device.
The first access node uses the estimated average interference power value obtained to calculate a transmission power value for the first device and provides the first device with this information in order for the first mobile device to adapt its transmission power. The first access node may either provide the first mobile device with calculated transmission power or may provide instruction on how much the first mobile device should increase or decrease its transmission power in order to reach the transmission power value calculated by the first access node.
By reducing the estimated interference power value calculated by the first access node, the method of the invention allows a reduction of the transmission power of the first mobile devices connected to the first access node. As the transmission power of the first mobile devices is reduced, the interference caused on the transmission channel established between the second mobile device and the second access node is also reduced, thus decreasing the outage probability of the second mobile device. By reducing transmission power of the first mobile device, this method enables reducing power consumption of the first mobile devices as well.
In a further embodiment of the present method, the estimated average interference power value is estimated by discarding a predetermined number of values of the second parameter.
In the prior art, it is known to determine estimated average interference value by calculating the average value of all measured values of second parameter.
In an additional embodiment of the present invention, the different measured values of the second parameter are sorted from the largest value to the smallest value and then a predetermined number of values are discarded, beginning by the highest values. By removing a predetermined number of values among the highest values, and then calculating the average value, the obtained result is lower than the average value obtained taking into account all the values of the second parameter, thus leading to a lower estimated average interference power.
In an additional embodiment, the estimated average interference power value is calculated by discarding measured values of the second parameter higher than or equal to a third predetermined threshold.
In said additional embodiment on the present invention, measured values of the second parameter higher than a third predetermined threshold are removed from the set of measured values. This third predetermined threshold can be fixed or calculated dynamically, for example by taking a multiple of previous estimations of average interference power. Discarding measured values of second parameter higher than a threshold before proceeding to the estimation of interference power is leading to decreasing the estimated average interference value.
In another embodiment, the estimated average interference power value is calculated by determining a median value of the measured values of the second parameter.
With some measured values of second parameter being much higher than the others, calculating the estimated interference power by calculating the median value instead of the average value is also leading to decreasing the estimated average interference power.
In a further embodiment, the method further comprises the steps of:
- Receiving a message emitted by the second access node indicating that the first parameter is lower than or equal to a fourth predetermined threshold;
- Determining the number of measured values of the second parameter higher than or equal to a second reference value determined according to the measured values of the second parameter; - When the determined number of the measured values of the second parameter is lower than or equal to a fifth threshold determined according to the total number of measured values, estimating an average interference power value by calculating an arithmetic mean of measured values of the second parameter; - Calculating a transmission power value for the first mobile device using the estimated average interference power value;
- Transmitting to the first mobile device the calculated transmission power value.
In said embodiment of the method of the invention, the first reference value and the second reference value are equals; the values for first threshold and fourth threshold are equals and the values for the second threshold and the fifth threshold are equals. In others implementations of the invention, these values can be different. By choosing some reference or threshold values to be equals, the system implementation is simplified and device power consumption is limited.
This step allows the first access node to be informed that the second mobile device considers that the first access node is not interfering on the transmission channel established with second access node as the first parameter is lower than or equal to a fourth threshold.
The first access node is then checking that interferences caused by the second mobile device are low, this is done by determining the number of measured values of the second parameter higher than or equal to a second reference value and then comparing the number of said determined number of measured values to a fifth threshold; if the number of said determined number of values is lower or equal to the fifth threshold, then the first access node is calculating the estimated average interference according to the prior art.
The present invention also discloses an access node capable of mitigating interference generated by at least a first mobile device connected to said access node on a transmission channel established between another access node and a second mobile device, said access node comprising:
- Means for receiving a message emitted by another access node indicating that a first parameter representing a power of a radio signal received by the second mobile device is greater than or equal to a first predetermined threshold, said radio signal being emitted by the first mobile device;
- Means for measuring a plurality of values of a second parameter representing an interference power received by the access node;
- Means for determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter; - Means for determining when the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values;
- Means for estimating an average interference power value according to selected values of the second parameter;
- Means for calculating a transmission power value for the first mobile device using the estimated average interference power value;
- Means for transmitting to the first mobile device the calculated transmission power value.
Furthermore, another object of the invention concerns a computer program, in particular computer programs on or in an information medium or memory, suitable for implementing the method for mitigating interference object of the invention. These programs can use any programming language, and be in the form of source code, binary code, or of code intermediate between source code and object code such as in a partially compiled form, or in any other desirable form for implementing the methods according to the invention.
The information medium may be any entity or device capable of storing the program. For example, the medium can comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or else a magnetic recording means, for example a diskette (floppy disk) or a hard disk.
Moreover, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from a network of Internet type.
FIGURES:
The present system and method are explained in further detail, and by way of example, with reference to the accompanying drawings wherein:
Figure 1 represents a mobile network comprising a Macrocell overlapping a Femtocell in which the method for mitigating interference object of the invention is implemented;
Figure 2 shows a flow diagram illustrating the method for mitigating interference object of the invention;
Figure 3 shows a system in accordance with an embodiment of present invention.
DESCRIPTION :
Figure 1 represents a mobile network comprising a Femtocell 100 overlapped by a Macrocell 110. Mobiles devices 102, 103 and 104 are connected to a Femtocell access node 101 covering the Femtocell 100, which means there is an established transmission channel between each mobile device 102, 103, 104 and the Femtocell access node 101 . Only three mobile devices have been represented on Figure 1 , but more mobile devices could be connected to the Femtocell access node 101 . Mobile devices 112, 113 and 114 are connected to the Macrocell access node 111 , which means there is an established transmission channel between each mobile device 112, 113, 114 and the Macrocell access node 111 . Only three mobile devices have been represented on Figure 1 , but more mobile devices could be connected to the Macrocell access node 111 . The Mobile device 114 attached to the Macrocell access node 111 is within range of the Femtocell 100 but is unable to connect to the Femtocell access node 101 because, for example, the Femtocell access node 101 is a Closed Subscriber Group Femtocell access node and the mobile device 114 is not part of the Subscriber Group; or the Femtocell access node 101 has reached its full connection capacity.
Thus, the mobile device 114 is not allowed to perform roaming from the Macrocell access node 111 to the Femtocell access node 101 and is keeping its connectivity via an established transmission channel with the Macrocell access node 111 .
As the mobile device 114 is getting closer to the Femtocell access node 101 , the interferences caused by the radio signals emitted by the mobile devices 102, 103, and 104 when transmitting data to the Femtocell access node 101 and the Femtocell access node 101 on the transmission channel established between the mobile device 114 and the Macrocell access node 111 are increasing. The mobile device 114 is measuring a first parameter representing the level of interference. When the first parameter is higher than or equal to a first threshold T1 , the mobile device 114 is sending an aggression notification message to the Macrocell access node 111 , said aggression notification message comprising an identifier of the Femtocell access node 101 .
The Macrocell access node 111 is sending to the Femtocell access node 101 this aggression notification message, informing the Femtocell access node 101 that the mobile device 114 is receiving a level of interference higher than or equal to the first threshold T1 .
The Femtocell access node 101 measures the interference power it receives : to do that, the Femtocell access node 101 measures several instantaneous received interference power values during some time intervals, for example during 20 or 30 ms and determines a number of instantaneous received interference power values that are higher than or equal to a first reference value. When the number of instantaneous received interference power values that are higher than or equal to a first reference value is higher than or equal to a second threshold the Femtocell access node 101 is proceeding to the calculation of the estimated average interference value with a proposed method, called hereafter "special uplink power control procedure", method that takes into account the fact that the mobile device 114 is also interfering on established transmission channels between the Femtocell access node 101 and the connected mobile devices 102, 103 and 104. The Femtocell access node 101 calculates transmission power for mobile devices 102, 103 and 104 using estimated average interference power value, and transmits to the mobile devices 102, 103 and 104 the transmission power value calculated or an instruction requesting in increase or a decrease in transmission power in order to reach the calculated transmission power value.
Thus, the present invention is reducing the outage probability of the mobile device 114 by detecting such a situation and adapting the uplink power control method executed by the Femtocell access node 101 , as described in Figure 2.
Figure 2 represents an implementation of the present invention in which the mobile device 114 is approaching a Femtocell 100, said mobile device 114 being unauthorized to connect to the Femtocell access node 101 .
In a step 201 , the mobile device 114 informs the Macrocell access node 111 that interferences caused by at least one mobile device, 102 for example, attached to the Femtocell access node 101 , on the transmission channel established between the mobile device 114 and the Macrocell access node 111 is higher than a first threshold T1 .
This detection can be performed by measuring the power of the radio signal emitted by the Femtocell access node 101 and comparing it to the first threshold T1 . More generally, when the mobile device 114 receives a radio signal from a non-serving access node, meaning a different access node than the one it is connected to, i.e. the Macrocell access node 111 , the mobile device 114 is sending a message, called aggression notification, to the Macrocell access node 111 . The aggression notification comprises an identification of the interfering Femtocell access node 101 .
The Macrocell access node 111 receiving the aggression notification sent by the mobile device 114 is then sending, during a step 21 1 , the notification message to the interfering Femtocell access node 101 . Thus, the Femtocell access node 101 is receiving a message emitted by the Macrocell access node 111 indicating that a first parameter representing a power of a radio signal received by the mobile device 114 is greater than or equal to a first predetermined threshold T1 , said radio signal being emitted by the first mobile device - 102.
Upon reception of the aggression notification during step 222, the Femtocell access nodes 101 is informed that a mobile device 114 is within range and that the transmission channel established between the mobile device 114 and the Macrocell access node 111 is interfered by the radio signal emitted by the Femtocell access node 101 . As the transmission channel established between the mobile device 114 and the Macrocell access node 111 is interfered by the radio signal emitted by the Femtocell access node 101 , channel reciprocity teaches that the transmission channel established between the mobile device 114 and the Macrocell access node 111 is also interfered by the radio signals emitted by mobile devices connected to the Femtocell access node 101 .
In step 223, the Femtocell access node 101 is measuring the interference power value received from all the mobile devices located in the vicinity of the Femtocell 100, knowing that the most dominant interfering mobile device is probably the second mobile device 114. In a 3G context, this is done by measuring a second parameter representing the received interference power (RIP) during several timeslots. The Femtocell access node 101 is determining the number of measured values of the second parameter higher than or equal to a first reference R1 value determined according to the measured values of the second parameter. When the determined number of the measured values of the second parameter is higher than or equal to a second threshold T2 determined according to the total number of measured values, the Femtocell access node 101 triggers a special uplink power control procedure an estimation of an average interference power value according to selected values of the second parameter.
The reference value R1 used in step 223 is either predetermined or dynamically defined according to, for example, an average value of RIP. In one implementation of the invention, the reference value R1 used in step 223 can be chosen as a multiple of previous average values of RIP.
The special uplink power control procedure 224 comprises the steps of:
- Measuring a plurality of values of a second parameter representing an interference power received by the first access node, for example this is done by measuring instantaneous received interference power values during several time intervals, e.g. 20 ms or 30 ms;
- Calculating using said instantaneous received interference power values an estimated average interference power;
- Calculating transmission power for mobile devices 102, 103 and 104 using said estimated average interference power value;
- Transmitting to the mobile devices 102, 103 and 104 connected to the
Femtocell access node 101 the transmission power value calculated or an instruction requesting an increase or a decrease in transmission power in order to reach the calculated transmission power.
All methods of calculation for estimated average interference power share the common principle of taking into account interferences created by the mobile device 114.
Three different implementations of the calculation step are described hereafter, but other implementations are possible, as long as they take into account the fact that some values of measured instantaneous received interference power are to be attenuated by the calculation method. In a first implementation, the estimated average interference power value is estimated by discarding a predetermined number of values of the second parameter, i.e. the highest values of the measured instantaneous received interference power are discarded. This is implemented by, for example, ordering the measured instantaneous received interference power values from the highest value to the lowest value, and then discarding a predetermined number of said values, beginning by the highest values of the measured instantaneous received interference power. Then, the Femtocell access node 101 is proceeding to the calculation of estimated average interference power based only on remaining values of the measured instantaneous received interference power.
In a second implementation of the invention, the estimated average interference power value is calculated by discarding measured values of the second parameter higher than or equal to a third predetermined threshold T3. The values of the measured instantaneous received interference power that are higher than or equal to the threshold T3 are discarded. The threshold T3 is predetermined, either by defining the threshold T3 as a fixed parameter or it could be determined dynamically, according to previous values of estimated average interference power or a combination of past values of estimated average interference power and past values of the threshold T3 itself. Once the values of measured instantaneous received interference power higher than or equal to the thresholds T3 are discarded, the Femtocell access node 101 is proceeding to the calculation of estimated average interference power based only on remaining values of measured instantaneous received interference power.
In a third implementation of the invention, the estimated average interference power value is calculated by determining a median value of the measured values of the second parameter. In this implementation all measured values of instantaneous received interference power are kept, but instead of proceeding to the calculation of the estimated average interference power by calculating an average value of measured values of instantaneous received interference power, the Femtocell access node 101 is proceeding by calculating a median value of instantaneous received interference power. This is particularly advantageous when there is a small number of much larger values, said larger values of measured received interference being caused by the mobile device 114.
Others implementation of calculation method are possible by, for example, combining previous methods, like discarding some values higher than or equals to a threshold and then determining an estimated average interference power by calculating the median value instead of the average value of remaining values.
Such a special uplink power procedure allows the Femtocell access node 101 to take into account in its calculation of the estimated power interference the presence of the mobile device 114. Moreover, by decreasing the transmission power of mobiles connected to the Femtocell access node, it reduces their power consumption, thus their autonomy. In step 203 the mobile device 114 is detecting that the interference created by Femtocell access node 101 is lower than or equal to a threshold T4, typically when the mobile device 114 is moving away from the Femtocell. Then in step 204 the mobile device 114 informs the Macrocell access node 111 by sending a retreat notification. Threshold used in step 203 could be the same as the threshold used in step 201 , allowing an easier implementation of the present invention. It is also advantageous to choose the threshold used in step 203 lower than the threshold used in step 201 as to prevent or limit any flapping phenomena when interference caused by the Femtocell access node is varying around one of the threshold values.
In step 212, the Macrocell access node 111 is relaying the retreat notification to the Femtocell access node 101 . It is to be noted that in step 21 1 and 212, Macrocell access node 111 is receiving and sending notification between the mobile device 114 and the Femtocell access node 101 . In one implementation, steps 21 1 or 212 may be as simple as forwarding the notification from the mobile device 114 to the Femtocell access node, but others implementations may include a system of management of the notification by, for example, implementing system of timers preventing the Macrocell access node 111 to send multiple aggression notification and retreat notification to the Femtocell access node. In one other implementation, the Macrocell access node 111 may also filter the notification as it may not be necessary to send an aggression notification received from a mobile device 114 if the Macrocell access node received and sent previously to the same Femtocell access node 101 another aggression notification received from another mobile device than mobile device 114. In this case, the Macrocell access node needs to keep in memory the received aggression notification and retreat notification in order to be able to send a retreat notification to the Femtocell access node 101 when all mobile devices which previously sent an aggression notification have also sent a retreat notification.
When the Femtocell access node 101 receives a retreat notification in step 225, the Femtocell access node 101 proceeds to step 226 where it determines the number of measured values of the second parameter higher than or equal to a second reference value R2, R2 being determined according to the measured values of the second parameter. The second reference value R2 can be chosen equal to the first reference value R1 , or predetermined or dynamically defined according to, for example, an average value of the second parameter. If the determined number of the measured values of the second parameter is lower than or equal to a fifth threshold T5, determined according to the total number of measured values, the Femtocell access node proceeds to step 221 , estimating an average interference power value by calculating an arithmetic mean of measured values of the second parameter. If not, the Femtocell access node 101 proceeds to step 224, keeping on calculating the estimated average interference via special uplink power control procedure. Figure 3 shows an example of hardware structure of the Femtocell access node 101 . Such a Femtocell access node 101 comprises means 300 for emitting and receiving a radio signal. Means 300 are capable of receiving a message emitted by another access node indicating that a first parameter representing a power of a radio signal received by the mobile device 114 is greater than or equal to a first predetermined threshold or lower than or equal to a fourth predetermined threshold.
Said means for receiving 300 are connected to an input of means 301 for measuring a plurality of values of a second parameter representing an interference power received by the Femtocell access node 101 . Means 301 are connected to an input of means 302 for determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter or higher than or equal to a second reference value determined according to the measured values of the second parameter.
The means 302 are connected to an input of means 303 for determining when the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values or lower than or equal to a fifth threshold determined according to the total number of measured values.
The Femtocell access node 101 comprises also, connected to the means for determining 303, means 304 for estimating an average interference power value according to selected values of the second parameter. In one embodiment of present invention, means 304 are capable of discarding a predetermined number of values of the second parameter, in an additional embodiment, means 304 are capable of discarding measured values of the second parameter higher than or equal to a third predetermined threshold and in a further embodiment, means 304 are capable of determining a median value of the measured values of the second parameter.
Means 304 are also capable of calculating an arithmetic mean of measured values of the second parameter. The means 304 for estimating the estimated average interference power value are connected to means 305 for calculating a transmission power value using the estimated average interference power value. The means for calculating the transmission power value 305 are connected to the means 300 for emitting and receiving a radio signal. The means 300 are capable of transmitting to a mobile device the calculated transmission power value.

Claims

A method for mitigating interference generated by at least a first mobile device connected to a first access node on a transmission channel established between a second mobile device and a second access node, said method being executed by the first access node and comprising the steps of:
- Receiving a message emitted by the second access node indicating that a first parameter representing a power of a radio signal received by the second mobile device is greater than or equal to a first predetermined threshold, said radio signal being emitted by the first mobile device;
- Measuring a plurality of values of a second parameter representing an interference power received by the first access node;
- Determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter;
- When the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values, estimating an average interference power value according to selected values of the second parameter;
- Calculating a transmission power value for the first mobile device using the estimated average interference power value;
- Transmitting to the first mobile device the calculated transmission power value.
The method of claim i wherein the estimated average interference power value is estimated by discarding a predetermined number of values of the second parameter.
The method of claim i wherein the estimated average interference power value is calculated by discarding measured values of the second parameter higher than or equal to a third predetermined threshold.
The method of claim i wherein the estimated average interference power value is calculated by determining a median value of the measured values of the second parameter.
The method of claim 1 further comprising the steps of:
- Receiving a message emitted by the second access node indicating that the first parameter is lower than or equal to a fourth predetermined threshold; - Determining the number of measured values of the second parameter higher than or equal to a second reference value determined according to the measured values of the second parameter;
- When the determined number of the measured values of the second parameter is lower than or equal to a fifth threshold determined according to the total number of measured values, estimating an average interference power value by calculating an arithmetic mean of measured values of the second parameter;
- Calculating a transmission power value for the first mobile device using the estimated average interference power value;
- Transmitting to the first mobile device the calculated transmission power value.
6. Access node capable of mitigating interference generated by at least a first mobile device connected to said access node on a transmission channel established between another access node and a second mobile device, said access node comprising:
- Means for receiving a message emitted by another access node indicating that a first parameter representing a power of a radio signal received by the second mobile device is greater than or equal to a first predetermined threshold , said radio signal being emitted by the first mobile device;
- Means for measuring a plurality of values of a second parameter representing an interference power received by the access node;
- Means for determining the number of measured values of the second parameter higher than or equal to a first reference value determined according to the measured values of the second parameter;
- Means for determining when the determined number of the measured values of the second parameter is higher than or equal to a second threshold determined according to the total number of measured values;
- Means for estimating an average interference power value according to selected values of the second parameter;
- Means for calculating a transmission power value using the estimated average interference power value;
- Means for transmitting to a mobile device the calculated transmission power value.
7. Computer program characterized in that it comprises program code instructions for the implementation of the steps of the method for mitigating interference as claimed in claim 1 when the program is executed by a processor.
PCT/CN2012/073405 2012-03-31 2012-03-31 A method of special uplink power control using selectively averaged interference in heterogeneous networks WO2013143142A1 (en)

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