BDS Mr Phuc Ngoc - Academia.edu (original) (raw)

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Papers by BDS Mr Phuc Ngoc

IET Communications, 2016

In this paper, we investigate the effect of of the primary network on the secondary network when ... more In this paper, we investigate the effect of of the primary network on the secondary network when harvesting energy in cognitive radio in the presence of multiple power beacons and multiple secondary transmitters. In particular, the influence of the primary transmitter's transmit power on the energy harvesting secondary network is examined by studying two scenarios of primary transmitter's location, i.e., the primary transmitter's location is near to the secondary network, where the primary transmitter can interfere the secondary receiver, and the primary transmitter's location is far from the secondary network, where the secondary receiver is free from the interference. In addition, the peak interference constraint at the primary receiver is also considered. In the scenario where the primary transmitter locates near to the secondary network, although secondary transmitter can be benefit from the harvested energy from the primary transmitter, the interference caused by the primary transmitter suppresses the secondary network performance. Meanwhile, in both scenarios, despite the fact that the transmit power of the secondary transmitter can be improved by the support of powerful power beacons, the peak interference constraint at the primary receiver limits this advantage. In addition, the deployment of multiple power beacons and multiple secondary transmitters can improve the performance of the secondary network. The analytical expressions of the outage probability of the secondary network in the two scenarios are also provided and verified by numerical simulations.

EURASIP Journal on Wireless Communications and Networking, 2014

The deployment of antenna subset selection on a per-subcarrier basis in MIMO-OFDM systems could i... more The deployment of antenna subset selection on a per-subcarrier basis in MIMO-OFDM systems could improve the system performance and/or increase data rates. This paper investigates this technique for the MIMO-OFDM systems suffering nonlinear distortions due to high-power amplifiers. At first, some problems pertaining to the implementation of the conventional per-subcarrier antenna selection approach, including power imbalance across transmit antennas and noncausality of antenna selection criteria, are identified. Next, an optimal selection scheme is devised by means of linear optimization to overcome those drawbacks. This scheme optimally allocates data subcarriers under a constraint that all antennas have the same number of data symbols. The formulated optimization problem to realize the constrained scheme could be applied to the systems with an arbitrary number of multiplexed data streams and with different antenna selection criteria. Finally, a reduced complexity strategy that requires smaller feedback information and lower computational effort for solving the optimization problem is developed. The efficacy of the constrained antenna selection approach over the conventional selection approach is analyzed directly in nonlinear fading channels. Simulation results demonstrate that a significant improvement in terms of error performance could be achieved in the proposed system with a constrained selection compared to its counterpart.

2012 IEEE 75th Vehicular Technology Conference (VTC Spring), 2012

ABSTRACT In this paper, the application of space time trellis codes to multiband orthogonal frequ... more ABSTRACT In this paper, the application of space time trellis codes to multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) systems is investigated. We propose a coding scheme that could fully exploit all the available channel diversity, including space diversity, frequency diversity and inter-subband diversity. Performance of the proposed system is compared with that of the conventional MB-OFDM UWB system in terms of packet error rate (PER). Simulation results show that this system outperforms the conventional one. As an example, an improvement of at least 5 dB at PER=10-2 could be achieved over the IEEE 802.15.3a channel models of CM1 and CM2 in the system equipped with only two transmit antennas and one receive antenna. Moreover, the system performance could be further improved when the number of antennas and/or the number of trellis states is increased.

2014 International Symposium on Wireless Personal Multimedia Communications (WPMC), 2014

In this paper, we investigate energy-efficiency in antenna selection OFDM-based systems. We show ... more In this paper, we investigate energy-efficiency in antenna selection OFDM-based systems. We show that an OFDM system with conventional antenna selection approaches, including per-subcarrier selection (i.e., selecting antennas independently for each subcarrier) and bulk-selection (i.e., choosing the same antennas for all subcarriers), suffers from a significant loss in energy-efficiency. To achieve a better energy-efficiency performance, we propose an adaptive antenna selection scheme where both the number of active RF (radio frequency) chains and the antenna indices are selected depending on the channel condition. This selection scheme could be implemented by exhaustive search. Moreover, we develop an algorithm that achieves a nearoptimal performance with much lower complexity when the number of antennas is large, compared to the (optimal) exhaustive search method. Simulation results demonstrate a significant improvement in terms of energy-efficiency in the proposed system compared to the conventional counterparts.

Wind Farm - Impact in Power System and Alternatives to Improve the Integration, 2011

Wind Farm-Impact in Power System and Alternatives to Improve the Integration 110 work considers o... more Wind Farm-Impact in Power System and Alternatives to Improve the Integration 110 work considers optimal operation of wind storage system as an optimization problem that deals with primary sources, storage capacity as well as demand. The main objective is to meet grid requirements in term of limiting the fluctuations and providing possible ancillary services. The intermittency management will be assessed into two steps: anticipation phase and reactivity phase. The first one, which will generally be done at Month-1, Week-1 or Day-1, consists in using forecast information (weather, network demand …) to define the optimal operation schedule for wind-storage system. On real time operation, the system has to deal with possible vagaries and take the right adjustment control with actual capacity. The problem is complex with numerous discrete control variables and continuous ones. A mixed-integer linear programming (MILP) is used to efficiency solve the problem. An example is given to illustrate the proposed method. Results indicate that wind power with storage can meet the network requirements while best ensure its profits. Results also show that the proposed optimal operation strategy which limits considerably the fluctuations on power system will facilitate the integration of more wind power. In this chapter, we deal with a wind system combined with a hydraulic storage (we name the system W+S since now) where the input is the network demand power and the output is the provided wind power. This system has to response to the management requirements in taking into account the wind vagaries, the storage and de-storage capacity, the energetic cost of the flux transfer and highlighting economical efficiency.