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2006, The IEEE 2006 International Conference on Ultra-wideband (ICUWB), pp. 441-446
In this paper, we study the achievable diversitymultiplexing gain (D-MG) tradeoffs over the IEEE 802.15.3a channel model. In particular, we give an exact expression of the D-MG tradeoff for single antenna systems. This expression is based on a statistical model of the integrated energy of the considered channels. At a second time, we evaluate lower and upper bounds on the D-MG tradeoffs of multi-antenna systems. This formulation gives us more insights on the real potential of multi-antenna techniques with UWB systems. It is shown that even though the asymptotical diversity gain has an infinite value, the multi-antenna techniques can be very beneficial in the practical range of signal-to-noise ratios.
IEEE Transactions on Information Theory, 2004
In a point-to-point wireless fading channel, multiple transmit and receive antennas can be used to improve the reliability of reception (diversity gain) or increase the rate of communication for a fixed reliability level (multiplexing gain). In a multiple-access situation, multiple receive antennas can also be used to spatially separate signals from different users (multiple-access gain). Recent work has characterized the fundamental tradeoff between diversity and multiplexing gains in the point-to-point scenario. In this paper, we extend the results to a multiple-access fading channel. Our results characterize the fundamental tradeoff between the three types of gain and provide insights on the capabilities of multiple antennas in a network context.
2014 Information Theory and Applications Workshop (ITA), 2014
In this work the optimal diversity-multiplexing tradeoff (DMT) is investigated for the multiple-input multiple-output fading multiple-access channel with no power constraints (infinite constellations). For K users (K > 1), M transmit antennas for each user, and N receive antennas, infinite constellations in general and lattices in particular are shown to attain the optimal DMT of finite constellations for N ≥ (K + 1)M − 1, i.e., user limited regime. On the other hand for N < (K + 1) M − 1 it is shown that infinite constellations can not attain the optimal DMT. This is in contrast to the point-to-point case in which infinite constellations are DMT optimal for any M and N . In general, this work shows that when the network is heavily loaded, i.e., K > max 1, N−M +1 M , taking into account the shaping region in the decoding process plays a crucial role in pursuing the optimal DMT. By investigating the cases in which infinite constellations are optimal and suboptimal, this work also gives a geometrical interpretation to the DMT of infinite constellations in multiple-access channels. • For r ∈ 0, min N K+1 , M the optimal symmetric DMT equals to the optimal DMT of a point-to-point channel with M transmit and N receive antennas d * ,(F C) M,N (r).
allerton conference on communication, control, and computing, 2004
We quantify the multiplexing-diversity tradeoff of a multiple-input multiple-output (MIMO) system, when the channel state information (CSI) is known perfectly at the receiver and partially at the transmitter. The partial knowledge of CSI at the transmitter consists of the quantized value of one of the eigenvalues and perfect knowledge of eigenvectors of the channel matrix. The key result is that while multiplexing gain cannot be increased beyond minimum number of transmit and receive antennas, diversity order for each multiplexing gain can be substantially increased by using only a few bits of feedback at the transmitter. For example, with 1 bit of feedback in a 2 × 3 system, for multiplexing gains of 0, 1, and 2, diversity gains of 42, 6, and 2 can be achieved, respectively. Thus, while the tradeoff between diversity advantage and multiplexing gain is still present, its behavior is significantly changed by channel knowledge at the transmitter. The major reason for this different tradeoff can be attributed to addition of long-term power control, which allows the transmitter to switch between modes for reducing outage and increasing throughput based on signal to noise ratio along different eigenvalues.
Computing Research Repository, 2006
We consider a general multiple antenna network with multiple sources, multiple destinations and multiple relays in terms of the diversity-multiplexing tradeoff (DMT). We examine several subcases of this most general problem taking into account the processing capability of the relays (half-duplex or full-duplex), and the network geometry (clustered or non-clustered). We first study the multiple antenna relay channel with a full-duplex relay to understand the effect of increased degrees of freedom in the direct link. We find DMT upper bounds and investigate the achievable performance of decode-and-forward (DF), and compress-and-forward (CF) protocols. Our results suggest that while DF is DMT optimal when all terminals have one antenna each, it may not maintain its good performance when the degrees of freedom in the direct link is increased, whereas CF continues to perform optimally. We also study the multiple antenna relay channel with a half-duplex relay. We show that the half-duplex DMT behavior can significantly be different from the full-duplex case. We find that CF is DMT optimal for half-duplex relaying as well, and is the first protocol known to achieve the halfduplex relay DMT. We next study the multiple-access relay channel (MARC) DMT. Finally, we investigate a system with a single source-destination pair and multiple relays, each node with a single antenna, and show that even under the idealistic assumption of full-duplex relays and a clustered network, this virtual multi-input multi-output (MIMO) system can never fully mimic a real MIMO DMT. For cooperative systems with multiple sources and multiple destinations the same limitation remains to be in effect.
It is well known that there exists a tradeoff between the diversity gain and the multiplexing gain achievable by a particular MIMO coding scheme. In this report we first look at the optimal trade-off in the infinite signal-to-noise (SNR) regime of both Rayleigh independent and identically distributed (i.i.d.) channels and a more general MIMO channel model. We then look at the tradeoff of both Space-Time Block Codes (such as Alamouti code) and BLAST Detection schemes. The effect of non-identically distributed and correlated channels is also briefly discussed. Finally, the diversity multiplexing (DIV-MUX) tradeoff is presented under the finite SNR regime.
2001
This paper provides a theoretical characterization of the multihop wireless communications channel with diversity, wherein intermediate terminals relay information employing spatial diversity techniques. Two channel models are proposed and developed: one where each intermediate terminal combines, digitally decodes, and re-encodes the received signals from all preceding terminals and the other where each intermediate terminal simply combines and amplifies the received signals from all preceding terminals. These models are compared, through analysis and simulations, with the singlehop reference channel on the basis of probability of outage and probability of error. Both models achieve significant gains over the singlehop reference channel, with the amplified relaying model outperforming the decoded relaying model despite noise propagation.
IEEE Transactions on Wireless Communications, 2005
2002
IEEE 802.11a/g devices promise to accommodate the increasing consumer demands for high data rate wireless communications. A novel optimal decoding method for receiver antenna diversity combining for a COFDM system is discussed in this paper to provide robust wireless connections for applications such as wireless multimedia communications. The proposed optimal diversity combining integrates the channel equalization, demodulation (bit metrics calculation) and diversity combining in the decoder, which is the maximum likelihood decoding method for the diversity combining for the COFDM system. The proposed method can have about 4-6 dB gain over a single antenna receiver and 2-4 dB gain over a traditional symbol level diversity combining receiver without increasing the implementation complexity.
IEEE Transactions on Communications, 2002
Optimal multi-antenna wide-band signaling schemes are derived for multipath channels assuming perfect channel state information at the transmitter. The scheme that minimizes the biterror probability in the single-user case is a rank-one space-time beamformer which focuses the signal transmission in the direction of the most dominant channel mode. Several suboptimal variations are discussed for multiuser applications. The optimal signaling scheme given channel statistics at the transmitter is also derived. The optimal scheme in this case is a full-rank space-time beamformer that transmits on all channel modes. Analysis and simulation results are used to compare the schemes proposed in this paper. Finally, we discuss the optimal signaling scheme when a delayed version of the channel state is available at the transmitter. It is shown that in this case the optimal scheme is a rank-1 beamformer when the channel variations are sufficiently slow and is a full rank beamformer in a sufficiently fast fading channel.
IEEE Transactions on Communications, 2012
This paper investigates the finite signal-to-noise ratio (SNR) diversity-multiplexing trade-off (DMT) of pointto-point wireless channels assisted by multiple relays. Results are derived for both amplify-and-forward (AF) and decode-andforward (DF) relaying protocols. For the AF protocol, we derive accurate approximations for the system outage probability when the relays are clustered between the source and destination. For the case where all the relays are clustered near the destination, an exact closed-form expression for the system outage probability is obtained. For the DF protocol, under general multiple relaying configurations, we derive an exact closed-form expression for the system outage probability. The outage results for AF and DF are used subsequently to yield expressions for the finite-SNR DMT. We also extract the conventional asymptotic DMTs as special cases of the finite-SNR results, and demonstrate that the asymptotic DMTs can significantly overestimate the level of diversity that is achievable for practical error rates and SNRs.
International Journal of …, 2008
We study the performance of multihop diversity systems with non-regenerative relays over independent and non-identical Rayleigh fading channels. The analysis is based on the evaluation of the instantaneous end-to-end signal-to-noise ratio (SNR), depending on the type of the relay and the diversity scheme used. A closed-form expression is derived for the average end-to-end SNR, when fixed-gain relays and a maximal ratio combiner are used; also, an analytical expression formula for the average symbol-error rate (ASER) for the above case is presented. The results show that, as expected, multihop diversity systems outperform conventional telecommunication systems in terms of ASER when the same amount of energy is assumed to be consumed in both cases. Copyright © 2008 John Wiley & Sons, Ltd.
2008 42nd Annual Conference on Information Sciences and Systems, 2008
Zheng and Tse have shown that over a quasi-static channel, there exists a fundamental tradeoff, known as the diversity-multiplexing gain (D-MG) tradeoff. In a realistic system, to avoid inefficiently operating the power amplifier, one should consider the situation where constraints are imposed on the Peak to Average Power Ratio (PAR) value of the transmitted signal. In this paper, we investigate the D-MG tradeoff of multi-antenna systems with PAR constraints. For Rayleigh fading channels, the result shows that the D-MG tradeoff remains the same even with PAR constraints.
2006 IEEE International Symposium on Information Theory, 2006
In this paper, an outage limited MIMO channel is considered. We build on Zheng and Tse's elegant formulation of diversity-multiplexing tradeoff to develop a better understanding of the asymptotic relationship between probability of error, transmission rate and signal-to-noise ratio. We identify the limitation imposed by the notion of multiplexing gain and develop a new formulation for the throughput-reliability tradeoff that avoids this limitation. The new characterization is then used to shed more light on the asymptotic trends exhibited by the outage probability curves of MIMO channels.
MIMO Systems, Theory and Applications, 2011
2013
Current and emergent services are demanding higher data rates, improved spectral efficiency and increased network capacity. To face this new requirements, it is important to find schemes able to reduce the effects of fading and explore new types of diversity. The current work performs a comparison between different multi-antenna techniques that can be employed to achieve the requirements of the Fourth Generation Cellular Systems (4G). The described schemes are studied at the link and system level using Bit Error Rate as the performance index.
2007
In this paper we analyze the performance of multiple relay channels when multiple antennas are deployed only at relays. Specifically, we investigate the simple repetition-coded decode-and-forward protocol and apply two antenna combining techniques at relays, namely maximum ratio combining (MRC) on receive and transmit beamforming (TB). We assume that the total number of antennas at all relays is fixed to N. With a reasonable power constraint at the relays, we show that the antenna combining techniques can exploit the full spatial diversity of the relay channels and can achieve the same diversity multiplexing tradeoff as achieved by more complex space-time distributed coding techniques, such as those proposed by Laneman and Womell (2003).
IEEE Transactions on Wireless Communications, 2007
In this paper, a new approach to improving reliability and bandwidth efficiency in communications over frequencyselective channels using multiple antennas is proposed. In the heart of the new approach is a novel space-time orthogonal frequency division multiplexing (OFDM) scheme. The proposed space-time OFDM modulator translates a multiple-input multiple-output (MIMO) channel into a single-input multipleoutput (SIMO) channel without the loss of system freedom (the available diversity gain). This translation simplifies code design as compared to that in the conventional MIMO OFDM approach. Instead of more complicated space-time codes, codes that are designed for single-input fading channels can be used with the proposed space-time modulation. For bandwidth-efficient applications, a channel multiplexing scheme is developed to work with the space-time modulator. Unlike the conventional spatial multiplexing schemes, an arbitrary number of data streams can be created and each layer occupies all the transmit antennas all the time. As a result, all the available degrees of freedom are preserved for each layer and a full range of optimal tradeoffs between data rate and reliability is possible. Several examples are given to demonstrate the advantages of the proposed approach over the conventional MIMO OFDM approach.
IET Communications, 2018
Multiple antennas can be used for increasing the amount of diversity or number of degrees of freedom in wireless communication systems. In this paper, we consider a wireless half-duplex relay network consisting of one source destination pair each with a single antenna and one relay with multiple antennas. We assume an approach where cooperation of the relay in the transmission depends on the decoding status at the relay. If the relay participates in transmission, the source and the relay use the distributed space-time code simultaneously. We derive the outage probability and the DMT for the proposed protocol at high SNR. We have shown that the use of the centralized antennas with simultaneously decoding compared to the distributed antennas with independently decoding can improve the system performance.
IEEE Transactions on Information Theory, 2007
Multiple-antenna concepts for wireless communication systems promise high spectral efficiencies and improved error rate performance by proper exploitation of the randomness in multipath propagation. In this paper, we investigate the impact of channel uncertainty caused by channel estimation errors on the capacity of Rayleigh and Ricean block-fading channels. We consider a training-based multiple-antenna system that reserves a portion of time to sound the channel. The training symbols are used to estimate the channel state information (CSI) at the receiver by means of an arbitrary linear estimation filter. No CSI is assumed at the transmitter. Our analysis is based on an equivalent system model for training-based multiple-antenna systems which specifies the channel by the estimated (and hence, known) channel coefficients and an uncorrelated, data-dependent, multiplicative noise. This model includes the special cases of perfect CSI and no CSI. We present new upper and lower bounds on the maximum instantaneous mutual information to compute ergodic and outage capacities, and extend previous results to arbitrary (and possibly mismatched) linear channel estimators and to correlated Ricean fading. Several numerical results for single-and multiple-antenna systems with estimated CSI are included as illustration. Index Terms-Ergodic and outage capacity, fading channels, linear channel estimation, maximum mutual information, multiple-antenna systems. I. INTRODUCTION M ULTIPLE-antenna concepts for fading channels have received considerable attention in the recent history of wireless communication systems. Significant increases in spectral efficiency [1] and large improvements in terms of error rate performance [2] can by achieved by properly exploiting the randomness in multipath propagation, without increase in transmit power or bandwidth. Information-theoretic work on the capacity of single and multiple-antenna fading channels originally assume perfect channel state information (CSI) available at the receiver [1]-[5]. Ericson [3] considered a Gaussian channel with slow fading and gave an explicit capacity expression. A generalization for multiple-an-Manuscript
In this literature review, we have studied the evolution of multiple antenna (MA) systems, viz. SIMO (single-input-multiple-output), MISO (multiple input- single-output) and MIMO (multiple-input-multiple output) and compared the system performance with SISO (single-input-single-output) system in terms of parameters like capacity and BER (bit error rate). The trade off between spatial multiplexing gain (which maximizes transmission rate using rich scattering) and diversity gain (which combats fading, improves reliability and minimizes probability of error) is addressed. Both transmit and receive diversities are canvassed in details. Discussion on receive diversity incorporates three most widely used schemes, viz. Selection Combining (SC), Maximal Ratio Combining (MRC) and Equal Gain Combining (EGC). Space time coding scheme is the main focus or transmit diversity study. Performance of different diversity schemes are compared both qualitatively and quantitatively. Finally we have explored how MIMO system can improve the channel capacity and the limits to which the betterment can be made under various channel conditions. The study is restricted to single user, narrow band, Rayleigh channel.
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