Results 1  10
of
143
On MaximumLikelihood Detection and the Search for the Closest Lattice Point
 IEEE TRANS. INFORM. THEORY
, 2003
"... Maximumlikelihood (ML) decoding algorithms for Gaussian multipleinput multipleoutput (MIMO) linear channels are considered. Linearity over the field of real numbers facilitates the design of ML decoders using numbertheoretic tools for searching the closest lattice point. These decoders are colle ..."
Abstract

Cited by 266 (7 self)
 Add to MetaCart
Maximumlikelihood (ML) decoding algorithms for Gaussian multipleinput multipleoutput (MIMO) linear channels are considered. Linearity over the field of real numbers facilitates the design of ML decoders using numbertheoretic tools for searching the closest lattice point. These decoders are collectively referred to as sphere decoders in the literature. In this paper, a fresh look at this class of decoding algorithms is taken. In particular, two novel algorithms are developed. The first algorithm is inspired by the Pohst enumeration strategy and is shown to offer a significant reduction in complexity compared to the ViterboBoutros sphere decoder. The connection between the proposed algorithm and the stack sequential decoding algorithm is then established. This connection is utilized to construct the second algorithm which can also be viewed as an application of the SchnorrEuchner strategy to ML decoding. Aided with a detailed study of preprocessing algorithms, a variant of the second algorithm is developed and shown to offer significant reductions in the computational complexity compared to all previously proposed sphere decoders with a nearML detection performance. This claim is supported by intuitive arguments and simulation results in many relevant scenarios.
FullDiversity, HighRate SpaceTime Block Codes from Division Algebras
 IEEE TRANS. INFORM. THEORY
, 2003
"... We present some general techniques for constructing fullrank, minimaldelay, rate at least one spacetime block codes (STBCs) over a variety of signal sets for arbitrary number of transmit antennas using commutative division algebras (field extensions) as well as using noncommutative division algeb ..."
Abstract

Cited by 178 (56 self)
 Add to MetaCart
(Show Context)
We present some general techniques for constructing fullrank, minimaldelay, rate at least one spacetime block codes (STBCs) over a variety of signal sets for arbitrary number of transmit antennas using commutative division algebras (field extensions) as well as using noncommutative division algebras of the rational field embedded in matrix rings. The first half of the paper deals with constructions using field extensions of . Working with cyclotomic field extensions, we construct several families of STBCs over a wide range of signal sets that are of full rank, minimal delay, and rate at least one appropriate for any number of transmit antennas. We study the coding gain and capacity of these codes. Using transcendental extensions we construct arbitrary rate codes that are full rank for arbitrary number of antennas. We also present a method of constructing STBCs using noncyclotomic field extensions. In the later half of the paper, we discuss two ways of embedding noncommutative division algebras into matrices: left regular representation, and representation over maximal cyclic subfields. The 4 4 real orthogonal design is obtained by the left regular representation of quaternions. Alamouti's code is just a special case of the construction using representation over maximal cyclic subfields and we observe certain algebraic uniqueness characteristics of it. Also, we discuss a general principle for constructing cyclic division algebras using the th root of a transcendental element and study the capacity of the STBCs obtained from this construction. Another family of cyclic division algebras discovered by Brauer is discussed and several examples of STBCs derived from each of these constructions are presented.
The Golden Code: A 2 × 2 fullrate spacetime code with nonvanishing determinants
 IEEE Transactions on Information Theory
, 2005
"... Abstract — In this paper we present the Golden ..."
(Show Context)
Perfect space–time block codes
 IEEE TRANS. INFORM. THEORY
, 2006
"... In this paper, we introduce the notion of perfect space–time block codes (STBCs). These codes have fullrate, fulldiversity, nonvanishing constant minimum determinant for increasing spectral efficiency, uniform average transmitted energy per antenna and good shaping. We present algebraic construct ..."
Abstract

Cited by 101 (17 self)
 Add to MetaCart
(Show Context)
In this paper, we introduce the notion of perfect space–time block codes (STBCs). These codes have fullrate, fulldiversity, nonvanishing constant minimum determinant for increasing spectral efficiency, uniform average transmitted energy per antenna and good shaping. We present algebraic constructions of perfect STBCs for 2, 3, 4, and 6 antennas.
The MIMO ARQ channel: Diversitymultiplexingdelay tradeoff
 IEEE Trans. Inf. Theory
, 2006
"... Abstract—In this paper, the fundamental performance tradeoff of the delaylimited multipleinput multipleoutput (MIMO) automatic retransmission request (ARQ) channel is explored. In particular, we extend the diversity–multiplexing tradeoff investigated by Zheng and Tse in standard delaylimited MIM ..."
Abstract

Cited by 82 (6 self)
 Add to MetaCart
(Show Context)
Abstract—In this paper, the fundamental performance tradeoff of the delaylimited multipleinput multipleoutput (MIMO) automatic retransmission request (ARQ) channel is explored. In particular, we extend the diversity–multiplexing tradeoff investigated by Zheng and Tse in standard delaylimited MIMO channels with coherent detection to the ARQ scenario. We establish the threedimensional tradeoff between reliability (i.e., diversity), throughput (i.e., multiplexing gain), and delay (i.e., maximum number of retransmissions). This tradeoff quantifies the ARQ diversity gain obtained by leveraging the retransmission delay to enhance the reliability for a given multiplexing gain. Interestingly, ARQ diversity appears even in longterm static channels where all the retransmissions take place in the same channel state. Furthermore, by relaxing the input power constraint allowing variable power levels in different retransmissions, we show that power control can be
A unified framework for tree search decoding: Rediscovering the sequential de coder
 IEEE Trans. Inform. Theory
, 2006
"... ..."
(Show Context)
An optimal two transmit antenna spacetime code and its stacked extensions
 in Proc. Asilomar Conf. on Signals, Systems and Computers
, 2003
"... Abstract—A space–time code is proposed that exhibits the highest coding gain among competing fullrate full transmit diversity space–time codes for the two transmit and receive antenna coherent quasistatic fading channel. The proposed code is derived from a layered architecture with real rotation o ..."
Abstract

Cited by 72 (1 self)
 Add to MetaCart
Abstract—A space–time code is proposed that exhibits the highest coding gain among competing fullrate full transmit diversity space–time codes for the two transmit and receive antenna coherent quasistatic fading channel. The proposed code is derived from a layered architecture with real rotation of quadrature amplitude modulation (QAM) information symbols in two dimensions. The existing codes of similar architecture concentrate on application of complex full modulation diversity rotations or asymmetric real rotations. An analytic evaluation illustrates the significant improvement in coding gain achieved with the proposed code. Moreover, the coding gain of the proposed code is independent of its rate. This implies that the proposed code achieves the optimal diversity–multiplexing tradeoff curve for the two transmit antenna system. A stacked extension of the proposed code offers a reduced complexity capacity optimal alternative to the full diversity codes for larger number of transmit antennas. Performance enhancement in several scenarios is verified through simulations. Index Terms—Capacity optimal codes, coding gain, diversity–multiplexing tradeoff, fading channel, real rotation, space–time coding, transmit diversity. I.
Achieving the full MIMO diversitymultiplexing frontier with rotationbased spacetime codes
 in Proc. Allerton Conf. Commun., Contr., Comput.,, IL
, 2003
"... The recently established diversitymultiplexing frontier characterizes the highSNR tradeoff between the best possible robustness and throughput gains obtainable by employing multiple antennas for digital communication in fading environments. We focus on the case of two transmit and at least two rec ..."
Abstract

Cited by 55 (1 self)
 Add to MetaCart
(Show Context)
The recently established diversitymultiplexing frontier characterizes the highSNR tradeoff between the best possible robustness and throughput gains obtainable by employing multiple antennas for digital communication in fading environments. We focus on the case of two transmit and at least two receive antennas, and show that a sufficient condition for a family of codebooks indexed by rate to achieve the full diversitymultiplexing frontier is that the worstcase codeword difference determinant either does not decay to zero with rate or decays subexponentially. We further provide a constructive proof that the full frontier is achievable by codes of length two by developing families of rotationbased spacetime block codes with rateindependent nonzero worstcase determinants. These determinants are optimized over reasonably rich code subspaces. By contrast, Gaussian codes of this length were known not to achieve the frontier, and earlier rotationbased codes were known only to achieve the extremal points of the frontier. Simulation results also verify that the new codes have sufficient coding gain to achieve error rates close enough to the infinite length code outage bound, and thus they provide superior performance to Alamouti’s orthogonal spacetime block code at spectral efficiencies beyond about 4 b/s/Hz. 1
Perfect SpaceTime Codes for Any Number of Antennas
"... In a recent paper, perfect (n × n) spacetime codes were introduced as the class of linear dispersion spacetime codes having full rate, nonvanishing determinant, a signal constellation isomorphic to either the rectangular or hexagonal lattices in 2n 2 dimensions and uniform average transmitted en ..."
Abstract

Cited by 39 (3 self)
 Add to MetaCart
In a recent paper, perfect (n × n) spacetime codes were introduced as the class of linear dispersion spacetime codes having full rate, nonvanishing determinant, a signal constellation isomorphic to either the rectangular or hexagonal lattices in 2n 2 dimensions and uniform average transmitted energy per antenna. Consequence of these conditions include optimality of perfect codes with respect to the ZhengTse DiversityMultiplexing Gain tradeoff (DMT), as well as excellent lowSNR performance. Yet perfect spacetime codes have been constructed only for 2, 3, 4 and 6 transmit antennas. In this paper, we construct perfect codes for all channel dimensions, present some additional attributes of this class of spacetime codes and extend the notion of a perfect code to the rectangular case.