KR100233085B1 - Backward link subscriber load condition loading method in a digital cellular system - Google Patents

Abstract

end. The technical field to which the invention described in the claims belongs:

Cell Optimization and Base Station Performance Verification in Digital Cellular System

I. The technical problem the invention is trying to solve:

Provides a method of calculating a noise source to implement a virtual subscriber environment that is identical to the environment where a real subscriber is talking.

All. The gist of the solution of the invention:

According to the present invention, in the method for adding a reverse link subscriber load condition in a digital cellular system, the gain (noise index) of the base station reception attenuator is controlled to be attenuated to make a virtual subscriber loaded.

la. Important uses of the invention:

Cell Optimization and Base Station Performance Verification in Digital Cellular System

Description

Reverse Link Subscriber Load Condition Method in Digital Cellular System

The present invention relates to a communication system, and more particularly, to a method for cell optimization and performance verification of a base station transceiver subsystem (BTS) in a digital cellular system.

The ultimate goal of the Code Division Multiple Access (CDMA) system is to improve cell capacity, call mobility, and call quality. The performance of each condition varies according to the noise shape and size, which is a characteristic of the CDMA system. The noise form may include noise caused by the subscriber. Since each subscriber acts as a noise to each other, the call quality decreases as the number of subscribers increases. Therefore, it is required to design a cell to satisfy a call quality desired by the consumer at the maximum capacity of the subscriber, and cell optimization is performed for this purpose. Against this backdrop, it makes sense to establish a maximum test environment for field testing. However, establishing a multi cell environment with real subscribers makes field testing practically impossible. Although it is possible, it can be a waste of manpower and test terminals. From this point of view, it is desirable to create a virtual subscriber environment in the system that is implemented in the same manner as the actual subscriber is calling.

Accordingly, an object of the present invention is to provide a method for adding a reverse link subscriber load condition in a digital cellular system.

Another object of the present invention is to provide a method for adding a reverse link subscriber load condition to implement a virtual subscriber environment that is identical to the environment where a real subscriber is talking.

It is still another object of the present invention to provide a method for reducing the time, manpower, and equipment cost of implementing a test environment for cell optimization.

According to the above object, the present invention provides a method for adding a reverse link subscriber load condition in a digital cellular system, wherein the gain (noise index) of the base station reception attenuator is controlled to be attenuated to create a state where a virtual subscriber is loaded. It is done.

1 is a view for explaining a noise source adding method according to an embodiment of the present invention.

FIG. 2 is a diagram showing results measured before and after noise source injection analyzed by spectrum analyzer 6 connected to the rear end of LNA 4 shown in FIG.

3 is a view for explaining a noise source adding method according to another embodiment of the present invention;

(A) to (c) are views showing the state of the thermal noise and the tone signal, (a) is a view showing the state measured by the spectrum analyzer 16 of FIG. 3 when the tone signal is applied, (b) FIG. 3 is a diagram illustrating a state at the output terminal of the receiver attenuator 12 when the gain of the receiver attenuator 12 is attenuated. FIG. (C) illustrates a state measured by the spectrum analyzer 16 of FIG. 3 when the gain of the receiver attenuator 12 is attenuated.

5A to 5C are diagrams of FIGS. 4A to 4C in which the increment of the noise by y is a state in which a virtual subscriber, that is, subscriber noise N _OU is loaded.

FIG. 6 is a diagram for explaining a Rx Attenuation structure in a CDMA system. FIG.

7 is a diagram illustrating values of the received power Prx (N, E _b / N _O ) for each subscriber number (N) obtained by the equation.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same elements in the figures are denoted by the same numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

In the embodiment of the present invention, in order to solve the difficulty of supply and demand, such as manpower and terminals generated during the full load environment during the field test, the virtual subscriber required to build the full load environment is adjusted in the system. The hypothetical subscriber becomes a subscriber noise source.

FIG. 1 is a diagram illustrating a method of adding a reverse subscriber load condition according to an embodiment of the present invention. The RF stage receiver of FIG. 1 includes an antenna 3, a directional coupler 4, a BPF (Band Pass Filter) 6, a low noise amplifier (LNA), a receiver attenuator 12, and an XCVR (Tranciver) including an AGC 14. have. Referring to FIG. 1, in the embodiment of the present invention, as a method of adding a load condition of a reverse link subscriber for establishing a full load environment, the subscriber noise generator 2 is made in a directional coupler 4 at a radio frequency (RF) terminal of a base station. Apply the subscriber noise source. The subscriber noise source becomes a virtual subscriber load. The input particle noise source applied to the directional coupler 4 is applied to the XCVR 10 via the BPF (Band Pass Filter) 6 and the LNA 8. On the other hand, a spectrum analyzer 16 is connected to the node between the LNA 8 and the XCVR 10 to measure the increment of the subscriber noise source applied by the subscriber noise generator 2. The reason why Spectrum Analyzer 16 should be connected to the back of the LNA is that the subscriber noise source is less than the system noise generated inside the base station. That is, after amplifying the other particle noise source through the LNA 8 to measure the increment of the noise.

According to an embodiment of the present invention, when the method of adding a reverse subscriber load condition is implemented as shown in FIG. 1, the tester matches the full load field environment in the real field by using the noise value generated in the real field without calculation. You can create a virtual subscriber load. This is because the noise source is supplied from the RF stage having the same or similar signal characteristics as that of the actual field environment.

FIG. 2 shows the measurement results of the spectrum analyzer 16 connected to the rear end of the LNA 8, before and after injection of the oppressor noise source. ② The condition is the result measured before injection of other particle noise source. In this case, it can be seen that only system noise (hereinafter referred to as "thermal noise N _th " or "background noise") is measured. ① State is the result measured after noise source injection. In this case, it can be seen that the particle noise N _ou is added to the thermal noise N _th component and measured. The particle noise N _ou component is a noise increment caused by the injected particle noise source. Therefore, the criterion for the noise increment can be defined as the thermal noise N _th component. If the thermal noise N _th component is set as the noise increment, the increment of the subscriber noise source can be known. In other words, it is possible to measure the size of the other particle noise source. After all, if the reference thermal noise N _th is kept constant, the subscriber state required by the investigator can be made by using the subscriber generator 2 of FIG. 1.

Unfortunately, under the real field environment, the thermal noise N _th component is constantly changing over time. As a result, the loaded subscriber noise source cannot be kept constant at all times.

In addition, under the actual field environment, the thermal noise N _th component also varies from sector to sector. This also acts as a factor in not being able to always keep the loaded subscriber noise source constant. More specifically, the contents mentioned that the thermal noise N _th component is different for each sector under the actual field environment are as follows. One cell is composed of three sectors, and each sector has two RX paths consisting of A and B. Therefore, one cell in which the base station is located includes a total of six reception paths. However, the important fact here is that the thermal noise (background noise) N _th is different for each sector. Eventually, the fact that the size of the subscriber noise is determined based on the thermal noise N _th results in the conclusion that six subscriber noise generators 2 as shown in FIG. 1 are needed. Otherwise, six attenuators are needed for one noise generator. In the test of a multi-cell environment, that is, the number of surrounding cells for one cell is approximately 6 cells, in order to implement the noise source through the equipment, the equipment is set up in 7 cells at the same time. Field optimization should be done. Therefore, this method is burdened with both manpower and equipment to be built and tested at the same time.

In another embodiment of the present invention, a virtual subscriber load condition is set through reception attenuation adjustment in order to reduce the above-mentioned burden generated in constructing a full load environment during field testing. Another embodiment of the present invention for setting a virtual subscriber load condition through reception attenuation will be described later.

3 is a diagram for describing a noise source adding method according to another exemplary embodiment of the present invention. The configuration of FIG. 3 is similar to that of FIG. 1, but the subscriber noise generator 2 shown in FIG. 1 is eliminated, and instead, the tone signal generator 20 is newly provided, and the spectrum analyzer 16 connected to the rear end of the LNA 8 of FIG. It is different from the configuration of FIG. 1 that is connected to the rear end of 10, that is, the rear end of AGC 14. Rx attenuation in the CDMA system occurs in the LNA 8 shown in FIG. 3, the reception attenuators 12 and the AGC 14 belonging to the XCVR module 10. FIG. The circuit for enabling dual receive attenuation control, i.e. gain control of the received signal, is the receive attenuator 12 in the XCVR module 10. In another embodiment of the present invention, reception attenuation adjustment is performed using the reception attenuator 12. When the reception attenuation is adjusted using the reception attenuator 12, the spectrum analyzer 16 should be connected to the rear end of the reception attenuator 12 to measure the result. However, because the receiver attenuator 12 is located in front of the AGC 14 in the XCVR module 10, the spectrum analyzer 16 cannot be connected to the output terminal of the receiver attenuator 12 in the XCVR module 10. Therefore, in another embodiment of the present invention, the spectrum analyzer 16 is connected to the rear end of the AGC 10. When the spectrum analyzer 16 is connected to the rear end of AGC 10, the signal strength of the output terminal of the XCVR module 10 is almost independent of the gain attenuator 12's gain adjustment by the function of AGC (Automatic Gain Control) 14 in the XCVR (Tranceiver) module 10. It becomes constant. In another embodiment of the present invention, the load condition of the other subscriber is set by using the fact that the signal strength of the output terminal of the XCVR module 10 is always constant regardless of the gain adjustment of the reception attenuator 12.

This will be described in more detail with reference to FIGS. 3 and 4. 4 (a) to (c) are views showing the state of the thermal noise and the tone signal, (a) is a state measured by the spectrum analyzer 16 of FIG. 3 when the tone signal is applied, (b) is a reception attenuator In the case where the gain of 12 is attenuated and controlled, it is a state at the output terminal of the receiver attenuator 12, and (c) is the state measured by the spectrum analyzer 16 of FIG. 3 when the gain of the attenuator 12 is attenuated.

When the tone signal generated by the tone signal generator 20 of FIG. You will get the same result as a). Referring to FIG. 4A, the spectrum analyzer 16 shows a tone signal 30 having a predetermined magnitude of thermal noise N _th and a magnitude of Slev. Then, if the tester attenuates and adjusts the gain of the attenuator 12, the magnitude of the tone signal 30 at the rear end of the receiver attenuator 12 will be reduced by x size than the initial size as shown in FIG. However, the tone signal reduced by the size of x is automatically gain-adjusted by AGC 14 so that the tone signal 30 of the Slev size is shown again as shown in FIG. Therefore, even if the gain attenuation is adjusted for the reception attenuator 12, the magnitude of the tone signal appearing in the spectrum analyzer 16 is as much as Slev as shown in FIG. However, looking at the magnitude of the thermal noise N _th in FIG. 4 (c), it can be seen that it is increased by y than the magnitude of the thermal noise N _th in FIG. 4 (a). This is because, in response to the attenuation adjustment of the reception attenuator 12, the AGC 14 increases and adjusts not only the tone signal but also the thermal noise N _th . In this case, (SNR) _out1 , which is the Signal to Noise Ratio (SNR) of FIG. 4B, and (SNR) _{out2, which} is the SNR of FIG. 4C, are the same, that is, (SNR) _out1 = (SNR) _out2. Should be understood. That is, the noise increment by y is generated by (SNR) _out1 = (SNR) _out2 . The noise increment by y is such that the virtual subscriber subscriber noise N _OU is loaded. Therefore, the state of (a) (b) (c) of FIG. 4 is represented as (a) (b) (c) of FIG. Referring to FIG. 5C, the increment of the noise by y is expressed as a state in which a virtual subscriber, that is, subscriber noise N _OU is loaded.

Hereinafter, a description of the state in which the virtual subscriber is loaded will be described later with reference to the reception attenuation structure inside the CDMA system.

FIG. 6 is a diagram for explaining a structure of Rx Attenuation in a CDMA system. Rx Attenuation is present in LNA 8, receive attenuator 12, and AGC 14. In such a reception attenuation structure, a typical (SNR) _out for the input signal S _i and the input noise N _i is expressed by Equation 1 below.

Where S _i = input signal

N _i = input noise

F ₁ = noise figure of LNA 8 (constant): constant

F ₂ = noise figure of receive attenuator 12: variable

F ₃ = noise figure of AGC 14: constant

G ₁ = gain of LNA 8: constant

G ₂ = gain of receive attenuator 12: variable

G ₃ = gain of AGC 14: variable

If the subscriber noise N _OU is included in the input noise Ni in Equation 1, Ni becomes N _th (thermal noise) + N _OU (subscriber noise). In this case, (SNR) _out is expressed as in Equation 2.

N _ou : Subscriber Noise

N _th : thermal noise

In such a state equation (2), for adjusting the (noise figure of the F2 or receive attenuators 12), receiving the gain G2 of the attenuator 12 (SNR) _out of (SNR) when "represented as shown in equation (3) _out.

Where G ' ₂ = gain value adjusted by receive attenuation

F ' ₂ = noise figure changed by reception attenuation

Therefore, if the gain G2 of the reception attenuator 12 (or the noise index F2 of the reception attenuator 12) is adjusted to satisfy the following expression (4), the virtual subscriber is loaded.

(SNR) _out = (SNR) ' _out

If (SNR) _{out and} (SNR) ' _out shown in Equations 1 to 4 correspond to Fig. 4, the (SNR) _out corresponds to (SNR) _out2 shown in Fig. 4C, and ( SNR) ' _out corresponds to (SNR) _out1 shown in FIG. 4B.

In FIG. 4, it is necessary to know how many subscribers the signal has been reduced by x based on the gain (or noise figure) control of the receiver attenuator 12, i. The subscriber load status value of can be known.

The received power according to the number of subscribers is calculated by calculation. The total received power P _{total_RX} received by the base station is obtained by Equation 1 below.

In Equation 5, it should be understood that all values except the number N of subscribers are known values. In FIG. 7, F = 0.65, S = 0.85, v = 0.45, Rb = 9600 pbs, W = 1.23 MHz, N _th W = -113 dBm / 1.23 MHz, and E _b / N _O are 6,7,8,9, In the case of 10, 11, 12, and 13, values of the received power Prx (N, E _b / N _O ) for each subscriber number (N) obtained by Equation 5 are shown as an example. Table 1 below shows the increment of the total received power P _{total_RX} compared to the thermal noise N _th of the base station receiver according to the number of subscribers N in call, which is obtained by Equation 1 below.

N Incremental Power Consumption vs. Thermal Noise N Incremental Power Consumption vs. Thermal Noise One 0.062 dB 7 0.999 dB 2 0.205 dB 8 1.176 dB 3 0.353 dB 9 1.362 dB 4 0.505 dB 10 1.555 dB 5 0.664 dB 11 1.758 dB 6 0.828 dB 12 1.97 dB

As shown in FIG. 7 and Table 1, the increment of the total received power P _{total_RX} versus the thermal noise N _th for the number of subscribers can be seen.

Therefore, assuming that the magnitude x of the signal shown in (b) of FIG. 4 is 1.97 dB shown in Table 1, the y-value shown in (c) of FIG. 4 (that is, the subscriber noise N shown in (c) of FIG. 5). _ou ) is the noise value for 12 subscribers as shown in Table 1.

_Since the increment of the total received power P _{total_RX} relative to the thermal noise N _th for the number of subscribers as shown in Table 1 can be obtained by Equation 5, the investigator can obtain the x value for the desired number of subscribers. The x value is adjusted by the gain (or noise figure) control of the receive attenuator 12 of FIG. As a result, another embodiment of the present invention adjusts the gain (or noise figure) of the base station receive attenuator 12 so that as many virtual subscribers as desired are loaded.

In the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be defined by the equivalents of the claims and the claims.

As described above, the present invention has the following effects.

First, you can do field tests in full load. In a fixed base station, the service area is very important for the advantage of call mobility. As the number of subscribers increases, the boundary of the reverse link decreases, and thus cell optimization test under full load is essential. The ultimate goal of the CDMA system is call capacity, call mobility, and call quality. The call should not be dropped while moving while maintaining the quality of the call with the maximum subscriber loaded. Therefore, the test under such conditions can create an effect that can create an environment in which call capacity, call mobility, and call quality can coexist with noise injection by OUNS. .

Secondly, it is possible to accurately calculate the call capacity in various cell environments within the system. The number of terminals required for a one-sector capacity test is approximately 80. The number of required terminals in capacity testing in a multi-cell environment can be roughly estimated by the number of required terminals in a sector system. Therefore, since the number of terminals required for the cell capacity test is implemented internally, the number of terminals required is greatly reduced.

Claims (4)

A subscriber signal generator generates a subscriber noise signal in a digital cellular system and inputs it to one end of the directional coupler, and receives a tone signal mixed with the subscriber noise signal through the directional coupler to reduce the intensity of the tone signal. 10. A method for adding a reverse link subscriber load condition to a base station radio receiver having an automatic gain control circuit for gain control of a reception attenuator and a tone signal attenuated by the reception attenuator to a state prior to input to the reception attenuator. Receiving a tone signal mixed with the subscriber particle noise signal through the directional coupler to the reception attenuator; Adjusting the gain of the receiver attenuator to attenuate and adjust the tone signal mixed with the subscriber noise signal to a desired size to generate a signal having a virtual subscriber noise loaded corresponding to the desired number of virtual subscribers. Subscriber load condition addition method. The method of claim 1, wherein the number of subscribers (N), Subscriber load condition addition method characterized in that it is calculated by the following equation (8).

The method of claim 1, wherein the virtual subscriber noise, And the signal-to-noise ratio at the output of the receiving attenuator is determined by the condition that the signal-to-noise ratio at the output of the automatic gain control circuit connected to the rear of the receiving attenuator is the same. The method of claim 1, wherein the attenuation adjustment, And adjusting the noise figure of the receiving attenuator.

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