Abstract: The present invention overcomes various problems by defining two upstream masks (UI, U2) and two downstream masks (DI, D2) and using a mask selectable system for the long reach digital subscriber line (LDSL), in which a unique modem feature is activated during handshake to automatically check for physical layer status in terms of spectral compatibility and, thus, automatically optimize the boosted mode with the use of the mask selectable system choose the best combination of upstream/downstream masks in any physical layer noise scenario.

Abstract: A method and system for enhancing reach-performance of a multi-carrier VDSL System estimates loop length, estimates maximum available bandwidth that can be utilized at that particular loop length, optimally selects an FFT size and sampling rate, and decides whether to apply a time domain equalization to its receiver and if so, selects a cyclic extension size. To minimize the implementation complexity, the sampling frequencies at receiver and transmitter are lowered to match the actual usable bandwidth. The FFT/IFFT sizes in the implementation are also required to set appropriately accordingly.

Abstract: Systems and methods for off-diagonal MIMO precoders are described. At least one embodiment includes a method for precoding data for transmission in a discrete multi-tone (DMT) xDSL system to cancel self-induced far end crosstalk (self-FEXT) comprising: learning characteristics associated with a plurality of N users within the xDSL system to determine an initial off-diagonal multiple input multiple output (MIMO) precoder (ODMP) for a given tone frequency; and converging towards an optimum ODMP from the initial ODMP in order to cancel downstream self-FEXT for the plurality of N users, wherein the ODMP is represented as a zero diagonal matrix with only off-diagonal terms, and wherein the converging towards the optimum ODMP comprises: maximizing the channel capacity for the plurality of N users for the given tone frequency; and minimizing an increase in transmit power of the xDSL system relative to an original transmit power where a precoder is not active.

Abstract: Systems and methods for a memory structure are described for increasing the throughput of double precision operations. Broadly, the present invention utilizes a novel memory system to process double precision data in a single memory access. In accordance with one embodiment, a method for increasing throughput of arithmetic operations on double precision data by reducing the number of memory accesses comprising: retrieving a double precision value from a memory, wherein the double precision value is comprised of a high word and a low word, wherein the double precision value is retrieved in a single memory access; selecting a word within the double precision value, wherein the portion selected is a single precision value; multiplying the word with a single precision operand to generate a single precision product; adding the product to a double precision operand to produce a double precision result; and forwarding the double precision result back to memory for storage.

Abstract: A method and apparatus implements a Virtual Exchange Reference Impact (VERI) technique to define a pattern to shape the spectrum of a cabinet deployed system to minimize its impact, e.g., FEXT, into an exchange deployed system while achieving effective cabinet system performance, e.g., in terms of data transmission rate. The invention shapes the cabinet system to replicate a self-impact of the exchange system on itself based on the known distance of the cabinet from the exchange. The shaping is required when both exchange and cabinet systems share the same bundle and exhibit overlapped bandwidths. A particular example consists of VDSL deployed from remote cabinet impacting ADSL2/ADSL2+ deployed from the exchange.

Abstract: The present invention overcomes various problems by defining two upstream masks (U1, U2) and two downstream masks (D1, D2) and using a mask selectable system for the long reach digital subscriber line (LDSL), in which a unique modem feature is activated during handshake to automatically check for physical layer status in terms of spectral compatibility and, thus, automatically optimize the boosted mode with the use of the mask selectable system choose the best combination of upstream/downstream masks in any physical layer noise scenario.

Abstract: Systems and methods for performing bit loading in a dual latency data transmission system. In a computer network, such as an XDSL-based network, carrier channels are allocated between two latency paths. Error sensitive information is transmitted over a latency path employing one or more forward error correction techniques. Latency sensitive information that is relatively more tolerant of errors is transmitted over the other latency path. Rather than employing the lowest coding gain for carrier channels having the two different latency paths, the highest coding gain for each path is used by applying different target S-N-R margins for carrier channels having different latency paths.

Abstract: Disclosed herein are various mechanisms for the adaptive cancellation of radio frequency interference (RFI) in Discrete Multitone (DMT)-based signal transmissions systems. various mechanisms for the adaptive cancellation of radio frequency interference (RFI) in Discrete Multitone (DMT) modulated signal transmissions systems. In at least one embodiment of the present invention, RFI introduced by one or more RFI disturbers (e.g., ham radios) into a DMT modulated signal may be detected by calculating an RFI canceller coefficient for some or all of the DMT bins of the signal, where the RFI canceller coefficient represents the correlation between the noise at the corrupted bin and the reference RFI noise. The RFI canceller coefficients for the corrupted bins may be calculated using an LMS adaptation process. Those bins where the magnitude of the corresponding RFI canceller coefficient is greater than a certain threshold may be marked as corrupted by RFI.

Abstract: A method and apparatus implements a Virtual Exchange Reference Impact (VERI) technique to define a pattern to shape the spectrum of a cabinet deployed system to minimize its impact, e.g., FEXT, into an exchange deployed system while achieving effective cabinet system performance, e.g., in terms of data transmission rate. The invention shapes the cabinet system to replicate a self-impact of the exchange system on itself based on the known distance of the cabinet from the exchange. The shaping is required when both exchange and cabinet systems share the same bundle and exhibit overlapped bandwidths. A particular example consists of VDSL deployed from remote cabinet impacting ADSL2/ADSL2+ deployed from the exchange.

Abstract: An economic low-complexity system and method for echo cancellation are disclosed. The system and method are particularly suited for multi-carrier VDSL using the U0 band. The techniques taught herein may be implemented in VDSL and VDSL2 systems and used to receive signals in three bands (e.g., U0, U1 and U2) simultaneously.

Abstract: A method and system for enhancing reach-performance of a multi-carrier VDSL System estimates loop length, estimates maximum available bandwidth that can be utilized at that particular loop length, optimally selects an FFT size and sampling rate, and decides whether to apply a time domain equalization to its receiver and if so, selects a cyclic extension size. To minimize the implementation complexity, the sampling frequencies at receiver and transmitter are lowered to match the actual usable bandwidth. The FFT/IFFT sizes in the implementation are also required to set appropriately accordingly.

Abstract: A system and method for performing pilot tone based timing recovery in a communication system using the discrete multi-tone (DMT) modulation. In DMT modulation, interference is introduced to the phase of the pilot tone in the transmitter due to the cyclic prefix. Broadly, a receiver is configured to detect and apply a phase offset to the pilot tone in a phase locked-loop upon recognition of far-end signal segments during transceiver initialization. The output of the phase locked-loop is then used to control the timing of the analog-to-digital (A/D) and digital-to-analog (D/A) conversions. In alternative embodiments, the receiver is configured to detect and remove the cyclic prefix from the far-end signal either prior to, or after, time-domain equalization. In a similar manner, the resulting signal stream is applied to the input of the timing recovery phase locked-loop (PLL). The output of the PLL is used to control the timing of the A/D and D/A converters.

Abstract: An improved ADSL modem is presented. The ADSL modem in cooperation with a remote ADSL modem will exchange manufacturer identification information during initial DSL system training to establish a DSL communication link. The improved ADSL modem may comprise a memory device containing system parameters and operational algorithms previously determined to maximize DSL link performance between ADSL modems manufactured by different vendors. The improved ADSL modem is well suited for central office applications as it provides a solution for optimizing system performance that is transparent to remotely located ADSL modems. An ADSL modem in accordance with the present invention may comprise a digital signal processor and a memory device configured to store appropriate system parameters and operational algorithms that provide an optimized DSL communication link once applied during system initialization. The present invention also provides a method for optimizing DSL system performance.

Abstract: A system and method for multiple inputs, multiple outputs (MIMO) PSD allocation in a DSL system is disclosed. In some embodiments, the method may comprise monitoring system performance by performing a multi-ended line test (MELT), processing the MELT and allocating PSD based on at least one of system coupling power and system traffic.

Abstract: A system and method for providing cancellation of interference in a repeater configuration is disclosed, wherein the repeater is located between a first endpoint and a second endpoint. A data signal received from the first end point is amplified in accordance with an amount of power required to drive the data signal to the second endpoint. Local echo introduced by the repeater is then removed from the amplified data signal. Coupled signals introduced by the repeater are then removed after which the data signal is transmitted to the second endpoint.

Abstract: The present invention is directed to implementing theoretical foundations of frequency domain methods aiming to locally decrease the impact of aggregate side lobes of a few discrete frequency tones, in the vicinity of other “victim” frequencies. The family of frequency methods referred to makes use of one or more “canceller tones.” The “canceller tones” loads are optimized to minimize the aggregate power in the neighborhood of the victim frequencies.

Abstract: A technique for improving multiple-channel multi-tone transmissions is disclosed. According to one particular embodiment, a method for transmitting data over at least two bonded channels is provided, wherein each of the at least two bonded channels comprises a plurality of tones. The method may comprise: transmitting a first symbol stream over a first tone in a first bonded channel and over a second tone in a second bonded channel, wherein the first tone is bonded to the second tone, and the transmissions over the first tone and the second tone are substantially in parallel; transmitting a second symbol stream over a third tone in the first bonded channel; and transmitting a third symbol stream over a fourth tone in the second bonded channel, wherein the third tone is bonded to the fourth tone, and the transmissions of the second symbol stream and the third symbol stream are substantially in parallel.

Abstract: Disclosed herein are various techniques for multilevel channel coding. For a given binary word comprising a plurality of bits, the least-significant bit may be encoded by a boosted coding technique, such as turbo channel coding or low density parity check (LDPC) channel coding. A subset of the remaining bits of the binary word may be encoded using trellis coded modulation (TCM) coding. The results of the boosted channel coding and the TCM coding may be mapped to one or more symbols. The one or more symbols then may be transmitted to a receiver using transmission techniques well known to those skilled in the art. The present invention finds particular benefit in digital subscriber line (DSL)-based systems in accord with the ITU G.992-1 Recommendation and similar standards.

Abstract: Systems and methods for increasing data capacity in communication systems is presented. In one embodiment, line characteristics are determined, and a downstream bandwidth is adaptively allocated in response to the determined line characteristics. In this regard, the upstream and downstream bandwidths may be seen as adaptively changing as a function of line characteristics.

Abstract: An evaluation of the spectral compatibility of two LDSL modes based on two different downstream masks, identified herein as LDSL Wide and Narrow, is disclosed. Spectral compatibility is evaluated in accordance with existing rules.