KR0120727B1 - Method for reducing the hand-off during calling in the cdma boundary cell - Google Patents

Abstract

The method is for minimizing hand-off phenomenon of the call generating on the service boundary region. The method is divided by 3 cell types like omni-cell, sector cell, and combination of two types. In omni-cell type, the pilot intensity(Ac/at) of the neighbor cell is calculated, and compared with predetermined value(T_Ac/at), if the call comes from the boundary region. If the intensity is less, the length between the mobile station and the cell antenna(DBMB) is calculated, and ordinary service is provided if the DBMB is greater than predetermined value(T_DBMB). In sector cell or combination cell types, the call is processed with different process according if the call is come from boundary cell or boundary sector.

Description

Reduction of In-Hand Handoff in Boundary Area Code Division Multiple Access Cells

1 is a diagram illustrating a method of using T_DBMB and pilot strength in omnicell.

2 is a diagram illustrating a scheme by sector division in a sector cell.

3 is a diagram illustrating a scheme based on T_DBMB and sector classification in a sectorized cell.

4 is a flowchart illustrating a call processing process in an om micelle.

5 is a flowchart illustrating a call processing process in a sector cell.

6 is a flowchart illustrating a mixed call processing process in a sector cell.

The present invention relates to a method for reducing handoff, and more particularly, to a method for reducing busy handoff in a CDMA cell in a border area.

If the base station is installed as a digital base station in the initial mobile communication network deployment and the subscriber demand is saturated, the number of frequency assignments per base station is increased. Is unnecessary.

If digital base stations are initially installed on main roads (such as highway toll gates) out of the city, the possibility of digital subscribers handing off to an analog system only occurs at the border area off the main road.

As an analog mobile communication system in Korea, APX (Autoplex) system in all regions except Busan region and EMX (Electronic Mobile Exchange) system in Busan region are installed and are in service.

Currently, IS-41 is implemented by Internetworking between APX and EMX.

A subscriber at the boundary of the two jurisdictions takes a considerable time (15 seconds) to handoff to another system during the call, and the subscriber must pause the call during handoff processing time. As a result, most subscribers drop the call during handoff processing between different models.

As a result, the completion rate of handoff calls between different models is low compared to the completion rate of handoff between base stations in the same system where APX and EMX systems are currently installed at the boundary.

The US EIA / TIA Standards Committee is preparing the IS-41C for interoperability between CDMA systems and other systems (analog systems, TDMA systems), but it has not yet been adopted as a standard and it will take some time before standardization is reached. .

In addition, since the system developed in Korea develops CDMA-only base station and exchanger, in order to interwork with analog system, CDMA system and analog system must newly implement signaling method (e.g. IS-41C) for interworking between different models. do.

On the contrary, CDMA mobile communication systems in the US have no differences from analog exchanges in terms of exchanges except for the radio part interface, and do not need a separate connection standard for interworking between exchanges.

As existing analog exchanges accept both CDMA and analog terminals, CDMA is used as an auxiliary means of analog, so existing IS-41 MAP is sufficient, and no other existing signaling method is required.

As a result, there is no enthusiasm for the need for standardization of IS ~ 41C, except for the rare development of CDMA dedicated exchanges.

Accordingly, an object of the present invention is to provide a method for improving call quality by reducing the probability of call disconnection without processing handoff between different types when the subscriber in the CDMA mobile communication system is at the boundary of the CDMA system service area.

In order to achieve the above object, the present invention is limited by dividing the cell into an omnicell, a sector cell, and a mixture of the two methods for a method of reducing handoff.

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

1 is a diagram illustrating a method of using T_DBMB and pilot strength in omnicell.

In connection with FIG. 4, the call processing process in Omnicell will be described.

If the cell antenna is omni-directional, that is, omni-cell, it allocates some of the traffic channels to the call flowing into the boundary cell and RTD (Round) in the boundary cell for the call occurring in the boundary cell. Calculate Distance Between Mobile Station and Base Station (hereinafter abbreviated as DBMB) using Trip Delay, etc., and the value is a certain distance (Threshold of DBMB: abbreviated as T_DBMB) If it is smaller, that is, it is unlikely that the call is unlikely to leave the boundary cell during the call, the traffic channel is allocated, and if the call to which the traffic channel is allocated leaves the T_DBMB region and approaches the boundary region, power is reduced. Increase the callable area through control, etc.

However, the received signal level (hereinafter, abbreviated as T_Ec / It) set for determining whether there is a boundary area among pilot set signals transmitted by other cells or sectors and received by the mobile station when the distance between the cell antenna and the mobile station is greater than a certain distance (for example, If none of the pilots is equal to or greater than the minimum value of Active and Candidate Set Threshold, it is determined to be out of the CDMA system service area of the mobile station and the generated call is blocked (see FIG. 4 for the call processing method thereof).

In the border zone cells, it is assumed that the border zone cell arrangement has been made so that the signal level received by the mobile station from the neighboring cell is greater than or equal to the T_Ec / It value when the T_DBMB value is reached within the border zone (area facing the CDMA cells). See also 1).

As shown in FIG. 1, the pilot strength of another cell received by the mobile station at a point greater than or equal to the T_DBMB distance from the boundary cell antenna does not exceed the CDMA system boundary until T_Ec / It is greater.

Given the call cutting probability and cell radius R required for subscribers running at maximum speed, the maximum value of T_DBMB required is:

For simplicity of analysis, assuming that the service time distribution of each call is an exponential distribution, the service time of the call in T_DBMB designation in the boundary direction direction (local road direction in Fig. 1) is the same probability as the service time of the call occurring at that point. Has a density function.

And it is assumed that the vehicle travels from its position in the opposite direction of the cell center, that is, at the maximum speed to the cell boundary area.

In addition, we only consider calls that exist at the T_DBMB point, because most of the subscribers leaving the cell due to the distance of T_DBMB from the cell center are hand roped to neighboring CDMA cells, and the subscribers leaving the boundary cell (the point where the distance from the cell antenna is T_RTD or more). In addition, it is assumed that the call generated at the boundary area where the pilot received signal strength is T_Ec / It or more is small, for simplicity of analysis.

If the maximum speed is the time until the Vmax call is completed, that is, the service time per call at t, the distance D traveled is

D = V _max × 9 (1)

The truncation probability of service time t per

(2)

The time t _req ) required to be less than the raw cutting probability ** no manuscript *** is obtained from equation (2).

(3)

Rewriting equation (3) as t _req ,

(4)

Pr (tt _req ), which is the probability of truncation of an arc generated in a vehicle running at full speed, and the average service time. If is given, the distance difference D between R and T_DBMB can be obtained by comparing the time obtained in Eq.

(5)

If T_DBMB is set using the D value obtained from Equation (5) and the cell radius R, the maximum value of T_DBMB at the truncation probability given to the call that moves at the maximum speed can be obtained as follows.

T_DBMB≤R-D (6)

In addition, the T_DBMB minimum value where the neighbor cell pilot signal strength received by the mobile station in the region adjacent to the CDMA cells in the boundary cell region satisfies T_Ec / It or more is obtained.

This value can be obtained from a real environment estimate for a given T_Ec / It or can be calculated quantitatively.

For a quantitative method of calculating cell pilot received signal strength, see Qualcomm Inc. See Chapter 10 System Planning in the CDMA System Engineering Training Handbook.

It is assumed that an appropriate T_DBMB value is set in the system with the T_DBMB obtained in this way and the T_DBMB value obtained in equation (6).

If the distance between the cell antenna and the mobile station is more than a certain distance, but the strength of the received pilot set of the mobile station is greater than T_Ec / It (also possible to set the active and Candidate Set signal peaks), it goes to the boundary area. Since you cannot see it, set the call path for the outgoing call.

In addition, if the mobile station supports dual mode, the mobile station may be instructed to additionally attempt to analog system.

2 is a diagram illustrating a scheme based on sector division in a sector section.

With reference to FIG. 5, a call processing process in a sector cell will be described.

If the cell antenna is directional, that is, in a system with multiple sectors in one base station, if it is a three sector cell, one of the sectors in the base station is dedicated to handoff and the other two support both the originating and handoff calls as the other cells. Configure the cell to

That is, one sector C is a handoff-only sector, and a call generated from the sector is not serviced, but only a handoff call entering the sector (see FIG. 5 for a call processing method thereof). ).

In other words, the call cut off during the call is suppressed as much as possible.

At this time, the call originating from the non-sector c flows into the sector c during the call and moves to the border area, and the power is controlled to increase the serviceable area of the call, or the antenna output of the sector c is higher than that of other sectors. Use ways to increase the area where possible.

Sector c processes only the handoff call, so the service area may be larger than other sectors.

In addition, if the mobile station supports dual mode, the mobile station may be further instructed to call the analog system.

FIG. 3 is a diagram for explaining a scheme based on T_DBMB and sector division in a sectorized cell.

6, a hybrid call processing process in a sector cell will be described.

The above two methods are mixed, and the cell is sectorized, and the sector c of the boundary area is divided into a region capable of processing an originating signal and an area capable of handoff call processing based on T_DBMB. Calls from mobile stations within T_DBMB are required to make calls, and calls outside the T_DBMB area to the border area extend the range of calls possible through power control.

However, if the distance between the originating point of the mobile station and the cell antenna in the border sector is greater than or equal to the boundary cell presence determination value, it is determined that it is out of the CDMA system area and blocks the trial call without service even if the mobile station attempts to do so. .

This reduces the area of processing only handoff calls within the cell and does not require pilot signal measurements, compared to the above two methods. have.

And if the mobile station supports dual mode, it can additionally instruct the mobile station to make a call to the analog system.

When the mobile station in the cell of the border area wants to handoff during the call, the call quality rarely occurs, so the quality of service is increased.

In other words, it is not necessary to implement a handoff function between the CDMA system and another system.

Claims (3)

A method for minimizing the possibility that a mobile station in a boundary cell of a CDMA mobile communication system service area leaves the system boundary cell during a call, in which the cell is omnicelled; A first step (40, 41, 42, 48) of checking whether a new call is received and providing a general call processing service if it is not a new call and determining whether the call is a boundary cell; A second step (43,48) of providing a general call processing service if it is not determined as a boundary cell in the first step and calculating adjacent cell pilot strength (Ec / It) if it is determined as a boundary cell; After performing the second process, if at least one of the pilot set signals received by the mobile station is greater than a predetermined value (T_Ec / It), the general call processing service is provided; otherwise, the distance between the mobile station and the cell antenna (DBMB) is determined. Third process 44, 45, 48 for calculating; And a fourth process (46, 47, 48, 49) that blocks the call if the DBMB is larger than a predetermined value (T_DBMB) and provides a general call processing service. How to reduce handoff during A method for maximally suppressing a possibility that a mobile station in a boundary cell of a CDMA mobile communication system service area leaves the system boundary cell during a call, comprising: a cell configured as a sector cell; A first step (50, 51, 52, 54) of determining whether the call is a new call and providing a general call processing service if the call is not a new call and determining whether the call is a boundary cell or a boundary sector (c); And a second process (53, 54, 55) for providing a general call processing service if the boundary cell is not the boundary cell or the boundary sector in the first process and blocking the call if the boundary cell is the boundary cell. Reduction of busy handoff in local CDMA cell. In a method for minimizing the possibility that the mobile station in the boundary cell of the CDMA mobile communication system service area leaves the system boundary cell during a call, the cells are mixed into omnicells and sectorcells; A first step (60, 61, 62, 66) of determining whether a call arrives and whether it is a new call, providing a general call processing service if it is not a new call, and determining whether the call is a boundary cell or a boundary sector (c); A second step (63, 66) of providing a general call processing service and calculating a boundary cell, a border sector, and DBMB if the border cell is not the border cell or the border sector (c) in the first step; And if the DBMB of the second process is larger than T_DBMB, the third party (65, 66, 67) blocks the call and provides a general call processing service. Reduction method.