IEEE Open Journal of the Communications Society, 2024
In this article, we focus on a generic multiterminal (remote) source coding scenario in which, vi... more In this article, we focus on a generic multiterminal (remote) source coding scenario in which, via a joint design, several intermediate nodes must locally compress their noisy observations from various sets of user / source signals ahead of forwarding them through multiple error-free and rate-limited channels to a (remote) processing unit. Although different local compressors might receive noisy observations from a / several common source signal(s), each local quantizer should also compress noisy observations from its own, i.e., uncommon source signal(s). This, in turn, yields a highly generalized scheme with most flexibility w.r.t. the assignment of users to the serving nodes, compared to the State-of-the-Art techniques designed exclusively for a common source signal. Following the Information Bottleneck (IB) philosophy, we choose the Mutual Information as the fidelity criterion here, and, by taking advantage of the Variational Calculus, we characterize the form of stationary solutions for two different types of processing flow/ strategy. We utilize the derived solutions as the core of our devised algorithmic approach, the GEneralized Multivariate IB (GEMIB), to (efficiently) address the corresponding design problems. We further provide the respective convergence proofs of GEMIB to a stationary point of the pertinent objective functionals and substantiate its effectiveness by means of numerical investigations over a couple of (typical) digital transmission scenarios.
In this chapter, two-way relaying networks using Physical-Layer Net- work Coding (PLNC) are consi... more In this chapter, two-way relaying networks using Physical-Layer Net- work Coding (PLNC) are considered with practical constraints. In a Multiple Access (MA) phase, two users transmit messages simultaneously on the same physical resources. The relay constructs a relay message based on the superimposed receive signal of both users. This message is broadcasted to the users which are able to extract the desired data from the other user. However, as the relay is not able to resolve shifts in time and frequency for the individual channels, the transmission scheme needs to be adjusted, if perfect synchronization cannot be ensured. This chapter deals with the proper selection of waveforms for multi-carrier systems in the Two-Way-Relay Channel (TWRC) using PLNC. We address Generalized Frequency Division Multiplexing (GFDM) compared to Orthogonal Frequency Division Multi-plexing (OFDM) under practical constraints like Carrier Frequency Offsets (CFOs) and Timing Offsets (TOs) within double dispersive channels. For OFDM rectangular transmit filters are used, which have a broad spectrum shape and are sensitive to shifts, especially in frequency domain. GFDM applies Gaussian waveforms that are inherently less susceptible to synchronization offsets than theirs rectangular counterparts, but additional interference is introduced even in a perfectly synchronized and flat fading channel. Thus, interferences caused by the channel or by the non-orthogonal Gaussian impulse shape are treated by an equalizer at the relay. The simulation results show that the Gaussian waveform outperforms the conventional OFDM system if the nodes are not perfectly synchronized.
The next frontier towards truly ubiquitous connectivity is the use of Low Earth Orbit (LEO) small... more The next frontier towards truly ubiquitous connectivity is the use of Low Earth Orbit (LEO) small-satellite constellations to support 5G and Beyond-5G (B5G) networks. Besides enhanced mobile broadband (eMBB) and massive machine-type communications (mMTC), LEO constellations can support ultra-reliable communications (URC) with relaxed latency requirements of a few tens of milliseconds. Small-satellite impairments and the use of low orbits pose major challenges to the design and performance of these networks, but also open new innovation opportunities. This paper provides a comprehensive overview of the physical and logical links, along with the essential architectural and technological components that enable the full integration of LEO constellations into 5G and B5G systems. Furthermore, we characterize and compare each physical link category and explore novel techniques to maximize the achievable data rates. INDEX TERMS 5G, Beyond-5G, low Earth orbit (LEO), radio access network, small-satellite constellations.
In this paper, we propose a novel approach for downlink transmission from a satellite swarm towar... more In this paper, we propose a novel approach for downlink transmission from a satellite swarm towards a ground station (GS). These swarms have the benefit of much higher spatial separation in the transmit antennas than traditional satellites with antenna arrays, promising a massive increase in spectral efficiency. The resulting precoder and equalizer have very low demands on computational complexity, inter-satellite coordination and channel estimation. This is achieved by taking knowledge about the geometry between satellites and GS into account. For precoding, each satellite only requires its angles of departure (AoDs) towards the GS and it turns out that almost optimal rates can be achieved if the satellites transmit independent data streams. For the equalizer, the GS requires only knowledge about the angles of arrival (AoAs) from all satellites. Furthermore, we show that, by choosing a proper intersatellite distance, the proposed low-complexity approach achieves the theoretical upper bound in terms of data rate. This optimal inter-satellite distance is obtained analytically under simplifying assumption and provides a heuristic for practical scenarios. Furthermore, a novel approach to increase the robustness of the proposed precoder and equalizer against imperfect AoD and AoA knowledge is proposed by exploiting the statistics of the estimation error. This article was presented in part at 2022 IEEE Wireless Communications and Networking Conference [1].
International series on intelligent systems, control and automation: science and engineering, Oct 24, 2019
Grasping objects under water is even today one of the biggest challenges when operating robotic s... more Grasping objects under water is even today one of the biggest challenges when operating robotic systems let it be tele-operated or autonomous. Currently, most of the manipulation tasks under water are performed using remotely operated vehicles (ROVs) which handle all industrial maintenance and inspection tasks where there is intervention involved. Manipulation on autonomous underwater vehicles (AUVs) is still a research topic as it involves the control of a moving base and the interacting forces in the most challenging configuration. The works and the intended further research presented here focus on the control and signal processing of the end-effector itself during autonomous mobile manipulation.
By using orthogonal frequency division multiplexing (OFDM) in multiple-input multiple-output (MIM... more By using orthogonal frequency division multiplexing (OFDM) in multiple-input multiple-output (MIMO) systems the equalization of frequency selective channels simplifies to a number of parallel MIMO detections. In order to gain from frequency diversity and of the correction capability of the code within a successive interference cancellation (SIC), forward error correction should be implemented for each antenna separately. In this paper we present a novel, computational efficient implementation for SIC in such a per-antenna-coded MIMO-OFDM system. It utilizes a parallelized version of the SQRD algorithm in order to achieve the same detection order for all subcarriers. In comparison to the most applied schemes from literature our approach requires only a fraction of computational complexity with almost the same performance.
Low Earth orbit (LEO) satellite systems enable close to global coverage and are therefore expecte... more Low Earth orbit (LEO) satellite systems enable close to global coverage and are therefore expected to become important pillars of future communication standards. However, a particular challenge faced by LEO satellites is the high orbital velocities due to which a precise channel estimation is difficult. We model this influence as an erroneous angle of departure (AoD), which corresponds to imperfect channel state information (CSI) at the transmitter (CSIT). Poor CSIT and non-orthogonal user channels degrade the performance of space-division multiple access (SDMA) precoding by increasing inter-user interference (IUI). In contrast to SDMA, there is no IUI in orthogonal multiple access (OMA), but it requires orthogonal time or frequency resources for each user. Rate-splitting multiple access (RSMA), unifying SDMA, OMA, and non-orthogonal multiple access (NOMA), has recently been proven to be a flexible approach for robust interference management considering imperfect CSIT. In this paper, we investigate RSMA as a promising strategy to manage IUI in LEO satellite downlink systems caused by non-orthogonal user channels as well as imperfect CSIT. We evaluate the optimal configuration of RSMA depending on the geometrical constellation between the satellite and users. Index Terms Low Earth orbit (LEO), Rate-Splitting Multiple Access, multiuser beamforming, MIMO satellite communications, beamspace MIMO, angle division multiple access, 3D networks I. INTRODUCTION Mobile networks are currently evolving from being focused on low-altitude and ground-based devices towards three-dimensional (3D) networks. Incorporating air-and spaceborne terminals into the sixth generation (6G) of mobile networks is expected to lead to ubiquitous global connectivity, a reduced carbon footprint of information This article is presented in part at the 2023 International ITG 26th Workshop on Smart Antennas and 13th Conference on Systems, Communications, and Coding.
Consider the following setup: Through a joint design, multiple observations of a remote data sour... more Consider the following setup: Through a joint design, multiple observations of a remote data source shall be locally compressed before getting transmitted via several error-prone, rate-limited forward links to a (distant) processing unit. For addressing this specific instance of multiterminal Joint Source-Channel Coding problem, in this article, the foundational principle of the Information Bottleneck method is fully extended to obtain purely statistical design approaches, enjoying the Mutual Information as their fidelity criterion. Specifically, the forms of stationary points for two types of distributed compression schemes are characterized here. Subsequently, those acquired solutions are utilized as the centerpiece of the proposed generic, iterative algorithm, termed the Multiterminal Forward-Aware Vector Information Bottleneck (M-FAVIB), for addressing the design optimizations. Leveraging an unfolding trick, it will be proven that both distributed compression schemes fall into the category of Successive Upper-Bound Minimization, ensuring their convergence to a stationary point. Eventually, the effectiveness of the proposed compression schemes will be substantiated as well by means of numerical investigations over some typical transmission scenarios.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Relays in wireless networks can be used to decrease transmit power while additionally increasing ... more Relays in wireless networks can be used to decrease transmit power while additionally increasing diversity. Distributed turbo coding as a special case of decode-and-forward is very powerful in relay networks when assuming error free decoding in the relay. In practical wireless networks, however, this assumption is only justifiable if an ARQ protocol is applied which leads to lower throughput. Soft-reencoding and transmission of the reliability of reencoded bits helps the destination to decode the message. Reencoding in the relay with a recursive convolutional code as used for turbo-codes, can lead to error propagation. In this paper the effects of error propagation in relay networks are investigated and more suitable distributed coding schemes are presented for soft-reencoding. As the often used assumption of Gaussian distributed disturbance at the destination is not valid for the considered system setup, the calculation of Log-Likelihood-Ratios (LLR) for the received noisy reliability information is derived analytically.
The increasing demand for highly customized products, as well as flexible production lines, can b... more The increasing demand for highly customized products, as well as flexible production lines, can be seen as trigger for the ''fourth industrial revolution'', referred to as ''Industry 4.0''. Current systems usually rely on wire-line technologies to connect sensors and actuators, but new use cases such as moving robots or drones demand a higher flexibility on communication services. Wireless technologies, especially 5th generation wireless communication systems (5G) are best suited to address these new requirements. Furthermore, this facilitates the renewal of brownfield deployments to enable a smooth migration to Industry 4.0. This paper presents results from the Tactile Internet 4.0 (TACNET 4.0) project and introduces a tailored architecture that is focused on the communication needs given by representative Industry 4.0 use cases while ensuring parallel compliance to latest developments in relevant standardization. INDEX TERMS 5G, industrial communication, wireless communications, industry 4.0, TACNET 4.0 architecture.
Multiple Input Multiple Output (MIMO) and massive MIMO (mMIMO) are key-enabling technologies for ... more Multiple Input Multiple Output (MIMO) and massive MIMO (mMIMO) are key-enabling technologies for 4G and 5G communications systems. mMIMO uses a high number of antennas, where the number of antennas at the base station exceeds in general the number of antennas in the mobiles. For uncorrelated channels, linear equalizers already achieve promising performance in the uplink due to the channel hardening effect. In contrast, we will focus on large symmetrical MIMO systems in this paper, where many antennas are employed at the transmitter and the receiver side resulting in a more challenging task for the receiver. Traditionally, receiver algorithms have been derived based on models for the communications system. Recently, machine learning approaches have been proposed where the design is data driven. In order to overcome the drawbacks of model-based and pure data driven approaches, hybrid approaches combining the benefits of both worlds have emerged. In this paper, we present the novel hybrid approach entitled Deep Equalization (DeEQ) based on model knowledge and a neural network like structure. As demonstrated by simulation results, this novel approach achieves very good performance with the advantage of only a very low error floor.
C loud computing draws significant attention in the information technology (IT) community as it p... more C loud computing draws significant attention in the information technology (IT) community as it provides ubiquitous ondemand access to a shared pool of configurable computing resources with minimum management effort. It gains also more impact on the communication technology (CT) community and is currently discussed as an enabler for flexible, cost-efficient and more powerful mobile network implementations. Although centralized baseband pools are already investigated for the radio access network (RAN) to allow for efficient resource usage and advanced multicell algorithms, these technologies still require dedicated hardware and do not offer the same characteristics as cloud-computing platforms, i.e., on-demand provisioning, virtualization, resource pooling, elasticity, service metering, and multitenancy. However, these properties of cloud computing are key enablers for future mobile communication systems characterized by an ultradense deployment of radio access points (RAPs) leading to severe multicell interference in combination with a significant increase of the number of access nodes and huge fluctuations of the rate requirements over time. In this article, we will explore the benefits that cloud computing offers for fifth-generation (5G) mobile networks and investigate the implications on the signal processing algorithms.
Direct Low Earth Orbit satellite-to-handheld links are expected to be part of a new era in satell... more Direct Low Earth Orbit satellite-to-handheld links are expected to be part of a new era in satellite communications. Space-Division Multiple Access precoding is a technique that reduces interference among satellite beams, therefore increasing spectral efficiency by allowing cooperating satellites to reuse frequency. Over the past decades, optimal precoding solutions with perfect channel state information have been proposed for several scenarios, whereas robust precoding with only imperfect channel state information has been mostly studied for simplified models. In particular, for Low Earth Orbit satellite applications such simplified models might not be accurate. In this paper, we use the function approximation capabilities of the Soft Actor-Critic deep Reinforcement Learning algorithm to learn robust precoding with no knowledge of the system imperfections.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The 10th Asia-Europe workshop in "Concepts in Information Theory and Communications" AE... more The 10th Asia-Europe workshop in "Concepts in Information Theory and Communications" AEW10 was held in Boppard, Germany on June 21-23, 2017. It is based on a longstanding cooperation between Asian and European scientists. The first workshop was held in Eindhoven, the Netherlands in 1989. The idea of the workshop is threefold: 1) to improve the communication between the scientist in the different parts of the world; 2) to exchange knowledge and ideas; and 3) to pay a tribute to a well respected and special scientist.
IEEE Open Journal of the Communications Society, 2024
In this article, we focus on a generic multiterminal (remote) source coding scenario in which, vi... more In this article, we focus on a generic multiterminal (remote) source coding scenario in which, via a joint design, several intermediate nodes must locally compress their noisy observations from various sets of user / source signals ahead of forwarding them through multiple error-free and rate-limited channels to a (remote) processing unit. Although different local compressors might receive noisy observations from a / several common source signal(s), each local quantizer should also compress noisy observations from its own, i.e., uncommon source signal(s). This, in turn, yields a highly generalized scheme with most flexibility w.r.t. the assignment of users to the serving nodes, compared to the State-of-the-Art techniques designed exclusively for a common source signal. Following the Information Bottleneck (IB) philosophy, we choose the Mutual Information as the fidelity criterion here, and, by taking advantage of the Variational Calculus, we characterize the form of stationary solutions for two different types of processing flow/ strategy. We utilize the derived solutions as the core of our devised algorithmic approach, the GEneralized Multivariate IB (GEMIB), to (efficiently) address the corresponding design problems. We further provide the respective convergence proofs of GEMIB to a stationary point of the pertinent objective functionals and substantiate its effectiveness by means of numerical investigations over a couple of (typical) digital transmission scenarios.
In this chapter, two-way relaying networks using Physical-Layer Net- work Coding (PLNC) are consi... more In this chapter, two-way relaying networks using Physical-Layer Net- work Coding (PLNC) are considered with practical constraints. In a Multiple Access (MA) phase, two users transmit messages simultaneously on the same physical resources. The relay constructs a relay message based on the superimposed receive signal of both users. This message is broadcasted to the users which are able to extract the desired data from the other user. However, as the relay is not able to resolve shifts in time and frequency for the individual channels, the transmission scheme needs to be adjusted, if perfect synchronization cannot be ensured. This chapter deals with the proper selection of waveforms for multi-carrier systems in the Two-Way-Relay Channel (TWRC) using PLNC. We address Generalized Frequency Division Multiplexing (GFDM) compared to Orthogonal Frequency Division Multi-plexing (OFDM) under practical constraints like Carrier Frequency Offsets (CFOs) and Timing Offsets (TOs) within double dispersive channels. For OFDM rectangular transmit filters are used, which have a broad spectrum shape and are sensitive to shifts, especially in frequency domain. GFDM applies Gaussian waveforms that are inherently less susceptible to synchronization offsets than theirs rectangular counterparts, but additional interference is introduced even in a perfectly synchronized and flat fading channel. Thus, interferences caused by the channel or by the non-orthogonal Gaussian impulse shape are treated by an equalizer at the relay. The simulation results show that the Gaussian waveform outperforms the conventional OFDM system if the nodes are not perfectly synchronized.
The next frontier towards truly ubiquitous connectivity is the use of Low Earth Orbit (LEO) small... more The next frontier towards truly ubiquitous connectivity is the use of Low Earth Orbit (LEO) small-satellite constellations to support 5G and Beyond-5G (B5G) networks. Besides enhanced mobile broadband (eMBB) and massive machine-type communications (mMTC), LEO constellations can support ultra-reliable communications (URC) with relaxed latency requirements of a few tens of milliseconds. Small-satellite impairments and the use of low orbits pose major challenges to the design and performance of these networks, but also open new innovation opportunities. This paper provides a comprehensive overview of the physical and logical links, along with the essential architectural and technological components that enable the full integration of LEO constellations into 5G and B5G systems. Furthermore, we characterize and compare each physical link category and explore novel techniques to maximize the achievable data rates. INDEX TERMS 5G, Beyond-5G, low Earth orbit (LEO), radio access network, small-satellite constellations.
In this paper, we propose a novel approach for downlink transmission from a satellite swarm towar... more In this paper, we propose a novel approach for downlink transmission from a satellite swarm towards a ground station (GS). These swarms have the benefit of much higher spatial separation in the transmit antennas than traditional satellites with antenna arrays, promising a massive increase in spectral efficiency. The resulting precoder and equalizer have very low demands on computational complexity, inter-satellite coordination and channel estimation. This is achieved by taking knowledge about the geometry between satellites and GS into account. For precoding, each satellite only requires its angles of departure (AoDs) towards the GS and it turns out that almost optimal rates can be achieved if the satellites transmit independent data streams. For the equalizer, the GS requires only knowledge about the angles of arrival (AoAs) from all satellites. Furthermore, we show that, by choosing a proper intersatellite distance, the proposed low-complexity approach achieves the theoretical upper bound in terms of data rate. This optimal inter-satellite distance is obtained analytically under simplifying assumption and provides a heuristic for practical scenarios. Furthermore, a novel approach to increase the robustness of the proposed precoder and equalizer against imperfect AoD and AoA knowledge is proposed by exploiting the statistics of the estimation error. This article was presented in part at 2022 IEEE Wireless Communications and Networking Conference [1].
International series on intelligent systems, control and automation: science and engineering, Oct 24, 2019
Grasping objects under water is even today one of the biggest challenges when operating robotic s... more Grasping objects under water is even today one of the biggest challenges when operating robotic systems let it be tele-operated or autonomous. Currently, most of the manipulation tasks under water are performed using remotely operated vehicles (ROVs) which handle all industrial maintenance and inspection tasks where there is intervention involved. Manipulation on autonomous underwater vehicles (AUVs) is still a research topic as it involves the control of a moving base and the interacting forces in the most challenging configuration. The works and the intended further research presented here focus on the control and signal processing of the end-effector itself during autonomous mobile manipulation.
By using orthogonal frequency division multiplexing (OFDM) in multiple-input multiple-output (MIM... more By using orthogonal frequency division multiplexing (OFDM) in multiple-input multiple-output (MIMO) systems the equalization of frequency selective channels simplifies to a number of parallel MIMO detections. In order to gain from frequency diversity and of the correction capability of the code within a successive interference cancellation (SIC), forward error correction should be implemented for each antenna separately. In this paper we present a novel, computational efficient implementation for SIC in such a per-antenna-coded MIMO-OFDM system. It utilizes a parallelized version of the SQRD algorithm in order to achieve the same detection order for all subcarriers. In comparison to the most applied schemes from literature our approach requires only a fraction of computational complexity with almost the same performance.
Low Earth orbit (LEO) satellite systems enable close to global coverage and are therefore expecte... more Low Earth orbit (LEO) satellite systems enable close to global coverage and are therefore expected to become important pillars of future communication standards. However, a particular challenge faced by LEO satellites is the high orbital velocities due to which a precise channel estimation is difficult. We model this influence as an erroneous angle of departure (AoD), which corresponds to imperfect channel state information (CSI) at the transmitter (CSIT). Poor CSIT and non-orthogonal user channels degrade the performance of space-division multiple access (SDMA) precoding by increasing inter-user interference (IUI). In contrast to SDMA, there is no IUI in orthogonal multiple access (OMA), but it requires orthogonal time or frequency resources for each user. Rate-splitting multiple access (RSMA), unifying SDMA, OMA, and non-orthogonal multiple access (NOMA), has recently been proven to be a flexible approach for robust interference management considering imperfect CSIT. In this paper, we investigate RSMA as a promising strategy to manage IUI in LEO satellite downlink systems caused by non-orthogonal user channels as well as imperfect CSIT. We evaluate the optimal configuration of RSMA depending on the geometrical constellation between the satellite and users. Index Terms Low Earth orbit (LEO), Rate-Splitting Multiple Access, multiuser beamforming, MIMO satellite communications, beamspace MIMO, angle division multiple access, 3D networks I. INTRODUCTION Mobile networks are currently evolving from being focused on low-altitude and ground-based devices towards three-dimensional (3D) networks. Incorporating air-and spaceborne terminals into the sixth generation (6G) of mobile networks is expected to lead to ubiquitous global connectivity, a reduced carbon footprint of information This article is presented in part at the 2023 International ITG 26th Workshop on Smart Antennas and 13th Conference on Systems, Communications, and Coding.
Consider the following setup: Through a joint design, multiple observations of a remote data sour... more Consider the following setup: Through a joint design, multiple observations of a remote data source shall be locally compressed before getting transmitted via several error-prone, rate-limited forward links to a (distant) processing unit. For addressing this specific instance of multiterminal Joint Source-Channel Coding problem, in this article, the foundational principle of the Information Bottleneck method is fully extended to obtain purely statistical design approaches, enjoying the Mutual Information as their fidelity criterion. Specifically, the forms of stationary points for two types of distributed compression schemes are characterized here. Subsequently, those acquired solutions are utilized as the centerpiece of the proposed generic, iterative algorithm, termed the Multiterminal Forward-Aware Vector Information Bottleneck (M-FAVIB), for addressing the design optimizations. Leveraging an unfolding trick, it will be proven that both distributed compression schemes fall into the category of Successive Upper-Bound Minimization, ensuring their convergence to a stationary point. Eventually, the effectiveness of the proposed compression schemes will be substantiated as well by means of numerical investigations over some typical transmission scenarios.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Relays in wireless networks can be used to decrease transmit power while additionally increasing ... more Relays in wireless networks can be used to decrease transmit power while additionally increasing diversity. Distributed turbo coding as a special case of decode-and-forward is very powerful in relay networks when assuming error free decoding in the relay. In practical wireless networks, however, this assumption is only justifiable if an ARQ protocol is applied which leads to lower throughput. Soft-reencoding and transmission of the reliability of reencoded bits helps the destination to decode the message. Reencoding in the relay with a recursive convolutional code as used for turbo-codes, can lead to error propagation. In this paper the effects of error propagation in relay networks are investigated and more suitable distributed coding schemes are presented for soft-reencoding. As the often used assumption of Gaussian distributed disturbance at the destination is not valid for the considered system setup, the calculation of Log-Likelihood-Ratios (LLR) for the received noisy reliability information is derived analytically.
The increasing demand for highly customized products, as well as flexible production lines, can b... more The increasing demand for highly customized products, as well as flexible production lines, can be seen as trigger for the ''fourth industrial revolution'', referred to as ''Industry 4.0''. Current systems usually rely on wire-line technologies to connect sensors and actuators, but new use cases such as moving robots or drones demand a higher flexibility on communication services. Wireless technologies, especially 5th generation wireless communication systems (5G) are best suited to address these new requirements. Furthermore, this facilitates the renewal of brownfield deployments to enable a smooth migration to Industry 4.0. This paper presents results from the Tactile Internet 4.0 (TACNET 4.0) project and introduces a tailored architecture that is focused on the communication needs given by representative Industry 4.0 use cases while ensuring parallel compliance to latest developments in relevant standardization. INDEX TERMS 5G, industrial communication, wireless communications, industry 4.0, TACNET 4.0 architecture.
Multiple Input Multiple Output (MIMO) and massive MIMO (mMIMO) are key-enabling technologies for ... more Multiple Input Multiple Output (MIMO) and massive MIMO (mMIMO) are key-enabling technologies for 4G and 5G communications systems. mMIMO uses a high number of antennas, where the number of antennas at the base station exceeds in general the number of antennas in the mobiles. For uncorrelated channels, linear equalizers already achieve promising performance in the uplink due to the channel hardening effect. In contrast, we will focus on large symmetrical MIMO systems in this paper, where many antennas are employed at the transmitter and the receiver side resulting in a more challenging task for the receiver. Traditionally, receiver algorithms have been derived based on models for the communications system. Recently, machine learning approaches have been proposed where the design is data driven. In order to overcome the drawbacks of model-based and pure data driven approaches, hybrid approaches combining the benefits of both worlds have emerged. In this paper, we present the novel hybrid approach entitled Deep Equalization (DeEQ) based on model knowledge and a neural network like structure. As demonstrated by simulation results, this novel approach achieves very good performance with the advantage of only a very low error floor.
C loud computing draws significant attention in the information technology (IT) community as it p... more C loud computing draws significant attention in the information technology (IT) community as it provides ubiquitous ondemand access to a shared pool of configurable computing resources with minimum management effort. It gains also more impact on the communication technology (CT) community and is currently discussed as an enabler for flexible, cost-efficient and more powerful mobile network implementations. Although centralized baseband pools are already investigated for the radio access network (RAN) to allow for efficient resource usage and advanced multicell algorithms, these technologies still require dedicated hardware and do not offer the same characteristics as cloud-computing platforms, i.e., on-demand provisioning, virtualization, resource pooling, elasticity, service metering, and multitenancy. However, these properties of cloud computing are key enablers for future mobile communication systems characterized by an ultradense deployment of radio access points (RAPs) leading to severe multicell interference in combination with a significant increase of the number of access nodes and huge fluctuations of the rate requirements over time. In this article, we will explore the benefits that cloud computing offers for fifth-generation (5G) mobile networks and investigate the implications on the signal processing algorithms.
Direct Low Earth Orbit satellite-to-handheld links are expected to be part of a new era in satell... more Direct Low Earth Orbit satellite-to-handheld links are expected to be part of a new era in satellite communications. Space-Division Multiple Access precoding is a technique that reduces interference among satellite beams, therefore increasing spectral efficiency by allowing cooperating satellites to reuse frequency. Over the past decades, optimal precoding solutions with perfect channel state information have been proposed for several scenarios, whereas robust precoding with only imperfect channel state information has been mostly studied for simplified models. In particular, for Low Earth Orbit satellite applications such simplified models might not be accurate. In this paper, we use the function approximation capabilities of the Soft Actor-Critic deep Reinforcement Learning algorithm to learn robust precoding with no knowledge of the system imperfections.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The 10th Asia-Europe workshop in "Concepts in Information Theory and Communications" AE... more The 10th Asia-Europe workshop in "Concepts in Information Theory and Communications" AEW10 was held in Boppard, Germany on June 21-23, 2017. It is based on a longstanding cooperation between Asian and European scientists. The first workshop was held in Eindhoven, the Netherlands in 1989. The idea of the workshop is threefold: 1) to improve the communication between the scientist in the different parts of the world; 2) to exchange knowledge and ideas; and 3) to pay a tribute to a well respected and special scientist.
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Papers by Dirk Wübben