Multi Path Research Articles

Soft Computing Technique for Recognition of Earthquake Precursor from Low Latitude Total Electron Content (TEC) Profiles

Electron Content (TEC) data from GPS are now used as tools for identifying an impending earthquake. The extraction of earthquake induced features from this parameter needs elaborate processing because it involves filtration of data with respect to disturbed day variations, contribution from multi path effects and also normal day-to-day fluctuations even during quiet days. In this paper we introduce, a peak detection algorithm, an automatic pattern matching approach and artificial neural network for processing GPS generated TEC record in where a template is framed from the time series of quiet day data for extraction of pre - seismic parameter. This matching algorithm is adopted to find deviation in TEC time series prior to an impending earthquake from the template and would be used as an index of earthquake induced signature. A few case studies using these techniques are presented in this paper. Work is based on TEC data collected from GPS at Gauhati (26o 10' N, 91o 45' E).

TCM-coded OFDM assisted by ANN in Wireless Channels

The objective of this paper is to use Artificial Neural Network (ANN) in conjunction with M-ary PSK Trellis Coded Modulation (TCM) based Orthogonal Frequency Division Multiplexing (OFDM) as a means of achieving higher throughput and performance improvement in multi path fading channel. Simulation results are presented, that shows the superiority of the ANN-based approach, as a means to decode the signal at the receiver side, over conventional TCM decoding schemes. The performance gain is due to the adaptive learning capability of the ANN that can use the Transmitter Side Information (TSI), Receiver Side Information (RSI) and Channel Side Information (CSI) to perform decoding and symbol recovery simultaneously. 4-PSK and 8-PSK TCM-codes have been considered in this work along with OFDM transmission technique.

ANN based STBC-MIMO set-up for Wireless Communication

Space Time Block Code is a powerful tool for improving performance in wireless communication. Multiple input multiple outputs (MIMO) are a promising application of multiple antennas at both transmitter and receiver to improve communication performance by achieving spatial diversity. MIMO, when used with appropriate STBC coding techniques and proper channel estimation, can achieve huge performance gains in multi path fading wireless links. Our work aims to simulate the space-time coding over worst fading environment and evaluate its performance in terms of BER. An Artificial Neural Network (ANN) can be used to provide an estimate of the channel which help to mitigate some of the deficiencies of multi-user transmission.

Reliability Analysis of Multi Path Multistage Interconnection Networks

As systems have grown more complex, the consequences on their reliable behavior have become severe in terms of cost, life, size etc, and the interest in accessing system reliability and the need for improving the reliability of systems have become very important. This paper presents an analytical model for the reliability evaluation of multipath multistage interconnection networks (MINs). In order to define the fault tolerance, behavior of various multi path MIN networks has been introduced. The results are compared and discussed.

Traffic And Security Using Randomized Dispersive Routes In Heterogeneous Sensor Network

Generally traffic and the sensor network security have many challenges in the transmission of data in the network. The existing schemes consider homogeneous sensor networks which have poor performance and scalability. Due to many-to-one traffic pattern, sensors may communicate with small portion of its neighbours. Key management is the critical process in sensor nodes to secure the data. Most existing schemes establish shared keys for all the sensors no matter whether they are communicating or not. Hence it leads to large storage overhead. Another problem in sensor network is compromised node attack and denial of service attack which occurs because of its wireless nature. Existing multi path routing algorithms are vulnerable to these attacks. So once an adversary acquires the routing algorithm, it can compute the same routes known to the source, and hence endanger all information sent over these routes. If an adversary performs node compromise attack, they can easily get the encryption/ decryption keys used by that node and hence they can intercept the information easily. In this paper we are proposing a key management scheme which only establishes shared keys with their communicating neighbour and a mechanism to generate randomized multipath routes for secure transmission of data to the sink. Here we are adopting heterogeneous sensor networks and we are utilizing elliptic curve cryptography for efficient key management which is more efficient, scalable, and highly secure and reduces communication overhead. The routes generated by our mechanism are highly dispersive, energy efficient and making them quite capable of bypassing the back holes at low energy cost.

Unambiguous Multipath Mitigation Technique for BOC(n,n) and MBOC-Modulated GNSS Signals

We propose an efficient scheme for side peaks cancelation and multipath (MP) mitigation in binary offset carrier (n,n) (BOC(n,n)) and multiplexed BOC (MBOC) modulated signals. The proposed scheme reduces significantly the band of variation of MP errors in global navigation satellite system (GNSS). It consists of two versions. The first one is based on the use of maximum likelihood estimator (MLE) of MP signals and reference correlation functions (CFs) like that of pseudorandom noise (PRN) code without BOC subcarrier. In the second version, the former (MLE) is used with the reference BOC(n,n) or MBOC CFs. Unlike traditional BOC(n,n) and MBOC, that have CFs containing multiple peaks leading to potential tracking ambiguities, our proposed scheme does not contain any side peaks. In addition, all the MP signals with medium and long delays have no effect on the estimation of the pseudorange. On the other hand, all the methods proposed for mitigating MP in no-BOC scheme are practical for our scheme due to its CF which is similar to that of the PRN code. The computer simulation results show that the proposed scheme has superior performances in the reduction of the errors produced in the process of the delay estimation of line of sight (LOS) and caused by MP propagation. In fact, the performances of the proposed scheme are better with regard to that of the traditional BOC(n,n) and MBOC. Moreover, in the presence of noise, our proposed scheme keeps better performances than the common side peaks cancelation methods.

Analysis of DS-CDMA System with Phase Synchronization Errors for Selection Diversity Scheme

Wireless communication is currently the most dynamic field with the invention of new technologies. Presently one of the main challenges in the wireless communication field is to combat fading. At the receiver, the signal may be lost completely due to destructive addition of multi paths signal components. Generally effect of fading is analyzed with channel compensation using different diversity combining schemes such as selection diversity, equal gain combining and maximal ratio combining techniques. Selection diversity is one of the preferred schemes due to its simplest implementation process. However, often channel estimation may not be perfect because of changing nature and other factors like correlation between the signals etc. The main aim of this paper is to observe the effect of imperfect channel estimation on the performance of the receiver. Analysis has been done for channel estimation along with selection diversity combining. Also, receiver may not be synchronized always with transmitter giving some phase errors. Such error is also incorporated along with selection diversity for performance evaluation of the system.

Patient satisfaction of in-patients treated in a university hospital in Turkey

Structural equation modelling (SEM) is a statistical method that emerged as a result of assembling and synthezing the confirmative factor analysis, path analysis and regression analysis in a model. In this respect, factor, canonic correlation, multivariate variance and covariance, multi regression and path analysis are also considered the special conditions of SEM. Additionally, the most important difference that separates SEM from these analyses is that it is more convenient to use it as confirmative rather than explicatory. It is aimed to develop a questionnaire in order to measure the patient satisfaction and modeling the satisfaction through this questionnaire. Questionnaires were filled by making face-to-face interviews with 298 people. Structure validity, structural model structural equation models were realized by using LISREL 8.54. Key words: Structural equation analysis, validity, patient satisfaction, questionnaire.

Multi-path routing based on load-balance for cognitive packet networks

Quality of service (QoS) routing algorithms have been hardly discussed in the scientific community, most previous work on QoS routing concentrates on the performance of the single route. Cognitive packet network (CPN) has been designed for providing QoS routing. In this paper, to balance the loads among networks, we present a multi-path routing algorithm based on load-balance (MPRLB), which is carried out in two steps. The algorithm with low computational complexity is firstly applied to establish multi path routing for each source and destination node pairs (SD-pair) nodes in the network. Then, we propose the hopfield neural network algorithm, which is applied to improve the efficiency of the flow deviation method for fast flow allocation among the links of the network based on load balance. Extensive simulation results demonstrate that the proposed scheme significantly improves the performance compared with the existing scheme that ignores load balancing.

수중 센서 네트워크에서 저전력 통신을 위한 변조기법의 적용성 연구

In this paper, we propose the result of PSSK(Phase Silence Shift Keying) modulation scheme that is mixed PSK(Phase Shift Keying) modulation and PPM(Pulse Position Modulation) method. The performance of underwater communication systems are influenced underwater channel characteristics. In particular, delay spread can make ISI(Inter Symbol Interference) because of reverberation and multi path. It degrade the performance of the communication system. Also underwater sensor networks consider about power efficient due to the particularities of their operating environment. PSSK modulation method transmit two orthogonal symbol and using silence period in a period so it can reduce the power. Increasing the distance of between modulation symbols, to enhance the performance of BER(Bit Error Rate) as well as to improve power efficient. The result of sea trial, QPSK modulation BER is and PSSK modulation BER is .

Enhancement of Matched filter BER performance in DS-UWB systems using a new channel estimation technique

One of the major challenges in ultra wideband (UWB) receivers is to recover the signal energy dispersed over too many multi path components, while preserving the receiver complexity as low as possible. To this achieve this, channel estimators based receivers are employed to enhance its Bit Error Rate (BER) performance. In this paper the problem of channel estimation for Direct Sequence ultra wideband (DS UWB) is investigated. Firstly, a modification of the received signal model is introduced. A new channel estimation algorithm is proposed .The proposed algorithm is cost effective, very simple and is independent of the number of paths of the UWB channel. Monte-Carlo simulation is used to calculate the Mean Square Error (MSE) of the proposed estimator by averaging the estimation error of a 1000 generated channel realizations for each of the four different IEEE 802.15.3a UWB channel models. The Mean Squared Error (MSE) of the proposed estimator is compared with that of the time domain Maximum Likelihood (ML) estimator. Simulation results show that The MSE performance of the proposed estimator is competitive to that of the ML even in the case of non perfect orthogonal spreading codes and approaches the behavior of the ML as the length of the spreading code increases.

WiMAX OFDM Adaptive Modulation with Broadband Wireless Technology HSDPA

This paper works comprises on the analysis of IEEE 802.16 WiMAX standards and the performance analysis of its physical layer using the OFDM adaptive modulation and it uses the concept of cyclic prefix that adds additional bits at the transmitter end. The signal is transmitted through the channel and it is received at the receiver end, then the receiver removes these additional bits in order to minimize the inter symbol interference, to improve the bit error rate and to reduce the power spectrum. An Additive white Gaussian noise (AWGN) channel model is used with Rayleigh fading to resemble the real world scenario. The transmitter and receiver are assumed to be in fixed positions and the channel coding is not used. The transmitted and received signals are considered to in perfect sync with each other in time and frequency. Losses from feeder cables, joints, connectors, jumpers are not taken in consideration. In our research work, we investigated the physical layer performance on the basis of bit error rate, signal to noise ratio, power spectral density and error probability. These parameters are discussed in two different models. The first model is a simple OFDM communication model without the cyclic prefix, while the second model includes cyclic prefix. The study reviewed scientific articles that provide in-depth knowledge that WiMAX provides increased throughput and better protection against multi path propagation and self interference as compared to HSDPA, furthermore, in this paper different aspects of the model were investigated and with MATLAB simulations it has been demonstrated that lower modulation schemes provide better performance in noisy conditions. Higher modulation schemes provide higher data rates, but encounter high BER in noisy and low SNR conditions.

Synthetic aperture navigation in multipath environments

Multipath propagation is one of the major error sources for radio navigation systems. While many new applications require ever more precise user positioning in urban and indoor settings, existing receivers are especially vulnerable to severe multipath, which is often present in such environments. This article reviews recent advances in the concept of synthetic aperture navigation, which enables the user to separate co-channel navigation signals, including combating the adverse effects of multipath. A deeply integrated RF receiver and an inertial measurement unit produce an estimate of the user trajectory, which makes it possible to form a synthetic aperture from the user's motion using a single-element antenna. In turn, using the synthetic aperture opens the door to applying modern direction finding and beamforming methods. These signal processing schemes are able to differentiate between the line of sight and multi path signals (or between different signals in the band in general), as they often arrive from different directions. The desired signal can be extracted in the presence of strong multipath, and its delay can be accurately estimated.

A New Recovery Mechanism in Superscalar Microprocessors by Recovering Critical Misprediction

Current trends in modern out-of-order processors involve implementing deeper pipelines and a large instruction window to achieve high performance, which lead to the penalty of the branch misprediction recovery being a critical factor in overall processor performance. Multi path execution is proposed to reduce this penalty by executing both paths following a branch, simultaneously. However, there are some drawbacks in this mechanism, such as design complexity caused by processing both paths after a branch and performance degradation due to hardware resource competition between two paths. In this paper, we propose a new recovery mechanism, called Recovery Critical Misprediction (RCM), to reduce the penalty of branch misprediction recovery. The mechanism uses a small trace cache to save the decoded instructions from the alternative path following a branch. Then, during the subsequent predictions, the trace cache is accessed. If there is a hit, the processor forks the second path of this branch at the renamed stage so that the design complexity in the fetch stage and decode stage is alleviated. The most contribution of this paper is that our proposed mechanism employs critical path prediction to identify the branches that will be most harmful if mispredicted. Only the critical branch can save its alternative path into the trace cache, which not only increases the usefulness of a limited size of trace cache but also avoids the performance degradation caused by the forked non-critical branch. Experimental results employing SPECint 2000 benchmark show that a processor with our proposed RCM improves IPC value by 10.05% compared with a conventional processor.

지상파 3D HDTV 전송을 위한 수정된 ATSC 전송 시스템의 프레임 구조에 관한 연구

.MNO/3D HDTV & OPQ2RS TATSC (Advanced Television Systems Committee) [2] UVW1AXYZ[ Q2\R]>^_R`V. ATSC [2]aSbATSC [1]XY3cd3QR], U>e QfghiOj ,TOV (Threshold of Visibility)O klf g^>L[R`V. mQn A, fg om ^_R`V.AbstractIn this paper, we propose a frame structure for modified ATSC transmission systems which is used for a terrestrial 3D HDTV broadcasting. The modified ATSC transmission systems [2] see the potential of increasing a transmission capacity at reasonable TOV (Threshold of Visibility) by modifying channel codes of conventional ATSC systems and varying modulations. We use PN symbols (Pseudorandom Noise) in a guard interval which is used for avoiding the ISI (Inter Symbol Interference) to estimate and compensate the time-varying multi path channel effectively with a maximum transmission payload. With PN symbols in the guard interval, a CIR (Channel Impulse Response) in a time domain can be estimated and a compensation in a frequency domain can be achieved for the accurate channel estimation and compensation. The prosed frame structure is applied to the modified ATSC systems and computer simulations are performed for SER (Symbol Error Rate) performances in TU (Typical Urban)-6 Channel.Keyword: Terrestial 3D HDTV broadcasting, Modified ATSC system, Frame structure™šMN 

MicroRNA-Integrated and Network-Embedded Gene Selection with Diffusion Distance

Gene network information has been used to improve gene selection in microarray-based studies by selecting marker genes based both on their expression and the coordinate expression of genes within their gene network under a given condition. Here we propose a new network-embedded gene selection model. In this model, we first address the limitations of microarray data. Microarray data, although widely used for gene selection, measures only mRNA abundance, which does not always reflect the ultimate gene phenotype, since it does not account for post-transcriptional effects. To overcome this important (critical in certain cases) but ignored-in-almost-all-existing-studies limitation, we design a new strategy to integrate together microarray data with the information of microRNA, the major post-transcriptional regulatory factor. We also handle the challenges led by gene collaboration mechanism. To incorporate the biological facts that genes without direct interactions may work closely due to signal transduction and that two genes may be functionally connected through multi paths, we adopt the concept of diffusion distance. This concept permits us to simulate biological signal propagation and therefore to estimate the collaboration probability for all gene pairs, directly or indirectly-connected, according to multi paths connecting them. We demonstrate, using type 2 diabetes (DM2) as an example, that the proposed strategies can enhance the identification of functional gene partners, which is the key issue in a network-embedded gene selection model. More importantly, we show that our gene selection model outperforms related ones. Genes selected by our model 1) have improved classification capability; 2) agree with biological evidence of DM2-association; and 3) are involved in many well-known DM2-associated pathways.

Precision aircraft attitude determination with multi-antennae GPS receivers

Attitude determination is a central problem to aircraft navigation for a wide variety of applications, i.e. airborne laser scanning, airborne gravimetry etc. Standard multi-antennae attitude determination, relying on typically four antennae, provides an attitude accuracy of about 0.1°–0.3° per epoch, where usual update rates are of the order of 5–10 /s; while the noise is quite big, the stability with time is excellent. However, phase centre, multi path and antennae near field effects may cause significant biases or slowly varying effects. On the other hand, gyros may provide attitude information at very high sampling rates and at significantly higher resolutions, however, most are prone to significant drift effects, except e.g., laser gyros of highest precision. For an optimal configuration in economical, operational and accuracy aspects, it is worth to invest also in an advanced multi-antennae GNSS receiver. On these grounds, we acquired a GNATTI antennae receiver of Geo++ company, assembled of typically eight single L1-receivers. The redundancy of this set allows to do an antenna calibration for antennae phase centre, near field, and multipath effects. We did a number of tests both at a test stand and also with an aircraft with various receivers. The paper discusses some details and test results.

Design and implementation of smart home energy management systems based on zigbee

Today, organizations use IEEE802.15.4 and to effectively deliver solutions for a variety of areas including consumer electronic device control, energy management and efficiency home and commercial building automation as well as industrial plant management. The Smart home energy network has gained widespread attentions due to its flexible integration into everyday life. This next generation green home system transparently unifies various home appliances, smart sensors and wireless communication technologies. The green home energy network gradually forms a complex system to process various tasks. Developing this trend, we suggest a new Smart Home Energy Management System (SHEMS) based on an IEEE802.15.4 and (we call it as a ZigBee sensor network). The proposed smart home energy management system divides and assigns various home network tasks to appropriate components. It can integrate diversified physical sensing information and control various consumer home devices, with the support of active sensor networks having both sensor and actuator components. We develop a new routing protocol DMPR (Disjoint Multi Path based Routing) to improve the performance of our sensor networks. This paper introduces the proposed home energy control system's design that provides intelligent services for users. We demonstrate its implementation using a real environment.

The Feedback Based Mechanism for Video Streaming Over Multipath Ad Hoc Networks

Ad hoc networks are multi-hop wireless networks without a pre-installed infrastructure. Such networks are widely used in military applications and in emergency situations as they permit the establishment of a communication network at very short notice with a very low cost. Video is very sensitive for packet loss and wireless ad-hoc networks are error prone due to node mobility and weak links. High quality video transport under ad hoc network is a challenging task due to low bandwidth, high loss rate, unpredictable node mobility, and severe interference characteristics of such kind of network. End to end packet delivery often exhibits low performance due to one hop-by-hop routing failure and misinterpretation to such failures. Multi path routing has been used to increase the robustness for video over ad-hoc networks. The key idea of proposed schema is based on sending video packets over two disjoint paths beside using buffering technique in special nodes of network. In each of every path there is only one node selected as cache node. The main task of these nodes is to realizing different packet types, buffering some of important video packets, reducing forward traffic rate while detecting loss in network and local error management to overcome high loss rate of video packets. Selecting these nodes in network can be as an agreement between video sender and receiver or based on network topological status. The goal of this work is to reduce network end to end delay and increased quality of service over application layer.

GPS/Galileo Multipath Mitigation Using the First Side Peak of Double Delta Correlator

In this paper, we propose an efficient scheme for the Line of Sight (LOS) delay estimation in satellite telecommunications. It aims to reduce errors caused by the Multipath (MP) fading channels in Global Navigation Satellite System (GNSS) such as Global Positioning System (GPS) and future Galileo. The scheme is based on the use of first side peaks of Double Delta Correlator (DDC) in combination with Savitzky-Golay Filter (SGF). The proposed scheme is called "Enhanced DDC (EDDC)". The DDC technique, like High Resolution Correlator (HRC) and Strobe Correlator (SC), uses the central peak of the Correlation Function (CF) for the LOS delay estimation. As a result, it enables to deal with the medium-delay MP. Yet, it presents a greater sensitivity to the noise and to the long-delay MP that we propose to mitigate, respectively, with the use of SGF and the measure of the first side peak (instead of the central). The obtained results show that our proposed scheme gives better performances over DDC scheme. In fact, it shows a significant error reduction caused by the presence of long-delay MP signals (up to 90%) compared to that of the DDC scheme.