Search

In this paper, we investigated the relationships between EEG and semantic long-term memory retrieval using spectral analysis and functional connectivity. We employed an EEG data set from a previous study, which was recorded from 34 healthy participants during a memory retrieval process. The data set consists of EEG collected during two tasks, a learning task, in which participants studied animated learning material, and a memory recall task, in which they recalled the learned information. We analyzed both EEG signals and behavioral responses. We conducted spectral analyses for the absolute power and relative power of EEG frequency bands, EEG coherence, absolute phase delay, and EEG amplitude asymmetry features. The delta-band EEG and theta-band absolute power were negatively correlated with task performance at frontal regions, while the alpha-band activity was positively correlated in frontal regions and negatively correlated in parietal and temporal sites. High-beta in the frontal lobe was positively correlated with memory recall score. EEG coherence was negatively correlated in the delta band at the fronto-parietal and fronto-central sites, and positively correlated in the gamma band at widespread regions, including all lobes. EEG phase delay showed the highest degree of connectivity in the delta and alpha bands at frontal sites, and was negatively correlated with memory recall score. The negative correlation in phase delay demonstrated the synchronization and positive correlation reflected the de-synchronization of electrode pairs during memory recollection in the delta and alpha frequencies. We concluded that neuronal networks producing low EEG frequencies at frontal regions and those producing high frequencies in widespread regions are active during the memory recollection process. Thus, semantic memory storage involves widespread neuronal networks across the brain.

Driver drowsiness is one of the major causes of road accidents. An estimated number of 1.2 million crashes, 8,000 lost lives, 500,000 injuries annually relates to drowsy-driving. From the information provided by a number of statistical reports, it can be proven that a large number of fatalities is caused by driver drowsiness. In earlier researches, to estimate the level of drowsiness, the measures to be focused on are single measures either vehicle-based, physiological measure, behavioural measure or subjective measure. This paper analyses two single measures which includes physiological and behavioural measures such as EEG signals and video sequences together. Features extracted from EEG signals are the Delta, Theta and Alpha frequency bands which includes Delta power (P_(δ-abs)), Theta power (P_(ϑ-abs)) and Alpha power (P_(α-abs)). Features extracted from the video sequences are eyes state specifically the eye closure. With the obtained features extracted, the significant features are combined with the physiological measure chosen to be measured to be the Theta band since it has previously been related to the drowsy state for numerous researches. The behavioural measure chosen are the eye states which are the eye closures. The results obtained through this research for the single physiological measure has an accuracy of 91% for all frequency bands. The behavioural measure obtained shows the eye opening and closing of the eyes. After fusing both the measures, one subject shows the most accurate detection of drowsiness. Three subjects give a contradictory result in detecting drowsiness. Overall, this study shows that EEG frequency band powers and eye closure can be used to infer drowsiness. Thus the study shows a promising prospect of detecting drowsiness and alerting the driver with an alarm.

International audience; This paper aims to optimize the coverage of a given area from a set of views to allow a complete mosaicing. Among the investigated methods to find the best camera positions, two of them are studied, namely the Particle Swarm Optimization (PSO) and the Genetic Algorithms (GA). After having performed experiments to compare the algorithms, the hybridization of GA and PSO is investigated. To validate the proposed method, it is simulated area of irregular shapes with the cameras mounted on a Unmanned Aerial Vehicles (UAVs). V-REP is used to simulate the UAVs in an indoor environment and satellite images are used for a large outdoor area. The simulation validates the efficiency of the proposed method to find the optimal position of cameras. Then by using the images acquired it is possible to monitor the area and to compute a full mosaic of it.

The immune system is a complex network of highly specialized cells (such as lymphocytes) and organs. All of these cells work together to reduce infection (antigens) such as bacteria, virus or tumor cell from the body. Biologic Response Modifiers (BRM) also known as immunotherapy, is a type of treatment which mobilizes and triggers the immune system of the body. This research work provides a description of noise nature of immunofluorescence microscope images. Thus, the study leads to determine the type of noise and choose the filter which best fit the noise presented in fluorescence microscope images. Image histogram and Fast Fourier Transform (FFT) have been applied on blood samples. However, the results show that the Gaussian noise is found in this kind of images. CLAHE filter has been applied to these images. The results obtained from CLAHE demonstrate the ability for this filter to deal with this kind of images.

This paper presents a method to measure the forearm's subcutaneous veins depth by using the theory of light propagation model. In this study, we proposed a practical method to measure the forearm's vein deep by designed an optical phantom and experiment setup to measure the diffuse reflectance (Rd). The Monte Carlo Multilayer (MCML) tool had been used to simulate the light migration into skin layer. This study is designed for those who wish to find the depth information of forearm subcutaneous vein and, in particular, for those investigating for a perfect peripheral intravenous (IVs) in clinical application. Besides covering those aspects of the measurement theory of this model, this study also includes the execution definition of the experiment setup and the fundamental design of tissue-like phantom. In this way, instructional, revision and remedial materials provide the conscientious researcher with a comprehensive text to plan and regulate for the research in vein's depth measurement.

The main objective of this research was to investigate the association between electroencephalogram (EEG) and semantic memory recall in human participant. A sample of 20 healthy participants was recruited and exposed to 10 minutes animated learning contents. After 30 minutes of the learning session, they performed a memory recall task; the correct and incorrect responses in recall task were recorded for computing the memory performance. EEG amplitude asymmetry was computed for six frequency band (delta, theta, alpha, beta, high beta, and gamma) and the correlation was checked with the memory recall. It was found that the EEG delta asymmetry correlated negatively (r=0.44−0.68; p-value

This paper proposes an evaluation metric which derive the effectiveness of background modeling algorithms. Background modeling is a key process on developing visual surveillance systems. The requirement of adapting to dynamic environments has motivated researchers to modify existing background modeling algorithms and develop new algorithms with better adaptability. Having the algorithms developed, credentials of each of the algorithms have to be assessed to exploit their effectiveness. Various evaluation metrics have been used for evaluating the rate of foreground extraction, foreground detection, and overall accuracy. However, the rate of background detection has not been exploited by these metrics. Therefore, this paper would provide an insight to the existing evaluation metrics and introduce our proposed metric for estimating the rate of background detection.

The main objective of this research was to investigate the association between electroencephalogram (EEG) and memory recall in human participant. A sample of 34 healthy participants was recruited and exposed to 10 minutes animated learning contents. After 30 minutes of the learning session, they performed a memory recall task; the correct and incorrect responses in recall task were recorded for computing the memory performance. EEG coherence was computed for six frequency band (delta, theta, alpha, beta, high-beta, and gamma) and the correlation was checked with the memory recall. It was found that the EEG delta coherence correlated (r=0.34–0.37; p-value

Venipuncture as a mode of gaining intravenous access is a crucial practice in pre-surgical and conventional drug administering procedures. Biomedical engineering has focused on the automation and aid in these processes to promote and encourage non-invasive catheterization of patients. Indeed, medical personnel are highly challenged by the various patient's skin tones and topologies. This paper proposes an in depth analysis of illuminant configuration to provide enhanced visual aids to medical personnel while performing vein catheterisation. The proposed study introduces an optimised illuminant selection to ensure an enhanced vein visualisation independent of patient skin tones. The further selection of combined LED configuration in terms of wavelength and power will improve the contrast of vessels, leading to automated and optimised illumination for all patients and better image quality.

Wireless Sensor Networks (WSNs) are vulnerable to clone attacks as they are deployed in hostile and unattended environtments. Also due to the lack of physical tamper-resistance, an adversary can easily capture and compromise sensor nodes and after replicating them, he inserts arbitrary number of clones into network. As a result the adversary is able to mount a wide variety of internal attacks. Several solutions have been proposed in the literature for the detection of these clones from which witness node based distributed solutions have shown satisfactory results. Random Walk (RAWL) is one of the witness node based distributed techniques in which witness nodes are randomly selected by initiating several random walks throughout the network. Although RAWL has achieved high security of witness nodes but in accomplishing high detection probability RAWL suffers from very high communication and memory overhead. In this paper we propose a novel enhancement in RAWL protocol aiming to decrease the communication and memory costs while keeping the detection probability high. Our simulation results show that this improvement in RAWL not only reduces the communication and memory costs but also ensures high security of witness node.

This paper presents a method to improve the real time Near-Infrared (NIR) subcutaneous veins localization by using the image processing technique based segmentation and fusion. The goal of this paper is to enhance the extraction of veins from NIR image through a series of image processing stages. In these image processing stages, input image is first partitioned to a new set of intensity band via the segmentation technique and they are re-combined through the fusion procedure in order to obtain the accurate information for next analysis procedure. After that, the procedure of segmentation and fusion is followed by the procedure of filtering and aggregation to produce an optimum image in the result. Lastly, the output from this veins extraction enhancement model is able to provide an optimum image for a better clinical diagnose of veins.

Blood vessels detection is a common task performed in numerous medical procedures. During regular medical treatments venipuncture procedures are performed for invasive medication and blood sampling. Near infrared imaging technology can be used to visualize the subcutaneous veins in cases of difficult venous access. In this paper the methods for veins centerline detection and back projection is presented. In order to highlight the suitable veins for venipuncture, the centerline of larger veins are detected and back projected to the original image. The method is applied on the near infrared images of subjects selected from four different classes of skin tone. This can be helpful to medical staff to select suitable vein for venipuncture procedures. The method is based on Frangi vesselness filter for 2D images. The artifacts like hair and small vessel-like structures are removed with morphological operations. The presented method shows consistent performance in terms of vascular structure detection for all skin tone classes.

Advance biomedical engineering technologies are continuously changing the medical practices to improve medical care of patients nowadays. In this paper, we describe the concept used to prototype a device for needle insertion navigation during intravenous catheterization process via Near Infrared (NIR) imaging technique. A vein locator prototype using the NIR imaging technique and augmented reality (AR) technology have been developed in this work which is meant to be used in the process of intravenous catheterization. The challenges faced during the development of this prototype included the calibration of composite images in the see-through display. In this prototype, the Vuzix STAR 1200XL eyewear system has been used as the head mounted display and the imaging video is input by IR CCD camera. Additional, We select the optimum illumination by using NIR LED with wavelength of 830nm and 850nm in prototying to obtain the best contrast NIR venous image for different types of skin tone.

In the matter of detecting clone attacks, we bring in a novel solution called Single Stage Memory Random Walk with Network Division (SSRAND) to circumvent the problems of simple random walk as exploited by both RAND and RAWL protocols. SSRAND combines the single stage memory random walk with network division for clone detection and simulation results verify that it not only reduces the communication and memory costs but also ensures high security of witness nodes with increased detection probability of clones.

This paper presented a compressed version of viewpoint feature histogram descriptor (VFH) for object classification based on shape recognition. VFH is known for representing geometrical features (3D rotation angles) of 3D points with concatenated histogram. However this histogram is large and sparse. The proposed descriptor employ eigenvalue decomposition to extract dominant orientation features from the point cloud and using it as a descriptor instead of sparse histogram. Using dominant features maintains the main properties of the object with minimal descriptor length which applicable for recognizing the geometrical class of 3D objects (sphere, rectangle, ... etc). This descriptor was tested for two class and multi-class 3D object classification using support vector machines (SVM). The new descriptor showed promising matching results of 88% for two class classification and 83% for multiple class classification of 3D objects.

Intensity noise (IN) or phase induced intensity noise (PIIN) is the key limiting factor of the performance in spectral amplitude coding optical code division multiple access (SAC OCDMA) systems. The PIIN can be mitigated in SAC OCDMA by splitting the signals and detecting each signal by a different photodiode if the independence between the split signals can be achieved. In this paper, we derive the upper and lower bounds for the bit error rate (BER) for a system that implements multiple photodiode structured balanced detectors. Additionally, a simulation using Optisystem is conducted to compare the performance of the conventional balanced detector and an ideal multi photodiode balanced detector.

Nowadays, the wireless devices are equipped with multiple network interfaces to support different wireless technologies, for example, Universal Mobile Telecommunications System (UMTS), Wireless Local Area Network (WLAN), and Bluetooth etc. However, while increasing the options to connect internet via different access networks, seamless mobility cannot be assured when the wireless device is roaming across heterogeneous wireless access domains. This limitation appears because multiple wireless interfaces cannot be utilized simultaneously for the same data session. Due to the enormous number of Internet Service Providers (ISPs) and the fragmented nature of wireless technologies, the wireless devices must support multiple wireless access networks concurrently. If more than one wireless interface is utilized for the internet connectivity then seamless mobility without any service degradation can be attained. The literature illustrates that most of the existing internetworking techniques are lacking to provide the seamless mobility. In this paper, we have proposed a Multi-homing Seamless Vertical Handoff Protocol (MSVHOP) for the seamless switching of active data session between UMTS and WLAN networks. In order to decrease the vertical handoff delay and transient lost information, the MSVHOP implements multi-homing feature in the proposed internetworking mechanism that leads to attain the less signaling and node processing cost during handoff.

Preserving inter-actor connectivity is essential in most wireless sensor and actor network (WSAN) applications as nodes have to collaborate and coordinate their actions against the events reported by the sensors. However, failure of a critical (i.e., cut-vertex) node partitions inter-actor network into disjoint segments and thus hinder network operation. The prime objective of this paper is to analyze the performance of reactive connectivity restoration algorithms for delay-tolerant WSAN applications. First, we provide insights to the state-of-the-art reactive connectivity restoration algorithms. Then, we present a Nearest Non-critical Neighbor (NNN) algorithm; a localized and distributed reactive approach for reconnecting network partitions. In NNN, each actor periodically determine its criticality (i.e., cut-vertex or not) based on 2-hop information and exchange with its neighbors. In case of a critical actor failure, the neighbors detect and trigger a connectivity restoration procedure that involves controlled and coordinated node relocation. NNN prefer to displace non-critical nodes during relocation in order to minimize recovery overhead in terms of distance movement and message coordination. We analyze the performance of reactive schemes through theoretical analysis and simulations.

In this paper we validate through software simulation that a Gamma probability density function (pdf) can give a very good approximation of the detected intensity of the incoherent light source. We performed two experiments, in the first experiment the pdf of 0.25 nm optical signal is measured for different photo detector's electrical bandwidth. In the second experiment the eye diagram reading is performed for the optical signal at 2.5 Gbps. Results show that the simulated pdf and computed pdf agree to very high extent. Results also show that the variance in the received signal for logic "0" is negligible, meanwhile for logic "1" the variance is very large and increases with electrical bandwidth.

This paper evaluates the performance of spatial multiplexing (SM) in beat noise mitigation in coherent spectral amplitude coding (SAC) OCDMA via the Optisystem software kit. We take into consideration two different laser source configurations; a centralized shared multi laser source and a precisely controlled multi laser source. For different performance merits, the results showed superiority of the SM SAC over the conventional SAC OCDMA. For example, an up to nine order of magnitude improvement in the bit error rate (BER) was reported for six users at 1.25 Gb/s.

We propose the use of a divided spectrum balanced detection (DSBD) to reduce the intensity noise in spectral amplitude coding (SAC) OCDMA systems. Simulation results show several order of magnitude improvements in bit error rate (BER) compared to the conventional balanced detection.

Cooperative spectrum sensing (CSS) is capable to improve the performance of signal detection. It is one solution to overcome fading, shadowing, and uncertainty noises. Unlike centralized networks, Secondary User (SU) in decentralized networks independently senses license channel without forwarding the sensing result to central coordinator. This paper investigates the performance of Decentralized Multiuser CSS (DMCSS) in Cognitive Radio (CS) system. Partially observable Markov decision process (POMDP) is used as an aid for SU to sense and access a license channel. It models spectrum as Markov discrete process where idle and busy states are represented by “0” and “1”. The comparisons are made against Centralized Multiuser Cooperative Spectrum Sensing (CMCSS). The derived results show that CMCSS has better performance than DMCSS model. However, at certain values of SNR, DMCSS performance outperforms the achievable throughput by CMCSS through setting of collision threshold (ζ).

This paper demonstrates a novel architecture of hybrid subcarrier multiplexing Wavelength Division Multiplexing network combining laser and light emitting diodes (LED) as the light sources. The performances are simulated using Optisys software and analyzed based on bit error rates (BER) and the eye pattern of the received signals. Results proved that the combination of the laser and LED light sources in one system can be considered an effective way to maximize system capacity and at the same time, reduce implementation cost of hybrid SCM WDM network architecture.

Cooperative sensing is one solution for fading, hidden node problems, and uncertainty noises in primary signal detection. In this case, each secondary user (SU) senses available channel and exchanges their local sensing results to decide which channel can be accessed. Subsequently, this technique is capable to reduce sensing errors and lead to the throughput improvement. In this paper, we investigate decentralized cooperative user (DCU) with limited sensing capability under Partially Observable Markov Decision Process (POMDP). It models license spectrum opportunities as Markov discrete process where the idle and busy state of spectrum is represented by 0 and 1. Each SU with limited sensing capability detect primary channel under the constraints of collision allowable by primary user (PU) and reduce the interference to PU activity. SUs exchanges their sensing results based on the local observation. To validate this work, the performance of DCU is compared with single user sensing and random cooperative user (RCU).

In this paper, we study the performance of the multi photodiode balanced detection (MPBD) scheme in phase induced intensity noise (PIIN) reduction for spectral amplitude coding Optical code division multiple access (SAC OCDMA) systems, when the PIIN is assumed to have a Gamma distribution. The PIIN is signal dependent source of noise which increases with signal power. The MPBD reduces the optical power at photodetection to mitigate the PIIN. To sustain the same average power, a multiple number of photodiodes are used. Our results show that the MPBD can support 67% more simultaneous users than the conventional differential balanced detection.

Mobile Wireless Sensor Network (mWSN) is one of the rising and emerging technologies for various application of NWGN. The enormous concerns of these networks are energy efficiency and data aggregation within the network. The aim of data aggregation is that eliminates redundant data transmission and enhances the lifetime of energy in mWSN. In this paper, we propose, analyze and validate efficient cluster head selection scheme in Mobile Data Collector based routing protocol for data aggregation, which is based on multi-hop routing strategy. Moreover, our approach is better than traditional LEACH in terms of energy consumption of sensor nodes and enhances the network lifetime due to less energy consumption during data transmission.

With the maturity and development of Wireless Sensor Networks, a large body of research is being assembled and several routing protocols have been developed for wireless sensor networks. Routing metric is very important for the performance of wireless sensor networks. But a little attention has been paid by the researchers to the evaluation metrics and design principles for routing protocols that should never be neglected while designing and evaluating routing protocols for wireless sensor networks. This paper depicts some vital evaluation metrics that are essential while designing, developing and evaluating the performance of routing protocols for wireless sensor networks. This research is an effort towards hoarding all the general metrics and guiding the researchers for designing efficient, professional and valuable routing protocols.

Real world contains a wide range of intensities that cannot be captured with traditional imaging devices. Moreover, even if these images are captured with special procedures, existing display devices cannot display them. This paper presents a comparative study of most famous tone mapping algorithms. Tone mapping is the process of compressing high dynamic range images into a low dynamic range so they can be displayed by traditional display devices. The study implements six tone mapping algorithms and performs a comparison between them by visual rating. Independent participant were asked to rate these images based on a given rating scheme. The study concluded that Reinhard tone mapping operators are the best in term of visual pleasure and maintaining image integrity. In addition, exponential tone mapping operators have achieved better rating compared the logarithmic operators.

A new code family has been proposed for the Spectral Amplitude Coding-Optical Code Division Multiple Access (SAC-OCDMA) networks. This new Multi Diagonal (MD) code family, proposed for SAC-OCDMA applications due to his advantage such as; the cross-correlation value still zeros in case of an increase the number of users for any weight value. Furthermore, the DCS code supports a large number of users and easy code construction. Based on the theoretical analysis MD code is shown here to provide a much better performance compared to Modified Quadratic Congruence (MQC) code and Random Diagonal (RD) code. Proof-of-principle simulations of encoding with 5 users with 10 Gbps data transmission at a BER of 1.1×10−13 have been successfully demonstrated together with the DIRECT detection scheme for 40 km fiber length without any amplification or side pumping.

A new code family for Spectral Amplitude Coding Optical Code Division Multiple Assess (SAC-OCDMA) system has been proposed in this paper. The new code family we call it Dynamic Cyclic Shift (DCS) code. The DCS code has many advantages. However, the DCS code can be generated without code parameter limitation. In addition, the shorter code length and variable cross correlation (λ c ≤ 1) of the DCS code can improve the SAC-OCDMA system performance. The mathematical results and simulation analysis shows that the DCS code in terms of the Bit-Error-Rate (BER) and eye diagram can effect on the suppression of Phase Induced Intensity Noise (PIIN). The simulation analysis carried the data rate 10 Gbps for 20 km with low BER value comparing with former SAC-OCMA code systems.

A construction of new code family for Spectral Amplitude Coding Optical Code Division Multiple Accesses (SAC-OCDMA) has been proposed. This new code family we call it Dynamic Cyclic Shift (DCS) code. The DCS code reduced the effect of Multi Access Interference (MAI) due to it is the property of variable cross correlation. We find that the performance of the DCS code is a batter than Random Diagonal (RD) code and Modified Frequency Hopping (MFH) code. Through the mathematical calculation and simulation analysis, for the bit-error rate of DCS code is significantly better than other SAC-OCDMA codes such as RD and MFH codes. We analyze the performance of the proposed codes and examine how the code size and correlation properties are related. Two different decoding schemes are used for implementing the SAC-OCDMA system: Fiber Brag Grating (FBG) and optical Butterworth filter such as Arrayed Wave Guide Grating (AWG) optical filter. Simulation results show that performance of AWG filter is better than Fiber Brag Grating for optical system with 10 Gbps bit rates. Finally, in terms of system cost, FBG offers cost effective than other type of filters (e.g., AWG, thin film filter)

Spectrum sensing over imperfect channel condition can cause errors in primary signal detection. False alarm detects idle states as a busy channel and makes secondary user (SU) refrain from data transmission, while miss-identification detects busy states as an idle channel and causes collision to primary user (PU). This paper study the performance of opportunistic spectrum access (OSA) system over imperfect channel sensing with the restriction of maximum collision probability allowed (collision threshold) by PU. The successful transmitted bits over T slot is used to evaluate OSA performance and make comparisons to those ones without sensing error as function of number of slot. The throughput performance as a function of signal to noise ratio (SNR) is presented as well. According to the obtained results show that SU can improve the throughput performance by gaining the information from the previous slot over perfect and imperfect channel sensing. SU can maximize the number of bit transmitted within T slot transmission. Subsequently, imperfect channel condition can degrade the throughput achievement since it causes error in primary signal detection.

The design of optimal sensor operating point in physical layer by considering the impact of the throughput performance in MAC layer is crucial issue. Spectrum sensing action must be performed as quickly as possible to obtain a good throughput performance. However, quick sensing makes the fidelity of sensing outcome becomes low. On the other hand, a long sensing time leads to the low throughput performance. Hence, it is important to find out how secondary users (SUs) in opportunistic spectrum access (OSA) system can improve the throughput performance while maintaining sensing time low. In this paper we study the fundamental design of spectrum sensing and throughput performance for cognitive radio (CR) user with limited sensing capability in OSA system. In the first done, we consider 3% of one slot is allocated for spectrum sensing action and observe the throughput performance by varying the channel measurement sample. The Optimal throughput performance is achieved at certain value of sample number and reduces as increasing it. Subsequently, we observed the throughput performance as a function of spectrum sensing slot allocation as well. Increasing the allocation for spectrum sensing action can degrade the throughput performance. Computer simulations are presented to evaluate the performances.

Currently, there is a need to provide communication services at anytime, anywhere with the low cost and the best quality. Moreover, deployment of WLAN network aiming to offer services in a hot-spot region, such as airports, hotels, railway stations, etc. tend towards the need to provide the integrated architecture of UMTS and WLAN. The integration of UMTS and WLAN is beneficial for both user and service provider. Many research proposals have been proposed to provide solutions to tackle problems concerning mobility and handover management in an integrated network environment. This paper gives an overview of the most recent research efforts made regarding mobility and handover management in heterogeneous network environment. The paper mainly focuses on the various coupling approaches used for the integration of UMTS and WLAN.

Ubiquitous communication networks is a keystone for New Generation Network (NWGN). Mobile Wireless Communication Networks (MWSN) is a viable solution to accomplish the requirements of NWGN. Due to mobility of sensor nodes, the data reliability and end-to-end delay with energy efficiency in the network is an enormous concern. Various real-time and delay sensitive applications enforced to use both environments mobile and fixed sensor nodes, whereas the others claims an entire mobile sensors environments in network. Packet loss ratio and end-to-end delay happened because of the nodes mobility which is directly impact to degrade the quality of service, network lifetime and energy consumption. This paper enlightens a comprehensive comparison between single and multi hop inter-cluster routing strategy from cluster head to base station. Moreover, the performance of multi hop routing is calculated and compared with single hop LEACH routing strategy. The simulation results reveal that multi hop routing strategy is to increase the sensor nodes throughput and network lifetime but not efficient approach for delay sensitive and data reliable applications.

To provide service anywhere and at anytime, there is a strong demand for integration of two promising technologies; UMTS and WLAN. By integrating these two, the user can have the benefits of using both technologies. The WLAN is capable of providing high data rate at low cost. However, its services are limited to a small geographical area. UMTS networks coverage area is wider, however, cost is high and the data rate provided does not fulfill the requirements of bandwidth intensive applications. Integration of these two technologies can provide ubiquitous connectivity and high data rate to wireless clients. This paper focuses on the different integration mechanisms of tight coupling i.e. connecting WLAN with GGSN and SGSN at the UMTS core packet based network. Moreover, it has been observed that the performance of G GSN-WLAN integration is better than SGSN-WLAN integration mechanism for all the applied services.

Future wireless networks will allow users to seamlessly roam among heterogeneous wireless networks. To provide services anywhere and anytime in such a diverse networking environment, vertical handoff is still a crucial target. In this paper we propose non-real time services vertical handoff decision algorithm NRS-VDA. NRS-VDA is an intelligent vertical handoff decision algorithm that can manage efficient vertical handoff initiation and decision procedure between UMTS and WL AN networks. NRS-VDA ensures the avoidance of unnecessary and detrimental vertical handoffs and provides high throughput and low blocking probability. NRS-VDA is defined for upward and downward vertical handoff scenarios. The proposed algorithm takes several metrics into account such as velocity of mobile terminal, bandwidth, and Received Signal Strength (RSS) of the network. It is suggested that NRS-VDA will improve the overall efficiency of vertical handoff in Next Generation Networks (NGN).

Energy efficiency is the major point of consideration in Wireless Sensor Networks (WSN). The protocols of Media Access Control (MAC) layer provide the most effective energy utilization. Idle listening is a major source of energy wastage in wireless sensor networks; the nodes do not remain in the idle listening state when no data is available to them. Lowering the duty cycle reduces the active period of the sensor nodes; a fixed duty cycle does not adapt to the varying traffic rate in sensor networks and a high duty cycle results in significant energy wastage when traffic rate is low. For a low traffic load, low message data delivery and long queuing delay occur, in fixed synchronous duty cycle increasing the possibility of collision. A basic mechanism is followed in this paper to achieve energy efficiency due to low duty cycle for periodic traffic. Moreover, we have aimed to reduce the energy cost of sensor nodes using Simple Energy Aware Medium Access Control (SEA-MAC) protocol. The performance enhancement work has been analyzed and validated in Network Simulator (NS-2).

In the future there is a need to provide seamless mobility to the heterogeneous wireless network user while on the move. To achieve this there is a need to design an efficient vertical handover mechanism. User preference and system condition should be taken into consideration for efficient vertical handover. As the 3GPP Long-term evolution or LTE is the upcoming WWAN technology, performing an efficient vertical handover between LTE and next generation wireless LAN will be the challenge for future research. In this paper a fuzzy based vertical handover algorithm NG-VDA is proposed to provide an efficient vertical handover between LTE and WLAN to the user on the basis of multiple parameters.

The vision of 4G network is to have a unified network of heterogeneous wireless networks. To achieve seamless mobility in such a diverse environment, vertical handoff is still a challenging problem. Traditional handoff mechanisms were based on the Received Signal Strength (RSS), but to have an efficient handoff decision in a heterogeneous network environment in addition to RSS other parameters, e.g. monetary cost, user preferences and network conditions must be taken into account. In many situations unnecessary handoffs are triggered causing degradation of services, reduction in throughput and increase the blocking probability and packet loss. In this paper we propose real time services vertical handoff decision algorithm (RS-VDA). RS-VDA, defined for upward and downward vertical handoff scenarios. The proposed algorithm takes several metrics into account such as velocity of mobile terminal, bandwidth, RSS and delay of the network. The proposed algorithm will improve the overall efficiency of seamless mobility in Next Generation Networks (NGN).

In this paper, we study the performance of optical code-division multiple access (OCDMA) systems using vector combinatorial (VC) code under various link parameters. The impact of the fiber dispersion effects on the multi-user interference (MUI) is reported using a commercial optical systems simulator, Virtual Instrument Photonic, VPItransmissionMaker™. The VC code is compared mathematically with other codes which use similar techniques. We have analyzed and optimized the data rate, fiber length, and channel spacing in order to reduce the BER without the need to deploy dispersion compensating devices. We have demonstrated that, for a high data rate (higher than 2.5 Gb/s), even if dispersion compensated devices are not deployed, the BER can be significantly improved when the VC code desired parameters are selected. It is clearly seen that the MUI noise has been eliminated effectively.