Underwater Acoustic Multimedia Communication Based on MIMO–OFDM

A transmission scheme is proposed based on multi-input multi-output orthogonal frequency-division multiplexing (OFDM) for underwater acoustic multimedia (UWAM) communication. The proposed scheme integrates direct mapping and space-time block code strategies, a power assignment mechanism, OFDM, adaptive modulation, and unequal error protection in a UWAM system. The proposed UWAM system employs high power, low speed modulation, with schemes providing significant error protection for transmission of sensor data messages requiring a stringent bit-error rate (BER). In contrast, low power, high speed modulation schemes with reduced error protection are provided for messages that can tolerate a high BER, such as image and audio signals. Simulation results show that the proposed scheme not only fulfils the quality of services requirements of a UWAM system, but also maximizes transmission bit rates or minimizes transmission power requirements.     

Efficient Optical MIMO–OFDM Channel Estimation Based on Correntropy Compressive Sensing

Wireless Personal Communications - The technological progress of wireless communication, embedded systems and health offers innovative alternatives to medical care, in particular, telemonitoring...     

An Efficient Test Data Compression Technique Based on Codes

提出了一种新的测试数据压缩/解压缩的算法,称为混合游程编码,它充分考虑了测试数据的压缩率、相应硬件解码电路的开销以及总的测试时间.该算法是基于变长-变长的编码方式,即把不同游程长度的字串映射成不同长度的代码字,可以得到一个很好的压缩率.同时为了进一步提高压缩率,还提出了一种不确定位填充方法和测试向量的排序算法,在编码压缩前对测试数据进行相应的预处理.另外,混合游程编码的研究过程中充分考虑到了硬件解码电路的设计,可以使硬件开销尽可能小,并减少总的测试时间.最后,ISCAS 89 benchmark电路的实验结果证明了所提算法的有效性.     

A TSK Fuzzy Approach to Channel Estimation for OFDM Systems

This paper proposes a TSK fuzzy approach to channel estimation for Orthogonal Frequency Division Multiplexing （OFDM） systems. The information of dispersive fading channel is described by using TSK fuzzy model, which is updated by the pilot symbols. The proposed approach can trace the variation of channel and it is computationally simple. Its performance is tested via simulations. Results show that it is comparable to that of ideal Minimum Mean-Square-Error （MMSE） method, especially at the low Signal to Noise Ratio （SNR）.     

Antenna Selection for MIMO–OFDM WLAN Systems

This paper discusses the packet error rate (PER) performance of multiple-input multiple-output (MIMO) wireless systems. We focus our discussion on communication systems based on the IEEE 802.11a/g standard. In particular, we study the performance of spatial multiplexing systems with joint encoding at the transmitter and linear detection at the receiver. We show that spatial multiplexing systems based on minimum mean square error (MMSE) or zero forcing (ZF) demultiplexing benefit greatly from antenna subset selection. These results agree with recent analytical results showing the equivalence in diversity order between a full system (all receive antennas) and a system with antenna selection.     

An Object Oriented Approach for Extraction Data from CAD Systems

1IntroductionThemostoftenuseddefinihonforthetermprocessplanningisthatitisconcernedwithdetendningthesequenceofprocessingandassemblystepsthatmustbeaccomplishedtomakeproducts.Theroutesheettypicallyliststheproduchonoperations,theirsequence,machinecellsorworkstationswhereeachoperationPerformed,fixtUresandtooling,andbinerequiredareforeachtask.Overtheyears,useofcomputersintheprocessplanninghasgeneratedconsiderableamountofinterests.Applicationofcomputersinprocessplainghasnotonlybeenasubjectofinterest…     

An Efficient Adaptive Channel Estimation Algorithm for MIMO OFDM Systems—Study of Doppler Spread Tolerance

In this paper we develop an adaptive MIMO channel estimation algorithm for space–time block coded OFDM systems. The presented algorithm is based on Expectation Maximization (EM) technique by decomposing the superimposed received signals into their signal components, and estimating the channel parameters of each signal component separately. We also study and compare our proposed EM-based algorithm with a previously introduced recursive-least-squares based algorithm for MIMO OFDM systems. At each iteration the EM algorithm decomposes the problem of multi-channel estimation into channel estimation for each transmit–receive link. In this paper we also study the Doppler spread tolerance of our proposed algorithm in a fast fading environment, and investigate how it affects the system BER performance.     

Improved FEC Code Based on Concatenated Code for Optical Transmission Systems

The improved three novel schemes of the super forward error correction(super-FEC) concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon(RS)+Bose-Chaudhuri-Hocguenghem(BCH) inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS(255,239)+RS(255,239) code and the RS(255,239)+RS(255,223) code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS(255,239) code and other codes, and their signal to noise ratio gains are respectively 2～3dB more than that of the RS(255,239)code at the bit error rate of 1×10 -13 . Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.     

Automata Based Hybrid PSO–GWO Algorithm for Secured Energy Efficient Optimal Routing in Wireless Sensor Network

The main objective in wireless sensor networks is to exploit efficiently the sensor nodes and to prolong the lifetime of the network. The discussion of energy is a significant concern to extend the lifetime of the network. Moreover, a nature inspired hybrid optimization approach called hybrid Particle Swarm Optimization–Grey Wolf Optimizer (PSO–GWO) is used in this work to efficiently utilize the energy and to transmit the data securely in an augmented path. A Learning Dynamic Deterministic Finite Automata (LD²FA) has been innovated and initiated to learn the dynamic role of the environment. LD²FA is mainly used to provide the learned and accepted string to hybrid PSO–GGWO so that the routes are optimized. Hybrid PSO–GWO is used to choose the optimal next node for each path to obtain the optimal route. The simulation results are obtained in MATLAB for 100–700 sensor nodes in a region of 500 × 500 m² which demonstrate that the proposed LD²FA based Hybrid PSO–GWO algorithm obtains better results when compared with existing algorithms. It is observed that LD²FA based Hybrid PSO–GWO has an increase of 18% and 48% betterment in lifetime of the network than PSO and GLBCA, nearly 57% and 75% increase in network lifetime when compared with GA and LDC respectively. It also shows an improvement of 24% increase compared to cluster-based IDS, nearly a rise of 90% throughput when compared with lightweight IDS. The consumption of energy is reduced by 13% and 15% than PSO and GA and an increase of 15% utilization of energy than LDC. Therefore, LD²FA based Hybrid PSO–GWO is been considered to efficiently utilize energy in an optimal route.

     

Performance of Hybrid ARQ Schemes for OFDM Systems

In this paper,four schemes of Hybrid Automatic-Repeat-Request(HARQ)for Orthogonal Frequency DivisionMultiplexing(OFDM)systems are evaluated when they are used in different channel environments.The AccumulativeCorrect Packet Reception Rate(ACPRR)performance of four HARQ schemes is compared in order to verify which ARQschemes are more suitable for different mobility OFDM systems.Computer simulation results show that the maximal ratiocombining frequency diversity ARQ scheme and type Ⅲ HARQ with frequency diversity is more suitable for low mobilityOFDM system.However the type Ⅲ HARQ without frequency diversity is more suitable for high mobility OFDM systembecause of the remarkable time diversity which reduces the required retransmission number to about 2 at the ACPRR of0.96.     

An Effective Channel Estimation for Massive MIMO–OFDM System

Wireless Personal Communications - Recently, internet of things has drawn attention among the academicians, governments and engineers from various sectors. There are many critical issues in IoT...     

Performance Analysis of STFT Based Timing Approach to OFDM Systems

1　IntroductionMuchinteresthasbeenfocusedonOrthogonalFrequencyDivisionMultiplexing (OFDM)inmanyareas,suchaswiredandwirelessapplications[1～ 1 5] .Synchronizationinbothtimeandfrequencydo mainisacriticalprobleminOFDMsystems.WEILandSCHLEGELC ,etalhavediscussedtheeffectsofsynchronizationerrorsandcarrierfrequencyoff sets[1～3] .ThemostremarkableworkbyBEEKJ[3]isajointMLestimatoroftimeandfrequencyoffsetutilizingtheCyclicPrefix (CP)withouttheaidofadditionalpilots.ThenJOHANSSONS ,eta…     

MEM-DnP—A Novel Energy Efficient Approach for Memory Integrity Detection and Protection in Embedded Systems

The pervasiveness of modern day embedded systems has led to the storing of huge amounts of sensitive information in them. These embedded devices often have to operate under insecure environments and are hence susceptible to software and physical attacks. Thus, security has been and will remain one of the prime concerns in the embedded systems. Although a lot of hardware and software techniques have been proposed to provide high levels of security, they are hampered by the trade-offs created by the design constraints in embedded systems. This paper presents a novel energy efficient approach for MEMory integrity Detection and Protection (MEM-DnP). The key feature of the proposed MEM-DnP is that it can be adaptively tuned to a memory integrity verification module by using a sensor module. This significantly reduces the energy overheads imposed on an embedded system as compared to the conventional memory integrity verification mechanisms. The simulation results show that the average energy saved in the combined detection and protection mechanism ranges from 85.5 % to 99.998 %. This is substantially higher compared to the results achieved in basecase simulations with traditional memory integrity verification techniques.     

Pilot Tones Optimization Using Artificial Bee Colony Algorithm for MIMO–OFDM Systems

How to design the pilot tones that are used in channel estimation has a significant effect on the estimation performance. To achieve good performance in least square (LS) algorithm, we propose the artificial bee colony (ABC) algorithm for optimizing the placement of pilot tones in MIMO–OFDM systems. We also derive the upper bound of mean square error of LS estimation with the help of Gerschgorin disc theorem for fitness function of ABC algorithm. The results show that designing pilot tones using the ABC algorithm outperforms other considered placement strategies in terms of high system performance and low computational complexity.     

Joint DOD–DOA Estimation Based on Signal Subspace Approach in MIMO Radars

This paper deals with joint direction of departure (DOD) and direction of arrival (DOA) estimation using a subspace-based approach in bistatic multiple-input multiple-output radars. First, a conventional rotational invariance technique is used to estimate DOD. Then the steering vector of DOA corresponding to the estimated DOD is obtained using the proposed signal subspace estimation method. The steering vector is then converted to the angle of arrival. This way, the DOD and DOA pairing are automatically obtained. Numerical simulations show that the estimated angles using the proposed approach are more accurate than those using the conventional methods.     

An efficient combinational approach for PAPR reduction in MIMO–OFDM system

The multiple input multiple output (MIMO) with orthogonal frequency division multiplexing (OFDM) has emerged as a promising solution to enhance the channel capacity and diversity of wireless communication system without any increase in bandwidth. In this paper, a parallel combinational scheme is proposed to reduce peak-to-average power ratio (PAPR) in MIMO–OFDM system under Rayleigh fading environment. The proposed method intelligently incorporates both active gradient project and partial transmit sequence schemes. The results show that the proposed method not only reduces the PAPR and computational complexity of the system but also maintains the bit error rate compared to other schemes.     

An Efficient Source–Channel Coding for Wireless Image Transmission Over Underwater Acoustic Channel

In this paper, a complete system for image transmission in harsh underwater environment is proposed. The key to increase the performance of the system is the use of an efficient image compression algorithm with a bandwidth-efficient modulation technique. The wavelet packet (WP) decomposition is used to get the best image representation and the set partitioning in hierarchical trees is applied on the WP coefficients. The parental conflicts are resolved, the parent–child relationships are adapted and thus the similarities between cross-subbands are preserved. Reed–Solomon is used for forward error correction to combat with the errors in wireless transmission. Orthogonal frequency division multiplexing with differential quadrature phase shift keying is used to transmit the generated bit stream. Effective image quality metrics are used for objective evaluation. Results show that the proposed system manages to transmit images over the limited bandwidth, and to effectively minimize the perceptual degradation.