Results 11  20
of
307
Linear precoding in cooperative MIMO cellular networks with limited coordination clusters
 IEEE J. Sel. Areas Commun
, 2010
"... ar ..."
(Show Context)
Space division multiple access with a sum feedback rate constraint
 IEEE Trans. Signal Processing
, 2007
"... Abstract—On a multiantenna broadcast channel, simultaneous transmission to multiple users by joint beamforming and scheduling is capable of achieving high throughput, which grows double logarithmically with the number of users. The sum rate for channel state information (CSI) feedback, however, incr ..."
Abstract

Cited by 34 (7 self)
 Add to MetaCart
(Show Context)
Abstract—On a multiantenna broadcast channel, simultaneous transmission to multiple users by joint beamforming and scheduling is capable of achieving high throughput, which grows double logarithmically with the number of users. The sum rate for channel state information (CSI) feedback, however, increases linearly with the number of users, reducing the effective uplink capacity. To address this problem, a novel space division multiple access (SDMA) design is proposed, where the sum feedback rate is upper bounded by a constant. This design consists of algorithms for CSI quantization, thresholdbased CSI feedback, and joint beamforming and scheduling. The key feature of the proposed approach is the use of feedback thresholds to select feedback users with large channel gains and small CSI quantization errors such that the sum feedback rate constraint is satisfied. Despite this constraint, the proposed SDMA design is shown to achieve a sum capacity growth rate close to the optimal one. Moreover, the feedback overflow probability for this design is found to decrease exponentially with the difference between the allowable and the average sum feedback rates. Numerical results show that the proposed SDMA design is capable of attaining higher sum capacities than existing ones, even though the sum feedback rate is bounded. Index Terms—Broadcast channels, feedback communication, multiuser channels, space division multiplexing. I.
On the user selection in MIMO broadcast channels
 IN PROC. OF INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY
, 2005
"... In this paper, a downlink communication system, in which a Base Station (BS) equipped with M antennas communicates with N users each equipped with K receive antennas, is considered. An efficient suboptimum algorithm is proposed for selecting a set of users in order to maximize the sumrate throughpu ..."
Abstract

Cited by 34 (5 self)
 Add to MetaCart
In this paper, a downlink communication system, in which a Base Station (BS) equipped with M antennas communicates with N users each equipped with K receive antennas, is considered. An efficient suboptimum algorithm is proposed for selecting a set of users in order to maximize the sumrate throughput of the system. For the asymptotic case when N tends to infinity, the necessary and sufficient conditions in order to achieve the maximum sumrate throughput, such that the difference between the achievable sumrate and the maximum value approaches zero, is derived. The complexity of our algorithm is investigated in terms of the required amount of feedback from the users to the base station, as well as the number of searches required for selecting the users. It is shown that the proposed method is capable of achieving a large portion of the sumrate capacity, with a very low complexity.
Performance of Orthogonal Beamforming for SDMA with Limited Feedback
 IEEE TRANS. VEHICULAR TECHNOLOGY
, 2007
"... On the multiantenna broadcast channel, the spatial degrees of freedom support simultaneous transmission to multiple users. Optimal multiuser transmission, known as dirty paper coding, requires noncausal channel state information (CSI) and extreme complexity and is hence not directly realizable. A ..."
Abstract

Cited by 33 (6 self)
 Add to MetaCart
(Show Context)
On the multiantenna broadcast channel, the spatial degrees of freedom support simultaneous transmission to multiple users. Optimal multiuser transmission, known as dirty paper coding, requires noncausal channel state information (CSI) and extreme complexity and is hence not directly realizable. A more practical design, named per user unitary and rate control (PU2RC), has been proposed for emerging cellular standards. PU2RC supports multiuser simultaneous transmission, enables limited feedback, and is capable of exploiting multiuser diversity. Its key feature is an orthogonal beamforming (or precoding) constraint, where each user selects a beamformer (or precoder) from a codebook of multiple orthonormal bases. In this paper, the asymptotic throughput scaling laws for PU2RC with a large user pool are derived for different regimes. In the interferencelimited regime, the throughput of PU2RC is shown to scale logarithmically with the number of users. In the normal and noiselimited regimes, the throughput is found to scale double logarithmically with the number of users and also linearly with the number of antennas at the base station. In addition, numerical results show that PU2RC achieves higher throughput and is more robust against CSI quantization errors than the popular alternative of zeroforcing beamforming if the number of users is sufficiently large.
Training and Feedback Optimization for Multiuser MIMO Downlink
, 2009
"... We consider a MIMO fading broadcast channel where the fading channel coefficients are constant over timefrequency blocks that span a coherent time × a coherence bandwidth. In closedloop systems, channel state information at transmitter (CSIT) is acquired by the downlink training sent by the base s ..."
Abstract

Cited by 32 (2 self)
 Add to MetaCart
(Show Context)
We consider a MIMO fading broadcast channel where the fading channel coefficients are constant over timefrequency blocks that span a coherent time × a coherence bandwidth. In closedloop systems, channel state information at transmitter (CSIT) is acquired by the downlink training sent by the base station and an explicit feedback from each user terminal. In openloop systems, CSIT is obtained by exploiting uplink training and channel reciprocity. We use a tight closedform lower bound on the ergodic achievable rate in the presence of CSIT errors in order to optimize the overall system throughput, by taking explicitly into account the overhead due to channel estimation and channel state feedback. Based on three timefrequency block models inspired by actual systems, we provide some useful guidelines for the overall system optimization. In particular, digital (quantized) feedback is found to offer a substantial advantage over analog (unquantized) feedback.
Cooperative Multicell Block Diagonalization with PerBaseStation Power Constraints
, 2010
"... ..."
Finiterate feedback MIMO broadcast channels with a large number of users
 Proc. of IEEE Intl. Symposium on Info. Theory
, 2006
"... Abstract — We analyze the sumrate performance of a multiantenna downlink system carrying more users than transmit antennas, with partial channel knowledge at the transmitter due to finite rate feedback. In order to exploit multiuser diversity, we show that the transmitter must have, in addition to ..."
Abstract

Cited by 31 (3 self)
 Add to MetaCart
(Show Context)
Abstract — We analyze the sumrate performance of a multiantenna downlink system carrying more users than transmit antennas, with partial channel knowledge at the transmitter due to finite rate feedback. In order to exploit multiuser diversity, we show that the transmitter must have, in addition to directional information, information regarding the quality of each channel. Such information should reflect both the channel magnitude and the quantization error. Expressions for the SINR distribution and the sumrate are derived, and tradeoffs between the number of feedback bits, the number of users, and the SNR are observed. In particular, for a target performance, having more users reduces feedback load. I.
Large System Analysis of Linear Precoding in MISO Broadcast Channels with Limited Feedback
, 2010
"... ..."
MultiAntenna Broadcast Channels with Limited Feedback and User Selection
, 2006
"... We analyze the sumrate performance of a multiantenna downlink system carrying more users than transmit antennas, with partial channel knowledge at the transmitter due to finite rate feedback. In order to exploit multiuser diversity, we show that the transmitter must have, in addition to directiona ..."
Abstract

Cited by 29 (3 self)
 Add to MetaCart
(Show Context)
We analyze the sumrate performance of a multiantenna downlink system carrying more users than transmit antennas, with partial channel knowledge at the transmitter due to finite rate feedback. In order to exploit multiuser diversity, we show that the transmitter must have, in addition to directional information, information regarding the quality of each channel. Such information should reflect both the channel magnitude and the quantization error. Expressions for the SINR distribution and the sumrate are derived, and tradeoffs between the number of feedback bits, the number of users, and the SNR are observed. In particular, for a target performance, having more users reduces feedback load.
Coordinated Beamforming with Limited Feedback in the MIMO Broadcast Channel
, 2008
"... In this paper, we propose a new joint optimization of linear transmit beamforming and receive combining vectors for the multipleinput multipleoutput (MIMO) broadcast channel. We consider the transmission of a single information stream to two users with two or more receive antennas. Unlike past wo ..."
Abstract

Cited by 26 (8 self)
 Add to MetaCart
In this paper, we propose a new joint optimization of linear transmit beamforming and receive combining vectors for the multipleinput multipleoutput (MIMO) broadcast channel. We consider the transmission of a single information stream to two users with two or more receive antennas. Unlike past work in which iterative computation is required to design the beamformers, we derive specific formulations for the transmit beamformers for two active users via a power iteration and a generalized eigen analysis. To enable practical implementation, a new limited feedback algorithm is proposed that exploits the structure of the algorithm to avoid full channel quantization. The feedback overhead of the proposed algorithm is independent of the number of receive antennas. Monte Carlo simulations are used to evaluate the bit error rate and the sum rate performances of the proposed algorithm. Simulation results show that the proposed method performs close to the sum capacity of the MIMO broadcast channel even with limited feedback.