WO2019058600A1

WO2019058600A1 - Communication method, communication device, communication program, and communication system

Info

Publication number: WO2019058600A1
Application number: PCT/JP2018/009694
Authority: WO
Inventors: 洋樹武田
Original assignee: Kddi株式会社
Priority date: 2017-09-19
Filing date: 2018-03-13
Publication date: 2019-03-28
Also published as: JP2019054478A

Abstract

A communication method according to one embodiment of the present invention executes: a determination step for determining, when a processor of a mobile station switches connection from a first base station to a second base station, whether the second base station supports reception of context information, on the basis of support information indicating that the second base station supports reception of the context information; and a first transmission step for transmitting, to the second base station, a first signal for requesting connection which uses the context information, when it is determined in the determination step that the second base station supports reception of the context information.

Description

Communication method, communication device, communication program and communication system

The present invention relates to a communication method, communication apparatus, communication program and communication system for performing communication between a mobile station and a base station.
Priority is claimed on Japanese Patent Application No. 2017-178623, filed September 19, 2017, the content of which is incorporated herein by reference.

As a mobile communication system, LTE (Long Term Evolution) and LTE-A (LTE-Advanced) communication standards based on LTE have been put to practical use. According to Patent Document 1, in the LTE and LTE-A mobile communication systems, when the quality of radio communication performed between the mobile station and the base station is deteriorated, the mobile station re-enters another base station. Techniques for making connections are described. In the technology described in Patent Document 1, the base station to which reconnection is performed re-connects to the mobile station by fetching context information including communication parameters of the mobile station from the base station of the reconnection source (also referred to as context fetching). A reconnection is established with the previous base station using the context information.

JP, 2016-129414, A

The technology described in Patent Document 1 assumes that both a reconnection source base station and a reconnection destination base station support context fetch. However, in an actual mobile communication system, even if the reconnection source base station supports context fetch, the reconnection target base station may not support context fetch. In this case, it occurs that the mobile station makes a reconnection request using context information to the reconnection destination base station, and the reconnection destination base station rejects or ignores the request. After that, the mobile station and the reconnection destination base station establish a new connection without using the context information held by the reconnection source base station.

As described above, in a mobile communication system in which a base station supporting context fetching and a base station not supporting mixing are mixed, useless communication for reconnection request using context information was performed. Since a new connection may be established later, a long time (short break time) may occur before the mobile station and the reconnection destination base station start communication.

The present invention has been made in view of these points, and occurs at reconnection in a mobile communication system in which a base station compatible with context fetching and a base station incompatible with context fetching are mixed. It is an object of the present invention to provide a communication method, a communication device, a communication program, and a communication system capable of reducing instantaneous interruption time.

In the communication method according to the first aspect of the present invention, when a processor of a mobile station switches a connection from a first base station to a second base station, the second base station responds to reception of context information. Determining that the second base station is capable of receiving the context information based on correspondence information indicating that the second base station has received the context information, and the second base station performs the context information in the determining step. And a first transmitting step of transmitting a first signal requesting the second base station to connect using the context information, when it is determined that the second base station is compatible with the reception of the second signal.

A second signal requesting a connection not using the context information to the second base station when it is not determined in the determination step that the second base station is compatible with reception of the context information A second sending step of sending may be further performed.

The second transmission step may transmit an RRC (Radio Resource Control) Connection Request as the second signal.

If it is possible to switch the connection from the first base station to the plurality of second base stations, the time until the mobile station discovers the second base station and the second base station before the determination step, and The method further includes a selection step of selecting any one of the plurality of second base stations from the plurality of second base stations based on the communication quality of two base stations, the determination step including the selection step It may be determined that the selected second base station supports reception of the context information.

The first transmission step may transmit RRC Connection Reestablishment Request as the first signal.

A receiving step of receiving the correspondence information from a base station capable of communicating with the mobile station may be further performed before the determination step.

In the receiving step, the correspondence information received from a plurality of the base stations may be accumulated and stored.

In the communication apparatus according to the second aspect of the present invention, when switching the connection from the first base station to the second base station, the communication apparatus indicates that the second base station is capable of receiving context information. A determination unit that determines that the second base station is compatible with the reception of the context information based on information; and the second base station responds to the reception of the context information by the determination unit. And a connection for transmitting a first signal requesting the second base station to connect using the context information.

In the communication program according to the third aspect of the present invention, when switching connection from a first base station to a second base station to a computer, the second base station supports reception of context information. A determination step of determining that the second base station is compatible with reception of the context information based on correspondence information indicating: and a second base station receiving the context information in the determination step. If it is determined that they correspond, the second base station is made to execute a first transmission step of transmitting a first signal requesting a connection using the context information.

The communication system according to the fourth aspect of the present invention comprises a mobile station, a first base station and a second base station, wherein the mobile station is connected to the second base station from the first base station. When switching, it is determined that the second base station supports reception of the context information based on correspondence information indicating that the second base station supports reception of context information. A determination unit, and when it is determined by the determination unit that the second base station is compatible with reception of the context information, a connection request using the context information is requested to the second base station The second base station receives the context information from the first base station when the first base station receives the first signal from the mobile station.

According to the present invention, in a mobile communication system in which a base station compatible with context fetching and a base station incompatible with context fetching are mixed, the effect of being able to reduce the momentary interruption time occurring at the time of reconnection can be reduced. Play.

It is a figure showing the communication system concerning a 1st embodiment. It is a figure which shows the connection switching which the mobile station which concerns on 1st Embodiment performs. It is a block diagram showing a communication system concerning a 1st embodiment. It is a flowchart which shows the communication method which concerns on 1st Embodiment. It is a sequence diagram which shows the communication method concerning a 1st embodiment. It is a figure which shows the connection switching which the mobile station which concerns on 2nd Embodiment performs. It is a flowchart which shows the communication method which concerns on 2nd Embodiment.

First Embodiment
FIG. 1 is a schematic view of a communication system S according to the present embodiment. The communication system S is a mobile communication system of the LTE system or the LTE-A system. The communication system S includes at least one mobile station 1 and at least two base stations 2. The communication system S may include devices such as other servers and terminals.

The base station 2 is a radio base station apparatus, and corresponds to an eNodeB in LTE or LTE-A. The base station 2 is connected to a mobility management entity (MME), a serving gateway (SGW) and a packet data network gateway (PGW) (not shown), and relays communication between the mobile station 1 and a network such as the Internet.

The mobile station 1 is a communication apparatus according to the present embodiment, and corresponds to UE (User Equipment) in LTE or LTE-A. As the mobile station 1, for example, a portable terminal such as a smartphone can be used. The mobile station 1 is connected to any of a plurality of base stations 2 by RRC (Radio Resource Control), and communicates with the network through the connected base station 2. The mobile station 1 can switch the connection between the base stations 2 (i.e., handover) when the communication status is deteriorated.

[Description of connection switching]
FIG. 2 is a schematic view of connection switching performed by the mobile station 1 according to the present embodiment. FIG. 2 planarly shows the arrangement of the mobile station 1 and the base station 2. In this specification, the switching source base station 2 is referred to as a source base station 2-1 (first base station), and the switching destination base station 2 is referred to as a target base station 2-2 (second base station).

The source base station 2-1 and the target base station 2-2 form a cell C-1 and a cell C-2, respectively. The cell C-1 and the cell C-2 are a range in which radio waves of the source base station 2-1 and the target base station 2-2 reach, that is, a range in which connection with the mobile station 1 is possible. In FIG. 2, the outer edges of the cell C-1 and the cell C-2 are represented by broken lines.

In the actual arrangement of the base station 2, the base station 2 supporting context fetch (CF) and the base station 2 not supporting the same are mixed. The context fetch is that the target base station 2-2 fetches context information including communication parameters of the mobile station 1 from the source base station 2-1. In FIG. 2, the base station 2 corresponding to the context fetch is represented in white, and the base station 2 not corresponding to the context fetch is represented in black.

When the target base station 2-2 supports context fetch, the target base station 2-2 maintains the connection setting between the source base station 2-1 and the mobile station 1 while maintaining the connection setting with the mobile station 1. Thus, the number of communication parameters that need to be negotiated between the mobile station 1 and the network can be reduced. As a result, it is possible to shorten the time taken to establish a connection between the target base station 2-2 and the mobile station 1.

On the other hand, when the target base station 2-2 does not support context fetch, the target base station 2-2 can not use the connection setting between the source base station 2-1 and the mobile station 1 Therefore, it is necessary to negotiate all communication parameters between the mobile station 1 and the network to establish a new connection. That is, processing is required when the mobile station 1 not connected to the base station 2 starts a new connection to the base station 2. Therefore, it takes a long time to establish a connection between the target base station 2-2 and the mobile station 1.

FIG. 2 describes a situation where the mobile station 1 switches the connection from the context fetch compatible source base station 2-1 to the context fetch compatible or non-compliant target base station 2-2. As described above, the conventional mobile station 1 performs connection (that is, reconnection) using context information to the target base station 2-2 regardless of whether or not the target base station 2-2 supports context fetching. The request was being made. Therefore, when the target base station 2-2 does not support context fetch, a reconnection request is wasted, and a long short break time occurs because a new connection is made instead of reconnection. .

On the other hand, the mobile station 1 according to the present embodiment determines whether or not the target base station 2-2 supports context fetch, and sends the target base station 2-2 only if it supports context fetch. Request a connection using context information. Therefore, it is possible to shorten the momentary interruption time when switching the connection.

[Configuration of Communication System S]
FIG. 3 is a block diagram of the communication system S according to the present embodiment. In FIG. 3, arrows indicate the flow of main data, and there may be flows of data other than those shown in FIG. In FIG. 3, each block is not a hardware (apparatus) -based configuration but a function-based configuration. Thus, the blocks shown in FIG. 3 may be implemented in a single device or may be implemented separately in multiple devices. Transfer of data between the blocks may be performed via any means such as a data bus, a network, a portable storage medium, and the like.

The mobile station 1 includes a control unit 11, a communication unit 12, and a storage unit 13. The control unit 11 includes a base station information acquisition unit 111, a base station determination unit 112, and a connection unit 113.

The communication unit 12 is a communication interface for communicating with the base station 2. The communication unit 12 performs predetermined processing on the communication signal received from the base station 2 to acquire data, and inputs the acquired data to the control unit 11. Further, the communication unit 12 performs predetermined processing on the data input from the control unit 11 to generate a communication signal, and transmits the generated communication signal to the base station 2.

The storage unit 13 is a storage medium including a read only memory (ROM), a random access memory (RAM), a hard disk drive, and the like. The storage unit 13 stores in advance a program to be executed by the control unit 11.

The control unit 11 is, for example, a processor such as a CPU (Central Processing Unit), and functions as the base station information acquisition unit 111, the base station determination unit 112, and the connection unit 113 by executing a program stored in the storage unit 13. Do. At least a part of the functions of the control unit 11 may be performed by an electric circuit. In addition, at least a part of the functions of the control unit 11 may be executed by a program executed via a network.

The mobile station 1 according to the present embodiment is not limited to the specific configuration shown in FIG. The mobile station 1 is not limited to one device, and may be configured by connecting two or more physically separated devices in a wired or wireless manner.

The base station information acquisition unit 111 receives the context fetch correspondence information of the base station 2 and stores the information in the storage unit 13. The correspondence information is information indicating that the base station 2 supports context fetching (at least that reception of context information is possible). Therefore, it can be determined that the base station 2 having the correspondence information corresponds to the context fetch, and it can be determined that the base station 2 having no correspondence information does not correspond to the context fetch.

Specifically, the base station information acquisition unit 111 receives, from the source base station 2-1, corresponding information of the base station 2 in the vicinity of the source base station 2-1. Generally, since the target base station 2-2 is in the vicinity of the source base station 2-1, the correspondence information received from the source base station 2-1 often includes the correspondence information of the target base station 2-2.

Alternatively, the base station information acquisition unit 111 may receive, from the base stations 2 other than the source base station 2-1, the corresponding information of the base station 2 in the vicinity of the base station 2. Alternatively, the base station information acquisition unit 111 may receive the correspondence information from a device such as MME connected to the base station 2.

The base station information acquisition unit 111 may accumulate the correspondence information received from the base station 2 or the like in the storage unit 13 and store it. In this case, the base station information acquisition unit 111 stores the received first correspondence information in the storage unit 13, adds the second correspondence information received after that to the first correspondence information, and stores the same. Remember to Alternatively, the base station information acquisition unit 111 may store only the received latest correspondence information in the storage unit 13 and may delete the correspondence information before that from the storage unit 13.

Then, when the mobile station 1 starts reconnection to the target base station 2-2, the base station information acquisition unit 111 reads out the correspondence information stored in the storage unit 13 to obtain the target base station 2-2. Get correspondence information.

The base station determination unit 112 determines that the target base station 2-2 to which the mobile station 1 is trying to connect corresponds to context fetch when there is correspondence information, and if there is no correspondence information, the context Determine that it does not support fetching.

Alternatively, the correspondence information may be information indicating that the base station 2 does not support context fetching. At this time, the base station determination unit 112 determines that the target base station 2-2 to which the mobile station 1 is trying to connect is not compatible with context fetch when there is correspondence information, and there is no correspondence information. Determines that it corresponds to context fetch.

As another method, the correspondence information may be information indicating whether each base station 2 supports context fetch. At this time, if the base station determination unit 112 indicates that the correspondence information corresponds to the context fetch for the target base station 2-2 to which the mobile station 1 is trying to connect, the base station determination unit 112 corresponds to the context fetch. If it indicates that the correspondence information does not correspond to context fetch, it determines that it does not correspond to context fetch.

The connection unit 113 transmits a signal requesting connection using context information or connection not using context information to the target base station 2-2 according to the determination result by the base station determination unit 112.

In connection using context information, the target base station 2-2 receives context information from the source base station 2-1, and reconnection between the target base station 2-2 and the mobile station 1 using this context information To do. In the connection not using context information, the target base station 2-2 does not receive context information from the source base station 2-1, and establishes a new connection between the target base station 2-2 and the mobile station 1. It means that.

Specifically, when the base station determination unit 112 determines that the target base station 2-2 supports context fetch, the connection unit 113 requests the first signal to request a connection using context information. , And transmits to the target base station 2-2 via the communication unit 12. Also, the connection unit 113 does not determine that the base station determination unit 112 determines that the target base station 2-2 supports context fetching (that is, the base station does not support the context fetching operation for the target base station 2-2). If the station determination unit 112 makes a determination, the second signal requesting connection without using context information is transmitted to the target base station 2-2 via the communication unit 12.

With such a configuration, it is possible to prevent the mobile station 1 from connecting to the base station 2 since it is possible to prevent the signal requesting connection using the context information from being transmitted to the target base station 2-2 not supporting context fetch. It is possible to shorten the momentary interruption time when switching.

[Flow chart of communication method]
FIG. 4 is a flowchart showing the communication method according to the present embodiment. FIG. 5 is a sequence diagram of a communication method corresponding to the flowchart of FIG. In FIG. 4 and FIG. 5, CF represents context fetch.

First, the base station information acquisition unit 111 receives correspondence information indicating that the base station 2 corresponds to context fetch, and stores the correspondence information in the storage unit 13 (S11). The mobile station 1 starts switching the connection from the source base station 2-1 to the target base station 2-2, for example, when the communication situation with the source base station 2-1 is deteriorated. When switching of connection has not been started (NO in S12), the mobile station 1 returns to step S11 and repeats the process.

When connection switching is started (YES in S12), the base station information acquisition unit 111 acquires correspondence information for the target base station 2-2, and the base station determination unit 112 determines the target base station based on the correspondence information. It is determined whether 2-2 corresponds to context fetch (reception of context information) (S13).

When the base station determination unit 112 determines that the target base station 2-2 supports context fetching in step S13 (YES in S14), the connection unit 113 requests a connection using context information; Are transmitted to the target base station 2-2 via the communication unit 12 (S15).

Specifically, as shown in the sequence diagram of FIG. 5, the connection unit 113 of the mobile station 1 transmits an RRC Connection Reestablishment Request as a first signal to the target base station 2-2. When the target base station 2-2 receives the RRC Connection Reestablishment Request, the target base station 2-2 transmits an RLF indication to the source base station 2-1. Upon receiving the RLF Indication, the source base station 2-1 transmits a HO Request to the target base station 2-2. At this time, the target base station 2-2 receives context information of the mobile station 1 from the source base station 2-1.

Next, when receiving the HO Request, the target base station 2-2 transmits an HO Request Ack to the source base station 2-1, and transmits an RRC Connection Reestablishment to the mobile station 1. At this time, the mobile station 1 receives communication parameters for performing reconnection using context information. When the mobile station 1 receives RRC Connection Reestablishment, it transmits RRC Connection Reestablishment Complete to the target base station 2-2. Thereby, reconnection between the mobile station 1 and the target base station 2-2 is established.

If the base station determination unit 112 does not determine that the target base station 2-2 supports context fetching in step S13 (NO in S14), the connection unit 113 requests a connection that does not use context information. The second signal is transmitted to the target base station 2-2 via the communication unit 12 (S16).

Specifically, as shown in the sequence diagram of FIG. 5, the mobile station 1 spontaneously transitions to a standby (RRC idle) state, and the connection unit 113 transmits a second signal to the target base station 2-2. Send RRC Connection Request. When receiving the RRC Connection Request, the target base station 2-2 transmits RRC Connection Setup to the mobile station 1. When receiving the RRC Connection Setup, the mobile station 1 transmits RRC Connection Setup Complete to the target base station 2-2. Thereby, a new connection is established between the mobile station 1 and the target base station 2-2.

The signals transmitted and received between the mobile station 1, the source base station 2-1 and the target base station 2-2 described here are an example, and any signal capable of executing LTE or LTE-A communication is transmitted and received. Ru.

Although the communication method shown in FIG. 4 and FIG. 5 targets one target base station 2-2, a plurality of target base stations 2-2 may be targeted. In this case, the base station information acquisition unit 111 acquires correspondence information for each of the plurality of target base stations 2-2 to which the mobile station 1 can connect, and the base station determination unit 112 determines a plurality of correspondence information based on the correspondence information. It is determined whether each of the target base stations 2-2 supports context fetch.

Then, connection section 113 selects one target base station 2-2 corresponding to the context fetch among the plurality of target base stations 2-2, and transmits it to the first signal requesting connection using the context information. Do. If none of the plurality of target base stations 2-2 support context fetch, the connection unit 113 selects any one target base station 2-2 among the plurality of target base stations 2-2. , Send a second signal requesting a connection that does not use context information. With such a configuration, the mobile station 1 can selectively connect to a base station that supports context fetch.

In addition, when none of the connectable target base stations 2-2 support context fetch, it is not necessary to transmit a second signal requesting a connection that does not use context information. That is, when there is no connectable target base station 2-2 corresponding to the context fetch, it is not necessary to switch the connection.

[Effect of First Embodiment]
When the mobile station 1, which is the communication apparatus according to the present embodiment, switches the connection from the source base station 2-1 to the target base station 2-2, whether or not the target base station 2-2 supports context fetching And transmits a first signal requesting a connection using context information to the target base station 2-2 only when context fetching is supported. Therefore, unnecessary connection time can be prevented by requesting the connection using the context information to the target base station 2-2 which does not support context fetch, and it is possible to shorten the instantaneous disconnection time generated at the time of connection switching. .

Second Embodiment
In this embodiment, when there are a plurality of connectable base stations, the base station to connect to is selected based on communication quality (radio quality), time until discovery, and presence or absence of support for context fetch. The other configurations and processes are similar to those of the first embodiment.

[Description of connection switching]
FIG. 6 is a schematic view of connection switching performed by the mobile station 1 according to the present embodiment. The representation of FIG. 6 is similar to that of FIG. The mobile station 1 which is a communication apparatus according to the present embodiment is configured as a flight apparatus (for example, a drone). In addition to the communication function similar to that of the first embodiment, the mobile station 1 which is a flight device has a function of flying according to a maneuver by a user or along a designated path.

Since the mobile station 1 which is a flight device flies in the sky without a shield, it tends to be able to connect with a plurality of target base stations 2-2. Therefore, in the present embodiment, the mobile station 1 switches the connection by selecting the target base station 2-2 (cell C-2) that can communicate under better conditions among the plurality of target base stations 2-2. The mobile station 1 is not limited to a flight device, and may be a portable terminal such as a smartphone.

[Flow chart of communication method]
FIG. 7 is a diagram showing a flowchart of the communication method according to the present embodiment. In FIG. 7, CF represents context fetch. First, the base station information acquisition unit 111 receives correspondence information indicating that the base station 2 is compatible with context fetch, and stores the correspondence information in the storage unit 13 (S21).

The mobile station 1 starts switching of the connection from the source base station 2-1 to the target base station 2-2, for example, when the communication status with the source base station 2-1 is deteriorated. If switching of connection has not been started (NO in S22), the mobile station 1 returns to step S21 and repeats the process.

When switching of connection is started (YES in S22), the base station information acquisition unit 111 searches for a connectable target base station 2-2 (S23). The base station information acquisition unit 111 acquires the communication quality with the target base station 2-2 found by the search. When the communication quality of the target base station 2-2 satisfies a predetermined condition (for example, the index indicating the communication quality is equal to or more than a predetermined threshold) (YES in S24), the base station determination unit 112 determines the target base station Add 2-2 as a candidate base station to the list (S25). When the communication quality with the target base station 2-2 does not satisfy the predetermined condition (NO in S24), the base station determination unit 112 does not set the target base station 2-2 as a candidate base station.

If the predetermined time has not elapsed since the first search start in step S23 (NO in S26), the mobile station 1 returns to step S23 and repeats the search for the connectable target base station 2-2. With such a configuration, the mobile station 1 can select the connection destination in consideration of the time until finding the target base station 2-2.

When a predetermined time has elapsed from the start of the first search in step S23 (YES in S26), the base station determination unit 112 sorts the candidate base stations in the list in order of communication quality (S27). The base station determination unit 112 uses the sorted list to select candidate base stations in descending order of communication quality. Then, the base station information acquisition unit 111 acquires correspondence information for the selected candidate base station, and the base station determination unit 112 causes the candidate base station to correspond to context fetch (reception of context information) based on the correspondence information. It is determined whether or not (S28).

If the base station determination unit 112 determines in step S28 that the candidate base station supports context fetching (YES in S29), the connection unit 113 generates a first signal requesting connection using context information. And transmits to the target base station 2-2 which is the candidate base station via the communication unit 12 (S30).

When the base station determination unit 112 does not determine that the candidate base station is compatible with context fetching in step S28 and the last candidate base station in the list is not reached (NO in S29, S31 (NO), the mobile station 1 returns to step S28, selects a candidate base station with good communication quality next, and repeats the process.

If the last candidate base station in the list is reached, that is, all the candidate base stations in the list do not correspond to context fetch (YES in S31), the base station determination unit 112 determines that the communication quality is the highest from the list. A good candidate base station is selected (S32). The connection unit 113 transmits, via the communication unit 12, the second signal requesting connection without using context information to the target base station 2-2 which is the candidate base station selected in step S32 (S33).

[Effect of Second Embodiment]
In addition to the same effects as in the first embodiment, the present embodiment can select the connection target target base station 2-2 based on communication quality, time to discovery, and presence or absence of support for context fetching. . Therefore, the mobile station 1 can selectively switch connection to the target base station 2-2 which can communicate under better conditions.

As mentioned above, although the present invention was explained using an embodiment, the technical scope of the present invention is not limited to the range given in the above-mentioned embodiment, and various modification and change are possible within the range of the gist. is there. For example, a specific embodiment of device distribution and integration is not limited to the above embodiment, and all or a part thereof may be functionally or physically distributed and integrated in any unit. Can. In addition, new embodiments produced by any combination of a plurality of embodiments are also included in the embodiments of the present invention. The effects of the new embodiment generated by the combination combine the effects of the original embodiment.

The control unit 11 (processor) of the mobile station 1 is a main body of each step (step) included in the communication method shown in FIGS. That is, the control unit 11 reads a communication program for executing the communication method shown in FIGS. 4, 5 and 7 from the storage unit 13, and executes the communication program to control each unit of the mobile station 1. The communication method shown in 4, 5, 7 is executed.

S communication system 1 mobile station 11 control unit 111 base station information acquisition unit 112 base station determination unit 113 connection unit 2 base station 2-1 source base station 2-2 target base station

Claims

The processor of the mobile station
When switching the connection from the first base station to the second base station, the second base station performs the connection based on correspondence information indicating that the second base station supports reception of context information. A determination step of determining that the reception of the context information is supported;
If it is determined in the determination step that the second base station is capable of receiving the context information, a first signal requesting the second base station to connect using the context information is received. A first sending step to send;
The communication method to perform.
A second signal requesting a connection not using the context information to the second base station when it is not determined in the determination step that the second base station is compatible with reception of the context information The communication method according to claim 1, further comprising: performing a second transmitting step of transmitting
The communication method according to claim 2, wherein the second transmission step transmits RRC Connection Request as the second signal.
If it is possible to switch the connection from the first base station to the plurality of second base stations, the time until the mobile station discovers the second base station and the second base station before the determination step, and Performing a selection step of selecting any one of the plurality of second base stations from the plurality of second base stations based on the communication quality of two base stations;
The communication method according to any one of claims 1 to 3, wherein the determination step determines that the second base station selected in the selection step corresponds to reception of the context information.
The communication method according to any one of claims 1 to 4, wherein the first transmission step transmits RRC Connection Reestablishment Request as the first signal.
The communication method according to any one of claims 1 to 5, further comprising a receiving step of receiving the correspondence information from a base station capable of communicating with the mobile station before the determination step.
The communication method according to claim 6, wherein in the receiving step, the correspondence information received from the plurality of base stations is accumulated and stored.
When switching the connection from the first base station to the second base station, the second base station performs the connection based on correspondence information indicating that the second base station supports reception of context information. A determination unit that determines that the reception of the context information is supported;
When the determination unit determines that the second base station is capable of receiving the context information, the first signal requesting the second base station to connect using the context information is selected. The connection to send,
A communication device having
On the computer
When switching the connection from the first base station to the second base station, the second base station performs the connection based on correspondence information indicating that the second base station supports reception of context information. A determination step of determining that the reception of the context information is supported;
If it is determined in the determination step that the second base station is capable of receiving the context information, a first signal requesting the second base station to connect using the context information is received. A first sending step to send;
Communication program to execute.
A mobile station, a first base station and a second base station, the mobile station comprising
When switching the connection from the first base station to the second base station, the second base based on correspondence information indicating that the second base station supports reception of context information. A determination unit that determines that the station supports reception of the context information;
When the determination unit determines that the second base station is capable of receiving the context information, the first signal requesting the second base station to connect using the context information is selected. The connection to send,
Have
A communication system in which the second base station receives the context information from the first base station when receiving the first signal from the mobile station.