Single carrier frequency division multiple access (SC-FDMA) has been comprehensively investigated and standardized in 4th generation (4G) and 5th generation (5G) mobile systems. Its significant advantage is low peak-to-average power ratio (PAPR), which makes it suitable for uplink channel communications. However, over a long time period, SC-FDMA has not made breakthrough especially in data rate enhancement, which may not catch up with the next generation evolution in communications. This work proposes to use a non-orthogonal waveform in SC-FDMA to promote a new concept, termed single carrier spectrally efficient frequency division multiple access (SC-SEFDMA). This non-orthogonal single carrier access technique maintains essentially similar complexity as SC-FDMA but advantageously can either achieve higher data rate for the same amount of power consumption or the same data rate with less power consumption.
This paper serves as an evaluation of an experimental wireless communications technique called space-time coded massive (STCM) multiple-input multiple-output (MIMO). The STCM-MIMO system utilizes two massive MIMO antenna arrays which transmit data over two channel vectors to a user with one receive antenna. This configuration permits the system to use the asymptotic orthogonal qualities of massive MIMO pre-coding to eliminate the interference from other users’ channel vectors and signals. The system also maintains the diversity of space-time codes to recover lost data through treating each transmitting massive MIMO array similarly to how a 2×1 Alamouti spacetime code would treat each transmitting antenna. Our results show that a wireless system with the proposed STCM-MIMO technology can significantly outperform those with space-time coding techniques.
This paper presents a mesh architecture proposal called Mobile mEsh Network to Aid in CountEring drug TRAffiCKing (M.E.N.A.C.E-TRACK). This project was born from the hypothesis we could establish a covert network channel independent of the cell phone companies infrastructures. Therefore, law enforcement agencies could establish connection with field personnel, in a fault tolerant fashion allowing the transmission of multimedia data (instead of only voice). The main contribution for this paper is the strategies involved to configure smartphones on the MANET side of this system. We present the main difficulties and one possible solution to implement ad hoc mode on our testbed so we can enable a MANET organization on M.E.N.A.C.E-TRACK.
This paper tackles the challenging task of developing accurate easy-to-use analytical models for performance evaluation of WiMAX networks. The need for precise fast-computing tools is of primary importance to face complex dimensioning issues of WiMAX cells. Here, we present generic Markovian models developed for the rtPS service class defined in the WiMAX standard. This service class is dedicated to real-time applications with constraints on both their bit rates and the latency of their packets (i.e., streaming). Our analytical modeling is performed in two steps. First, we focus on the connection level only considering the bit rate constraint. Then, we extend the model to the packet level to formulate the packet delay QoS parameter. The resulting models can account for multiple traffic profiles at both levels while always keeping an instantaneous resolution. The models are compared with simulations that show their accuracy. Finally, we show how our models can be used to solve dimensioning issues while avoiding days of simulations.
In cellular industry, security has been a major concern for both service providers and subscribers. Service providers are primarily concerned with security to prevent fraudulent operations such as cloning or subscription fraud, while subscribers are mainly concerned with privacy issues. This paper gives a description of the access security mechanism found in CDMA2000 technology and discusses how CDMA2000 solves the three major features of mobile security: authentication, data protection, and anonymity.
Extracting an electrical energy from various environmental sources, called energy harvesting (or energy scavenging), has been attracting researchers’ attention in energy replenishable networks. In particular, a piezoelectric device based energy harvesting from ambient vibrations is a promising technique for easy of battery energy replenishment in vibration-motivated wireless sensor networks (WSNs). In this paper, we address two major issues of vibration-based energy harvesting: impact spread and energy conversion. A simple analytical model of the impact spread is proposed to estimate the impact over time and distance, in which diffusion equation is used for easy of analysis. Then we propose a modified inverse Bezier curve method for an explicit interpolation function to support a seamless energy conversion. The overall analyses and numerical results indicate that the proposed techniques are proven to be a viable approach for analyzing vibration-motivated WSNs.
Today there are many proposals of middlewares for sensor and actuator networks (SAN). Each of them introduces programming paradigms for creating distributed applications. There are middlewares with different philosophies in terms of architecture and organization (database, clustering, etc.). From the standpoint of the programmer these considerations influence the development process and, in most cases, determine the programming paradigm. Although these middlewares are so different, there is a common issue: they assume the SAN is logically separated from the main network. Thus, it forces the programmers to think a lot on specific stuff for the SAN and provides a dissociated vision of the whole system. In this paper we propose a new development model for SAN based on standard object oriented middlewares. Moreover, we provide a language as a new programming paradigm so that it is possible to have a homogeneous view of the whole system (including main network and the SAN).
In this paper, we present a state of the art on applications of mobile devices to support decision of a tourist running on a trip. We focus on two types of applications, tourism recommendation and tourism guide, making a brief description of the main characteristics of each one of them. We also refer the main problems encountered on the development of applications for mobile devices, and present PSiS (Personalized Sightseeing Tours Recommendation System) Mobile, our proposal to a mobile recommendation and planning support system, which is designed to provide an effective support during the tourist visit, providing contextaware information and recommendations about places of interest (POI) to visit, based on tourist preferences and his current context.
