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 \(^{2n+1}-1\) }.     

Closed-Form Error Analysis of AF-CARQ with CSI-Assisted Relay over Nakagami-m Fading Channels

This paper presents a new Amplify-and-Forward Cooperative Automatic Repeat reQuest protocol with channel state information-assisted relay which is more suitable for the only-read access networks. The channels of any pair of terminations are quasi static flat Nakagami- \(m\) fading channels, which are mutually independent and non-identically distributed. Assuming that the coherent equal gain combining is adopted to combine the retransmitted signals from the same link at the destination and selective combining is adopted to the signals from different links. Based on the approximation of product of Nakagami- \(m\) variables, we obtain the end-to-end signal-to-noise rate of any link. The closed-form expression of the average bit error rate for several modulation schemes is obtained by analyzing cumulative distribution function (CDF) and Gaussian Q-function. Then we analyze the amount of fading of the fading channels by the \(n\) order moment which is obtained by CDF. Numerical simulation results show that the relay node can resist the fading of system effectively comparing with the system without relay node. And with the increasing of the number of transmission, the performance advantage of relay link is more and more obviously. It is better to let the maximum transmission time \(F=6\) , which is very useful for improving the transmission efficiency of the truncated ARQ system. The maximum reduction of amount of fading can be reached when \(t=3\) , if the total number of transmission is \(f=6\) . The number of bits in the frame should not have too big.     

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.     

Approximation algorithms for broadcasting in duty cycled wireless sensor networks

Broadcast is a fundamental operation in wireless sensor networks (WSNs). Given a source node with a packet to broadcast, the aim is to propagate the packet to all nodes in a collision free manner whilst incurring minimum latency. This problem, called minimum latency broadcast scheduling (MLBS), has been studied extensively in wireless ad-hoc networks whereby nodes remain on all the time, and has been shown to be NP-hard. However, only a few studies have addressed this problem in the context of duty-cycled WSNs. In these WSNs, nodes do not wake-up simultaneously, and hence, not all neighbors of a transmitting node will receive a broadcast packet at the same time. Unfortunately, the problem remains NP-hard and multiple transmissions may be necessary due to different wake-up times. Henceforth, this paper considers MLBS in duty cycled WSNs and presents two approximation algorithms, BS-1 and BS-2, that produce a maximum latency of at most \((\Delta -1) TH\) and \(13TH\) respectively. Here, \(\Delta\) is the maximum degree of nodes, \(T\) denotes the number of time slots in a scheduling period, and \(H\) is the broadcast latency lower bound obtained from the shortest path algorithm. We evaluated our algorithms under different network configurations and confirmed that the latencies achieved by our algorithms are much lower than existing schemes. In particular, compared to OTAB, the best broadcast scheduling algorithm to date, the broadcast latency and transmission times achieved by BS-1 is at least \(\frac{1}{17}\) and \(\frac{2}{5}\) that of OTAB respectively.     

E-TCAM: An Efficient SRAM-Based Architecture for TCAM

Ternary content addressable memories (TCAMs) perform high-speed search operation in a deterministic time. However, when compared with static random access memories (SRAMs), TCAMs suffer from certain limitations such as low-storage density, relatively slow access time, low scalability, complex circuitry, and higher cost. One fundamental question is that can we utilize SRAM to combine it with additional logic to achieve the TCAM functionality? This paper proposes an efficient memory architecture, called E-TCAM, which emulates the TCAM functionality with SRAM. E-TCAM logically divides the classical TCAM table along columns and rows into hybrid TCAM subtables and then maps them to their corresponding memory blocks. During search operation, the memory blocks are accessed by their corresponding subwords of the input word and a match address is produced. An example design of \(512\times 36\) of E-TCAM has been successfully implemented on Xilinx Virtex- \(5\) , Virtex- \(6\) , and Virtex- \(7\) field-programmable gate arrays (FPGAs). FPGA implementation results show that E-TCAM obtains \(33.33\)  % reduction in block-RAMs, \(71.07\)  % in slice registers, \(77.16\)  % in lookup tables, \(53.54\)  % in energy/bit/search, and offers \(63.03\)  % improvement in speed, compared with the best available SRAM-based TCAM designs.     

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.     

Outage Performance of Hybrid Decode–Amplify–Forward Protocol with the nth Best Relay Selection

In this paper, we consider the Hybrid Decode–Amplify–Forward protocol with the \(n\) th best-relay selection scheme. In the best-relay selection scheme, the best relay only forwards the source signal to the destination, regardless of working in the Amplify-and-Forward mode or the Decode-and-Forward mode. However, the best relay might be unavailable due to some reasons; hence we might bring into play the second, third or generally the \(n\) th best relay. We derive closed-form expression for the outage probability using the probability density function and moment generating function of the signal-to-noise ratio of the relayed signal at the destination node. Results show that with the \(n\) th best relay the diversity order is equal to \((m-n+2)\) where \(m\) is the number of relays. Simulation results are also given to verify the analytical results.     

Diagnosis of Wireless Sensor Networks in Presence of Permanent and Intermittent Faults

In this paper we consider the problem of distributed fault diagnosis in Wireless Sensor Networks (WSNs). The proposed Fault Diagnosis Algorithm (FDA) aims to handle both permanent and intermittent faults. The sensor nodes with permanent communication faults can be diagnosed by using the conventional time-out mechanism. In contrast, it is difficult to detect intermittent faults due to their inherent unpredictable behavior. The FDA is based on the comparison of sensor measurements and residual energy values of neighboring sensor nodes, exploiting their spatial correlations. To handle intermittent faults, the comparisons are made for \(r\) rounds. Two special cases of intermittent faults are considered: one, when an intermittently faulty node sends similar sensor measurement and similar residual energy value to some of its neighbors in all \(r\) rounds; another, when it sends these values, either or both of which deviates significantly from that of some neighbors in all \(r\) rounds. Through extensive simulation and analysis, the proposed scheme is proved to be correct, complete, and efficient to handle intermittent faults and hence, well suited for WSNs.     

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.     

Positive L_1 Observer Design for Positive Switched Systems

This paper investigates the problem of \(L_1\) observer design for positive switched systems. Firstly, a new kind of positive \(L_1\) observer is proposed for positive switched linear delay-free systems with observable and unobservable subsystems. Based on the average dwell time approach, a sufficient condition is proposed to ensure the existence of the positive \(L_1\) observer. Under the condition obtained, the estimated error converges to zero exponentially, and the \(L_1\) -gain from the disturbance input to the estimated error is less than a prescribed level. Then the proposed design result is extended to positive switched systems with mixed time-varying delays, where the mixed time-varying delays are presented in the form of discrete delay and distributed delay. Finally, two numerical examples are given to demonstrate the feasibility of the obtained results.     

A microphone readout interface with 74-dB SNDR

A continuous-time (CT) sigma-delta modulator (SDM) for condenser microphone readout interfaces is presented in this paper. The CT SDM can accommodate a single-ended input and has high input impedance, so that it can be directly driven by a single-ended condenser microphone. A current-sensing boosted OTA-C integrator with capacitive feedforward compensation is employed in the CT SDM to achieve high input impedance and high linearity with low power consumption. Fabricated in a \(0.35\) - \(\upmu\) m complementary metal-oxide-semiconductor (CMOS) process, a circuit prototype of the CT SDM achieves a peak signal-to-noise-and-distortion ratio of 74.2 dB, with 10-kHz bandwidth and \(801\) - \(\upmu\) W power consumption.     

BER Evaluation of IEEE 802.15.4 Compliant Wireless Sensor Networks Under Various Fading Channels

This paper presents bit error rate (BER) analysis of wireless sensor networks (WSNs) consisting of sensor nodes based on an IEEE 802.15.4 RF transceiver. Closed-form expressions for BER are obtained for WSNs operating over AWGN, Rayleigh and Nakagami-m fading channels. For the purpose of analysis, we consider an IEEE 802.15.4 RF transceiver using direct sequence spread spectrum-offset quadrature phase shift keying (DSSS-OQPSK) modulation under 2.4 GHz frequency band in a WSN. Analytical expressions for BER are derived for a wireless link between sensor nodes that act as a transmitter unit and a base station without considering the effect of interferers in the wireless environment. Numerical results for BER are obtained by varying the IEEE 802.15.4 standard specific physical layer parameters, such as number of bits used to represent a Zigbee symbol, number of modulation levels used in an OQPSK modulator, and various values of Rayleigh and Nakagami-m fading parameters, denoted as \(\alpha \) and \(m\) , respectively. Moreover, optimum values of physical layer parameters are identified for improved system performance. It is found that error performance analysis of WSN shows improvement when lower number of bits is used to represent a Zigbee symbol. Specifically, under a Rayleigh fading channel which reflects a real-time WSN environment, the network exhibits better performance only when it is operated at high SNR values, i.e., BER of order \(10^{-2}\) is achieved when SNR lies in the range 5–15 dB. Also, the effect of fading parameters on network performance shows that better results are obtained for higher values of \(\alpha \) and \(m\) for Rayleigh and Nakagami-m fading channels, respectively.     

Mutual Distance Bounding Protocol with Its Implementability Over a Noisy Channel and Its Utilization for Key Agreement in Peer-to-Peer Wireless Networks

In order to protect a wireless sensor network and an RFID system against wormhole and relay attacks respectively, distance bounding protocols are suggested for the past decade. In these protocols, a verifier authenticates a user as well as estimating an upper bound for the physical distance between the user and itself. Recently, distance bounding protocols, each with a mutual authentication, are proposed to increase the security level for such systems. They are also suggested to be deployed for key agreement protocols in a short-range wireless communication system to prevent Man-in-the-Middle attack. In this paper, a new mutual distance bounding protocol called NMDB is proposed with two security parameters ( \(n\) and \(t\) ). The parameter \(n\) denotes the number of iterations in an execution of the protocol and the parameter \(t\) presents the number of errors acceptable by the verifier during \(n\) iterations. This novel protocol is implementable in a noisy wireless environment without requiring final confirmation message. Moreover, it is shown that, how this protocol can be employed for the key agreement procedures to resist against Man-in-the-Middle attack. NMDB is also analyzed in a noisy environment to compute the success probability of attackers and the rejection probability of a valid user due to channel errors. The analytically obtained results show that, with the proper selection of the security parameters ( \(n\) and \(t\) ) in a known noisy environment, NMDB provides an appropriate security level with a reliable performance.     

Construction of (2k,k, 2) Convolutional Codes with Double-Loop Cyclic Codes

In this paper, by taking multiple-time information in blocks into the coding of linear block codes, a new class of (2 \(k\) , \(k\) , 2) convolutional codes is constructed, by which a new way of constructing long codes with short ones is obtained. After that, the type of embedded codes is determined and the optimal values of the linear combination coefficients are derived by using a three-dimensional state transfer matrix to analyze and testify the constructing mechanism of the codes. Finally, the simulation experiment tests the error-correcting performance of the (2 \(k\) , \(k\) , 2) convolutional codes for different value of \(k\) , it is shown that the performance of the new convolutional codes compares favorably with that of traditional (2, 1, \(l\) ) convolutional codes.     

Delay-dependent robust H_\infty control for 2-D discrete nonlinear systems with state delays

This paper investigates the problem of robust \(H_\infty \) control for a class of 2-D (two-dimensional) discrete state delayed systems with sector nonlinearity described by a model of Roesser type. Firstly, a delay-dependent sufficient condition of robust exponential stability for such 2-D discrete systems is derived in linear matrix inequalities (LMIs) form. Secondly, a delay-dependent exponential stability criterion with \(H_\infty \) performance for the considered systems is also proposed. Then a state feedback \(H_\infty \) controller is constructed based on the above results. Finally, numerical examples are given to illustrate the effectiveness of the proposed method.     

On centralized and distributed algorithms for minimizing data aggregation time in duty-cycled wireless sensor networks

We study the problem of minimizing data aggregation time in wireless sensor networks (WSNs) under the practical duty-cycle scenario where nodes switch between active states and dormant states periodically for energy efficiency. Under the protocol interference model, we show that the problem is NP-hard and present a lower bound of delay for any data aggregation scheme. To solve the problem efficiently, we then construct a routing tree based on connected dominator set and propose two aggregation scheduling algorithms, which are the centralized Greedy Aggregation Scheduling (GAS) and the distributed Partitioned Aggregation Scheduling (PAS), so as to generate collision-free transmission schedules for data aggregation in duty-cycled WSNs. To minimize the total delay, GAS tries to achieve maximal concurrent transmissions in each time-slot during each frame by using global information, while PAS leverages a network partition based strategy and local information to ensure the largest degree of channel reuse across space and time domains. Theoretical analysis indicates that each algorithm consumes at most \(O(R+\varDelta)\) frames and achieves nearly constant factor approximation on the optimal delay. Here R and \(\varDelta\) are the network radius and the maximum node degree, respectively. We also evaluate the practicability of our algorithms by extensive simulations under various network conditions and the results corroborate our theoretical analysis.     

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 \(^{2}\) .     

Another Look at Performance Analysis of Energy Detector with Multichannel Reception in Nakagami-m Fading Channels

Energy detection is the most dominant method used for reliable wireless detection owing to its non-coherent structure and low implementation complexity. The main challenge for performance analysis of energy detection comes from the generalized Marcum \(Q\) -function involved. To overcome this hurdle, this paper revisits the detection problem and introduces a new framework based on the incomplete Toronto function that allows analyzing the performance for non-fading and fading scenarios in a very simple way. Based on newly-derived expressions for the incomplete Toronto function, performance analysis of energy detection is firstly formulated for unfaded Gaussian noise channels. Second, novel closed-from expressions are derived for the average probability of detection over Nakagami- \(m\) fading channels. The analyses are based on two approaches: the probability density function-based and the moment generating function-based (MGF). The former uses the canonical series representation of the incomplete Toronto function while the latter employs MGF-derivative method which is based on the \(n\) th order derivative of the MGF. The analysis is then extended to cases with diversity receptions including maximal ratio combining and switch and stay combining (SSC). For the SSC diversity case, an analytical expression that can be used to determine optimum switching thresholds in a maximum average detection probability is also derived. The analytical results are verified by numerical computations and Monte-Carlo simulations.     

Design of An Arcak-Type Generalized H_2 Filter for Delayed Static Neural Networks

In this paper, an Arcak-type generalized \(H_2\) filter is designed for a class of static neural networks with time-varying delay. By employing some inequalities and constructing a suitable Lyapunov functional, a delay-dependent condition is derived by means of linear matrix inequalities such that the filtering error system is globally asymptotically stable and a prescribed generalized \(H_2\) performance is achieved. It is shown that the design of such a desired filter for a delayed static neural network is successfully transformed into solving a convex optimization problem subject to some linear matrix inequalities. It is thus facilitated readily by some standard algorithms. A numerical example is finally provided to show the effectiveness of the developed approach. A comparison on the generalized \(H_2\) performance for different gain parameters of the activation function is also given.     

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.