| 1. |
- Biswas, Sinchan, 1988-
(författare)
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Distributed Detection and Its Applications with Energy Harvesting Wireless Networks
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the advent and widespread applications of high data-rate wireless services and devices, two of the fundamental resources in wireless communication have become extremely important and are scarce. These two resources are bandwidth and energy respectively. To tackle the problem of the ever-growing requirements of bandwidth, the paradigm of cognitive radio has been proposed in the literature where the users without any license are capable of utilizing the wireless radio spectrum allocated to the licensed user when it is idle. The performance of such a dynamic spectrum allocation policy depends heavily on the unlicensed users' ability to detect the vacancy in a licensed user's radio spectrum. Different types of detection algorithms have been investigated in the literature for this purpose. Some classic detection techniques like energy detection, matched filter detection, cyclo-stationary detector, generalized likelihood ratio test detector have found significant applications in sensing the licensed spectrum. These group of detection techniques focuses on collecting samples and performing the detection in a non-sequential fashion. The sequential counterpart of such techniques which are implemented sequentially at every time instant has also been studied extensively.Tackling the evergrowing energy requirement has been the other major challenge for wireless communication. To address this issue, a significant amount of research has been dedicated to the idea of incorporating the capability of energy harvesting in wireless devices. Further research in this domain has also introduced the idea of wireless energy sharing, where individual users are additionally capable of sharing energy with each other. The problem with such systems is the inherently stochastic nature of the energy harvesting process. Furthermore, there are practical limitations of the size of the battery for each user, which limits the amount of energy that can be stored at a particular time instant.Motivated by these two factors, the work presented in this thesis has its focus on cognitive radio networks with energy harvesting capability. In the aforementioned network, unlicensed users are concerned with achieving two fundamental goals. Firstly, they want to efficiently utilize the radio spectrum when the licensed user is not active, which results in the sum-throughput maximization problem with energy harvesting constraint. We have also investigated this problem where individual unlicensed users are capable of sharing energy with each other. Secondly, they want to detect the change in the activity in the licensed user spectrum as soon as possible. Motivated by this goal, we have investigated the problem of change point detection delay minimization in wireless sensor networks with energy harvesting constraints in a decentralized setting. Furthermore, we have explored the detection delay parameter for the decentralized settings with local decisions with similar constraints of energy availability due to energy harvesting.
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| 2. |
- Ciuonzo, Domenico, et al.
(författare)
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Massive MIMO Channel-Aware Decision Fusion
- 2015
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 63:3, s. 604-619
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we provide a study of channel-aware decision fusion (DF) over a "virtual" multiple-input multiple-output (MIMO) channel in the large-array regime at the DF center (DFC). The considered scenario takes into account channel estimation and inhomogeneous large-scale fading between the sensors and the DFC. The aim is the development of (widely) linear fusion rules, as opposed to the unsuitable optimum log-likelihood ratio (LLR). The proposed rules can effectively benefit from performance improvement via a large array, differently from existing suboptimal alternatives. Performance evaluation, along with theoretical achievable performance and complexity analysis, is presented. Simulation results are provided to confirm the findings. Analogies and differences with uplink communication in a multiuser (massive) MIMO scenario are underlined.
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| 3. |
- Ciuonzo, Domenico, et al.
(författare)
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Massive MIMO meets decision fusion : Decode-and-fuse vs. decode-then-fuse
- 2014
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Ingår i: 2014 IEEE 8TH Sensor Array and Multichannel Signal Processing Workshop (SAM). - 9781479914814 ; , s. 265-268
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Konferensbidrag (refereegranskat)abstract
- We study channel-aware decision fusion over a multiple-input multiple-output (MIMO) channel in the large-array regime at the decision-fusion center (DFC). Inhomogeneous large-scale fading between the sensors and the DFC is consider in addition to the small-scale fading, and pilot-based channel estimation is performed at the DFC. Linear processing techniques are analyzed in order to design low-complexity alternatives to the optimum log-likelihood ratio test (LLRT). Performance evaluation based on Monte Carlo simulations are presented.
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| 4. |
- Hammarberg, Peter, et al.
(författare)
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EXIT chart evaluation of a receiver structure for multi-user multi-antenna OFDM systems
- 2009
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Ingår i: Proc. IEEE Global Telecommunications Conference (GLOBECOM) 2009. - 9781424441488 ; , s. 2402-2407
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Konferensbidrag (refereegranskat)abstract
- In this paper we evaluate, by means of Extrinsic Information Transfer (EXIT) charts, an iterative receiver that has emerged as a promising candidate for non-coherent multi-user multi-antenna OFDM systems. The receiver performs parallel interference cancellation (followed by linear filtering) and channel estimation, using soft symbols obtained from a bank of single-user decoders. For the sake of conceptual clarity we study a system with two single antenna users and a receiver with two antennas, and we demonstrate how the convergence behavior of the receiver can be visualized using paired three dimensional EXIT surfaces. Our results show that the actual decoder trajectories obtained through simulations are well predicted from the EXIT charts. For the iterative receiver under investigation we identify a very specific problem with EXIT chart generation; the EXIT curve for the inner component decoder depends on the outer encoder. To handle this problem we propose a modification to the iterative receiver which solves the aforementioned problem; the performance degradation is demonstrated to be small.
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| 5. |
- Hammarberg, Peter, et al.
(författare)
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On the performance of iterative receivers for interfering MIMO-OFDM systems in measured channels
- 2008
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Ingår i: 42nd Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781424429400 ; , s. 141-145
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the gains harvested through base station cooperation in the up-link for a multi-user (MU) Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system, operating in a real indoor environment. The base stations perform joint detection using an iterative receiver that carries out multi-user detection and channel estimation via soft information from the single-user decoders. Performance evaluation is carried out using real channels from an indoor dynamic dual MIMO link measurement campaign. The measured scenario represent a real life situation where two users communicate with two base stations, each with two antennas, in an environment resembling a shopping mall or an airport terminal. System performance is evaluated in terms of both Bit-Error Rate (BER) vs. Signal-to-Interference Ratio (SIR) and Cumulative Distribution Functions (CDF) for the instantaneous BER. Also, the impact of using soft information in the channel estimation is analyzed.
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| 6. |
- Panigrahi, Smruti Ranjan, 1983-
(författare)
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Unraveling the potential of Wireless Sensors in the age of Industry 4.0
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human civilization is now staring at the fourth industrial revolution, where wireless technologies will play a pivotal role in its success. Wireless sensors’ role is also becoming more significant in the present day to facilitate industrial automation and manufacturing processes and address health, safety, and environmental concerns. However, wireless communication is primarily unreliable due to noise, interference, and channel fading. Several factors, like hardware quality of the sensors, imperfect calibration, harsh environment, and deployment locations, can also affect the sensors’ observation, which throws further challenges for information reliability and latency. These challenges must be addressed urgently for the success of Industry 4.0.The scope of this Ph.D. research works is broadly divided into two research problems. The first research problem, this dissertation investigates, is how to retrieve and process the local detection of wireless sensors in critical industrial applications. Diversity techniques are known to improve the reliability of wireless communication. Therefore, various spatial diversity techniques using an antenna array with a large number of elements at the receiver are investigated first to find out the suitability of wireless communication for critical industrial applications. Moreover, in order to improve sensors’ detection performance, distributed detection methods are popularly used. This Ph.D.thesis proposes techniques and algorithms to transmit and fuse local decisions from non-identical wireless sensors, e.g., sensors with different detection capabilities. The fusion center utilizes the spatial diversity or spatial multiplexing based scheme to retrieve the sensors’ local decisions.In order to design a reliable wireless communication system, it is highly desirable to understand the channel characteristics of the wireless medium. The second research problem this dissertation address is to characterize the radio propagation channel in one of the millimeter wave frequency bands. Millimeter wave wireless technologies bring several benefits, which can further revolutionize the industrial manufacturing and automation processes. In this.D. research work, the radio channel measurements were carried out at the24 GHz ISM band in various industrial environments within Gävle, Sweden, with the help of highly competent in-house assembled affordable testbeds. Several radio propagation aspects, like, the large scale fading, small scale fading, multipath propagation, and Doppler effect, are studied.
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| 7. |
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| 8. |
- Rossi, Pierluigi Salvo, et al.
(författare)
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Iterative Joint Channel Estimation and Multiuser Detection for Wireless MIMO-OFDM Systems: Performance in a Real Indoor Scenario
- 2007
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Ingår i: Proc. International Symposium on Wireless Communication Systems. - 9781424409792 ; , s. 772-776
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Konferensbidrag (refereegranskat)abstract
- An iterative receiver for Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) wireless systems is presented and tested on channel measurements from a real indoor scenario. The receiver jointly performs channel estimation and multiuser detection, with soft information iteratively provided by the singleuser decoders. Results for the performance are presented in terms of Bit Error Rate (BER) and relative Minimum Mean Square Error (MMSE) vs Signal-to-Noise Ratio (SNR). Comparison with the Single-User Bound (SUB) shows a loss in performance due to frequency correlation.
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| 9. |
- Salvo Rossi, Pierluigi, et al.
(författare)
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Linear MMSE estimation of time-frequency variant channels for MIMO-OFDM systems
- 2011
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Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 91:5, s. 1157-1167
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes two low-complexity two-dimensional channel estimators for MIMO-OFDM systems derived from a joint time–frequency channel estimator. The estimators exploit both time and frequency correlations of the wireless channel via use of Slepian-basis expansions. The computational saving comes from replacing a two-dimensional Slepian-basis expansion with two serially concatenated one-dimensional Slepian-basis expansions. Performance in terms of normalized mean square error (NMSE) vs. signal-to-noise ratio (SNR) is analyzed via numerical simulations and compared with the original estimator. The analysis of the performance takes into account the impact of both system and channel parameters. The estimators are finally tested when used within the loop of an iterative receiver for MIMO-OFDM systems.
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| 10. |
- Salvo Rossi, Pierluigi, et al.
(författare)
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Performance of an Iterative Multi-User Receiver for MIMO-OFDM Systems in a Real Indoor Scenario
- 2008
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Ingår i: [Host publication title missing]. - 1930-529X. - 9781424423248
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Konferensbidrag (refereegranskat)abstract
- This paper aims at validation of an iterative receiver for multiple-input multiple-output with orthogonal frequency division multiplexing (MIMO-OFDM) systems using real-measurement channel data from an indoor scenario. The receiver performs iterative multi-user detection (MUD) and Channel Estimation (CE) via soft information from the single- user decoders. The channel measurements were performed for a dynamic dual MIMO link scenario. The case with two users with multiple antennas interfering each other is considered. CE at the receiver exploits the frequency correlation of the MIMO link. Simulation results for the performance are shown in terms of bit- error rate (BER) vs. signal-to-noise ratio (SNR). Performance for the whole system are provided and compared with respect to the case of perfect channel-state information (PCSI) at the receiver, as well as for the single user. We also provide an analysis of BER with respect to signal-to-interference ratio (SIR). CE performance are evaluated in terms of normalized mean square error (NMSE).
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