The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Robert W. Heath - One of the best experts on this subject based on the ideXlab platform.
-
ergodic capacity of spatial multiplexing mimo systems with zf receivers for log normal shadowing and rayleigh fading channels
Personal Indoor and Mobile Radio Communications, 2007Co-Authors: Myonghee Park, Chanbyoung Chae, Robert W. HeathAbstract:This paper presents a derivation of an expression for the ergodic capacity of spatial multiplexing multiple-input-multiple-output (MIMO) systems with zero-forcing (ZF) receivers and independent Substream detection. Assuming that the channel is unknown at the transmitter but known at the receiver, the ergodic capacity is formulated as a function of log-normal shadowing and Rayleigh fading. Gauss-Hermite quadrature integration is used to approximate the ergodic capacity expression in a concise form. The proposed analytical approach allows investigation of the effects of the shadowing standard deviation and the transmit correlation. Numerical and simulation results confirm that under various composite channel scenarios, the analytical results match well with the simulation results.
-
multimode precoding for mimo wireless systems
IEEE Transactions on Signal Processing, 2005Co-Authors: David James Love, Robert W. HeathAbstract:Multiple-input multiple-output (MIMO) wireless systems obtain large diversity and capacity gains by employing multielement antenna arrays at both the transmitter and receiver. The theoretical performance benefits of MIMO systems, however, are irrelevant unless low error rate, spectrally efficient signaling techniques are found. This paper proposes a new method for designing high data-rate spatial signals with low error rates. The basic idea is to use transmitter channel information to adaptively vary the transmission scheme for a fixed data rate. This adaptation is done by varying the number of Substreams and the rate of each Substream in a precoded spatial multiplexing system. We show that these Substreams can be designed to obtain full diversity and full rate gain using feedback from the receiver to transmitter. We model the feedback using a limited feedback scenario where only finite sets, or codebooks, of possible precoding configurations are known to both the transmitter and receiver. Monte Carlo simulations show substantial performance gains over beamforming and spatial multiplexing.
-
Multimode antenna selection for spatial multiplexing systems with linear receivers
IEEE Transactions on Signal Processing, 2005Co-Authors: Robert W. Heath, David James LoveAbstract:Spatial multiplexing is a simple transmission technique for multiple-input multiple-output (MIMO) wireless communication links in which data is multiplexed across the transmit antennas. In Rayleigh fading matrix channels, however, spatial multiplexing with low-complexity linear receivers suffers due to a lack of diversity advantage. This paper proposes multimode antenna selection, which uses a low-rate feedback channel to improve the error rate performance of spatial multiplexing systems with linear receivers. In the proposed technique, both the number of Substreams and the mapping of Substreams to antennas are dynamically adjusted, for a fixed total data rate, to the channel based on limited feedback from the receiver. Dual-mode selection, where spatial multiplexing or selection diversity is adaptively chosen, dramatically improves the diversity gain achieved. Multimode selection (i.e., allowing any number of Substreams to be dynamically selected) provides additional array gain. Various criteria for selecting the number of Substreams and the optimal mapping of Substreams to transmit antennas are derived. Relationships are made between the selection criteria and the eigenmodes of the channel. A probabilistic analysis of the selection criteria are provided for Rayleigh fading channels. Applications to nonlinear receivers are mentioned. Monte Carlo simulations demonstrate significant performance improvements in independent and identically distributed (i.i.d.) flat-fading Rayleigh matrix channels with minimal feedback.
-
multi mode precoding using linear receivers for limited feedback mimo systems
International Conference on Communications, 2004Co-Authors: David J Love, Robert W. HeathAbstract:Multiple-input multiple-output (MIMO) wireless systems obtain large diversity and capacity gains by employing multi-element antenna arrays at both transmitter and receiver. The theoretical performance benefits, however, are irrelevant unless low error rate, high spectral efficiency spatio-temporal signaling techniques are found. Most work in space-time coding concentrates on either designing low error rate codes or high data-rate codes but not both simultaneously. This paper proposes a new method for designing high data-rate spatio-temporal signals with low error rates. The basic idea is to use transmitter channel information in the form of limited feedback to adaptively vary the transmission scheme for a fixed data-rate. This adaptation is done by varying the number of Substreams and the rate of each Substream in a precoded spatial multiplexing system. We show how this method can be implemented in a limited feedback scenario where only finite sets, or codebooks, of possible precoding configurations are known to both the transmitter and receiver. Monte Carlo simulations show substantial performance gains over beamforming and spatial multiplexing.
-
limited feedback precoding for spatial multiplexing systems
Global Communications Conference, 2003Co-Authors: David James Love, Robert W. HeathAbstract:Spatial multiplexing multiple-input multiple-output (MIMO) wireless systems are of both theoretical and practical importance because they can achieve high spectral efficiencies by demultiplexing the incoming bit stream into multiple Substreams. It has been shown that sending fewer Substreams than the number of transmit antennas by linear precoding can provide improved error rate performance. Methods for designing linear precoders using perfect channel knowledge have previously been proposed. In many wireless systems, the assumption of complete channel knowledge is unrealistic because of the lack of forward and reverse channel reciprocity. To overcome this difficulty, we propose a precoding scheme that does not require transmit channel knowledge. The precoder is designed at the receiver and conveyed to the transmitter using a limited number of bits. The limited feedback represents an index within a finite set, or codebook, of precoding matrices. The receiver selects one of these codebook matrices using a modified version of a previously proposed full channel knowledge precoder selection criterion. A precoder codebook design method for maximizing the average effective channel power is shown to relate to chordal distance Grassmannian subspace packing. Simulation results show this technique outperforms antenna subset selection spatial multiplexing.
Yasushi Takatori - One of the best experts on this subject based on the ideXlab platform.
-
high data rate transmission with eigenbeam space division multiplexing e sdm in a mimo channel
Vehicular Technology Conference, 2002Co-Authors: K Miyashita, Takeo Ohgane, Yasutaka Ogawa, Toshihiko Nishimura, Yasushi TakatoriAbstract:When channel state information is known at a transmitter in multiple-input multiple-output systems, the optimum capacity is given by eigenmode channel division with water-pouring power control. In this eigenbeam-space division multiplexing (E-SDM), bit assignment to Substreams based on the capacity is not optimum due to the fact that the number of assigned bits is expressed by a discrete quantity. In the paper, a method to assign both bit and transmit power to each Substream based on the criterion minimizing total bit error rate (BER) is developed, and the BER performance is numerically analyzed in comparison to spatial division multiplexing (SDM). The simulation results assuming 5-transmit and 2-receive antennas show that the E-SDM provides about 10 dB gain compared to the conventional SDM at average BER of 10/sup -3/.
-
high data rate transmission with eigenbeam space division multiplexing e sdm in a mimo channel
Vehicular Technology Conference, 2002Co-Authors: K Miyashita, Takeo Ohgane, Yasutaka Ogawa, Toshihiko Nishimura, Yasushi TakatoriAbstract:When channel state information is known at a transmitter in multiple-input multiple-output systems, the optimum capacity is given by eigenmode channel division with water-pouring power control. In this eigenbeam-space division multiplexing (E-SDM), bit assignment to Substreams based on the capacity is not optimum due to the fact that the number of assigned bits is expressed by a discrete quantity. In the paper, a method to assign both bit and transmit power to each Substream based on the criterion minimizing total bit error rate (BER) is developed, and the BER performance is numerically analyzed in comparison to spatial division multiplexing (SDM). The simulation results assuming 5-transmit and 2-receive antennas show that the E-SDM provides about 10 dB gain compared to the conventional SDM at average BER of 10/sup -3/.
David James Love - One of the best experts on this subject based on the ideXlab platform.
-
multimode precoding for mimo wireless systems
IEEE Transactions on Signal Processing, 2005Co-Authors: David James Love, Robert W. HeathAbstract:Multiple-input multiple-output (MIMO) wireless systems obtain large diversity and capacity gains by employing multielement antenna arrays at both the transmitter and receiver. The theoretical performance benefits of MIMO systems, however, are irrelevant unless low error rate, spectrally efficient signaling techniques are found. This paper proposes a new method for designing high data-rate spatial signals with low error rates. The basic idea is to use transmitter channel information to adaptively vary the transmission scheme for a fixed data rate. This adaptation is done by varying the number of Substreams and the rate of each Substream in a precoded spatial multiplexing system. We show that these Substreams can be designed to obtain full diversity and full rate gain using feedback from the receiver to transmitter. We model the feedback using a limited feedback scenario where only finite sets, or codebooks, of possible precoding configurations are known to both the transmitter and receiver. Monte Carlo simulations show substantial performance gains over beamforming and spatial multiplexing.
-
Multimode antenna selection for spatial multiplexing systems with linear receivers
IEEE Transactions on Signal Processing, 2005Co-Authors: Robert W. Heath, David James LoveAbstract:Spatial multiplexing is a simple transmission technique for multiple-input multiple-output (MIMO) wireless communication links in which data is multiplexed across the transmit antennas. In Rayleigh fading matrix channels, however, spatial multiplexing with low-complexity linear receivers suffers due to a lack of diversity advantage. This paper proposes multimode antenna selection, which uses a low-rate feedback channel to improve the error rate performance of spatial multiplexing systems with linear receivers. In the proposed technique, both the number of Substreams and the mapping of Substreams to antennas are dynamically adjusted, for a fixed total data rate, to the channel based on limited feedback from the receiver. Dual-mode selection, where spatial multiplexing or selection diversity is adaptively chosen, dramatically improves the diversity gain achieved. Multimode selection (i.e., allowing any number of Substreams to be dynamically selected) provides additional array gain. Various criteria for selecting the number of Substreams and the optimal mapping of Substreams to transmit antennas are derived. Relationships are made between the selection criteria and the eigenmodes of the channel. A probabilistic analysis of the selection criteria are provided for Rayleigh fading channels. Applications to nonlinear receivers are mentioned. Monte Carlo simulations demonstrate significant performance improvements in independent and identically distributed (i.i.d.) flat-fading Rayleigh matrix channels with minimal feedback.
-
limited feedback precoding for spatial multiplexing systems
Global Communications Conference, 2003Co-Authors: David James Love, Robert W. HeathAbstract:Spatial multiplexing multiple-input multiple-output (MIMO) wireless systems are of both theoretical and practical importance because they can achieve high spectral efficiencies by demultiplexing the incoming bit stream into multiple Substreams. It has been shown that sending fewer Substreams than the number of transmit antennas by linear precoding can provide improved error rate performance. Methods for designing linear precoders using perfect channel knowledge have previously been proposed. In many wireless systems, the assumption of complete channel knowledge is unrealistic because of the lack of forward and reverse channel reciprocity. To overcome this difficulty, we propose a precoding scheme that does not require transmit channel knowledge. The precoder is designed at the receiver and conveyed to the transmitter using a limited number of bits. The limited feedback represents an index within a finite set, or codebook, of precoding matrices. The receiver selects one of these codebook matrices using a modified version of a previously proposed full channel knowledge precoder selection criterion. A precoder codebook design method for maximizing the average effective channel power is shown to relate to chordal distance Grassmannian subspace packing. Simulation results show this technique outperforms antenna subset selection spatial multiplexing.
-
Limited feedback precoding for spatial multiplexing systems using linear receivers
IEEE Military Communications Conference 2003. MILCOM 2003., 2003Co-Authors: David James Love, Robert W. HeathAbstract:Multiple-input multiple-output (MIMO) spatial multiplexing wireless systems achieve high spectral efficiencies by demultiplexing the incoming bit stream into multiple Substreams. Spatial multiplexing is of practical importance because the multiple Substreams can be decoded using linear receivers. Unfortunately, this reduction in complexity degrades the probability of error performance. To overcome this difficulty, error rate performance of spatial multiplexing systems can be improved by sending fewer Substreams than the number of transmit antennas by linear preceding. Criteria have been proposed for designing these precoders when complete channel knowledge is available to the transmitter. The assumption of complete channel knowledge is often unrealistic in many communication systems such as those with low rate feedback channels. Thus a quantized preceding scheme is proposed where the receiver sends back a fixed number of bits to the transmitter. This bit pattern corresponds to an index within a finite set of preceding matrices. A previously proposed criterion is used to determine the matrix in this precoder codebook to choose. A design method for these codebooks using techniques from Grassmannian subspace packing is presented. Simulation results show this technique outperforms typical antenna selection.
K Miyashita - One of the best experts on this subject based on the ideXlab platform.
-
high data rate transmission with eigenbeam space division multiplexing e sdm in a mimo channel
Vehicular Technology Conference, 2002Co-Authors: K Miyashita, Takeo Ohgane, Yasutaka Ogawa, Toshihiko Nishimura, Yasushi TakatoriAbstract:When channel state information is known at a transmitter in multiple-input multiple-output systems, the optimum capacity is given by eigenmode channel division with water-pouring power control. In this eigenbeam-space division multiplexing (E-SDM), bit assignment to Substreams based on the capacity is not optimum due to the fact that the number of assigned bits is expressed by a discrete quantity. In the paper, a method to assign both bit and transmit power to each Substream based on the criterion minimizing total bit error rate (BER) is developed, and the BER performance is numerically analyzed in comparison to spatial division multiplexing (SDM). The simulation results assuming 5-transmit and 2-receive antennas show that the E-SDM provides about 10 dB gain compared to the conventional SDM at average BER of 10/sup -3/.
-
high data rate transmission with eigenbeam space division multiplexing e sdm in a mimo channel
Vehicular Technology Conference, 2002Co-Authors: K Miyashita, Takeo Ohgane, Yasutaka Ogawa, Toshihiko Nishimura, Yasushi TakatoriAbstract:When channel state information is known at a transmitter in multiple-input multiple-output systems, the optimum capacity is given by eigenmode channel division with water-pouring power control. In this eigenbeam-space division multiplexing (E-SDM), bit assignment to Substreams based on the capacity is not optimum due to the fact that the number of assigned bits is expressed by a discrete quantity. In the paper, a method to assign both bit and transmit power to each Substream based on the criterion minimizing total bit error rate (BER) is developed, and the BER performance is numerically analyzed in comparison to spatial division multiplexing (SDM). The simulation results assuming 5-transmit and 2-receive antennas show that the E-SDM provides about 10 dB gain compared to the conventional SDM at average BER of 10/sup -3/.
Bertrand M. Hochwald - One of the best experts on this subject based on the ideXlab platform.
-
high rate codes that are linear in space and time
IEEE Transactions on Information Theory, 2002Co-Authors: Babak Hassibi, Bertrand M. HochwaldAbstract:Multiple-antenna systems that operate at high rates require simple yet effective space-time transmission schemes to handle the large traffic volume in real time. At rates of tens of bits per second per hertz, Vertical Bell Labs Layered Space-Time (V-BLAST), where every antenna transmits its own independent Substream of data, has been shown to have good performance and simple encoding and decoding. Yet V-BLAST suffers from its inability to work with fewer receive antennas than transmit antennas-this deficiency is especially important for modern cellular systems, where a base station typically has more antennas than the mobile handsets. Furthermore, because V-BLAST transmits independent data streams on its antennas there is no built-in spatial coding to guard against deep fades from any given transmit antenna. On the other hand, there are many previously proposed space-time codes that have good fading resistance and simple decoding, but these codes generally have poor performance at high data rates or with many antennas. We propose a high-rate coding scheme that can handle any configuration of transmit and receive antennas and that subsumes both V-BLAST and many proposed space-time block codes as special cases. The scheme transmits Substreams of data in linear combinations over space and time. The codes are designed to optimize the mutual information between the transmitted and received signals. Because of their linear structure, the codes retain the decoding simplicity of V-BLAST, and because of their information-theoretic optimality, they possess many coding advantages. We give examples of the codes and show that their performance is generally superior to earlier proposed methods over a wide range of rates and signal-to-noise ratios (SNRs).
-
linear dispersion codes
International Symposium on Information Theory, 2001Co-Authors: Babak Hassibi, Bertrand M. HochwaldAbstract:Multiple-antenna systems that operate at high rates require simple yet effective space-time transmission schemes to handle the large traffic volume in real time. At rates of tens of bits/sec/Hz, V-BLAST, where every antenna transmits its own independent Substream of data, has been shown to have good performance and simple encoding and decoding. Yet V-BLAST suffers from its inability to work with fewer receive antennas than transmit antennas. Furthermore, because V-BLAST transmits independent data streams on its antennas there is no built-in spatial coding to guard against deep fades from any given transmit antenna. On the other hand, there are many previously-proposed space-time codes that have good fading resistance and simple decoding, but these codes generally have poor performance at high data rates or with many antennas. We propose a high-rate coding scheme that can handle any configuration of transmit and receive antennas and that subsumes both V-BLAST and many proposed space-time block codes as special cases. The scheme transmits Substreams of data in linear combinations over space and time. The codes are designed to optimize the mutual information between the transmitted and received signals. Because of their linear structure, the codes retain the decoding simplicity of V-BLAST, and because of their information theoretic optimality, they possess many coding advantages. We give examples of the codes and show that their performance is generally superior to earlier proposed methods over a wide range of rates and SNRs.
-
high rate linear space time codes
International Conference on Acoustics Speech and Signal Processing, 2001Co-Authors: Babak Hassibi, Bertrand M. HochwaldAbstract:Multiple-antenna systems that operate at high rates require simple yet effective space-time transmission schemes to handle the large traffic volume in real time. V-BLAST, where every antenna transmits its own independent Substream of data, has been shown to have good performance and simple encoding and decoding. Yet its drawbacks include its inability to work with fewer receive antennas than transmit antennas, and its absence of built-in spatial coding. On the other hand, there are many previously-proposed space-time codes that have good fading resistance and simple decoding, but generally poor performance at high data rates or with many antennas. We propose a high-rate coding scheme that can handle any configuration of transmit and receive antennas and that subsumes both V-BLAST (Vertical Bell Labs Layered Space-Time) and many proposed space-time codes as special cases. The scheme transmits Substreams of data in linear combinations over space and time and the codes are designed to optimize the mutual information between the transmitted and received signals. Because of their linear structure, the codes retain the decoding simplicity of V-BLAST, and because of their information-theoretic optimality, they possess many coding advantages.
