JPH0832624A - Link establishment system for layer two levels - Google Patents

Abstract

PURPOSE:To provide the link establishment system of a layer two levels, which can establish a data link in short time and can avoid communication impossibility, by permitting one of two exchanges for establishing the link to be set at a self address in a different state. CONSTITUTION:The transmission/reception control part 3 of the exchange 10 transmits a command frame that a frame forming part 2 generates from a transmission/reception part 1 and monitors a response by a response waiting timer time limit value calculated by the self station node number of a self station node number setting part 6 in a time limit arithmetic setting part 4. When the transmission/reception part 1 does not receive a response frame within the time limit value, the command frame is retransmitted from the transmission/ reception part 1. When the retransmission counter of the transmission/reception control part 3 counts the number of times of the retransmission of the command frame and the count value exceeds the set number of times of retransmission calculated by the self station node number of the self station node number setting part 6 in a retransmission frequency arithmetic setting part 5, the transmission/reception control part 3 switches the self address.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a layer 2 level link establishing system for establishing a data link between exchanges in a mobile communication network having moving exchanges, and particularly when a frame having the same own address collides. The present invention relates to a layer 2 level link establishment method for guaranteeing the establishment of a link.

[0002]

BACKGROUND OF THE INVENTION In a mobile communication network which is currently composed of a packet network, a packet-based data link control procedure is adopted for communication between exchanges. That is, when establishing a layer-2 level data link by the OSI (Open System Interconnection) basic reference model, the exchange sends a SABM command and then receives a UA response in accordance with a packet-based data link control procedure. Confirming link establishment. The own address is inserted from each exchange into the frames of the SABM command and the UA response.

Since the exchange also moves within the mobile communication network, as shown in FIG.
And the exchange 20 having its own address 3 establish a data link and are communicating with each other, the exchange 20 moves away and leaves its own address 1
The exchange 30 may move and approach. In this state, the exchange 10 needs to reconnect the link with the exchange 20 to the link with the exchange 30. in this case,
Either the exchange 10 or the exchange 30 switches its own address 1 to its own address 3 to establish a data link.

[0004]

2. Description of the Related Art Conventionally, in this type of layer 2 level link establishing system, as shown in FIG. 6, a transmission / reception control unit 43 provided in a switch 40 transmits / receives a command frame created by a frame forming unit 42. 41, the response frame for this command is transmitted and received within the time limit value preset in the time limit value setting unit 44.
If not received, the command frame is retransmitted from the transmission / reception unit 41. When the number of times the command frame is retransmitted exceeds the number of times set in the retransmission number setting unit 45, the transmission / reception control unit 43 switches its own address.

Next, referring to FIG. 7, exchanges 40, 50
The data link establishment sequence when the response waiting time limit value t and the number of retransmissions 2 are set will be described. As shown in the figure, the exchanges 40 and 5 both having their own address 1 set.
0 is the own address 1 for establishing the link at the layer 2 level after the flag synchronization is established between the exchanges 40 and 50.
The frame a of the SABM command in which is inserted is transmitted.
Since the exchanges 40 and 50 read the own address 1 from the received frame a, they are discarded as invalid frames. Therefore, in the exchanges 40 and 50, the transmitted SAB
The response to the M command cannot be received, and the time limit value t of the response waiting time is exceeded. Exchanges 40, 50
Waits for a response, and when the time limit value t is reached, retransmits the frame a. In this state, the exchanges 40 and 50 retransmit again, and after two predetermined retransmissions, switch the own address 1 to the own address 3 and insert the own address 3 into the frame of the SABM command. b is being transmitted.

[0006]

In the conventional layer 2 level link establishment method described above, there is no response to the transmitted SABM command and the command frame is retransmitted as a result of the occurrence of the response waiting time limit value t exceeding the time limit value. ing. When this retransmission exceeds the predetermined number of times, the own address is switched, and the SABM command frame in which the switched own address is inserted is transmitted. In this configuration, command frames that are transmitted after flag synchronization has been established between the two exchanges occur at substantially the same time, so there is a problem in that a link cannot be established and communication cannot be established.

[0007]

According to the layer 2 level link establishment method of the present invention, when a data link between exchanges is established in a mobile communication network having a moving exchange, the exchange transmits a predetermined command. In the layer 2 level link establishment method in which the own address is changed and the command is transmitted when the predetermined monitoring time limit until the reception of a predetermined response is exceeded, each exchange has different monitoring time limit values. have.

The monitoring time limit value is calculated and set by using the own station unique number assigned to each exchange, and the own station unique number is uniquely assigned within the mobile communication network. The node number.

Further, a response waiting time limit value of a response responding to the transmitted command and the number of resends of the command are set, and the monitoring time limit value retransmits the command when the response waiting time limit value is reached, In a state where the number of times of the retransmission reaches the time when the predetermined number of times is reached, the response waiting time limit value is a time limit value obtained by multiplying the own station unique number by a predetermined constant, and The predetermined number of times is set by the odd / even number of the own station unique number.

[0010]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The exchange 10 shown in FIG. 1 includes a time limit value calculation setting unit 4 for calculating and setting a response waiting time limit value, a retransmission number calculation setting unit 5 for calculating and setting the number of retransmissions, and each exchange in the mobile communication network. This is different from FIG. 5 in that a local station node number setting unit 6 that stores the local station node number set uniquely for each as a local station unique number is provided.

As shown in the figure, the transmission / reception control unit 3 provided in the exchange 10 transmits a command frame created by the frame forming unit 2 from the transmission / reception unit 1 and then sends a response frame for this command to the time limit value of the response waiting timer. Are being monitored by. This time limit value is set by the time limit value calculation setting unit 4
When the transmitting / receiving unit 1 does not receive the response frame within the time limit value, the command frame is retransmitted from the transmitting / receiving unit 1 when the transmitting / receiving unit 1 does not receive the response frame within the time limit value. The number of retransmissions of this command frame is counted by the retransmission counter of the transmission / reception control unit 3. When the count value of the number of retransmissions exceeds the number of retransmissions set calculated by the own node number set in the own node number setting unit 6 in the number of retransmissions calculation setting unit 5, the transmission / reception control unit 3 sets the own address. Are switching.

Next, with reference to FIG. 2A together with FIG. 1, the procedure for setting the time limit value of the time limit value calculation setting unit 4 will be described.
The time value calculation setting unit 4 reads the own node number set in the own node number setting unit 6 (procedure 11), multiplies this own node number by 100 (procedure 12), and waits for this calculated value as a response. The time limit value is set (step 13) and stored.

Next, the procedure for setting the number of retransmissions by the retransmission number calculation setting unit 5 will be described with reference to FIG. The retransmission number calculation setting unit 5 reads the own node number set in the own node number setting unit 6 (procedure 21), investigates this own node number (procedure 22), and determines the number of retransmissions as
If the own node number is an even number, set it to once (procedure 23)
However, in the case of an odd number, it can be set twice (step 24).

Next, referring also to FIG. 1 and FIG.
A data link setting procedure by transmitting the M command will be described.

First, under the control of the transmission / reception control unit 3 in the exchange 10, the transmission / reception unit 1 transmits the frame of the SABM command created by the frame formation unit 2 (procedure 101). The transmission / reception control unit 3 activates the response waiting timer according to the time limit value set in the time period value calculation setting unit 4 (step 102), and when the time limit value of the response waiting timer is exceeded (YES in step 103), the transmission counter The count is added (procedure 104).
Here, the count value of the retransmission counter exceeds the retransmission setting number set in the retransmission number calculation setting unit 5 (YE in step 105).
In the case of S), the transmission / reception control unit 3 changes the own address (procedure 106), instructs the frame forming unit 2 to create a frame of the SABM command with the new self address, and proceeds to procedure 101. If “NO” in step 105, the procedure proceeds to step 107.

In step 103, when the transmitter / receiver 1 receives the U frame without exceeding the time limit (step 111), the transmission / reception controller 3 analyzes the address of the received frame (step 11).
2) If this address is not your own address (procedure 1
(NO of 13), it is determined that the regular response frame is received. When this response is a UA response (YES in step 104), the transmission / reception control unit 3 resets the count value of the retransmission counter to zero (step 115) and also resets the count value of the response waiting timer to zero (step 116), The establishment of the data link (procedure 117) is completed.

If the own address (YES) in step 113, it is considered that the command frame is received, and the received frame is discarded (step 121). In step 114, UA
In the case of other than the response (NO), the normal processing (procedure 122) corresponding to the received response is performed.

Next, the procedure for establishing the data link between the exchanges 10 and 30 will be described with reference to FIG. 2 and the sequence chart of FIG. First, exchange 1
For example, “10” is assigned to 0 as the local node number, and “13” is assigned to the exchange 30 as the local node number. In this case, as shown in FIG. 2 (A), the exchange 10 has the time limit value t1 of the response waiting timer,
For example, if the unit is ms, 1000 (10 × 100)
The time limit value t2 of the response waiting timer is set to 1300 (13 × 100) ms in the exchange 30. As the number of times retransmission is set by the retransmission counter, as shown in FIG.
Is set once, and the number of times retransmission is set is set twice for the exchange 30 having the local node number "13".

As shown in FIG. 3, the exchanges 10, 30
After the flag synchronization is established between both exchanges 10 and 30,
In order to establish the link at the layer 2 level, the SABM command frame a in which the own address 1 is inserted is transmitted. The exchanges 10 and 30 receive their own address 1 from the received frame a.
Is read out, it is discarded as an invalid frame as shown in steps 113 and 121 of FIG. Therefore, in the exchanges 10 and 30, there is no response to the transmitted SABM command, and the time limit values exceed the time limit values t1 and t2. As a result of exceeding the time limit value, the exchanges 10 and 30 retransmit the frame a.

As shown in FIG. 2 (B), "1" is set as the number of times retransmission is set in the exchange 10, so that the exchange 10 is set to the next response waiting timer as shown in FIG. When the time limit value is exceeded after the time limit value t1 elapses, the own address 1 is switched to the own address 3, and the SABM command frame b in which the own address 3 is inserted is transmitted. Exchange 30
During this period, since the number of times the time limit has been exceeded due to the elapse of the time limit value t2 of the response waiting timer has not reached the retransmission setting number 2, the frame a is transmitted with the own address 1. At this point, the exchanges 10 and 30 already have different own addresses 1 and 3, respectively.

As a result, the exchange 30 judges that the frame b received from the exchange 10 is a normal SABM command, and returns the frame c of the UA response to the exchange 10. The exchange 10 also processes the frame a received from the exchange 30 after switching to the own address 3 as a normal SABM command, and returns the frame d of the UA response to the exchange 30. The exchange 10 exchanges the frame c with the exchange 3
0 normally receives and confirms the data link establishment with the exchange 30, and the exchange 30 normally receives the frame d from the exchange 10 and confirms the data link establishment with the exchange 10.

In the above description, the response waiting time limit value is calculated by the own station node number, and the retransmission setting number is set by the odd / even number of the own station node number, but it is predetermined within the same communication network. It may be calculated or set by the own station unique number set for each exchange. Further, although the number of times of retransmission setting is set by the odd / even number of the node number of the own station, it may be set by calculation by the unique number of the own station. A simple method is preferable as the arithmetic expressions for the response waiting time limit value and the number of times retransmission is set. Further, although it has been described that the response waiting time limit value and the number of times of retransmission are set in advance, they may be calculated and set each time when the numerical value excess judgment is made in step 103 or step 105.

As described above, the functional blocks and procedures illustrated and described above are examples, and the arrangement, order, etc. are not limited to the above description as long as the above-described functions are satisfied.

[0025]

As described above, according to the present invention, when a data link between exchanges is established in a mobile communication network having a moving exchange, a predetermined response is received in response to the transmission of a predetermined command. When the predetermined monitoring time limit values up to are exceeded, each exchange sends a command with its own address changed and is also given its own unique number. The exchange obtains a different monitoring time limit value for each exchange using this own station unique number. With this configuration, of the two exchanges having the same own address for establishing the data link, the exchange having the shorter monitoring time limit value can switch the own address first. Therefore, the two exchanges that are trying to establish the data link have different addresses and can obtain a normal UA response to the transmission of the SABM command, so that the data link can be established in a short time and communication failure can be avoided. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flow chart showing an embodiment of the main part of FIG.

FIG. 3 is a flow chart illustrating an embodiment according to FIG.

FIG. 4 is a sequence chart showing an embodiment according to FIG.

FIG. 5 is a switch layout showing an example of a mobile communication network.

FIG. 6 is a block diagram showing a conventional example.

7 is a sequence chart showing an example according to FIG.

[Explanation of symbols]

 1 Transmitter / Receiver 2 Frame Former 3 Transmitter / Receiver 4 Timed Value Calculation Setting Unit 5 Retransmission Number Calculation Setting Unit 6 Own Node Number Setting Unit 10, 30 Switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04Q 7/24 7/26 7/30 H04Q 7/04 A

Claims (5)

[Claims] 1. When establishing a data link between exchanges in a mobile communication network having moving exchanges, the exchanges are
In the layer 2 level link establishment method in which the own address is changed and the command is sent when a predetermined monitoring time limit until a predetermined response is received in response to the transmission of a predetermined command is exceeded, A layer 2 level link establishment method having different monitoring time values. 2. The monitoring time limit value according to claim 1,
A layer 2 level link establishment method characterized in that it is calculated and set using its own unique number assigned to each exchange. 3. The layer 2 level link establishing system according to claim 2, wherein the own station unique number is a own station node number uniquely assigned in the mobile communication network. 4. The response waiting time limit value of a response in response to a transmitted command according to claim 2, and the number of retransmissions of the command are set, and the monitoring time limit value is set when the response waiting time limit value is reached. It is configured by the time until the command is retransmitted and the number of times of the retransmission reaches a predetermined number, and the response waiting time limit value is a time limit value obtained by multiplying the own station unique number by a predetermined constant. Layer 2 level link establishment method. 5. The response waiting time limit value for a response in response to a transmitted command and the number of retransmissions of the command are set according to claim 2, and the monitoring time limit value is set when the response waiting time limit value is reached. Layer 2 characterized by comprising the time until the command is retransmitted and the number of retransmissions reaches a predetermined number, and the predetermined number of retransmissions is set by the odd / even number of the own station unique number. Level link establishment method.