共查询到20条相似文献,搜索用时 31 毫秒
1.
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. 相似文献
2.
Wireless Sensor Networks (WSNs) have many characteristics that are attractive to a myriad of applications. In particular, nodes employ multi-hop communications to collaboratively forward sensed data back to one or more sinks. In this context, reducing the end-to-end delay between the sink and sensor/source nodes is of interest to many applications. In particular, those that require a fixed, upper bound on end-to-end delays. To this end, we focus on bounding the end-to-end delay from the sink to each source. We first formulate the problem as a Binary Integer Program (BIP). As the problem is NP-hard, this paper proposes and studies two centralized, heuristic algorithms: Tabu and Domino. The key approach used by both algorithms is to determine the minimal number of extra wake-up slots required by a given network in order to ensure the delay of all end-to-end paths is within a given bound. We conducted two sets of experiments. The first set compares BIP, Tabu, and Domino in WSNs with up to 80 nodes. These experiments serve to compare the proposed algorithms against BIP, which become computationally expensive in large scale WSNs. The results show that, compared to BIP, the number of additional wake-up times generated by Tabu and Domino are within 5 and 10 % of the optimal solution. In the second set of experiments, which evaluates the algorithms in WSNs with 100–500 nodes, the average number of extra wake-up slots activated by Domino is 13 % greater than Tabu. These algorithms have a time complexity of \({\mathcal {O}} (\alpha n^2 T + n^3)\) and \({\mathcal {O}}(n^3)\) respectively, where \(n\) is the number of nodes, \(T\) is the number of slots in one period, and \(\alpha\) is the maximum number of iterations carried out by the Tabu algorithm. 相似文献
3.
Mohammad Reza Noorimehr Mehdi Hosseinzadeh Keivan Navi 《Circuits, Systems, and Signal Processing》2014,33(10):3145-3163
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 \(^{2n+1}-1\) }. 相似文献
4.
Packet delay control in mobile ad hoc networks (MANETs) is critical to support delay-sensitive applications in such networks. By combining erasure coding and packet redundancy techniques, this paper proposes a general two-hop relay algorithm 2HR- \((x,\tau ,f)\) for a flexible control of packet delivery delay in MANETs, where a group of x packets in source node are first encoded into \(x\cdot \tau\) encoded packets based erasure coding, and each encoded packet is then delivered to at most f distinct relay nodes (f-cast) that will help to forward the encoded packet to destination node. To understand the delay performance in a 2HR- \((x,\tau ,f)\) MANET, we then develop a discrete time multi-dimensional Markov chain model to depict the packet delivery process in the network, based on which closed-form results on mean and variance of packet delivery delay are further derived. Finally, extensive simulation and theoretical results are provided to illustrate the efficiency of our delay models as well as the capability of the 2HR- \((x,\tau ,f)\) algorithm in delay control. 相似文献
5.
Zahid Ullah Manish Kumar Jaiswal Ray C. C. Cheung 《Circuits, Systems, and Signal Processing》2014,33(10):3123-3144
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. 相似文献
6.
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. 相似文献
7.
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 \(^{2}\) . 相似文献
8.
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. 相似文献
9.
This paper presents the fractional order model of a nonlinear autonomous continuous-time difference-differential equation with only one variable. Numerical simulation results of the fractional order model demonstrate the existence of chaos when system order $q\ge 0.2$ . Values of the delay time $\tau $ in which chaotic behavior is observed at system order $q$ are quantitatively defined using the largest Lyapunov exponents obtained from the output time series. 相似文献
10.
Shuo Li Zhengrong Xiang Hamid Reza Karimi 《Circuits, Systems, and Signal Processing》2014,33(7):2085-2106
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. 相似文献
11.
V. Nithya B. Ramachandran Vidhyacharan Bhaskar 《Wireless Personal Communications》2014,77(4):3105-3124
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. 相似文献
12.
Xianling Lu Yuqing Zhu Deying Li Biaofei Xu Wenping Chen Zhiming Ding 《Wireless Networks》2014,20(7):1859-1872
Mobile phones with embedded sensors have been applied in various collaborative sensing applications. To encourage mobile phone users to perform collaborative sensing, the data demanders usually pay mobile phone users for required data. In this paper, we study the Minimum Payment of Attaining the Required Data with mobile phones (MPARD) problem in collaborative sensing network: given sensing regions \(R = \{R_1, R_2, \ldots , R_m\}\) , the set of requisite data \(D_i\) for each sensing region \(R_i\) and a set of mobile phones \(M\) , the \(MPARD\) problem studies how to select mobile phones to obtain all the required data such that the data demanders’ total payment to mobile phone users is minimized. In reality, some systems need the fresh sensing data from mobile phones at each pre-determined time slot, and others don’t require the real-time data and the sensing data from previous time slots is also deemed useful. Based on the above two different requirements of data timeliness, we first define two subproblems derived from \(MPARD\) problem: \(MPARD_t\) and \(MPARD_p\) . After that, for each subproblem, we propose an approximation algorithm for the situation where the trajectories of mobile phones are determinate and a heuristic for the situation where trajectories are unknown. Simulation results demonstrate that our algorithms are efficient. 相似文献
13.
Mohamed A. Shaheen Yvon Savaria Anas A. Hamoui 《Analog Integrated Circuits and Signal Processing》2014,79(3):569-582
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 $35.5\,\upmu \hbox {W}.$ 相似文献
14.
Wireless sensor networks (WSNs) are the main infrastructure for machine to machine (M2M) and Internet of thing (IoT). Since various sophisticated M2M/IoT services have their own quality-of-service (QoS) requirements, reliable data transmission in WSNs is becoming more important. However, WSNs have strict constraints on resources due to the crowded wireless frequency, which results in high collision probability. Therefore a more efficient data delivering scheme that minimizes both the transmission delay and energy consumption is required. This paper proposes energy efficient and reliable data transmission ARQ scheme, called energy efficient and reliable ACK (E \(^2\) R-ACK), to minimize transmission delay and energy consumption at the same time. The proposed scheme has three aspects of advantages compared to the legacy ARQ schemes such as ACK, NACK and implicit-ACK (I-ACK). It consumes smaller energy than ACK, has smaller transmission delay than NACK, and prevents the duplicated retransmission problem of I-ACK. In addition, resource considered reliability (RCR) is suggested to quantify the improvement of the proposed scheme, and mathematical analysis of the transmission delay and energy consumption are also presented. The simulation results show that the E \(^2\) R-ACK scheme achieves high RCR by significantly reducing transmission delay and energy consumption. 相似文献
15.
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. 相似文献
16.
Bazil Taha Ahmed 《Wireless Personal Communications》2013,72(2):941-956
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. 相似文献
17.
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. 相似文献
18.
Khurram Saleem Alimgeer Shahid A. Khan Shahzad A. Malik 《Wireless Personal Communications》2013,72(2):1351-1359
These days most of the research work in the area of filter-antenna design is focused on having high quality factor for certain frequency band. These type of filter-antennas are difficult to design as the design engineers are required to have low quality factor for the radiating band of frequency. Hence a precise value of $Q$ -factor is required to understand the radiating and filtering properties of filter-antennas. Filter-antennas are single port devices as the second port is considered as radiating port. Return loss is used, in order to yield $Q$ -factor through calculations for such devices. However, the conventional method for calculating $Q$ -factor found to be inaccurate in most of the low $Q$ -factor cases. This paper proposes a method that out performs the conventional method of calculating $Q$ -factor. Non-ideal fabrication process is also discussed for accurate evaluation of $Q$ -factor. Experimental results show that proposed method can be employed to calculate $Q$ -factor with reasonable accuracy for simulated and measured results. 相似文献
19.
Wence Zhang Cunhua Pan Bo Du Ming Chen Xue Gong Jianxin Dai 《Wireless Personal Communications》2014,79(2):1539-1556
In this paper, the downlink signal-to-interference-plus-noise ratio (SINR) performance in multiuser large scale antenna systems with matched filter (MF) and regularized zero-forcing (RZF) precoding is investigated. The probability density function (PDF) for MF is derived and the distribution in high signal-to-noise ratio (SNR) regime is studied. Results indicate that the PDF of downlink SINR for MF converges to \(\mathcal F\) distribution when the interference is dominant over noise. For MF, the asymptotic SINR is just the reciprocal of the ratio of the number of users \(U\) to the number of transmit antennas \(N\) , and is irrelevant to the average transmit power when \(N\) and \(U\) grow with fixed ratio. However, when \(U\) is a large constant, the transmit power could be proportional to \(\ln N \big /N \) to maintain a specified quality of service, as a result of the large scale antenna system effect. In addition, the closed form of asymptotic SINR for RZF is derived by solving two mathematical expectations related to eigenvalues of large dimensional random matrices. Simulation results validate the derived PDF and analytical results. 相似文献
20.
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. 相似文献