Abstract:
The present invention is directed to methods and apparatuses for performing concurrent vectoring of systems having communications performed at different symbol rates. In embodiments, where a common binder includes different sub-groups of lines having corresponding different symbol rates, the invention includes methods and apparatuses for managing and concurrently vectoring all the lines of the different sub-groups.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 USC 119(e) of prior co-pending U.S. Provisional Patent Application No. 61/949,447, filed Mar. 7, 2014, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to xDSL systems, and more particularly to methods and apparatuses for performing concurrent vectoring of systems having communications performed at different symbol rates. 
       BACKGROUND OF THE INVENTION 
       [0003]    In xDSL (VDSL, VDSL2, G.Fast, etc.) systems, vectoring is an effective way to perform crosstalk cancellation (e.g. FEXT cancellation), thereby improving performance. For example, in a central office (CO) DSLAM, a vectoring system can effectively cancel FEXT between all lines in a vectoring group (e.g. all lines in a common binder). A problem exists when a binder includes lines coupled to CPE modems that do not all support the same symbol rates, for example some CPE modems that support VDSL2 with approximately a 4 KHz symbol rate, and other CPE modems that support G.Fast with approximately a 48 KHz symbol rate. In such situations, the vectoring group can either contain only the lines coupled to VDSL2 modems, or only the lines coupled to G.Fast modems. In other words, it is currently not possible to vector (i.e. perform crosstalk cancellation for) all the lines simultaneously. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to methods and apparatuses for performing concurrent vectoring of systems having communications performed at different symbol rates. In embodiments, where a common binder includes different sub-groups of lines having corresponding different symbol rates, the invention includes methods and apparatuses for managing and concurrently vectoring all the lines of the different sub-groups. 
         [0005]    In accordance with these and other aspects, a method according to embodiments of the invention includes concurrently performing vectoring with a plurality of xDSL modems, wherein certain of the xDSL modems use a first symbol rate, and certain other of the xDSL modems use a second symbol rate, wherein the second symbol rate is slower than the first symbol rate. 
         [0006]    In further accordance with these and other aspects, an apparatus according to embodiments of the invention includes a plurality of xDSL modems, wherein certain of the xDSL modems use a first symbol rate, and certain other of the xDSL modems use a second symbol rate, wherein the second symbol rate is slower than the first symbol rate, and a vector control entity that concurrently performs vectoring with both the certain of the xDSL modems using the first symbol rate, and the certain other of the xDSL modems using the second symbol rate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These and other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein: 
           [0008]      FIG. 1  is a block diagram illustrating an example system for concurrent vectoring of lines coupled to modems operating at different symbol rates according to embodiments of the invention; 
           [0009]      FIG. 2  is a diagram illustrating vectoring for a system including lines with only G.Fast modems; 
           [0010]      FIG. 3  is a diagram illustrating vectoring for a system including sub-groups of lines with G.Fast and VDSL2 modems according to embodiments of the invention; 
           [0011]      FIG. 4  is a block diagram illustrating an example implementation of a CO side apparatus for performing concurrent vectoring of lines coupled to modems operating at different symbol rates according to embodiments of the invention; and 
           [0012]      FIG. 5  is a flowchart illustrating an example method for performing concurrent vectoring of lines coupled to modems operating at different symbol rates according to embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. Embodiments described as being implemented in software should not be limited thereto, but can include embodiments implemented in hardware, or combinations of software and hardware, and vice-versa, as will be apparent to those skilled in the art, unless otherwise specified herein. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the invention is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration. 
         [0014]    As set forth above, embodiments of the invention allow for concurrent FEXT cancellation to be performed across lines coupled to xDSL modems that support vectoring but operating at different symbol rates.  FIG. 1  is a block diagram illustrating an example system for performing such concurrent FEXT cancellation according to embodiments of the invention. 
         [0015]    As shown, bundle  106  includes wire pairs  104 , certain of which wire pairs  104  are coupled between M CPE transceivers  110  that operate with low symbol rates such as 4 kHz (e.g. VDSL2 compatible modems) and corresponding CO transceivers  120 , while other pairs  104  are coupled between N CPE transceivers  112  that operate at higher symbol rates such as 48 kHz (e.g. G.Fast compatible modems) and corresponding CO transceivers  122 . Given that portions of the wire pairs  104  to these different types of CPE modems  110 ,  112  can exist in the same bundle  106 , crosstalk (e.g. FEXT) between the lines having the same type of CPE modems exists, which leads to a reduction in performance. 
         [0016]    Vectoring technologies can improve performance due to FEXT between lines coupled to modems that support such technologies. For example, conventional vectoring systems can allow for FEXT cancellation between lines  104  coupled to the M modems  110  and for FEXT cancellation between lines  104  coupled to the N modems  112 . However, in cases such as that shown in  FIG. 1 , where lines  104  are in the same bundle  106  and/or where CO modems  120  and  122  are incorporated together in the same hardware having the same vector processing, the CO  102  must choose only one set of lines on which to perform vectoring (i.e. either the lines  104  coupled to the M modems  110  or the lines  104  coupled to the N modems  112 ). In other words, in cases such as that shown in  FIG. 1 , conventional vectoring technologies and systems cannot allow for FEXT cancellation to be simultaneously performed on lines  104  coupled to both types of CPE modems  110  and  112 , even though such CPE modems support vectoring. 
         [0017]    According to one aspect, embodiments of the invention allow for simultaneous FEXT cancellation between the lines  104  associated with the two different symbol-rate modems  110 ,  112  by creating two different vector-groups, one vector-group for performing FEXT cancellation on lines  104  coupled to modems  110 , and one vector-group for performing FEXT cancellation on lines  104  coupled to modems  112 . 
         [0018]    It should be noted that the symbol rates used by the modems  110 ,  112  of the different vector-groups do not need to be integer multiples. 
         [0019]    To illustrate aspects of the invention,  FIG. 2  shows an example of how vectoring is performed among lines coupled to G.Fast modems operating at a symbol rate of approximately 48 kHz. According to certain aspects, in embodiments of the invention, communication of tone-data in the system (e.g. from/to a vector control entity) during each symbol period is separated into uBands according to the amount of data associated with total numbers of tones and lines in the system. Accordingly, as shown in this example, each G.Fast symbol (i.e.  12   n ,  12   n+ 1, etc.) includes 2048 tones that are split into 128 microbands (i.e. uBands)  202 , with each uBand including 16 tones. Therefore, in order to perform vectoring on all G.Fast lines, FEXT cancellation data (e.g. 8×8 FEXT cancellation matrix data for an 8-port vector-group) must be generated at each G.Fast symbol period (i.e.  12   n ,  12   n+ 1, etc.) for all 2048 tones and all lines in the vector-group, and communicated to each of the G.Fast modems in the vector-group in batches associated with each of the uBands. 
         [0020]      FIG. 3  provides an illustration of how embodiments of the invention perform concurrent vectoring of a system having lines coupled to both VDSL2 modems  110  operating at 4 kHz symbol rates and G.Fast modems  112  operating at 48 kHz symbol rates such as that shown in  FIG. 1 . 
         [0021]    In this example, as in the previous example, each G.Fast symbol with 2048 tones is split into 128 uBands, with 16 tones in each uBand. Meanwhile, each VDSL2 symbol with 4096 tones at 4 KHz is split into 256 uBands, with 16 tones in each uBand to match the uBands of the G.Fast vectoring scheme. 
         [0022]    As mentioned above, in this example, the vectoring system in embodiments of the invention creates two different vector-groups, one vector-group for performing FEXT cancellation on lines  104  coupled to VDSL2 modems  110 , and one vector-group for performing FEXT cancellation on lines  104  coupled to G.Fast modems  112 . However, the vectoring system needs to operate at the higher symbol rate (i.e. 48 kHz) to accommodate the rate at which vector cancellation data needs to be generated for the G.Fast modems  122 . Accordingly, in this example, tone-data  302  for the VDSL2 modems is generated and split across two G.Fast symbol periods,  12   n  and  12   n+ 1, and spliced into the 128 G.Fast uBands as shown in  FIG. 3 , thereby concurrently performing vectoring for both vector-groups. In symbol periods  12   n+ 2 to  12   n +11, vectoring is performed only for the G.Fast vector-group. In an example where the total number of lines is 8, and where there are three VDSL2 lines and five G.Fast lines, this means that both 5×5 vectoring for the G.Fast group and 3×3 vectoring for the VDSL2 group is performed in G.Fast symbol periods  12   n  and  12   n+ 1, while only 5×5 vectoring is performed for the G.Fast vector group in symbol periods  12   n+ 2 to  12   n +11. 
         [0023]    It should be noted that G.Fast uses time division duplexing (TDD), while most other xDSL systems such as VDSL2 use frequency division duplexing (FDD). However, this is not an issue according to embodiments of the invention, where the frequencies used in the different systems are non-overlapping. 
         [0024]    A block diagram illustrating an example CO  102  for implementing aspects of the present invention is shown in  FIG. 4 . As shown, in addition to components illustrated in  FIG. 1 , CO  102  includes central controller  402 , bit mask  404 , vectoring engine  406  and vector control entity (VCE)  408 . 
         [0025]    Central controller  302 , vectoring engine  306  and VCE  308  can be implemented by processors, chipsets, firmware, software, etc. such as NodeScale Vectoring products provided by Ikanos Communications, Inc. Those skilled in the art will be able to understand how to adapt these and other similar commercially available products after being taught by the present examples. 
         [0026]    Meanwhile, CO transceivers  120  and  122  include conventional processors, chipsets, firmware, software, etc. that implement communication services such as those defined by VDSL2 and G.Fast, respectively. Further details thereof will be omitted for sake of clarity of the invention. It should be noted that CO transceivers  120  and CO transceivers  122  are shown separately for ease of illustration; however, it is possible that the same CO transceivers can include functionality for communicating both with VDSL2 CPE transceivers  110  and G.Fast CPE transceivers  112 , depending on the capabilities of the CPE modem connected at the downstream end, as learned in an initialization stage for example. It should be further noted that CO transceivers  120 ,  122  can include functionality for communicating with CPE transceivers that only support non-vectoring protocols such as ADSL2. Still further, although shown separately for ease of illustration, some or all of components  402 ,  404 ,  406 ,  408 ,  420  and  422  may be incorporated into the same chip or chipsets. 
         [0027]    According to aspects of the invention illustrated in  FIG. 4 , CO transceivers  120  and CO transceivers  122  are incorporated into the same device  420 , for example an 8-port transceiver chip which communicates with vectoring engine  406  to perform vectoring (i.e. FEXT cancellation). For example, as is known in the art, this includes performing vector decoding of downstream symbols in the frequency domain before they are converted to time domain signals transmitted on lines  404 . 
         [0028]    In operation, when a CPE modem  110 ,  112  first connects to one of lines  104 , controller  402  and the corresponding CO transceiver  120 ,  122  communicate the type of modem attached (i.e. VDSL2 or G.Fast), and controller  402  causes VCE  408  to update the vector-group associated with that type of modem to indicate the port of device  420  to which that modem  110 ,  112  is connected. As in the conventional manner, controller  102  then causes the VCE  408  to start learning down-stream coefficients for FEXT coupling other of lines  104  coupled to the same type of modem (i.e. VDSL2 or G.Fast) and update the associated channel matrix used by vectoring engine  406 . It should be noted that, although not shown in  FIG. 4 , VCE  408  can maintain two separate channel matrices for the two vector-groups. 
         [0029]    When FEXT coefficients have been learned, they are programmed into the precoder used by vectoring engine  406  by VCE  408 . During Showtime, for example as described above in connection with  FIG. 3 , G.Fast and VDSL2 communications by transceivers  120 ,  122  can then proceed with concurrent vectoring by VCE  408  and vectoring engine  406  of both G.Fast and VDSL2 communications according to the invention. 
         [0030]      FIG. 4  further illustrates an example embodiment where a bit mask approach is used to manage the two vector-groups. For example, assume that of a total of 8 lines coupled to transceiver chip  420 , there are five lines  104  coupled to G.Fast modems  112  and three lines  104  coupled to VDSL2 modems  110 . Accordingly, controller  402  sets the bit mask  404  for the two vector-groups (where G.Fast is 1 and VDSL2 is 0) to 11110001, where each bit identifies a port corresponding to one line in the 8-port system. 
         [0031]    Knowing the bit mask configuration, VCE  408  can thus manage concurrent vectoring of both of the G.Fast and VDSL2 vector groups. In the example shown in  FIG. 3 , in symbols  12   n+ 2 to  12   n +11, vectoring is performed only for the G.Fast vector-group (e.g. 5×5 vectoring in the above bit mask example). In symbols  12   n  and  12   n+ 1, concurrent vectoring is performed for both the G.Fast vector-group (e.g. 5×5 vectoring in the above bit mask example) and the VDSL2 vector-group (e.g. 3×3 vectoring in the above bit mask example). In embodiments using microbands according to the invention, this includes splicing VDSL2 tone-data communicated with vectoring engine  406  for the VDSL2 lines into the microbands together with G.Fast tone-data for the G.Fast during the first two G.Fast symbols  12   n  and  12   n+ 1, while only communicating G.Fast tone-data for the ten remaining G.Fast symbols  12   n+ 2 to  12   n +11 in each twelve symbol sequence. 
         [0032]    It should be noted that the principles of the invention are not limited to two vector-groups and/or two different types of vectoring protocols. For example, if there are modems associated with three different types of communication protocols that support vectoring, then three different vector-groups can be created, and a look-up table used instead of a bit mask. 
         [0033]      FIG. 5  is a flowchart illustrating an example methodology for performing concurrent vectoring of lines connected to modems operating at different symbol rates. 
         [0034]    As shown, in step S 502 , controller  402  determines when a new modem  110 ,  112  is connected to one of lines  104 . 
         [0035]    When a new modem is detected, in  5504  controller  402  determines the type of modem connected, such as VDSL2 or G.Fast. Controller  402  then causes the associated CO transceiver  120 ,  122  to initialize the modem, including causing the modem  110 ,  112  to use tones that do not overlap in frequency with tones used by the other types of modems. For example, where the types of modems can be either VDSL2 or G.Fast, which use 4096 and 2048 tones, respectively, controller  402  prevents overlapping frequencies in the two types of modems by setting the highest tone used by VDSL2 modems  110  to be lower in frequency than the starting tone used by G.Fast modems  112 . 
         [0036]    Next in S 506 , FEXT coefficients are learned by VCE  408  in the conventional manner using transceivers  120 ,  122  and the channel matrix for the associated type of modem (e.g. VDSL2 or G.Fast) is updated. 
         [0037]    Further in step S 508 , controller  402  updates the vector-group associated with the type of modem that has newly connected so VCE  408  knows how to control vectoring among lines  104 . For example, this can include communicating to VCE  408  the port of chip  420  to which the modem is connected. As shown, step S 508  can include setting a bit mask  404  used by VCE  408  to control concurrent vectoring. 
         [0038]    In step S 510 , with the newly updated vectoring parameters, concurrent vectoring of communications with modems connected to lines  104  is performed as described in more detail above, and as configured as described in the preceding steps. 
         [0039]    Although the present invention has been particularly described with reference to the preferred embodiments thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the invention. It is intended that the appended claims encompass such changes and modifications.