JP2003244218A - Call reception control method for changing assignment of priority class and node device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a call reception control method for receiving a call even when it is judged that any new call is not received in a conventional method. <P>SOLUTION: In this priority control system for assigning a priority class according to the request quantity of each call, and for realizing different quality for each priority class in a packet transfer type multi-media communication network, when any call to start new communication is present, whether the reception of the new call is valid or invalid is judged by a call reception control method. The quantity of each class when the new call is added is estimated, and when it is judged that the quality of a certain class does not satisfy the request quality of the call assigned to the class, the class of the call whose request quality is low among all the calls assigned to the class is re-assigned to the lower priority class so that the quality of the class can be improved, and that the reception of the new class can be made valid. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to call admission control in a packet transfer type multimedia communication network, and more particularly to a technique capable of guaranteeing the quality of all connected calls and newly connected calls.

[0002]

2. Description of the Related Art In a packet transfer type communication network represented by an IP network, a so-called best effort type service in which a transmission band of communication that can be used by each call is not guaranteed has become mainstream. In the best-effort service, the transmission bandwidth is shared by all calls, so if the number of calls that are connected at the same time is small, the available bandwidth per call becomes large, but on the contrary, the calls that are connected at the same time are large. If the number of calls is large, the available bandwidth per call becomes small, so it cannot be said that it is stable in terms of communication quality, but the bandwidth for each call is typified by the telephone network. Compared with the circuit switching type communication network that is fixedly allocated, the transmission band can be effectively used, and as a result, the communication fee can be reduced.

However, with the rise of Internet communication, calls handled in a packet transfer type communication network do not require real-time characteristics unlike the conventional simple data transfer. There are increasing demands for different quality requirements, such as those requiring real-time processing and those requiring security represented by credit card numbers for online shopping.

In order to cope with such a situation, in a recent packet transfer type communication network, a priority class corresponding to the required quality is assigned to each call, and each node in the network responds to the priority class. A method of differentiating quality by controlling has been adopted.

FIG. 1 illustrates a transfer packet of a call to which a priority class is assigned and control according to the priority class in a node. The node devices 100 installed in the network include buffer devices 121, 122, .... The call transfer packet 201 to which the priority class 1 is assigned is accommodated in the buffer device 121 corresponding to the priority 1, and the call packets 202 and 203 to which the priority class 2 is assigned are
Each packet is accommodated in the buffer device of the corresponding priority according to the assigned priority class, such as being accommodated in the buffer device 122 corresponding to the priority level 2. The packet reading device 111 reads a packet from each buffer according to the priority and transfers the packet to the physical line 301. The order in which the packet reading device 111 reads the packets is, for example, that all packets with a high priority class are always read before packets with a low priority class, or one packet with a low priority class has several high priority classes. The quality is changed for each priority class by reading it. Since the number of priorities assigned within the node device 100 is limited, and the number of calls that can be simultaneously connected is generally larger, the quality realized by the buffer device corresponding to each priority class is appropriate. It is necessary to meet the strictest quality requirement value of the calls assigned the priority to

In the communication network using the priority control method as described above, it is possible to differentiate the quality according to the type of call. For example, by increasing the priority of an application that transfers video, It is possible to shorten the delay time of intra-network transfer as compared with a file transfer service that handles a large amount of data with low priority. However, the quality differentiation in this scheme is relative, and when the number of connected calls becomes very large,
Even if the call is assigned the priority class 1 having the highest priority, the original required quality is not always protected.

In order to avoid such a situation, it is necessary to protect the quality of the already connected calls by limiting the number of calls that are connected at the same time. This method is generally called a call admission control method and has often been used in conventional circuit switching networks and ATM (asynchronous transfer mode) networks. 2 and 3
Shows the state of call admission control at the node. The call admission control device 131 installed in the node device 100
When a request to start communication of a new call 211 is made, first, based on the required quality of the new call 211 and the packet quality for each priority class assigned in the node device 100, a new call 211 is set. Determine the priority class assigned. Next, the call admission control device 131 receives a packet of priority class 1 accommodated in the buffer device 121, a packet of priority class 2 accommodated in the buffer device 122, ...
Estimates the quality that will be achieved after accepting a new call 211. If it can be determined that the quality of each priority class packet satisfies all the required quality of the call to which the corresponding priority is assigned, the communication of a new call 211 is permitted, but the packet of a certain priority class is accepted. When it is determined that the quality estimation value cannot satisfy the required quality of the call to which the priority is assigned, the communication of the new call 211 is rejected. As a result, the quality of the calls 201, 201, 203, ...

[0008] As a matter to be noted regarding this method,
For example, in the call 211 for requesting a new communication start, the priority class 1
When a packet is assigned (Fig. 2), not only the packet of priority class 1 but also the packets of other priority classes may change, so it is necessary to estimate the quality of other priority classes. Is mentioned. Therefore, if it is determined that the quality of packets of a certain priority class is not satisfied, new calls will not be accepted and the accommodation efficiency will be improved no matter how good the quality of packets of all other priority classes is. There is a problem that it may not exist.

[0009]

An object of the present invention is to determine the priority assigned to each call when it is judged that a new call cannot be accepted by the above-mentioned call admission control method in the packet transfer network. It is to provide a new call admission control method capable of admitting a new call by reviewing, and consequently improving the accommodation efficiency at the node, and a node device implementing the method.

[0010]

In order to achieve this object, in a packet transfer type multimedia communication network,
In a priority control method that assigns priority classes according to the required quality of each call and realizes different qualities for each priority class, when there is a call to start a new communication, it is judged whether a new call can be accepted. The call admission control method of the present invention estimates the quality for each class when a new call is added, and when it is determined that the quality of a certain class cannot satisfy the required quality of the call assigned to that class. , Of all calls assigned to that class, by reassigning the class of the call with a looser required quality to a lower priority class, improve the quality of the class and enable the acceptance of new calls. Is characterized by.

Further, in the packet transfer type multimedia communication network, the node device of the present invention newly assigns priority classes according to the required quality of each call and executes priority control for realizing different quality for each priority class. A call admission control device that determines whether or not a new call can be admitted when there is a call to start communication, and the admission control device estimates the quality for each class when a new call is added. , If it is judged that the quality of a certain class cannot meet the required quality of the calls assigned to that class, then the class of the call with a looser required quality is set to be lower among all the calls assigned to that class. By reassigning to a priority class, the quality of the class is improved and a new call can be accepted.

[0012]

According to the conventional call admission control method, when the quality of each class cannot satisfy the call request, it is necessary to immediately reject the admission of a new call. Changing the priority class assigned to will increase the likelihood that new calls will be accepted.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention extends a conventional call admission control method and allows a call admission control method to accept a call even when it is judged that a new call cannot be accepted by the conventional method. The call admission control procedure according to the present invention will be described with reference to the node device shown in FIG. 2 and the flow chart shown in FIG. First, when a communication start request for a new call 211 is generated in the priority control node device 100 as shown in FIG. 2, the call admission control device 131 starts the call admission control in the start step 400, and in the first step 401, The priority class assigned to the new call 211 is determined from the required quality condition of the new call 211. Next, in a second step 402, quality is estimated for all priority classes realized in the node assuming that a new call has been accepted. In the third step 403, it is determined whether the quality for each class estimated in the second step 402 can satisfy the required quality of each call already in communication with the new call. If it is determined that the required quality of all the calls is satisfied, the acceptance of the new call 211 is permitted in the ending step 407, and the call admission control procedure is ended. If not, proceed to the next fourth step 404.

In the fourth step 404, the class to which the call whose quality is not satisfied is assigned is specified. When there are a plurality of applicable classes, the class (j) having the highest priority is targeted. In the fifth step 405, the fourth
Of the class identified in step 404 of step 404. If the class is the lowest priority class realized in the node, the process proceeds to end step 408 and it is determined that quality cannot be improved. Then, the acceptance of the new call 211 is rejected and the call admission control procedure is ended. If not, proceed to the next sixth step 406.

In the sixth step 406, the call with the least required quality is selected from the calls assigned to the class identified in the fourth step, and the class of the call is assigned a class with a priority one step lower ( Reassign to j + 1).
This improves the quality of this class by reducing the number of calls assigned to the class identified in the fourth step. On the other hand, for the class with low priority, the call originally assigned to the class with high priority is
Since this class is newly added, the quality to be satisfied by this class becomes more stringent according to the required quality of the call. As the quality in each class changes in this way,
To re-estimate the quality, return to the second step. The above procedure is repeated until it is finally determined whether to accept the new call 211.

Next, the call admission control method will be described more specifically. It is assumed that there are n calls that communicate via the node and that all the calls are numbered in ascending order regarding the delay time that the node can tolerate. That is, the required quality of the _first call is ω ₁ , the required quality of the _second call is ω ₂ , ...
.., _where ω _n is the required quality of the _nth call, ω ₁ ≤ω ₂ ≤
It is assumed that ≦ ω _n holds. Each call is classified into k priority classes on the node, calls 1 to n (1) are class 1, and calls n (1) +1 to n (1) + n (2). Is a class 2, ..., n (1) + ... + n (k-1) +1 to n (1) + ... + n (k) = n calls are assigned to class k Suppose Therefore, the quality of class 1 needs to satisfy ω ₁ , the quality of class 2 needs to satisfy ω _{n (1) +1} , and the quality of class k needs to satisfy ω _{n ( 1) + ... + n (k-1) +1} .

Now, suppose that the n + 1-th new call makes a communication start request to the node. First, for the new call quality requirement ω _{n + 1} , ω _{n (1) + ... + n (i-1) +1} ≤ω
_i that satisfies _{n + 1} ≤ ω _{n (1) + ... + n (i) +1} is obtained.
At this time, the required quality of class i is the required quality ω of the new call.
_{Since it} is stricter than _{n + 1 and} the required quality of class i + 1 is less than ω _{n + 1} , the new call is classified into class i (first step 401).

Next, the quality W ₁ of class ₁ , the quality W ₂ of class ₂ , and the class k when a call of number n + 1 is added
The quality W _k is estimated (second step 402), and whether the required quality for each class is satisfied, that is, (S ₁ ) W ₁ ≦ ω ₁ (S ₂ ) W ₂ ≦ ω _{n (1) +1} ... It is confirmed whether (S _k ) W _k ≤ω _{n (1) + ... + n (k-1) +1} holds (third step 403).
If (S ₁ ) to (S _k ) are all satisfied, it can be determined that there is no quality problem even if a new call is accepted, and thus the new call can be accepted and the call acceptance control procedure can be ended.

Now, consider the case where the quality is not satisfied for a certain class j, that is, (S _k ) W _j > ω _{n (1) + ... + n (j-1) +1} (step 4). . If j = k, that is, if it is determined that the quality is not satisfactory for the class with the lowest priority (fifth step 405), the quality problem cannot be solved, so a new call is rejected. The call admission control procedure ends. In other cases, the call from n (1) + ... + n (j-1) +1 to n (1) + ... + n (j) assigned to class j is the most The priority of the call of the number n (1) + ... + n (j) whose requirement quality is loose is changed and assigned to the class j + 1 (sixth step 406). As a result, the amount of communication assigned to class j decreases, and as a result, quality improvement can be expected. On the other hand, since the communication amount assigned to the class j + 1 increases, the quality may deteriorate as a result. Furthermore,
Regarding the required quality, so far, n (1) + ... + n (j)
Ω, which is the required quality of the + 1st call
_It suffices if _{n (1) + ... + n (j) +1} is satisfied, but in the future, the demanded quality of call n (1) + ... + n (j), ω _{n (1) + ... + n (j)} must be satisfied. Therefore, the quality of each class is estimated using the combination of the new class assignment and the required quality, and it is determined whether a new call can be accepted. If all of (S ₁ ) to (S _k ) can be finally satisfied by repeating this procedure, it can be determined that there is no problem in quality, so a new call is accepted and call admission control is performed. The procedure ends, but if not, the quality problem cannot be solved, so the new call is rejected and the call admission control procedure ends.

Although the procedure of the call admission control method of the present invention has been described above, these procedures can be executed by the computer included in the call admission control apparatus in the node device.
The present invention also includes a computer program for executing such a call admission control procedure and a recording medium recording the computer program within the scope of the present invention.

In implementing the above call admission control method, the quality estimation for each class in the second step can be performed based on the average delay time in the node as described above, but the delay fluctuation in the node It can also be done based on time or packet loss rate at the node.

[0022]

According to the conventional call admission control method, the above-mentioned third method is used.
If the quality of each class could not satisfy the call request in the step, it was necessary to immediately reject the acceptance of the new call.However, by using the proposed method, the priority class assigned to the call can be changed. , There is an increased likelihood that new calls will be accepted. This means that, from the viewpoint of the user requesting communication, the probability that the start of communication is rejected is reduced and the serviceability is improved, and from the viewpoint of the network operator side, the requested quality is This means that the efficiency of use of communication equipment can be improved by increasing the number of calls that can simultaneously communicate while satisfying.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a node device that realizes priority control.

FIG. 2 is a diagram showing a node device that realizes priority control and has a call admission control function.

FIG. 3 is a flowchart showing a conventional call admission control procedure.

FIG. 4 is a flowchart showing a call admission control procedure according to the present invention.

[Explanation of symbols]

100 node device 121, 122, ... Buffer device 111 Packet reading device 131 Call admission control device 201, 202, 203, ... 211 packets 301 physical line

Claims (10)

[Claims] 1. In a packet transfer type multimedia communication network, a call to newly start communication in a priority control method in which a priority class is assigned according to the required quality of each call and a different quality is realized for each priority class. Is a call admission control method that determines whether a new call can be admitted, and the quality of each class when a new call is added is estimated, and the quality of a certain class is assigned to that class. If it is determined that the required quality of the call cannot be satisfied, of all the calls assigned to that class,
A call admission control method that reassigns a class of a call having a low required quality to a lower priority class to improve the quality of the class and to admit a new call. 2. The call admission control method according to claim 1, wherein the average delay time at the node is estimated as the quality of each class. 3. The call admission control method according to claim 1, wherein the delay fluctuation time at the node is estimated as the quality of each class. 4. The call admission control method according to claim 1, wherein the packet loss rate at the node is estimated as the quality of each class. 5. A node device according to the present invention, which assigns a priority class according to a required quality of each call in a packet transfer type multimedia communication network and executes priority control for realizing different quality for each priority class, When there is a call to start a new communication, a call admission control device that determines whether or not to accept a new call is provided, and the admission control device determines the quality for each class when a new call is added. If it is estimated that the quality of a class cannot satisfy the required quality of calls assigned to that class,
Of all the calls assigned to that class, by reassigning the class of a call with a looser required quality to a lower priority class, it is possible to improve the quality of the class and to accept new calls. A characteristic node device. 6. The node device according to claim 5, wherein the call admission control device estimates the average delay time at the node as the quality of each class. 7. The node device according to claim 5, wherein the call admission control device estimates the delay fluctuation time at the node as the quality of each class. 8. The node device according to claim 5, wherein the call admission control device estimates the packet loss rate at the node as the quality of each class. 9. In a packet transfer type multimedia communication network, a node device according to the present invention is newly provided for assigning a priority class according to a required quality of each call and executing priority control for realizing different quality for each priority class. When there is a call to start communication, a computer that constitutes a call admission control device that determines whether or not to accept a new call, a step of estimating the quality for each class when a new call is added, If it is determined that the quality of a class cannot meet the required quality of calls assigned to that class, the class of calls with lesser quality of all the calls assigned to that class is given lower priority. A computer program that causes the steps of reassigning to a class to be performed. 10. A computer-readable recording medium in which the computer program according to claim 9 is recorded.