Formalizing REST APIs for web-based communication and SIP interworking

This paper proposes an instantaneous recovery route design scheme using multiple coding-aware link protection scenarios to achieve higher link cost reduction in the network. In this scheme, two protection scenarios, namely, (i) traffic splitting (TS), and (ii) two sources and a common destination (2SD) are used to integrate multiple sources and a common destination. The proposed scheme consists of two phases. In the first phase, the proposed scheme determines routes for 2SD and TS scenarios of all possible source-destination pairs to minimize the total link cost. In this phase, the network coding is applied to the common path within each scenario, individually. In the second phase, network coding is applied to the common path between two scenarios (or a scenario pair) in order to enhance the resource saving. This phase develops conditions that select the most appropriate combination of scenario pairs, such as TS–TS, 2SD–2SD, and 2SD–TS for network coding, including their proofs. Using these conditions, a heuristic algorithm is introduced in order to select the most appropriate combination of scenario pairs for further enhancing of resource saving. Simulation results show that the proposed scheme outperforms the conventional 1 + 1 protection scheme, the TS scenario, and the 2SD scenario in terms of link cost reduction in the network.     

Fault Leveling Techniques for Yield and Reliability Enhancement of NAND Flash Memories

Novel fault leveling techniques based on address remapping (AR) are proposed in this paper. We can change the logical-to-physical address mapping of the page buffer such that faulty cells within a flash page can be evenly distributed into different codewords. Therefore, the adopted ECC scheme can correct them effectively. Based on the production test or on-line BIST results, the fault bitmap can be used for executing the heuristic fault leveling analysis (FLA) algorithm and evaluating control words used to steer fault leveling. A new page buffer architecture suitable for address remapping is also proposed. According to experimental results, repair rate, yield, and reliability can be improved significantly with negligible hardware overhead.     

Computationally Efficient Motion Estimation Algorithm for HEVC

In this paper, we present a novel computationally efficient motion estimation (ME) algorithm for high-efficiency video coding (HEVC). The proposed algorithm searches in the hexagonal pattern with a fixed number of search points at each grid. It utilizes the correlation between contiguous pixels within the frame. In order to reduce the computational complexity, the proposed algorithm utilizes pixel truncation, adaptive search range, sub-sampling and avoids some of the asymmetrical prediction unit techniques. Simulation results are obtained by using the reference software HM (e n c o d e r_l o w d e l a y_P_m a i n and e n c o d e r_r a n d o m a c c e s s_m a i n profile) and shows 55.49% improvement on search points with approximately the same PSNR and around 1% increment in bit rate as compared to the Test Zonal Search (TZS) ME algorithm. By utilizing the proposed algorithm, the BD-PSNR loss for the video sequences like B a s k e t b a l l P a s s_416 × 240@50 and J o h n n y_1280 × 720@60 is 0.0804 dB and 0.0392 dB respectively as compared to the HM reference software with the e n c o d e r_l o w d e l a y_P_m a i n profile.     

Discrete Logarithm Problems with Auxiliary Inputs

Let g be an element of prime order p in an abelian group, and let α∈? _p . We show that if g,g ^α , and \(g^{\alpha^{d}}\) are given for a positive divisor d of p?1, the secret key α can be computed deterministically in \(O(\sqrt{p/d}+\sqrt{d})\) exponentiations by using \(O(\max\{\sqrt{p/d},\sqrt{d}\})\) storage. If \(g^{\alpha^{i}}\) (i=0,1,2,…,2d) is given for a positive divisor d of p+1, α can be computed in \(O(\sqrt{p/d}+d)\) exponentiations by using \(O(\max\{\sqrt{p/d},\sqrt{d}\})\) storage. We also propose space-efficient but probabilistic algorithms for the same problem, which have the same computational complexities with the deterministic algorithm.As applications of the proposed algorithms, we show that the strong Diffie–Hellman problem and related problems with public \(g^{\alpha},\ldots,g^{\alpha^{d}}\) have computational complexity up to \(O(\sqrt{d}/\log p)\) less than the generic algorithm complexity of the discrete logarithm problem when p?1 (resp. p+1) has a divisor d≤p ^1/2 (resp. d≤p ^1/3). Under the same conditions for d, the algorithm is also applicable to recovering the secret key in \(O(\sqrt{p/d}\cdot \log p)\) for Boldyreva’s blind signature scheme and the textbook ElGamal scheme when d signature or decryption queries are allowed.     

Adaptive Lattice Filters for Systems of Space-Time Processing of Non-Stationary Gaussian Processes

Adaptive systems protecting pulse radars from non-stationary in time (range) clutter echoes are usually tuned using training vectors composed of complex amplitudes of input signals and comprising a finite-length “sliding window” of data. From any current range gate to a subsequent one, a training sample is partially updated (or modified) by means of excluding the “old” training vectors (correspond to the current range gate) and including the “new” ones (correspond to the next range gate). As a consequence, respective estimates of adaptive system parameters are corrected according to a modified sample correlation matrix (CM), which is typically a sum of an initialCMand a modifying matrix of rank K ≥ 1. In this case it is possible to avoid re-computing these parameters based on a new training sample of full size and, instead of this, we correct them in an “economical” way employing K-rank modification of a matrix inverse to the CM estimate.This paper is devoted to comparative analysis of various (K ≥ 1)-rank modification algorithms that correct the parameters of adaptive lattice filters (ALF). Main attention is paid to synthesis as well as theoretical and experimental study of algorithms of direct (K > 1)-rank modification of the ALF parameters. These algorithms attain the said objective omitting the K-fold application of known rank-one (K = 1) modification algorithms. We also synthesize a combined algorithm (CA) of (K ≥ 1)-rank modification of the ALF parameters that is more computationally simple and more numerically robust compared to known algorithms. The ALF employing the CA can serve as an effective tool for solving various tasks of space-time adaptive signal processing in pulse radars of different purpose.     

Computation-skip Error Mitigation Scheme for Power Supply Voltage Scaling in Recursive Applications

Aggressive power supply voltage V_dd scaling is widely utilized to exploit the design margin introduced by the process, voltage and environment variations. However, scaling beyond the critical V_dd results to numerous setup timing errors, and hence to an unacceptable output quality. In this paper, we propose computation-skip (CS) scheme to mitigate setup timing errors, for recursive digital signal processors with a fixed cycles per instruction (CPI). A coordinate rotation digital computer (CORDIC) with the proposed CS scheme still functions when scaling beyond the error-free voltage. It enables better-than-worst-case design constraint and achieves 1.82 X energy saving w.r.t. nominal V_dd condition, another 1.49 X energy saving without quality degradation, and another 1.09 X energy saving when sacrificing 8.35 dB output quality.     

Statistical characteristics of an ensemble of ultrawideband communications channels under the conditions of multipath signal propagation in rooms

The estimates of data rates in the ultrawideband direct chaotic scheme of data transmission in rooms, which can be achieved at a specified level of error probability under the conditions of multipath signal propagation in wireless communications networks, are presented. The estimates have been obtained via direct numerical simulation of energy reception of chaotic signals at the output of communications channels. The channel impulse responses were formed according to the statistical model developed by the IEEE 802.15 working group for indoor applications. In the approximation of a dominant reverberation interference (multipath propagation), the portion of channels making it possible to transmit data with rates from 10 to 50 Mb/s and the practically important error probability (P _b ～ 10^?5?10^?4) is determined for the chaotic signal bandwidths Δf = 500 and 2000 MHz. It have been first revealed that, in the given ensemble of channels, the small portion of channels (5–20%) with high levels of error probability P _b substantially affects the dependence of the error probability averaged over the given type of channels (\(\bar P_b \) (R)) on the transmission rate. It has been demonstrated that quantity \(\bar P_b \) (R) is the practically important characteristic of noise immunity for the significant portion (～80–95%) of channels of the given type.     

Photoconverters based on gallium arsenide diffused <Emphasis Type="Italic">p-n</Emphasis> junctions formed on a microprofile GaAs surface

The p-n junctions promising for photoconverters have been fabricated using diffusion from the gaseous phase and studied with the analysis of mass transport of the doping impurity (Zn) through the microprofile GaAs surface taken into account. Depending on the conditions of diffusion (the diffusant’s mass and diffusion duration), the formation of both a p-n junction in a microprofile and a planar p-n junction in the GaAs bulk with a heavily doped near-surface p ⁺ type layer is possible. Photoelectric characteristics of device structures with textured p-n junction and a thin wide-gap Al _x Ga_{1 ? x} As window obtained by liquid-phase epitaxy are reported.     

Specific features of electrical properties of the In<Subscript>x</Subscript>Ga<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>N alloy

Temperature dependences of the Hall coefficient and resistivity of the In_xGa_{1 ? x} N alloys (0 ≤ x ≤ 1) are investigated. It is found that, at x ≤ 0.4, the temperature dependences of the Hall coefficient and resistivity have the activation-related portion. The activation energy depends linearly on the In content in the alloy. At x ≈0.5, the activation portion vanishes. The main scattering mechanism depends on the temperature, on the defect density in the film (this density is largely determined by the used intermediate GaN layers), and on the alloy composition x.     

Using <Emphasis Type="Italic">G</Emphasis> Features to Improve the Efficiency of <Emphasis Type="Italic">Function Call Graph</Emphasis> Based Android Malware Detection

In this paper, we proposed a G features based Android malware detecting scheme with information of Function Call Graph. The experimental results showed that our G features based detecting scheme obtained a high detecting performance in up-to-date malware testing dataset. Besides, the collapsing issue induced by the high-dimension vectors of traditional Function Call Graph detection can also be avoided with our methods.     

Performance analysis of opportunistic CSMA schemes in cognitive radio networks

In this paper, we consider underlay cognitive radio (CR) networks where an amount of interference caused by secondary stations (STAs) has to be kept below a predefined level, which is called interference temperature. We propose opportunistic p-persistent carrier sense multiple access schemes for the CR networks, which opportunistically exploit wireless channel conditions in transmitting data to the secondary access point. We also devise an adaptive interference-level control technique to further improve quality-of-service of a primary network by limiting the excessive interference due to collisions among STAs. The performances of the proposed schemes are mathematically analyzed, and they are validated with extensive computer simulations. The simulation results show that the proposed schemes achieve near optimal throughput of the secondary network while they are backward-compatible to the conventional p-persistent CSMA scheme.     

Design of complex adaptive multiresolution directional filter bank and application to pansharpening

This paper proposes a new 2-D transform design, namely complex adaptive multiresolution directional filter bank, to represent the spatial orientation features of an input image adaptively. The proposed design is completely shift invariant and represents the input image by one low-pass and multiscale N directional band-pass subbands. Here, N represents estimated number of dominant directions present in the input image. Our design consists of two main filter bank stages. A fix partitioned complex-valued directional filter bank (CDFB) is at the core of the design followed by a novel partition filter bank stage. Fine partitioning of the CDFB subbands is used to get the adaptive nature of the proposed transform. The partitioning decision is made based on the directional significance of range of CDFB subband angle selectivity in the input image. Partition filter bank stage which nonuniformly partitions the CDFB subbands provides total N dominant direction selective subbands. Local orientation map of the input image is used to determine the dominant directions and hence N. For better sparsity properties, we design the multiresolution stage with filters having high vanishing moments and better frequency selectivity. Applicability of the proposed adaptive design is shown for pansharpening of multispectral images. Our proposed pansharpening approach is evaluated on images captured using QuickBird and IKONOS-2 satellites. Results obtained using the proposed approach on these datasets show considerable improvements in qualitative as well as quantitative evaluations when compared to state-of-the-art pansharpening approaches including transform-based methods.     

PAPR reduction in CO-OFDM systems using IPTS and modified clipping and filtering

Aiming at the problem of the peak to average power ratio (PAPR) in coherent optical orthogonal frequency division multiplexing (CO-OFDM), a hybrid PAPR reduction technique of the CO-OFDM system by combining iterative partial transmit sequence (IPTS) scheme with modified clipping and filtering (MCF) is proposed. The simulation results show that at the complementary cumulative distribution function (CCDF) of 10^-4, the PAPR of proposed scheme is optimized by 1.86 dB and 2.13 dB compared with those of IPTS and CF schemes, respectively. Meanwhile, when the bit error rate (BER) is 10^-3, the optical signal to noise ratio (OSNR) are optimized by 1.57 dB and 0.66 dB compared with those of CF and IPTS-CF schemes, respectively.     

Efficient Multicast Association to Improve the Throughput in IEEE 802.11 WLAN

This paper deals with the problem of optimal association of stations (S T A s) to access points (A P s) for mulicast services in IEEE 802.11 WLAN. In a multicast session, all the subscribed S T A s receive the multicast data packet at the same data rate (R _{m i n} ) from their respective serving A P s. A higher value of R _{m i n} improves the multicast throughput by completing the ongoing multicast session in lesser time. This also improves the unicast throughput as the cycle duration is shared by the unicast and multicast sessions. To provide multicast services to the S T A s, we need to select a minimum cardinality subset of A P s as the system message overhead depends on this cardinality. However, such a minimum cardinality subset of A P s may not be possible to activate simultaneously due to the limited number of available orthogonal frequency channels. In this paper, we develop a combined greedy algorithm that selects a subset of A P s with minimum cardinality for which a conflict-free frequency assignment exists and finds an association between the S T A s and the selected A P s that maximizes the R _{m i n} value. Through simulation we have shown that the proposed algorithm selects significantly less number of A P s for different R _{m i n} values in comparison to the well-known metrics for multicast association like RSSI, minimum hop-distance, normalized-cost and in-range STA number.     

Secure Relay Selection of Cognitive Two-Way Denoise-and-Forward Relaying Networks

In this paper, secrecy performance of a cognitive two-way denoise-and-forward relaying network consisting of two primary user (PT and PD) nodes, two secondary source (SA and SB) nodes, multiple secondary relay (\({\textit{SR}}_i\)) nodes and an eavesdropper (E) node is considered, where SA and SB exchange their messages with the help of one of the relays using a two-way relaying scheme. The eavesdropper tries to wiretap the information transmitted between SA and SB. To improve secrecy performance of the network, two relay selection schemes called maximum sum rate and maximum secrecy capacity based relay selection (MSRRS and MSCRS) are proposed and analyzed in terms of intercept probability. It is proved that the MSRRS and MSCRS schemes have the same secrecy performance. Two parameters called average number gain and average cost gain are proposed to show the performance of the proposed relay selection schemes. Numerical results demonstrated that with 10 relay nodes, the proposed relay selection schemes can achieve, respectively, 3.7 dB and 1.9 dB’s improvements in terms of the reduced intercept probability and the enhanced secrecy capacity compared to the traditional round-robin scheme.     

Surface roughness and magnetic properties of Co/SiO<Subscript>2</Subscript>/Si(100) polycrystalline films deposited via DC magnetron sputtering

For polycrystalline films of cobalt that have the thickness t ≈ 1.3–133 nm and that are deposited via DC magnetron sputtering on SiO₂(0.1 μm)/Si(100) substrates, surface-roughness root-mean-square amplitude σ and surface correlation length ξ, which characterize the roughness of film surfaces, as well as saturation magnetization 4πM ₀, width of ferromagnetic-resonance line ΔH, coercitivity H _C, and saturation fields H _S, are studied as functions of film thickness t. It is shown that the behavior of dependences H _C(t) and H _S(t) coincides with the behavior of dependence σ(t)/t, whereas the behavior of 4πM ₀(t) depends on ratio t/σ(t). The dependence of the FMR line width on the film thickness, ΔH(t), is characterized by a minimum of ΔH ≈ 60 Oe present in the region of thicknesses of 30 to 60 nm. The behavior of dependence ΔH(t) is determined by ratio σ(t)/t at small thicknesses t ≤ 5 nm and by the behavior of σ(t) at t ≥ 5 nm.     

Quantized feedback MIMO scheduling for heterogeneous broadcast networks

One-bit quantization of signal-to-interference-plus-noise ratio is discussed in literature for user scheduling in homogeneous network where users are assumed to have equal signal-to-noise ratio (SNR). It is mentioned in literature that 1-bit quantization with fixed quantization threshold does not achieve multiuser diversity. Moreover, the system sum-rate achieved by this lags significantly behind that of full feedback scheme. Two multi-bit quantized feedback scheduling schemes are proposed for broadcast network with heterogeneous users experiencing different channel statistics. It is presented that these two schemes with fixed optimum quantization thresholds profit from the diversity provided by independent and identically distributed channels. Moreover, proposed optimistic multi-bit quantized scheduling scheme achieves higher system sum-rate than the proposed multi-bit quantized scheme by addressing the limitations of the later one. The optimum quantization thresholds depend on the number of transmit antennas and system SNR. Moreover, these multi-bit quantized feedback scheduling schemes also ensure user fairness. Simulation results are presented to support the numerical analysis.     

Determination of the fractal dimension for the epitaxial <Emphasis Type="Italic">n</Emphasis>-GaAs surface in the local limit

Atomic-force microscopy studies of epitaxial n-GaAs surfaces prepared to deposit barrier contacts showed that major relief for such surfaces is characterized by a roughness within 3–15 nm, although “surges” up to 30–70 nm are observed. Using three independent methods for determining the spatial dimension of the surface, based on the fractal analysis for the surface (triangulation method), its section contours in the horizontal plane, and the vertical section (surface profile), it was shown that the active surface for epitaxial n-GaAs obeys all main features of behavior for fractal Brownian surfaces and, in the local approximation, can be characterized by the fractal dimension D _f slightly differing for various measuring scales. The most accurate triangulation method showed that the fractal dimensions for the studied surface of epitaxial n-GaAs for measurement scales from 0.692 to 0.0186 μm are in the range D _f = 2.490?2.664. The real surface area S _real for n-GaAs epitaxial layers was estimated using a graphical method in the approximation δ → 0 δ is the measurement scale parameter). It was shown that the real surface area for epitaxial n-GaAs can significantly (ten times and more) exceed the area of the visible contact window.     

On Measurements of the Electrons and Holes Impact-Ionization Coefficients in 4<Emphasis Type="Italic">H</Emphasis>–SiC

All published results of measurements (at 300 K) of the impact ionization coefficients for electrons α_n and holes α_p in 4H–SiC are analyzed. It is shown that the most plausible approximations of dependences of α_{n, p} on electric-field strength E have the usual form α_{n, p} = a_{n, p} exp(–E_{n, p}/E) at fitting-parameter values of a_n = 38.6 × 106 cm^–1, E_n = 25.6 MV/cm, a_p = 5.31 × 106 cm^–1, and E_p = 13.1 MV/cm. These dependences α_{n, p}(E) are used to calculate the highest field strength E_b and thickness w_b of the space-charge region at the breakdown voltage U_b. A number of new formulas for calculating α_{n, p}(E) are obtained from the results of measuring the avalanche-multiplication coefficients and the excess-noise factors under the single-sided illumination of photodiodes with stepped doping.     

Integer quantum Hall effect and correlated disorder

The effect of the form of the random potential of impurities and defects on the longitudinal σ _xx and Hall σ _xy components of conductivity in the mode of the integer quantum Hall effect is theoretically investigated. It is shown that the width of the Hall conductivity plateau as well as the peak values of the longitudinal conductivity heavily depend on the ratio λ/a _H between the random potential correlation length and the magnetic length. For the first time, it is established that in the case of the short-wavelength potential λ ? a _H, the peak values of σ _xx ^(N) are directly proportional to the Landau level number N ≥ 1, σ _xx = 0.5Ne ²/h, whereas the peak values of σ _xx ^(N) are independent of the Landau level number in the case of the long-wavelength potential λ ? a _H, and their magnitude is much lower than 0.5e ²/h. The obtained results are in good agreement with the available experimental data.