Usable Bit Research Articles

Parameter set for computer-assisted texture analysis of fetal brain.

BackgroundMagnetic resonance data were collected from a diverse population of gravid women to objectively compare the quality of 1.5-tesla (1.5 T) versus 3-T magnetic resonance imaging of the developing human brain. MaZda and B11 computational-visual cognition tools were used to process 2D images. We proposed a wavelet-based parameter and two novel histogram-based parameters for Fisher texture analysis in three-dimensional space.ResultsWavenhl, focus index, and dispersion index revealed better quality for 3 T. Though both 1.5 and 3 T images were 16-bit DICOM encoded, nearly 16 and 12 usable bits were measured in 3 and 1.5 T images, respectively. The four-bit padding observed in 1.5 T K-space encoding mimics noise by adding illusionistic details, which are not really part of the image. In contrast, zero-bit padding in 3 T provides space for storing more details and increases the likelihood of noise but as well as edges, which in turn are very crucial for differentiation of closely related anatomical structures.ConclusionsBoth encoding modes are possible with both units, but higher 3 T resolution is the main difference. It contributes to higher perceived and available dynamic range. Apart from surprisingly larger Fisher coefficient, no significant difference was observed when testing was conducted with down-converted 8-bit BMP images.Electronic supplementary materialThe online version of this article (doi:10.1186/s13104-016-2300-3) contains supplementary material, which is available to authorized users.

Improving efficiency of quantum key distribution with probabilistic measurements

The first part of this paper presents two efficient cryptographic protocols, based on quantum entanglement, for secure exchange of secret keys. While the first protocol requires storage of entangled qubits, the second protocol has no storage requirements and presents a probabilistic model. We show that there is a tradeoff between security against eavesdropping and the efficiency of the protocol in terms of usable bits available for the secret key. This security parameter s can be varied by the communicating parties based on practical considerations. In the second part of the paper, we apply the probabilistic model to BB84 and show how it can be used to improve the efficiency of BB84.

Reversible Data Hiding in Encrypted JPEG Bitstream

This correspondence proposes a framework of reversible data hiding (RDH) in an encrypted JPEG bitstream. Unlike existing RDH methods for encrypted spatial-domain images, the proposed method aims at encrypting a JPEG bitstream into a properly organized structure, and embedding a secret message into the encrypted bitstream by slightly modifying the JPEG stream. We identify usable bits suitable for data hiding so that the encrypted bitstream carrying secret data can be correctly decoded. The secret message bits are encoded with error correction codes to achieve a perfect data extraction and image recovery. The encryption and embedding are controlled by encryption and embedding keys respectively. If a receiver has both keys, the secret bits can be extracted by analyzing the blocking artifacts of the neighboring blocks, and the original bitstream perfectly recovered. In case the receiver only has the encryption key, he/she can still decode the bitstream to obtain the image with good quality without extracting the hidden data.

Estimation of the optimal frame rate for video communications under bit‐rate constraints

AbstractThe use of applications related to real‐time video communications is spreading. But it is becoming difficult to secure the bandwidth, because of the increase in the number of the users as well as the bandwidth requirements of each user. In this context, a transcoder that can recode the video data to a usable bit rate for transmission is needed. In order to maintain as high a quality of service as possible, as seen by the user, there must be a criterion for assessment of image quality, by which the amounts of video information in the space and time directions can be reduced with good balance. In the conventional transcoder, control is based mostly on the square error, but it is not always true that the square error can directly represent the video quality seen or subjectively perceived by the user (subjective assessment quality). Consequently, this paper proposes a method of estimating the frame rate (optimal frame rate) that maximizes the subjective assessment quality in the recoding of video data (original data) stored in a video server to a specified bit rate. In the proposed method, the mean opinion score (MOS) obtained by a large number of subjective assessment tests is approximated by a function containing a small number of parameters, and the parameters of the function are estimated on the basis of the features of the original image. By specifying the bit rate for the function, the optimal frame rate is determined by determining the maximum. Interval estimation of the optimal frame rate was performed by applying the proposed method to open data, and it was verified that the frame rate could be estimated with a mean error of approximately 4 frames/s. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(12): 54–67, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10102

Carrier reuse with gain compression and feed-forward semiconductor optical amplifiers

The results of two techniques for optical carrier regeneration and wavelength reuse using semiconductor optical amplifiers (SOAs) are presented in this paper. The main objective is to recover an optical carrier by erasing its amplitude modulation. The first technique employs gain compression of deeply saturated SOAs. The second technique uses a feed-forward approach, where a delayed current signal is injected into the SOA with the same shape of the incoming optical pulse. The second technique could be capable to recover the optical carrier with less than 3-dB noise. However, it was observed that the SOA gain recovery time limits the maximum usable bit rate. Theoretical simulation showed good agreement with experimental results.

Adaptive Rate Subscriber Loop Data Transmission using Ethernet Interfaces

The increasing demand for Internet and World Wide Web access from the home has stimulated research into finding methods of providing access at rates greater than the 33.6 kb/s offered by current computer modems. Most copper telephone pairs have bandwidth capacities much greater than the 3.4 kHz voice-band. Using this excess bandwidth it is possible to substantially exceed current modem rates. This paper describes an inexpensive and readily deployable network access technology capable of providing bit rates ranging from hundreds of kb/s to potentially greater than 1 Mb/s on existing copper telephone lines. The usable bit rate, which varies depending on the length and gauge of the wire, is adaptively determined at system start up. The results of rate adaption testing are presented, as well as the results of throughput testing when TCP is used to provide flow control across the adaptive rate transmission line. It is also shown that current IBM compatible computers are only capable of supporting data rates of slightly more than 1 Mb/s through Ethernet adaptor cards; providing access rates beyong a few Mb/s is currently unnecessary.

Implementing a flexible synchronous network

The SYNET project, undertaken by Deutsche Telekom to modernize its transmission network, is discussed. The SYNET technology is based on the synchronous digital hierarchy (SDH), which uses synchronous transport modules of 155 Mbit/s (STM-1). The latter include a maximum usable bit rate of about 50 Mbit/s as well as a variety of additional information intended for network management. Since the transmission network is divided into several network levels characterized by different traffic loads and structures, a range of synchronous components geared to the requirements of the different network levels have been developed. The major differences between the trunk network and the local networks are described. The implementation of SYNET is reviewed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Equalization of Multimode Optical Fiber Systems

Decision feedback equalization (DFE) may provide a simple way to dramatically increase the bit rate on multimode optical systems. Computer simulations of digital multimode systems with tapped delay-line linear equalization and/or DFE are described. Results indicate that with relatively simple hardware it may be possible to increase by many times the usable bit rate on dispersion-limited optical channels, with a power penalty less than that for multilevel transmission and without the latter's complexity. For example, one could double the bit rate of a two-level system by paying an equalization power penalty of about 3 dB with DFE, whereas doubling the bit rate by going to four levels requires a penalty of 4.8 dB.

Multiple word/bit line redundancy for semiconductor memories

Multiple word/bit line redundancy techniques at the chip level are shown to be powerful enough to obtain good yields for chips with much higher rates of faults/chip than without redundancy. This is possible because, in many instances, chips which are rejected as being bad still have a high percentage of usable bits on them. The redundancy techniques described consist of putting spare decoders and spare word and bit lines on a chip in order to be able to replace defective lines of the chip with good lines while still maintaining the same address. Based on a first-pass design of a 16K chip, a significant improvement in the number of usable bits per wafer appears possible. The leverage for improvement is shown to be strongly dependent upon the type of cell, the layout, and the technology used.

Proximity effect in beam-addressed metal-oxide semiconductor memory

Electron scattering in a semiconductor target of a an electron-beam-addressed MOS memory can result in proximity effects between a number of adjoining memory locations (bits). As bit spacings decrease, there can be significant unintended charge accumulation in regions unirradiated by the electron beam. This can set a limit to usable bit packing density in the memory.

A Logical Reading System for Nonreturn-to-Zero Magnetic Recording

The nonreturn-to-zero method for the magnetic recording of binary information saturates the surface in a continuous fashion, one sense of saturation being used for a ``1'' and the opposite sense of saturation for a ``O.'' A system is described for reading NRZ digital data which utilizes the inherent alternating characteristic of the readback signal waveform to effect a logical correction. The reading system corrects the ``normal'' sources of error which limit the usable bit storage density and set the degree of reliability. The system employs only amplitude sensitive waveform operators and samples the readback signal only at the regular clock times.