Vol. 70, n° 5-6, May-June 2015
Content available on Springerlink
DWT-IDWT-based MB-OFDM UWB with digital down converter and digital up converter for power line communication in the frequency band of 50 to 578 MHz
Abstract Over the last few years, power line communication (PLC) has gained importance for high-speed data communication. One of the major concerns in PLC is noise and high data rate, thus, several schemes have been adopted to minimize noise over PLCs and improve data rate. One of the promising approaches is the use of multi band (MB)–orthogonal frequency division multiplexing (OFDM) ultra wideband (UWB) to achieve date rates over 200 Mbps. One of the approaches is to integrate MB-OFDM UWB with digital down converter (DDC) for power line communication. A modified discrete wavelet transform (DWT) architecture with reduced memory, two-stage DDC, and modified DDS blocks are designed to generate MB-OFDM signal for PLC. From the results obtained, it is found that DWT-based MB-OFDM UWB outperformed FFT-based MB-OFDM UWB by approximately 6-dB gain in bit error rate (BER). Haar wavelet showed best performance over Biorthogonal (bior3.3, bior5.5), Daubechies (db2, db4), and reverse Biorthogonal (rbior3.3, rbior5.5) by approximately 2 dB. Though QPSK yielded better BER through observations, it is used for a constant power output transmitter, while QAM works better for a linear transmitter.
Keywords MB-OFDM – UWB – PLC – Integrated system – Down converter – High data rate
Joint cumulant estimate correction and decision for cooperative modulation classification by using multiple sensors
Goran B. Markovic and Miroslav L. Dukic
University of Belgrade, Serbia
Abstract In this paper, several data fusion and soft decision fusion methods are proposed for cooperative automatic modulation classification (AMC) by using multiple sensors. A well-known AMC using fourth-order cumulant is considered. Also, a novel joint cumulant estimate correction is proposed. The AMC performance of proposed fusion methods with and without joint estimate correction is evaluated through the extensive Monte Carlo trials for different multipath fading channels, sensor spatial distributions, and application scenarios, and compared to those of the existing methods. Numerical results have confirmed huge performance improvement achievable with here proposed methods, especially in the non-idealized application scenarios.
Keywords Modulation classification – Cognitive radio (CR) – Higher-order cumulants – Wireless sensor networks (WSN)
A maximally radio-disjoint geographic multipath routing protocol for MANET
(2) Nanjing University of Science and Technology, People’s Republic of China
Abstract Multipath routing has been considered as one of the most efficient and reliable real-time routing solutions for high-rate streaming in mobile ad hoc networks. Many researches focused on how to construct multiple node-disjoint paths but ignored the interference of using multiple paths simultaneously. In fact, some nodes in the network located in other active paths may interfere with their own communications that degrades the effective throughput. This paper presents a maximally radio-disjoint geographic multipath routing protocol (RD-GMR) which is capable of maximally avoiding the interference among the multiple paths. The forwarding area between the source node and the destination node is divided into three areas and different forwarding strategies are adopted in the corresponding areas. These customized strategies for each area effectively reduce the interferences between each path. Furthermore, the proposed protocol estimates the interference radius of nodes by using the distance between two nodes that increases the accuracy of obtaining the interference range of paths. Simulation results show that the RD-GMR can construct multiple paths with minimum interference that improves the packet delivery rate and the network throughput. Moreover, the end-to-end delay is also reduced.
Joint distributions for total lengths of shortest-path trees in telecommunication networks
Keywords Shortest-path tree – Palm calculus – Parametric copula – Tree length – Network planning – Pseudo-maximum-likelihood – Stochastic geometry
A d-dimensional irregular compact interleaver design for turbo code
Abstract Our paper presents a new irregular interleaver design based on the sphere bound (upper bound of the maximum spread value) of a d-dimensional turbo code; in addition, a new normalized dispersion measurement definition for random and irregular interleavers is proposed. The estimation of the normalized dispersion that is used to be chosen by intuitive guess then verified experimentally with heavy simulations can now be estimated directly using analytical formulas developed by our method. Furthermore, we have found a new characteristic parameter that we named “interleaver dimension” that simplify the analysis and the conception of interleaver structures starting from any desired value of normalized dispersion. The dimension parameter is the main variable in our proposed experimental formula giving the normalized width parameter of the d-dimensional irregular compact interleaver (DIC).
A user-centric game selection model based on user preferences for the selection of the best heterogeneous wireless network
Abstract Next-generation wireless networks offer Internet connection through various technologies anytime and anywhere. The selection of an optimal technology from these available technologies is essential to guarantee user mobility and service continuity in a heterogeneous wireless environment. This paper proposes a new network selection model which is based on the integration of simple additive weighting (SAW) method in the framework of trading market non-cooperative game theory and the analytic hierarchy process (AHP) method was utilized to estimate the weights of the parameters that affect the network selection process. The proposed solution enables the mobile user to negotiate with competing networks by providing the user preference to be considered for the network selection process. The proposed solution is analyzed and tested through simulations. The results show the efficiency of proposed method which is able to optimize the user’s satisfaction.
Keywords Heterogeneous wireless networks – Network selection – Game theory – Simple additive weighting – Analytic hierarchy process – User preferences
Availability analysis of shared backup path protection under multiple-link failure scenario in WDM networks
Abstract Dedicated protection and shared protection are the main protection schemes in optical wavelength division multiplexing (WDM) networks. Shared protection techniques surpass the dedicated protection techniques by providing the same level of availability as dedicated protection with reduced spare capacity. Satisfying the service availability levels defined by the user’s service-level agreement (SLA) in a cost-effective and resource-efficient way is a major challenge for networks operators. Hence, evaluating the availability of the shared protection scheme has a great interest. We recently developed an analytical model to estimate network availability of a WDM network with shared-link connections under multiple link-failures. However, this model requires the information of all possible combinations of the unshared protection paths, which is somehow troublesome. In this paper, we propose a more practical analytical model for evaluating the availability of a WDM network with shared-link connections under multiple link-failures. The proposed model requires only an estimate of the set of shared paths of each protection path. The estimated availability of the proposed model accurately matched with that of the previous model. Finally, we compare the previous model with the proposed model to demonstrate the merits and demerits of both models illustrating the threshold at which each model performs better based on the computational complexity. The proposed model significantly contributes to the related areas by providing network operators with a practical tool to evaluate quantitatively the system-availability and, thus, the expected survivability degree of WDM optical networks with shared connections under multiple-link failures.
Keywords WDM networks – Multiple link-failures – Shared-link connections – Availability analysis
WLAN planning: Separate and joint optimization of both access point placement and channel assignment
Abstract In this paper, we are interested to the problem of designing wireless local networks (WLANs), which involves deciding where to install the access points (APs), and assigning frequency channels to them with the aim to cover the service area and to guarantee enough capacity to users. Our proposal provides different solutions to the problems related to the WLAN design and can be divided into two main parts. In the first part, we focus on the problem of designing a WLAN by treating separately the AP positioning and the channel assignment problems. For AP positioning issue, we formulate it as a set covering problem. Since the computation complexity limits the exact solution, we propose two heuristics to offer efficient solution. While, for the channel assignment, we define this issue as a minimum interference frequency assignment problem and propose three heuristics. Two heuristics aim to minimize the interference at AP locations. Whereas, the objective of the third heuristic is to minimize the interference at the TPs level. In the second part, we treat jointly the two aforementioned issues based on the concept of virtual forces. In this case, we start from an initial solution provided by the separated approach and try to enhance it by adjusting the APs’ positions and reassigning their operating frequencies. In each part of this work, we start first by describing the problem, then presenting the algorithms proposed to resolve it efficiently and finally we illustrate the obtained results and analyze them.
Keywords WLAN planning – Channel assignment – Set covering problem – Clustering Virtual forces – Heuristics – Graph coloring