| 1. |
- Bengtsson, Lars, et al.
(författare)
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The REMAP Reconfigurable Architecture : a Retrospective
- 2006
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Ingår i: FPGA Implementations of Neural Networks. - New York : Springer-Verlag New York. - 0387284850 ; , s. 325-360
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Bokkapitel (refereegranskat)abstract
- The goal of the REMAP project was to gain new knowledge about the design and use of massively parallel computer architectures in embedded real-time systems. In order to support adaptive and learning behavior in such systems, the efficient execution of Artificial Neural Network (ANN) algorithms on regular processor arrays was in focus. The REMAP-β parallel computer built in the project was designed with ANN computations as the main target application area. This chapter gives an overview of the computational requirements found in ANN algorithms in general and motivates the use of regular processor arrays for the efficient execution of such algorithms. REMAP-β was implemented using the FPGA circuits that were available around 1990. The architecture, following the SIMD principle (Single Instruction stream, Multiple Data streams), is described, as well as the mapping of some important and representative ANN algorithms. Implemented in FPGA, the system served as an architecture laboratory. Variations of the architecture are discussed, as well as scalability of fully synchronous SIMD architectures. The design principles of a VLSI-implemented successor of REMAP-β are described, and the paper is concluded with a discussion of how the more powerful FPGA circuits of today could be used in a similar architecture. © 2006 Springer.
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| 2. |
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| 3. |
- Jakovljevic, M., et al.
(författare)
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VDSL Power Back-Off Parameter Optimization for a Cable Bundle
- 2007
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Ingår i: Proceedings European Signal Processing Conference. - Poznan : Poznań University of Technology. - 9788392134022 - 9788392134046 ; , s. 550-554
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Konferensbidrag (refereegranskat)abstract
- To better utilize the capacity of the twisted-pair access networks, operators deploying very high-speed digital subscriber line (VDSL) systems need accurate parameters for power back-off (PBO). However, VDSL standards give almost no guidance on how these parameters should be established for a particular network. In this paper we present a new technique for optimizing PBO parameters for a cable bundle, which is based on the Nelder-Mead simplex search algorithm. In this way each operator can easily calculate PBO parameters that match its actual access network down to the individual cable bundle. Using the properties of the PBO, as defined in the VDSL standard, we show how a normalized FEXT coupling can replace the knowledge of the individual couplings during the optimization of the PBO parameters. By simulations based on measured cable data we show that our approach using cable bundle unique PBO (CUPBO) achieves a significant improvements compared to the performance achieved with the ordinary PBO. © 2007 EURASIP.
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| 4. |
- Magesacher, Thomas, et al.
(författare)
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Verification of multipair copper-cable model by measurements
- 2007
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - Piscataway, N.J. : IEEE Press. - 0018-9456 .- 1557-9662. ; 56:5, s. 1883-1886
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Tidskriftsartikel (refereegranskat)abstract
- Analysis, assessment, and design of advanced wire-line transmission schemes over multipair copper cables require accurate knowledge of the channel properties. This paper investigates modeling of multiconductor cables based on interpair impedance measurements. A unified approach to the application of the "Cioffi" model is introduced. The direct measurement approach of the underlying interpair impedances yields a good, match with the alternative approach suggested in the recent study of Cioffi et al. Crosstalk coupling functions derived from the model exhibit a good match with the corresponding direct measurements in the case in which the modeled length is close to the length of the interpair impedance measurements. However, the prediction power of this model,with respect to termination impedance is limited.
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| 5. |
- Nordström, Tomas, et al.
(författare)
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Energy Efficient Power Back-Off Management for VDSL2 Transmission
- 2009
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Konferensbidrag (refereegranskat)abstract
- Recently energy saving has become an important issue also for wired communication. In this paper we investigate the potential of using power back-off (PBO) as a means to achieve higher energy efficiency. Based on a global energy optimisation formulation we derive an energy efficient PBO (EEPBO) algorithm. Through simulation we compare EEPBO with continuous bit-loading to the near-optimal energy efficient spectrum balancing (EESB) algorithm and an integer bit-loading version of EEPBO with energy efficient iterative spectrum balancing (EEISB). By restricting the search to practical levels of PBO parameters instead of optimizing the bit-loading on each and every carrier separately we see a significant reduction in computational complexity. It also means that EEPBO is already supported by current VDSL2 systems. Still, even after restricting the spectrum to what the PBO in VDSL2 allows we can show, through simulations, that EEPBO achieves the same level of energy efficiency as the near-optimal methods. This high performance and low-complexity together with standard compliance makes EEPBO a very attractive choice for future energy efficient transmission in VDSL2. © EURASIP, 2009.
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| 6. |
- Statovci, D., et al.
(författare)
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Dynamic Spectrum Management for Standardized VDSL
- 2007
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Ingår i: IEEE International Conference on Acoustics, Speech and Signal Processing. - Piscataway, N.J. : IEEE Press. - 1424407273 ; , s. III-73
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Konferensbidrag (refereegranskat)abstract
- Dynamic spectrum management (DSM) improves the capacity utilization of twisted-pair cables by adapting the transmit power spectral density (PSD) of modems to the actual noise environment and channel conditions. Earlier proposed DSM algorithms do not take into account the standardized very high speed digital subscriber line (VDSL) constraints on the allowable transmit PSDs. However, VDSL modems support only restricted transmit PSD shapes resulting from the standardized power back-off (PBO) method, which is controlled by a small set of parameters. Furthermore, since all modems are currently using the same PBO parameters their bit rate performance is severely limited. In this paper, we show how to effectively exploit the standardized PBO concept for DSM to significantly boost bit rates. We also present a low complex DSM algorithm, the user unique PBO (UUPBO) algorithm, for calculating PBO parameters that are uniquely optimized for each modem. © 2007 IEEE.
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| 7. |
- Statovci, D., et al.
(författare)
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Method of optimizing bit rate capacities of DSL user lines
- 2008
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Patent (populärvet., debatt m.m.)abstract
- A method of optimizing the bit rate capacities of DSL user lines subject to far-end crosstalk by adjusting the transmit power spectral densities at the far ends of the user lines by means of parameterized power back-off functions is characterized by the steps of : a) selecting a desired bit rate share for each user line, b) measuring the noise and losses on each user line, and c) determining an individual set of power back-off parameters for each user line by calculating a global sum of the bit rates of all user lines and iterating the power back-off parameters until a maximum value of the global sum is found under the constraint that the desired bit rate shares are met.
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| 8. |
- Statovci, Drtiton, et al.
(författare)
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Revised upstream power back-off for VDSL
- 2006
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Ingår i: 2006 IEEE International Conference on Acoustics, Speech and Signal Processing. - Piscataway, N.J. : IEEE Signal Processing Society. - 142440469X ; , s. IV-633-IV-636
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Konferensbidrag (refereegranskat)abstract
- Accurate upstream power back-off (PBO) parameters are needed by operators deploying very high-speed digital subscriber line (VDSL) modems. Although a standardized PBO method for VDSL exist, the standard gives little or no guidance to an operator how to establish these optimized PBO parameters for its particular network and customers. In this paper, we present an efficient algorithm based on the Nelder-Mead simplex search which calculates optimized upstream PBO parameters. To make the PBO parameter calculation independent of the network scenario we present a new method for establishing worst-case far-end crosstalk (FEXT) noise, which is based on virtual modems
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| 9. |
- Statovci, D., et al.
(författare)
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Spectrum Balancing for DSL with Restrictions on Maximum Transmit PSD
- 2007
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Ingår i: Proceedings of the AccessNets 2007. - Piscataway, N.J. : IEEE Press. - 9781424411504 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- The importance of a power spectral density (PSD) mask restriction is often overlooked when optimizing the spectrum usage for multiuser digital subscriber lines (DSL) systems. However, by developing the optimization strategies based only on the PSD constraints (masks) we can tremendously reduce the computation complexity compared to the methods only based on the total power restriction. In this paper we introduce a mask-based spectrum balancing (MSB) algorithm and demonstrate the near optimum performance of this optimization approach. Furthermore, we show that besides standards compliance, PSD restriction is also needed to ensure the convergence of iterative spectrum balancing methods, which use dual decomposition optimization.
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| 10. |
- Statovci, Driton, et al.
(författare)
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The normalized-rate iterative algorithm : a practical dynamic spectrum management method for DSL
- 2006
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Ingår i: EURASTP journal an applied signal processing. - : Springer. - 1110-8657 .- 1687-0433. ; 2006:95175, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- We present a practical solution for dynamic spectrum management (DSM) in digital subscriber line systems: the normalized-rate iterative algorithm (NRIA). Supported by a novel optimization problem formulation, the NRIA is the only DSM algorithm that jointly addresses spectrum balancing for frequency division duplexing systems and power allocation for the users sharing a common cable bundle. With a focus on being implementable rather than obtaining the highest possible theoretical performance, the NRIA is designed to efficiently solve the DSM optimization problem with the operators' business models in mind. This is achieved with the help of two types of parameters: the desired network asymmetry and the desired user priorities. The NRIA is a centralized DSM algorithm based on the iterative water-filling algorithm (IWFA) for finding efficient power allocations, but extends the IWFA by finding the achievable bitrates and by optimizing the bandplan. It is compared with three other DSM proposals: the IWFA, the optimal spectrum balancing algorithm (OSBA), and the bidirectional IWFA (bi-IWFA). We show that the NRIA achieves better bitrate performance than the IWFA and the bi-IWFA. It can even achieve performance almost as good as the OSBA, but with dramatically lower requirements on complexity. Additionally, the NRIA can achieve bitrate combinations that cannot be supported by any other DSM algorithm.
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