Estimate of channel capacity in Rayleigh fading environment
TL;DR: In this article, the authors derived the channel capacity in a Rayleigh fading environment and showed that channel capacity is always lower than that in a Gaussian-noise environment and that diversity schemes can improve channel capacity.
Abstract: The channel capacity in a Rayleigh fading environment is derived. The result shows that the channel capacity in a Rayleigh fading environment is always lower than that in a Gaussian-noise environment. When operating a digital transmission in a mobile radio environment that has Rayleigh fading statistics, it is very important to know the degradations in channel capacity due to Rayleigh fading, and also to what degree the diversity schemes can raise the channel capacity in a Rayleigh fading environment. The curves are generated to show the degradation of channel capacity in a Rayleigh fading environment and its improvement by diversity schemes. >
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28 Apr 1996
TL;DR: There is a constant power gap between the spectral efficiency of the proposed technique and the channel capacity, and this gap is a simple function of the required bit-error rate (BER).
Abstract: We propose a variable-rate and variable-power MQAM modulation scheme for high-speed data transmission over fading channels. We first review results for the Shannon capacity of fading channels with channel side information, where capacity is achieved using adaptive transmission techniques. We then derive the spectral efficiency of our proposed modulation. We show that there is a constant power gap between the spectral efficiency of our proposed technique and the channel capacity, and this gap is a simple function of the required bit-error rate (BER). In addition, using just five or six different signal constellations, we achieve within 1-2 dB of the maximum efficiency using unrestricted constellation sets. We compute the rate at which the transmitter needs to update its power and rate as a function of the channel Doppler frequency for these constellation sets. We also obtain the exact efficiency loss for smaller constellation sets, which may be required if the transmitter adaptation rate is constrained by hardware limitations. Our modulation scheme exhibits a 5-10-dB power gain relative to variable-power fixed-rate transmission, and up to 20 dB of gain relative to nonadaptive transmission. We also determine the effect of channel estimation error and delay on the BER performance of our adaptive scheme. We conclude with a discussion of coding techniques and the relationship between our proposed modulation and Shannon capacity.
2,355 citations
18 Jun 1995
TL;DR: By examining the bit error-rate with antipodal signalling, it is shown that an increase in capacity over a perfectly-power controlled (Gaussian) channel can be achieved, especially if the number of users is large, and the inherent diversity in multiuser communications over fading channels is shown.
Abstract: We consider a power control scheme for maximizing the information capacity of the uplink in single-cell multiuser communications with frequency-flat fading, under the assumption that the users attenuations are measured perfectly. Its main characteristics are that only one user transmits over the entire bandwidth at any particular time instant and that the users are allocated more power when their channels are good, and less when they are bad. Moreover, these features are independent of the statistics of the fading. Numerical results are presented for the case of single-path Rayleigh fading. We show that an increase in capacity over a perfectly-power controlled (Gaussian) channel can be achieved, especially if the number of users is large. By examining the bit error-rate with antipodal signalling, we show the inherent diversity in multiuser communications over fading channels.
2,265 citations
TL;DR: This paper describes the statistical models of fading channels which are frequently used in the analysis and design of communication systems, and focuses on the information theory of fading channel, by emphasizing capacity as the most important performance measure.
Abstract: In this paper we review the most peculiar and interesting information-theoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information theory of fading channels, by emphasizing capacity as the most important performance measure. Both single-user and multiuser transmission are examined. Further, we describe how the structure of fading channels impacts code design, and finally overview equalization of fading multipath channels.
2,017 citations
TL;DR: Some information-theoretic considerations used to determine upper bounds on the information rates that can be reliably transmitted over a two-ray propagation path mobile radio channel model, operating in a time division multiplex access (TDMA) regime, under given decoding delay constraints are presented.
Abstract: We present some information-theoretic considerations used to determine upper bounds on the information rates that can be reliably transmitted over a two-ray propagation path mobile radio channel model, operating in a time division multiplex access (TDMA) regime, under given decoding delay constraints. The sense in which reliability is measured is addressed, and in the interesting eases where the decoding delay constraint plays a significant role, the maximal achievable rate (capacity), is specified in terms of capacity versus outage. In this case, no coding capacity in the strict Shannon sense exists. Simple schemes for time and space diversity are examined, and their potential benefits are illuminated from an information-theoretic stand point. In our presentation, we chose to specialize to the TDMA protocol for the sake of clarity and convenience. Our main arguments and results extend directly to certain variants of other multiple access protocols such as code division multiple access (CDMA) and frequency division multiple access (FDMA), provided that no fast feedback from the receiver to the transmitter is available. >
1,216 citations
TL;DR: In this paper, the Shannon capacity of adaptive transmission techniques in conjunction with diversity-combining was studied. And the authors obtained closed-form solutions for the Rayleigh fading channel capacity under three adaptive policies: optimal power and rate adaptation, constant power with optimal rate adaptation and channel inversion with fixed rate.
Abstract: We study the Shannon capacity of adaptive transmission techniques in conjunction with diversity-combining. This capacity provides an upper bound on spectral efficiency using these techniques. We obtain closed-form solutions for the Rayleigh fading channel capacity under three adaptive policies: optimal power and rate adaptation, constant power with optimal rate adaptation, and channel inversion with fixed rate. Optimal power and rate adaptation yields a small increase in capacity over just rate adaptation, and this increase diminishes as the average received carrier-to-noise ratio (CNR) or the number of diversity branches increases. Channel inversion suffers the largest capacity penalty relative to the optimal technique, however, the penalty diminishes with increased diversity. Although diversity yields large capacity gains for all the techniques, the gain is most pronounced with channel inversion. For example, the capacity using channel inversion with two-branch diversity exceeds that of a single-branch system using optimal rate and power adaptation. Since channel inversion is the least complex scheme to implement, there is a tradeoff between complexity and capacity for the various adaptation methods and diversity-combining techniques.
1,036 citations
References
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Book•
01 Jan 1966
TL;DR: An introductory, graduate-level look at modern communications in general and radio communications in particular, with valuable insights into the fundamental concepts underlying today's communications systems, especially wireless communications.
Abstract: An introductory, graduate-level look at modern communications in general and radio communications in particular. This seminal presentation of the applications of communication theory to signal and receiver design brings you valuable insights into the fundamental concepts underlying today's communications systems, especially wireless communications. Coverage includes AM, FM Phase Modulation, PCM, fading, and diversity receivers.
1,415 citations
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01 Jan 1970
TL;DR: This edition features improved treatment of signal analysis, including representations in signal space, as well as a more complete and modern presentation of random variables and random processes.
Abstract: From the Publisher:
Here is a text for the introduction to principles of communications,the introduction to digital communications,and the introduction to data communications. A clear and readable tutorial style is combined with thorough coverage of both basic and advanced concepts. And the second edition acquaints students with the state of the art,including treatment of topics that have only recently become important and which many available texts ignore. This edition features improved treatment of signal analysis,including representations in signal space,as well as a more complete and modern presentation of random variables and random processes,with illustrative examples to teach detection of signals in noise. There is also a complete discussion of modulation techniques and synchronization and error rate calculation.
512 citations
Book•
01 Jan 1968
TL;DR: The major in communication systems combines the theoretical focus of communication studies with the practical skills of information technology, resulting in a program that prepares students to perform on the cutting edge of modern media systems.
Abstract: The major in communication systems combines the theoretical focus of communication studies with the practical skills of information technology, resulting in a program that prepares students to perform on the cutting edge of modern media systems. This program is flexible, emphasizing the interdisciplinary study and project work that are critical in a rapidly-changing field. With a communications systems background, students can enter the dynamic fields of the information industry, media and communication, management, public policy, and a variety of other corporate and non-profit areas.
433 citations