A Simple Iterative Gaussian Detector for Severely Delay-Spread MIMO Channels

Wo, Tianbin; Hoeher, Peter Adam

doi:10.1109/icc.2007.759

Cited by 17 publications

(18 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Afterwards in each iteration, the message updating operation is performed once per node. Using the same analysis as in [4], we will find that the complexity of this algorithm is strictly linear in the number of transmit/receive antennas and the spreading factor.…”

Section: E Scheduling and Phase Correctionmentioning

confidence: 97%

See 1 more Smart Citation

Graph-Based Soft Channel and Data Estimation for MIMO Systems with Asymmetric LDPC Codes

Liu

Hoeher

2008

2008 IEEE International Conference on Communications

Self Cite

View full text Add to dashboard Cite

In this paper, we propose an iterative soft channel estimation and data detection algorithm based on a factor graph. Channel coefficients as well as data symbols are treated as variable nodes and are all estimated in a low-complexity element-wise manner. Applying asymmetric LDPC codes, this algorithm is able to deliver ambiguity-free outputs for MIMO systems with or without training symbols. Training symbols are inherently utilized as a type of a priori information. This algorithm thoroughly relaxes the troublesome constraints on training design in the sense that an arbitrary (even zero) number of training symbols can be placed at arbitrary positions within a data burst.

show abstract

Section: E Scheduling and Phase Correctionmentioning

confidence: 97%

“…The authors would refer interested readers to[4],[5] for detailed explanation on this issue.This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the ICC 2008 proceedings.…”

mentioning

confidence: 99%

Graph-Based Soft Channel and Data Estimation for MIMO Systems with Asymmetric LDPC Codes

Liu

Hoeher

2008

2008 IEEE International Conference on Communications

Self Cite

View full text Add to dashboard Cite

show abstract

“…As shown in (2), when we have A = N I M , ML estimation is easily performed at each entry independently, in which case no local optima exist. As discussed in [6], in systems with a lot of diversity branches, the variance of A from the diagonal matrix is guaranteed to decrease by the weak law of the large numbers.…”

Section: Theoretical Upper Boundmentioning

confidence: 97%

“…in [4][5][6]. In this paper, we propose an alternative approach based on the hillclimbing method [7], referred to as a bit-flipping equalizer, which we use in conjunction with the low-complexity FD-MMSE equalizer.…”

Section: Introductionmentioning

confidence: 99%

Bit-Flipping Equalizer and ML Search-Space Analysis in Ultra-Wideband MIMO Channels

Koike‐Akino

2008

IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference

View full text Add to dashboard Cite

In this paper, we propose a low-complexity equalizer whose performance approaches that of the optimum maximumlikelihood (ML) estimator, in ultra-wideband (UWB) multipleinput multiple-output (MIMO) channels. Although the ML estimation offers the excellent performance, it is generally of high complexity due to the large size of searching space. Through a theoretical search-space analysis, we reveal that local searching algorithms may approximate the ML estimator when a large number of diversity branches is available. Based on the analysis, we develop a novel equalizer with simple bit-flipping for severely frequency-selective fading in UWB-MIMO channels. I. INTRODUCTIONThe recent demand of ubiquitous networking has necessitated breakthroughs realizing high-speed radio communications. One promising technique is termed multiple-input multiple-output (MIMO), where multiple antennas are used at both transmitter and receiver. A lot of theoretical and experimental studies have revealed that the MIMO systems can significantly improve the channel capacity [1][2][3]. For the near future, the signal bandwidth will likely increase to several GHz to accommodate higher data-rate transmissions. For instance, ultra-wideband (UWB) techniques have drawn much attention especially for body area networks. Future systems envision boosting the capacity even further by incorporating UWB into MIMO. In the UWB-MIMO systems, we require sophisticated equalization techniques to deal with dispersive channels.In frequency-selective MIMO channels, an equalizer employing the maximum-likelihood sequence estimation (MLSE) offers an optimum performance. However, it is of high complexity in general due to the large number of trellis states, which increases exponentially according to the channel memory length. Among low-complexity sub-optimum equalizers, frequency-domain (FD) equalization has received recent attention due to its reasonable tradeoff of performance and complexity. Although the FD equalizer based on the minimum mean-square error (MMSE) may outperform that based on the zero-forcing (ZF), it is still significantly inferior to the optimum MLSE equalizer in general.We start off by analyzing a search space of the ML estimator in order to derive an insight for complexity reductions. The high complexity of the ML estimation comes from the fact that it needs to search for the global optimum over all the possible candidates in the very large search space. By focusing on the behavior of undesired local optima in the search space, we discover that the probability of hitting local optima decreases exponentially with the number of diversity branches. This

show abstract

“…BP is well suited in several communication problems as well [9]; e.g., decoding of turbo codes and LDPC codes [10], [11], multiuser detection [12], [13], signal detection in ISI channels [14], [15], and MIMO detection [16], [17]. Recently, in [18], Wo and Hoeher has adopted BP for equalization in severely delayspread MIMO-ISI channels, using message passing on factor graphs. However, in terms of performance, the algorithm exhibited high error floors.…”

Section: Introductionmentioning

confidence: 99%

Damped Belief Propagation Based Near-Optimal Equalization of Severely Delay-Spread UWB MIMO-ISI Channels

Som

Chockalingam

2010

2010 IEEE International Conference on Communications

View full text Add to dashboard Cite

In this paper, we present a belief propagation (BP) based equalizer for ultrawideband (UWB) multiple-input multiple-output (MIMO) inter-symbol interference (ISI) channels characterized by severe delay spreads. We employ a Markov random field (MRF) graphical model of the system on which we carry out message passing. The proposed BP equalizer is shown to perform increasingly closer to optimal performance for increasing number of multipath components (MPC) at a much lesser complexity than that of the optimum equalizer. The proposed equalizer performs close to within 0.25 dB of SISO AWGN performance at 10 −3 bit error rate on a severely delay-spread MIMO-ISI channel with 20 equal-energy MPCs. We point out that, although MIMO/UWB systems are characterized by fully/densely connected graphical models, the following two proposed features are instrumental in achieving near-optimal performance for large number of MPCs at low complexities: i) use of pairwise compatibility functions in densely connected MRFs, and ii) use of damping of messages.

show abstract

A Simple Iterative Gaussian Detector for Severely Delay-Spread MIMO Channels

Cited by 17 publications

References 9 publications

Graph-Based Soft Channel and Data Estimation for MIMO Systems with Asymmetric LDPC Codes

Graph-Based Soft Channel and Data Estimation for MIMO Systems with Asymmetric LDPC Codes

Bit-Flipping Equalizer and ML Search-Space Analysis in Ultra-Wideband MIMO Channels

Damped Belief Propagation Based Near-Optimal Equalization of Severely Delay-Spread UWB MIMO-ISI Channels

Contact Info

Product

Resources

About