Analysis of cyclic delay diversity on DVB-H systems over spatially correlated channel

The objective of this work is to research and analyze the performance of Cyclic Delay Diversity (CDD) with two transmit antenna on DVB-H systems operating in spatially correlated channel. It is shown in this paper that CDD can achieve desirable transmit diversity gain over uncorrelated channel with or without receiver diversity. However, in reality, the respective signal paths between spatially separated antennas and the mobile receiver is likely to be correlated because of insufficient antenna separation at the transmitter and the lack of scattering effect of the channel. Under this spatially correlated channel, it is apparent that CDD cannot achieve the same diversity gain as obtained under the uncorrelated channel. In this paper, a new upper bound on the pairwise error probability (PEP) of the CDD with spatial correlation of two transmit antennas is derived. The upper bound is used to study the CDD theoretical error performance and diversity gain losses over a generalized spatially correlated Rayleigh channel. This theoretical analysis is validated by the simulation of DVB-H systems with two transmit antennas and the CDD scheme. Both the theoretical and simulated results give the valuable insight that the CDD ability to perform well with a certain amount of channel correlation

Analysis of DVB-H network coverage with the application of transmit diversity

This paper investigates the effects of the Cyclic Delay Diversity (CDD) transmit diversity scheme on DVB-H networks. Transmit diversity improves reception and Quality of Service (QoS) in areas of poor coverage such as sparsely populated or obscured locations. The technique not only povides robust reception in mobile environments thus improving QoS, but it also reduces network costs in terms of the transmit power, number of infrastructure elements, antenna height and the frequency reuse factor over indoor and outdoor environments. In this paper, the benefit and effectiveness of CDD transmit diversity is tackled through simulation results for comparison in several scenarios of coverage in DVB-H networks. The channel model used in the simulations is based on COST207 and a basic radio planning technique is used to illustrate the main principles developed in this paper. The work reported in this paper was supported by the European Commission IST project—PLUTO (Physical Layer DVB Transmission Optimization)

Retrospective turn continuations in Mandarin Chinese conversation

How the status of further talk past the point of a turn's possible completion should he described, and what functions different kinds of turn continuation might serve - these are questions that have engaged many scholars since Sacks, Schegloff and Jefferson's turn-taking model (1974). In this paper, a general scheme is proposed with which one can tease out four interlocking strands in analyzing different kinds of turn continuation: Syntactic continuity vs. discontinuity, main vs. subordinate intonation, retrospective vs. prospective orientation, and information focus vs. non-focus. These parameters combine to form different configurations and interact in interesting ways, accounting for different kinds of turn continuation. The scheme is tested on, and illustrated with, a body of naturally occurring conversational data in Chinese.published_or_final_versio

Pairwise Confusion for Fine-Grained Visual Classification

Fine-Grained Visual Classification (FGVC) datasets contain small sample sizes, along with significant intra-class variation and inter-class similarity. While prior work has addressed intra-class variation using localization and segmentation techniques, inter-class similarity may also affect feature learning and reduce classification performance. In this work, we address this problem using a novel optimization procedure for the end-to-end neural network training on FGVC tasks. Our procedure, called Pairwise Confusion (PC) reduces overfitting by intentionally {introducing confusion} in the activations. With PC regularization, we obtain state-of-the-art performance on six of the most widely-used FGVC datasets and demonstrate improved localization ability. {PC} is easy to implement, does not need excessive hyperparameter tuning during training, and does not add significant overhead during test time.Comment: Camera-Ready version for ECCV 201

Measurements, processing functions and laboratory test-bed experiments for evaluating diversity in broadcast network

This paper presents a test-bed development and measurement plan for evaluating transmit diversity and on-channel repeaters in the Digital Video Broadcasting Network. Transmit diversity reduces the complexity and improves the power consumption of the personal receiving devices by enhancing the transmission of signals in NLOS cluttered environments. It is more practical than receive diversity due to the difficulty of locating two receive antennas far enough apart in a small mobile device. The on-channel repeater is to extend the coverage of the DVB-T/H network in areas where services are inaccessible by receiving the DVB-T/H signals off air, amplifying and then retransmitting it on the same frequency as received. Test service scenarios were developed to illustrate the benefits of such technologies so that effectiveness can be researched in a variety of service and terrain scenarios using purpose built test systems.The work presented in this paper was supported by the European Commission IST project PLUTO

DFT-based Hybrid Beamforming Multiuser Systems: Rate Analysis and Beam Selection

This paper considers the discrete Fourier transform (DFT) based hybrid beamforming multiuser system and studies the use of analog beam selection schemes. We first analyze the uplink ergodic achievable rates of the zero-forcing (ZF) receiver and the maximum-ratio combining (MRC) receiver under Ricean fading conditions. We then examine the downlink ergodic achievable rates for the ZF and maximum-ratio transmitting (MRT) precoders. The long-term and short-term normalization methods are introduced, which utilize long-term and instantaneous channel state information (CSI) to implement the downlink power normalization, respectively. Also, approximations and asymptotic expressions of both the uplink and downlink rates are obtained, which facilitate the analog beam selection solutions to maximize the achievable rates. An exhaustive search provides the optimal results but to reduce the time-consumption, we resort to the derived rate limits and propose the second selection scheme based on the projected power of the line-of-sight (LoS) paths. We then combine the advantages of the two schemes and propose a two-step scheme that achieves near optimal performances with much less time-consumption than exhaustive search. Numerical results confirm the analytical results of the ergodic achievable rate and reveal the effectiveness of the proposed two-step method

Laboratory measurement campaign of DVB-T signal with transmit delay diversity

The requirements for future DVB-T/H networks demand that broadcasters design and deploy networks that provide ubiquitous reception in challenging indoors and other obstructed situations. It is essential that such networks are designed cost-effectively and with minimized environmental impact. The EC funded project PLUTO has since its start in 2006 explored the use of diversity to improve coverage in these difficult situations. The purpose of this paper is to investigate the performance of Transmit Delay Diversity (DD) with two antennas to improve the reception of DVB-T/H systems operating in different realistic propagation conditions through a series of tests using a SPIRENT SR5500 dual channel emulator. The relationship between correlation coefficient between channels, receiver velocity and diversity gain is nvestigated. It is shown that transmit delay diversity significantly improves the quality of reception particularly in simulated fast fading mobile broadcasting applications. This paper documents research conducted by Brunel University and Broadreach Systems

Dispersive Fourier transform using few-mode fibers for real-time and high-speed spectroscopy

Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XIIDispersive Fourier Transform (DFT) is a powerful technique for real-time and high-speed spectroscopy. In DFT, the spectral information of an optical pulse is mapped into time using group velocity dispersion (GVD) in the dispersive fibers with an ultrafast real-time spectral acquisition rate (>10 MHz). Typically, multi-mode fiber (MMF) is not recommended for performing DFT because the modal dispersion, which occurs simultaneously with GVD, introduces the ambiguity in the wavelength-to-time mapping during DFT. Nevertheless, we here demonstrate that a clear wavelength-to-time mapping in DFT can be achieved by using the few-mode fibers (FMFs) which, instead of having hundreds of propagation modes, support only a few modes. FMF-based DFT becomes appealing when it operates at the shorter wavelengths e.g. 1-μm range-a favorable spectral window for biomedical diagnostics, where low-cost single mode fibers (SMFs) and high-performance dispersion-engineered fibers are not readily available for DFT. By employing the telecommunication SMFs (e.g. SMF28), which are in effect FMFs in the 1-μm range as their cut-off wavelength is ∼1260 nm, we observe that a 3nm wide spectrum can be clearly mapped into time with a GVD as high as -72ps/nm and a loss of 5 dB/km at a spectral acquisition rate of 20 MHz. Moreover, its larger core size than the high-cost 1-μm SMFs renders FMFs to exhibit less nonlinearity, especially high-power amplification is implemented during DFT to enhance the detection sensitivity without compromising the speed. Hence, FMF-based DFT represents a cost-effective approach to realize high-speed DFT-based spectroscopy particularly in the biomedical diagnostics spectral window. © 2012 SPIE.published_or_final_versio

Demonstration of minute continuous-wave triggered supercontinuum generation at 1 µm for high-speed biophotonic applications

Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIUltra-broadband supercontinuum (SC) at 1-μm wavelength is regarded as diagnostics window in bio-photonics due to its large penetration depth in tissues and less Rayleigh scattering. Dispersive Fourier transform (DFT) is an important technique to realize the high-speed, ultra-fast and high-throughput spectroscopy. Thus, a stable light source with good temporal stability plays an important role in the bio-imaging and spectroscopy applications. We here demonstrate stabilized and enhanced SC generation at 1 μm by a minute continuous-wave (CW) triggering scheme. By introducing a weak CW (200,000 times weaker than the pump), a significant broadening in the SC bandwidth and an improvement in the temporal stability can be obtained. Over 8 dB gain is achieved in both blue and red edges and the SC spectrum can span from 900 nm to over 1300 nm with the CW trigger. We present the CW-triggered SC capability of enabling highspeed spectroscopy based on DFT at 1 μm. In regards to the performance of DFT, the wavelength-time mapping fluctuation reduced by 50% which is an indication of the improvement of the temporal stability. This triggering scheme allows, for the first time, 1-μm DFT at a spectral acquisition rate of 20 MHz with good temporal stability - paving the way toward realizing practical real-time, ultrafast biomedical spectroscopy and imaging.published_or_final_versio

Maximizing the network outage rate for fast fluid antenna multiple access systems

Using reconfigurable fluid antennas, it is possible to have a software-controlled position-tuneable antenna to realize spatial diversity and multiplexing gains that are previously only possible using multiple antennas. Recent results illustrated that fast fluid antenna multiple access (f-FAMA) which always tunes the antenna to the position for maximum signal-to-interference ratio (SIR) on a symbol-by-symbol basis, could support hundreds of users on the same radio channel, all by a single fluid antenna at each user without complex coordination and optimization. The network outage rate, nevertheless, depends on the SIR threshold chosen for each user. Motivated by this, this paper adopts a first-order approximation to obtain the outage probability expression from which a closed-form solution is derived for optimizing the SIR threshold in maximizing the network outage rate. Moreover, a closed-form expression is provided to estimate the number of users in the f-FAMA network in which the outage rate begins to plateau. Numerical results show that the proposed SIR threshold achieves near-maximal outage rate performance