CN106411338A - Receiving circuit capable of correcting signal-to-noise characteristic value estimation and related method - Google Patents

Abstract

The invention provides a receiving circuit capable of correcting signal-to-noise characteristic value (such as signal-to-noise ratio) estimation and a related method. The equalizer provides an equalized signal according to a received signal. The slicer interprets the digital information in the equalized signal and provides a sliced signal accordingly. The estimation circuit provides an initial SNR value according to a difference between the equalized signal and the truncated signal. The correction circuit can provide a corresponding correction value according to the value of the initial signal-to-noise characteristic value, and correct the initial signal-to-noise characteristic value according to the corresponding correction value to generate a corrected signal-to-noise characteristic value.

Description

Receiver Circuit and Correlation Method for Modified Signal-to-Noise Eigenvalue Estimation

technical field

The present invention relates to a receiving circuit and related method capable of correcting signal-to-noise eigenvalue estimation, especially a receiving circuit capable of correcting erroneous overestimation of signal-to-noise ratio caused by hard decision slicing and related methods.

Background technique

Wired and/or wireless network systems are indispensable in the modern information society. The wired and/or wireless network system includes a transmitter and a receiver, and the transmitter and receiver are connected by a channel; for example, the channel can be a wireless channel formed by air medium/space, or a network cable , Power line (power line), etc. to form a wired channel. The transmitting end can encode and modulate the digital information into a transmission signal, transmit it to the channel, propagate to the receiving end through the channel, and then receive, demodulate and decode it into digital information at the receiving end.

However, when a signal is transmitted in a network system, it must be affected by noise, such as additive white Gaussian noise (AWGN, additive white Gaussian noise). Therefore, the relationship between signal and noise has become an important consideration when designing, implementing, deploying, and optimizing network systems. The relationship between signal and noise can be quantified as signal-to-noise characteristic value, such as signal-to-noise ratio, which is used to reflect the ratio of signal power to noise power. Compared with the power of the transmission signal that actually carries information, if the power of the noise is relatively low, the value of the signal-to-noise ratio will be higher, and the transmission signal from the transmitter to the receiver is less susceptible to noise interference, so it can be used at a higher The correct rate (lower error rate, error rate) sends information from the transmitter to the receiver.

In a modern network system, the receiving end will estimate the SNR, so that the receiving end and/or the transmitting end can adaptively adjust the operation of signal transmission and/or reception according to the SNR. For example, in an advanced power line network system, when the signal-to-noise ratio value estimated by the receiving end is high, the receiving end will think that the current information transmission is in good condition, and then feed back to notify the transmitting end, so that the transmitting end increases the rate ( rate). Conversely, when the signal-to-noise ratio value estimated by the receiving end is low, the receiving end will think that the current information transmission situation is not good, and data transmission is prone to errors, so the receiving end can feedback to the transmitting end to reduce the transmission rate, so The best throughput can be obtained.

However, for the receiving end, since the nature of the noise is random and will be mixed (superimposed) with the real information-carrying signal, the receiving end can only obtain an estimated SNR, and this estimated SNR The ratio does not necessarily reflect the true signal-to-noise ratio. If the difference between the estimated SNR and the real SNR at the receiving end is too large, when the network system adaptively adjusts the operation of signal transmission and/or reception according to the estimated SNR, the operation efficiency of the network system will be affected. For example, if the signal-to-noise ratio estimated by the receiver is optimistic and higher than the real signal-to-noise ratio, it will mistakenly cause the transmitter to increase the rate of information transmission; however, although the information transmission traffic is high, the error rate will also be high , because the signal actually received by the receiving end has been interfered by high noise; therefore, the amount of information that can be correctly and effectively transmitted is reduced instead.

Contents of the invention

One object of the present invention is to provide a receiving circuit (such as 20, Fig. 1 ) that can correct the estimation of signal-to-noise characteristic value (such as signal-to-noise ratio), which can be installed in a receiving end of a network system, and includes a An equalizer (such as 24), a clipper (such as 26), an estimation circuit (such as 28) and a correction circuit (such as 30). The equalizer can provide an equalized signal (such as s2) according to a received signal (such as s1). The clipper is coupled to the equalizer and can interpret digital information in the equalized signal to provide a clipped signal (eg s3 ) according to the equalized signal. The estimation circuit is coupled to the equalizer and the clipper, and is used for providing an initial signal-to-noise characteristic value (such as SNRi[k]) according to the difference between the equalized signal and the clipped signal. The correction circuit is coupled to the estimation circuit, provides a corresponding correction value (such as r[k]) according to the value of the initial signal-to-noise characteristic value, and corrects the initial signal-to-noise characteristic value according to the corresponding correction value to generate a corrected signal-to-noise characteristic value Eigenvalues (such as SNRc[k]).

The correction circuit may include a look-up table circuit (such as 34) and a multiplier (such as 32). The look-up table circuit can store multiple preset correction values (such as e[p,1] to e[p,N], Figure 6), and provide the corresponding correction value based on the initial signal-to-noise characteristic value and these preset correction values ; Wherein, each of the preset correction values corresponds to one of a plurality of preset signal-to-noise characteristic values (such as SNRt[1] to SNRt[N]). The multiplier is coupled to the look-up table circuit and the estimation circuit, and can multiply the initial signal-to-noise characteristic value by the corresponding correction value to generate the modified signal-to-noise characteristic value. In one embodiment, when the look-up table circuit provides the corresponding correction value according to the initial signal-to-noise characteristic value and these preset correction values, a characteristic closest to the initial signal-to-noise characteristic is found from these preset signal-to-noise characteristic values value (such as SNRt[n]), and the preset correction value (such as e[p,n]) associated with the found preset signal-to-noise characteristic value is used as the corresponding correction value. As the preset signal-to-noise characteristic values are arranged from small to large, at least some of the corresponding preset correction values will first change in a first increasing or decreasing trend, and then change in a second increasing or decreasing trend, and The first increasing-decreasing trend is opposite to the second increasing-decreasing trend. For example, the first increasing-decreasing trend may be strictly decreasing (or monotonically decreasing), and the second increasing-decreasing trend may be strictly increasing (or monotonically increasing).

The correction circuit further provides the corresponding correction value according to a modulation setting of the received signal. In one embodiment, the received signal includes a second number (greater than or equal to 1, such as K) of carriers (such as s1[1] to s1[K]), and on each of the carriers (such as s1[k]) according to a The corresponding modulation setting (such as ms[k]) carries corresponding digital information, and the corresponding modulation setting of each carrier is a first number (greater than or equal to 1, such as P) preset modulation setting MS[1] to MS[P]. For example, the default modulation settings MS[1] to MS[P] can be binary phase shift keying (binary phase shift keying, hereinafter referred to as BPSK), quadrature phase shift keying (quadrature phase shift keying, hereinafter referred to as QPSK), eight-element quadrature amplitude modulation (hereinafter referred to as 8QAM), sixteen-element quadrature amplitude modulation (hereinafter referred to as 16QAM), sixty-four element quadrature amplitude modulation (hereinafter referred to as 64QAM), two hundred and fifty Six-element quadrature amplitude modulation (hereinafter referred to as 256QAM), 1024-element quadrature amplitude modulation (hereinafter referred to as 1024QAM) and 4096-element quadrature amplitude modulation (hereinafter referred to as 4096QAM).

The estimation circuit provides an initial signal-to-noise characteristic value SNRi[k] for each carrier s1[k]. The correction circuit provides a corresponding correction value r[k] for each carrier according to the initial signal-to-noise characteristic value SNRi[k] of each carrier and the corresponding modulation setting ms[k] of each carrier, and The initial signal-to-noise characteristic value of each carrier is corrected according to the corresponding correction value of each carrier, so as to generate a modified signal-to-noise characteristic value SNRc[k] for each carrier. In the correction circuit, the look-up table circuit stores a plurality of preset correction values e[p,1] to e[p, N], and according to the corresponding modulation setting ms[k] of each carrier, the initial signal-to-noise characteristic value SNRi[k] of each carrier and the preset modulation settings MS[1] to MS[P] These preset correction values e[1,1] to e[P,1], ..., e[1,N] to e[P,N] provide the corresponding correction value SNRc for each carrier s1[k] [k]. Wherein, each of the preset correction values e[p,n] (for n=1 to N) of each of the preset modulation settings MS[p] is related to a plurality of preset signal-to-noise characteristic values SNRt[1] to One of SNRt[n] SNRt[n]. The multiplier is used for multiplying the initial signal-to-noise characteristic value of each carrier by the corresponding modified value of each carrier, and accordingly generating the modified signal-to-noise characteristic value of each carrier.

When the table look-up circuit provides the corresponding correction value r[k] for each carrier s1[k], one of the preset modulation settings MS[1] to MS[P] is found to match each carrier The corresponding modulation setting is ms[k] (assumed to be MS[p1]), and the initial signal closest to each carrier is found from these preset signal-to-noise characteristic values SNRt[1] to SNRt[N] noise eigenvalue SNRi[k] (assumed to be SNRt[n1]), with these preset correction values e[p1,1] to e[p1,N] in the corresponding preset modulation setting MS[p] The preset correction value e[p1,n1] associated with the found preset signal-to-noise characteristic value SNRt[n] is used as the corresponding correction value r[k] of each carrier. As these preset signal-to-noise characteristic values SNRt[1] to SNRt[N] are arranged from small to large, these preset correction values e[p,1] to e in the same preset modulation setting MS[p] Among [p, N], at least some of the preset correction values will first change in a first increasing-decreasing trend, and then change in a second increasing-decreasing trend, and the first increasing-decreasing trend and the second increasing-decreasing trend The decreasing trend is opposite. With these preset modulation settings MS[1] to MS[P] the number of bits carried per unit time is arranged from small to large, corresponding to the same preset signal-to-noise characteristic value SNRt[n] and corresponding to different Among the plurality of preset correction values e[1,n] to e[P,n] of the preset modulation settings, at least some of the numbers show a decreasing trend.

In an embodiment, the second number of carriers is a plurality of carriers under Orthogonal Frequency-Division Multiplexing (OFDM, Orthogonal Frequency-Division Multiplexing).

In one embodiment, the receiving circuit further includes a bit loading (bit loading) setting circuit (such as 38), coupled to the correction circuit, for generating a feedback signal ( Such as s4, Fig. 1) to the transmitting circuit (such as 10), to update the corresponding modulation setting of each carrier, so that the transmitting circuit can carry on each carrier according to the updated corresponding modulation setting of each carrier Download subsequent digital information.

An object of the present invention is to provide a method for correcting signal-to-noise eigenvalue estimation in a receiving circuit, comprising: providing an equalized signal (equalized signal) according to a received signal received by the receiving circuit, wherein the received signal may include The second number (K) of carriers s1[1] to s1[K] carry corresponding digital information on each carrier s1[k] according to a corresponding modulation setting ms[k], and each of the carriers The corresponding modulation setting ms[k] is selected from the first number (P) of preset modulation settings MS[1] to MS[P]; a clipping step is performed to provide a clipping step based on the equalized signal signal; perform an estimation step, provide an initial signal-to-noise characteristic value SNRi[k] for each of the carriers according to the difference between the equalized signal and the truncated signal; and perform a correction step, based on the initial SNR of each of the carriers The value of the eigenvalue provides a corresponding correction value r[k], and correcting the initial signal-to-noise characteristic value of each carrier according to the corresponding correction value and the initial signal-to-noise characteristic value of each carrier, so as to generate a Correct the signal-to-noise eigenvalue SNRc[k].

Wherein, the step of providing the corresponding correction value according to the initial signal-to-noise characteristic value further includes: providing the corresponding correction value according to a modulation setting of the received signal, the initial signal-to-noise characteristic value and a plurality of preset correction values; wherein, Each of the preset correction values corresponds to one of a plurality of preset signal-to-noise characteristic values; and a preset correction value whose corresponding preset signal-to-noise characteristic value is closest to the The initial signal-to-noise characteristic value is used to provide the corresponding correction value.

For example, when the corresponding correction value is provided for each carrier, one of the preset modulation settings MS[1] to MS[P] is found to match the corresponding modulation setting ms[k] of each carrier. (assumed to be MS[p1]), and from these preset signal-to-noise characteristic values SNRt[1] to SNRt[N], one of the initial signal-to-noise characteristic values closest to each carrier (assumed to be SNRt[n1] is found ]), to correspond to the found preset signal-to-noise characteristic value SNRt[n1] among the preset correction values e[p1,1] to e[p1,N] of the corresponding preset modulation setting The preset correction value e[p1,n1] is used as the corresponding correction value r[k] of each carrier.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

FIG. 1 schematically illustrates a receiving circuit according to an embodiment of the present invention.

FIG. 2 illustrates constellation points on a scatter diagram under a default modulation setting.

FIG. 3 schematically shows a division of a decision interval.

Figures 4a and 4b respectively illustrate the division of decision intervals with fixed boundaries and the misestimation of signal-to-noise eigenvalues.

Fig. 5 illustrates the misestimation of signal-to-noise characteristic values under different modulation settings under the division of decision-making intervals with fixed boundaries.

FIG. 6 illustrates a table for providing correction values according to an embodiment of the present invention.

FIG. 7 illustrates an embodiment of the table in FIG. 6 .

FIG. 8 shows the uncorrected initial signal-to-noise feature value and the corrected corrected signal-to-noise feature value.

FIG. 9 schematically shows a process according to an embodiment of the present invention.

10: Transmitting circuit

12: channel

20: Receive circuit

22: Channel estimation circuit

24: Equalizer

26: Clipper

28: Estimation circuit

30: Correction circuit

32: Multiplier

34: Look-up table circuit

36: Application circuit

38: Bit load setting circuit

s0-s4: signal

s0[k]-s3[k]: Carrier

SNRi[k]: initial signal-to-noise eigenvalue

SNRc[k]: corrected signal-to-noise eigenvalue

r[k]: correction value

MS[1]-MS[P]: preset modulation settings

ms[k]: modulation setting

c[p,1,1]-c[p,I[p],Q[p]]: constellation point

a[p]: distance

SNRt[1]-SNRt[N]: preset signal-to-noise characteristic value

e[1,1]-e[P,N]: preset correction value

sa0, sa, sb, sc, z1-z4, a1-a4, a20, a30, a40, b1-b4, b20, b30, b40: point

B[p]: boundary

D[p]: decision interval division

d[p,1,1]-d[p,I[p],Q[p]]: decision interval

va, vb, vc, v0, v1e-v4e, v2-v3: vector

400, 500, 600, 700: Straight line

410, 501-508, 610, 701-708, 901-908, 1000-1002, 1100-1102: curve

SNR0: correct signal-to-noise eigenvalue

h1-h3, h11, h12, h1a, h2a, h10, u1, u11: value

800: Form

1200: process

1202-1208: Steps

detailed description

Please refer to FIG. 1 , which shows a receiving circuit 20 according to an embodiment of the present invention, which can receive a signal s0 from a transmitting circuit 10 through a channel 12 . For example, the transmitting circuit 10 and the receiving circuit 20 may be respectively disposed at a transmitting end and a receiving end of a network system. Channel 12 may be a wired or wireless channel; for example, channel 12 may be a power line that transmits AC power. When the transmitting circuit 10 wants to transmit digital information to the receiving circuit 20, the transmitting circuit 10 can encode and modulate the digital information into a signal s0, and the signal s0 is transmitted to the receiving circuit 20 through the channel 12; the signal s0 will be affected by noise when transmitted through the channel 12 becomes a signal s1 (reception signal). A channel estimation circuit 22, an equalizer 24, a clipper 26, an estimation circuit 28 and an application circuit 36 may be included in the receiving circuit 20; A correction circuit 30 is included.

In an example, the signal s0 may include K carriers s0[1] to s0[K]; within a unit time, the transmitting circuit 10 may transmit a modulation setting ms[k] (not shown) The digital information modulation of the symbol smb[k] (not shown) is carried on the carrier s0[k]. The modulation setting ms[k] of the carrier s0[k] may be selected from P preset modulation settings MS[1] to MS[P]; taking P=8 as an example, the preset modulation setting MS[1] to MS[8] can be OFDM modulation modes BPSK, QPSK, 8QAM, 16QAM, 64QAM, 256QAM, 1024QAM and 4096QAM respectively. The modulation settings ms[k1] and ms[k2] of different carriers s0[k1] and s0[k2] can be the same or different. The modulation setting ms[k] of the same carrier s0[k] can be fixed or dynamically changed; for example, when a first symbol is to be transmitted, the modulation setting ms[k] of the carrier s0[1] 1] The default modulation setting MS[1] (BPSK) can be used; when another symbol is to be transmitted, the modulation setting ms[1] of the carrier s0[1] can be changed to the default modulation setting MS[2] (QPSK).

Each preset modulation setting MS[p] can carry digital information according to M[p] constellation points; continuing FIG. 1, please refer to FIG. 2 together, which shows a certain preset modulation setting in a scatter diagram Determine M[p] constellation points c[p,i,q] of MS[p] (i=1 to I[p], q=1 to Q[p]); where M[p]=I[ p]*Q[p]. The horizontal axis of Fig. 2 represents the parallel phase (in-phase) component of each constellation point c[p,i,q], and the vertical axis represents the quadrature-phase (quadrature-phase) component of each constellation point c[p,i,q]. ) component; for example, if a certain preset modulation setting MS[4] is 16QAM, it can be based on M[4]=I[4]*Q[4]=4*4=16 constellation points c [4,1,1], c[4,1,2], c[4,2,1], c[4,2,2], ..., c[4,i,q], ... to c[ 4,4,4] to carry digital information. The coordinates (AI[p,i,q], AQ[p,i,q]) (not shown) of each constellation point c[p,i,q] can be equal to ((i-0.5*I[p] -0.5)*a[p],(q-0.5*Q[p]-0.5)*a[p]); Among them, the item a[p] is the distance between two adjacent constellation points, as shown in Figure 2 . For example, if a certain preset modulation setting MS[4] is 16QAM, i=1, q=1, then the coordinates of constellation point c[4,1,1] (AI[4,1,1] ,AQ[4,1,1]) is equal to ((1-0.5*4-0.5)*a[p],(1-0.5*4-0.5)*a[p])=(-1.5*a[p ],-1.5*a[p]). Each constellation point c[p,i,q] can correspond to digital preset information SMB[p,i,q] of one symbol (not shown), and each preset information SMB[p,i,q] can be log A combination of ₂ (M[p]) bits; taking a certain preset modulation setting MS[4] as 16QAM as an example, each digital preset information SMB[ 4,i,q] can be a combination of log ₂ (16)=4 bits. In the signal s0, when the transmitting circuit 10 (Fig. 1) wants to use the preset modulation setting MS[p] on the carrier s0[k] as its modulation setting ms[k] to carry a certain preset information SMB[p ,i,q], it can be based on AI[p,i,q]*cos(2*π*f[k]*t)+AQ[p,i,q]*sin(2*π*f[ k]*t) (not shown) to form the carrier s0[k], wherein the item f[k] is the frequency of the carrier s0[k], and the item t is the time.

For example, if a certain preset modulation setting MS[p1] is QPSK, then it has M[p1]=4 constellation points c[p1,1,1], c[p1,2,1], c [p1,1,2] and c[p1,2,2], the corresponding preset information SMB[p1,1,1], SMB[p1,2,1], SMB[p1,1,2] to SYM[p1,2,2] can be log ₂ (M[p1])=log ₂ (4)=2 bits 00, 10, 01, 11, respectively. Due to power normalization, for different preset modulation settings MS[p1] and MS[p2], the distances a[p1] and a[p2] between adjacent constellation points can be different of. For example, if the default modulation settings MS[1] to MS[P] are BPSK, QPSK, 8QAM, 16QAM, 64QAM, 256QAM, 1024QAM and 4096QAM respectively, then the distance a[1]>a[2]>… >a[P].

Please refer to Figure 1 again. Through the transmission of the channel 12 , the K carriers s0 [ 1 ] to s0 [K] of the signal s0 respectively form the K carriers s1 [ 1 ] to s1 [K] of the signal s1 . In the receiving circuit 20, the equalizer 24 is coupled to the channel 12, and is used to equalize the carriers s1[1] to s1[K] in the signal s1 to form the carriers s2[1] to s2[ in the signal s2 respectively. K]. The clipper 26 is coupled to the equalizer 24, and is used to interpret the digital information carried by the carriers s2[1] to s2[K] in the signal s2, and accordingly provide a signal s3 (cut signal) of each carrier s3 [1] to s3[K]. The estimation circuit 28 is coupled to the equalizer 24 and the clipper 26, and can provide an initial signal-to-noise characteristic value SNRi[k] for each carrier s1[k] according to the difference between the carrier s2[k] and the carrier s3[k].

Continuing with FIG. 1 and FIG. 2 , please refer to FIG. 3 , which illustrates the operations of the equalizer 24 and the clipper 26 in a scatter diagram. When the transmitting circuit 10 modulates a preset information SMB[p,i,q] to the carrier s0[k] of the signal s0 (Fig. 1 ) according to a preset modulation setting MS[p], and transmits the When becoming the carrier s1[k] in the signal s1 received by the receiving circuit 20, due to factors such as noise, the point corresponding to the carrier s1[k] on the scatter diagram cannot be compared with the carrier s0[k] on the scatter diagram. The corresponding constellation points c[p,i,q] coincide; for example, the constellation point corresponding to carrier s0[1] is c[p,1,1], and the point corresponding to carrier s1[1] can be Point sa0, sb or sc. The equalizer 24 performs equalization processing on the carrier s1[k] so that the equalized carrier s2[k] converges to a boundary B[p]; for example, suppose the point sa0 corresponding to the carrier s1[1] exceeds the boundary B[p], then the point sa corresponding to the equalized carrier s2[1] will be located on the boundary B[p]; for another example, suppose the point corresponding to the carrier s1[1] is on the boundary B[ p], such as sb or sc, the point corresponding to the equalized carrier s2[1] will still be located within the boundary B[p].

Then, the clipper 26 uses the decision interval division D[p] associated with the default modulation setting MS[p] adopted by the carrier s0[k] to interpret the digital information carried by the carrier s0[k]. Decision interval division D[p] is to divide multiple decision intervals d[p,1,1] to d[p,I[p],Q[p]] in the boundary B[p], as shown in Figure 3 , each decision interval d[p,i,q] can cover the corresponding constellation point c[p,i,q], which are respectively related to the M[p] preset information SMB[ of the preset modulation setting MS[p] p,1,1] to SMB[p,I[p],Q[p]]. Among them, in a decision interval division of a variable boundary, each decision interval d[p,i,q] can be centered on the constellation point c[p,i,q], and the side length is equal to the distance between adjacent constellation points A square with a distance of a[p]; and in a decision interval division with a fixed boundary, the decision interval d[p,1,1] to d[p,I[p],1] adjacent to the boundary B[p], d[p,1,1] to d[p,1,Q[p]], d[p,1,Q[p]] to d[p,I[p],Q[p]] and d[ p, I[p], 1] to d[p, I[p], Q[p]] (that is, the boundary decision interval) can have at least one side whose side length is greater than the distance a between adjacent constellation points [p], a rectangle not centered on the constellation point c[p,i,q], the other decision intervals outside the boundary decision interval can be centered on the constellation point c[p,i,q] and the side length is equal to The square of the distance a[p] between adjacent constellation points. The clipper 26 determines the constellation point corresponding to the carrier s0[k] transmitted by the transmitting circuit 10 on the scatter diagram by judging which decision interval the corresponding point of the carrier s2[k] on the scatter diagram is located in. c[p,i,q] to interpret the digital information carried by the carrier s0[k]. For example, as shown in FIG. 3, if the carrier s2[1] is located at point sa, since the point sa falls in the decision interval d[p,1,2], the clipper 26 will determine that the carrier s0[1] is The corresponding constellation point is c[p,1,2], and the digital information carried by the carrier s1[1] is interpreted as the preset information SMB[p,1,2]; if the carrier s2[1] is located at point sb, Since the point sb also falls in the decision interval d[p,1,2], the clipper 26 will determine that the constellation point corresponding to the carrier s0[1] is c[p,1,2], and the carrier s1[ 1] The digital information carried is interpreted as the preset information SMB[p,1,2]; if the carrier s2[1] is located at point sc, since point sc falls in the decision interval d[p,1,1], the interception The clipper 26 determines that the constellation point corresponding to the carrier s0[1] is c[p,11], and interprets the digital information carried by the carrier s1[1] as the preset information SMB[p,1,1].

Then, the estimation circuit 28 will calculate the carrier s1[k] according to the coordinate difference between the point corresponding to the carrier s2[k] and the constellation point c[p,i1,q1] corresponding to the carrier s3[k] on the scatter diagram. ] provides the initial signal-to-noise eigenvalue SNRi[k]. For example, if the carrier s2[k] is located at the point sa on the scatter diagram, the clipper 26 will consider the original carrier s0[k] to be at the constellation point c[p,1,2], and the estimation circuit 28 will The difference vector va between the point sa and the constellation point c[p,1,2] is regarded as the error caused by noise, and the initial signal-to-noise eigenvalue SNRi[k] is calculated according to the length of the vector va. Similarly, if the carrier s2[k] falls on the point sb, the clipper 26 will also consider that the original carrier s0[k] is located at the constellation point c[p,1,2], and the estimation circuit 28 will set the point sb The difference vector vb between the constellation point c[p,1,2] is regarded as the error caused by noise, and the initial signal-to-noise eigenvalue SNRi[k] is calculated according to the length of the vector vb. Since the point sb is closer to the constellation point c[p,1,2] than the point sa, the difference vector vb is smaller than the difference vector va, so when the carrier s2[k] is located at the point sb, the initial signal-to-noise characteristic value obtained by the estimation circuit 28 will be smaller The initial signal-to-noise characteristic value obtained by the estimation circuit 28 is high when the carrier s2[k] is located at the point sa.

However, according to the above principles, the estimation operation of the estimation circuit 28 will cause estimation errors, because the clipper 26 cannot really know which constellation point the carrier s0[k] is originally in when transmitting the data frame. For example, assume that the carrier s0[k] of the transmitting circuit 10 is originally at the constellation point c[p,1,1], but the carrier s2[k] obtained by the receiving circuit 20 drifts due to large noise to point sb. In this case, the real signal-to-noise eigenvalue should be calculated according to the difference vector v0 between the point sb and the constellation point c[p,1,1]. However, since the point sb is located in the decision interval d[p,1,2], the clipper 26 will mistakenly determine that the carrier s0[k] is originally located at the constellation point c[p,1,2]; jointly, The estimation circuit 28 will erroneously calculate the wrong signal-to-noise characteristic value based on the difference vector vb between the point sb and the constellation point c[p,1,2]. Because the vector vb is shorter than the vector v0, the false signal-to-noise characteristic value will be higher than the true signal-to-noise characteristic value; in other words, in the above situation, the estimation circuit 28 will estimate the signal-to-noise characteristic value too optimistically. If the signal-to-noise characteristic value is misestimated, the adaptive operation of the network system based on the signal-to-noise characteristic value will also cause errors. For example, if the receiving end mistakenly overestimates the SNR, it will mistakenly cause the transmitting end to increase the rate of information transmission; however, although the information transmission rate is high, the error rate will also be high, because the receiver actually receives The signal is already corrupted by high noise; therefore, the number of bits of information that can be correctly and efficiently conveyed is reduced instead.

Continuing from FIG. 1 to FIG. 3, please refer to FIG. 4a and FIG. 4b; for the original carrier s0[k] sent by the transmitting circuit 10 according to the preset modulation setting MS[p], if the clipper 26 adopts a decision with a fixed boundary Interval division D[p] interprets the equalized carrier s2[k] as carrier s3[k], when the estimation circuit 28 provides the initial signal-to-noise characteristic value SNRi[k] according to the carrier s2[k] and s3[k], its The situation of misestimating the signal-to-noise characteristic value can be schematically illustrated by the scatter diagram distribution in Figure 4a, and Figure 4b schematically compares the real signal-to-noise characteristic value SNR0 (horizontal axis, which can be a logarithmic scale) with the initial signal-to-noise characteristic value SNR[ k] (vertical axis, can be logarithmic scale). In the example of Fig. 4a and Fig. 4b, the (true, initial) signal-to-noise characteristic value may refer to the signal-to-noise ratio.

Since the example in Fig. 4b and Fig. 4b adopts the decision interval division D[p] with a fixed boundary (Fig. 4a), the boundary decision interval (the decision interval with at least one side coincident with the boundary B[p]) has at least one side longer than the constellation The distance between points is a[p], and the side length of the remaining decision intervals (decision intervals whose sides do not coincide with the boundary B[p]) is equal to the distance a[p].

As shown in FIG. 4 b, the correct (ideal) relationship between the initial signal-to-noise characteristic value SNRi[k] produced by the estimation circuit 28 and the real signal-to-noise characteristic value SNR0 should be linear, as shown in the straight line 600; however, at a fixed Under the division of the boundary decision interval, the relationship between the initial signal-to-noise characteristic value SNRi[k] and the real signal-to-noise characteristic value SNR0 shows a curve 610 , and the reason can be explained as follows.

In FIG. 4a, the original carrier wave s0[k] of the transmitting circuit 10 is formed according to the constellation points c[p, i0, q0]. If the real signal-to-noise characteristic value SNR0 is equal to a higher value h1 (Figure 4b), it means that the noise interference is small, and the carrier s2[k] transmitted through channel 12 will fall on the constellation point c[p,i0,q0] In the surrounding decision interval d[i,p0,q0], for example, it is located at point z1; in this case, the clipper 26 will correctly judge that the carrier s2[k] is corresponding to the constellation point c[p,i0, q0], when the estimation circuit 28 regards the difference vector v1e between the interpreted constellation point c[p, i0, q0] and point z1 as noise to estimate the initial signal-to-noise characteristic value SNRi[k], the initial signal-to-noise characteristic The value SNRi[k] will also be very close to the true signal-to-noise characteristic value SNR0, as shown by point b1 in Fig. 4b.

If the real signal-to-noise eigenvalue SNR0 is a small value h2 (h2<h1), it means that the noise interference is large, and the position of the carrier s2[k] will be far away from the original constellation point c[p,i0,q0] interval d[p,i0,q0]; for example, the position of carrier s2[k] may drift to point z2, which is in decision interval d[p,i2,q2] of constellation point c[p,i2,q2]; thus , the clipper 26 will misjudge that the carrier s2[k] corresponds to the constellation point c[p, i2, q2]; The difference vector v2e from point z2 is treated as noise to estimate the initial signal-to-noise eigenvalue SNRi[k], forming point b2 on curve 610 ( FIG. 4 b ). However, since the real original constellation point is c[p,i0,q0] instead of c[p,i2,q2], the real noise should be the difference vector between constellation point c[p,i0,q0] and point z2 v2, not v2e. That is, the correct value of the initial signal-to-noise characteristic value SNRi[k] should be at the point b20 on the straight line 600 . Because the length of vector v2e is shorter than vector v2, the initial signal-to-noise eigenvalue SNRi[k] will be higher than the real signal-to-noise eigenvalue SNR0. In Fig. 4b, the difference between points b2 and b20 is related to the difference between vectors v2e and v2.

If the real signal-to-noise eigenvalue SNR0 is a smaller value h3 (h3<h2), it means that the noise interference is greater, and the position of the carrier s2[k] will be farther away from the decision interval of the original constellation point c[p,i0,q0] d[p,i0,q0]; for example, the position of carrier s2[k] may drift to point z3 in Figure 4a, in the decision interval d[p,i3,q3] of constellation point c[p,i3,q3] middle. Therefore, the clipper 26 will misjudge that the carrier s2[k] corresponds to the constellation point c[p, i3, q3]; The difference vector v3e from point z3 is regarded as noise to estimate the initial signal-to-noise eigenvalue SNRi[k], forming point b3 on curve 610 . However, the real original constellation point is c[p, i0, q0] instead of c[p, i3, q3], and the difference vector v3 between the constellation point c[p, i0, q0] and point z3 can correctly reflect the real Noise, not vector v3e; the correct value of the initial signal-to-noise eigenvalue SNRi[k] should be at point a30 on the straight line 400 and coincide with the real signal-to-noise eigenvalue SNR0. Because the length of vector v3e is shorter than vector v3, the initial signal-to-noise eigenvalue SNRi[k] obtained by treating vector v3e as noise will be higher than the real signal-to-noise eigenvalue SNR0. In Fig. 4b, the difference between points b3 and b30 is related to the difference between vectors v3e and v3. It can be seen from FIG. 4a that the difference between vectors v3e and v3 is greater than the difference between vectors v2e and v2, so the difference between points b3 and b30 is greater than the difference between points b2 and b20.

If the real signal-to-noise eigenvalue SNR0 is a smaller value h4 (h4<h3), it means that the noise interference is greater, and the position of the carrier s2[k] will be farther away from the original constellation point c[p,i0,q0], drifting to near the boundary B[p]; for example, the position of carrier s2[k] may drift to point z4 in Fig. 4a, in the boundary decision interval d[p,1,q4] of constellation point c[p,1,q4] . Therefore, the clipper 26 will misjudge that the carrier s2[k] corresponds to the constellation point c[p,1,q4]; The difference vector v4e from point z4 is regarded as noise to estimate the initial signal-to-noise eigenvalue SNRi[k], forming point b4 on the curve 610 . However, since the real original constellation point is c[p,i0,q0] instead of c[p,1,q4], the difference vector v4 between constellation point c[p,i0,q0] and point z4 can correctly reflect the real noise, not vector v4e; the correct value of the initial signal-to-noise eigenvalue SNRi[k] should be at point a40 on straight 600 to match the real signal-to-noise eigenvalue SNR0. Because the length of the vector v4e is shorter than the vector v4, the initial signal-to-noise eigenvalue SNRi[k] obtained according to the vector v4e will be higher than the real signal-to-noise eigenvalue SNR0. As shown in Fig. 4b, the difference between points b4 and b40 is related to the difference between vectors v4e and v4.

As shown in Figure 4a, the decision intervals d[p, i2, q2] and d[p, i3, q3] where points z2 and z3 are located may not be boundary decision intervals, so the lengths of vectors v2e and v3e are still limited by The distance a[p]/2. However, under the decision interval division with fixed boundaries, at least one side of the boundary decision interval is longer than the distance a[p], so the length of the vector v4e will not be limited by the distance a[p]/2, and the initial signal-to-noise eigenvalue SNRi[k] decreases and is closer to the real signal-to-noise characteristic value SNR0, and the height of the vertical axis corresponding to point b4 (FIG. 6B) is therefore lower than the height of the vertical axis of points b2 and b3.

That is, under the decision interval division with fixed boundaries, as the real signal-to-noise eigenvalue SNR0 decreases from h1 to h2, h3, and h4, the initial signal-to-noise eigenvalue SNRi[k] will gradually move away from the real signal-to-noise eigenvalue SNR0( Such as the trend of the curve 610 between the values h1 and h3), and then it will approach the real signal-to-noise characteristic value SNR0 (such as the trend of the curve 610 between the values h3 to h4), this is because the larger-sized boundary decision interval There is more space to reflect longer noise vectors (such as vector v4e), so that noise vectors are not restricted to non-boundary decision intervals with smaller sizes.

Continuing from Figure 4a and 4b, please refer to Figure 5; under the decision interval division with fixed boundaries, if the modulation setting ms[k] adopted by the carrier s0[k] is BPSK, QPSK, 8QAM, 16QAM, 64QAM, 256QAM, 1024QAM or 4096QAM can carry digital information of 1, 2, 3, 4, 6, 8, 10 or 12 bits per unit time, then the initial signal-to-noise characteristic value SNRi[k] (the vertical axis can be a logarithmic scale, such as decibels) and the true signal-to-noise characteristic value SNR0 (horizontal axis, can be a logarithmic scale, such as in decibels) will be presented as curves 701, 702, 703, 704, 705, 706, 707 or 708 (curves 701 and 702 almost coincide); relatively, the correct (ideal) relationship between the initial signal-to-noise characteristic value SNRi[k] and the real signal-to-noise characteristic value SNR0 should be a linear relationship of a straight line 700 . For example, when the real signal-to-noise characteristic value SNR0 is equal to the value u11, the correct value of the initial signal-to-noise characteristic value SNRi[k] should be equal to the value h10; however, as shown in Figure 5, under the same real signal-to-noise characteristic value SNR0, The more bits the modulation setting ms[k] carries per unit time, the larger the gap between SNR0 between the initial signal-to-noise characteristic value SNRi[k] and the real signal-to-noise characteristic value will be. For example, when the real signal-to-noise characteristic value SNR0 is equal to the value h10, if the modulation setting ms[k] is 256QAM to carry symbols of 6 bits per unit time, the initial signal-to-noise characteristic value SNRi[k] will be erroneously overestimated as the value h1a; if the modulation setting ms[k] is 4096QAM to carry 12-bit symbols per unit time, the initial signal-to-noise eigenvalue SNRi[k] will be erroneously overestimated is the value h1b, and the value h1b>h1a>h10. The higher the number of bits carried per unit time, the shorter the shortest distance between adjacent constellation points, and the smaller the size of the non-boundary decision interval; when the value of the real signal-to-noise characteristic value SNR0 is not too small (for example greater than the value u11), the noise vector misestimated by the estimation circuit 28 is more likely to fall in the same non-boundary decision interval, the smaller the non-boundary decision interval, the smaller the initial signal-to-noise eigenvalue SNRi[k] provided by the estimation circuit 28 will be overestimated, and the gap between the true signal-to-noise eigenvalue SNR0 will be larger.

On the other hand, when the value of the real signal-to-noise characteristic value SNR0 is smaller (for example, smaller than the value u11), the noise vector misestimated by the estimation circuit 28 is more likely to fall within the boundary decision interval. As described above, under the division of decision intervals with fixed boundaries, the side lengths of the non-boundary decision intervals of different preset modulation settings MS[p1] and MS[p2] are respectively equal to the distances a[p1] and a[ p2], and the boundary decision interval has at least one longer side, whose side lengths are respectively greater than the distances a[p1] and a[p2] between the constellation points. For example, assuming that the default modulation settings MS[p1] and MS[p2] are 256QAM and 4096QAM respectively, the side length ratio a[p1] and a[p2] of the non-boundary decision interval is about 4:1, but the boundary The longer sides of the decision interval are roughly equal in length. Therefore, when the actual noise characteristic value SNR0 is large, the difference between the initial signal-to-noise characteristic values under the two preset modulation settings is relatively large (such as the difference between values h1a and h2a), because it is different from the non-boundary decision interval The side lengths are relatively correlated, but the side lengths of the non-boundary decision intervals of the two are quite different. On the other hand, if the real signal-to-noise eigenvalue SNR0 is small, the difference between the initial signal-to-noise eigenvalues under the two preset modulation settings is small and they approach each other, because the length of the longer side of the boundary decision interval is relatively small. are correlated, and the difference in the length of the longer side of the boundary decision interval between the two is small.

In order to correct the difference between the initial signal-to-noise characteristic value SNRi[k] and the real signal-to-noise characteristic value SNR0, a correction circuit 30 is provided in the transmitting circuit 30 . Please refer to FIG. 1 again; in the transmitting circuit 30, the correction circuit 30 is coupled to the estimation circuit 28, and can provide each carrier s1[k] according to the value of the initial signal-to-noise characteristic value SNRi[k] of each carrier s1[k]. A corresponding correction value r[k], and modify the initial signal-to-noise characteristic value SNRi[k] according to the corresponding correction value r[k], so as to generate a revised signal-to-noise characteristic value SNRc[k] for each carrier s1[k], for k=1 to K.

In one example, the calibration circuit 30 may include a table lookup circuit 34 and a multiplier 32 ; the multiplier 32 is coupled to the table lookup circuit 34 and the calibration circuit 30 . Continuing with FIG. 1 , please also refer to FIG. 6 , which shows a table 800 according to an example of the present invention. In an example of this case, the look-up table circuit 34 can record the table 800, and store a plurality of preset correction values e[p,1] to e[p,N] for each preset modulation setting MS[p] (for p= 1 to P), and according to the corresponding modulation setting ms[k] of each carrier s1[k], the initial signal-to-noise characteristic value SNRi[k] of each carrier s1[k] and each preset modulation setting MS[p] The preset correction values e[p,1] to e[p,N] (for p=1 to P) provide a corresponding correction value r[k] for each carrier s1[k], for k=1 to K. Wherein, each preset correction value e[p,n] of each preset modulation setting MS[p] is related to one of a plurality of preset signal-to-noise characteristic values SNRt[1] to SNRt[N] SNRt [n]. In one embodiment, the network system may only use one modulation setting (that is, K=1), such as the default modulation setting MS[1]; therefore, the table 800 may only have one column (column) to record the default correction value e[1,1] to e[1,N].

In one example, the look-up table circuit 34 finds a preset modulation setting ms[k] (such as QPSK) corresponding to the carrier s1[k] from the preset modulation settings MS[1] to MS[P] Modulation set MS[p1] (eg QPSK). In an example, the look-up table circuit 34 will find a signal-to-noise characteristic value SNRi[k] closest to the initial signal-to-noise characteristic value SNRi[k] (for example, -3.6 db) preset signal-to-noise characteristic value SNRt[n1] (for example-4db); thus, the look-up table circuit 34 finds the correspondence between the preset modulation setting MS[p1] and the preset signal-to-noise characteristic value SNRt[n1] The preset correction value e[p1,n1] of is used as the corresponding correction value r[k] of the carrier s1[k]. In another example, the look-up table circuit 34 will find the two closest initial signal-to-noise characteristic values SNRi[k] for the carrier s1[k] from the preset signal-to-noise characteristic values SNRt[1] to SNRt[N] (for example The preset signal-to-noise characteristic values SNRt[n1] and SNRt[n2] (such as -3db and -4db) of the upper and lower bounds of -3.6db); in this way, the look-up table circuit 34 can set MS[p1] according to the preset modulation Find the corresponding preset correction value e[p1,n1] and value e[p1,n2] with the preset signal-to-noise characteristic value SNRt[n1] and SNRt[n2], and according to the initial signal-to-noise characteristic value SNRi[k] , the preset signal-to-noise eigenvalues SNRt[n1] and SNRt[n2] of its upper and lower bounds interpolate e[p1,n1] and value e[p1,n2], and use the calculated result as carrier s1[ The corresponding correction value r[k] of k].

Utilize the initial signal-to-noise characteristic value SNRi[k] and the corresponding correction value r[k] that estimation circuit 28 and look-up circuit 34 provide, multiplier 32 (Fig. 1) can be multiplied by the initial signal-to-noise characteristic value SNRi[k] Corresponding to the corrected value r[k], the corrected signal-to-noise characteristic value SNRc[k] is generated according to the product r[k]*SNRi[k].

Each preset correction value e[p,n] in the table 800 ( FIG. 6 ) can be calculated by numerical simulation. For example, in order to correct the misestimated initial signal-to-noise characteristic value SNRi[k] under fixed-boundary decision-making interval division in Fig. Under the condition that the value SNRt[n] and the modulation setting ms[k] are equal to a preset modulation setting MS[p], the carrier s2[k] affected by noise (such as superimposed white Gaussian noise) is simulated, and the simulation The clipper 26 performs the hard decision operation on the carrier s2[k] and the estimation circuit 28 on the signal-to-noise characteristic value estimation operation of the carrier s2[k] and s3[k] under the division of the fixed boundary decision interval, and simulates the estimation circuit accordingly 28 to generate the initial signal-to-noise characteristic value SNRi[k]; thus, the preset correction value e[p,n] can be calculated according to the ratio SNRt[n]/SNRi[k].

An example of the table 800 is listed below, which is used to modify the initial signal-to-noise characteristic value under the fixed boundary decision interval division; in this example, the default modulation settings MS[1] to MS[P] are BPSK, QPSK, 8QAM, 16QAM, 64QAM, 256QAM, 1024QAM and 4096QAM (number P can be equal to 8), the preset signal-to-noise characteristic values SNRt[1] to SNRt[N] are arranged from small to large, from -6dB to 41dB (Number N may be equal to 48).

An example of the above table can also be shown in Figure 7, the horizontal axis represents the preset signal-to-noise characteristic values SNRt[1] to SNRt[N] (it can be a logarithmic scale, such as in decibels), and the vertical axis represents each preset The value of the correction value e[p,n] (may be a linear scale); in FIG. 7, the curve 901 shows the preset correction value e[1, 1] to e[1,N], the curve 902 shows the preset correction values e[2,1] to e[2,N] associated with the preset modulation setting MS[2] (ie QPSK), the curve 903 shows the default correction values e[3,1] to e[3,N] related to the default modulation setting MS[3] (ie 8QAM), and the curve 904 shows the default modulation setting MS[ 4] (i.e. 16QAM) associated with the preset correction values e[4,1] to e[4,N], the curve 905 shows the preset associated with the default modulation setting MS[5] (i.e. 64QAM) The correction values e[5,1] to e[5,N], the curve 906 shows the default correction values e[6,1] to e[ 6,N], the curve 907 shows the preset correction values e[7,1] to e[7,N] related to the preset modulation setting MS[7] (ie 1024QAM), and the curve 908 shows the The default correction values e[8,1] to e[8,N] associated with the default modulation setting MS[8] (ie 4096QAM).

It can be seen from the above table example and Figure 7 that, with the preset signal-to-noise characteristic values SNRt[1] to SNRt[N] arranged from small to large, the preset correction value e of the same preset modulation setting MS[p] [p,1] to e[p,N], at least some of the preset correction values will first show a first increasing-decreasing trend (such as monotonically decreasing or strictly decreasing), and then show a second increasing-decreasing trend (eg, monotonically increasing or strictly increasing), and the first increasing-decreasing trend is opposite to the second increasing-decreasing trend. If the offset of the initial signal-to-noise characteristic value SNRi[k] is relatively large, the correction circuit 30 (FIG. 1) needs to select a preset correction value e[p,n] with a smaller value as the corresponding correction value r[k] to use The multiplier 32 multiplies the larger initial signal-to-noise characteristic value SNRi[k] to the smaller corrected signal-to-noise characteristic value SNRc[k]. Therefore, as the preset signal-to-noise characteristic value SNRt[1] increases to SNRt[N], at least some of the preset correction values e[p,n] will first change from large to small (gradually decrease), and then from small to small Get bigger (increasing).

In the above table and the example in Fig. 7, as the number of bits carried by the preset modulation settings MS[1] to MS[P] per unit time is arranged from small to large, when related to the same preset signal-to-noise characteristic Among the preset correction values e[1,n] to e[P,n] with the value SNRt[n] and belonging to different preset modulation settings, at least some of them show a decreasing trend. For example, under the same preset signal-to-noise characteristic value SNRt[12], the preset correction values e[1,12] to e[8,12] show a decreasing trend. Similarly, under the same preset signal-to-noise characteristic value SNRt[21], the preset correction values e[1, 21] to e[8, 21] show a decreasing trend. As shown in Figure 5, under the same real signal-to-noise characteristic value SNR0 (for example, value h1), the preset modulation setting MS[p1] (such as 4096QAM of curve 708) carrying more bits per unit time will be higher than the bit number The preset modulation setting MS[p2] with a small number (such as 256QAM of the curve 706) is farther away from the real signal-to-noise characteristic value SNR0, so the preset modulation setting MS[p1] that carries a larger number of bits per unit time needs The preset signal-to-noise eigenvalue e[p1,n] with a smaller value is used for more downward revision during multiplication. Continuing the above table and FIG. 7, please refer to FIG. 8, which shows the uncorrected initial signal-to-noise characteristic value SNRi[k] and the corrected corrected signal-to-noise characteristic value SNRc[k], and the horizontal axis is the receiving circuit 20 The actual signal-to-noise eigenvalue SNR0 at the time of reception (it can be a logarithmic coordinate, and the unit is decibel), and the vertical axis represents the value of the initial signal-to-noise eigenvalue SNRi[k] or the corrected signal-to-noise eigenvalue SNRc[k]. If the receiving circuit 20 estimates the signal-to-noise characteristic value based on the reception of the sounding packet, the variation relationship of the signal-to-noise characteristic value to the real signal-to-noise characteristic value SNR0 can be represented by a curve 1000; since the content of the sounding packet is the receiving circuit 20 can be known in advance, so the curve 1000 can represent the ideal situation of signal-to-noise eigenvalue estimation. In contrast, if the receiving circuit 20 estimates the initial signal-to-noise characteristic value SNRi[k] based on the reception of the data frame, then the relationship between the initial signal-to-noise characteristic value SNRi[k] and the real signal-to-noise characteristic value SNR0 It can be represented by curve 1001; since the digital information in the data frame cannot be known in advance by the receiving circuit 20, the initial signal-to-noise characteristic value SNRi[k] will be wrongly overestimated, so that the curve 1001 deviates from the curve 1000. In contrast, the curve 1002 shows the relationship between the corrected signal-to-noise characteristic value SNRc[k] after compensation by the correction circuit 30 and the real signal-to-noise characteristic value SNR0; it can be seen from FIG. 8 that compared with the curve 1001 The initial SNR characteristic value, the corrected SNR characteristic value of the curve 1002 is very close to the curve 1000, which means that the correction circuit 30 can indeed correct the misestimated initial SNR characteristic value, so that the corrected SNR characteristic value can approach the ideal situation.

Please refer to Figure 1 again. In an advanced modern network system, the operation of signal transmission and/or reception can be adaptively adjusted according to the signal-to-noise characteristic value estimated by the receiving circuit 20 . The application circuit 36 in the receiving circuit 20 can assist the above-mentioned adaptive operation according to the corrected signal-to-noise characteristic values SNRc[1] to SNRc[K]. For example, the application circuit 36 may include a bit load setting circuit 38, coupled to the correction circuit 30, for updating the signal-to-noise characteristic value SNRc[k] of each carrier s1[k] to update the Corresponding modulation sets ms[k] for k=1 to K. The updated corresponding modulation setting ms[k] can be fed back to the transmitting circuit 10 by a feedback signal s4, and the transmitting circuit 10 can transmit on each carrier s0[k] according to the updated corresponding modulation setting ms[k] Carry subsequent digital information. For example, assuming that the transmitting circuit 10 first adopts a certain preset modulation setting MS[p1] as the corresponding modulation setting ms[k] of the carrier s0[k], if the receiving circuit 20 obtains a better value ( The corrected signal-to-noise eigenvalue SNRc[k] that is higher) represents that the current information transmission condition of the channel 12 is good, so the bit load setting circuit 38 can feed back and notify the transmitting circuit 10 to make the transmitting circuit 10 change to another preset The modulation setting MS[p2] is used as the corresponding modulation setting ms[k] of the carrier s0[k]; wherein, the number of bits carried by the preset modulation setting MS[p2] in unit time (ie bit load) can be as high as The default modulation setting MS[p1] used previously. In this way, the throughput of information transmission can be effectively increased. For example, the receiving circuit 20 can feed back a tone-map to the transmitting circuit 10, which can describe the corresponding modulation settings ms[1] to ms that the carriers s0[1] to s0[K] should adopt. [K].

Relatively, if the receiving circuit 20 obtains a poorer (lower) corrected signal-to-noise characteristic value SNRc[k] after receiving, it means that the current information transmission condition of the channel 12 is not good, so the bit load setting circuit 38 can The feedback notifies the transmitting circuit 10, so that the transmitting circuit 10 can continue to use the previous preset modulation setting MS[p1], or change to another preset modulation setting MS[p3] as the corresponding modulation setting of the carrier s0[k]. ms[k]; wherein, the bit loading of the default modulation setting MS[p3] may be lower than that of the previously used default modulation setting MS[p1]. In this way, high noise can be prevented from affecting the accuracy of digital data transmission.

However, the premise of the above adaptive operation is that the signal-to-noise characteristic value estimated by the receiving circuit 30 must be close to the real signal-to-noise characteristic value; if the difference between the signal-to-noise characteristic value estimated by the receiving circuit 30 and the real signal-to-noise characteristic value is too large, the The adaptive operation based on the estimated signal-to-noise characteristic value will affect the correct operation of the network system. For example, if the bit load setting circuit 38 in the application circuit 36 is based on the initial signal-to-noise characteristic value SNRi[k] rather than the corrected signal-to-noise characteristic value SNRc[k], since the initial signal-to-noise characteristic value SNRi[k] Will be more optimistic and higher than the real signal-to-noise characteristic value, so the bit load setting circuit 38 will mistakenly make the transmitting circuit 10 change the modulation setting with higher bit load to increase the flow of information transmission; although the flow of information transmission is high, but The error rate will also be higher, because the signal s1[k] actually received by the receiving circuit 20 has actually been interfered by high noise, and the amount of information that can be correctly and effectively transmitted is actually reduced.

Not limited to adaptive bit-loading characteristics, the signal-to-noise eigenvalues estimated by the receiving circuit 20 can also be used for other advanced functions, such as soft-bit decoding, soft-decision decoding, adaptive modulation and coding ( AMC (adaptive modulation and coding), turbo (turbo) decoding and/or dynamic power control, etc.; these advanced functions require excellent signal-to-noise eigenvalue estimation in order to operate correctly and effectively. The corrected signal-to-noise characteristic value SNRc[k] corrected by the correcting circuit 30 of the present invention can just meet the needs of these advanced functions; correspondingly, the application circuit 36 in FIG. A bit decoding circuit (not shown), etc., can be coupled to the correction circuit 30 to use the corrected signal-to-noise characteristic value SNRc[k] generated by the correction circuit 30 .

Continuing with FIG. 1 , please refer to FIG. 9 , which shows a process 1200 according to an example of the present invention; the receiving circuit 20 in FIG. 1 can implement the process 1200 to modify the signal-to-noise characteristic value estimation. The main steps of the process 1200 can be described as follows.

Step 1202: The equalizer 24 in the receiving circuit 20 provides an equalized signal s2 according to a received signal s1. Wherein, the received signal s1 includes K (greater than or equal to 1) carriers s1[1] to s1[K], and corresponding digital information is carried on each carrier s1[k] according to a corresponding modulation setting ms[k]; corresponding The modulation setting ms[k] is selected from P (greater than or equal to 1) preset modulation settings MS[1] to MS[P]. The equalizer 24 can perform an equalization operation on each carrier s1[k] to generate a carrier s2[k] in the equalized signal s2.

Step 1204: Perform a clipping step by the clipper 26 to judge the digital information smb[k] carried by each carrier s1[k] from the equalized signal s2, and provide a clipped signal s3 accordingly, which includes Carriers s3[1] to s3[K]. For example, if the corresponding modulation setting ms[k] of the carrier s2[k] conforms to the default modulation setting MS[p], the clipper 26 may adopt the decision interval division D[p] shown in FIG. 3 , Based on the position of carrier s2[k] on the scatter diagram, the decision interval d[p,i,q] of its location is judged, and the digital information smb[k] carried by carrier s2[k] is interpreted as the associated constellation The preset information SMB[p,i,q] corresponding to the point c[p,i,q] is reflected in the carrier s3[k]. As discussed above (as shown in FIG. 3 ), the decision interval division D[p] adopted by the clipper 26 may be a decision interval division with a fixed boundary.

Step 1206: The estimation circuit 28 performs an estimation step to provide an initial SNR characteristic value SNRi[k] for each carrier s1[k] according to the difference between the equalized signal s2 and the clipped signal s3. For example, if the clipper 26 interprets the carrier s2[k] as a constellation point c[p,i,q], the estimation circuit 28 can base the distance between the carrier s2[k] and the constellation point c[p,i,q] The difference vectors of the scatter plots estimate the initial signal-to-noise eigenvalue SNRi[k].

Step 1208: Perform a correction step by the correction circuit 30 to provide a corresponding correction value r[k] according to the initial signal-to-noise characteristic value SNRi[k] of each carrier s1[k], and provide a corresponding correction value r[k] according to each carrier s1[k] The corresponding correction value r[k] modifies the initial signal-to-noise characteristic value SNRi[k] of each carrier s1[k], so as to generate a corrected signal-to-noise characteristic value SNRc[k] for each carrier s1[k]. For example. N (greater than 1) preset correction values e[p,1] to e[p,N] can be stored for each preset modulation setting MS[p] by the look-up table circuit 34, and according to each carrier s1[k] Corresponding to the modulation setting ms[k], the initial signal-to-noise characteristic value SNR[k] of each carrier s1[k] and the preset correction value e[1] of each preset modulation setting MS[1] to MS[P], 1] to e[P, N] and provide the corresponding correction value r[k] for each carrier s1[k]; The corrected signal-to-noise characteristic value SNRc[k] of each carrier s1[k] is generated based on the corresponding correction value r[k] of each carrier s1[k]. Wherein, each preset correction value e[p,n] of each preset modulation setting MS[p] is related to one of N preset signal-to-noise characteristic values SNRt[1] to SNRt[N] SNRt[ n].

When the table look-up circuit 34 provides the corresponding correction value r[k] for each carrier s1[k], the corresponding modulation setting ms[k] is found from the preset modulation settings MS[1] to MS[P]. The corresponding preset modulation setting MS[p], and from the preset signal-to-noise characteristic values SNRt[1] to SNRt[N], find an initial signal-to-noise characteristic value SNRi[k] corresponding to each carrier s1[k] ] the closest preset signal-to-noise characteristic value SNRt[n], so that the preset signal-to-noise The preset correction value e[p,n] associated with the characteristic value SNRt[n] is used as the corresponding correction value r[k] of each carrier s1[k].

The process 1200 can be implemented by hardware, software, firmware or any combination of the three. For example, step 1208 can be implemented by the hardware correction circuit 30, and the look-up table circuit 34 can include a static random access memory (SRAM) to store the table 800 (FIG. 6); or, step 1208 can be executed by a processor (not shown) Implemented in software and/or firmware, and store table 800 in dynamic random access memory (DRAM).

In summary, the present invention can improve (modify) the estimate of the signal-to-noise characteristic value at the receiving end; for example, the receiving end will mistakenly overestimate the signal-to-noise characteristic value due to the hard decision operation of the clipper, and the technology of the present invention can Appropriately modify the overestimated initial signal-to-noise eigenvalues to more correct corrected signal-to-noise eigenvalues, so that the network system can correctly judge the communication (such as channel) conditions based on the corrected signal-to-noise eigenvalues, and correctly perform adaptive Transceiver adjustment, for example, adjusting the bit load setting of each carrier.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims.

Claims (15)

1. a kind of receiving circuit revising the estimation of signal-to-noise characteristic value, comprises：

One balanced device, provides an equalizing signal (equalized signal) according to a receipt signal；

One slicer, couples this balanced device, provides one to cut signal (sliced signal) according to this equalizing signal；

One estimating circuit, couples this balanced device and this slicer, in order to cut letter according to this equalizing signal with this Number difference provide an initial signal-to-noise characteristic value；And

One correcting circuit, couples this estimating circuit, provides a corresponding correction value according to this initial signal-to-noise characteristic value, And produce a correction signal-to-noise characteristic value according to this corresponding correction value and this initial signal-to-noise characteristic value.

2. receiving circuit as claimed in claim 1 is it is characterised in that this correcting circuit comprises：

One lookup table circuit, stores multiple preset correction value, and pre- with the plurality of according to this initial signal-to-noise characteristic value If correction value provides this correspondence correction value；Wherein, respectively this preset correction value corresponds to multiple default noises spies One of them of value indicative；And

One multiplier, couples this lookup table circuit and this estimating circuit, this initial signal-to-noise characteristic value is multiplied by this right Correction value is answered to produce this correction signal-to-noise characteristic value.

3. receiving circuit as claimed in claim 2 is it is characterised in that this lookup table circuit is to be repaiied by the plurality of presetting On the occasion of in seek its corresponding default signal-to-noise characteristic value of a preset correction value closest to this initial signal-to-noise characteristic value This correspondence correction value to be provided.

4. receiving circuit as claimed in claim 2 it is characterised in that with the plurality of default signal-to-noise characteristic value by Little to longer spread, corresponding the plurality of preset correction value at least fractional numbers meeting is in first one first increase and decrease Long-term change trend, then in one second growth trend change, and this first growth trend and this second growth trend phase Instead.

5. receiving circuit as claimed in claim 4 it is characterised in that this one first growth trend be strictly decreasing, This second growth trend is strictly increasing.

6. receiving circuit as claimed in claim 1 is it is characterised in that this correcting circuit is more according to this receipt signal A modulation set this corresponding correction value be provided.

7. receiving circuit as claimed in claim 2 is it is characterised in that this lookup table circuit is more according to this receipt signal A modulation set this corresponding correction value be provided；Respectively this preset correction value corresponds to multiple default signal-to-noise characteristics One of value, corresponding to same default signal-to-noise characteristic value and multiple corresponding to different default modulation settings In preset correction value, it is set in the bit number carrying in the unit interval from small to large with the plurality of default modulation Arrangement, at least fractional numbers preset correction value can assume trend decrescence.

8., as the receiving circuit of claim 6, further include：

One bit load (bit loading) initialization circuit, couples this correcting circuit, special according to this correction noise Value indicative produces a feedback signal a to radiating circuit, is set with this modulation updating this receipt signal.

9. a kind of method that can revise the estimation of signal-to-noise characteristic value in a receiving circuit, comprises：

There is provided an equalizing signal (equalized signal) according to the receipt signal that this receiving circuit is received；

One is provided to cut signal according to this equalizing signal；

There is provided an initial signal-to-noise characteristic value according to the difference that this equalizing signal cuts signal with this；

There is provided a corresponding correction value according to this initial signal-to-noise characteristic value；And

Produce a correction signal-to-noise characteristic value according to this corresponding correction value and this initial signal-to-noise characteristic value.

10. method as claimed in claim 9 is it is characterised in that provide this right according to this initial signal-to-noise characteristic value The step answering correction value further includes：

There is provided this corresponding correction value according to this initial signal-to-noise characteristic value with multiple preset correction value；Wherein, respectively should Preset correction value corresponds to one of them of multiple default signal-to-noise characteristic values.

11. as claim 10 method it is characterised in that according to this initial signal-to-noise characteristic value with the plurality of Preset correction value provides the step of this correspondence correction value to further include：

By seek in the plurality of preset correction value its corresponding default signal-to-noise characteristic value of a preset correction value connects most This initial signal-to-noise characteristic value nearly is providing this correspondence correction value.

12. such as claim 10 method is it is characterised in that with the plurality of default signal-to-noise characteristic value by little To longer spread, corresponding the plurality of preset correction value at least fractional numbers meeting is in first that one first increase and decrease becomes Gesture changes, then in one second growth trend change, and this first growth trend is contrary with this second growth trend.

13. as claim 12 method it is characterised in that this one first growth trend be strictly decreasing, This second growth trend is strictly increasing.

14. such as claim 10 method is it is characterised in that pre- with multiple according to this initial signal-to-noise characteristic value If correction value provides the step of this correspondence correction value to further include：

More setting according to a modulation of this receipt signal provides this corresponding correction value.

15. as claim 14 method it is characterised in that respectively this preset correction value correspond to multiple pre- If one of them of signal-to-noise characteristic value, corresponding to same default signal-to-noise characteristic value and corresponding to different default modulation In the multiple preset correction value setting, it is set in, with the plurality of default modulation, the bit carrying in the unit interval Number arranges from small to large, and at least fractional numbers preset correction value can assume trend decrescence.