KR19980050420A - How to manage Active Set through Code Division Multiple Access (CDMA) handoff zone adjustment - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for maintaining an active group of a mobile communication system.

2. The technical problem to be solved by the invention

An object of the present invention is to provide an active group maintenance method for maintaining an optimal active group by adjusting a handoff area by appropriately selecting system parameter values when performing soft handoff, which is a main function of a code division multiple access mobile communication system.

3. Summary of Solution to Invention

According to the present invention, unlike the conventional method of adjusting the handoff area by applying the system parameter value related to the handoff area setting to all mobile stations belonging to a specific base station, the mobile station is piloted by appropriately applying the system parameter for each mobile station. Finds the best time to send a strength measurement message and maintains the active group, minimizing the rate of occupying multiple call channels for a single call, reducing system resources and load on the system by reducing resource waste and load on the system. The call disconnection rate caused by the loss of control messages can be reduced.

4. Important uses of the invention

Code Division Multiple Access Used for handoff of mobile communication systems.

Description

How to maintain active set through code division multiple access (CDMA) handoff area adjustment

The present invention is optimal by appropriate selection of system parameters (T_ADD, T_DROP, T_COMP, T_TDROP) when performing soft handoff and hard handoff, which are the main functions of the code division multiple access (CDMA) mobile communication system. It relates to an active set maintenance method for maintaining the active group of (Active Set).

The terms used in the present invention are defined as follows.

The Power Measurement Report Message (PMRM) is a message for forward power control that the base station / base station controller receives periodically or aperiodically from the mobile station through the reverse call channel.

A pilot strength measurement message (PSMM) is a pilot strength measurement message received by a base station / base station controller from a mobile station.

The Handoff Direction Message is a message used by the base station / base station controller to request handoff to the mobile station.

The Handoff Completion Message (HCM) is a message sent by the mobile station to the base station / base station controller as confirmation of the Handoff Instruction Message (HDM).

T_ADD is a value of base station pilot strength (hereinafter referred to as T_ADD) that a neighbor base station must satisfy to enter a candidate base station.

T_COMP is a value (hereinafter referred to as T_COMP) that compares the difference between the pilot strength of the candidate group, the pilot strength of the active group, and the strength difference of the pilots belonging to the active group for the base station of the candidate group to enter the active group.

T-TDROP is a channel drop timer value (hereinafter referred to as T_TDROP) required for the pilot belonging to the active group to be deleted from the active group.

ADD refers to the pilot of a neighbor sector or cell being added to an active group when the mobile station moves to a neighbor sector or cell in a code division multiple access (CDMA) handoff scheme.

DROP means that pilots existing in the active group are deleted in the code division multiple access (CDMA) handoff scheme.

SWAP means that ADD and DROP occur at the same time.

Ec / Io is the ratio of the pilot energy Ec accumulated during one pseudo-noise (PN) chip period to the total power spectral density (Io) in the reception bandwidth (hereinafter referred to as Ec / Io).

The conventional handoff processing method was developed to improve call quality compared to the analog method by introducing a soft handoff technique between sectors, base stations, and base station control periods. As a result of the frequent occupying of two or three call channels, the call channel is wasted and the hand load of the system is increased due to frequent handoff. Looking at this in detail.

1 is a flowchart illustrating a conventional method for maintaining a handoff active group.

The mobile station transmits a pilot strength measurement message (PSMM) based on the system parameters received from the mobile communication system when the call is attempted, and the base station / base station controller analyzes the pilot strength measurement message (PSMM) received from the mobile station (11). Candidate pilots satisfying s (i.e., pilots satisfying the ADD condition are not null pilots, T_TDROP must not expire, pilots belonging to the active group, and pilot strengths must be T_ADD or more). In step 12, one of the strongest pilots is selected.

Then, a series of verification procedures for the selected candidate pilots (are there selected candidate pilots, pilots of the same mobile switchboard, and how many pilots of the active group are currently operated?) Determining (13) sending a handoff indication message (HDM) to the mobile station (14) requesting to add the selected candidate pilot to the active group and notifying the mobile station that the handoff indication message (HDM) has been successfully performed. The base station / base station controller receives a handoff completion message (HCM) (15) and the base station / base station controller replaces the old neighbor list managed by the mobile station with a neighbor list of a new active group. The series of handoff ADD procedures is terminated by sending a Neighbor List Update Message (16) to the mobile station. In this case, when the mobile station transmits the handoff complete message (HCM), it means that the base station / base station controller also changes the system parameter value included in the handoff indication message (HDM).

In the prior art, since the parameters related to handoff area setting (T_ADD, T_DROP, T_COMP, T_TDROP) are consistently applied to all mobile stations, even when the pilot strength of the active group is sufficiently strong, the mobile station is adjacent to T_ADD or more. When a pilot of a group is found, the pilot strength measurement message (PSMM) is transmitted to the base station / base station controller from time to time to increase the load of the system, and the base station / base station controller receiving the pilot strength measurement message (PSMM) receives the received pilot strength measurement message. (PSMM) must perform a procedure, and in some cases, the handoff ADD, DROP, SWAP procedure is a waste of communication channel resources, the mobile station checks the transmitted PSMM (PSMM) message If a message is not received from the base station / base station controller, the current call is forcibly disconnected. Separately from the actual propagation environment, the frequent pilot strength measurement message (PSMM) has an adverse effect on the call quality.

In order to solve the above problems, the present invention, unlike the conventional method for adjusting the handoff area by applying the same system parameter value closely related to handoff area setting to all mobile stations belonging to a specific base station, for each mobile station unit Appropriately different system parameters are used to find the best time for the mobile station to send a pilot strength measurement message (PSMM) to maintain the active group, thereby unnecessarily occupying two or three call channels for one call. It provides an active set maintenance method that minimizes the rate, increases the system capacity by reducing the waste of call channel resources and the system load, and reduces the call disconnection rate caused by the loss of control messages during handoff. There is a purpose.

1 is a flow chart for a conventional handoff active group maintenance method,

2 is a configuration diagram of a general mobile communication system;

3 is a flowchart illustrating a method for maintaining an active group through handoff area adjustment according to the present invention;

4 is an explanatory diagram showing pilot strength and time according to the present invention.

* Explanation of symbols for main parts of the drawings

21: mobile station 22: base station

23: base station controller 24: mobile switching center / visitor location register

25: home location register 26: general public telephone network

In order to achieve the above object, the present invention provides an active set maintenance method applied to a mobile communication system, wherein the base station / base station controller receives a power measurement report message (PMRM) from a mobile station. A first step of analyzing the ratio (Ec / Io) to the pilot energy (Ec) accumulated during one pseudo-noise (PN) chip period to the received bandwidth total power spectral density (Io) included in the PMRM; A second step of determining whether a system parameter is changed by finding a handoff area close to the radio wave environment in which the radio wave environment is located; and if the system parameter is changed as a result of the determination of the second step, if the system parameter is changed, the mobile station is transmitted to each radio station. Determining a system parameter value accordingly and transmitting a system parameter change message to the corresponding mobile station.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

2 is a block diagram of a general mobile communication system, where 21 is a mobile station, 22 is a base station, 23 is a base station controller, 24 is a mobile switching / visitor location register, 25 is a home location register, and 26 is a public public telephone network.

The mobile station 21 is a public cellular wireless service radio station that can be used while moving, and the mobile station includes a portable mobile terminal and a vehicle mounting terminal. The base station 22 is a wireless station that performs a cellular wireless communication service with the mobile station 21. The base station controller 23 is a device for controlling the base station 22. The mobile exchange / visitor location register 24 switches the subscriber call and stores the visitor's information. The home location register 25 is a database that stores subscriber information, subscriber location information, and the like.

3 is a flowchart illustrating an active group maintenance method through handoff area adjustment according to the present invention.

When attempting a call, the mobile station periodically or aperiodically transmits a power measurement report message (PMRM) to the base station / base station controller through the assigned reverse talk channel, and the base station / base station controller receives the received power measurement report message (PMRM). Perform forward power control using. The mobile station then finds a time to transmit a pilot strength measurement message (PSMM) based on the system parameters received from the system during the call attempt.

The present invention predicts the radio wave environment encountered by the mobile station by using the Ec / Io value included in the power measurement report message (PMRM) and changes the system parameter value owned by the mobile station according to the good or bad radio wave environment. -Traffic system parameter messages can be used to apply the system parameter values that are closest to the particular radio environment encountered by each mobile station. For example, a mobile station that is in close proximity to a base station and has a good propagation environment has a high T_ADD value to reduce the handoff area, thereby reducing the number of pilot strength measurement messages (PSMM) received by the base station / base station controller. The mobile station receiving service at the edge of the base station, i.e., lowering the T_ADD value, expands the handoff area, so that the system manages the handoff area close to the special radio environment of each mobile station in the call, so that the system performance, resource management, and call quality Various effects such as can be seen.

Looking at the treatment process according to the invention in detail as follows.

When the base station / base station controller receives a pilot strength measurement message (PSMM) from the mobile station after the mobile station attempts a call and is allocated a call channel, the base station / base station controller performs the DROP and SWAP processes as it is, including the conventional handoff ADD process.

Apart from the pilot strength measurement message (PSMM), the base station / base station controller receives the power measurement report message (PMRM) from the mobile station (31) to perform forward power control and additionally the active group contained in the power measurement report message (PMRM). Review the Ec / Io value (32). In other words, Ec / Io contained in periodic or non-periodically received power measurement report messages (PMRMs) can be analyzed to find handoff areas in close proximity to the specific propagation environment of each mobile station, thereby optimizing the active groups of the system. Find time to manage with.

When the Ec / Io review process included in the power measurement report message (PMRM) is completed, it is determined whether the system parameter is changed by predicting whether the mobile station is in a good radio wave environment (33).

As a result of the determination, if it is not the system parameter change, the process immediately terminates. If the system parameter change is made, a new optimal system parameter value is determined (34), and a system parameter change message (In-Traffic system parameter message) is transmitted to the mobile station (35). The mobile station receiving the system parameter change message operates according to the new value.

Of course, at this time, the system has an initial system parameter value unique to the system and assigns this value to a mobile station requesting a new call connection first, and then determines and assigns a separate system parameter value suitable for the special propagation environment of the mobile station in the call. do. In other words, the mobile station requesting the first call connection is assigned a system-specific system parameter, and after that, a separate system parameter determined according to the change of the radio environment of each mobile station is changed aperiodically through a system parameter change message.

4 is an explanatory diagram in which the handoff parameter threshold according to the present invention is expressed by pilot strength and time, and T_ADD and T_DROP values may be varied by ± ΔT according to the propagation environment of the mobile station.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

As described above, the present invention increases subscriber capacity of a code division multiple access (CDMA) mobile communication system by setting an optimal handoff area, reduces the load on the system by not performing frequent handoff processing, and handoffs. It can reduce the call cutting rate due to lack of resources.

Claims (3)

In the active set maintenance method applied to the mobile communication system, When the base station / base station controller receives a power measurement report message (PMRM) from the mobile station, it accumulates for one pseudo noise (PN) chip period for the received bandwidth total power spectral density (Io) included in the power measurement report message (PMRM). A first step of analyzing the ratio (Ec / Io) to the pilot energy (Ec), a second step of determining whether a system parameter is changed by finding a handoff area close to the radio environment where each mobile station is located, and the second step If it is determined that the system parameter change is not finished, and the system parameter change, the active group maintenance comprising the third step of determining the system parameter value according to the radio wave environment of each mobile station and sending a system parameter change message to the mobile station. Way. The method of claim 1, wherein the first step of receiving power measurement report message (PMRM) is characterized in that the power measurement report message (PMRM) is received periodically or aperiodically from the mobile station. 3. The base station pilot according to claim 1 or 2, wherein the determination of the system parameter value in the third step includes a base station pilot that must be satisfied for a neighboring base station to enter a candidate base station for a mobile station that is serviced while having a good radio wave environment in close proximity to the base station. Increasing the value of the strength (T_ADD) reduces the handoff area, reducing the number of times the pilot strength measurement message (PSMM) is received by the base station / base station controller, and conversely, a mobile station (a mobile station serving at the edge of the base station) having a poor propagation environment. The system parameter value is determined so that the system manages the handoff area in close proximity to the special propagation environment of each mobile station by expanding the handoff area by lowering the value of the base station pilot strength (T_ADD) that the neighboring base station must satisfy to enter the candidate base station. Maintaining the active group, characterized in that Li method.