Exploiting Long-Term Channel Correlation in Limited Feddback SDMA through Channel Phase Codebook

in IEEE Transactions on Signal Processing (2011), 59(3), 1217-1228

Improving channel information quality at the base station (BS) is crucial for the optimization of frequency division duplexed (FDD) multi-antenna multiuser downlink systems with limited feedback. To this ... [more ▼]

Improving channel information quality at the base station (BS) is crucial for the optimization of frequency division duplexed (FDD) multi-antenna multiuser downlink systems with limited feedback. To this end, this paper proposes to estimate a particular representation of channel state information (CSI) at the BS through channel norm feedback and a newly developed channel phase codebook, where the long-term channel correlation is efficiently exploited to improve performance. In particular, the channel representation is decomposed into a gain-related part and a phase-related part, with each of them estimated separately. More specifically, the gain-related part is estimated from the channel norm and channel correlation matrix, while the phase-related part is determined using a channel phase codebook, constructed with the generalized Lloyd algorithm. Using the estimated channel representation, joint optimization of multiuser precoding and opportunistic scheduling is performed to obtain an SDMA transmit scheme. Computer simulation results confirm the advantage of the proposed scheme over state of the art limited feedback SDMA schemes under correlated channel environment. [less ▲]

A New Multi-Lateral Filter for Real-Time Depth Enhancement

in 8th IEEE International Conference on Advanced Video and Signal-Based Surveillance (2011)

Energy-Efficient MMSE Beamforming and Power Optimization in Multibeam Satellite Systems

in Energy-Efficient MMSE Beamforming and Power Optimization in Multibeam Satellite Systems (2011)

Spiral Colour Model: Reduction from 3-D to 2-D

in International Conference on Acoustics, Speech and Signal Processing (2011)

Computational Framework for Optimal Robust Beamforming in Coordinated Multicell Systems

in Computational Framework for Optimal Robust Beamforming in Coordinated Multicell Systems (2011)

Coordinated beamforming can significantly improve the performance of cellular systems through joint interference management. Unfortunately, such beamforming optimization problems are typically NP-hard in ... [more ▼]

Coordinated beamforming can significantly improve the performance of cellular systems through joint interference management. Unfortunately, such beamforming optimization problems are typically NP-hard in multicell scenarios, making heuristic beamforming the only feasible choice in practice. This paper proposes a new branch-reduce-and-bound algorithm that solves such optimization problems globally, with a complexity suitable for benchmarking and analysis. Compared to prior work, the framework handles robustness to uncertain intercell interference and numerical analysis shows higher efficiency. [less ▲]

Joint Precoding with Flexible Power Constraints in Multibeam Satellite Systems

in Joint Precoding with Flexible Power Constraints in Multibeam Satellite Systems (2011)

Optimal V-BLAST Ordering in Fast Rayleigh Fading: A Linear Assignment Problem

in Signal Processing Advances in Wireless Communications (SPAWC), 2011 IEEE 12th International Workshop on (2011)

We explore a novel approach to perform decoding-order optimization in the vertical Bell Labs layered space-time (V-BLAST) architecture. Allowing for simultaneous transmission of multiple, separately ... [more ▼]

We explore a novel approach to perform decoding-order optimization in the vertical Bell Labs layered space-time (V-BLAST) architecture. Allowing for simultaneous transmission of multiple, separately encoded data streams, the V-BLAST transmit-receive scheme applies to the uplink of a multi-user communication system. A multi-antenna receiver decodes data streams successively, dealing with inter-stream interference by means of cancelling and nulling; interference from previously decoded streams is cancelled by subtraction, and remaining interference is nulled by linear equalization. The order in which the streams are decoded can have a noticeable impact on system performance. We consider the optimization of a fixed decoding order in fast Rayleigh fading, based on long-term channel-fading parameters. For a wide range of performance measures, we show that the fast-fading ordering problem can be treated as a classical linear assignment problem, allowing a solution using existing, efficient algorithms. [less ▲]

Robust binary least squares: Relaxations and algorithms

in Acoustics, Speech and Signal Processing (ICASSP), 2011 IEEE International Conference on (2011)

Finding the least squares (LS) solution s to a system of linear equations Hs = y where H, y are given and s is a vector of binary variables, is a well known NP-hard problem. In this paper, we consider ... [more ▼]

Finding the least squares (LS) solution s to a system of linear equations Hs = y where H, y are given and s is a vector of binary variables, is a well known NP-hard problem. In this paper, we consider binary LS problems under the assumption that the coefficient matrix H is also unknown, and lies in a given uncertainty ellipsoid. We show that the corresponding worst-case robust optimization problem, although NP-hard, is still amenable to semidefinite relaxation (SDR)-based approximations. However, the relaxation step is not obvious, and requires a certain problem reformulation to be efficient. The proposed relaxation is motivated using Lagrangian duality and simulations suggest that it performs well, offering a robust alternative over the traditional SDR approaches for binary LS problems. [less ▲]

Statistical Precoding and Detection Ordering in MIMO Multiple-Access Channels with Decision Feedback Equalization

in Communications (ICC), 2011 IEEE International Conference on (2011)

We present a novel approach for joint transmitter-receiver design in the uplink of a wireless multiple-input multiple-output communication system. It applies to, e.g., a fast-fading frequency-division ... [more ▼]

We present a novel approach for joint transmitter-receiver design in the uplink of a wireless multiple-input multiple-output communication system. It applies to, e.g., a fast-fading frequency-division duplexing system with periodic pilot signaling from each user - a scenario hindering transmitter optimization based on channel state information (CSI), while CSI-based receiver optimization is possible. Each user multiplexes data onto several, independently coded subchannels processed by a linear precoder, and detected at a base station (BS) employing zero-forcing decision feedback (DF) equalization, eliminating all interference prior to detection. We target the problem of jointly designing fixed linear precoders for all users as well as a fixed detection order for the DF receiver based on long-term channel statistics. We propose an efficiently implementable alternating-minimization technique that is verified numerically to converge fast, and to outperform the popular V-BLAST scheme - a computationally more complex ordered-DF receiver with limited applicability by requiring equal-rate subchannels in the system. [less ▲]

Capacity Analysis of Multibeam Joint Decoding over Composite Satellite Channels

in Proceeding of IEEE (2011)