In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. ...
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We investigate the issues in voice communications using IP over tandem connections of wireline and wireless links with the goal of determining end-to-end system performance. We study the particular example of using G....
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We investigate the issues in voice communications using IP over tandem connections of wireline and wireless links with the goal of determining end-to-end system performance. We study the particular example of using G.711 speech coding in the backbone wireline network and adaptive multi-rate (AMR) speech coding in a wireless LAN tandem network and study the impact of specific methods of adaptive re-encoding, error concealment, error control coding, and network protocol design to deliver the desired end-to-end quality of service. In addition to simulation results and objective speech quality measures, we present estimation-theoretic and information-theoretic analyses for the tandem packet loss link connections.
The use of multiple antennas at both the transmitter and receiver can significantly increase the channel capacity. These systems are called the multiple-input multiple-output (MIMO) systems. By using orthogonal freque...
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The use of multiple antennas at both the transmitter and receiver can significantly increase the channel capacity. These systems are called the multiple-input multiple-output (MIMO) systems. By using orthogonal frequency division multiplexing (OFDM) transmission techniques, the MIMO-OFDM system can achieve high spectral efficiency, which makes it an attractive candidate for high-data-rate wireless applications. In this paper, we propose a convolutionally coded MIMO-OFDM system with EM-based channel estimation and a QRD-M data detection algorithm. In our systems, one training symbol is transmitted from each transmit antenna for the MEMO channel estimation at the receiver. With the channel estimates available, we apply the QRD-M algorithm on the estimated channel matrix for suboptimal data detection with reasonable computational cost. The bit error rate (BER) and packet error rate (PER) performance of the MIMO-OFDM systems are compared. In the simulations, the bit error rate performance of our systems is 9 (or 5) dB better than that of uncoded (or coded) BLAST systems.
The use of multiple antennas at both the transmitter and receiver can significantly increase the channel capacity. These systems are called the multiple-input multiple-output (MIMO) systems. By using orthogonal freque...
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The use of multiple antennas at both the transmitter and receiver can significantly increase the channel capacity. These systems are called the multiple-input multiple-output (MIMO) systems. By using orthogonal frequency division multiplexing (OFDM) transmission techniques, the MIMO-OFDM system can achieve high spectral efficiency, which makes it an attractive candidate for high-data-rate wireless applications. In this paper, we propose a convolutionally coded MIMO-OFDM system with EM-based channel estimation and a QRD-M data detection algorithm. In our systems, one training symbol is transmitted from each transmit antenna for the MIMO channel estimation at the receiver. With the channel estimates available, we apply the QRD-M algorithm on the estimated channel matrix for suboptimal data detection with reasonable computational cost. The bit error rate (BER) and packet error rate (PER) performance of the MIMO-OFDM systems are compared. In the simulations, the bit error rate performance of our systems is 9 (or 5) dB better than that of uncoded (or coded) BLAST systems.
In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. ...
详细信息
In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. Two new derivations of Campbell's rate coefficient rate are presented. One derivation solidifies the interpretation of this quantity as a coefficient rate and allows definition of an effective bandwidth for the process. The second derivation implies a new approach for realization adaptive source compression. The coefficient rate can be used for realization adaptive coefficient selection in a sequence of source representations. Furthermore, the effective bandwidth is designated as Campbell bandwidth and contrasted with Fourier bandwidth and Shannon bandwidth. Several specific examples are presented that illustrate the differences among the three quantities.
Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose space-time ...
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Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose space-time block coded OFDM systems that use training symbols coded by STBC. We use two training symbols at the beginning of each of two OFDM frames that are simultaneously transmitted from two corresponding transmit antennas. Based on the orthogonality of space-time block codes, we perform channel estimation by using training symbols, and compare to EM-based channel estimation methods. From the simulation results, we observe that our space-time block coding technique offers a good approach to channel estimation and better signal quality than the EM-based method.
Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. We propose space-time block coded OFD...
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Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. We propose space-time block coded OFDM systems that use training symbols coded by STBC. We use two training symbols at the beginning of each of two OFDM frames that are simultaneously transmitted from two corresponding transmit antennas. Based on the orthogonality of space-time block codes, we perform channel estimation by using training symbols, and compare to EM-based channel estimation methods. From the simulation results, we observe that our space-time block coding technique offers a good approach to channel estimation and better signal quality than the EM-based method.
A new system enhancement method is proposed for the EIA/TIA-136 system offering both channel operational range extension and improved performance within the current operational range. The research presented investigat...
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A new system enhancement method is proposed for the EIA/TIA-136 system offering both channel operational range extension and improved performance within the current operational range. The research presented investigates the application of the narrowband adaptive multi-rate (NB-AMR) speech codec and the wideband AMR (WB-AMR) codec, both originally designed for the 200 kHz GSM channel, in the TDMA (TIA/EIA-136) 30 kHz system. In particular, we investigate adaptively allocating bits between NB/WB speech coding and error control within the limited channel bandwidth. Four modes out of seventeen have been carefully chosen for the new TDMA/AMR system. Switching between codec rates as channel conditions change produces range extension below a C/I of 15 dB while also improving performance in the existing operational range above 15 dB. Time slot formats are unchanged so that the method is completely compatible with existing 136 systems.
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