1.
Stigwall, Johan, 1977, et al.
(författare)
Photonic GHz to THz tunable signal generation by chirped-pulse mixing
2006
Ingår i: 2006 European ISIS Workshop, Emerging Optical Broadband Technologies, Boppard am Rhein, Germany, May 29 - June 1, 2006.
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.
2.
Liu, Yang, et al.
(författare)
A Study Towards Enhanced Reliability Performance of Remote Control and Monitoring Application Over Commercial Wireless Communication Networks
2006
Ingår i: 2006 International Conference on Wireless Communications, Networking and Mobile Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1424405173 - 1424405173 ; , s. 1-4
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.
3.
Liu, Yang, et al.
(författare)
A Study Towards Reliability- and Delay-Critical Wireless Communication for RoboCup Robotic Soccer Application
2007
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
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.
4.
Selén, Yngve, et al.
(författare)
RAKE Receiver for Channels with a Sparse Impulse Response
2007
Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 6:9, s. 3175-3180
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.
5.
Banik, Biddut Kumar, 1978, et al.
(författare)
Catadioptric Dielectric Lens for Imaging Applications
2008
Ingår i: Proceedings of 33rd International Conference on Infrared, Millimeter, and Terahertz Waves. - 9781424421190 ; , s. 1 - 2
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.
6.
Chiragwandi, Zackary, 1968, et al.
(författare)
Properties of a bio-photovoltaic nano-device
2008
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:48, s. 18717-18721
Tidskriftsartikel (refereegranskat) abstract
Properties of an on-chip photovoltaic nanodevice are demonstrated. The dyes comprise green florescent proteins(GFP). Dependence of recently reported zero external potential bias (ZEPB) photocurrent (I) on temperature,power, and wavelength (λ) is shown. Correlation between UV-vis spectrum of the GFP and the ZEPB I(λ)of the device is reported. The temperature dependence suggests the ZEPB photocurrent to reflect a liquidcrystal type ordering where the current declines monotonically with increasing temperature. The influence ofan external bias on the photocurrent is demonstrated. The resulting light-induced current is analyzed in termsof resistive and quantum mechanical contributions.
7.
Liu, Yang
(författare)
Enhancement of Short Range Wireless Communication Performance Using Adaptive Frequency Hopping
2008
Ingår i: 2008 4th International Conference on Wireless Communications, Networking and Mobile Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781424421077 - 9781424421084 ; , s. 1-5
Konferensbidrag (refereegranskat) abstract
In this paper, a typical commercial short range wireless communication module which has weak immunity to interference has been tested and its performance has been evaluated with test bed. An adaptive frequency hopping scheme has been proposed to improve its immunity to interference and therefore enhance the wireless communication performance for reliability and delay-critical applications. Such scheme can be easily adopted to similar short range wireless communications.
8.
Khormuji, Majid Nasiri, et al.
(författare)
Finite-SNR Analysis and Optimization of Decode-and-Forward Relaying Over Slow-Fading Channels
2009
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 58:8, s. 4292-4305
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.
9.
Banik, Biddut Kumar, 1978
(författare)
Photonic THz Generation and Quasioptical Integration for Imaging Applications
2009
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This thesis deals with the analysis and optimisation of the uni-travelling-carrier photodiode (UTC-PD) for continuous-wave generation in terahertz (THz) frequencyrange. Photonic THz generation using UTC-PDs is extremely promising as it offers wide tunability, adequate output power and room temperature operation. Furthermore, a noveland compact catadioptric lens is proposed and investigated for realising compact sensing systems. Radiating elements and components can be physically coupled to the lens inorder to achieve short-range focusing and sensing ability. Using physical device modelling, the limitations and optimisation of InGaAs/InP based UTC-PDs for attaining higher bandwidth as well as higher output power are discussed. A hydrodynamic (HD) carrier transport model is used to analyse the device. Optimising for output power requires trade-offs involving the epitaxial layer design, optical coupling, circuit design and antenna design. An example of UTC-PD epitaxial layer optimisationfor continuous-wave THz generation at 340 GHz is shown using the HD model. The output power and the optimum embedding impedance for the UTC-PD, as a function ofdevice parameters, are also studied at different optical injection levels. Several plausible integration schemes and antenna design examples at 340 GHz are explored. A novel catadioptric lens, suitable for microwave and terahertz applications, is presented. The focusing property of the lens is investigated using 3D full-wave electromagnetic solvers. The proposed catadioptric lens is designed and fabricated from Delrin and Macor. Simulation and characterisation results are presented at microwave and terahertz frequencies (108 GHz). The results show that although being a few wavelengths (λ) in dimension, the catadioptric lens provides short-range focusing in theclose vicinity (~λ) and therefore provides a compact solution for short-range imaging systems. Finally, several short-range imaging examples at 108 GHz, employing thecatadioptric lenses, are also presented and discussed.
10.
Wuhib, Fetahi, et al.
(författare)
Gossiping for Threshold Detection
2009
Ingår i: 2009 IFIP/IEEE INTERNATIONAL SYMPOSIUM ON INTEGRATED NETWORK MANAGEMENT (IM 2009) VOLS 1 AND 2. - NEW YORK : IEEE. - 9781424434879 ; , s. 259-266
Konferensbidrag (refereegranskat) abstract
We investigate the use of gossip protocols to detect threshold crossings of network-wide aggregates. Aggregates are computed from local device variables using functions such as SUM, AVERAGE, COUNT, MAX and MIN. The process of aggregation and detection is performed using a standard gossiping scheme. A key design element is to let nodes dynamically adjust their neighbor interaction rates according to the distance between the nodes' local estimate of the global aggregate and the threshold itself. We show that this allows considerable savings in communication overhead. In particular, the overhead becomes negligible when the aggregate is sufficiently far above or far below the threshold. We present evaluation results from simulation studies regarding protocol efficiency, quality of threshold detection, scalability, and controllability.
