KR200427975Y1 - Automatic gain control apparatus in wireless telecommunication system - Google Patents

Abstract

The present invention relates to an automatic gain control apparatus of a wireless communication system for measuring a received signal strength using a preamble symbol in a wireless communication system and automatically adjusting the gain of an amplifier based on the result.

According to an aspect of the present invention, an automatic gain control apparatus of a wireless communication system obtains an average value of a sample power for a unit symbol period after measuring sample power on a sample basis with respect to an input signal. After detecting the maximum value, it is characterized in that the automatic gain control to calculate the gain adjustment value based on this.

Description

Automatic gain control apparatus and module device for wireless communication system

1 is a schematic diagram of an automatic gain control apparatus of a wireless communication system.

2 is a detailed configuration diagram of an automatic gain control apparatus for a wireless communication system according to the present invention.

3 is a diagram illustrating a structure of a frame that can be used in the present invention.

4 is another detailed configuration diagram of an automatic gain control apparatus for a wireless communication system according to the present invention.

5 is a flowchart illustrating an operation process of an automatic gain control apparatus of a wireless communication system according to the present invention.

Explanation of symbols on the main parts of the drawings

110: antenna 120: low noise amplifier (LNA)

130: gain control amplifier (GCA) 140: analog-to-digital converter (ADC)

150: Matched Filter 160: Decimator

170, 200: automatic gain control module 180: RF / IF interface

210: sample power measurement unit 220: interval average unit

230: peak detection unit 240: gain adjustment value calculation unit

250: AGC loop filter 260: timing controller

The present invention relates to an automatic gain control apparatus for a wireless communication system, and more particularly, to measure a received signal strength using a preamble symbol so as to be applicable to a wireless broadband system (Wibro). An automatic gain control apparatus for a wireless communication system for automatically adjusting the gain of an amplifier based on the present invention.

In general, in the wireless communication system, the strength of the input signal is not kept constant and varies within a specific range. This is because the distance between the base station and the terminal, the interference caused by obstacles, the movement of the terminal, and the surrounding environment of the terminal. Due to change. In this case, in order to keep the strength of the signal delivered to the baseband demodulator of the terminal constant, an RF / Intermediate Frequency (IF) module uses an amplifier whose gain can be adjusted. This is accomplished by measuring the strength of the current input signal in the RF / IF module or baseband modem and determining the gain adjustment based on it.

Referring to Figure 1 briefly described the structure of the automatic gain control apparatus for a wireless communication system according to the prior art. Signals received through the antenna are RF components, low noise amplifiers (LNAs), gain controlled amplifiers (GCAs), IF components, analog to digital converters, matching filters (Matched Filter), Decimator, etc., is passed to the baseband modem. In addition, the signal from the decimator is input to the automatic gain control (AGC) module again for automatic gain control, and the automatic gain control module determines the gain adjustment value by measuring the intensity of the input signal, and the gain The adjustment value is fed back to the low noise amplifier and gain control amplifier via the RF / IF interface to form an automatic gain control loop. The automatic gain control loop may be subdivided into a low noise amplifier, a gain control amplifier, an analog part of an analog / digital converter and a digital part of a matching filter, a decimator, an auto gain control module, and an RF / IF interface.

However, when the automatic gain control technique according to the prior art is applied to a time division wireless communication system (for example, a time division portable internet system), the sample interval used to calculate the strength of the input signal becomes important, which is downward in the time division portable internet system. This is because the sample period should be determined within the DL frame and the strength of the input signal should be changed for every symbol within the downlink frame. This problem can have a very serious effect, especially when synchronization is not achieved at the initial time of operation of the terminal.

The present invention was devised to solve the problems of the prior art as described above, and an object of the present invention is to measure a received signal strength using a preamble symbol and to wirelessly adjust the gain of an amplifier based on the result. It is to provide an automatic gain control device of the system.

Another object of the present invention is to provide an automatic gain control apparatus in a wireless communication system capable of easily detecting a preamble symbol by using an AGC mode selection signal and a preamble and timing signal according to frame synchronization during automatic gain control. .

Another object of the present invention is to optimize the gain using AGC ROM in which the gain control value data, which are previously measured and calculated in advance in calculating the gain control value for the input signal strength in the automatic gain control module, are embedded in the form of a ROM table. It is to provide an automatic gain control apparatus in a wireless communication system that can easily calculate a value.

To this end, the automatic gain control apparatus of the wireless communication system according to the present invention, a gain control amplifier for performing a gain control on the input signal received from the antenna; An analog / digital converter for converting the analog signal output from the gain control amplifier into a digital signal; A matched filter for filtering a digital signal output from the analog / digital converter to improve a signal-to-noise ratio; A decimator for re-sampling oversampled digital signals output from the matching filter; After measuring the sample power with respect to the sample output from the decimator, the average value of the sample power during the unit symbol interval is calculated, and the gain control value is calculated based on the maximum value of the average value of the sample power calculated in one frame interval. An automatic gain control module; And an RF / IF interface for transmitting the gain control value determined by the automatic gain control module to the gain control amplifier.

In addition, the automatic gain control module apparatus of the wireless communication system according to the present invention, the sample power measuring unit for measuring the sample power for the input signal in the sample unit; An interval average unit configured to calculate an average value of sample power for a predetermined interval with respect to the sample; A peak detector for detecting a maximum value during one frame period with respect to the sample power average value; And a gain adjustment value calculator configured to calculate a gain adjustment value based on the sample power average value.

Preferably, the automatic gain control module device further includes a timing controller for providing an AGC mode selection signal according to frame synchronization as an input of the gain adjustment value calculation unit, and when the frame power is before frame synchronization, the detected average power of the sample power. The gain adjustment value is calculated based on the maximum value, and the gain adjustment value is calculated based on a value corresponding to a preamble and timing setting position among sample power average values after frame synchronization.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments. For reference, in the following description, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention are omitted.

First, an outline of an automatic gain control apparatus for a wireless communication system according to the present invention will be described with reference to FIG. 1.

The signal received through the antenna 110 is transmitted to the low noise amplifier (LNA) 120 through the RF components, the low noise amplifier 120 is a reception path for minimizing noise generated in the terminal First amplifier on path. The signal amplified by the low noise amplifier 120 is input to a gain control amplifier (GCA) 130 through an RF component, and the gain control amplifier 130 amplifies an input signal to perform a gain adjustment function. On the other hand, the signal amplified by the gain control amplifier 130 is passed through the IF component to the analog-to-digital converter (ADC) 140, where the analog signal is converted into a digital signal. In addition, the signal converted into a digital signal is input to the matching filter 150, which is a low-band filter indicating an optimal signal-to-noise ratio (SNR) for the received signal. The signal filtered by the matching filter 150 is input to the decimator 160, and the decimator 160 re-samples the over-sampled signal. The signal passing through the decimator 160 proceeds to the baseband demodulation process and is input to the automatic gain control module for automatic gain control.

For reference, the RF component and the IF component described herein with reference to FIG. 1 collectively referred to RF / IF elements, such as various switches, filters, demodulators, and one less related to the core technical features of the present invention It is expressed as an integrated block, and thus a detailed description thereof will be omitted.

In the automatic gain control module, the strength measurement of the input signal and the gain adjustment value, which are the most important operations of the automatic gain control, are performed. In this embodiment, the input signal passes through an analog / digital converter, a matching filter, and a decimator in order. The gain adjustment value determined by the automatic gain control module is transferred to the low noise amplifier and the gain control amplifier properly through the RF / IF interface. That is, the automatic gain control module device measures the sample power of the signal input through the decimator at every sample timing and measures the intensity of the input signal by taking the average of the sample power results for a predetermined period. . The obtained intensity of the input signal is compared with the intensity of the predetermined input signal (the intensity of the reference input signal), and a gain adjustment value is determined to compensate for the difference. Lastly, the RF / IF interface is an interface for transmitting the control result determined by the automatic gain control module device to the RF / IF module.

Hereinafter, the automatic gain control apparatus according to the present invention will be described in detail with reference to FIGS. 2 to 6.

FIG. 2 is a detailed configuration diagram of an automatic gain control apparatus for a wireless communication system according to the present invention. The automatic gain control module 200 illustrated in FIG. 2 is a diagram illustrating the general structure of the automatic gain control apparatus. Corresponding to the automatic gain control module 170, and includes a specific component for implementing the present invention. For reference, the automatic gain control module 200 of FIG. 2 uses the reference numeral '200' to distinguish it from the automatic gain control module 170 of FIG. 1.

The automatic gain control module 200 according to the present invention includes a sample power calculation part 210, a moving averaging part 220, a peak detection part 230, and a gain control value. An automatic gain control value production part 240 and an AGC loop filter 250 are included.

,

이라고 할 경우, 그 출력은 하기 수학식 1과 같다.The sample power measurement unit 210 measures the instantaneous sample power with respect to the input signal of the sample unit received through the decimator 160 (S510). For example, the input signal of the sample power measurement unit 210

,

In this case, the output is as shown in Equation 1 below.

은 n번째 샘플의 정 위상(In-phase) 신호이고,

은 n번째 샘플의 직각 위상(Quadrature-phase) 신호를 의미한다.here,

Is the in-phase signal of the nth sample,

Denotes a quadrature-phase signal of the n th sample.

The section average unit 220 obtains an average value of the sample power for a predetermined section from the current sample time point (S520). At this time, the cumulative section for calculating the average value is set to "unit symbol section". The reason why the cumulative interval is the same length as the unit symbol interval is to use only the interval corresponding to the preamble symbol for measuring the strength of the input signal, which is one of the main technical features of the present invention, which is distinguished from the prior art. If the preamble is composed of two or more symbols, the cumulative interval may be set as a unit symbol interval, or alternatively, may be implemented to be equal to the interval of symbols constituting the preamble. If the cumulative interval is set equal to the length of the interval (that is, n times the unit symbol interval, where n is an integer greater than or equal to 2) of the symbols constituting the preamble, more accurate auto gain control is performed than if the cumulative interval is set to the unit symbol interval. can do.

Assuming that Equation 1 is an input of the section average unit 220, the output is as follows.

Hereinafter, with reference to FIG. 3, a brief description will be made of a frame structure used in a wireless broadband network (Wibro) system of time division duplexing (TDD).

The time division duplexing scheme divides one frame inside for transmission and reception in time in a time division transmission scheme. As shown in FIG. 3, one frame is downlinked with a downlink frame 310 and an uplink. (Uplink) The frame 320 is divided into two-way communication at the same frequency. One frame includes a plurality of samples. In FIG. 3, one frame includes N _frm samples, the downlink frame 310 includes N _DL samples, and the uplink frame 320. _Shows that it consists of N _UL samples. In addition, a TTG (Transmit / receive Transition Gap) section 330 is present between the downlink frame 310 and the uplink frame 320, and the current uplink frame 320 and the next downlink frame are at the end of the frame. There is a Receive / Transmit Transition Gap (RTG) section 340 to distinguish 310. Meanwhile, N _symb samples are collected in the downlink frame 310 and the uplink frame 320 to form one symbol. In this respect, one frame is composed of a plurality of symbols.

In the portable Internet system, the first symbol 350 of the downlink frame is a preamble, and a specific [PN] random code is transmitted after being subjected to binary phase shift keying (BPSK) on the frequency axis. The preamble symbol is used for initial synchronization, cell search, frequency offset, channel estimation, etc. In general, the transmission power of the preamble symbol is the largest of all symbols. Symbols other than the preamble symbols show different input signal strengths depending on the amount of data allocated from the base station. Therefore, they are not suitable for use as a factor of automatic gain control. Therefore, the present invention easily detects the preamble symbol by setting the cumulative section to the same length as the unit symbol section in calculating the average sample power, and uses only the section corresponding to the detected preamble symbol to measure the strength of the input signal.

Referring back to FIG. 2, the sample power average value calculated by the section average unit 220 is input to the peak detector 230, where the maximum sample power average value is detected and used for automatic gain control. In detail, the position of the preamble is not known until the frame synchronization is performed during the initial operation of the terminal. The peak detector 230 determines that the average value of the input signal strength (sample power average value) measured during the symbol period is determined. The largest point of time is detected within one frame period, and this is assumed to be a value corresponding to a preamble symbol.

Assuming that Equation 2 is an input of the peak detector 230, the output is as shown in Equation 3 below.

After the frame synchronization of the terminal is performed, it is not necessary to use the peak detector 230, and a value corresponding to a preamble end timing setting position among the results of the average sample power is used for the automatic gain control.

To this end, the automatic gain control module according to the present invention controls the signal input to the gain adjustment value calculator 240 using the AGC mode selection signal. For example, before the frame synchronization, the AGC mode selection signal is set to '0' (S530), and the sample power average value output from the section average unit is input to the gain control unit 240 through the peak detector 230. It is switched (S540). On the contrary, since the preamble symbol and timing can be known after the frame synchronization, the AGC mode selection signal is set to '1' (S530), and the peak detector 230 and the gain control value calculator 240 are open ( and a value corresponding to a preamble and timing setting position among the sample power average values output from the section average unit is switched to the gain adjustment value calculating unit 230 (S550).

2 illustrates that a switch is provided between the peak detector 230 and the gain adjustment value calculator 240 to perform switching according to an AGC mode selection signal output from the timing controller 260. On the other hand, as shown in Figure 4, the switch controlled by the AGC mode selection signal may be implemented to be provided between the section average unit 220 and the peak detector 230. In this case, the output of the peak detector 230 may be '0', or the peak detector and the gain control value calculator 240 may be opened.

The AGC mode selection signal and the preamble and timing signal according to frame synchronization are output from the timing controller 260. The timing controller 260 used in the present invention is a controller for outputting an AGC mode selection signal and a preamble and timing signal. Although shown in FIG. 2 and FIG. 4 as being included in the automatic gain control module 200, the automatic gain control module is not limited thereto. It does not need to be provided inside. In other words, the timing controller 250 may be a controller that manages timing signals of the entire terminal, and the AGC mode selection signal and / or preamble and timing signals must be output directly from one timing controller 260. It may be indirectly output from other components or logic elements.

The gain adjustment value calculator 240 calculates a gain adjustment value based on the sample power average value output from the peak detector 230 or the section average unit 220 (S560). The gain adjustment value calculation unit 240 is preferably implemented in a ROM form. The gain adjustment value calculation unit 240 uses the measured intensity of the input signal (sample power average value) as an input address of the ROM and uses the gain adjustment value data previously measured and calculated in advance. Gain control values can be easily obtained by embedding them in the form of a ROM table.

On the other hand, if the automatic gain control result (gain control value) determined in a certain frame is applied directly to the next frame, over-damping may occur, which may adversely affect performance. In order to do so, the output through the AGC loop filter 250 may be applied without directly applying the gain control value output from the gain control value calculator 240. That is, the AGC loop filter 250 may determine an adaptation speed of the automatic gain control loop by setting an appropriate loop bandwidth by applying a specific loop gain.

The output of the AGC loop filter 250 is input to the low noise amplifier 120 and / or the gain control amplifier 130 via the RF / IF interface 180 for automatic gain control.

Finally, Figure 5 is a flow chart illustrating the operation of the automatic gain control device of a wireless communication system according to the present invention. For reference, the flowchart illustrated in FIG. 5 illustrates a process performed by the automatic gain control module during the entire automatic gain control process of the wireless communication system.

First, in step S510, the sample power is measured in units of samples for each sample timing with respect to the input signal. In operation S520, a sample power average value of the samples for the time corresponding to the unit symbol interval from the current sample time point is calculated. The obtained sample power average value is the basis of the gain control value calculation. In this case, not all sample power average values are used, but only a specific sample power average value (specifically, the sample power average value corresponding to the preamble symbol interval) is used to calculate the gain control value. Is used. In this case, the detection method is different depending on whether the frame is synchronized, and whether or not the frame is synchronized can be known by a signal input from the timing controller.

In step S530, it is determined whether or not the frame is synchronized. If the frame of the preamble symbol is not known before the frame is synchronized, the flow proceeds to step S540, where the maximum value of the average sample power is used to calculate the gain control value. On the contrary, since the frame of the preamble symbol is known after the frame synchronization, the process proceeds to step S550, and a value corresponding to the preamble and timing setting position among the sample power average values is used to calculate the gain adjustment value. In step S560, a gain adjustment value is calculated based on the previously determined sample power average value. Finally, in step S570, automatic gain control is performed by controlling the amplifier gain based on the calculated gain adjustment value.

Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art to which the present invention pertains can be implemented in other specific forms without changing the technical spirit or essential features, The examples are to be understood in all respects as illustrative and not restrictive.

And, the scope of the present invention is specified by the utility model registration claims to be described later than the above detailed description, and all changes or modifications derived from the meaning and scope of the utility model registration claims and the equivalent concept of the present invention It should be construed as being included in the scope.

According to the present invention, when performing the automatic gain control of the wireless communication system, in particular, the portable Internet system, it is possible to solve the problem of the measurement interval in the time division system to perform the optimal automatic gain control.

In addition, according to the present invention, even during the initial operation of the terminal prior to frame synchronization, by measuring the strength of the input signal for the section corresponding to the preamble symbol and reflecting it in the gain adjustment value calculation, the optimum automatic gain control is performed regardless of frame synchronization. Has the effect of performing.

In addition, according to the present invention, when calculating the gain adjustment value for the input signal strength, the measured intensity control value (sample power average value) of the input signal is used as the input address of the ROM, and the gain adjustment value data previously measured and calculated in advance are used in the ROM table. The gain control value can be easily obtained by embedding in the form of table, and the gain control value for the input signal strength can be easily changed by changing the embedded ROM table value.

Claims (12)

An automatic gain control device for a wireless communication system, A gain control amplifier for performing gain control on the input signal received from the antenna; An analog / digital converter for converting the analog signal output from the gain control amplifier into a digital signal; A matched filter for filtering a digital signal output from the analog / digital converter to improve a signal-to-noise ratio; A decimator for re-sampling oversampled digital signals output from the matching filter; After measuring the sample power with respect to the sample output from the decimator, the average value of the sample power during the unit symbol interval is calculated, and the gain control value is calculated based on the maximum value of the average value of the sample power calculated in one frame interval. An automatic gain control module; And And an RF / IF interface for transmitting the gain control value determined by the automatic gain control module to the gain control amplifier. The method of claim 1, A timing controller for transmitting the AGC mode selection signal according to the frame synchronization to the automatic gain control module, The automatic gain control module, when determined before frame synchronization by the AGC mode selection signal, calculates a gain adjustment value based on a maximum value of the average value of the sample power, and determines after frame synchronization by the AGC mode selection signal. And a gain adjustment value is calculated based on a value corresponding to a preamble and timing setting position among the sample power average values. The method according to claim 1 or 2, A low noise amplifier for reducing the noise to the input signal received from the antenna to transmit to the gain control amplifier, And the RF / IF interface transmits the gain adjustment value to the low noise amplifier. The method according to claim 1 or 2, The unit symbol interval is the same as the preamble symbol interval automatic gain control apparatus of a wireless communication system. The method according to claim 1 or 2, And the wireless communication system is a portable Internet system using at least one of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme and a Time Division Duplex (TDD) scheme. An automatic gain control module device of a wireless communication system, A sample power measuring unit measuring sample power with respect to the input signal in a sample unit; An interval average unit configured to calculate an average value of sample power for a predetermined interval with respect to the sample; A peak detector for detecting a maximum value during one frame period with respect to the sample power average value; And And a gain adjustment value calculating unit for calculating a gain adjustment value based on the sample power average value. The method of claim 6, And a timing controller for providing an AGC mode selection signal according to frame synchronization to an input of the gain adjustment value calculator. The gain adjustment value calculator is switched according to the AGC mode selection signal, and calculates a gain adjustment value based on a sample power average value output from the peak detection unit before frame synchronization, and in the interval average unit after frame synchronization. And a gain adjustment value is calculated based on a value corresponding to a preamble and timing setting position among the output sample power average values. The method of claim 6, Further comprising a timing controller for providing the AGC mode selection signal according to whether the frame synchronization to the input of the peak detector, The peak detector is switched according to the AGC mode selection signal to transmit the detected maximum value to the gain adjustment value calculator for a sample power average value before frame synchronization, and to the gain adjustment value calculation unit after frame synchronization. An automatic gain control module device for a wireless communication system, characterized in that it does not transmit an output signal. The method according to any one of claims 6 to 8, And an AGC loop filter for determining an adaptive speed of an automatic gain control loop by applying a predetermined loop gain to the calculated gain adjustment value to set a loop bandwidth. The method according to any one of claims 6 to 8, And the predetermined section is n times the unit symbol section, and n is a natural number. The method according to any one of claims 6 to 8, The predetermined period is the same as the preamble symbol interval automatic gain control module apparatus of a wireless communication system. The method according to any one of claims 6 to 8, And said gain adjustment value calculating section is a ROM for setting said sample power average value as an input address and said gain adjustment value as an output value.

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