KR100327900B1 - Multicast handoff method of multi-tier cell - Google Patents

Abstract

According to the present invention, a multi-tier cell system may be configured as a higher layer or a lower layer in consideration of the number of cells in a lower layer where the users of a specific multicast group are located and the load of the upper layer and the lower layer. An object of the present invention is to provide a multicast method for handing off a service of a multicast group.

According to the present invention, in a handoff method for a multicast service in a multi-tier cell system, a lower part in which loads of upper and lower layers and users belonging to a multicast group are located There is provided a multicast handoff method in a multi-layer cell system, wherein an inter-layer handoff is performed using the number of cells in the layer.

Description

Multicast handoff method in multi-layer cell system {Multicast handoff method of multi-tier cell}

The present invention relates to a multicast method in a multi-layer cell system, and more particularly, in a multi-layer cell system in consideration of the number of cells in a lower layer where the users of a specific multicast group are located and the load of the upper layer and the lower layer. Or it relates to a multicast method for handing off a service of a specific multicast group to a lower layer.

Mobile communication technology has developed into the first generation analog mobile communication and the second generation digital mobile communication technology. Recently, the research on IMT-2000 service which provides high quality call service with anyone, anywhere, anytime has been conducted by 3GPP (3rd Generation Partnership Project). ) And 3GPP2. The IMT-2000 system adopts a multi-layer cell structure as a basic structure to accommodate high-speed users and provide high quality service to a wide range of regions.

Meanwhile, in order to provide an efficient service in a multi-layer cell, a method of efficiently performing handoff between layers in consideration of mobility and cell capacity has been researched, but handoff considering multicast group service in a handoff study between multi-layer cells There is no research on.

That is, the conventional method is a method of performing a handoff between layers for a general call such as voice and data, and typical methods of considering mobility and capacity between layers are typical.

The inter-layer handoff scheme in consideration of mobility is a method of providing a high-quality service to a high-speed user by measuring / predicting the mobility of the user and handing off the high-speed user to a higher layer.

The method of performing handoff in consideration of capacity between layers performs handoff of a call to a higher layer when the capacity of a lower layer is insufficient. In this scheme, if the capacity of the lower layer cell is sufficient for the call that has performed the handoff to the upper layer, the handoff is performed again to the lower layer if the capacity of the lower layer cell is sufficient, or if it is moved to the neighbor cell by mobility, the hand is transferred to the lower layer cell again. There is a scheme for performing the off.

1 is a diagram illustrating an environment of a multi-layer cell system according to the prior art, wherein the multi-layer cell system is a two-layer cell system in which an upper layer and a lower layer are composed of a macro cell and a micro cell, respectively. to be.

The method of performing the multicast group service only in the macro cell has the advantage of efficiently supporting mobility, but considering the increase in the number of multicast groups in the next generation mobile communication system such as IMT-2000, the capacity of the macro cell This is expected to be lacking. In addition, by using a channel of a macro cell, which is relatively expensive compared to a micro cell, the efficiency of the channel is reduced.

In other words, when the number of multicast groups increases in the future and all multicast services are provided in a macro cell, the macro cell cannot process a general call having high mobility or a call in an area not covered by the micro cell. In particular, even when the number of users belonging to a specific multicast group is small, providing a service in a macro cell causes inefficiency in terms of channel usage by using a channel of a relatively expensive macro cell. In addition, when the multicast group service is provided only in the macro cell, the service cannot be provided when the capacity of the macro cell is insufficient.

In the case of providing a multicast group service only in a microcell, the number of channels for serving a general call in the microcell is reduced because the multicast service must be provided in all microcells in which users belonging to the multicast group are located. Therefore, there is a disadvantage in that the blocking ratio of the call is increased. On the other hand, in the case of providing a multicast service in the micro cell, there is an advantage in that acknowledgment of the service is easy in the reverse direction, and power consumption of the terminal is reduced compared to the macro cell.

Therefore, in consideration of the load and capacity of the micro cell and the macro cell, it is desirable to perform a handoff between the macro cell and the micro cell in the multicast group service. However, the technology for this has not been implemented yet.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and in a multi-layer cell system, taking into account the number of cells in a lower layer where the users of a specific multicast group are located and the load of the higher layer and lower layer Another object is to provide a multicast method for handing off a service of a specific multicast group to a lower layer.

1 is a view showing the environment of a multi-layer cell system according to the prior art,

2 and 3 are flowcharts illustrating a multicast handoff method according to an embodiment of the present invention, FIG. 2 is a flowchart illustrating a method for performing inter-layer handoff from an upper layer to a cell of a lower layer, and FIG. 3 is a lower layer. Is a flowchart illustrating a method for performing inter-layer handoff to a cell of a higher layer in

4 is an exemplary diagram showing an example of a multicast handoff according to an embodiment of the present invention.

According to the present invention for achieving the above object, in the handoff method for a multicast service in a multi-tier cell system, the load and load of the upper layer and lower layer Provided is a multicast handoff method in a multi-layer cell system, wherein an inter-layer handoff is performed using the number of cells of a lower layer in which users belonging to a multicast group are located.

In addition, in a computer-readable recording medium capable of executing a handoff method for a multicast service in a multi-tier cell system, an upper layer has a high load and a lower layer has a high load. A first step of handing off a multicast group having a small number of cells of a lower layer in which users belonging to the same group among multicast groups of a higher layer are located to a lower layer; And a second step of handing off a multicast group having a large number of cells of a lower layer in which users belonging to the same group among the multicast groups of the lower layer, in which the load of the lower layer is high and the load of the upper layer is small, to the upper layer. Provided is a computer readable recording medium capable of executing what is included.

In the following, with reference to the accompanying drawings, a preferred embodiment according to the present invention will be described in detail.

The present invention uses the load and channel capacity of upper layer and lower layer cells, the number of lower layer cells in which users belonging to a multicast group are located, and the threshold value, and the inter-layer multicast handoff between cells of upper layer and lower layer. As a scheme for performing the multicast service, a handoff scheme for efficiently using channels of upper layer and lower layer cells.

2 and 3 are flowcharts illustrating a multicast handoff method according to an embodiment of the present invention, FIG. 2 is a flowchart illustrating a method for performing inter-layer handoff from an upper layer to a cell of a lower layer, and FIG. 3 is a lower layer. Is a flowchart illustrating a method for performing inter-layer handoff to a cell of a higher layer in FIG.

When the upper layer's load (L _upper ) reaches a certain threshold T _{upper_load} (the threshold at which to start _{multicatalytic handoff} from the upper layer to the lower layer), the lower layer where users belonging to a particular multicast group are located When the number of cells M _Si is smaller than the threshold T _down , the multicast group is handed off to cells of a lower layer. In this case, when the load L _{lower_ij} of the cells of the lower layer performing the handoff is greater than a specific threshold value T _{lower_capacity} , the handoff is not performed to the lower layer.

On the other hand, when the load (L _{lower_ij} ) of the lower layer cells is greater than the specific threshold T _{lower_load} , the number of lower layer cells (M _Si ) where the users belonging to a specific multicast group are located is higher than the multicast group having the threshold T _up or more. Perform handoff to the layer. However, if the load of the upper layer is larger than the threshold value T _{upper_capacity} , handoff is not performed.

2 is a flowchart illustrating a method of performing multicast handoff from an upper layer to a lower layer.

First, in step S201, the number of i-th multicast groups is Si, the number of users belonging to Si is Ui, and the number of cells in the lower layer where Ui is located is M _Si , and in step S202, the load of the upper layer L _upper ) _Is greater than or equal to T _{upper_load} .

As a result of the determination in step S202, if the load L _upper of the upper layer is greater than T _{upper_load} , in step S203, in order to determine the necessity of handoff to the lower layer, the lower layer in which users belonging to each multicast group are located. The number of cells of _{Si Si} is examined to determine whether the number of lower layer cells in which users belonging to a specific multicast group are located is smaller than a threshold. That is, it is determined whether M _Si is smaller than T _down .

As a result of the determination in step S203, if M _Si is smaller than T _down , in step S204, it is checked whether load can be accommodated in each cell of a lower layer where users belonging to the multicast group are located to accommodate the multicast group service. To judge. That is, it is determined whether the load L _{lower_ij} of the lower layer is smaller than T _{lower_capacity} for every j from 1 to M _Si .

As a result of the determination in step S204, if the multicast group service can be accommodated, in step S205, a command for performing multicast handoff is instructed to each cell of the lower layer to provide the multicast service to each cell of the lower layer. do.

As a result of the determination in step S204, if the multicast group service cannot be accommodated, in step S206, the service is continued in the upper layer without performing multicast handoff between layers.

On the other hand, when M _Si is larger than T _{down as a} result of the determination in step S203, the process proceeds to step S206.

If the load L _upper of the upper layer is smaller than T _{upper_load as a} result of the determination in step S202, the flow proceeds to step S206.

3 is a flowchart illustrating a method of performing multicast handoff from a lower layer to a higher layer, which will be described in detail as follows.

First, in step S301, the number of i-th multicast groups is set to Si, the number of users belonging to Si is Ui, and the number of cells of a lower layer in which Ui is located is M _Si . In step S302, the multicast service is set to lower layers. It is determined whether the load L _{lower_ij} of the providing cell is greater than T _{lower_load} . At this time, j is 1 or more and M _Si or less.

As a result of the determination in step S302, if the load L _{lower_ij} of the upper layer is greater than T _{lower_load,} it is determined in step S303 whether the load of the cell of the lower layer where the user belonging to the multicast service group is located is very large. That is, it is determined whether L _{lower_ij} is greater than T _{lower_load2} . At this time, T _{lower_load2} ≫ T _{lower_load} .

As a result of the determination in step S303, if the load of the cell of the lower layer where the user belonging to the multicast service group is not very large, in step S304 it is determined whether the number of cells of the lower layer where the user belonging to the multicast service group is located is large. To judge. That is, it is determined whether M _Si is larger than T _up (preset value).

As a result of the determination in step S304, if the number of cells in the lower layer where the user belonging to the multicast service group is located is large, in step S305, it is determined whether the multicast group service can be accommodated in the higher layer. That is, it is determined whether L _{upper_ij} is smaller than T _{upper_capacity} .

As a result of the determination in step S305, if the upper layer can accommodate the multicast group service, in step S306, regardless of the number of micro cells in which the users belonging to the multicast group are located, all the multicast groups in the cell are transferred to the higher layer. Hand off.

As a result of the determination in step S305, if the multicast group service cannot be accepted in the upper layer, in step S307, the multicast service is provided in the lower layer without performing handoff to the upper layer.

On the other hand, if the number of cells of the lower layer where the user belonging to the multicast service group is located is small as a result of the determination in step S304, the flow proceeds to step S307.

As a result of the determination in step S303, if the load of the cell of the lower layer where the user belonging to the multicast service group is located is very large, the flow proceeds to step S305.

If the load L _{lower_ij} of the upper layer is smaller than T _{lower_load as a} result of the determination in step S302, the flow advances to step S307.

4 is an exemplary diagram showing an example of multicast handoff according to an embodiment of the present invention, in which Case1 and Case 2 perform handoff from a lower layer to a higher layer and a case of performing a handoff from a higher layer to a lower layer. Representative examples in the case of performing each are shown.

Case 1 is a case where the number of micro cells in which a user of a specific multicast group is located exceeds a threshold value T _up because a new user requests a multicast group service. At this time, if a macro cell can accommodate a specific multicast group, inter-layer multicast handoff is performed to the macro cell.

Case 2 is a case where a user of a specific multicast group terminates the service while providing a multicast service in a macro cell, so that the number of microcells in which a specific multicast group user is located is smaller than a threshold value T _down . In this case, when each user can accommodate the multicast service in the microcells in which the user is located, the microcells are handed off to the multicast group.

The present invention as described above is recorded on a computer-readable recording medium, and can be processed by a computer.

As described in detail above, the present invention is a method of performing a handoff of a multicast service between layers, and can provide a service to a larger number of users as compared to a method of providing a multicast service only in an upper layer or a lower layer. As a result, the channel efficiency can be increased.

That is, the multicast service is handed off to the cells of the lower layer even when the upper layer cell is overloaded, compared to the method of providing the multicast service only in the upper layer, thereby reducing the load of the upper layer cell and thus increasing the number of users. There is an effect that can provide a service.

In addition, by performing a multicast handoff from a lower layer to a higher layer, the channel shortage of the lower layer cells generated by providing multicast service in each lower layer cells for the same multicast group can be reduced and the channel can be efficiently There is an effect that can be used.

Therefore, there is an advantage in that the channel can be efficiently used in various environments in a multi-layer cell system.

In addition, by providing a multicast service by an upper layer cell or a lower layer cell, there is an advantage that power consumption of the terminal can be reduced as compared with the case where the multicast service is provided only by an upper layer (an existing macro cell).

The technical spirit of the present invention has been described above with reference to the accompanying drawings, but this is by way of example only and not by way of limitation to the present invention. In addition, it is obvious that any person with ordinary skill in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (10)

In a handoff method for a multicast service in a multi-tier cell system, Multicast handoff method in a multi-layer cell system, characterized in that inter-layer handoff is performed using loads of upper layers and lower layers and the number of cells of lower layers in which users belonging to the multicast group are located. . The method of claim 1, When the load of the upper layer is high and the load of the lower layer is small, handing off the multicast group to the lower layer, the multicast group having a small number of cells of the lower layer in which users belonging to the same group among the multicast groups of the upper layer are located Multicast Handoff Method in Multi-Layer Cell Systems. The method of claim 2, A method of multicast handoff in a multi-layer cell system, characterized by using location information of users of each multicast group and the number of cells of lower layers in which users belonging to each multicast group are located. The method of claim 3, wherein If the number of cells in the lower layer where the users belonging to each group is smaller than a predetermined threshold, the multicast handoff method in the multi-layer cell system, characterized in that performing the inter-layer handoff to the lower layer. . The method of claim 4, wherein The threshold value is determined dynamically according to the load of the upper layer and the lower layer, the type of the multicast group, and the distribution of users belonging to the multicast group. The method of claim 1, When the load of the lower layer is high and the load of the upper layer is low, the multicast group having a large number of cells of the lower layer in which users belonging to the same group among the multicast groups of the lower layer are located is handed off to the upper layer. Multicast Handoff Method in Multi-Layer Cell Systems. The method of claim 6, A method of multicast handoff in a multi-layer cell system, characterized by using location information of users of each multicast group and the number of cells of lower layers in which users belonging to each multicast group are located. The method of claim 7, wherein If the number of cells of the lower layer in which the users belonging to each group is greater than a predetermined threshold, the inter-layer handoff to the upper layer performs a multicast handoff method in a multi-layer cell system. The method of claim 8, The threshold value is determined dynamically according to the load of the upper layer and the lower layer, the type of the multicast group, and the distribution of users belonging to the multicast group. A computer-readable recording medium capable of executing a handoff method for a multicast service in a multi-tier cell system, A first step of handing off a multicast group to a lower layer if the number of cells of the lower layer in which users belonging to the same group among the multicast groups of the upper layer are located is high; And If the load of the lower layer is high and the load of the upper layer is small, the second step of handing off the multicast group to the upper layer where the number of cells in the lower layer in which users belonging to the same group among the multicast groups in the lower layer are located is higher. A computer readable recording medium capable of carrying out what has been done, including.