KR20020048408A - Multicarrier system with stored application profiles for supporting multiple applications - Google Patents

Abstract

Systems and methods are disclosed for supporting a number of applications. The digital subscriber line system includes two transceivers that communicate over a communication channel using multicarrier modulation. The application profile defines an application profile that characterizes the transmission of information over a communication channel. Each application profile is a set of parameters associated with one or more applications of a particular set that can be activated between transceivers and specifies the transmission requirements for each application. Each transceiver stores an application profile and transmits information over a communication channel in accordance with one of the stored application profiles. When a change occurs in multiple active applications between transceivers, a second profile of the application profile is retrieved. The transceiver switches to sending information over a communication channel according to the second application profile. This switching can be made without interrupting communication between the transceivers to retrain the transceiver.

Description

Multicarrier system with stored application profiles for supporting multiple applications

The present invention relates to a transmission system using multicarrier modulation. In particular, the present invention relates to a multicarrier transmission system supporting multiple applications.

In a conventional multicarrier transmission system, a transceiver communicates over a communication channel using multicarrier modulation or discrete multitone modulation (DMT). Carriers or subchannels located within the usable frequency band of the communication channel are modulated at the system's desired transmission rate. In an Asynchronous Digital Subscriber Line (ADSL) system, the symbol transmission rate is approximately 4 kHz. Every 250 microseconds, the transmitting transceiver allocates a new set of bits for transmission to the subchannel such that the bit error rate of the subchannel is generally uniform at the receiving transceiver. As a result, the number of bits during a given symbol period may vary from subchannel to subchannel.

The International Telecommunication Union (ITU) standards G.992.1 and G.992.2 specify parameters that indicate the operating characteristics of an ADSL DMT transceiver. Examples of parameters (named with a few exceptions) include the data rate (b / s) for the connection between the transceivers, the number of subchannels in the upstream and downstream directions, and the number of bits allocated to each subchannel. It includes. In general, these parameters remain fixed after initial configuration and installation of the transceiver. Some parameters depend on the connection data rate and can change when an ADSL connection is made at a high or low data rate. Some parameters may change as the channel conditions change. However, after the type of application, i.e. voice, data, video, etc., is determined, the parameters are optimized and fixed for that application.

During splitterless operation, as described in the ITU G.922.2 standard, an ADSL transceiver contains a "channel" that contains a subset of parameters that are used when the conditions of the communication channel change (for example, when the telephone connection is lost). Save the "profiles". When channel conditions change due to an event that the ADSL transceiver does not control (for example, when the phone is connected to the same line when the ADSL transceiver is disconnected), the ADSL transceiver checks for new channel conditions and some receiver functions. (E.g., equalizers, echo cancellers, etc.) must be retrained and switched to the channel profile used for the new channel condition. This process, defined as the "Fast Retrain" procedure in ITU G.922.2, takes approximately 1-2 seconds. However, this channel profile depends only on the channel conditions and not on the application (s) running on the ADSL connection.

As technological advances have increased the data rate throughput of multicarrier transmission systems, ADSL transceivers can support multiple applications. To support multiple applications, it is necessary to enable the ADSL transceiver to quickly and effectively adapt the transmission parameters as the number and type of active applications change over time. For example, if an ADSL transceiver is accessing data over the Internet when a voice telephone call being sent over an ADSL connection is activated, the ADSL transceiver should be able to modify the transmission parameters to accommodate all of the active applications. When other voice telephone calls and other applications (eg, video on demand, video conferencing) are activated and deactivated via an ADSL connection, the ADSL transceiver must also be able to support various transmission needs of various combinations of concurrently active applications. For example, video signals have higher reliability than voice and data signals but lower transmission delay requirements. For some transmission systems, it is necessary to find a compromise between high reliability and transmission delay.

Therefore, what is needed is a system and method that can support various transmission needs of multiple active applications as the number and type of active applications change over time.

This application is filed on March 10, 2000, which claims the benefit of priority of US Provisional Application No. 60 / 124,222, entitled "Seamless Rate Adaptive (SRA) ADSL System," filed March 12, 1999. Pending US patent application Ser. No. 09 / 522,869, and US Provisional Application No. 60 / 161,115, entitled "Multicarrier System with Stored Application Profiles," filed October 22, 1999, and 2000 1 The invention, filed Jan. 19, is part of US Provisional Application No. 60 / 177,081 entitled "Seamless Rate Adaptive (SRA) Multicarrier Modulation System and Protocols." The present application also discloses US Provisional Application No. 60 / 154,116, entitled "Transceiver Supporting Multiple Applications," filed September 15, 1999, and "Multicarrier, filed October 22, 1999. US Provisional Application No. 60 / 161,115, entitled "System with Stored Application Profiles," and US Provisional Application No. entitled "Seamless Rate Adaptive (SRA) Multicarrier Modulation System and Protocols," filed Jan. 19, 2000. Claiming the benefit of priority of 60 / 177,081, the pending preliminary applications are hereby incorporated by reference in their entirety.

The invention is particularly indicated by the appended claims. Advantages of the present invention as described above and other advantages of the present invention will be better understood with reference to the following description in conjunction with the accompanying drawings.

1 illustrates an embodiment of a digital subscriber line multicarrier transmission system including a remote discrete multitone modulation (DMT) transceiver in communication with a central station transceiver and supporting multiple applications using an application profile, in accordance with the theory of the present invention. A block diagram is shown.

2 is a block diagram illustrating one embodiment of a transmitter of a remote DMT transceiver having two latency paths to support multiple applications with different latency requirements.

3 is a flow diagram illustrating one embodiment of a process for initially exchanging and storing an application profile at a central station and a remote DMT transceiver.

4 is a flow diagram illustrating one embodiment of a receiver-initialization process used by a remote DMT transceiver and a CO transceiver to switch to a stored application profile.

5 is a flow diagram illustrating one embodiment of a transmitter initialization process used by a remote DMT transceiver and a CO transceiver to switch to a stored application profile.

One object of the present invention is to provide a DMT transceiver that can support multiple applications when applications are activated or deactivated and can quickly and effectively modify transmission parameters over time. In one aspect of the invention, a multicarrier modulation system has two transceivers that communicate with each other over a communication channel. The present invention features a method for supporting multiple applications. Multiple application profiles are defined. Each application profile corresponds to one or more applications in a particular set and specifies at least one transmission parameter for each application in that particular set of applications for transmitting information associated with that application over a communication channel.

Multiple application profiles are stored in one of the transceivers. The information is transmitted according to the stored first application profile corresponding to the current active application set. The stored second application profile is selected in response to the change in the current active application set. This second application profile corresponds to one or more applications in the changed set of currently active applications. The information transfer does not interfere with communication between the transceivers in order to retrain the transceiver and switches to the use of the stored second application profile.

A message is sent to one of the transceivers confirming the second application profile as the application profile for use in subsequent communication between the transceivers. This message may act to request a change in the second application profile. The receiver or transmitter of the transceiver may send a message to initiate the change.

The response message is received from the transceiver to which the message was sent. When the receiver sent the first message, the response message approves the request and synchronizes the use of the second application profile. In one embodiment, the inverted sync symbol is used in the response message. When there is a switch to transmitter initialization, the response message acknowledges the switch request to the second application profile. Thereafter, another message is sent that notifies the approval and synchronizes the use of the second application profile. In one embodiment, this other message is an inverted sync symbol.

Each application profile may be sent to another transceiver over a communication channel with or without performing a full initialization of the transceiver. An application profile may be created after a particular set of active applications is initially created and associated with that particular set of applications. In one embodiment, each transceiver locally generates at least one transmission parameter for one of the stored application profiles using a predefined process implemented by two transceivers. In another embodiment, the transceiver may be preconfigured including the stored application profile.

In the application profile, the transmission parameters specified for each application are the transmission data rate, the subchannels allocated for downstream and upstream transmission, the number of bits assigned to each subchannel, the performance gain, and the fine gain for each subchannel. At least one of adjustment, interleave depth, minimum and maximum QAM array size, length of cyclic prefix, codeword size, framing mode and trellis code.

In another aspect, the invention features a method for supporting multiple applications that are active between transceivers. A number of application profiles have been developed that feature transmitting information over a communication channel. Each application profile is associated with one or more applications in a particular set that can be activated between transceivers. Application profiles are stored in the transceiver. The information is sent over the communication channel according to the stored first application profile corresponding to the current set of active applications. The second profile of the application profile corresponding to the changed set of current active applications is retrieved in response to the change in the current set of active applications that is active between the transceivers. The transceiver switches to information transmission over a communication channel according to the second application profile. This switching can be done with or without retraining the transceivers.

In another aspect, the invention features a method for supporting multiple applications in which multiple application profiles are defined. Each application profile specifies at least one transmission parameter for each application in that particular set of applications to correspond to one or more applications in that particular set and transmit information associated with that application over a communication channel. Multiple application profiles are stored in one of the transceivers.

In another aspect of the invention, a multicarrier modulation system has a transceiver for communicating over a communication channel. Multiple application profiles are defined. Each application profile specifies at least one transmission parameter for each application in that particular set of applications to correspond to one or more applications in that particular set and transmit information associated with that application over a communication channel.

Multiple application profiles are stored in the transceiver. The information is transmitted according to the stored first application profile corresponding to the current active application set. The stored second application profile is selected in response to the change in the current active application set. This second application profile corresponds to one or more applications in the changed set of currently active applications. The information transfer switches to using the stored second application profile without having to retrain the transceiver. The transceiver may send or receive a message confirming the second application profile with the application profile for use in subsequent communications.

In another aspect of the invention, each application profile corresponds to at least one for each application within that particular set of applications to correspond to one or more applications of the particular set and receive information associated with that application over a communication channel. Specify the reception parameters. Receipt of information transitions from using the stored first application profile to using the stored second application profile without having to retrain the transceiver. Again, the transceiver may send or receive a message confirming the second application profile as an application profile for use in subsequent communications.

1 illustrates an asymmetric DSL including a remote discrete multitone modulation (DMT) transceiver 10 (eg, a modem) in communication with a central office (CO) transceiver 14 via a communication channel 18. The transmission system 2 is shown. The remote DMT transceiver 10 includes a memory 30, a transmitter 22, and a receiver 26 that store multiple application profiles (APs) 34 in accordance with the principles of the present invention. The CO transceiver 14 includes a memory 46, a transmitter 38, and a receiver 42 that store multiple application profiles 50 having one-to-one correspondence with the application profile 34 of the remote DMT transceiver 10. do.

The communication channel 18 of one embodiment is a pair of twisted wires of a telephone subscriber line. The communication channel 18 is an upstream transmission path from the transmitter 22 of the remote DMT transceiver 10 to the receiver 42 of the CO transceiver 14 and the remote DMT transceiver (from the transmitter 38 of the CO transceiver 14). Provide a downstream transmission path to receiver 26 of 10). System 2 is asymmetric because the bandwidth of the downstream transmission path is greater than the bandwidth of the upstream transmission path.

Remote DMT transceiver 10 and CO transceiver 14 receive and transmit application streams 54, 54 '(generally 54) using application profiles 34, 50 in accordance with the principles of the present invention. Each application stream 54 (hereinafter referred to as application 54) carries one type of signal (eg, digital data, voice, video, etc.). For example, one stream of voice signal is one application, one stream of digital data signal is another application, and one stream of video signal is also another application. The voice application corresponds to one or more active voice phone calls. One example of a digital data application is Internet access Web browsing (IAWB), and one example of a video application is video on demand. The ADSL system 2 can also send applications 54 of other signal types. Although shown as a separate application stream, this application stream may reach the transceiver 10 as part of a single stream of transmit packets (eg, ATM cells) having various types of signals.

ADSL system 2 supports multiple active applications 54 simultaneously. For example, the transmitter 22 of the remote DMT transceiver 10 transmits the signals of the voice application and the signals of the digital data application to the receiver 42 of the CO transceiver 14 via an upstream transmission path of the communication channel 18. Can transmit at the same time. As another example, FIG. 1 illustrates an ADSL system 2 that simultaneously transmits signals associated with digital data, voice, and video applications 54 over upstream and downstream transmission paths. At any given point in time, the DSL system 2 has zero, one or more applications 54 that are currently active. Each particular combination of one or more active applications (hereafter referred to as a set of applications or a set of applications) represents a particular active communication state of the transceivers 10, 14. An example of an application set 54 includes two or more other types of concurrently active applications (eg, an internet access web browsing application that includes a voice telephone application consisting of one or more voice telephone calls). Another example of an active application set has only one active application (eg, an internet access web browsing application, or one or more active voice phone calls).

Each application 54 is one of two kinds of applications: (1) fixed data rate application and (2) variable data rate application. Fixed data rate applications require a specific bandwidth and must obtain that bandwidth to pass through the communication channel 18. If the required data rate is not currently available, the application is not currently supported. An example of a fixed data rate application is a voice telephony application that requires 64 kb / s for each active telephone call. Some video applications may also require special fixed data rates. Variable data rate applications can operate over a wide range of data rates (eg, 1 Mb / s to 2 Mb / s). Therefore, if the available channel bandwidth is within this range, the application is supportable. One example of various data rate applications is digital data applications (eg, internet access web browsing). Some video applications are other examples of variable data rate applications that can operate within a data rate range.

Such data rate requirements will be described in more detail below, but locally determine the content of the application profiles 34, 50. In general, application profiles 34 and 50 that support one or more fixed data rate applications specify specific data rate requirements for each such fixed data rate application. Application profiles 34 and 50 that support variable data rate applications specify up to the maximum amount of usable data rate that is within the scope of a particular variable data rate application. Application profiles 34 and 50, which support fixed data rate and variable data rate applications, first assign special data rate requirements to specific fixed data rate application (s) and then allocate the remaining available bandwidth to the variable data rate application (s). Assign to

Other types of applications 54 also typically have different transmit and receive requirements for reliability and transmission delay. In particular, requirements for data rate, latency, burst or impulse noise, bit error rate (BER), and data rate symmetry can vary significantly in other applications. For example, high speed video applications that require high downstream data rates, for example 1.5 Mb / s to 6 Mb / s, and low upstream data rates, for example 16 kb / s to 64 kb / s, are asymmetric. In addition, video applications have low immunity to impulse noise because video signals are compressed at a high density when transmitted. As a result, video applications require low BER below 1E-9. High latency above 20ms is acceptable.

In contrast, digital data applications such as web browsing over the Internet using downstream data rates of 32 kb / s to 6 Mb / s and upstream data rates of 32 kb / s to 1 Mb / s are less asymmetric than video applications. Bit error rate requirements for digital data applications are below 1E-7 and are generally more immune to impulse noise than in video applications. Also, typical latency of 5 ms or less is generally acceptable.

Voice applications (i.e. phone calls) requiring 64kb / s data rates on both the upstream and downstream transmission paths are symmetric. Voice applications may have a BER of 1E-3 or less, while being highly immune to impulse noise. In contrast to video and digital data applications, a small latency of approximately 1.5 ms or less is required.

Different types of applications may have different requirements.

Various digital multitone transmit (or receive) parameters control this requirement. For example, the bit allocation table BAT controls the data rate and bit error rate. Reed-Solomon (R / S) coding control and interleaving provide lower bit error rates. They increase immunity to impulse noise instead of increasing latency. The number of tones used in the upstream and downstream paths determines the data rate symmetry. As a result, various parameters characterize the DMT transmission and reception of a signal associated with a given application 54 over communication channel 18. (Hereinafter, the parameters are generally referred to as transmission parameters even if they are used for receiving signals). These transmission parameters are

The data rate (bits / sec) for a given application (upstream and / or downstream) between the transceivers 10 and 14,

The subchannels assigned to the upstream and downstream transmission paths for a given application,

The number of bits allocated to each subchannel for a given application,

The minimum and maximum spherical amplitude modulation (QAM) array sizes used on each subchannel for a given application,

Inclusion or exclusion of grid code for a given application,

The length of the cyclic prefix for a given application,

Coding parameters (e.g. R / S codeword size) for a given application,

If an interleaver is used for a given application, the interleaver depth,

Framing mode for a given application (for example, the ITU ADSL transmission standard G.922.1 specifies four different framing modes),

Fine gain adjustments made to each tone of a given application, and

Performance gain for a given application

It includes.

In order to transmit and receive signals associated with one or more active applications, the remote DMT transceiver 10 and the CO transceiver 14 use application profiles 34 and 50 to characterize such communication. In particular, each application profile 34, 50 is a parameter set that specifies transmission parameters for one or more currently active applications 54 of a particular set. The application profile corresponding to the set of applications representing only one active application specifies the transmission parameters for that one application. As described below, the values assigned to the parameters of each application profile 34, 50 depend on the type and type of each application in the application set corresponding to that application profile.

For an application set representing two or more currently active applications, the corresponding application profiles 34, 50 specify transmission parameters that simultaneously accept all active applications in the application set. Effectively, the application profile 34, 50 operates to combine the individual transmit (or receive) requests of the individual applications 54 into one set of transmit parameters to achieve simultaneous transmission of all active applications.

For example, suppose the total data rate of the connection is 1.532 Mb / s. When a variable data rate application (eg a digital data application) is running alone, it uses a fully available data rate of 1.532 Mb / s, which data rate is within the data rate range of the variable data rate application. Estimate. Therefore, one embodiment of an application profile corresponding to this variable data rate application assigns the fully available data rate of the connection to the variable data rate application. When a fixed data rate application (eg, a voice application) is running alone, this fixed data rate application uses a specifically required data rate (eg, 64 kb / s data rate for voice applications). do. Therefore, one embodiment of an application profile corresponding to this fixed data rate application assigns a specifically required data rate to a fixed data rate application.

When the fixed and variable data rate applications described above operate simultaneously, an application profile corresponding to these two sets of applications is first provided to the data rate requirements of the fixed data rate application and then the channel remaining after satisfying the fixed data rate application. The bandwidth is used for variable data rate applications. Therefore, if a fixed data rate application is a voice application requiring 64 Kb / s, the application profile assigns the required 64 Kb / s to the voice application and assigns the remaining channel bandwidth of 1.468 Mb / s data rate to the variable data rate application. do. In another example, if the fixed data rate application is a voice application consisting of two voice calls each requiring 64 Kb / s, the application profile specifies the required 128 Kb / s to the voice application and 1.404 Mb / s data. Provide the remaining channel bandwidth of the rate to variable data rate applications. In these examples, the reduced bandwidth for variable data rate applications (ie, from 1.532 Mb / s to 1.468 Mb / s or 1.404 Mb / s) is estimated to be within the acceptable data rate of the variable data rate application. Effectively, the parameters associated with sending and receiving signals for each active application are individually combined in the application profile in a manner that achieves simultaneous transmission and reception of signals for all concurrently active applications.

Although described above as specifying a data rate for particular applications, each application profile 34, 50 may be associated with the parameters described above to characterize the DMT transmission (and reception) of signals associated with each application within that application profile. One or any combination of other parameters not listed can be specified. For example, other transmission parameters that application profiles 34 and 50 may specify are the number of latency paths required to support an application in the application profile and the data rate of each latency path.

As another example, the application profile may also specify the allocation of subchannels for the application. For example, when a variable data rate application is running alone, the corresponding application profile allocates all available subchannels to convey the bits associated with the variable data rate application. When a fixed data rate application is running alone, the corresponding application profile is sufficient available sub to achieve the specifically required data rate of the fixed data rate application (eg, 64 kb / s data rate for voice applications). Allocates a subset of channels. When these fixed and variable data rate applications operate simultaneously, the application profiles corresponding to these two sets of applications specify the allocation of several subchannels for fixed data rate applications and the assignment of other subchannels for variable data rate applications. . It is possible for one or more subchannels to be allocated for both fixed and variable data rate applications.

The application profile can also be illustrated by the following five examples of application profiles that can be created and stored in the transceivers 10 and 14, namely AP # 1-AP # 5. These exemplary profiles transmit for five different communication states, including two types of applications: fixed data rate voice applications consisting of one or more voice calls and variable data rate Internet access web browsing (IAWB) applications. Specify the property. For these examples, the total data rate of the connection between the transceivers 10 and 14 is 1.532 Mb / s, and the IAWB application assumes that it has a minimum and maximum data rate range of 1 Mb / s to 2 Mb / s. Each voice call of a voice application requires 64 kp / s. In general, fixed data rate applications receive the data rate they each require, and variable data rate applications receive a balance of the bandwidth capacity of the connection.

Application Profile # 1

Application profile # 1 (hereafter also AP # 1) corresponds to only one variable data rate application, that is, an application set of IAWB applications having a data rate range of 1 Mb / s and 2 Mb / s. Therefore, AP # 1 specifies the full connection capacity (here, 1.532 Mb / s) for transmitting signals associated with the IAWB application. All available subchannels are allocated to the IAWB data stream with 1E-7BER on each subchannel. The R-S codeword size is 200 bytes with an interleaver depth of 5 codewords.

Application Profile # 2

Application profile # 2 (hereafter also AP # 2) corresponds to an application set of only one fixed data rate application, namely a voice telephony (VT) application requiring 64 kb / s. Therefore, AP # 2 specifies 64kb / s for transmitting signals associated with the VT application. Subsets of sufficient subchannels to achieve 64 kb / s are allocated to the VT data stream with 1E-3 BER on each subchannel. No coding or interleaving

Application Profile # 3

Application Profile # 3 (hereafter also AP # 3) is a single fixed data rate application, in particular one consisting of two voice telephone (VT) calls on separate voice channels where each call requires 64 kb / s. Corresponds to an application set of voice applications. Thus, AP # 3 specifies a data rate of 128 kb / s (ie 2 x 64 kb / s) for transmitting signals associated with this VT application. Subsets of sufficient subchannels to achieve 128 kb / s are allocated to the VT data stream with 1E-3 BER on each subchannel. Again, there is no coding and interleaving.

Application Profile # 4

Application profile # 4 (hereafter also AP # 4) corresponds in particular to an application set of two different types of applications, a variable data rate IAWB application and one fixed data rate VT application. To transmit signals associated with IAWB and VT applications, AP # 4 specifies a data rate of 64 kb / s for the VT stream and a data rate of 1.468 Mb / s (1532 kb / s-64 kb /) for the IAWB stream. s). A subset of subchannels sufficient to achieve 64 kb / s is allocated to the VT stream with IE-3 BER on each subchannel thus allocated. A subset of enough subchannels to achieve 1.468 Mb / s is allocated to the IAWB stream with 1E-7 BER on each subchannel thus allocated. For IAWB streams, the R-S codeword size is 200 bytes with an interleaver depth of 5 codewords. For VT streams, there is no coding or interleaving.

Application Profile # 5

Application Profile # 5 (hereafter AP # 5) is a combination of one fixed data rate VT application and two variable data rate LAWB applications, each consisting of two voice telephone calls on separate channels where each call requires 64 kb / s. Corresponds to an application set of two applications. To transmit signals associated with IAWB and VT applications, AP # 5 assigns a 128 kb / s data rate to the VT stream and a 1.404 Mb / s (1532 kb / s-128 kb / s) data rate to the IAWB stream. do. Subsets of sufficient subchannels to achieve 128 kb / s are allocated to the VT data stream with 1E-3 BER on each subchannel thus allocated. A subset of enough subchannels to achieve 1.404 Mb / s is allocated to the IAWB stream with 1E-7 BER on each subchannel thus allocated. For IAWB streams, the R-S codeword size is 200 bytes with an interleaver depth of 5 codewords, again for the VT stream, there is no coding or interleaving.

When the application 54 is activated and deactivated over time, the remote DMT transceiver 10 and the CO transceiver 14 quickly and effectively change the transmission parameters and store the stored application profile to accommodate the transmission request of the current active application (s). (34,50) is used. Each time a change occurs in the current set of active applications, the remote DMT transceiver 10 and the CO transceiver 14 select the appropriate application profile from the stored set of profiles 34 and 50. In one embodiment, if an application profile does not yet exist for the current set of active applications, one of the transceivers 10, 14 creates a suitable application profile and transfers the new application profile to the other via communication channel 18. Replace with transceiver. In other embodiments, the transceivers 10 and 14 may consist of predefined application profiles and / or dynamically generate an application profile during operation of the ADSL system 2 when a need for such a profile arises. In another embodiment, the transmission parameters of the application profile are mutually generated locally by each transceiver 10,14.

2 illustrates an exemplary embodiment of a transmitter 22 of a remote DMT transceiver 10 that includes two latency paths 56, 58 to support multiple applications 54 with different latency requirements. . The transmitter 38 of the CO transceiver 14 includes the same paths and functions as the transmitter 22. Receivers 26 and 42 also contain the same latency paths, but in the opposite direction and perform operations opposite to those of transmitters 22 and 38 to demodulate information received over communication channel 18.

Multiple latency paths 56 and 58 are used to send other application bit streams with different latency requirements through ADSL DMT transceiver 10. In FIG. 2, two other applications 54 ″, 54 ′ ″ are shown. One example application 54 '' is a digital data stream (eg, ATM (Asynchronous Transfer Mode) data stream) and another example application is a voice telephony application. Additional applications and / or other applications may be used, and it should be understood that the use of digital data and voice telephony applications is merely illustrative of the theory of the invention. The digital data application 54 '' is sent over a latency path 56 that can withstand typical magnitude latency (i.e., approximately 5ms or less) and has interleaving. Voice telephony application 54 with low latency requirements is directed through another latency path 54 without interleaving.

The transmitter 22 may have additional latency paths and / or other latency paths. For example, in one embodiment, ADSL system 2 has video applications in addition to digital data and voice telephony applications. This video application can tolerate higher latency than the typical latency of ATM data applications 54 'and the low latency of voice telephony applications 54' ''. In this embodiment, the ADSL system 2 can accommodate the latency requirements of the video application by providing a third, different latency path.

Each latency path 56, 58 includes three blocks, namely a MUX block 60, a framer / coder / interleaver (FCI) block layer 64, 64 ′ and a modulator block 68. MUX block 60 has a number of inputs for receiving a signal stream of active application 54 and an output for each latency path 56, 58. The MUX block 60 directs the signal stream of the digital data application 54 '' to the first latency path 56 and directs the signal stream of the voice data application 54 '' 'to the second latency path 58. Point to.

Each FCI block 64, 64 '(typically 64) prepares a bit stream for modulation, converts the received signal into frames and superframes, and overhead channels (i.e., AOC and EOC) in that frame. Add information and, where applicable, provide functions related to performing coding and interleaving. The operation performed by each FCI block 64 depends on the type of application 54 '', 54 '' 'and the latency paths 56, 58 taken by that application.

On the first latency path 56, the FCI block 64 includes a framer block 72, a cyclic redundancy check (CRC) and scrambler (SCR) block 76, a forward error correction (FEC) block 80 ( RS coding) and interleaving (INT) block 84, for example. On the second latency path 58, the FCI block 64 'includes a framer block 76' and a CRC and SCR block 80 '. The second latency path 58 through the FCI block 64 is different from the first path 56 (ie, smaller than the first path) because the second path 58 does not perform interleaving or coding on the speech stream. ) Has a latency size.

The modulator block 68 provides functionality related to DMT modulation and includes a quadrature amplitude modulation (QAM) encoder 88 and an Inverse Fast Fourier Transform (IFET) modulator 92. QAM encoder 88 has multiple inputs to receive signal streams from latency paths 56 and 58 and combine them into one signal stream that is sent to IFFT 92 for modulation. IFFT 92 modulates the bits received from QAM encoder 88 into the multicarrier subchannel of communication channel 18.

Five example application profiles, AP # 1-AP # 5, shown in FIG. 1 are also shown in FIG. Application profiles # 1, # 4, and # 5 communicate with the FCI block 64 of the first latency path 54 because each of these profiles specifies one or more transmission parameters that characterize the ATM data stream. . Application profiles # 2, # 3, # 4, and # 5 specify the FCI block 64 'of the second latency path 58 because each of these profiles specifies one or more transmission parameters that characterize the voice stream. Communicate In one embodiment, these five application profiles AP # 1-AP # 5 each specify one or more transmission parameters that characterize the bit allocations for the subchannels of the communication channel 18 so that all these five applications The profiles are in communication with a modulator block 68.

Store and exchange application profiles

Predefined Profile

Before the transceiver 10, 14 can communicate over the communication channel 18 using an application profile characterizing the communication, the application profile is stored in a suitable local memory 30,46. In one embodiment, each transceiver 10,14 is preconfigured (e.g., factory set), i.e. the application profile is such that the transceiver 10,14 is routed to the ADSL system 2; It is pre-stored in local memory 30, 46 before being integrated.

Profiles exchanged and saved at initial creation of an application set

In another embodiment, the transceivers 10 and 14 exchange application profiles via communication channel 18 and then store the application profiles. 3 illustrates one embodiment of a process used to achieve a profile exchange. To illustrate this process, assuming that the remote DMT and CO transceivers 10 and 14 are exchanging signals associated with the Internet Access Web Browsing (IAWB) application according to AP # 1 in FIG. 1, a new voice application may be activated. As a result, new application profiles are needed. In general, either the remote DMT transceiver 10 or the CO transceiver 14 may function as an initiator for exchanging a new application profile. Moreover, either the transmitter 22 or receiver 26 of the remote DMT transceiver 10 or the transmitter 38 or receiver 42 of the CO transceiver 14 may initiate a new application profile exchange.

During the exchange of IAWB signals, activation of the new voice application 54 is detected (step 100). One of the transceivers 10, 14 or other component of the DSL system 2 (eg, a computer system in which the transceivers 10, 14 operate internally) may perform this detection. After detection of this new voice application 54, a determination is made as to whether an application profile for combining the active IAWB application with the new voice application already exists (step 104). Again, the transceivers 10, 14 or another component of the DSL system 2 can make this determination. When no such application profile exists, a transmission parameter is determined to accept the current transmission of the signal associated with the IAWB application and the new voice application (step 108). It should be noted that inactivation of the active application may also appear in a particular set of currently active applications for which no application profile currently exists. In such a case, a transmission parameter for transmitting signals related to one or more applications currently active after deactivation is likewise determined (step 108).

These transmission parameters represent new application profiles. One embodiment of this new application profile may be an application profile # 4 (AP # 4) because AP # 4 supports one LAWB application and one voice application, as shown in FIG. The identifier is associated with the new application profile. For example, at the time of activation of this new application, if there are three application profiles already stored, the new application profile is fourth. Because of the one-to-one correspondence between the application profile of the CO transceiver 14 and the application profile of the remote DMT transceiver 10, the same identifier is assigned by the remote DMT 10 and the CO transceiver 14 to confirm the new application profile. Used.

One of the transceivers 10,14 then exchanges the new application profile with the other transceivers 14,10 and sends the transmission parameters associated with the new application profile over the communication channel 18 using the AOC or EOC channel ( Step 112). In one embodiment, the transmission of this new application profile is used as a message requiring the use of the new application profile.

Profiles exchanged and saved during full initialization

In another embodiment, the transceivers 10 and 14 may be configured to transmit and receive transmission information between the transceivers or the ITU compatible "Full Initialization" protocol of the G.992.2 or G.992.1 ITU standard. 14) exchange new application profiles with each other using similar initialization protocols that interfere with application data communication between them. The use of a fully initialized protocol results in a 10-second drop in the link. This 10 second interruption occurs only once after the first occurrence of a particular set of currently active applications in which a new application profile is exchanged and subsequently stored. In another embodiment, after initialization, the transceivers 10, 14 mediate the supported applications and exchange profiles in response to all possible combinations of active applications.

After the application profiles are exchanged, the transceivers 10 and 14 store the application profiles in local memory 30 and 46 (step 116). As a result, when a new voice application is activated while transceivers 10 and 14 are communicating according to AP # 1 (FIG. 1), the exchange of application profiles over communication channel 18 is not performed (no exchange is required). As will be explained in more detail below, changes to stored AP # 4 (FIG. 1) occur quickly.

Local generation of parameters in application profiles

When exchanging a new application profile between the transceivers 10 and 14, the transceivers 10 and 14 do not need to exchange all transmission parameters of the new application profile over the communication channel 18. In one embodiment, each transceiver 10, 14 may locally generate one or more transmission parameters (e.g., assign them to an application of a subchannel) and generate these locally generated parameters in a suitable application. You can save it to a profile. Local generation of these transmission parameters can be done when initially creating or updating an application profile.

For example, assume that the transceivers 10 and 14 are running two applications, a digital data application and a voice application. The transceivers 10 and 14 exchange information with each other indicating that the connection supports these two applications. Based on this information exchange, each transceiver 10, 14 locally generates one or more transmission parameters for the application profile corresponding to these two applications. Since the two transceivers 10 and 14 mutually generate these transmission parameters, the transceivers 10 and 14 do not exchange locally generated transmission parameters with each other via the communication channel 18. Other transmission parameters, such as those related to framing, coding and interleaving, are determined in the exchange of information between the transceivers 10 and 14.

Mutual generation of transmit parameters has the advantage of reducing or eliminating long exchange messages when initially creating or updating an application profile. For example, if a change in channel condition results in a decrease in the overall data rate of channel 18, then the bit capacity for some subchannels will be lower, and transceivers 10 and 14 will typically receive these affected subs. You will need to exchange updates for all application profiles that specify channels. By mutually generating transmission parameters in the application profile, the transceivers 10 and 14 can locally update the application profile, respectively, without having to exchange update information with each other.

The following three examples illustrate the use of mutually generated parameters when applied to subchannel allocation for two applications, where digital data applications and voice applications. Each example shows an application profile that designates an allocation subchannel for the application as a transmission parameter, which includes (1) one application profile when the digital data application is running alone, and (2) a voice application. This is another application profile for when operating alone, and (3) another application profile for when digital data and voice applications operate simultaneously.

For the first application profile, the transceivers 10, 14 locally assign both available data rates and available subchannels to the digital data application after establishing the connection, respectively. Other transmission parameters that are not mutually generated by the transceivers 10, 14, such as those related to framing, coding and interleaving, are determined in the exchange of information between the transceivers 10, 14.

For the second application profile, transceivers 10 and 14 allocate 64 kb / s to the voice application, regardless of the data rate capability of the connection. Each transceiver 10, 14 uses a predefined technique (e.g., a technique specified by the standard) to select subchannels that are allocated for delivering 64 kb / s of voice application. An example of a scheme that iterates through the available subchannels to select subchannels for voice applications includes: (1) rising from the lowest frequency subchannel to the highest frequency subchannel, and (2) raising the highest frequency. Descend from a usable subchannel to a lower frequency subchannel, (3) from a subchannel with the least number of bits to a subchannel with a large number of bits, and (4) a subchannel with the most number of bits Descent from subchannel with fewer bits. Again, the transceivers 10 and 14 may perform framing, coding and interleaving in a predefined manner or in a manner determined at the time of exchange during initialization.

For the third application profile, each transceiver 10, 14 allocates 64 kb / s to the voice application and the remaining data rate to the digital data application. Similar to the second application profile, each transceiver 10, 14 is assigned to deliver a voice application (e.g., the highest or lowest frequency subchannel or the least or most array of subchannels). Use predefined techniques to select subchannels. In addition, framing, coding, and interleaving are predefined or determined during the exchange as described above.

The transceivers 10 and 14 use a coordinated numbering scheme coordinated against locally generated application profiles (e.g., # 6 = only for digital data applications, # 7 = only for voice applications, # 8 = used for both digital data and voice applications). The numbering scheme may be predefined or the transceivers 10 and 14 may exchange the numbering scheme via the communication channel 18.

The theory of the present invention extends to an embodiment with two or more applications. For such an embodiment, in order to individually combine and generate a corresponding application profile for each possible active application, the transceivers 10, 14 may define rules for selecting application profile transmission parameters and their corresponding parameter values. Follow.

Quick switch to saved application profiles

Through operation of the DSL system 2, applications can be activated and deactivated over time. This change in the active application (i.e. change through activation or deactivation of the application) is known by the transceiver 10 (or receiver), so fast retraining as defined in the ITU G.922.1 and G.922.2 standards. Retrain need not be identified. Because application profiles are changing not because of changes in channel conditions, but because of changes in active applications, retrieval functions such as echo cancellers, equalizers, etc., are being performed as in fast retraining. There is no need to train.

Saving an application profile for continuous use is used by the transceivers 10 and 14 to switch to another application profile since the transceiver does not have to go through the process of creating, exchanging and storing a new application profile. Shorten the handshake between the transceivers 10 and 14.

The remote DMT transceiver 10 or the CO transceiver 14 and one of the receivers or transmitters of the transceivers 10 and 14 may initiate the transition. The stored application profile is verified to allow the transmitter and receiver to simply notify the other party which profile should be used. Information related to the application profile does not need to be sent again. In one embodiment, stored application profiles are numbered. Thus, one transceiver simply assigns a number of application profiles to another transceiver.

Receiver-Initialize Fast Application Profile Switching

4 shows one embodiment of a receiver-initialization process used by remote DMT transceiver 10 and CO transceiver 14 to switch to a stored application profile. Although this process is illustrated by a perspective view of the receiver 26 of the remote DMT transceiver 10, it should be understood that the receiver 42 of the CO transceiver 14 may also initiate the transition. In one embodiment, a change occurs in the current set of active applications (step 140) and requires a switch to another application profile. This change may be the result of an application being activated or deactivated, or an existing application requiring additional bandwidth (e.g., a second voice channel is opened for a voice application that already has only one voice channel in advance). ).

After the change in the active application, the receiver 26 determines which application profile corresponds to the current set of active applications (step 142). Receiver 26 sends a message to transmitter 38 using the AOC or EOC channel specifying the stored application profile that should be used for transmission based on this current set of active applications (step 148). This message corresponds to a request by the receiver 26. For example, if the transceivers 10 and 14 are communicating according to AP # 1 (FIG. 1) when a voice telephone call is activated, the receiver 26 may request to switch to AP # 4 (FIG. 1). Is sent to the transmitter 38. In one embodiment, this request identifies AP # 4 by number 4.

After receiving the request, the transmitter 38 sends an inverted sync symbol as a flag to signal the receiver 26 that the required stored application profile is used for transmission and is ready to synchronize its use (step 152). ). The transmitter 38 uses its stored copy of the designated application profile for transmission on the first frame or on a predetermined number of frames, followed by an inverted sync symbol. This inverted sync symbol corresponds to the "Go" message sent by the transmitter 38. The receiver 26 detects the inverted sync symbol (step 156) and uses a predetermined number of frames received after the inverted sync symbol, or in a designated application profile on the first frame, in synchronization with the transmitter 38.

The inverted sync symbol is a sync symbol in which phase information of the QAM signal is shifted by 180 degrees. Phase shifts of sync symbols other than 180 degrees may also be used in the "Go" message. The sync symbol is defined in the ANSI and ITU standards as a fixed non-data-transfer DMT symbol transmitted every 69 symbols. The sync symbol is constructed by modulating all DMT carriers with a predefined pseudorandom sequence using basic QPSK (2-bit QAM) modulation. This sync symbol signal, used through the transceiver initialization process, has a special autocorrelation characteristic that can detect sync symbols and inverted sync symbols even in very noisy environments.

Because of its general invulnerability to channel noise, using an inverted sync symbol to synchronize the use of a new application profile by the transceiver 10, 14 is more robust than using an EOC or AOC channel. robust. In contrast, messages sent over an EOC or AOC channel can be more easily damaged by noise on communication channel 18 than inverted sync symbols. This overhead channel is multiplexed in the data stream in framer 72 and therefore transmitted in spherical amplitude modulation over a finite number of DMT subchannels. Impulse noise or other noise occurring on communication channel 18 may cause a bit error in an EOC or AOC channel message, so the message may be lost. Although the sensitivity to noise of the EOC or AOC channel is greater than that of the inverted sync symbol, in one embodiment, the EOC or AOC channel is used to convey a "Go" message.

The receiver-initialization switch to the stored application profile is completed quickly, requiring only the exchange of two messages (a request and a "Go" message) since the appropriate application profile does not need to be stored and exchanged. Again, using the inverted sync symbol as the "Go" message makes the synchronization between the transceivers 10 and 14 robust in noisy environments.

Transmitter-Initialization Fast Application Profile Switching

5 illustrates one embodiment of a transmitter-initialization process used by remote DMT transceiver 10 and CO transceiver 14 for switching to a stored application profile. Although this process is shown in perspective view of transmitter 22 of remote DMT transceiver 10, it should be understood that transmitter 38 of CO transceiver 14 may also initiate a transition. Before that, when a change occurs in the current set of active applications (step 160), the change requires a switch to another application profile. Again, this change results from the application being activated or deactivated or added to the existing application. This may be the result of requiring an extra bandwidth (eg, the second voice channel is opened for a voice application that already has only one voice channel).

After the change in the active application, the transmitter 22 determines which application profile corresponds to the current set of applications. The transmitter 22 sends a message to the receiver 42 using the AOC or EOC channel specifying the stored application profile used for transmission based on the current set of active applications (step 168). The message may identify, by number or by any other identification method, a suitable stored application profile specifically associated with that stored application profile. This message corresponds to a request by the transmitter 22. After receiving the request, receiver 42 returns a " grant " or " deny " message to transmitter 22 (step 172).

When the transmitter 22 receives the "OK" message, the transmitter 22 sends an inverted sync symbol as a flag to signal the receiver 42 that the required stored application profile will be used for transmission (step 176). The transmitter 22 then uses that stored copy of the designated application profile for transmission on the first frame or on a predetermined number of frames, followed by an inverted sync symbol. The inverted sync symbol corresponds to the "Go" message sent by the transmitter 22. The receiver 42 detects the inverted sync symbol ("Go") (step 180) and initiates communication using the application profile designated for reception on the first frame or on the predetermined number of frames, and the transmitter 22 Followed by a sync symbol inverted to sync.

Transmitter-initialization transitions for stored application profiles are completed quickly, requiring the exchange of three messages (request, reject or acknowledgment messages, and Go messages) when the transmitter-initialization does not need to store and exchange the appropriate application profile. do. Again, using the inverted sync symbol as the "Go" message makes the synchronization between the transceivers 10 and 14 robust in noisy environments.

In another embodiment, the transceivers 10, 14 are applications of the transceivers 10, 14 for training and exchanging transmission information between the transceivers, or the "fast retraining" protocol defined in the ITU G.922.2 specification. Switch to a stored application profile using a similar fast initialization protocol that interferes with data communication. Fast retraining results in a 1 to 2 second outage between the transceivers 10 and 14.

Update of application profile

In some circumstances, the contents of the stored application profile 34 (and corresponding application profile 50) may require an update. For example, communication channel 18 conditions may change (eg, when the telephone connection is lost), which means that the data rate performance of channel 18 and other bit capacities of any subchannels of channel 18. This results in an increase or decrease in. The transceivers 10 and 14 need to update all stored application profiles that specify the bit capacity of the affected subchannels. In one embodiment, each transceiver 10, 14 locally updates its own stored copy of the affected application profile without having to exchange update information with each other. In yet another embodiment, the transceivers 10 and 14 exchange update information with each other.

Although the present invention has been shown and described with reference to certain preferred embodiments, the invention is not to be construed to depart from the spirit and scope of the invention as defined in the following claims by those skilled in the art. It is to be understood that various changes in details and details may be made. For example, although the present invention has been described with respect to DMT modulation, the theory of the present invention can also be applied to DWMT (Discrete Wavelet Multitone) modulation. In addition, IP frames can be used to transmit data instead of ATM packets. In addition, although the specification uses ADSL to describe the present invention, it should be understood that any form of DSL, ie, VDSL, SDSL, HDSL, HDSL2 or SHDSL, may also be used. The theory of the present invention also applies to any DMT communication system that supports multiple sets of applications, where the applications are activated or deactivated over time. Although some embodiments described above include Internet and voice applications, the present invention also provides for any of the applications delivered via a DSL system (e.g. telecommuting, video conferencing, high speed Internet access, video on demand). It should be understood that this applies to the combination of.

Claims (26)

In a multicarrier modulation system comprising two transceivers communicating with each other via a communication channel, a method for supporting a plurality of applications, the method comprising: Create a plurality of application profiles each corresponding to one or more applications in a particular set and each specifying at least one transmission parameter for each application in the particular application set for transmitting information associated with the application over the communication channel. Defining steps, Storing the plurality of application profiles in one of the transceivers; Transmitting information in accordance with the stored first application profile corresponding to the current set of active applications; In response to a change in a current set of active applications, selecting a stored second application profile corresponding to the one or more applications in the changed set of current active applications, and Switching to transmit information in accordance with the stored second application profile without disrupting communication between the transceivers to retrain the transceiver. Application support method comprising a. 2. The method of claim 1, further comprising receiving a message confirming the second application profile with an application profile for use in subsequent communications. 2. The method of claim 1, further comprising sending a message to one of the transceivers confirming the second application profile as an application profile for use in subsequent communication between the transceivers. 2. The method of claim 1 further comprising sending a message to one of the transceivers requesting a switch to the second application profile. 5. The method of claim 4, further comprising receiving a response message from the one transceiver acknowledging the request to switch to the second application profile. 6. The method of claim 5, further comprising sending another message to the one transceiver acknowledging acknowledgment and synchronizing the use of the second application profile. 6. The method of claim 5 wherein the other message is an inverted sync symbol. 5. The method of claim 4, further comprising receiving a response message from the one transceiver acknowledging the request and synchronizing use of the second application profile. 9. The method of claim 8, wherein the response message is an inverted sync symbol. 2. The method of claim 1, further comprising transmitting at least one of the application profiles to the other transceiver over the communication channel without performing full initialization of the transceiver. 2. The method of claim 1, further comprising performing a complete initialization of the transceivers to exchange one of the application profiles between the transceivers. The method of claim 1, further comprising generating one of the application profiles after initial generation of a specific set of active applications and associating the generated application profile with the specific application set. 2. The method of claim 1, further comprising locally generating at least one transmission parameter for one of the stored application profiles by each transceiver. 2. The method of claim 1 wherein the transceiver is preconfigured with the stored application profile. The method of claim 1, wherein the at least one transmission parameter specified for each application of one of the stored application profiles is a subchannel allocated for transmission data rate, downstream and upstream transmission, and assigned to each of the subchannels. At least one of number of bits, performance margin, fine gain adjustment for each of the subchannels, interleaved depth, minimum and maximum QAM array size, length of cyclic prefix, codeword size, framing mode and grid code. The application of claim 1, wherein the stored first application profile is characterized by transmission of a signal associated with a web browsing application, wherein the stored second application profile is characterized by simultaneous transmission of a signal associated with a voice telephony application and the web browsing application. How to apply. CLAIMS What is claimed is: 1. A method for supporting a plurality of applications that are active between transceivers in a multicarrier modulation system comprising transceivers that communicate with each other via a communication channel. Creating a plurality of application profiles characterizing information transmission over the communication channel; Associating each application profile with a particular set of one or more applications that are activated between the transceivers; Storing the application profile in the transceiver; Transmitting information over the communication channel according to a stored first application profile corresponding to a current set of active applications; Responsive to a change in a current set of active applications that is active between the transceivers, retrieving a second profile of the application profile corresponding to the changed set of currently active applications, and Switching to transmit information over the communication channel according to the second application profile Application support method comprising a. 18. The method of claim 17, wherein the switching is performed to retrain the transceiver without disrupting communication between the transceivers. 18. The method of claim 17, wherein the switching comprises retraining the transceiver to communicate in accordance with the stored second application profile. A multicarrier modulation system comprising a transceiver in communication with one another over a communication channel, the method for supporting a plurality of applications, the method comprising: Create a plurality of application profiles each corresponding to one or more applications in a particular set and each specifying at least one transmission parameter for each application in the particular application set for transmitting information related to the application over the communication channel. Defining steps, Storing the plurality of application profiles in one of the transceivers Application support method comprising a. In a multicarrier modulation system comprising a transceiver for communicating over a communication channel, A method for supporting multiple applications is Create a plurality of application profiles each corresponding to one or more applications in a particular set and each specifying at least one transmission parameter for each application in the particular application set for transmitting information related to the application over the communication channel. Defining steps, Storing the plurality of application profiles in the transceiver; Transmitting information in accordance with the stored first application profile corresponding to the current set of active applications; In response to the change in the current set of active applications, selecting a stored second application profile corresponding to the changed set of currently active applications, and Switching to transmit information according to the stored second application profile without having to retrain the transceiver; Application support method comprising a. 22. The method of claim 21, further comprising sending a message confirming the second application profile to an application profile for use in subsequent communications. 22. The method of claim 21, further comprising receiving a message identifying the second application profile as an application profile for use in subsequent communications. In a multicarrier modulation system comprising a transceiver for communicating over a communication channel, A method for supporting multiple applications is Create a plurality of application profiles each corresponding to one or more applications in a particular set and each specifying at least one receiving parameter for each application in the particular application set for receiving information related to the application over the communication channel; Defining steps, Storing the plurality of application profiles in the transceiver; Receiving information according to a stored first application profile corresponding to a current set of active applications; In response to the change in the current set of active applications, selecting a stored second application profile corresponding to the changed set of currently active applications, and Switching to transmit information according to the stored second application profile without having to retrain the transceiver Application support method comprising a. 25. The method of claim 24, further comprising sending a message confirming the second application profile with an application profile for use in subsequent communications. 25. The method of claim 24, further comprising receiving a message identifying the second application profile as an application profile for use in subsequent communications.