The Experts below are selected from a list of 381 Experts worldwide ranked by ideXlab platform
J M Cioffi - One of the best experts on this subject based on the ideXlab platform.
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an outer code assisted rfi cancellation method for dmt dsl systems
Global Communications Conference, 2004Co-Authors: Dimitris Toumpakaris, J M Cioffi, Jungwon Lee, A Ekbal, F Gauthier, Ahmed ZeddamAbstract:In order to obtain high transmission rates DSL systems have to cope with stationary and non-stationary disturbances, as well as the non-ideal characteristic of the twisted pair channel. To mitigate non-stationary interference, a forward error correction (FEC) scheme is employed that consists of a Reed-Solomon outer code and interleaving. By augmenting the interleaving delay, protection against increasingly long noise bursts can he achieved. however, when radio frequency ingress (RFI) also affects the Subscriber Loops, the required interleaving delay may potentially increase to undesired levels. The additional delay that is required for combined impulse noise and RFI protection can be lowered by using more redundant RS codes, or by employing RFI cancellation techniques. In the latter case, additional digital cancellation is also necessary in order to mitigate the effect of RFI on the transmitted data. This paper proposes a digital RFI cancellation scheme for DMT-DSL systems that is based on information exchange between the DSL demodulator and the RS decoder at the receiver. It is shown that the technique can be seamlessly incorporated in current DMT-DSL systems, since no changes are required at the transmitter. The method can partly cancel the effect of RFI, and can help bridge the gap between the required interleaving delay when only impulse noise is present and the increased delay when RFI also affects transmission.
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a bandwidth optimized reduced complexity equalized multicarrier transceiver
IEEE Transactions on Communications, 1997Co-Authors: Naofal Aldhahir, J M CioffiAbstract:A bandwidth-optimized and equalized multicarrier transceiver that achieves near-optimum performance at a practical complexity level is described. The equalizer used is a relatively short FIR filter whose taps and delay are set to optimize the performance of the multicarrier transceiver. Simulation results on a set of carrier-serving-area digital Subscriber Loops are also presented to demonstrate the separate and joint effects of bandwidth optimization and equalization on performance. Finally, the intriguing idea of using a pole-zero equalizer to achieve the high performance of long FIR equalizers at a much lower implementation cost is investigated.
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Stable pole-zero modeling of long FIR filters with application to the MMSE-DFE
IEEE Transactions on Communications, 1997Co-Authors: N. Al-dhahir, A.h. Sayed, J M CioffiAbstract:The problem of approximating a long FIR filter by a reduced-parameter stable pole-zero filter is addressed. We derive a computationally efficient order-recursive algorithm that achieves this task with high accuracy. Our main emphasis is on applying this algorithm to reduce the implementation complexity of the decision feedback equalizer's long FIR feedforward and feedback filters encountered in high-speed data transmission on digital Subscriber Loops.
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achievable information rates on digital Subscriber Loops limiting information rates with crosstalk noise
IEEE Transactions on Communications, 1992Co-Authors: J T Aslanis, J M CioffiAbstract:The capacity and cutoff rates for channels with linear intersymbol interference, power dependent crosstalk noise, and additive white noise are examined, focusing on high speed digital Subscriber line data transmission. The effects of varying the level of additive white noise, crosstalk coupling gain, sampling rate, and input power levels are studied in detail for a set of simulated two-wire local Loops. A closed-form expression for the shell constrained Gaussian cutoff rate on the crosstalk limited channel is developed and related to the capacity, showing that the relationship between these two rates is the same as on a channel without crosstalk noise. The study also projects achievable rates on a digital Subscriber line, inside and outside of a carrier serving area, with a sophisticated but realizable receiver. >
S. Takashima - One of the best experts on this subject based on the ideXlab platform.
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Design and performance of a novel automatic fiber line testing system with OTDR for optical Subscriber Loops
Journal of Lightwave Technology, 1994Co-Authors: N. Tomita, F. Takaesu, H. Takasugi, N. Atobe, I. Nakamura, S. TakashimaAbstract:This paper proposes architecture for a novel automatic fiber line testing system with an optical time-domain reflectometer (OTDR) and describes the system requirements, the design method, and the system evaluation. The results of a trial on a manufactured system and an evaluation of its characteristics are presented with evidence that an in-service optical fiber can be tested with no degradation in communication quality and the desired measurement accuracy and system component characteristics can be realized. In addition, it is confirmed that a failure between an optical fiber cable and a digital service unit (DSU) can be identified with 100% accuracy.
D D Falconer - One of the best experts on this subject based on the ideXlab platform.
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BASEBAND TRELLIS CODED MODULATION WITH COMBINED EQUALIZATION / DECODING FOR HIGH BIT RATE DIGITAL Subscriber Loops
2013Co-Authors: P Mohanraj, D D Falconer, T KwasniewskiAbstract:We present simulation based study evaluating the performance of trellis coded modulation with combined code/ISI sequence estimation, for high bit rate (800Kbits/sec) transmission on Subscriber Loops. The receiver contains the fractionallyspaced forward filter of a decision feedback equalizer (DFE) as a front end; this is shown to suppress phase-synchronized crosstalk very effectively. The performance is further enhanced by the use of a trellis code with a large number of states, and a M-algorithm sequence-estimating receiver with a smaller number of states. the range ( loop length) of the high bit rate digital Subscriber loop system using an 8 state M-algorithm receiver by evaluating the probability of error for various loop lengths. FSE 1
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cyclostationary crosstalk suppression by decision feedback equalization on digital Subscriber Loops
IEEE Journal on Selected Areas in Communications, 1992Co-Authors: M Abdulrahman, D D FalconerAbstract:Interference from digital signals in multipair cables has been shown to be cyclostationary under some conditions. This work evaluates the performance of a decision feedback equalizer (DFE) in the presence of cyclostationary interference (CI), intersymbol interference (ISI), and additive white noise (AWN). A comparison between a DFE with CI and one with stationary interference (SI) shows the ability of the DFE to substantially suppress CI. Fractionally spaced and symbol-rate DFE equalizers are also compared and the former is found to yield better performance, especially in the presence of CI. The use of a symbol-rate DFE using an adaptive timing technique that finds the receiver's best sampling phase is proposed for when the fractionally spaced DFE cannot be used because of its complexity. The results also demonstrate the potential benefits of synchronizing central office transmitter clocks, if a fractionally spaced DFE is used at the receiver. >
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baseband trellis coded modulation with combined equalization decoding for high bit rate digital Subscriber Loops
IEEE Journal on Selected Areas in Communications, 1991Co-Authors: P Mohanraj, D D Falconer, T KwasniewskiAbstract:The authors present a simulation study evaluating the performance of trellis-coded modulation with combined code/ISI sequence estimation for high bit rate (800 kb/s) transmission on Subscriber Loops. The receiver contains a fractionally spaced forward filter of a decision feedback equalizer (DFE) as a front end. This is shown to suppress phase synchronized crosstalk very effectively. The performance is further enhanced by the use of trellis code with a large number of states received with an M algorithm sequence-estimating receiver with a smaller number of states. >
Lajos Hanzo - One of the best experts on this subject based on the ideXlab platform.
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Discrete Multi-Tone Digital Subscriber Loop Performance in the Face of Impulsive Noise
IEEE Access, 2017Co-Authors: Hongming Zhang, Rong Zhang, Lie-liang Yang, Anas Al F. Rawi, Jiankang Zhang, Lajos HanzoAbstract:As an important solution to “the last mile”access, digital Subscriber Loops (DSLs) are still maintained in a huge plant to support low-cost but high-quality broadband network access through telephone lines. The discrete multi-tone (DMT) transmissions constitute a baseband version of the ubiquitous orthogonal frequency division multiplexing. While the DMT is ideally suited to deal with the frequency selective channel in DSL, the presence of bursty impulsive noise tends to severely degrade the transmission performance. In this paper, we analyze the statistics of impulsive noise and its effects on the received signals, with the aid of a hidden semi-Markov process. The closed-form bit error rate expression is derived for the DMT system for Q-ary quadrature amplitude modulation under practical noise conditions and for measured dispersive DSL channels. Instead of relying on the simplified stationary and impulsive noise process, our noise model considers both the temporal and spectral characteristics based on the measurement results. The simulation results confirm the accuracy of the formulas derived and quantify the impact both of the impulsive noise and of the dispersive channel in DSL.
N. Tomita - One of the best experts on this subject based on the ideXlab platform.
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Design and performance of a novel automatic fiber line testing system with OTDR for optical Subscriber Loops
Journal of Lightwave Technology, 1994Co-Authors: N. Tomita, F. Takaesu, H. Takasugi, N. Atobe, I. Nakamura, S. TakashimaAbstract:This paper proposes architecture for a novel automatic fiber line testing system with an optical time-domain reflectometer (OTDR) and describes the system requirements, the design method, and the system evaluation. The results of a trial on a manufactured system and an evaluation of its characteristics are presented with evidence that an in-service optical fiber can be tested with no degradation in communication quality and the desired measurement accuracy and system component characteristics can be realized. In addition, it is confirmed that a failure between an optical fiber cable and a digital service unit (DSU) can be identified with 100% accuracy.
