60/344,486, filed on November 9,2001 and entitled"Installation Mode For DSL Transceivers, "which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION The present invention generally relates to data communication systems and, more particularly, to a system and method for initiating communication between transceivers.

BACKGROUND OF THE INVENTION The transmission of voice and data at faster rates and in larger volumes is in increasing demand. One solution to fulfilling these demands is digital subscriber line (DSL) technology. DSL technology has been introduced into the field of broadband networking, among other reasons, to overcome issues faced by traditional voice-band technology. Such issues include, but are not limited to, bandwidth limitations. Multiple DSL technologies exist including, but not limited to, rate adaptive DSL (RADSL), symmetric DSL (SDSL), multi- rate SDSL (M/SDSL), high bit-rate DSL (HDSL), very high bit-rate DSL (VDSL), and asymmetric DSL (ADSL).

ADSL technology utilizes the infrastructure already in place in a public switched telephone network (PSTN), including copper loops, constructed of copper wires, between a customer premise and a central office. Advantageously, ADSL technology does not require replacement of network equipment such as routers, switches, firewalls and Web servers, which are commonly used in today's paradigm for broadband access.

A DSL modem provides communication capabilities for the transmission and reception of information utilizing, for example, ADSL technology. Typically, discrete multi- tone (DMT) line coding is utilized by the DSL modem for the transmission of DMT symbols from a source to a destination. Several DMT communication schemes, or sometimes phrased, line coding techniques, are known in the art, each of which has benefits and drawbacks based on several variables, such as bit rate, error rate, and reach. Below are a few communication schemes that are well known in the art.

A first set of DMT communication schemes is defined by the G. 992 Annex A ADSL recommendation made by the International Telecommunication Union (ITU-T). In general, Annex A is targeted for the North American, Asian, and part of the European markets. Two general types of communication schemes in Annex A are Frequency Division Multiplexing (FDM) and Echo Cancelled (EC). In FDM mode, the downstream and upstream signals use separate frequency bands. The usable upstream band is from 0-138kHz and the downstream band is defined from 138kHz-1. 104MHz. In EC mode, the downstream signals can coexist with the upstream signals in the same band, thus having more downstream bandwidth. So, in EC mode, the downstream signal can use OHz-1. 104MHz, while the upstream band is the same as in FDM mode. The advantage of EC techniques over FDM techniques obviously being increased downstream bandwidth. The disadvantage being that, due to the overlap in the 0-138kHz range, cross-talk can occur and necessary resources are required to combat this.

There are basically two leading technologies for DSL in Japan. Another set of DMT communication schemes is defined by Annex C of the G. 992 recommendation and is based upon special network characteristics in Japan. These factors include a very large existing base of ISDN users, where ISDN refers to Time Compression Multiplexed (TCM) ISDN-a type of"ping-pong"time-division transmission with a high transmit signal level and poor low-pass filter that causes a significant level of cross-talk interference. In addition to the existence of TCM-ISDN, paper-insulated cables are used, and this causes higher attenuation at high frequencies. The combination of these factors creates a situation where high levels of interference occur if Annex A ADSL is used, rendering this type of device unusable on many copper loops. Annex C employs sophisticated techniques of synchronization and noise margin calculation (to alleviate the detrimental effects of interference and attenuation) to meet the requirements for a high level of quality and efficiency for ADSL in Japan.

Within Annex C, there are two types of transmission : Far End Cross-Talk Bit Map (FBM) and Dual Bit Map (DBM) where FBM is typically understood to be the more simple of the two. FBM transmits only during the Far End Cross-Talk (FEXT) cycle to match transmission direction of ISDN. The limitation of FBM is that the bit rate is limited because it uses only 37% of the symbols. This translates to data rates of only a little more than 3 Mbps downstream for full rate ADSL.

The second type of transmission, DBM, is more difficult to implement since some transmission is on the NEXT cycle. The difficulty is worthwhile to overcome, however, because in lines without too much ISDN noise, rates up to Annex A levels can be achieved.

Annex H of the G. 992 recommendation is another communication scheme and is similar to Annex C FBM, except that it is symmetric and transmits only during the FEXT cycle, while using all available frequency bins. This technology requires a digital signal processing (DSP) core powerful enough to handle up to 255 bins upstream and downstream.

The benefit of the line coding technique of Annex H is clear-it provides DSL for Japanese markets and can achieve rates higher than Annex C FBM because more downstream bins are used.

Thus, several different communication schemes currently exist, each with its own advantages and drawbacks. As is known however, loop conditions vary significantly. A communication scheme which performs best for one loop, may be outperformed by a different scheme for another loop. Unfortunately, loop characteristics (of the same loop) may change over time, such that a communication scheme, or line coding technique, which performs best one day, may be outperformed by another on another day.

Accordingly, it is desired to find a solution to these problems.

SUMMARY OF THE INVENTION The present invention is directed to methods, systems, devices, and programs for initiating and synchronizing communication between transceivers, such that the best communication scheme is implemented based on the conditions of the loop. The transceivers can communicate in any of a plurality of communication schemes. A representative method includes: detecting a remote transceiver communicatively coupled with a central office transceiver; determining a preferred communication scheme to be utilized by the central office transceiver and the remote transceiver; training the central office transceiver and the remote transceiver to communicate in the preferred communication scheme; and initiating communication between the central office transceiver and the remote transceiver.

Another embodiment may be interpreted as a method for operating a first communication transceiver, wherein the first communication transceiver can communicate in a plurality of communication schemes. The method includes: starting up operation in an installation mode such that an order of preference of the plurality of communication schemes is established; switching to a retraining mode, if necessary, to retrain in a selected communication scheme as dictated by the order of preference of the plurality of communication schemes; and communicating with a second communication transceiver in the selected communication scheme.

Another embodiment may be interpreted as a communication system. The system includes a first transceiver configured to communicate in any of a plurality of communication schemes and a second transceiver communicatively coupled to the first transceiver, wherein the second transceiver is configured to communicate in at least one of the plurality of communication schemes. The first and second transceivers are further configured to negotiate a preferred communication scheme. The first and second transceivers are also configured to, if necessary, train to communicate in the preferred communication scheme, and initialize and synchronize communication in the preferred communication scheme.

Another embodiment may be interpreted as a first transceiver that includes means for communicatively coupling to a second transceiver and means for negotiating a preferred communication scheme, wherein the first transceiver is configured to communicate in any of a plurality of communication schemes and the second transceiver is configured to communicate in at least one of the plurality of communication schemes. The first transceiver also includes means for training the first transceiver and the second transceiver to communicate in the preferred communication scheme and means for initializing and synchronizing communication in the preferred communication scheme.

Yet another embodiment may be interpreted as a program for initiating and synchronizing communication between a central office transceiver and a remote transceiver, wherein the central office transceiver is configured to communicate in any of a plurality of communication schemes and the remote transceiver is configured to communicate in at least one of the plurality of communication schemes, wherein the program is stored on a computer readable medium. The program includes logic configured to detect the remote transceiver communicatively coupled with the central office transceiver, logic configured to determine a preferred communication scheme to be utilized by the central office transceiver and the remote transceiver, logic configured to train the central office transceiver and the remote transceiver to communicate in the preferred communication scheme, and logic configured to initiate communication between the central office transceiver and the remote transceiver using the preferred communication scheme.

BRIEF DESCRIPTION OF THE DRAWINGS The invention can be better understood with reference to the following drawings. The components of the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like referenced numerals designate corresponding parts throughout the several views.

FIG. 1 is a block diagram illustrating a communication system in which the present invention may be provided.

FIG. 2 is a block diagram further illustrating a connection between an xDSL modem of the central office and an xDSL modem of the customer premise, both of FIG. 1.

FIG. 3 is a flow chart illustrating a method for initiating and synchronizing communication between a central office transceiver and a remote transceiver as performed by embodiments of the present invention.

FIG. 4 is a flow chart illustrating a general method of operation of a communication transceiver in accordance with embodiments of the present invention.

FIG. 5 is a flow chart illustrating a method for installing communication as performed during the installation mode of the method of operation of FIG. 4.

FIG. 6 is a flow chart illustrating a method for retraining as performed during the retraining mode of the method of operation of FIG. 4.

FIG. 7 is a flow chart illustrating a general method for determining a preferred communication scheme in accordance with embodiments of the present invention.

FIG. 8 is a flow chart illustrating a general method for synchronizing and training a remote transceiver to communicate in a preferred communication scheme in accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the drawings, wherein like referenced numerals designate corresponding parts throughout the drawings, FIG. 1 is a block diagram illustrating a communication system 12 in which embodiments of the present invention may be provided.

Specifically, FIG. 1 illustrates communication between a central office 20 and a customer premise 22 by way of a local loop 24. While the customer premise 22 may be a single dwelling residence, a small business, or other entity, it is generally characterized as having POTS equipment, such as a telephone 26, PSTN modem 27, fax machine (not shown), etc.

The customer premise 22 may also include an xDSL communication device, such as an xDSL modem 28, comprising an ADSL interface card 100A for handling ADSL services. When an xDSL service is provided, such as, but not limited to, ADSL, a POTS filter 30 may be interposed between the POTS equipment 26 and the local loop 24. Of course, the POTS filter 30 need not be provided when G. Lite, ADSL. Lite, or other similar communication schemes are used. As is known, the POTS filter 30 includes a low-pass filter in order to filter high frequency transmissions from the xDSL communication device 28 and protect the POTS equipment.

It should be noted that although the present disclosure is made with reference to ADSL technology, one skilled in the art will appreciate that other DSL technologies requiring different modulation and communication schemes could be used.

Additional circuitry is provided at the central office 20. Generally, an xDSL modem 40 containing line-interface circuitry is provided for electrical connection to the local loop 24.

In fact, multiple modems may be provided 40,42 to serve a plurality of local loops 24. In the same way, additional circuit cards are typically provided at the central office 20 to handle different types of services. For example, an integrated services digital network (ISDN) interface card (not shown) and other circuit cards, for supporting similar and other communication services, may be provided. Particular to the present synchronization system, an ADSL interface card 100B may also be provided at the central office 20, also for handling ADSL services. It should be noted that the ADSL interface card 100A (or 100B) might alternatively be located exclusively at the central office 20, or exclusively at the customer premise 22.

A digital switch 50 is also typically provided at the central office 20 and is disposed for communication with each of the various modems 40 and 42. On the outgoing side of the central office 20 (i. e., the side opposite the various local loops), a plurality of trunk cards 52, 54,56 are typically provided. Typically, these cards have outgoing lines that support numerous multiplexed transmissions and are typically destined for other central offices or long distance toll offices.

FIG. 2 is a block diagram further illustrating a connection between the xDSL modem 40 of the central office 20 (hereinafter, the CO modem 40) and the xDSL modem 28 of the customer premise 22 (FIG. 1) (hereinafter, the CP modem 28). Transmission of data may be directed from the customer premise 22 to the central office 20, from the central office 20 to the customer premise (CP) 22, or in both directions at the same time via the local loop 24. In general each modem 28 and 40 may include a processor 120, memory 110, and an ADSL interface card 100 all coupled via a local interface 130. The CO modem 40 may include a network interface 140 that facilitates communication with the digital switch 50 (See FIG. 1) of the CO 20. Similarly, the CP modem 28 may include an I/O interface 150 which facilitates communication to a computing device, such as a PC. A home local area network (LAN) (not shown) may be connected to the CP modem 28, in which case the I/O interface 150 may interface communication between the appropriate hardware (i. e. servers or routers and the CP modem 28) with the LAN. In the discussion that follows, when similar elements of the two modems are mentioned, one reference number will be named. When an element from one of the modems is mentioned, a reference number with a letter will be named. For example, when referring to both local interfaces 130A and 130B, reference number 130 will be used. When referring to only one of the local interfaces, either 130A or 130B will be used. Those with'A'will represent the CP modem 28 components and those with'B'will represent the CO modem 40 components.

The local interface 130 can be, for example, but not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface 130 may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Further, the local interface 130 may include address, control, and/or data connections to enable appropriate communications among the aforementioned components.

The processor 120 is preferably a hardware device for executing software or firmware, particularly that stored in memory 110. The processor 120 can be any custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the modems 28 or 40, a semiconductor based microprocessor (in the form of a microchip or chip set), a macro processor, or generally a device for executing software instructions.

The memory 110 can include any one or combination of volatile memory elements (e. g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)) and nonvolatile memory elements (e. g., hard disk drive, tape, NVRAM, CDROM, etc.).

Moreover, the memory 110 may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory 110 can have a distributed architecture, where various components are situated remote from one another, but can be accessed by the processor 120.

The memory includes appropriate resources or drivers 111 for various communication schemes. For example, the necessary drivers to provide for Frequency Division Multiplexed (FDM) Discrete Multi-Tone (DMT) modulation, may be stored in the memory 110. The CP modem 28 may include the similar drivers 111A as that of the CO modem 40 for corresponding communication schemes. In other instances, the CP modem 28 may be capable of communicating in another set of communication schemes as the CO modem 40, and so a different set of drivers 111A will be included in the memory 110A of the CP modem 28 than that of the CO modem 40.

Also stored in the memory 110 of both modems 28 and 40 is a program 115 for determining a preferred communication scheme and subsequently establishing and synchronizing communication between the modems 28 and 40. The program 115 may be a segmented, modular program and so segments 116-119 of the program 115 may be distributed and/or replicated between the two modems 28 and 40. Several segments 116-119 have been illustrated in FIG. 2 for exemplary purposes. A training segment 116 of the program 115 may provide the resources for training either or both the CO modem 40 and the CP modem 28 for communication in a particular communication scheme, whereby the appropriate resources for this communication scheme may be included with the drivers 111.

Other segments of the program 115 include a monitoring segment 117, a synchronizing segment 118, and a testing segment 119. Each provide the resources for a variety of functional aspects for the program 115. As mentioned, the segments, as well as others, may be included with the program 115B and/or the program 115A of the CP modem 28. This provides for flexibility in the configuration of the communication link between the two modems 28 and 40. Generally, in the preferred embodiment, the CP modem 28 would act as a slave to the CO modem 40, and so the CO modem 40 would tend to provide most of the control of the link.

In general, the program 115 provides for the execution of the various algorithms and methods disclosed herein. Further discussion is provided regarding the various functions and methods of the present invention in subsequent figures. The various functional aspects of the program 115 will become clear through these figures.

In alternative embodiments, the resources to communicate in a variety of communication schemes and the programs and/or algorithms that perform the methods disclosed herein may be located in memory remote from the modems 28 or 40. A remote server or PC coupled to the CP modem 28 or a remote location at the CO 20 are non-limiting examples of alternative locations. It should be noted that modems that have the available resources to communicate in a variety of communication schemes are sometimes referred to in the art as multi-mode modems, and similarly another term often used in the art for a modem, in general, is a transceiver.

The ADSL interface card 100 is generally a hardware component that acts to properly send and receive electronic signals carrying information line coded with a particular communication scheme. In a simplified description, the processor 120 executes relevant software and/or firmware instructions stored in the memory 110 on the ADSL interface card 100. Signaling instructions, coding instructions, modulation instructions, and instructions involved with methods of the present invention are non-limiting examples of instructions that are performed by the ADSL interface card 100. The ADSL interface card 100 generally comprises a digital signal processor (DSP), which receives information from either the network interface 140 or I/O interface 150 and sends information to an analog front end (AFE). The AFE interfaces between the local loop 24 and the DSP and functions to convert digital data, from the DSP, into a continuous time analog signal. The analog signal is delivered via a line driver. Incoming signals process through the interface card 100, generally in the same fashion. A hybrid at the front end of the loop 24 separates the transmit and receive signal. The DSP and other components may be required to perform the various instructions mentioned above.

In the upstream direction, basically, digital data is received by the CP modem 28 via the I/O interface 150, processed, and provided to the ADSL interface card 100A via the local interface 130A. There, the data is modulated according to the utilized communication scheme, converted to analog form, and transmitted out along the loop 24. The information subsequently is converted back to digital by the ADSL interface card 100B of the CO modem 40. It then is demodulated using the same communication scheme and provided to the network interface 140 for further transmission and/or processing.

Several operations occur before data is communicated across the local loop 24. Initial handshaking algorithms are utilized by the modem 28 and 40 to determine if a local loop connection is established. The International Telecommunication Union (ITU) has standardized a handshake procedure for DMT communication in the G. 994 recommendation.

Training of the modems is performed to measure the performance and/or error rates in relation to the local loop 24. Proper synchronization occurs between the two modems as well. These operations can vary with the different communication schemes, or line coding techniques. It should be noted that, for the purposes of this document, that the term line coding techniques has been used interchangeably with the term communication schemes.

The results of the operations depend on the conditions of the local loop 24, which can change at any time. The operation of the system 12, and in particular, the modems or transceivers 40 and 28 according to embodiments of the present invention, can best be described in the subsequently provided flow charts.

In the discussion that follows, flow charts are provided. It is to be understood that any process steps or blocks in these flow diagrams represent modules, segments, or portions of code that include one or more executable instructions for implementing specific logical functions or steps in the process. To that, some or all of these steps or blocks may be performed it software, hardware, firmware, or any combination therein. It will be appreciated that, although particular example process steps are described, alternative implementations are feasible. Moreover, steps may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as will be understood by persons skilled in the art.

It will be appreciated that the methods in accordance with the present invention disclosed herein and alternative implementations may comprise an ordered listing of executable instructions for implementing logical functions and can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a"computer-readable medium"can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the information system, apparatus, or device. The computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable media would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM) (electronic), a read- only memory (ROM) (electronic), an erasable programmable read-only memory (EPROM or Flash memory) (electronic), an optical fiber (optical), and a portable compact disc read-only memory (CDROM) (optical). Note that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.

FIG. 3 is a flow chart illustrating a method 200 for initiating and synchronizing communication between a central office transceiver and a remote transceiver as performed by embodiments of the present invention. The central office transceiver may be the CP modem 40 of FIGS. 1 and 2 and the remote transceiver may be the CP modem 28. The method 200 begins when the CO and the CP transceivers detect that they are communicatively coupled to each other (step 210). This may be initiated at either end, but more typically would be initiated at the CP end. This can mean several things. First, a loop has been established between the two transceivers. Second, both transceivers are powered up or if not, they could be enabled to do so. Detecting a connection between the two devices can be done in several possible way known in the art, and any particular method for doing so is beyond the scope of this document.

The method 200 proceeds with determining a preferred communication scheme among several communication schemes (step 220). A non-limiting example of schemes may be those DMT modulation schemes mentioned above, Annex-A Echo Cancelled (EC), Frequency Division Multiplexed (FDM), Annex-C Far End Cross Talk Bit Map (FBM), and Dual Bit Map (DBM). Other communication schemes could be utilized including those that do not use DMT modulation. Methods for determining the preferred communication scheme will be described in subsequent flow charts.

Once the preferred communication scheme is determined, the CO and the CP can be trained to communicate in the preferred communication scheme (step 230) on the given loop.

In some embodiments it may be necessary to train both devices, whereas in others, only one device, either one, will require training. In yet other embodiments, it may not be necessary for either device to be trained, in which case, this step can be removed altogether. To train the devices each of the modems (or transceivers) may send specific signals as defined in the given DSL standard. Using these known signals each transceiver can synchronize to the other one, estimate the channel signal to noise ratio (SNR), which in turn determines the final data rate, negotiate rates, performance margin, etc. In general, the method in which the transceiver (s) is/are trained can vary. Training devices is a well known function in the art and is beyond the scope of this document.

Once the transceivers are properly trained, communication between the two devices begins (step 240). Communication is in the preferred communication scheme.

While communication between the two devices is occurring, the performance of the communication may be monitored (step 250), including the monitoring of channel characteristics. Several parameters of performance may be measured and will be discussed in further detail herein. Either one or both of the devices may be configured to monitor the performance of the communication. Upon monitoring the communication, several things may occur. In this embodiment, the utilized communication scheme may be changed (step 260). This may require re-determining the preferred communication scheme from the various communication schemes available to the two devices (minus the scheme just utilized). In essence, steps 220-250 may be repeated as needed until a communication scheme produces consistent results after initialization of the communication. Prompting to switch communication schemes may be done automatically upon monitoring the communication scheme. In some embodiments, this may be done by setting prefixed parameters for performance variables. Once these parameters are exceeded step 260 may be initiated. In other embodiments, this may be done manually by a technician or a user at the CP. The devices may be capable of doing both, i. e. in normal operation an automatic approach to switching schemes may be operating, but the system can be overridden to switch to the communication scheme. In which case, step 220 may be utilized, or a particular scheme can be designated by either device. In the preferred embodiment, the CO transceiver would have the capability of overriding the system to switch communication schemes, if necessary. A well known method in the art for sending commands from one device to another is done via the Embedded Operations Channel (EOC). The EOC is a dedicated channel used in some xDSL technologies apart from the standard data channels and is typically used for maintenance purposes. Commands may be sent from one device to another from the CO device to the CP device to dictate what communicating scheme to operate in. Other methods for communication these commands can be utilized as well.

FIG. 4 is a flow chart illustrating a general method of operation 290 of a communication transceiver in accordance with embodiments of the present invention. In general, this method may be performed by the master transceiver in a master-slave configuration. While it is not necessary to have a master-slave configuration, it may help set up precedence as to what communication scheme to utilize. In the preferred embodiment, the CO transceiver may be the master device and the CP transceiver may be the slave device. In other embodiments, the opposite could certainly be utilized. It should also be noted that the method of operation 290 disclosed herein has been configured for multi-mode modems, or multi-mode transceivers. Even more particularly, for multi-mode xDSL modems that utilize DMT modulation techniques, or DMT communication schemes. In general though, any transceiver configured to communicate over any medium and with any communication scheme can utilize this method of operation 290. To that, single-mode transceivers, can utilize this method of operation as well.

The method 290 begins in an Installation Mode (IM) (step 400). In general, startup of communication between two devices in a preferred communication scheme may be accomplished in the IM. Therefore, determination of the preferred communication scheme may likewise be accomplished in the IM. The IM initiates upon the power up of the transceiver for the first time on a given line. On subsequent start-ups of either device, operation may begin with the preferred communication scheme, therefore skipping the potentially timely IM. If on subsequent start-ups the preferred communication scheme is not available, the next preferred communication scheme may be attempted, and so forth until either a connection is established, or no communication schemes currently work, which could signify a serious defect in the channel. The IM is discussed further in FIG. 5.

Once the IM is complete, a startup of communication begins in the preferred communication scheme. Communication between the two devices is labeled as the devices operating in Data Mode (DM) (step 440). That is, data is being communicated between the two devices. If necessary though, the transceiver may switch to a Retraining Mode (RM) (step 500) to properly begin the appropriate training sequence of the two devices prior to beginning operation in the DM. At any point in the DM, the transceiver may be switched back into Installation Mode. This can be done automatically, upon monitoring the performance of the communication. This can also be done manually by overriding the system to switch back into the IM. A technician may want to test a particular communication scheme (s) and so this can be accomplished by switching to the IM. The system can be overridden at any point of operation including during the RM.

The RM mode may be initiated if one or all of the devices in the communication system must be (re) trained for the utilized communication scheme. Once (re) trained, the device (s) may return back to the DM. The RM will be discussed in further detail in FIG. 6.

FIG. 5 is a flow chart illustrating the method 400 for installing communication as performed during the Installation Mode of the method of operation 290 of FIG. 4. The method 400, or the IM, begins when the master transceiver powers up for the first time (step 410). In this embodiment, the CO transceiver is the master transceiver, although in other embodiments, the opposite could be true.

Once powered-up the CO transceiver begins detection of a CP transceiver at the other end of a given line (step 420). As mentioned, there are many methods known in the art for detecting another transceiver and so explanation of any particular method has been excluded from this document. Generally, the CO transceiver will attempt to detect the CP transceiver until one is detected or until the algorithm times out.

Once detected, the several modes of communication, or the several communication schemes may be evaluated (step 300). The CO transceiver may be capable of communicating in a different group of communication schemes than that of the CP. Upon evaluation, a list of complying communication schemes can be generated and a log of relative performance measurements for each. An ordered listing of preference to the communication schemes may be generated as well. This step will be discussed in further detail in FIG. 7.

Start-up of communication in the preferred communication scheme from the ordered listing of communication schemes is then attempted (step 430). If necessary, the CO transceiver may be switched to RM (See FIG. 4) to begin the proper train sequence for the newly-determined preferred communication scheme.

From there, operation begins in the DM (step 440). Monitoring of the performance of the communication between the two devices is performed. Either one, or both, of the devices may be capable of monitoring the performance. A log may be kept to track and store the performance over time. If upon an anomaly, or a dramatic change in the line conditions, the CO transceiver may be switched back to Installation Mode. As mentioned above, the preferred embodiment utilizes xDSL transceivers configured to utilize DMT line coding. The several line coding techniques discussed in the background, as well as several others, may be utilized. As an alternative to immediately switching to the IM, a re-start can be attempted in the utilized communication scheme. If this attempt times-out, either the next communication scheme in the ordered list of communication schemes can be attempted, or the device can be switched back to the IM. The time-out for a reattempt of the utilized communication scheme may be on the order of minutes, to allow for the lines to clear, if necessary.

On subsequent start-ups, the timely step 300 of evaluating the different communication schemes can be skipped. Start-up can initiate in the first communication scheme available in the ordered list of communication schemes. If an attempt to start-up in the next communication scheme fails, i. e. the attempt times-out, the next communication scheme may be attempted. The time-out length can vary but typically is on the order of seconds.

FIG. 6 is a flow chart illustrating a method 500 for retraining as performed during the retraining mode of the method of operation 290 of FIG. 4. This method 500 may be initiated at any time. For example, the method 500 may be initiated once the IM determines the preferred communication scheme. Training in that scheme can then be performed. In another example, the method 500 can initiate during DM if it is determined that retraining in the utilized communication scheme increases performance.

In general, the method 500 begins when the transceiver switches to RM. If not already known, the transceiver verifies if the devices need be retrained (step 510). This may be accomplished in several ways, such as communicating with the reciprocal transceiver via the EOC (See FIG. 3). If it is determined that no retraining is necessary, the transceiver can be switched into the DM (step 440). If it is determined that the receivers need be retrained, an appropriate training sequence is initiated (step 520). As mentioned earlier, several training sequences are known in the art and any particular method or sequence training is beyond the scope of this document.

FIG. 7 is a flow chart illustrating a general method 300 for determining a preferred communication scheme in accordance with embodiments of the present invention. The method 300 is generally the method utilized by the Installation Mode of the method of operation 290 as well as the method 200 for initiating and synchronizing communication between a central office transceiver and a remote transceiver as performed by embodiments of the present invention. In the latter, this method 300 can fall under step 220, that is "Determining a Preferred Communication Scheme."The method 300 begins once a first transceiver (preferably the CO transceiver, but not necessarily) detects a second transceiver (preferably the CP transceiver, but not necessarily). The first step is to attempt communication in a first communication scheme, obviously a scheme in which the first transceiver is capable of communicating in. The second transceiver may not be able to communicate in any one, some, or all of the communication schemes within the capability of the first transceiver. Regardless, a first communication scheme is attempted. Upon this attempt, several performance characteristics are measured. For one, connectability-can the second transceiver communicate in this communication scheme. In terms of this document, connectability shall be construed to mean whether or not a communication connection can be established with a second transceiver with a given communication scheme. As opposed to this qualitative measurement, several quantitative measurements may be made. These quantitative measurements include, but are not limited to: down stream rates, upstream rates, down stream SNR margin, upstream SNR margin, etc.. Several variables can affect the performance measurements of each communication scheme. For example, paper-insulated cables are commonly used in the local loop in Japan. Annex A DMT schemes (e. g. EC and FDM) for xDSL may not be the best suited for these conditions because high attenuation can occur at higher frequencies, which can lead to high levels of interference. Annex C techniques, such as FBM and DBM employ techniques to alleviate the effects caused by attenuation. The downfall being that only about a third of the downstream bit rate can be used in Annex C.

In the preferred embodiment, multi-mode xDSL modems that utilize DMT communication schemes are utilized. In this case, the testing of each communication scheme may be done in accordance with standards defined by the G. 994 recommendation of the International Telecommunication Union-Telecommunication Standardization Sector (ITU- T). This allows for compatibility with components that already comply with the standards recommended by the ITU-T. Ease of design, marketing, and other business decisions lend this compliance with industry standards to be useful. It should be noted, however, that in other embodiments the methods of testing and parameters tested may vary on the technology at hand, and so the preferred embodiment should not be construed as a limiting example.

After each communication scheme is attempted and tested, performance data can be collected (step 320). A log of performance data is created and maintained, subsequently upon monitoring. Step 310 and 320 can be repeated for all communication schemes attempted.

Further calculations may be done on the various performance characteristics to generate an order of preference (step 330). These calculations may vary with the customer profile of the serviced market as well as the technical and functional aspects of the plant under test. In general, the method, algorithm, equation, etc. for determining the order of preference of the communication schemes may vary and may be created and manipulated as needed by the service provider. It should also be noted that the order of preference, and subsequently the preferred communication scheme can be overridden by the service provider.

Once an order of preference has been generated, the best mode of operation, or the preferred communication scheme can be selected (step 340).

Turning now to FIG. 8 where a flow chart of a general method 600 for synchronizing and training a remote transceiver to communicate in a preferred communication scheme in accordance with embodiments of the present invention is illustrated. The method 600 begins when the remote transceiver, or the CP transceiver, powers up (step 610). The CO transceiver detects this both during Installation Mode and during Data Mode.

In Installation Mode, the various communication schemes are attempted and tested for performance. The specific sequence in how the various communication schemes are tested may vary but method 600 describes a preferred method. Once powered-up, a first set of communication schemes may be attempted (step 620). In this embodiment, the Annex A schemes are tested. For example, Echo Cancelled DMT may be tested for a period of time.

If connectability is found, performance of the scheme can be measured on the line. After the determined period of time, another Annex A scheme may be tested, e. g. FDM DMT. Again performance measurements can be made. Schemes in Annex C can then be tested, by toggling through the various communication schemes in compliance with Annex C (step 640). Once all communication schemes have been tested, the CO transceiver may have all the information necessary to determine an ordered list of communication schemes, with the first being the preferred communication scheme.

Upon any start-up, the same general sequence can be performed. Here, the CP transceiver simply acts as a slave to the CO transceiver. The first communication scheme is attempted. If it is detected that it is an Annex A scheme, the method proceeds to step 625, where communication begins in that communication scheme. If necessary, the CP transceiver can prepare for the retraining sequence for the current communication scheme (step 630). If the first communication scheme were not an Annex A scheme, step 620 may time-out and the method 600 can proceed to step 640, where Annex C schemes can be attempted. Again, the CP transceiver waits for a period of time for the CO to establish a communication link in an Annex C communication scheme. If one is established, thus signifying the first communication scheme is an Annex C scheme, communication can begin in the first communication scheme (step 645). Again, if necessary, the CP transceiver can prepare for the retraining sequence for the current communication scheme (step 650).

In general the time allotted for steps 620 and 640 can vary, but the time allotted would allow for self-synchronizing, in other words no manual coordination may be needed.

It should be emphasized that the above described embodiments of the present invention are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment (s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.