RELATED APPLICATIONS

This application is the U.S. National Phase of Application No. PCT/FR2018/052427 entitled “METHOD FOR TRANSFERRING A MOBILE TERMINAL BETWEEN ACCESS STATIONS IN A MULTI-OPERATOR CONTEXT” and filed Oct. 2, 2018, which claims the benefit of French Patent Application No. 1759353, filed Oct. 5, 2017, each of which is incorporated by reference in its entirety.

1. FIELD OF THE INVENTION

The patent application lies in the field of mobile access networks in a context of cooperation between operators of mobile infrastructures controlling the access networks.

2. PRIOR ART

A mobile terminal is attached at a given instant to a base station of a mobile network controlled by an operator. A base station can be a BTS (Base Transceiver Station) station, a NodeB station, an eNodeB station or else any other type of station affording radio connection to a mobile terminal. In particular, it may entail a BBU (Base Band Unit) virtual entity or some other virtual or physical entity which manages an RRH (Remote Radio Head) entity in an architecture of C-RAN (Cloud Radio Access Networks) type. By virtue of this attachment, the mobile terminal, and therefore the user if this entails for example a smartphone, communicates with another terminal, fixed or mobile, attached to the same mobile network or to another network, of fixed or mobile type. The operator deploys base stations over a geographical area in such a way that a mobile terminal, when it is traveling around, can attach to one of the base stations deployed and benefit from good communication quality for data transmission. A “handover” mechanism is implemented to allow the terminal to transmit and receive data without interruption when the mobile terminal attaches successively to several base stations. According to the prior art techniques, when the mobile terminal is not traveling around, it has no reason a priori to attach to another base station, of the same operator or of a different operator. Furthermore, even if it had reason to do so, an operator of the network does not generally deploy multiple base stations for a given geographical area but aims rather at distributing the base stations over a territory so as to prevent so-called white geographical areas from not having any base station to which a mobile terminal, present in these white areas, can attach.

Thus, when a mobile terminal has poor connectivity in a mobile network of an operator, it is not generally possible for it to attach to another base station of the operator's network, either because it is outside the range of this other station or else because the handover techniques do not provide therefor. This problem relating to poor connectivity impacts the mobile terminal itself since the terminal's data bitrate is lower, its battery is impaired for low connection quality and operation of the applications on the mobile terminal suffer thereby. This poor connectivity also affects the operator of the mobile network since transmission capacities are used in an ineffective manner. Furthermore, the electromagnetic interactions are accentuated by the fact that the mobile terminal starts searching for higher-performance transmission channels, for example by using a larger transmission power, and the operator must furthermore place data in cache while waiting to be able to transmit them to the mobile terminal which may lie out of range.

With the aim of solving this problem, a solution based on cooperation of operators controlling distinct mobile networks appears beneficial. This type of cooperation, in particular described in the document “Why user swapping could be the best coordination mechanism in a cellular network?” (Globecom, Wireless Network Symposium, 2013), allows a mobile terminal for which the connection quality turns out to be of low performance to be transferred over to a base station of a mobile network controlled by another operator. This mechanism thus makes it possible to offer mobile terminals better connection quality and therefore to improve operators' geographical coverage by virtue of collaboration between operators present over the geographical area. This solution makes it possible as it were to extend the roaming possibilities to problems of connection quality and not only to problems of radio coverage. Roaming is indeed implemented so that an operator can benefit from radio coverage in a given geographical area, by virtue of other operators' networks, when the former does not itself have a radio network in this area. The roaming techniques furthermore assume that a terminal can attach to a base station of another operator by virtue of an agreement made between the operators guaranteeing a terminal the ability to attach to a base station of the other operator without taking into account the traffic conditions on the base station and without any condition other than the existence of a global agreement at the time the terminal connects.

Though the idea of cooperation between operators to ensure the connectivity of a mobile terminal is known, no method exists which makes it possible to carry out in a dynamic manner, and while taking into account the conditions relating to the flow of the data traffic, the transfer of a mobile terminal attached to a first base station to a second station controlled by a different operator.

The object of the present invention is to remedy drawbacks of the prior art.

3. DISCLOSURE OF THE INVENTION

The invention seeks to improve the situation with the aid of a method for transferring a mobile terminal attached to a first access entity of an operator to a second access entity of a set of access entities controlled by at least one other operator within a communication network, implemented by a control device for conveying data of the terminal, characterized in that it comprises:a step of receiving, originating from the entities of the set, a connectivity message comprising at least one parameter relating to the quality of transmission of the data between said terminal and each said entity,a step of determining an eligibility value relating to each entity, on the basis of the at least one parameter received and of a factor of cooperation between the first entity and each other access entity of the set,a step of selecting the second entity on the basis of the eligibility value determined,a step of sending, destined for the first entity and for the second entity, a transfer message comprising a transfer instruction and furthermore comprising an identifier of the first access entity and an identifier of the second access entity.

According to the proposed method, the transfer of a terminal from a first access entity, so-called origin entity, controlled by a first operator, to a second access entity, so-called destination entity, controlled by a different operator from the first, makes it possible to enable the terminal to be afforded better connectivity at this instant, and to do so even if the terminal is not moving. Furthermore, this transfer allows operators to control their access entities so as to avoid the latter becoming overloaded, in terms of connected terminals and volume of traffic. To implement the method, the terminal must be able to attach to a second access entity, that is to say be within range of a radio transmission of this access entity. Furthermore, attachment also assumes the terminal's ability to register with the second access entity, thus assuming an agreement between the two distinct operators controlling the two access entities. The agreement of the operator that controls the second access entity is obtained in a dynamic manner by virtue of the cooperation factor involved in determining an eligibility value, thus rendering the method more beneficial relative to a simple roaming technique used by the operators, where the agreement is not specific to a transfer such as proposed. Furthermore, on the basis of the eligibility values calculated for each access entity, the control device can note that the terminal must be transferred over to a second access entity. Indeed, if the control device determines that the quality of connection to the first access entity is not satisfactory, it decides to implement the transfer of the terminal over to the second access entity. The quality of the data transmission between the terminal and an access entity is advantageously used for selecting the second entity. An entity thus transmits an estimation of the quality of the channel for the terminal. If this entails the first entity, a real value of the quality of the channel can be transmitted to the control device. In particular the quality can be expressed by virtue of the SINR (Signal-to-Interference-plus-Noise Ratio) ratio widely used in radio networks and which can be used to estimate a value of eligibility to an access entity. This value used for example with an item of information about the load of the access entities and in addition to a cooperation factor, allows best choice of the entity to which the terminal will be transferred while reusing an indicator widely used by the various operators. Another option consists in the entities transmitting an estimated information item of CQI (Channel Quality Indicator) type or indeed both items of information, namely the SINR ratio and the CQI information item.

The eligibility value can therefore be based on a transmission parameter, such as a CQI or SINR value, and on a factor of cooperation between the operators controlling respectively the first and the second entity. The cooperation factor may for example be a binary value indicating effective or non-effective cooperation of the operators (1 if cooperation, 0 if no cooperation for this transfer). The cooperation factor can be an incremented (respectively decremented) value provided that a transfer between two entities of each operator has succeeded (respectively failed). The selection of the second access entity is carried out as a function of the eligibility values calculated for each entity to which the terminal can potentially attach. The control device may for example select the entity having the highest eligibility value. Once a second access entity is selected, the control device sends the transfer decision to the two entities concerned in the transfer. Thus, the first access entity learns that a terminal which is attached to it must be transferred to a second access entity and the item of information about this second access entity is communicated to the first access entity.

The item of information about the second access entity can be an IP (Internet Protocol) address, a name of FQDN (Fully Qualified Domain Name) type or any other item of information allowing the first access entity to know, or indeed to invoke, the second access entity for the effective implementation of the transfer. The second access entity also receives the transfer message so as in particular not to reject the attachment request of the terminal when the latter attaches to it. The effective transfer of the terminal to the second access entity is carried out in accordance with the 3GPP (3rd Generation Partnership Project) known “handover” techniques.

According to one aspect of the invention, the transfer method furthermore comprises a step of receiving, originating from the first and from the second entity, an indication message comprising a datum acknowledging the transfer.

The first entity and the second entity can advantageously transmit an indication message to the control device, thus informing the control device that the transfer of the terminal has been executed in accordance with the transfer message received. The control device can use this message for example to update the factor of cooperation between the two operators controlling the two access entities. Indeed, a successful transfer makes it possible to give an indication about a successful cooperation between the two operators, it being possible for this indication to be exploited by the control device in respect of the forthcoming transfers to be managed.

According to another aspect of the invention, the indication message of the transfer method furthermore comprises the at least one parameter, updated following the transfer, in respect of data transmission between said terminal and each of the two access entities.

In addition to the acknowledgment datum, the first and the second access station transmit their respective data transmission parameters, updated following the transfer, thus allowing the control device to update the information about the access stations of the set. The control device can thus for example know the number of connected terminals, the available transmission channels and the information of CQI type. These parameters can be used by the control device during a future transfer to be managed.

According to another aspect of the invention, the transfer method furthermore comprises a step of sending by the control device, destined for each of the two entities, a message of updating of their eligibility value following the transfer.

Once the transfer has taken place and the control device has calculated a new eligibility value for each access entity, taking into account the information transmitted by the access entities as well as the updated cooperation factor, it transmits it to the two entities. This dispatch enables these two entities to thereafter be able to manage mobilities of terminals in an autonomous manner, without resorting systematically to a centralized control device. If each access entity has the updated eligibility value at its disposal, they can manage transfers between themselves, without invoking the centralized control device, thus saving resources of this device and the transmission networks.

According to another aspect of the invention, the transfer method furthermore comprises a step of receiving, originating from the terminal, an information message comprising at least one communication datum.

In addition to the transmission parameters transmitted by the various entities of the set, the control device receives an information message from the terminal, this message comprising data for communication, which can be used in a complementary manner, to the parameters received from the access entities. These data are used by the control device to improve the determination of the eligibility value and consequently, to better select the second access entity. In particular, the terminal can transmit information, such as noted by the terminal, in respect of send and receive bitrate, which information may be different from the bitrate parameters transmitted by the access entities (for example the number of PRBs (Physical Resource Block) allocated in a given period).

According to another aspect of the invention, the information message of the transfer method furthermore comprises a parameter of geographical positioning of the terminal.

The information message transmitted by the terminal comprises in particular a geographical positioning parameter which the control device exploits to determine the eligibility values associated with the access entities by taking into account in an enhanced manner the position of the terminal. In the absence of such a parameter, the control device can only use location information originating from the access entities, which do not know in a precise manner the location of the terminals that are attached to them. By virtue of this item of information, the second access entity selected will be better positioned with respect to the effective geographical location of the terminal. The element may for example be a GPS (Global Positioning System) datum.

According to another aspect of the invention, in the transfer method, the connectivity message furthermore comprises a datum about the load of the entity.

One of the parameters used by the control device for the determination of the eligibility value is the load of each access entity, which may correspond to the number of terminals simultaneously attached to each access entity or else to the total bitrate of the communications of the terminals attached to each access entity at a given moment. It may also entail two items of information (number of terminals and bitrate). This item of information is particularly relevant, on the one hand in the decision making to transfer a terminal from a first access entity to a second access entity and on the other hand for selecting the second access entity to which the terminal is transferred. This item of information is not considered in the cases of roaming between two access entities controlled by one and the same operator, according to the prior art techniques, and turns out to be particularly useful for better distributing the traffic on the access entities of a set of entities located in a geographical area.

According to another aspect of the invention, the transfer message of the transfer method furthermore comprises an item of information relating to the duration of the transfer.

It may be beneficial to the operators to limit the duration for which a terminal initially attached to the first access entity can attach to a second access entity of another operator. Indeed, the terminals attaching to the second access entity according to the method use resources that the terminals having a contract with the operator controlling the second entity may not use. The clients of the operator controlling the second entity could therefore suffer as a result of overly great use of the resources of the second entity, which could require their own transfer to an entity of a second operator, increasing the number of transfers and the management of these associated transfers by the control server. Limiting the duration of transfer therefore makes it possible to limit the consumption of the resources of the destination entity, controlled by the other operator. If the transferred terminal needs a larger duration of transfer than the duration fixed, a new transfer can be effected.

According to another aspect of the invention, in the transfer method, the cooperation factor is determined as a function of earlier transfers.

The cooperation factor is updated regularly to exploit the successful transfers as well as the transfers that have failed. Thus, knowing that the transfers are implemented in a dynamic manner so as to take account of the transmission parameters and also of the interactions between the operators, the learning technique is significant. The control device, by taking account of the past transfers, and of their past successes or failures, can take transfer decisions that have more chances of success. Indeed, if for diverse reasons, and in spite of transmission capacities available on access entities controlled by a given operator, failures of transfer to an access entity of an operator are recorded, the device will be able to unfavorably weight a cooperation with such an access entity for the future transfers.

According to another aspect of the invention, in the transfer method, the set of access entities is situated in a geographical area delimited as a function of the geographical location of the first entity.

The method is implemented to allow the transfer of the terminal to an access entity within radio transmission range of the terminal. It may therefore be necessary to circumscribe the area within which an access entity can actually be selected. This circumscription can be performed on the basis of geographical datum of the first access station, to which the terminal is initially attached, or on the basis of the location of the terminal. This item of information in respect of location of the first access station can be obtained in the connectivity message or else be obtained on the basis of an identifier of the access station transmitting the connectivity message. The control device can thus use a database to determine the geographical location of the first access entity on the basis of the identifier received. A database can also be used to obtain the area of circumscription of the first access entity and the set of the access entities of the area.

According to another aspect of the invention, in the transfer method, the connectivity message furthermore comprises a network slice identifier.

The transfer between two access entities can also depend on the network slice to which the terminal is attached. In this case a transfer will be able to take place only to an access entity also supporting the network slice in such a way that there is no break in communication and that the terminal does not lose any data during the transfer. In this case it is necessary that the control device obtains the network slice identifier so as to integrate it with the determination of the eligibility value and therefore with the selection of an access entity compatible with the network slice to which the terminal is attached.

The various aspects of the transfer method which have just been described can be implemented independently of one another or in combination with one another.

The invention also relates to a device for transferring a mobile terminal attached to a first access entity of an operator to a second access entity of a set of access entities controlled by at least one other operator within a communication network, characterized in that it comprises:a receiver, intended to receive, originating from the entities of the set, a connectivity message comprising at least one parameter relating to the quality of transmission of the data between said terminal and each said entity,a determination module, intended to determine an eligibility value relating to each entity, on the basis of the at least one parameter received and of a factor of cooperation between the first entity and each other access entity of the set,a selection module, intended to select the second entity on the basis of the eligibility value determined,a sender, intended to send, destined for the first entity and for the second entity, a transfer message comprising a transfer instruction and furthermore comprising an identifier of the first access entity and an identifier of the second access entity.

This device, able to implement in all its embodiments the transfer method which has just been described, is intended to be implemented in a server which is independent of the operators or in a device which is controlled by one of the operators.

The invention also relates to a transfer system comprising:a control device comprising a transfer device,a first access entity of an operator,a second access entity controlled by another operator.

The invention also relates to a computer program comprising instructions for the implementation of the steps of the transfer method which has just been described, when this program is executed by a processor.

This program can use any programming language, and be in the form of source code, object code, or of code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

The invention is also aimed at an information medium readable by a computer, and comprising instructions of the computer program such as mentioned hereinabove.

The information medium can be any entity or device capable of storing the programs. 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 can be a transmissible medium such as an electrical or optical signal, which can be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be in particular downloaded over a network of Internet type.

Alternatively, the information medium can be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

