Vuong V. Mai

Design and performance evaluation of VLC indoor positioning system using optical orthogonal codes

In this paper, a VLC indoor positioning system utilizing optical orthogonal codes (OOCs) is proposed. The use of OOC is to distinguish different transmitted signals at the receiver, the trilateration method then calculate the position of receiver based on these distinguished signals. To expand the scale of system and use efficiently OOC resource, a strategy of reusing/combining codeword is proposed. We also create a combination of simulation and mathematical modeling to investigate the performance of proposed system. Numerical results confirm that the proposed system can achieve a good positioning accuracy level in average.

Performance of TCP over free-space optical atmospheric turbulence channels

This paper presents an analytical study of the performance of transmission control protocol (TCP) over free-space optical (FSO) turbulence channels when the automatic-repeat request, selective-repeat (ARQ-SR) scheme is employed. Different TCP versions, including Tahoe, Reno, and selective acknowledgement, are considered. In the TCP throughput analysis, a three-dimensional Markov model is used. In addition, to analyze the joint effect of ARQ-SR and FSO turbulence channels in terms of both TCP throughput and energy consumption, a newly defined joint throughput ¿ energy-efficiency parameter is analytically derived. In the numerical results, we discuss cross-layer design strategies for the selection of FSO system parameters and the ARQ-SR scheme in order to maximize the TCP throughput and to achieve the trade-off between the energy consumption and the throughput under various conditions of the FSO turbulence channel.

Adaptive multi-rate designs for hybrid FSO/RF systems over fading channels

This paper proposes a concept of adaptive multi-rate (AMR), which jointly employs switching between two links and adaptive rate on each link, for hybrid free-space optical/radio-frequency (FSO/RF) systems. Moreover, to support the operation of AMR, we propose the cross-layer design of AMR switching, which is based on both the physical and link layers with automatic-repeat request (ARQ) scheme. System performance metrics, including frame-error rate, goodput and outage probability, are analytically studied under the presence of atmospheric turbulence and Rician fading in FSO and RF links, respectively. Numerical results quantitatively show how the proposed systems significantly outperform conventional ones with physical layer-based design and/or fixed-rate switching operation.

Hybrid free-space optics/millimeter-wave architecture for 5G cellular backhaul networks

This paper proposes a cost-effective, scalable network architecture, which combines millimeter-wave (MMW) and free space optics (FSO) technologies that can be employed as a complementary solution for pre-deployed optical fiber based 5G cellular backhaul networks.

Performance analysis of TCP over visible light communication networks with ARQ-SR protocol

This paper theoretically studies the performance of transmission control protocol TCP over visible light communications VLC networks when the automatic-repeat request, selective repeat ARQ-SR protocol is employed in the link layer. We analytically derive TCP throughput considering the impact of ARQ-SR parameters and different VLC physical factors, including inter-symbol interference ISI, signal reflection and light power distribution. Numerical results show that TCP throughput is strongly dependent on the location of VLC user due to impacts of ISI and signal reflection. It is also seen that the use of ARQ-SR could significantly improve both the maximum value and the distribution of TCP throughput in the VLC network. Especially, with a proper selection of the number of re-transmissions by the ARQ-SR protocol, the dependence of TCP throughput on user location caused by ISI, light signal reflection and distribution could be effectively remedied. Copyright

Adaptive rate-based MAC protocols design and analysis for integrated FSO/PON networks

This paper proposes two novel medium access control (MAC) protocols, which jointly employ bandwidth allocation and adaptive rate concepts, to enhance the performance of uplink transmission of the integrated free-space optical/passive optical networks (FSO/PON). System performance metrics, including frame-loss rate, goodput and delay, are analytically studied under the presence of atmospheric turbulence. Numerical results quantitatively show how the proposed protocols significantly outperform the conventional one with fixed bandwidth allocation/fixed rate.

Tweaked binary tree algorithm to cope with capture effect and detection error in RFID systems

This paper proposes a new RFID binary tree-based identification protocol, namely Tweaked Binary Tree (TBT), to cope with hidden tag problem caused by capture effect and detection error phenomena. In TBT, the whole identification process is divided into multiple binary tree cycles, and the hidden tags in a cycle are checked and re-transmitted in the first slot of the next one. The average number of slots for a successful detection of a tag, and the tag loss rate, defined as a ratio between the number of missing tags and the whole tag cardinality, are theoretically analyzed. Computer simulations are also performed to validate the theoretical analysis. We also confirm the superiority of the proposed method in comparison with a conventional General Binary Tree (GBT) one.

Performance analysis of parallel FSO/MMW systems with adaptive rate under weather effects

This paper presents a concept of parallel Free-Space Optics/Millimeter-Wave (FSO/MMW) systems, in which adaptive rate is employed in both FSO and MMW links. We newly propose an analytical framework based on Markov chain model for system performance analysis. System performance metrics, including throughput and reliability rate, are analytically studied under the presence of various weather conditions. Numerical results quantitatively show how the adaptive-rate FSO/MMW significantly outperform conventional ones, and how weather conditions affect on the systems performance.

Performance analysis of TCP over free-space optical links with ARQ-SR

This paper presents an analytical study on the performance of transmission control protocol (TCP) over free-space optical (FSO) links when the automatic-repeat request, selective repeat (ARQ-SR) scheme is used for the link layer. Using a three-dimensional (3-D) Markov model, we analytically derive the TCP throughput and energy-throughput efficiency, which is the the ratio between the TCP throughput and the average energy for transmitting an unit data of TCP. In the numerical analysis, we quantitatively discuss the impact of various FSO physical and link layer parameters on the trade-off between the energy consumption and the TCP throughput.

TCP over free-space optical links with ARQ and AMC: A cross-layer performance analysis

This paper presents a comprehensive cross-layer analysis framework on the performance of transmission control protocol (TCP) over free-space optical (FSO) links, which employ the automatic repeat request (ARQ) and adaptive modulation and coding (AMC) schemes. From the framework, we quantify the impacts of different parameters/settings of ARQ, AMC and FSO links on TCP throughput performance. We also discuss several optimization aspects for TCP performance.