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Topic

Orthogonal frequency-division multiplexing

About: Orthogonal frequency-division multiplexing is a(n) research topic. Over the lifetime, 50541 publication(s) have been published within this topic receiving 682648 citation(s). The topic is also known as: Ορθογώνια Πολύπλεξη Διαίρεσης Συχνότητας & OFDM.


Papers
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Journal ArticleDOI
Thomas L. Marzetta1
TL;DR: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval and a complete multi-cellular analysis yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve.
Abstract: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval. Time-division duplex operation combined with reverse-link pilots enables the base station to estimate the reciprocal forward- and reverse-link channels. The conjugate-transpose of the channel estimates are used as a linear precoder and combiner respectively on the forward and reverse links. Propagation, unknown to both terminals and base station, comprises fast fading, log-normal shadow fading, and geometric attenuation. In the limit of an infinite number of antennas a complete multi-cellular analysis, which accounts for inter-cellular interference and the overhead and errors associated with channel-state information, yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve. In particular the effects of uncorrelated noise and fast fading vanish, throughput and the number of terminals are independent of the size of the cells, spectral efficiency is independent of bandwidth, and the required transmitted energy per bit vanishes. The only remaining impairment is inter-cellular interference caused by re-use of the pilot sequences in other cells (pilot contamination) which does not vanish with unlimited number of antennas.

5,634 citations

Journal ArticleDOI
TL;DR: A rapid synchronization method is presented for an orthogonal frequency-division multiplexing (OFDM) system using either a continuous transmission or a burst operation over a frequency-selective channel.
Abstract: A rapid synchronization method is presented for an orthogonal frequency-division multiplexing (OFDM) system using either a continuous transmission or a burst operation over a frequency-selective channel. The presence of a signal can be detected upon the receipt of just one training sequence of two symbols. The start of the frame and the beginning of the symbol can be found, and carrier frequency offsets of many subchannels spacings can be corrected. The algorithms operate near the Cramer-Rao lower bound for the variance of the frequency offset estimate, and the inherent averaging over many subcarriers allows acquisition at very low signal-to-noise ratios (SNRs).

3,348 citations

Journal ArticleDOI
TL;DR: The results show that the proposed algorithm outperforms multiuser OFDM systems with static time-division multiple access (TDMA) or frequency-divisionmultiple access (FDMA) techniques which employ fixed and predetermined time-slot or subcarrier allocation schemes.
Abstract: Multiuser orthogonal frequency division multiplexing (OFDM) with adaptive multiuser subcarrier allocation and adaptive modulation is considered. Assuming knowledge of the instantaneous channel gains for all users, we propose a multiuser OFDM subcarrier, bit, and power allocation algorithm to minimize the total transmit power. This is done by assigning each user a set of subcarriers and by determining the number of bits and the transmit power level for each subcarrier. We obtain the performance of our proposed algorithm in a multiuser frequency selective fading environment for various time delay spread values and various numbers of users. The results show that our proposed algorithm outperforms multiuser OFDM systems with static time-division multiple access (TDMA) or frequency-division multiple access (FDMA) techniques which employ fixed and predetermined time-slot or subcarrier allocation schemes. We have also quantified the improvement in terms of the overall required transmit power, the bit-error rate (BER), or the area of coverage for a given outage probability.

2,884 citations

Book
01 Jan 1996
TL;DR: The Principles of Mobile Communication, Third Edition stresses the "fundamentals" of physical-layer wireless and mobile communications engineering that are important for the design of "any" wireless system.
Abstract: Principles of Mobile Communication, Third Edition, is an authoritative treatment of the fundamentals of mobile communications. This book stresses the "fundamentals" of physical-layer wireless and mobile communications engineering that are important for the design of "any" wireless system. This book differs from others in the field by stressing mathematical modeling and analysis. It includes many detailed derivations from first principles, extensive literature references, and provides a level of depth that is necessary for graduate students wishing to pursue research on this topic. The book's focus will benefit students taking formal instruction and practicing engineers who are likely to already have familiarity with the standards and are seeking to increase their knowledge of this important subject. Major changes from the second edition: 1. Updated discussion of wireless standards (Chapter 1). 2. Updated treatment of land mobile radio propagation to include space-time correlation functions, mobile-to-mobile (or vehicle-to-vehicle) channels, multiple-input multiple-output (MIMO) channels, improved simulation models for land mobile radio channels, and 3G cellular simulation models. 3. Updated treatment of modulation techniques and power spectrum to include Nyquist pulse shaping and linearized Gaussian minimum shift keying (LGMSK). 4. Updated treatment of antenna diversity techniques to include optimum combining, non-coherent square-law combining, and classical beamforming. 5. Updated treatment of error control coding to include space-time block codes, the BCJR algorithm, bit interleaved coded modulation, and space-time trellis codes. 6. Updated treatment of spread spectrum to include code division multiple access (CDMA) multi-user detection techniques. 7. A completely new chapter on multi-carrier techniques to include the performance of orthogonal frequency division multiplexing (OFDM) on intersymbol interference (ISI) channels, OFDM residual ISI cancellation, single-carrier frequency domain equalization (SC-FDE), orthogonal frequency division multiple access (OFDMA) and single-carrier frequency division multiple access (SC-FDMA). 8. Updated discussion of frequency planning to include OFDMA frequency planning. 9. Updated treatment of CDMA cellular systems to include hierarchical CDMA cellular architectures and capacity analysis. 10. Updated treatment of radio resource management to include CDMA soft handoff analysis. Includes numerous homework problems throughout.

2,773 citations

Journal ArticleDOI
Jr. L.J. Cimini1
TL;DR: The analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel using the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel is discussed.
Abstract: This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference.

2,573 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202221
20211,280
20201,800
20192,095
20182,314
20172,522