| 1. |
- Tran, Thi-Thuy-Quynh, et al.
(author)
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Network Coding with Multimedia Transmission and Cognitive Networking: An Implementation based on Software-Defined Radio
- 2020
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In: REV Journal on Electronics and Communications. ; 10:3-4, s. 72-84
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Journal article (peer-reviewed)abstract
- Network coding (NC) is considered a breakthrough to improve throughput, robustness, and security of wireless networks. Although the theoretical aspects of NC have been extensively investigated, there have been only few experiments with pure NC schematics. This paper presents an implementation of NC under a two-way relay model and extends it to two non-straightforward scenarios: (i) multimedia transmission with layered coding and multiple-description coding, and (ii) cognitive radio with Vandermonde frequency division multiplexing (VFDM). The implementation is in real time and based on software-defined radio (SDR). The experimental results show that, by combining NC and source coding, we can control the quality of the received multimedia content in an on-demand manner. Whereas in the VFDM-based cognitive radio, the quality of the received content in the primary receiver is low (due to imperfect channel estimation) yet retrievable. Our implementation results serve as a proof for the practicability of network coding in relevant applications.
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| 2. |
- Duong, Quang Trung, et al.
(author)
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Ergodic Capacity of Cooperative Networks Using Adaptive Transmission and Selection Combining
- 2009
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Conference paper (peer-reviewed)abstract
- Closed-form expressions for channel capacity of repetition-based cooperative networks under adaptive transmission with selection combining are presented under the assumption of independent Rayleigh fading. Specifically, three different adaptive techniques are investigated: optimal simultaneous power and rate adaptation (OPRA), constant power with optimal rate adaptation (OPA) and channel inversion with fixed rate (TIFR). Among them, for an arbitrary number of relays, TIFR gives the worst channel capacity; OPRA gives the best channel capacity and ORA has a channel capacity quality in between the others. The analysis results, based on the upper and lower bound of the end-to-end SNR, agree very well with the simulated results and definitely show the impact of selection combining on the calculated channel capacity per unit bandwidth
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| 3. |
- Edgren, Gustaf, et al.
(author)
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Improving health profile of blood donors as a consequence of transfusion safety efforts
- 2007
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In: Transfusion. - : Wiley. - 0041-1132 .- 1537-2995. ; 47:11, s. 2017-2024
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Journal article (peer-reviewed)abstract
- Background: Transfusion safety rests heavily on the health of blood donors. Although they are perceived as being healthier than average, little is known about their long-term disease patterns and to which extent the blood banks' continuous efforts to optimize donor selection has resulted in improvements. Mortality and cancer incidence among blood donors in Sweden and Denmark was investigated. Study Design and Methods: All computerized blood bank databases were compiled into one database, which was linked to national population and health data registers. With a retrospective cohort study design, 1,110,329 blood donors were followed for up to 35 years from first computer-registered blood donation to death, emigration, or December 31, 2002. Standardized mortality and incidence ratios expressed relative risk of death and cancer comparing blood donors to the general population. Results: Blood donors had an overall mortality 30 percent lower (99% confidence interval [CI] 29%-31%) and cancer incidence 4 percent lower (99% CI 2%-5%) than the background population. Mortality rates and cancer incidence were lowest for outcomes that are recognized as being related to lifestyle factors such as smoking or to the selection criteria for blood donation. Blood donors recruited in more recent years exhibited a lower relative mortality than those who started earlier. Conclusion: Blood donors enjoy better than average health. Explicit and informal requirements for blood donation in Scandinavia, although mostly of a simple nature, have successfully refined the selection of a particularly healthy subpopulation.
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| 4. |
- Hoang, Van-Phuc, et al.
(author)
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An Energy Efficient, Long Range Sensor System for Real-Time Environment Monitoring
- 2023
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In: Lecture Notes on Data Engineering and Communications Technologies. - Singapore : Springer Science and Business Media Deutschland GmbH. ; , s. 823-830
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Book chapter (peer-reviewed)abstract
- Vietnam is among the top countries in the world at risk of natural hazards so that efficient real-time environment monitoring is becoming essential. The continuous development in information and communication technology is inspiring the development of the smart monitoring systems for environmental management and protection. This paper presents an energy efficient, long range sensor system for Internet of Things (IoT)-based smart environment monitoring and early warning. The proposed system combines the novel energy efficient temperature. Beat sensors integrated with the LoRaWAN communication protocol and web interface. The experimental results are achieved to clarify the efficiency of the proposed sensor system and its potential applications in the real systems.
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| 5. |
- Kim, Kyeong Jin, et al.
(author)
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Performance Analysis of Cognitive Spectrum-Sharing Single-Carrier Systems With Relay Selection
- 2012
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In: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 60:12, s. 6435-6449
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Journal article (peer-reviewed)abstract
- In this paper, we analyze the performance of cooperative spectrum sharing single-carrier (SC) relay systems. Taking into account the peak interference power at the primary user (PU) and the maximum transmit power at the secondary user (SU) network, two separate power allocation constraints are formed. For a two-hop decode-and-forward (DF) relaying protocol and two power allocation constraints, two relay selection schemes, namely, a full-channel state information (CSI)-based best relay selection (BRS) and a partial CSI-based best relay selection (PBRS), are proposed. The distributions of the end-to-end signal-to-noise ratios (e2e-SNRs) for the four cases are derived first, and then their outage probabilities and asymptotic outage probabilities are derived in closed-form. The derived asymptotic outage probabilities are utilized to see different diversity gains. Monte Carlo simulations have verified the derived diversity gains for the four different cases. We also present upper bounds on the ergodic capacities for two particular cases.
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| 6. |
- Ngo, Hien Quoc, 1984-, et al.
(author)
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Energy Efficiency Optimization for Cell-Free Massive MIMO
- 2017
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In: 2017 IEEE 18TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509030095 - 9781509030101
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Conference paper (peer-reviewed)abstract
- This paper considers a time-division duplex cell-free massive multiple-input multiple-output downlink with imperfect channel station information and conjugate beamforming scheme. The total energy efficiency is investigated taking into account the hardware power consumption and the backhaul power consumption. We propose an optimal power allocation algorithm which aims to maximize the total energy efficiency, under a per-access point power constraint and a per-user spectral efficiency constraint. This optimization problem can be approximately solved via a sequence of second-order cone programs. Compared with the case of without power control, our proposed power allocation scheme can double the total energy efficiency. Furthermore, we show that, when the number of access points is large, the backhaul power consumption affects significantly the total energy efficiency.
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| 7. |
- Ngo, Hien Quoc, et al.
(author)
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On the Total Energy Efficiency of Cell-Free Massive MIMO
- 2018
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In: IEEE Transactions on Green Communications and Networking. - : IEEE. - 2473-2400. ; 2:1, s. 25-39
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Journal article (peer-reviewed)abstract
- We consider the cell-free massive multiple-input multiple-output (MIMO) downlink, where a very large number of distributed multiple-antenna access points (APs) serve many single-antenna users in the same time-frequency resource. A simple (distributed) conjugate beamforming scheme is applied at each AP via the use of local channel state information (CSI). This CSI is acquired through time-division duplex operation and the reception of uplink training signals transmitted by the users. We derive a closed-form expression for the spectral efficiency taking into account the effects of channel estimation errors and power control. This closed-form result enables us to analyze the effects of backhaul power consumption, the number of APs, and the number of antennas per AP on the total energy efficiency, as well as, to design an optimal power allocation algorithm. The optimal power allocation algorithm aims at maximizing the total energy efficiency, subject to a per-user spectral efficiency constraint and a per-AP power constraint. Compared with the equal power control, our proposed power allocation scheme can double the total energy efficiency. Furthermore, we propose AP selections schemes, in which each user chooses a subset of APs, to reduce the power consumption caused by the backhaul links. With our proposed AP selection schemes, the total energy efficiency increases significantly, especially for large numbers of APs. Moreover, under a requirement of good quality-of-service for all users, cell-free massive MIMO outperforms the colocated counterpart in terms of energy efficiency.
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| 8. |
- Tran, Nguyen Nam, et al.
(author)
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Training Design upon Mutual Information for Spatially Correlated MIMO-OFDM
- 2010
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Conference paper (peer-reviewed)abstract
- Our goal in this paper is to address channel estimations for spatially correlated multiple-input multiple-output with orthogonal frequency-division multiplexing (MIMO-OFDM) system upon the conditional mutual information (CMI). The design of superimposed training signal by maximizing the channel CMI is fully investigated. First, the interior-point-method is employed to obtain the optimal superimposed training signals for the general case of channel correlations. In addition, two efficient approximate designs are also proposed by invoking Karush-Kuhn-Tucker condition for optimality of convex programming. The first approximate design is obtained by proposing a iterativebisection-procedure (IBP), while the second one is in “waterfilling” closed-form. Numerical results demonstrate the excellent performance of the proposed designs and give the connection between channel estimation error and mutual information.
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