Tad Matsumoto - Academia.edu (original) (raw)

Papers by Tad Matsumoto

IEEE Transactions on Vehicular Technology, 2005

In this paper, an iterative (turbo) technique, soft-cancellation followed by minimum mean squared... more In this paper, an iterative (turbo) technique, soft-cancellation followed by minimum mean squared error filtering (SC/MMSE), is applied to the diversity combining of broadband single-carrier signals using multiple antennas. The major aim of this approach is to reduce the computational complexity of the original SC/MMSE equalization algorithm. It is shown that the performance of the proposed turbo diversity technique can asymptotically achieve that of the original SC/MMSE equalizer.

Research Letters in Communications, 2007

The primary goal of this letter is to provide comparative assessments to the two cases where diff... more The primary goal of this letter is to provide comparative assessments to the two cases where different criteria are used in joint over antenna minimum mean squared error (JA-MMSE) spatial filtering for space-time coded systems in the presence of unknown interference. It is shown that additional constraints to preserve the space-time coded signal structure in JA-MMSE spatial filtering place floor in bit error rate (BER) performance, while imposing no additional constraint places no error floor.

2018 IEEE 29th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2018

Wireless sensor networks (WSNs) are the core component in the big data era. Due to the unreliable... more Wireless sensor networks (WSNs) are the core component in the big data era. Due to the unreliable transmission environment, it is significantly useful to introduce a helper to refine the system performance. To begin with, we formulate the system model of WSNs as a problem of multiterminal source coding. Subsequently, we propose a 3D distributed compress-bin scheme and derive a corresponding inner bound by analyzing the expected rate-distortion. Finally, we investigate the performance improvement of a helper by comparing the derived inner bound with the Berger-Tung inner bound and through simulation. Both the theoretical bounds and simulation results indicate that a helper can obviously improve the system performance.

あらまし 本論文の目的は,「ターボ概念」に関する理解を読者に提供することである.そのために,ターボ 概念に基づくアルゴリズムの動作を理解する上で不可欠な相互情報量の伝達特性を評価するために便利な... more あらまし 本論文の目的は,「ターボ概念」に関する理解を読者に提供することである.そのために,ターボ 概念に基づくアルゴリズムの動作を理解する上で不可欠な相互情報量の伝達特性を評価するために便利なツー ルである,EXtrinsic Information Transfer (EXIT) チャートの概念を解説する.そのための題材としてター ボ等化を取り上げ,現実性と柔軟性に富む Soft Canceller followed by Minimum Mean Squared Error filter (SC-MMSE) 型ターボ等化アルゴリズムについて概説する.また,その特性を漸近特性と収束特性の両面から解 析する.更に,合理的な拡張としてターボ等化の空間多重を行う MIMO システムに適用する場合には,収束特 性は多次元 EXIT チャートを用いて評価されなければならないことを示す.最後に,今後の課題や研究動向につ いても述べる. キーワード ターボ等化,EXIT チャート,相互情報量,漸近特性,収束特性

IEEE Communications Letters, 2018

This letter proposes a practical source coding scheme, so-called hybrid majority voting (HMV) cod... more This letter proposes a practical source coding scheme, so-called hybrid majority voting (HMV) code, for lossy compression with discrete memoryless source. Inspired by the coding scheme used in the classic rate-distortion theorem, we find a series of basic MV codes and analyze their rate-distortion performance. We then present an algorithm to find two component MV codes and apply them to lossy compression, group by group, to construct HMV codes. Finally, we show an example of joint source-channel coding based on the HMV code. The performance evaluation indicates that the HMV code makes it possible to easily control efficiency and complexity.

IEEE Wireless Communications Letters, 2017

We develop a joint source-channel coding (JSCC) scheme based on an unequal power allocation strat... more We develop a joint source-channel coding (JSCC) scheme based on an unequal power allocation strategy, in which different levels of power are allocated according to a priori probability distribution of the information bits. Two protograph low-density parity-check codes are used as the source code and the channel code, respectively, in the proposed JSCC scheme. With fixed row weight and row element alphabet, optimization on the source code is conducted via random search to obtain a bestfound base matrix with the lowest decoding threshold among all the searched base matrices. Simulation results show that the new JSCC scheme outperforms the traditional equal power allocation based JSCC by exploiting the source statistics at the decoder. Moreover, theoretical threshold analysis is in agreement with the practical simulation results. Index Terms-Joint protograph extrinsic information transfer (JPEXIT), joint source-channel coding (JSCC), protograph low-density parity-check (LDPC) codes, unequal power allocation (UPA) This work is partially supported by China NSF under Grants 61401050 and 11461031. J. He, and Q. Xue are with the Centre for Wireless Communications,

2016 IEEE International Conference on Communications Workshops (ICC), 2016

We investigate the transmission of multiple correlated binary sources to a single destination ove... more We investigate the transmission of multiple correlated binary sources to a single destination over non-orthogonal Gaussian multiple access channels (MACs). By considering a binary codebook, we derive the admissible rate regions of the two-source Gaussian MAC. It is demonstrated that the admissible rate region increases as the correlation between the sources increases. Furthermore, we develop an iterative joint source channel decoding scheme based on systematic irregular lowdensity parity-check codes by exploiting the correlation between the two sources. The constituent decoders corresponding to each source are implemented in parallel via local iterations, exchanging extrinsic information with each other during the global iterations. Simulation results are provided to verify the performance improvement of the transmission of correlated sources compared to its independent sources counterpart. Index Terms-Non-orthogonal Gaussian multiple access channel (MAC), joint source channel decoding (JSCD), systematic irregular low-density parity-check (LDPC) codes, log-likelihood ratio (LLR).

2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2015

This paper investigates the outage behavior of transmitting correlated binary sources with arbitr... more This paper investigates the outage behavior of transmitting correlated binary sources with arbitrary code rate over quasi-static Rayleigh fading multiple access channel (MAC). The sufficient condition for lossless communication with arbitrary code rate is obtained by assuming separate source and channel coding, which indicates the two rate regions specified by the Slepian-Wolf theorem and the MAC capacity region intersect. An upper bound of the outage probability is derived based on the sufficient condition. Asymptotic property shows the second order diversity gain can be achieved only when the tow sources are fully correlated. Numerical results demonstrate the accuracy of the derived upper bound. The-outage achievable rate, which is the largest rate of transmission such that the outage probability is smaller than a predefined value, is also analyzed. It is found the-outage achievable rate becomes lager with higher transmit power and/or stronger source correlation.

2006 3rd International Symposium on Wireless Communication Systems, 2006

Coded space-time soft cancellation minimum mean squared error filtering (CST SC-MMSE) based turbo... more Coded space-time soft cancellation minimum mean squared error filtering (CST SC-MMSE) based turbo equalization, which exploits transmit diversity and coding gains through two turbo iteration loops, horizontal and vertical iterations, has been introduced in Ill for uplink single carrier signaling. In this paper, performance of the CST SC-MMSE equalizer is evaluated in realistic scenarios using multi-dimensional channel measurement data. Measurement data consists of snapshots measured in different channel conditions in terms of spatial and temporal properties. It is shown that the CST SC-MMSE equalizer can achieve excellent performance even at the lower SNR range due to the vertical iterations between the decoders that can achieve a coding gain on top of the diversity gain. However, performance depends on channel conditions. The impact of the horizontal and vertical iterations is studied in different channel conditions.

ITG Workshop on Smart Antennas (IEEE Cat. No.04EX802)

In turbo diversity technique, soft-cancellation followed by minimum mean squared error filtering ... more In turbo diversity technique, soft-cancellation followed by minimum mean squared error filtering (SUMMSE) is applied to diversity combining of broadband single-carrier signals using multiple antennas in order to reduce the computational complexity. In this paper, OUT proposed turbo diversity technique is evaluated using field measurement data gathered in a suburban area in Germany. It is verified through the field measurement data-based simulations that the performance of the complexity-reduced turbo diversity technique can asymptotically achieve that of the original SCMMSE equalizer. This research is funded by National Technology Agency of Rnland (TEKES), Nokia. Elektrobil and Finnish Air Farce, which is grarefully acknowledged.

Asilomar Conference on Signals, Systems & Computers, 2004

Turbo MIMO equalization in multiuser space-time-trellis-coded (STTrC) system is considered in thi... more Turbo MIMO equalization in multiuser space-time-trellis-coded (STTrC) system is considered in this paper. The low complexity MMSE receiver with soft cancellation (SC) is proposed for joint inter-symbol-interference (ISI), known co-channel interference (CCI) and unknown co-channel interference (UCCI) suppression. It is shown that in the multiuser scenario without UCCI the proposed iterative receiver achieves maximum-likelihood (ML) bound on performance of the

EURASIP Journal on Wireless Communications and Networking, 2004

Iterative multiuser detection in a single-carrier broadband multiple-input multiple-output (MIMO)... more Iterative multiuser detection in a single-carrier broadband multiple-input multiple-output (MIMO) system is studied in this paper. A minimum mean squared error (MMSE) low-complexity multiuser receiver is derived for space-division multiple-access (SDMA) space-time trellis-coded (STTrC) systems in frequency-selective fading channels. The receiver uses MMSE filtering to jointly detect several transmit antennas of the user of interest, while the interference from the undetected transmit antennas, cochannel interference (CCI), and intersymbol interference (ISI) are all cancelled by the soft cancellation. The performances of two extreme receiver cases are evaluated. In the first case, only one transmit antenna of the user of interest is detected at a time and the remaining ones are cancelled by soft cancellation. In the second case, all the transmit antennas are detected jointly. The comparison of the two cases shows improvement with the latter one, both in single-user and multiuser communications and in the presence of unknown cochannel interference (UCCI). It is further shown that in the multiuser case, the proposed receivers approach the corresponding single-user bounds. The number of receive antenna elements required to achieve single-user bound is thereby equal to the number of users and not to the total number of transmit antennas.

Research Letters in Communications, 2007

The primary goal of this letter is to provide comparative assessments to the two cases where diff... more The primary goal of this letter is to provide comparative assessments to the two cases where different criteria are used in joint over antenna minimum mean squared error (JA-MMSE) spatial filtering for space-time coded systems in the presence of unknown interference. It is shown that additional constraints to preserve the space-time coded signal structure in JA-MMSE spatial filtering place floor in bit error rate (BER) performance, while imposing no additional constraint places no error floor.

2008 5th International Symposium on Turbo Codes and Related Topics, 2008

This paper studies mutual information transfer properties of iterative multiuser detector with li... more This paper studies mutual information transfer properties of iterative multiuser detector with linear precoding schemes for single carrier communications in multipoint-to-point multiple input multiple output (MIMO) channels. Based on multidimensional extrinsic information transfer (EXIT) analysis, we analyze the impact of linear precoding on the convergence properties of the detectors jointly designed with the precoders based on minimum sum mean squared error (MMSE) and maximum sum mutual information rate criteria. Results demonstrate that the use of the linear precoding schemes enhance the separability of the EXIT curves of the simultaneous streams over without precoding; This invokes the idea that different code rate be allocated to the each transmitted streams at the transmitters.

2007 IEEE 65th Vehicular Technology Conference - VTC2007-Spring, 2007

In this paper, we address the problem of multiple-input multiple-output (MIMO) spatial multiplexi... more In this paper, we address the problem of multiple-input multiple-output (MIMO) spatial multiplexing (SM) systems in the presence of antenna fading correlation. It is well known that severe spatial correlations present at the transmitter and/or receiver can significantly compromise the performance of existing SM systems. Recent results showed that joint-over-antenna (JA) iterative detection schemes can improve the performance of SM systems in correlated channels as compared to schemes that detected the signals on an antenna-byantenna basis. We extend this idea in this paper by incorporating a so-called antenna doping (AD) scheme into the SM system, in order to further counteract the detrimental effects of spatial correlation. Through simulations, we show that AD can improve the performance by 3-4 dB in severe spatial correlation as compared to non-doping systems. This improvement is explained with the aid of extrinsic information transfer (EXIT) charts, which illustrate the convergence behavior of the JA iterative detection with and without AD.

2014 IEEE International Conference on Communications (ICC), 2014

Peak to average power ratio (PAPR) constrained power allocation in single carrier multiuser (MU) ... more Peak to average power ratio (PAPR) constrained power allocation in single carrier multiuser (MU) single-input multiple-output (SIMO) systems with iterative frequency domain (FD) soft cancelation (SC) minimum mean squared error (MMSE) equalization is considered in this paper. To obtain full benefit of the iterative receiver, its convergence properties need to be taken into account also at the transmitter side. In this paper, we extend the existing results on the area of convergence constrained power allocation (CCPA) to consider the instantaneous PAPR at the transmit antenna of each user. In other words, we will introduce a constraint that PAPR cannot exceed a predetermined threshold. By adding the aforementioned constraint into the CCPA optimization framework, the power efficiency of a power amplifier (PA) can be significantly enhanced by enabling it to operate on its linear operation range. Hence, PAPR constraint is especially beneficial for power limited celledge users. In this paper, we will derive the instantaneous PAPR constraint as a function of transmit power allocation. Furthermore, successive convex approximation is derived for the PAPR constrained problem. Numerical results show that the proposed method can achieve the objectives described above.

A goal of this paper is to combine the advantageous properties of multiple access codes (MAC) and... more A goal of this paper is to combine the advantageous properties of multiple access codes (MAC) and space-time transmission (STT) in wireless relay communication systems. The use of MAC provides transmission with the separability of the signals transmitted from multiple users, and STT the diversity gain. It is shown both by model-based numerical results and measurement data-based simulation results that the combined use of MAC and STT achieves significant improvement in bit error rate (BER) as well as signaling throughput of relay systems.

2005 IEEE 61st Vehicular Technology Conference

The so-called space-time weighted nonbinary repeataccumulate (ST-WNRA) codes are capable of achie... more The so-called space-time weighted nonbinary repeataccumulate (ST-WNRA) codes are capable of achieving full antenna diversity in single-user flat fading channels. In this paper, the performance of these codes is evaluated over a frequency-selective Rayleigh fading multiple-input multiple-output channel in a multiuser environment. Under this channel condition, the full antenna diversity supported by the ST-WNRA codes can no longer be achieved due to the presence of intersymbol interference and multiple access interference. Hence, in order to suppress these interferences, a turbo equalization technique based on the minimum mean square-error filtering with soft interference cancellation (SC-MMSE) is employed. The SC-MMSE detector is designed such that the diversity that can be gleaned from the multiple antennas as well as from the multipath components can be fully exploited. Computer simulations demonstrate that our proposed turbo-equalized system with ST-WNRA codes is capable of achieving the maximum diversity order and hence achieving an excellent bit error rate performance with a reasonable spectral efficiency at a low complexity cost.

2012 International ITG Workshop on Smart Antennas (WSA), 2012

Chained turbo equalization (CHATUE) is a simple detection scheme for block transmission without c... more Chained turbo equalization (CHATUE) is a simple detection scheme for block transmission without cyclic prefix (CP), where turbo equalizers for the several consecutive frames exchange information about the interference components in the form of a posteriori Log-Likelihood Ratio (LLR). Although elimination of CP in the block transmission can significantly increase bandwidth efficiency, the received signal suffers from inter-block interference (IBI), which can not be effectively compensated by block-by-block equalization. In this paper, we apply the CHATUE algorithm to effectively suppress inter-symbol interference (ISI), inter-carrier interference (ICI), and multiple-access interference (MAI) in a Multiuser Single Input Multiple Output Orthogonal Frequency Division Multiplexing (MU-SIMO-OFDM) system without CP. Results of computer simulations show the superiority of our proposed MU-SIMO-OFDM to conventional CP-aided systems, without requiring high computational complexity. The convergence property of the proposed technique is analyzed using the extrinsic information transfer (EXIT) chart. Doped accumulator is used to achieve a mutual information point close enough to the (1,1) point, and also to obtain better matching between the equalizer and decoder EXIT curves.

International Symposium on Wireless Personal Multimedia Communications, 2002

This paper describes the methodology and the results of performance investigations of the turbo M... more This paper describes the methodology and the results of performance investigations of the turbo MIMO equalizer concept for broadband MIMO systems. Different application setups are introduced and realistic simulations based on measured propagation data are described. Relationships between the propagation characteristics, the antenna configurations, and the achievable bit error rates are shown. Although in many of the considered constellations turbo

IEEE Transactions on Vehicular Technology, 2005

In this paper, an iterative (turbo) technique, soft-cancellation followed by minimum mean squared... more In this paper, an iterative (turbo) technique, soft-cancellation followed by minimum mean squared error filtering (SC/MMSE), is applied to the diversity combining of broadband single-carrier signals using multiple antennas. The major aim of this approach is to reduce the computational complexity of the original SC/MMSE equalization algorithm. It is shown that the performance of the proposed turbo diversity technique can asymptotically achieve that of the original SC/MMSE equalizer.

Research Letters in Communications, 2007

The primary goal of this letter is to provide comparative assessments to the two cases where diff... more The primary goal of this letter is to provide comparative assessments to the two cases where different criteria are used in joint over antenna minimum mean squared error (JA-MMSE) spatial filtering for space-time coded systems in the presence of unknown interference. It is shown that additional constraints to preserve the space-time coded signal structure in JA-MMSE spatial filtering place floor in bit error rate (BER) performance, while imposing no additional constraint places no error floor.

2018 IEEE 29th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2018

Wireless sensor networks (WSNs) are the core component in the big data era. Due to the unreliable... more Wireless sensor networks (WSNs) are the core component in the big data era. Due to the unreliable transmission environment, it is significantly useful to introduce a helper to refine the system performance. To begin with, we formulate the system model of WSNs as a problem of multiterminal source coding. Subsequently, we propose a 3D distributed compress-bin scheme and derive a corresponding inner bound by analyzing the expected rate-distortion. Finally, we investigate the performance improvement of a helper by comparing the derived inner bound with the Berger-Tung inner bound and through simulation. Both the theoretical bounds and simulation results indicate that a helper can obviously improve the system performance.

あらまし 本論文の目的は,「ターボ概念」に関する理解を読者に提供することである.そのために,ターボ 概念に基づくアルゴリズムの動作を理解する上で不可欠な相互情報量の伝達特性を評価するために便利な... more あらまし 本論文の目的は,「ターボ概念」に関する理解を読者に提供することである.そのために,ターボ 概念に基づくアルゴリズムの動作を理解する上で不可欠な相互情報量の伝達特性を評価するために便利なツー ルである,EXtrinsic Information Transfer (EXIT) チャートの概念を解説する.そのための題材としてター ボ等化を取り上げ,現実性と柔軟性に富む Soft Canceller followed by Minimum Mean Squared Error filter (SC-MMSE) 型ターボ等化アルゴリズムについて概説する.また,その特性を漸近特性と収束特性の両面から解 析する.更に,合理的な拡張としてターボ等化の空間多重を行う MIMO システムに適用する場合には,収束特 性は多次元 EXIT チャートを用いて評価されなければならないことを示す.最後に,今後の課題や研究動向につ いても述べる. キーワード ターボ等化,EXIT チャート,相互情報量,漸近特性,収束特性

IEEE Communications Letters, 2018

This letter proposes a practical source coding scheme, so-called hybrid majority voting (HMV) cod... more This letter proposes a practical source coding scheme, so-called hybrid majority voting (HMV) code, for lossy compression with discrete memoryless source. Inspired by the coding scheme used in the classic rate-distortion theorem, we find a series of basic MV codes and analyze their rate-distortion performance. We then present an algorithm to find two component MV codes and apply them to lossy compression, group by group, to construct HMV codes. Finally, we show an example of joint source-channel coding based on the HMV code. The performance evaluation indicates that the HMV code makes it possible to easily control efficiency and complexity.

IEEE Wireless Communications Letters, 2017

We develop a joint source-channel coding (JSCC) scheme based on an unequal power allocation strat... more We develop a joint source-channel coding (JSCC) scheme based on an unequal power allocation strategy, in which different levels of power are allocated according to a priori probability distribution of the information bits. Two protograph low-density parity-check codes are used as the source code and the channel code, respectively, in the proposed JSCC scheme. With fixed row weight and row element alphabet, optimization on the source code is conducted via random search to obtain a bestfound base matrix with the lowest decoding threshold among all the searched base matrices. Simulation results show that the new JSCC scheme outperforms the traditional equal power allocation based JSCC by exploiting the source statistics at the decoder. Moreover, theoretical threshold analysis is in agreement with the practical simulation results. Index Terms-Joint protograph extrinsic information transfer (JPEXIT), joint source-channel coding (JSCC), protograph low-density parity-check (LDPC) codes, unequal power allocation (UPA) This work is partially supported by China NSF under Grants 61401050 and 11461031. J. He, and Q. Xue are with the Centre for Wireless Communications,

2016 IEEE International Conference on Communications Workshops (ICC), 2016

We investigate the transmission of multiple correlated binary sources to a single destination ove... more We investigate the transmission of multiple correlated binary sources to a single destination over non-orthogonal Gaussian multiple access channels (MACs). By considering a binary codebook, we derive the admissible rate regions of the two-source Gaussian MAC. It is demonstrated that the admissible rate region increases as the correlation between the sources increases. Furthermore, we develop an iterative joint source channel decoding scheme based on systematic irregular lowdensity parity-check codes by exploiting the correlation between the two sources. The constituent decoders corresponding to each source are implemented in parallel via local iterations, exchanging extrinsic information with each other during the global iterations. Simulation results are provided to verify the performance improvement of the transmission of correlated sources compared to its independent sources counterpart. Index Terms-Non-orthogonal Gaussian multiple access channel (MAC), joint source channel decoding (JSCD), systematic irregular low-density parity-check (LDPC) codes, log-likelihood ratio (LLR).

2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2015

This paper investigates the outage behavior of transmitting correlated binary sources with arbitr... more This paper investigates the outage behavior of transmitting correlated binary sources with arbitrary code rate over quasi-static Rayleigh fading multiple access channel (MAC). The sufficient condition for lossless communication with arbitrary code rate is obtained by assuming separate source and channel coding, which indicates the two rate regions specified by the Slepian-Wolf theorem and the MAC capacity region intersect. An upper bound of the outage probability is derived based on the sufficient condition. Asymptotic property shows the second order diversity gain can be achieved only when the tow sources are fully correlated. Numerical results demonstrate the accuracy of the derived upper bound. The-outage achievable rate, which is the largest rate of transmission such that the outage probability is smaller than a predefined value, is also analyzed. It is found the-outage achievable rate becomes lager with higher transmit power and/or stronger source correlation.

2006 3rd International Symposium on Wireless Communication Systems, 2006

Coded space-time soft cancellation minimum mean squared error filtering (CST SC-MMSE) based turbo... more Coded space-time soft cancellation minimum mean squared error filtering (CST SC-MMSE) based turbo equalization, which exploits transmit diversity and coding gains through two turbo iteration loops, horizontal and vertical iterations, has been introduced in Ill for uplink single carrier signaling. In this paper, performance of the CST SC-MMSE equalizer is evaluated in realistic scenarios using multi-dimensional channel measurement data. Measurement data consists of snapshots measured in different channel conditions in terms of spatial and temporal properties. It is shown that the CST SC-MMSE equalizer can achieve excellent performance even at the lower SNR range due to the vertical iterations between the decoders that can achieve a coding gain on top of the diversity gain. However, performance depends on channel conditions. The impact of the horizontal and vertical iterations is studied in different channel conditions.

ITG Workshop on Smart Antennas (IEEE Cat. No.04EX802)

In turbo diversity technique, soft-cancellation followed by minimum mean squared error filtering ... more In turbo diversity technique, soft-cancellation followed by minimum mean squared error filtering (SUMMSE) is applied to diversity combining of broadband single-carrier signals using multiple antennas in order to reduce the computational complexity. In this paper, OUT proposed turbo diversity technique is evaluated using field measurement data gathered in a suburban area in Germany. It is verified through the field measurement data-based simulations that the performance of the complexity-reduced turbo diversity technique can asymptotically achieve that of the original SCMMSE equalizer. This research is funded by National Technology Agency of Rnland (TEKES), Nokia. Elektrobil and Finnish Air Farce, which is grarefully acknowledged.

Asilomar Conference on Signals, Systems & Computers, 2004

Turbo MIMO equalization in multiuser space-time-trellis-coded (STTrC) system is considered in thi... more Turbo MIMO equalization in multiuser space-time-trellis-coded (STTrC) system is considered in this paper. The low complexity MMSE receiver with soft cancellation (SC) is proposed for joint inter-symbol-interference (ISI), known co-channel interference (CCI) and unknown co-channel interference (UCCI) suppression. It is shown that in the multiuser scenario without UCCI the proposed iterative receiver achieves maximum-likelihood (ML) bound on performance of the

EURASIP Journal on Wireless Communications and Networking, 2004

Iterative multiuser detection in a single-carrier broadband multiple-input multiple-output (MIMO)... more Iterative multiuser detection in a single-carrier broadband multiple-input multiple-output (MIMO) system is studied in this paper. A minimum mean squared error (MMSE) low-complexity multiuser receiver is derived for space-division multiple-access (SDMA) space-time trellis-coded (STTrC) systems in frequency-selective fading channels. The receiver uses MMSE filtering to jointly detect several transmit antennas of the user of interest, while the interference from the undetected transmit antennas, cochannel interference (CCI), and intersymbol interference (ISI) are all cancelled by the soft cancellation. The performances of two extreme receiver cases are evaluated. In the first case, only one transmit antenna of the user of interest is detected at a time and the remaining ones are cancelled by soft cancellation. In the second case, all the transmit antennas are detected jointly. The comparison of the two cases shows improvement with the latter one, both in single-user and multiuser communications and in the presence of unknown cochannel interference (UCCI). It is further shown that in the multiuser case, the proposed receivers approach the corresponding single-user bounds. The number of receive antenna elements required to achieve single-user bound is thereby equal to the number of users and not to the total number of transmit antennas.

Research Letters in Communications, 2007

The primary goal of this letter is to provide comparative assessments to the two cases where diff... more The primary goal of this letter is to provide comparative assessments to the two cases where different criteria are used in joint over antenna minimum mean squared error (JA-MMSE) spatial filtering for space-time coded systems in the presence of unknown interference. It is shown that additional constraints to preserve the space-time coded signal structure in JA-MMSE spatial filtering place floor in bit error rate (BER) performance, while imposing no additional constraint places no error floor.

2008 5th International Symposium on Turbo Codes and Related Topics, 2008

This paper studies mutual information transfer properties of iterative multiuser detector with li... more This paper studies mutual information transfer properties of iterative multiuser detector with linear precoding schemes for single carrier communications in multipoint-to-point multiple input multiple output (MIMO) channels. Based on multidimensional extrinsic information transfer (EXIT) analysis, we analyze the impact of linear precoding on the convergence properties of the detectors jointly designed with the precoders based on minimum sum mean squared error (MMSE) and maximum sum mutual information rate criteria. Results demonstrate that the use of the linear precoding schemes enhance the separability of the EXIT curves of the simultaneous streams over without precoding; This invokes the idea that different code rate be allocated to the each transmitted streams at the transmitters.

2007 IEEE 65th Vehicular Technology Conference - VTC2007-Spring, 2007

In this paper, we address the problem of multiple-input multiple-output (MIMO) spatial multiplexi... more In this paper, we address the problem of multiple-input multiple-output (MIMO) spatial multiplexing (SM) systems in the presence of antenna fading correlation. It is well known that severe spatial correlations present at the transmitter and/or receiver can significantly compromise the performance of existing SM systems. Recent results showed that joint-over-antenna (JA) iterative detection schemes can improve the performance of SM systems in correlated channels as compared to schemes that detected the signals on an antenna-byantenna basis. We extend this idea in this paper by incorporating a so-called antenna doping (AD) scheme into the SM system, in order to further counteract the detrimental effects of spatial correlation. Through simulations, we show that AD can improve the performance by 3-4 dB in severe spatial correlation as compared to non-doping systems. This improvement is explained with the aid of extrinsic information transfer (EXIT) charts, which illustrate the convergence behavior of the JA iterative detection with and without AD.

2014 IEEE International Conference on Communications (ICC), 2014

Peak to average power ratio (PAPR) constrained power allocation in single carrier multiuser (MU) ... more Peak to average power ratio (PAPR) constrained power allocation in single carrier multiuser (MU) single-input multiple-output (SIMO) systems with iterative frequency domain (FD) soft cancelation (SC) minimum mean squared error (MMSE) equalization is considered in this paper. To obtain full benefit of the iterative receiver, its convergence properties need to be taken into account also at the transmitter side. In this paper, we extend the existing results on the area of convergence constrained power allocation (CCPA) to consider the instantaneous PAPR at the transmit antenna of each user. In other words, we will introduce a constraint that PAPR cannot exceed a predetermined threshold. By adding the aforementioned constraint into the CCPA optimization framework, the power efficiency of a power amplifier (PA) can be significantly enhanced by enabling it to operate on its linear operation range. Hence, PAPR constraint is especially beneficial for power limited celledge users. In this paper, we will derive the instantaneous PAPR constraint as a function of transmit power allocation. Furthermore, successive convex approximation is derived for the PAPR constrained problem. Numerical results show that the proposed method can achieve the objectives described above.

A goal of this paper is to combine the advantageous properties of multiple access codes (MAC) and... more A goal of this paper is to combine the advantageous properties of multiple access codes (MAC) and space-time transmission (STT) in wireless relay communication systems. The use of MAC provides transmission with the separability of the signals transmitted from multiple users, and STT the diversity gain. It is shown both by model-based numerical results and measurement data-based simulation results that the combined use of MAC and STT achieves significant improvement in bit error rate (BER) as well as signaling throughput of relay systems.

2005 IEEE 61st Vehicular Technology Conference

The so-called space-time weighted nonbinary repeataccumulate (ST-WNRA) codes are capable of achie... more The so-called space-time weighted nonbinary repeataccumulate (ST-WNRA) codes are capable of achieving full antenna diversity in single-user flat fading channels. In this paper, the performance of these codes is evaluated over a frequency-selective Rayleigh fading multiple-input multiple-output channel in a multiuser environment. Under this channel condition, the full antenna diversity supported by the ST-WNRA codes can no longer be achieved due to the presence of intersymbol interference and multiple access interference. Hence, in order to suppress these interferences, a turbo equalization technique based on the minimum mean square-error filtering with soft interference cancellation (SC-MMSE) is employed. The SC-MMSE detector is designed such that the diversity that can be gleaned from the multiple antennas as well as from the multipath components can be fully exploited. Computer simulations demonstrate that our proposed turbo-equalized system with ST-WNRA codes is capable of achieving the maximum diversity order and hence achieving an excellent bit error rate performance with a reasonable spectral efficiency at a low complexity cost.

2012 International ITG Workshop on Smart Antennas (WSA), 2012

Chained turbo equalization (CHATUE) is a simple detection scheme for block transmission without c... more Chained turbo equalization (CHATUE) is a simple detection scheme for block transmission without cyclic prefix (CP), where turbo equalizers for the several consecutive frames exchange information about the interference components in the form of a posteriori Log-Likelihood Ratio (LLR). Although elimination of CP in the block transmission can significantly increase bandwidth efficiency, the received signal suffers from inter-block interference (IBI), which can not be effectively compensated by block-by-block equalization. In this paper, we apply the CHATUE algorithm to effectively suppress inter-symbol interference (ISI), inter-carrier interference (ICI), and multiple-access interference (MAI) in a Multiuser Single Input Multiple Output Orthogonal Frequency Division Multiplexing (MU-SIMO-OFDM) system without CP. Results of computer simulations show the superiority of our proposed MU-SIMO-OFDM to conventional CP-aided systems, without requiring high computational complexity. The convergence property of the proposed technique is analyzed using the extrinsic information transfer (EXIT) chart. Doped accumulator is used to achieve a mutual information point close enough to the (1,1) point, and also to obtain better matching between the equalizer and decoder EXIT curves.

International Symposium on Wireless Personal Multimedia Communications, 2002

This paper describes the methodology and the results of performance investigations of the turbo M... more This paper describes the methodology and the results of performance investigations of the turbo MIMO equalizer concept for broadband MIMO systems. Different application setups are introduced and realistic simulations based on measured propagation data are described. Relationships between the propagation characteristics, the antenna configurations, and the achievable bit error rates are shown. Although in many of the considered constellations turbo