SwePub - sökning: WFRF:(Skoglund Mikael)

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1.	Händel, Peter, 1962-, et al. (författare) METHOD AND SYSTEM FOR CALIBRATING ANALOG-TO-DIGITAL CONVERSION 2000 Patent (populärvet., debatt m.m.)abstract A method and system enables ADCs to be calibrated from reference signals with unknown parameters. A given analog reference signal (i(s)(i(t))) is suplied to an ADC (310). The output (i(x)(i(k))) of the ADC (310) is used by calibration logic (320) to estimate at least one parameter of the reference signal (i(s)(i(t))). A FIR filter (455) accepts as input the i(x)(i(k)) signals and outputs an estimate (Å(i(k))) as the sampled instances of the i(s)(i(t)) signal. A reconstruction table (So,...,SM-1) is created that approximates the analog input signal in the digital domain using the knowledge of the analog input signal waveform type. The actual ADC outputs (i(x)(i(k))) are compared to the values in the reconstruction table (So,...,SM-1) to produce a correction table (350) for calibration. A continuous time reference signal may be utilized for training the correction table (350). The method and system is data adaptive, so it may be applied, for example, with any sinusoidal reference input.
2.	Ljungqvist, Johan, et al. (författare) Clinical Evaluation of a Microwave-Based Device for Detection of Traumatic Intracranial Hemorrhage 2017 Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert Inc. - 0897-7151 .- 1557-9042. ; 34:13, s. 2176-2182 Tidskriftsartikel (refereegranskat)abstract Traumatic brain injury (TBI) is the leading cause of death and disability among young persons. A key to improve outcome for patients with TBI is to reduce the time from injury to definitive care by achieving high triage accuracy. Microwave technology (MWT) allows for a portable device to be used in the pre-hospital setting for detection of intracranial hematomas at the scene of injury, thereby enhancing early triage and allowing for more adequate early care. MWT has previously been evaluated for medical applications including the ability to differentiate between hemorrhagic and ischemic stroke. The purpose of this study was to test whether MWT in conjunction with a diagnostic mathematical algorithm could be used as a medical screening tool to differentiate patients with traumatic intracranial hematomas, chronic subdural hematomas (cSDH), from a healthy control (HC) group. Twenty patients with cSDH and 20 HC were measured with a MWT device. The accuracy of the diagnostic algorithm was assessed using a leave-one-out analysis. At 100% sensitivity, the specificity was 75%-i.e., all hematomas were detected at the cost of 25% false positives (patients who would be overtriaged). Considering the need for methods to identify patients with intracranial hematomas in the pre-hospital setting, MWT shows promise as a tool to improve triage accuracy. Further studies are under way to evaluate MWT in patients with other intracranial hemorrhages.
3.	PETTERSSON, Mikael, et al. (författare) FULL SCALE CALIBRATION OF ANALOG-TO-DIGITAL CONVERSION 2000 Patent (populärvet., debatt m.m.)abstract Methods and arrangements enable ADCs (105) to be calibrated from reference signals with unknown parameters and/or with amplitudes that exceed the dynamic range of the ADCs (105). A given analog reference signal s(t) is supplied to an ADC (105). The output x(k) of the ADC (105) is used by calibration logic (320) to estimate at least one paramater of the reference signal. A FIR filter (455) accepts as input the x(k) signals and outputs and estimate ((k)) as the sampled instances of thes(t) signal. A reconstruction table is created that approximates the analog input signal in the digital domain using the knowledge of the analog input signal waveform type. The actual ADC (105) outputs are compared to the values in the reconstruction table to produce a correction table (350) for calibration. In an alternative embodiment, calibration logic (320) interpolates the output (x(k)) of the ADC (105) to reconstruct clipped portion(s) of the input analog reference signal s(t) when the amplitude of the input analog reference signals s(t) exceeds the full swing of the ADC (105). The FIR filter can thereafter use the reconstructed signal from the interpolation.
4.	Skoglund, Mikael, et al. (författare) A case study on regression test suite maintenance in system evolution 2004 Ingår i: 20TH IEEE INTERNATIONAL CONFERENCE ON SOFTWARE MAINTENANCE, PROCEEDINGS. - 0769522130 ; , s. 438-442 Konferensbidrag (refereegranskat)abstract When a system is maintained, its automated test suites must also be maintained to keep the tests up to date. Even though practice indicates that test suite maintenance can be very costly we have seen few studies considering the actual efforts for maintenance of test-ware. We conducted a case study on an evolving system with three updated versions, changed with three different change strategies. Test suites for automated unit and functional tests were used for regression testing the extended applications. With one change strategy more changes were made in the tests code than in the system that was tested, and with another strategy no changes were needed for the unit tests to work.
5.	Andersson, Mattias, 1980- (författare) Coding and Transmission Strategies for Secrecy 2014 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract In this thesis we consider several problems relating to information theoretic security. The wiretap channel is the simplest information theoretic setting which takes security into account, and in the first chapters of the thesis we design some practical coding schemes for this channel model.First we consider the design of two edge type low density parity check (LDPC) codes for the binary erasure wiretap channel (BEC-WT). For the scenario when the main channel is error free and the wiretapper's channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the BEC-WT. We generalize a method of Méasson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wiretapper. We apply this method to relatively simple ensembles and find very good secrecy performance.We then show that Arikan's polar codes can be used to achieve the whole capacity-equivocation region of for any degraded symmetric binary input wiretap channel. We also design capacity achieving polar codes for the decode-and-forward scheme for the physically degraded relay channel, and for the bidirectional broadcast channel with common and confidential messages.In the subsequent chapter we consider a Gaussian system model. We show that sparse regression codes (SPARCS) as introduced by Joseph and Barron achieve the secrecy capacity of the additive white Gaussian noise (AWGN) wiretap channel, and can be used to implement the decode-and-forward scheme for the Gaussian relay channel. We also consider secret key agreement using correlated Gaussian random variables and a rate-limited public channel. We show that SPARCs attain the capacity region also for this problem.Finally we consider secret key agreement over reciprocal fading channels. We first consider a multiple-antenna setup in the high signal-to-noise-ratio (SNR) regime and propose a scheme based on training and randomness sharing. We then consider a single antenna setup in the low SNR regime, where one of the terminals is only allowed to transmit pilot signals. We propose a bursty transmission scheme based on training and opportunistic transmission using a wiretap channel code, and show that this scheme is optimal.
6.	Andersson, Mattias (författare) Coding for the Wiretap Channel 2011 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract We consider code design for Wyner’s wiretap channel. Optimal coding schemes for this channel require an overall code that is capacity achieving for the main channel, partitioned into smaller subcodes, all of which are capacity achieving for the wiretapper’s channel. To accomplish this we introduce two edge type low density parity check (LDPC) ensembles for the wiretap channel. For the scenario when the main channel is error free and the wiretapper’s channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the binary erasure wiretap channel (BEC- WT). We generalize a method of M ́easson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wire- tapper. This conditional entropy is a measure of how much information is leaked to the wiretapper. We apply this method to relatively simple ensembles and find that they show very good secrecy performance. Based on the work of Kudekar, Richardson, and Urbanke, which showed that regular spatially coupled codes are capacity achieving for the BEC, we construct a regular two edge type spatially coupled ensem- ble. We show that this ensemble achieves the whole capacity-equivocation region for the BEC-WT. We also find a coding scheme using Arıkans polar codes. These codes achieve the whole capacity-equivocation region for any symmetric binary input wiretap channel where the wiretapper’s channel is degraded with respect to the main channel.
7.	Andersson, Mattias, 1980-, et al. (författare) Equivocation of Eve using two edge type LDPC codes for the binary erasure wiretap channel 2010 Ingår i: 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers (ASILOMAR). - 9781424497225 ; , s. 2045-2049 Konferensbidrag (refereegranskat)abstract We consider transmission over a binary erasure wiretap channel using the code construction method introduced by Rathi et al. based on two edge type Low-Density Parity-Check (LDPC) codes and the coset encoding scheme. By generalizing the method of computing conditional entropy for standard LDPC ensembles introduced by Méasson, Montanari, and Urbanke to two edge type LDPC ensembles, we show how the equivocation for the wiretapper can be computed. We find that relatively simple constructions give very good secrecy performance and are close to the secrecy capacity.
8.	Andersson, Mattias, et al. (författare) Nested Polar Codes for Wiretap and Relay Channels 2010 Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 14:8, s. 752-754 Tidskriftsartikel (refereegranskat)abstract We show that polar codes asymptotically achieve the whole capacity-equivocation region for the wiretap channel when the wiretapper's channel is degraded with respect to the main channel, and the weak secrecy notion is used. Our coding scheme also achieves the capacity of the physically degraded receiver-orthogonal relay channel. We show simulation results for moderate block length for the binary erasure wiretap channel, comparing polar codes and two edge type LDPC codes.
9.	Andersson, Mattias, 1980-, et al. (författare) Nonlinear distributed sensing for closed-loop control over Gaussian channels 2011 Ingår i: Communication Technologies Workshop (Swe-CTW), 2011 IEEE Swedish. - : IEEE conference proceedings. - 9781457718779 ; , s. 19-23 Konferensbidrag (refereegranskat)abstract A scenario of distributed sensing for networked control systems is considered and a new approach to distributed sensing and transmission is presented. The state process of a scalar first order linear time invariant dynamical system is sensed by a network of wireless sensors, which then instantaneously transmit their measurements to a remotely situated control unit over parallel Gaussian channels. The control unit aims to stabilize the system in mean square sense. The proposed non-linear delay-free sensing and transmission strategy is compared with the well-known amplify-and-forward strategy, using the LQG control cost as a figure of merit. It is demonstrated that the proposed nonlinear scheme outperforms the best linear scheme even when there are only two sensors in the network. The proposed sensing and transmission scheme can be implemented with a reasonable complexity and it is shown to be robust to the uncertainties in the knowledge of the sensors about the statistics of the measurement noise and the channel noise.
10.	Andersson, Mattias, et al. (författare) Polar codes for bidirectional broadcast channels with common and confidential messages 2012 Ingår i: International Symposium on Wireless Communication Systems (ISWCS), 2012. - : IEEE conference proceedings. - 9781467307604 ; , s. 1014-1018 Konferensbidrag (refereegranskat)abstract We consider the bidirectional broadcast channel with common and confidential messages. We show that polar codes achieve the capacity of binary input symmetrical bidirectional broadcast channels with confidential messages, if one node's channel is a degraded version of the other node's channel. We also find a new bound on the cardinality of the auxiliary random variable in this setup.
11.	Andersson, Mattias, et al. (författare) Polar Coding for Bidirectional Broadcast Channels with Common and Confidential Messages 2013 Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 31:9, s. 1901-1908 Tidskriftsartikel (refereegranskat)abstract The integration of multiple services such as the transmission of private, common, and confidential messages at the physical layer is becoming important for future wireless networks in order to increase spectral efficiency. In this paper, bidirectional relay networks are considered, in which a relay node establishes bidirectional communication between two other nodes using a decode-and-forward protocol. In the broadcast phase, the relay transmits additional common and confidential messages, which then requires the study of the bidirectional broadcast channel (BBC) with common and confidential messages. This channel generalizes the broadcast channel with receiver side information considered by Kramer and Shamai. Low complexity polar codes are constructed that achieve the capacity region of both the degraded symmetric BBC, and the BBC with common and confidential messages. The use of polar codes allows an intuitive interpretation of how to incorporate receiver side information and secrecy constraints as different sets of frozen bits at the different receivers for an optimal code design. In order to show that the constructed codes achieve capacity, a tighter bound on the cardinality of an auxiliary random variable used in the converse is found using a method by Salehi.
12.	Andersson, Mattias, 1980-, et al. (författare) Secret-key agreement over a non-coherent block-fading MIMO wiretap channel 2012 Ingår i: Information Theory Workshop (ITW), 2012 IEEE. - : IEEE. - 9781467302234 ; , s. 153-157 Konferensbidrag (refereegranskat)abstract We study secret-key agreement over a non-coherent block-fading multiple input multiple output (MIMO) wiretap channel. We give an achievable scheme based on training and source emulation and analyze the rate in the high SNR regime. Based on this analysis we find the optimal number of antennas to use for training. Our main result is that if the sum of the number of antennas at Alice and Bob is larger than the coherence time of the channel, the achievable rate does not depend on the number of antennas at Eve. In this case source emulation is not needed, and using only training is optimal. We also consider the case when there is no public channel available. In this case we show that secret-key agreement is still possible by using the wireless channel for discussion, giving the same number of secure degrees of freedom as in the case with a public channel.
13.	Andersson, Mattias, et al. (författare) Secure key agreement over reciprocal fading channels in the low SNR regime 2013 Ingår i: 2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - : IEEE. - 9781467355773 ; , s. 674-678 Konferensbidrag (refereegranskat)abstract We study the low SNR scaling of the non-coherent secret-key agreement capacity over a reciprocal, block-fading channel. For the restricted class of strategies, where one of the nodes is constrained to transmit pilot-only symbols, we show that the secret-key capacity scales as SNR ·log T if T ≤ 1/SNR, where T denotes the coherence period, and as SNR·log(1/SNR) otherwise. Our upper bound is inspired by the genie-aided argument of Borade and Zheng (IT-Trans 2010). Our lower bound is based on bursty communication, channel training, and secret message transmission.
14.	Andersson, Tomas, et al. (författare) A COVQ-Based image coder for channels with bit errors and erasures 2008 Ingår i: IEEE Transactions on Communications. - : IEEE Communications Society. - 0090-6778 .- 1558-0857. ; 56:2, s. 161-165 Tidskriftsartikel (refereegranskat)abstract We illustrate how channel optimized vector quantization (COVQ) can be used for channels with both bit-errors and bit-erasures. First, a memoryless channel model is presented, and the performance of COVQ's trained for this channel is evaluated for an i.i.d. Gaussian source. Then, the new method is applied in implementing an error-robust sub-band image coder, and we present image results that illustrate the resulting performance. Our experiments show that the new approach is able to outperform a traditional scheme based on separate source and channel coding.
15.	Andersson, Tomas, et al. (författare) Design of n-channel multiple description vector quantizers 2005 Ingår i: 2005 39th Asilomar Conference on Signals, Systems and Computers. - NEW YORK : IEEE. ; , s. 13-17 Konferensbidrag (refereegranskat)abstract A new design approach for multiple description vector quantizers over more than two channels is presented. The design is inspired by the concept of channel optimized vector quantization. While most previous works have split the decoder into several independent entities, identifying the appropriate channel model makes it straightforward to implement the multiple description design problem using only one decoder. Our simulation results compare systems with 2, 4 and 8 channels. We demonstrate significant gains over previous designs, as well as over a benchmark scheme based on separate quantization and forward erasure-correcting error control.
16.	Andersson, Tomas, et al. (författare) Frequency estimation by 1-bit quantization and table look-up processing 2000 Ingår i: Proceedings European Signal Processing Conference. ; , s. 1807-1810 Konferensbidrag (refereegranskat)
17.	Andersson, Tomas, et al. (författare) Frequency estimation utilizing the Hadamard transform 2001 Ingår i: 2001 IEEE WORKSHOP ON STATISTICAL SIGNAL PROCESSING PROCEEDINGS. - NEW YORK : IEEE. - 0780370112 ; , s. 409-412 Konferensbidrag (refereegranskat)abstract Fast analog to digital conversion with only one bit per sample does not only make high sampling rates possible but also reduces the required hardware complexity. For short data buffers or block lengths, it has been shown that tone frequency estimators can be implemented by a simple table look-up. In this paper we present an analysis of such tables using the Hadamard transform. As an outcome of the analysis, we propose a class of nonlinear estimators of low complexity. Their performance is evaluated using numerical simulations. Comparisons are made with the proper Cramer-Rao bound and with the table look-up approach.
18.	Andersson, Tomas, et al. (författare) Multiple description image coding based on multi-stage vector quantization 2007 Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS. - NEW YORK : IEEE. ; , s. 243-246 Konferensbidrag (refereegranskat)abstract A new design approach for multiple description coding, based on multi-stage vector quantizers, is presented. The design is not limited to systems with two descriptions, but is also well suited for the n-descriptions case. Inspired by the concept of channel optimized vector quantization, the design can easily be tailored to suit different erasure channels, e.g. packet erasure channels with memory (burst-losses). The optimization procedure used in the design takes a sample-iterative approach. All stage codebooks; are updated simultaneously for each vector in the training database. The resulting algorithm has the behaviour of a simulated annealing algorithm, with several good properties, e.g. it usually provides codebooks with good index assignments. Image results are presented for systems with 2 and 4 channels. The image coder is based on a subband transform followed by 64-dimensional vector quantization, to illustrate the capacity of the design to handle large problem sizes.
19.	Andersson, Tomas, 1978- (författare) On error-robust source coding with image coding applications 2006 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract This thesis treats the problem of source coding in situations where the encoded data is subject to errors. The typical scenario is a communication system, where source data such as speech or images should be transmitted from one point to another. A problem is that most communication systems introduce some sort of error in the transmission. A wireless communication link is prone to introduce individual bit errors, while in a packet based network, such as the Internet, packet losses are the main source of error. The traditional approach to this problem is to add error correcting codes on top of the encoded source data, or to employ some scheme for retransmission of lost or corrupted data. The source coding problem is then treated under the assumption that all data that is transmitted from the source encoder reaches the source decoder on the receiving end without any errors. This thesis takes another approach to the problem and treats source and channel coding jointly under the assumption that there is some knowledge about the channel that will be used for transmission. Such joint source--channel coding schemes have potential benefits over the traditional separated approach. More specifically, joint source--channel coding can typically achieve better performance using shorter codes than the separated approach. This is useful in scenarios with constraints on the delay of the system. Two different flavors of joint source--channel coding are treated in this thesis; multiple description coding and channel optimized vector quantization. Channel optimized vector quantization is a technique to directly incorporate knowledge about the channel into the source coder. This thesis contributes to the field by using channel optimized vector quantization in a couple of new scenarios. Multiple description coding is the concept of encoding a source using several different descriptions in order to provide robustness in systems with losses in the transmission. One contribution of this thesis is an improvement to an existing multiple description coding scheme and another contribution is to put multiple description coding in the context of channel optimized vector quantization. The thesis also presents a simple image coder which is used to evaluate some of the results on channel optimized vector quantization.
20.	Bao, Lei, et al. (författare) A scheme for joint quantization, error protection and feedback control over noisy channels 2007 Ingår i: 2007 AMERICAN CONTROL CONFERENCE, VOLS 1-13. - : IEEE. - 9781424409884 ; , s. 2456-2461 Konferensbidrag (refereegranskat)abstract We study a closed-loop scalar control system with feedback transmitted over a discrete noisy channel. For this problem, we propose a joint design of the state measurement quantization, protection against channel errors, and control. The goal is to minimize a linear quadratic cost function over a finite horizon. In particular we focus on a special case where we verify that certainty equivalence holds, and for this case we design joint source-channel encoder and decoder/estimator pairs. The proposed algorithm leads to a practically feasible design of time-varying non-uniform quantization and control. Numerical results demonstrate the promising performance obtained by employing the proposed iterative optimization algorithm.
21.	Bao, Lei, 1976- (författare) Control over Low-Rate Noisy Channels 2009 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Networked embedded control systems are present almost everywhere. A recent trendis to introduce radio communication in these systems to increase mobility and flex-ibility. Network nodes, such as the sensors, are often simple devices with limitedcomputing and transmission power and low storage capacity, so an important prob-lem concerns how to optimize the use of resources to provide sustained overall sys-tem performance. The approach to this problem taken in the thesis is to analyzeand design the communication and control application layers in an integrated man-ner. We focus in particular on cross-layer design techniques for closed-loop controlover non-ideal communication channels, motivated by future control systems withvery low-rate and highly quantized sensor communication over noisy links. Severalfundamental problems in the design of source–channel coding and optimal controlfor these systems are discussed.The thesis consists of three parts. The first and main part is devoted to the jointdesign of the coding and control for linear plants, whose state feedback is trans-mitted over a finite-rate noisy channel. The system performance is measured by afinite-horizon linear quadratic cost. We discuss equivalence and separation proper-ties of the system, and conclude that although certainty equivalence does not holdin general it can still be utilized, under certain conditions, to simplify the overalldesign by separating the estimation and the control problems. An iterative opti-mization algorithm for training the encoder–controller pairs, taking channel errorsinto account in the quantizer design, is proposed. Monte Carlo simulations demon-strate promising improvements in performance compared to traditional approaches.In the second part of the thesis, we study the rate allocation problem for statefeedback control of a linear plant over a noisy channel. Optimizing a time-varyingcommunication rate, subject to a maximum average-rate constraint, can be viewedas a method to overcome the limited bandwidth and energy resources and to achievebetter overall performance. The basic idea is to allow the sensor and the controllerto communicate with a higher data rate when it is required. One general obstacle ofoptimal rate allocation is that it often leads to a non-convex and non-linear problem.We deal with this challenge by using high-rate theory and Lagrange duality. It isshown that the proposed method gives a good performance compared to some otherrate allocation schemes.In the third part, encoder–controller design for Gaussian channels is addressed.Optimizing for the Gaussian channel increases the controller complexity substan-tially because the channel output alphabet is now infinite. We show that an efficientcontroller can be implemented using Hadamard techniques. Thereafter, we proposea practical controller that makes use of both soft and hard channel outputs.
22.	Bao, Lei, et al. (författare) Encoder-controller design for control over the binary-input Gaussian channel 2010 Ingår i: IEEE International Symposium on Spread Spectrum Techniques and Applications. - : IEEE. - 9781424460151 ; , s. 23-28 Konferensbidrag (refereegranskat)abstract In this paper, we consider the problem of the joint optimization of encoder-controller for closed-loop control with state feedback over a binary-input Gaussian channel (BGC). The objective is to minimize the expected linear quadratic cost over a finite horizon. Thisencoder-controller optimization problem is hard in general, mostly because of the curse of dimensionality. The result of this paper is a synthesis technique for a computationally feasible suboptimal controller which exploits both the soft and hard information of thechannel outputs. The proposed controller is efficient in the sense that it embraces measurement quantization, error protection and control over a finite-input infinite-output noisy channel. How to effectively implement this controller is also addressed in the paper. In particular, this is done by using Hadamard techniques. Numerical experiments are carried out to verify the promising gain offered by the combined controller, in comparison to the hard-information-based controller.
23.	Bao, Lei, et al. (författare) Encoder-decoder design for event-triggered feedback control over bandlimited channels 2006 Ingår i: 2006 American Control Conference. - : IEEE. - 1424402093 ; , s. 4183-4188 Konferensbidrag (refereegranskat)abstract Bandwidth limitations and energy constraints set severe restrictions on the design of control systems that utilize wireless sensor and actuator networks. It is common in these systems that a sensor node needs not be continuously monitored, but communicates to the controller only at certain instances when it detects a disturbance event. In this paper, such a scenario is studied and particular emphasis is on efficient utilization of the shared communication resources. Encoder-decoder design for an event-based control system with the plant affected by pulse disturbances is considered. A new iterative procedure is proposed which can jointly optimize encoder-decoder pairs for a certainty equivalent controller. The goal is to minimize a design criterion, in particular, a linear quadratic cost over a finite horizon. The algorithm leads to a feasible design of time-varying non-uniform encoder-decoder pairs. Numerical results demonstrate significant improvements in performance compared to a system using uniform quantization.
24.	Bao, L., et al. (författare) Encoder-decoder design for feedback control over the binary symmetric channel 2006 Ingår i: 2006 IEEE International Symposium on Information Theory, Vols 1-6, Proceedings. - : IEEE. - 9781424405053 ; , s. 2481-2485 Konferensbidrag (refereegranskat)abstract Encoder-decoder design is considered for a closed-loop scalar control system with feedback transmitted over a binary symmetric channel. We propose an iterative procedure which can jointly optimize adaptive encoder-decoder pairs for a certainly equivalence controller. The goal is to minimize a design criterion, in particular, the linear quadratic (LQ) cost function over a finite horizon. The algorithm leads to a practically feasible design of time-varying non-uniform encoding and decoding. Numerical results demonstrate the promising performance obtained by employing the proposed iterative optimization algorithm.
25.	Bao, Lei, et al. (författare) Iterative encoder-controller design based on approximate dynamic programming 2010 Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. Konferensbidrag (refereegranskat)abstract In this paper, we study the iterative optimization of the encoder-controller pair for closed-loop control of a multi-dimensional plant over a noisy discrete memoryless channel. With the objective to minimize the expected linear quadratic cost over a finite horizon, we propose a joint design of the sensor measurement quantization, channel error protection, and optimal controller actuation. It was shown in our previous work that despite this optimization problem is known to be hard in general, an iterative design procedure can be derived to obtain a local optimal solution. However, in the vector case, optimizing the encoder for a fixed controller is in general not practically feasible due to the curse of dimensionality. In this paper, we propose a novel approach that uses the approximate dynamic programming (ADP) to implement a computationally feasible encoder updating policy with promising performance. Especially, we introduce encoder updating rules adopting the rollout approach. Numerical experiments are carried out to demonstrate the performance obtained by employing the proposed iterative design procedure and to compare it with other relevant schemes.
26.	Bao, Lei, et al. (författare) Iterative Encoder-Controller Design for Feedback Control Over Noisy Channels 2011 Ingår i: IEEE Transactions on Automatic Control. - : IEEE. - 0018-9286 .- 1558-2523. ; 56:2, s. 265-278 Tidskriftsartikel (refereegranskat)abstract We study a closed-loop control system with state feedback transmitted over a noisy discrete memoryless channel. With the objective to minimize the expected linear quadratic cost over a finite horizon, we propose a joint design of the sensor measurement quantization, channel error protection, and controller actuation. It is argued that despite that this encoder-controller optimization problem is known to be hard in general, an iterative design procedure can be derived in which the controller is optimized for a fixed encoder, then the encoder is optimized for a fixed controller, etc. Several properties of such a scheme are discussed. For a fixed encoder, we study how to optimize the controller given that full or partial side-information is available at the encoder about the symbols received at the controller. It is shown that the certainty equivalence controller is optimal when the encoder is optimal and has full side-information. For a fixed controller, expressions for the optimal encoder are given and implications are discussed for the special cases when process, sensor, or channel noise is not present. Numerical experiments are carried out to demonstrate the performance obtained by employing the proposed iterative design procedure and to compare it with other relevant schemes.
27.	Bao, Lei, et al. (författare) On Iterative System Design and Separation in Control Over Noisy Channels 2008 Ingår i: IFAC World Congress, Volume 17, Part 1. - : IFAC. Konferensbidrag (refereegranskat)abstract We study a closed-loop control system with feedback transmitted over a noisy discrete memoryless channel. We design encoder-controller pairs that jointly optimize the sensor measurement quantization, protection against channel errors, and control. The designgoal is to minimize an expected linear quadratic cost over a finite horizon. As a result of deriving optimality criteria for this problem, we present new results on the validity of theseparation principle subject to certain assumptions. More precisely, we show that the certainty equivalence controller is optimal when the encoder is optimal and has full side-information about the symbols received at the controller. We then use this result to formulate tractable design criteria in the general case. Finally, numerical experiments are carried out to demonstrate the performance obtained by various design methods.
28.	Bao, Lei, et al. (författare) On optimal system design for feedback control over noisy channels 2007 Ingår i: 2007 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS, VOLS 1-7. - : IEEE. - 9781424413973 ; , s. 2486-2490 Konferensbidrag (refereegranskat)abstract We study a closed-loop multivariable control system with sensor feedback transmitted over a discrete noisy channel. For this problem, we propose a joint design of the state measurement quantization, protection against channel errors, and control. The proposed algorithm leads to a practically feasible design of time-varying non-uniform encoding and control. Numerical results demonstrate the performance obtained by employing the proposed iterative optimization algorithm.
29.	Bao, Lei, et al. (författare) On rate allocation for multiple plants in a networked control system 2012 Ingår i: 2012 American Control Conference (ACC). - : IEEE Computer Society. - 9781457710957 ; , s. 2024-2029 Konferensbidrag (refereegranskat)abstract The problem of allocating communication resources to multiple plants in a networked control system is investigated. In the presence of a shared communication medium, a total transmission rate constraint is imposed. For the purpose of optimizing the rate allocation to the plants over a finite horizon, two objective functions are considered. The first one is a single-objective function, and the second one is a multi-objective function. Because of the difficulty to derive the closed-form expression of these functions, which depend on the instantaneous communication rate, an approximation is proposed by using high-rate quantization theory. It is shown that the approximate objective functions are convex in the region of interest both in the scalar case and in the multi-objective case. This allows to establish a linear control policy given by the classical linear quadratic Gaussian theory as function of the channel. Based on this result, a new complex relation between the control performance and the channel error probability is characterized.
30.	Bao, Lei, et al. (författare) On the separation principle in optimal control over noisy channels 2008 Konferensbidrag (refereegranskat)
31.	Bao, Lei, et al. (författare) Optimized Rate Allocation for State Estimation over Noisy Channels 2009 Ingår i: 2009 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY. - NEW YORK : IEEE. ; , s. 2684-2688 Konferensbidrag (refereegranskat)abstract Optimal rate allocation in a networked control system with limited communication resources is instrumental to achieve satisfactory overall performance. In this paper, a practical rate allocation technique for state estimation in linear dynamic systems over a noisy channel is proposed. The method consists of two steps: (i) the overall distortion is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize the overall distortion is solved by using Lagrange duality. Monte Carlo simulations illustrate the proposed scheme, which is shown to have good performance when compared to arbitrarily selected rate allocations.
32.	Bao, Lei, et al. (författare) Optimized rate allocation for state feedback control over noisy channels 2009 Ingår i: Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference. CDC/CCC 2009. Proceedings of the 48th IEEE Conference on. - : IEEE. - 9781424438716 ; , s. 573-578 Konferensbidrag (refereegranskat)abstract Optimal rate allocation in a networked control system with highly limited communication resources is instrumental to achieve satisfactory overall performance. In this paper, we propose a rate allocation technique for state feedback control in linear dynamic systems over a noisy channel. Our method consists of two steps: (i) the overall distortion is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize the overall distortion is solved. We show that a non-uniform quantization is in general the best strategy for state feedback control over noisy channels. Monte Carlo simulations illustrate the proposed scheme, which is shown to have good performance compared to arbitrarily selected rate allocations.
33.	Bao, Lei, et al. (författare) Rate Allocation for Quantized Control Over Binary Symmetric Channels 2012 Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 60:6, s. 3188-3202 Tidskriftsartikel (refereegranskat)abstract Utility maximization in networked control systems (NCSs) is difficult in the presence of limited sensing and communication resources. In this paper, a new communication rate optimization method for state feedback control over a noisy channel is proposed. Linear dynamic systems with quantization errors, limited transmission rate, and noisy communication channels are considered. The most challenging part of the optimization is that no closed-form expressions are available for assessing the performance and the optimization problem is nonconvex. The proposed method consists of two steps: (i) the overall NCS performance measure is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize a weighted quadratic objective function is solved. The proposed method is applied to the problem of state feedback control and the problem of state estimation. Monte Carlo simulations illustrate the performance of the proposed rate allocation. It is shown numerically that the proposed method has better performance when compared to arbitrarily selected rate allocations. Also, it is shown that in certain cases nonuniform rate allocation can outperform the uniform rate allocation, which is commonly considered in quantized control systems, for feedback control over noisy channels.
34.	Bao, Lei, et al. (författare) Rate allocation for quantized control over noisy channels 2009 Ingår i: Final Proceedings of the 2009 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks. - 9781424449200 ; , s. 595-603 Konferensbidrag (refereegranskat)abstract To achieve satisfactory overall performance, optimal rate allocation in a networked control system with highly limited communication resources is instrumental. In this paper, a rate allocation technique for state feedback control in linear dynamic systems over a noisy channel is proposed. The method consists of two steps: (i) the overall cost is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize the overall distortion is solved. It is shown that a non-uniform quantization is in general the best strategy for state feedback control over noisy channels. Monte Carlo simulations illustrate the proposed scheme, which is shown to have good performance when compared to arbitrarily selected rate allocations.
35.	Bao, Lei, 1976- (författare) Source-channel coding for closed-loop control 2006 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Networked embedded control systems are present almost everywhere. A recent trend is to introduce wireless sensor networks in these systems, to take advantage of the added mobility and flexibility offered by wireless solutions. In such networks, the sensor observations are typically quantized and transmitted over noisy links. Concerning the problem of closed-loop control over such non-ideal communication channels, relatively few works have appeared so far. This thesis contributes to this field, by studying some fundamentally important problems in the design of joint source--channel coding and optimal control. The main part of the thesis is devoted to joint design of the coding and control for scalar linear plants, whose state feedbacks are transmitted over binary symmetric channels. The performance is measured by a finite-horizon linear quadratic cost function. The certainty equivalence property of the studied systems is utilized, since it simplifies the overall design by separating the estimation and the control problems. An iterative optimization algorithm for training the encoder--decoder pairs, taking channel errors into account in the quantizer design, is proposed. Monte Carlo simulations demonstrate promising improvements in performance compared to traditional approaches. Event-triggered control strategies are a promising solution to the problem of efficient utilization of communication resources. The basic idea is to let each control loop communicate only when necessary. Event-triggered and quantized control are combined for plants affected by rarely occurring disturbances. Numerical experiments show that it is possible to achieve good control performance with limited control actuation and sensor communication.
36.	Barros da Silva Jr., José Mairton, Dr. 1990-, et al. (författare) Smart Antenna Assignment is Essential in Full-Duplex Communications 2021 Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 69:5, s. 3450-3466 Tidskriftsartikel (refereegranskat)abstract Full-duplex communications have the potential to almost double the spectralefficiency. To realize such a potentiality, the signal separation at base station’s antennasplays an essential role. This paper addresses the fundamentals of such separationby proposing a new smart antenna architecture that allows every antenna to beeither shared or separated between uplink and downlink transmissions. The benefitsof such architecture are investigated by an assignment problem to optimally assignantennas, beamforming and power to maximize the weighted sum spectral efficiency.We propose a near-to-optimal solution using block coordinate descent that divides theproblem into assignment problems, which are NP-hard, a beamforming and powerallocation problems. The optimal solutions for the beamforming and power allocationare established while near-to-optimal solutions to the assignment problems are derivedby semidefinite relaxation. Numerical results indicate that the proposed solution isclose to the optimum, and it maintains a similar performance for high and low residualself-interference powers. With respect to the usually assumed antenna separationtechnique and half-duplex transmission, the sum spectral efficiency gains increase withthe number of antennas. We conclude that our proposed smart antenna assignment forsignal separation is essential to realize the benefits of multiple antenna full-duplexcommunications.
37.	Bassi, Germán, et al. (författare) Lossy Communication Subject to Statistical Parameter Privacy 2018 Ingår i: 2018 IEEE International Symposium on Information Theory (ISIT) - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538647806 ; , s. 1031-1035 Konferensbidrag (refereegranskat)abstract We investigate the problem of sharing (communi-cating) the outcomes of a memoryless source when some of its statistical parameters must be kept private. Privacy is measured in terms of the Bayesian statistical risk according to a desired loss function while the quality of the reconstruction is measured by the average per-letter distortion. We first bound -uniformly over all possible estimators- the expected risk from below. This information-theoretic bound depends on the mutual information between the parameters and the disclosed (noisy) samples. We then present an achievable scheme that guarantees an upper bound on the average distortion while keeping the risk above a desired threshold, even when the length of the sample increases.
38.	Bassi, Germán, et al. (författare) On the Mutual Information of Two Boolean Functions, with Application to Privacy 2019 Ingår i: Proceedings 2019 IEEE International Symposium on Information Theory (ISIT). - : IEEE. - 9781538692912 ; , s. 1197-1201 Konferensbidrag (refereegranskat)abstract We investigate the behavior of the mutual information between two Boolean functions of correlated binary strings. The covariance of these functions is found to be a crucial parameter in the aforementioned mutual information. We then apply this result in the analysis of a specific privacy problem where a user observes a random binary string. Under particular conditions, we characterize the optimal strategy for communicating the outcomes of a function of said string while preventing to leak any information about a different function.
39.	Bassi, Germán, et al. (författare) Statistical Parameter Privacy 2020 Ingår i: Privacy in Dynamical Systems. - Singapore : Springer Nature. ; , s. 65-82 Bokkapitel (refereegranskat)abstract We investigate the problem of sharing the outcomes of a parametric source with an untrusted party while ensuring the privacy of the parameters. We propose privacy mechanisms which guarantee parameter privacy under both Bayesian statistical as well as information-theoretic privacy measures. The properties of the proposed mechanisms are investigated and the utility-privacy trade-off is analyzed.
40.	Bergh, Niklas, 1979, et al. (författare) Risk of Heart Failure in Congenital Heart Disease: A Nationwide Register-based Cohort Study. 2023 Ingår i: Circulation. - 1524-4539. ; 147:12, s. 982-984 Tidskriftsartikel (refereegranskat)
41.	Bergström, Göran, 1964, et al. (författare) Body weight at age 20 and in midlife is more important than weight gain for coronary atherosclerosis: Results from SCAPIS. 2023 Ingår i: Atherosclerosis. - : Elsevier BV. - 1879-1484 .- 0021-9150. ; 373, s. 46-54 Tidskriftsartikel (refereegranskat)abstract Elevated body weight in adolescence is associated with early cardiovascular disease, but whether this association is traceable to weight in early adulthood, weight in midlife or to weight gain is not known. The aim of this study is to assess the risk of midlife coronary atherosclerosis being associated with body weight at age 20, body weight in midlife and body weight change.We used data from 25,181 participants with no previous myocardial infarction or cardiac procedure in the Swedish CArdioPulmonary bioImage Study (SCAPIS, mean age 57 years, 51% women). Data on coronary atherosclerosis, self-reported body weight at age 20 and measured midlife weight were recorded together with potential confounders and mediators. Coronary atherosclerosis was assessed using coronary computed tomography angiography (CCTA) and expressed as segment involvement score (SIS).The probability of having coronary atherosclerosis was markedly higher with increasing weight at age 20 and with mid-life weight (p<0.001 for both sexes). However, weight increase from age 20 until mid-life was only modestly associated with coronary atherosclerosis. The association between weight gain and coronary atherosclerosis was mainly seen in men. However, no significant sex difference could be detected when adjusting for the 10-year delay in disease development in women.Similar in men and women, weight at age 20 and weight in midlife are strongly related to coronary atherosclerosis while weight increase from age 20 until midlife is only modestly related to coronary atherosclerosis.
42.	Bilal, Ibrahim, et al. (författare) An Optimized Linear Scheme for Stabilization Over Multi-User Gaussian Networks 2013 Ingår i: 2013 Information Theory And Applications Workshop (ITA). - New York : IEEE. - 9781467346481 ; , s. 290-297 Konferensbidrag (refereegranskat)abstract Remote stabilization of linear dynamical systems over Gaussian networks is studied. Two linear time invariant systems (plants) with arbitrary distributed initial states are monitored by two separate sensors. The sensors communicate their measurements to two remotely situated controllers over a Gaussian interference, possibly with the assistance from a relay node. The common goal of the sensors, relay, and controllers is to stabilize the plants in mean-square sense. An optimized linear delay-free sensing and control scheme is proposed and sufficient conditions for mean-square stability are derived. These conditions reveal the relationship between plants' stability and communication channel parameters. It is shown that the proposed linear scheme can significantly outperform the existing estimation based control scheme in multi-user Gaussian networks.
43.	Bilal, Ibrahim, et al. (författare) Feedback stabilization over a Gaussian interference relay channel 2013 Ingår i: 2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - : IEEE. - 9781467355773 ; , s. 560-564 Konferensbidrag (refereegranskat)abstract A transmission scheme for mean square stabilization of two linear systems over a Gaussian interference relay channel is studied. A delay-free linear sensing and control strategy is proposed and an achievable stability region is derived. It shows that the stability region can be significantly enlarged by deploying a relay node in such a multi-user Gaussian channels. Furthermore we observe that the separation structure between estimation and control is inadequate in high interference regime.
44.	Bilal, Ibrahim, et al. (författare) Managing interference for stabilization over wireless channels 2012 Ingår i: Intelligent Control (ISIC), 2012 IEEE International Symposium on. - : IEEE. - 9781467345989 ; , s. 933-938 Konferensbidrag (refereegranskat)abstract The remote stabilization of a first order linear plant over a wireless channel is studied. The plant is assumed to have an arbitrary distributed initial state and the wireless channel between the plant's sensor and the controller is modeled as a white Gaussian channel subject to an external interference signal. In order to combat the interference a dedicated sensor (relay) node is deployed adjacent to the interferer, which relays the interference information to both the plant's sensor and the controller. The sensor and the controller utilize this information to mitigate interference. We use delay-free linear sensing and control scheme in order to derive sufficient conditions for mean square stability. The achievable stability region significantly enlarges with the relay assisted interference cancelation scheme. Moreover the effect of interference can be completely eliminated if the encoder knows all the future values of the interference.
45.	Blasco-Serrano, Ricardo, et al. (författare) A Measurement Rate-MSE Tradeoff for Compressive Sensing Through Partial Support Recovery 2014 Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 62:18, s. 4643-4658 Tidskriftsartikel (refereegranskat)abstract We study the fundamental relationship between two relevant quantities in compressive sensing: the measurement rate, which characterizes the asymptotic behavior of the dimensions of the measurement matrix in terms of the ratio m/ log n (m being the number of measurements and n the dimension of the sparse signal), and the mean square estimation error. First, we use an information-theoretic approach to derive sufficient conditions on the measurement rate to reliably recover a part of the support set that represents a certain fraction of the total signal power when the sparsity level is fixed. Second, we characterize the mean square error of an estimator that uses partial support set information. Using these two parts, we derive a tradeoff between the measurement rate and the mean square error. This tradeoff is achievable using a two-step approach: first support set recovery, then estimation of the active components. Finally, for both deterministic and random signals, we perform a numerical evaluation to verify the advantages of the methods based on partial support set recovery.
46.	Blasco-Serrano, Ricardo, et al. (författare) An Achievable Measurement Rate-MSE Tradeoff in Compressive Sensing Through Partial Support Recovery 2013 Ingår i: 2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - New York : IEEE. - 9781479903566 ; , s. 6426-6430 Konferensbidrag (refereegranskat)abstract For compressive sensing, we derive achievable performance guarantees for recovering partial support sets of sparse vectors. The guarantees are determined in terms of the fraction of signal power to be detected and the measurement rate, defined as a relation between the dimensions of the measurement matrix. Based on this result we derive a tradeoff between the measurement rate and the mean square error, and illustrate it by a numerical example.
47.	Blasco-Serrano, Ricardo, et al. (författare) Bandwidth efficient compress-and-forward relaying based on joint source-channel coding 2011 Ingår i: 2011 IEEE Wireless Communications and Networking Conference, WCNC 2011. - : IEEE conference proceedings. - 9781612842554 ; , s. 1800-1804 Konferensbidrag (refereegranskat)abstract We propose a new code design for compress-and-forward relaying over bandlimited relay-to-destination channels. The main contribution of this paper is a code design based on joint (source-channel) coding and modulation that uses the correlation between the observations at the relay and the destination as protection against channel errors. This allows for relay nodes with reduced complexity, shifting most of the processing requirements to the destination node. Moreover, by using scalar quantizers with an entropy constraint our system provides remarkable performance in channel conditions where neither amplify-and-forward nor compress-and-forward efficiently exploit the presence of a relay node. Simulation results confirm the benefits of our proposed system.
48.	Blasco-Serrano, Ricardo, 1983- (författare) Coding Strategies for Compress-and-Forward Relaying 2010 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract The deployment of large communication networks with many autonomous devices has opened new possibilities for transmission. In particular cooperation among the different nodes has been identified as an enabling technology to satisfy the increasing demand of resources. This thesis studies different coding strategies for cooperation in relay channels in the form of compress-and-forward.In the first part of this thesis we consider the application of the newly introduced polar codes for compress-and-forward relaying in relay channels with orthogonal receivers. First we construct polar codes for compress-and-forward relaying based on Slepian-Wolf coding for the scenario where the capacity of the relay-destination channel is large enough. We then consider the more general picture where the capacity of the relay-destination channel is arbitrary. As for Wyner-Ziv coding, we employ nested polar codes for source and channel coding that allow for compression at any desired distortion and exploit the correlation between the observations of the source transmission to minimize the transmission rate over the relay-destination channel. This construction allows for transmission at the prominent compress-and-forward rate under some additional constraints.In the second part of this thesis we propose a new coding strategy for compress-and-forward relaying for half-duplex Gaussian channels. Our code construction is based on simple code concatenation for joint source-channel coding at the relay and iterative decoding at the destination. Finally, we propose several realizations of the structure at the relay and different iterative decoding algorithms in order to adapt the construction to different scenarios. Our simulation results show remarkable performance gains over other cooperation strategies such as decode-and-forward and amplify-and-forward in the scenarios where both source-relay and relay-destination links have low signal-to-noise ratios.
49.	Blasco-Serrano, Ricardo, et al. (författare) Communication and interference coordination 2014 Ingår i: 2014 Information Theory and Applications Workshop, ITA 2014 - Conference Proceedings. - : IEEE conference proceedings. ; , s. 6804218- Konferensbidrag (refereegranskat)abstract We study the problem of controlling the interference created to an external observer by a communication processes. We model the interference in terms of its type (empirical distribution), and we analyze the consequences of placing constraints on the admissible type. Considering a single interfering link, we characterize the communication-interference capacity region. Then, we look at a scenario where the interference is jointly created by two users allowed to coordinate their actions prior to transmission. In this case, the tradeoff involves communication and interference as well as coordination. We establish an achievable communication-interference region and show that efficiency is significantly improved by coordination.
50.	Blasco-Serrano, Ricardo, et al. (författare) Comparison of Underlay and Overlay Spectrum Sharing Strategies in MISO Cognitive Channels 2012 Ingår i: 2012 7th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications (CROWNCOM). - : IEEE Computer Society. - 9781936968558 ; , s. 224-229 Konferensbidrag (refereegranskat)abstract We consider an extension of the cognitive radio channel model in which the secondary transmitter has to obtain (“learn”) the primary message in a first phase rather than having non-causal knowledge of it. We propose an achievable rate region that combines elements of decode-and-forward relaying with coding for the pure cognitive radio channel model. Moreover, we find the choice of parameters that maximize the secondary rate under a primary rate constraint. Finally, we compare numerically the performance of our system to that of an underlay scheme that combines beamforming, rate splitting, and successive decoding. We observe that although the overlay design provides higher rates, the losses due to the first phase are quite severe. In fact, for the considered scenarios, cleverly designed underlay schemes can provide comparable performance.

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