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    ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ๋ฅผ ์œ„ํ•œ ์ „๋ ฅ์„  ํ†ต์‹ ์˜ ์‹ ๋ขฐ์„ฑ ํ–ฅ์ƒ ๊ธฐ๋ฒ• ์—ฐ๊ตฌ

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์ „๊ธฐยท์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€, 2014. 8. ๊น€์„ฑ์ฒ .์ง€๊ตฌ ์˜จ๋‚œํ™”, ์ฆ๊ฐ€ํ•˜๋Š” ์—๋„ˆ์ง€ ์š”๊ตฌ ๋ฐ ์ตœ๋Œ€ ๋ถ€ํ•˜์— ๋”ฐ๋ฅธ ์œ„ํ—˜ ๋ฌธ์ œ ๋“ฑ์„ ํ•ด๊ฒฐํ•˜๊ธฐ ์œ„ํ•ด, ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ ๊ตฌ์ถ•์„ ์œ„ํ•œ ๋งŽ์€ ๋…ธ๋ ฅ๋“ค์ด ์ง„ํ–‰ ์ค‘์ด๋‹ค. ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ๋ฅผ ๊ตฌํ˜„ํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ํ–ฅ์ƒ๋œ ์ •๋ณดํ†ต์‹  ๊ธฐ์ˆ ์ด ํ•„์š”ํ•˜๋ฉฐ, ์ด๋Š” ํ†ต์‹  ๋„คํŠธ์›Œํฌ๋ฅผ ํ†ตํ•œ ์•ˆ์ •์„ฑ ์žˆ๋Š” ๋ฐ์ดํ„ฐ ์ „์†ก ์—ฌ๋ถ€์— ๋‹ฌ๋ ค์žˆ๋‹ค. ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ๋ฅผ ์œ„ํ•œ ์—ฌ๋Ÿฌ ํ†ต์‹ ๊ธฐ์ˆ  ํ›„๋ณด ์ค‘ ์ „๋ ฅ์„ ํ†ต์‹  (PLC), ํŠนํžˆ ์ค‘์ „์•• (MV) ์ „๋ ฅ์„  ์ƒ์˜ ๊ณ ์† PLC์— ์ง‘์ค‘ํ•˜์˜€๋‹ค. ์ „๋ ฅ์„  ํ†ต์‹  ๋„คํŠธ์›Œํฌ์˜ ์‹ ๋ขฐ์„ฑ์€ ์ „๋ ฅ์„ ์ด ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ์˜ ํ†ต์‹  ๋งค์ฒด๋กœ ์˜ฌ๋ฐ”๋ฅด๊ฒŒ ๋™์ž‘ํ•˜๊ธฐ ์œ„ํ•œ ์„ ๊ฒฐ ์กฐ๊ฑด์ด๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ์ „๋ ฅ์„  ํ†ต์‹ ์„ ๋ณด๋‹ค ์‹ ๋ขฐ์„ฑ ์žˆ๊ณ  ๊ฐ•๊ฑดํ•˜๊ฒŒ ๋งŒ๋“ค๊ธฐ ์œ„ํ•œ ๋ฐฉ์•ˆ์— ๋Œ€ํ•˜์—ฌ ์—ฐ๊ตฌํ•œ๋‹ค. ์ด๋ฅผ ์œ„ํ•ด OFDM ๊ธฐ๋ฐ˜์˜ ์ „๋ ฅ์„  ํ†ต์‹  ์‹œ์Šคํ…œ์—์„œ ์ตœ๋Œ€๋น„ํ•ฉ์„ฑ (MRC) ๋‹ค์ด๋ฒ„์‹œํ‹ฐ ๊ตฌ์กฐ๋ฅผ ๊ณ ์•ˆํ•œ๋‹ค. ์ด๋Ÿฌํ•œ ์‹œ์Šคํ…œ์—์„œ ์ตœ๋Œ€๋น„ํ•ฉ์„ฑ ๋‹ค์ด๋ฒ„์‹œํ‹ฐ ์ด๋“์„ ์ตœ๋Œ€ํ™”ํ•˜๊ธฐ ์œ„ํ•œ ์ตœ์ ์˜ ๋ถ€๋ฐ˜์†กํŒŒ ํŽ˜์–ด๋ง (subcarrier pairing) ๊ธฐ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ๋ชจ์˜์‹คํ—˜์„ ํ†ตํ•ด ์ œ์•ˆํ•˜๋Š” ๊ธฐ๋ฒ•์˜ ์„ฑ๋Šฅ ํ–ฅ์ƒ ์—ฌ๋ถ€๋ฅผ ๊ฒ€์ฆํ•œ๋‹ค. ๋‹ค์ด๋ฒ„์‹œํ‹ฐ ์ด๋“์€ ์ฃผํŒŒ์ˆ˜ ํšจ์œจ์˜ ๊ฐ์†Œ๋ฅผ ์œ ๋ฐœํ•œ๋‹ค. ์•ž์˜ ์ œ์•ˆ๋œ ๋ถ€๋ฐ˜์†กํŒŒ ํŽ˜์–ด๋ง ๊ธฐ๋ฒ•์œผ๋กœ ์ธํ•ด ๋ณธ์งˆ์ ์œผ๋กœ ๋ฐœ์ƒํ•˜๋Š” ์ฃผํŒŒ์ˆ˜ ํšจ์œจ ๊ฐ์†Œ๋ฅผ ํ•ด๊ฒฐํ•˜๊ธฐ ์œ„ํ•ด, ๋ฌด์„  MIMO ์ฑ„๋„์˜ ์ „์ฒ˜๋ฆฌ (precoding) ๊ธฐ๋ฒ•์„ ์ ์šฉํ•œ๋‹ค. ๋ชจ์˜์‹คํ—˜ ๊ฒฐ๊ณผ๋ฅผ ํ†ตํ•ด, ๋†’์€ ๋ณ€์กฐ ์ง€์ˆ˜๋กœ ํŽ˜์–ด๋ง ๊ธฐ๋ฒ•์„ ์ด์šฉํ•˜๋Š” ๊ฒƒ์ด ๋งค์šฐ ๋งŽ์€ ๊ณ„์‚ฐ๋Ÿ‰์ด ํ•„์š”ํ•œ ์ „์ฒ˜๋ฆฌ ๊ธฐ๋ฒ•๊ณผ ๋น„๊ตํ•˜์—ฌ ์œ ์‚ฌํ•œ ์„ฑ๋Šฅ์„ ๋‚˜ํƒ€๋ƒ„์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ๋‹ค์Œ์œผ๋กœ ์ตœ๋Œ€๋น„ํ•ฉ์„ฑ ๊ธฐ๋ฐ˜ ์ตœ์  ๋ถ€๋ฐ˜์†กํŒŒ ํŽ˜์–ด๋ง ๊ธฐ๋ฒ•์„ ์ „๋ ฅ์„ /๋ฌด์„  ๋‹ค์ด๋ฒ„์‹œํ‹ฐ ์‹œ์Šคํ…œ์— ํ™•์žฅํ•œ๋‹ค. ์ด ์‹œ์Šคํ…œ์—์„œ ์ „๋ ฅ์„ ๊ณผ ๋ฌด์„ ์‹œ์Šคํ…œ์˜ ๊ฐ ๋ถ€๋ฐ˜์†กํŒŒ๋“ค์€ ์ง์„ ์ด๋ฃจ์–ด ์ตœ๋Œ€๋น„ํ•ฉ์„ฑ์„ ์ˆ˜ํ–‰ํ•œ๋‹ค. ์ „์ฒด ๋ฐ์ดํ„ฐ ์ „์†ก๋ฅ ์„ ์ตœ๋Œ€ํ™”ํ•˜๊ธฐ ์œ„ํ•ด ์•ž๊ณผ ์œ ์‚ฌํ•œ ์ตœ์  ๋ถ€๋ฐ˜์†กํŒŒ ํŽ˜์–ด๋ง ๊ธฐ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ๋ชจ์˜์‹คํ—˜ ๊ฒฐ๊ณผ๋ฅผ ํ†ตํ•ด ์ œ์•ˆ๋œ ๊ธฐ๋ฒ•์ด ๋ฐ์ดํ„ฐ ์ „์†ก๋ฅ ๊ณผ ์•„์›ƒํ‹ฐ์ง€ ํ™•๋ฅ  ์ธก๋ฉด์—์„œ ์ƒ๋‹นํ•œ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.To solve the problems of global warming effects, rising energy-hungry demands, and risks of peak loads, many efforts to build a Smart Grid system are underway. A smart grid requires advanced information, and communication technologies to support its intelligent features, and it depends on the reliable data transmission via a communication network. Among the candidates of communication technology for smart grid, we focus on a power line communications (PLC), especially a broadband PLC over a medium voltage (MV) powerline network. The reliability of the PLC network are prerequisite for an appropriate communication medium for smart grid. This dissertation considers a strategy to make the PLC network more reliable and robust. We consider a maximal ratio combining (MRC) diversity scheme for a power line orthogonal frequency division multiplexing (OFDM) system. An optimal subcarrier pairing scheme is proposed to maximize the MRC gain. Numerical results are presented to verify that the proposed scheme provides enhanced performance. Diversity gain comes at the expense of spectral loss. We adopt the precoding scheme proposed for wireless MIMO system to compensate the spectral loss due to the inherent transmission mechanism of the above subcarrier pairing scheme. It is shown that the proposed pairing scheme with higher modulation order achieves a comparable performance to the precoding scheme which requires high computational cost. We extend the optimal subcarrier pairing with MRC approach to powerline/wireless diversity system, where the powerline and wireless subcarriers are paired to perform maximal ratio combining (MRC). An similar optimal subcarrier pairing scheme is proposed to maximize the data rate for MRC reception in powerline/wireless diversity OFDM systems. Numerical results show that, by using the proposed optimal subcarrier pairing, significant performance enhancement can be achieved in terms of Ergodic data rate and outage probability.1 Introduction 1 1.1 Smart Grid 1 1.2 Communication and Networking in the Smart Grid 5 1.2.1 Network Topologies 6 1.2.2 Communication Technologies for the Smart Grid 8 1.3 Dissertation Outline 11 2 Power Line Communications for Smart Grid 12 2.1 Power Line Channel Characteristics 15 2.2 PLC Channel Modeling 15 2.3 PLC Channel Noise Characteristics 17 2.4 MV Channel Description for This Dissertation 19 2.4.1 Implementation of Powerline Channel 19 2.4.2 Typical Topology 22 2.5 MV Powerline Noise 25 3 Optimal Subcarrier Pairing for Maximal Ratio Combining in OFDM Power Line Communications 27 3.1 Motivation 27 3.2 Optimal Subcarrier Pairing for Maximal Ratio Combining 28 3.2.1 System Model 28 3.2.2 Optimal Subcarrier Pairing 31 3.3 Numerical Results 33 3.3.1 Simulation Environments 33 3.3.2 SER Performance Analysis 35 3.3.3 Performance Comparison with Equal Gain Combining 38 3.4 Precoding Scheme to Compensate Spectral Loss Due to Diversity Transmission 40 3.4.1 Review of the Minimum Distance-Based Precoder for MIMO Spatial Multiplexing Systems 41 3.4.2 Optimal Minimum Distance-Based Precoder for QPSK Constellation 41 3.4.3 Application to PLC OFDM System 44 3.4.4 Performance Comparison of max-dmin Precoder for QPSK Modulation 44 3.4.5 Performance Comparison of max-dmin Precoder for 16-QAM Modulation 49 3.4.6 Complexity Analysis 53 3.5 Conclusion 53 4 Optimal Subcarrier Pairing for MRC in Powerline/Wireless Diversity OFDM Systems 55 4.1 Motivation 55 4.2 Powerline/Wireless Diversity OFDM Systems 57 4.3 Optimal Subcarrier Pairing for Powerline/Wireless Diversity 60 4.4 Numerical Results 62 4.4.1 Channel Models 63 4.4.2 Performance Comparison 67 4.5 Conclusion 76 5 Concluding Remarks 77 5.1 Summary 77 5.2 Future Works 78Docto
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