| 1. |
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| 2. |
- Cidronali, Alessandro, et al.
(författare)
-
A 280 W LDMOS broadband Doherty PA with 52% of fractional bandwidth based on a multi-line impedance inverter for DVB-T applications
- 2016
-
Ingår i: International Journal of Microwave and Wireless Technologies. - 1759-0787. ; 8:8, s. 1141-1153
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce a new technique for the design of an output combiner for Doherty power amplifier (DPA) and its effective exploitation for the development of a wideband laterally diffused metal oxide semiconductor (LDMOS) DPA. The design is enabled by a two-line impedance inverter for the DPA back-off operation, which is capable of 52% of fractional bandwidth. The technique is validated by the development of a DPA prototype for Ultra high frequency terrestrial digital video broadcast (DVB-T) applications, with optimized peak power and efficiency over 470–806 MHz. The prototype delivers between 40 and 53% of average efficiency across the band, at 49 dBm output power in average across the bandwidth, and supporting DVB-T signals with 8 MHz bandwidth and a peak-to-average power ratio of 10.5 dB. It achieves the target adjacent channel power ratio of −52 dBc at 750 MHz if digital pre-distortion is applied, and provides 47.8 dBm of output power with a drain efficiency of 44.3%.
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| 3. |
- Fertner, Antoni, et al.
(författare)
-
Applications of Backscattering for the Study of Twisted Pair Transmission Lines
- 2018
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 66:12, s. 5230-5237
-
Tidskriftsartikel (refereegranskat)abstract
- The phenomenon of backscattering in copper cables has been recently observed and initially explicated. It can provide promising techniques to address the problem of loop diagnostic and maintenance. The backscattering is analyzed both in frequency and time domains. To demonstrate the practical use of the phenomenon, we estimate certain properties of the loop using wideband, high-frequency $\selevenf(f)$ measurements performed in the laboratory on real cables. The results corroborate the usefulness and accuracy of the investigated method.
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| 4. |
- Fertner, Antoni, et al.
(författare)
-
Backscattering in Twisted-Pair Nonhomogeneous Transmission Lines
- 2018
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 66:6, s. 2674-2682
-
Tidskriftsartikel (refereegranskat)abstract
- The development of the communication networks tends gradually toward exploiting higher frequencies, sometimes even reaching the lowest microwave band (P-band). As the signal bandwidth used for transmission over twisted-pairs increases, as recommended by G.fast and other broadband systems, new phenomenon was observed, namely, backscattering. Motivated by the measurements of copper cables in frequency band up to 400 MHz, we propose a novel backscattering model. It may be productively applied to the problem of loop diagnostics. The methods to accurately and reliable determine the relevant transmission-line parameters are sine qua non condition to appropriately exploit the potential of short-to-medium range access lines. In this paper, a recursive formulation of the frequency-domain response of the backscattering is used for a space-time characterization. To confirm the practical use of the finding, we evaluate the properties of a loop using wideband, high-frequency S₁₁ measurements of the real cables. These laboratory results confirm the effectiveness and accuracy of the proposed method.
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| 5. |
- Huang, Yezi, et al.
(författare)
-
Enabling DSL and Radio on the Same Copper Pair
- 2015
-
Ingår i: 2015 IEEE International Conference on Communications (ICC). - 9781467364324 ; , s. 1031-1035
-
Konferensbidrag (refereegranskat)abstract
- To increase indoor coverage for mobile services, we propose a residential small cell infrastructure making use of the existing copper plant. The system is cabinet-based, collocated with VDSL2 and uses small pieces of spectrum next to VDSL2. Inspired by the Ericsson Radio Dot System, it challenges the femtocell paradigm offering full macro functionality in the small cells. An interesting service potential is offered albeit the added mobile traffic capacity is moderate as it is limited by the copper fronthaul.
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| 6. |
- Huang, Yezi, et al.
(författare)
-
Fast Mitigation of Sudden Termination Changes in Wideband Wireline Systems
- 2016
-
Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 64:6, s. 2610-2621
-
Tidskriftsartikel (refereegranskat)abstract
- Vectoring enables cooperative crosstalk mitigation in wideband wireline systems. A sudden termination change within a vectored group alters the entire perceived channel matrix and thus disturbs the vectoring operation since the precoder, which is tuned to the channel before the change, is no longer up to date. We analyze the resulting residual crosstalk and its impact on performance degradation during showtime for both linear and non-linear precoding systems. To cover, a new channel matrix must be estimated to update the precoder accordingly. We use a model-based approach to track a vector instead of estimating the full matrix. Based on this vector, simplified precoder updating methods for both precoding systems are presented accounting for a sudden line deactivation or (re)activation in a vectored group. As an alternative to the state-of-the-art methods, the proposed procedures significantly reduce the complexity of both channel estimation and precoder updating and minimize the disturbed period for active users.
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| 7. |
- Huang, Yezi, et al.
(författare)
-
LTE Over Copper - Potential and Limitations
- 2015
-
Ingår i: 2015 IEEE 26th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). - 9781467367820 ; , s. 1339-1343
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Konferensbidrag (refereegranskat)abstract
- The densification of mobile networks in order to meet increased capacity demands is ongoing, needed and costly. A few papers have been published based on the insight that the fixed broadband networks offer a multitude of sites, for instance our homes, for potential small cell deployment providing backhaul capacity and power without site costs. However, in order to reach economical large-scale benefits, we explore the case when radio systems are deployed in coexistence with DSL. In this paper, we establish the feasibility of such a concept under constraints invoked by state-of-the-art and emerging systems (3GPP, VDSL2 and G.fast) and make statements about the required architecture. We also point out that the enthusiasm of previously published results should be lowered a notch.
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| 8. |
- Huang, Yezi, et al.
(författare)
-
Mitigating Disorderly Leaving Events in G.fast
- 2015
-
Ingår i: 2015 IEEE International Conference on Communications (ICC). ; , s. 939-944
-
Konferensbidrag (refereegranskat)abstract
- Vectoring is a vital component of wideband wire- line communication systems. A disorderly leaving event (DLE) disturbs the vectoring operation since the precoder, which was designed for the channel before the change, is no longer up to date. Measurements indicate that the impact of a DLE can be serious for frequencies beyond 30 MHz, which corresponds to the band used by emerging wideband communication systems over short multi-pair copper cables such as G.fast. As an alternative to the state-of-the-art update procedure, this paper presents an approach to mitigating the DLE problem. By interpreting DLE with the FEXT-reflected-NEXT (FRN) model, we propose a scheme that enables the showtime lines to return to disturbance-free transmission once the loss of signal on a certain line is detected while updating the precoder as a background process. Furthermore, the estimation complexity for a K-user vectoring group is reduced from O(K^2) to O(K).
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| 9. |
- Huang, Yezi, et al.
(författare)
-
Rate-Boosting Using Strong Crosstalk in Next Generation Wireline Systems
- 2016
-
Ingår i: 2015 IEEE Global Communications Conference (GLOBECOM). - 9781467395267 ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- Next-generation wireline systems may exploit fre- quencies up to several hundred MHz on short lines. Strong crosstalk coupling, comparable to the direct paths, is one of the main channel characteristics at high frequencies. Instead of fully cancelling all crosstalk, we utilize strong crosstalk paths to boost data-rate for active users. Two linear precoding schemes, based on maximum ratio-combining (MRC) and convex optimization, respectively, are proposed and applied to a common network topology. The precoding schemes exploit constructive crosstalk signals on unused lines or in unused parts of the spectrum on neighboring lines to boost data-rate while still complying with the regulated spectral power limits per line. More than 500 Mbps throughput gain per active user can be achieved compared to state-of-the-art linear precoding.
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| 10. |
- Huang, Yezi, et al.
(författare)
-
Time-Domain Precoding for LTE-over-Copper Systems
- 2016
-
Ingår i: 2016 IEEE International Conference on Communications (ICC). - 9781479966646 - 9781479966653 ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- Crosstalk cancellation is a crucial issue for traditional digital subscriber line systems. For LTE-over-copper systems, however, the need for crosstalk cancellation varies depending on the analog fronthauling architecture and its parameters. A crosstalk handler that is decoupled as much as possible from the rest of the system architecture is thus preferred. Therefore, we propose a time-domain precoding scheme specifically in downstream direction to separate the precoding unit from the LTE signal flow, and perform crosstalk cancellation in an on-demand manner. Estimation of all direct and crosstalk paths is assisted by LTE cell-specific reference signals. The time-domain precoder transforms the interference channel into a crosstalk-free channel with identical direct paths, which allows for low-complexity inter-symbol interference mitigation. We evaluate the concept in terms of signal-to-noise ratio provided for LTE signals using measured wireline channel data.
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| 11. |
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| 12. |
- Lindqvist, Fredrik, et al.
(författare)
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Estimation of Nonhomogeneous and Multi-Section Twisted-Pair Transmission-Line Parameters
- 2015
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 63:11, s. 3568-3578
-
Tidskriftsartikel (refereegranskat)abstract
- In emerging and future copper access networks, the trend goes towards exploiting higher transmission bandwidths on shorter twisted-pair cables. Methods to accurately determine relevant transmission-line parameters are a prerequisite to exploit the potential of these short-to-medium range access lines. In this paper, we propose a model-based space-frequency optimization approach initially developed for microwave applications. By utilizing the concept of capacitive length, two major advances are achieved. First, we overcome the requirement of a priori information of physical line length. Second, the number of parameters is reduced compared to prior art. We introduce two estimators to illustrate the concept. A low-complexity estimator with only two parameters per spatial unit primarily targets higher frequencies. A wideband estimator with three parameters per spatial unit extends to the lower frequencies used by operational digital subscriber line services. Performance and limitations of the approach are illustrated by both computer simulations and measurements.
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| 13. |
- Lindqvist, Fredrik, et al.
(författare)
-
Low-order and causal twisted-pair cable modeling by means of the Hilbert transform
- 2008
-
Ingår i: AIP Conference Proceedings. - : AIP. ; , s. 301-310
-
Konferensbidrag (refereegranskat)abstract
- A new low-order and causal twisted-pair cable model for the copper access network is derived. From the serial resistance of the widely used, but non-causal, BT0 model, the serial inductance is computed via the Hilbert transform. By doing so, a causal cable model is obtained containing fewer parameters compared to the BT0 model. The deviation between the two models is evaluated for the standardized ETSI cables.
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| 14. |
- Magesacher, Thomas, et al.
(författare)
-
A fair comparison of transmitter-based spectral shaping techniques
- 2006
-
Ingår i: 11th International OFDM-Workshop (InOWo'06).
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses multicarrier communications over the additive white Gaussian noise channel under a power spectral density (PSD) constraint. Depending on the shape of the PSD mask, straightforward power loading according to the waterfilling principle may yield poor throughput results. Several information processing techniques have been proposed to enhance the spectral properties of a multicarrier transmit signal and consequently increase the resulting throughput. Two promising spectral shaping techniques that require information processing exclusively in the transmitter are spectral compensation and intersymbol transmit windowing. This work presents prerequisites for a fair comparison and a performance assessment of these techniques
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| 15. |
- Magesacher, Thomas, et al.
(författare)
-
Adaptive Interference Cancellation Using Common-Mode Information in DSL
- 2005
-
Ingår i: Proc. European Signal Processing Conference 2005.
-
Konferensbidrag (refereegranskat)abstract
- Exploiting the common-mode (CM) receive signal in wireline communication can yield significant improvements in terms of channel capacity compared to using only the differential-mode (DM) signal. Recently published, independent, scientific work proposed the employment of an adaptive CM-reference based interference canceller and reported performance improvements based on simulation results. Adaptive processing of correlated receive signals, however, bears the potential danger of cancelling the useful component—an undesired effect we will address. We present an analysis of the linear adaptive cancellation approach in this application. For a large class of practically relevant cases, it can be shown that a canceller, whose coefficients are adapted while the far-end transmitter is silent, yields a signal-tonoise-and-interference power ratio (SNIR) which is higher than the SNIR of the DM-only channel output. Moreover, the performance of a canceller with this tap-setting is close to the performance of the front-end that is optimum in the sense of maximising the SNIR at its output. Adaptation while the useful far-end signal is present yields a front-end whose output SNIR is considerably lower compared to the SNIR of the DM channel output. The results and their practical impact are demonstrated by an example.
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| 16. |
- Magesacher, Thomas, et al.
(författare)
-
An adaptive mixed-signal narrowband interference canceller for wireline transmission systems
- 2001
-
Ingår i: The 2001 IEEE International Symposium on Circuits and Systems, ISCAS 2001.. - 0780366859 ; , s. 450-453
-
Konferensbidrag (refereegranskat)abstract
- Narrowband radio transmitters like radio amateurs and broadcast radio stations are considered to be a serious problem for high-bitrate data transmission over twisted pairs. Due to its high power level, radio frequency interference (RFI) has the potential of overloading the receiver's analog-to-digital converter (ADC). Once the ADC is in saturation, any countermeasure taken in the digital domain will fail, so the problem has to be faced at least partly in the analog domain. This paper proposes an adaptive, mixed-signal, narrowband interference canceller employing a modified recursive least-squares (RLS) algorithm which is split into an analog and a digital part. The mixed-signal approach enables the circuit to generate an interference-cancelling signal of several MHz while operating the adaptive algorithm at some kHz. The structure is fast enough to prevent the ADC from overloading due to radio amateur interference, thus protecting the data transmission from interruption. Simulation results as well as measurements indicate a practical disturbance rejection potential of about 40-50 dB
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| 17. |
- Magesacher, Thomas, et al.
(författare)
-
Analysis of Adaptive Interference Cancellation Using Common-Mode Information in Wireline Communications
- 2007
-
Ingår i: Eurasip Journal on Advances in Signal Processing. - : Springer Science and Business Media LLC. - 1687-6172 .- 1687-6180.
-
Tidskriftsartikel (refereegranskat)abstract
- Joint processing of common-mode (CM) and differential-mode (DM) signals in wireline transmission can yield significant improvements in terms of throughput compared to using only the DM signal. Recent work proposed the employment of an adaptive CM-reference-based interference canceller and reported performance improvements based on simulation results. This paper presents a thorough investigation of the cancellation approach. A subchannel model of the CM-aided wireline channel is presented and the Wiener solutions for different adaptation strategies are derived. It is shown that a canceller, whose coefficients are adapted while the far-end transmitter is silent, yields a signal-to-noise power ratio (SNR) that is higher than the SNR at the DM channel output for a large class of practically relevant cases. Adaptation while the useful far-end signal is present yields a front-end whose output SNR is considerably lower compared to the SNR of the DM channel output. The results are illustrated by simulations based on channel measurement data.
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| 18. |
- Magesacher, Thomas, et al.
(författare)
-
Benchmarking of learning architectures for digital predistortion
- 2017
-
Ingår i: Conference Record of the 50th Asilomar Conference on Signals, Systems and Computers, ACSSC 2016. - 9781538639542 ; , s. 648-651
-
Konferensbidrag (refereegranskat)abstract
- Indirect and direct learning architectures are the two main parameter identification approaches for digital predistortion systems. While the indirect scheme is less complex, its inherent shortcomings are avoided by the direct learning approach. Trying to answer the question whether this advantage of the direct approach can be exploited in terms of measurable linearization-performance improvement in a predistortion platform for advanced power amplifier structures, we present a performance comparison based on laboratory results for wideband high-power Doherty amplifiers. Rather than using single-shot least-squares estimates, each architecture is combined with an adaptive parameter-update scheme to reach the desired performance range and allow for a fair comparison. In conclusion, although the direct learning approach may excel in peak performance, the indirect learning approach achieves virtually the same average performance over linearization runs and has a clear advantage in terms of robustness.
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| 19. |
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| 20. |
- Magesacher, Thomas, et al.
(författare)
-
Capacity of an extension of cover's two-look Gaussian channel
- 2003
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Ingår i: IEEE International Symposium on Information Theory - Proceedings. ; , s. 262-262
-
Konferensbidrag (refereegranskat)abstract
- We extend Cover's two-look Gaussian channel to dispersive, linear, time-invariant channels. An arbitrary number of colored, additive, stationary, Gaussian noise/interference sources is considered. Each noise/interference source may cause correlated or uncorrelated components observed by the two looks. The novelty of this work is a capacity formula derived using the asymptotic eigenvalue distribution of block-Toeplitz matrices as well as the application of this result to wireline communications.
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| 21. |
- Magesacher, Thomas, et al.
(författare)
-
Capacity of the swedish copper access network
- 2005
-
Ingår i: Proceedings of RVK 05 RadioVetenskap och Kommunikation.
-
Konferensbidrag (refereegranskat)abstract
- This paper aspires to indicate how much broadband communication the Swedish copper access network can offer when developed to its full potential. We look at a number of different infrastructure deployment scenarios and calculate the Shannon capacity of the copper loops using different deployment-dependent loop-length distributions with different deployment-dependent and technology-dependent noise models. We investigate both deployment from the central-office and from the cabinet. We consider non-cooperative scenarios, where the deployment is carried out system by system following only the mandatory standardised rules and every line is operated autonomously without cooperation of transceivers. We also investigate scenarios with mechanisms for better exploitation of the access plant through dynamic spectral management, multiple-input multiple-output techniques, and common-mode aided interference suppression. The choice of elementary parameters, like transmit power and background noise, is based on today’s digital subscriber line (DSL) standards. Statistical models are used for the main parameters of the network topology. Note that we are not calculating a capacity in an information theoretic sense, but rather a data rate under given constraints.
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| 22. |
- Magesacher, Thomas
(författare)
-
Common-Mode Aided Wireline Communications
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireline communication is the Internet access technology with the largest number of subscribers worldwide. On physical-layer level, the traditional way to transmit signals at one end of a wire pair and to extract receive signals at the other end is to apply differential-mode signalling: transmit and receive signals correspond to voltage differences between the two wires. Differential-mode signalling over twisted-wire pairs, proposed and patented more than hundred years ago, yields a communication channel with good and stable transmission characteristics and high immunity to noise and interference. The differential mode is the only propagation mode in a two-conductor system. Taking into account earth as a third conductor yields a second independent mode, the so-called common mode, which can be used for communication. This thesis deals with information processing methods to exploit both modes jointly in order to improve transmission. The material can be divided into three parts. The first part investigates basic characteristics of the common mode and the resulting channel when taking into account the common-mode signal at the receiver. Measurements of common-mode signals and common-mode cable properties are presented and analysed. The design of receivers that use the common-mode signal for mitigation of both narrowband disturbers and broadband interference is addressed. The second part focuses on the potential gain in throughput that can be achieved with common-mode aided transmission techniques. The Shannon capacity of the common-mode aided wireline channel is derived and evaluated, and the performance under specific constraints of existing digital subscriber line techniques is addressed. A rough prospect of the Swedish copper access network used with common-mode aided methods and other advanced techniques is presented. The third part of the thesis deals with techniques to reduce unwanted spectral egress, which is a prerequisite for employing the common mode as active mode for transmission. The investigations focus on discrete Fourier-transform based multicarrier systems with a Gaussian channel known to transmitter and receiver. Information processing techniques that maximise the throughput under arbitrary power spectral density constraints are devised. In particular, transmit-windowing techniques and the so-called spectral-compensation method are investigated.
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| 23. |
- Magesacher, Thomas, et al.
(författare)
-
Exploiting the Common-Mode Signal in xDSL
- 2004
-
Ingår i: 12th European Signal Processing Conference, EUSIPCO 2004. - 9783200001657 ; , s. 1217-1220
-
Konferensbidrag (refereegranskat)abstract
- Communication over the copper twisted-pair channel is performed by transmitting and receiving differential-mode (DM) signals. In this paper, we extend the conventional DM receive scheme by incorporating the common-mode (CM) signal, which can be extracted at the end of every wire pair. We assess the potential of this idea for digital subscriber line systems (xDSL) in terms of channel capacity using channel measurement data. We show that especially those scenarios that suffer strong interference benefit most from joint DM-CM processing, since the interference at the DM port is strongly correlated with the interference at the CM port in these cases. Numerical evaluation of VDSL example scenarios shows that the capacity of the twisted-pair channel when using also the CM signal can exceed the capacity of the conventional DM channel by a factor of up to three.
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| 24. |
- Magesacher, Thomas, et al.
(författare)
-
Information rate bounds in common-mode aided wireline communications
- 2006
-
Ingår i: European Transactions on Telecommunications. - : Wiley. - 1541-8251 .- 1124-318X. ; 17:5, s. 533-545
-
Tidskriftsartikel (refereegranskat)abstract
- Communication over the copper twisted-pair channel is performed by transmitting and receiving differential-mode (DM) signals. In this paper, we extend the conventional DM receiver scheme by incorporating the common-mode (CM) signal, which is strongly correlated with the DM signal and can be extracted at the end of every wire pair. The wireline channel, including the CM receive signal, is modelled as a Gaussian vector (multiple-input multiple-output) channel with memory and an arbitrary number of disturbers that introduce interference which can be correlated both temporally and spatially. We investigate the potential of CM-aided reception in terms of information rate for single-user digital subscriber line systems (xDSL) operating on a single pair. Numerical results of information rate calculations using measured channel data are presented. The achievable information rate of the twisted-pair channel when incorporating the CM signal in practically relevant example scenarios can exceed the information rate of the conventional DM channel by a factor of up to two. Copyright (C) 2005 AEIT.
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| 25. |
- Magesacher, Thomas, et al.
(författare)
-
Limits of Ultra-Wideband Communication Over Copper
- 2006
-
Ingår i: Proc. Intl. Conference on Communication Technology (ICCT) 2006. - 1424408016 ; , s. 1437-1440
-
Konferensbidrag (refereegranskat)abstract
- Wireline communication using the copper plant is one of the major access techniques. The shorter the wires, the larger is the frequency band that can be exploited in an economically feasible way. Several technologies using frequency bands up to 30MHz have been standardized during the last decade. Properties of the wireline channel for frequencies above 30MHz are to a large extent unexplored. This paper investigates the limits of "ultra-wideband" communication over very short copper cables in terms of exploitable bandwidth and data rate. Extrapolations of standard cable models, whose validity has been verified by means of measurements, are used for channel modeling. The CISPR 22 standard forms the basis for the analysis of ingress and egress.
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| 26. |
- Magesacher, Thomas, et al.
(författare)
-
Longitudinal Signals in DSL
- 2005
-
Ingår i: Temporary Document TD 06, 053t06, ETSI STC TM6.
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this contribution is twofold. First, we revisit the longitudinal component (also referred to as common-mode component, asymmetric component or antenna-mode component) occurring at the receive side of a twisted-pair loop. Second, we propose a simple setup for RFI tests that captures reality more accurately than performing differential-mode and common-mode tests separately. In essence, we agree with and support the test environments proposed in [1][2][3]. We stress the fact that differential-mode and common-mode signals should be generated jointly in order to account for their correlation.
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| 27. |
- Magesacher, Thomas, et al.
(författare)
-
Measurement and modeling of short copper cables for ultra-wideband communication
- 2006
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6390, s. 39006-39006
-
Konferensbidrag (refereegranskat)abstract
- High-speed communication using the copper network, originally installed for telephony, is one of the dominant Internet access techniques. Several variants of a technology referred to as digital subscriber line (DSL) have been developed, standardized and installed during the last two decades. Essentially, DSL achieves high rates by exploiting wide bands of the copper cable channel. The shorter the cable, the wider the band that can be used efficiently for communication. Current DSL standards foresee the use of bands up to 30MHz. Cable properties have been studied by means of measurements, characterization and modeling up to frequencies of 30MHz. Recent investigations have shown that it is feasible both from technical and from economical point of view to exploit very short cables (up to 200m) even further and use bands above 30MHz. A prerequisite for further evaluation and the design of such ultra-wideband copper (UWBC) systems is the extension of existing cable models to higher frequencies. This paper presents wideband measurement results of insertion loss and crosstalk coupling in a 10-pair cable of various length values for frequencies up to 200MHz. We compare the results with extrapolations of cable models that are established in the 30MHz-range.
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| 28. |
- Magesacher, Thomas, et al.
(författare)
-
Modeling and measurement of short copper cables for ultra-wideband communications
- 2006
-
Ingår i: Proc. SPIE OpticsEast Broadband Access Communication Technologies.
-
Konferensbidrag (refereegranskat)abstract
- High-speed communication using the copper network, originally installed for telephony, is one of the dominant Internet access techniques. Several variants of a technology referred to as digital subscriber line (xDSL) have been developed, standardized and installed during the last two decades. Essentially, xDSL achieves high rates by exploiting wide bands of the copper cable channel. The shorter the cable, the wider is the band that can be used efficiently for communication. Current xDSL standards use bands up to 18MHz. Cable properties have been studied by means of measurements, characterization and modeling up to frequencies of 30MHz. Recent investigations have shown that is feasible both from technical and from economical point of view to exploit very short cable (up to 300m) even further and use bands above 30MHz. A prerequisite for further evaluation and the design of such ultra-wideband copper (UWBC) systems is the extension of existing cable models to higher frequencies. This paper presents wide-band measurement results of insertion loss and crosstalk coupling in a 10-pair cable of various length values for frequencies up to 400MHz. We compare the results to extrapolations of cable models that are established in the 30MHzrange.
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| 29. |
- Magesacher, Thomas, et al.
(författare)
-
On the Capacity of the Copper Cable Channel Using the Common Mode
- 2002
-
Ingår i: IEEE Global Telecommunications Conference GLOBECOM '02.. - 0780376323 ; 2, s. 1269-1273
-
Konferensbidrag (refereegranskat)abstract
- The common-mode (CM) signal in wireline transmission systems has proven to provide valuable information exploited for mitigating narrowband noise at the receive side. We focus on the case of broadband noise. Treating the CM signal as an additional receive signal, we investigate the capacity of the copper cable channel for different levels of coordination among the users. We introduce a channel model which includes the common-mode paths and derive a suitable form of the channel capacity formula. CM crosstalk measurement results, essential for evaluation of the channel capacity, are presented. Using the measurement data, exemplary results of capacity gain achievable by CM-aided data transmission over the copper cable are shown.
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| 30. |
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| 31. |
- Magesacher, Thomas, et al.
(författare)
-
Optimal intersymbol transmit windowing for multicarrier modulation
- 2006
-
Ingår i: 2006 7th Nordic Signal Processing Symposium (IEEE Cat. No.06EX1392). - 1424404134 - 1424404126 ; , s. 70-73
-
Konferensbidrag (refereegranskat)abstract
- Time-domain windowing of transmit blocks in multicarrier transmission is a technique frequently used to improve the properties of the transmit spectrum. An intersymbol window is longer than a multicarrier symbol including its cyclic extension. Before windowing, additional cyclic extensions at the beginning and at the end of each multicarrier symbol are introduced. Since the window only shapes these extended parts of each symbol, the orthogonality of the received basis functions is preserved. Most intersymbol transmit window designs exclusively focus on the spectral properties of the resulting basis functions. In this paper, we propose a window design that is optimal in the sense of maximising the information rate for a Gaussian channel with memory under power spectral density constraints and suggest some design guidelines
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| 32. |
- Magesacher, Thomas, et al.
(författare)
-
Optimal intra-symbol spectral compensation for multicarrier modulation
- 2006
-
Ingår i: International Zurich Seminar on Digital Communications. ; 2006, s. 138-141
-
Konferensbidrag (refereegranskat)abstract
- Spectral compensation aims at maximising the throughput of a multicarrier transmission system under a given power spectral density (PSD) constraint. A set of carefully chosen tones, the so called compensation tones, is modulated with a linear combination of the data transmitted over the complementary set of tones. The compensation tones support shaping of the transmit PSD so that the overall transmit power and thus the throughput increase. The contribution of this paper is twofold. First, we compute the optimal solution for a given set of compensation tones - optimal in the sense of maximising the mutual information between transmit and receive blocks for a time-dispersive Gaussian channel known to the transmitter. Second, we present a low-complexity heuristic to find the set of compensation tones.
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| 33. |
- Magesacher, Thomas
(författare)
-
Optimal intra-symbol transmit windowing for multicarrier modulation
- 2006
-
Ingår i: Proc. Intl. Symp. on Communications, Control and Signal Processing ISCCSP 2006.
-
Konferensbidrag (refereegranskat)abstract
- Windowing of the transmitted blocks in a multicarrier system yields an improved spectral containment of the resulting basis functions, which allows larger transmit power compared to no windowing while fulfilling the power spectral density (PSD) requirements. Most transmit window designs proposed so far aim at maximising the mainlobe energy and thus the spectral containment of the transmit basis functions. In this paper, we compute the transmit window that is optimal in the sense of maximising the information rate for a time-dispersive Gaussian channel known to the transmitter and compare it to the maximum mainlobe-energy window. It is shown that the maximum-rate window outperforms the maximum mainlobe-energy window in terms of information rate, particularly for low SNRs and for short cyclic extensions. The out-of-band PSD characteristics of the maximum mainlobeenergy window is superior for short cyclic extensions but gradually deteriorates with the length of the cyclic extension.
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| 34. |
- Magesacher, Thomas, et al.
(författare)
-
Optimal Segmentation for Piecewise RF Power Amplifier Models
- 2016
-
Ingår i: IEEE Microwave and Wireless Components Letters. - 1531-1309. ; 26:11, s. 909-911
-
Tidskriftsartikel (refereegranskat)abstract
- Accurate modeling of an RF power amplifier and/or its inverse is the core element of every digital predistortion system. An interesting alternative to the family of classic polynomial models are piecewise models, which divide the magnitude range into segments and define gain/phase-distortion through complex-valued functions on a per-segment basis. Naturally, the question arises whether a well-chosen non-uniform segmentation outperforms straightforward uniform segmentation and whether the benefit outweighs the extra effort. This work has two contributions: First, the segmentation that is optimal in the least-squares sense is determined jointly with the model coefficients and its benefit in terms of linearization improvement is demonstrated through measurements on a Doherty power amplifier. Second, a reduced-complexity approach with negligible performance loss is proposed.
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| 35. |
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| 36. |
- Magesacher, Thomas, et al.
(författare)
-
Performance analysis of vectored wireline systems embracing channel uncertainty
- 2013
-
Ingår i: 2013 IEEE International Conference on Communications (ICC). - Piscataway, NJ : Institute of Electrical and Electronics Engineers. - 9781467331227 ; , s. 3986-3990
-
Konferensbidrag (refereegranskat)abstract
- Future wireline communication systems aspire to boost the throughput in two ways: First, they exploit higher frequencies to gain more bandwidth on shorter lines in combination with vectoring. Second, they use non-differential transmission modes (such as phantom modes, common modes, split-pair modes) to exploit more dimensions. Performance predictions for systems exploiting these techniques are of great importance for upgrading copper networks to provide Internet access or deploying copper-based backhaul systems to connect mobile base-stations. Good predictions require accurate channel models. However, channel modeling for higher frequencies and nondifferential modes is still in its infancy. A mixed deterministic/stochastic channel model is proposed to remedy this problem. The outage rate is derived based on an asymptotic (in the number of participating transceivers) analysis. As application examples, performance predictions in access networks using phantom modes and frequencies up to 200 MHz are presented.
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| 37. |
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| 38. |
- Magesacher, Thomas
(författare)
-
Spectral Compensation for Multicarrier Communication
- 2007
-
Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 55:7, s. 3366-3379
-
Tidskriftsartikel (refereegranskat)abstract
- Spectral compensation is an information-processing technique applied in the transmitter to improve the spectral efficiency of multicarrier modulation under a given power spectral density constraint. A set of carefully chosen tones, the so-called information tones, carries data. The. remaining tones, referred to as compensation tones, are modulated with a linear combination of the data, such that the spectral characteristic of the transmit signal and thus the throughput are improved. This paper investigates strategies to find the set of compensation tones and presents the optimal solution for the linear combination of the data given the tone-set split. The optimality criterion is maximization of throughput for a time-dispersive Gaussian channel known to the transmitter. Furthermore, a. suboptimal design is proposed, which has low runtime-complexity and achieves near-optimal performance.
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| 39. |
- Magesacher, Thomas, et al.
(författare)
-
Splitting the Least-Mean-Square Algorithm
- 2002
-
Ingår i: Proceedings of the 5th Nordic Signal Processing Symposium.
-
Konferensbidrag (refereegranskat)abstract
- The least-mean-square (LMS) algorithm is an adaptation scheme widely used in practice due to its simplicity. In some applications the involved signals are continuous-time. Then, usually either a fully analog implementation of the LMS algorithm is applied or the input data are sampled by analog-to-digital (AD) converters to be processed digitally. A purely digital realization is most often the preferred choice, however, it becomes costly for high-frequency input signals since fast AD converters are needed. In this paper we propose a hybrid analog/digital approach allowing the AD conversion rate to be as low as the update-rate of the LMS algorithm. We demonstrate the advantage of this approach applying it to an interference cancellation problem occurring in wireline communications: the sampling rate of the AD converters is reduced by a factor of 250.
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| 40. |
- Magesacher, Thomas, et al.
(författare)
-
Verification of multipair copper-cable model by measurements
- 2007
-
Ingår i: IEEE Transactions on Instrumentation and Measurement. - Piscataway, N.J. : IEEE Press. - 0018-9456 .- 1557-9662. ; 56:5, s. 1883-1886
-
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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| 41. |
- Medeiros, Eduardo, et al.
(författare)
-
Crosstalk Mitigation for LTE-over-Copper in Downlink Direction
- 2016
-
Ingår i: IEEE Communications Letters. - 1089-7798. ; 20:7, s. 1425-1428
-
Tidskriftsartikel (refereegranskat)abstract
- Radio-over-copper is a niche idea that has potential to become a cornerstone in the deployment of dense 5G networks. We address one of the remaining hurdles and present an architecture for transparent crosstalk mitigation in LTE-over-copper systems. By taking advantage of reference symbols present in the downlink LTE signals we propose two methods for estimating the copper channel. System performance is evaluated using channel measurements and error vector magnitude calculations with promising results.
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| 42. |
- Medeiros, Eduardo, et al.
(författare)
-
How Vectoring in G.fast May Cause Neighborhood Wars
- 2014
-
Ingår i: [Host publication title missing]. - 9781479920037 ; , s. 3865-3870
-
Konferensbidrag (refereegranskat)abstract
- Emerging wireline transmission systems such as G.fast use bands up to around 200 MHz on short cables. A key enabler for achieving the aspired throughput of several hundred Mbit/s is joint processing of transmit signals in downstream direction as well as joint processing of receive signals in upstream direction through techniques referred to as vectoring. A new challenge in such systems are sudden and severe changes in the channel matrix caused by changing terminations on lines outside the vectoring group. Such events can be caused by users disconnecting their modems, turning them on or off, or on-/off- hook events on lines that still support the plain old telephony service. This work presents channel measurements capturing the impact of termination changes caused by modems or handsets. An analysis of the impact of these sudden changes on the signal- to-noise-power-ratio in vectoring systems reveals that throughput and stability can be seriously degraded. The potential of decision- directed channel tracking based on least squares estimation is investigated.
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| 43. |
- Medeiros, Eduardo, et al.
(författare)
-
Modeling Alien-Line Impedance Mismatch in Wideband Vectored Wireline Systems
- 2014
-
Ingår i: IEEE Communications Letters. - 1089-7798. ; 18:9, s. 1527-1530
-
Tidskriftsartikel (refereegranskat)abstract
- Sudden changes of channel coefficients in a wideband vectored wireline system (such as G.fast) due to changes in the terminating impedance of lines outside the vectored group can seriously degrade stability and throughput. This letter presents a model that predicts the impact of termination mismatch based exclusively on crosstalk data for the properly-terminated state. Experimental results confirm a tight fit between model and mea- surements. The model allows analysis of system performance and stability without dedicated crosstalk measurements for mismatch cases.
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| 44. |
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| 45. |
- Singerl, Peter, et al.
(författare)
-
A 2.7-GHz multi-level PWM carrier-bursting RF transmitter
- 2015
-
Ingår i: European Microwave Week 2015: "Freedom Through Microwaves", EuMW 2015 - Conference Proceedings; 2015 45th European Microwave Conference Proceedings, EuMC. - 9782874870392 ; , s. 1124-1127
-
Konferensbidrag (refereegranskat)abstract
- Carrier-bursting is an attractive RF transmitter concept to achieve high efficiency. The power amplifier (PA) itself either operates at its peak efficiency or is turned off. Another efficiency-enhancing approach is the Doherty concept, where the main PA reaches its peak efficiency already in back-off and the peak PA contributes at high input levels to reach the desired output power. In this work, we attempt to combine the best of both concepts and derive a two-level dual-output pulse width modulator driving two PAs whose outputs are combined. We have evaluated the concept by a real-Time FPGA implementation of the modulator for a 2.7GHz carrier driving two Class-AB PAs with a combined peak output power of 30W. The approach exhibits a potentially more pronounced back-off efficiency peak compared to the Doherty concept. Furthermore, the overall efficiency scales with the drain efficiency of the PAs and can thus be improved by employing Class-D or Class-F PAs.
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| 46. |
- Singerl, Peter, et al.
(författare)
-
A 2.7-GHz multi-level PWM carrier-bursting RF transmitter
- 2015
-
Ingår i: European Microwave Week 2015: "Freedom Through Microwaves", EuMW 2015 - Conference Proceedings; 2015 10th European Microwave Integrated Circuits Conference Proceedings, EuMIC. - 9782874870408 ; , s. 273-276
-
Konferensbidrag (refereegranskat)abstract
- Carrier-bursting is an attractive RF transmitter concept to achieve high efficiency. The power amplifier (PA) itself either operates at its peak efficiency or is turned off. Another efficiency-enhancing approach is the Doherty concept, where the main PA reaches its peak efficiency already in back-off and the peak PA contributes at high input levels to reach the desired output power. In this work, we attempt to combine the best of both concepts and derive a two-level dual-output pulse width modulator driving two PAs whose outputs are combined. We have evaluated the concept by a real-time FPGA implementation of the modulator for a 2.7GHz carrier driving two Class-AB PAs with a combined peak output power of 30W. The approach exhibits a potentially more pronounced back-off efficiency peak compared to the Doherty concept. Furthermore, the overall efficiency scales with the drain efficiency of the PAs and can thus be improved by employing Class-D or Class-F PAs.
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| 47. |
- Singerl, Peter, et al.
(författare)
-
Drive-characteristic design for dual-input Doherty power amplifiers
- 2016
-
Ingår i: 2016 IEEE MTT-S International Microwave Symposium, IMS 2016. - 9781509006984 ; 2016-August
-
Konferensbidrag (refereegranskat)abstract
- Doherty power amplifiers (PAs) can achieve high efficiency with modulated signals since they exhibit an efficiency-peak in backoff that can, in theory, reach full-scale efficiency. Unfortunately, the backoff efficiency of real Doherty PAs is lowered by unavoidable losses. The purpose of this work is to study the potential of re-gaining some of this efficiency loss through nonlinear drive-curve design for dual-input Doherty PAs. Several drive characteristics are compared in terms of efficiency and linearity performance measured with a modulated signal and applying digital pre-distortion. A single-parameter drive-curve model suitable for analog implementation is proposed that allows the adjustment of the efficiency/linearity tradeoff.
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| 48. |
- Singerl, Peter, et al.
(författare)
-
Predistortion- and development-platform for multi-input RF power amplifiers
- 2016
-
Ingår i: EuMIC 2016 - 11th European Microwave Integrated Circuits Conference. - 9782874870446 ; , s. 29-32
-
Konferensbidrag (refereegranskat)abstract
- We present a real-time digital predistortion (DPD) and RF power amplifier (PA) development platform with separate synchronous and coherent RF channels to evaluate multi-input RF PAs with realistic modulated test signals. The platform is based on a Xilinx FPGA and wideband analog frontends to support signal bandwidths up to 312.5 MHz. We describe both the implemented hardware as e.g. DPD core and digital splitter and the algorithms used to estimate the required DPD parameters. Furthermore we demonstrate the wideband linearization and efficiency optimization capabilities on two different 2 GHz Doherty PAs.
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| 49. |
- Statovci, Driton, et al.
(författare)
-
Analysis of Fast Initialization for Vectored Wireline Systems
- 2013
-
Ingår i: ; , s. 2868-2873
-
Konferensbidrag (refereegranskat)abstract
- Cooperation of transceivers on signal level at the remote terminal—often referred to as vectoring—is an effective approach to mitigate crosstalk in wireline transmission systems. While the gain in bitrate compared to crosstalk-limited transmis- sion is substantial, the initialization of a vectoring system requires time and care to ensure system stability. In this contribution, a fast initialization scheme for vectored wireline systems based on spectral protection is analyzed. Two scenarios are considered, where in the first one no prior channel information is available, and in the second one erroneous prior knowledge of channel coefficients is utilized. Measurements on a commercial VDSL2 vectoring platform and throughput simulations demonstrate the potential of the fast initialization scheme.
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| 50. |
- Werner, Karl, et al.
(författare)
-
Moving the PAR reduction criterion into the line driver
- 2015
-
Ingår i: European Signal Processing Conference. - : European Signal Processing Conference, EUSIPCO. ; , s. 1939-1942, s. 1939-1942
-
Konferensbidrag (refereegranskat)abstract
- Traditionally, Peak to Average Ratio (PAR) reduction in digital subscriber line (DSL) transmitters focuses on a digital-domain signal, either at the output of the baseband processing block or at the input of the digital-to-analogue converter (DAC). However, analysis of a DSL transceiver shows that the power dissipation is highly dependent on the PAR at a certain node inside the line driver. Thus, in order to be fully effective, the algorithm design should include the power amplifier dynamics. A typical, actively terminated, line driver is analysed and a model is constructed for PAR reduction purposes. The PAR reduction algorithm is then extended to take advantage of the model. Simulations show that algorithms which are designed to reduce PAR at the new, physically motivated, node obtain about 0.5 dB lower PAR evaluated at this node compared to methods that focus on the PAR of the DAC input.
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