A Rate \text{ M }_{\mathrm{T}} Full Diversity STF Block Coded 4\times 4 MIMO-OFDM System with Reduced Complexity

Multiple input multiple output (MIMO) communication systems with orthogonal frequency division multiplexing (OFDM) has a great role to play for 4G broadband wireless communications. In this paper, a space time frequency (STF) code is presented with reduced decoder complexity and to achieve code rate $\text{ M }_\mathrm{T}$ with full diversity of $\text{ M }_{\mathrm{T}} \text{ M }_{\mathrm{R}} \text{ N }_{\mathrm{b}}$ L i.e., product of number of transmit antennas ( $\text{ M }_\mathrm{T}$ ), receive antennas $(\text{ M }_{\mathrm{R}})$ , fading blocks $(\text{ N }_{\mathrm{b}})$ and channel taps (L). The maximum achievable diversity with high rate of STF block coded MIMO-OFDM is analyzed and verified by simulation results. The decoder complexity is resolved by employing several approaches like maximum likelihood (ML), sphere decoder (SD) and array processing. The performance of STF code is compared with existing layered algebraic STF code in terms of decoder complexity and bit error rate (BER). Further, the closed form expressions for BER performance of STFBC MIMO-OFDM systems are derived and evaluated for frequency selective block fading channels with MPSK constellations.     

Efficient Reverse Converters for 4-Moduli Sets {2^{2n-1}-1, 2^{n}, 2^{n}+1, 2^{n}-1} and {2^{2n-1}, 2^{2n-1}-1, 2^{n}+1, 2^{n}-1} Based on CRTs Algorithm

Speed and complexity of a reverse converter are two important factors that affect the performance of a residue number system. In this paper, two efficient reverse converters are proposed for the 4-moduli sets {2 \(^{2n-1}-1\) , 2 \(^{n}\) , 2 \(^{n}+1\) , 2 \(^{n}-1\) } and {2 \(^{2n-1}\) , 2 \(^{2n-1}-1\) , 2 \(^{n}+1\) , 2 \(^{n}-1\) } with 5 \(n\) -bit and 6 \(n\) -bit dynamic range, respectively. The proposed reverse converter for moduli set {2 \(^{2n-1}-1\) , 2 \(^{n}\) , 2 \(^{n}+1\) , 2 \(^{n}-1\) } has been designed based on CRT and New CRT-I algorithms and in two-level structure. Also, an efficient reverse converter for moduli set {2 \(^{2n-1}\) , 2 \(^{2n-1}-1\) , 2 \(^{n}+1\) , 2 \(^{n}-1\) } has been designed by applying New CRT-I algorithm. The proposed reverse converters are based on adders and hence can be simply implemented by VLSI circuit technology. The proposed reverse converters offer less delay and hardware cost when compared with the recently introduced reverse converters for the moduli sets {2 \(^{n}+1\) , 2 \(^{n}-1\) ,2 \(^{n}\) , 2 \(^{2n+1}-1\) } and {2 \(^{n}+1\) , 2 \(^{n}-1\) , 2 \(^{2n}\) , 2 \(^{2n+1}-1\) }.     

Performance Analysis of 4\times 4 and 8\times 8 MIMO System,to Achieve Higher Spectral Efficiency in Rayleigh and Rician Fading Distributions

The proposed work deals with the performance analysis of \(4 \times 4\) and \(8 \times 8\) multiple input multiple output (MIMO) wireless communication system to achieve higher spectral efficiency in Rayleigh and Rician fading distributions. The key channel model used is spatial multiplexing. Singular value decomposition is used to carry out the simulation of \(4\times 4\) and \(8\times 8\) MIMO channel. This scheme also employs the Waterfilling algorithm which allocates the power in all sub-channels improving the Spectral Efficiency. Next generation wireless communication systems require implementations of MIMO to realize higher spectral efficiency.     

WCDMA Multiclass Downlink Capacity and Interference Statistics of Cigar-Shaped Microcells in Highways

In this paper, the multiclass downlink capacity and the interference statistics of the sectors of a cigar-shaped microcells using wideband code-division multiple-access with soft handover mode are analyzed. The two-slope propagation model with log-normal shadowing is used in the analysis where a model of 8 cigar-shaped microcells is utilized. The performance of the downlink is studied for different [sector range R, standard deviation of the shadowing ( $\sigma _{1}$ and $\sigma _{2})$ and propagation exponents ( $\text{ s}_{1}$ and $\text{ s}_{2})$ ]. It is found that increasing the sector range from 500 to 1,000 m will increase the sector downlink capacity. Also, it is found that increasing the value of the propagation parameters ( $\sigma _{1}$ and $\sigma _{2})$ will reduce the downlink sector capacity. It is noticed that, the effect of changing the propagation exponent $\text{ s}_{1}$ is null while increasing the propagation exponent $\text{ s}_{2}$ will increase the downlink capacity.     

An Ideal Multi-secret Sharing Scheme Based on Connectivity of Graphs

Secure communication has become more and more important for many modern communication applications. In a secure communication, every pair of users need to have a secure communication channel (each channel is controlled by a server) In this paper, using monotone span programs we devise an ideal linear multi-secret sharing scheme based on connectivity of graphs. In our proposed scheme, we assume that every pair of users, \(p\) and \(q\) , use the secret key \(s_{pq} \) to communicate with each other and every server has a secret share such that a set of servers can recover \(s_{pq} \) if the channels controlled by the servers in this set can connect users, \(p\) and \(q\) . The multi-secret sharing scheme can provide efficiency for key management. We also prove that the proposed scheme satisfies the definition of a perfect multi-secret sharing scheme. Our proposed scheme is desirable for secure and efficient secure communications.     

A 5 GHZ CMOS Power VCO with Novel Frequency-Modulation for RF Transmitter

A 5 GHz transformer-feedback power oscillator with novel frequency modulation (FM) up to 10 MHz is presented in this paper. The novel FM is achieved by a CMOS transistor between transformer and ground, which is designed for varying the equivalent inductance and mutual inductance of the transformer and shows no DC connection with the oscillation circuit. The major frequency tuning is realized by the variable capacitor which is controlled by a phase lock loop. The RF VCO with 210 MHz tuning range operates in class-E mode to achieve a cost-effective transmitter, which demonstrates a high DC-to-RF conversion efficiency of 39 %. A RF power of 15.1 dBm and phase noise better than \(-\) 109 dBc/Hz @ 100 kHz from the central frequency of 5.5 GHz is obtained with the biasing conditions V \(_\mathrm{ds}\) = 1.8 V and V \(_\mathrm{gs}\) = 0.65 V. The VCO also demonstrates an ultra-low voltage operation capability: with V \(_\mathrm{ds}\) = V \(_\mathrm{gs}\) = 0.6 V and DC power consumption of 9 mW, the output power is 4.5 dBm and the phase noise better than \(-\) 93 dBc/Hz @ 100 kHz. The die size of the transformer-feedback power oscillator is only \(0.4\times 0.6\) mm \(^{2}\) .     

Method for Designing Efficient Mixed Radix Multipliers

The multiplication of two signed inputs, \(A {\times } B\) , can be accelerated by using the iterative Booth algorithm. Although high radix multipliers require summing a smaller number of partial products, and consume less power, its performance is restricted by the generation of the required hard multiples of B ( \(\pm \phi B\) terms). Mixed radix architectures are presented herein as a method to exploit the use of several radices. In order to implement efficient multipliers, we propose to overlap the computation of the \(\pm \phi B\) terms for higher radices with the addition of the partial products associated to lower radices. Two approaches are presented which have different advantages, namely a combinatory design and a synchronous design. The best solutions for the combinatory mixed radix multiplier for \(64\times 64\) bits require \(8.78\) and \(6.55~\%\) less area and delay in comparison to its counterpart radix-4 multiplier, whereas the synchronous solution for \(64\times 64\) bits is almost \(4{\times }\) smaller in comparison with the combinatory solution, although at the cost of about \(5.3{\times }\) slowdown. Moreover, we propose to extend this technique to further improve the multipliers for residue number systems. Experimental results demonstrate that best proposed modulo \(2^{n}{-}1\) and \(2^{n}{+}1\) multiplier designs for the same width, \(64{\times }64\) bits, provide an Area-Delay-Product similar for the case of the combinatory approach and \(20~\%\) reduction for the synchronous design, when compared to their respective counterpart radix-4 solutions.     

A Novel 2.5–3.1 GHz Wide-Band Low-Noise Amplifier in 0.18 \upmu \hbox {m} CMOS

Aiming for the simultaneous realization of constant gain, accurate input and output impedance matching and minimum noise figure (NF) over a wide frequency range, the circuit topology and detailed design of wide broadband low noise amplifier (LNA) are presented in this paper. A novel 2.5–3.1 GHz wide-band LNA with unique characteristics has been presented. Its design and layout are done by TSMC 0.18  \(\upmu \hbox {m}\) technology. Common gate stage has been used to improve input matching. In order to enhance output matching and reduce the noise as well, a buffer stage is utilized. Mid-stages which tend to improve the gain and reverse isolation are exploited. The proposed LNA achieves a power gain of 15.9 dB, a NF of 3.5 dB with an input return loss less than \(-\) 11.6, output return loss of \(-\) 19.2 to \(-\) 19 and reverse isolation of \(-\) 38 dB. The LNA consumes 54.6 mW under a supply voltage of 2 V while having some acceptable characteristics.     

Effect of the stoichiometric composition of the Si(111)\sqrt {21} × \sqrt {21} -(Au, Ag) surface phase on substrate conductivity

The conductivity of a silicon substrate with a Si(111) $\sqrt {21} $ × $\sqrt {21} $ -(Au, Ag) surface phase is studied. It is found that the surface conductivity of such a substrate varies depending on the ratio of the amounts of gold and silver in the given structure. An analysis of the behavior of the Si(111) $\sqrt {21} $ × $\sqrt {21} $ -(Au, Ag) surface conductivity during silver adsorption indicates the effect of a space-charge layer in the surface region of the substrate on the measurement results.     

Novel Tight Closed-Form Bounds for the Symbol Error Rate of EGC and MRC Diversity Receivers Employing Linear Modulations Over \alpha -\mu Fading

In this paper, we propose novel lower and upper bounds on the average symbol error rate (SER) of the dual-branch maximal-ratio combining and equal-gain combining diversity receivers assuming independent branches. \(M\) -ary pulse amplitude modulation and \(M\) -ary phase shift keying schemes are employed and operation over the \(\alpha -\mu \) fading channel is assumed. The proposed bounds are given in closed form and are very simple to calculate as they are composed of a double finite summation of basic functions that are readily available in the commercial software packages. Furthermore, the proposed bounds are valid for any combination of the parameters \(\alpha \) and \(\mu \) as well as \(M\) . Numerical results presented show that the proposed bounds are very tight when compared to the exact SER obtained via performing the exact integrations numerically making them an attractive much simpler alternative for SER evaluation studies.     

Design and modeling of high-resolution multibit log-domain \Delta \Sigma modulators

Log-domain Delta-Sigma ( $\Delta \Sigma$ ) modulators are attractive for implementing analog-to-digital (A/D) converters (ADCs) targeting low-power low-voltage applications. Previously reported log-domain $\Delta \Sigma$ modulators were limited to 1-bit quantization and, hence, could not benefit from the advantages associated with multibit quantization (namely, reduced in-band quantization noise, and increased modulator stability). Unlike classical $\Delta \Sigma$ modulators, directly extending a log-domain $\Delta \Sigma$ modulator with a 1-bit quantizer to a log-domain $\Delta \Sigma$ modulator with a multibit quantizer is challenging, in terms of CMOS circuit implementation. Additionally, the realization of log-domain $\Delta \Sigma$ modulators targeting high-resolution applications necessitates minimization of distortion and noise in the log-domain loop-filter. This paper discusses the challenges of multibit quantization and digital-to-analog (D/A) conversion in the log-domain, and presents a novel multibit log-domain $\Delta \Sigma$ modulator, practical for CMOS implementation. SIMULINK models of log-domain $\Delta \Sigma$ modulator circuits are proposed, and the effects of various circuit non-idealities are investigated, including the effects of log-domain compression–expansion mismatch. Furthermore, this paper proposes novel low-distortion log-domain analog blocks suitable for high-resolution analog-to-digital (A/D) conversion applications. Circuit simulation results of a proposed third-order 3-bit class AB log-domain $\Delta \Sigma$ loop-filter demonstrate 10.4-bit signal-to-noise-and-distortion-ratio (SNDR) over a 10 kHz bandwidth with a $0.84\,V_{pp}$ differential signal input, while operating from a 0.8 V supply and consuming a total power of $35.5\,\upmu \hbox {W}.$      

Partner Selection Technique for Wireless Cooperative Communication

In wireless cooperative communication scheme, transmit diversity is achieved by coupling the distributed users. In this paper, a new partner selection algorithm is proposed. The selection scheme utilizes the basic work done by Almawgani on RS coded cooperation for wireless network. Users are classified into weak and strong ones based on the signal-to-Noise Ratio (SNR) uplink matrix. Users with good uplink channel SNR (strong users) are coupled with those experiencing weak uplink channel conditions (weak users). The proposed algorithm offers an improvement to the outage probability, \(P_{out}\) and power efficiency as compared to the established work. The algorithm shows a significant improvement of \(P_{out}\) at lower values of uplink SNR.     

Statistical Analysis of Cognitive Radio Operation in a Periodic Pattern of Sensing and Transmission

A Cognitive Radio must sense the channel to detect spectrum holes. To this end, it senses the channel for $T_S$ and transmits its data for $N T_S$ , if the channel is not occupied by Primary User. It is expected that the more frequent arrivals of PU, characterized by the arrival rate $\lambda $ , provides CR with less opportunity. The aim of this paper is two-fold: analysis of the interaction between $N$ and $\lambda $ , as well as the access time of CR on the one hand and study of the possible benefits a variable decreasing modulation order might provide for CR on the other. In both cases, data rate of CR and the interference it causes for PU are considered as the performance measures.     

A 97 dB 400 MHz rail to rail fully differential opamp based on split length FGMOS-MOS cell

Recently introduced MOS-FGMOS split length cell has been used to increase the DC gain of a fully differential op amp. Resultant proposed opamp structure exhibits gain of 97 dB and unity gain bandwidth of 400 MHz with power consumption of 1.2 mW. An opamp design has been verified with Cadence Spectre using a 130 nm technology at 1.2 V and has a slew rate of \(53\,\hbox {V}/\mu \hbox {s}\) with a phase margin of \(78^{\circ }\) .     

A novel image segmentation model with an edge weighting function

A variational model for image segmentation consists of a data term and a regularization term. Usually, the data term is chosen as squared $\text{ L }_{2}$ norm, and the regularization term is determined by the prior assumption. In this paper, we present a novel model in the framework of MAP (maximum a posteriori). A new iteratively reweighted $\text{ L }_{2}$ norm is used in the data term, which shares the advantages of $\text{ L }_{2}$ and mixed $\text{ L }_{21}$ norm. An edge weighting function is addressed in the regularization term, which enforces the ability to reduce the outlier effects and preserve edges. An improved region-based graph cuts algorithm is proposed to solve this model efficiently. Numerical experiments show our method can get better segmentation results, especially in terms of removing outliers and preserving edges.     

Extended Robust \mathcal{H}_{2} and \mathcal{H}_{\infty} Filter Design for Discrete Time-Invariant Linear Systems with Polytopic Uncertainty

This paper is concerned with the problem of robust $\mathcal{H}_{2}$ and $\mathcal{H}_{\infty}$ filter design for discrete-time linear time-invariant systems with polytopic parameter uncertainties. Less conservative robust $\mathcal{H}_{2}$ and $\mathcal{H}_{\infty}$ filter design procedures are proposed in terms of single-parameter minimization problems with linear matrix inequality constraints. To this end, we generalize the filter structures available in the literature to date in such a way that the filter’s next state is built by summing the filter’s states over several samples from the past to the present. For stability of the filtering error system, the homogeneous polynomial parameter-dependent Lyapunov functions are employed. Finally, illustrative examples are given to demonstrate the merits of the proposed methods.     

Decentralized \mathcal{L}_{2}–\mathcal{L}_{\infty} Filtering for Interconnected Markovian Jump Systems with Delays

This paper deals with the problem of decentralized $\mathcal{L}_{2}$ – $\mathcal{L}_{\infty}$ filtering for a class of interconnected (or large-scale) Markovian jump systems with constant time delays. The purpose is to present delay-dependent conditions for the existence of mode-dependent decentralized filters, which guarantees that the filtering error system is stochastically stable with a prescribed $\mathcal{L}_{2}$ – $\mathcal{L}_{\infty}$ disturbance attenuation level. Such a purpose is achieved by using a mode-dependent centralized Lyapunov functional together with the so-called Jensen’s inequality. The obtained synthesis conditions are expressed in terms of linear matrix inequalities (LMIs), which leads to a convex design method for the concerned filters. An example including numerical and simulation results is provided finally to illustrate the effectiveness of the proposed design method.     

Terahertz LC Microcavities: From Quantum Cascade Lasers to Ultrastrong Light-Matter Coupling

We review research on the physics of intersubband transitions in the THz range in a sub wavelength microcavity environment. Laser action was achieved at 1.5 THz by inserting quantum cascade gain material between the capacitor plates of a new resonant LC cavity, achieving a normalized mode volume ratio of only $V_{eff}/(\lambda /2n)^{3}=0.12$ of the cavity mode $V_{eff}$ and the normalized optical volume $(\lambda /2n)^{3}$ . By using the same cavity as the constituting meta-atom of a THz metamaterial, strong and ultra strong light matter coupling was observed up to room temperature. Finally, the same metamaterial coupled to parabolic semiconductor quantum wells was investigated in the regime of electrical in-plane pumping, showing THz emission in the ultra strong coupling regime.     

Ultra-Low Power Read-Decoupled SRAMs with Ultra-Low Write-Bitline Voltage Swing

We propose an ultra-low power memory design method based on the ultra-low ( \(\sim \) 0.2 V) write-bitline voltage swing to reduce the write power dissipation for read-decoupled SRAM (RD-SRAM) cells. By keeping the write bitlines at ground level (0 V) during standby and charging them to a low voltage \(V_\mathrm{L}\) ( \(\sim \) 0.2 V) during write operations, the power dissipation for the write bitlines is greatly reduced (0.2 V/ \(V_\mathrm{DD})^{ 2 }\,\times \) 100 %) due to reduced voltage swing (from \(V_\mathrm{DD }\)  = 1.2 to 0.2 V) on the write bitlines. The proposed method is applicable to both dual-voltage and single-voltage operations. We analyze the proposed ultra-low write-bitline voltage swing method and investigate its reliability based on 10K Monte-Carlo simulations. We further verify the functionality and performance of our proposed design through measurements on the fabricated prototypes based on the 65 nm CMOS process. By means of a \(256 \times 64\) bit RD-SRAM memory implementation, we show that our proposed method reduces 87 % write power dissipation when compared to a conventional design.     

Performance Comparison Analyses of the Nth Best Relay Selection Schemes Over Independent and Non-identically Distributed Nakagami-m Fading Channels

In this work, we study the $N$ th best relay selection schemes with the consideration that in some case the best relay is unavailable due to the restriction of practical implementation. With amplify-and-forward relaying protocols, the interested $N$ th best relay schemes are investigated over independent and non-identically distributed (i.ni.d) Nakagami- $m$ fading channels. For such opportunistic relaying schemes, we first obtain the closed-form expressions to the probability density function (PDF) and cumulative distribution function (CDF) of the instantaneous end-to-end signal-to-noise ratio with appropriate mathematical proof. Then, with the obtained CDF and PDF, three main measurements are investigated as well as the corresponding explicit solutions, $i.e.$ , outage probability, average symbol error ratio (SER), and ergodic capacity. At the same time, as a byproduct, the corresponding performance metrics over Rayleigh fading are also derived. Finally, the detailed performance comparison analyses are presented under different values of $N$ and different Nakagami- $m$ channel fading severity parameters. The numerical results show that the increase of $N$ incurs the very severe loss in performance such outage probability, SER, and ergodic capacity. However, the loss in performance can be decreased greatly when the $N$ th systems have bigger fading severity factors. The derivations are of significance because the Nakagami- $m$ fading spans via the fading severity parameters a wide range of fading scenarios that are typical in realistic wireless relay networks.