Method for setting a decision feedback equalizer and associated decision feedback equalizer

Abstract

A decision feedback equalizer and a method for setting a decision feedback equalizer, the decision feedback equalizer comprising a feedforward equalizer, a feedback equalizer, a decision device, and a decision adjustment device. The feedforward equalizer is configured to generate a feedforward output signal based on an input signal. The feedback equalizer is coupled to the feedforward equalizer and configured to generate a feedback output signal based on a decision output signal. The decision device is coupled to the feedforward equalizer and the feedback equalizer and is controlled by a decision adjustment parameter, wherein the decision device is configured to make a decision based on a sum of the feedforward output signal and the feedback output signal to generate the decision output signal. The decision adjustment device is coupled to the decision device and is configured to adjust the decision adjustment parameter based on a system sleep state.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication, and in particular to a decision feedback equalizer that adjusts decision strategy according to system sleep state or communication quality, and a method of setting the equalizer. BACKGROUND

[0002] During the transmission of a signal through a channel, the non-ideal nature of the channel often results in inter symbol interference (ISI), which prevents the receiving end from correctly identifying the signal. Therefore, the receiving end usually employs a circuit known as a decision feedback equalizer (DFE) to eliminate the inter symbol interference that occurs after the signal is transmitted through the channel.

[0003] Figure 1 An architecture of a decision feedback equalizer is shown, which includes a slicer, a feed-forward equalizer, and a feedback equalizer. The feedback equalizer uses the decision output generated by the slicer as input to eliminate the inter symbol interference caused by the channel. Since the feedback equalizer is a feedback circuit, when the symbol decided by the slicer is incorrect, the error will be fed back to the input of the feedback equalizer, thereby affecting the feedback output of the feedback equalizer next time, and ultimately affecting the subsequent symbol decision. Moreover, when the amount of decision error is too large, the error is likely to repeatedly circulate in the feedback equalizer, which is known as error propagation.

[0004] In order to shorten the time of error propagation, a soft decision feedback equalizer (SDFE) is widely used, which adds a non-linearity slicer to the architecture of the traditional decision feedback equalizer. The non-linearity slicer effectively limits the input size of the feedback equalizer, thereby reducing the size of the error amount. The architecture of this equalizer is shown in Figure 2

[0005] ​Non-linear decision mainly makes soft decision, thus introduces extra symbols which do not exist in the system originally, and uses these extra symbols to reflect the reliability of the decision. Although non-linear decision can effectively compress the amount of errors fed back to the feedback equalizer when the communication environment is poor, and thus reduce the probability and duration of error propagation. But in the case of stable communication environment, the extra symbols introduced by non-linear decision may cause more errors to be fed back to the feedback equalizer. Therefore, it is necessary to propose a mechanism that can properly control the non-linear decision maker. SUMMARY

[0006] Therefore, in order to avoid error propagation caused by soft decision, the present application provides a mechanism for controlling decision feedback equalizer. In the control mechanism of the present application, the system sleep state or the communication quality is considered for decision making. In the embodiment of the present application, the decision maker can be set to linear decision (i.e. hard decision) or non-linear decision (i.e. soft decision), and the setting is completed by the decision regulator. The decision regulator refers to the stage of system sleep state or the parameter related to communication quality, changes the linear / non-linear decision operation of the decision maker, or further adjusts the non-linear degree of non-linear decision. Through such control mechanism, the error propagation caused by using soft decision when the communication environment is good can be avoided.

[0007] An embodiment of the present application provides a decision feedback equalizer, comprising: a feedforward equalizer, a feedback equalizer, a decision maker and a decision regulator. The feedforward equalizer is used to generate a feedforward output signal according to an input signal. The feedback equalizer is coupled to the feedforward equalizer and is used to generate a feedback output signal according to a decision output signal. The decision maker is coupled to the feedforward equalizer and the feedback equalizer and is controlled by a decision regulation parameter, wherein the decision maker is used to make a decision judgment according to the sum of the feedforward output signal and the feedback output signal, thereby generating the decision output signal. The decision regulator is coupled to the decision maker and is used to adjust the decision regulation parameter according to a system sleep state.

[0008] An embodiment of the present invention provides a decision feedback equalizer, comprising: a feedforward equalizer, a feedback equalizer, a decision device, and a decision adjustment device. The feedforward equalizer is configured to generate a feedforward output signal based on an input signal. The feedback equalizer is coupled to the feedforward equalizer and configured to generate a feedback output signal based on a decision output signal. The decision device is coupled to the feedforward equalizer and the feedback equalizer and controlled by a decision adjustment parameter, wherein the decision device is configured to make a decision based on a summation of the feedforward output signal and the feedback output signal to generate the decision output signal. The decision adjustment device is coupled to the decision device and configured to adjust the decision adjustment parameter based on at least one quality-related parameter related to a communication quality.

[0009] An embodiment of the present invention provides a method for setting a decision feedback equalizer, comprising: generating a decision output signal by making a decision based on a summation of a feedforward output signal generated by a feedforward equalizer in the decision feedback equalizer and a feedback output signal generated by a feedback equalizer in the decision feedback equalizer, wherein the decision is controlled by a decision adjustment parameter; and adjusting the decision adjustment parameter based on a system sleep state.

[0010] An embodiment of the present invention provides a method for setting a decision feedback equalizer, comprising: generating a decision output signal by making a decision based on a summation of a feedforward output signal generated by a feedforward equalizer in the decision feedback equalizer and a feedback output signal generated by a feedback equalizer in the decision feedback equalizer, wherein the decision is controlled by a decision adjustment parameter; and adjusting the decision adjustment parameter based on at least one quality-related parameter related to a communication quality. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A block diagram of a decision feedback equalizer is shown.

[0012] Figure 2 A block diagram of a soft decision feedback equalizer is shown.

[0013] Figure 3 A block diagram of a decision feedback equalizer of an embodiment of the present invention is shown.

[0014] Figure 4 An application diagram of a decision feedback equalizer of an embodiment of the present invention is shown.

[0015] Figure 5A With Figure 5B Detailed block diagrams of a feedforward equalizer and a feedback equalizer in a decision feedback equalizer of an embodiment of the present invention are shown.

[0016] Figure 6A WithFigure 6B It shows how the decision regulator adjusts the decision maker in an embodiment of the present invention.

[0017] Figure 7 The figure shows the LPI mode flow chart defined in the IEEE 802.3 specification.

[0018] Figure 8 A simplified flow chart of a method for setting a decision feedback equalizer according to an embodiment of the present invention is shown.

[0019] Figure 9 A flow chart showing how to adjust decision adjustment parameters according to communication distance in one embodiment of the present invention.

[0020] Figures 10A to 10D It shows the change of decision criteria caused by the adjustment of decision adjustment parameters in the embodiment of the present invention.

[0021] Figure 11 A simplified flow chart of a method for setting a decision feedback equalizer in another embodiment of the present invention is shown.

[0022] Explanation of symbols

[0023] 10 Main unit

[0024] 20 Slave device

[0025] 25 Receiver

[0026] 100 Decision Feedback Equalizer

[0027] 110 Feedforward Equalizer

[0028] 120 Feedback EQ

[0029] 130 Decision Maker

[0030] 140 Decision Regulator

[0031] Steps 210-220, 310-340, 410-420 DETAILED DESCRIPTION

[0032] In the following text, many specific details are described to provide the reader with a thorough understanding of the embodiments of the present invention. However, those skilled in the art will understand how to implement the present invention without one or more specific details, or using other methods, components, materials, etc. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the core concepts of the present invention.

[0033] Reference in the specification to "one embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment. Further, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0034] Reference is made to Figure 3 FIG. 1 is a functional block diagram of an embodiment of a decision feedback equalizer. As shown, the decision feedback equalizer 100 includes a feedforward equalizer 110, a feedback equalizer 120, a decision device 130, and a decision adjuster 140. The feedforward equalizer 110 receives an input signal r[t] from a channel and generates a feedforward output signal FF[t] after correcting distortion of the input signal. The decision device 130 makes a decision based on a summation x[t] of the feedforward output signal FF[t] and a feedback output signal FB[t] output by the feedback equalizer 120, and generates a decision output signal d[t]. The feedback equalizer 120 generates the feedback output signal FB[t] based on the decision output signal d[t] after correcting distortion of the decision output signal.

[0035] Further, as Figure 4 shown, the decision feedback equalizer 100 can be disposed in a receiver 25 of a communication device 20 in a communication system, and the communication device 20 can be a slave device in the communication system and communicate with a master device 10 through a communication channel. In one embodiment, the communication system can be an Ethernet communication system, and the master device 10 and the slave device 20 can both be Ethernet communication devices. If both devices support Energy-Efficient Ethernet (EEE), the devices can enter a sleep mode when there is no communication demand, and the physical layer circuit can enter a Low Power Idle (LPI) mode to save power.

[0036] Further, detailed architecture diagrams of the feedforward equalizer 110 and the feedback equalizer 120 are shown in Figure 5A and Figure 5B respectively. The feedforward equalizer 110 and the feedback equalizer 120 each include a plurality of delay line segments 112_1-112_K and 122_1-122_N. The signals r[t] and d[t] input to the feedforward equalizer 110 and the feedback equalizer 130 are delayed by the delay line segments 112_1-112_K and 122_1-122_N, and the delayed results are multiplied by weight coefficients cf1-cf K and cb1-cb NAmplify and sum them to obtain the equalizer outputs: feedforward output signal FF[t] and feedback output signal FB[t].

[0037] In the present invention, the decision regulator 130 can adjust the decision strategy of the decision maker 130 so that the decision maker 130 can make a linear decision or a nonlinear decision, or adjust the nonlinear decision made by the decision maker 130. Figure 6A and Figure 6B First, refer to Figure 6A , which shows a schematic diagram of when the decision maker 130 makes a linear decision. As shown in the figure, it is assumed that there are three-order symbols in the system (such as the receiver 25): -2, 0, +2. If the value of the input signal x[t] of the decision maker 130 is less than -1, the decision maker 130 will make a decision with a symbol of -2, and obtain a decision output d[t]=2. When the value of the input signal x[t] of the decision maker 130 is greater than -1 and less than 1, the decision maker 130 will make a decision with a symbol of 0, and obtain a decision output d[t]=0. When the value of the input signal x[t] of the decision maker 130 is greater than 1, the decision maker 130 will make a decision with a symbol of 2, and obtain a decision output d[t]=2. On the other hand, Figure 6B The figure shows a schematic diagram of nonlinear decision making by the decision maker 130. As shown in the figure, although there are only three order symbols in the system: -2, 0, and +2, when the decision maker 130 makes nonlinear decisions, more order decision results will be obtained, thereby reflecting the reliability of signal transmission. Figure 6BAn example of the fifth order is shown. When the value of the input signal x0 of the decision maker 130 is less than (-1-A), the decision maker 130 will make a decision with the sign -2, and the decision output d[t]=-2 is obtained. When the value of the input signal x[t] of the decision maker 130 is greater than (-1-A) and less than (-1+A), the decision maker 130 will make a decision with the sign -1, and the decision output d[t]=-1 is obtained. When the value of the input signal x[t] of the decision maker 130 is greater than (-1+A) and less than (1 -A), the decision maker 130 will make a decision with a sign of 0, resulting in a decision output d[t] = 0. When the value of the input signal x[t] to the decision maker 130 is greater than (1-A) and less than (1+A), the decision maker 130 will make a decision with a sign of 1, resulting in a decision output d[t] = 1. And when the value of the input signal x[t] to the decision maker 130 is greater than (1+A), the decision maker 130 will make a decision with a sign of 2, resulting in a decision output d[t] = 2. The value A is a decision adjustment parameter of the decision maker 130, which can be determined by the decision adjuster 140. As the decision adjustment parameter A changes, the nonlinear decision made by the decision maker 130 will produce different decision outputs for the same output signal.

[0038] In nonlinear decision making, a symbol hierarchy (-1, +1) that does not originally exist in the system is introduced, which reflects the reliability of signal transmission and can limit the amount of error. Therefore, when the communication environment is poor, the reliability of signal transmission is low and symbol decisions are prone to errors. In this case, increasing the size of the adjustment parameter A can effectively compress the amount of error fed back to the feedback equalizer 120, thereby reducing the probability and duration of error propagation. However, in the case of a stable and good communication environment, the nonlinear decision maker will decide the ideal received signal as a symbol (+1, -1) that does not exist in the system. This will cause additional errors to be fed back to the feedback equalizer 120. To avoid or alleviate this situation, the present invention controls the decision strategy of the decision maker 130 through the decision adjuster 140.

[0039] First, in one embodiment of the present invention, the decision adjuster 140 adjusts the decision maker 130 based on the sleep state of the system (i.e., the slave device 20), causing it to operate based on either linear decision-making (i.e., hard decision-making) or nonlinear decision-making (i.e., soft decision-making). When there is no data transmission between the master device 10 and the communication device 20, they enter sleep mode to save power. At this time, both devices enter LPI mode, with some physical layer circuits disabled. However, in LPI mode, regardless of whether there is data to be transmitted between the devices, they still need to periodically transmit signals and wake up each other for a period of time to maintain synchronization. Figure 7The flow of 1000BASE-T PHY LPI mode defined in IEEE 802.3 specification is shown. In the WAKE SILENT stage and the WAKE TRAINING stage of the flow, the master device 10 and the slave device 20 need to be woken up for system synchronization and convergence. At this time, the master device 10 will first enter the WAKE TRAINING stage, send a signal to the slave device 20, and wait until the slave device 20 converges stably in the WAKE SILENT stage before entering the WAKE TRAINING stage to send a signal back to the master device. When both sides are synchronized and converged stably in the WAKE TRAINING stage, they will return to the initial UPDATE stage together. If there is a packet transmission requirement, the LPI mode will be left, and if not, it will continue to enter the QUIET stage, and the above flow will be repeated.

[0040] Since the master device 10 and the slave device 20 will turn off the operation of part of the physical layer circuit in the QUIET stage, after waking up, it may cause the phase inconsistency of the two, and the slave device 20 needs to perform a fast phase scan to find the best ADC sampling phase, so as to ensure system synchronization and convergence. However, in the process of phase scanning, a phase with a large difference from the best phase may be selected, resulting in a higher error amount, thus causing the decision maker 130 to make an error decision, and further causing the feedback equalizer 120 to produce error propagation. In the worst case, the best phase may be missed in the phase scanning, the time of system synchronization and convergence is too long, and finally it may also affect the wake-up operation of the master device 10 and the slave device 20, so there is a concern that packets may be lost.

[0041] Accordingly, in one embodiment of the present application, once the slave device 20 enters the wake-up phase from the sleep phase, the decision adjuster 140 causes the decision maker 130 to perform the non-linear decision operation, i.e., sets the decision adjustment parameter A to a non-zero value. Until the slave device 20 exits the wake-up phase, the decision adjuster 140 causes the decision maker 130 to return to the linear decision operation, i.e., sets the decision adjustment parameter A to zero or a value close to zero. In one embodiment, when the slave device 20 enters the WAKE SILENT phase and the WAKE TRAINING phase in the LPI mode of the IEEE 802.3 specification, the decision adjuster 140 causes the decision maker 130 to perform the non-linear decision operation (sets the decision adjustment parameter A to a non-zero value) until the slave device 20 exits the WAKE TRAINING phase, the decision adjuster 140 causes the decision maker 130 to return to the linear decision operation (sets the decision adjustment parameter A to zero or a value close to zero). In this way, the probability of error propagation when the slave device 20 performs the phase scan can be reduced, and the chance of finding the optimal phase can be increased. In addition, the above mechanism can also shorten the duration of error propagation when error propagation occurs, speed up the synchronization and convergence of the slave device 20, and ensure that the master device 10 and the slave device 20 can return to the sleep state within the specified time and without missing packets.

[0042] Figure 8 A simplified flowchart showing the adjustment of the decision adjustment parameter according to the sleep state of the system in the above embodiment is shown, which includes the following steps:

[0043] Step 210: generating a decision output signal according to the decision judgment of the sum of the feedforward output signal generated by the feedforward equalizer in the decision feedback equalizer and the feedback output signal generated by the feedback equalizer in the decision feedback equalizer, wherein the decision judgment is controlled by the decision adjustment parameter; and

[0044] Step 220: adjusting the decision adjustment parameter according to a sleep state of a system.

[0045] In other embodiments of the present application, the decision adjuster 140 can adjust the decision maker 130 according to a parameter related to the communication quality. In one embodiment, the adjustment of the decision maker 130 by the decision adjuster 140 can be determined according to the communication distance between the master device 10 and the slave device 20. Generally, in a communication system, the longer the communication distance, the more severe the ISI phenomenon, and vice versa. Therefore, when the communication distance is longer, the decision adjuster 140 can increase the decision adjustment parameter A of the decision maker 130, so that the decision strategy of the decision maker 130 tends to be the non-linear decision; and when the communication distance is shorter, the decision adjuster 140 can decrease the decision adjustment parameter A of the decision maker 130, so that the decision strategy of the decision maker 130 tends to be the linear decision.

[0046] For the above examples, please refer to Figure 9 Flowchart shown. In step 310, the decision regulator 140 determines whether the communication distance is greater than the first critical value TH1. If so, the process proceeds to step 315 and sets the decision adjustment parameter A to 0.2; if not, the process proceeds to step 320. In step 320, the decision regulator 140 determines whether the communication distance is greater than the second critical value TH2. If so, the process proceeds to step 325 and sets the decision adjustment parameter A to 0.1. If not, the process proceeds to step 330. In step 330, the decision regulator 140 determines whether the communication distance is greater than the third critical value TH3. If so, the process proceeds to step 335 and sets the decision adjustment parameter A to 0.05; if not, the process proceeds to step 340. In step 340, the decision regulator 140 sets the decision adjustment parameter A to 0, and at this time, the decision maker 130 returns to the linear decision operation. Figures 10A to 10D The following diagrams illustrate the changes in the decision strategy resulting from the adjustment of the decision adjustment parameter A in the above process. Please note that although in the above embodiment, the decision adjuster 140 adjusts the decision adjustment parameter A to varying degrees using three preset thresholds, this is not a limitation of the present invention. In different embodiments of the present invention, more or fewer thresholds may be set to adjust the decision adjustment parameter A, and the magnitude of each adjustment of the decision adjustment parameter A may also vary. Therefore, any operation involving changing the decision adjustment parameter of the decision maker based on communication distance, switching the decision maker's decision strategy to linear or nonlinear decision making, or changing the degree of nonlinearity falls within the scope of the present invention.

[0047] Furthermore, in addition to adjusting based on communication distance, the decision adjuster 140 also adjusts the decision maker 130 based on other parameters related to communication quality. In one embodiment, the decision adjuster 140 may adjust the decision maker 130 based on the system's signal-to-noise ratio (SNR). Generally speaking, a lower system SNR indicates more severe ISI, and vice versa. Therefore, when the system SNR is lower, the decision adjuster 140 may increase the decision adjustment parameter A of the decision maker 130, shifting its decision strategy toward nonlinear decision making. Conversely, when the system SNR is higher, the decision adjuster 140 may decrease the decision adjustment parameter A of the decision maker 130, shifting its decision strategy toward linear decision making. In this embodiment, similar to the previous embodiment, the decision adjuster 140 may compare the system SNR with one or more thresholds related to the system SNR and, based on the comparison results, adjust the decision adjustment parameter A of the decision maker 130 to varying degrees, or switch the decision strategy of the decision maker 130 between linear and nonlinear decision making.

[0048] In another embodiment, the decision adjuster 140 can also adjust the decision maker 130 according to the absolute value summation of the weight coefficients cb_l~cb_N in the feedback equalizer 120. Generally speaking, the higher the absolute value summation of the weight coefficients cb_l~cb_N in the feedback equalizer 120, the more severe the ISI phenomenon in the communication channel, and vice versa. Therefore, when the absolute value summation of the weight coefficients cb_l~cb_N is lower, the decision adjuster 140 can lower the decision adjustment parameter A of the decision maker 130, so as to make the decision strategy of the decision maker 130 tend to linear decision; and when the absolute value summation of the weight coefficients cb_l~cb_N is higher, the decision adjuster 140 can increase the decision adjustment parameter A of the decision maker 130, so as to make the decision strategy of the decision maker 130 tend to nonlinear decision. Similarly to the aforementioned embodiment, the decision adjuster 140 can compare the absolute value summation of the weight coefficients cb_l~cb_N with one or more threshold values related to the absolute value summation of the weight coefficients cb_l~cb_N, and adjust the decision adjustment parameter A of the decision maker 130 according to the comparison result, or make the decision strategy of the decision maker 130 switch between linear / nonlinear decision.

[0049] Figure 11 A simplified flowchart of adjusting the decision adjustment parameter according to the quality-related parameter related to the communication quality in the aforementioned embodiments is shown, which comprises the following steps:

[0050] Step 410: generating a decision output signal according to the decision judgment of the feedforward output signal generated by the feedforward equalizer in the decision feedback equalizer and the feedback output signal generated by the feedback equalizer in the decision feedback equalizer, wherein the decision judgment is controlled by the decision adjustment parameter; and

[0051] Step 420: adjusting the decision adjustment parameter according to at least one quality-related parameter related to the communication quality.

[0052] Since the principles and operation details of the aforementioned steps have been explained in the previous embodiments, no further explanation is provided herein, and it is worth noting that in other embodiments of the present application, other additional steps based on the known techniques in the field can be added to improve the overall effect.

[0053] In addition, although in the above embodiments the decision adjuster 140 is considered in relation to a single parameter related to communication quality, such as communication distance, system SNR, and the sum of absolute values of the weight coefficients of the equalizer, in other embodiments of the present application, the decision adjuster 140 can consider multiple parameters related to communication quality and adjust the decision adjustment parameter A accordingly. Furthermore, although in the above embodiments the decision feedback equalizer 100 includes only one decision device 130 controlled by the decision adjuster 140 to perform linear or nonlinear decision, in other embodiments of the present application, the decision feedback equalizer 100 can have an architecture as shown in FIG. 4, including multiple decision devices, one of which performs nonlinear decision and the other performs linear decision. Similarly, the decision adjuster 140 can turn on or off the nonlinear decision device and adjust the decision adjustment parameter A of the nonlinear decision device according to the conditions described above, such as system sleep state or parameters related to communication quality, to cause the decision device 130 to tend toward linear decision or nonlinear decision, thereby achieving the same effects as the above embodiments. Figure 2

[0054] In summary, the present application provides a method for adjusting the decision strategy of a decision device in a decision feedback equalizer. According to the stage of system sleep state or parameters related to communication quality, the decision device is caused to tend toward linear or nonlinear decision operation, or the nonlinear degree of nonlinear decision is further adjusted. Through such a control mechanism, the error propagation caused by using soft decision strategy when the communication environment is good can be avoided.

[0055] Embodiments of the present application can be implemented using hardware, software, firmware, and any combination thereof. Through a suitable instruction execution system, software or firmware stored in a storage memory can be used to implement embodiments of the present application. In terms of hardware, any of the following technologies or their combinations can be used: a separate operation logic with logic gates that can perform logic functions according to data signals, an application specific integrated circuit (ASIC) with appropriate combination of logic gates, a programmable gate array (PGA) or a field programmable gate array (FPGA), etc.

[0056] ​The flow diagrams within the specification illustrate the architecture, functionality, and operations of systems, methods, and computer program products in accordance with various embodiments of the present application. In this regard, each block within the flow diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical functions ("instructions"). It should also be noted that in different embodiments, the flow diagrams can include a number of discrete blocks, or the blocks can be combined or the order of the blocks can be re-arranged. In some embodiments, the blocks can be implemented as electronic hardware, computer software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components have been shown to be separate. However, various components can be implemented in one or more computers or processors. It will be appreciated that computers or processors can be located in a single site, or distributed over a wide area network for purposes of administering the system. Moreover, the unique structure of the computer program product can be packaged on a variety of non-transitory computer readable media. Thus, the computer program product can comprise a computer readable medium having stored thereon computer executable instructions that, when implemented by a computer or like data processing apparatus, can cause the computer or like data processing apparatus to carry out the functions / acts specified in the flow diagrams and / or functional block diagrams.

[0057] While the application has been described by way of example, it should be appreciated that modifications and additions can be made without departing from the scope of the application.

Claims

1. A decision feedback equalizer, comprising: a feedforward equalizer for generating a feedforward output signal according to an input signal; a feedback equalizer coupled to the feedforward equalizer, for generating a feedback output signal according to a decision output signal; a decision maker coupled to the feedforward equalizer and the feedback equalizer, controlled by a decision adjustment parameter, for making a decision based on the sum of the feedforward output signal and the feedback output signal, thereby generating the decision output signal; as well as A decision adjuster is coupled to the decision maker and is configured to adjust the decision adjustment parameter according to a system sleep state, wherein when the decision adjustment parameter is zero, the decision maker performs a linear / hard decision, and when the decision adjustment parameter is non-zero, the decision maker performs a non-linear / soft decision.

2. The decision feedback equalizer of claim 1 , wherein when a communication device including the decision feedback equalizer is awakened from a sleep state and until the communication device enters the sleep state again, the decision adjustment parameter has a first value; otherwise, the decision adjustment parameter has a second value, wherein the second value is less than the first value and a minimum value of the second value is zero.

3. The decision feedback equalizer of claim 2 , wherein when the communication device operates in a WAKE_SILENT phase and a WAKE_TRAINING phase of a low power idle mode of the IEEE 802.3 specification, the decision adjustment parameter has the first value; otherwise, the decision adjustment parameter has the second value.

4. A decision feedback equalizer, comprising: a feedforward equalizer for generating a feedforward output signal according to an input signal; a feedback equalizer coupled to the feedforward equalizer, for generating a feedback output signal according to a decision output signal; a decision maker coupled to the feedforward equalizer and the feedback equalizer, controlled by a decision adjustment parameter, for making a decision based on the sum of the feedforward output signal and the feedback output signal, thereby generating the decision output signal; as well as A decision adjuster is coupled to the decision maker and is configured to adjust the decision adjustment parameter according to at least one quality-related parameter related to communication quality, wherein when the decision adjustment parameter is zero, the decision maker performs a linear / hard decision, and when the decision adjustment parameter is non-zero, the decision maker performs a nonlinear / soft decision.

5. A decision feedback equalizer as described in claim 4, wherein the quality-related parameter is a communication distance, when the communication distance is greater than a predetermined value, the decision adjustment parameter has a first value, and when the communication distance is less than the predetermined value, the decision adjustment parameter has a second value, wherein the second value is less than the first value, and the minimum value of the second value is zero.

6. The decision feedback equalizer of claim 4 , wherein the quality-related parameter is a system signal-to-noise ratio (SNR), and when the SNR is less than a predetermined value, the decision adjustment parameter has a first value, and when the SNR is greater than the predetermined value, the decision adjustment parameter has a second value, wherein the second value is less than the first value, and a minimum value of the second value is zero.

7. A decision feedback equalizer as described in claim 4, wherein the feedback equalizer includes multiple delay line segments and is controlled by a set of weight coefficients, and the quality-related parameter is the sum of the absolute values ​​of the current values ​​of the set of weight coefficients; when the sum of the absolute values ​​is greater than a predetermined value, the decision adjustment parameter has a first value, and when the sum of the absolute values ​​is less than the predetermined value, the decision adjustment parameter has a second value, wherein the second value is less than the first value, and the minimum value of the second value is zero.

8. A method for configuring a decision feedback equalizer according to any one of claims 1 to 7, comprising: Performing a decision based on a sum of a feedforward output signal generated by a feedforward equalizer in the decision feedback equalizer and a feedback output signal generated by a feedback equalizer in the decision feedback equalizer to generate a decision output signal, wherein the decision is controlled by a decision adjustment parameter; and The decision adjustment parameter is adjusted according to a system sleep state.

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