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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.

International audience; Intravenous (IV) catheterization is the most important phase in medical practices of daily life. It is hard to localize veins in patients who have deep veins, minor age or dark skin; hence multiple attempts become indispensable for proper catheterization in such cases. Near Infrared (NIR) Imaging allow to visualize the veins underneath the skin of persons having non-visibility of veins problem. This paper reports the pre-selection of illuminants that ensure best veins/tissues contrast for patients having different skin tone. The sample subjects have been divided in four different classes based on the Luminance value of their skin tone in order to extract the best illuminant wavelengths range for each class. A multispectral approach has been used which provides the flexibility of wavelength range from visible to NIR (380 to 1040nm). The veins/tissue reflectance contrast obtained helps in determining the best wavelengths range where the contrast is maximum for each of the four classes. Using these results, we are planning to build a prototype system which can automatically select the illuminants based on different physiological characteristics of a subject.

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.

In this paper we investigate the use of wavelength multiplexed spectral amplitude coding (WM SAC) codes in beat noise mitigation in coherent source SAC OCDMA systems. A WM SAC code is a low weight SAC code, where the whole code structure is repeated diagonally (once or more) in the wavelength domain to achieve the same cardinality as a higher weight SAC code. Results show that for highly populated networks, the WM SAC codes provide better performance than SAC codes. However, for small number of active users the situation is reversed. Apart from their promising improvement in performance, these codes are more flexible and impose less complexity on the system design than their SAC counterparts.

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).

In this paper, we investigate the effect of noise on 3D point cloud descriptors. Various types of point cloud descriptors have been introduced in the recent years due to advances in computing power, which makes processing point cloud data more feasible. Most of these descriptors describe the orientation difference between pairs of 3D points in the object and represent these differences in a histogram. Earlier studies dealt with the performances of different point cloud descriptors; however, no study has ever discussed the effect of noise on the descriptors performances. This paper presents a comparison of performance for nine different local and global descriptors amidst 10 varying levels of Gaussian and impulse noises added to the point cloud data. The study showed that 3D descriptors are more sensitive to Gaussian noise compared to impulse noise. Surface normal based descriptors are sensitive to Gaussian noise but robust to impulse noise. While descriptors which are based on point's accumulation in a spherical grid are more robust to Gaussian noise but sensitive to impulse noise. Among global descriptors, view point features histogram (VFH) descriptor gives good compromise between accuracy, stability and computational complexity against both Gaussian and impulse noises. SHOT (signature of histogram of orientations) descriptor is the best among the local descriptors and it has good performance for both Gaussian and impulse noises.

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.

In the era of New Generation Networks (NWGN) many emerging and future enable technologies accomplish the requirements of ubiquitous communication networks. 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 data gathering with energy efficiency. Routing protocol act as middleware, which is responsible to enhance the network performance with less energy consumption. In this paper we propose, analyze and validate mobile data collector (MDC) based LEACH routing protocol for environmental application which is based on multi-hop routing strategy. MDC based LEACH routing protocol utilizes self-organized sensor nodes with distributed cluster formation technique, randomly selection of cluster heads to equally balance the energy consumption among the sensor nodes and finally forward the data to base station by the support of MDC. Moreover, our approach shows the significant improvement in terms of energy consumption of sensor nodes, enhance network lifetime and data gathering at base station are outperform when compared with LEACH protocol. Key words: Mobile wireless sensor networks, wireless sensor networks, network protocol, cluster based routing, data gathering technique.

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.

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.

In Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) system, Multip-user Interference (MUI) problem which increases with the number of users severely limits the performance of the system. However, phase induce intensity noise (PIIN) arising from spontaneous emission of broad band source is another problem leads to system deterioration should be addressed. Moreover, a proper design of detection scheme which is being able to extract the wanted signal from the unwanted signal successfully needs to be considered as well. In order to overcome the stated problems, Vectors Combinatorial Codes (VCC) with ideal in-phase cross correlation, based on combinations of specific vectors is proposed. In our approach, any integer number of users and weights can be used in code constriction. This makes our proposed code a strong candidate for future optical communication systems. The complementay detection schem can be used to give accurate results if the cross correlation (CC) is fixed, therefore, a new detection scheme based on XOR logic is proposed. This new detection scheme can be used even if the CC is not fixed. In addition, a new encoder/decoder structure based on this new scheme using fiber Brag gratings (FBGs) for VCC is proposed. It has been shown that, performance can be improved significantly when VCC used with XOR detection scheme instead of complementary and AND detection schems.

Optical Code Division Multiple Access (OCDMA) is considered as the strongest candidates for the future high speed optical networks due to the large bandwidth offered by the system, Based on the vast amount of bandwidth, OCDMA systems have received much attention in fiber optic Local Area Networks where the traffic is typically bursty. However, Multiple Access Interference (MAI), which is originated from other simultaneous users, severely limits the capacity of the system. Optical Parallel Interference Cancellation (OPIC) has been used to reduce the effect of MAI. However, the usage of OPIC in OCDMA systems will increase the demand for hardware complexity which results in higher processing time and cost. The hardware complexity increases in the receiver side of OPIC when the number of transmitter (users) increases. To overcome these difficulties, an efficient method is presented in this paper called, One Stage Optical Parallel Interference Cancellation (OS-OPIC) which is based mainly on the OPIC. Optical Orthogonal Code (OOC) is adopted as a signature sequence for the performance analysis and a new expression for the error probability is derived. It is shown that, the proposed method is effective to reduce the hardware complexity, processing time and cost while maintaining the same bit error probability at the cost of increasing threshold value.

A new code of optical code division multiple access (OCDMA) namely optical zero cross correlation (ZCC) is proposed in this paper. The code construction design is flexible since the number of user and weight can easily be increased using mapping and transformation method respectively .The performance of the system with the proposed code is simulated and analyzed using Optisys 5.0 in comparison the distance of network used. Besides, ZCC code demonstrates an excellent performance of BER since it was designed in such that no cross correlation between the users. In other words element of phase induced intensity noise (PIIN) is eliminated. The results show that by using ZCC code the distance can achieve up to 100 km with acceptable BER. The combination of direct decoding also contribute a great effect to the overall system performance.

When mapping is applied for the double weight code family to increase the number of users, for spectral amplitude coding optical code division multiple access (SAC OCDMA) systems, the conventional complementary detection technique cannot be used to retrieve the intended signal because of the unfixed cross-correlation value between different code sequences. This paper studies the software simulation for two alternative detection schemes that can support mapping; the hybrid WDM/SAC and a proposed reduced set of fiber Bragg gratings (FBG) for the hybrid WDM/SAC. The performance of the two systems have been simulated and analyzed by the virtual photonics instrument (VPI) version 7.1.

Achieving optimal transmission throughput in data networks is known as a fundamental but hard problem. The situation is aggravated in mobile wireless networks due to interference among local wireless transmission. In this paper, we provided a cross-layer optimization for mobile ad-hoc network. We selected two protocols. These protocols are not applicable in mobile environment. We proposed two control packets, busy node list and overall link state table and used adaptive array antennas to achieve the optimal performance. Results show that the proposed scheme improves the performance of the selected MAC protocols.

Optical code division multiple access multiple (OCDMA) is considered as the strongest candidates for the future ultra-high speed optical networks due to the huge bandwidth offered by the system. However, multiple access interference (MAI) which is originated from other simultaneous users is the major reason for the system degradation in the OCDMA systems. MAI increases with the number of simultaneous users, resulting in higher bit error rate and limits the maximum number of simultaneous users in the OCDMA system. Several techniques have been proposed and discussed in the literature aiming at lowering the effect of MAI. In particular, optical parallel interference cancellation (OPIC) has been extensively studied for the sake of reducing the MAI. In this paper, an optical hard limiter (OHL) has been used in front of the receiver side to reduce the effects of MAI. OHL improves the performance of OPIC system because of its ability to exclude some combinations of interference patterns from becoming heavily localized in a smaller part of non-zero positions of signature codes. Moreover, it is found that high performance of OPIC can be obtained by selecting the minimum threshold value for the desired user. The results reveal that, the optical hard limiter improves the performance of the conventional OPIC while reducing the effect of MAI. Concurrently the system.

Optical parallel interference cancellation (OPIC) is effective technique to reduce the multiple access interference (MAI) in the optical code division multiple access (OCDMA). However, the increasing demands for hardware in the OPIC system results into more complexity, higher processing time and cost. In this paper a new receiver is presented which is based mainly on the optical parallel interference cancellation (OPIC) for the optical code division multiple access (OCDMA) local area networks. Optical orthogonal code (OOC) is adopted as a signature sequence for the performance analysis and a new expression for the error probability is derived. The results show that the proposed method is effective to reduce the hardware complexity, processing time and cost while maintaining the same bit error probability at the cost of increasing the threshold value.

This paper the construction of the double weight (D\V) code family, one the recent codes for spectral amplitude coding (SAC) is studied. The DW code family is constructed using a matrix construction technique and a mapping scheme to increase the number of users. To obtain a single user's codeword the whole matrix must be constructed. In this paper a simplified equation based construction technique for the DW code family is proposed. This new simplified construction scheme depends on the three basic building blocks for the DW code family. General equations for the codeword construction and code length are given.

To increase the number of users in the double weight (DW) code family, a mapping technique is applied. This mapping technique increases the number of users but at a cost of unfixed cross-correlation property. The complementary detection technique used in spectral amplitude coding (SAC) systems, can completely cancel the multiple access interference (MAI) only if there is a fixed cross-correlation between different code sequences. In this paper we study the performance of the DW code family a alternative detection scheme that can support balance detection for unfixed cross-correlation property. Also a mathematical approach is proposed to reduce the number of fiber Bragg gratings and minimize the phase induced intensity noise.

In this paper, we conducted a comparison study of the existing directional MAC protocols that use Smart Antennas by contrasting their features. We found that, most of these protocols are not applicable in mobile environment This investigation discusses the challenges in improving some of these smart antenna-based MAC protocols. We proposed to upgrade two protocols, Tone-DMAC protocol and Angular-MAC protocol. We proposed to model the behavior of these two protocols analytically and carry the improvement performance by using two omni-directional control packets. We suggested that using these two packets and Adaptive Array Antennas in the above protocols will make them applicable in mobile environment and as well as improve routing performance.

This paper concentrates on double weight code family as a proposed code for the optical spectrum code division multiple access (OSCDMA) which has one cross correlation value. By eliminating the intersection columns of this code, the cross correlation value will be zero instead of one. This new derived code is called zero cross-correlation code (ZCC) (S. Amar et al., 2006). In ZCC code, the performance is expected to be better than MDW code because it offers low cross correlation value. It is easy to distinguish the desired signal from the interfering signal if the cross correlation value is low. Besides, a general new equation is obtained for code which has zero cross correlation value instead of basic matrix and mapping technique which are used in modified double weight code to obtain a specific code word.

In this paper, we consider the potential use of adaptive arrays to improve the performance of multihop-RTS MAC protocol. In addition to this, we proposed to improve the performance of this MAC protocol by using two omni-directional control packets. These control packets are busy node list (BNL) and overall link state table (OLST). The performance of the protocol is evaluated and compared with existing MMAC that uses switched-beam antenna and IEEE 802.11. The results show that MMAC can produce improvement in throughput when using adaptive arrays and the two omnidirectional control packets.

Multiple access interference (MAI) is a primary concern in optical coded division multiple access (OCDMA). To alleviate this issue, first cancellation stage of an optical serial interference cancellation (O-SIC) can be employed. In this paper, we investigate the effect of optical serial interference cancellation for the first cancellation stage on bit error rate (BER). We compare the first cancellation stage with the conventional correlation method by utilizing different threshold values with the various length and different number of users. We have successfully shown that the optical serial interference cancellation yields a better performance than the conventional correlation method by choosing the optimum value in the first cancellation stage. We provide the results of computer simulations showing the BER improvement when the first cancellation stage of optical serial interference cancellation (OP- SIC) is used over the cancellation technique. The comparisons are done for several numbers of users.

This paper presents the study of a receiver device for the optical code division multiple access (OCDMA) called the optical parallel interference cancellation (Opt-PIC). The performance of OCDMA system is known to be easily influenced by the multiple access interference (MAI) caused by other simultaneous users. To overcome this problem, there is a strong demand for the design of new detection scheme that will be efficient enough to improve the performance of the OCDMA system, while minimizing the effects of the MAI. In this paper, some studies have been conducted on the Opt-PIC specifically for the lowest threshold value. Studies have been carried out not only using the conventional method but also using a hard limiter. The results are compared to the previous techniques used to mitigate the effect of MAI.

The need for high speed networks has motivated the telecommunication community to investigate the potential of optical code division multiple access (OCDMA) in local area networks. However, multiple access interference (MAI), which increases with the number of simultaneous users, severely limits the capacity of the system. Optical parallel interference cancellation (OPIC) has been used to reduce the effect of MAI. The drawback of OPIC is that, it increases the demand for hardware complexity, resulting into higher processing time and cost. To overcome these difficulties, an efficient method is presented in this paper called, one stage optical parallel interference cancellation (OS-OPIC) which is based mainly on OPIC. Performance analysis of the proposed design is done using optical orthogonal code (OOC) as signature sequence and new expression for error probability is demonstrated. It is shown that, the proposed method is effective to reduce the hardware complexity, processing time and cost while maintaining the same bit error probability at the cost of increasing threshold value

Multiple Access Interference (MAI) is the major reason for the system degradation in the Optical Code Division Multiple Access (OCDMA). MAI increases with the number of simultaneous users, resulting in deterioration in the performance and limits the maximum number of simultaneous users. Optical Hard Limiter (OHL) is known to improve the performance of the conventional OCDMA system. However, in the present of other sources of noise, the improvement is not considerable. Moreover, the need for dynamic threshold value in the conventional OCDMA receiver to recover the data is very demanding requirement particularly in the high speed LANs. To overcome these limitations, some studies have been conducted on the Optical Parallel Interference Cancellation (OPIC) through this paper. OHL is placed in front of the receiver side to mitigate the effect of MAI. The study focuses on the lowest threshold value i.e. Th=1. The results are compared to the conventional OCDMA and it shows that, OHL is effective to reduce the power of MAI and a better performance can be obtained by selecting the smallest threshold value.

In this paper the double weight code (DW) family which is used as a proposed code in optical spectral code division multiple access system (OSCDMA) has been studied using the modified double weight code (MDW) which has across correlation value equals to one. By eliminating the intersection columns of this code we can reduce the cross correlation value from one to zero. This code is named zero cross-correlation code (ZCC) . Therefore, the multiple access interference (MAI) can be reduced. Also, a general equation is used to generate the basic matrix of the code with the cross correlation equal zero instead of that in the existing construction technique. In this paper, we also show the advantages of this equation. All of these studies concentrate on the basic matrix of modified double weight code with zero cross correlation value.

Wireless Sensor Networks (WSNs) are vulnerable to clone attacks or node replication attacks as they are deployed in hostile and unattended environments where they are deprived of physical protection, lacking physical tamper-resistance of sensor nodes. As a result, an adversary can easily capture and compromise sensor nodes and after replicating them, he inserts arbitrary number of clones/replicas into the network. If these clones are not efficiently detected, an adversary can be further capable to mount a wide variety of internal attacks which can emasculate the various protocols and sensor applications. Several solutions have been proposed in the literature to address the crucial problem of clone detection, which are not satisfactory as they suffer from some serious drawbacks. In this paper we propose a novel distributed solution called Random Walk with Network Division (RWND) for the detection of node replication attack in static WSNs which is based on claimer-reporter-witness framework and combines a simple random walk with network division. RWND detects clone(s) by following a claimer-reporter-witness framework and a random walk is employed within each area for the selection of witness nodes. Splitting the network into levels and areas makes clone detection more efficient and the high security of witness nodes is ensured with moderate communication and memory overheads. Our simulation results show that RWND outperforms the existing witness node based strategies with moderate communication and memory overheads.

This paper handles the Double Weight (DW) Code family, one of the proposed codes used in Spectral-Amplitude-Coding Optical Code Division Multiple Access (OCDMA). The DW code family is constructed using a matrix technique which produces the whole basic code matrix in order to get a specified codeword. An additional mapping technique is used to increase the number of users. Both techniques add more complication to the code construction. A general equation is derived and analyzed in order to compare with the conventional method. Detailed examples are given on how to generate codes using a general equation. We also show in this paper the advantages of this formula compared to the existing construction technique. This newly designed technique allows us to use an equation-based constructing method to build any specified codeword for the DW code family.