WO2009092177A1

WO2009092177A1 - An apparatus and method for realizing automatic gain control in orthogonal frequency division multiple access system

Info

Publication number: WO2009092177A1
Application number: PCT/CN2008/000145
Authority: WO
Inventors: Jing Zhang; Jia Qiao
Original assignee: Utstarcom Telecom Co., Ltd.
Priority date: 2008-01-21
Filing date: 2008-01-21
Publication date: 2009-07-30
Also published as: CN101926144A

Abstract

An apparatus for realizing automatic gain control in OFDMA system is provided, the apparatus includes: the automatic gain controller, the Analog-Digital Converter and baseband processing module. A method for realizing automatic gain control in OFDMA system is provided, the method uses the following steps: measuring the Carrier to Interference-plus-Noise Ratio and the receiving power on the data burst of each uplink on a frame-by-frame basis; computing the Interference-plus-Noise power of the (n-1)th frame; obtaining the Interference-plus-Noise receiving power and the available signal receiving power of the nth frame; computing the total receiving power of the nth frame; and obtaining the needed digital AGC gain value according to the corresponding relationship between the total receiving power and the AGC gain value of the nth frame. Using the apparatus and method for realizing automatic gain control in OFDMA system, estimating the available receiving power of the current frame with the amounts of the power adjustment from the base station, the total receiving power of the current frame may be more accurately computed, and the automatic gain control can be realized through the corresponding relationship between the total receiving power and the digital AGC gain.

Description

Mold and method for realizing automatic gain control in orthogonal frequency division multiple access system

The present invention relates to an apparatus and method for controlling a digital automatic gain controller in a wireless communication system, and more particularly to an apparatus and method for automatic gain control in an orthogonal frequency division multiple access communication system. Background technique

In the prior art, for a digital wireless communication system, an analog down-conversion is usually used to convert a radio frequency signal to an intermediate frequency signal, and then an analog-to-digital converter (ADC: Analog-Digital Converter) is usually used to sample the analog signal at the input end. Quantize the process and convert it to a digital signal. Specifically, the conversion process is a digital signal that quantizes the analog signal to a predetermined number of bits of the ADC. For example, for an 8-bit ADC, if the conversion range is defined as 0-5V, then 1 1 1 1 1 1 1 1 can be used to represent an analog signal with a voltage amplitude of 5V. However, the power of the analog signal received by the receiver will constantly change. If the analog signal input to the analog downconversion is too large or too small, and the operating range of the analog down conversion is up or down, the simulation will be performed. The signal output of the variable frequency output is saturated or the signal to noise ratio is deteriorated. If the analog signal power input to the analog-to-digital converter is too large to saturate the ADC, the ADC will clip the signal (also known as saturation distortion); if the analog signal power at the front end of the receiver is too low, Produces large quantization interference noise. Therefore, in a digital wireless communication system, a receiving opportunity uses an automatic gain control device to adjust the amplitude of the received analog signal to an appropriate range to avoid a corresponding saturation distortion or signal-to-noise ratio due to excessive or too small analog signal power. Deterioration and other issues.

Especially for an Orthogonal Frequency Division Multiple Address (OFDMA) communication system, which uses multi-carrier and performs scheduling on a frame-by-frame basis, the number of subcarriers allocated to each user and the number of allocated subcarriers vary from frame to frame. Therefore, the power variation between the previous frame and the next frame will be large. In the Chinese Patent Application Publication No. CN 1741519A, the Applicant discloses an apparatus and method for implementing automatic gain control in an OFDMA communication system, which obtains EL(n-1) and EL(n) using the following equation: Where EL(n-1) represents an estimate of the uplink signal to noise J±(SNR: Signal Noise Ratio) of the n-1th frame, and EL(n) represents an estimate of the uplink SNR of the nth frame: Confirmation

In the above formula, N _buret represents the number of data bursts to be transmitted from the mobile station, that is, the number of uplink data bursts allocated in the frame; N _FFT indicates the total number of subcarriers; Ν _{υ τ} indicates each The number of uplink data symbols of the frame; CINR(m) represents the target CINR of the mth data burst; N _SCH (m) represents the number of subchannels allocated to the mth data burst; and k represents each The power allocated by the subchannels. For the above equation, since the previous data burst for a certain user may be transmitted before many frames, the noise and interference levels before many frames may differ greatly from the noise and interference levels of the current frame. In addition, the target CINR (Carrier Interference-plus-Noise Ratio is used in the application text to estimate the useful received power of the current frame, but the target CINR does not always match the CINR value of the real-time measurement, and thus It will reduce the accuracy when estimating the user's useful received power.

In view of the above technical drawbacks caused by the prior art orthogonal frequency division multiple access communication system in performing automatic gain control, the present invention provides an apparatus and method for implementing automatic gain control in an OFDMA communication system.

According to an aspect of the present invention, an automatic gain control apparatus for controlling automatic gain in an orthogonal frequency division multiple access communication system is provided, which includes:

An automatic gain controller for receiving an analog signal from the RF terminal and performing a gain adjustment on the analog signal;

An analog to digital converter for converting a signal at an output of the automatic gain controller to a digital signal;

Baseband processing module, which includes:

a carrier-to-interference-and-noise ratio measuring unit for receiving the digitally down-converted digital signal and measuring a carrier-to-interference-and-noise ratio on a data burst of each uplink on a frame-by-frame basis;

a received power measuring unit for receiving the digitally downconverted digital signal and measuring the received power on each uplink data burst on a frame-by-frame basis;

The received power estimation module of the current frame is configured to estimate the received power of the current frame according to the carrier interference to noise ratio and the received power.

The baseband processing module further includes a radio resource allocation unit, configured to generate power control information. And sending it to the received power estimation module of the current frame.

The baseband processing module may further include an AGC gain calculator configured to acquire an AGC gain value according to the estimated correspondence between the received power of the current frame and the AGC gain value.

According to still another aspect of the present invention, there is provided an automatic gain control method for controlling automatic gain in an orthogonal frequency division multiple access communication system, comprising the steps of:

Measuring the carrier-to-interference and noise ratio on the data burst of each uplink frame by frame;

Measuring the received power on each uplink data burst on a frame-by-frame basis;

Calculating the interference noise power on the data burst of the (i-1)th frame allocated to the i-th user whose data burst number is m(i);

Obtaining the interference noise received power of the nth frame and the received power of the useful signal;

Adding the interference noise received power to the useful signal received power to obtain a total received power of the nth frame;

The required digital AGC gain value is obtained based on the correspondence between the total received power of the nth frame and the AGC gain value.

The power resource allocation unit in the baseband processing module generates power control information and sends it to the received power estimation module of the current frame.

The AGC gain value is obtained by using the AGC gain calculator in the baseband processing module based on the correspondence between the received power of the current frame and the AGC gain value.

The correspondence between the received power of the current frame and the AGC gain value may be expressed in the form of a formula, or a table form 'or an experimental data corresponding curve.

According to still another aspect of the present invention, a baseband processing module for use in an automatic gain control apparatus for an orthogonal frequency division multiple access communication system is provided, wherein the baseband processing module has a received power estimation module of a current frame. And the estimation module calculates the received power of the current frame by using the following equation:

Ρ, ο, (")

Where N _FFT is the number of points of the FFT; N _symb is the number of symbols of the uplink subframe; N _buret is the number of data bursts of the uplink radio resource; N _m(i ) is the data burst number assigned to the i-th user is m (i) the number of subcarriers and symbols included in the data burst; P _s , _m(i ) represents the useful signal on the data burst of the data burst number m(i) assigned to the i-th user Receive power; P _l+N , _m(i ) represents the power of interference and noise on the data burst of the data burst number _m(i ) assigned to the i-th user; and P _t . _t (n) represents the total received power of the nth frame. According to still another aspect of the present invention, a receiver in an orthogonal frequency division multiple access communication system is provided. The receiver includes the baseband processing module described above for use in an automatic gain control apparatus, the baseband processing module having a received power estimation module for a current frame, and the estimating module calculates the received power of the current frame using the following equation:

^Ρ '. '(") = NIN (") ^{x P} SO (") + _NN 3⁄4 "(" - " x ^p ' , (" - 1) Automatic gain control implemented in the orthogonal frequency division multiple access communication system of the present invention The apparatus and method can estimate the useful received power of the current frame by using the power adjustment amount from the base station, can calculate the total received power of the current frame more accurately, and realize the automatic gain by the correspondence between the total received power and the digital AGC gain. Control.

The various aspects of the present invention will become more apparent from the written description of the appended claims. among them ,

1 is a block diagram showing a digital automatic gain control apparatus used in a wireless communication system in the prior art; FIG. 2 is a flow chart showing the control of digital AGC gain in the OFDMA communication system shown in FIG. 1. FIG. A block diagram of a digital automatic gain control device for use in a wireless communication system;

Fig. 4 is a flow chart showing the control of the digital AGC gain in the OFDMA communication system shown in Fig. 3. detailed description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be further described in detail with reference to the accompanying drawings.

1 is a block schematic diagram of a digital automatic gain control device used in a wireless communication system in the prior art. As shown, the digital automatic gain control device includes an automatic gain controller 101, a valid bit detector 102, a power measurer 103, a gain calculator 104, and an SNR estimator 105. Referring to FIG. 1, the power measurer 103 measures the power of the received signal frame by frame, and the SNR estimator 105 estimates the SNR value of the next frame by using the MAP information (or channel allocation information) and the CINR of the next frame. In more detail, the gain calculator 104 calculates the gain value of the automatic gain controller 101 using the received power measurement received from the power measurer 103 and the SNR estimate received from the SNR estimator 105. Next, the automatic gain controller 101 applies the gain value to the received signal so that the output has the expected amplitude. Valid bit detector 102 removes unnecessary LSBs from the data stream received by the automatic gain controller 101 and outputs the formed digital signal to the channel plug-in for channel demodulation. Wherein, the SNR estimator 105 can be separately implemented or configured in the gain calculator 104, and the gain calculator 104 uses the data MAP information received from the LMAC (Low Media Access Control) digital signal processor DSP. The SNR value of the next frame is estimated, and the gain of the automatic gain controller 101 is calculated by using the SNR estimate and the received power measurement.

Fig. 2 is a flow chart showing the control of the digital AGC gain in the OFDMA communication system shown in Fig. 1. Referring to Figure 2, the flow diagram includes the following steps:

Step 200: The base station estimates an uplink SNR value of the (n-1)th frame in an uplink time period of the (n-2)th frame using the following equation (1), where, in Equation (1) N _burst represents the number of data _{bursts to} be transmitted from the mobile station, ie the number of uplink data bursts allocated in the frame; N _FFT represents the total number of subcarriers; Ν _{υ τ} represents the uplink of each frame The number of data symbols; CINR(m) represents the target CINR of the mth data burst; N _seH (m) represents the number of _subchannels allocated to the mth data burst; and k represents the allocation of each subchannel power.

Step 202: The base station calculates an uplink of the nth frame in an uplink time period of the (n-1)th frame.

SNR estimate EL(n);

Step 204: The base station measures the uplink received power PM (n-1) of the (n-1)th frame, and uses EL(n-1) and PM based on the following equation in the uplink time period of the nth frame. (n-1) to estimate the uplink noise power EN(n) of the nth frame;

EL(n - \) = S(n - \)/ N(n - \) . _Ar ,, - PM{n - \)

PM{n - 1) = S(n - 1) + N(n - 1) EL(n - l) + l

In an OFDMA communication system, the uplink noise power is substantially constant, and the uplink noise power EN(n) of the nth frame can be expressed as:

ΕΝ, (, , = PM(n - )≡ Ν(η—, 1) 1)―

EL(n-1) + 1

Step 206: The base station calculates the gain of the digital AGC using the uplink noise power estimate EN(n) of the nth frame or the uplink received power estimate EP(n). The conversion relationship between EP(n) and EN(n) can be expressed as

EP(n) = S(n) + N(n)

= N(n) x EL(n) + N(n)

= EN(n) x [EL(n) + \]

= ^PM ("—x just _{+ 1} ]

EL(n - l) + l

Among them, using EN(n) and EP(n) to control the gain value can be linearly calibrated to

Or

Gain(n) = \ ^P ' ^hreshM

EP(n)

Further, when the EN(n) linearity is used, the expected noise power value N^ _{es/) is} preset. _w and based on the N _thres EN (n) value to control the gain ratio; when using EP (n) linear scaling, the preset power value ^^ expected signal. _/£/ and control the gain value based on the ratio of P _thres to EP(n).

Figure 3 is a block schematic diagram of a digital automatic gain control device for use in a wireless communication system in accordance with the present invention. Referring to FIG. 3, the digital automatic gain control apparatus mainly includes a low noise amplifier, an automatic gain controller 300, an analog down conversion 302, an analog to digital converter 304, a digital down conversion 306 (DDC: Digital Down Conversion), and a baseband processing module 308. More specifically, the baseband processing module 308 has a CINR measuring unit 3081, a received power measuring unit 3082, an AGC gain calculator 3083, a radio resource allocation unit 3084, and a received power estimation module 3085 of the current frame.

The working principle of Figure 3 above is described in detail from the perspective of signal flow. First, the antenna receives the analog signal and is amplified by the low noise amplifier, and the amplified analog signal is input to the automatic gain controller 300, and the analog down conversion 302 is used to convert the radio frequency signal to the intermediate frequency signal and enter the analog to digital converter 304; The analog to digital converter 304 processes and outputs the quantized digital signal; the digital down conversion 306 receives the quantized digital signal and sends it to the baseband processing module 308. For the digital automatic gain control device of the present invention, the received power estimation module 3085 of the current frame is a key component. Using the CINR measuring unit 3081 and the received power measuring unit 3082, the baseband processing module 308 performs received power measurement and CINR measurement on each data burst allocated to each user, and transmits the measured received power and CINR values. Go to the received power estimation module 3085 of the current frame; at the same time, the radio resource allocation unit 3084 generates power control The information is sent to the received power estimation module 3085 of the current frame. The received power estimation module 3085 of the current frame estimates the received power of the current frame based on the received received power and CINR values and power control information. Finally, the AGC gain value is calculated by the AGC gain calculator 3083 using the correspondence between the received power of the current frame and the AGC gain value. As shown in FIG. 3, the AGC gain value is fed back to the automatic gain controller 300 at the input of the analog to digital converter 304 to effect automatic gain adjustment in the automatic gain control device of the present invention.

FIG. 4 is a flow chart showing the control of the digital AGC gain in the OFDMA communication system shown in FIG. Before the process of implementing automatic gain control by the automatic gain control device of the present invention is described in detail, the following physical parameters are defined in advance, and Pm(i) represents a data burst of the data burst number m(i) assigned to the i-th user. Total received power; CINRm(i) represents the signal-to-interference and noise ratio on the data burst of the data burst number m(i) assigned to the i-th user; P _s , _m and P _l+N , _{m( i} ) respectively indicates the power of the useful signal and the power of the interference and noise on the data burst of the data burst number m(i) assigned to the i-th user.

Step 400: Measure the total received power p _m (i) on the data burst allocated to the i-th user with the data burst number _m (i) and the data burst number assigned to the i-th user as m (i) Signal signal interference noise ratio on data burst) CINRm(i);

Step 402: Calculate the interference and noise power P _l+N , _m(i ) on the data burst of the data burst of the i-th frame allocated to the i-th user with the data burst number _m(i );

= corpse, ",) (" - 1) =

CINR _m{i) = P _SMi) /P _I+NMi) ― '+ C Cliff _mW (" _l) + l

Similarly, if the user's previous useful received power of the nth frame to which the data burst is allocated is P _S (,), the user's previous total received power of the nth frame to which the data burst is allocated, and the nth frame allocation If the user's previous signal to interference and noise ratio of the data burst is C/Ni?^), the relationship between the useful received power ^^,) and the signal to interference and noise ratio C/N ? can be obtained by the following equation:

Pp ^re - p ^pre -p ^pre rMpp ^e

^Γ Ι+ΝΜ ^^(Ο― —— ^ ppre ₌ ^JJVA m(Q _{χ p pr} e

' S,m(i) ^J JO pre i ^m (

7ΚΪΏ Ρ ^Γβ ― PP ^re I p ^re ^ ^K m(i) Step 404: Calculate the interference and noise receiving power P _l+N (n) of the nth frame;

First, the interference and noise reception power P _l+N (n-1 ) of the n-1th frame can be obtained by the following equation: ρ _{Ι + Ν} (" - = N _N ∑ ^N (" - " x P' + NM ( " - Considering the interference and noise received power of the nth frame relative to the n-1th frame in the OFDMA communication system The amount of interference and noise received power is small, then

PN (") = _MT ∑N _m{i) (nl)x P _I+NM{I) (n - 1)

I\ _FFT XJ\ _SYMB

Where N _FFT is the number of points of the FFT (Fast Fourier Transform); N _symb is the number of symbols of the uplink subframe; N _buret is the number of data bursts of the uplink radio resource, and the useless subcarrier is also regarded as a virtual data burst; _m(i ) is the number of subcarriers and symbols included in the data burst of the data burst number _m(i ) assigned to the i-th user.

Step 406: Calculate the useful signal received power P _s (n) of the nth frame. As described above, 'P _s , _m(i ) denotes the received power of the useful signal on the data burst of the data burst number _m(i ) assigned to the i-th user. Then, the useful signal received power P _s (n) can be obtained by the following equation:

1

^P s(^ = _N χ _Ν ∑N _m(l) {n), P _SMl) {n) where, if defined as the adjustment parameter of the base station's power to the i-th user, then

υ") = 0 (ι+Δ _; )

Step 408: Calculate the total received power P _{t of} the nth frame. _t (n). It should be understood by those skilled in the art that the total received power of the nth frame can be expressed as the sum of the useful signal received power of the nth frame and the interference of the nth frame and the received power of the noise, that is,

P _tot (n) = P _s {n) + P _I+N {n)

As described above, the interference and noise reception power of the _nth frame and the useful signal reception power of the nth frame have been respectively obtained in steps 402 and 404, and the total received power of the nth frame can be expressed by the following equation:

P _l0 , (") = _Λ . ¹ _M ∑N _m0) (n) x P _SMl) (") + ∑N _m( ("-1) x P _1+NMi) (n-1) Step 410: According to The correspondence between the total received power of the current frame and the AGC gain value yields the AGC gain value in the automatic gain control device of the present invention. It should be noted that the correspondence may be a formula or a test data. A linear calibration based on the current frame's uplink noise power or received power, such as described above with respect to Figure 2, may also be employed. If a lookup table is used to determine the gain of the AGC, a structure similar to the following table may be used:

Hereinabove, the specific embodiments of the present invention have been described with reference to the drawings. However, it will be apparent to those skilled in the art that various modifications and changes can be made to the embodiments of the present invention without departing from the spirit and scope of the invention. Such changes and substitutions are intended to fall within the scope of the appended claims.

Claims

Rights request

What is claimed is: 1. An automatic gain control apparatus for controlling automatic gain in an orthogonal frequency division multiple access communication system, wherein: the automatic gain control apparatus comprises:

Baseband processing module, which includes:

2. The automatic gain control apparatus according to claim 1, wherein the baseband processing module further comprises a radio resource allocation unit, configured to generate power control information and transmit the same to a receive power estimation module of the current frame. .

3. The automatic gain control apparatus according to claim 1, wherein the baseband processing module further comprises an AGC gain calculator for determining between the received power of the current frame and the AGC gain value. Correspondence to obtain the AGC gain value.

4. The automatic gain control apparatus according to claim 3, wherein the acquired AGC gain value is fed back to the automatic gain controller.

5. An automatic gain control method for controlling automatic gain in an orthogonal frequency division multiple access communication system, characterized in that the automatic gain control method adopts the following steps:

Calculating the interference noise power on the data burst of the data burst number m(i) assigned to the i-th user by the (n-1)th frame;

Obtaining interference noise receiving power of the nth frame and useful signal receiving power; Adding the interference noise received power to the useful signal received power to obtain a total received power of the nth frame;

6. The control method according to claim 5, wherein the power control information is generated by the radio resource allocation unit in the baseband processing module and transmitted to the received power estimation module of the current frame.

The control method according to claim 5, wherein the AGC gain value is obtained based on a correspondence between a received power of the current frame and an AGC gain value by using an AGC gain calculator in the baseband processing module.

8. The control method according to claim 7, wherein the correspondence between the received power of the current frame and the AGC gain value may be expressed in the form of a formula, or a table form, or an experimental data corresponding curve or the like.

9. The control method according to claim 5, wherein obtaining the total received power of the nth frame is implemented by a received power estimation module of the current frame.

10. A baseband processing module in an automatic gain control apparatus for an orthogonal frequency division multiple access communication system, wherein the baseband processing module has a received power estimation module of a current frame, and the estimation module utilizes the following Calculate the received power of the current frame:

1 1

P,. , (") = τ; ~~ 7—∑ N _{m 0} (") x P _{S i)} {n) + - ~~ --∑ N _m(l) (" - 1) x P _1+NMl) ( " - 1)

I _FFr xi _{symb m( )=1} j _FFT xj _{symb m(i)=1}

Where N _FFT is the number of points of the FFT; N _symb is the number of symbols of the uplink subframe; N _{bl St} is the number of data bursts of the uplink radio resource; N _m(i ) is the data burst number assigned to the i-th user The number of subcarriers and symbols included in the data burst of m(i); P _s , _m(i ) represents the useful signal on the data burst of the data burst number m(i) assigned to the i-th user Receive power; P _l+N , _m(i ) represents the power of interference and noise on the data burst of the data burst number _m(i ) assigned to the i-th user; and P _t . _t (n) represents the total received power of the nth frame.

The baseband processing module according to claim 10, wherein the received power P _s , _m of the useful signal on the data burst of the data burst of the i-th user assigned to the i-th user is m(i) _(i ) Obtained using the following equation:

^ ") = (,) x (l + A, )

Where P o is the user's previous useful received power for which the data burst is allocated for the nth frame; Δ ί is the base The station adjusts the power of the i-th user.

12. A receiver in an orthogonal frequency division multiple access communication system having the baseband processing module of claim 10.