This paper studies transmission of sources over noisy channels by a communication system subject ... more This paper studies transmission of sources over noisy channels by a communication system subject to a power constraint at the transmitter. We consider the transmission of continuous- or discrete-time Gaussian sources and assume that the processing on the signals are within the family of linear operations. For stationary signals, a constraint on the power at the output of the transmission filter results in bandpass transmit and receive filters whose bandpass region include the frequencies at which the source spectra is above some threshold. This result shows similarities between the rate distortion arguments and the minimum mean square error (MSE) attainable by the optimum linear systems. Examples for frequently encountered source statistics are also studied and it is shown that linear processing both at the transmitter and at the receiver reduces the estimation errors significantly compared to the standard Wiener filtering approach. It is shown that for communication of a bandlimited source with arbitrary spectrum over a bandlimited channel with the same bandwidth as the source, using proposed linear processing approach attains the same distortion exponent as the theoretically optimum system does
In this paper, we study the energy-efficient distributed estimation problem for a wireless sensor... more In this paper, we study the energy-efficient distributed estimation problem for a wireless sensor network where a physical phenomena that produces correlated data is sensed by a set of spatially distributed sensor nodes and the resulting noisy observations are transmitted to a fusion center via noise-corrupted channels. We assume a Gaussian network model where (i) the data being sensed at different sensors are correlated and the correlation structure (in the form of a correlation matrix) is known at the fusion center, (ii) the links between the local sensors and the fusion center are subject to multipath fading plus AWGN, and the fading gains are available to the receiver node, and (iii) the central node uses the squared error distortion metric. We first determine the optimum power-distortion regions assuming (i) a multiple-letter, and (ii) a single-letter square distortion characterization. Next, for the two distortion characterization, we investigate the performance of an uncoded transmission approach where the noisy observations are only amplified-and-forwarded to the fusion center. At the fusion center, two different estimators are considered: (i) minimum mean-square error estimator (MMSE) that exploits the correlation, and (ii) best linear unbiased estimator (BLUE) that does not require or exploit the knowledge of the correlation matrix. For both estimators, we solve for the optimal power allocation that results in a minimum total transmission power while satisfying some distortion level for the estimate (for both multiple-letter and single-letter distortion metrics). The numerical comparisons between the two schemes indicate that the MMSE requires less power to attain the same distortion provided by the BLUE. Furthermore, comparisons between power-distortion region achieved by the theoretically optimum system and the uncoded system indicates that the performance gap between the two system becomes small for low level of correlation between the sensor observatio- ns. If observations at all sensor nodes are uncorrelated, the uncoded system attains the theoretically optimum system performance.
In the above-named work (ibid., vol. 49, no. 10, pp. 2669??2681, Oct. 2003) the authors developed... more In the above-named work (ibid., vol. 49, no. 10, pp. 2669??2681, Oct. 2003) the authors developed performance bounds for multiple antenna systems that use receive antenna selection and proved results regarding the diversity and coding gains in such systems. In reference to above correspondence, the probability density function given by eq. (30) should not include the scaling factor of 1/L. This is shown via a short derivation. As a result, the factor 1/L should be omitted from the pairwise error probability expressions, and (32), (34), (35), and (38)??(41) are corrected herein. The main results regarding the diversity gain of the system are not effected by the absence of this scaling factor, while the ones on the coding gain should be modified accordingly.
In this paper, turbo-based coding scheme for relay systems together with iterative decoding algor... more 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.
Parallel distributed detection for wireless sensor networks is studied in this paper. The network... more 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
This paper focuses on the interaction and integration of several critical components of a Mobile ... more 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
Space-time coding is well established for high data rate communications in wireless channels with... more 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
IEEE Transactions on Wireless Communications, 2004
Space-time coding is well established for high data rate communications over wireless channels wi... more 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.
We present a scheme employing turbo codes together with unitary space-time constellations for Ray... more 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 10-5
Multiantenna systems employing space-time coding over quasistatic Rayleigh fading channels is con... more Multiantenna systems employing space-time coding over quasistatic Rayleigh fading channels is considered. We prove that by selecting a subset of the antennas that observe the largest instantaneous signal-to-noise ratios (SNRs) at the receiver one can achieve the same diversity order as the full complexity system, provided that the subchannels are independent and the underlying space-time code has full spatial diversity.
Serial distributed detection for wireless sensor networks is studied in this paper. Unlike the tr... more 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
This paper studies transmission of sources over noisy channels by a communication system subject ... more This paper studies transmission of sources over noisy channels by a communication system subject to a power constraint at the transmitter. We consider the transmission of continuous- or discrete-time Gaussian sources and assume that the processing on the signals are within the family of linear operations. For stationary signals, a constraint on the power at the output of the transmission filter results in bandpass transmit and receive filters whose bandpass region include the frequencies at which the source spectra is above some threshold. This result shows similarities between the rate distortion arguments and the minimum mean square error (MSE) attainable by the optimum linear systems. Examples for frequently encountered source statistics are also studied and it is shown that linear processing both at the transmitter and at the receiver reduces the estimation errors significantly compared to the standard Wiener filtering approach. It is shown that for communication of a bandlimited source with arbitrary spectrum over a bandlimited channel with the same bandwidth as the source, using proposed linear processing approach attains the same distortion exponent as the theoretically optimum system does
In this paper, we study the energy-efficient distributed estimation problem for a wireless sensor... more In this paper, we study the energy-efficient distributed estimation problem for a wireless sensor network where a physical phenomena that produces correlated data is sensed by a set of spatially distributed sensor nodes and the resulting noisy observations are transmitted to a fusion center via noise-corrupted channels. We assume a Gaussian network model where (i) the data being sensed at different sensors are correlated and the correlation structure (in the form of a correlation matrix) is known at the fusion center, (ii) the links between the local sensors and the fusion center are subject to multipath fading plus AWGN, and the fading gains are available to the receiver node, and (iii) the central node uses the squared error distortion metric. We first determine the optimum power-distortion regions assuming (i) a multiple-letter, and (ii) a single-letter square distortion characterization. Next, for the two distortion characterization, we investigate the performance of an uncoded transmission approach where the noisy observations are only amplified-and-forwarded to the fusion center. At the fusion center, two different estimators are considered: (i) minimum mean-square error estimator (MMSE) that exploits the correlation, and (ii) best linear unbiased estimator (BLUE) that does not require or exploit the knowledge of the correlation matrix. For both estimators, we solve for the optimal power allocation that results in a minimum total transmission power while satisfying some distortion level for the estimate (for both multiple-letter and single-letter distortion metrics). The numerical comparisons between the two schemes indicate that the MMSE requires less power to attain the same distortion provided by the BLUE. Furthermore, comparisons between power-distortion region achieved by the theoretically optimum system and the uncoded system indicates that the performance gap between the two system becomes small for low level of correlation between the sensor observatio- ns. If observations at all sensor nodes are uncorrelated, the uncoded system attains the theoretically optimum system performance.
In the above-named work (ibid., vol. 49, no. 10, pp. 2669??2681, Oct. 2003) the authors developed... more In the above-named work (ibid., vol. 49, no. 10, pp. 2669??2681, Oct. 2003) the authors developed performance bounds for multiple antenna systems that use receive antenna selection and proved results regarding the diversity and coding gains in such systems. In reference to above correspondence, the probability density function given by eq. (30) should not include the scaling factor of 1/L. This is shown via a short derivation. As a result, the factor 1/L should be omitted from the pairwise error probability expressions, and (32), (34), (35), and (38)??(41) are corrected herein. The main results regarding the diversity gain of the system are not effected by the absence of this scaling factor, while the ones on the coding gain should be modified accordingly.
In this paper, turbo-based coding scheme for relay systems together with iterative decoding algor... more 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.
Parallel distributed detection for wireless sensor networks is studied in this paper. The network... more 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
This paper focuses on the interaction and integration of several critical components of a Mobile ... more 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
Space-time coding is well established for high data rate communications in wireless channels with... more 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
IEEE Transactions on Wireless Communications, 2004
Space-time coding is well established for high data rate communications over wireless channels wi... more 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.
We present a scheme employing turbo codes together with unitary space-time constellations for Ray... more 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 10-5
Multiantenna systems employing space-time coding over quasistatic Rayleigh fading channels is con... more Multiantenna systems employing space-time coding over quasistatic Rayleigh fading channels is considered. We prove that by selecting a subset of the antennas that observe the largest instantaneous signal-to-noise ratios (SNRs) at the receiver one can achieve the same diversity order as the full complexity system, provided that the subchannels are independent and the underlying space-time code has full spatial diversity.
Serial distributed detection for wireless sensor networks is studied in this paper. Unlike the tr... more 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
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