KR100277033B1 - Method for optimize softer hand-off in cdma wireless comunication system - Google Patents

Abstract

The present invention relates to a CDMA network softer handoff optimization method.

A configuration of the present invention includes the steps of establishing a test route and confirming system status; Setting and adjusting high frequency parameters; Optimizing coverage; Checking whether the received power, the mobile station transmit power, and the Ec / Io parameters satisfy the criterion, and if not, returning to the step of setting and adjusting the high frequency parameters; Establishing a handoff route if the criterion is satisfied; Optimizing handoff by function; If the softer handoff does not satisfy the function, returning to adjusting the system parameters and optimizing the functional handoff; Improving coverage and call quality if the softener handoff satisfies the function; Checking whether parameter adjustment is possible and returning to the step of improving coverage and call quality if possible; And reporting a primary coverage state diagram, a handoff failure history, and a shadow area diagram, thereby optimizing the softener handoff.

In the CDMA system according to the present invention, the softer handoff method includes setting up a test route, checking a system state, setting and adjusting high frequency parameters, optimizing coverage, receiving power, mobile station transmission power, and Ec. Investigate whether the / Io parameter satisfies the criterion, and if not satisfied, returns to the step of setting and adjusting the high frequency parameter, if the criterion is satisfied, setting the handoff route, optimizing the handoff by function, If the handoff does not satisfy the function, adjust the system parameters and return to the step of optimizing the function-specific handoff, if the softener handoff satisfies the function, improve the coverage and call quality, investigate whether the parameter can be adjusted. Where possible, steps to improve coverage and call quality again It comprises a step back and the primary coverage and the state diagram handoff failure history and the steps to see the shaded area also.

According to the present invention, it is possible to maximize the capacity of the system according to the high frequency parameter adjustment and the system parameter change, while maintaining good sound quality.

Description

Optimizing Softener Handoff in Code Division Multiple Access Mobile Communication System {METHOD FOR OPTIMIZE SOFTER HAND-OFF IN CDMA WIRELESS COMUNICATION SYSTEM}

The present invention relates to a softener handoff method in a CDMA mobile communication system, and more particularly, to a method for optimizing softener handoff by adjusting high frequency parameters and system parameters.

In general, handoffs made in a code division multiple access mobile communication system include soft handoff, softer handoff, and hard handoff. Among them, soft handoff means that the transfer of a call from an existing busy base station to the same scheduled base station is performed without forced disconnection of the existing busy channel. In other words, a cell serviced by a given base station is divided into a plurality of sectors, and a handoff required as a mobile station currently serving is moving between sectors is called a softer handoff.

On the other hand, subscribers in the softer handoff period are power controlled by both sectors during softer handoff to mitigate path loss differences due to different fading standard deviations. In this case, in the active region, both sector antennas operate to separate the multipath reception levels. The soft handoff differs from the soft handoff in that it is a handoff in the same base station, and the remaining functions are almost identical.

The above-described soft handoff is performed by the steps described below.

In the first step, when a mobile station moves from one sector in the base station to another sector of the same base station and the target cell exceeds the T_add of the pilot channel, the mobile station transmits the pilot channel measurement result to the pilot strength measurement message and reports it to the base station. Step. In the second step, the base station transmits a handoff direction to the mobile station through a handoff direction message. In the third step, the mobile station transmits the handoff completion to the base station through the handoff completion message. In the fourth step, when the pilot strength of the serving cell falls below T_drop, the mobile station operates the handoff drop timer. In the final step, the mobile station disconnects the serving cell when the handoff drop timer passes T_tdrop.

However, the above-mentioned softener handoff occupies one channel and thus does not have a significant effect on the channel capacity, but may increase the total capacity by increasing the intersector interference.

Accordingly, an object of the present invention is to provide a method for performing an optimum softener handoff through high frequency parameter adjustment and system parameter adjustment in order to optimize the softener handoff.

According to the present invention for achieving the above object, in a code division multiple access mobile communication system serving a mobile station located in one cell composed of a plurality of sectors, a test route is established and the system state is confirmed. Setting parameters to optimize coverage; and determining whether the received power corresponding to the set high frequency parameters, the mobile station transmit power, and the Ec / Io parameters satisfy the criterion. Optimizing soft handoff for each function by setting a route for softer handoff when the criteria for satisfying the set and adjusted high frequency parameters are satisfied. If not satisfied, the softener handoff satisfies the function. Adjusting a system parameter so as to report a first coverage state diagram, a softener handoff failure history, and a shadow area diagram corresponding to the high frequency parameter and the system parameter set such that the softer handoff satisfies a function. A soft handoff method is proposed.

1 is a diagram illustrating a control flow for optimizing softener handoff in a code division multiple access mobile communication system according to an embodiment of the present invention.

FIG. 2 is a diagram for showing a handoff region of a sector antenna having a horizontal beam width of 110 degrees. FIG.

3 is a diagram for showing a handoff region of a sector antenna having a horizontal beam width of 105 degrees.

4 shows a handoff region of a sector antenna with a horizontal beamwidth of 85 degrees.

5 is a diagram for showing a handoff area of a sector antenna having a horizontal beam width of 65 degrees.

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

First, in the present invention, it is preferable to provide a criterion for receiving power greater than -91 dBm, mobile station transmit power less than +10 dBm, and Ec / Io greater than -14 dB. Accordingly, it is desirable to optimize the application according to the purpose of using a narrow beamwidth antenna to use a large capacity and to reduce the coverage, or to use a wide beamwidth antenna to widen the coverage and reduce the capacity. In addition, it is preferable to increase the T_Add, T_drop and T_comp values and decrease the T_tdrop value in order to reduce the handoff area but increase the capacity. It is desirable to raise.

On the other hand, as mentioned above, since softer handoff occupies one channel, there is no significant effect on channel capacity, but the increase in inter-sector interference can lead to a decrease in overall capacity. Therefore, in the optimization process of softer handoff, the handoff area between sectors should be adjusted to an appropriate level.

The softer handoff is greatly influenced by which antenna is used for the antenna. Therefore, when selecting an antenna, the horizontal beam width of the antenna is very important, and the softer handoff area varies depending on the type of antenna. The same applies to the CDMA mobile communication system, and the softener handoff region varies according to the beam width of the sector antenna, and the handoff incidence rate is also different.

For example, in the CDMA mobile communication system, the softer handoff area increases as the wider beamwidth antenna is used. For this reason, it is common to use 65-degree antennas in high-traffic areas, and 90-degree antennas in other areas. The use of the 65-degree antenna can accommodate a large amount of capacity, but the coverage decreases, and the larger the beamwidth, the larger the coverage, but the capacity is reduced. In other words, when an antenna having a narrow beam width is used, channel resources are not affected, and high frequency output is appropriately distributed for each sector.

However, when the antenna having a wide beam width widens the overlapping range between sectors, channel resources are not affected, but all high frequency outputs are required for each sector, thereby limiting the high frequency output. Therefore, an antenna with an appropriate beam width according to the coverage of the base station should be optimized to satisfy both coverage, quality, and capacity.

In addition, handoff optimization should be performed not only by high frequency parameters but also by system parameters.

The present invention is largely composed of an optimization method by adjusting a high frequency parameter and an optimization method by adjusting a system parameter.

The high frequency parameters include total antenna transmit attenuation, antenna direction, antenna tilt, and antenna beamwidth. The dual antenna beamwidth has the greatest effect on the handoff area of softer handoff.

System parameters include T_add, T_drop, T_comp, and T_Tdrop.

▶ Optimization by adjusting high frequency parameter

Optimization by antenna beamwidth

This parameter is the most important factor in determining the softer handoff area.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.

As mentioned above, the softer handoff region varies according to the beam width of the sector antenna. Therefore, using an antenna with proper handoff is the most important factor in optimizing capacity.

There are various kinds of antennas such as 65 degrees, 85 degrees, 105 degrees, and 110 degrees. As the antenna having a wide beam width is used, the softer handoff area increases. Replacing the antennas makes a lot of changes to the overall system, so it's easy to optimize later if you choose the best antenna for the initial network design. In general, the use of a narrow beamwidth antenna can accommodate a large amount of capacity, but the coverage is reduced and the use of a wider beamwidth antenna increases coverage but decreases capacity.

Other high frequency parameters affect the softer handoff slightly, but the basic, most basic and important factor in softer handoff is most affected by the adjustment of the beamwidth. This is shown in Figures 2-5.

FIG. 2 is a diagram illustrating a handoff region of a sector antenna having a horizontal beam width of 110 degrees, and FIG. 3 is a diagram illustrating a handoff region of a sector antenna having a horizontal beam width of 105 degrees. 4 is a diagram illustrating a handoff region of a sector antenna having a horizontal beam width of 85 degrees, and FIG. 5 is a diagram illustrating a handoff region of a sector antenna having a horizontal beam width of 65 degrees. As shown in FIG. 2 to FIG. 5, the narrower the beam width, the narrower the coverage due to softer handoff.

▶ Optimization by system parameter

When reducing the handoff area, the values of T_add, T_drop, and T_comp are raised and T_tdrop is lowered.

When increasing the handoff area, the T_add, T_drop and T_comp values are lowered and the T_tdrop value is raised.

If you explain this in detail for each parameter,

Lowering T_add increases the handoff area and decreases the capacity.

Increasing the T_add value decreases the handoff area and increases the capacity.

Decreasing T_drop increases the handoff area and decreases the capacity.

Increasing the T_drop value decreases the handoff area and increases the capacity.

Decreasing T_comp increases the handoff area and decreases the capacity.

Increasing the T_comp value decreases the handoff area and increases the capacity.

Reducing the T_tdrop value can improve the sound quality by reducing the handoff area and quickly removing low-level signals, but it is more likely that the handoff will fail in areas where the propagation environment changes rapidly. On the other hand, increasing the T_tdrop value increases the handoff area and holds the low level signal for a long time, which is bad in terms of sound quality and capacity, but increases the success rate of handoff.

If the handoff area is too wide, the channel capacity is irrelevant in softer handoff, but the overall system capacity is reduced because of interference, and too narrow the handoff success rate. Therefore, setting the proper handoff area is the most important part of the optimization.

Referring to Figure 1 the operation of the present invention,

Initially set up a test route and check the system status;

Adjust and adjust the high frequency parameters. In particular, the beamwidth of the sector antenna is set at this time;

This process optimizes coverage;

Then if the received power is greater than -91 dBm, the mobile station transmit power is less than +10 dBm, and Ec / Io is greater than -14 dB, the radio frequency parameter is reset;

If the criterion is satisfied, a route of handoff is established;

After that, the optimization of handoff by function is performed;

At this time, if the function of the softener handoff is not satisfied, the system parameters are adjusted again to perform the function-specific optimization work again;

Coverage and call quality are improved if the function of softer handoff is satisfied;

Then check if the parameter is adjustable and if possible improve coverage and call quality again;

If the parameter is not adjustable, it is optimized, so it operates as a step of reporting the primary coverage status diagram, the handoff failure history, and the shadow area diagram.

The adjustment of system parameters and high frequency parameters play an important role in determining how much softer handoff area will eventually be determined.

Optimizing the softer handoff can also be seen as determining the extent to which the softer handoff area is to be made.

If the handoff area is too narrow and the handoff success rate is too low or too wide to reduce the overall capacity due to interference, the system parameters and the high frequency parameters can be adjusted in an optimal order to maximize the system's performance.

The present invention operating as described above has the effect of maintaining a good sound quality while maximizing the capacity of the system according to the change of the system parameters, and adjust the system parameters for optimal soft handoff.

Claims (5)

A soft handoff method of a code division multiple access mobile communication system serving a mobile station located in one cell composed of a plurality of sectors, Setting up a test route, checking the system status and setting high frequency parameters to optimize coverage; Determining whether the received power, the mobile station transmit power, and the Ec / Io parameter corresponding to the set high frequency parameters satisfy the criterion if not satisfied, and adjusting the set high frequency parameters; Optimizing soft handoff for each function by setting a route for softer handoff when the criterion is satisfied in response to the set and adjusted high frequency parameters; Adjusting a system parameter such that the softer handoff satisfies a function if the softener handoff according to the optimization does not satisfy a function; And reporting a primary coverage state diagram, a softener handoff failure history, and a shadow area diagram corresponding to the high frequency parameter and the system parameter, wherein the softer handoff is set to satisfy a function. Softer handoff method in a connected mobile communication system. The method of claim 1, wherein the criterion is And said criterion is presented such that the received power is greater than -91 dBm, the mobile station transmit power is less than +10 dBm, and the Ec / Io is greater than -14 dB. The method of claim 1, In setting and adjusting the beamwidth of the sector antenna, which is one of the high frequency parameters, it is necessary to use a narrow beamwidth antenna to use a large capacity and to reduce the coverage, or to use a wide beamwidth antenna to broaden the coverage and reduce the capacity. A soft handoff method of a code division multiple access mobile communication system, characterized in that for optimizing the sigma. The method of claim 1, And a T_Add, T_drop, T_comp value, and a T_tdrop value, in order to increase the capacity in adjusting the system parameters. The method of claim 1, A soft handoff method of a code division multiple access mobile communication system, characterized in that the T_Add, T_drop and T_comp values are lowered and the T_tdrop value is raised to increase the handoff area in adjusting the system parameters.

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