JP2004088502A - Exchange and method for controlling congestion of exchange - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exchange and a switching center congestion controlling method capable of suitably controlling congestion in the exchange even when the exchange is extremely frequently transited between a congested state and a non-congested state by regulating communication with mobile stations at optimum probability in accordance with a congestion level. <P>SOLUTION: The probability of congestion control, i.e. a communication rejection rate, is changed in accordance with the congestion level. For instance, data transmission is rejected at 25% probability in 1st congestion of a low congestion level and data transmission is rejected at 100% probability in 4th congestion of a higher congestion level. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exchange and an exchange congestion control method, and more particularly to an exchange that restricts communication to mobile stations during congestion and an exchange congestion control method.
[0002]
[Prior art]
Conventionally, when a switching station becomes congested, a signal indicating that congestion is occurring is returned to a data signal from the mobile station. In FIG. 5, in a communication system including the mobile station MS and the exchange 1, a layer access procedure for digital mobile channel (LAPDM) is used for layer 2 of OSI (open system interconnection). An example is shown. As shown in FIG. 1A, an I frame is transmitted from the mobile station MS to the exchange 1 to transfer information. FIG. 2B shows a state of communication between the mobile station MS and the exchange 1 when the exchange 1 is congested in the same system. When the exchange 1 becomes congested, the switching center 1 sets the “own reception busy state” in the own station busy state flag of the LAPDM procedure control referred to for performing the communication procedure control. Thereafter, when the mobile station MS sends an I frame to the switching station 1, the switching station 1 returns an RNR (Receive Not Ready) indicating congestion to all the mobile stations MS-1 to MS-4. . As a result, the communication processing load of the exchange 1 is reduced, and congestion control of the exchange is performed.
[0003]
[Problems to be solved by the invention]
As described above, when congestion occurs, the exchange notifies all mobile stations of a signal indicating that congestion is occurring, regardless of the degree of congestion, that is, regardless of the congestion level. Also, when there is no congestion, the I-frame is received without notifying any mobile station of such a signal. That is, a two-stage control method is used such as "notify" all mobile stations or "not notify" all mobile stations. When such a control method is used, for example, when the congestion level is low, the congestion state recovers immediately, and the congestion level recovery time greatly changes depending on the congestion level. For this reason, depending on the state of the communication network, for example, when a low-level congestion state continues, a phenomenon that transitions between the congestion state and the non-congestion state very frequently may occur. In such a case, since the communication control must be frequently switched, there is a possibility that a load higher than usual is applied to the exchange.
[0004]
An object of the present invention is to regulate communication with a mobile station at an optimal probability according to a congestion level, so that congestion control can be appropriately performed even when transitioning between a congestion state and a non-congestion state is performed very frequently. It is to provide a possible switching center and a switching center congestion control method.
[0005]
[Means for Solving the Problems]
An exchange according to claim 1 of the present invention is an exchange that controls the congestion by suppressing the communication processing load by rejecting data transmission from a communication terminal performed at the time of congestion,
The communication device is characterized in that the communication device further comprises a restriction means for restricting the communication while increasing or decreasing the communication rejection rate for rejecting data transmission from the communication terminal stepwise according to the increase or decrease of the congestion level.
[0006]
In this way, by rejecting individual data transmission with a specific probability, it is possible to suppress the overall rate of communication processing simultaneously involved in the exchange, reduce the load, and reduce congestion. . At this time, according to the congestion level, by performing multi-stage congestion control, it is possible to perform appropriate congestion control without inducing a state where the conventional congestion state and non-congestion state frequently transition. Can be. Also, by controlling congestion with a high probability when the congestion level is high and with a low probability when the congestion level is low, congestion control can be performed with an optimum probability according to the congestion level. Furthermore, according to the time change of the congestion level, by switching to the communication refusal rate at any time according to the congestion level, it is possible to prevent a sudden change in the processing load and to minimize the number of regulated communications. it can.
[0007]
According to a second aspect of the present invention, in the first aspect, the switching unit according to the first aspect, wherein the regulation unit refers to a communication rejection rate correspondence table in which a correspondence relationship between the congestion level and the communication rejection rate is determined. The communication rejection rate is specified based on the congestion level at the time of data transmission, and the communication is regulated according to the communication rejection rate.
In addition, other than the communication rejection rate correspondence table, for example, a method of deriving the communication rejection rate using a function of the congestion level value may be used.
[0008]
The switching station according to claim 3 of the present invention is the switching station according to claim 1 or 2, wherein the restricting unit is configured to control a first data transmission from the same mobile station with respect to retransmission of data from the same mobile station during congestion. The restriction is performed according to the result of the restriction performed on the data transmission.
The switching center congestion control method according to claim 4 of the present invention suppresses the load of communication processing by rejecting data transmission from a communication terminal to the switching center when the switching station is congested, thereby reducing the congestion. An exchange congestion control method for controlling,
The method further comprises a regulation step of regulating the communication while increasing / decreasing a communication rejection rate for rejecting data transmission from the communication terminal stepwise according to an increase / decrease of the congestion level.
[0009]
In the switching station congestion control method according to claim 5 of the present invention, in claim 4, in the restricting step, by referring to a communication rejection rate correspondence table in which a correspondence between a congestion level and a communication rejection rate is determined in advance, The communication rejection rate is specified based on the congestion level at the time of data transmission from the communication terminal, and the communication is regulated according to the communication rejection rate.
[0010]
The switching station congestion control method according to claim 6 of the present invention is the switching station congestion control method according to claim 4 or 5, wherein in the restricting step, the same mobile station is not transmitted again from the same mobile station during congestion. The restriction is performed according to the result of the restriction performed on the first data transmission from.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. In each of the drawings referred to in the following description, parts equivalent to those in other drawings are indicated by the same reference numerals.
FIG. 1 shows a state of congestion control realized by the switching center congestion control system according to the present embodiment. As shown in FIG. 1, the switching center congestion control system includes a mobile station MS and a switching center 1. In the figure, the congestion state of the exchange 1 is represented as first to fourth congestion in ascending order of the level. FIG. 2A shows a state where 25% regulation is performed in the first congestion state. In FIG. 1A, an I frame for transferring information is transmitted from each of the four mobile stations MS-1 to MS-4. Of these, the RNR is returned only for the I frame transmitted from one mobile station MS-1, and data transmission is rejected. That is, as a result of restricting each mobile station MS at a communication rejection rate of 25%, the mobile stations MS corresponding to 25% of the entire mobile stations MS that have transmitted data are rejected from communicating. FIG. 2B shows that 50% regulation is performed in the second congestion state. As a result of restricting each mobile station MS with a 50% communication rejection rate, data transmission is performed. The mobile stations MS, which account for 50% of the total mobile stations MS, have been refused data transmission. Similarly, FIG. 3C shows that the mobile station MS is regulated at a communication rejection rate of 75% in the third congestion state, and FIG. 4D shows each mobile station MS in the fourth congestion state. A state is shown in which the station MS is regulated at a communication rejection rate of 100%. That is, when the congestion level is low, the RNR is returned with a low probability, and when the congestion level is high, the RNR is returned with a high probability.
[0012]
Next, the configuration of the exchange used in the present embodiment will be described with reference to FIG. As shown in FIG. 1, the exchange 1 includes a receiving unit 1a, a determining unit 1b, a data holding unit 1c, and a regulating unit 1d.
The receiving unit 1a is connected to the mobile station and receives a signal from the mobile station.
The determination unit 1b has a function of determining whether to reject data transmission from a mobile station. In the present embodiment, the communication rejection rate corresponding to the congestion level in the exchange 1 is specified by referring to the communication rejection rate correspondence table held in the data holding unit 1c, and the data is rewritten at the specified communication rejection rate. It is determined whether to reject the transmission. This determination is, for example, a random number generating means for generating a random number, a table in which a random number provided for each communication refusal rate such as rejecting communication when the random number value is an odd number and a determination result, This is performed using
[0013]
The data holding unit 1c holds data necessary for regulation, in this embodiment, a communication rejection rate correspondence table and a regulation determination result table.
The restricting unit 1d receives the result of the determination by the determining unit 1b, and transmits a signal of rejection of communication to the mobile station when the rejection of communication is determined.
Next, a communication sequence in the switching center congestion control system and a specific operation of the switching center will be described with reference to FIG. 3 and FIG.
[0014]
In step S101 in FIG. 3, an I frame is transmitted from the mobile station MS-1 to the exchange.
In step S102 of the figure, the exchange determines whether or not to reject the communication request. Here, since the exchange is currently congested and the congestion level is “2”, the exchange specifies the communication rejection rate based on the communication rejection rate correspondence table 2. In the figure, the communication rejection rate is specified as “50%”. Then, according to the probability of “50%”, it is determined whether or not to reject data reception by using, for example, a random number as described above. In the figure, the result of the determination is "restriction", that is, the determination of data transmission refusal is made. This determination result is recorded in the regulation determination result table 3. As shown in the figure, the determination result table 3 holds the correspondence between the mobile station and the result of the determination performed on the mobile station. As information for identifying a mobile station, information that can be obtained by the exchange when data is transmitted from the mobile station, for example, a telephone number of the mobile station or a mobile station number assigned to each mobile station is used.
[0015]
In step S103, based on the determination result in step S102, the RNR is returned to mobile station MS-1, and data transmission is rejected.
In step S104, this time, an I frame is transmitted from the mobile station MS-2 to the exchange.
In step S105, similarly to step S102, it is determined whether to reject the data transmission based on the reception of the I frame. In the figure, it is determined not to reject data transmission. Therefore, data transmission from the mobile station MS-2 is permitted. Regarding this determination result, “OK” is recorded in the regulation determination result table 3.
[0016]
In step S106, data transmission is performed from the mobile station MS-3.
In step S107, similarly to the above, a determination is made as to whether or not to reject the data transmission, a determination is made that data transmission is permitted, and the determination result is recorded.
In step S108, an I frame is transmitted from the mobile station MS-4, a determination is made on the data transmission (step S109), and the determination result is recorded. In step S110, based on the result of the determination in step S109, an RNR signal is returned, and data transmission from mobile station MS-4 is rejected.
[0017]
As described above, in the state of the congestion level “2”, the data transmission from each of the mobile stations MS-1 to MS-4 is restricted at the communication rejection rate of 50%, and as a result, the mobile stations MS-1 and MS-4 -4 has been rejected.
FIG. 4 shows a communication sequence after the restriction by the communication rejection rate determined in FIG. 3 and an operation flow of the exchange.
[0018]
In step S201 of FIG. 4, the I-frame is transmitted again from the mobile station MS-1 which has been once subject to regulation during the congestion of FIG. 3 and whose communication has been rejected. Here, the exchange refers to the regulation determination result table 3 to check whether data transmission from the mobile station MS-1 has been performed during congestion. In FIG. 4, since it is found that data transmission has already been performed during the congestion and that the data transmission has been rejected, the RNR signal is also returned for the data transmission in step S201 and the reception is rejected according to the result. .
[0019]
Thereby, it is possible to maintain the determination result in FIG. 3 and perform regulation according to the regulation result performed once during the congestion. That is, it is possible to prevent a determination from being made repeatedly and repeatedly for one communication, and to reject or maintain the communication at a predetermined communication rejection rate. In addition, by maintaining the determination result for the mobile station in this way, it is possible to perform regulation quickly and with a low processing load without performing a determination process every time an I frame is transmitted.
[0020]
Similarly, even after step S203, if data transmission is permitted once with reference to the regulation determination result table 3, data transmission from the mobile stations MS-2 and MS-3 is permitted. (Steps S203, S204), an I frame is received. If the mobile station MS-4 transmits an I frame (step S205), the mobile station MS-4 returns the RNR (step S206).
[0021]
As a result, only the communication from the mobile stations MS-2 and MS-3 is finally permitted, and the rate of rejected communication can be maintained at a rate corresponding to the congestion level.
[0022]
【The invention's effect】
As described in detail above, according to the switching center according to claim 1 of the present invention and the switching station congestion control method according to claim 4, the conventional congestion state and non-congestion state frequently occur. Appropriate congestion control can be performed without incurring a transition state. Furthermore, if the communication rejection rate is switched in accordance with the temporal change of the congestion level, the seamless congestion control that prevents a sudden change in the processing load, and the efficient number of restricted communications is minimized It can provide communication services.
[0023]
According to the switching center according to claim 2 of the present invention and the switching center congestion control method according to claim 5, by using the communication rejection rate correspondence table, for example, by the congestion level at the time of data transmission, By specifying an appropriate communication rejection rate, the communication can be restricted. Incidentally, the congestion level is not limited to the congestion level at the time of the data transmission, for example, by a communication rejection rate corresponding to the congestion level at the beginning of the congestion, even if it regulates data transmission until the congestion is reduced Good. However, as described above, by switching the communication rejection rate to a corresponding appropriate communication rejection rate according to the time change of the congestion level, more seamless congestion control and the like can be performed.
[0024]
According to the switching center according to the third aspect of the present invention and the switching center congestion control method according to the sixth aspect, it is possible to prevent a determination from being made repeatedly and repeatedly for one communication. The communication can be rejected or maintained at a predetermined communication rejection rate. In addition, by maintaining the determination result for the mobile station in this way, it is possible to perform the regulation quickly and with a low processing load without performing the determination process every time data is transmitted.
[Brief description of the drawings]
FIG. 1A is a diagram illustrating a state of congestion control in a first congestion state in the switching center congestion control system according to the present embodiment, and FIG. 1B is a diagram illustrating congestion control in a second congestion state; (C) is a diagram illustrating the state of congestion control in the third congestion state, and (D) is a diagram illustrating the state of congestion control in the fourth congestion state.
FIG. 2 is a block diagram illustrating a configuration of an exchange according to the embodiment;
FIG. 3 is a diagram for explaining a communication sequence of rejecting communication at a communication rejection rate according to a congestion level in the switching center congestion control system according to the present embodiment.
FIG. 4 is a diagram illustrating a communication sequence for rejecting communication while maintaining a communication rejection rate during congestion in the switching center congestion control system according to the present embodiment.
FIG. 5A is a diagram illustrating a state in which a switching station is in a non-congested state in a communication system including a mobile station and a switching station, and FIG. 5B is a diagram illustrating a conventional switching station congestion control; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exchange 1a Receiving part 1b Judgment part 1c Data holding part 1d Restriction part 2 Communication rejection rate correspondence table 3 Restriction judgment result table MS Mobile station

Claims (6)

By rejecting data transmission from the communication terminal made at the time of congestion, an exchange that controls the congestion by suppressing the load of communication processing,
An exchange having a restriction means for restricting the communication while increasing / decreasing a communication rejection rate for rejecting data transmission from a communication terminal stepwise according to an increase / decrease in a congestion level. The restricting means specifies a communication rejection rate based on the congestion level at the time of data transmission from the communication terminal by referring to a predetermined communication rejection rate correspondence table for the correspondence between the congestion level and the communication rejection rate. The exchange according to claim 1, wherein the communication is regulated in accordance with the communication refusal rate. The restricting means is characterized in that, for retransmission of data from the same mobile station during congestion, the restriction is performed according to a restriction result performed on the first data transmission from the same mobile station. The exchange according to claim 1. At the time of congestion of the exchange, the exchange congestion control method for controlling the congestion by suppressing the communication processing load by rejecting data transmission made to the exchange from the communication terminal,
A congestion control method for an exchange, comprising a regulation step of regulating the communication while gradually increasing or decreasing a communication rejection rate for rejecting data transmission from a communication terminal according to an increase or decrease in a congestion level. In the regulating step, the communication rejection rate is specified based on the congestion level at the time of data transmission from the communication terminal by referring to a communication rejection rate correspondence table in which the correspondence between the congestion level and the communication rejection rate is predetermined. 5. The switching center congestion control method according to claim 4, wherein said communication is regulated in accordance with said communication rejection rate. In the restricting step, for re-transmission of data from the same mobile station during congestion, restricting is performed according to a restriction result performed on the first data transmission from the same mobile station. The switching center congestion control method according to claim 4.

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