This paper presents a novel interference cancellation (IC) scheme for both synchronous and asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless channels. In the DS-CDMA system, the multiple access interference (MAI) and the near-far problem (NFP) are the two factors which reduce the capacity of the system. In this paper, we propose a new algorithm that is able to detect all interference signals as an individual MAI signal by maximum correlation detection. It is based on the discovery of all the unknowing spreading codes of the interference signals. Then, all possible MAI patterns so called replicas are generated as a summation of interference signals. And the true MAI pattern is found by taking correlation between the received signal and the replicas. Moreover, the receiver executes MAI cancellation in a successive manner, removing all interference signals by single-stage. Numerical results will show that the proposed IC strategy, which alleviates the detrimental effect of the MAI and the near-far problem, can significantly improve the system performance. Especially, we can obtain almost the same receiving characteristics as in the absense of interference for asynchrnous system when received powers are equal. Also, the same performances can be seen under any received power state for synchronous system.

An intra refresh matrix, which models the importance of each macroblock, is first created. This matrix can be used to decide the coding mode of the macroblocks. The proposed technique can greatly improve the decoded video quality over the variable and error-prone channel with high packet loss rate.

Exact bit error probabilities (BEP) are derived in closed-form for binary pulsed direct sequence (DS-) and hybrid direct sequence time hopping code division multiple access (DS/TH-CDMA) systems that have potential applications in ultra-wideband (UWB) communications. Flat Nakagami fading channel is considered and the characteristic function (CF) method is adopted. An exact expression of the CF is obtained through a straightforward method, which is simple and good for any arbitrary pulse shape. The CF is then used to obtain the exact BEP that requires less computational complexity than the method based on improved Gaussian approximation (IGA). It is shown under identical operating conditions that the shape of the CF, as well as, the BEP differs considerably for the two systems. While both the systems perform comparably in heavily faded channel, the hybrid system shows better BEP performance in lightly-faded channel. The CF and BEP also strongly depend on chip length and chip-duty that constitute the processing gain (PG). Different combinations of the parameters may result into the same PG and the BEP of a particular system for a constant PG, though remains nearly constant in a highly faded channel, may vary substantially in lightly-faded channel. A comparison of the results from the exact method with those from the standard Gaussian approximation (SGA) reveals that the SGA, though accurate for both the systems in highly-faded channel, becomes extremely optimistic for low-duty systems in lightly-faded channel. The SGA also fails to track several other system trade-offs.

In Mobile Ad hoc Networks (MANET) geographic routing is characterized by local forwarding decision. Links with a long progress are preferred under the greedy forwarding rule. However in a real system long links tend to have a high packet loss rate due to multipath fading. A sub-optimal solution may separately exploit path diversity or rate adaptation. In this paper we study channel efficiency of multi-hop forwarding and try to jointly optimize rate adaptation and forwarder selection in geographic routing by the tradeoff between progress and instantaneous rate. We define a new metric -- Bit Transfer Speed (BTS) -- as the ratio of the progress made towards the destination to the equivalent time taken to transfer a payload bit. This metric takes overhead, rate and progress into account. Then we propose a packet forwarding scheme that Opportunistically exploits both long Progress and Adaptive Rate (OPAR) by a cross-layer design of routing and MAC. In OPAR each node selects for a packet the forwarder with the highest BTS. The forwarder changes as local topology (progress), packet size (overhead ratio) or channel state (data rate) varies. Simulation results show that compared with the normalized advance (NADV) [7] scheme and contention-based forwarding (CBF) [17] scheme, OPAR has lower packet loss and can effectively reduce channel occupation time by over 30% in the scenario with moderate mobility speeds.

A new paradigm in the design of optical coatings connected with an outstanding computational efficiency of modern design techniques is discussed. Several other topics including pre-production error analysis, monitoring of coating production, and computational manufacturing of optical coatings are considered.

This letter presents an efficient adaptive beamformer to deal with the multipath environments created by signal source scatterings. To improve the performance possible with the fixed forgetting factor, the regular adaptive forgetting factor algorithm is derived and applied to the subarray recursive least squares (RLS) beamforming. Simulations confirm that the proposed scheme has better performance than not only the conventional RLS algorithm but also the subarray RLS and adaptive forgetting factor RLS algorithms.

The authors have demonstrated the local alignment of nematic liquid crystal with local micro-grating structure fabricated by the curing of an ultraviolet curable material via a three dimensional micro-fabrication technique known as two photon excitation direct laser writing [1]. The molecular alignment of the nematic liquid crystals on the fabricated micro-grating structures was firstly investigated by the observations of a local twisted nematic region in a liquid crystal cell made of a substrate with locally fabricated micro-grating structure and a counter substrate with rubbed polyimide. The optical polarizing microscope observation of the micro-grating structures indicated that liquid crystals molecules have aligned parallel to the grooves of the micro-grating structure and that local alignment was successfully achieved. The alignment characteristics of the liquid crystals on these micro-gratings was also investigated and discussed quantitatively in details through the measurement of anchoring energy by the conventional torque balance method and the Berreman method. The azimuthal anchoring energy for the micro-grating was found to be in the order of 10-6 J/m2 and inversely proportional to the grating period.

Experimental and theoretical studies of light coupling to various magnetic nanostructured media and nanocomposites are briefly reported. Enhancement of the magneto-optical response is shown to occur when the constitutive materials of photonic crystals are magnetic. Transmission and reflection types of 1D magnetophotonic crystals (MPCs) have been studied. New possibility to enhance the magneto-optical response has been found when utilizing localized surface plasmon resonances in bismuth-substituted yttrium iron garnet (Bi:YIG) films impregnated with Au nanoparticles. Examples of integrated optic devices are discussed in which functional elements are 1D and 2D magnetophotonic crystals.

Transmit diversity systems based on orthogonal space-time block coding (OSTBC) usually suffer from rate loss and power spreading. Proper antenna selection scheme can help to more effectively utilize the transmit antennas and transmission power in such systems. In this paper, we propose a new antenna selection scheme for such systems based on the idea of antenna switching. In particular, targeting at reducing the number of pilot channels and RF chains, the transmitter now replaces the antennas with the lowest received SNR with unused ones if the output SNR of space time decoder at the receiver is below a certain threshold. With this new scheme, not only the number of pilot channels and RF chains to be implemented is decreased, the average amount of feedback information is also reduced. To analyze the performance of this scheme, we derive the exact integral closed form for the probability density function (PDF) of the received SNR. We show through numerical examples that the proposed scheme offers better performance than traditional OSTBC systems using all available transmitting antennas, with a small amount of feedback information. We also examine the effect of different antenna configuration and feedback delay.

This paper proposes an improved dynamic bandwidth allocation algorithm for dual Quality of Service (QoS) classes to maximize the utilization rate of the Resilient Packet Ring (RPR). To achieve dynamic bandwidth allocation for the two QoS classes in the RPR, each node measures the high priority traffic flow and assigns the appropriate bandwidth; the remaining bandwidth is used for low priority traffic. It passes a control frame containing the measured bandwidth of the high priority traffic to the other nodes. Based on the advertised high priority traffic bandwidth, any node that is congested transmits, to the other nodes, a fairness message to fairly allocate the remaining low priority bandwidth. Simulations demonstrate that the proposed algorithm enhances the utilization rate and reduces the delay of high priority frames.

The properties of the surface-conduction electron-emitter display (SED) are mainly decided by the surface-conduction electron emitters (SCE), which are normally made from the expensive metal Pd. In this study, we propose to use metal Zn instead of Pd as the emitter material. Both the device electrode and ZnO thin film are deposited by a sputter, and the electron emitters (SCE) are formed by the electro-forming process. The electron emission characteristic is obtained and the luminescence is observed.

The polycrystalline silicon (poly-Si) TFT has two insulator interfaces between the polycrystalline silicon and front and back insulators. These interfaces have trap states, which affect the characteristics of poly-Si TFT. In the silicon-on-insulator (SOI) technology area, using the dual-gated, fully-depleted SOI MOSFET under the depleted back-channel condition, the back-interface trap density can be calculated through the front-channel threshold voltage and film thicknesses. The front-interface trap density is also evaluated changing the roles of both gates. This evaluation method for front- and back- interface trap densities is called the threshold-voltage method. To apply this threshold-voltage method to the "medium-thickness" poly-Si TFT, of which the channel is not fully depleted in normal single gate bias operation, the biases for both front and back gates are controlled to realize full depletion. Under the fully-depleted condition, the front- or back- threshold voltage of poly-Si TFT is carefully extracted by the second-derivative method changing back- and front- gate biases. We evaluated the front- and back- interface trap densities not only for normal operation but also under stress. To evaluate the bias and temperature stress effect, we used two types of samples, which are made by different processes. The evaluated front- and back- interface trap densities for both samples in initial state are around 51011 to 1.31012 cm-2eV-1, which are almost the same as the reported values. Applying bias and temperature stress shows the variation of these interface-trap densities. Samples with large shifts of the front-channel threshold voltage show large trap density variation. On the other hand, samples with small threshold voltage shifts show small trap density variation. The variation of the back-interface trap density during the stress application showed a correlation to the front-channel threshold voltage shift.

The damage to the organic layer of aluminum (III) bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq) film was investigated on the basis of the change in photoluminescence (PL) intensity. To suppress the bombardment of the substrate with high-energy particles such as γ-electrons and negative oxygen ions, we used a facing-target sputtering (FTS) system. A marked reduction, however, of the PL intensity of the organic layer was still observed upon the deposition of an indium tin oxide (ITO) film on the organic film. To reduce this reduction, we proposed the insertion of a sector-shaped metal shield near the target electrode, and we showed its effectiveness in reducing the damage. This reduction of the damage is thought to be caused by the elimination of γ-electrons incident to the organic film surface escaping from the target area near the substrate side. We confirmed that high-energy electron bombardment leads to a significant reduction of PL intensity of the organic layer. This indicates that high-energy electrons incident to the organic film surface play a key role in the damage of the organic layer during the sputtering process.

In this study, attenuated total reflection (ATR) utilizing surface plasmon (SP) excitation and SP emission lights were observed for the adsorption of polystyrene (PS) spheres and a water-soluble polymer. The PS spheres contained fluorescent dyes and exhibited red fluorescence. The ATR properties indicated film deposition with increasing number of adsorption cycles. The SP emission light induced by the fluorescent dye in the spheres was also measured, and an increase in the peak intensity, as well as an angle shift, was observed. Furthermore, the SP emission light spectra were investigated at various emission angles. The dispersion relation obtained from the SP emission light almost corresponded to that obtained from the ATR curves.

A strip line broadside hybrid coupler which is tolerant to manufacturing errors in a multi-layered LTCC substrate has been developed. The tolerance to a displacement error and a thickness variation in the multi-layered LTCC substrate can be achieved by using the tandem arrangement of diagonally shifted coupled lines with adjacent ground walls. It has been demonstrated that the coupling deviation from designed characteristics in our proposed hybrid coupler is very small.

This paper describes a new color segmentation based on a normalized RGB chromaticity diagram for face detection. Face skin is extracted from color images using a coarse skin region with fixed boundaries followed by a fine skin region with variable boundaries. Two newly developed histograms that have prominent peaks of skin color and non-skin colors are employed to adjust the boundaries of the skin region. The proposed approach does not need a skin color model, which depends on a specific camera parameter and is usually limited to a particular environment condition, and no sample images are required. The experimental results using color face images of various races under varying lighting conditions and complex backgrounds, obtained from four different resources on the Internet, show a high detection rate of 87%. The results of the detection rate and computation time are comparable to the well known real-time face detection method proposed by Viola-Jones [11],[12].

In this paper, BER (Bit Error Rate) performance in 22 MIMO (Multiple-Input Multiple-Output) spatial multiplexing systems under Rician fading channels is evaluated. We examine BER performances employing inverse channel detection (ICD) under Rician fading channels, adding the phase of the direct path and Rician factor as a parameter. The results clearly indicate that the phase of the direct path and Rician factor have a great influence on BER performances employing ICD under Rician fading channels.

This paper considers a proportional fairness of end-to-end session rates in a multihop wireless network through the rate control framework. In multihop wireless networks, there are two classes of rate control problem. One focuses in optimizing the transmission attempt probabilities at the lower layers, but not the transmit powers while other problem is closely related to jointly optimal congestion control and power control. Proportional fairness is a fundamental concept in flow control problems. In this paper, we give in-depth analysis and show that the optimal solutions of these problems are proportionally fair provided that the objective functions are suitably chosen.

A fast class-of-service oriented packet scheduling (FCOPS) has a service fairness problem since a credit pool for a service class is initialized at the beginning of a transmission cycle whose starting moment is fixed at a specific ONU. To remedy the service unfairness of FCOPS, we suggest an enhanced class-of-service oriented packet scheduling (ECOPS) that uses a new initialization cycle whose starting moment is fairly distributed to each ONU. Also, ECOPS generates a colorless grant to utilize the resource wastage, when traffic is light and the total sum of grants of an ONU is less than a minimum size. Using simulation, we validate ECOPS as superior to FCOPS in the mean delay and the service fairness.

Partial transmit sequence (PTS) is a well known technique used to reduce the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. However, it has relatively high complexity due to the computation of multiple inverse fast Fourier transforms (IFFTs). To reduce this complexity, we use intermediate signals within a decimation in frequency (DIF) radix IFFT and propose a new PTS subblocking technique which requires the computation of only partial IFFTs. Performance results are presented which show a PAPR reduction similar to that with other techniques such as original PTS (O-PTS). Further, we show that complexity reduction can be achieved with either low or high radix IFFT algorithms.