Handover Management In Mobile Satellite Communications

Mobile satellite communication offers vast coverage area with moderate bandwidth demands. However, in mobile satellite communication using Low Earth Orbits (LEO) satellite service, handover frequently occurs due to high velocity and large number of mobile satellites. With increase demand of multimedia traffic, an optimum utilization of network resources has been investigated. To accommodate and maintain Quality of Service (QoS) of handover calls in mobile satellite communication, priority for handover calls are applied. Traffic parameters of traffic arrival rate, traffic duration and priority among traffic applications are introduced. Traffic applications of type voice, video and data are observed and analysis of traffic behavior on handover has been done. An optimum set of channels to serve the different traffic types is proposed after considering the handover initiation and handover execution criteria. The algorithm proposes a more accurate measurement of handover initiation angle, introduced as look-up angle, which further reduces handover rate and successfully conserve the network resources

A New Super Wideband Fractal Monopole-Dielectric Resonator Antenna.

The small physical size and multiband capability are significant in the design of ultrawideband (UWB) antennas. Fractal geometry provides a good method for achieving the desired miniaturization and multiband performances. Furthermore, using a dielectric resonator improves bandwidth and radiation characteristics. A combination of these methods in the UWB antenna design is presented. The proposed design is a new hybrid dielectric resonator antenna (DRA) excited by a new fractal monopole antenna. The simulation and optimization have been carried out using Ansoft HFSS. The simulation and measurement results show that the proposed structure provides a huge bandwidth ranging from 2 to 40 GHz. Radiation patterns and gains show a good agreement over the bandwidth

Danger theory based node replication attacks detection in mobile wireless sensor network

Mobile wireless sensor networks (MWSNs) are commonly deployed in a harsh climate, notably unattended without any tamper-resistant tools; thereby an attacker can easily capture the sensor nodes in a very limited time. Once captured, the attacker can duplicate the sensor and subsequently deploys numerous clone nodes into the network in minimum time duration. This new breed of attack is called node replication attack, and while several solutions have been proposed to address such a security threat, they are mainly centralized and somewhat limited to static WSN. In this paper, we propose a hybrid (centralized and distributed) node replication attack detection method for MWSN, which operates based on Danger Theory in human immune system. As depicted in Danger Theory, the proposed method consists of two main security approaches, namely attack detection and security control. These approaches perform a multi-level detection, which is not only responsible to identify but also to verify the existence of clone nodes in the network. Performance evaluation demonstrates the efficiency (in terms of true and false positives) of the proposed detection method in detecting clone nodes in MWSN environment

Integrated adaptive approach for reliable multicast transmission over geostationary satellite networks

Multiple retransmission passes, in order to ensure bit-perfect reliability in multicast transmission, results in lower resource utilization and higher session delay. Hence, an integrated adaptive transmission via the use of a cross-layer strategy is proposed in this paper in order to increase forward and return link resource utilization. Specifically, the integration of Channel State Information (CSI) collection policies in the uplink and Channel-Aware Scheduling (CAS) in the downlink is proposed in the face of fluctuating channel conditions observed by multicast terminals. The integration approach can be mathematically represented by suppression error due to the way CSI is collected and suppressed in the return link. Particularly, the suppression error occurs since only a subset of users update their CSI values at any CSI collection instant. In relation to the analytical representation of the suppression error, the performance parameters are then verified via simulation results. From the comparison, it was found that the simulation and analytical results approach agreement at large numbers of terminals. This observation suits the multicast transmission over satellite networks which expect large numbers of terminals over wide coverage

Gain Enhancement of Octagon Microstrip Yagi Antenna Utilizing 1-D Photonic Crystal (PCs) Cover

A high gain Octagon Microstrip Yagi Antenna (OMYA) for Worldwide Interoperability for Microwave Access (WiMAX) application at unlicensed frequency of 5.8 GHz is presented in this paper. The proposed antenna was simulated and optimized using full-wave EM simulator. The simulated results show that the gain of the proposed antenna at frequency of 5.8 GHz is 13.45 dB with S11 of -32.57 dB. Hence, an extra gain of about 5.47 dB can be obtained through this design

Enhanced handover mechanism in long term evolution (LTE) networks

Over the past decade, there have been great interests in cellular and fixed radio access technologies for providing mobile, nomadic and fixed telecommunication services. The fast pace development of this technology and the challenges it presents due to the increasing number of user equipments and the demand to have the service on-the-go, have presented new challenges on base stations capability and the handover (HO) techniques. To address these challenges intensive researches are being carried out to define algorithms that can handle the HO decisions based on user equipment (UE) requirements and quality of service (QoS) expectations. This paper investigates the improvement steps for HO mechanisms in long term evolution (LTE) system which is being formally submitted as a candidate 4G system. LTE network is expected to support mobility with speeds of up to 500 km/h, when the HO will then become more frequent and fast. The basis of the approach is to reduce the number of unnecessary HOs. The strengths and weaknesses for each algorithm are discussed, and conclusions are subsequently made

Energy trust system for detecting sybil attack in clustered wireless sensor networks

Wireless Sensor Network (WSN) is an emerging technology that offers great promise for various applications. The sensing capabilities combined with relatively small processing power and wireless communication makes it one of the main technologies to be exploited in the future. Despite its attractive features, WSN is vulnerable to various security attacks. The constraints of WSN such as limited energy and memory make the security problem even more critical. One of the security issues of WSN is it is susceptible to sybil attack. In this attack, the adversary forges multiple entities to disrupt the entire network. This paper addresses the problem by developing a lightweight trust system using energy as a metric parameter for a hierarchical WSN. The performance evaluation of this system shows efficiency and scalability for detecting sybil attacks in terms of true and false positive detection in a heterogeneous WSN. Furthermore, this system reduces the communication overhead in the network by cancelling feedback and recommendations among sensor nodes (SNs)

A forwarding strategy for DWSIGF routing protocol

Routing protocols in Wireless Sensor Network (WSN) are responsible for propagating and coordinating of information transfer from one end of the network to the other. Dynamic Window Secured Implicit Geographic Forwarding (DWSIGF) is a robust, cross layer, security bound routing protocol that propagates information in a multi-hop network using the greedy and random forwarding strategies. These strategies are known for their poor resistivity to interference and erratic behavior in path selection. In this paper, we propose a forwarding strategy that uses an optimal distance to mitigate these problems. The optimal distance is computed based on the path loss coefficient and energy dissipated in the hardware (sensor). Extensive simulations have been conducted to evaluate the performance of the proposed approach. The results illustrate that the proposed approach performs better than the compared strategies in terms of packet delivery ratio and energy consumption

Efficient back-off mechanism for IEEE802.15.4 wireless sensor networks

IEEE 802.15.4 is one of the most prominent MAC protocol standard designed to achieve low-power and low-rate wireless personal area networks. The contention access period of IEEE 802.15.4 employs carrier sense multiple access with collision avoidance (CSMA/CA) algorithm. A long random backoff time causes longer average delay, while a small one gives a high collision rate. In this book, we propose an efficient backoff algorithm, called EBA-15.4MAC that enhances the performance of slotted CSMA/CA algorithm. EBA-15.4MAC is designed based on two new techniques; firstly, it updates the contention window size based on the probability of collision parameter. Secondly, EBA-15.4MAC resolves the problem of access collision via the deployment of a novel Temporary Backoff (TB) and Next Temporary Backoff (NTB). In this case, the nodes not choose backoff exponent randomly as mentioned in the standard but they select TB and NTB values which can be (10–50)% of the actual backoff delay selected by the node randomly. By using these two new methods, EBA-15.4MAC minimizes the level of collision since the probability of two nodes selecting the same backoff period will be low