A. K. Jaiswal

Chiari I malformation associated with atlanto-axial dislocation: focussing on the anterior cervico-medullary compression.

SummaryBackground. Chiari I malformation with atlantoaxial dislocation may cause both posterior and anterior cervicomedullary compression. We studied the clinicoradiological features and surgical outcome in patients having Chiari I malformation with atlantoaxial dislocation.Method. Thirty-nine patients with Chiari I malformation with atlanto-axial dislocation underwent preoperative and follow-up neurological status assessment. In Chiari I malformation with reducible atlanto-axial dislocation (n = 11), a direct posterior stabilization was done. In Chiari I malformation with irreducible atlanto-axial dislocation (n = 28), a single stage transoral decompression with posterior stabilization and/or posterior decompression and duraplasty were done in 18 patients. In 10 patients, only posterior decompression and/or posterior stabilization was performed. Seven among the latter patients subsequently deteriorated and required transoral decompression. Comparison of mean neurological status scores of patients with Chiari I malformation with irreducible atlanto-axial dislocation who underwent single stage transoral decompression with posterior stabilization versus the posterior procedure alone was done using T-test and proportional significance also calculated.Findings. Patients with Chiari I malformation with atlanto-axial dislocation have a high incidence of long tract signs and sphincteric disturbances with a decrease in the mean foramen magnum diameter. The mean neurological status scores of patients with Chiari I malformation with irreducible atlanto-axial dislocation who underwent single stage transoral decompression with posterior stabilization were significantly better than those patients who underwent the posterior procedure alone. The latter patients also showed significant clinical improvement following transoral decompression. In the presence of Chiari I malformation with reducible atlanto-axial dislocation, reduction and stabilization of atlanto-axial dislocation resulted in neurological improvement. The follow up neurological status scores of these patients improved after surgical intervention even in the presence of poor preoperative grades.Conclusions. Patients with Chiari I malformation should be investigated for the presence of atlanto-axial dislocation. In case atlantoaxial dislocation coexists, priority must be given to relieving anterior cervicomedullary compression.

Performance Analysis of Dispersion Compensation in Long Haul Optical Fiber with DCF

In this paper, We investigate post, pre and symmetrical/mix dispersion compensation methods for 40 Gb/s non-return to zero link using standard and dispersion compensated fiber through FBG compensator to optimize high data rate optical transmission. The influence of dispersion of FBG compensator and increases in the power of CW laser has been studied to evaluate the performance of optical communication systems. The simulation model of the WDM based on the Optisystem 11.0 is presented according to the above principle. The simulation results are validated by analysing the Q-factor and Bit error rate (BER) in the numerical simulator. It is found that post compensation performance is best and the input fiber power is taken as 5-10dB, the corresponding BER performance is better. Keywords - BER, Dispersion compensation, Q-factor, WDM.

Design and Performance Analysis of Radio over Fiber System Incorporating Differential Phase Shift Keying Modulation in High Speed Transmission System

The fast growth of mobile-cellular telephone subscribers and mobile or fixed broadband internet users has triggered a traffic explosion and raised the demands for high broadband capacity and wide coverage network. Radio over fiber is an integration of wireless and fiber optic networks that provides untethered access to broadband wireless communications in a range of applications including last mile solutions, extension of existing radio coverage and capacity, and back haul.In this paper ,after investigating the variations in Q factor , BER and eye opening with respect to the wavelength, bit rate and fiber length we have compared DPSK,MSK,CPFSK and OQPSK modulation techniques used in RoF system for a bit rate in Gbps.

Analysis of energy model and Performance of IEEE 802.15.4 WSNs under Different Duty Cycle

IEEE 802.15.4 is an emerging communication protocol for low rate-wireless personal network (LR- WPAN) which has gained importance in last few years, in practical and research field. Nowadays Zigbee used in many applications such as home automation, industrial, and medical system etc. The low rate WPANs provide low power consumption, low cost and small range wireless networking. Zigbee uses IEEE 802.15.4 as its communication protocol for medium access control (MAC) layer and physical (PHY) layer. Since in WSNs, nodes are powered by limited capacity of batteries and densely deployed in any geographic region to perform sensing. So that energy efficient operation and better QoS are always desired in WSNs. In this paper, we have focused on two energy model i.e. Mica mote and mica z and beacon enable mode operation of IEEE802.15.4 with different duty cycle under different traffic load. The duty cycle operation achieve by setting two system parameters, macBeaconOrder (BO) and macSuperframeorder (SO). This paper, comparatively analyzed the energy model and performance of IEEE 802.15.4 with different percentage of duty cycle on the basis of energy consumption and QoS parameter. The matrices used in performance evaluation are packet loss rate (PLR), average end to end delay, throughput, residual battery capacity and energy consumption using Qualnet 6.1 simulator. Keywords -WSN, IEEE 802.15.4, Bacon order (BO), Super frame order (SO), Duty Cycle, CBR traffic, and Qualnet 6.1.

QOS Analysis in IEEE 802. 15. 4 and Impact of Flag Mobility on Network Performance in WSN

Wireless Sensor Network (WSN) consists of large number of sensor nodes that are capable of communication, computation and sensing. Inherent limitations of WSN include limited storage, processing and transmission power. As compared to other network topologies, WSN has less communication Protocols mainly Zigbee/IEEE 802.15.4. IEEE 802.15.4 is a new standard, uniquely designed for low rate Wireless Personal Area Network (LR-WPAN), which is developed for applications that demand low throughput. IEEE 802.15.4 was designed for short range, low power, low complexity, low rate and low cost wireless network which provides two way wireless communication technology. For the analysis purpose, we have considered AODV as the Adhoc-routing protocol. Simulation has been carried out by using Qualnet Simulator 6.1. In this paper, we proposed a mobility control scheme and the impact of mobility over the performance of WSN is seen. In this paper, we have designed two scenarios, one is used with Random waypoint Mobility and the other is used by Mobility with Flag. Results of both the mobility schemes are compared to find out which mobility scheme gives overall best services. This paper provides the performance evaluation of quality of service parameters such as total packets received, received throughput, average end to end delay, average jitter and energy consumption as the performance metrics.

To Evaluate the Performance of IEEE 802. 16 Routing Protocols using Qualnet 6. 1 Simulator

Wireless networking has become an important area of research in academic and industry. Worldwide Interoperability for Microwave Access (WiMAX) is one of the most efficient and well known area based networking system that provide fixed, and more newly, mobile broadband connectivity between fixed and mobile network access in a define coverage areas. It provides the same subscriber experience for fixed and mobile user. The main aspect of WiMAX is large coverage areas with high data rate than other wireless networks. This network is easily deployable and guaranteed Quality of service. In this paper, we have investigated different routing protocols and evaluated their performances on 802.16 WiMAX networks and provided performance comparison of routing protocols such as AODV, OLSR, ZRP and RIP based on the parameters including average throughput, average jitter and average End-to-End delay by using Qualnet 6.1simulators.We also tried to improve the performance of WiMAX by analysing the network with and without mobility.

Performance Evaluation of FSR, LAR1 and ZRP Routing Protocols in MANET based on RWP Mobility Model

Mobile Ad Hoc Networks (MANETs) are self-configuring, infrastructure-less wireless ad hoc networks. It has a routable networking environment on top of the Link Layer ad hoc network. Routing is based on multi-hop pattern from source to a destination node/ nodes. Routing protocols for MANETs have to face the challenges of frequently & arbitrarily changing topology, low transmission power and asymmetric links. In this paper different routing protocols, namely FSR, LAR1 & ZRP, are comparatively discussed on the basis of Average End to end delay, Received Through-put and Average Jitter. An outline of these protocols has been presented in this paper by comparing their functionality, benefits, characteristics, limitations and analysis. RWP (random waypoint) mobility model has been used and simulations are performed using QualNet 6.1 version Simulator from Scalable Networks.

Security Based Performance Analysis in Optical CDMA Network Systems

OCDMA) is an alternative method, which performs encoding and decoding through an optical signature code, in order to allow the selection of a desired signal so that different users can share the same bandwidth. In such a systems, data signal overlap both in time and wavelength. Tradeoffs between security and performance in optical CDMA are presented. Confidentiality against eavesdropper interception strategies for optical CDMA is considered. Coherent detection and combining signals shows better confidentiality than the incoherent one. Spectral amplitude optical CDMA based on Modified Double Weight (MDW) systems, with different code dimension, is investigated. Increasing the network system capacity or maximizing authorized specified SNRs will lead to eavesdropper to detect high SNRs.

Performance Analysis of Radio over Fiber System with Ook Based Dwdm for Fiber to Home Network

In the recent trends in optical communication to overcome one of the major problems in the new generation of radio over fiber networks that requires being concentrated, is decreasing the quantity of bit error rate in the lowest power penalty. This paper also evaluates the results of down-link 5 Gbps OOK signal of five radio base stations over 60 km dense wavelength division multiplexing single mode fiber. The BER performance of our scheme shows that our scheme is a practical solution to meet the data rate and cost-efficient of the optical links simultaneously in tomorrows ROF access networks. This amount of bit error rate can be supposed as a negligible value in the performance of radio over fiber system for multimedia and real time applications.

MEACSRA: Mobility and energy-aware cross-layer searching routing algorithm for wireless sensor network

WSNs with randomly deployed nodes, to reduce energy consumption while ensuring the connectivity and power of entire network is an important issue of research. A mobility and energy-aware cross-layer searching routing algorithm works in stationary and mobile scenario with the satisfactory performance in addition to mobility handling, provides route to nodes which forward data between each other directly in a single hop, or indirectly through multiple hops via neighbouring nodes and considers the channel assessing mechanism as well. This algorithm performs better in both CFP and CAP. Markov model analysis shows the state of each step. Cross-layer design considering MAC and PHY layer yields better performance. Simulated result shows energy consumption is efficient in both stationary and mobile scenario for larger scale network.