System for optimizing achievable rate and method adapted to a digital subscriber line communication system

Abstract

For digital subscriber lines, the entire system needs to deal with the crosstalk problem of adjacent cable pairs in the same cable bundle. The present disclosure provides a mechanism for dynamic spectrum management to reduce crosstalk between subscriber lines by reducing the unnecessary power spectral density on some subscriber lines to optimize the overall performance of many subscriber lines. The decision of this reduction (or power back-off) is generally based on the loop distance between the central office and the customer equipment. The shorter the loop distance, the lower the power. However, this does not take into account the quality of each subscriber line, i.e., its background noise and external interference. The transceivers can receive this information, such as background noise and external interference. The negotiation procedure includes this information to adjust the power reduction so that the reduction does not degrade the potential best performance of these subscriber lines.

Description

Technical Field

[0001] This disclosure relates to high-speed synchronous data transmission systems using multiple signal subcarriers, such as systems operating on Digital Subscriber Line (DSL). More specifically, this disclosure relates to global and local performance optimization of DSL systems, particularly for Very High-Bit-Rate Digital Subscriber Line (VDSL) and future variants, which are more susceptible to crosstalk throughout the system. Background Technology

[0002] Since its invention and standardization in 1999, Asymmetric Digital Subscriber Line (ADSL) has enjoyed immense popularity. ADSL represented a significant technological leap forward from voiceband modems, which used only a 4 kHz voice band. In many countries around the world, ADSL became ubiquitous, providing broadband internet access to homes alongside the widespread deployment of telephone lines. Broadband speeds increased from just 50 kilobits per second (Kbps) with voiceband modems to 8 megabits per second (Mbps) with the 1 MHz bandwidth of ADSL. Over the years, ADSL technology has continued to advance. With these advancements, more and higher bandwidth has been used to increase attainable speeds. The fundamental frequency bandwidth is distributed between 1MHz and 2MHz (ADSL2+), 8MHz / 17MHz / 35MHz (VDSL2), and 106MHz / 212MHz (GFAST). This bandwidth is averaged across a set of subcarriers with orthogonal frequencies; this technique is called Discrete Multitone (DMT). With technological advancements, it was discovered that crosstalk between telephone lines within the same cable bundle becomes increasingly severe as the bandwidth increases. To achieve optimal overall system performance, a technique called vectorization was subsequently developed to eliminate most of the crosstalk in the same digital subscriber line technology. Crosstalk can be evaluated at subcarrier frequency levels within the same bandwidth. With a good estimate of crosstalk, the terminals of the Digital Subscriber Line Access Multiplexer (DSLAM) stationed at the central office (CO) can effectively eliminate most unwanted crosstalk. However, with the emergence of new technologies, the bandwidth involved will become higher and higher, and the crosstalk problem will become more and more serious. Therefore, how to eliminate crosstalk has become more and more important.

[0003] To address the increasing crosstalk interference throughout the digital subscriber line (DSL) system, several ideas have been proposed and implemented. One such idea is Dynamic Spectrum Management (DSM), primarily contributed by Professor John Cioffi and his team at Stanford University. DSM techniques are categorized into several levels of coordination. At level 0, there is no coordination mechanism; each user treats other users' signals as noise and seeks to maximize its own data rate in a distributed manner. This is known as Iterative Water-filling (IWF). Then, at level 1, since it is not necessary to reach the service rate of short-distance users close to the central office, the Spectrum Management Center (SMC) at the DSL multiplexer terminal can coordinate some power back-off for short-distance users, thereby reducing crosstalk to other long-distance users who require full power to reach their service rates. Subsequently, in Level 2, the spectrum management center can centrally coordinate the spectrum of all modems, using an optimal spectrum balancing (OSB) mechanism to maximize the weighted sum of rates for all users. The spectrum management center can determine the upstream and downstream power spectrum densities (PSDs) to achieve the aforementioned goal (i.e., maximizing the weighted sum of rates for all users). In Level 3 of dynamic spectrum management, coordination or vectorization is completed when all modems terminate at the same digital subscriber line access multiplexer, creating multiple-input multiple-output (MIMO) channels.

[0004] In the application of asymmetric digital subscriber lines (ADSL or G.DMT), only downstream power reduction / politeness is considered. This can be considered Level 0 of dynamic spectrum management, as it is only to avoid signal saturation of the shortest loop length. Second-generation asymmetric digital subscriber lines (ADSL2 and ADSL2+) consider Level 1 of dynamic spectrum management, which provides power reduction for both upstream and downstream, and can be jointly determined by the central office terminal and the customer premises equipment (CPE) terminal. However, second-generation asymmetric digital subscriber lines only have one-way negotiation, meaning that if one terminal (the central office terminal or the CPE terminal) chooses a larger power reduction, that is the final decision.

[0005] In the application of Generation II High Bit Rate Digital Subscriber Line (VDSL2), it can be considered the second level of dynamic spectrum management. The detailed power spectrum shape of the uplink and downlink can be determined by the central office terminal and negotiated jointly by the central office and the user equipment. With the advent of vectorization standards, Generation II High Bit Rate Digital Subscriber Line also implemented the third level of dynamic spectrum management. The Vectoring Control Entity (VCE) resident at the central office terminal controls all connected user equipment to align symbol boundaries, thereby making the desired signal orthogonal to crosstalk, and eliminating crosstalk through matrix operations. Through these dynamic spectrum management techniques, the overall rate of all users is significantly improved. By using vectorization techniques to eliminate most crosstalk, the high-frequency bands affected by crosstalk between users are greatly improved. This allows the overall average user data rate to reach at least 95% of the data rate under crosstalk-free conditions. In contrast, without these techniques, the overall average user data rate may have degraded by 30-50% due to crosstalk between users.

[0006] Despite the insights gained from these existing technologies, some areas remain unconsidered. Level 2 of dynamic spectrum management strictly considers power backoff or power spectral density patterns based on electrical length (the estimated loop distance between the central office and user equipment). For shorter loop distances, the power spectral density or power tends to decrease because less power is required to meet service demands. This reduction in power and power spectral density also benefits the overall system by reducing crosstalk to other users. The final decision on power / power spectral density is made by the central office terminal, while user equipment can only negotiate and suggest lower power than the central office terminal. In poor line conditions (e.g., with static ambient noise or RF interference), the reduced power / power spectral density may prevent the line from reaching its desired optimized rate. The line may even fail to reach its service rate. Summary of the Invention

[0007] In view of the above, this disclosure provides an improved system and method thereof. Due to the shorter distance and consideration of the noise floor, this disclosure can maintain an optimized rate of power and power spectral density reduction with a balance.

[0008] In some embodiments, this disclosure provides an improved initialization switching protocol. The final decision on power and power spectral density levels is simplified by taking into account electrical length and noise profile.

[0009] In some embodiments, this disclosure provides an improved system and method for balancing the overall system's far-end crosstalk (FEXT) and each noise feature.

[0010] In some embodiments, this disclosure applies the aforementioned method to any high-speed digital subscriber line system, and the high-speed digital subscriber line system may require reduced power control to achieve the system's far-end crosstalk performance while also achieving the optimal performance of a single digital subscriber line.

[0011] In some embodiments, the system of this disclosure eliminates potential suboptimal rates resulting from decisions to reduce power alone by referencing an estimated electrical length between the terminal of the central office and the terminal of the user equipment. In a preferred embodiment, the signal carries information according to known protocols and standards. First, the system includes a training protocol to identify characteristics of a single system, such as loop distance, static ambient noise, and radio frequency interference. Self-crosstalk is becoming increasingly important throughout digital subscriber line systems, but fortunately, it can be significantly reduced through advanced digital subscriber line technologies. One important technique is reducing the transmission power or power spectral density level of lines with shorter distances between the terminal of the central office and the terminal of the user equipment. This technique is used to mitigate crosstalk in the near-far problem, where a shorter distance means the user equipment is close to the central office and the central office generates strong crosstalk to more distant user equipment. Because the signal attenuation of the lines is less, these lines do not need to achieve the service rate at full power or power spectral density level. When the estimated loop distance or electrical length is known, the power back-off described herein can be implemented by the transmitters of the two terminals (such as the central office terminal and the user terminal). This power back-off technique can effectively reduce the high-intensity crosstalk (self-far-end crosstalk) from these shorter lines to other longer lines. Both the central office terminal and the user terminal measure the received signal, and knowing the power spectral density level of the peer transmission, the central office terminal and the user terminal further eliminate signal attenuation and loop distance. The central office terminal and the user terminal also measure their noise or signal-to-noise ratio (SNR) to determine whether the power back-off will prevent them from achieving the target service rate.

[0012] Without this invention, power backoff determined solely by loop distance may result in an excessively low power spectral density. In such cases, the reduced signal level is insufficient to provide a adequate signal-to-noise ratio (SNR) to match the service rate, compared to the noise level. This situation is undesirable for those skilled in the art, given the very high quality requirements of short loops. Once it is determined that the resulting SNR may not support the service rate, a mechanism is needed to adjust the power spectral density or power backoff to ensure the new transmitted signal has the desired SNR level.

[0013] In one embodiment, an additional switching phase is added so that once the receiver has collected noise information and the signal-to-noise ratio (SNR), the power spectral density (PSD) level of the transmitter at the same level can be adjusted as needed. In high-bit-rate digital subscriber line (DLC) standards, the protocol for PSD / power backoff decisions is completed during the channel exploration phase, the first phase of initialization. Signal and noise measurements can be performed during this phase. However, in the current protocol, this phase is susceptible to self-far-end crosstalk (SAC), which can mislead noise measurements. In the second phase (i.e., the training and analysis phase), SAC can be measured and eliminated. Afterward, the actual noise measurements and their resulting SNR become meaningful for the final service. Therefore, in one embodiment, a retraining mechanism can be included to restart a new initialization procedure so that the PSD / power backoff decision takes noise into account. This procedure is optional if the measured noise does not affect the target service rate under the current power backoff.

[0014] During the channel exploration phase, multiple pieces of information are exchanged between the central office's terminal and the user terminal's terminal. The "O-Signature Information" is the first piece of information in this phase. This first information conveys the central office's settings regarding the power spectral density mask, uplink power backoff parameters, and many other settings. The user terminal can begin measuring the signal in the "O-Signature Information"; using the actual power spectral density information transmitted by the central office contained in this information, the user terminal can deduce the channel attenuation, and thus the loop distance / electrical length. Channel attenuation, or loop attenuation, refers to the signal interval between the transmitter's power spectral density level and the receiver's power spectral density level. The physical loop distance or electrical length is a single value "kl0," representing the loop attenuation across the operating bandwidth. Power backoff is determined by predetermined rules involving uplink power backoff parameters "a" and "b," the electrical length "kl0," and the subcarrier frequency. Next, the user terminal begins transmitting its first information (i.e., the "R-MSG1 Information," which contains the actual power spectral density / uplink power backoff). Subsequently, the central office measures the signal and, together with the power spectral density information in the "R-MSG1 message," derives the channel attenuation and loop distance (or electrical length). The user terminal equipment also transmits its estimated electrical length to the central office's terminal, and the central office will generate a final decision on the electrical length in the next message (i.e., the "O-UPDATE message"). The central office can specify a power spectral density ceiling to further limit the uplink power spectral density. Uplink power back-off is finalized by the final electrical length and can be implemented by the user terminal equipment at the beginning of the training phase. Downlink power back-off is finalized after receiving the "R-UPDATE message," where the user terminal equipment can request the downlink power spectral density ceiling and can also be implemented by the user terminal equipment at the beginning of the training phase. Similarly, in the "O-PRM message," the central office transmits the final decision on power spectral density / downlink power back-off to the user terminal equipment. In the "R-PRM message," the user terminal equipment transmits the final decision on power spectral density / uplink power back-off to the central office's terminal.

[0015] As mentioned above, both terminals (the central office terminal and the user terminal terminal) need to measure noise beyond the signal. To better measure the actual noise after far-end crosstalk is eliminated, this procedure can be performed in the second phase (training and analysis phase). The central office terminal will coordinate all its connected lines and attempt to eliminate far-end crosstalk in the best possible way. Then, the two terminals measure the actual residual noise and determine if the signal-to-noise ratio (SNR) is sufficient to support its target service rate. There are two possibilities: first, the SNR is sufficient, therefore the power backoff / power spectral density level is appropriate, and the final phase can proceed; or second, the SNR is insufficient, therefore the power backoff / power spectral density level needs adjustment. In the second case, since the power spectral density level is finalized at the beginning of the training and analysis phase, recalibration may be necessary. This recalibration can be performed in the "R-UPDATE information" and "O-PRM information". The “R-UPDATE message” conveys a request for upshifting the downlink power backoff power spectral density (DPBO PSD) to increase the received signal level and thus improve the signal-to-noise ratio. The “O-PRM message” conveys a request for upshifting the uplink power backoff power spectral density (UPBO PSD) to achieve the same effect in the uplink direction as in the downlink direction. The two terminals determine the final power spectral density and power backoff, and apply them to the initial period of the training phase as described above.

[0016] Although the following description illustrates a preferred embodiment of the present disclosure relating to a high bit rate digital subscriber line transceiver, it will be apparent to those skilled in the art that the present disclosure can be helpful in many situations where insufficient data rates are caused by power back-off. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a typical digital subscriber line system and circuit according to an embodiment of the present disclosure, and its connection with a peer system and circuit.

[0018] Figure 2 This is a schematic diagram of a high bit rate digital subscriber line protocol phase according to an embodiment of the present disclosure, and can be implemented according to a standard.

[0019] Figure 3 A flowchart illustrating the general process for making decisions about power / power spectral density as defined in the standard.

[0020] Figure 4 This is a flowchart illustrating the decision-making and recommendation process for power / power spectral density as disclosed in this publication.

[0021] Figure 5 This is a flowchart illustrating the algorithm involved in this disclosure.

[0022] Symbol Explanation

[0023] 100: System

[0024] 101: Central Processing Unit

[0025] 102: Memory

[0026] 103: Digital Application-Specific Integrated Circuits

[0027] 104: Digital Front End

[0028] 105: Simulated Front-end

[0029] 110: Path

[0030] 120: Same-level system

[0031] 201: System

[0032] 202: Exchange Agreement

[0033] 203: Channel Exploration Phase

[0034] 204: Training and Analysis Phase

[0035] 205: Exchange Phase

[0036] 206: Performance Time Phase

[0037] 210: Recalibration Phase

[0038] 301-306: Steps

[0039] 401-406: Steps

[0040] 500-510: Steps Detailed Implementation

[0041] Reference Figure 1 . Figure 1A system 100 according to an embodiment of the present disclosure is shown. System 100 is a typical digital subscriber line system, comprising a central processing unit 101, a memory 102, an application-specific integrated circuit (ASIC) 103, a digital front-end 104, and an analog front-end 105. The central processing unit 101 performs intelligent operations, including protocol implementation, control of the design of the ASIC 103 and the ASIC 105, and execution of important algorithms. Because telephone circuits have lower quality compared to Ethernet or fiber optics, it is important to achieve the theoretical limits of this medium through many innovative algorithms. Thus, the protocols themselves are more complex than other technologies. The central processing unit 101 may include logic units responsible for executing algorithms and protocols. The algorithms for negotiating power spectral density levels or power backoff levels of the present disclosure are stored in the logic of the central processing unit 101 and its associated memory 102. The digital subscriber line signal generated from the application-specific integrated circuit (digital application-specific integrated circuit 103) is transmitted to the telephone line via digital and analog signal processing units (digital front-end 104 and analog front-end 105), i.e. Figure 1 The path 110 is shown. At the other end, an embodiment of a similar system represents a peer digital subscriber line modem (i.e., peer system 120).

[0042] Reference Figure 2This is a preferred embodiment of system 201 of the present disclosure. System 201 is used to implement the High Bit Rate Digital Subscriber Line (HDR) protocol as defined in standard “ITU-T G.993.2”. Block 202 is a common exchange protocol representing all relevant standards for digital subscriber lines (hereinafter referred to as exchange protocol 202). This common exchange protocol 202 is referred to as “G.944.1”, “G.hs”, or “G.handshaking”. Both parties to the data exchange use this protocol to identify the capabilities supported by the other party. Once the parties agree on the capabilities of the HDR, the HDR protocol continues. Phase 203 (hereinafter referred to as channel exploration phase 203) is the first phase of HDR. In this phase (i.e., channel exploration phase 203), the central office and the user terminal equipment send their first signals and measure the signals they receive. First, the central office and the user terminal equipment send invalid data signals or mute signals for a predetermined period of time, so that peer points can prepare to detect the first valid data signal or the first non-mute signal. After the predetermined time period has elapsed, the central office and user terminal equipment send signals with a first predetermined pattern for detection and analysis by peer points. This signal detection and analysis is performed by applying a Fast Fourier Transform (FFT) to the signals in the time domain or frequency domain of signal processing. The central office and user terminal equipment calculate the average and variance based on these signals with repeating patterns in the frequency domain. The central office and user terminal equipment analyze these signal patterns to explore channel characteristics, including electrical length. Further information exchange is then conducted to ultimately determine the electrical length, thereby determining the power spectral density level. The new power spectral density level includes power backoff (uplink power backoff / downlink power backoff) and is implemented at the start of the next phase. Phase 204 (hereinafter referred to as Training and Analysis Phase 204) is the second phase of the High Bit Rate Digital Subscriber Line (HLT) protocol. In this phase (i.e., training and analysis phase 204), the central office and user-end equipment further train and fine-tune their receivers (e.g., equalizers) and gain control. The central office will also train its crosstalk cancellers (referred to as the pre-encoder and post-encoder). The vectorized control entity at the central office performs matrix operations on the uplink pre-encoder and on the downlink post-encoder. After this crosstalk cancellation phase of the high bit-rate digital subscriber line protocol training and analysis, the actual residual signal-to-noise ratio and noise floor can be measured.

[0043] This disclosure introduces a new test for the signal-to-noise ratio to ensure that its target service rate is not affected by power backoff. Block 210 (i.e., recalibration to set a new power spectral density, hereinafter referred to as recalibration phase 210) is an additional phase executed when power backoff is inappropriate, after which the process returns to channel exploration phase 203 to renegotiate the power backoff. Detailed negotiation procedures will be provided later. Figure 4 Note: If the power back-off is found to be appropriate for its service, this additional phase (i.e., recalibration phase 210) may be unnecessary, and the next phase can proceed directly.

[0044] Block 205 (hereinafter referred to as Exchange Phase 205) is the third phase. The two parties will finalize the remaining parameters and prepare to enter the Showtime procedure. They will also exchange these parameters so that peer points can simultaneously prepare their transmitters. If all goes well, the two parties enter phase 206 (hereinafter referred to as Showtime Phase 206). At this point, training and initialization are complete, and data transmission and service can begin. In this embodiment, any of the Channel Exploration Phase 203, Training and Analysis Phase 204, and Exchange Phase 205 can be an initialization phase of a high bit-rate digital subscriber line performed by System 100.

[0045] Reference Figure 3 ,for Figure 2A detailed flowchart illustrating the information exchange during channel exploration phase 203 is provided. Step 301 includes the step of the central office sending the first message (i.e., the "O-SIGNATURE message") to the user terminal equipment in this phase (i.e., channel exploration phase 203). This first message (i.e., the "O-SIGNATURE message") is also the first signal from the central office to the user terminal equipment for initial locking and measurement. The central office embeds some information in the message (i.e., the "O-SIGNATURE message") to inform the user terminal equipment of the power spectral density level it is transmitting. In this way, the user terminal equipment can estimate signal attenuation and loop attenuation, and further derive the electrical length and the power spectral density (UPBOPSD) of the transmitter's uplink power backoff. Step 302 includes the step of the user terminal equipment sending the first message (i.e., the "R-MSG1 message") to the central office's terminal. This allows the central office to perform initial locking and measurement. The "R-MSG1 message" also embeds the power spectral density level (UPBO PSD level) of the uplink power backoff transmitted by the user terminal equipment. The central office (COA) can estimate signal attenuation and loop attenuation to derive the electrical length. In the “R-MSG1 message,” the user terminal equipment also transmits its estimated electrical length so that the COA can make a final decision on the accuracy of the electrical length. Next, in step 303, the COA sends a second message (“O-UPDATE message”) specifying the final electrical length followed by the user terminal equipment and specifying the limits of the uplink power back-off power spectral density level (UPBO PSD level), which provides an upper limit to the power spectral density used to limit the uplink power back-off. In step 304, the user terminal equipment then sends its “R-UPDATE message,” which provides the limits of the downlink power back-off power spectral density level. Finally, in steps 305 and 306, both parties (i.e., the central office and the user terminal equipment) transmit information to the other regarding the form of their final power back-off power spectral density (PBOPSD) (i.e., "O-PRM" and "R-PRM") to take electrical length and limits into account. This clarifies the decision-making process for transmitter power and power spectral density levels as defined by the high bit rate digital subscriber line standard.

[0046] Reference Figure 4This is a flowchart illustrating the information exchange process in channel exploration phase 203. Steps 401, 402, and 403 are the same as steps 301, 302, and 303, and will not be repeated here. In step 404, the "R-UPDATE information" has a new information field for the user terminal equipment to provide a power spectral density upshift (DPBO PSD upshift) for downlink power backoff. This upshift is an embodiment of this disclosure; if the user terminal equipment measures its noise floor and the received downlink power backoff cannot support its optimized rate, the user terminal equipment can provide a nonzero upshift in the power spectral density level. The central office can consider this upshift in its final downlink power backoff power spectral density. Next, in step 405, specifically in the "O-PRM Information," the central office transmits the final determined power spectral density shape (DPBO PSD shape) for downlink power backoff. The central office can also, after measuring its noise floor, choose to shift a non-zero value upwards on the power spectral density level for uplink power backoff. Ultimately, the "R-PRM Information" in step 406 is unchanged from the "R-PRM Information" in step 306 (that is, step 406 is the same as step 306, and will not be repeated here).

[0047] Reference Figure 5This is a flowchart illustrating the algorithm involved in this disclosure. Step 500 includes the algorithm used. Step 501 is the agreed starting point, which in high bit rate digital subscriber lines is the channel exploration phase 203. Step 502 is the signal and noise measurement, wherein the signal and noise can be measured at different appropriate times. Step 503 is the signal-to-noise ratio estimation and bit-load allocation algorithm. The signal-to-noise ratio can be simply derived from the difference between the signal and noise of each subcarrier obtained above, or obtained by other more advanced techniques. A simple bit-load allocation per subcarrier can be proportional to the signal-to-noise ratio of the subcarrier. Once the bit-load allocation per subcarrier is determined, the estimated potential data rate can be obtained by summing the data bits of each subcarrier in a set of subcarriers (step 504). The sum of data bits represents the total number of data bits per symbol, and the achievable data rate is obtained by multiplying the symbol rate (number of symbols per second) and the total number of bits per symbol, and then subtracting the framing and coding overhead. Next, in step 505 (i.e., the decision block), the obtained achievable data rate is compared with the target service rate, resulting in two different process paths (executing step 510 or step 506). In embodiments of this disclosure, the process path leading to step 510 is implemented, namely, recalibration to implement negotiation of a new power spectral density. Specifically, if the obtained achievable data rate cannot support the target service rate, step 510 is executed. Conversely (if the obtained achievable data rate can support the target service rate), step 506 is executed to continue with the remaining agreement phases (which are the same as in the prior art). Once the final phase is completed, the performance time phase in step 507 is entered.

[0048] In the ideal channel exploration phase 203, all information, including signal, noise, attenuation, and the transmitter's power spectral density level, can be collected. However, the noise measured in this phase is not the final result; the high-intensity crosstalk in the digital subscriber line system will be addressed in the training and analysis phase in the next phase. Once the pre-encoder and post-encoder have been trained against crosstalk, it is generally not expected that the power spectral density level will be adjusted again. Therefore, the standard does not allow any changes to the power spectral density at this point. After most of the crosstalk has been eliminated, the actual noise floor can be used to estimate the final achievable rate. Once it determines whether the power spectral density level is too low (insufficient) or sufficient, subsequent steps can be executed based on the decision. If the power spectral density level is too low, a recalibration can be triggered to return to the channel exploration phase 203. At this point, an upward shift of the power spectral density can be proposed to achieve a higher rate. If it is determined that the power spectral density level is sufficient to support the target service rate, the final phase and performance time can continue.

[0049] Although this disclosure has been described with reference to preferred embodiments, it will be apparent to those skilled in the art that many modifications and variations can be made to the embodiments while retaining the teachings of this disclosure. For example, although the foregoing description uses high bit rate digital subscriber line as an example, the teachings of this disclosure can also be applied to other digital subscriber line technologies, such as G.fast and various family members of technologies commonly referred to as xDSL. It should be noted that, generally, the recalibration action in recalibration stage 210 can occur in a stage later than step 304 or in step 304. Regarding the decision process for power / power spectral density levels, the supplements to the exchanged information fields may be added to other information or added to “R-UPDATE” (step 404) and “O-PRM information” (step 405). Therefore, the scope of this disclosure should not be defined solely by reference to the foregoing description, but rather by reference to the appended claims and their equivalents.

Claims

1. A system for optimizing achievable rates adapted for when a power spectral density reduction based on loop distance is affected by a noise floor, wherein a handshake protocol of the system for optimizing achievable rates includes an additional information field to recalibrate and set a power spectral density level, the system for optimizing achievable rates comprising a processor and a memory to execute a program, the program comprising: a logic to execute a noise measurement algorithm after a stage of crosstalk cancellation; a logic to execute a signal measurement algorithm, wherein the signal measurement algorithm is compared to a known power spectral density level at a transmitter end; a signal-to-noise ratio and data rate estimation algorithm comprising: calculating an estimated data bit loading allocation for one of a set of subcarriers based on a signal-to-noise ratio of the subcarrier; summing the estimated data bit loading allocation for each of the set of subcarriers; and determining an estimated data rate by a total number of bits per symbol and a number of symbols per second; and a decision block to compare the estimated data rate to a target service rate and to: continue a training phase when the target service rate is met; or recalibrate to set new parameters and negotiate a power spectral density level or a power backoff level to meet the target service rate.

2. The system for optimizing achievable rates as recited in claim 1, wherein, The system for optimizing achievable rates implements an initialization protocol between a central office end and a customer premises equipment end to prepare for a data transmission service by a digital subscriber line transceiver comprising a transmitter and a receiver.

3. The system for optimizing achievable rates as recited in claim 2, wherein, The initialization protocol includes at least one of a channel sounding phase, a training and analysis phase, and a handshake phase.

4. The system for optimizing achievable rates as recited in claim 1, wherein, The power spectral density reduction is a technique for crosstalk mitigation of near-end far-end problem, the power spectral density reduction is made based on loop distance such that the transceiver has a power backoff for shorter loop distance and the transceiver does not have the power backoff for longer loop distance.

5. The system for optimizing achievable rates as recited in claim 4, wherein, The power backoff is determined by the transceiver, a power spectral density level of a peer transmitter, and a measured received signal such that the transceiver and the peer transmitter derive a signal attenuation and a loop attenuation.

6. The system for optimizing achievable rates as recited in claim 1, wherein, The crosstalk cancellation is a technique to align adjacent digital subscriber lines to mathematically leave a main signal and crosstalk to quadrature terms and to cancel crosstalk by a matrix operation.

7. The system for optimizing achievable rates as recited in claim 6, wherein, The matrix operation involved in an upstream direction is a post-coder implemented at the central office end, the matrix operation involved in a downstream direction is a pre-coder implemented at the central office end, and the matrix operation is operated by a vectoring control entity module at the central office end.

8. A method for a digital subscriber line communication system comprising: (a) receiving a digital subscriber line signal transmitted from a peer point; (b) transmitting a digital subscriber line signal to the peer point; (c) processing data of the received digital subscriber line signal; (d) detecting a valid data pattern after a period of invalid data; (e) measuring the valid data pattern of the digital subscriber line signal for a predetermined period of time; (f) determining a signal power by analyzing the measured valid data pattern of the digital subscriber line signal. (g) estimating a signal attenuation and determining an electrical length from the received information of the signal power and a power spectral density level of the transmitter; (h) adjusting the power spectral density level of the transmitter with a power backoff according to a predetermined rule related to the electrical length; (i) negotiating a new power spectral density level offset of the power backoff when an estimated data rate is compared to a target service rate; and (j) re-adjusting from steps (a) to (i) to start a new information exchange to set the power backoff.

9. The method for a digital subscriber line communication system as claimed in claim 8, wherein, The electrical length in step (g) is defined by a predetermined formula representing a physical loop distance between a digital subscriber line system and a peer digital subscriber line system and an estimated value of signal attenuation across the used frequency bandwidth.

10. The method for a digital subscriber line communication system as claimed in claim 8, wherein, The estimated data rate in step (i) further comprises: a final measurement of signal-to-noise ratio of frequency subcarriers on the available frequency bandwidth; an overall bit loading of a symbol from a bit loading allocation algorithm of signal-to-noise ratio of single subcarriers; and a final calculation of an achievable data rate of symbol rate, coding and burden fraction.

Images