KR100198814B1 - Method of distributing traffic load in cdma system by frame error rate - Google Patents

Abstract

The present invention relates to a method and apparatus for periodically managing an average value and a standard deviation using a frame error rate (FER) used in an outer-loop power control in a control station of a code division multiple access mobile system (CMS) To a traffic load balancing method using a frame error rate in a code division multiple access mobile station controller.

Description

Traffic Load Balancing Method Using Frame Error Ratio in Code Division Multiple Access Mobile System Controller

The present invention relates to a traffic load balancing method using a frame error rate in a CBS (Code Division Multiple Access) mobile communication system, and more particularly, The present invention relates to a method for dynamically distributing a traffic load by periodically managing an average value and a standard deviation of a frame error rate (FER) used for outer-loop power control.

Field of the Invention [0002] The present invention relates to a traffic control field of a code division multiple access mobile system. The prior art in this field is a traffic load balancing method based on signal-to-noise ratio (SNR).

Traffic control in a conventional time division multiple access (TDMA) system or a frequency division multiple access (FDMA) system is possible by recalibrating frequency channel allocation between cells so that call blocking does not occur in a certain cell. However, the phenomenon of call blocking in a code division multiple access (CDMA) system occurs mainly when the level of the interference noise level caused by the call of other users becomes a certain level or more. Therefore, traffic control in a code division multiple access (CDMA) system should control the number of subscribers by adjusting the power so that the interference noise level is reduced to prevent call blocking. Therefore, the existing code division multiple access system (CDMA) can reduce the transmission power of the base station by adjusting the transmission power of the base station itself when the SNR received by the base station exceeds a given reference SNR A traffic load balancing method of handing off mobile stations in a coverage area of a severe base station to an adjacent base station having a small load is used.

The conventional traffic load balancing method is a method of reducing the number of valid calls due to an increase in the SNR of temporary traffic and a reduction in the effective coverage of each cell due to a sudden increase in the traffic load of neighboring cells The domino phenomenon is likely to occur.

Therefore, the present invention controls the average value and the standard deviation periodically using the frame error rate (FER) used for the outer-loop power control in the control station of the CMS, And a traffic load balancing method using a frame error ratio in a code division multiple access mobile station controller that distributes a traffic load.

According to another aspect of the present invention, there is provided a method for controlling traffic load balancing in a control station, the method comprising: comparing a measured value of a base station requesting traffic load balancing with a threshold value; If the compared measured value is greater than the threshold value, comparing the measurement value and the allowed value of the neighbor base station after finding the neighbor base station; The method comprising the steps of: sending a traffic load balancing message to the base station if the measured value is less than the allowed value and terminating the process after sending a new call blocking message of the base station to the corresponding base station if the compared measured value is greater than the allowed value .

FIG. 1 is a schematic diagram of a CDMA mobile system (CMS).

2 is a flow diagram of closed loop power control using outer-loop power control in a Code Division Multiple Access (CDMA) system to which the present invention is applied.

FIG. 3 is a flow chart illustrating a traffic load balancing method using a frame error rate (FER) according to the present invention; FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

10: base station 11: control station

12: Transcoder 13: Mobile switching center

14: Call control system 15:

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

FIG. 1 is a structural diagram of a code division multiple access (CMS) system to which the present invention is applied. The control station 11 periodically manages a frame error rate (FER) in each base station 10, .

A code division multiple access system (CMS) is composed of a mobile station, a base station 10 which manages radio resources and cells, a control station 11 which connects with the base station 10 and the exchange 15, and a mobile switching center 13 . The control station 11 is constituted by a switching center 15, a transcoder 12 and a communication control system 14. [

In order to maximize the capacity of the system, all mobile stations in the cell have forward power control, reverse (open loop, closed loop, outer-loop) power control to allow the base station to receive signals of the same size Should be.

The base station 10 is a subsystem for managing radio resources and cells, and has software for providing a radio interface function to the mobile switching center 13 and performing a call processing function (Access, Paging channel).

The control station 11 is provided with an E1 relay processing function between the base station 10 and the E1 / T1 and the mobile switching center 13, a signal message transfer function between the mobile switching center 13 and the base station 10, System.

The transcoder 12, which is a submodule in the control station 11, is a submodule that provides transcoding, power control, and soft-handoff functions.

The mobile switching center 13 functions as an interworking function between the network elements of the code division multiple access mobile communication system (CMS), the public switched telephone network (PS number) and the AMPS mobile network, It is a subsystem that provides various functions.

FIG. 2 is a flow diagram of closed loop power control using outer-loop power control in a Code Division Multiple Access (CDMA) system to which the present invention is applied.

From the start signal, in step 20, the mobile station transmits an initial access channel to the base station. In step 21, the signal-to-noise ratio (Eb / No) of the signal received from the mobile station is calculated as a received value, and the process proceeds to step 22. In step 22, the transcoder changes the reference signal-to-noise ratio Eb / No according to the frame error rate (FER) of the received signal, based on the reverse signal-to-noise ratio (Eb / No) reference value for all the mobile stations in the cell - loop power control). Thereafter, in step 23, the two values are compared in the base stations 21 and 22, and if the reference value is larger, the process proceeds to step 24 to set the power control bit to 0. If the reference value is smaller than the received value, The process proceeds to step 25 where the power control bit is set to 1, and then the process proceeds to step 26. [ In step 26, the base station transmits a power control command to each mobile station every 1.25 ms. Thereafter, in step 27, the mobile station determines the received power control bit and adjusts the transmission power level. The above-mentioned variable threshold value is determined by an outer-loop power control in which the variable threshold value changes according to the frame error rate (FER) of the reverse traffic signal received at the transcoder (TSB). When the number of mobile stations is continuously increased, the average value of the frame error rate (FER) of the reverse traffic signal received in the transcoder TSB increases and the average value of the signal-to-noise ratio Eb / No of the variable threshold value also increases.

Tables 1 and 2 are tables showing reverse link frame error ratios and mobile station transmission gain adjustment value characteristics used in the present invention.

In order to obtain the characteristics of the reverse link, the system performance is analyzed and evaluated by analyzing various data and messages collected through the modeling and simulation method of the entire code division multiple access mobile communication system and the system test call, Characteristics can be derived. However, in the former method, the degree of sophistication due to the difference from the actual environment in the modeling of the system drops, and it is not suitable as a method for installing and operating the system because it involves a vast amount of work to perform this process for the system as a whole . Therefore, the present invention is based on the result of the field test of the mobile communication system of the code division multiple access (CDMA) method.

Table 3 shows the frame error ratio list managed by the control station.

The management module reports the frame error rate (FER) used by the transcoder (TSB) to the call control system (CCP) in the control. The call control system (CCP) periodically calculates the average value and standard deviation of the frame error rate (FER) of each base station and manages it as shown in Table 3. In Table 3, the threshold value and the permission value are different according to the front environment of each base station. Therefore, the threshold values and the allowed values measured in the field test should be included at system initialization.

FIG. 3 is a flowchart illustrating a traffic load balancing method using a frame error rate (FER) according to the present invention.

From the start signal, in step 51, the control station sends a traffic load balancing request message if the SNR received by the base station is greater than the reference SNR.

The control station receiving the message compares the measured value of the base station requesting traffic load balancing with a threshold value. If the comparison result in step 51 is greater than the threshold value, the process proceeds to step 52 to find a neighboring base station and proceeds to step 53. If the measured value is smaller than the threshold value in step 51, the flow advances to step 55 to transmit a traffic load balancing message to the base station and then terminate. In step 53, the measured values of the neighboring base stations are compared with the allowed values. If the comparison result in step 53 is smaller than the allowed value, the flow proceeds to step 54, where a traffic load distribution permission message is transmitted to the corresponding base station, and the process ends. If the measured value is greater than the allowed value in step 53, the process proceeds to step 56, where a new call blocking message of the base station is transmitted to the corresponding base station, and the process ends.

The present invention sends a traffic load balancing request message to a control station if the SNR received by the base station is greater than a reference SNR. Upon receiving the traffic load balancing message of the base station, the control station compares the measured value of the base station requesting traffic load balancing with the threshold value. If the measured value is greater than the threshold value, the neighboring base station is searched. If the measured value is smaller than the threshold value, If the measured value is smaller than the allowed value, a message of allowing traffic load distribution to the base station is sent. If the measured value is larger than the allowed value, the corresponding traffic load balancing message is transmitted. A new call blocking message of the base station is transmitted to the corresponding base station to periodically manage the frame error rate (FER) of the base station, thereby preventing a temporary effective coverage reduction and an effective coverage right domino phenomenon.

As described above, according to the present invention, by managing the frame error rate (FER) of the base station periodically, it is possible to reduce the effective coverage area due to the increase in the SNR and to reduce the effective coverage area of the base station, There is an excellent effect that it is possible to prevent the dominance phenomenon of the effective coverage of each cell that may occur due to a sudden increase in load.

Claims (1)

The control station having received the message from the base station may further include a step of comparing the measured value of the base station requesting the traffic load balancing to a threshold value, and if the measured value is less than the threshold value, Comparing a measured value of a neighbor base station with a granted value after finding the neighbor base station if the compared measured value is greater than a threshold value; and if the measured value is less than the allowed value, And sending a grant message to the corresponding base station and terminating after sending the grant message to the corresponding base station if the compared measured value is greater than the allowed value. A Traffic Load Balancing Method Using Frame Error Ratio.