CN111181877A

CN111181877A - Communication receiving device and signal processing method thereof

Info

Publication number: CN111181877A
Application number: CN201811343638.XA
Authority: CN
Inventors: 魏逢时; 赖科印; 童泰来
Original assignee: MediaTek Inc
Current assignee: MediaTek Inc
Priority date: 2018-11-13
Filing date: 2018-11-13
Publication date: 2020-05-19

Abstract

The present invention provides a communication receiving device, which includes a spectrum generating circuit, a peak value selecting circuit, and a signal-to-noise ratio estimation circuit. The spectrum generating circuit is used to generate a spectrum for a received signal. The peak value selecting circuit is used to select an in-band inspection range in a data band of the spectrum, select an out-of-band inspection range in a guard band of the spectrum, and select an in-band energy peak value in the in-band inspection range and an out-of-band energy peak value in the out-of-band inspection range. The signal-to-noise ratio estimation circuit is used to estimate a signal-to-noise ratio based on the in-band energy peak value and the out-of-band energy peak value.

Description

Communication receiving device and signal processing method thereof

Technical Field

The present invention relates to communication systems, and more particularly to techniques for estimating the signal-to-noise ratio at the receiving end of a communication system.

Background

In recent years, Orthogonal Frequency Division Multiplexing (OFDM) technology has advantages of high spectrum utilization rate and simple hardware architectureIs widely used in wireless communication systems. Fig. 1 shows a partial circuit of an OFDM receiving end. The spectrum generation circuit 110 is responsible for generating the spectrum S of the received signal Y. Channel estimation circuit 120 generates a channel impulse response estimate based on spectrum S

Which is provided to the equalization circuit 130. Then, the equalized signal generated by the equalizing circuit 130

Is sent to the demapping/decoding circuit 140 for subsequent processing. The SNR provided by the SNR estimation circuit 150 is output to subsequent circuits to determine whether to enable a multi-path (multi-path) cancellation function. The following illustrates how an exemplary signal-to-noise ratio estimation circuit 150 produces a signal-to-noise ratio SNR.

The relationship between the received signal Y, the channel impulse response H, and the signal X actually transmitted by the transmitting end can be expressed as follows:

Y_k＝H_kX_k+N_k(formula one)

Wherein the symbol k represents a sampling index and the symbol N represents_kRepresenting a noise signal.

Pilot symbols (pilot) in the OFDM signal are inserted on a specific subcarrier (sub-carrier) at a specific frequency interval; the signal content X of these pilot symbols_kTo clarify known data carried in the OFDM specification. In obtaining the estimated value of the channel impulse response

The snr estimation circuit 150 then utilizes the signal content X of the pilot symbol_kAnd the following operation formula to obtain a noise signal estimation value

In seekingNoise signal estimation

Then, the SNR estimation circuit 150 calculates SNR corresponding to the kth sub-carrier according to the following operation_k：

The SNR estimation circuit 150 may then estimate the SNR from the SNR of the multiple subcarriers_kFor example, an average is used to generate a SNR representing the quality of the current overall communication environment. As can be seen from equation three, the SNR of each subcarrier_kAccuracy of the calculated result and the estimated value of the channel impulse response

The accuracy of the calculated result is closely related. However, when initial estimation is performed, the channel is often in an unstable state, and at this time, the channel impulse response estimation value

The calculation of (a) may be inaccurate. Therefore, in the initial stage, when the channel is in an unstable state, the SNR estimation method is not ideal. In contrast, if the estimated value of the channel impulse response is to be waited for

And entering a stable state, and delaying the time point of acquiring the signal-to-noise ratio (SNR) later.

Disclosure of Invention

In order to solve the above-mentioned problems, the present invention provides an estimation method for obtaining the snr more efficiently and accurately, and provides a new communication receiving apparatus and a signal processing method thereof.

An embodiment of the present invention is a communication receiving apparatus, which includes a spectrum generating circuit, a peak selecting circuit, and a snr estimating circuit. The spectrum generating circuit is used for generating a spectrum for a received signal. The peak value selecting circuit is used for selecting an in-band inspection range from a data band of the frequency spectrum, selecting an out-band inspection range from a guard band of the frequency spectrum, selecting an in-band energy peak value from the in-band inspection range and selecting an out-band energy peak value from the out-band inspection range. The SNR estimation circuit is used for estimating an SNR according to the in-band energy peak and the out-of-band energy peak.

Another embodiment of the present invention is a signal processing method applied to a communication receiving apparatus. First, a spectrum of a received signal is generated. Next, an in-band inspection range is selected from a data band of the spectrum, and an out-of-band inspection range is selected from a guard band of the spectrum. An in-band energy peak is then selected from the in-band viewing range and an out-of-band energy peak is selected from the out-of-band viewing range. A signal-to-noise ratio is estimated based on the in-band energy peak and the out-of-band energy peak.

The advantages and spirit of the present invention can be further understood by the following detailed description of the invention and the accompanying drawings.

Drawings

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below, wherein:

fig. 1 shows a partial circuit of an ofdm receiver.

Fig. 2 is a functional block diagram of a communication receiving device according to an embodiment of the present invention.

FIGS. 3A-3C are diagrams illustrating an in-band inspection range B according to the present invention_INAnd an outside viewing range B_OUTExample of the frequency spectrum of (c).

Fig. 4 shows an embodiment in which the communication receiving apparatus further includes a low pass filter according to the present invention.

FIG. 5 is a diagram illustrating the in-band inspection range B according to the present invention_INAnd an outside viewing range B_OUTAnother example of a frequency spectrum.

FIG. 6 is a block diagram of an SNR estimation circuit according to an embodiment of the present invention.

FIG. 7 is a block diagram of a smoothing loop filter according to an embodiment of the present invention.

Fig. 8 shows an embodiment in which the communication receiving apparatus further comprises a fine snr estimation circuit according to the present invention.

Fig. 9 is a flowchart illustrating a signal processing method of a communication receiving apparatus according to an embodiment of the invention.

It is noted that the drawings of the present invention include functional block diagrams that represent various functional blocks that can be associated with each other. The drawings are not detailed circuit diagrams, and the connecting lines are only used for representing signal flows. The various interactions between functional elements and/or processes need not be achieved through direct electrical connections. In addition, the functions of the individual elements do not have to be distributed as shown in the drawings, and the distributed blocks do not have to be implemented by distributed electronic elements.

Description of the symbols

110: frequency spectrum generating circuit

120: channel estimation circuit

130: equalizing circuit

140: demapping/decoding circuit

150: signal-to-noise ratio estimation circuit

210: frequency spectrum generating circuit

220: channel estimation circuit

230: equalizing circuit

240: demapping/decoding circuit

250: signal-to-noise ratio estimation circuit

251: first smoothing loop filter

251A: multiplier and method for generating a digital signal

251B: adder

251C: delay circuit

251D: multiplier and method for generating a digital signal

252: second smoothing loop filter

253: ratio calculation circuit

260: peak value selection circuit

270: low-pass filter

280: fine signal-to-noise ratio estimation circuit

310: energy rising edge

320: energy falling edge

B_DATA: data frequency band

B_GUARD: guard band

B_IN: in-band inspection range

B_OUT: outside viewing range

P_IN: peak value of in-band energy

P_OUT: peak out of band energy

S901 to S906: procedure step

Detailed Description

A functional block diagram of a communication receiving device according to an embodiment of the present invention is shown in fig. 2. The communication receiver 200 comprises a spectrum generating circuit 210, a channel estimation circuit 220, an equalization circuit 230, a demapping/decoding circuit 240, a snr estimation circuit 250, and a peak selection circuit 260. The operation of each circuit is described below.

The spectrum generating circuit 210 is used for generating a spectrum S for the received signal Y. The channel estimation circuit 220 is responsible for generating a channel impulse response estimation value according to the frequency spectrum S

Which is provided to the equalization circuit 230. The equalized signal generated by the equalization circuit 230 is then output

Is sent to the demapping/decoding circuit 240 for subsequent processing. The SNR provided by the SNR estimation circuit 250 is output to subsequent circuits to determine whether to enable the multipath cancellation function.

As shown in fig. 2, the spectrum S output from the spectrum generating circuit 210 is also transmitted to the peak selecting circuit 260. Peak value selection electricityThe path 260 begins at a data band B of the spectrum S_DATASelecting an in-band inspection range B_INAnd in one or more guard bands (B) of the spectrum S_GUARDSelect an out-of-band inspection range B_OUT. More specifically, data band B_DATAThe frequency band where the required data exists for the communication receiving device 200, and the guard band B_GUARDRefers to data band B_DATAThe outside is not the frequency band used to transmit the desired data. In practice, data band B_DATAAnd guard band B_GUARDSometimes specified in the specification and known in advance to the communication receiver 200, and sometimes known by the communication receiver 200 by analyzing the spectrum S. It should be noted that the peak selecting circuit 260 obtains the data band B_DATAAnd guard band B_GUARDAre known to those skilled in the art, and are not described herein.

FIG. 3A shows an example of a spectrum S comprising a data band B_DATAAnd two guard bands B_GUARD. In one embodiment, as shown in FIG. 3B, the peak selection circuit 260 directly uses the data band B_DATAAs the in-band inspection range B_INAnd two guard bands B in the spectrum S_GUARDRegarded as the out-of-band inspection range B_OUT(including the lower frequency range B_{OUT_1}And the range B with higher frequency_{OUT_2}). In another embodiment, as shown in FIG. 3C, the peak selecting circuit 260 can identify the data band B in the spectrum S according to the trend of the energy_DATAAnd excluding the rising edge or the falling edge from the in-band viewing range B_INAnd an outside viewing range B_OUTAnd (c) out. In the example presented in FIG. 3C, data band B_DATAIs shown as dashed range 310 and its energy falling edge is shown as dashed range 320. As can be seen in FIG. 3C, the in-band inspection range B_INAnd an outside viewing range B_OUTNeither of the energy rising edge nor the energy falling edge is included. The reason for avoiding the use of energy rising and falling edges is that,in practice, the energy lifting edge is often delayed such that the lifting edge exhibits a non-ideal slope, which can cause inaccuracy if the energy lifting edge is brought into the viewing range.

Within the selected zone, viewing range B_INAnd an outside viewing range B_OUTThe peak selection circuit 260 then inspects the in-band range B_INIn which an in-band energy peak P is selected_INAnd an out-of-band inspection range B_OUTSelecting an out-of-band energy peak value P_OUTI.e., the highest energy value in each of the two viewing ranges, such as that labeled in fig. 3C.

Then, the SNR estimation circuit 250 will find the in-band energy peak P according to the peak selection circuit 260_INWith peak out-of-band energy P_OUTA signal-to-noise ratio SNR is estimated. For example, the SNR estimation circuit 250 may generate the SNR according to the following operation:

compared with the prior art based on the estimation of the channel impulse response

To generate SNR (i.e., the third equation), the SNR estimation circuit 250 advantageously does not receive the channel impulse response estimate

The accuracy of the calculated result is not required to be equal to the estimated value of the channel impulse response

A reliable SNR can only be obtained after entering a steady state.

As shown in fig. 4, the communication receiver 200 may further include a low pass filter 270 coupled before the spectrum generating circuit 210 for reducing high frequency noise in the received signal Y. In such an embodiment, the peak selection circuit 260 may be implemented inSelecting the out-of-band inspection range B_OUTThe cut-off frequency of the low-pass filter 270 is taken into account. Please refer to the example of the spectrum presented in fig. 5. The cut-off frequency of the low-pass filter 270 is denoted by the symbol F_CUTOFF. As shown in fig. 5, the peak selection circuit 260 will be below the cutoff frequency F_CUTOFFIs excluded from the out-of-band inspection range B_{OUT_1}And (c) out. The reason is that the frequency is lower than the cut-off frequency F_CUTOFFHas been distorted by the action of the low pass filter 270 and is of less reference value to the peak selection circuit 260.

Assuming that the received signal Y conforms to an Orthogonal Frequency Division Multiplexing (OFDM) specification, the spectrum generation circuit 210 can generate a spectrum S for each of N symbols (symbols) in the received signal Y_i(N is an integer greater than one, and the integer index i is 1 to N), and the peak selection circuit 260 selects an in-band energy peak P for each of the N frequency spectrums_{IN_i}And an out-of-band energy peak P_{OUT_i}. The SNR estimation circuit 250 may then estimate the N in-band energy peaks P based on the N_INWith the N out-of-band energy peaks P_OUTThe signal-to-noise ratio SNR is determined. In one embodiment, the SNR estimation circuit 250 combines the N in-band energy peaks P_INSum and calculate the mean value P_{IN_avg}Taking the N out-of-band energy peak values P_OUTSum and calculate the mean value P_{OUT_avg}Then by the average value P_{IN_avg}And the average value P_{OUT_avg}The ratio of (d) is taken as the SNR, i.e. let:

in practice, the SNR estimation circuit 250 may use the N in-band energy peaks P in other ways_INWith the N out-of-band energy peaks P_OUT. As shown in fig. 6, in one embodiment, the snr estimation circuit 250 includes two smoothing loop filters (smoothing loop filters) 251, 252 and a ratio calculation circuit 253. The first smoothing loop filter 251 is used to apply the N in-band energy peak values P according to a predetermined addition method_INAdding, thereby generating a post-addition in-band energyPeak value P_{IN_add}. Fig. seven shows a detailed implementation example of the first smoothing loop filter 251. The N in-band energy peaks P_INAre sequentially fed into the first smoothing loop filter 251. The multiplier 251A is responsible for multiplying the peak value P_{IN_i}multiplying a predetermined value α (which may be selected by a circuit designer based on practical experience) as one of the input signals of the adder 251B, the other input signal of the adder 251B is P through the functions of the delay circuit 251C and the multiplier 251D_{IN_add_(i-1)}product of the value (α -1) the peak of energy P in N bands_INAre sequentially added to obtain energy P_{IN_add_N}I.e. the in-band energy peak value P after addition_{IN_add}. Similarly, the second smoothing loop filter 252 is used to filter the N out-of-band energy peaks P_OUTAdding to thereby produce a post-addition out-of-band energy peak P_{OUT_add}. The ratio calculation circuit 253 is then responsible for calculating the post-addition in-band energy peak P_{IN_add}And the added out-of-band energy peak P_{OUT_add}As the signal-to-noise ratio SNR:

the benefit of taking multiple symbols into account is that a larger time frame can be observed, avoiding that short term disturbances in the communication environment affect the overall accuracy of the SNR.

In practice, the snr estimation circuit 250 and the peak selection circuit 260 may be implemented as fixed and/or programmable digital logic circuits, including programmable gate arrays, asics, microcontrollers, microprocessors, digital signal processors, and other necessary circuits. Those skilled in the art will appreciate that there are numerous circuit configurations and components which can implement the concepts of the present invention without departing from the spirit of the invention.

It should be noted that the SNR generated by the SNR estimation circuit 250 may also be used as a reference value for setting various system parameters, and is not limited to determining whether to activate the multipath cancellation function of the subsequent circuit.

Fig. 8 shows an embodiment of the communication receiver 200 according to the present invention, further comprising a fine snr estimation circuit in addition to the snr estimation circuit 250. The fine signal-to-noise ratio estimation circuit 280 functions similarly to the signal-to-noise ratio estimation circuit 150 of fig. 1. More specifically, the fine snr estimation circuit 280 estimates the cir corresponding to the kth subcarrier based on the received signal Y

And known pilot symbol signal content X_kGenerating SNR corresponding to k-th sub-carrier_k. The respective SNR's generated by the fine SNR estimation circuit 280 are different from the SNR's generated by the SNR estimation circuit 250_kDirectly and respectively corresponding to different sub-carriers. In practice, the fine SNR estimation circuit 280 may wait for the channel impulse response estimate

The SNR begins to be calculated after the SNR becomes stable_k. In addition, the SNR is compared with the plurality of SNR_kMay be provided to different circuits as reference data.

Another embodiment of a signal processing method applied to a communication receiving apparatus according to the invention is illustrated in fig. 9. First, step S901 generates a spectrum for a received signal. Subsequently, step S902 selects an in-band inspection range from a data band of the spectrum. In step S903, an out-of-band inspection range is selected from a guard band of the spectrum. Step S904 is to select an in-band energy peak in the in-band inspection range. In step S905, an out-of-band energy peak is selected from the out-of-band inspection range. Step S906 is to estimate a signal-to-noise ratio according to the in-band energy peak and the out-of-band energy peak.

It can be understood by those skilled in the art that in fig. 9, the sequence of some steps can be changed or performed simultaneously, and the overall effect of the signal processing method is not affected. In addition, various operation changes described in the introduction of the communication receiving apparatus 200 can also be applied to the signal processing method in fig. 9, and details thereof are not repeated.

Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A communication receiving device, comprising:

a spectrum generating circuit for generating a spectrum for a received signal;

a peak selection circuit for selecting an in-band viewing range in a data band of the spectrum, selecting an out-of-band viewing range in a guard band of the spectrum, and selecting an in-band energy peak in the in-band viewing range, Selecting an out-of-band energy peak in the out-of-band viewing range; and

a signal-to-noise ratio estimation circuit for estimating a signal-to-noise ratio according to the in-band energy peak and the out-of-band energy peak.

2 . The communication receiving device of claim 1 , wherein the peak selection circuit identifies an energy rising edge or an energy falling edge between the data band and the guard band in the frequency spectrum, and makes the band The in-band viewing range and the out-of-band viewing range do not include the energy rising edge and the energy falling edge.

3. The communication receiving device of claim 2, further comprising:

a low-pass filter, coupled before the spectrum generating circuit, for reducing high-frequency noise in the received signal;

The peak selection circuit takes a cutoff frequency of the low-pass filter as one of the conditions for selecting the out-of-band viewing range.

4. The communication receiving device of claim 1, wherein the received signal conforms to an OFDM specification, the spectrum generating circuit generates a spectrum for each of N symbols in the received signal, and the The peak selection circuit selects an in-band energy peak and an out-of-band energy peak for each of the N frequency spectra, and the signal-to-noise ratio estimation circuit determines the signal-to-noise ratio according to the N in-band energy peaks and the N out-of-band energy peaks, wherein N is an integer greater than one.

5. The communication receiving apparatus of claim 4, wherein the signal-to-noise ratio estimation circuit comprises:

a first smoothing loop filter for adding the N in-band energy peaks, thereby generating an added in-band energy peak;

a second smoothing loop filter for summing the N out-of-band energy peaks, thereby generating a summed out-of-band energy peak; and

a ratio calculation circuit for calculating a ratio of the added in-band energy peak to the added out-of-band energy peak as the signal-to-noise ratio.

6. A signal processing method applied to a communication receiving device, comprising:

generating a spectrum for a received signal;

selecting an in-band viewing range in a data band of the spectrum;

selecting an out-of-band viewing range in a guard band of the spectrum;

Select an in-band energy peak in the in-band viewing range;

selecting an out-of-band energy peak in the out-of-band viewing range; and

A signal-to-noise ratio is estimated from the in-band energy peak and the out-of-band energy peak.

7. The signal processing method of claim 6, wherein selecting the in-band viewing range and the out-band viewing range comprises:

identifying an energy rising edge or an energy falling edge between the data band and the guard band in the spectrum; and

The energy rising edge or the energy falling edge is excluded from the in-band viewing range and the out-of-band viewing range.

8. The signal processing method of claim 7, further comprising:

performing a low-pass filtering procedure with a cutoff frequency before generating the spectrum to reduce high frequency noise in the received signal;

The selection of the out-of-band viewing range is related to the cutoff frequency.

9. The signal processing method of claim 6, wherein the received signal conforms to an OFDM specification; the signal processing method comprises:

Generate a spectrum for each of N symbols in the received signal, where N is an integer greater than one;

selecting an in-band energy peak and an out-of-band energy peak for each of the N frequency spectra; and

The signal-to-noise ratio is estimated from the N in-band energy peaks and the N out-of-band energy peaks.

10. The signal processing method of claim 9, wherein estimating the signal-to-noise ratio comprises:

Utilizing a smoothing loop filter procedure to add the N in-band energy peaks, thereby generating an added in-band energy peak;

Summing the N out-of-band energy peaks using the smoothing loop filter, thereby generating a summed out-of-band energy peak; and

A ratio of the added in-band energy peak to the added out-of-band energy peak is calculated as the signal-to-noise ratio.