REV Journal on Electronics and Communications
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Performance Analysis of AntNet-LA Protocol for Ad-hoc Networks based on Disaster Area Mobility Model
Get PDFAvailability of cheap positioning instruments like GPS receivers makes it possible for routing algorithms to use the position of nodes in an ad hoc mobile network. Regular position based routing algorithms fail to find a route from a source to a destination in some cases when the network contains nodes with irregular transmission ranges or they find a route that is much longer than the shortest path. On the other hand routing algorithms based on Ant Colony Optimization (ACO) find routing paths that are close to the shortest paths even if the nodes in the network have different transmission ranges. The drawback of these algorithms is the large number of messages that needs to be sent or the long delay before the routes are established. In this paper, we propose a novel protocol AntNet-LA which combines the idea of ACO with information about position of all nodes. In this technique the distance between the nodes is considered to transmit the packets, hence overcomes the drawbacks of AntNet algorithm which considers only cumulative probability for packet transmission. We compare performance of AntNet-LA with AntNet, Ad-hoc On Demand Distance Vector (AODV), Ad-hoc On Demand Multipath Distance Vector (AOMDV), Dynamic Source Routing (DSR) and Destination-Sequenced Distance-Vector Routing (DSDV) protocols. We also compare performance of AntNet-LA with distance-aware protocols such as Location Aided Routing (LAR), Geographical AODV GeoAODV and Position Based ANT colony optimization (PBANT)
Lattice-Reduction-Aided Detection with Successive Interference Cancelation for Multiuser Space-Time Block Coded Systems
Get PDFEffective detectors with low-complexity are considered for the Alamouti’s multiuser space-time block coded (STBC) systems. Viewing the noiseless received signals from Q users as a lattice with basis vectors being the columns of the total channel matrix H, we apply lattice reduction to transform the original basis into a nearly orthogonal one which improves the decision regions against noise. Then, linear detection using zero-forcing (ZF) and minimum-mean-square-error (MMSE) methods is performed on the transformed basis to detect transmitted signals from the Q users. These lattice-reduction-aided (LRA) linear detectors significantly improve BER of the linear detectors and, more importantly, allow us to achieve full diversity at high Eb/N0 regions
Interference Analysis for OFDM Transmissions in the Presence of Time-Varying Channel Impairments
Get PDFThis paper is concerned with the detrimental effect of phase noise on the performance of orthogonal frequency division multiplexing (OFDM) transmissions over time-selective channels. In the literature, most of the existing papers analyze the performance of OFDM systems in the presence of either time-selective channels or phase noise. Unlike the existing studies, this paper formulates an approximate expression of signal-to-interference-plus-noise ratio (SINR) at an OFDM receiver in the presence of both phase noise and time-selective channel response. The formulated SINR expression can be used as a guideline in determining appropriate OFDM transmission settings under a given quality-of-service (QoS) requirement. To illustrate the tightness of the approximate SINR formulation, empirical and theoretical values of SINR under different OFDM system settings are presented in this paper
Improving the Performance of Concatenated Convolutional Codes in the Error Floor Region
Get PDFThe idea of the Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is applied to classic schemes of both parallel and serial concatenation of convolutional codes (PCCC and SCCC) with Binary Phase Shift Keying (BPSK) modulation. Simulation results show that slightly modified PCCC and SCCC schemes provide significant improved performance of the encoder in the error floor region in terms of much lower bit error rate (BER)
An Improved Iterative Nonlinear Least Square Approximation Method for the Design of SISO Wideband Mobile Radio Channel Simulators
Get PDFIn this paper, we present an improved version of the iterative nonlinear least square approximation (INLSA) method for designing measurement-based single-input single-output (SISO) wideband channel simulators. The proposed method aims to fit the time-frequency correlation function (TFCF) of the simulation model to that of a measured channel. The parameters of the simulation model are determined iteratively by minimizing the Frobenius norm, which serves as a measure for the fitting error. In contrast to the original INLSA method, the proposed approach provides a unique optimized set of model parameters, which guarantees a quasi-perfect fitting with respect to the TFCF. We analyze the performance of the proposed method in terms of the goodness of fit to the measured data. The investigations will be carried out with respect to the TFCF and the scattering function. We demonstrate that the proposed approach is a powerful tool for the design of measurement-based wideband channel simulators, which are important for the performance evaluation of mobile communication systems under real-world propagation conditions
Forecasting the Bandwidth of Digital Links to the Internet
Get PDFIn this paper, we propose a new efficient technique for forecasting the bandwidth of digital access links to the Internet. This technique can be used for calculating the throughput of access links in implementing electronic document management systems and in organizing information portals. The main idea is to estimate the bandwidth of digital access links to the Internet using the statistics of the service load. The main result is the derivation of analytical expressions to estimate the required bandwidth
A Hybrid of T-Dipole and Quasi-Yagi Antenna for Dual-band WLAN Access Point
Get PDFIn this paper, a hybrid of T-dipole and quasi-Yagi antenna is presented for using in dual-band Wireless Local Area Network (WLAN) access point. The antenna is made up of combination of T-dipole and quasi-Yagi antenna structures, which are distinctly designed to operate at 2.4 and 5.5 GHz frequency bands. A simply integrated balun that consists of a curved microstrip line and a circular slot to allow broadband characteristic is used to feed the antenna. The final antenna design presents measured bandwidths (RL ≤ − 10 dB) of 2.35 – 2.55 GHz and 4.30 – 6.56 GHz which cover completely the two bands of WLAN. Simulated and measured results of peak gain and radiation patterns in both E- and H-plane validate potential of the design
On the Practical Implementation of VFDM-based Opportunistic Systems: Issues and Challenges
Get PDFVandermonde-subspace frequency division multiplexing (VFDM) is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing (OFDM) legacy system and a cognitive secondary system in a time division duplex mode. It consists of a linear null-space precoder used by the secondary transmitter to effectively cancel the interference towards one or more primary receivers, while guaranteeing a non-negligible rate to a served secondary receiver. In this work, we propose an implementation of an experimental test-bed using the new SDR4All platform developed at the Alcatel-Lucent Chair on Flexible Radio (SUPELEC) to take a step towards a proof of concept of a VFDM-based system. We focus on the secondary link, where an opportunistic transmitter/receiver pair communicates over moderately frequency selective channels, characterized by very short root mean square (r.m.s.) delay spreads and non uniform power delay profiles (PDP). The obtained results show the practical feasibility of a VFDM transmission over a secondary link. However, a significant bit error rate (BER) loss with respect to the previously shown achievable theoretical performance is evident. A thorough analysis of the structure of the VFDM precoder is carried out and the impact of the channel characteristics on the performance of the opportunistic system is discussed. Numerical findings demonstrate that the potential BER drop can be addressed by designing a suitable flexible receiver able to deal with the effect induced by non uniform PDP and short r.m.s. delay spread channels
Multihop Decode-and-Forward Relay Networks: Secrecy Analysis and Relay Position Optimization
Get PDFRelay communication has advantages over direct transmission in terms of secrecy capacity. In this paper, the performance of secrecy, offered by multihop decode-and-forward relaying, is investigated and compared to its counterpart in direct transmission. Three key performance measures are derived over Rayleigh fading channels: probability of non-zero secrecy capacity, secure outage probability and secrecy capacity, which are valid for an arbitrary number of hops. Based on the tractable form of the probability of non-zero secrecy capacity, the optimization problem of trusty relay replacement is also studied. Numerical results indicate that a proper relay replacement can increase the network security without extra network resources. The correctness of analytical results is confirmed by using a MATLAB-based independent simulation model