KR19990058815A - Optimization of Reverse Link Service Zones for Code Division Multiple Access Networks - Google Patents

Abstract

The present invention relates to a reverse service area optimization method of a code division multiple access (CDMA) network, and more particularly, to optimize a service area of a terminal in which sufficient power is allocated to overcome an overall interference level of a base station in a reverse link. The present invention relates to a reverse power control and a transmission and reception link balancing method.

In the method of optimizing reverse service area of a code division multiple access network according to the present invention, a service area determination criterion for each base station for setting a service area for each base station of a code division multiple access network is set, and system parameters are adjusted to adjust the service area for each base station. To set, the forward link service area is adjusted by comparing the transmit power value, the transmit / receive link balance, and the reverse frame error rate value among the reverse link control parameters with a reference value.

Through the above process, it is possible to set the optimal reverse service area in consideration of the terrain and propagation characteristics of a specific area, set the link balanced service area in consideration of the reverse link, and perform accurate optimization by presenting various parameters. To help.

Description

Optimization of Reverse Link Service Zones for Code Division Multiple Access Networks

The present invention relates to a method for optimizing a reverse coverage area of a code division multiple access (CDMA) network, and in particular, sufficient power to overcome the total interference level of the base station at the reverse link. The present invention relates to a reverse power control and a transmission / reception link balancing method for optimizing the service area of the allocated terminal.

According to the International Organization for Standardization (IS-95), typical mobile communication systems such as cellular and personal communication systems using Code Division Multiple Access (CDMA) technology are provided with a mobile terminal provided with a service ( MS) and a base station (BTS) providing a service.

The base station is connected to an existing public switched telephone network (PSTN), and a mobile terminal in each cell forms a radio channel with a base station serving a corresponding cell and performs communication. In this case, a channel formed in the direction of the mobile station from the base station is called a forward channel, and a channel formed in the direction of the base station from the mobile station is called a reverse channel.

Each base station is assigned several frequencies according to system capacity and uses as many frequency channels. Each frequency channel is called frequency assignment (FA). CDMA systems can include multiple access channels by varying frequency offset and sequence per frequency channel. The mobile station and the base station transmit and receive voice information and data by using a traffic channel, and pilot, synchronous, and paging channels except for the traffic channel are transmitted and received. It is called an additional channel, ie an overhead channel.

In order to optimize the mobile communication system configured as described above, steps such as base station basic test, service area optimization, system capacity optimization, exchange period hard handoff optimization, call quality optimization, and location registration success rate optimization are required.

Optimization of the service area requires power control to optimize the quality of the forward and reverse communication links. CDMA systems, by their nature, can service multiple access channels at one frequency. Therefore, minimizing interference between access channels is one of the very important functions in the CDMA system. In order to minimize the interference between channels, it is necessary to optimize a forward coverage, which is a service area by a forward channel, and a reverse coverage, which is a service area by a reverse channel.

This operation is called maintaining the balance of the link. 1 shows an operation diagram of a link balancing method according to the prior art. As shown, in FIG. 1A, the base station 100 has a circular service area 130 without a load. The service area of the base station 100 is balanced between the forward and reverse service areas without load. The base station 110 also has a circular service area 140 with no load. The base stations 100 and 110 have the same service boundary of 120 under no load.

Referring to (b) of FIG. 1, the base station 110 has a large load, and the base station 100 has a small load. Then, the reverse service area of the base station 110 is reduced to 145. Then, the reverse service boundary of the base station 100 and the base station 110 moves to 125. On the other hand, the forward service boundary is maintained at 120. In order to eliminate such link unbalance, a link balancing process is performed.

In FIG. 1 (c), the base station 110 reduces the forward service area through a link balancing process. Therefore, the reverse service area matches the forward service area, and the reverse service boundary and the forward service boundary coincide.

First, the reverse link power level received at the first and second base stations for the optimization test of the link is measured.

The first based on the reverse link power level measurement at the first and second base stations to maintain equilibrium between locations having equivalent forward link efficiency relative to locations having equivalent reverse link efficiency between the first and second base stations. And adjust the forward link power level at the second base station.

A link balancing method according to the prior art operated as described above is disclosed in US Patent No. 5,548,812, entitled "METHOD AND APPARATUS FOR BALANCING THE FORWARD LINK HANDOFF BOUNDARY TO THE REVERSE LINK HANDOFF BOUNDARY IN A CELLULAR COMMUNICATION SYSTEM."

In the conventional mobile communication system operated as described above, the reverse service area simply depends on the terminal output level in the state in which the output level of the signal transmitted from the base station is set to the maximum. That is, since various parameters used in the operation of the actual system are not used, there is a disadvantage in that the performance of the system is not exhibited to the maximum.

Therefore, in order to solve the problems as described above, to set the service area determination criteria for each base station for setting the service area for each base station of the code division multiple access network, and to adjust the system parameters to set the service area for each base station, An object of the present invention is to provide a method for optimizing a cell service area of a code division multiple access network.

1 is an operation diagram of a link balancing method according to the prior art.

2 is a flowchart illustrating a reverse service area optimization method according to the present invention.

<Description of the symbols for the main parts of the drawings>

100,110: base station 120,125: boundary line

130,140,145: service area

One preferred embodiment of the present invention devised to achieve the object as described above,

A mobile communication system having a reverse link service area and a forward link service area by a base station, comprising: a first step of configuring a preliminary environment for performing a reverse service area optimization process; A second process of applying loading to the reverse link; A third step of driving and testing the link and analyzing the frequency allocation; A fourth step of adjusting the transmission power value from the analyzed result by comparing with the reference value; A fifth step of checking and adjusting whether the transmission / reception link is in balance among the analyzed results; A sixth step of adjusting the reverse frame error rate among the analyzed results by comparing with a reference value; A seventh process of determining a corresponding region as a service area of a satisfied reverse link when the transmission power, link balancing, and reverse frame error rate items satisfy an overall network design criterion; And an eighth process of determining a corresponding region as a shaded region when the transmission power, link balancing, and reverse frame error rate items do not satisfy the overall network design criteria.

In the present invention, the first process preferably comprises the step of identifying and analyzing the terrain to predict the maximum value of the path loss,

Preferably, the first process includes determining an azimuth, tilt, gain, and cell type of the antenna in consideration of the amount of traffic and the surrounding cells of the region.

Preferably, the first process includes allocating power suitable for each service area condition determined by the pilot service area, and the service area of the traffic channel is the same as the pilot service area. Preferably, the service area of is greater than or equal to the pilot service area, and the service area of the paging channel is preferably greater than or equal to the pilot service area.

Preferably, the first process includes determining the frequency allocation / output per sector so that the service area for each frequency allocation is the same.

Preferably, the first process includes determining an access parameter based on a reception attenuation value of an OUNS or a system by another subscriber,

Preferably, the first process includes adjusting a closed loop and outer loop power control related parameter to determine a reverse power control parameter.

In the fourth process, the reference value of the transmission power value is preferably within 1 dBm,

The fourth process may include adjusting a slope and azimuth angle of the base station receiving antenna if the transmission power value does not satisfy the reference value.

In the fifth process, it is preferable to check whether the transmission / reception link is balanced by checking whether the transmission / reception link balance value is between the defined minimum value and the maximum value.

The path loss of the forward link L _forward Path loss on the reverse link, L _reverse When the link balance value B Is L _forward [dB] -L _reverse [dB] Is preferably given by

P _m Is the power amplifier output of the terminal, G _c The cell antenna gain, including line loss, G _m Terminal antenna gain, including line loss, L Reverse link path loss, α Is the average negative active factor, F Frequency recycling efficiency, (N _o W) _c Denotes thermal noise at the cell amplifier input, the ratio of the carrier to the noise power at the base station CNR silver Will be (N _o W) _c of σ ² Express it, P _m ⋅G _c ⋅G _m ⋅1 / L Call channel interference value I , Cell loading X Is Is the maximum allowable reverse link path loss when L _MAX silver P _m + G _c + G _m -CNR _minreq- (N _o W) _c +10 log ₁₀ (1-X) Is preferably,

If the transmission and reception link is not balanced, the fifth process may include adjusting the forward link by adjusting the tilt and azimuth angle of the antenna and measuring and analyzing the background noise of the base station.

In the sixth step, the reference value of the reverse frame error rate is preferably within 2%,

The sixth process may include adjusting a reverse power control parameter, adjusting a reception / transmission related parameter of the terminal, and measuring and analyzing the background noise of the base station if the reverse frame error rate does not satisfy the reference value.

In the seventh and eighth processes, the overall network design criterion of the transmission power, link balancing and reverse frame error rate items is preferably 95% or more of the total network design area.

The limited output of the mobile terminal on the reverse link depends on the pathloss from the mobile terminal to the base station. This path loss is eventually related to the maximum distance between the mobile terminal and the base station. As the load on the base station itself increases the amount of interference, many subscribers or external interferences distributed in nearby base stations also cause a decrease in the maximum distance, which is the service area of the base station. As cell loading increases, the maximum distance of the base station also decreases.

Cell loading is an important factor in determining the service area on the reverse link, as the maximum distance is reduced when there are many subscribers in the neighboring base station or when external interference occurs. Hereinafter, a process of obtaining the maximum value of the reverse link path loss is as follows.

The carrier power for the noise power in a particular cell is as shown in Equation 1.

In Equation 1,

CNR represents a carrier to noise power ratio at the base station, P _m Is the mobile's power amplifier output, G _c Is the cell antenna gain including the cable loss, G _m Terminal antenna gain, including line loss, L Is the reverse link path loss, α Is the average voice activity factor, F Frequency reuse efficiency, (N _o W) _c Denotes thermal noise at the cell amplifier input, respectively.

In the above formula (N _o W) _c of σ ² Express it, P _m ⋅G _c ⋅G _m ⋅1 / L Call channel interference value I When you say, cell loading X May be represented as in Equation 2.

The maximum allowed reverse link path loss is L _MAX Can be expressed as in Equation 3.

L _MAX = P _m + G _c + G _m -CNR _minreq- (N _o W) _c + 10log ₁₀ (1-X)

remind P _m and, G _c , G _m , CNR _minreq And (N _o W) _c Is calculated in decibels (dB). As shown in Equation 3 above L _MAX Once determined, the service area on the reverse link can be calculated. The service area of the reverse link determined by cell loading must balance the link compared to the service area on the forward link. Link Equilibrium Value B Is given by Equation 4.

Link Balance B = L _forward [dB] -L _reverse [dB]

B If is negative, the service area of the system is limited by the reverse link; if it is positive, the service area of the system is limited by the forward link. In order to balance the link, it is necessary to allocate a value optimized for a pilot signal of a cell transmitter output.

2 is a flowchart illustrating a reverse service area optimization method according to the present invention. Hereinafter, the operation of the present invention will be described in detail with reference to the accompanying drawings.

First, for the preliminary design process, the topology of the region is identified, and a path loss model to be used as network design reference data is selected to predict the maximum value of the path loss (201). The azimuth, tilt, gain, and cell type (sector-cell or omni-cell) of the antenna are determined based on the amount of traffic and the surrounding cells of the region (202).

An appropriate digital gain is calculated by calculating the power allocation ratio for each channel (203). The conditions of the service area for each channel to allocate power are as follows. The service area by the traffic channel is the same as the pilot service area. The service area by the sync channel is greater than or equal to the pilot service area. The service area by the paging channel is larger than or equal to the pilot service area.

A frequency allocation (FA) / sector-specific output is determined (204). In order to perform hard handoff, the service area for each frequency allocation must be the same, so the output must be identical.

The access parameter is set (205) by adding the received attenuation value in another noise noise simulator (OUNS) or system by another user's call to suit the test environment.

The reverse power control parameter is determined (206). Adjust parameters related to closed loop and outer loop power control.

After the adjustment of the parameters, the loading is applied to the reverse link (207). The reverse link is analyzed by frequency allocation using the results of a drive test by the application of loading (208).

The transmit power value of the analyzed result is compared with a threshold of 1 dBm (209). If the transmission power is greater than the reference value, the slope and azimuth of the base station reception antenna are adjusted (210).

It is checked whether the transmission / reception link is balanced (211). If the service area of the forward link is smaller than the service area of the reverse link, pilot acquisition is impossible in the overlapping area between cells, and thus fails in handoff. Conversely, if the forward link service area is larger than the reverse link service area, not only does handoff fail in the overlapping area between cells, but also the pilot signals of both base stations interfere with each other. For this reason, even when the optimization of the forward link service area is completed, if the link balance is not achieved with the reverse link service area, the optimization work must be readjusted. For link balancing, it is checked whether the link balancing value determined by Equation 4 is included in the range between the reference minimum value and the maximum value.

If the forward and reverse link service areas are not balanced, i.e. if the link balance value is between the reference minimum and maximum values, then adjust the forward link by adjusting the tilt and azimuth angle of the antenna, and the background noise of the base station. After the noise is measured, the corresponding noise is performed (212).

The reverse frame error rate (RFER) value is compared with the reference value of 2% among the analyzed results (213). If it is larger than the reference value E _b / N _o The power control parameters of the reverse link such as parameters are adjusted, the reception / transmission related parameters of the mobile terminal are adjusted, and the background noise of the base station receiver is measured and analyzed (214).

Check that the transmit power (Tx_Power), reverse frame error rate, and link balance items satisfy 95% or more when compared to the standard compared to the total network design area (215). If the criterion is satisfied, the corresponding region is determined to be a service area of the satisfied reverse link (217).

The present invention operating as described above, in optimizing the service area of the reverse link, it is possible to obtain the effect of reducing the time and manpower waste, because it does not change a number of parameters without a predetermined work flow, and each parameter is optimized Segmentation always ensures accurate segmentation. In addition, another effect of the present invention is as follows.

By establishing the network design criteria considering the topography and the propagation characteristics of the area first and then optimizing the service area, it is possible to derive the service area linked with the surrounding environment by region.

In the code division multiple access system limited by the reverse link, a link balanced service area can be obtained by considering the reverse link.

In addition, if the transmission power and the reverse frame error rate do not meet the network design reference value, the parameter is adjusted so that the optimization can be performed by performing corrective measures.

Claims (23)

A mobile communication system having a reverse link service area and a forward link service area by a base station, A first step of constructing a preliminary environment for performing a reverse service area optimization process; A second process of applying loading to the reverse link; A third step of driving and testing the link and analyzing the frequency allocation; A fourth step of adjusting the transmission power value from the analyzed result by comparing with the reference value; A fifth step of checking and adjusting whether the transmission / reception link is in balance among the analyzed results; A sixth step of adjusting the reverse frame error rate among the analyzed results by comparing with a reference value; A seventh process of determining a corresponding region as a service area of a satisfied reverse link when the transmission power, link balancing, and reverse frame error rate items satisfy an overall network design criterion; And And an eighth process of determining a corresponding region as a shaded region when the transmission power, link balancing and reverse frame error rate items do not satisfy the overall network design criterion. The method of claim 1, wherein the first process comprises: Identifying and analyzing topography to predict the maximum value of path loss. The method of claim 1, wherein the first process comprises: Determining the azimuth, tilt, gain, and cell type of the antenna in consideration of the amount of traffic and the surrounding cells of the region. The method of claim 1, wherein the first process comprises: And allocating power suitable for service area conditions for each channel. 5. The method of claim 4, wherein the service area for each channel is determined by a pilot service area. 5. The method of claim 4, wherein the service area of the traffic channel is the same as the pilot service area. 5. The method of claim 4, wherein the service area of the sync channel is greater than or equal to the pilot service area. 5. The method of claim 4, wherein the service area of the paging channel is greater than or equal to the pilot service area. The method of claim 1, wherein the first process comprises: Determining the frequency allocation / sector-specific output such that the service area for each frequency allocation is the same. The method of claim 1, wherein the first process comprises: Determining an access parameter; a method of optimizing reverse service area for a code division multiple access network. 11. The method of claim 10, wherein the access parameter is determined by a noise simulator (OUNS) by another subscriber. 11. The method of claim 10, wherein the access parameter is determined by a received attenuation value of the system. The method of claim 1, wherein the first process comprises: Determining a reverse power control parameter. 14. The method of claim 13, adjusting the closed loop and outer loop power control related parameters. The method of claim 1, wherein the reference value of the transmit power value of the fourth process is within 1 dBm. 2. The method of claim 1, wherein the fourth step includes adjusting a slope and azimuth of a base station receiving antenna if the transmit power value does not satisfy a reference value. 2. The method of claim 1, wherein the fifth process checks whether the transmit / receive link is balanced by checking whether the transmit / receive link balance value is between a defined minimum value and a maximum value. . 18. The method of claim 17, wherein the path loss of the forward link is L _forward Path loss on the reverse link, L _reverse When the link balance value B Is L _forward [dB] -L _reverse [dB] A method of optimizing reverse service area of a code division multiple access network, which is given by The method of claim 18, P _m Is the power amplifier output of the terminal, G _c The cell antenna gain, including line loss, G _m Terminal antenna gain, including line loss, L Reverse link path loss, α Is the average negative active factor, F Frequency recycling efficiency, (N _o W) _c Denotes thermal noise at the cell amplifier input, the ratio of the carrier to the noise power at the base station CNR silver Will be (N _o W) _c of σ ² Express it, P _m ⋅G _c ⋅G _m ⋅1 / L Call channel interference value I , Cell loading X Is When this happens, Maximum allowable reverse link path loss L _MAX silver P _m + G _c + G _m -CNR _minreq- (N _o W) _c +10 log ₁₀ (1-X) The reverse service area optimization method of the code division multiple access network. The code division multiple access network of claim 1, wherein the fifth process includes adjusting a forward link by adjusting an inclination and azimuth angle of an antenna when the transmission and reception link is not balanced, and measuring and analyzing background noise of a base station. Reverse Service Zone Optimization Method. The method of claim 1, wherein the reference value of the reverse frame error rate of the sixth step is within 2%. The method of claim 1, wherein the sixth step includes adjusting a reverse power control parameter, adjusting a reception / transmission related parameter of the terminal, and measuring and analyzing a background noise of a base station receiving end if the reverse frame error rate does not satisfy a reference value. Reverse service area optimization method of a code division multiple access network. 2. The reverse service of a code division multiple access network according to claim 1, wherein in the seventh and eighth processes, the overall network design criterion of the transmission power, link balancing and reverse frame error rate items is 95% or more of the total network design area. Zone optimization method.