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A Numerical Study on Optical Concentrators for Visible Light Communications
Pituk Panthong,Paramin Sangwongngam,Jutaphet Wetcharungsri,Keattisak Sripimanwat,Adisorn Kaewpukdee,Piya Kovintavewat,Lunchakorn Wuttisittikulkij 대한전자공학회 2015 ITC-CSCC :International Technical Conference on Ci Vol.2015 No.6
Optical design has played a key role in the optical wireless communications since it can enhance the gains and the fields of view (FOVs) of the receivers without power consumption. In this paper, we propose an optical front end which is comprised of a multipleradius concave mirror, lens, and a detector so as to enlarge coverage areas of the optical wireless access point for an indoor scenario. The numerical investigation into performance of the proposed and the conventional optical concentrators has been conducted and presented. From the numerical studies, it is clear that although the proposed concentrator offers a smaller gain, it provides a significantly larger FOV in the indoor environment, resulting the substantially large coverage areas. As the proposed optical front end facilitates the ease of the manufacture and the broad coverage, its deployment at the uplink could reduce the installation cost.
Vanichchanunt, Pisit,Sangwongngam, Paramin,Nakpeerayuth, Suvit,Wuttisittikulkij, Lunchakorn The Korea Institute of Information and Commucation 2008 Journal of communications and networks Vol.10 No.1
In this paper, an iterative multiple symbol differential detection for turbo coded differential unitary space-time modulation using a posteriori probability (APP) demodulator is investigated. Two approaches of different complexity based on linear prediction are presented to utilize the temporal correlation of fading for the APP demodulator. The first approach intends to take account of all possible previous symbols for linear prediction, thus requiring an increase of the number of trellis states of the APP demodulator. In contrast, the second approach applies Viterbi algorithm to assist the APP demodulator in estimating the previous symbols, hence allowing much reduced decoding complexity. These two approaches are found to provide a trade-off between performance and complexity. It is shown through simulation that both approaches can offer significant BER performance improvement over the conventional differential detection under both correlated slow and fast Rayleigh flat-fading channels. In addition, when comparing the first approach to a modified bit-interleaved turbo coded differential space-time modulation counterpart of comparable decoding complexity, the proposed decoding structure can offer performance gain over 3 dB at BER of $10^{-5}$.
An alternative state diagram of HDB3
Kampol Woradit,Norrarat Wattanamongkhol,Paramin Sangwongngam,Lunchakorn Wuttisittikulkij 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
This paper presents a new state diagram with the reduced number of system states for HDB3 line coding. Mathematical analysis for its autocorrelation as well as power spectral density are systematically derived in details and compared to existing approaches. It is shown that the proposed model provides an exact solution and the same as known results, thus serving as an alternative and effective means to solve this problem.
Efficient Key Management Protocol for Secure RTMP Video Streaming toward Trusted Quantum Network
Montida Pattaranantakul,Kittichai Sanguannam,Paramin Sangwongngam,Chalee Vorakulpipat 한국전자통신연구원 2015 ETRI Journal Vol.37 No.4
This paper presents an achievable secure videoconferencing system based on quantum key encryption in which key management can be directly applied and embedded in a server/client videoconferencing model using, for example, OpenMeeting. A secure key management methodology is proposed to ensure both a trusted quantum network and a secure videoconferencing system. The proposed methodology presents architecture on how to share secret keys between key management servers and distant parties in a secure domain without transmitting any secrets over insecure channels. The advantages of the proposed secure key management methodology overcome the limitations of quantum point-to-point key sharing by simultaneously distributing keys to multiple users; thus, it makes quantum cryptography a more practical and secure solution. The time required for the encryption and decryption may cause a few seconds delay in video transmission, but this proposed method protects against adversary attacks.
Efficient Rate-Adaptive Reconciliation Based on LDPC Accumulate Codes for Quantum Key Distribution
Tharathorn Phromsa-ard,Patcharapong Treeviriyanupab,Paramin Sangwongngam,Keattisak Sripimanwat,Kamol Kaemarungsi,Pisit Vanichchanunt,Lunchakorn Wuttisittikulkij 대한전자공학회 2015 ITC-CSCC :International Technical Conference on Ci Vol.2015 No.6
In this paper, a rate-adaptive method is proposed an alternative reconciliation protocol by employing the LDPC-accumulate codes to the practical implementation in the quantum key distribution (QKD). The proposed rate-adaptive reconciliation is adapted in the Slepian-Wolf scheme where specific low-density parity-check (LDPC) codes are constructed by accumulated syndrome encoding/decoding. Its objective is to skip the step of quantum bit error rate (QBER) estimation by the traditional key sampling that increases the final secret key length in practice. From the numerical results, the proposed method achieves a good performance in terms of the number of disclosed bits and reconciliation efficiency comparable to the conventional Winnow, Cascade, and fixed-rate compatible LDPC based protocols. Moreover, it can cover the possible cases of error rates in the QKD system. Therefore, method is suitable for the highspeed discrete-variable QKD applications.
Implementation of CIDS - BC- LDPC Decoder on FPGA
Sakdinan Jantarachote,Jutaphet Wetcharungsri,Paul Sikangwan,Paramin Sangwongngam,Keattisak Sripimanwat,Chumnarn Punyasai,Nitin Afzulpurkar 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
This paper introduces an implementation of Low-density parity-check codes (LDPC) regarding to the combination of Cycle-Invariant Difference Set (CIDS) block-circulant (BC) matrix, the λ-min decoding algorithm, and the benefit of using field programmable gate array (FPGA) to reduce the complexity area. The semi-parallel architecture is constructed in order to reach the optimum point of the number of used slice, throughput and the limitation of hardware resources on an FPGA. The architecture is suitable for such a communication systems requiring acceptable performance and expense. As a result, the decoder implemented by this combination will be applicable for various applications.