KR0171022B1 - Routing method for high speed hand-off treatment - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a routing method for fast handoff processing under a multi-layer cell structure. When handing off to a cell), the present invention relates to a routing method for quickly and effectively handling call connections between two different cells.

Description

Routing Method for Fast Handoff Processing in Multi-Layer Cell Structures

1 is an exemplary diagram for explaining a general model of a mobile communication cell structure composed of multi-layer fine.

2 is an exemplary diagram illustrating a connection form (tree structure) between different layer cells in a multi-layer cell structure.

3 is a configuration diagram of a mobile communication system composed of multi-layer cells.

4 is a flowchart illustrating a routing method for call connection between different layer cells in a multi-layer cell structure.

5 is a diagram illustrating an example of routing when an originating mobile terminal is handed off from a cell (a serving cell) that is currently being serviced to a cell (target cell) to be newly connected, through an exchange network.

* Explanation of symbols for main parts of the drawings

11,21,31: Upper layer 12,22,32: Middle layer

13,23,33: lower layer 20: multilayer base station area

24: Network

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a routing method for fast handoff processing under a multi-layer cell structure, and more particularly to a layer cell (serving cell) currently serving by a mobile terminal in a mobile communication system having a multi-layered hierarchical cellular structure. In the case of handoff to a newly connected hierarchical cell (target cell), the present invention relates to a routing method for quickly and effectively processing call connection between two different cells.

In a mobile communication network, whenever a handoff occurs, a new link connection procedure between a serving cell and a target cell is required. This connection process should be done so quickly that subscribers can reduce call loss due to handoff and do not notice the communication loss. As a solution to this problem, a dynamic channel allocation scheme and a method for quickly realizing a call connection using an ATM switched access scheme in an abnormal stage of a switching center have been proposed while giving priority to a handoff call. However, there is no specific plan for the link connection process (routing) in a multi-layer cell structure in which a link configuration for connecting various types of cells is complicated and frequent handoff may occur. In addition, in a multi-layer hierarchical cell structure that passes through multiple nodes (base stations) and links (communication communication paths between base stations), communication disruption may occur due to traffic congestion or failure on some nodes or links during connection with a target cell. There was this. Unlike the fixed communication network, the link connection process dynamically changes the link configuration. Therefore, the link connection between cells due to handoff has a fundamentally different characteristic.

Accordingly, an object of the present invention is to provide a routing method for quickly and effectively handling call connection between two different cells when a mobile terminal hands off from a serving cell to a target cell in a mobile communication system having a multi-cell structure. The technical feature of the present invention for achieving the above object is that the HO-WX for hand-off control depending on whether the target cell belongs to the same switching station as the serving cell, the serving switching station (S-WX) or the target switching station. A first process of initializing to (T-WX), a second process of performing a backward call transfer to a target cell using a shortest distance path according to whether the target cell belongs to a serving switching station after the initialization, and the path A third step of determining whether or not a resource can be provided; and a step of checking whether a transfer path exists in a target cell if the resource is not available based on the determination of the third step; By the step 4 and the search for the transfer path in the fourth process, if there is no transfer path, the handoff call is treated as a failure, and if there is a transfer path, the bypass path is accessible to the node to which the called party belongs. To set characterized in that for performing the fifth step.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

A general model of a multi-layer cell structure is shown in FIG.

The layer with the largest cell radius is the high-layer cell (H # 1, 11), the smallest cell is the low-layer cell (L # 1, 13), and the middle cell is the middle layer. Named a cell (Mediul-layer Cell, M # m, 12).

The upper layer cell 11 may include a plurality of middle layer cells 12, and one middle layer cell 12 may include a plurality of lower layer cells 13. The lower hierarchical cells 13 may be arranged in a distributed or isolated cell (Island-type Cell) like the hatched portion of FIG.

Such cell configuration is determined according to the traffic characteristics of the service area.

A connection model between layer cells in a mobile communication system composed of multi-layer cells is shown in FIG. 2.

Assume that the lower layer cell 23 is directly connected to the next higher layer cell in a tree-type.

By having such a tree-type connection structure, the shape of the cells in a complex overlapping cell structure can be managed systematically. In addition, there is an advantage that the hole connection can be made hierarchically during the handoff between each layer cell. 2 shows that a switched network area 24 connecting a top layer cell 21 includes a mobile communication switch, a public fixed communication network, a common line signaling network, and an ATM (Asynchronous Trnasfer Mode) switching network. Here, the multilayer base station area 20 is composed of an upper layer base station 21, a middle layer base station 22 and a lower layer base station 23, as shown.

3 shows an example in which triple layer cells overlap with each other as an example of a multi layer cell configuration.

The upper layer cell 31 has a high cell radius and low-density traffic that provides a voice-oriented service, compared to a macro-cell area for a fast mobile station, and the middle layer cell 32 has a small cell radius. It may correspond to a micro-cell area in which low-speed mobile subscribers are concentrated in an area. The lower layer cell 33 may be likened to a pico-cell area of a building center using a wireless LAN, PBX / Centex. Each layer cell has one or more base stations (hereinafter referred to as BS, base station, macro cell base station 34, micro cell base station 35, pico cell base station 36) and these base stations are layered as shown in FIG. Is connected to. Each base station (e.g., pico-cell base stations 36 and 36-1) may be directly connected to a network node through a base station 35 of the upper layer or directly, where a network node is a switch node. It can be represented by a mobile switching center (hereinafter referred to as WX, 37) that controls the handoff call using the connection structure and network information of the WX (37), WX (Wireless, Exchange), fixed network and various mobile communication It is connected to a database center (such as HLR, AC, 38), etc. When a mobile terminal (generally referred to as a general mobile terminal) moves between cells in communication, it is connected to the WX 37 through the base station. ) Manages the channel resources, and the switching center 37 oversees the handoff control of the base station under its control, and uses the Network Configuration Table (37-1) for this purpose. Processed by terminal and network (exchange station 37) All.

4 is a flowchart illustrating a call connection between different layer cells in a multi-layer cell structure.

One of the major differences between the mobile communication and the general wired communication is the mobility of the mobile terminal. The mobility is guaranteed by handoff and registration. If location registration is an optional function for efficient paging of the terminating mobile terminal, handoff is an essential function for maintaining communication of the mobile subscriber. In particular, the handoff is a complex combination of the required time, type determination, determination of the target cell and the like, and the handoff operation characteristics largely depend on the propagation environment and the cell configuration. Therefore, handoff is regarded as one of the most complicated and important functions in mobile communication systems. The call connection during handoff is affected by the infrastructure, handoff protocol, and routing method of the mobile communication network. Unlike the fixed communication network, routing (link connection process) in a multi-layer cell structure in which a link configuration connecting various types of cells is complicated and frequent handoff may occur is very dynamic. Therefore, the link connection between cells due to handoff has a fundamentally different characteristic.

In the present invention, a network configuration table (37-1 in FIG. 3), which is essential for performing handoff call routing in a multi-layer cell structure, is used.

The main functions of the table are as follows.

First, this file contains routing information of all cells managed by the network (WX), and this information is updated whenever a handoff occurs.

Secondly, if a handoff occurs between different cell layers, this file is used to determine the target cell.

Third, it has handoff state management information necessary for handoff control, and it is connected with call control and consistently connects call processing state between general call setup and handoff call setup.

Fourth, it has a global admission control function for the frequency bandwidth and channel resources allocated to the handoff call.

This function is provided by the network (37-1 in FIG. 3) to collectively control resource management due to inter-cell handoff and handoff between networks in each layer.

The routing method of the present invention connects a link with a target cell so as to maintain a predetermined communication quality while maintaining the existing linked resources as much as possible.

The basic concept of the routing method is as follows.

The handoff is a call-forwarding technique in which the other subscriber moves a position while one side of the subscriber is fixed. And, unlike the general communication system, the routing control right is called the called party rather than the calling party (reverse call-forwarding). This routing technique is particularly effective when there are many regret routes in the path configuration to the target cell due to handoff.

The routing method of FIG. 4 is largely performed in two steps.

The first step is Reverse Call-forwarding (41). In this case, the reverse call transfer is different from the ones who own the call forearding and the routing control right used in the existing wired communication system, and the processing method is the same. That is, in the existing call transfer process, the calling party has a routing control right, but in the case of reverse call transfer processing, the called party has a routing control right. Therefore, in the case of the method of the present invention, the handoff routing control node becomes a handoff-controlling wireless eXchange (HO-WX), and if the UE belongs to the same exchange as the serving cell of the target cell, the HO-WX is a serving WX (Serving WX). In other cases, the HO-WX is set to T-WX (Targer WX) to make the initial state. If it is determined that the other cell belongs to the S-WX (step 1-1), the HO-WX becomes S-WX. HO-WX performs a reverse call 41 from the current serving cell to the target cell using the shortest path. However, if it does not belong, HO-WX becomes T-WX. The HO-WX to which the serving cell belongs performs reverse call-forwarding from the serving cell to the target cell, and then checks whether the set path is the shortest distance path (41).

If it is determined that the shortest path is a T-WX, the second step is performed. If not, the T-WX is a cross node (e.g. n6 in FIG. 5) and the node to which the called party belongs (n4 in FIG. 5). Find the shortest path of), and perform steps 1-2 to the second step.

The second step is a resource admission control step 42, in which the resource admission control for the allocated resource is checked. As a detailed step, step 2-1 determines whether the established path can provide resources (frequency bandwidth) necessary to maintain the existing QOS (43). If available, accept the handoff call, complete all procedures, and if unavailable, perform steps 2-2. Step 2-2 ignores the path where resource allocation is denied in step 2-1 and performs step 2-3, which is the next step. Step 2-3 is a step 47 of resetting the bypass path accessible to the node to which the called party belongs, and ends after establishing a path connection between the target cell and the end unit. At this time, if the reset is possible, the first step 1-1 is performed. If the reset is impossible, the handoff call is treated as a failure 47 and all procedures are completed.

5 is an incoming call through the switching network (WX, 57) when the originating mobile station (O-MT, 51) is handed off from the serving microcell (n2, 53) currently being serviced to the target cell (n3, 54) The example of setting routing connected with the mobile terminal T-MT 52 is shown. The WX 57 performs reverse call forwarding to obtain routing information for accessing the target cell 54.

The procedure is as follows.

Before the handoff, the originating mobile terminal (O-MT, 51) is communicating with the terminating mobile terminal (T-MT, 52), and the communication path is the communication mobile terminal (O-MT, 51) → microcell (n2, 53). ), It is composed of the macrocells (n5, 55), the handoff routing control node (HO-WX, 57), the macrocells (n6, 56), and the microcells (n4, 554-1). At this time, the calling terminal moves from the microcells n2 and 53 to the microcells n3 and 54 to start a handoff. First, the WX 57 requests a handoff channel to the target cell base stations n3 and 54, and receives channel resources in response thereto. Admission control is performed on the assigned channel. Next, the WX 57 connects the new links 16 → 13, 59 → 58 between the mobile terminal 51 and the target cell 54. To this end, the WX 57 instructs the MT 51 to respond to the handoff using the designated channel resource. The handoff request is made through the serving cell 53 and the target cell 54, and the primary response is received through the serving cell 53 currently in communication. The MT 51 switches the channel resource being used to the newly allocated channel resource. Thereafter, the MT 51 informs the WX 57 that the call connection is completed through the re-aquisition with the target cell 54.

The present invention as described above is an efficient routing method that applies the existing call transfer function to the handoff call setup in the cell configuration between the upper and lower layers connected in a tree structure, and various methods such as picocell / microcell / macrocell / megacell and the like. It is easy to design a handoff algorithm in the mobile communication field having a cell shape, and the effect is particularly high when there are many bypass routes in the path configuration to the target cell due to the handoff.

Claims (1)

A first process of initializing the handoff control mobile switching center (HO-WX) to the serving switching center (S-WX) or the target switching station (T-WX) according to whether the target cell belongs to the same switching station as the serving cell; A second process of performing a reverse call transfer to the target cell using the shortest distance path according to whether the target cell belongs to the serving switching center after initialization, and a third process of determining whether the path can provide resources; A fourth step of searching for whether a transfer path exists in the target cell if it is impossible to provide resources based on the determination of the third step, and if possible, accepting the handoff call and ending; If there is no transfer path, the handoff call is treated as a failure, and if there is a transfer path, a fifth process of setting a bypass path that can be connected to the node to which the called party belongs is characterized in that it comprises a. A routing method for fast handoff processing under a multilayer cell structure.