| 1. |
- Stigwall, Johan, 1977, et al.
(författare)
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Photonic GHz to THz tunable signal generation by chirped-pulse mixing
- 2006
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Ingår i: 2006 European ISIS Workshop, Emerging Optical Broadband Technologies, Boppard am Rhein, Germany, May 29 - June 1, 2006.
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Konferensbidrag (refereegranskat)abstract
- Frequency-tunable generation of pulsed tones in the millimeter to sub-millimeter range was demonstrated by mixing of two chromatically dispersing femtosecond laser pulses split up in time by an adjustable differential group delay (DGD) and a polarizer. The signal frequency was set by adjusting the amount of DGD and the amount of dispersion, and was here tuned from below 1 GHz to 0.9 THz. Time-domain measurements were conducted using a sampling oscilloscope for the lower frequencies and an auto-correlator for the higher frequencies. Near 100% modulation depth was obtained, and the signal phase was very stable, being locked to the pulses from the femtosecond laser. The line-width of the mm-wave waveform was found to be transform-limited if the signal chirp induced by higher order dispersion was compensated for. Suggested applications for this system are for instance THz spectroscopy, characterization of high performance photo-diodes and real-time dispersion measurements.
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| 2. |
- Do, Hieu, et al.
(författare)
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An Achievable Rate Region for the Gaussian Z-interference Channel with Conferencing
- 2009
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Ingår i: 2009 47TH ANNUAL ALLERTON CONFERENCE ON COMMUNICATION, CONTROL, AND COMPUTING, VOLS 1 AND 2. - NEW YORK : IEEE. ; , s. 75-81
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Konferensbidrag (refereegranskat)abstract
- This paper presents an achievable rate region for a 2-user Gaussian Z-interference channel with a noiseless and bidirectional digital communication link between the receivers. The region is achieved by utilizing the rate-splitting encoding technique, and the decode-and-forward and compress-and-forward strategies. In the very strong interference regime, the capacity region is achieved. In the weak interference regime, the asymptotic sum rate is characterized and shown to be possibly unbounded, which is in contrast to a recent result by Yu and Zhou for a similar scenario, however, with a unidirectional communication link between the receivers.
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| 3. |
- Liu, Yang, et al.
(författare)
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A Study Towards Enhanced Reliability Performance of Remote Control and Monitoring Application Over Commercial Wireless Communication Networks
- 2006
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Ingår i: 2006 International Conference on Wireless Communications, Networking and Mobile Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1424405173 - 1424405173 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- Remote control and monitoring systems provide many useful operating advantages in industrial automation and demand highly reliable and secure communication means. Their widespread use is, however, limited because of the high cost of current communications in use making them economically infeasible. Hence, there is a need to develop new low cost communication and control concepts by making such solutions economically feasible. In this paper, we present a scheme for implementing reliable wireless communication links for application of remote control and monitoring system based on current available commercial wireless communication networks, e.g. GPRS/EDGE/UMTS. The reliability enhancement over wireless networks has been proposed and its performance has been studied. This paper examines the proposed solution by means of both analytical and numerical evaluation, and has shown that the demanded reliability performance can be met by using only commercial wireless communication networks.
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| 4. |
- Selén, Yngve, et al.
(författare)
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RAKE Receiver for Channels with a Sparse Impulse Response
- 2007
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 6:9, s. 3175-3180
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Tidskriftsartikel (refereegranskat)abstract
- We derive the optimal receiver for RAKE diversity combining on channels with a sparse impulse response. The receiver is based on the Bayesian philosophy and thus it requires the knowledge of certain a priori parameters. However, we also derive an empirical Bayesian version of our receiver, which does not require any a priori knowledge, nor the choice of any user parameters. We show that both versions of our detector can outperform a classical training-based maximum-ratio-combining detector.
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| 5. |
- Ahsin, Tafzeel Ur Rehman, et al.
(författare)
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Constellation Selection in Network Coded Distributive Antenna System
- 2009
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Ingår i: GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference. - : IEEE. - 9781424441471 ; , s. 342-346
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Konferensbidrag (refereegranskat)abstract
- Relays can improve wireless links by providing an extra path to the direct path which together form a virtual multiple antenna system. Network Coded-Distributive Antenna System (NC-DAS) and Plain-Distributive Antenna System (P-DAS) are examples of realizations of such scenario. Although the asymptotic diversity gain for both the schemes is comparable, the network coded scheme can further take advantage of the redundancy and the extra dimension provided by the relay link. This extra signal dimension can be very useful when multilevel modulation is employed as it gives the possibility for a better spread of the modulation signal points within the augmented signal space. This article presents a simple and effective Constellation Selection (CS) scheme for all the three links within the NC-DAS system. This selection procedure improves the bit error probability in both AWGN and Rayleigh fading channels. Two different detections schemes are considered in the paper. Joint detection where the both users are decoded simultaneously and detection with successive cancelation where the strongest user is detected first followed by cancelation and maximum ratio combining. Analytical expressions for the error probability supported by simulation results are presented. The obtained results show that constellation selection provides good performance gain as compared to the case of same constellation.
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| 6. |
- Jia, Kelin, 1981-, et al.
(författare)
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PSpice Modeling of Electrified Railway Propulsion Drive Rectifiers for Harmonic Analysis
- 2009
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Ingår i: ITST. - New York : IEEE. ; , s. 113-116
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Konferensbidrag (refereegranskat)abstract
- A method to construct the electrified railway propulsion drive rectifier in PSpice for EMC assessment is developed. The working mechanisms of a three level NPC PWM rectifier and its logical signal generator are elaborated. Besides that, the convergence problem of PSpice is explained and the proper parametric settings for simulation in this paper are given. At last, the noise spectra for two different loads are compared and the causes for this difference are discussed as well.
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| 7. |
- Liu, Yang, et al.
(författare)
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A Study Towards Reliability- and Delay-Critical Wireless Communication for RoboCup Robotic Soccer Application
- 2007
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Ingår i: 2007 International Conference on Wireless Communications, Networking and Mobile Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1424413117 - 9781424413119 - 1424413125 - 1424413125 - 1424413117 ; , s. 633-636
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Konferensbidrag (refereegranskat)abstract
- RoboCup is an international competition for a team of multiple fast-moving robots under a dynamic environment to autonomously play soccer game against another team. Due to the nature of the competition, the requirements and constraints for the wireless communication are extremely tight. The challenge is that wireless communication is involved in the control loop and therefore the reliability and propagation delay are vital factors which directly affect the team performance. Beside, various interferences with known and unknown frequency / transmission power usually exist at the competition site, which are hazardous environment to achieve reliable and low latency performance for wireless communication. This paper investigates the performance strengths and weaknesses of wireless communication means e.g. RF, IEEE 802.11a/b, IEEE 802.15.4, DECT, Linx, etc, which are commonly used nowadays in different RoboCup teams and propose improvements towards reliable and delay-critical wireless communication.
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| 8. |
- Banik, Biddut Kumar, 1978, et al.
(författare)
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Catadioptric Dielectric Lens for Imaging Applications
- 2008
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Ingår i: Proceedings of 33rd International Conference on Infrared, Millimeter, and Terahertz Waves. - 9781424421190 ; , s. 1 - 2
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Konferensbidrag (refereegranskat)abstract
- The design and characterization results of a novel catadioptric dielectric lens are presented. Although being electrically small, the lens provides a focus in the close vicinity which makes it suitable to be used in microwave and terahertz systems. Several lenses of different dielectric materials and dimensions have been fabricated. A simple backscattering measurement method has been implemented in order to determine the focusing property of the lens.
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| 9. |
- Khormuji, Majid Nasiri, et al.
(författare)
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Finite-SNR Analysis and Optimization of Decode-and-Forward Relaying Over Slow-Fading Channels
- 2009
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 58:8, s. 4292-4305
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Tidskriftsartikel (refereegranskat)abstract
- We provide analytical results on the finite signal-to-noise ratio (SNR) outage performance of packet-based decode-and-forward relaying over a quasi-static fading channel, with different types of transmitter channel state information (CSI). At the relay, we consider repetition coding (RC) and parallel coding (PC). At the destination, we consider receivers based on selection combining (SC), code combining (CC), and maximum-ratio combining (MRC) (the latter only for the case of RC at the relay). Based on available CSI, we optimize the number of channel uses consumed by the source and by the relay for each packet. In doing so, we consider three different protocols that make use of different combinations of long-term CSI, 1-bit CSI, and complete CSI, respectively, at the source node. Several interesting observations emerge. For example, we show that for high SNRs, SC and CC provide the same outage probabilities when the source has perfect CSI.
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| 10. |
- Stigwall, Johan, 1977
(författare)
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Managing non-linear signal distortion in photonic time-stretch systems
- 2007
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Ingår i: International Microwave Symposium, Workshop on Ultrafast Analog-to-digital (A/D) Conversion Technique and its Applications.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Photonic time-stretch systems effectively boost the bandwidth of existing real-time oscilloscopes by temporally stretching a piece of a signal using dispersive optics. The stretch is, however, not perfect – the very same dispersion that actually enables the stretch also introduces signal distortions. Although the optical system is linear, the dispersive propagation and the modulator response introduce harmonic signal distortion when considering the signal from electrical input to electrical output. In this talk, two methods developed for the compensation of non-linear as well as linear distortions are presented. The first method recovers the original signal by calculation of the optical phase at the detection point followed by numerical back-propagation to the modulation point whereas the second method iteratively retrieves the signal using the Gerchberg-Saxton algorithm, which frequently is used for phase retrieval in free-space and diffraction optics. To enable fast numerical propagation, which is required for both methods, a very efficient numerical propagation technique specialized for photonic time-stretch systems is also presented.
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