Abstract:
The present invention provides a network apparatus capable of canceling far-end crosstalk (FEXT). When the network apparatus is under a training mode, hard data is provided to a FEXT canceller for performing FEXT cancellation. When the network apparatus is under a data mode, soft data is provided to the FEXT canceller for performing FEXT cancellation as well. Therefore, FEXT is effectively canceled, and consumption power of the network apparatus is saved.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a network apparatus and a network signal processing method, and more particularly, to a network apparatus capable of canceling far-end-crosstalk (FEXT) and a network signal processing method thereof. 
     2. Description of the Prior Art 
     In a communication system, a transmitter or a receiver could include a plurality of channels. However, signals in different channels may interfere with each other, which is generally called crosstalk. Crosstalk can be categorized into near end crosstalk (NEXT) and far end crosstalk (FEXT). NEXT indicates a crosstalk phenomenon as measured at the end of the cable nearest to the transmitter while FEXT indicates a crosstalk phenomenon as measured at the end of the cable nearest the receiver. Both will cause the result of lowering signal qualities at a corresponding receiver. 
     In conventional FEXT cancellation techniques, a precode FEXT canceller is disposed at a transmitter for partially canceling in advance crosstalk noises due to other channels, and a FEXT canceller is also disposed at a corresponding receiver for further canceling the noises. Related arts of FEXT cancellation techniques may be gathered from U.S. Pat. No. 7,164,764. However, since FEXT cancellers are disposed and simultaneously used at both the transmitter and the receiver, related power consumption throughout a communication system becomes significant. Moreover, parameters referenced by the FEXT canceller at the receiver will continuously vary significantly so that noises cannot be stably filtered off. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems, an object of the invention is to provide a network apparatus capable of effectively canceling FEXT with low power consumption. 
     The claimed invention discloses a network apparatus. The network apparatus comprises a first equalization module, a multiplexer, a far-end-crosstalk (FEXT) canceller, and a second equalization module. The first equalization module is for equalizing a first network signal to output a first output equalization signal, and for outputting both a first calculated value and a second calculated value in equalization. The first calculated value is a soft data value, and the second calculated value is a hard data value. The multiplexer is coupled to the first equalization module, for determining output of the first calculated value or the second calculated value according to a selection control signal. The FEXT canceller coupled to the multiplexer, for outputting a FEXT canceling signal according to the first calculated value or the second calculated value outputted from the multiplexer. The second equalization module is coupled to the FEXT canceller, for equalizing a second network signal according to the FEXT canceling signal, and for outputting a second output equalization signal. When the network apparatus is operated under a data mode, the multiplexer is controlled according to the selection control signal to output the first calculated value to the FEXT canceller. When the network apparatus is operated under a training mode, the multiplexer is controlled according to the selection control signal to output the second calculated value to the FEXT canceller. 
     The claimed invention discloses a network signal processing method used on a network apparatus. The network signal processing method comprises equalizing a first network signal for outputting a first calculated value and a second calculated value; determining to output the first calculated value or the second calculated value with a multiplexer; outputting a FEXT canceling signal according to the first calculated value or the second calculated value outputted from the multiplexer; and equalizing a second network signal and outputting an output equalization signal according to the FEXT canceling signal. The first calculated value is a soft data value, and the second calculated value is a hard data value. When the network apparatus is operated under a first mode, the multiplexer outputs the first calculated value so as to output the FEXT canceling signal. When the network apparatus is operated under a second mode, the multiplexer outputs the second calculated value so as to output the FEXT canceling signal. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a FEXT model at a transmitter of a network apparatus according to a preferred embodiment of the present invention. 
         FIG. 2  illustrates a FEXT model of a receiver in the network apparatus of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 1 , which illustrates a FEXT model of a transmitter disposed in a network apparatus according to a preferred embodiment of the present invention. Transmitter  100  of the network apparatus includes a first channel  104 , a first FEXT coupler  106 , a first adder  110 , a first Tomlison-Harashima Precoding (THP) filter  122 , a second channel  114 , a second FEXT coupler  116 , a second adder  120 , and a second THP filter  132 . It is noted that both the first THP filter  122  and the second THP filter  132  can be enabled or disabled by switch signal sel_THP according to different operation modes of the network apparatus. 
     The transmitter  100  is configured to utilize transmitting signals T A  and T B  to generate and transmit the receiving signals R A  and R B  to a receiver. The first channel  104  has a channel response CH A (z), which may also be indicated as a channel response of a channel A, whereas the second channel  114  has a channel response CH B (z), which may also be indicated as a channel response of a channel B. The first FEXT coupler  106  has a response A B (z), whereas the second FEXT coupler  116  has a response B A (z). The first THP filter  122  has a response THP A , whereas the second THP filter  132  has a response THP B . 
     First of all, a training mode of the network apparatus of the present invention is introduced. Under the training mode, both the first THP filter  122  and the second THP filter  132  are disabled. The receiver signal R A  is indicated as:
 
 R   A   =T   A   *CH   A ( z )+ T   B   *B   A ( z )  Equation (1);
 
The receiver signal R B  is indicated as:
 
 R   B   =T   B   *CH   B ( z )+ T   A   *A   B ( z )  Equation (2).
 
     In Equation (1), the term T B *B A (z) indicates FEXT generated from the channel B to the channel A. Similarly, the term T A *A B (z) indicates FEXT generated from the channel A to the channel B. 
     Secondly, a data mode of the network apparatus of the present invention is introduced, where the data mode is activated right after the training mode completed. Under the data mode, both the first THP filter  122  and the second THP filter  132  are enabled. At this time, the receiver signal R A  is indicated as:
 
 R   A   =T   A *THP A   *CH   A ( z )+ T   B *THP B   *B   A ( z )  Equation (3);
 
The receiver signal R B  is indicated as:
 
 R   B   =T   B *THP B   *CH   B ( z )+ T   A *THP A   *A   B ( z )  Equation (4).
 
     The term T B *THP B *B A (z) indicates FEXT generated from the channel B to the channel A, whereas the term T A *THP A *A B (z) indicates FEXT generated from the channel A to the channel B. 
     One object of the present invention is to minimize the parameter variations of the FEXT cancellers, stabilizing noise filtering whether the THP filters are activated or disabled. According to the descriptions related to  FIG. 1 , FEXT noises shown in Equations (1), (2), (3), and (4) are required to be taken into considerations for stabilizing noise filtering. 
     Please further refer to  FIG. 2 , which illustrates a FEXT model of receiver  200  disposed in the network apparatus according to a preferred embodiment of the present invention. It is noted that though the network apparatus shown in  FIG. 2  merely uses two channels, a network apparatus having two or more channels according to other embodiments of the present invention may also be implemented. In other words, a number of used channels in the network apparatus of the present invention should not be limited to this embodiment. 
     As shown in  FIG. 2 , a receiver  200  of the network apparatus includes a first equalization module  201 , a second equalization module  203 , a first multiplexer  218 , a second multiplexer  268 , a first FEXT canceller  220 , and a second FEXT canceller  270 . The first equalization module  201  includes a first feed-forward equalizer  204 , a first subtractor  206 , a second subtractor  208 , a first modulo processor  210 , a first decision processor  212 , a first feedback equalizer  214 , and a first adder  216 . The second equalization module  203  includes a second feed-forward equalizer  254 , a third subtractor  256 , a fourth subtractor  258 , a second modulo processor  260 , a second decision processor  262 , a second feedback equalizer  264 , and a second adder  266 . The first equalization module  201  is used for equalizing a first network signal for outputting a first output equalization signal, where the first network signal is the receiving signal R A , and the first output equalization signal corresponds to the transmitting signal T A  shown in  FIG. 1 . 
     The second equalization module  203  is used for equalizing a second network signal according to a FEXT canceling signal outputted from the first FEXT canceller  220 , and for outputting a second output equalization signal, where the second network signal is the receiving signal R B , and the second output equalization signal is corresponds to the transmitting signal T B  shown in  FIG. 1 . The feed-forward equalizer  204  receives and equalizes the receiving signal R A  for outputting a feed-forward equalization signal. Both the subtractors  206  and  208  are used for operating on both the feed-forward equalization signal and a FEXT canceling signal inputted from the second equalization module  203  to output a calculated value. Note that the subtractor  206  is used for subtracting the FEXT canceling signal from the feed-forward equalization signal to output a first intermediate calculated value, and that the subtractor  208  is used for subtracting a feedback equalization signal from the first intermediate calculated value to output the calculated value. The modulo processor  210  is used for performing a modulo operation on the calculated value to output a modulo processing signal. The decision processor  212  is used for outputting the transmitting signal T A  according to the modulo processing signal. The feedback equalizer  214  is used for feedback-equalizing the first output equalization signal for outputting the feedback equalization signal. The adder  216  is used for adding the transmitter signal T A  with the feedback equalization signal for outputting a second intermediate calculated value. 
     According to a preferred embodiment of the present invention, both the first FEXT canceller  220  and the second FEXT canceller  270  may be implemented with finite impulse response (FIR) filters. Coupling and connection between all the above-mentioned elements and related input/output signals is shown in  FIG. 2 , and omitted herein for the sake of brevity. It is noted that both the first feedback equalizer  214  and the second feedback equalizer  264  are also enabled or disabled by the switch signal sel_FBE, and both the first modulo processor  210  and the second modulo processor  260  are enabled or disabled by the switch signal sel_MOD as well. 
     Operations of the receiver  200  are described in detail as follows. First, right after the network apparatus of the present invention is booted, both the first THP filter  122  and the second THP filter  132  of the transmitter  100  are disabled under the training mode of said network apparatus. At this time, according to a selection control signal sel the first multiplexer  218  outputs the second intermediate calculated value from the first adder  216  of the first equalization module  201 , where the calculated value from the first adder  216  is a hard data value in equalization, to the first FEXT canceller  220  to perform FEXT cancellation on the second equalization module  203 . Similarly, under the training mode of the network apparatus of the present invention, according to the selection control signal sel the second multiplexer  268  outputs a second intermediate calculated value from the second adder  266  of the second equalization module  203 , which is a hard data value as well, to the second FEXT canceller  270  to perform FEXT cancellation on the first equalization module  201 . Note that in the present embodiment, though the calculated values from both the first adder  216  and the second adder  266  are determined to be respectively outputted by the first multiplexer  218  and the second multiplexer  268  and serve as reference signals in FEXT cancellation, the determination should not be limitations to the present invention. In other words, the first multiplexer  218  and the second multiplexer  268  may also determine other hard data as the reference signals in FEXT cancellation. For example, the first output equalization signal T A  from the first decision processor  212  and the second output equalization signal T B  from the second decision processor  262  may also serve as the reference signals in FEXT cancellation in other embodiments of the present invention. 
     Under the training mode of the network apparatus of the present invention, FEXT processed by the first feed-forward equalizer  204  is indicated as:
 
T B *B A (z)*F A (z)  Equation (5);
 
An output signal from the third subtractor  256  is indicated as:
 
T B *CH B (z)*F B (z)  Equation (6).
 
     For completely canceling FEXT from the first feed-forward equalizer  204 , and according to both Equation (5) and Equation (6), the following equation has to be satisfied:
 
 T   B   *B   A ( z )* F   A ( z )=[ T   B   *CH   B ( z )* F   B ( z )]* FC   BA ( z )  Equation (7);
 
Suppose H B (z)=CH B (z)*F B (z) is satisfied so that Equation (7) may be rewritten as follows:
 
 T   B   *B   A ( z )* F   A ( z )= T   B   *H   B ( z )* FC   BA ( z )=( T   B *( H   B ( z )−1)+ T   B )* FC   BA ( z )  Equation (8).
 
     The term H B (z)−1 indicates a response of the second feedback equalizer  264  so that the term T B *(H B (z)−1)+T B  indicates an output signal of the second adder  266 . Appropriate parameters in a response FC BA (z) of the second FEXT canceller  270  may be simulated according to Equation (8) as follows:
 
 FC   BA ( z )= B   A ( z )* F   A ( z )/ H   B ( z )  Equation (9).
 
     Similarly, parameters of a response FC AB (z) of the first FEXT canceller  220  may also be simulated according to the following:
 
 T   A   *A   B ( z )* F   B ( z )= T   A   *H   A ( z )* FC   AB ( z )=( T   A *( H   A ( z )−1)+ T   A )* FC   AB ( z )  Equation (10);
 
     Therefore, appropriate parameters in the response FC AB (z) may also be simulated according to Equation (10) and be indicated as follows:
 
 FC   AB ( z )= A   B ( z )* F   B ( z )/ H   A ( z )  Equation (11).
 
     As can be observed in the abovementioned equations, under the training mode of the network apparatus of the present invention, parameters used in the first FEXT canceller  220  and the second FEXT canceller  270  may be derived according to Equation (11) and Equation (10) respectively. 
     After the network apparatus of the present invention is booted for a while, the first THP filter  122  and the second THP filter  132  of the transmitter  100  are enabled, and both the first feedback equalizer  214  and the second feedback equalizer  264  are shut down or disabled by continuously inputting bits  0  so that the network apparatus of the present invention enters the data mode. At this time, according to the selection control signal sel the first multiplexer  218  outputs the first intermediate calculated value from the first subtractor  206  of the first equalization module  201 , where the first intermediate calculated value is a soft data value in equalization, to the first FEXT canceller  220  for performing FEXT cancellation on the second equalization module  203 . Similarly, under the data mode of the network apparatus of the present invention, according to the selection control signal sel the second multiplexer  268  outputs a calculated value from the third subtractor  256  of the second equalization module  203 , where the calculated value is a soft data value in equalization, to the second FEXT canceller  270  for performing FEXT cancellation on the first equalization module  201 . Note that a reference signal in FEXT cancellation herein is not limited to the calculated values from the first subtractor  206  and the third subtractor  256  in the present invention, i.e., other types of soft data may also be determined to be the reference signal in FEXT cancellation. Therefore, under the data mode of the network apparatus of the present invention, reference signals of the first FEXT canceller  220  or the second FEXT canceller  270  do not vary significantly so that system stability is raised. 
     Under the data mode of the network apparatus of the present invention, after the receiver signal R A  is processed by the feed-forward equalizer  204 , a corresponding FEXT is T R *THP B *B A (z)*F A (z). Moreover, a clean signal on the channel B, which is not interfered by FEXT from the channel A, is T B *THP B *CH B (z). For entirely canceling FEXT from the first feed-forward equalizer  204 , the following equation has to be satisfied:
 
 T   B *THP B   *B   A ( z )* F   A ( z )=[ T   B *THP B   *CH   B   *F   B ( z )]* FC   BA ( z )  Equation (12).
 
     Note that the first THP filter  122  and the second THP filter  132  acquire the following properties for each channel:
 
THP A =1 /H   A ( z )  Equation (13);
 
THP B =1 /H   B ( z )  Equation (14).
 
     According to the definition of the response H B (z), Equation (12), and Equation (13), Equation (12) may be rewritten as follows:
 
 T   B *THP B   *B   A ( z )* F   A ( z )= T   B   *FC   BA ( z )  Equation (15).
 
     According to Equation (13) and Equation (15), the FEXT response FC BA (z) from the channel B toward the channel A is indicated as follows:
 
 FC   BA ( z )=THP B   *B   A ( z )* F   A ( z )= B   A ( z )* F   A ( z )/ H   B ( z )  Equation (16).
 
     As can be observed from Equation (9) and Equation (16), whether the THP filters are activated or shut down, parameters in the FEXT response FC BA (z) are substantially the same. 
     Similarly, the FEXT response FC BA (z) from the channel A toward the channel B is indicated as follows:
 
 FC   B ( z )=THP A   *A   B ( z )* F   B ( z )= A   B ( z )* F   B ( z )/ H   A ( z )  Equation (17).
 
     As can be observed from Equation (11) and Equation (17), whether the THP filters are activated or shut down, parameters in the FEXT response FC AB (z) are the same. 
     According to the above descriptions, under the training mode of the network apparatus of the present invention, hard data are determined to be reference signals in FEXT cancellation; whereas under the data mode of the network apparatus of the present invention, soft data are determined to be reference signals in FEXT cancellation; and both modes lead to a same FEXT response. Therefore, under the data mode of the network apparatus of the present invention, even though soft data are used in FEXT cancellation, FEXT may also be entirely canceled, and moreover, related system stability is raised. 
     In a preferred embodiment of the present invention, under the training mode of the network apparatus of the present invention, the first feedback equalizer  214  and the second feedback equalizer  264  are enabled, and the first THP filter  122 , the second THP filter  132 , the first modulo processor  210 , and the second modulo processor  260  are disabled. Under the data mode of the network apparatus of the present invention, the first feedback equalizer  214  and the second feedback equalizer  264  are disabled, and the first THP filter  122 , the second THP filter  132 , the first modulo processor  210 , and the second modulo processor  260  are enabled. With the above disclosures, power consumption of the network apparatus is significantly reduced since some elements are disabled in different modes. In a preferred embodiment of the present invention, the network apparatus of the present invention is used on 10 GBASE-T Ethernet networks, however, the network apparatus of the present invention may also be used in other types of network. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.