The poor capability of bandwidth management on the current CATV network hinders the promotion of multi-media streaming services. This paper proposes a solution by applying stream-code partition on the S-CDMA system adopted in the DOCSIS 2.0 standard. The method makes use of the Fine Granularity Scalability source coding and offers an efficient way for uplink rate control, so that bandwidth management can be performed in an extremely flexible manner.

A mechanical phase shifter is designed for beam scanning in co-phase fed single-layer slotted waveguide arrays. The multiple-way power divider in this array consists of a series of π-junctions with one guide wavelength spacing in a feed waveguide. The movable narrow walls placed between the π-junctions perturb the guide wavelength as well as the phase of output ports. Method of Moment (MoM) analysis for one unit consisting of one movable plate and two junctions is conducted to estimate the available phase shift as well as the degradation of reflection. A phase shift of 86 degrees is predicted between two π-junctions under the condition of reflection below -20 dB; experiments at 4 GHz confirmed the design. The beam scanning capability of the arrays is also surveyed and the beam-scanning of about 10 degrees is predicted.

We propose binary-quantized and spatio-temporally discretized network models of linear diffusion systems and investigate their filtering effect on single-bit sigma-delta (ΣΔ) modulated signals. The network consists of only one kind of elements that add ΣΔ modulated signals and quantize the sum in the form of single-bit signal. A basic one-dimensional network is constructed first. Then, the network is extended into two dimensions. These networks have characteristics equivalent to those of linear diffusion systems in both time and frequency domains. In addition, network noise caused by the quantization in the elements contains low-level low-frequency components and high-level high-frequency components. Therefore, the proposed networks have possibility to be used as signal propagation and diffusion media of ΣΔ domain filters.

This paper examines the Inter Carrier Interference (ICI) due to Doppler spread in OFDM mobile reception and proposes the use of Beam-Space Adaptive Array Antennas for moving receivers. In the proposed system, firstly we separate the multi-path signals into multi-beams according to their incident directions, then correct the frequency shift of each beam signal, considering the beam direction, and finally combine the corrected signals based on Maximal Ratio Combining (MRC). Further this paper clarifies the excellent performance of the proposed system in suppressing the influence of Doppler spread by carrying out computer simulation. Particularly, it was certified that it is possible to suppress the influence of the Doppler spread efficiently for all the receiving directions by using eight-element beam-space array antenna with element spacing of (3/8)λ, and referring three past symbol data when calculating the weight vector of MRC.

We present a new keystream generator (KSG) MUGI, which is a variant of PANAMA proposed at FSE '98. MUGI has a 128-bit secret key and a 128-bit initial vector as parameters and generates a 64-bit string per round. The design is particularly suited for efficient hardware implementations, but the software performance of MUGI is excellent as well. A speed optimized implementation in hardware achieves about 3 Gbps with 26 Kgates, which is several times faster than AES. On the other hand, the security of MUGI has been evaluated by analyzing the applicability of re-synchronization attacks, related-key attacks, and attacks that exploit the linear correlation of an output sequence. Our analysis confirms that MUGI is a secure KSG.

The Communications Research Laboratory (CRL) started a new project named the New Generation Mobile Network Project in April 2002. The target of this project is the development of new technologies to enable seamless and secure integration of various wireless access networks such as 3rd and 4th generation cellular, wireless LAN, high-speed mobile wireless, wired communications, and broadcasting networks. This paper presents an overview of CRL's new generation mobile communication system that is called The Multimedia Integrated Network by Radio Access Innovation Plus (MIRAI+), as well as details the role of Software Radio Technology (SDR) in MIRAI+.

We propose a stochastic model for signals generated through the electron multiplying effect of detectors in charged particle beam equipments. This model is based on a stochastic variable characterized by a log-normal type distribution. The model is simple and can be used to represent a wide dynamic range of signals from pulse-like signals when the primary beam current is small to continuous signals when the primary beam current is large. For the model base reference a normalization of actual signal detectors is presented. This base reference yields the unique stochastic parameter used in our model. The proposed model better approximates the actual signals in the power spectrum distribution as compared to the filtered Poisson method presented elsewhere.

A two-dimensional laser beam profiler has been developed that can measure the intensity distribution on a sample surface of a single-shot of an excimer-laser light beam from not only the macroscopic viewpoint, but also the microscopic viewpoint, which is important to excimer-laser triggered lateral large-grain growth of Si. A resolution as fine as 0.4 µm was obtained with a field of view of as large as 30 µm 30 µm. The effects of homogenizers, phase-shifters, and their combination on beam profiles were quantitatively investigated by using this apparatus. The relationship between the microscopic beam profile and the surface morphology of laterally grown grains was also examined.

Combining a layered space-time receiver with the OFDM for high-rate transmissions requires the multi-channel estimation process. So, this letter proposes a time-domain approach for new preamble structure in OFDM-based multiple antenna systems, and investigates the channel estimation performance based on the semi-blind processing and its imperfectness by using time-domain windowing. The proposed preamble can estimate the multi-channel up to the 8 transmit antennas in the WLAN standards using two long preambles.

Beam-space time coding methods are being extensively investigated, since they provide levels of performance appropriate for the next and future generations of wireless communication systems. In this paper, we focus on beam-domain space-time coding, especially considering the case when transmit beams have inter-beam interference (IBI). A new beam-space time coding scheme that takes into account the overlap amount among beams is proposed. We observe that the overlap of beams introduces an amount of correlation to the channels in a similar way to the well-known Partial Response (PR) channel in magnetic recording. Based on that observation, the proposed system can make use of IBI to encode and decode the signals. We evaluate the proposed system both via theoretical upper bound and via computer simulations. The Bit Error Rate (BER) performance of the proposed system using IBI is better than that of the system with no-IBI because the proposed system delivers more coding gain. However, the overlap of beams decreases the diversity gain. The tradeoff relationship between diversity gain and coding gain is investigated.

A TlGaAs/GaAs multiple quantum-well (MQW) structure having four identical well layers was grown on a GaAs (001) substrate by low-temperature molecular-beam epitaxy (MBE) at 190. The (004) X-ray diffraction (XRD) curve of this sample showed satellite peaks up to the 3rd order at least. The measured XRD curve agreed well with the theoretically simulated one with a Tl content of x=7% and a width of 57 for the TlxGa1-xAs well layers. This result indicates that the grown MQW structure has good single-crystalline quality as well as flat and sharp interfaces.

Knudsen et al. proposed an efficient method based on a tree-search algorithm with recursive process for reconstructing the internal state of RC4 stream cipher. However, the method becomes infeasible for word size n > 5 because its time complexity to reconstruct the internal state is too large. This letter proposes a more efficient method than theirs. Our method can reconstruct the internal state by using the pre-known internal-state entries, which are fewer than their method.

A new beamforming method based on simplex downhill optimaization process has been presented for the reverse link CDMA systems. The proposed system performs code-filtering at each antenna for each user. The new beamforming method gives lower computations and faster convergence properties than existing algorithms. The simulation results show that the proposed algorithm has a better BER performance in the case of the time-varing channel.

Adaptive arrays with signal blocking have the advantages of fast convergence and robustness to pointing errors as well as of rejecting a coherent interference in addition to incoherent ones. In this paper, we propose a novel method for performance improvement in such arrays with no increase in complexity. The proposed method utilizes all of the array elements to obtain the adaptive output so that its performance is superior to that of the conventional method which does not utilize one of the elements. Their performances are compared analytically and by computer simulation.

A nonlinear combiner random number generator is a general keystream generator for certain stream ciphers. The generator is composed of several linear feedback shift registers and a nonlinear function; the output is used as a keystream. A fast correlation attack is a typical attack for such keystream generators. Mihaljevi, Fossorier, and Imai have proposed an improved fast correlation attack. The attack is based on error correction of information bits only in the corresponding binary linear block code; APP threshold decoding is employed for the error correction procedure. In this letter, we propose a method which improves the success rate of their attacks with similar complexity. The method adds some intentional error to original parity check equations. Those equations are then used in APP threshold decoding.

In this paper, a new video broadcast protocol is proposed for video-on-demand (VoD) in shared environment. The new protocol is developed by modifying the first segment delivery scheme for the skyscraper protocol using the idea of patching. The results show that the start-up latency for users is greatly reduced when using our new protocol.

In medical diagnosis, cone beam CT increases the dose absorbed by a patient. However, the radiographic noise (such as quantum noise) in a CT image increases when radiation exposure is reduced. In this paper, we propose a method to improve the CT image degraded by the quantum mottle based on 2-D wavelet transform modulus sum (WTMS). The noise and regular parts of an image can be observed by tracing the evolution of its 2-D WTMS across scales. Our experimental results show that most of the quantum mottle in the 2-D projections is removed by the proposed method and the edges preserved well. We investigate the relation between the number of X-ray photons and the quality of the denoised images. The result shows the possibility that a patient's dose can be reduced about 10% with the same visual quality by our method.

A Cyclotron Wave Converter, having decreased magnetic intensity is discussed. Two microwave cavities with uniform and quadruple (or six-pole) electric field in the gap of interaction are used to transform microwave power into the kinetic power of the electron beam fast cyclotron wave. As a result of it, magnetic flux density occurs in two (or three) times lower. The latter is very important to create a compact, powerful and efficient microwave/DC power converters operating at different frequencies including short centimetric and long millimetric wavebands.

In this paper, an optical signal processing beam forming network (BFN) for two-dimensional (2-D) beam steering is proposed and experimentally demonstrated. Two lightwaves, called the signal and reference, are both Fourier transformed, combined, and then down-converted into RF signals using an optical heterodyne technique. A simple combination of orthogonal one-dimensional position scannings of the signal and reference lightwaves generates RF signals with phase distributions for 2-D beam steering. The system operation and optical losses are theoretically analyzed. Using graded index fiber (GIF) lensed single mode fibers (SMFs), total optical loss of the sampling fiber array is evaluated to be 4.5 dB from the fiber to fiber loss measurements. Using an experimental optical signal processing BFN at 25 GHz, 2-D beam steering is demonstrated at 0, 10, 20, and 30through the measured amplitudes and phases of RF signals for 16 position sets of the signal and reference fibers. The proposed method has the potential to provide ultra-fast beam scanning by utilizing optical switching technologies.

Binary and ternary 5-bit programmable dispersion matrix, based on fiber Bragg reflectors, is built to control a two-channel receive/transmit beamformer at 1550 nm. RF phase measurements for the 32/31 delay configurations are presented. The programmable dispersion matrix is fully demonstrated and characterized for RF signals from 0.2 to 1 GHz.