Abstract:
Methods, systems, devices, and computer readable medium for processing data in a digital subscriber line environment are disclosed. In one aspect methods include establishing a first data channel in a first system utilizing a first frequency band. Methods also include conveying, for a second system that establishes a second data channel over a second frequency band, handshake information using the first system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) of Patent Application No. EP14167069 entitled “Data processing in a digital subscriber line environment,” filed May 5, 2014, which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    This document relates to data processing in a digital subscriber line environment. DSL or xDSL is a family of technologies that provide digital data transmission over the wires of a local telephone network. 
         [0003]    xDSL technologies, e.g., ADSL G.992.1, ADSL2plus G.992.5, VDSL2 G.993.2, vectored VDSL2 G.993.2 and G.993.5 (“G” referring to an ITU-T recommendation), are applied for high speed Internet services. During network upgrades, new generation technology (e.g., VDSL2 or vectored VDSL2) may be deployed to provide higher data rates to subscribers. While typical downstream service rates for ADSL2plus are up to 16 Mbit/s, vectored VDSL2 can provide 100 Mbit/s. In case new systems or technology generations are introduced, it is beneficial that the new service can coexist with legacy technology and legacy subscribers without any detrimental impact on the service quality (e.g., data rate). 
       SUMMARY 
       [0004]    In order to overcome this problem, a method is provided for processing data in a digital subscriber line environment comprising at least one network element, wherein the network element includes a first system utilizing a first frequency band and a second system utilizing a second frequency band, the method comprising the step: conveying a handshake information of the second system via the first system. 
         [0005]    This approach allows for conducting a handshake for the second system. This handshake is an adapted (or modified) handshake compared to the handshake according to G.994.1. 
         [0006]    The first system may be a low-frequency (LF) system and the second system may be a high frequency (HF) system. This, however, is only an option and the first and second systems may utilize frequency bands without such limitation. 
         [0007]    This solution has the advantage that the handshake of the second system does not require sending tones that fall in the range of the first frequency band and avoids any disturbance of the first system by the second system. Also, the solution presented allows the adapted handshake to be fast, because the infrastructure of the first system may be used. 
         [0008]    Each of the first and second system may include a transceiver that is arranged for operating in the respective first or second frequency band. 
         [0009]    In an embodiment, the handshake information includes at least one of the following: a handshake message based on or equivalent to G.994.1, a message used for handshake purposes, a message used for handshake purposes to determine a communication capability of the second system, a message of a handshake protocol, or at least one frequency used for conducting a handshake as set forth in G.994.1. 
         [0010]    In another embodiment, the second frequency band is at least partially or completely above the first frequency band. Hence, the first system may operate on lower frequencies as does the second system. The first frequency band may in particular cover all or a substantial amount of frequencies that are used as handshake tones pursuant to G.994.1. 
         [0011]    It is noted that G.994.1 references an ITU-T recommendation “Handshake procedures for digital subscriber line transceivers”. Hence “G.994.1” may be understood as a recommendation directed to handshake procedures for DSL systems, in particular DSL transceivers. 
         [0012]    In a further embodiment, the second frequency band is at least partially or completely below the first frequency band. It is noted that the first frequency band and the second frequency band may include disjoint (e.g., separate) frequencies or frequency ranges. As an option, the first frequency band and the second frequency band may at least partially include overlapping frequencies. 
         [0013]    In some implementations, methods further include conveying the handshake information of the second system via at least one frequency of the first system. Hence, the second system may use the first system as a proxy for conducting a(n adapted) handshake, in particular for sending tones as defined in G.994.1 
         [0014]    In some implementations, methods further include conveying the handshake information of the second system via a data channel of the first system. Hence, the data channel of the (already running first system) can be used for conducting the adapted handshake process of the second system. The data channel may be a communication channel that may be available after the first system entered showtime. 
         [0015]    In some implementations, the method includes, prior to using the data channel of the first system, conducting a handshake of the first system based on G.994.1 and initializing the first system. As a result of the initialization, the first system may reach showtime. 
         [0016]    In some implementations, methods further include conveying the handshake information of the second system across the first system via Ethernet frames, e.g., HDLC frames that are encapsulated in the Ethernet frames. 
         [0017]    In some implementations, the first system and/or the second system is one of the following an ADSL system, a VDSL system, a vectored xDSL system, or a G.fast system. 
         [0018]    It is noted that xDSL may refer to any DSL system. The VDSL system includes also VDSL-alike systems, e.g., VDSL2. Also, different profiles may be used for each of the xDSL systems, e.g., VDSL2 profile 17a, VDSL profile 30a, etc. The same applies for ADSL systems. It is further noted that the examples described herein may in particular use vectored systems. 
         [0019]    In some implementations, the network element is a de-centrally deployed device, such as a customer premises equipment, or a central device, such as a digital subscriber line access multiplexer (DSLAM). 
         [0020]    A centralized unit may be any entity comprising at least one modem, in particular several modems, to be connected to a modem of a decentralized unit. The centralized unit may be a DSLAM or a central office (CO). The decentralized unit may be a customer premises equipment (CPE). According to an embodiment, the DSLAM may be deployed at a central office or at a cabinet. 
         [0021]    In some implementations, methods further include initializing the second system. As a result of the initialization, the first system may enter showtime. 
         [0022]    In some implementations, a device includes a first system utilizing a first frequency band; a second system utilizing a second frequency band; and a processing unit that is arranged for conveying a handshake information of the second system via the first system. 
         [0023]    It is noted that the steps of the method stated herein may be executable on this processing unit or device as well. It is further noted that said processing unit can include at least one, in particular several means that are arranged to execute the steps of the method described herein. The means may be logically or physically separated; in particular several logically separate means could be combined in at least one physical unit. 
         [0024]    Said processing unit may include at least one of the following: a processor, a microcontroller, a hard-wired circuit, an ASIC, an FPGA, a logic device. In some implementations, the first system includes a first transceiver that is connected via a low pass filter to a line; and the second system includes a second transceiver that is connected via a high pass filter to the line. 
         [0025]    The low pass filter and the high pass filter may be deployed in a diplexer. The cutting frequency of the low pass filter may substantially correspond to the cutting frequency of the high pass filter. In particular, based on filters, the transceivers may utilize different frequency bands over the line. 
         [0026]    In some implementations, the device is a network element, in particular a de-centrally deployed device, in particular a customer premises equipment, or a central device, in particular a digital subscriber line access multiplexer. 
         [0027]    In some implementations, a system includes two devices, such as two network elements, e.g., a CPE and a DSLAM, wherein the system is arranged to conduct a handshake process based on G.994.1 between the first systems of the two devices and to conduct an adapted handshake based on G.994.1 by exchanging the handshake information between the second systems 
         [0028]    In some implementations, a computer program product directly loadable into a memory of a digital computer and executable by one or more devices, includes software code portions that upon execution cause the one or more devices to perform operations described herein. 
         [0029]    In some implementations, computer-readable medium, e.g., storage of any kind, is encoded with computer-executable instructions that upon execution cause a computer system to perform operations described herein. 
         [0030]    In some implementations, a communication system includes at least one device as described herein. 
         [0031]    In some implementations, a device includes a first system utilizing a first frequency band; a second system utilizing a second frequency band; and means for conveying a handshake information of the second system via the first system. 
         [0032]    Problems solved by (and/or advantages of) the subject matter of this application include providing an efficient solution for conducting a handshake process using LF systems and HF systems in an xDSL environment that may utilize a single line. 
         [0033]    The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a schematic block diagram of two network elements having HF transceivers that communicate with each other via LF transceivers to provide for an adapted handshake. 
           [0035]      FIG. 2  shows a frame structure according to G.994.1. 
           [0036]      FIG. 3  shows a block diagram illustrating steps for several xDSL technologies deployed in a single network element reaching showtime. 
           [0037]      FIG. 4  shows a DSLAM with the units depicted and explained with regard to  FIG. 1 . 
           [0038]      FIG. 5  shows a block diagram illustrating steps for a HF system using a LF system as a proxy. 
       
    
    
       [0039]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0040]    When service providers deploy vectored VDSL2, all DSL lines that can potentially generate FEXT in vectored bands may have to be considered during crosstalk cancellation. Hence, if a VDSL2 profile 30a shall be deployed to provide new premium services with higher data rates in an environment where vectored VDSL2 profile 17a was already deployed, both systems share the same frequency bands up to 17.6 MHz. In case crosstalk from VDSL2 profile 30a loops that is coupled into the vectored VDSL2 profile 17a system is not cancelled, the performance of the vectored system will be severely degraded. Crosstalk cancelation between the VDSL2 profile 17a and VDSL2 profile 30a systems is complex and difficult to realize due to the different tone spacings (4.3125 kHz versus 8.625 kHz) and symbol rates (4k versus 8k). Therefore, in such situation, the VDSL2 profile 30a system cannot be easily deployed to provide higher data rates. 
         [0041]    When two VDSL2 systems share the same line during showtime, there is still the problem of successfully conducting the handshake process based on G.994.1 at the beginning of the initialization. According to ITU-T, showtime is a state that is reached after the initialization procedure has been completed. 
         [0042]    The known handshake process uses dedicated tone sets to start the communication between two transceivers. These tone sets consist of two or three upstream and downstream subcarriers that are located in the lower up- and downstream band. Usually, the applied tone set is specific to a region or network and is chosen according to applied band plans (e.g., “B43” in Germany). This universal handshake process is independent of the type of xDSL, even G.fast (based on, e.g., ITU-T G.9700 and/or G.9701) uses the same handshake process and tone sets. The highest specified tone set is “V43” using the following frequencies: 
         [0043]    Downstream: 4.0710 MHz; 4.1917 MHz; 4.3082 MHz; and 
         [0044]    Upstream: 1.1083 MHz; 1.6517 MHz; 2.2037 MHz. 
         [0045]    Also, during handshake, a capabilities list may be communicated or exchanged and/or it may be agreed on a common mode for training and operation. 
         [0046]    Hence, if a VDSL2 profile 17a system is considered for a low-frequency (LF) transceiver, all tone sets defined in G.994.1 are below 17.6 MHz and are hence inside the bands dedicated to the LF system. The high frequency (HF) system (e.g., the VDSL2 profile 30a) uses the same frequencies for its handshake process. Hence, the handshake of the HF system interferes with the LF system in case both systems use one physical connection. This problem exists for any HF channel technology that uses the handshake process as defined in or based on G.994.1 or similar low-frequency signaling for the start of the initialization. 
         [0047]    Examples provided herein suggest that a HF transceiver of a network element, e.g., a DSLAM or a CPE, does not use the handshake process according to G.994.1 (also referred to as G.hs procedure). In other words, an adapted handshake may be applied for the HF transceiver that may not use tone sets of a low frequency band. 
         [0048]    In some implementations, at least one LF transceiver starts its handshake process based on G.994.1 (i.e. in a way as defined in the standard using tone sets (e.g., “B43”) that fall within the frequency band of the LF transceiver). Then, the at least one LF transceiver will conduct its initialization and it may reach the showtime state. When showtime is reached, a data channel between the two LF transceivers is established and such data channel can be used to convey user data or other data between the network elements, e.g., between the DSLAM and the CPE. 
         [0049]    This data channel is used to perform the transaction required for the adapted handshake process of the HF transceiver. Advantageously, such an adapted handshake process of the HF transceiver may not require using tone sets defined in G.994.1. Instead, equivalent messages between the HF transceivers can be exchanged using the service of the data channel provided by the LF transceivers. 
         [0050]    The LF transceiver may multiplex such messages with its ordinary data stream and pass it to the other side. The LF transceiver at the other side may extract the messages comprising handshake data from the data stream received and it may forward the messages to the HF transceiver of the network element. Responses to handshake messages may use the same process in reverse direction. When the handshake process is completed, the HF transceivers may start their normal initialization process as defined in the corresponding recommendation (e.g., G.993.2 or G.9701). 
         [0051]    This approach is applicable for any HF channel technology that uses handshake messages or similar low-frequency signaling before starting the initialization (e.g., for VDSL2 or G.fast). The HF channel technology may in particular utilize vectoring. In this regard, the “handshake process” may refers to an “ITU-T G.994.1 handshake phase of the initialization procedure”, whereas the initialization refers to the steps conducted after such “handshake process” until the respective system enters showtime. For example, initialization may include a channel discovery phase and a channel analysis and exchange phase. 
         [0052]      FIG. 1  shows a schematic block diagram of two network elements, i.e. a DSLAM  101  and a CPE  102 , which are connected via a line  104  (i.e. a xDSL line). An Ethernet connection  103  is fed to a bonding unit  106  of the DSLAM  101 , to which a LF transceiver  107  and a HF transceiver  108  are connected. The LF transceiver  107  and the HF transceiver  108  are connected to the line  104  via a diplexer  109 . The line  104  is connected to a diplexer  110  of the CPE  102 , to which a LF transceiver  111  and a HF transceiver  112  are connected. The LF transceiver  111  and the HF transceiver  112  are connected to an Ethernet connection  105  via a bonding unit  113 . 
         [0053]    It is noted that the Ethernet connection  103  may be supplied via an optical fiber; in such scenario, an optical signal conveyed via said fiber may be fed to a central card that is connected via a backplane to a line card. The central card may convert the optical signal into an electrical signal for processing at the line card. In the opposite direction, the electrical signal is conveyed via the line card to the central card, converted to the optical signal and transmitted via the fiber. 
         [0054]    The bonding unit may include a bonding function that may (at least partially) be implemented on the line card, on the central card or separate to the DSLAM or the CPE, e.g., within the network to which the Ethernet connection  103  may be connected. 
         [0055]    The bonding unit may utilize “Ethernet in the First Mile” according to or based on IEEE P802.3ah bonding, link aggregation based on IEEE 802.3ad, G.bond according to G.998.x, ATM (Asynchronous Transfer Mode) bonding or PTM (Packet Transfer Mode) bonding. 
         [0056]    The DSLAM  101  can be connected to the CPE  102  via at least one line  104 , in particular via several physical lines, wherein each line may include two wires. The LF transceiver  107  of the DSLAM  101  may communicate with the LF transceiver  111  of the CPE  102  and the HF transceiver  108  of the DSLAM  101  may communicate with the HF transceiver  112  of the CPE  102 . 
         [0057]    The LF transceivers  107 ,  111  may be VDSL2 profile 17a transceivers. The HF transceivers  108 ,  112  may be any transceiver utilizing a frequency band above 17.6 MHz (e.g., VDSL2 profile 30a transceivers with a high pass band plan or G.fast transceivers). 
         [0058]      FIG. 1  in particular visualizes how a combination of LF transceivers  107 ,  111  and HF transceivers  108 ,  112  in different network elements  101 ,  102  may be used to perform a start-up procedure. Such start-up procedure may in particular not involve the HF transceivers  108 ,  112  using handshake tones according to G.994.1. 
         [0059]    The LF transceivers  107 ,  111  may conduct the handshake process in an common way using handshake messages and an appropriate tone set (for example, B43) according to G.994.1. When showtime is reached between the LF transceivers  107 ,  111 , this may be indicated to the HF transceiver  108  at the DSLAM  101  (CO side). 
         [0060]    The LF transceiver  111  at the CPE  102  may also signal to its HF transceiver  112  that the data channel of the LF system has been established. Now, the adapted handshake process for the HF transceivers may commence utilizing the already established data channel of the LF system. Hence, there is no need for a G.994.1 equivalent start-up procedure (C-TONES, R-TONE1, . . . ), so the HF transceivers  108 ,  112  may directly start exchanging G.994.1 equivalent messages via the data channel of the LF system (in  FIG. 1  indicated as connection  114 ). 
         [0061]      FIG. 2  shows a frame structure according to G.994.1. This corresponds to a HDLC frame structure, wherein each frame begins and ends with a standard HDLC flag octet (“01111110”). For the reason of an efficient adaptation to provide the adapted handshake process as suggested herein, the content of such HDLC frame can be encapsulated into an Ethernet frame that is passed between HF transceivers via the LF data channel. In order to identify packages that are directed to the HF transceivers, unique MAC addresses may be used that are dedicated to the individual transceivers (e.g., for the start-up process). Hence, the specific Ethernet frames may be filtered out from user traffic and the filtered frames may be forwarded to the respective transceiver identified by its MAC address (e.g., via a management interface). 
         [0062]    Such an Ethernet frame may include a destination MAC address (MAC address of the G.994.1 process of the destination HF transceiver), a source MAC address (MAC address of the G.994.1 process of the source HF transceiver), a length field (as per the IEEE 802.3 MAC frame format), a LLC PDU header coding for the SNAP protocol (3 bytes, AA-AA-03), a SNAP PDU header containing a 3-octet organization code and a 2-octet Protocol ID for a private protocol, a Protocol Payload Data (G.994.1 HDLC frame including Flags, Message segment, FCS), and a standard Ethernet 4-byte FCS (as per the IEEE 802.3 Ethernet frame FCS). 
         [0063]    The HF transceivers  108 ,  112  may then exchange G.994.1 messages using the Ethernet frames described above. The G.994.1 protocol may remain unchanged including ACK and NACK messages. 
         [0064]    For example, in case the HF transceiver  112  at the CPE  102  wants to send a Capabilities List and Request (CLR) message to the corresponding HF transceiver  108  at the DSLAM  101 , it may encode the CLR message according to G.994.1, wherein each HDLC frame is put in a separate Ethernet frame as described above. The HF transceiver  112  then forwards the Ethernet frames to the LF transceiver  111 , which multiplexes the packets with ordinary user data and transmits them via the data channel to the LF transceiver  107  of the DSLAM  101 . 
         [0065]    The LF transceiver  107  forwards all data received to its network processor. The network processor identifies the packets based on the specific MAC address. The destination MAC address allows the network processor to determine the destination HF transceiver  108  and the network processer may then forward the respective frame (with the destination MAC address of the HF transceiver  108 ) to the HF transceiver  108 . 
         [0066]    The HF transceiver  108  decodes the G.994.1 content of the Ethernet frame and prepares a Capabilities List (CL) response. The response Ethernet frames are passed via the network processor of the DSLAM  101  to the LF transceiver  107 , which sends it to the LF transceiver  111  of the CPE  102 . The network processor of the CPE  102  identifies and forwards the frame from the LF transceiver  111  to the HF transceiver  112 . After the adapted handshake is concluded, the initialization process between the HF transceivers  108  and  112  utilizing the respective frequencies of the HF transceivers  108 ,  112  may begin. After such initialization process, the HF transceivers  108 ,  112  reach showtime. 
         [0067]      FIG. 3  shows a block diagram illustrating steps for several xDSL technologies (in this example a LF system and a HF system) deployed in a single network element reaching showtime. In a step  301 , the LF system conducts the handshake process according to G.994.1 using the tones as defined in G.994.1. In a step  302 , the LF system is initialized and thereinafter reaches showtime. In a step  303 , the data channel of the LF system (which is available when the LF system is in showtime) is used for an adapted handshake of the HF system. This is achieved by conveying messages equivalent to the messages described in or based on G.994.1 via the data channel of the LF system from one HF system to another HF system (of a different network element). Based on the messages exchanged between the HF systems, the HF system is able to conclude the adapted handshake process. Then, in a step  304 , the HF system is initialized and may enter showtime. 
         [0068]    This approach has the advantage that no significant (e.g., less than a specified amount of) disturbance due to FEXT or NEXT occurs. Also, the diplexer design is easier and more cost-efficient, because there is no need for passing handshake tones through specific filters. Furthermore, no band pass filters (BPF) are needed. It is also an advantage that the handshake process of the HF system is faster, because of the high data rate of the already established data channel provided by the LF system. 
         [0069]      FIG. 4  shows a DSLAM  101  with the units depicted and explained with regard to  FIG. 1  above, where the diplexer includes an efficient filter solution. 
         [0070]    The LF transceiver  107  is connected via a  100  Ohm line to a low pass filter (LPF)  401  with a cutoff frequency amounting to 17.6 MHz. The HF transceiver  108  is connected via a 100 Ohm line to a high pass filter (HPF)  402  with a cutoff frequency amounting to 17.6 MHz. The outputs of the LPF  401  and the HPF  402  are connected to the line  105 . The LPF  401  and the HPF  402  are part of the Diplexer  109 . 
         [0071]    According to another example, G.fast may be launched from distribution points (DPs) close to the subscriber or from a basement of a building. In a migration scenario, merely G.fast is used. However, it would be beneficial to re-use (existing) hardware (CPEs) comprising a G.fast transceiver (as HF system) and a transceiver of a LF system. Without supporting the LF system, however, there is no handshake for the LF system and no LF system that could reach showtime and supply a data channel for an adapted handshake of the G.fast system. Utilizing a network element that is configured for the adapted handshake of the HF system as described above, the HF system may not be able to conduct a handshake using the tones set forth in G.994.1, because such tones would not get passed the HPF  402  of the diplexer  109 . 
         [0072]    However, the HF system G.fast can run the adapted handshake without the need of an active LF data channel by utilizing the LF transceiver as a proxy for exchanging handshake messages according to G.994.1. 
         [0073]    In such case, the LF transceiver of the CPE may only be used for the handshake process. When the LF transceiver at the CPE detects handshake tones or receives G.994.1 messages it will pass this information directly to the HF transceiver (the G.fast transceiver in this example) via the same packet mechanism described above. The handshake response message from the HF transceiver may be passed via CPE internal data connections to the LF transceiver and the LF transceiver may transmit the messages via G.994.1 tone-based modulation to the G.fast transceiver at the DP. After the handshake process of the HF system using the LF transceiver as a proxy is finished, the LF transceiver may shut down and the HF transceiver may continue with its initialization. 
         [0074]      FIG. 5  shows a block diagram illustrating steps for a HF system deployed in a network element together with a LF system, wherein the LF system is used by the HF system as a proxy. In a step  501 , the HF system conducts an adapted handshake process using the LF system as a proxy for conveying tones as set forth in G.994.1. Hence, the LF system is used by the HF system to convey the handshake messages. In a step  502 , after the adapted handshake, the LF system may be shut down, the HF system is initialized and may thereinafter reach showtime. 
         [0075]    In this scenario, the LF system is not initialized and does not reach showtime. Only, the handshake capability of the LF system is used by the HF system to conduct the adapted handshake of the HF system even without a data channel of the LF system. 
         [0076]    Although various embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. It will be obvious to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. It should be mentioned that features explained with reference to a specific figure may be combined with features of other figures, even in those cases in which this has not explicitly been mentioned. Further, the methods of the invention may be achieved in either all software implementations, using the appropriate processor instructions, or in hybrid implementations that utilize a combination of hardware logic and software logic to achieve the same results. Such modifications to the inventive concept are intended to be covered by the appended claims. 
       LIST OF ABBREVIATIONS 
       [0000]    
       
         ACK Acknowledgement 
         ADSL Asynchronous Digital Subscriber Line 
         BPF Band pass filter 
         CL Capabilities List 
         CLR Capabilities List and Request 
         CO Central Office 
         CPE Customer Premises Equipment 
         DP Distribution point 
         DSL Digital Subscriber Line 
         DSLAM DSL Access Multiplexer 
         FCS Frame Check Sequence 
         FEXT Far-end crosstalk 
         HDLC High-Level Data Link Control 
         HF High Frequency 
         HPF High pass filter 
         LF Low Frequency 
         LLC Logical Link Control 
         LPF Low pass filter 
         NACK Negative Acknowledgement 
         NEXT Near-end crosstalk 
         PDU Protocol Data Unit 
         SNAP Subnetwork Access Protocol 
         VDSL Very High Speed Digital Subscriber Line