Employing fractional frequency reuse (FFR) in OFDMA cellular systems is very attractive since it offers large capacity and single cell frequency reuse. However, its performance in practical environments, e.g. scheduling and arbitrary cell configurations, has not been well revealed. This paper analyzes the theoretical capacity and outage rate of an OFDMA cellular system employing FFR. Numerical examples show that FFR achieves higher capacity than the non-FFR equivalent when the outage rate is low.

Performance of band-limited baseband synchronous CDMA using orthogonal Independent Component Analysis (ICA) spreading sequences is investigated. The orthogonal ICA sequences have an orthogonality condition in a synchronous CDMA like the Walsh-Hadamard sequences. Furthermore, these have useful correlation properties like the Gold sequences. These sequences are obtained easily by using the ICA which is one of the brain-style signal processing algorithms. In this study, the ICA is used not as a separator for received signal but as a generator of spreading sequences. The performance of the band-limited synchronous CDMA using the orthogonal ICA sequences is compared with the one using the Walsh-Hadamard sequences. For limiting bandwidth, a Root Raised Cosine filter (RRC) is used. We investigate means and variances of correlation outputs after passing the RRC filter and the Bit Error Rates (BERs) of the system in additive white Gaussian noise channel by numerical simulations. It is found that the BER in the band-limited system using the orthogonal ICA sequences is much lower than the one using the Walsh-Hadamard sequences statistically.

In this letter, we propose an integer carrier frequency offset (IFO) estimator in the presence of symbol timing error for an ultra-wideband multi-band orthogonal frequency division multiplexing (UWB MB-OFDM) system. The proposed IFO estimator uses frequency-domain spreaded data symbol which is provided in the MB-OFDM system. To demonstrate the accuracy of the proposed IFO estimator, comparisons are made with conventional estimators via computer simulation.

To increase both the capacity and the processing speed for input-queued (IQ) switches, we proposed a fair scalable scheduling architecture (FSSA). By employing FSSA comprised of several cascaded sub-schedulers, a large-scale high performance switches or routers can be realized without the capacity limitation of monolithic device. In this paper, we present a fair scheduling algorithm named FSSA_DI based on an improved FSSA where a distributed iteration scheme is employed, the scheduler performance can be improved and the processing time can be reduced as well. Simulation results show that FSSA_DI achieves better performance on average delay and throughput under heavy loads compared to other existing algorithms. Moreover, a practical 64 64 FSSA using FSSA_DI algorithm is implemented by four Xilinx Vertex-4 FPGAs. Measurement results show that the data rates of our solution can be up to 800 Mbps and the tradeoff between performance and hardware complexity has been solved peacefully.

For a graph G, a biclique edge partition SBP(G) is a collection of bicliques (complete bipartite subgraphs) Bi such that each edge of G is contained in exactly one Bi. The Minimum Biclique Edge Partition Problem (MBEPP) asks for SBP(G) with the minimum size. In this paper, we show that for arbitrary small ε>0, (6053/6052-ε)-approximation of MBEPP is NP-hard.

This paper investigates the performance of ARQ-aided downlink Time Switched Transmit Diversity (TSTD) in the WCDMA Low Chip Rate (LCR)-Time Division Duplex (TDD) system, when antenna switching and power ramping are applied. With the help of the ARQ signal, where the receiver sends the acknowledgement (ACK or NACK) to the transmitter, the proposed TSTD scheme switches the transmit antenna and ramps up the transmission power for the retransmitted data, when the transmitter receives a NACK signal. Simulation results demonstrate, that when the mobile speed is 3 km/h and a frame error rate (FER) is set to 1%, the antenna switching scheme yields 2 dB to 3 dB performance gain in terms of average Eb/N0, and the power ramping gives 0.7 dB to 1.6 dB gain, compared with the conventional ARQ-aided TSTD. In addition, 6% of throughput gain is shown by amalgamating the antennas switching as well as the power ramping, when the average Eb/N0 is equal to 0 dB.

The precise noise modeling of complementary metal oxide semiconductor image sensor (CMOS image sensor: CIS) is a significant key in understanding the noise source mechanisms, optimizing sensor design, designing noise reduction circuit, and enhancing image quality. Therefore, this paper presents an accurate random telegraph signal (RTS) noise analysis model and a novel quantitative evaluation method in motion picture for the visual sensory evaluation of CIS. In this paper, two main works will be introduced. One is that the exposure process of a video camera is simulated, in which a Gaussian noise and an RTS noise in pinned-photodiode CMOS pixels are modeled in time domain and spatial domain; the other is that a new video quality evaluation method for RTS noise is proposed. Simulation results obtained reveal that the proposed noise modeling for CIS can approximate its physical process and the proposed video quality evaluation method for RTS noise performs effectively as compared to other evaluation methods. Based on the experimental results, conclusions on how the spatial distribution of an RTS noise affects the quality of motion picture are carried out.

We introduce a complexity measure r for the class F of read-once formulas over the basis {AND,OR,NOT, XOR, MUX} and show that for any Boolean formula F in the class F, r(F) is a lower bound on the quantum query complexity of the Boolean function that F represents. We also show that for any Boolean function f represented by a formula in F, the deterministic query complexity of f is only quadratically larger than the quantum query complexity of f. Thus, the paper gives further evidence for the conjecture that there is an only quadratic gap for all functions.

This letter investigates the space-time block codes from quasi-orthogonal design as a tradeoff between high transmission rate and low decoding complexity. By studying the role orthogonality plays in space-time block codes, upper bound of transmission rate and lower bound of decoding complexity for quasi-orthogonal design are claimed. From this point of view, novel algorithms are developed to construct specific quasi-orthogonal designs achieving these bounds.

It is well known that the performance of turbo codes can be improved by optimizing the energy allocation on coded symbols. Based on this fact, we propose an optimized 16-quadrature amplitude modulation (QAM) constellation for binary turbo codes. In the proposed scheme, the energy allocated on turbo coded symbols is optimized by modifying the constellation of QAM. The proposed 16-QAM constellation combined with a binary turbo code offers better coding gain compared to the conventional combination of binary turbo code and QAM.

In photonic label routing networks, recognition of optical labels is one of the key functions. We have proposed passive waveguide-type devices for recognition of optical labels coded in quadri-phase-shift-keying (QPSK) form. In this paper, we consider wavelength dependence of the devices. The basic module of the proposed device consists of a 3-dB directional coupler, two Y-junctions, and an asymmetric X-junction. The Y-junction and an asymmetric X-junction have basically no wavelength dependence. Although the 3-dB directional coupler has weak wavelength dependence, the device for two-symbol label recognition is found to work in wavelength 1.5-1.6 µm. The performance of the device is confirmed by simulation using beam propagation method (BPM).

A secret image transmission scheme based on vector quantization (VQ) and a secret codebook is proposed in this article. The goal of this scheme is to transmit a set of good-quality images secretly via another high-quality cover image with the same image size. In order to reduce the data size of secret images, the images are encoded by an adaptive codebook. To guarantee the visual quality of secret images, the adaptive codebook applied at the transmitter is transmitted to the receiver secretly as well. Moreover, to enhance the security of the proposed scheme and to compact the data size of the codebook, the adaptive codebook is encoded based on VQ using another codebook generated from the cover image. Experiments show impressive results.

A 0.9-V 12-bit 40-MSPS pipeline ADC with I/Q amplifier sharing technique is presented for wireless receivers. To achieve high linearity even at 0.9-V supply, the clock signals to sampling switches are boosted over 0.9 V in conversion stages. The clock-boosting circuit for lifting these clocks is shared between I-ch ADC and Q-ch ADC, reducing the area penalty. Low supply voltage narrows the available output range of the operational amplifier. A pseudo-differential (PD) amplifier with two-gain-stage common-mode feedback (CMFB) is proposed in views of its wide output range and power efficiency. This ADC is fabricated in 90-nm CMOS technology. At 40 MS/s, the measured SNDR is 59.3 dB and the corresponding effective number of bits (ENOB) is 9.6. Until Nyquist frequency, the ENOB is kept over 9.3. The ADC dissipates 17.3 mW/ch, whose performances are suitable for ADCs for mobile wireless systems such as WLAN/WiMAX.

We propose an extension method of quaternary low correlation zone (LCZ) sequence set with odd period. From a quaternary LCZ sequence set with parameters (N, M, L, 1), the proposed method constructs a new quaternary LCZ sequence set with parameters (2N, 2M, L, 2), where N is odd. If the employed LCZ sequence set in the construction is optimal, the extended LCZ sequence set becomes also optimal where N = kL, L > 4, and k>2.

Recently, the marginalized particle filter (MPF) has been applied to blind symbol detection problems over selective fading channels. The MPF can ease the computational burden of the standard particle filter (PF) while offering better estimates compared with the standard PF. In this paper, we investigate the application of the blind MPF detector to more realistic situations where the systems suffer from analog imperfections which are non-linear signal distortion due to the inaccurate analog circuits in wireless devices. By reformulating the system model using the widely linear representation and employing the auxiliary variable resampling (AVR) technique for estimation of the imperfections, the blind MPF detector is successfully modified to cope with the analog imperfections. The effectiveness of the proposed MPF detector is demonstrated via computer simulations.

Traditional wavelet-based speech enhancement algorithms are ineffective in the presence of highly non-stationary noise because of the difficulties in the accurate estimation of the local noise spectrum. In this paper, a simple method of noise estimation employing the use of a voice activity detector is proposed. We can improve the output of a wavelet-based speech enhancement algorithm in the presence of random noise bursts according to the results of VAD decision. The noisy speech is first preprocessed using bark-scale wavelet packet decomposition ( BSWPD ) to convert a noisy signal into wavelet coefficients (WCs). It is found that the VAD using bark-scale spectral entropy, called as BS-Entropy, parameter is superior to other energy-based approach especially in variable noise-level. The wavelet coefficient threshold (WCT) of each subband is then temporally adjusted according to the result of VAD approach. In a speech-dominated frame, the speech is categorized into either a voiced frame or an unvoiced frame. A voiced frame possesses a strong tone-like spectrum in lower subbands, so that the WCs of lower-band must be reserved. On the contrary, the WCT tends to increase in lower-band if the speech is categorized as unvoiced. In a noise-dominated frame, the background noise can be almost completely removed by increasing the WCT. The objective and subjective experimental results are then used to evaluate the proposed system. The experiments show that this algorithm is valid on various noise conditions, especially for color noise and non-stationary noise conditions.

In this paper, we address the following problems: Given a sequence A of n real numbers, and four parameters I,J,X and Y with I≤ J and X≤ Y, find the longest (or shortest) subsequence of A such that its length is between I and J and its sum is between X and Y. We present an online and an offline algorithm for the problems, both run in O(nlog n) time, which are optimal.

We propose a surface profiling algorithm by white-light interferometry that extends sampling interval to twice of the widest interval among those used in conventional algorithms. The proposed algorithm uses a novel function called an in-phase component of an interferogram to detect the peak of the interferogram, while conventional algorithms used the squared-envelope function or the envelope function. We show that the in-phase component has the same peak as the corresponding interferogram when an optical filter has a symmetric spectral distribution. We further show that the in-phase component can be reconstructed from sampled values of the interferogram using the so-called quadrature sampling technique. Since reconstruction formulas used in the algorithm are very simple, the proposed algorithm requires low computational costs. Simulation results show the effectiveness of the proposed algorithm.

An orthogonal sequence based MIMO common feedback method for multicast hybrid automatic-repeat-request (H-ARQ) transmission is presented. The proposed method can obtain more diversity gain proportional to the number of transmit antennas than the conventional on-off keying (OOK) based common feedback method. The ACK/NACK detection performance gain of the proposed scheme over the OOK based method is verified by analysis and computer simulation results.

In conventional preamble based channel estimation in OFDM/offset QAM (OFDM/OQAM) system, both the even index subcarriers and the odd index subcarriers are with identical value selected from { 1 } respectively to avoid inter-carrier interference (ICI), if and only if channel frequency response in neighbor few subcarriers remain invariable. However, it requires larger coherent bandwidth. In this paper, we propose an effective preamble design with ICI cancellation for channel estimation in OFDM/OQAM system. With this structure, we only utilize even (or odd) index of subcarriers as reference signal to avoid ICI, and then the channel information of remaining subcarriers can be estimated by the interpolation approach. Based on the sampling theorem, the mean square error (MSE) performance of the proposed preamble design is analyzed, where channel estimation performance is same for all subcarriers. Simulation and analytical results demonstrate that the proposed preamble design with ICI cancellation method outperforms the conventional one in term of channel estimation accuracy in OFDM/OQAM system.