KR19990061205A - Optimization of Softer Handoff in Code Division Multiple Access Networks - 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

Optimization of Softer Handoff in Code Division Multiple Access Networks

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

As is well known to those skilled in the art, softer handoff refers to the transfer of a call from an existing busy base station to the same scheduled base station without forced disconnection of the existing busy channel.

Subscribers in the handoff interval are power controlled by both sectors during softer handoff to mitigate path loss differences due to different fading standard deviations.

In the active region, both sector antennas operate to separate the multipath reception levels.

The difference from soft handoff is that it is a handoff in the same base station, and the remaining functions are almost the same as soft handoff.

The soft handoff process is performed when the mobile station moves from one sector in the base station to another sector in the same base station, and the mobile station transmits the pilot channel measurement result to the pilot strength measurement message when the pilot channel strength exceeds T_add. Reporting to the base station;

The base station transmitting the handoff direction to the mobile station through a handoff direction message;

Sending, by the mobile station, the handoff completion to the base station through the handoff completion message;

When the pilot strength of the serving cell falls below T_drop, the mobile station operating a handoff drop timer; And

And disconnecting with the serving cell when the handoff drop timer has passed by T_tdrop.

However, since softer handoff occupies one channel, there is no significant effect on channel capacity, but the increase in intersector interference can lead to a reduction in overall capacity.

Accordingly, an object of the present invention is to provide an optimal handoff method through high frequency parameter adjustment and system parameter control in order to optimize the softer handoff.

1 is a flowchart illustrating a softener handoff optimization method according to the present invention.

2 is a handoff area diagram of a sector antenna having a horizontal beam width of 110 degrees;

3 is a handoff area diagram of a sector antenna having a horizontal beam width of 105 degrees;

4 is a handoff area diagram of a sector antenna having a horizontal beam width of 85 degrees;

5 is a handoff area diagram of a sector antenna having a horizontal beam width of 65 degrees;

One preferred embodiment of the softer handoff method in the CDMA system according to the present invention for achieving the above object is,

Establishing a test route and verifying 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 for each 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

And reporting the primary coverage status map, handoff failure history, and shadow map.

In the present invention, it is preferable to present a criterion 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.

Depending on the beamwidth of the sector antenna among the high frequency parameters, it is best to optimize the application according to the purpose of using a narrow beamwidth antenna to use a large capacity and a small coverage, or to use a wide beamwidth antenna to broaden the coverage and reduce the capacity. Desirable,

In order to reduce the handoff area, but to increase the capacity, it is preferable to increase the T_Add, T_drop and T_comp and lower the T_tdrop value.

In order to reduce the capacity, but to increase the handoff area, it is preferable to decrease the T_Add, T_drop and T_comp and increase the T_tdrop.

Softer handoff occupies one channel, so there is no significant effect on channel capacity, but increased intersector interference can lead to a reduction in overall capacity.

Therefore, in the optimization process of softer handoff, the handoff area between sectors should be adjusted to an appropriate level.

Softer handoff is heavily influenced by the type of antenna used.

When selecting an antenna, the horizontal beam width of the antenna is very important, and the handoff area varies depending on the type of antenna.

Softer handoff does not have a significant effect on channel capacity since it occupies one channel, but may increase capacity due to increased intersector interference.

According to the beam width of the sector antenna used in the CDMA system, the softener handoff area is changed, and the handoff incidence rate is also different.

As the antenna uses a wider beamwidth antenna, the softer handoff area increases.

In general, 65-degree antennas are used in high-traffic areas, such as busy streets, and 90-degree antennas are used in other areas.

When using a 65-degree antenna, it can accommodate a lot of capacity, but the coverage is reduced, and the use of a wider beamwidth antenna increases coverage but decreases capacity.

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.

If this is described with reference to FIGS.

The softer handoff area varies depending on the beamwidth of the sector antenna. Therefore, using an antenna with proper handoff is the most important factor in optimizing capacity.

There are various 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, 65-degree antennas are used in high-traffic areas such as busy areas, and 90-degree antennas are used in areas where there is not much traffic.

The use of narrow beamwidth antennas can accommodate a lot of capacity, but the coverage is reduced, while the use of a wider beamwidth antenna increases coverage but reduces 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.

▶ 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.

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 handoff success rate.

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.

According to the present invention operating as described above, it is possible to maintain a good sound quality while maximizing the capacity of the system in accordance with high frequency parameter adjustment and system parameter change.

Claims (5)

Establishing a test route and verifying 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 for each 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 A method for softer handoff in a code division multiple access network, comprising reporting a primary coverage status diagram and a handoff failure history and a shadow map. 2. The method of claim 1 wherein a criterion is presented such that 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. According to claim 1, According to the beam width of the sector antenna of the high-frequency parameters, whether to use a large capacity and narrow coverage using a narrow beamwidth antenna, or to use a wide beamwidth antenna to increase the coverage and reduce the capacity Softer handoff method in code division multiple access networks optimized for use. 2. The method of claim 1, wherein the handoff area is reduced but the T_Add, T_drop, T_comp values are increased and the T_tdrop values are decreased to increase the capacity. 2. The method of claim 1, wherein the capacity is reduced but the T_Add, T_drop, T_comp values are lowered and the T_tdrop value is raised to increase the handoff area.