| 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. |
|
|
| 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.
|
|
