9:30, SPCOM-P3.1
HIGH THROUGHPUT WIDEBAND SPACE-TIME SIGNALING USING CHANNEL STATE INFORMATION
E. ONGGOSANUSI, B. VAN VEEN, A. SAYEED
An orthogonal decomposition of a general wideband space-time multipath channel is derived assuming antenna arrays at both the transmitter and receiver. This decomposition provides a framework for efficiently managing the available space-time channel dimensions using channel state information at the transmitter and receiver. Signaling and receiver designs for high throughput applications are derived using this decomposition. For a fixed throughput system, we investigate a power allocation scheme that minimizes the effective bit-error rate. In addition, a strategy to maximize the average throughput is discussed.

9:30, SPCOM-P3.2
MAXIMUM-SNR SPACE-TIME DESIGNS FOR MIMO CHANNELS
P. STOICA, G. GANESAN
We consider a communication scenario involving an $m \times n$ MIMO linear channel whose input is a symbol stream multiplied prior to transmission by an $n \times \bar{n}$ space-time coding matrix $X$, and whose output is fed into an $m \times \bar{n}$ linear combiner $Z$. We show how to choose the matrices $X$ and $Z$ to maximize the SNR of the linear combiner output data that are used for detection, under total power constraint (TPC), elemental power constraint (EPC), or total and elemental power constraint (TEPC). The TEPC design (considered here for the first time) is shown to include the TPC and EPC designs (previously considered by the authors) as special cases, and hence to provide a theoretically and practically interesting unifying framework. We make use of this framework to discuss various tradeoffs of the three space-time designs considered, such as transmission rate and requirements for channel status information at the transmission side.

9:30, SPCOM-P3.3
SPACE-TIME DIVERSITY SYSTEMS BASED ON UNITARY CONSTELLATION-ROTATING PRECODERS
Y. XIN, Z. WANG, G. GIANNAKIS

9:30, SPCOM-P3.4
PERFORMANCE OF UNITARY SPACE-TIME MODULATION IN A CONTINUOUSLY CHANGING CHANNEL
C. PEEL, A. SWINDLEHURST
The fast fading channel is a significant problem in many communications environments. In this paper, we examine the performance of unitary space-time modulation in a time-varying channel. We use a Gauss-Markov model of the continuously varying channel to characterize performance of differential and trained modulation. We find a performance floor at high SNR where the effect of the changing channel dominates. We show that while trained modulation provides an advantage at low SNR, above a certain SNR differential modulation gives better performance. We conclude with simulation results that support our analysis. See also http://www.ee.byu.edu/~peel/

9:30, SPCOM-P3.5
PERFORMANCE OF SPATIAL MULTIPLEXING IN THE PRESENCE OF POLARIZATION DIVERSITY
H. BOLCSKEI, R. NABAR, V. ERCEG, D. GESBERT, A. PAULRAJ
In practice large antenna spacings are needed to achieve high capacity gains in multiple-input multiple-output (MIMO) wireless systems. The use of dual-polarized antennas is a promising cost effective alternative where two spatially separated antennas can be replaced by a single antenna element employing orthogonal polarizations. This paper investigates the performance of spatial multiplexing in MIMO wireless systems with dual-polarized antennas. We compute estimates of the symbol error rate as a function of cross-polarization discrimination (XPD) and spatial fading correlations. Using these estimates, we show that dual-polarized antennas can significantly improve the performance of spatial multiplexing systems. It is demonstrated that improvements in terms of symbol error rate of up to an order of magnitude are possible. We furthermore find that in general for a given SNR there is an optimum XPD for which the symbol error rate is minimum. Finally, we present simulation results and we show that our estimates closely match the numerical results.

9:30, SPCOM-P3.6
SPACE-TIME BLOCK CODING WITH OPTIMAL ANTENNA SELECTION
D. GORE, A. PAULRAJ
Space-time block codes provide maximal diversity advantage over a fading channel. This paper presents a novel technique that provides additional diversity gain by coupling antenna selection with a space-time block code. Specifically, we provide a choice of transmit antenna elements at the transmitter and transmit a space-time code over the optimal antenna pair. We present the optimal selection rule and quantify the improved performance in terms of gain in average SNR. The average SNR gain is calculated as a function of the number of transmit antenna elements and the number of receive antennas. We also investigate the improvement in outage capacity.

9:30, SPCOM-P3.7
SPACE-TIME SIGNALING AND FRAME THEORY
R. HEATH JR., H. BOLCSKEI, A. PAULRAJ
Wireless systems with multiple transmit and receive antennas (MIMO systems) provide high capacity due to the plurality of modes available in the channel. Previous code designs for MIMO systems have focused primariliy on multiplexed signaling for high data rate or diversity signaling for high link reliability. In this paper, we present a MIMO space-time code design which bridges the gap between multiplexing and diversity. Based on results from frame theory, we provide code designs which perform well both in terms of ergodic capacity as well as error probability. In particular, we demonstrate that designs performing well from an ergodic capacity point of view do not necessarily perform well from an error probability point of view. Simulations illustrate performance of the proposed codes in narrowband MIMO Rayleigh fading channels.

9:30, SPCOM-P3.8
WALSH CODING ACROSS MULTIPLE ANTENNAS FOR HIGH DATA RATE WIRELESS SERVICES
A. MCCORMICK, P. GRANT, J. THOMPSON
The combination of Walsh coding with a layered space-time architecture is investigated. This provides a system with flexible coding rates and low complexity linear decoding. The codes allow exploitation of the diversity of the multiple antenna channel while allowing code rates up to 1, while still providing a performance improvement over an uncoded system. Simulations provide comparison with repetition coded and uncoded systems.

9:30, SPCOM-P3.9
JOINT BEAMFORMER ESTIMATION AND CO-ANTENNA INTERFERENCE CANCELATION FOR TURBO-BLAST
M. SELLATHURAI, S. HAYKIN
TURBO-BLAST is a novel multi-transmit multi-receive (MTMR) antenna scheme for high-throughput wireless communications. It exploits a novel space-time coding scheme based on the independent block forward error correction (FEC) codes and space-time interleaving, and a near optimal iterative decoder, for decoding a new generation of space-time codes. The proposed iterative decoder has two decoding stages: a soft interference cancelation detector and a set of soft-in soft-out decoders. In this paper, we focus on designing a robust parallel interference cancelation scheme that jointly estimates the soft interference and the linear beamformer weights to minimize the mean-square error (MMSE) between the true and estimated signals. Using simulation results, we show that the proposed scheme outperform the previously proposed soft interference cancelation receivers based on maximum ratio combining (MRC) principle.

9:30, SPCOM-P3.10
DIFFERENTIAL SPACE-TIME MODULATION SCHEMES FOR DS-CDMA SYSTEMS
J. LI, J. LIU
Differential space-time modulation (DSTM) schemes were recently proposed to fully exploit the receive and transmit antenna diversities without the need for channel state information. DSTM is attractive in fast flat fading channels since accurate channel estimation is difficult to achieve. In this paper, we propose a new modulation scheme to improve the performance of DS-CDMA systems in fast time-dispersive fading channels, referred to as the differential space-time modulation for DS-CDMA (DST-CDMA). We present two new demodulation schemes, referred to as the differential space-time Rake receiver (DSTR) and differential space-time deterministic receiver (DSTD), respectively. DSTD exploits the known information of the spreading sequences and their delayed paths deterministically besides the Rake type combination. Consequently, it outperforms DSTR, which employs the Rake type combination only. The new modulation and demodulation schemes are especially suited for the fast fading down-link transmission in DS-CDMA systems employing multiple transmit antennas and one receive antenna.