JP2001217769A - Radio base station selecting method, multicast method, radio base station and radio terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utility efficiency of radio resources by reducing the number of radio base stations for transmitting the same information to radio terminals. SOLUTION: First, radio terminals (a) are connected to a radio base station A as a multicast group G1. In such a state, a radio terminal b tries to be newly participated in the same group G1 (A). In this case, the radio terminal b exists at a position connectable to radio base stations A and B. The radio terminal banalyzes the announce signal of a perch channel transmitted by each of radio base stations and knows the radio base station A is under services to the multicast group G1. The radio terminal b selects the radio base station A and receivers multicast information under services (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radio base station selection method, a multicast method, a radio base station, and a radio terminal.

[0002]

2. Description of the Related Art The concept of assuming an IP (Internet Protocol) network as an access backbone network has been widespread.

As a multicast protocol that can be realized on an IP network, IGMP (Internet
t Group Management Protocol
ol). IGMP is a protocol for determining whether or not a router sends multicast information to a subnetwork in order to avoid network congestion. IG
As an access communication system connected to a network supporting MP, it is preferable to use an access control flow compatible with IGMP.

In IGMP, in order to avoid sending unnecessary information to a subnet, a packet of a group address not existing in the subnet is not multicast.

[0005] Even in a wireless access system that supports multicasting, unnecessary information is prevented from being sent into a subnet, thereby saving wireless resources.

However, at different routers A and B,
If the same group exists, each of the routers A and B multicasts the group to the respective subnet. Similarly, when the same group exists in different wireless base stations, it is easy to perform multicasting for the group in each service area and perform an operation similar to a router.

In a radio communication system in which a plurality of radio base stations cover a service area, it is common practice that the service areas of the radio base stations overlap. In a situation where service areas overlap and a plurality of wireless base stations to which a wireless terminal can connect exist, the wireless terminal is generally connected to a wireless base station with the best communication quality.

FIG. 10 shows this state. Wireless base station A
Is 1 and the service area of the radio base station B is 2.

[0009] In FIG. 1A, a radio terminal a is connected to a radio base station A. The wireless terminal b can be connected to both the wireless base station A and the wireless base station B.

[0010] However, since the wireless terminal b is located closer to the wireless base station B than the wireless base station A, the wireless terminal b connects to the wireless base station B and receives a service in expectation of improved reception quality. Will be.

[0011] When the service area 4 of the radio base station A exists within the service area 3 of the radio base station B, as shown in FIG.
And the wireless base station B, but can be connected to the wireless base station A having the best communication quality.

In FIG. 10 (A), even if the wireless terminal b belongs to the same IGMP group (group GI) as the wireless terminal a and receives the same information, the wireless terminal b has a wireless reception quality. Since the base station was selected, the wireless terminal a was connected to the wireless base station A, and the wireless base station A transmitted the same information as the information received by the wireless terminal b to the wireless terminal a.

However, when the radio base station B is in the service area 2
If there is no wireless terminal belonging to the same group other than the wireless terminal b in the area, the wireless terminal b changes the connection to the wireless base station A, and the wireless base station B
Is stopped, and the bandwidth required for transmission of the group G1 can be used for other services.

Further, even when the service area 4 of the radio base station A exists within the service area 3 of the radio base station B as shown in FIG.
Since the communication is most advantageous in terms of quality, the wireless terminal a is connected to the wireless base station A, and the wireless base station A transmits the same information as the information received by the wireless terminal c.

However, since the wireless terminal a is located in an area where the wireless terminal a can communicate with the wireless base station B, if the wireless terminal a receives service from the wireless base station B, the wireless resources of the wireless base station A can be saved.

In the prior art, in the case of a multicast service in which wireless terminals connected to different wireless base stations belong to the same group and receive the same information, the same information is transmitted to each wireless base station. There are cases where transmission is performed at the same time.

In such a case, for the overlapping area,
Since the same information is transmitted, the radio resource is used twice, and the utilization efficiency of the radio resource is reduced.

The present invention has been made in view of the above problems, and has as its object to reduce the number of radio base stations that transmit the same information to radio terminals, and to increase the use efficiency of radio resources. .

[0018]

According to the first aspect of the present invention, there is provided a wireless base station selecting method in which a wireless terminal selects a wireless base station for performing multicasting, wherein the wireless terminal includes a plurality of wireless base stations. When the same multicast information can be received from the wireless terminal, the wireless terminal selects a wireless base station so as to reduce the number of wireless base stations transmitting the same information.

According to a second aspect of the present invention, in the wireless base station selecting method according to the first aspect, the wireless base station is connectable to the wireless terminal, and transmits multicast information to be received by the wireless terminal. When there is a transmitting radio base station, the radio terminal selects this radio base station as a connection destination.

According to a third aspect of the present invention, there is provided the radio base station selecting method according to the first aspect, wherein the radio terminal is a radio base station connectable to the radio terminal, and transmits multicast information to be received by the radio terminal. A wireless base station having the largest number of connected wireless terminals when the selected wireless base station is selected from a plurality of transmitting wireless base stations is selected as a connection destination.

According to a fourth aspect of the present invention, a wireless base station selected by the wireless base station selecting method according to any one of the first to third aspects performs multicasting.

According to a fifth aspect of the present invention, there is provided a wireless base station which performs multicasting on a wireless terminal, based on selection by the wireless terminal such that the number of wireless base stations transmitting the same information is reduced. Multicast is performed to the wireless terminal.

According to a sixth aspect of the present invention, in a radio base station that multicasts to a radio terminal, the radio base station counts down by receiving a leaving message from the radio terminal, and counts down by receiving a participation message from the radio terminal. The wireless terminal is provided with a counter that increases, and the value of the counter is transmitted to the wireless terminal.

According to a seventh aspect of the present invention, in the wireless base station according to the sixth aspect, when the counter value is changed, the changed value of the counter is transmitted to the wireless terminal. I do.

According to an eighth aspect of the present invention, in the wireless base station according to the sixth or seventh aspect, when the counter value becomes 0, multicasting is stopped.

According to a ninth aspect of the present invention, in a wireless terminal that receives a multicast service from a wireless base station that performs multicasting, an analysis unit that analyzes a control message from the wireless base station, and a wireless participant in a multicast service group A comparing unit for comparing the number of terminals,
The analysis unit detects the number of participating wireless terminals of a service group from a control message from the wireless base station, and the comparing unit compares the number of participating wireless terminals for each service group, thereby transmitting the same information. The wireless base station is selected so as to reduce the number.

Note that the selection naturally includes the selection accompanying the movement of the wireless terminal.

[0028]

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

An embodiment of the present invention relating to new participation in multicast will be described with reference to FIG.

The service area of the radio base station A is 1, and the service area of the radio base station B is 2.

FIG. 1A shows a state before the wireless terminal b has joined, and FIG. 1B shows a state in which the wireless terminal b has joined according to the embodiment of the present invention.

First, a wireless terminal a is connected to a wireless base station A as a multicast group G1. In this state, the wireless terminal b newly tries to join the same group G1 (A).

The radio terminal b is located at a position where it can be connected to the radio base stations A and B.

In this case, conventionally, the radio terminal b measures the quality of signals from both radio base stations, and selects the radio base station that provides the best quality. However, in the present invention, the broadcast signal of the perch channel transmitted by the wireless base station is analyzed, and the wireless base station A determines that the multicast group G1
Know that it is in service. The wireless terminal b
Select the radio base station A already in service, and select the radio base station A
(B).

Thus, the radio base station B is in the group G1
It is not necessary to transmit a multicast to, and radio resources can be allocated to other services.

Next, an embodiment of the present invention relating to switching of a radio base station during a multicast service will be described with reference to FIG. The service area of the wireless base station A is 1,
The service area of the radio base station B is 2.

FIG. 2A shows a state before the radio terminal b switches the radio base station, and FIG. 2B shows a state where the radio terminal b changes the radio base station according to the embodiment of the present invention. The state has been switched.

In FIG. 2, a radio terminal a is connected to a radio base station A,
It is assumed that the wireless terminals b and c are connected to the wireless base station B, and each wireless terminal receives the service of the same multicast group G1 (A).

Here, when the wireless terminal c moves and leaves the service area of the wireless base station B, only the wireless terminal b becomes G
1 multicast service. The wireless terminal b is a wireless terminal that can be connected to both the wireless base stations A and B. Therefore, the wireless terminal b switches connection to the wireless base station A and receives the service. As a result, the radio base station B can suspend the service for the group G1, and use the suspended radio resource for another service.

An embodiment relating to a multicast service in an overlapping service area will be described with reference to FIG.

FIG. 3 shows a case where the radio base station B has the service area 3
This is the case where the service area 4 of the wireless base station A exists in the area to be described, and the service areas overlap.

FIG. 3A shows a state before the wireless terminal a switches the wireless base station, and FIG. 3B shows a state where the wireless terminal a establishes the wireless base station according to the embodiment of the present invention. The state has been switched.

First, it is assumed that the wireless terminal a is connected to the wireless base station A and belongs to the multicast group G1 and is receiving a service (A).

Next, the wireless terminal c is connected to the wireless base station B and joins the group G1. In such a situation, both the wireless base station A and the wireless base station B transmit the same information.

This embodiment avoids this. Note that, as described later, the wireless base station transmits the number of wireless terminals transmitting by the wireless base station to the wireless terminals by a perch channel for each multicast group.

The wireless terminal a can be connected to both the wireless base stations A and B. Therefore, the wireless terminal a detects the number of wireless terminals transmitting at each wireless base station from the perch channels of both wireless base stations.

The wireless terminal a compares the number of connected wireless terminals for each multicast group transmitted by the wireless base stations A and B. At this time, since the wireless base station A has only the wireless terminal a, the number of connected wireless terminals is one. In the wireless base station B, the number of connected wireless terminals is one because the wireless terminal b is already connected, but the number of connected wireless terminals increases to two when the wireless terminal a participates.

In this case, the wireless terminal a operates to change the connection to the wireless base station B and increase the number of connected wireless terminals. As a result, for the group G1, the radio base station B
Only transmit (B).

Next, a description will be given of how the number of wireless terminals transmitting at the wireless base station is notified to the wireless terminals for each multicast group.

Each radio base station needs to know that the radio terminal no longer receives its service due to movement or that only one radio terminal remains in the service area. Also, the wireless terminal needs to know that only the user receives the service of the group G1.

For this reason, when the wireless terminal wants to receive the service, it sends a participation message to the wireless base station, and when leaving the group, it sends a leaving message. The radio base station counts up or down the number of radio terminals currently receiving service for each group each time it receives the join and leave messages.

The result of the count is reflected in the notification message of the perch channel, and is notified to the wireless terminal.

The wireless terminal that can receive this broadcast message and connect to a plurality of wireless base stations compares the number of wireless terminals in service and changes the connection to the larger one as described with reference to FIG.

The radio base station stops the multicast service for the group in which the radio terminals to receive the service are no longer available.

Transmission and reception of a wireless terminal can be performed by a conventional control message transmission method such as message transmission by random access and allocation of a dedicated control channel.

FIGS. 4 and 5 show the processing procedure on the radio base station side by joining and leaving.

As shown in FIG. 4, when a wireless terminal wants to join a multicast group, it sends a join message to the wireless base station. The wireless base station receives the participation message (S11).

In the radio base station receiving the participation message, the counter counts up (S1).
2). At the same time, the content of the number of participating wireless terminals in the notification message is updated (S13), and the notification message is transmitted (S1).
4).

As shown in FIG. 5, when leaving from the participating group, a leaving message is transmitted to the radio base station. The wireless base station receives the leaving message (S21). The received wireless base station counts down the counter (S22) and recognizes a decrease in the number of wireless terminals participating in the group. At the same time, the content of the number of participating wireless terminals in the notification message is updated (S23). When the counter value becomes 0 as a result of the countdown (S24: YE
S), the absence of the wireless terminal participating in the group is notified to the scheduler in charge of wireless resource assignment and the like (S25), and the scheduler stops the assignment of the wireless resource assigned to the group and transmits the information. It stops (S26). After that, update the notification message,
A notification that the wireless terminal participating in the group is 0 or a notification message in which information on the group has been deleted is transmitted (S27).

If the counter value is not 0 (S24:
NO), a notification message is transmitted (S27).

FIG. 6 shows a processing procedure on the wireless terminal side upon participation.

In FIGS. 6 and 7, it is assumed that a radio terminal to which radio base station A and radio base station B can be connected.

As shown in FIG. 6, a radio terminal desiring to join a certain group first receives a broadcast message from neighboring radio base stations A and B (S31), and receives the broadcast message in the desired group. Then, the number of wireless terminals participating in is compared (S32). If there is no information on the group, it is interpreted that the number of wireless terminals is zero. For example, if the number of wireless terminals of the wireless base station A is larger, the wireless base station A is assigned to (S3
3) If the number of wireless terminals of the wireless base station B is larger, a join message is transmitted to the wireless base station B (S34), and the multicast service of the group is received (S34, S3).
6).

A case where a wireless terminal receiving a service from the wireless base station B switches to the wireless base station A will be described with reference to FIG.

The wireless terminal receiving the service from the wireless base station B (S41) intermittently receives notification messages from a plurality of nearby wireless base stations. Since the radio base stations A and B are connectable, the radio terminal knows the number of radio terminals receiving the service from the perch channel broadcast messages from the radio base stations A and B. The number of participating wireless terminals of the wireless base station A and the wireless base station B is compared (S42). If the number of wireless terminals participating in the group is greater for the wireless base station A than for the wireless base station B (S42:
YES), and sends a leaving message to B (S4).
3) Connect to A and send a join message (S4)
4). Thereby, the service of the multicast group A is received (S45).

If the wireless base station B has a larger number of participating wireless terminals in the group (S42: NO), the wireless base station is not switched.

In the case where the wireless terminal simply leaves, the wireless terminal only needs to transmit a leave message to the wireless base station.

FIG. 8 shows an example of the configuration of a wireless base station according to the present invention.

The receiving unit 10 of the radio base station receives control messages such as joining and leaving in addition to receiving information.
The message analysis unit 11 extracts the participation / withdrawal message and notifies the counter 12 of the message. The counter 12 counts up or down according to the notified content, and notifies the notification message creation unit 13 when the counter value is changed. Further, when the count value becomes 0, it notifies the radio resource scheduler 14 and stops the allocation of radio resources. If there is a request from a wireless terminal that wants to join a new group, that is, if the counter value is changed from 0 to 1, it is notified to the wireless resource scheduler 14 and the wireless resources for the new group are allocated. The assignment and the multicast information are transmitted from the transmission unit 15. The transmitting unit 15 transmits the message created by the notification message creating unit 13.

FIG. 9 shows an example of the configuration of a wireless terminal.

The receiving unit 20 receives a control message such as a broadcast message in addition to the information. The message analyzer 21 extracts the broadcast message and analyzes the number of participating wireless terminals in the service group. When a notification message is received from a plurality of wireless base stations, the comparing unit 22 compares the number of participating wireless terminals and determines whether to change the connection destination wireless base station. When changing the connection destination, the joining / leaving message creating unit 23 and the wireless base station switching processing unit 2
Notify 4. If you do not need to change the connected wireless base station,
No particular processing is performed. Participation / withdrawal message creation unit 23
Then, in accordance with the content notified from the comparing unit 22, a message is created to send a leave message to the connected wireless base station and a join message to the connection destination. In addition, the notification of the transmission destination is transmitted to the transmission unit 25 together with the transmission message. The transmitting unit transmits these pieces of information. The radio base station switching processing unit 24 sets a state in which a participation message can be transmitted to the connection destination radio base station in accordance with a procedure necessary for the system, such as synchronization with the connection destination radio base station.

[0072]

According to the present invention as described above, the following various effects can be obtained.

According to the present invention, in a multicast service situation in which wireless terminals connected to different wireless base stations belong to the same group and receive the same information, the wireless terminal serving the same information to the wireless terminals is provided. The number of base stations can be reduced.

As a result, the radio resources are less frequently allocated to the same information, and the radio resources can be effectively used, and the overall system capacity can be improved.

[0075]

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of new participation in multicast.

FIG. 2 is a diagram for describing an embodiment relating to wireless base station switching during a multicast service.

FIG. 3 is a diagram for describing an embodiment relating to a multicast service in an overlapping service area.

FIG. 4 is a diagram showing a processing procedure of a wireless base station in participation of a wireless terminal.

FIG. 5 is a diagram showing a processing procedure of a wireless base station when a wireless terminal leaves.

FIG. 6 is a diagram illustrating a processing procedure of the wireless terminal in the participation of the wireless terminal.

FIG. 7 is a diagram illustrating a processing procedure of a wireless terminal in switching a wireless base station.

FIG. 8 is a diagram illustrating a device configuration example of a wireless base station according to the present invention.

FIG. 9 is a diagram illustrating a device configuration example of a wireless terminal according to the present invention.

FIG. 10 is a diagram showing a conventional technique.

[Explanation of symbols]

 1-4 Service area of wireless base station 10, 20 receiving unit 11 message analyzing unit 12 counter 13 broadcast message creating unit 14 wireless resource scheduler 15, 25 transmitting unit 21 analyzing unit 22 comparing unit 23 joining / leaving message creating unit 24 Wireless base station switching processing unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Narumi Umeda Inventor NTT Mobile Communication Network Co., Ltd. 2-1-1 Toranomon, Minato-ku, Tokyo (72) Inventor Isao Shimada Port of Tokyo, Japan 2-10-1, Toranomon-ku, NTT F-term (reference) in NTT Mobile Communication Network Co., Ltd. JJ12 KK56

Claims (9)

[Claims] 1. A wireless base station selecting method in which a wireless terminal selects a wireless base station to perform multicasting, wherein the wireless terminal can receive the same multicast information from a plurality of wireless base stations. A radio base station selecting method, wherein radio base stations are selected so as to reduce the number of radio base stations transmitting the same information. 2. The radio base station selection method according to claim 1, wherein there is a radio base station connectable to the radio terminal, wherein the radio base station is transmitting multicast information that the radio terminal intends to receive. In this case, the wireless terminal selects the wireless base station as a connection destination. 3. The radio base station selecting method according to claim 1, wherein the radio base station is connectable to the radio terminal, and the radio base station is transmitting multicast information to be received by the radio terminal. A radio base station selecting method, wherein a radio base station having the largest number of connected radio terminals when the radio base station is selected is selected as a connection destination. 4. A multicasting method, wherein the wireless base station selected by the wireless base station selecting method according to claim 1 performs multicasting. 5. A wireless base station that performs multicasting to wireless terminals, such that the number of wireless base stations transmitting the same information is reduced.
A wireless base station that performs multicasting to the wireless terminal based on selection by the wireless terminal. 6. A radio base station that performs multicasting to a radio terminal, comprising: a counter that counts down when a leaving message is received from the radio terminal, and counts up when a participation message is received from the radio terminal. A wireless base station transmitting a counter value to the wireless terminal. 7. The radio base station according to claim 6, wherein when the counter value is changed, the changed counter value is transmitted to the radio terminal. 8. The radio base station according to claim 6, wherein the multicast is stopped when the counter value becomes zero. 9. A wireless terminal receiving a multicast service from a wireless base station performing multicast, an analyzing unit for analyzing a control message from the wireless base station, and a comparing unit comparing the number of participating wireless terminals in a multicast service group. The analysis unit detects the number of participating wireless terminals of a service group from a control message from the wireless base station, and the comparing unit compares the number of participating wireless terminals for each service group, thereby transmitting the same information. A radio base station that selects radio base stations so as to reduce the number of radio base stations to perform.