High-quality Channel Research Articles

Expectation–maximization‐based joint data detection and channel estimation for a cellular multi‐carrier code division multiple access network using single‐hop relaying

SUMMARYThis paper is concerned with channel estimation and data detection for a cellular multi‐carrier code division multiple access network using single‐hop relaying in the presence of frequency selective fading channels. The proposed expectation–maximization (EM) algorithm was used to jointly estimate both the coefficients of the channel between a relay and a base station and the data. EM algorithm is particularly suited to multi‐carrier code division multiple access systems because they have multi‐carrier signal format. The considered network uses single‐hop relaying technique to provide a higher quality transmission to the users with low quality channels. The base station (managing mechanism) gives them an opportunity to send their messages via the users with high quality channels in a time sharing mode. The performance of the proposed EM algorithm, with and without hopping and with cooperative communication technique, was analyzed by a computer simulation, and the results are presented. Copyright © 2011 John Wiley & Sons, Ltd.

Visibility of Digital Video Artifacts in Stereoscopic 3DTV

Georgia Tech has developed a testbed to explore new encoding techniques and other enhancements to stereoscopic 3DTV. A methodical subjective testing program is important in evaluating new approaches, so the testbed has been designed to explore issues such as (1) whether typical compression and network artifacts are more or less visible in stereoscopic 3DTV than in 2DTV, (2) what new artifacts specific to stereoscopic 3DTV exist and what might be an actionable taxonomy of these artifacts, and (3) how the visibility of stereoscopic 3DTV artifacts depends on the content, the codec and codec bit rate, and the transport method (e.g., frame-compatible transport). This paper describes the research testbed and initial content database, provides initial results of subjective testing using stereoscopic 3DTV video containing artifacts with both active shutter and passive polarization displays, and discusses the next steps in the research program. Initial subjective results from the work thus far show that (1) compared with passive polarization, the active shutter display gave a better experience in full 3D as well as greater visibility of artifacts, and better viewing of two independent channels by multiple viewers; (2) subjects were evenly split in terms of noticing a significant difference in frame-compatible format versus full 3D format; (3) subjects were evenly split on whether compression and network artifacts were more or less visible in 3D versus 2D format; and (4) the isolation between left and right eye in both active shutter and passive polarization glasses is currently insufficient to support high-quality independent channel viewing using 3D technology.

Zinc Oxide Thin-Film Transistors with Location-Controlled Crystal Grains Fabricated by Low-Temperature Hydrothermal Method

High-performance zinc oxide (ZnO) bottom-gate (BG) thin-film transistors (TFTs) with a single vertical grain boundary in the channel have been successfully fabricated by a novel low-temperature (i.e., 85°C) hydrothermal method. The ZnO active channel was laterally grown with an aluminum-doped ZnO seed layer underneath the Ti/Pt film. Consequently, such BG-TFTs (W/L = 250 μm/10 μm) demonstrated the high field-effect mobility of 9.07 cm2/V - s, low threshold voltage of 2.25 V, high on/off-current ratio above 106, superior current drivability, indistinct hysteresis phenomenon, and small standard deviations among devices, attributed to the high-quality ZnO channel with the single grain boundary.

Incomplete oxidation in back channel of GaInZnO thin-film transistor grown by rf sputtering

Thin-film transistors (TFT's) may have a low-quality back channel in addition to the high-quality main channel. The presence of the back channel can deteriorate TFT turn-off characteristics. We studied properties of the back channel in bottom-gate GaInZnO TFT's grown by rf sputtering. X-ray photoelectron spectroscopy (XPS) results confirmed existence of low-quality oxide in the back channel. We observed that 200 °C annealing increased binding energies of metals and oxygen on the surface. This energy increase can be explained as a result of tighter bonding between metals and oxygen. When the top surface of GaInZnO was removed by Ar etching, XPS did not show such energy increase after the annealing. XPS also showed that the top surface has significantly higher In concentration compared to the bulk.

Low-Voltage Organic Thin-Film Transistors Using a Hybrid Gate Dielectric Consisting of Aluminum Oxide and Poly(vinyl phenol)

This study presents low-voltage organic thin-film transistors (OTFT) using a hybrid gate dielectric consisting of aluminum oxide and poly(vinyl phenol). Aluminum oxide with a thickness of 5 nm is directly formed on an aluminum gate electrode by an oxygen plasma process. The poly(vinyl phenol) film with a thickness of 10 nm is deposited on the aluminum oxide by a spin coating process. The proposed OTFTs are able to operate at low voltages lower than 5 V because of the thin gate dielectric. The surface of the hybrid gate dielectric is finished with a hydrophobic poly(vinyl phenol) so that a pentacene semiconductor, which is deposited on the gate dielectric, produces a high quality channel, resulting in a high mobility with 0.63 cm2 V-1 s-1. Additionally, the poly(vinyl phenol) layer reduces the leakage current through the gate dielectric, generating a low off-state current of 0.02 pA/µm and thus a high on/off current ratio of 4.4×105. Finally, the pin-hole free poly(vinyl phenol) layer protects the thin aluminum oxide gate dielectric from being penetrated by source and drain electrodes; thus, an OTFT with a bottom contact structure is achieved with short channel length.

Measurement of IPTV traffic from an operative network

AbstractIn this paper, we present measurement results of IP TeleVision (IPTV) multicast traffic collected from real of the FastWeb network. FastWeb is an ISP provider, which is the main broadband telecommunication company in Italy. The network relies on an IP architecture and, besides television channels, delivers to the user services such as data transfer and VoIP over a single broadband connection. The traffic we focus on consists of 83 high‐quality digital TV channels encoded using different MPEG‐2 encoders. The results show that, depending on the encoder and based on the bitrate, flows can be classified as being: 1‐VBR, i.e. with one typical value of the mean bit rate, 2‐VBR, i.e. two typical bitrate values are observed, and VBR. Measurement of the packet loss, jitter and inter‐packet gap show that, independently from the class, packet generation process of the flows can have various degrees of burstiness. Despite the packet level burstiness, average jitter is limited to few milliseconds and no packet loss was ever observed in the backbone. Moreover, the evolution of inter‐packet gap over time remains basically unchanged when observing a flow in different time periods. Our results prove that the FastWeb network is properly carrying IPTV traffic, and that today technology is mature to make TV over IP feasible and of good quality. Copyright © 2009 John Wiley & Sons, Ltd.

Effects of distribution channel structure in markets with vertically differentiated products

This study examines how the structure of distribution channels may influence firms’ quality and price strategies and how they may in turn affect consumer welfare. It treats product quality as a decision variable so that the degree of product substitution becomes endogenous rather than exogenous as in previous studies. We find that, with vertically differentiated firms, the changes in channel structure have asymmetric effects depending on whether they occur in the high-quality channel or in the low-quality channel. The product quality of the high-quality channel decreases when it decentralizes unilaterally. However, product quality of the low-quality channel would increase when it decentralizes. The high-quality manufacturer and its channel suffer more from decentralization in comparison with their low-quality counterparts, and the low-quality manufacturer actually receives greater profits when both channels are decentralized. An important driver behind these asymmetries is the interaction between firms’ pricing incentives in integrated versus decentralized channels and what consumer segments they serve. Our analysis indicates that decentralization may reduce consumer welfare, but decentralization in the high-quality channel hurts consumers more than that in the low-quality channel. Therefore in a competitive environment where firms make both quality and price decisions, channel integration would have significant welfare enhancement effects through the elimination of double marginalization, especially if it happens in the high-quality channel. Moreover, we demonstrate that once quality is endogenized, integration is the only equilibrium of channel structure choices. This suggests that the private incentives of firms may actually benefit consumers but do not have to be in line with the general preference of industry regulation for decentralization.

Three-Dimensional stacked CMOS Inverters Using Laser-Crystallized Poly-Si TFTs

High-performance three-dimensional (3-D) stacked poly-Si complementary metal-oxidesemiconductor (CMOS) inverters with a high-quality laser-crystallized channel were fabricated. Lowtemperature crystallization methods of an a-Si lm using excimer-laser annealing (ELA) and sequential lateral solidi cation (SLS) were performed. The n-channel metal-oxide-semiconductor (NMOS) thinlm transistors (TFT) at the lower CMOS layer were fabricated on an oxidized bulk Si substrate and p-channel metal-oxide semiconductor (PMOS) TFT at the upper CMOS layer were fabricated on an interlayer dielectric lm. Considerably uniform silicon grains were obtained by laser annealing. Sub-threshold swings of the fabricated NMOS TFTs at the lower layer and PMOS TFTs at the upper layer were 78 mV/dec. and 86 mV/dec., respectively. The eld e ect mobilities of the NMOS and the PMOS TFTs were 42.5 cm2/V s and 76 cm2/V s, respectively. The on/o current ratio of both TFTs was larger than 107. 3-D stacked poly-Si CMOS inverter showed excellent electrical characteristics and can be used the vertical integrated CMOS applications.

Reliable Low-Cost Fabrication of Low-Loss $\hbox{Al}_{2}\hbox{O} _{3}{:}\hbox{Er}^{3+}$ Waveguides With 5.4-dB Optical Gain

A reliable and reproducible deposition process for the fabrication of Al2O3 waveguides with losses as low as 0.1 dB/cm has been developed. The thin films are grown at ~ 5 nm/min deposition rate and exhibit excellent thickness uniformity within 1% over 50times50 mm2 area and no detectable OH- incorporation. For applications of the Al2O3 films in compact, integrated optical devices, a high-quality channel waveguide fabrication process is utilized. Planar and channel propagation losses as low as 0.1 and 0.2 dB/cm, respectively, are demonstrated. For the development of active integrated optical functions, the implementation of rare-earth-ion doping is investigated by cosputtering of erbium during the Al2O3 layer growth. Dopant levels between 0.2-5times1020 cm-3 are studied. At Er3+ concentrations of interest for optical amplification, a lifetime of the 4I13/2 level as long as 7 ms is measured. Gain measurements over 6.4-cm propagation length in a 700-nm-thick Al2O3:Er3+ channel waveguide result in net optical gain over a 41-nm-wide wavelength range between 1526-1567 nm with a maximum of 5.4 dB at 1533 nm.

Windowed Fourier-filtered and quality-guided phase-unwrapping algorithm

We propose a windowed Fourier-filtered and quality-guided phase-unwrapping algorithm that is an extension and improvement of our previous phase-unwrapping algorithm based on windowed Fourier transform [Opt. Laser Technol.37, 458 (2005), Key Eng. Mater.326-328, 67 (2006). First, the filtered amplitude is used as a real-valued quality map, rather than a binary mask, which makes the phase-unwrapping algorithm more tolerant to low-quality regions in a wrapped-phase map, and the process is more automatic. Second, the window size selection is considered, which enables the algorithm to be adapted to tackle different phase-unwrapping problems. A large window size is useful for removing noise, building long barriers along phase discontinuities, and identifying invalid regions, while a small window size is useful for preserving local features, such as small regions and high-quality narrow channels. Eight typical examples in Ghiglia and Pritt's excellent book Two-Dimensional Phase Unwrapping: Theory, Algorithm and Software (Wiley, 1998) are used to evaluate the proposed algorithm. The proposed algorithm is able to unwrap all these examples successfully. The windowed Fourier ridges algorithm, another algorithm based on windowed Fourier transform, is also tested and found to be useful in building barriers along phase discontinuities.

Maintaining dynamic channel profiles on the web

This work addresses a novel problem of maintaining channel proflies on the Web. Such channel maintenance is essential for next generation of Web 2.0 applications that provide sophisticated search and discovery services over Web information channels. Maintaining a fresh channel profile is extremely difficult due to the the dynamic nature of the channel, especially under the constraint of a limited monitoring budget. We propose a novel monitoring scheme that learns the channels' monitoring rates. The monitoring scheme is further extended to consider the content that is published on the channels. We describe a novelty detection filter that refines the monitoring rate according to the expected rate of novel content published on the channels. We further show how inter-channel profile similarities can be utilized to refine the channel monitoring rates. Using real-world data of Web feeds we study the performance of the monitoring scheme. We experiment with several monitoring policies over a large set of Web feeds and show that a policy based on learning the monitoring rate of the channels, combined with novelty detection, outperforms alternative channel monitoring policies. Our results show that the suggested content-based policy is able to maintain high quality channel profiles under limited monitoring resources.

High-Performance Solid-Phase Crystallized Polycrystalline Silicon Thin-Film Transistors with Floating-Channel Structure

High-performance solid-phase crystallized polycrystalline silicon thin-film transistors with a floating-channel active region (FC poly-Si TFTs) are proposed in this study. A high-quality poly-Si channel film accompanied by a larger grain size and fewer microstructural defects could be obtained. Compared with the conventional poly-Si TFTs (CN poly-Si TFTs), the fabricated FC poly-Si TFTs exhibit superior electrical characteristics, including lower threshold voltage, higher field-effect mobility, and lower trap state density. These electrical performance improvements could be attributed to the fact that the α-Si film with a floating-channel structure can relieve the stress generated from the crystallization process accompanying the trap state density reduction and grain size enhancement. In addition, the FC poly-Si TFTs also exhibit improved hot-carrier stress immunity due to the reduced weak Si–H bonds from fewer grain boundaries in the poly-Si channel. Therefore, the proposed FC poly-Si TFTs can be easily fabricated by conventional solid-phase crystallization, and suitable for future high-performance flat-panel display applications.

On Networked Control Architectures for MIMO Plants

In this work we focus on control of MIMO LTI plants and explore the potential benefits of replacing a traditional diagonal non-networked control architecture with a networked full MIMO one. Diagonal terms of the networked MIMO architecture employ transparent links, whereas the off-diagonal terms use communication channels which are subject to signal-to-noise ratio constraints. Within this setup, we show how to design LTI coding systems which optimize overall performance. Unsurprisingly, for high-quality channels the full MIMO architecture is preferable to decentralized architectures. However, our analysis reveals that the achievable performance in the networked situation may become arbitrarily poor, if the signal-to-noise ratio constraints in the communication links are sufficiently severe. In these cases, traditional decentralized controller structures are preferable. In the present work, we limit our analysis to the two-input two-output case and illustrate our results for networked control systems with bit-rate limited communication channels.

Fabrication of Ge channels with extremely high compressive strain and their magnetotransport properties

Ge channels with extremely high compressive strain were fabricated. SiGe buffer layers with Ge concentration from 40% to 65% were grown on Si substrates by gas source molecular beam epitaxy (MBE), and subsequently modulation-doped Ge channel structures were grown on the buffers by solid source MBE. High crystal quality Ge channel layers with the compressive strain as high as 2.4% were realized due to low-temperature growth. Magnetotransport properties were investigated for the structures. Well-resolved Shubnikov–de Haas oscillations were observed and Dingle ratios beyond 10 were obtained. This indicated that remote impurity scattering is dominant rather than interface roughness scattering, reflecting high-quality channel layers in spite of the large strain. Moreover, reduced effective masses due to the large strain were demonstrated.

Experimental Study of Effective Carrier Mobility of Multi-Fin-Type Double-Gate Metal–Oxide–Semiconductor Field-Effect Transistors with (111) Channel Surface Fabricated by Orientation-Dependent Wet Etching

We present an experimental study of effective carrier mobility ( µeff) of multi-fin-type double-gate metal–oxide–semiconductor field-effect transistors (FinFETs) with a (111) channel surface fabricated by orientation-dependent wet etching. The peak values of the obtained µeff of electrons and holes are approximately 300 and 160 cm2/(V s), respectively, which are close to those in (111) bulk metal–oxide–semiconductor field-effect transistors (MOSFETs). Moreover, the effective electric field (Eeff) dependence of the µeff of electrons and holes shows a good agreement with the mobility universal curves of (111) bulk MOSFETs. These results indicate that the quality and channel surface roughness of Si-fins by orientation-dependent wet etching are excellent. The obtained results of µeff are very useful for the modeling and design of FinFET-complementary metal–oxide–semiconductor (CMOS) circuits and the developed wet etching technique is very attractive in the fabrication of ultrathin and high-quality Si-fin channels.

Seismic multi-attribute analysis for lithology discrimination in Ganso Field, Oficina Formation, Venezuela

Even extensively drilled and supposedly well-understood fields have the capacity to surprise and challenge the reservoir modeling. This paper describes the unexpected discovery of a new reservoir based on the quantitative seismic attribute analysis performed to identify the target reservoir sand and determine a development strategy for the reservoir. While drilling a fairly routine development well in Ganso Field in the Oficina Basin of eastern Venezuela, ENI Dacion discovered a new shallow accumulation, reservoired in high-quality channel facies sandstone that was 30 ft thick and full of relatively light oil. The reservoir flowed at the excellent rate of 950 b/d with 0% watercut on testing. The unexpected element of this discovery was that the accumulation was found with the landing section of a horizontal well targeting a deeper level, and the sand was completely absent in the pilot hole some 120 m away (Figure 1).

Nanostructural characterization and two-dimensional electron-gas properties in high-mobility AlGaN∕AlN∕GaN heterostructures grown on epitaxial AlN/sapphire templates

Al 0.26 Ga 0.74 N ∕ Al N ∕ Ga N heterostructures with a 1nm-thick AlN interfacial layer were grown on epitaxial AlN/sapphire templates by metal-organic vapor phase epitaxy, and they exhibited excellent film qualities and very high electron mobilities, such as over 2100cm2∕Vs at room temperature and over 25 000cm2∕Vs at 15K with a two-dimensional electron-gas (2DEG) density of approximately 1×1013∕cm2. Cross-sectional transmission electron microscopy images revealed that the thin AlN layer with a thickness of 1nm is continuously grown between AlGaN and GaN layers with atomically abrupt and flat interfaces. The experimental and calculated results for 2DEG transport properties indicated that an AlN interfacial layer between AlGaN and GaN layers effectively suppresses alloy disorder scattering and that epitaxial AlN/sapphire templates largely contribute to the high electron mobility because they allow for the realization of a high-quality GaN channel with a low dislocation density and a smooth interface.

Low Optical Loss Perfluorinated Methacrylates for a Single-Mode Polymer Waveguide

Perfluoroalkyleneoxy methacrylate containing polar functional carbonate (−O−C(O)−O−) or carbamate (−NH−C(O)−O−) groups were synthesized to improve optical and adhesion properties of optical waveguide materials. Transparent polymer films were prepared by photocuring of a solution containing methacryloyl perfluoroalkyleneoxy carbonate and a photoinitiator. Optical loss of 0.35 dB/cm at 1550 nm was determined from the photocured film, for TE polarization by measuring the transmitted power along the slab waveguide length. The refractive indices at 1550 nm were determined as 1.4337 and 1.4334 for TE and TM modes, respectively, indicating low birefringence of Δn = 0.0003 ± 0.0002. Adhesion between the substrate and the polymer layer was enhanced by introducing carbonates and carbamates as determined from a SEM cross section and low surface energy of the photocured polymer film. Low-loss optical waveguides have been fabricated from a solution containing methacryloyl perfluoroalkyleneoxy carbonate by photo-cross-linking and then reactive ion etching to produce high-quality channel waveguides with very smooth surfaces. The propagation loss of the channel waveguides was 0.50 and 0.70 dB/cm at the monitoring light of 1550 nm for TE and TM polarizations, respectively.

Turbidite reservoirs of the Sele Formation, Central North Sea: geological challenges for improving production

Turbidite reservoirs of the Sele Formation in the Central North Sea produce from fields such as Forties, Nelson, Montrose–Arbroath, Scoter, Pierce, the Gannet cluster, Guillemot A, Mirren and are under appraisal/development in fields such as Merganser, Phyllis, Starling and Blane. These reservoirs form part of the ‘Forties’ submarine fan system that was sourced from feeder channels in the northwest and west. Blanket 3D seismic coverage tied to wells shows that nearer their updip sources the turbidites are thicker, higher in net:gross, and more channelized. Downdip, the turbidite reservoirs are thinner bedded, finer grained and with depositional architectures that are characterized by stacked lobes and minor channels controlled by accommodation space and salt movement. In updip fields, such as Nelson and Forties, production is mature. High-quality reservoir channel sands are mostly drained. Recovery factors of 60–62% are achievable by application of water injection and 4D seismic technologies. The remaining challenge in these reservoirs is to (1) find by-passed oil in the channel facies and (2) to identify/model oil remaining in non-channelized facies, such as channel margin and interchannel facies. Portions of the channelized reservoirs have not been swept because of non-uniform water ascent and breakthrough or shale barriers. Non-channelized reservoirs have not been swept because their sands are thin bedded, interbedded with shales and of lower reservoir quality. Remaining oil zones are not correlatable between existing wells, emphasizing the uncertainties of lateral heterogeneities away from the wellbore and the importance of static reservoir modelling techniques to properly model, identify and plan infill targets with multiple realizations. Higher recovery factors (possibly as high as 70%) may be achievable with higher resolution seismic interpretations and reservoir models, application of enhanced oil recovery and sharpshooter drilling techniques and improved water management. In downdip fields, such as Scoter, Merganser, Pierce and Guillemot A, production is not as mature and wells are not as abundant. Consequently, development planning is more dependent on high-quality static and dynamic reservoir models to predict the interwell reservoir character, volumetrics and performance. In general, turbidite reservoir sandstones are thinner and finer grained. The thickest sands may be more correlatable as lobes/sheets. Permeability is lower than in updip reservoirs of equivalent porosity (tens of mD as opposed to hundreds or thousands of mD), probably due to reductions in mean grain size and textural maturity and a corresponding increase in detrital clay matrix. The greatest challenges lie in modelling lateral changes in net:gross, bed thickness, facies (especially shale bed architecture) and cementation. Where depositional slopes were oversteepened by the growth of salt diapirs, slumps and slides introduce lateral heterogeneities and reduce predictability in the reservoir section. Multiple faults radiate from such salt diapirs and may compartmentalize the reservoir. These effects may be mitigated by the construction of robust conceptual models of reservoir accumulation and architecture, supported by relevant field analogues and detailed biostratigraphy which may delineate multiple widespread marker horizons. For liquid hydrocarbons, recovery factors are typically 40–45%. Gas recovery factors are projected to be 60–65%.

OAR: An Opportunistic Auto-Rate Media Access Protocol for Ad Hoc Networks

The IEEE 802.11 wireless media access standard supports multiple data rates at the physical layer. Moreover, various auto rate adaptation mechanisms at the medium access layer have been proposed to utilize this multi-rate capability by automatically adapting the transmission rate to best match the channel conditions. In this paper, we introduce the Opportunistic Auto Rate (OAR) protocol to better exploit durations of high-quality channels conditions. The key mechanism of the OAR protocol is to opportunistically send multiple back-to-back data packets whenever the channel quality is good. As channel coherence times typically exceed multiple packet transmission times for both mobile and non-mobile users, OAR achieves significant throughput gains as compared to state-of-the-art auto-rate adaptation mechanisms. Moreover, over longer time scales, OAR ensures that all nodes are granted channel access for the same time-shares as achieved by single-rate IEEE 802.11. We describe mechanisms to implement OAR on top of any existing auto-rate adaptation scheme in a nearly IEEE 802.11 compliant manner. We also analytically study OAR and characterize the delay jitter and the gains in throughput as a function of the channel conditions. Finally, we perform an extensive set of ns-2 simulations to study the impact of such factors as node velocity, channel conditions, and topology on the throughput of OAR.