Maximum Likelihood Receiver for Multiple Channel Transmission Systems
01 Jan 2007-pp 305-312
TL;DR: In this paper, a maximum likelihood estimator for digital sequences disturbed by Gaussian noise, intersymbol interference (ISI) and interchannel interference (ICI) is derived.
Abstract: A maximum likelihood (ML) estimator for digital sequences disturbed by Gaussian noise, intersymbol interference (ISI) and interchannel interference (ICI) is derived. It is shown that the sampled outputs of the multiple matched filter (MMF) form a set of sufficient statistics for estimating the input vector sequence. Two ML vector sequence estimation algorithms are presented. One makes use of the sampled output data of the multiple whitened matched filter and is called the vector Viterbi algorithm. The other one is a modification of the vector Viterbi algorithm and uses directly the sampled output of the MMF. It appears that, under a certain condition, the error performance is asymptotically as good as if both ISI and ICI were absent.
Citations
More filters
TL;DR: This novel list-sequential (LISS) decoder avoids most of the drawbacks of the classical sequential decoders, and achieves the optimal (genie) or APP performance at a bit-error rate after the outer decoder of less than 10-4.
Abstract: For iterative detection/decoding (turbo) schemes, we modify sequential decoding, which contrary to a posteriori probability (APP) Bahl-Cocke-Jelinek-Raviv (BCJR) decoding, enjoys a complexity almost independent of the number of states. This novel list-sequential (LISS) decoder avoids most of the drawbacks of the classical sequential decoders, such as variable workload and erased frames when working within a turbo scheme. It uses a metric containing a priori and channel values, a metric length bias term for speeding up the tree search, a soft extension of paths without increasing the stack size, and soft weighting to obtain a soft output. We present several turbo applications using the LISS including equalization, single-antenna interference cancellation, multiuser and multiple-input multiple-output detection. It is shown that the LISS achieves the optimal (genie) or APP performance at a bit-error rate after the outer decoder of less than 10-4, but it also works with channels which have a high number of taps, constellation points, antennas, and states where the APP (BCJR) algorithm becomes infeasible
94 citations
Additional excerpts
...Therefore, it has been proposed in [28] and [29] to perform joint...
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TL;DR: This two-stage demodulator/decoder outperforms more complex turbo CDMA methods for equal power modes (users) and it is shown that arbitrary numbers of modes can be supported if an unequal power distribution is adopted.
Abstract: Iterative processing for linear matrix channels, aka turbo equalization, turbo demodulation, or turbo code-division multiple access (CDMA), has traditionally been addressed as the concatenation of conventional error control codes with the linear (matrix) channel. However, in several situations, such as CDMA, multiple-input-multiple-output (MIMO) channels, orthogonal frequency-division multiplexing (OFDM), and intersymbol-interference (ISI) channels, the channel itself either contains inherent signal redundancy or such redundancy can readily be introduced at the transmitter. For such systems, iterative demodulation of the linear channel exploiting this redundancy using simple iterative cancellation demodulators, followed by conventional feedforward error control decoding, provides a low-complexity, but extremely efficient decoding alternative. This two-stage demodulator/decoder outperforms more complex turbo CDMA methods for equal power modes (users). Furthermore, it is shown that arbitrary numbers of modes can be supported if an unequal power distribution is adopted. These power distributions are nested, which means that additional modes can be added without disturbing an existing mode population. The main result shows that these nested power distributions enable the two-stage receiver to approach the Shannon capacity of the channel to within less than one bit for any signal-to-noise ratio (SNR).
42 citations
TL;DR: This paper addresses the issue of advanced equalization methods for space-time communications over multiple-input multiple-output block fading channel with intersymbol interference with a different point of view, and separate time equalization from space equalization, thus introducing a higher degree of freedom in the overall space- time equalizer design.
Abstract: This paper addresses the issue of advanced equalization methods for space-time communications over multiple-input multiple-output block fading channel with intersymbol interference. Instead of resorting to conventional multiuser detection techniques (based on the straightforward analogy between antennas and users), we adopt a different point of view, and separate time equalization from space equalization, thus introducing a higher degree of freedom in the overall space-time equalizer design. Time-domain equalization relies on minimum mean-square error criterion and operates on multidimensional modulation symbols, whose individual components can be detected in accordance with another criterion. In particular, when the optimum maximum a posteriori criterion is chosen, substantial performance gains over conventional space-time turbo equalization have been observed for different transmission scenarios, at the price of an increased, albeit manageable, computational complexity.
35 citations
TL;DR: It is shown how the different types of factorizations can be transformed onto a prototype factorization task, which in turn can be solved by first performing an unsorted factorization and then determining the optimal processing order.
Abstract: Sorted spectral factorization of matrix polynomials is studied. Such type of factoring Hermitian matrix polynomials is the key step in calculating the optimum receive filter matrices in spatial/temporal decision-feedback equalization as well as the optimum transmit filter matrices in spatial/temporal Tomlinson-Harashima-type precoding schemes. Contrary to other approaches, we inherently consider asymptotic rather than finite-length results for transmission over MIMO channels with intersymbol interference. It is shown how the different types of factorizations can be transformed onto a prototype factorization task, which in turn can be solved by first performing an unsorted factorization and then determining the optimal processing order. An easy-to-use iterative algorithm for unsorted spectral factorization and the adjustment of the optimized order in DFE and precoding are explained. Numerical simulations cover the impact of sorted and unsorted spectral factorization on the performance of DFE and precoding schemes.
31 citations
19 May 2008
TL;DR: A soft-output trellis-based equalizer is proposed, taking into account the cyclic ISI structure arising in SC-FDMA, which is especially suited for turbo-encoded transmission over channels with low- to-moderate signal-to-noise ratios (SNRs).
Abstract: For the uplink of the E-UTRA long term evolution (LTE) system, single-carrier frequency-division multiple access (SC-FDMA) transmission has been selected. Frequency-domain linear and decision-feedback equalizers have been already given in the literature for an SC-FDMA transmission over a multiple- input multiple-output (MIMO) intersymbol interference (ISI) channel. In this paper, a soft-output trellis-based equalizer is proposed, taking into account the cyclic ISI structure arising in SC-FDMA, which is especially suited for turbo-encoded transmission over channels with low-to-moderate signal-to-noise ratios (SNRs). A preprocessing stage is necessary for the trellis- based equalizer consisting of a minimum mean-squared error (MMSE) MIMO linear equalizer and a MIMO prediction-error filter, whose design is addressed. Simulation results for an LTE scenario demonstrate that the novel receiver yields significant gains compared to MMSE linear equalization in particular for square MIMO systems.
30 citations
Cites methods from "Maximum Likelihood Receiver for Mul..."
...Because MIMO trellis–based equalization adopting the squared Euclidean metric [15] requires a signal impaired by spatially and temporally white Gaussian noise, a finite impulse response (FIR) prediction–error filter of order qp is employed in a second stage for approximate removal of the temporal noise correlations, reinserting ISI in a controlled manner....
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References
More filters
TL;DR: This novel list-sequential (LISS) decoder avoids most of the drawbacks of the classical sequential decoders, and achieves the optimal (genie) or APP performance at a bit-error rate after the outer decoder of less than 10-4.
Abstract: For iterative detection/decoding (turbo) schemes, we modify sequential decoding, which contrary to a posteriori probability (APP) Bahl-Cocke-Jelinek-Raviv (BCJR) decoding, enjoys a complexity almost independent of the number of states. This novel list-sequential (LISS) decoder avoids most of the drawbacks of the classical sequential decoders, such as variable workload and erased frames when working within a turbo scheme. It uses a metric containing a priori and channel values, a metric length bias term for speeding up the tree search, a soft extension of paths without increasing the stack size, and soft weighting to obtain a soft output. We present several turbo applications using the LISS including equalization, single-antenna interference cancellation, multiuser and multiple-input multiple-output detection. It is shown that the LISS achieves the optimal (genie) or APP performance at a bit-error rate after the outer decoder of less than 10-4, but it also works with channels which have a high number of taps, constellation points, antennas, and states where the APP (BCJR) algorithm becomes infeasible
94 citations
TL;DR: This two-stage demodulator/decoder outperforms more complex turbo CDMA methods for equal power modes (users) and it is shown that arbitrary numbers of modes can be supported if an unequal power distribution is adopted.
Abstract: Iterative processing for linear matrix channels, aka turbo equalization, turbo demodulation, or turbo code-division multiple access (CDMA), has traditionally been addressed as the concatenation of conventional error control codes with the linear (matrix) channel. However, in several situations, such as CDMA, multiple-input-multiple-output (MIMO) channels, orthogonal frequency-division multiplexing (OFDM), and intersymbol-interference (ISI) channels, the channel itself either contains inherent signal redundancy or such redundancy can readily be introduced at the transmitter. For such systems, iterative demodulation of the linear channel exploiting this redundancy using simple iterative cancellation demodulators, followed by conventional feedforward error control decoding, provides a low-complexity, but extremely efficient decoding alternative. This two-stage demodulator/decoder outperforms more complex turbo CDMA methods for equal power modes (users). Furthermore, it is shown that arbitrary numbers of modes can be supported if an unequal power distribution is adopted. These power distributions are nested, which means that additional modes can be added without disturbing an existing mode population. The main result shows that these nested power distributions enable the two-stage receiver to approach the Shannon capacity of the channel to within less than one bit for any signal-to-noise ratio (SNR).
42 citations
TL;DR: This paper addresses the issue of advanced equalization methods for space-time communications over multiple-input multiple-output block fading channel with intersymbol interference with a different point of view, and separate time equalization from space equalization, thus introducing a higher degree of freedom in the overall space- time equalizer design.
Abstract: This paper addresses the issue of advanced equalization methods for space-time communications over multiple-input multiple-output block fading channel with intersymbol interference. Instead of resorting to conventional multiuser detection techniques (based on the straightforward analogy between antennas and users), we adopt a different point of view, and separate time equalization from space equalization, thus introducing a higher degree of freedom in the overall space-time equalizer design. Time-domain equalization relies on minimum mean-square error criterion and operates on multidimensional modulation symbols, whose individual components can be detected in accordance with another criterion. In particular, when the optimum maximum a posteriori criterion is chosen, substantial performance gains over conventional space-time turbo equalization have been observed for different transmission scenarios, at the price of an increased, albeit manageable, computational complexity.
35 citations
TL;DR: It is shown how the different types of factorizations can be transformed onto a prototype factorization task, which in turn can be solved by first performing an unsorted factorization and then determining the optimal processing order.
Abstract: Sorted spectral factorization of matrix polynomials is studied. Such type of factoring Hermitian matrix polynomials is the key step in calculating the optimum receive filter matrices in spatial/temporal decision-feedback equalization as well as the optimum transmit filter matrices in spatial/temporal Tomlinson-Harashima-type precoding schemes. Contrary to other approaches, we inherently consider asymptotic rather than finite-length results for transmission over MIMO channels with intersymbol interference. It is shown how the different types of factorizations can be transformed onto a prototype factorization task, which in turn can be solved by first performing an unsorted factorization and then determining the optimal processing order. An easy-to-use iterative algorithm for unsorted spectral factorization and the adjustment of the optimized order in DFE and precoding are explained. Numerical simulations cover the impact of sorted and unsorted spectral factorization on the performance of DFE and precoding schemes.
31 citations
19 May 2008
TL;DR: A soft-output trellis-based equalizer is proposed, taking into account the cyclic ISI structure arising in SC-FDMA, which is especially suited for turbo-encoded transmission over channels with low- to-moderate signal-to-noise ratios (SNRs).
Abstract: For the uplink of the E-UTRA long term evolution (LTE) system, single-carrier frequency-division multiple access (SC-FDMA) transmission has been selected. Frequency-domain linear and decision-feedback equalizers have been already given in the literature for an SC-FDMA transmission over a multiple- input multiple-output (MIMO) intersymbol interference (ISI) channel. In this paper, a soft-output trellis-based equalizer is proposed, taking into account the cyclic ISI structure arising in SC-FDMA, which is especially suited for turbo-encoded transmission over channels with low-to-moderate signal-to-noise ratios (SNRs). A preprocessing stage is necessary for the trellis- based equalizer consisting of a minimum mean-squared error (MMSE) MIMO linear equalizer and a MIMO prediction-error filter, whose design is addressed. Simulation results for an LTE scenario demonstrate that the novel receiver yields significant gains compared to MMSE linear equalization in particular for square MIMO systems.
30 citations