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80
Achieving near-capacity on a multiple-antenna channel
- IEEE Trans. Commun
, 2003
"... Recent advancements in iterative processing of channel codes and the development of turbo codes have allowed the communications industry to achieve near-capacity on a single-antenna Gaussian or fading channel with low complexity. We show how these iterative techniques can also be used to achieve nea ..."
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Cited by 402 (2 self)
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Recent advancements in iterative processing of channel codes and the development of turbo codes have allowed the communications industry to achieve near-capacity on a single-antenna Gaussian or fading channel with low complexity. We show how these iterative techniques can also be used to achieve near-capacity on a multiple-antenna system where the receiver knows the channel. Combining iterative processing with multiple-antenna channels is particularly challenging because the channel capacities can be a factor of ten or more higher than their single-antenna counterparts. Using a “list ” version of the sphere decoder, we provide a simple method to iteratively detect and decode any linear space-time mapping combined with any channel code that can be decoded using so-called “soft ” inputs and outputs. We exemplify our technique by directly transmitting symbols that are coded with a channel code; we show that iterative processing with even this simple scheme can achieve near-capacity. We consider both simple convolutional and powerful turbo channel codes and show that excellent performance at very high data rates can be attained with either. We compare our simulation results with Shannon capacity limits for ergodic multiple-antenna channel. Index Terms—Wireless communications, BLAST, turbo codes, transmit diversity, receive diversity, fading channels, sphere decoding, soft-in/soft-out, concatenated codes 1
Distributed space-time coding in wireless relay networks,”IEEE Trans.
- on Wireless Communications,
, 2006
"... Abstract In this paper, we present a coding strategy for half duplex wireless relay networks, where we assume no channel knowledge at any of the transmitter, receiver or relays. The coding scheme uses distributed space-time coding, that is, the relay nodes cooperate to encode the transmitted signal ..."
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Cited by 225 (16 self)
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Abstract In this paper, we present a coding strategy for half duplex wireless relay networks, where we assume no channel knowledge at any of the transmitter, receiver or relays. The coding scheme uses distributed space-time coding, that is, the relay nodes cooperate to encode the transmitted signal so that the receiver senses a space-time codeword. It is inspired by noncoherent differential techniques. The proposed strategy is available for any number of relays nodes. It is analyzed, and shown to yield a diversity linear in the number of relays. We also study the resistance of the scheme to relay node failures, and show that a network with R relay nodes and d of them down behaves, as far as diversity is concerned, as a network with R − d nodes. Finally, our construction can be easily generalized to the case where the transmitter and receiver nodes have several antennas.
Universal Space-Time Coding
- IEEE Trans. Inform. Theory
, 2003
"... A universal framework is developed for constructing full-rate and full-diversity coherent space--time codes for systems with arbitrary numbers of transmit and receive antennas. The proposed framework combines space--time layering concepts with algebraic component codes optimized for single-input--si ..."
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Cited by 143 (7 self)
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A universal framework is developed for constructing full-rate and full-diversity coherent space--time codes for systems with arbitrary numbers of transmit and receive antennas. The proposed framework combines space--time layering concepts with algebraic component codes optimized for single-input--single-output (SISO) channels. Each component code is assigned to a "thread" in the space--time matrix, allowing it thus full access to the channel spatial diversity in the absence of the other threads. Diophantine approximation theory is then used in order to make the different threads "transparent" to each other. Within this framework, a special class of signals which uses algebraic number-theoretic constellations as component codes is thoroughly investigated. The lattice structure of the proposed number-theoretic codes along with their minimal delay allow for polynomial complexity maximum-likelihood (ML) decoding using algorithms from lattice theory. Combining the design framework with the Cayley transform allows to construct full diversity differential and noncoherent space--time codes. The proposed framework subsumes many of the existing codes in the literature, extends naturally to time-selective and frequency -selective channels, and allows for more flexibility in the tradeoff between power efficiency, bandwidth efficiency, and receiver complexity. Simulation results that demonstrate the significant gains offered by the proposed codes are presented in certain representative scenarios.
Linear Dispersion Codes for MIMO Systems Based on Frame Theory
"... Abstract—Multiple-input multiple-output (MIMO) wireless communication systems provide high capacity due to the plurality of modes available in the channel. Existing signaling techniques for MIMO systems have focused primarily on multiplexing for high data rate or diversity for high link reliability. ..."
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Cited by 48 (0 self)
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Abstract—Multiple-input multiple-output (MIMO) wireless communication systems provide high capacity due to the plurality of modes available in the channel. Existing signaling techniques for MIMO systems have focused primarily on multiplexing for high data rate or diversity for high link reliability. In this paper, we present a new linear dispersion code design for MIMO Rayleigh fading channels. The proposed design bridges the gap between multiplexing and diversity and yields codes that typically perform well both in terms of ergodic capacity as well as error probability. This is important because, as we show, designs performing well from an ergodic capacity point of view do not necessarily perform well from an error probability point of view. Various techniques are presented for finding codes with good error probability performance. Monte Carlo simulations illustrate performance of some example code designs in terms of ergodic capacity, codeword
Leveraging coherent space-time codes for noncoherent communication via training
- IEEE TRANS. INFORM. THEORY
, 2004
"... Training codes are introduced for the multiple-antenna, noncoherent, multiple block-Rayleigh-fading channel in which the fading coefficients, which are constant over a fixed number of dimensions (coherence interval) for each block and then change independently to a new realization, are known neithe ..."
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Cited by 18 (2 self)
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Training codes are introduced for the multiple-antenna, noncoherent, multiple block-Rayleigh-fading channel in which the fading coefficients, which are constant over a fixed number of dimensions (coherence interval) for each block and then change independently to a new realization, are known neither at the transmitter nor at the receiver. Each codeword of a training code consists of a part known to the receiver—used to form a minimum mean-squared error (MMSE) estimate of the channel—and a part that contains codeword(s) of a space–time block or trellis code designed for the coherent channel (in which the receiver has perfect knowledge of the channel). The channel estimate is used as if it were error-free for decoding the information-bearing part of the training codeword. Training codes are hence easily designed to have high rate and low decoding complexity by choosing the underlying coherent code to have
Unitary space-time modulation via Cayley transformation
- IEEE Trans. Signal Processing
, 2003
"... Abstract—A recently proposed method for communicating with multiple antennas over block fading channels is unitary space-time modulation (USTM). In this method, the signals transmitted from the antennas, viewed as a matrix with spatial and temporal dimensions, form a unitary matrix, i.e., one with o ..."
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Cited by 14 (1 self)
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Abstract—A recently proposed method for communicating with multiple antennas over block fading channels is unitary space-time modulation (USTM). In this method, the signals transmitted from the antennas, viewed as a matrix with spatial and temporal dimensions, form a unitary matrix, i.e., one with orthonormal columns. Since channel knowledge is not required at the receiver, USTM schemes are suitable for use on wireless links where channel tracking is undesirable or infeasible, either because of rapid changes in the channel characteristics or because of limited system resources. Recent results have shown that if suitably designed, USTM schemes can achieve full channel capacity at high SNR and, moreover, that all this can be done over a single coherence interval, provided the coherence interval and number of transmit antennas are sufficiently large, which is a phenomenon referred to as autocoding. While all this is well recognized, what is not clear is how to generate good performing constellations of (nonsquare) unitary matrices that lend themselves to efficient encoding/decoding. The schemes proposed so far either exhibit poor performance, especially at high rates, or have no efficient decoding algorithms. In this paper, we propose to use the Cayley transform to design USTM constellations. This work can be viewed as a generalization, to the nonsquare case, of the Cayley codes that have been proposed for differential USTM. The codes are designed based on an infor-mation-theoretic criterion and lend themselves to polynomial-time (often cubic) near-maximum-likelihood decoding using a sphere decoding algorithm. Simulations suggest that the resulting codes allow for effective high-rate data transmission in multiantenna communication systems without knowing the channel. However, our preliminary results do not show a substantial advantage over training-based schemes. Index Terms—Cauchy random matrices, Cayley transform, diversity product, fading channels, isotropic distribution, unitary space-time codes, unitary space-time modulation, wireless com-munications. I.
Training-Codes for the Noncoherent Multi-Antenna Block-Rayleigh-Fading Channel
, 2003
"... We consider signal design for the noncoherent block-Rayleigh-fading channel, in which neither the transmitter nor the receiver know the fading coefficients. We show that several recently proposed signal designs for this channel can be interpreted as training-based, i.e., part of the coherence interv ..."
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Cited by 12 (2 self)
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We consider signal design for the noncoherent block-Rayleigh-fading channel, in which neither the transmitter nor the receiver know the fading coefficients. We show that several recently proposed signal designs for this channel can be interpreted as training-based, i.e., part of the coherence interval is used to transmit known symbols to learn the channel and in the remainder a "coherent " information symbol is transmitted. At the receiver, the estimated channel is then used as if correct, which allows to employ efficient implementations (like the sphere-decoder) for the coherent decision rule. We establish conditions for which such a strategy is equivalent to the optimal noncoherent decision rule. Motivated by the good performance of the training schemes even when the coherence time is very small (indeed minimal), we propose the paradigm of training-codes to build signalconstellations for the noncoherent block-Rayleigh-fading channel. Training-codes leverage the advances made in coherent codes and thus can often address the signal-design and efficient-decoding problems simultaneously.
Systemetic and optimal cyclotomic lattices and diagonal space-time block code designs
- IEEE Trans. Inform. Theory
, 2004
"... In this correspondence, a new and systematic design of cyclotomic lattices with full diver-sity is proposed by using some algebraic number theory. This design provides innitely many full diversity cyclotomic lattices for a given lattice size. Based on the packing theory and the concrete form of the ..."
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Cited by 10 (5 self)
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In this correspondence, a new and systematic design of cyclotomic lattices with full diver-sity is proposed by using some algebraic number theory. This design provides innitely many full diversity cyclotomic lattices for a given lattice size. Based on the packing theory and the concrete form of the design, optimal cyclotomic lattices are presented by minimizing the mean transmission signal power for a given minimum (diversity) product (or equivalently maximiz-ing the minimum product for a given mean transmission signal power). The newly proposed cyclotomic lattices can be applied to both space-time code designs for multi-antenna systems and linear precode design for signal space diversity in single antenna systems over fast Rayleigh fading channels. Although there are some cyclotomic lattices/space-time codes existed in the literature, most of them are not optimal.
Differential space-time turbo codes
- IEEE Trans
, 2001
"... The serial concatenation of simple error control codes and differential space-time modulation is considered. Decoding is performed iteratively by passing symbol-wise a-posteriori probability information between the decoders of the inner space-time code and the outer code. An input-output extrinsic i ..."
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Cited by 9 (0 self)
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The serial concatenation of simple error control codes and differential space-time modulation is considered. Decoding is performed iteratively by passing symbol-wise a-posteriori probability information between the decoders of the inner space-time code and the outer code. An input-output extrinsic information transfer analysis is used to predict thresholds for outer convolutional codes of various memory orders and simple outer parity check codes. It is shown that the simple parity check code is best matched to the inner differential space-time code and achieves a bit error rate of 10 −6 less than 2 dB from the Shannon capacity of the fast fading multiple antenna channel. The differential space-time code can also be used to generate a-priori information in the absence of channel knowledge. This information can be exploited by a channel estimator inserted into the decoding iteration. It is demonstrated that the inner space-time code provides soft training symbols from periodically inserted training symbols. The reliability of these soft training symbols does not depend on the speed of the channel variations, but on the structure of the inner code and the signal-to-noise ratio. Simulation studies confirm these findings and show that the proposed system with no initial channel knowledge achieves a performance very close to that of the system with perfect channel knowledge.
