Performance of COFDM in Underwater Acoustic Channel with Frequency Selective Fading

(1)

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ȋǡ ǡǦǡ Ȍ ҙąʂॡİ܁҃ࣀ֪ėॡę

ۿսێۙțښێ޽࢘ێۙțښێ

ొ ߧ: սܼڼॳࣀ֪޽ȇقԴܳࣷսԸ࢘ۺगۋˮقÌॢOFDM(Orthogonal Frequency Division Multiplexing)قۻѓ١Ϊ܁܁şѪںۺڌॢCOFDM(Coded OFDM)ۆՁɠںथÀॠٕɰ. OFDMڹġʂً֪

঒εঊʂً֪঒ͿǣɀرۻբॠəşѪڷͿɰܼąͿقۆॢՁɠ۹ॠε३ĀॠəʚমęۺۍۻբşѪۋݓχ,

࣢܁ҙ޽ȇقŪڹगۋˮۋەəąڍق١ΪÀݒÀॠيՁɠۋ۹ॠʽɰ. ۋ͠ॢगۋˮقʂॢ١ΪεÇՙ֨ࢅ

şڦ३࠸ѧΘՎࡑ˚εۺڌॢCOFDMں܃؋ॢɰ. ɰܼąͿ޽ȇقԴCOFDMۋOFDMقҼ३ԜʂۺڷͿڍ սॢۻբՁɠںٕ҃ɰ.

ෑਕ૳ઘ:սܼڼॳࣀ֪, սܼɰܼąͿ޽ȇ, OFDM, ܳࣷսԸ࢘ۺगۋˮ, ࠸ѧΘՎࡑ˚, COFDM

ABSTRACT: In this paper, performance of COFDM (Coded Orthogonal Frequency Division Multiplexing) which is OFDM with a forward error correction code, is studied in frequency selective fading underwater acoustic communication channel. The OFDM is a multiplexing technique resistant to frequency selective multipath channel. In OFDM, a broadband information signal is transformed into several narrow band signals and transmits narrow band signals whose bandwidths are less than the channel coherence bandwidth. However, its performance is degraded in a specific narrow band signal due to its deep fading by multipath. To mitigate this degradation, COFDM which is OFDM with convolution code as a forward error correction code, is evaluated. The performance of COFDM is found to be better than that of OFDM in multipath channel.

Keywords:Underwater acoustic communication, Underwater multipath channel, OFDM, Frequency selective fading, Convolutional code, COFDM

PACS numbers: 43.30. Zk, 43.60. Dh

“ۋȦЛڹ2013țॢĶڼॳॡধߺćॡցʂধق࣊Č॰ʏȦЛۓɦɰ.”

Dept. of Information and Communications Engineering Pukyoung National University, Daeyeon 3dong, Namgu, Busan 608-737, Republic of Korea

(Tel: 82- 51-629-6233, Fax: 82-51-629-6210)

*Դ΁

սܼڼॳࣀ֪(underwater acoustic communication) ۆۻբՁɠڹ޽ȇۆ֨ėÂۺঞąѺʴقٖॳں

ы؉܁҃ۻբՁɠۋս֯kbpsۋॠͿ܃ॢʽɰ.

սܼڼॳࣀ֪ۆۻբՁɠقٖॳںй࠘əʂश

ۺۍঞąڅۍڹ՜֬(loss), ѕąۡڼ(ambient noise), ɰܼąͿ(multipath), ʪ॔͠(Doppler) ˣۋەɰ.^[1]ۋ

͢ঞąڅۍܼۻբՁɠں܃ॢॠəܳʽڅۍڹ

ɰܼąͿۋɰ. ɰܼąͿə޽ȇۆ֨ėÂۺѺʴ, ˣقۆ३ٖॳںыəɰ. ۋͿۍ३ɰܼąͿ޽ȇ Ϳբ֪ʽ֪঒əɰܼąͿۆ࣢Ձق˰͆ݕफ, ڦ Ԝ, ܳࣷս, ս֪֨Âˣۋٖॳںыəɰ. ۋ͢սܼ

ɰܼąͿ ޽ȇۆ ѺʴՁę Ձɠۆ ěćق ʂ३

Chitre^[2]ˣڹսܼɰܼąͿ޽ȇقԴݓٍঝԓ(delay

(2)

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ڼॳࣀ֪֨֟ࢰۆۻբՁɠقٖॳںй࠘əìں

ঝۍॠٕɰ.

սܼɰܼąͿ޽ȇقԴբ֪֪঒əąćϸقъ ԐʼرÁąͿεࣀ३֨Âݓٍ(time delay)^[3]ʼر

ս֪ʽɰ. ˰͆Դ޽ȇۆێěՁʂًफۋ܃ॢʼ ر, ISI(Inter Symbol Interference)ٮܳࣷսԸ࢘Ձ (frequency selectivity)ۋݒÀॠيսܼڼॳࣀ֪֨

֟ࢰۆۻբՁɠں۹ॠ֨ࢇɰ. սܼɰܼąͿ޽ȇ قԴۻբՁɠںॳԜ֨ࢅşڦ३Ribas^[4]ˣڹOFDM şѪںսܼٖԜۻբقۺڌॠٕɰ.

OFDM şѪڹ޽ȇۆێěՁʂًफۋ܃ॢʼə

ܳࣷսԸ࢘ۺगۋˮঞąقÌۍॢşѪۋɰ. ġ ʂً֪঒εঊʂً(narrowband) ֪঒ͿǣɀرÁ

޽ȇѻͿۻբ॥ڷͿ׆ܳࣷսԸ࢘ۺ޽ȇںঊʂ

ًۆܳࣷսҼԸ࢘ۺ޽ȇͿŖԐॢɰ. Ŕ͠ǣݓ

ٍঝԓقۆॢICI(Inter Carrier Interference)ٮ࣢܁ҙ

ъբࣷ(sub-carrier)ۆŪڹगۋˮ(deep fading)قۆ ३ٍݚ١Ϊ(burst error)ÀьԦॢɰ.^[5]

ۋ͠ॢٍݚ١Ϊε३Āॠşڦ३࠸ѧΘՎࡑ˚

(convolutional code), R-Sҙ঒(Reed-Solomon code)^[6]ф

ࢢ҃ࡑ˚(turbo code)ٮÏڹۻѓ١Ϊ܁܁(forward error correction)şѪںۺڌॢCOFDMۋۺڌʽɰ.

҆ȦЛقԴə֬३ًथÀۆԸॱٍĵͿڼॳ

޽ȇۆѺսεڌۋॠó܃رॣսەəսܓقԴ

OFDMęCOFDMۆՁɠںҼİथÀॠٕɰ. ۻѓ ١Ϊ܁܁şѪڹ࣢܁ҙъբࣷۆŪڹगۋˮقۆ

ॢٍݚ١ΪÇՙقমęÀەə࠸ѧΘՎࡑ˚ε

ۺڌॠٕڷ϶OFDM ҙъբࣷə4޽ȇںԐڌॠٕ

ɰ. 100×100(8bit)ۋйݓۆۻբέق˰δOFDM Á

޽ȇۆܳࣷսԸ࢘Ձę١Ϊ࣢Ձں३ԵॠٕČ

OFDMęCOFDMۆՁɠںҼİथÀॠٕɰ.

**սܼɰܼąͿ޽ȇقԴݓٍঝԓę

ܳࣷսԸ࢘Ձ

սܼɰܼąͿ޽ȇڹąćϸۆԜࢗٮբ · ս֪

şۆڦ࠘قٖॳںыəɰ. Fig. 1ęÏۋբ֪ʽ֪

঒əąćϸъԐقۆ३ÁąͿۆݓٍ֨Âۋɵ νս֪ʼ϶, ÁąͿقԴս֪ʼə֪঒ۆݓٍڹ

֩(1)ęÏɰ.^[7]

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يşԴƊ_ƎəƎѥݫۻࣷąͿۆţۋۋ϶,Ɓəսܼ

قԴۆڼ՚(ÎÒ××î)ۋɰ.

ąćϸۆ࣢Ձق˰δÁąͿۆܳࣷսڿɻڹ

֩(2)ٮÏɰ.

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, (2)

يşԴ ġ_ƎəƎѥݫ ۻࣷąͿۆ ъԐćսۋ϶, ö^ć^ÞƊƎìƄßəÁąͿţۋق˰δۻࣷ՜֬,Ƅəܳ

ࣷս(Hz)ۋɰ.

֩(1)ę(2)εۋڌॢսܼɰܼąͿ޽ȇۆےऑ

֟ڿɻڹ֩(3)ęÏɰ.

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ā

_Ǝ ^Ɔ^Ǝ^{Þƒà ŉ}^Ǝ^ß^, ⁽³⁾

يşԴƆƎÞƒßə¡ƎÞƄßۆًऻνقѺঞ(inverse fast Fourier transform)ۋɰ.

ɰܼąͿقۆॢRMS(Root Mean Square) ݓٍঝ ԓڹ֩(4)ٮÏڷ϶, ֩(4)ۆथŒߣęݓٍ(mean excess delay) ćŉٮथŒ܃ĕݓٍ(mean square delay) ćŉ^Ïə֩(5)ٮÏɰ.^[8-9]

ŉ_ƐƋƑáö^ć^ćŉ^Ïà Þćŉß^Ï, (4)

(3)

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(c) (d)

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يşԴ©Þŉƌßəƌ޲ąͿۆۻͳнʪۋɰ. Fig. 2^[10]

əێěՁʂًफęܳࣷսԸ࢘Ձں҃ۋə३Ԝ

֬ॹۆĀęͿFig. 2(a)əݔۿࣷۆ֨Âࣷ঍ۋ϶, Fig. 2(b)əݔۿࣷٮъԐࣷÀܕۦॠə֨Â֪঒ۋ ɰ. Figs. 2(c)ę2(d)əFigs. 2(a)ę2(b)ۆ֟घ࣡ͤڷ ͿFig. 2(c)ۆݔۿࣷۆ֟घ࣡ͤęFig. 2(d)ۆݔۿ

ࣷфъԐࣷۆ֟घ࣡ͤںҼİॠϸFig. 2(d)əۻ բ֪঒ʂًफǴقԴۻբ֪঒ۆݕफڹܳࣷսق

˰͆ɰδÉں҃يܳࣷսԸ࢘ՁۋݒÀ॥ں؎

սەɰ.

֩(4)ۆRMS ݓٍঝԓę޽ȇۆێěՁʂًफۆ

ěćə֩(6)ęÏɰ.^[8]

_Ɓá ćÒŉÎ_{Ɛ ƋƑ}. (6)

֩(6)قԴ޽ȇۆێěՁʂًफ_ƁÀբ֪֪঒ۆ

ʂًफ_Ƒ҃ɰȉɰϸ, բ֪֪঒ۆϿ˜ܳࣷսՁ қڹFig. 2(d)ق҃ۋəٷčইԜۋػۋս֪ʽɰ.

ъʂͿ޽ȇۆێěՁʂًफƁÀբ֪֪঒ۆʂ

ًफƑ҃ɰܙɰϸ, ٷčইԜۋەəܳࣷսԸ࢘

ۺۍ޽ȇͿISIÀьԦॠي١ΪÀݒÀॢɰ.

OFDMڹ܃ॢʽێěՁʂًफǴقԴÁ޽ȇۆ

ƑεƁ҃ɰܙóॠيۻբॠəɰܼজ(multiplexing) şցۋɰ.

***0'%.ę$0'%.

սܼɰܼąͿ޽ȇقۆ३ьԦʼəISI фܳࣷս

Ը࢘ۺगۋˮقۆॢՁɠ۹ॠεॳԜ֨ࢅşڦॢ

ѓѪܼOFDM ѓ֩ۋۺڌʼČەɰ.

OFDMѓ֩ڹFig. 3ęÏۋɰܼąͿ޽ȇقۺڌ ʼəɳێъբࣷɰܼজۻբѓ֩ۍFDM(Frequency Division Multiplexing)ęɵνݔİՁںÍəҙъբ

ࣷε ۋڌॠي ԜʂۺڷͿ ʂًমڱۋ ȭڷ϶, SNR(Signal to Noise Ratio)ق˰δÁҙъբࣷۆʚۋ ࢢۻբέںܓۼॠيۻբڌ͟ںࡾóॳԜ֨࢈ս

ەɰ.̚ॢ޽ȇʂًۆমڱۺটڌęݓٍঝԓں҃

Ԝॠəˣজşۺڌںक़ॣսەڷ϶,ঊʂًÂԾق

Ìॢɰܼজѓ֩ۋɰ.^[5]

Fig. 4əOFDMۆҸ΀ɰۋرŔ͖ۋɰ. 2ݕ܁֪҃

(4)

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঒əݔ· ѿ͵ѺজşεۋڌॠيÁҙъբ֪ࣷ঒Ϳ

қॣ֨ࡈQPSK(Quadrature Phase Shift Keying)^[10-11]Ѻ ܓॢɰ. Ѻܓʽ ֪঒ə IFFT(Inverse Fast Fourier Transform)εࣀ३ҙъբࣷۆ०ڷͿĵՁʽɰ.֨Â

ƒ á ƒ_ƑقԴ֨ۚॠəOFDM ֮ѧڹ֩(7)ęÏڷ϶,^[5]

֩(7)ۆˣÀ҄ՙսş۹ʂًۆशইڹ֩(8)ęÏۋ

ǣࢍǷսەɰ.

ƑÞƒß á «ƃ Ē ē Ĕ

ĕ ĕ ā

Ƈ áà ćÏ

§Ƒ

ćÏ

§Ƒà Î

Ƃ_{Ƈ â §}_Ƒ_îÏÞ^ƈÏņÞ^Ƅ^Ɓ^{à ć}^Ƈâ×íÒ ß^Þ^{ƒ à ƒ}^Ƒ^ßß^Ĝ^ĝ

Ğ

ĕ ĕ

^,

ƒ_Ƒ= ƒ = ƒ_Ƒâ

(7)

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ĕ ĕ ā

Ƈ á ćÏ

§Ƒ

ćÏ

§Ƒà Î

Ƃ_{Ƈ â §}_Ƒ_îÏÞ^ƈÏņć^{Ƈ Þƒàƒ}^Ƒ^ßß^Ĝ^ĝ

Ğ

ĕ ĕ

^, ⁽⁸⁾

يşԴƂ_Ƈə҄ՙս঍ࢗͿशইʽ֮ѧۋ϶,§ڹ

ҙъբࣷۆսۋ϶,ə֮ѧĵÂ,Ƅ_Ɓəъբܳࣷս ۋɰ.

Fig. 5əսܼɰܼąͿ޽ȇقۆॢ࣢܁ҙъբ

ࣷÂۆŪڹगۋˮقۆॢٍݚ١ΪεÇՙ֨ࢅş

ڦ३܃؋ʽCOFDMۆҸ΀ɰۋرŔ͖ۋɰ. Fig. 4 قԴۓͳ2ݕ܁֪҃঒ٮݔ · ѿ͵ѺঞşԐۋق

ۻѓ١Ϊ܁܁şѪۋ߸ÀʽìڷͿCOFDMقԴ

ۺڌʼə١Ϊ܁܁ࡑ˚ə࠸ѧΘՎࡑ˚, R-S ࡑ

˚, ࢢ҃ࡑ˚ˣۋԐڌʼ϶, ۋ˞ܼ࠸ѧΘՎࡑ

˚əFig. 6ęÏۋ࣢܁ҙъբࣷۆŪڹगۋˮڷ Ϳۍॢٍݚ١Ϊε३Āॠي, ԜʂۺڷͿǰڹ

SNRقʂ३҃ɰڍսॢՁɠں҃ۋóʽɰ.^[5]

Fig. 7ڹ҆ȦЛقԴۺڌॢ࠸ѧΘՎࡑ˚Ϳĵ

՚ۤk=3ۋČ,^[13-14]ҙ঒ڱۋ1/2ۍۍࡑʌۆҸ΀ʪ ۋɰ. ࠸ѧΘՎࡑ˚əҙ঒kҼ࣡ۆٍ՚ʽÁۓͳ

َںnÒۆ߻ͳҼ࣡Ϳϙय़֨ࢅ϶, Âɳॢͪݓ֟ࢢ (register)ٮʖՇşͿĵইॣսەɰ.^[5]ܳͿAWGN (Additive White Gaussian Noise)޽ȇę֬֨ÂߌνÀ

څĵʼə޽ȇقĵ՚ۤţۋεۚóॠيۺڌॠČ

ەڷ϶, ࠸ѧΘՎ˥ࡑ˚əҼࢢҼ(viterbi) ؎Čνݏ

[15]ۋۺڌʽɰ.

ҼࢢҼ؎Čνݏڹ߯ʂڮԐʪ(maximum likelihood)

߸܁ںࣀ३ԜʂۺڷͿݥڹĵ՚ۤۆţۋεÍə

ࡑ˚ۆ˥ࡑ˚قԐڌʽɰ. ҃ࣀݥڹĵ՚ۤţۋε

Íə࠸ѧΘՎࡑ˚قԐڌʼəҼࢢҼ؎Čνݏڹ

trellisεࣀ३Ͽ˜ÀɠՁەəąͿεҼİॠيъ҄

ॠə؎Čνݏۋɰ. ۋ؎Čνݏڹĵ՚ۤk=10 ۋॠ ێ˺ۺڌॠ϶, ÂɳॢĵܓεÀݕɰ.

*7ՁɠथÀĀę

OFDMęCOFDMۆՁɠथÀεڦॢսܓ֬ॹۆ

ĵՁʪəFig. 8ٮÏɰ. բ֪şəITC-1032, ս֪ş əB&K 8106ںԐڌॠٕڷ϶, LabVIEW ֨֟ࢰں

(5)

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Modulation QPSK

Multiplexing OFDM, COFDM

Sub-carrier numbers 4

Carrier Frequency 30 kHz Coding Method 1/2 Convolutional Code Each sub-carrier

transmission rate (sps) 50, 100, 200 sps

Cyclic Prefix 2.5 ms

Coherence Bandwidth ~95 Hz

Range 0.6 m

Transmitter and Receiver depth 0.3 m and 0.3 m Data Image size(100×100)pixel 8 bit

total bit : 80,000 bit System LabVIEW

Water Tank 2m×1.5m×1m

Wdeoh#51#Wudqvplvvlrq#udwhv#dqg#vxe0fduulhu#iuhtxhqflhv1 each

sub-carrier transmission

rate (sps)

OFDM transmission

rate(sps)

Sub-carrier frequency (kHz)

1ch 2ch 3ch 4ch

50 200 30 30.05 30.1 30.15

100 400 30 30.1 30.2 30.3

200 800 30 30.2 30.4 30.6

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ۋڌॠيՁɠںथÀॠٕɰ.

բ · ս֪şۆս֮ڹÁÁ0.3 mۋ϶, բ · ս֪ş ۆۻբäνə0.6 mۋɰ. ֬Ǵսܓۆս֮ڹ0.6 m ͿѕąۡڼڹИ֨ॠٕɰ. Table 1ڹ֬ॹࣷ͆ϭࢍ

ͿÁҙъբࣷۆѺܓѓ֩ڹQPSKۋ϶, OFDMۆ

ҙъբࣷə4ÒͿۻբʂًڹ30 kHz ~ 30.6 kHzۋ ɰ. Áҙъբࣷۆۻբ՚ʪə50 sps, 100 sps, 200 sps Ϳ, OFDMۆۻբ՚ʪəÁÁ200 sps, 400 sps, 800 sps Ϳ4ѕݒÀॢۻբ՚ʪεÍəɰ. ۻբʚۋࢢə

100 × 100(8bit) ۋйݓͿߪ80,000 Ҽ࣡εۻբॠٕɰ.

Table 2əÁÁۆɳێ޽ȇقʂॢۻբ՚ʪٮ4

޽ȇقʂॢOFDMۆۻբ՚ʪŔνČÁҙъբࣷ

ۆܳࣷսۋɰ.

Fig. 9ə սܓۆ ޽ȇڿɻ࣢ՁڷͿ LFM(Linear Frequency Modulation)֪঒ε1ߣÂüڷͿߪ60ߣÂ

ս֪ॢ֪঒ۆथŒۋɰ. ߯ʂݓٍঝԓ֨Âڹأ

20 msۋ϶, ֩(4)εۋڌॢRMS ݓٍঝԓڹ2.1 msۋ

϶, ֩(6)ۆRMS ݓٍঝԓقۆॢ޽ȇۆێěՁʂ

ًफƁə95 HzͿ߯ʂۻբ՚ʪə95 sps ۋॠͿ܃

ॢʽɰ. OFDMۆÁҙъբࣷ޽ȇۆۻբέڹ߯

ՙॢ95 sps ۋॠͿԺćʼرآॠݓχٍ҆ĵقԴ əTable 2ٮÏۋҙъբࣷսε4ÒͿॠČۻբέ ںѺজ֨ࢅ϶֬ॹॠٕɰ.

Fig. 10ڹOFDMۆբ֪֪঒ۆ॒ͪےĵܓۋɰ.

޽ȇڿɻ࣢ՁқԵںڦॢLFMęʴşεڦ३

(6)

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ri#vxe0fduulhu#iuhtxhqflhv#dw#;33#vsv1

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+e,

+f,

Ilj1#461#Frqvwhoodwlrq#ri#hdfk#fkdqqho#iru#RIGP>#+d,#

533#vsv/#+e,#733#vsv/#dqg#+f,#;33#vsv1

PN(Pseudo Noise) sequence ŔνČCP(Cyclic Prefix)ٮ

֮ѧͿĵՁʽʚۋࢢĵÂڷͿ1ߣ॒ͪےڷͿĵ Ձॠٕɰ. Fig. 11ڹսܓقԴբ֪ॢ֪঒ۆ1ߣ॒

ͪےںս֪ॢ֪঒ۋ϶, Fig. 12əTable 2قԴ҃ۋ əOFDM ۻբ՚ʪ800 spsقʂॢ30 kHz ~ 30.6 kHz ۆ4Òҙъբࣷقʂॢܳࣷս֟घ࣡ͤڷͿFig. 6 ęÏۋɰܼąͿقۆॢगۋˮڷͿÁҙъբࣷə

ԴͿɰδࡾşͿ࣢܁ҙъբࣷقԴٍݚ١ΪÀь Ԧॣìۋɰ.

Fig. 13ڹTable 2ۆۻբ՚ʪقʂॢOFDMۆÁ

ҙъբࣷ1ҙࢢ4ūݓقʂॢՁԜʪۋɰ. Fig. 13(a) ə200 spsقʂॢĀęͿێěՁʂًफ_Ɓ҃ɰÁ

ҙъբࣷۆʂًफۋܙ؉١ΪəьԦʼݓ؍əɰ.

Fig. 13(b)ə400 spsقʂॢĀęͿێěՁʂًफ҃

ɰÁҙъբࣷۆʂًۋ5 Hzȉɰ. ۋͿۍ३ʂً

फ܃ॢقۆॢISIٮ30.4 kHzقԴьԦॠəŪڹग

ۋˮۆٖॳںыş֨ۚॠə2 ѥݫٮ4 ѥݫ޽ȇ قԴۍۿ޽ȇۆܳࣷսʂًقۆॢICIۆٖॳڷ Ϳ١ΪҼ࣡ÀьԦॠČ١Ϊڱڹأ0.003ۋؽɰ.

Fig. 13(c)ə800 spsقʂॢĀęͿÁҙъբࣷۆʂ

ًफۋێěՁʂًफ҃ɰ105 Hz ȉɰ. ۋͿۍ३

ISIۆݒÀٮܳࣷսԸ࢘ۺ޽ȇۆŪڹगۋˮق

ʂॢٖॳڷͿۍ३2 ѥݫٮ3 ѥݫ޽ȇ, ࣢০3ѥ ݫ޽ȇܳࣷս30.4 kHzقԴ١ΪҼ࣡ÀٍݚڷͿ

ьԦॠČ١Ϊڱڹأ0.02 ۋؽɰ.

սܼɰܼąͿقۆॢێěՁʂًफ܃ॢęܳࣷ

սԸ࢘ՁݒÀقۆॢՁɠ۹ॠε҃ۋəFig. 13ۆ

ĀęεÒԸॠşڦ३OFDMق࠸ѧΘՎࡑ˚εۺ ڌॢCOFDMۆՁɠ֬ॹںսॱॠٕɰ.

ۻբ՚ʪق˰δOFDMęCOFDMۆՁɠ޲ۋə

ۋйݓٮۋйݓۆ١ΪڱͿঝۍॠٕɰ. Fig. 14(a) ə200 spsͿۻբॢĀęͿÁҙъբࣷۻբ֪঒

ʂًफۋ޽ȇێěՁʂًफ҃ɰܙČÁ޽ȇۆ

ҙъբࣷقŪڹगۋˮۋьԦॠݓ؍əąڍۋɰ.

֬ॹĀęOFDMęCOFDM Ͽ˃١Ϊڱڹ0ڷͿ١ ΪÀьԦॠݓ؍ؕɰ. Fig. 14(b)ə400 spsͿÁҙъ բࣷۆۻբ֪঒ʂًफۋێěՁʂًफęҼ֦ॠ Č2ѥф4ѥ޽ȇقगۋˮۋьԦॠəąڍۋɰ.

OFDMۆ١Ϊڱڹأ0.003ۋݓχ, COFDMڹ١Ϊ ÀьԦॠݓ؍ؕɰ. ۋεࣀ३ۻѓ١Ϊ܁܁şѪ

(7)

RIGP FRIGP

EHU#=#3 EHU#=#3

+d,

EHU#=#313367:8 EHU#=#3

+e,

EHU#=#313564 EHU#=#31333:8 +f,

Ilj1#471#Lpdjh#ri#h{shulphqwdo#uhvxowv#iru#FRIGP>#+d,#

533#vsv/#+e,#733#vsv/#dqg#+f,#;33#vsv1

ۍ࠸ѧΘՎࡑ˚ÀۺڌʽąڍێěՁʂً܃ॢق

ۆॢISIٮٍݚ١ΪεÇՙ֨ࡈۻբՁɠۋॳԜʿ ںঝۍॠٕɰ. Fig. 14(c)ə800 spsͿÁҙъբࣷۆ

ۻբ֪঒ʂًफۋێěՁʂًफ҃ɰأ2ѕȉڹ

ąڍͿOFDMۆ١Ϊڱڹأ0.02ۋݓχ, COFDMۆ

١Ϊڱڹأ0.0008ͿŪڹगۋˮقۆॢÒѻҙъ բࣷۆ١ΪÀÒԸʼرۻߕۺڷͿأ25 ѕ١Ϊ ڱۋÒԸʼؽɰ. ˰͆ԴCOFDMڹŪڹगۋˮق

ۆॢٍݚ١ΪٮێěՁʂًफ܃ॢقۆ३ьԦʼ ə١Ϊε܁܁ॣսەəɠͳۋOFDMقҼ३ڍ սॠɰČࣺɳʽɰ.

7Ā΁

OFDMڹġʂًۻբ֪঒εঊʂً֪঒Ϳқν

ॠيÁҙъբࣷ޽ȇͿۻբ॥ڷͿ׆սܼɰܼ

ąͿقۆॢܳࣷսԸ࢘ۺगۋˮ١ΪεÇՙ֨ࡈ

Ձɠ۹ॠεŕ҄ॠəşѪۋɰ. ˰͆ԴÁҙъբ

ࣷۆʂًۋɰܼąͿقۆ३Ā܁ʼə޽ȇێěՁ

ʂًफ҃ɰȉں˺ə࣢܁ҙъբࣷۆŪڹगۋˮ

ڷͿٍݚ١ΪÀьԦॠيՁɠۋ۹ॠʽɰ. ۋε

ÒԸॠşڦ३ٍ҆ĵقԴəOFDMقۻѓ١Ϊ܁

܁ࡑ˚Ϳ࠸ѧΘՎࡑ˚εۺڌॢCOFDMۆՁɠ ںथÀॠٕɰ.

OFDMęCOFDMۆՁɠںսܓ֬ॹںࣀ३Ҽ İथÀॢĀę, OFDMۆÁҙъբࣷ޽ȇۋɰܼ

ąͿقۆ३ܳࣷսԸ࢘ۺۍ޽ȇۋʼəąڍقʪ

࠸ѧΘՎࡑ˚ÀۺڌʽCOFDMڹ࣢܁ҙ޽ȇۆ

Ūڹगۋˮقۆॢ١ΪεÇՙ֨ࢅəʚমęۺۋ ؽɰ.

ÇԐۆŘ

ۋȦЛڹ2010ॡțʪҙąʂॡİٍĵțİսݓ ڙԐغقۆॠيٍĵʼؽڼ(PS-2010-027).

3FGFSFODFT

1. R. J. Urick, Principles of Underwater Sound 3th Edition, (McGraw-Hill, New York, 1983), pp. 99-233.

2. M. Chitre, S. Shahabudeen and M. Stojanovic, “Underwater acoustic communications and networking: recent advances and future challenges,” J. Marine Tech. Soc., 42, 103-116 (2008).

3. G. Zhang, J. M. Hovem, H. Dong, and L. Liu, “Experimental studies of underwater acoustic communications over multipath channels,” SENSORCOMM 2010, IEEE, 458-461 (2010).

4. J. Ribas, D. Sura, and M. Stojanovic, “Underwater wireless video transmission for supervisory control and inspection using acoustic OFDM,” IEEE OCEANS 2010, IEEE, 1-9 (2010).

5. R. V. Nee and R. prasad, OFDM for Wireless Multimedia Communications (Artech House, Norwood 2000), pp.33-58.

6. L. Liu, Y, Wang, L. Li, X. Zhang, and J. Wang, “Design and implementation of channel coding for underwater acoustic system,” ASICON, IEEE, 497-500 (2009).

7. M. Stojanovic and J. C. Preisig, “Underwater acoustic communication channels: propagation models and stat- istical characterization,” Communications Magazine, IEEE,

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47, 84-89 (2009).

8. K. Park, J. Park, S. W. Lee, J. W. Jung, J. Shin, and J. R.

Yoon, “Performance evaluation of underwater acoustic communication in frequency selective shallow water” (in Korean), J. Acoust. Soc. Kor. 32, 95-103 (2013).

9. J. Kim, K. Park, J. Park, and J. R. Yoon, “Coherence bandwidth effects on underwater image transmission in multipath channel,” Jpn. J. Appl. Phys. 50, 07HG05-1-07HG05- 5 (2011).

10. J. Park, J. Kim and J. R. Yoon,“Effect of text transmission performance on delay spread by water surface fluctuation in underwater multipath channel” (in Korean), J. Electronic.

Soc. Kor, TC1,1-5 (2011).

11. W. K. Lam and R. F. Ormondroyd, “A coherent COFDM modulation system for a time-varying frequency selective underwater acoustic channel,” 7th Oceanography Eng., IEEE, 198-203 (1997).

12. J. Huang, C. He, X. Shen, and Q. Zhang, “High-speed underwater acoustic communication based on OFDM,”

Convention 2005, IEEE, 1135-1138 (2005).

13. J. F. Sifferlen, H. C. Song, W. S. Hodgkiss, W. A. Kuperman, and J. M. Stevenson, “An iterative equalization and decoding approach for underwater acoustic communication,” J.

Oceanic Eng. 33, 182-197 (2008).

14. J. Trubuil, A. Goalic, and N. Beuzelin, “An overview of channel coding for underwater acoustic communications,”

MILCOM 2012, IEEE, 1-7 (2012).

15. A. Goalic, J. Trubuil, and N. Beuzelin, “Channel coding for underwater acoustic communication system,” Oceans 2006, IEEE, 1-4 (2006).

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ছశ଀ $IVMXPO4FP

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Performance of COFDM in Underwater Acoustic Channel with Frequency Selective Fading

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