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A Novel Scheme for Seamless Hand-off in WMNs
( Hung Quoc Vo ),( Daesun Kim ),( Choong Seon Hong ),( Sungwon Lee ),( Eui-nam Huh ) 한국인터넷정보학회 2009 KSII Transactions on Internet and Information Syst Vol.3 No.4
Although current wireless mesh network (WMN) applications experience a perceptually uninterrupted hand-off, their throughput after the hand-off event may be significantly degraded due to the low available bandwidth of the mobile client`s new master. In this paper, we propose a novel mobility management scheme for 802.11-based WMNs that enables both seamless hand-off for transparent communications, and bandwidth awareness for stable application performance after the hand-off process. To facilitate this, we (i) present a new buffer moment in support of the fast Layer-2 hand-off mechanism to cut the packet loss incurred in the hand-off process to zero and (ii) design a dynamic admission control to grant joining accepts to mesh clients. We evaluate the benefits and drawbacks of the proposal for both UDP and TCP traffic, as well as the fairness of the proposal. Our results show that the new scheme can not only minimize hand-off latency, but also maintain the current application rates of roaming users by choosing an appropriate new master for joining.
Bioactive Constituents from the n-Butanolic Fraction of Aruncus dioicus var. kamtschaticus
Quoc Hung Vo,Phi Hung Nguyen,Bing Tian Zhao,Yen Nguyen Thi,Duc Hung Nguyen,김원일,서유민,민병선,우미희 한국생약학회 2014 Natural Product Sciences Vol.20 No.4
Six compounds were isolated from the n-BuOH fraction of the aerial parts of Aruncus dioicus var. kamtschaticus including: sambunigrin (1), prunasin (2), aruncide A (3), aruncide C (4), 1-O-caffeoyl-β-D-glucopyranose (5), and caffeic acid (6). Their structures were confirmed by comparing the spectral data with those reported in the literature. The isolated compounds (1 - 6) were then examined for their cytotoxic effects towards MCF-7, HL-60, and HeLa cancer cell lines, as well as their DPPH radical scavenging activity. The results indicated that compound 4 possessed the strongest inhibitory effect toward HeLa cell line with IC50 value of 5.38 ± 0.92 μM. Compound 3 possessed selective cytotoxic activity on HL-60 cells with IC50 value of 6.27 ± 0.17 μM, compound 5 was found as the best in inhibiting proliferation with IC50 value of 2.25 ± 0.09 μM, and the other compounds showed significant inhibition with IC50 values ranging from 6.10 to 11.27 μM. Compound 5 also displayed the strongest cytotoxic effect toward MCF-7 cell line (IC50 4.32 ± 0.15 μM). Both 5 and 6 demonstrated strong radical scavenging activity (IC50 6.87 ± 0.03 and 4.33 ± 0.22 μM, respectively). Compounds 1 and 5 were isolated for the first time from this plant.
Improving Overall WMN Performance in Peak Times Using Load-sharing Aware Gateways
( Hung Quoc Vo ),( Tran Thanh Dai ),( Choong Seon Hong ) 한국정보처리학회 2007 한국정보처리학회 학술대회논문집 Vol.14 No.1
In recent years, Wireless Mesh Network (WMN) is a compelling topic to many network researchers due to its low cost in deployment, ease and simplicity in installation and scalability and robustness in operation. In WMN, Gateway nodes (Access Point-AP) are in charge of steering the traffic from the external network (e.g. Internet…) to client devices or mesh clients. The limited bandwidth of wireless links between Gateways and intermediate mesh routers makes the Gateways becomes the bottleneck of the mesh network in both uplink stream and downlink stream. In this paper, we propose a mechanism to permit Gateways collaboratively work to manipulate the traffic to fit our network. They will move the traffic from congested links to the unused capacityon other links.
Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI
Hung Nguyen-Le,Vien Nguyen-Duy-Nhat,Chien Tang-Tan,Vo Nguyen Quoc Bao 한국통신학회 2016 Journal of communications and networks Vol.18 No.5
This paper studies the problem of precoding and post-coding design for multicellmultiuser downlink transmissions in theabsence of perfect channel state information (CSI). Using statisti-cal information of imperfect CSI, an iterative multiuser multicelltransceiver design is formulated by minimizing the mean squarederror (MSE) cost function of signal and leakage interference underper-base station power constraint (PBPC). The convergence of theiterative precoding and postcoding algorithm is verified by analyt-ical and empirical results. The proposed precoding and postcodingalgorithm offers a low computational complexity and robustnessagainst CSI imperfection.
Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI
Nguyen-Le, Hung,Nguyen-Duy-Nhat, Vien,Tang-Tan, Chien,Bao, Vo Nguyen Quoc The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5
This paper studies the problem of precoding and post-coding design for multicell multiuser downlink transmissions in the absence of perfect channel state information (CSI). Using statistical information of imperfect CSI, an iterative multiuser multicell transceiver design is formulated by minimizing the mean squared error (MSE) cost function of signal and leakage interference under per-base station power constraint (PBPC). The convergence of the iterative precoding and postcoding algorithm is verified by analytical and empirical results. The proposed precoding and postcoding algorithm offers a low computational complexity and robustness against CSI imperfection.
Jong-Wook Lee,Duong Huynh Thai Vo,Quoc-Hung Huynh,Sang Hoon Hong IEEE 2011 IEEE transactions on industrial electronics Vol.58 No.6
<P>We present a fully integrated small-size HF-band passive RF identification (RFID) tag chip with authentication and security functions. The design of the RF transceiver and digital control of the tag IC is based on the International Organization for Standardization-14443 type-B protocol. The design of the key analog part of the tag IC is presented, which includes a robust demodulator for 10% amplitude shift keying envelope detection, a high-quality random number generator, and a voltage regulator that can handle a range of output load currents. To implement the secure data transaction with a reader, a 128-b advanced encryption standard (AES) with a new cyclic key generation is used for the data encryption and decryption. An on-chip 4-kb electrically erasable programmable ROM (EEPROM) is used to support the AES operation, tag identification, and tag self-destruction. The read and write accesses of the EEPROM are performed using a 128-b wide buffer with self-timed bursts. The tag chip is fabricated in a one-poly six-metal low-power 0.18-μm CMOS process with a CoSi<SUB>2</SUB> Schottky diode and EEPROM process. Using the scaled-down CMOS technology, the size of the tag chip is only 1.1 × 1 mm<SUP>2</SUP>, providing a cost-effective solution for everyday RFID applications.</P>