Israfil Bahceci

Antenna selection for multiple-antenna transmission systems: performance analysis and code construction

This correspondence studies antenna selection for wireless communications systems that employ multiple transmit and receive antennas. We assume that (1) the channel is characterized by quasi-static Rayleigh flat fading, and the subchannels fade independently, (2) the channel state information (CSI) is exactly known at the receiver, (3) the selection is available only at the receiver, and it is based on the instantaneous signal-to-noise ratio (SNR) at each receive antenna, and (4) space-time codes are used at the transmitter. We analyze the performance of such systems by deriving explicit upper bounds on the pairwise error probability (PEP). This performance analysis shows that (1) by selecting the set of antennas that observe the largest instantaneous SNR, one can achieve the same diversity gain as the one obtained by using all the receive antennas, provided that the underlying space-time code has full spatial diversity, and (2) in the case of rank-deficient space-time codes, the diversity gain may be dramatically reduced when antenna selection is used. However, we emphasize that in both cases the coding gain is reduced with antenna selection compared to the full complexity system. Based on the upper bounds derived, we describe code design principles suitable for antenna selection. Specifically, for systems with two transmit antennas, we design space-time codes that perform better than the known ones when antenna selection is employed. Finally, we present numerical examples and simulation results that validate our analysis and code design principles.

Smart antenna system analysis, integration and performance for mobile ad-hoc networks (MANETs)

This paper focuses on the interaction and integration of several critical components of a mobile ad-hoc network (MANET) using smart antenna systems. A MANET is a wireless network where the communicating nodes are mobile and the network topology is continuously changing. One of the central motivations for this work comes from the observed dependence of the overall network throughput on the design of the adaptive antenna system and its underlying signal processing algorithms. In fact, a major objective of this work is to study and document the overall efficiency of the network in terms of the antenna pattern and the length of the training sequence used by the beamforming algorithms. This study also considers in sufficient detail problems dealing with the choice of direction of arrival algorithm and the performance of the adaptive beamformer in the presence of antenna coupling effects. Furthermore, the paper presents strategies and algorithms to combat the effects of fading channels on the overall system.

Trellis-coded unitary space-time modulation

Space-time coding is well established for high data rate communications over wireless channels with perfect channel state information. On the other hand, the case where the channel state information is unknown has received limited attention. Recently, a new signaling scheme called unitary space-time modulation that is suitable for the latter case has been proposed. We describe the use and design of trellis-coded space-time modulation schemes that use unitary space-time constellations. We construct these codes using a novel suboptimal code design criteria and study the performance of trellis-coded unitary space-time modulation for block fading channels under the assumption of no channel state information. Simulation results show that the proposed schemes improve the performance compared to uncoded transmission with the same spectral efficiency. The results are also compared with the turbo-coded modulation scheme Bahceci (2002) and the differential detection scheme described Jafarkhani (2001) under the same assumptions.

Parallel distributed detection for wireless sensor networks: performance analysis and design

Parallel distributed detection for wireless sensor networks is studied in this paper. The network consists of a set of local sensors and a fusion center. Each local sensor makes a binary (single-bit) or M-ary (multi-bit) decision and passes it to the fusion center where a final decision is made. The links between the local sensors and the fusion center are subject to fading and additive noise resulting in corruption of the transmitted decisions. We analyze the performance of the decision fusion based on likelihood ratio tests and derive false alarm and detection probabilities. Based on the theoretical probability expressions, we design optimal decision rules for the local sensors and the fusion center. Finally, we illustrate the performance of the parallel fusion by numerical examples

Capacity approaching codes for relay channels

In this paper, turbo-based coding scheme for relay systems together with iterative decoding algorithms is designed. The performance of the proposed schemes is about 1.0-1.5 dB away from the information theoretical limits for various channel models.

Trellis coded unitary space-time modulation

Space-time coding is well established for high data rate communications in wireless channels with perfect channel state information. On the other hand, the case where channel state information is unknown has received limited attention. Recently, a new signaling scheme called unitary space-time modulation has been proposed for the latter case. In this paper, we describe the use and design of trellis coded space-time modulation schemes that use unitary space-time constellations. Simulation results show that the proposed schemes improve the performance compared to uncoded transmission with the same spectral efficiency.

Serial distributed detection for wireless sensor networks

Serial distributed detection for wireless sensor networks is studied in this paper. Unlike the traditional serial distributed detection schemes where it is assumed that the sensor decision at one stage is known exactly to the subsequent sensor node, we assume that the links between the consecutive sensor nodes are subject to fading and additive noise resulting in corruption of the transmitted decisions. Incorporating the effect of fading in the detection process, a decision fusion rule based on likelihood ratio tests is derived. Optimality of likelihood ratio test is also investigated. By numerical examples, we illustrate the performance of the proposed serial detection scheme and compare it with that of the parallel distributed detection

Combined turbo coding and unitary space-time modulation

We present a scheme employing turbo codes together with unitary space-time constellations for Rayleigh block fading channels when no channel state information (CSI) is available. We present via simulations that coding gains up to 16 dB is possible over the original uncoded system at a bit error rate of 10/sup -5/.

A turbo-coded multiple-description system for multiple antennas

We propose a joint source-channel coding scheme for wireless communication systems with multiple transmit and receive antennas. The source coder is realized by a multiple description encoder that generates multiple bit streams. Each description is then separately turbo coded and transmitted using multiple antennas. For the receiver, we describe a suitable iterative joint source-channel decoding technique that exploits the correlations between the descriptions. We present several examples that illustrate the performance of the proposed system, and compare it with other approaches.

A turbo coded multiple description system for multiple antennas

We propose a joint source-channel coding scheme for wireless communication systems with multiple transmit and receive antennas. The source coder is realized by a multiple description encoder that generates multiple bit streams. Each description is then separately turbo coded and transmitted using multiple antennas. For the receiver, we describe a suitable iterative joint source-channel decoding technique that exploits the correlations between the descriptions. We present several examples that illustrate the performance of the proposed system, and compare it with other approaches.We propose a joint source-channel coding scheme for wireless communication systems with multiple transmit and receive antennas. The source coder is realized by a multiple description encoder that generates multiple bit streams for the same source. Each description is then separately turbo coded and transmitted using multiple antennas. For the receiver, we describe a suitable iterative joint source-channel decoding technique that exploits the correlations between the descriptions. Finally, we present several examples that illustrate the performance of the proposed system and compare it with other approaches.