| 1. |
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| 2. |
- Cidronali, Alessandro, et al.
(författare)
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A 280 W LDMOS broadband Doherty PA with 52% of fractional bandwidth based on a multi-line impedance inverter for DVB-T applications
- 2016
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Ingår i: International Journal of Microwave and Wireless Technologies. - 1759-0787. ; 8:8, s. 1141-1153
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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)
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Applications of Backscattering for the Study of Twisted Pair Transmission Lines
- 2018
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 66:12, s. 5230-5237
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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)
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Backscattering in Twisted-Pair Nonhomogeneous Transmission Lines
- 2018
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 66:6, s. 2674-2682
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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)
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Enabling DSL and Radio on the Same Copper Pair
- 2015
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Ingår i: 2015 IEEE International Conference on Communications (ICC). - 9781467364324 ; , s. 1031-1035
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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)
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Fast Mitigation of Sudden Termination Changes in Wideband Wireline Systems
- 2016
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Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 64:6, s. 2610-2621
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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)
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LTE Over Copper - Potential and Limitations
- 2015
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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)
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Mitigating Disorderly Leaving Events in G.fast
- 2015
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Ingår i: 2015 IEEE International Conference on Communications (ICC). ; , s. 939-944
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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)
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Rate-Boosting Using Strong Crosstalk in Next Generation Wireline Systems
- 2016
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Ingår i: 2015 IEEE Global Communications Conference (GLOBECOM). - 9781467395267 ; , s. 1-6
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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)
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Time-Domain Precoding for LTE-over-Copper Systems
- 2016
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Ingår i: 2016 IEEE International Conference on Communications (ICC). - 9781479966646 - 9781479966653 ; , s. 1-6
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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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