Reducing energy consumption in wireless communications has attracted increasing attention recently. Advanced physical layer techniques such as multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM), cognitive radio, network coding, cooperative communication, etc.; new network architectures such as heterogeneous networks, distributed antennas, multi-hop cellulars, etc.; as well as radio and network resource management schemes such as various cross-layer optimization algorithms, dynamic power saving, multiple radio access technologies coordination, etc. have been proposed to address this issue. In this article, we overview these technologies and present the state-of-the-art on each aspect. Some challenges that need to be solved in the area are also described.

A survey of energy-efficient wireless communications

With explosive growth of high-data-rate applications, more and more energy is consumed in wireless networks to guarantee quality of service. Therefore, energy-efficient communications have been paid increasing attention under the background of limited energy resource and environmental- friendly transmission behaviors. In this article, basic concepts of energy-efficient communications are first introduced and then existing fundamental works and advanced techniques for energy efficiency are summarized, including information-theoretic analysis, OFDMA networks, MIMO techniques, relay transmission, and resource allocation for signaling. Some valuable topics in energy-efficient design are also identified for future research.

Energy-efficient wireless communications: tutorial, survey, and open issues

Conventional design of wireless networks mainly focuses on system capacity and spectral efficiency (SE). As green radio (GR) becomes an inevitable trend, energy-efficient design is becoming more and more important. In this paper, the fundamental tradeoff between energy efficiency (EE) and SE in downlink orthogonal frequency division multiple access (OFDMA) networks is addressed. We first set up a general EE-SE tradeoff framework, where the overall EE, SE and per-user quality-of-service (QoS) are all considered, and prove that under this framework, EE is strictly quasiconcave in SE. We then discuss some basic properties, such as the impact of channel power gain and circuit power on the EE-SE relation. We also find a tight upper bound and a tight lower bound on the EE-SE curve for general scenarios, which reflect the actual EE-SE relation. We then focus on a special case that priority and fairness are considered and suggest an alternative upper bound, which is proved to be achievable for flat fading channels. We also develop a low-complexity but near-optimal resource allocation algorithm for practical application of the EE-SE tradeoff. Numerical results confirm the theoretical findings and demonstrate the effectiveness of the proposed resource allocation scheme for achieving a flexible and desirable tradeoff between EE and SE.

Energy- and Spectral-Efficiency Tradeoff in Downlink OFDMA Networks

To facilitate the efficient allocation of limited transmit power, a bit error rate (BER) constraint based power allocation scheme is proposed in this paper for the downlink of multi-carrier code division multiple access (MC-CDMA) systems with linear minimum mean square error (MMSE) receiver. According to the instantaneous channel conditions, the proposed scheme can adaptively allocate the required minimum transmit power on each channel to meet the BER constraint. The simulation results show that the proposed scheme is efficient in reducing the transmit power while meeting BER constraint, and thereby improve the system performance.

BER constraint based power allocation for downlink MC-CDMA systems with linear MMSE receiver

Large-scale plasma produced in nitrogen gas at room temperature and pressures ranging from 4 ? 103 to 1.2 ? 105 Pa by high-power laser-induced dielectric breakdown (LIDB) has been investigated. Time-integrated optical nitrogen gas spectra excited from a CO2 laser have been measured and analysed. The spectrum of the generated plasma is dominated by the emission of strong N+ and N and very weak N2+ atomic lines and molecular features of N+2(B2?+u?X2?+g), N+2(D2?g?A2?u), N2(C3?u?B3?g) and very weak N2(B3?g?A3?+u). The relative intensities of the 0?0 band heads in the N2(C?B) and N+2(B?X) systems are very weak as compared with the chemiluminescence spectrum of nitrogen formed in a glow discharge. An excitation temperature Texc = 21?000 ? 1300 K was calculated by means of the relative intensity of ionized nitrogen atomic lines assuming local thermodynamic equilibrium. Optical breakdown threshold intensities in N2 at 9.621 ?m have been determined. The physical processes leading to the LIDB of nitrogen in the power density range 0.4 < J < 4.5 GW cm?2 have been analysed. From our experimental observations we can suggest that, although the first electrons must appear via multiphoton ionization or natural ionization, electron cascade is the main mechanism responsible for the LIDB in nitrogen.

/pdf/optical-emission-studies-of-nitrogen-plasma-generated-by-ir-4xv5ppv11q.pdf

Optical emission studies of nitrogen plasma generated by IR CO2 laser pulses

Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e., policies) potentially provide significant performance gains for various systems. In this article we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by means of dynamic resource allocation. Two specific areas are treated separately: models and dynamic approaches for single transmitter/receiver pairs (i.e., a point-to-point communication scenario) as well as models and approaches for point-to-multipoint communication scenarios (e.g., the downlink of a wireless cell). This article provides basic knowledge in order to investigate future OFDM cross-layer-optimization issues

/pdf/dynamic-resource-allocation-in-ofdm-systems-an-overview-of-30ibcqtbyi.pdf

Dynamic resource allocation in OFDM systems: an overview of cross-layer optimization principles and techniques

Light emission induced by inner-shell excitation of [Formula Presented] molecules has been investigated in the wavelength region [Formula Presented] Synchrotron radiation from the SuperACO storage ring in Orsay (France) has been used for the photoexcitation and a high-resolution secondary monochromator [Formula Presented] for the spectral analysis of the fluorescence light. Vibrationally resolved molecular [Formula Presented] [Formula Presented] transitions show clearly the coupling between the [Formula Presented] core excitation and the ionization of the [Formula Presented] valence electron. The main contribution to the fluorescence spectra stems from excited neutral and excited singly charged atoms produced by the dissociation of highly excited molecular states. The singly ionized [Formula Presented] atoms are produced upon resonant [Formula Presented] excitation as well as upon excitation to the [Formula Presented] continuum resonance. Fluorescence transitions of the type [Formula Presented] [Formula Presented] as well as [Formula Presented] and [Formula Presented] have been analyzed. The neutral N fragment is found nearly exclusively after excitation of the [Formula Presented] resonance, and mainly radiative decay of the N [Formula Presented] excited states has been observed. The obtained experimental results represent additional and very detailed information on the final states of the molecular dissociation and provide a necessary basis for a theoretical treatment of the relaxation processes of inner-shell excited molecules. (Less)

Analysis of uv-visible fluorescence following inner-shell excitation of N 2 molecules

o It is well known that applying dynamic resource allocation to down-link transmissions of OFDMA systems provides a signicant performance increase, by taking advantage of diversity effects. In order to quantify the maximum possible gain achiev- able by applying dynamic mechanisms, several opti- mization problems have been suggested for studying a dynamic system's optimal behavior. However, so far these optimization problems do not take into account sophisticated system requirements, as there are dif- ferent packet-arrival processes, buffering constraints, scheduling policies, as well as QoS requirements per service class. In this paper we present a new optimiza- tion model that is based on a packet-centric system view and includes the system requirements mentioned above. We compare the performance results of the conventional and the new approach and study the impact of dynamic power allocation in both cases. 1

/pdf/a-new-optimization-model-for-dynamic-power-and-sub-carrier-30l8yuclq7.pdf

A New Optimization Model for Dynamic Power and Sub-Carrier Allocations in Packet-Centric OFDMA Cells

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Michael Meyer

Author Tools

Chat about Author

Papers

Dynamic resource allocation in OFDM systems: an overview of cross-layer optimization principles and techniques

Analysis of uv-visible fluorescence following inner-shell excitation of N 2 molecules

A New Optimization Model for Dynamic Power and Sub-Carrier Allocations in Packet-Centric OFDMA Cells