KR20000052153A - method for optimizing the parameters of common FA hard hondoff in the CDMA system - Google Patents

Abstract

PURPOSE: A method of optimizing frequency assignment hard hand off parameter in CDMA system is provided to curtail the hand off cost during the frequency assignment and increase the success rate of handoff, eventually to come to the optimal capability condition. CONSTITUTION: A method of optimizing frequency assignment hard hand off parameter in CDMA system comprises the steps of: analyzing the data logging about frequency assignment in traffic situation during the service in the real field on common frequency assignment hard hand off-test; confirming the traffic hand off block in frequency assignment related to common frequency assignment and EC/IO level; confirming EC/IO level in the traffic block related to the common frequency assignment of frequency assignment subject to the border frequency assignment; configuring the initial parameter; performing the test block of common frequency assignment hand off; analyzing the cause in case of call drop; operating the optimal parameter value through parameter change.

Description

Method for optimizing the parameters of common FA hard hondoff in the CDMA system

The present invention relates to a method for optimizing a common frequency assignment hard handoff parameter in a code division multiple access system, and in particular, to implement a common frequency assignment hard handoff method, which is an intra-cell frequency assignment hard handoff method, to achieve an optimal performance condition. The present invention relates to a common frequency allocation hard handoff parameter optimization method in a division multiple access system.

Inter-frequency hard handoff is performed to ensure continuity of a call when resources of the same FA currently being tuned by the UE to the neighbor cell to be handoff are unavailable and resources of the other FA are available.

The inter-frequency hard handoff (H / O) method implemented in a code division multiple access (CDMA) system includes a common cell hard handoff shown in FIGS. 1A to 1C, There are three methods: inter cell hard handoff and intra cell.

Among the three methods, the common cell and the internal cell hard handoff method include hard handoff by a dummy pilot, and are implemented in a personal communication system (PCS) 3.1.0 (package version). Common Frequency Assignment (FA) hard handoff is an intra-cell hard handoff scheme.

In the common cell and internal cell hard handoff scheme, the terminal detects the strength of the pilot through dummy frequency allocation of the target base station and requests a handoff to the system. OFF will be performed.

cell B Ec / Io intensity (target) ≥ cell A Ec / Io intensity (serving) + T_comp

: Perform Intra Cell Hard Handoff

cell B Ec / Io intensity (target) ≥ cell A Ec / Io intensity (serving) + T_comp

: Perform Common Cell Hard Handoff

In case of the two handoffs, there is an economical problem of using dummy frequency allocation and an optimization problem that can improve the success rate of handoff only when the coverage of the overhead channel (pilot, sync, paging channel) of dummy frequency allocation is matched. have.

In addition, the common frequency allocation hard handoff, which is one of the hard handoff methods between frequency allocations, is a hard handset between frequency allocations through the Ec / Io level of the serving cell received from the system to the current terminal by a configuration parameter without dummy frequency allocation. Determining the execution time of the off and transmitting the EHDM (Extended Handoff Direction Message) of the hard handoff to the terminal between the frequency allocation, the terminal performs a soft handoff with the target cell after changing the frequency allocation.

In order to increase the success rate of the common frequency assignment hard handoff, it is important to perform the common frequency assignment hard handoff. However, the terminal performs the common frequency assignment hard handoff too late to perform the handoff. Out of coverage will result in a call drop.

If there is no frequency allocation currently serving in the serving base station in the target base station, the UE receives a PIMM (Pilot Strength Measurement Message) from the system and performs intra-cell handoff from the current serving frequency allocation to the frequency allocation existing in the target cell. By performing the soft handoff to the target cell.

In addition, the number of resources of one base station depends on the call demand in the area, and the area where the call demand is high, that is, a specific cell in a city center or a border cell of a city, is used for radio access to reduce the probability of call blocking. There is a need for more channels, and there is a method of increasing frequency allocation as an increase of radio access channels for base stations in areas where call demand is high.

However, when the frequency allocation of only a specific base station is increased, a problem occurs in handoff with another base station, and when the handoff process is performed in a CDMA system, the mobile station measures and reports the strength of the pilot channel of a neighbor cell to the base station. If the neighboring cell does not have the same frequency allocation currently tuned by the mobile station, the mobile station does not know the existence of the neighboring cell and thus cannot report the signal strength of the pilot channel of the neighboring cell, which is a starting procedure.

Accordingly, an object of the present invention, which is designed to solve the problems of the prior art operating as described above, implements a common frequency allocation hard handoff, which is an intra-cell frequency allocation hard handoff scheme, to derive optimal related parameters. A method of optimizing common frequency allocation hard handoff parameters in a multiple access system is provided.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention and the accompanying drawings.

1A illustrates a configuration of a common cell hard handoff.

1B illustrates the configuration of an internal cell hard handoff.

1C illustrates a configuration of intra cell hard handoff.

2 is a configuration diagram of a bitmap that specifies frequency allocation of a target to be harded down.

3 is an operation flowchart of a common frequency allocation hard handoff.

4 is a channel mode configuration diagram of a subcell.

5 illustrates traffic data analysis.

6 is a flowchart illustrating a radio environment analysis method for a section to which the present invention common frequency allocation hard handoff test is performed.

7 is a flowchart illustrating a method for deriving and setting an optimal parameter through a task for changing a parameter related to the present invention.

<Description of Symbols for Main Parts of Drawings>

FA: Frequency Assignment

PSMM: Pilot Strength Measurement Message

PMRO: Pilot Measurement Request Order

EHDM: Extended Handoff Direction Message

A preferred embodiment of the radio environment analysis method for the section to be subjected to the common frequency assignment hard handoff test according to the present invention, which was created to achieve the above object,

Analyzing data logging in traffic conditions for frequency allocation during actual field service for the interval for which the common frequency allocation hard handoff test is to be performed;

Identifying a traffic handoff period and an Ec / Io level at the time of handoff in frequency allocation corresponding to the common frequency allocation;

Checking the level of Ec / Io in the traffic period corresponding to the common frequency allocation in the frequency allocation corresponding to the boundary frequency allocation;

The initial parameter is set.

The Ec / Io level at the handoff is represented by level 1_A cell, and the level of Ec / Io in the traffic period corresponding to the common frequency allocation is represented by level 2_A cell. In setting the initial parameter, the T_DOWN value should be better than the Ec / Io value for the frequency allocation designated as the boundary frequency allocation at the traffic handoff occurrence point, and the T_DOWN value is greater than the Ec / Io value. The equation that should be better is represented by T_DOWN level ≥ level 2_A cell.

The parameter consists of CDMA_Ch_Mode, PSMM Request Period, T_DOWN, T_TDOWN, and Handdown_FA. The CDMA_Ch_Mode indicates whether the frequency allocation of the subcell is common frequency allocation or boundary frequency allocation.

In the common frequency allocation, the same frequency allocation currently in service exists in a neighboring subcell, and in the boundary frequency allocation, there is no same frequency allocation currently in service in a neighboring subcell, and the PSMM Request Period is a frequency of the corresponding subcell. When the allocation is defined as a border, the system determines the period of sending a Pilot Measurement Request Order (PMRO) to the forward link so that the UE periodically reports the PSMM.

The default setting value of the PSMM Request Period is 1 second, and indicates the common frequency allocation hard handoff when the strength of the pilot received by the mobile station in the sector selected as the boundary frequency allocation in T_DOWN is T_DOWN or less.

The default setting value of the T_DOWN is 10 (-5 dB), and the T_TDOWN is a common frequency allocation hard hand when T_TDOWN seconds elapses while the strength of the pilot received by the mobile station in the sector set to the boundary frequency allocation is less than or equal to T_DOWN. Instructs off.

The default setting value of T_TDOWN is 0 seconds, and Handdown_FA is a bitmap that designates a target frequency allocation to be handed down when the mobile station satisfies the handdown condition in the boundary subcell.

Each bit represents the allow / disallow of the handdown to the corresponding frequency assignment, respectively, and the allow of the handdown represents 0 and the non-permission represents 1. And the default value of Handdown_FA is 1.

Preferred embodiments of the optimal parameter derivation and setting method through the operation of changing the relevant parameters according to the present invention,

Conducting a common frequency allocation handoff test interval in the test interval;

Analyzing the cause at the time of call drop;

It is a step of setting the optimal parameter derivation value through the parameter change operation.

The analyzing of the cause at the time of the call drop confirms whether the wireless environment is poor in frequency allocation after handdown due to the inflow of a signal not designated as Border_FA.

In the step of setting the optimal parameter derivation value through the parameter change operation, the maximum success rate is obtained by changing the T_DOWN level value for the same test section and changing the channel mode for the signal flowing into the test section.

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

First of all, change and display of function control parameters related to common frequency allocation (FA) hard handoff are possible in the base station manager (BSM) and subcells.

CDMA_ch_Mode

: Indicates whether or not frequency allocation of a subcell is common frequency allocation.

If the same frequency allocation does not exist in the target cell targeted for soft handoff with respect to the frequency allocation of the currently serving subcell, set 'Border_FA' for the frequency allocation of the serving subcell and the same frequency allocation is the neighboring target cell. Presence at is defined as 'Common_FA'.

* Common_FA: The same frequency assignment currently being served exists in the neighboring subcells.

* Border_FA: There is no same frequency allocation currently serving in neighboring subcells.

Setting value: Common_FA or Border_FA

PSMM Request Period

: When frequency allocation of a corresponding subcell is defined as a border, the system determines a period of sending a pilot measurement request order (PMRO) to the forward link so that the UE periodically reports the PSMM.

Default setting value: 1 second (unit: second)

-T_DOWN

The common frequency allocation hard handoff is indicated when the strength of the pilot received by the mobile station (MS) is less than or equal to T_DOWN in the sector selected as the boundary frequency allocation.

Default setting value: 10 (-5dB)

-T_TDOWN

: T_TDOWN seconds in the state that the pilot received by the mobile station in the sector set to the boundary frequency allocation is less than or equal to T_DOWN, instructs common frequency allocation hard handoff.

Default setting value: 0 seconds (unit: seconds)

-Handdown_FA

: A bitmap that designates a target frequency allocation to hand down when a mobile station meets a hand down condition in a boundary subcell.

Each bit shown in FIG. 2 represents a handdown enable / disallow to a corresponding frequency assignment.

Values: 0 (disallow handdown), 1 (allow handdown)

Example: If FA2 is Border_FA and allows handdown to FA0 and FA1, it is designated as '00000011', so Handdown_FA = '3'.

Default setting value: 1 (Hand down to 00000001 → FA0 only)

3 is an operation flowchart of a common frequency allocation hard handoff according to the present invention. As shown in FIG. 3, if an active set condition is generated in which intra-cell frequency allocation hard handoff is generated, the UE may perform periodic PMRO transmission. Check the condition of

If all of the active sets of the UE fall below T_DOWN, a timer with a time of T_TDOWN is operated. When the timer is terminated, intra cell frequency allocation hard handoff is performed.

The conditions for performing the intra cell frequency allocation hard handoff are as follows.

Condition checking and handoff are performed on a sector basis. If the following three conditions are satisfied, the handoff is performed.

-Mobile station has only boundary frequency allocation because it is active set

All pilots in the active set of the mobile station shall have a weaker pilot strength than T_DOWN

-When T_TDOWN has passed under the second condition (T_TDOWN> 0)

(→ Handoff to better frequency common frequency assignment by comparing the strength of pilots when 2 pilots or more)

In addition, as shown in FIG. 4, Border_FA is a designation for a sector using a frequency band that does not exist in a neighboring base station, and Common_FA is a designation for a sector using a frequency band that all neighboring base stations have.

The common frequency allocation hard handoff is performed as follows.

When the handoff results from the active-set consisting of boundary frequency assignments only

-Check the base station status by transmitting PMRO at PSMM request period.

Receive the PSMM for the PMRO and check if the pilot strength of the active set is weaker than T_DOWN.

In this state, the PSMM is received and the following conditions are handled.

-All active sets have a pilot strength less than or equal to T_DOWN

-Start a timer with a time of T_TDOWN.

-If T_TDOWN = 0, common frequency allocation hard handoff is performed without timer setting.

-When a pilot other than boundary frequency allocation is added

Abort periodic base station status checks.

-When another pilot with boundary frequency allocation is added

After processing the added handoff request, perform a condition check when the active sets all have a pilot strength of T_DOWN or less.

If drop is required for all pilots in the active set

Perform common frequency allocation hard handoff;

-All active sets have a pilot strength less than or equal to T_DOWN

-When the timer (T_TDOWN) is finished

Perform a common frequency hard handoff.

If a drop is required for all pilots in the active set before the timer expires

Perform common frequency allocation hard handoff;

-Cancel the timer.

If addition of a pilot other than boundary frequency allocation is required

-Cancel the timer and stop the periodic base station status check.

-The strength of all pilots in the active set recovers above T_DOWN

Cancel the timer and perform a periodic check of the status of the base station.

FIG. 5 is a flowchart illustrating a method for analyzing a radio environment for a section for performing the common frequency allocation hard handoff test of the present invention. As shown in FIG. Analyze data logging in the traffic state for (s1).

The traffic handoff period in the frequency allocation corresponding to the common frequency allocation and the Ec / Io level at the time of handoff are checked (s2).

In the frequency allocation corresponding to the boundary frequency allocation, the level of Ec / Io in the traffic section corresponding to the common frequency allocation is checked (s3), and an initial parameter is set (s4).

FIG. 6 is a flowchart illustrating a method for deriving and setting an optimal parameter through the operation of changing parameters related to the present invention. As shown in FIG. 6, a common frequency allocation handoff test section is performed in a test section (s1), and a call drop is performed. Analyze the cause when dropping (s2).

After that, the optimal parameter derivation value is set through the parameter change operation (s3).

This section describes the procedures that follow the derivation of optimal parameters through actual field tests for common frequency assignment hard handoffs implemented and applied in PCS 3.1.0 (package version).

-Stage 1

: Analysis of wireless environment for test section for common frequency allocation hard handoff test

-Second stage

: Derivation and setting of optimal parameter by changing related parameters

As described above, in performing the common frequency allocation hard handoff, the first step of analyzing the wireless environment in the application section and the step of deriving and setting the optimal parameter through the optimal parameter setting and the change test according to the analysis result It can be divided into the second stage.

The verification method for each step is as follows.

-Stage 1

-Logging and analyzing the data in the traffic state of the frequency assignment in service at the actual site.

-Traffic data analysis

-Analysis of incoming pilot signal by frequency allocation for test interval

: Analyze the traffic handoff interval and the Ec / Io level (level 1_A cell) at the time of handoff in the frequency allocation corresponding to the common frequency allocation.

(→ Confirm traffic handoff occurrence point and Ec / Io level of 1FA in cell A and B as shown in FIG. 7)

The Ec / Io level (level 2_A cell) in the traffic handoff period corresponding to the common frequency allocation in the frequency allocation corresponding to the boundary frequency allocation is checked.

Initial parameter setting

The T_DOWN value should be better than the Ec / Io value (level 2_A cell) for the frequency allocation designated as the boundary frequency allocation at the traffic handoff occurrence point.

For example, if the Ec / Io value (-4dB) of level 2_A cell is set to 10 (-5dB), even if a handoff is performed from T_DOWN value to 1FA, which is a common frequency allocation, there is a possibility of already falling out of coverage of 1FA. Since it is high, the setting value of T_DOWN should be set better than Ec / Io of level 2_A cell.

CDMA _CH_MODE is set to Border_FA for the base station for the incoming signal in the handoff area.

→ If the terminal is introduced with a signal that is not designated as Border_FA at the time when the common frequency allocation handoff is to be performed, the T_TDOWN timer is canceled, and thus the probability of failing to perform the proper handoff is high.

-Whether the success of the common frequency allocation hard handoff is important is the time of handdown, so the parameters of the T_TDROP and PSMM request periods use existing default values and set the T_DOWN level according to the analysis result.

(→ T_DOWN level ≥ level 2_A cell)

-Second stage

-Common frequency allocation hard handoff test in test interval

-The success rate is calculated by repeating the common frequency allocation hard handoff test for the test section several times.

-Analysis of drop cause when call drop occurs

→ Missing of proper handdown time due to the inflow of signals not designated as Border_FA, and confirming whether the radio environment is poor in frequency allocation after handdown.

-Derivation of optimal parameter setting value through parameter change work

-The maximum success rate is obtained by changing the T_DOWN level value for the same test section and changing the channel mode for the signal flowing into the test section.

An embodiment of the process of initializing a related parameter when applying a common frequency allocation hard handoff field is as follows.

-Test environment

-BSC5-BTS15: 2-FA 3 sectors (PN: 36 (alpha), 204 (beta), 372 (gamma)) ?? wus ??-BSC4-BTS13: 1-FA 2 sectors (PN: 20 (alpha) ), 180 (beta))

On the moving path for the test, BSC5-BTS15 gamma is an environment bordered by BSC4-BTS13.

Parameter setting (subcell-info. Of BSC5-BTS15)

PSMM_REQ_PERIOD = 1 second

T_TDOWN = 0 seconds

HANDDOWN_FA = 1

- Test Methods

-1st test

Gamma (372) and FA-1 (freq. = 125) of BSC5-BTS15 are specified as Border_FA and the basic common frequency allocation hard handoff operation and call-setup are tested.

-The relevant parameters (T_DOWN, PSMM_REQ_PERIOD, etc.) shall be tested by default.

-2nd test

-Experiment with changing Border_FA designation for two sectors of BSC5-BTS15 and changing T_DOWN value.

-Set up 5 terminals to call the FA-1 (freq. = 125) in the beta (204) area of the BSC5-BTS15 and drive the road to the BSC4-BTS13 (20,180) area after specifying the gamma (372) of the BSC5-BTS15. Go to.

- Test result

-1st test

It is confirmed that the basic operation and call setup of the common frequency allocation hard handoff are performed in the same manner as the proposed method.

-2nd test

Border_FA settings T_DOWN Handoff Success Rate (Success / Try) Only Gamma (372) of BSC5-BTS15 specifies Border_FA 10 (-5 dB) 90% (27/30) 12 (-6 dB) 53% (8/15) 14 (-7 dB) 20% (1/5) 8 (-4dB) 100% (14/14) Gamma (372) and alpha (36) of BSC5-BTS15 are designated Border_FA 10 (-5 dB) 100% (15/15) 12 (-6 dB) 90% (9/10) 14 (-7 dB) 40% (2/5)

The present invention can be variously modified and can take various forms and only the specific embodiments thereof are described in the detailed description of the invention. It is to be understood, however, that the present invention is not limited to the specific forms mentioned in the detailed description of the invention, but rather includes all modifications, equivalents, and substitutions within the spirit and scope of the invention as defined by the appended claims. It should be understood to do.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention implements a common frequency allocation hard handoff to derive optimal related parameters, thereby reducing the handoff cost between frequency allocations and improving the handoff success rate, thereby providing an optimal performance condition.

Claims (21)

Analyzing data logging in traffic conditions for frequency allocation during actual field service for the interval for which the common frequency allocation hard handoff test is to be performed; Identifying a traffic handoff period and an Ec / Io level at the time of handoff in frequency allocation corresponding to the common frequency allocation; Checking the level of Ec / Io in the traffic period corresponding to the common frequency allocation in the frequency allocation corresponding to the boundary frequency allocation; A method for optimizing a common frequency allocation hard handoff parameter in a code division multiple access system, comprising: setting an initial parameter. The method of claim 1, wherein the Ec / Io level at the time of handoff is represented by a level 1_A cell. The method according to claim 1, wherein the level of Ec / Io in the traffic period corresponding to the common frequency allocation is represented by level 2_A cell. The method of claim 1, wherein in setting the initial parameter: A method of optimizing a common frequency allocation hard handoff parameter in a code division multiple access system in which the T_DOWN value should be better than the value of Ec / Io for the frequency allocation designated as the boundary frequency allocation at the traffic handoff occurrence point. The equation of claim 4, wherein the value T_DOWN should be better than the value Ec / Io. A method of optimizing a common frequency allocation hard handoff parameter in a code division multiple access system represented by T_DOWN level ≥ level 2_A cell. 2. The method of claim 1, wherein the parameter is CDMA_Ch_Mode, PSMM Request Period, T_DOWN, T_TDOWN, Handdown_FA. The method of claim 6, wherein the CDMA_Ch_Mode is, A method for optimizing a common frequency allocation hard handoff parameter in a code division multiple access system, wherein the frequency allocation of the subcell indicates whether the common frequency allocation or the boundary frequency allocation is performed. The code division multiple access according to claim 7, wherein the common frequency allocation includes the same frequency allocation currently being serviced in a neighboring subcell, and the boundary frequency allocation does not have the same frequency allocation currently serving in a neighboring subcell. A method of optimizing common frequency assignment hard handoff parameters in a system. The method of claim 6, wherein the PSMM Request Period, In the code division multiple access system, when the frequency allocation of the corresponding subcell is defined as a border, the system determines the period of sending a pilot measurement request order (PMRO) to the forward link so that the terminal reports the PSMM periodically. How to optimize common frequency assignment hard handoff parameters. 10. The method of claim 6 or 9, wherein the default setting value of the PSMM Request Period is 1 second. The method of claim 6, wherein in T_DOWN, A method for optimizing a common frequency allocation hard handoff parameter in a code division multiple access system instructing a common frequency allocation hard handoff when the strength of a pilot received by a mobile station in a sector selected for boundary frequency allocation is equal to or smaller than T_DOWN. 12. The method of claim 6 or 11, wherein the default setting of T_DOWN is 10 (-5 dB). The method of claim 6, wherein T_TDOWN, Common Frequency Assignment Hard Handoff in Code Division Multiple Access Systems Instructing Common Frequency Assignment Hard Handoff When T_TDOWN Seconds Have Elapsed with the Strength of the Pilot Received by the Mobile Station in the Sector Set to Boundary Frequency Assignment Parameter optimization method. 14. The method of claim 6 or 13, wherein the default setting value of T_TDOWN is 0 seconds. The method of claim 6, wherein Handdown_FA is A method for optimizing a common frequency allocation hard handoff parameter in a code division multiple access system, wherein the bitmap specifies a target frequency allocation to hand down when the mobile station satisfies the handdown condition in a boundary subcell. 16. The method of claim 15, wherein each bit represents an allow / disallow of handdowns to corresponding frequency assignments. 17. The method of claim 16, wherein granting handdown indicates 0 and disallowing indicates 1. 16. The method of claim 6 or 15, wherein the default setting of Handdown_FA is one. Conducting a common frequency allocation handoff test interval in the test interval; Analyzing the cause at the time of call drop; A method for optimizing a common frequency assignment hard handoff parameter in a code division multiple access system, comprising: setting an optimal parameter derivation value through a parameter change operation. The method of claim 7, wherein analyzing the cause of the call drop, A method for optimizing a common frequency allocation hard handoff parameter in a code division multiple access system that misses an appropriate handdown point due to an inflow of a signal not designated as Border_FA or checks whether the radio environment is poor in frequency allocation after handdown. The method of claim 8, wherein the setting of the optimal parameter derivation value through the parameter change operation, A method of optimizing a common frequency allocation hard handoff parameter in a code division multiple access system, which obtains a maximum success rate by changing a T_DOWN level value and changing a channel mode for a signal flowing into a test section for the same test section.