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On the Distribution of the Sum of Gamma-Gamma Variates and Applications in RF and Optical Wireless Communications  [PDF]
Nestor D. Chatzidiamantis,George K. Karagiannidis
Mathematics , 2009,
Abstract: The Gamma-Gamma (GG) distribution has recently attracted the interest within the research community due to its involvement in various communication systems. In the context of RF wireless communications, GG distribution accurately models the power statistics in composite shadowing/fading channels as well as in cascade multipath fading channels, while in optical wireless (OW) systems, it describes the fluctuations of the irradiance of optical signals distorted by atmospheric turbulence. Although GG channel model offers analytical tractability in the analysis of single input single output (SISO) wireless systems, difficulties arise when studying multiple input multiple output (MIMO) systems, where the distribution of the sum of independent GG variates is required. In this paper, we present a novel simple closed-form approximation for the distribution of the sum of independent, but not necessarily identically distributed GG variates. It is shown that the probability density function (PDF) of the GG sum can be efficiently approximated either by the PDF of a single GG distribution, or by a finite weighted sum of PDFs of GG distributions. To reveal the importance of the proposed approximation, the performance of RF wireless systems in the presence of composite fading, as well as MIMO OW systems impaired by atmospheric turbulence, are investigated. Numerical results and simulations illustrate the accuracy of the proposed approach.
Wireless Cellular Mobile Communications
V. Zalud
Radioengineering , 2002,
Abstract: In this article is briefly reviewed the history of wireless cellularmobile communications, examined the progress in current secondgeneration (2G) cellular standards and discussed their migration to thethird generation (3G). The European 2G cellular standard GSM and itsevolution phases GPRS and EDGE are described somewhat in detail. Thethird generation standard UMTS taking up on GSM/GPRS core network andequipped with a new advanced access network on the basis of codedivision multiple access (CDMA) is investigated too. A sketch of theperspective of mobile communication beyond 3G concludes this article.
Wireless Communications in the Era of Big Data  [PDF]
Suzhi Bi,Rui Zhang,Zhi Ding,Shuguang Cui
Computer Science , 2015,
Abstract: The rapidly growing wave of wireless data service is pushing against the boundary of our communication network's processing power. The pervasive and exponentially increasing data traffic present imminent challenges to all the aspects of the wireless system design, such as spectrum efficiency, computing capabilities and fronthaul/backhaul link capacity. In this article, we discuss the challenges and opportunities in the design of scalable wireless systems to embrace such a "bigdata" era. On one hand, we review the state-of-the-art networking architectures and signal processing techniques adaptable for managing the bigdata traffic in wireless networks. On the other hand, instead of viewing mobile bigdata as a unwanted burden, we introduce methods to capitalize from the vast data traffic, for building a bigdata-aware wireless network with better wireless service quality and new mobile applications. We highlight several promising future research directions for wireless communications in the mobile bigdata era.
Cooperative Communications: A New Trend in the Wireless World
Gordhan Das Menghwar,Akhtar Ali Jalbani,Mukhtiar Memon,Mansoor Hyder
International Journal on Computer Science and Engineering , 2012,
Abstract: This Wireless channel while offering independence of movement also introduces un-reliability in the messages received at the destination. Various strategies have been introduced so far to mitigate the effects of the channel on the message received. In this paper, we give an introductory overview of cooperative communications, a new trend in this field of wireless Communications where the transmitting users help each other to overcome the Effects of wireless channel on the message received at the destination. We compare the new idea of cooperative communications with traditional direct or noncooperative communications. In particular, we discuss the achievable rates and simulate the system to get the probability of outage performance of cooperative communications and compare it with direct or noncooperative communications.
The Next Frontier for Openness: Wireless Communications  [PDF]
Eli M. Noam
Computer Science , 2001,
Abstract: For wireless communications, the FCC has fostered competition rather than openness. This has permitted the emergence of vertically integrated end-to-end providers, creating problems of reduced hardware innovation, software applications, user choice, and content access. To deal with these emerging issues and create multi-level forms of competition, one policy is likely to suffice: a Carterfone for wireless, coupled with more unlicensed spectrum.
Decentralized learning for wireless communications and networking  [PDF]
Georgios B. Giannakis,Qing Ling,Gonzalo Mateos,Ioannis D. Schizas,Hao Zhu
Mathematics , 2015,
Abstract: This chapter deals with decentralized learning algorithms for in-network processing of graph-valued data. A generic learning problem is formulated and recast into a separable form, which is iteratively minimized using the alternating-direction method of multipliers (ADMM) so as to gain the desired degree of parallelization. Without exchanging elements from the distributed training sets and keeping inter-node communications at affordable levels, the local (per-node) learners consent to the desired quantity inferred globally, meaning the one obtained if the entire training data set were centrally available. Impact of the decentralized learning framework to contemporary wireless communications and networking tasks is illustrated through case studies including target tracking using wireless sensor networks, unveiling Internet traffic anomalies, power system state estimation, as well as spectrum cartography for wireless cognitive radio networks.
The Laboratory of Wireless and Mobile Communications
S. Hanus
Radioengineering , 2001,
Abstract: The paper presents the basic information about establishing of thelaboratory for Mobile Communications on the Dept. of Radio Electronics,Brno University of Technology. This information allows to experts fromthe practice to obtain the general notion about the extent oftheoretical knowledge and practical experiences of our students in thisfield. This information can be also useful for the specialists fromuniversities comparing simple their pedagogical activity in this fieldrespecting the activity in another institute.
Secure Wireless Communications via Cooperation  [PDF]
Lun Dong,Zhu Han,Athina P. Petropulu,H. Vincent Poor
Mathematics , 2008,
Abstract: The feasibility of physical-layer-based security approaches for wireless communications in the presence of one or more eavesdroppers is hampered by channel conditions. In this paper, cooperation is investigated as an approach to overcome this problem and improve the performance of secure communications. In particular, a decode-and-forward (DF) based cooperative protocol is considered, and the objective is to design the system for secrecy capacity maximization or transmit power minimization. System design for the DF-based cooperative protocol is first studied by assuming the availability of global channel state information (CSI). For the case of one eavesdropper, an iterative scheme is proposed to obtain the optimal solution for the problem of transmit power minimization. For the case of multiple eavesdroppers, the problem of secrecy capacity maximization or transmit power minimization is in general intractable. Suboptimal system design is proposed by adding an additional constraint, i.e., the complete nulling of signals at all eavesdroppers, which yields simple closed-form solutions for the aforementioned two problems. Then, the impact of imperfect CSI of eavesdroppers on system design is studied, in which the ergodic secrecy capacity is of interest.
The Effect Of Communications on the Lifetime of Wireless Sensor Networks  [PDF]
Abdelrahman Elleithy,Gonhsin Liu
Journal of Emerging Trends in Computing and Information Sciences , 2012,
Abstract: In this paper we present a model for the lifetime of wireless sensor networks that incorporates the effect of the communications model. The model takes into consideration several parameters such as the total number of sensors, network size, percentage of sink nodes, location of sensors, the mobility of sensors, power consumption when nodes move and the power consumption of the communications circuitry. A definition of the lifetime of the network based on three different criteria is introduced; percentage of available power to total power, percentage of alive sensors to total sensors,and percentage of alive sink sensors to total sink sensors. A Matlab-based simulator is developed for the introduced model. A number of wireless sensor networks scenarios are presented and discussed.
Advanced Signal Processing for Wireless Multimedia Communications  [PDF]
Xiaodong Wang
Informing Science The International Journal of an Emerging Transdiscipline , 2000,
Abstract: There is at present a worldwide effort to develop next-generation wireless communication systems. It is envisioned that many of the future wireless systems will incorporate considerable signal-processing intelligence in order to provide advanced services such as multimedia transmission. In general, wireless channels can be very hostile media through which to communicate, due to substantial physical impediments, primarily radio-frequency interference and time-arying nature of the channel. The need of providing universal wireless access at high data-rate (which is the aim of many merging wireless applications) presents a major technical challenge, and meeting this challenge necessitates the development of advanced signal processing techniques for multiple-access communications in non-stationary interference-rich environments. In this paper, we present some key advanced signal processing methodologies that have been developed in recent years for interference suppression in wireless networks. We will focus primarily on the problem of jointly suppressing multiple-access interference (MAI) and intersymbol interference (ISI), which are the limiting sources of interference for the high data-rate wireless systems being proposed for many emerging application areas, such as wireless multimedia. We first present a signal subspace approach to blind joint suppression of MAI and ISI. We then discuss a powerful iterative technique for joint interference suppression and decoding, so-called Turbo multiuser detection, that is especially useful for wireless multimedia packet communications. We also discuss space-time processing methods that employ multiple antennas for interference rejection and signal enhancement. Finally, we touch briefly on the problems of suppressing narrowband interference and impulsive ambient noise, two other sources of radio-frequency interference present in wireless multimedia networks.
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