Due to the large bandwidth available, millimeter-Wave (mmWave) bands are considered a viable oppo... more Due to the large bandwidth available, millimeter-Wave (mmWave) bands are considered a viable opportunity to significantly increase the data rate in cellular and wireless networks. Nevertheless, the need for beamforming and directional communication between the transmitter and the receiver increases the complexity of the channel estimation and link establishment phase. Location-aided beamforming approaches have the potential to enable fast link establishment in mmWave networks. However, these are often very sensitive to location errors. In this work, we propose a beamforming algorithm based on tracking spatial correlation of the available strong paths between the transmitter and the receiver. We show that our method is robust to uncertainty in location information, i.e., location error and can provide a reliable connection to a moving user along a trajectory. The numerical results show that our approach outperforms benchmarks on various levels of error in the location information accuracy. The gain is more prominent in high location error scenarios.
Symposium on Communications and Vehicular Technology in the Benelux, 1993
Transmitter power control is a necessity to combat "near-far" problems in radio systems using rec... more Transmitter power control is a necessity to combat "near-far" problems in radio systems using receivers with limited "dynamic range" (such as conventional DS-CDMA systems). Transmitter power control, however, can also be used to control cochannel interference, i.e. interference from other users using the same channel (code or time slot). For this purpose, it has been shown that the optimum transmitter power configuration is found by solving an eigenvalue problem. The paper reviews some recent results in this area. The basic models as well as the concepts of achievable C/I, up/down-link equivalence and C/Ibalancing are introduced. Both the interference limited (noise-less) case as well as models including thermal noise are treated. Results show that substantial improvements in system capacity can be achieved, particulary in conjunction with Dynamic Channel Allocation. The optimum power control schemes are shown to be robust against implementational shortcomings. Throughout the paper we will study a large, but finite, cellular radio system. The system is assumed to use perfectly orthogonal signals ("channels") such as, for instance, TDMA or FDMA schemes. To each active mobile-base pair, we have
It has become increasingly clear that the current design paradigm for mobile broadband systems is... more It has become increasingly clear that the current design paradigm for mobile broadband systems is not a scalable and economically feasible way to solve the expected future "capacity crunch", in particular in indoor locations with large user densities. "Moore's law", e.g. state-of-the art signal processing and advanced antenna techniques now being researched, as well as more millimeter wave spectrum indeed provide more capacity, but are not the answer to the 3-4 orders of magnitude more capacity at today's cost, that is needed. We argue that solving the engineering problem of providing high data rates alone is not sufficient. Instead we need to solve the techno-economic problem to find both business models and scalable technical solutions that provide extreme area capacity for a given cost and energy consumption. In this paper we will show that achieving very high capacities is indeed feasible in indoor environments. However, to become economically viable, approaches with radically different fundamental cost factors compared to those used in today's cellular systems are needed. To reach very high capacity we must venture beyond the ultra-dense barrier, i.e. networks where the number of access points in an area is (considerably) larger than the active number mobile terminals. In such networks area capacities of more than 1 Gbit/s/m 2 are perfectly feasible. The problem set encountered in such Ultra-Dense Networks (UDN) is very different from conventional cellular systems and their solution requires conceptually new tools. We will address some of the fundamental aspects and performance limits, modeling of propagation, deployment and user traffic, and discuss the techno-economics of various network architectures. Finally we will summarize some of the most significant unsolved research questions in the field.
In cellular and cellular-IoT systems, random access has the utmost importance as it is the gateke... more In cellular and cellular-IoT systems, random access has the utmost importance as it is the gatekeeper that assures conflict-free access to radio resources. The main drawback of the legacy protocols ...
Optimum transmitter power control schemes to minimize the outage probability due to cochannel int... more Optimum transmitter power control schemes to minimize the outage probability due to cochannel interference have been investigated in (SI, (a. The main drawback of the previously proposed algorithms is that they would require reliable measurements of the gains in all radio paths in the system. In this paper, distributed power control algorithms that use only the signal-to-interference (C/I) ratios in those links actually in use, are investigated. An algorithm, that successfully approximates the behavior of the best known algorithms is proposed. The algorithm involves a novel distributed C/I-balancing scheme. Numerical results show that capacity gains in the order of 3-4 times can be reached also with these distributed schemes. Further, the effects of imperfect C/I estimates due to noise, vehicle mobility, and fast multipath fading are considered. Results show that the balancing procedure is very robust to measurement noise, in particular if C/I requirements are low or moderate. However, for required high C/I levels or for a rapidly changing path loss matrix, convergence may be too slow to achieve substantial capacity improvements.
Designations used by companies to distinguish their products are often claimed as trademarks. All... more Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The Publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.
Determining the efficiency of an HF-antenna by measurements requires is a complex procedure invol... more Determining the efficiency of an HF-antenna by measurements requires is a complex procedure involving expensive equipment, calibrated instruments for field strengths. In this paper we evaluate a simple, inexpensive method to determine the relative efficiency of an antenna relative a reference antenna. The method uses the Weak Signal Propagation Reporter(WSPR) network of receivers that are located all over the world. These receivers report the estimated signal-to-noise ratio of received beacon signals to the WSPR.net database where the data can be retrieved (almost) in real time. In the paper we analyze the method, estimate its accuracy and discuss advantages and limitations. Some preliminary measurement results are presented.
Personal, Indoor and Mobile Radio Communications, 1999
Third generation wireless systems, e.g. the UMTS/UTRA scheme will provide bearer services suitabl... more Third generation wireless systems, e.g. the UMTS/UTRA scheme will provide bearer services suitable for for wideband multimedia communications. The physical implementation of the different bearer services includes the solution of new and interesting radio resource management problems. In particular the non-real time applications have been in the focus of standardization efforts since applications like wireless internet and web browsing are considered as driving the wireless evolution. These applications offer new challenges since they will be able to use any excess bandwidth that the system may be able to provide in a best effort fashion as soon as minimum rate guarantees have been honored. Choosing how the transmitter power should be controlled to achieve these minimum rate requirements is a straightforward task given the previous work in the field. In this paper, we will however, address the problem how the scheduling of transmission bursts and the transmitter power should be controlled to maximize the use of the excess capacity to achieve maximal total throughput. The system chosen as example here is a UMTS TD/CDMA system in a "bunch"-configuration allowing centralized resource management [6,7] as proposed in the ACTS/FRAMES project[9]. The problem is formalized and several of its properties are demonstrated. Results show that depending on the link configuration and the propagation conditions, either sequential scheduling of bearer slots as well as simultaneous slot reuse may achieve optimum throughput.
In this paper, we develop an algorithm for joint handover and beam tracking in millimeter-wave (m... more In this paper, we develop an algorithm for joint handover and beam tracking in millimeter-wave (mmWave) networks. The aim is to provide a reliable connection in terms of the achieved throughput along the trajectory of the mobile user while preventing frequent handovers. We model the association problem as an optimization problem and propose a reinforcement learning-based solution. Our approach learns whether and when beam tracking and handover should be performed and chooses the target base stations. In the case of beam tracking, we propose a tracking algorithm based on measuring a small spatial neighbourhood of the optimal beams in the previous time slot. Simulation results in an outdoor environment show the superior performance of our proposed solution in achievable throughput and the number of handovers needed in comparison to a multiconnectivity baseline and a learning-based handover baseline.
Millimeter-wave and terahertz systems rely on beamforming/combining codebooks to determine the be... more Millimeter-wave and terahertz systems rely on beamforming/combining codebooks to determine the best beam directions during the initial access and data transmission. Existing approaches suffer from large codebook sizes and high beam searching overhead in the presence of mobile devices. To address this issue, we utilize the similarity of the channel in adjacent locations to divide the user trajectory into a set of separate regions and maintain a set of candidate beams for each region in a database. Due to the tradeoff between the number of regions and the signalling overhead, i.e., the greater number of regions results in a higher signal-to-noise ratio (SNR) but also a larger signalling overhead for the database, we propose an optimization framework to find the minimum number of regions based on the trajectory of a mobile device. Using a ray tracing tool, we demonstrate that the proposed method provides high SNR while being more robust to the location information accuracy in comparison to the lookup table baseline and fixed size region baseline. Index Terms-Millimeter-wave systems, terahertz systems, beamforming codebook, beam alignment.
Due to the large bandwidth available, millimeter-Wave (mmWave) bands are considered a viable oppo... more Due to the large bandwidth available, millimeter-Wave (mmWave) bands are considered a viable opportunity to significantly increase the data rate in cellular and wireless networks. Nevertheless, the need for beamforming and directional communication between the transmitter and the receiver increases the complexity of the channel estimation and link establishment phase. Location-aided beamforming approaches have the potential to enable fast link establishment in mmWave networks. However, these are often very sensitive to location errors. In this work, we propose a beamforming algorithm based on tracking spatial correlation of the available strong paths between the transmitter and the receiver. We show that our method is robust to uncertainty in location information, i.e., location error and can provide a reliable connection to a moving user along a trajectory. The numerical results show that our approach outperforms benchmarks on various levels of error in the location information accuracy. The gain is more prominent in high location error scenarios.
Symposium on Communications and Vehicular Technology in the Benelux, 1993
Transmitter power control is a necessity to combat "near-far" problems in radio systems using rec... more Transmitter power control is a necessity to combat "near-far" problems in radio systems using receivers with limited "dynamic range" (such as conventional DS-CDMA systems). Transmitter power control, however, can also be used to control cochannel interference, i.e. interference from other users using the same channel (code or time slot). For this purpose, it has been shown that the optimum transmitter power configuration is found by solving an eigenvalue problem. The paper reviews some recent results in this area. The basic models as well as the concepts of achievable C/I, up/down-link equivalence and C/Ibalancing are introduced. Both the interference limited (noise-less) case as well as models including thermal noise are treated. Results show that substantial improvements in system capacity can be achieved, particulary in conjunction with Dynamic Channel Allocation. The optimum power control schemes are shown to be robust against implementational shortcomings. Throughout the paper we will study a large, but finite, cellular radio system. The system is assumed to use perfectly orthogonal signals ("channels") such as, for instance, TDMA or FDMA schemes. To each active mobile-base pair, we have
It has become increasingly clear that the current design paradigm for mobile broadband systems is... more It has become increasingly clear that the current design paradigm for mobile broadband systems is not a scalable and economically feasible way to solve the expected future "capacity crunch", in particular in indoor locations with large user densities. "Moore's law", e.g. state-of-the art signal processing and advanced antenna techniques now being researched, as well as more millimeter wave spectrum indeed provide more capacity, but are not the answer to the 3-4 orders of magnitude more capacity at today's cost, that is needed. We argue that solving the engineering problem of providing high data rates alone is not sufficient. Instead we need to solve the techno-economic problem to find both business models and scalable technical solutions that provide extreme area capacity for a given cost and energy consumption. In this paper we will show that achieving very high capacities is indeed feasible in indoor environments. However, to become economically viable, approaches with radically different fundamental cost factors compared to those used in today's cellular systems are needed. To reach very high capacity we must venture beyond the ultra-dense barrier, i.e. networks where the number of access points in an area is (considerably) larger than the active number mobile terminals. In such networks area capacities of more than 1 Gbit/s/m 2 are perfectly feasible. The problem set encountered in such Ultra-Dense Networks (UDN) is very different from conventional cellular systems and their solution requires conceptually new tools. We will address some of the fundamental aspects and performance limits, modeling of propagation, deployment and user traffic, and discuss the techno-economics of various network architectures. Finally we will summarize some of the most significant unsolved research questions in the field.
In cellular and cellular-IoT systems, random access has the utmost importance as it is the gateke... more In cellular and cellular-IoT systems, random access has the utmost importance as it is the gatekeeper that assures conflict-free access to radio resources. The main drawback of the legacy protocols ...
Optimum transmitter power control schemes to minimize the outage probability due to cochannel int... more Optimum transmitter power control schemes to minimize the outage probability due to cochannel interference have been investigated in (SI, (a. The main drawback of the previously proposed algorithms is that they would require reliable measurements of the gains in all radio paths in the system. In this paper, distributed power control algorithms that use only the signal-to-interference (C/I) ratios in those links actually in use, are investigated. An algorithm, that successfully approximates the behavior of the best known algorithms is proposed. The algorithm involves a novel distributed C/I-balancing scheme. Numerical results show that capacity gains in the order of 3-4 times can be reached also with these distributed schemes. Further, the effects of imperfect C/I estimates due to noise, vehicle mobility, and fast multipath fading are considered. Results show that the balancing procedure is very robust to measurement noise, in particular if C/I requirements are low or moderate. However, for required high C/I levels or for a rapidly changing path loss matrix, convergence may be too slow to achieve substantial capacity improvements.
Designations used by companies to distinguish their products are often claimed as trademarks. All... more Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The Publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.
Determining the efficiency of an HF-antenna by measurements requires is a complex procedure invol... more Determining the efficiency of an HF-antenna by measurements requires is a complex procedure involving expensive equipment, calibrated instruments for field strengths. In this paper we evaluate a simple, inexpensive method to determine the relative efficiency of an antenna relative a reference antenna. The method uses the Weak Signal Propagation Reporter(WSPR) network of receivers that are located all over the world. These receivers report the estimated signal-to-noise ratio of received beacon signals to the WSPR.net database where the data can be retrieved (almost) in real time. In the paper we analyze the method, estimate its accuracy and discuss advantages and limitations. Some preliminary measurement results are presented.
Personal, Indoor and Mobile Radio Communications, 1999
Third generation wireless systems, e.g. the UMTS/UTRA scheme will provide bearer services suitabl... more Third generation wireless systems, e.g. the UMTS/UTRA scheme will provide bearer services suitable for for wideband multimedia communications. The physical implementation of the different bearer services includes the solution of new and interesting radio resource management problems. In particular the non-real time applications have been in the focus of standardization efforts since applications like wireless internet and web browsing are considered as driving the wireless evolution. These applications offer new challenges since they will be able to use any excess bandwidth that the system may be able to provide in a best effort fashion as soon as minimum rate guarantees have been honored. Choosing how the transmitter power should be controlled to achieve these minimum rate requirements is a straightforward task given the previous work in the field. In this paper, we will however, address the problem how the scheduling of transmission bursts and the transmitter power should be controlled to maximize the use of the excess capacity to achieve maximal total throughput. The system chosen as example here is a UMTS TD/CDMA system in a "bunch"-configuration allowing centralized resource management [6,7] as proposed in the ACTS/FRAMES project[9]. The problem is formalized and several of its properties are demonstrated. Results show that depending on the link configuration and the propagation conditions, either sequential scheduling of bearer slots as well as simultaneous slot reuse may achieve optimum throughput.
In this paper, we develop an algorithm for joint handover and beam tracking in millimeter-wave (m... more In this paper, we develop an algorithm for joint handover and beam tracking in millimeter-wave (mmWave) networks. The aim is to provide a reliable connection in terms of the achieved throughput along the trajectory of the mobile user while preventing frequent handovers. We model the association problem as an optimization problem and propose a reinforcement learning-based solution. Our approach learns whether and when beam tracking and handover should be performed and chooses the target base stations. In the case of beam tracking, we propose a tracking algorithm based on measuring a small spatial neighbourhood of the optimal beams in the previous time slot. Simulation results in an outdoor environment show the superior performance of our proposed solution in achievable throughput and the number of handovers needed in comparison to a multiconnectivity baseline and a learning-based handover baseline.
Millimeter-wave and terahertz systems rely on beamforming/combining codebooks to determine the be... more Millimeter-wave and terahertz systems rely on beamforming/combining codebooks to determine the best beam directions during the initial access and data transmission. Existing approaches suffer from large codebook sizes and high beam searching overhead in the presence of mobile devices. To address this issue, we utilize the similarity of the channel in adjacent locations to divide the user trajectory into a set of separate regions and maintain a set of candidate beams for each region in a database. Due to the tradeoff between the number of regions and the signalling overhead, i.e., the greater number of regions results in a higher signal-to-noise ratio (SNR) but also a larger signalling overhead for the database, we propose an optimization framework to find the minimum number of regions based on the trajectory of a mobile device. Using a ray tracing tool, we demonstrate that the proposed method provides high SNR while being more robust to the location information accuracy in comparison to the lookup table baseline and fixed size region baseline. Index Terms-Millimeter-wave systems, terahertz systems, beamforming codebook, beam alignment.
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