TECHNICAL FIELD

The present invention relates generally to the field of wireless communication. More particularly, it relates to mobility management for cell selection when a first and second cell applies a first and second RAT, respectively.

BACKGROUND

The field of mobile and telecommunication is an ever growing and rapidly developing field.

It is anticipated that in the fifth generation (5G) mobile communication system development there will typically be evolvement of the current Universal Mobile Telecommunication System Long Term Evolution (UMTS-LTE) system, which provides legacy networks such as 2G (e.g. Global System for Mobile communication, Time Division Multiple Access (GSM TMDA), 3G (e.g. UMTS Wideband Code Division Multiple Access (WCDMA) and 4G (e.g. WCDMA and Orthogonal Frequency Division Multiplexing (OFDM)), into the International Mobile Telecommunications for the year 2020 (IMT-2020) such as LTE next generation (LTE-NX). One purpose for IMT-2020 is to typically improve throughput and capacity compared to LTE. This may, for example, be achieved by increasing the sample rate (e.g. by a factor of 5) and also by enabling 5 times larger band width per carrier (100 MHz), IMT-2020 is also typically focusing on the use of higher carrier frequencies (above 5-10 GHz). Future 5G systems may also be based on a lean design where the transmission of broadcast signals, like master information blocks/system information blocks (MIB/SIB) or similar, synchronization (sync) and common reference symbols only are transmitted when necessary. One of the reasons for this is typically to reduce unnecessary interference as well as reducing the network node power consumption.

Another important aspect of 5G is that it typically should be tightly integrated with 4G, meaning that the handover (HO) and mobility between 4G and 5G should be fast and seamless.

Deploying a new Radio Access Technology typically brings a significant investment cost to the operator, especially if one needs to upgrade legacy RATs for tight interaction with the newly deployed RAT. Therefore, based on historical deployment of earlier cellular communication generations, the interaction between the RATs can be very rudimentary, especially at the initial employment.

The 5G cellular system may also open up for new operators that may not have any legacy system. Instead they will typically rely on roaming, i.e. where the 5G operator will pay a 4G operator in order for their subscribers to have coverage also in non-5G coverage areas. In this case it is also unlikely that the 4G and 5G system will be able to have tight interaction, due to the lack of a central node connecting the 4G and 5G cells to each other.

Hence, for tight interaction between cells utilizing the same or different RATs in all kind of deployment scenarios there is a need for device methods for fast and efficient cell selections while keeping coverage advantage as well as high throughput performance.

SUMMARY

It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

It is an object of some embodiments to obviate at least some of the above disadvantages and to provide fast and efficient methods for a wireless communication device, arrangements of a wireless communication device, wireless communication devices and computer program products for cell connection. Preferably, this is achieved while keeping coverage advantage as well as high throughput performance.

According to a first aspect this is achieved by a method of a wireless communication device operably connectable to a first cell of a first public land mobile network—PLMN—applying a first radio access technology—RAT.

The method comprises detecting a second cell of a second PLMN which applies a second RAT. The method also comprises determining whether a network relation exists between the first cell and the second cell. Also, the method comprises performing a connection set up to the first cell if it is determined that a network relation exists between the first cell and the second cell, and performing the connection set up to the second cell if it is determined that there does not exist a network relation between the first cell and the second cell.

Operably connectable may e.g. mean that the wireless communication device may wirelessly connect to the first cell for communication, e.g. when entering cell coverage. The wireless communication device may also disconnect from the cell, e.g. when moving out of cell coverage.

In some embodiments, the wireless communication device may already be connected to the first cell when the second cell is detected.

In some embodiments, the method may also comprise determining a need for connection prior to performing the connection set up and connect either to the first or the second cell based on the need for connection and the network relation.

In some embodiments, the need for connection may be a need for transmitting large amount of data and/or a need for fast transmission of data.

In some embodiments, the need for a connection may be determined by a Session Management Entity in a Non-Access Stratum layer (NAS).

The NAS may receive a request from an application processor, wherein the request comprises information of the data transfer.

The NAS may be comprised in the wireless communication device or in a NW node, then preferably within a mobility management entity (MME).

In some embodiments, determining whether a network relation exists between the first cell and the second cell may comprise determining whether the first PLMN of the first cell and the second PLMN of the second cell coincide.

In some embodiments, the first PLMN of the first cell and the second PLAN of the second cell may coincide if it is determined that the first PLMN and second PLMN are home PLMN—hPLMN—of the wireless communication device.

In some embodiments, determining whether a network relation exists between the first cell and the second cell may comprise determining whether there exists a backhaul connection between the first cell and the second cell.

For example, determining if a backhaul connection exists may in some embodiments be done when it is detected that the first PLMN is a visitor PLMN—vPLMN—and the second PLMN is a hPLMN.

In some embodiments, if a backhaul connection exists between the first cell and the second cell, it may still be possible to perform seamless cell switch (e.g. handover) of the wireless communication device even though the PLMN of the first cell and the PLMN of the second cell do not coincide.

In some embodiments, determining whether a network relation exists between the first cell and the second cell may further comprise reading first and second system information—SI—respectively associated with the first and second cells and comprising information indicative of a relationship between the first PLMN and the second PLMN, wherein the relationship implies that a network connection exists between the first cell and the second cell.

In some embodiments, the SI may be received by the wireless communication device through dedicated signaling from the first and/or second cell.

In some embodiments, the SI may comprise information explicitly stating that the relationship between the first PLMN and the second PLMN is a backhaul connection.

In some embodiments, the SI may comprise information indicative whether the first and/or second PLMN are vPLMN or hPLMN.

In some embodiments, information of backhaul connection may be received by the wireless communication device on the first cell in an application information table—AIT—broadcast associated with the second cell.

In some embodiments, the method may further comprise the wireless communication device camping on the first cell when the wireless communication device is in an idle or non active mode.

In some embodiments, the wireless communication device may avoid camping on the second cell when in idle or non active mode.

In some embodiments, the method may further comprise, after connection set up to the first cell, determining if a request for increased data is received and connecting to the second cell if it is determined that a request for increased data is received.

In some embodiments, a network node may decide that the wireless communication device should connect to the second cell and perform a hand over—HO—or any other type of cell switch e.g. connection release with redirect or a cell change order of the wireless communication device from the first cell to the second cell.

In some embodiments the increased data may be at least one of an increased transmission rate or an increased transmission size.

In some embodiments, the method may further comprise storing an indication of the first PLMN associated with the first cell and an indication of the second PLMN associated with the second cell in a memory of the wireless communication device.

In some embodiments, the indication may be stored in association with a respective geographical indication, e.g. GPS data.

In some embodiments, the method may further comprise that upon detecting a new cell, the wireless communication device may check its memory to see if an indication of a PLMN pertaining to the new cell is stored in the memory, and perform the connection set up based on the stored indication.

In some embodiments, the first RAT of the first cell may be a legacy-RAT. E.g. the first RAT may be a 2G, 3G or 4G RAT.

The 2G RAT may pertain to a global system for mobile communication—GSM—network. The 3G RAT may pertain to a universal mobile telecommunication system—UMTS network. The 4G RAT may pertain to a long term evolution—LTE—network.

In some embodiments, the second RAT may be a IMT-2020—RAT. E.g. the second RAT may be a 5G RAT.

A second aspect is a computer program product comprising a computer readable medium, having thereon a computer program comprising program instructions.

The computer program is loadable into a data-processing unit having a processor and a memory for storing the program instructions. The processor is configured to cause execution of the method according to the first aspect when the computer program is run by the data-processing unit.

A third aspect is an arrangement of a wireless communication device operably connectable to a first cell of a first public land wireless network—PLMN—applying a first radio access technology—RAT. The arrangement comprises a controller configured to cause detection of a second cell of a second PLMN applying a second RAT and cause determination of whether a network relation exists between the first cell and the second cell. Then the controller is configured to cause the wireless communication device to perform a connection set up to the first cell if it is determined that a network relation exists between the first cell and the second cell, and cause the wireless communication device to perform the connection set up the second cell if it is determined that there does not exist a network relation between the first cell and the second cell.

In some embodiments, the controller may further comprise a detector configured to detect the second cell.

In some embodiments, the controller may further comprise a determinator configured to determine whether a network relation exists between the first cell and the second cell.

In some embodiments, the controller may be further configured to cause determination of whether a network relation exists between the first cell and the second cell by causing determination of whether the first PLMN of the first cell and the second PLMN of the second cell coincide.

In some embodiments, the controller may be further configured to cause determination of whether a network relation exists between the first cell and the second cell by causing determination of whether there exist a backhaul connection between the first cell and the second cell.

In some embodiments, the controller may be further configured to cause determination of whether a network relation exists between the first cell and the second cell by causing reading of first and second system information—SI—respectively associated with the first and second cells and comprising information indicative of a relation between the first PLMN and the second PLMN, wherein the relationship implies that a network connection exists between the first cell and the second cell.

In some embodiments, the controller may be further configured to cause the wireless communication device to camp on the first cell when the wireless communication device is in an idle mode.

In some embodiments, the controller may be further configured to, after connection set up to the first cell, cause determination of if a request for increased data is received and cause a connection to the second cell if it is determined that a request for increased data is received.

In some embodiments, the controller may be further configured to cause a storing of an indication of the first PLMN associated with the first cell and an indication of the second PLMN associated with the second cell in a memory of the wireless communication device.

A fourth aspect is a wireless communication device comprising the arrangement according to the third aspect.

In some embodiments, the third and fourth aspects may additionally have features identical with or corresponding to any of the various features as explained above for the first aspect.

An advantage of some embodiments is that fast reselection between different RATs is enabled will still maximizing network coverage and high throughput.

Another advantage of some embodiments is that it is avoided that cells utilizing 5G RATs such as IMT-2020 are over encumbered by idle devices degrading the overall performance of the cell.

Another advantage of some embodiments is that overall network performance may be improved compared to prior art systems since a wireless communication device will connect to the system (legacy or LTE NX) providing best possible throughput while still maintaining low power consumption for both the network node and the wireless communication device by camping on the legacy system.

Another advantage of some embodiments is that a user which has subscribed to an IMT-2020 RAT may experience that the connection is to the subscribed RAT even though another RAT may be used by the camping cell, which will improve user satisfaction.

