KR0170187B1 - Control method of traffic carrying capacity of base station of cdma mobile communication system - Google Patents

Abstract

In the present invention, since the call blocking phenomenon in the CDMA mobile communication system is a phenomenon that occurs mainly when the amount of interference noise is caused by a call of other users, the traffic control in the system has a strong interference noise level so that call blocking does not occur. In order to control the interference noise level in the base station, the base station and the control station manages the maximum Eb / No of the mobile station, so that the MSR of the base station with a large interference noise level is larger than MSRsc_th, MSR of the neighboring cell is smaller than MSRnc_th In addition, by reducing the pilot channel power of the base station, and controlling the amount of interference noise level, it is possible to actively manage the traffic of the system by adjusting the size of the heavy cell during system operation.

Description

Traffic Capacity Control Method of Base Station in CDMA Mobile Communication System

1 is a simplified structural diagram of a general CDMA mobile communication system.

2 is a closed loop power control flow chart in a typical CDMA mobile communication system.

3 is a flowchart of power increase and decrease of a typical mobile station and base station.

4 is a dynamic traffic control flow diagram of a base station according to the present invention.

5 is a change state diagram of a mobile station according to the control flow chart of the present invention.

* Explanation of symbols for main parts of the drawings

10: base station 11: control station

12: mobile switching center 13: transcoder

The present invention relates to a method for controlling traffic capacity of a base station in a CDMA mobile communication system, and in particular, a control station and a base station received in a base station using a function of outer-loop power control in a CDMA mobile communication system. It manages the maximum energy value (Eb / No: (Energy / bit) / Noise) of the mobile station and decreases the cell size by reducing the power strength of the pilot channel of the base station with a large MSR of the base station, thereby reducing the size of the cell. The mobile station is a method of dynamically controlling the traffic capacity of a base station that can be handed off and can be controlled by an adjacent cell.

In general, the blocking phenomenon in TDMA and FEMA systems is that all channels are in use, so that a new caller receives no service without receiving a service. Traffic control in a conventional TDMA and FDMA system is a specific cell. This is possible by rescheduling the frequency channel assignments between cells so that no call blocking occurs at.

However, since the call blocking phenomenon in the CDMA system is a phenomenon that occurs mainly when the amount of interference noise caused by the call of other users exceeds a certain level, traffic control in the CDMA system is performed so that the interference noise level is reduced so that call blocking does not occur. Power should be adjusted to control the number of subscribers.

Accordingly, an object of the present invention to prevent the occurrence of call blocking in the CDMA system as described above is to provide outer-loop power control when the number of mobile stations in a cell increases and the interference by other mobile stations in the cell increases. The maximum Eb / No of the mobile station is used to manage the MSR (Maximum Eb / No Mobile / Service Mobile Rate) of the base station. Self-Cell Threshold (hereinafter referred to as 'MSRsc_th') in the CDMA system that can reduce the size of the cell by reducing the power strength of the pilot channel, thereby allowing the mobile station to be fluidly controlled by the other station of the adjacent cell It is to provide a traffic capacity control method of a base station of the.

A feature of the present invention for achieving the above object, in controlling an unevenly distributed mobile station in a CDMA system,

The first step of setting the variable for the total number of mobile stations in service and the number of mobile stations with the highest energy value (Eb / No) received from the base station, and performing the outer loop power control in the transcoder, A second step of transmitting a signal (MEM_sig) informing the control station of the maximum value when the reference energy value (reference Eb / No) received by the maximum value (maximum Eb / No) is transmitted to the control station; A third step of receiving the signal MEM_sig transmitted from the coder to increase the number of mobile stations having the maximum energy value (Eb / No) received from the base station and calculating the ratio of the increased number of mobile stations to the total number of mobile stations; And the ratio of the number of mobile stations having the maximum energy value (Eb / No) received from the base station to the number of mobile stations of the neighboring base station when the ratio calculated from the third process is greater than the ratio of the threshold value, and the mobile station of the neighboring cell. A fourth process of comparing the threshold of the number of mobile stations having the maximum energy value (Eb / No) received by the base station with respect to the number, and an energy value received by the base station for the number of mobile stations of the neighboring base station as a result of the comparison of the fourth process; A signal that reduces the pilot to the base station if the ratio of the number of mobile stations with the maximum (Eb / No) is less than the threshold of the number of mobile stations with the maximum energy value (Eb / No) received from the base station for the number of mobile stations in the neighboring cell. And a sixth step of reducing the range of the corresponding base station by receiving the signal transmitted from the fifth step and reducing the strength of the pilot signal.

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

FIG. 1 is a diagram illustrating the overall structure of a CDMA mobile communication system to which the present invention is applied. The CDMA mobile communication system includes a base station transmitter subsystem (BTS) 10 located in a plurality of corresponding cell regions, and the base station. A base station controller (BSC) 11 and a mobile eXchange subsystem (MX) 12, which are connected to 10, are configured.

The control station 11 includes a transcoding Seletor Bank (TSB) 13 which performs subcoding, such as transcoding, power control, and soft-handoff. .

The base station 10 is a subsystem for managing radio resources and cells, and provides software for providing a radio interface function to the mobile switching center 12 and performing a call processing function (Access, Paging channel).

The control station 11 has an E1 relay processing function between the base station 10 and E1 / T1 and the mobile switching center 12, a signal message transfer function between the mobile switching station 12 and the base station 10, and call processing. It is a subsystem that provides functionality.

The mobile switching center 12 provides the interworking function between the network elements of the CDMA mobile communication system and other networks such as PSTN and AMPS mobile networks and various functions performed in the existing switching system.

In the CDMA mobile communication system configured as described above, all mobile stations in the cell of the system are forward power control and reverse power control, i.e., open to receive signals of the same size sufficient for the base station to maximize system capacity. Loop, closed loop, and outer-loop power control must be performed.

In particular, the present invention manages the maximum Eb / No of the mobile station by using the closed loop power control of the outer-loop power control, thereby reducing the power strength of the pilot channel of the base station having a large MSR of the base station, thereby reducing the traffic of the base station. The capacity can be controlled.

2 is a closed-loop power control flowchart for managing maximum Eb / No of a mobile station by using closed-loop power control of outer-lttp power control applied to the present invention.

Referring to FIG. 2, the operation flow chart of the outer-loop power control will be described below.

When the mobile station transmits an initial access channel to the base station (S20), the base station sets the Eb / No of the signal received from the mobile station to the received value (S21), and the reverse Eb for all mobile stations in the cell in the transcoder of the control station. The / No reference value controls the outer-loop power by changing the reference Eb / No according to the frame error rate (FER) of the received signal. (S22)

The base station compares two values of the Eb / No received value received in step S21 and the Eb / No reference value set in step S22 at step S23. If the reference value is large, the power control bit is set to 1 (S23). S24), if the reference value is not greater than the received value, make the power control bit zero. (S25)

Subsequently, the base station transmits a power control command to each mobile station every 1.25 ms (S26).

Thus, the mobile station looks at the power control bit received by step S26 to adjust the transmit power level. (S27)

At this time, the base station and the transcoder control the power of each mobile station by the same method as above, but there is a limit value of the reference value Eb / No (for example, 7 dB to 10.5 dB) so that the reference value Eb / No is transmitted to the receiving FER. Therefore, it cannot increase infinitely.

FIG. 3 is a flowchart showing the increase and decrease of power and interference noise of a base station serving many mobile stations to which the present invention is applied using the characteristic of the maximum value of Eb / No in FIG.

Referring to FIG. 3, the increase and decrease of power of a mobile station and a base station and the change of interference noise are as follows.

In the state where the base station's transcoder sets the reverse Eb / No reference values for all mobile stations in the cell (S30), when the number of mobile stations in one cell increases (S31) and the interference noise increases (S32), the radio environment in which the interference noise increases The signal of the mobile station is transmitted to the base station at. (S33)

When the base station receives the signal transmitted by the mobile station in the step S33, since the interference noise is high, the reception Eb / No decreases. Accordingly, the FER measured by the control station increases, and the reference by the increased FER is increased. Eb / No also increases. (S34)

Subsequently, the base station transmits a power control command to the mobile station by setting the power control bit to 1 since the reception Eb / No is less than the reference Eb / No.

The mobile station analyzes the power control command signal received from the step S35, that is, the power control bit (S36), and increases the power of the mobile station according to the result and transmits it to the base station (S37).

However, despite increasing the transmission power of the mobile station, the interference noise is also increased and received at the base station. (S38)

At this time, if a plurality of mobile stations increase power, interference noise continues to increase. (S39)

Thus, the increase in the interference noise by other mobile stations does not reduce the FER of the received frame. (S3a)

That is, even if the FER of the mobile station signal is not improved and the steps S34 to S37 are continued to increase the reference Eb / No to the maximum value, the FER is not improved.

FIG. 4 presents the following traffic control algorithm to solve the problems occurring in the environment as shown in FIG.

Referring to FIG. 4, the algorithm proposed by the present invention will be described.

Variable for the number of mobile stations currently serviced at the control station (Service Mobile Count; hereinafter abbreviated as SM_Con) and variable for the number of mobile stations with maximum value Eb / No (Maximum Eb / No Mobile Count; abbreviated as MEM_Con) (S40), while performing an outer loop power control in the transcoder (S41), and checking whether Eb / No is the maximum value of Eb / No as a result of the step (S41). (S42) When it is determined that the reference Eb / No is the maximum Eb / No, a signal (Maximum Eb / No Mobile Signal Message; abbreviated MEM_sig) is transmitted to the control station indicating that the Eb / No of the mobile station is the maximum value (S43). )All.

In this case, the control station checks whether the MEM_sig has been received (S44), and if the MEM_sig is not received, the process continues to wait for the MEM_sig, and when the MEM_sig is received, increases the MEM_con by one (MEM_Con ++), and MEM_Con is SM_Con. Now calculate the MSR (S45).

Then, a comparison is made whether the number ratio of mobile stations having the maximum value Eb / No (MEM / SC Self Cell; hereinafter abbreviated as MSRsc) to the calculated number of mobile stations in the own cell is greater than or less than MSRsc_th (S46). When the MSRsc is greater than MSRsc_th, the control station calculates an MSR (MEM / SC Neighbor Cell; hereinafter abbreviated as MSRnc) of the neighboring base station (S47), and then compares the calculated MSRnc with the neighboring cell MSRnc. If the neighbor cell is less than MSR (MSR Neighbor Cell Threshold; hereinafter referred to as MSRnc_th), a signal for reducing pilot (Pilot_strength_low_signal; hereinafter, referred to as Pilot_st_low_sig) is transmitted to the corresponding base station (S4a).

At this time, the base station receiving the Pilot_st_low_sig signal (S4b) decreases the strength of the pilot signal (S4c), and accordingly, the pilot strength of the corresponding base station is reduced, so that the mobile station in the cell boundary area is handed to the neighboring cell base station. It can be turned off to reduce the mobile station load in that cell.

FIG. 5 is a diagram illustrating a change in cell range and a change of a mobile station in a cell boundary area when the algorithm shown in FIG. 4 is used. Referring to FIG. 5, FIG. It shows the communication process before the control method is applied. In the case of FIG. 5 (b), as the traffic capacity of the base station 51 increases, the range of the base station 51 is reduced, and the signal which is to be transmitted from the base station 52 to the base station 51 is a base station. 53, the signal to be transmitted from the base station 54 to the base station 51 is transmitted to the base station 55.

As described above, in the present invention, a base station in a CDMA system manages maximum Eb / No of a mobile station by using an outer-loop power control function, and power strength of a pilot channel of a base station having a large MSR of the base station In order to reduce the size of the cell and reduce the size of the cell, the mobile station at the edge of the base station can dynamically control the integrated cell.

Claims (1)

In controlling an unevenly distributed mobile station in a CDMA system, a first variable for setting a variable for the number of mobile stations totally serviced by the base station and a number for the mobile station having the maximum energy value (Eb / No) received from the base station is maximum. Process; If the transcoder performs outer-loop power control and determines that the reference energy value (reference Eb / No) received from the base station is the maximum value (maximum Eb / No), it transmits a signal (MEM_sig) indicating the maximum value to the control station. A second process of notifying the control station of the fact; Receiving the signal (MEM_sig) transmitted from the transcoder to increase the number of mobile stations with the maximum energy value (Eb / No) received from the base station, and calculates the ratio of the increased number of mobile stations to the total number of mobile stations The third process; When the ratio calculated from the third process is greater than the ratio of the threshold, the ratio of the number of mobile stations whose energy value (Eb / No) received from the base station to the number of mobile stations of the neighboring base station is the maximum, and the number of mobile stations of the neighboring cell. A fourth step of comparing a threshold of the number of mobile stations with the highest energy value (Eb / No) received from the base station; As a result of the comparison of the fourth step, the ratio of the number of mobile stations having the maximum energy value (Eb / No) received by the base station to the number of mobile stations of the neighboring base station is the energy value (Eb / No received by the base station relative to the number of mobile stations of the neighboring cell) Transmitting a signal to reduce the pilot to the corresponding base station when C) is less than a threshold of the number of mobile stations having the maximum number; And a sixth step of reducing the range of the corresponding base station by receiving the signal transmitted from the fifth step and reducing the strength of the pilot signal.