On the Energy Efficiency of LT Codes in Proactive Wireless Sensor Networks

This paper presents an in-depth analysis on the energy efficiency of Luby Transform (LT) codes with Frequency Shift Keying (FSK) modulation in a Wireless Sensor Network (WSN) over Rayleigh fading channels with pathloss. We describe a proactive system model according to a flexible duty-cycling mechanism utilized in practical sensor apparatus. The present analysis is based on realistic parameters including the effect of channel bandwidth used in the IEEE 802.15.4 standard, active mode duration and computation energy. A comprehensive analysis, supported by some simulation studies on the probability mass function of the LT code rate and coding gain, shows that among uncoded FSK and various classical channel coding schemes, the optimized LT coded FSK is the most energy-efficient scheme for distance d greater than the pre-determined threshold level d_T , where the optimization is performed over coding and modulation parameters. In addition, although the optimized uncoded FSK outperforms coded schemes for d < d_T , the energy gap between LT coded and uncoded FSK is negligible for d < d_T compared to the other coded schemes. These results come from the flexibility of the LT code to adjust its rate to suit instantaneous channel conditions, and suggest that LT codes are beneficial in practical low-power WSNs with dynamic position sensor nodes.Comment: accepted for publication in IEEE Transactions on Signal Processin

Adaptive Demodulation in Differentially Coherent Phase Systems: Design and Performance Analysis

Adaptive Demodulation (ADM) is a newly proposed rate-adaptive system which operates without requiring Channel State Information (CSI) at the transmitter (unlike adaptive modulation) by using adaptive decision region boundaries at the receiver and encoding the data with a rateless code. This paper addresses the design and performance of an ADM scheme for two common differentially coherent schemes: M-DPSK (M-ary Differential Phase Shift Keying) and M-DAPSK (M-ary Differential Amplitude and Phase Shift Keying) operating over AWGN and Rayleigh fading channels. The optimal method for determining the most reliable bits for a given differential detection scheme is presented. In addition, simple (near-optimal) implementations are provided for recovering the most reliable bits from a received pair of differentially encoded symbols for systems using 16-DPSK and 16- DAPSK. The new receivers offer the advantages of a rate-adaptive system, without requiring CSI at the transmitter and a coherent phase reference at the receiver. Bit error analysis for the ADM system in both cases is presented along with numerical results of the spectral efficiency for the rate-adaptive systems operating over a Rayleigh fading channel.Comment: 25 pages, 11 Figures, submitted to IEEE Transactions on Communications, June 1, 201

Design of Matched and Mismatched Filters Based on Peak Sidelobe Level Minimization

‎This paper focuses on the design of matched filters with low peak sidelobe level as well as mismatched‎ ‎filters with low loss in processing gain and peak sidelobe level‎, ‎for phase codes‎. ‎We propose an algorithm ‎which employs the least-p-th norm minimax based on the genetic algorithm‎, ‎and a method based on the‎ ‎semidefinite programming to deal respectively with the resulting matched and mismatched optimization problems‎. A framework is also presented to design mismatched filters that are robust to Doppler shifts. ‎Simulation results show that using the proposed methods for finding matched filters leads to better peak sidelobe‎ ‎level and integrated sidelobe level for binary and polyphase codes compared to previous works‎. ‎In addition‎, ‎the mismatched filters designed by the proposed methods have very low peak sidelobe level in‎ ‎the binary and polyphase cases‎

Interference Aware Routing Game for Cognitive Radio Ad-hoc Networks

Cognitive radio is a new communication paradigm that is able to solve the problem of spectrum scarcity in wireless networks. In this paper, interference aware routing game, (IRG), is proposed that connects the flow initiators to the destinations. A network formation game among secondary users (SUs) is formulated in which each secondary user aims to maximize its utility, while it reduces the aggregate interference on the primary users (PUs) and the end-to-end delay. In order to reduce the end-to-end delay and the accumulated interference, the IRG algorithm selects upstream neighbors in a view point of the sender. To model the interference between SUs, IRG uses the signal-to-interference-plus noise (SINR) model. The effectiveness of the proposed algorithm is validated by evaluating the aggregate interference from SUs to the PUs and end-to-end delay. A comprehensive numerical evaluation is performed, which shows that the performance of the proposed algorithm is significantly better than the Interference Aware Routing (IAR) using network formation game in cognitive radio mesh networks

Fast-decodable MIMO HARQ systems

Due to copyright restrictions, the access to the full text of this article is only available via subscription.This paper presents a comprehensive study on the problem of decoding complexity in a Multi-Input Multi-Output (MIMO) Hybrid Automatic Repeat reQuest (HARQ) system based on Space-Time Block Codes (STBCs). We show that there exist two classes of fast-decodable MIMO HARQ systems: independent and dependent STBC structures. For the independent class, two types of protocols namely, fixed and adaptive threshold-based are presented and their effectiveness in both computational complexity reduction and spectral efficiency preservation are discussed. For the dependent class, a fast Sphere Decoder (SD) algorithm with a low computational complexity is proposed for decoding process of HARQ rounds. Two new concepts are introduced to leverage the fast-decodable notion in MIMO HARQ systems. Simulation results show that the proposed fast-decodable MIMO HARQ protocols in both classes provide a significant reduction in the decoding complexity as compared with the original MIMO HARQ method

On the Application of Machine Learning to the Design of UAV-Based 5G Radio Access Networks

A groundbreaking design of radio access networks (RANs) is needed to fulfill 5G traffic requirements. To this aim, a cost-effective and flexible strategy consists of complementing terrestrial RANs with unmanned aerial vehicles (UAVs). However, several problems must be solved in order to effectively deploy such UAV-based RANs (U-RANs). Indeed, due to the high complexity and heterogeneity of these networks, model-based design approaches, often relying on restrictive assumptions and constraints, exhibit severe limitation in real-world scenarios. Moreover, design of a set of appropriate protocols for such U-RANs is a highly sophisticated task. In this context, machine learning (ML) emerges as a useful tool to obtain practical and effective solutions. In this paper, we discuss why, how, and which types of ML methods are useful for designing U-RANs, by focusing in particular on supervised and reinforcement learning strategies

Promoted chondrogenesis of hMCSs with controlled release of TGF-β3 via microfluidics synthesized alginate nanogels

The field of cartilage tissue engineering has been evolved in the last decade and a myriad of scaffolding biomaterials and bioactive agents have been proposed. Controlled release of growth factors encapsulated in the polymeric nanomaterials has been of interest notably for the repair of damaged articular cartilage. Here, we proposed an on-chip hydrodynamic flow focusing microfluidic approach for synthesis of alginate nanogels loaded with the transforming growth factor beta 3 (TGF-β3) through an ionic gelation method in order to achieve precise release profile of these bioactive agents during chondrogenic differentiation of mesenchymal stem cells (MSCs). Alginate nanogels with adjustable sizes were synthesized by fine-tuning the flow rate ratio (FRR) in the microfluidic device consisting of cross-junction microchannels. The result of present study showed that the proposed approach can be a promising tool to synthesize bioactive -loaded polymeric nanogels for applications in drug delivery and tissue engineering