KR19980041002A - Determination Method of Handoff Type in Digital Mobile Communication System - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Determination Method of Handoff Type in Digital Mobile Communication System

2. The technical problem to be solved by the invention

Call quality caused by determining handoff type without determining SWAP between base stations and executing 3-way handoff (mobile station establishes call path to 3 base stations at the same time) in general digital mobile communication system It is to solve the problem of degradation and disconnection of arc.

3. Summary of Solution to Invention

In a digital mobile communication system for determining handoff resting when a mobile station requests a handoff during a call, each mobile station receives a message indicating a pilot strength and a drop tamer state of an active set and a candidate set transmitted by the mobile station. A first step (ST1-ST4) of initializing a variable and selecting only a specific pilot for handoff type determination among the received messages; A second step (ST5) of comparing a unique number of the pilot to be added among the pilots selected in the first step with a corresponding unique number of the control station; A third step (ST6) of determining a handoff type according to a handoff type transition degree if the unique number of the mobile station and the unique number of the control station match; A fourth step (ST7) of comparing the strength of the pilot to be added with the strength of the active pilot if the unique number of the mobile station and the control station are different; As a result of the comparison of the fourth process, when the strength of the pilot to be added is greater than the strength of the active pilot, a handoff type is determined in the control station, and when the strength of the pilot to be added is less than the strength of the active pilot, the pilot to be added and the drop may be dropped. After reselecting the pilot, a fifth process (ST8-ST10) for determining a handoff type is performed.

4. Important uses of the invention

It is applied to determine the handoff type when requesting handoff from mobile station in digital mobile communication system.

Description

Determination Method of Handoff Type in Digital Mobile Communication System

In general, in a digital mobile communication system, it is important to ensure mobility and maintain call quality when a mobile station moves between switching periods, between base stations, and sectors within a base station. A technology that meets these goals is the core of digital mobile communication as a handoff. However, handoffs occur 50-60% or even more for regular calls. Therefore, if the proper handoff type and timing are not specified, the frequency of the handoff is high and the system is overloaded, and an inappropriate handoff to the base station can cause the call to be disconnected.

The handoff type determination should therefore determine the appropriate type of handoff so that the mobile station performs a handoff to the appropriate base station.

A general handoff process in a code division multiple access (CDMA) digital mobile communication system is as follows.

When the strength of the pilot of each base station / sector sensed by the mobile station exceeds the threshold or the existing one falls below the threshold, information of the pilot strength is transmitted to the base station. The base station then sends this information to the control station, which in turn determines which base station / sector to hand off and instructs the mobile station to hand off. The mobile station sends a handoff complete message to the base station after performing the handoff. The control station reports the completion of the handoff from the base station, thereby completing a series of handoff procedures.

The above types of handoffs are roughly classified into handoffs that are enlarged, soft handoffs and softer handoffs.

Here, the hard handoff includes a hard handoff, an inter-frequency handoff, and an interframe handoff, and a soft handoff refers to an inter-base station, and a softer handoff refers to an intersectoral handoff.

However, the general handoff method is limited by determining the handoff type without determining SWAP between base stations (simultaneously performing ADD and DROP) and 3-way handoff (mobile station establishes call paths to three base stations at the same time). Due to the type of handoff, the call quality is degraded and the call is disconnected.

In addition, there is a problem that it is difficult to adequately cope with the environment of the field that changes every moment by the handoff method lacking flexibility.

Accordingly, the present invention has been proposed to solve various problems occurring in the general handoff type determination method as described above, and an object of the present invention is to provide a handoff type transition using a handoff type transition diagram in a CDMA digital cellular mobile communication system. The present invention provides a method for determining the handoff type of a digital mobile communication system to facilitate decision making and to easily modify the field environment to prevent overload and disconnection of the system and to ensure call quality.

The method for achieving the object of the present invention, when receiving a message indicating the pilot strength and drop tire state of the active set and the candidate set transmitted by the mobile station, initializes each variable and determines the handoff type of the received message. Selecting a specific pilot only; A second step of comparing a unique number of a pilot to be added among the pilots selected in the first step with a corresponding unique number of a control station; A third step of determining a handoff type according to a handoff type transition degree if the unique number of the mobile station and the unique number of the control station match; A fourth step of comparing the strength of the pilot to be added with the strength of the active pilot if the unique number of the mobile station and the control station are different; As a result of the comparison of the fourth process, when the strength of the pilot to be added is greater than the strength of the active pilot, a handoff type is determined in the control station, and when the strength of the pilot to be added is less than the strength of the active pilot, the pilot to be added and the drop may be dropped. After selecting the pilot, a fifth process of determining a handoff type is performed.

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

1 is a handoff type transition diagram of a digital mobile communication system applied to the present invention;

2 is a flowchart illustrating a handoff type determination method of a digital mobile communication system according to the present invention;

3 is a detailed flowchart of a handoff type determination process of FIG. 2;

4 is a flowchart of a handoff type determination state of FIG. 3;

2 is a flowchart illustrating a method for determining a handoff type in a digital mobile communication system according to the present invention.

As shown, when receiving a message indicating the pilot strength of the active set and the candidate set and the drop tire state transmitted by the mobile station, the mobile station initializes each variable and selects only the specific pilot whose handoff type is determined from the received messages. Processes ST1-ST4; A second step (ST5) of comparing a unique number of the pilot to be added among the pilots selected in the first step with a corresponding unique number of the control station; A third step (ST6) of determining a handoff type according to a handoff type transition degree if the unique number of the mobile station and the unique number of the control station match; A fourth step (ST7) of comparing the strength of the pilot to be added with the strength of the active pilot if the unique number of the mobile station and the control station are different; As a result of the comparison of the fourth process, when the strength of the pilot to be added is greater than the strength of the active pilot, a handoff type is determined in the control station, and when the strength of the pilot to be added is less than the strength of the active pilot, the pilot to be added and the drop may be dropped. After reselecting the pilot, a fifth process (ST8-ST10) is performed again to determine the handoff type.

Referring to Figures 1 to 4 attached to the handoff type nodular method according to the present invention made as described above are as follows.

First, when the control station BSC receives a PSMM message indicating the pilot strength and the drop timer state of the active set and the candidate set transmitted by the mobile station TSB (ST1), it determines the handoff type based on this.

Here, the determination of the handoff type is actually the starting point of the handoff, and maintaining the continuity of the call by determining the appropriate type.

In this case, the active set is a pilot currently opening a channel, and the candidate set is a pilot who wants a handoff.

The maximum number of active sets is three, the mobile station (TSB) has three vs-ports, the sectors in the same base station can be up to two active pilots, and the number of pilots added (ADD) is One at a time, and one pilot at a time (DROP).

Under these conditions, the control station initializes the variable upon receipt of the PSMM message (Init_Proc ()) (ST2), and removes any non-neighbor pilots among the received PSMM pilots (ST3). After selecting a pilot to be ADD / DROP among the neighbor pilots (ST4), the system ID, network ID, BSC ID of the selected added pilot is compared with the system ID, network ID, BSC ID of the active pilot (ST5), If it is the same, the handoff type is determined by the handoff type transition diagram as shown in FIG. 1, and in contrast, when the IDs are different, the handoff type is compared by comparing the strengths of the pilots to be added and the strengths of all active pilots. It is decided (ST7-ST10).

That is, as shown in Fig. 3, the headoff type determination searches for the presence or absence of a pilot to be added to the DROP (ST6a), and if there is a pilot to be added to the ADD or DROP, it sets a depression for the handoff type determination (ST6b). If the pilots to be ADD and DROP exist at the same time, but it is difficult to determine the handoff type (ST6c), the ADD pilot is discarded (ST6d) to determine only when dropped. The handoff type is determined by the decision process (ST6e).

Next, if ADD and DROP pilots exist at the same time and handoff type determination is possible, it is determined whether it is SOFT_ADD or SOFT_SWAP (ST6f). If the strength of the pilot to be added is t_comp more than the strength of all active pilots (ST6g), and if the strength of the added pilot is more than t_comp more than the strength of all the active pilots, the handoff in the base station (FA / FO hand) Off) (ST6h).

In addition, when the strength of the pilot to be added is less than t_comp of the strengths of all active pilots, the dummy state of the added pilot is judged to be returned if not the dummy state, and if the dummy state is the dummy state, the handoff type is not determined (ST6i). ) (ST6j).

That is, each state of the handoff type transition diagram is represented as shown in FIG.

Here, the horizontal direction of each state represents a base station, and the vertical direction represents a sector of the base station in no particular order. For example, state 0 * 24 in FIG. 1 represents two different base stations, where the first column indicates two sectors and the second column consists of one sector. The status value indicates the number of each column as 2-bit binary number, the most significant bit (MSB) on the left and the least significant bit (LSB) on the right.

0 * 24 in FIG. 1 is represented by 10,01,00 since the number of sectors per base station is 2,1,0, respectively, which is represented by binary 100100 (0 * 24).

The next state (Next_State) is obtained by using the pilot and the active set to hand off Cur_State in the current active set, and the handoff type is determined according to the arrow.

For example, if sector 0 of base station A is currently in a call and the mobile station requests handoff of sector 2 of base station B, the control station can know that Cur_State is 0 * 10 using the sector in call.

In addition, it can be seen that the next state (Next_State) is obtained by using the currently talking sector and the sector of the candidate set.

The control station thus determines the SOFT-ADD handoff. Subsequently, if the mobile station sends the PSMM to include sector 1 of base station A in the candidate set, Cur_State becomes 0 * 14 and the next state becomes 0 * 24, so that the control station determines SOFTER-ADD handoff.

If the mobile station then sends the PSMM to include sector 1 of the base station B in the candidate set, the CuR_State becomes 0 * 24 and the next state becomes 0 * 28, so that the control station does not determine handoff.

1 is a state in which only the hatched portion of the handoff type transition diagram may have an active set, and the basic concept is to determine the type of handoff by obtaining the next state in the state (see FIG. 4).

However, in order to protect the above constraints and resources of the system, an extension of the handoff type determination method is required.

For example, if Cur_State is 0 * 24 and the next state is 0 * 30, it should conceptually be SOFTER_ADD on a handoff type transition diagram. Only in situations, as shown in FIG. 1, the SOFTER_SWAP may be determined only when the strength of the pilot to be handed off is better than the active set pilots, thereby increasing the quality of the call and reducing the frequency of the handoff.

In this basic handoff type transition diagram, the type of handoff can be easily determined by adding or removing a state according to the situation of the field or the change of the constraint.

As described above, the present invention determines the appropriate handoff type when the mobile station requests a handoff, so that the mobile station can maintain the quality of the call without disconnection of the call.

Also, by preventing unnecessary handoff, the system load can be reduced and stable system operation can be performed.

In addition, by determining the handoff type using the handoff type transition degree, it is possible to grasp the number of cases where handoff can occur as a whole.

The present invention relates to the determination of a handoff type in a digital mobile communication system. In particular, it is easy to determine the handoff type by using a handoff type transition diagram in a CDMA digital cellular mobile communication system and can be modified according to a field environment. Thus, the present invention relates to a method for determining a handoff type of a digital mobile communication system which prevents overload and disconnection of a system and guarantees call quality.

Claims (5)

A digital mobile communication system for determining handoff suspension when a mobile station requests handoff during a call, Receiving a message (PSMM) indicating the pilot strength of the active set and the candidate set and the drop tamer state transmitted by the mobile station, the first variable initializes each variable and selects only a specific pilot for handoff type determination among the received messages. Processes ST1-ST4; A second step (ST5) of comparing a unique number of the pilot to be added among the pilots selected in the first step with a corresponding unique number of the control station; A third step (ST6) of determining a handoff type according to a handoff type transition degree if the unique number of the mobile station and the unique number of the control station match; A fourth step (ST7) of comparing the strength of the pilot to be added with the strength of the active pilot if the unique number of the mobile station and the control station are different; As a result of the comparison of the fourth process, when the strength of the pilot to be added is greater than the strength of the active pilot, a handoff type is determined in the control station, and when the strength of the pilot to be added is less than the strength of the active pilot, the pilot to be added and the drop may be dropped. And a fifth process (ST8-ST10) of re-selecting the pilot and determining the handoff type again. The method of claim 1, The first process is to discard only the non-neighbor pilots among the received PSMM pilots and select only pilots to be added and dropped among the neighbor pilots as a specific pilot. The method of claim 1, The second process compares the system ID, network ID, and control station ID of the pilot to be added acquired in the first process with the system ID, network ID, and control station ID of the active pilot. How to determine the handoff type. The method of claim 1, The handoff type determination may be performed at step ST6a (ST6c) of searching for the possibility of handoff type determination if there is a pilot to be added and dropped in the pilot of the received mobile station, and the pilot to be added and dropped at the same time may be present. If it is impossible to determine the handoff type, a step (ST6a) (ST6c) of discarding the pilot to be added and determining the handoff type only with the pilot to be dropped to determine only if it is dropped, and determining the handoff type with the extracted addition and pilot to be dropped If possible, comparing the strengths of the pilots to be added with the strengths of all active pilots (ST6f) (ST6g) based on the handoff type transition diagram, and the strength of the pilots to be added is The strength of the pilot to be added and set the possibility of determining intra-base handoff type if greater than all active pilots. If intensity than the threshold value of all active pilots is less than the dummy search condition to hand-off type of a digital mobile communication system, characterized by made of an step (ST6i) (ST6j) for determining whether a handoff decision type determination method. The method of claim 4, wherein And if the strength of the pilots to be added is less than the threshold of all active pilots and not in a dummy state, returning, and if the dummy state is not determined, the handoff type is not determined.