The Experts below are selected from a list of 1572 Experts worldwide ranked by ideXlab platform
Robert W. Heath - One of the best experts on this subject based on the ideXlab platform.
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Multimode antenna selection for MIMO amplify-and-forward relay systems
IEEE Transactions on Signal Processing, 2010Co-Authors: Kien Trung Truong, Robert W. HeathAbstract:Obtaining the most from multiple-antenna relay systems requires algorithms that configure the source and relay adaptively to instantaneous channel conditions. In this paper, we define an antenna selection mode of operation as the number of selected transmit antennas at the source (which is equal to the number of data Substreams), the substream-to-antenna mapping at the source, the number of selected transmit antennas at the relay, and the substream-to-antenna mapping at the relay. We develop dualmode and multimode antenna selection algorithms to choose the mode that is most likely to deliver the lowest vector symbol error rate assuming the overall data rate is fixed. The effective condition numbers of both the two-hop channel and the relay channel are derived to give intuition on how the spatial characteristics of the constituent channels affect mode selection and to derive low complexity algorithms. Link-level simulations show that our proposed algorithms usually select the best mode, thus improving the diversity performance of spatial multiplexing relay systems and providing array gains over the existing single-stream relay transmission strategies. The two-hop multimode algorithms are shown by system-level simulations to improve the reliability of transmission and extend spatial multiplexing capability to cell-edge users in a multi-cell network.
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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.
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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.
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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.
David James Love - One of the best experts on this subject based on the ideXlab platform.
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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.
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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.
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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.
Yasushi Takatori - One of the best experts on this subject based on the ideXlab platform.
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high data rate transmission with eigenbeam space division multiplexing e sdm in a mimo channel
Vehicular Technology Conference, 2002Co-Authors: K Miyashita, Toshihiko Nishimura, Takeo Ohgane, Yasutaka Ogawa, 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/.
Yucel Altunbasak - One of the best experts on this subject based on the ideXlab platform.
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A multiple-substream unequal error-protection and error-concealment algorithm for SPIHT-coded video bitstreams
IEEE Transactions on Image Processing, 2004Co-Authors: Russell M. Mersereau, Yucel AltunbasakAbstract:This work presents a coordinated multiple-substream unequal error-protection and error-concealment algorithm for SPIHT-coded bitstreams transmitted over lossy channels. In the proposed scheme, we divide the video sequence corresponding to a group of pictures into two subsequences and independently encode each subsequence using a three-dimensional SPIHT algorithm. We use two different partitioning schemes to generate the Substreams, each of which offers some advantages under the appropriate channel condition. Each substream is protected by an FEC-based unequal error-protection algorithm, which assigns unequal forward error correction codes to each bit plane. Any information that is lost during the transmission for any substream is estimated at the receiver by using the correlation between the Substreams and the smoothness of the video signal. Simulation results show that the proposed multiple-substream UEP algorithm is simple, fast, and robust in hostile network conditions, and that the proposed error-concealment algorithm can achieve 2-3-dB PSNR gain over the case when error concealment is not used at high packet-loss rates.
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ICME - Network-adaptive video streaming using multiple description coding and path diversity
2003 International Conference on Multimedia and Expo. ICME '03. Proceedings (Cat. No.03TH8698), 2003Co-Authors: Russell M. Mersereau, Yucel AltunbasakAbstract:This paper presents a TCP-friendly rate allocation algorithm for multiple description coding combined with path diversity. A 3-D SPIHT-based multiple description coding is used to generate two independent Substreams and each substream is protected with an FEC-based unequal error protection algorithm. In the proposed video streaming framework, two senders simultaneously stream complementary Substreams to the receiver over different paths. The proposed rate allocation algorithm coordinates distributed video streaming from multiple senders to a single receiver to minimize the overall distortion. Simulation results show that the proposed algorithm increases tolerance to packet loss due to network congestion and achieves higher visual quality compared to non-adaptive methods.
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ICIP (3) - An integrated multiple-substream unequal error protection and error concealment algorithm for Internet video applications
Proceedings. International Conference on Image Processing, 2002Co-Authors: Russell M. Mersereau, Yucel AltunbasakAbstract:This paper presents a coordinated multiple-substream unequal error protection and error concealment algorithm for SPIHT-coded bitstreams transmitted over lossy channels. In the proposed scheme, we divide the video sequence corresponding to a group of pictures into two sub-sequences in the temporal domain and independently encode each sub-sequence with a 3-D SPIHT algorithm to generate two independent Substreams. Each substream is protected by an FEC-based unequal error protection algorithm that assigns unequal forward error correction codes for each substream with bit-plane granularity. The information that is lost during transmission for one substream is estimated at the receiver by using the correlation between the two Substreams and the smoothness of the video signal. Simulation results show that the proposed multiple-substream UEP algorithm is simple, fast, and robust in hostile network conditions, and that the proposed error concealment algorithm achieves about 1-3 dB PSNR gain over the case where there is no error concealment at high packet loss rates.
Parviz Kermani - One of the best experts on this subject based on the ideXlab platform.
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a generic bandwidth allocation scheme for multimedia Substreams in adaptive networks using genetic algorithms
Wireless Communications and Networking Conference, 1999Co-Authors: M R Sherif, I Habib, Mahmoud Naghshineh, Parviz KermaniAbstract:In this paper we propose a generic call admission control scheme based on genetic algorithms. The scheme is applied to a wireless network using an adaptive resource allocation framework. A multimedia connection is represented in terms of three Substreams (video, audio and data) each with a pre-specified range of acceptable quality of service (QoS) requirements. This range of requirements make the application adaptive in the sense that each of its Substreams specify to the network a number of acceptable QoS levels instead of just a single one. For example, MPEG-based video can be transmitted at different levels of varying qualities. As resource availability in the wireless network changes, the control scheme selects the best possible QoS level that each substream can obtain for a certain period of time. In case of congestion, the control scheme attempts to free up some wireless resources by degrading the QoS of existing calls to a lesser level in order to accommodate new calls. This is done, however, under the constraint of achieving maximum utilization of the resources; and sharing them fairly among the calls. The degradation in the QoS is limited to a minimum value for each multimedia substream defined in a user-defined profile. From the user perspective, the perception of the QoS degradation is very graceful and happens only during over-load periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Genetic algorithms have been used to solve the optimization problem. Simulation results for a wireless ATM network demonstrate that the proposed scheme performs well in terms of increasing the number of calls admitted while effectively utilizing the available bandwidth fairly among the calls.
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WCNC - A generic bandwidth allocation scheme for multimedia Substreams in adaptive networks using genetic algorithms
WCNC. 1999 IEEE Wireless Communications and Networking Conference (Cat. No.99TH8466), 1999Co-Authors: M R Sherif, I Habib, Mahmoud Naghshineh, Parviz KermaniAbstract:In this paper we propose a generic call admission control scheme based on genetic algorithms. The scheme is applied to a wireless network using an adaptive resource allocation framework. A multimedia connection is represented in terms of three Substreams (video, audio and data) each with a pre-specified range of acceptable quality of service (QoS) requirements. This range of requirements make the application adaptive in the sense that each of its Substreams specify to the network a number of acceptable QoS levels instead of just a single one. For example, MPEG-based video can be transmitted at different levels of varying qualities. As resource availability in the wireless network changes, the control scheme selects the best possible QoS level that each substream can obtain for a certain period of time. In case of congestion, the control scheme attempts to free up some wireless resources by degrading the QoS of existing calls to a lesser level in order to accommodate new calls. This is done, however, under the constraint of achieving maximum utilization of the resources; and sharing them fairly among the calls. The degradation in the QoS is limited to a minimum value for each multimedia substream defined in a user-defined profile. From the user perspective, the perception of the QoS degradation is very graceful and happens only during over-load periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Genetic algorithms have been used to solve the optimization problem. Simulation results for a wireless ATM network demonstrate that the proposed scheme performs well in terms of increasing the number of calls admitted while effectively utilizing the available bandwidth fairly among the calls.
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An Adaptive QoS Representation and Resource Allocation Scheme for Multimedia and Wireless ATM Networks Using Genetic Algorithms
Multiaccess Mobility and Teletraffic in Wireless Communications: Volume 4, 1999Co-Authors: M R Sherif, I Habib, Mahmoud Naghshineh, Parviz KermaniAbstract:An adaptive resource allocation and call admission control scheme based on genetic algorithms is proposed. The scheme is applied to both wired broadband networks and wireless ATM networks using an adaptive resource allocation framework. A multimedia application consists of three distinct Substreams (video, audio and data). Each substream declares to the network a preset range of acceptable quality of service (QoS) requirements (e.g., high, medium, low) instead of just a single one. For example, MPEG-based video can be transmitted at different levels of varying qualities. As resource availability in the wireless network changes, the control scheme selects the best possible QoS level that each substream can obtain. In case of congestion, the control scheme attempts to free up some resources by degrading the QoS of existing calls to a lesser level in order to accommodate new calls. This is done, however, under the constraint of achieving maximum utilization of the resources; and sharing them fairly among the calls. The degradation in the QoS is limited to a minimum value for each substream defined in a user-defined profile. From the user perspective, the perception of the QoS degradation is very graceful and happens only during over-load periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Genetic algorithms have been used to solve the optimization problem. Simulation results demonstrate that the proposed scheme performs well in terms of increasing the number of calls admitted while effectively utilizing the available bandwidth fairly among the calls
