Michael Fitz

Silvus Technologies

Atmospheric turbulence causes the receive signal intensity on free space optical (FSO) communication links to vary over time. Scintillation fades can stymie connectivity for milliseconds at a time. To approach the information-theoretic limits of communication in such time-varying channels, it necessary to either code across extremely long blocks of...

Outage probability and outage ergodic constrained capacity are important performance metrics of broadband satellite communication networks operating above 10 GHz. The objective of this letter is to propose a simple method, using piecewise linear fitting, for the calculation of these figures of merit in rain fading channels. Rain fading affecting th...

Atmospheric turbulence causes the receive signal intensity on free space optical (FSO) communication links to vary over time. Scintillation fades can stymie connectivity for milliseconds at a time. To approach the information-theoretic limits of communication in such time-varying channels, it necessary to either code across extremely long blocks of...

DARPA's Shared Spectrum Access for Radar and Communications (SSPARC) program seeks to improve radar and communications capabilities through spectrum sharing. Spectrum sensing is an integral component of this vision. For example, a spectrally-agile military radar system could adapt the frequency bands it uses according to the sensed spectrum. Curren...

In this work, we present an interference canceler that can enable blue force communications signal reception in the presence of a co-located jamming system. Unlike existing simultaneous transmit and receive (STAR) systems targeted for commercial WiFi, our Joint Analog and Digital Cancellation (JADIC) architecture requires no prior knowledge about t...

Tethered interference cancelation is an important operation in a multitude of scenarios, both commercial (named "full-duplex" operation) as well as military (interference excision). The fundamental assumption behind active or tethered cancellation is that a copy of the interference is available in realtime, and its removal therefore is somehow poss...

Ever growing demand for wireless services and a dearth of quality spectrum requires more efficient use of available bandwidth. Cross-layer design has the potential for more efficient system design than is possible considering each layer in isolation. In this article, we consider goodput optimization of pilot-symbol assisted modulation with orthogon...

The driving force behind this work is the desire to obtain one method for estimating the ergodic capacity of lognormal (LN) channels for both Shannon capacity and constrained capacity. In recent years, researchers have determined methods for calculating the ergodic Shannon capacity for LN channels. However, in practical communication systems, the i...

The nonlinear distortion in efficiently operated wide bandwidth and high power amplifiers often limits the throughput and performance of satellite communications. Volterra series decomposition provides an efficient and analytically tractable way to represent the nonlinear satellite communication channel. Realizing that only a few dominant terms in...

This manuscript presents an iterative detector based on a generalized Schnorr-Euchner enumeration for the case of imperfect channel state information. The detector determines the most contributive N∈{1,2} terms in each of the two log-sum-exponents. The objective function of the tree search is modified to account for (a) the channel estimation error...

Opportunistic Spatial Orthogonalization (OSO) is a cognitive radio scheme that allows the existence of secondary users and hence increases the sum throughput, even if the primary user occupies all the frequency bands all the time. The key idea is to exploit the spatial dimensions to orthogonalize users and hence minimize interference. However, unli...

This paper presents and compares two iterative coded modulation techniques for deep-space optical communications using pulse-position modulation (PPM). The first code, denoted by SCPPM, consists of the serial concatenation of an outer convolutional code, an interleaver, a bit accumulator, and PPM. The second code, denoted by LDPC-PPM, consists of t...

A simple 4-state nonlinear trellis code with Gray-mapped QAM signals is designed which restricts certain symbol transitions in the constellation in order to shape the spectrum. The resulting spectral shaping subset selection code employs sign bit (most significant bit) coding, and is realized as a nonlinear binary convolutional code followed by an...

Two kinds of iterative sphere detectors based on modifications of the Schnorr-Euchner enumeration are presented. The first is capable of finding "good" candidate lattice points relatively soon. Its complexity and performance are controlled by an adaptive radius backlash update strategy. The second systematically searches for the most contributive t...

Location aware applications benefit from accurate position information. The position uncertainty can be reduced through cooperative localization in distributed systems with accurate point-to-point ranging. Received signal strength (RSS) measurement enables low cost, low complexity distance estimation. The distance estimate suffers from two sources...

The multistrata space-time codes proposed by Wachsmann et al. were intended then to fix the drawback of orthogonal space-time block codes which is the relatively low spectral efficiency. However, these codes lack two things: 1) their performance is worse than codes designed using number theory like the Golden code. 2) The advantages of their struct...

The most common physical layer models for network simulations are the bit error rate and the SNR threshold model. In time-varying channels such as those experienced in vehicular networks, these models are assumed valid as long as the packet duration is less than the coherence time of the channel. The coherence time is a statistical measure of the c...

Researchers have investigated the Shannon capacity of satellite links that have log-normal rain-fading channels in the Ka band (20-30 GHz). This paper uses information theoretic tools to expand on the previous work by computing the constrained capacity of log-normally distributed rain-fading channels in which practical constellations, such as those...

This paper considers the use of site diversity to mitigate rain effects. It uses information theoretic tools to compute the constrained capacity of log-normally distributed rain-fading channels in the Ka band (20-30 GHz) in which practical constellations, such as those found in the DVB-S2 standard are used, as opposed to the Gaussian distribution a...

A nonlinear binary code with a single carrier M-QAM linear modulation is designed to control certain transitions in the symbol constellation. This concept is employed to develop spectral shaping modulation codes with M-QAM linear modulations so as to reduce out-of-band power. The code is realized as a nonlinear binary convolutional code, and the co...

Deliberately designed bits-to-symbols mappings were introduced to provide significant coding gains compared to the simple Gray mapping for iteratively-decoded BICM on both AWGN and fading channels. The performance of these powerful mappings has always been illustrated in conjunction with relatively weak outer channel codes like convolutional codes...

The problem of efficient communication over a scalar quasi-static fading channel is considered. The single-layer transmission (SLT) and multi-layer transmission (MLT) schemes do not require any knowledge of the channel state information (CSI) at the transmitter, but their performance is also limited. It is shown that using Hybrid-ARQ (HARQ) can sig...

An iterative sphere detector is presented that takes into account channel estimation errors. It evolves from the class of the most contributive 2N generalized Schnorr-Euchner detectors for N ¿ 2. The later were recently introduced for iterative detection and decoding receivers of ST-BICM over flat fading channels under the assumption of perfect ch...

The optimization of baseband processing is proposed to compensate for high power amplifier (HPA) nonlinear distortion and channel noise, and to meet an output spectral constraint without the use of a spectral containment filter. Global compensation data predistortion with memory and square root raised cosine pulse shaping are employed, and the spec...

Channel estimation of coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) in fast time-varying channels are considered. Maintaining high performance with manageable complexity relies on iterative soft-in soft-out equalization and decoding. Conventional frequency domain channel estimation methods have an irr...

Orthogonal frequency division multiplexing (OFDM) system suffers extra performance degradation in fast fading channels due to intercarrier interference (ICI). Combining frequency domain equalization and bit-interleaved coded modulation (BICM), the iterative receiver is able to harvest both temporal and frequency diversity. Realizing that ICI channe...

Two efficient iterative sphere detectors based on the Schnorr-Euchner enumeration are the topic of this manuscript. The first one is capable of finding dasiagoodpsila candidate lattice points soon enough and its efficiency/performance are controlled by an adaptive radius update strategy. The second is a max-log detector. Because of the Schnorr-Euch...

This paper focuses on studying the fundamental performance limits and linear dispersion code design for the MIMO-ARQ slow fading channel. Optimal average rate of well-known HARQ protocols is analyzed. The optimal design of space-time coding for the MIMO-ARQ channel is discussed. Information-theoretic measures are used to optimize the rate assignmen...

Opportunistic spatial orthogonalization (OSO) is a new cognitive radio scheme that allows the existence of secondary users and hence increases the system throughput, even if the primary user occupies all the frequency bands all the time. Notably, this throughput advantage is obtained without sacrificing the performance of the primary user, if the i...

Data detection of coded multiple-input multipleoutput (MIMO) orthogonal frequency division multiplexing (OFDM) in fast time-varying channels are considered. Maintaining high performance with manageable complexity relies on iterative soft-in soft-out equalization and decoding. This paper derives the optimum front-end demodulation structure by extend...

Orthogonal frequency division multiplexing (OFDM) systems suffer performance degradation in fast fading channels due to intercarrier interference (ICI). Combining frequency domain equalization and bit-interleaved coded modulation (BICM), the iterative receiver is able to harvest both temporal and frequency diversity. In order to perform coherent de...

Orthogonal frequency division multiplexing (OFDM) systems suffer performance degradation in fast fading channels due to intercarrier interference (ICI). Combining frequency domain equalization and bit-interleaved coded modulation (BICM), the iterative receiver is able to harvest both temporal and frequency diversity. In order to perform coherent de...

This paper studies Hybrid ARQ (HARQ) schemes in a multiple-antenna slow fading channel. Optimal average rate performance of several well-known HARQ protocols is analyzed. We then proceed to the design of Space-Time Coding (STC) for MIMO-HARQ channel. Information-theoretic performance measures are used to optimize the rate assignment and derive the...

The MIMO-OFDM beamforming design problem is addressed from a system level standpoint. A beamforming method is proposed which helps improve the receiver channel estimation performance without degrading any benefit of a conventional beamformer. To that end, the smoothed singular value decomposition (SSVD) algorithm is first developed to get "close" e...

The observation that different bit positions in a constellation typically have different error protection capabilities is utilized to design unequal error protection (UEP) with multilevel coding (MLC) in AWGN and fading channels. Both parallel independent decoding (PID) and multi-stage decoding (MSD) are considered. The design tool in this work is...

According to the MPS simulation of Ka band satellite signals, used in conjunction with a typical cloud-present turbulence profile, there can be a substantial diversity benefit from using multiple antennas for links with elevation angles less than 20 degrees. It should be noted that this analysis method can also be applied to horizontal paths (i.e....

This paper proposes improved space-time multiple TCM (ST-MTCM) codes via a systematic expansion of space- time block code (STBC) for two transmit antennas. Starting from the orthogonal STBC, the STBC set is expanded into super- orthogonal STBC, and further expanded up to spatial multiplexing in the case of BPSK and QPSK constellations. Exploiting t...

The problem of efficient communication over a quasi-static wireless fading channel is considered in this paper. The disadvantages of two well-known schemes, single-layer transmission (SLT) and multi-layer transmission (MLT), are pointed out. A new scheme named aggressive transmission with ARQ (AT-ARQ) is developed and optimized to provide better pe...

Different error protection capabilities associated with different bit positions in a constellation are utilized to provide unequal error protection (UEP) with multilevel coding (MLC) on AWGN and fast/slow fading channels. Unlike previous work on this problem, the design tool in this paper is the symmetric information rate (SIR), which is well suite...

This paper proposes a new peak-to-average power ratio (PAPR) reduction scheme in multiple transmit antenna environments. Instead of applying individual PAPR reduction on each antenna, a joint PAPR reduction technique is proposed. By applying a relevant unitary rotation over the transmit antennas, overall PAPR of the multiple transmit antenna system...

The desire for higher data rates and the need for available bandwidth has pushed satellite communications into the Ka band (20-30 GHz). At these higher carrier frequencies the effects of scintillation due to turbulence-induced index of refraction irregularities in the troposphere is known to become more prevalent, particularly on slant paths. Mitig...

Iterative turbo processing between detection and decoding shows near-capacity performance on a multiple-antenna system. Combining iterative processing with optimum front-end detection is particularly challenging because the front-end maximum a posteriori (MAP) algorithm has a computational complexity that is exponential. Sub-optimum detector such a...

This article investigates the properties of several non-Jakes Doppler spectra proposed for the vehicle-to-vehicle nonisotropic scattering environment of the open highway. Expressions for the ideal model correlations, level-crossing rates, and average fade durations are derived. The classic Clarke channel model is modified to generate fading signals...

Orthogonal frequency division multiplexing (OFDM) system suffers extra performance degradation in fast fading channels due to intercarrier interference (ICI). Combining frequency domain equalization and bit-interleaved coded modulation (BICM), the iterative receiver is able to harvest both temporal and frequency diversity. Using the fact that ICI e...

A geometric decoding technique for finite lattices was presented by Seethaler et al. for flat-fading multiple-input multiple-output channels in the case of linear modulations with constant amplitude (PSK). In this paper, geometric decoding is extended to square PAM and QAM constellations. Geometric decoding is suboptimal but has the advantage that...

Space-Time trellis-coded modulation (ST-TCM) which combines modulation and coding in a single entity delivers exceptional performance in static enviroment such as AWGN and flat fading channels. On the other hand, bit- interleaved coded modulation (BICM) which gives up the joint decoder/demodulator architecture in favor of two separate entities outp...

This paper is a study of high-performance soft-output demodulation for slow or moderate frequency-selective and flat Rayleigh fading using an autoregressive (AR) channel model. For channel taps modeled as AR processes, the discrete-time-equivalent channel model is derived for a matched filter (matched to the transmit pulse) and symbol rate-sampled...

Orthogonal frequency division multiplexing (OFDM) system suffers extra performance degradation in fast fading channels due to intercarrier interference (ICI). Combining frequency domain equalization and bit-interleaved coded modulation (BICM), the iterative receiver is able to harvest both temporal and frequency diversity. Using the fact that ICI e...

This paper presents and compares two iterative coded modulation techniques for deep-space optical communications using pulse-position modulation (PPM). The first code, denoted by SCPPM, consists of the serial concatenation of an outer convolutional code, an interleaver, a bit accumulator, and PPM. The second code, denoted by LDPC-PPM, consists of t...

This paper investigates the properties of several non- Jakes Doppler spectra proposed for the vehicle-to-vehicle non- isotropic scattering environment of the open highway. Expressions for the ideal model correlations, level-crossing rates, and average fade durations are derived. The classic Clarke channel model is modified to generate fading signal...

Traditional constellations are uniformally spaced. By giving up uniform spacing, constellations can be designed to have larger joint (i.e. overall) capacity or parallel decoding capacity. In this paper non-uniformally spaced (i.e. `geometrically' shaped) constellations are designed to maximize either of these quantities. By way of numerical capacit...

The multistrata space-time codes were proposed by Wachsmann et al. to increase the spectral efficiency of orthogonal space-time block codes. However, these codes lack two things: 1) their performance is worse than codes designed using number theory like the Golden code. 2) The advantages of their structure were never exploited in reducing the detec...

This work compares the system-level performance of two laptop antenna array designs for MIMO communications. The arrays are integrated into laptop display housings and differ in that one array has elements with directional radiation patterns while the other has elements designed for omnidirectional radiation. The performance of each laptop array is...

MIMO radio communications presents a paradigm shift for antenna array design. This is because system performance depends on how a pair of antenna arrays jointly affect the eigenvalue distributions of MIMO channels. Very little experimental work has been done to confirm what characteristics MIMO arrays must have so that channel capacity is preserved...

A new method of specifying the performance of a transmitter in a receiver/demodulator agnostic way is proposed. The concept of amplitude and phase error vector magnitude (EVM) is proposed. Experimental results demonstrate that amplitude and phase EVM gives a better characterization of a transmitter than traditional EVM metrics

The authors develop a generalized layered orthogonal lattice detector (G-LORD) for the golden code. G-LORD includes the previously developed LORD algorithm and exhaustive search ML detection as special cases, and is proved to achieve the perfect balance between error performance and complexity. Meanwhile, G-LORD is suitable for parallel implementat...

Recently a soft-output multiple-input multiple-output (MIMO) detector has been proposed, namely LORD (layered orthogonal lattice detector), able to achieve maximum-likelihood (ML) performance (in the max-log sense) for two transmit antennas, and near-optimal for greater than two, in MIMO-OFDM bit interleaved coded modulation (BICM) systems. This pa...

In this paper, we study the effect of the scattering environment on the capacity of a single carrier linear modulation used in a multipath, multiple antenna channel. The work incorporates detailed 3D geometric channel models to assess the effect of spatial correlation. The analysis techniques, based on the pioneering work of Hirt and Massey (1988),...

This chapter presents a brief introduction of wireless communication. Communication theory has been driven by the pioneering work of Claude Shannon and his idea of a channel capacity. On channels that are not highly random (e.g., free space wireless or wire-line), near capacity performance is achievable in a complexity that is implementable with mo...

Realizing antenna arrays that preserve channel capacity in multiple-input multiple-output (MIMO) radio communications is a challenge because of the detrimental effects of mutual coupling. The fact that mutual coupling becomes more pronounced as antenna spacing decreases is therefore a critical issue with compact arrays used in portable MIMO radios....

Singular Value Decomposition (SVD) is a powerful tool for multivariate analysis. However, independent computation of the SVD for each sample taken from a bandlimited matrix random process will result in singular value sample paths whose tangled evolution is not consistent with the structure of the underlying random process. The solution to this pro...

This paper takes a system view of the MIMO-OFDM beamformer design problem. We present a design method that helps improve the receiver channel estimation performance without damaging the optimality of beamforming. We design a so-called smoothed singular value decomposition (SSVD) algorithm to get smooth equivalent channels after beamforming, and thu...

The singular value decomposition (SVD) is a important tool for MIMO radio communications. However, independent computation of the SVD for each matrix in a MIMO channel sample path places an ordering condition on the singular values that results in singular value sample paths whose evolution is not consistent with the structure of the underlying ran...

STBC-MTCM scheme which achieves high rate, full diversity and large coding gains is an outstanding example of transmit diversity scheme for multiple-antenna system. In the case of time selective fast fading (TSFF) or frequency selective fading (FSF) channels, the performance of current existing STBC-MTCM decoder suffers from an irreducible error fl...

STBC-MTCM scheme which achieves high rate, full diversity and large coding gains is an outstanding example of transmit diversity scheme for multiple-antenna system. In the case of time selective fast fading (TSFF) or frequency selective fading (FSF) channels, the performance of current existing STBC-MTCM decoder suffers from an irreducible error fl...

This paper presents a soft-output lattice detector algorithm for multiple-input multiple-output (MIMO) communications called layered orthogonal lattice detector (LORD). LORD adopts a new lattice formulation and relies on a channel orthogonalization process. Building on the optimality of LORD for two transmit antennas this paper is a generalization...

Iterative turbo processing between detection and decoding shows near-capacity performance on a multiple-antenna system. Combining iterative processing with optimum front-end detection is particularly challenging because the front-end maximum a posteriori (MAP) algorithm has a computational complexity that is exponential in the throughput. Sub-optim...

Iterative turbo processing between detection and decoding shows near-capacity performance on a multiple-antenna system. Combining iterative processing with optimum front-end detection is particularly challenging because the front-end maximum a posteriori (MAP) algorithm has a computational complexity that is exponential in the throughput. Sub-optim...

In multiple-input multiple-output (MIMO) fading channels maximum likelihood (ML) detection is desirable to achieve high performance, but its complexity grows exponentially with the spectral efficiency. The current state of the art in MIMO detection is list decoding and lattice decoding. This paper proposes a new class of lattice detectors that comb...

In this correspondence, a new bound on the performance of multiuser receivers in fading channels is presented. The bound is based on a novel criterion for decomposability of error sequences. A constructive method to find the set of indecomposable error sequences under the new criterion is presented. Although the presentation is in the context of a...

This paper introduces a super-orthogonal space-time block code (STBC). The code construction is based on the expansion of orthogonal block code via a unitary matrix transformation. By expanding the orthogonal block code, both the code rate can be increased and the performance improved in terms of E b /N 0 , with a moderate increase of the receiver...

In this paper, we study the effect of the scattering environment on the capacity of a single carrier linear modulation used in a multipath, multiple antenna channel. The work incorporates detailed 3D geometric channel models to assess the effect of spatial correlation. The analysis techniques, based on the pioneering work of Hirt and Massey (1988),...

This demonstration will present a radio testbed that is being used to characterize the quality of directional peer-to-peer wireless communications in wilderness environments.

This paper describes a Dedicated Short Range Communications (DSRC) testbed which demonstrates the use of common, off-the- shelf (COTS) products to enable rapid algorithm dev elopment from conception to hardware implementation and test.

Introduction Over the past decade, there has been a great deal of research to improve the performance of wireless communications in fading environments by exploiting transmitter and/or receiver diversity. The pioneering work by Teletar (1995), Foschini and Gans (1998) showed that multiple antennas in a wireless communication system can greatly impr...

In this paper, a new technique to design improved high-rate space-time (ST) codes is proposed based on the concept of concatenated ST block code (STBC) and outer trellis-coded modulation (M-TCM) encoder constructions. Unlike the conventional rate-lossy STBC-MTCM schemes, the proposed designs produce higher rate ST codes by expanding the codebook of...

This paper proposes a new peak-to-average power ratio (PAPR) reduction scheme for short packet communications in multiple transmit antenna environments. Instead of applying individual PAPR re-duction on each antenna, a joint PAPR reduction technique is proposed. By applying a relevant unitary rotation over the transmit antennas, overall PAPR of the...

The achievable spectral efficiency of multiple antenna radios is greatly improved by Multiple Input Multiple Output (MIMO) signaling. However, the benefit of MIMO is lessened in practice due to mutual coupling in the antenna arrays. This problem is exacerbated by the size restrictions on antenna arrays in portable devices. We present a compact ante...

This paper provides details about experiments in realistic, urban, and frequency flat channels with space-time coding that specifically examines the impact of the number of receive antennas and the design criteria for code selection on the performance. Also the performance characteristics are examined of the coded modulations in the presence of fin...

A novel detector for multiple-input multiple-output (MIMO) communications is presented. The algorithm belongs to the class of the lattice detectors, i.e. it finds a reduced complexity solution to the problem of finding the closest vector to the received observations. The algorithm achieves optimal maximum-likelihood (ML) performance in case of two...

This paper provides details about experiments in realistic, urban, and frequency flat channels with space-time coding that specifically examines the impact of the number of receive antennas and the design criteria for code selection on the performance. Also the performance characteristics are examined of the coded modulations in the presence of fin...

This paper proposes a new peak-to-average power ratio (PAPR) reduction scheme in multiple transmit antenna environments. By applying a unitary rotation, overall PAPR of the multiple transmits antenna system is reduced. This scheme doesn't require any side information to decode the signal in the receiver, enabling throughput-lossless PAPR reduction....

This paper introduces an open access wideband multi-antenna wireless testbed. The testbed is configured as a four transmit antenna by four receive antenna system based on software defined radio techonology. It operates in the 2.4GHz ISM band and supports an RF bandwidth compatible to IEEE 802.11a/g standard. A robotic positioning system has been de...

This paper presents an overview of a new wireless network research testbed being developed by several wireless communications and networking research groups at UCLA. Its primary objective is to provide researchers at every layer of the protocol stack, from physical devices to transport protocols, a testbed to evaluate the impact of their technology...

Wireless communication systems present unique challenges and trade-offs at various levels of the system design process. Since a variety of performance measures are important in wireless communications, a family of testbeds becomes essential to validate the gains reported by the theory. Wireless testbeds also play a very important role in academia f...

Pilot symbol assisted modulation (PSAM) is a method to reduce the effects of fading in mobile communications by periodically inserting known symbols in the data stream. The receiver uses these pilot symbols to derive its amplitude and phase reference. One aspect of this procedure which has not received much attention in the literature is the method...

This paper presents a signaling scheme and channel estimation algorithm designed to characterize frequency selective MIMO channels. This scheme has been implemented in a wideband MIMO radio testbed and used to measure the achievable channel capacity in an indoor office environment. Also, we report the achievable capacity for a real hardware platfor...

This paper discusses the design of a packet detection algorithm for a burst mode continuous phase modulation (CPM) modem over flat Rayleigh fading channels in the 220 MHz frequency band. The modem design focuses on bandwidth efficiency while maintaining good synchronization performance and low complexity. The packet structure meets the Federal Comm...

This paper reports on some experiments with multiple antenna radios. Specifically this paper compares the performance between an experimental system with training and coherent demodulation and a system using noncoherent techniques of communication. The paper also examines robustness in performance across a variety of channel conditions.

In this paper, we present an adaptive Wiener filtering channel estimation method in the context of pilot symbols assisted multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) communications in low mobility environment. Optimal Wiener filtering requires known channel statistics. When there exists channel model mism...

The paper introduces a super-orthogonal space-time block coding scheme. The code construction is based on the expansion of an orthogonal block code via a unitary matrix transformation. By expanding the orthogonal block code, we can both increase the code rate and improve the performance in terms of E_b/N₀, with a moderate incre...

We present a radio telemetry solution for remote sensor networks that uses rotational actuation of directional antennas. The benefits of this solution over either omnidirectional or fixed directional antennas for intra-nodal communications include greater energy efficiency, sparse node deployment, and robustness to node failure. Four strategies for...

In this work, we analyze the pairwise error probability (PEP) performance of space-time codes in the presence of transmit fading correlation. Unlike receive correlation, the effect of transmit correlation depends on the specific space-time code used. We show that at low SNR, depending on the code, transmit correlation can either improve or degrade...

A two-dimensional space-time pilot-symbol assisted demodulation system is proposed in this paper. Since complex scattering environments can produce nontrivial space-time correlation characteristics, this paper proposes coherent demodulation by estimating the fading channel distortion using pilot observations across both space and time. The optimum...

We derive the exact pairwise error probability (PEP) for space-time coding over quasi-static Rayleigh fading channels in the presence of spatial fading correlation. We show that receive correlation always degrades the PEP for all signal-to-noise ratios (SNRs). We quantify the effect of receive correlation by employing the notion of "majorization"....

In this letter, we present a simple generalization of the maximum ratio combining principle for space--time coded systems. This result leads to a maximum-likelihood decoder implementation that does not depend on the number of receive antennas and avoids the loss in performance incurred in the decoders proposed by Tarokh and Lo and Biglieri et al. T...

Recently, the authors introduced an algebraic design framework for space--time coding in flat-fading channels [1]--[4]. In this correspondence, we extend this framework to design algebraic codes for multiple-input multiple-output (MIMO) frequency-selective fading channels. The proposed codes strive to optimally exploit both the spatial and frequenc...

In this correspondence, we propose an algorithm for computing the distance spectrum of a space-time trellis code achieving maximal diversity gain in quasi-static fading channels. We further present a state reduction technique for trellis codes that can reduce the complexity of the distance spectrum computation. We provide numerical results supporti...

Multiple antenna radios are recently the subject of much research due to the significant improvements they offer in throughput and reliability in wireless communications. Research in the field of space-time coding has led to the design of modulation techniques offering improved performance. Their performance, although promising in simulations, need...