Ayman F. Naguib

Combined array processing and space-time coding

The information capacity of wireless communication systems may be increased dramatically by employing multiple transmit and receive antennas. The goal of system design is to exploit this capacity in a practical way. An effective approach to increasing data rate over wireless channels is to employ space-time coding techniques appropriate to multiple transmit antennas. These space-time codes introduce temporal and spatial correlation into signals transmitted from different antennas, so as to provide diversity at the receiver, and coding gain over an uncoded system. For large number of transmit antennas and at high bandwidth efficiencies, the receiver may become too complex whenever correlation across transmit antennas is introduced. This paper dramatically reduces encoding and decoding complexity by partitioning antennas at the transmitter into small groups, and using individual space-time codes, called the component codes, to transmit information from each group of antennas. At the receiver, an individual space-time code is decoded by a novel linear processing technique that suppresses signals transmitted by other groups of antennas by treating them as interference. A simple receiver structure is derived that provides diversity and coding gain over uncoded systems. This combination of array processing at the receiver and coding techniques for multiple transmit antennas can provide reliable and very high data rate communication over narrowband wireless channels. A refinement of this basic structure gives rise to a multilayered space-time architecture that both generalizes and improves upon the layered space-time architecture proposed by Foschini (see Bell Labs Tech. J., vol.1, no.2, 1996).

Space-time codes for high data rate wireless communication: mismatch analysis

We revisit space-time codes for a mobile communication system that employs multiple antennas at the base station and optional antenna diversity at the mobile station. The realistic case when the channel state is not completely known is considered. It is assumed that the channel estimator extracts the fade coefficients using orthogonal pilot tones. Mismatch analysis is then carried out. It is proved that in the absence of ideal channel state information the design criteria for space-time codes developed in Tarokh et al. (1997) is still valid for the equal energy constellation case. Using our derivation, it is observed that channel estimation techniques commonly used over rapidly fading channels can be used in conjunction with space-time codes provided that the number of transmit antennas is small.

Low-rate multi-dimensional space-time codes for both slow and rapid fading channels

We consider the design of channel codes for improving the data rate and/or the reliability of communications using multiple transmit antennas over a fading channel. It is assumed that the transmitter does not know the channel but seeks to choose a codebook that guarantees a diversity gain of r/sub 1/ when there is no mobility and a diversity gain of r/sub 2//spl ges/r/sub 1/ when the channel is fast fading. A solution to this problem is unveiled in this paper. Here, the encoded data is split into n streams that are simultaneously transmitted using n transmit antennas. The signal received at each receive antenna is a superposition of the faded versions of the n transmitted signals. We derive performance criteria for designing codes having the aforementioned properties. Performance is shown to be determined by diversity advantage quantified by a rank/distance and coding advantage quantified by a determinant/product criterion. The criteria is used to design codes for both slow and rapid fading channels. The constructed codes have remarkable performance in low signal to noise ratios and are suitable for improving the frequency reuse factor under a variety of mobility conditions.

FIR MIMO decision feedback equalization for space-time block-coded transmission over multipath-fading channels

A finite-length optimized-delay multi-input multi-output mean-square-error decision-feedback equalizer for space-time block-coded transmission over multipath fading channels is presented. Alamoutis space-time block code with 2 transmit and 2 receive antenna on a typical urban EDGE channel is taken as a case study. We propose a combined equalization and decoding scheme under the constraint of linear processing complexity (no trellis search) at the receiver. Performance comparisons are made with the single-transmit/single-receive antenna case and the case of multi-input multi-output feedforward linear equalization only with no decision feedback.

Recent progress in space-time block and trellis coding

Techniques for transmission and reception over wireless channels using multiple transmit antennas are presented.