Earticle

The drawbacks of high peak to average power ratio (PAPR) can outweigh all the potential benefits of Orthogonal Frequency Division Multiplexing (OFDM) signals. In this Paper, a sophisticated PAPR reduction technique, named Iterative Clipping and filtering (ICF) with DCT/IDCT transformation, is proposed for OFDM system. By considering the example of OFDM, with Quadrature Phase-Shift Keying (QPSK) mapping, simulation results under Matlab environment show that the new proposed method performs well in reducing PAPR.

Future Heterogeneous Network (HetNet) will foster interoperability to achieve seamless multimedia services. To exploit the ubiquitous diversity across HetNet, Mobile Nodes (MNs) will prefer to perform Vertical Handover (VHO) for better guaranteed Quality of Experience (QoE) and optimal resource utilization. To perform VHO, the radio frequency part of the emerging wireless standards needs to accurately estimate the channel for network selection. Further in HetNet, MNs may perform VHO in group (in bus/ train) where HetNet utility increases abruptly due to simultaneous VHO requests and severely degrades the HetNet performance. Therefore, paper proposes a proactive group VHO model, whose network discovery is based on error vector magnitude (EVM) measurement which can be mobile or network controlled for optimal network selection (new attachment node). Proposed model is compared with probabilistic and non-cooperative selection schemes. Performance is evaluated in terms of link availability, packet loss rate, transmission delay, resource utilization to achieve overall optimal load balance.

The concept of caching is a fundamental feature in modern computing architectures and, has no doubt, found wide applications in diverse areas. Performance evaluation of systems is functionally related to how caching is implemented on a given computing platform, a metric influenced by the cache replacement policy. This paper describes an online learning-induced, self-adjusting cache management strategy with low overhead and scan-resistant characteristics that outperforms the LRU replacement algorithm using adaptation to balance between workload frequency and recency patterns.

Cooperative communication is a promising technique for combating the effects of channel fading by exploiting diversity gain achieved via node cooperation. However, how to apply it into sensor networks in a feasible and efficient manner still remains as a problem. To address the issue, this paper proposes a new adaptive transmission scheme, which adaptively adjusts transmission mode between direct communication and cooperative communication for node pairs to achieve energy efficiency in wireless sensor networks. The scheme is implemented by a simple yet effective cross-layer design between the network and MAC layers. Extensive simulation results are presented to illuminate the distinguished performance of the proposed scheme.

Acoustic analysis is a proper method in vocal fold pathology diagnosis so that it can complement and in some cases replace the other invasive, based on direct vocal fold observation, methods. There are different approaches and algorithms for vocal fold pathology diagnosis. These algorithms usually have three stages which are Feature Extraction, Feature Reduction and Classification. While the third stage implies a choice of a variety of machine learning methods (Support Vector Machines, Artificial Neural Networks, etc), the first and second stages play a critical role in performance and accuracy of the classification system. In this paper we present initial study of feature extraction and feature reduction in the task of vocal fold pathology diagnosis. A new type of feature vector, based on wavelet packet decomposition and Mel-Frequency-Cepstral-Coefficients (MFCCs), is proposed. Also a new SVM-Based method for feature reduction stage is proposed and compared with conventional methods such as Principal Component Analysis (PCA). Support vector machine is used as a classifier for evaluating the performance of the proposed method. The results show the priority of the proposed method in comparison with current methods.

The huge increase of the MIMO (multiple input multiple output) capacity required perfect channel knowledge at the receiver. In this paper, we analyze the effect of imperfect channel estimation error on MIMO systems’ BER performance. By utilizing whitening-rotation (WR) algorithm for recovering the detected signal at the receiver and calculating channel coefficients, it can be proved that semi-blind channel estimation obtains better results in comparison with blind ones. In addition, we also analyze symbol error rate (SER) of MIMO systems in such estimation schemes.

Satellite network is the essential part of the future generation of hybrid communication networks. Considering the surging demands for multimedia traffic across the globe, the dynamic time-varying topology of low earth orbit (LEO) satellite network and the flaws of existing QoS (Quality of Service) routing algorithms, a novel QoS routing algorithm applying multi-agent system (MAQR) for LEO satellite network is proposed in this paper. The algorithm design three types of mobile agents: node management agent (NMA), active perception agent (APA) and executive agent (EA). NMA adaptively perceives external environment and deals with traffic request and controls routing. APA is responsible for collecting information of non-local satellite nodes and links. EA is in charge of path maintenance and update. MAQR algorithm introduces link duration into a cost function and then minimizes the cost function to find optimum paths that simultaneously satisfy delay and bandwidth constrains. Besides, when current QoS path is deteriorated, new QoS path can be discovered without rerouting. Simulation results show that MAQR algorithm not only has lower call blocking probability and handover call dropping probability, but takes both routing efficiency and algorithm overhead into account as well.

Clustering is an efficient method adopted in various routing algorithms for wireless sensor networks. In this paper, we propose a Density-based Energy-efficient Clustering Algorithm (DECA). In DECA, we define the density of each node and regard it as an important evaluation metric. Together with nodes' residual energy under consideration, each cluster head is selected based on the density of nodes. We design an intra-cluster algorithm as well as a multi-hop inter-cluster routing algorithm. Moreover, we discuss the optimal number of clusters. Simulation results show that cluster heads are evenly distributed and our proposed routing algorithm do consume much less energy than some existed algorithms. The network lifetime is also largely prolonged.

Worldwide Interoperability for Microwave Access (WiMAX) is one of the next generation broadband wireless access technologies. The WiMAX features longer transmission distance and more accomplished support of Quality of Service (QoS) than other wireless access technologies such as IEEE 802.11. Specifically, QoS has become an important role in the context of a variety of applications which utilize network resources. Radio Resource Management (RRM) always plays important role in providing the QoS guarantees. In WiMAX, Medium Access Control (MAC) protocol defines a wide variety of mechanisms for bandwidth allocation and QoS provision. Although different types of QoS classes have been defined by WiMAX, the scheduling architecture is left to be vendor specific. Numerous QoS schemes in WiMAX have proposed for real-time services, but few novel QoS schemes are designed for non-real-time services due to their lower strict priority. In this paper, we propose a QoS scheme based on Modified Deficit Round Robin (MDRR) of packet scheduling and Call Admission Control (CAC) with the channel condition for non-real-time service. Simulation results illustrate the proposed scheme can increase the throughput and decrease the packet loss rate in non-real-time service significantly.

Communication Protocols are specified by using either formal or graphical notations. For this purpose, Specification and Description Language (SDL) is a formal language used extensively in telecommunication for development of software and hardware. Its diagrammatic version with complementary Message Sequence Chart (MSC) diagrams provides a description of system communication in the form of message flows. Still, the resultant diagrams are fragmented and lack continuity in depicting the succession of events. This paper proposes a model that can serve as a base for protocol specification. The aim is to introduce a conceptual and complete description of basic streams of flow among entities in order to identify rules of data transfer. The resultant specification is a map over which a protocol can be superimposed.

The security issues are more complex and challenging in Mobile Ad hoc Networks (MANETs) than other conventional wireless networks due to peer to peer behavior of the participating nodes, absence of centralized routers and routing through intermediate nodes. For successful communication between a pair of source and destination it is vital that the intermediate nodes be trustworthy and don’t drop packets. Nodes in an ad hoc network may not be trustworthy either due to selfishness created by power loss or due to maliciousness relating to rogue intentions. A node that was earlier trust worthy may no longer be so at later stages due to loss of power making the continuous dynamic evaluation of trust a necessity. Also the security requirements may vary as per the conditions on the scenario. This paper proposes an intelligent protocol that takes care of both selfishness and maliciousness by evaluating the trust dynamically. The protocol is able to adjust the trust level requirement as per the demand of the situation and can work in various levels of insecure environments. With the help of exhaustive simulations, the performance of this protocol has been demonstrated and compared with the normal AODV protocol in standard lab environment.