Seabed-Rock-Layer Electromagnetic Communication Channel Model with Low Path Loss Based on Evanescent Wave

RADIOENGINEERING, VOL. 7, NO., JUNE 8 43 Seabed-Rock-Layer Electromagnetc Communcaton Channel Model wth Low Path Loss Based on Evanescent Wave Zhqang NIE, Shlan WANG, Daha CHEN, Tan DENG Dept. of Electronc Scence, Natonal Unversty of Defense Technology, 9 Deya Road, 473 Changsha, Chna Inst. of Electronc Engneerng, Chna Academy of Engneerng Physcs, 64 Manshan Road, 6 Manyang, Chna wangsl@nudt.edu.cn Submtted August 5, 7 / Accepted January 5, 8 Abstract. The man lmtaton of the development of underwater wreless electromagnetc communcaton s severe attenuaton ntroduced by the seawater characterstcs of hgh permttvty and hgh conductvty. Fortunately, n prevous studes, t was found through experments that the loss between two underwater antennas near seawater surface or seabed s much smaller than the hgher order severe attenuaton for the lne of sght (LOS) path n seawater. But no one has gven reasonable explanaton for ths phenomenon. To solve ths problem, we nvestgate the propagaton mechansm of ths phenomenon theoretcally. The man component of seabed-rock-layer s basalt, an alternatve seabed-rock-layer communcaton channel model based on evanescent wave generated by the total reflecton on the seabed-rock-layer surface s proposed n ths paper. Then we analyze the performance of ths model accordng to Goos-Hanchen (GH) Shft of evanescent wave. Smulaton results show that the path loss n ths model s about / of that n seawater and the propagaton velocty can be ncreased tmes. Proposed technology s expected to become an mportant part of underwater hgh speed and relable communcaton. Keywords Underwater electromagnetc communcaton, seabedrock-layer, evanescent wave, low loss, hgh speed. Introducton In recent years, low loss, hgh relablty and hgh speed underwater wreless data transmsson lnks are demanded urgently n cvl and mltary domans such as petroleum exploraton ndustry, marne envronment montorng and mltary command []. So the underwater wreless communcaton s an mportant topc n ocean that has attracted worldwde attenton. Contemporary underwater acoustc communcaton, wth long communcaton range of up to km, s wdely used n most long-range underwater wreless data transmsson applcatons []. However, narrow-band acoustc waves yeld poor performance because of the susceptblty to multpath and Doppler effects, resultng n a sgnfcant lmtaton of the allowable bandwdth [3]. Fortunately, these problems can be overcome by reconsderng the use of electromagnetc communcaton n short-range transmsson lnks due to the hgh bandwdth and strong ant-nose ablty. Another opton for underwater s optcal communcaton, whch has the greatest advantage of extremely large capacty [4]. Unfortunately, optcal waves are severely affected by the scatterng of suspended partcles and marne plankton, and only delver good performance n very clear water. In comparson wth optcal communcaton, electromagnetc wave can be operated under non-lne-of-sght (NLOS) condtons and s nsenstve to water turbdty, salt concentraton and pressure gradents. Thus, electromagnetc communcaton s an deal choce for underwater wreless communcaton applcatons. The development of underwater wreless electromagnetc communcaton s manly lmted by severe attenuaton. At the begnnng of the study, researchers used extremely low frequency to launch electromagnetc wave n order to overcome the attenuaton [5]. But very hgh transmttng power and large antenna sze are requred. Later, the researchers demonstrated that antennas coated wth nsulatng materal or wrapped nsde the nsulaton cylnder shell for electromagnetc wave emsson, whch greatly mprove launchng effcency [6], [7]. A. A. Abdou proved t s feasble to utlze electromagnetc wave n an underwater communcaton system usng loop antennas [8]. However, these methods cannot solve the core problem of exponental attenuaton of electromagnetc wave n seawater. Reference [9] referred to the use of surface wave produced by the propagaton of electromagnetc wave gong from seawater nto the ar, along the ar-water nterface, and fnally down to seawater, whose path loss s much smaller than the hgher order severe attenuaton path n seawater and, hence, the communcaton range can even reach several klometers. A. Shaw et al. took experments to verfy the formulaton and found that the attenuaton of electro- DOI:.364/re.8.43 ELECTROMAGNETICS

43 Z. Q. NIE, S. L. WANG, D. H. CHEN, T. DENG, SEABED-ROCK-LAYER ELECTROMAGNETIC COMMUNICATION CHANNEL magnetc wave wll become smaller f the antennas are n shallow ocean zone and the electromagnetc wave can spread over 9 m [6]. But the artcle dd not gve reasonable theoretcal analyss and explanaton for the propagaton mechansm. Snce the permttvty and conductvty of seabed-rock-layer are much lower than those of seawater, electromagnetc wave could be guded through the seabedrock-layer wth the smlar effect of surface wave for the deeply submerged transcever. We explot the effect to establsh a low loss channel model for hgh speed underwater communcaton through the seabed-rock-layer path wth theoretcal dervaton and smulaton verfcaton n ths paper.. Propagaton Characterstcs n Seawater Seawater has a hgh permttvty and hgh conductvty so that the propagaton characterstcs of electromagnetc wave n the seawater medum are greatly dfferent from n ar. In ths secton, the attenuaton constant, phase constant, propagaton velocty and wavelength of electromagnetc wave n seawater are analyzed and dscussed.. Attenuaton Constant and Phase Constant The propagaton constant of electromagnetc wave n seawater [], [] s expressed as: j j j () where ω = πf, f s the propagaton frequency, and σ s conductvty. ε = ε ε r accounts for permttvty, and the permttvty n vacuum s / c. c s lght speed, ε r s relatve permttvty, μ = μ μ r s permeablty and μ =.6 4 H/m s permeablty n vacuum, we assume the seawater and seabed-rock-layer are non-ferromagnetc medum so the relatve permeablty μ r =. The propagaton constant has a real attenuaton constant α (Np/m) and magnary phase constant β (rad/m) respectvely calculated as:, (). (3) Seawater s a good conductve medum due to the conductvty s σ = 4 S/m and the permttvty s ε r = 8 ε, so α and β can be smplfed as: f. (4) It can be seen that the attenuaton constant and phase constant n seawater are not only related to the characterstc parameters of conductvty, permeablty and permttvty, but also closely related to the frequency and ncrease wth the frequency. Therefore, the hgher frequences of electromagnetc wave are not sutable for long-range communcaton n seawater.. Wavelength The wavelength of electromagnetc wave n seawater [] s expressed as: 4 =. (5) f f We can observe that the wavelength of electromagnetc wave s related to the frequency, the hgher the frequency, the shorter the wavelength. It s found that the wavelength of khz frequency n seawater s only 5 m, whle n the ar t wll reach 3 m. Therefore, the sze of the antenna n seawater can be much smaller than that n ar..3 Propagaton Velocty The propagaton velocty of electromagnetc wave [] s expressed as: 4 f vp /. (6) As the conductvty n seawater s not, the propagaton velocty s a functon of frequency. The propagaton velocty of electromagnetc wave n seawater, though less than the speed of lght, ncreases wth hgher frequency. When the frequency s more than 4 khz, the propagaton velocty of electromagnetc wave n seawater s about 4 tmes faster than that of acoustc waves. Ths result s very mpressve whch ndcates that underwater electromagnetc wave communcaton has the advantages of hgh speed, real-tme n data transmsson. 3. Proposed Channel Model Seawater has characterstcs of hgh permttvty and hgh conductvty such that the propagaton range of the electromagnetc wave through the seawater path s lmted. In [], a wavelength-compensated path loss model was proposed. It found that a low frequency electromagnetc wave wth khz would have an attenuaton loss of 4 db when spreadng 5 m n seawater path. Hgh absorpton loss s the nherent characterstcs of the seawater medum. But the electromagnetc waves whch cross the seawaterar nterface are very sharply refracted between two shallowly underwater antennas and the waves wll be guded through a low loss path leadng from one antenna drectly up to the surface, along the surface, and drectly down to

RADIOENGINEERING, VOL. 7, NO., JUNE 8 433 the another antenna. Smlarly, for the deeply submerged transcever, there wll be the same advantage for electromagnetc wave propagated through the nterface between seawater and seabed-rock-layer [3]. Therefore, we can optmze the channel model by changng the propagaton path for the deeply submerged transcever. In ths secton we analyze the evanescent wave effect produced by the total reflecton n seabed-rock-layer, and optmze the channel model for underwater wreless electromagnetc communcaton from fve stages of propagaton. 3. Propagaton Mechansm Antenna s an mportant factor for the transmsson of underwater electromagnetc wave communcaton. Drectly puttng the any metallc antenna nto the seawater for electromagnetc wave emsson wll cause short-crcut. Most of the researchers use crcular antenna whch coated wth nsulatng materal (such as PTFE layer) or wrapped nsde the nsulaton cylnder shell for underwater experments. The crcular antenna wll match the mpedance of the seawater due to the permttvty of nsulaton materals s close to the seawater, whch can greatly mprove the emsson effcency [6], [7], [4], [5]. The man component of seabed-rock-layer s basalt, whose standard permttvty s ε = 8ε, conductvty s σ =. S/m whch are far less than the parameters of seawater. Long-range underwater communcaton cannot be realzed through seawater path at present, however, when the transcever s located near the deep-sea bottom, the electromagnetc wave can be propagated through the seabed-rock-layer due to the evanescent wave generated by the total reflecton, and the path loss can be much smaller than that of the seawater path, whch s deduced and analyzed theoretcally n ths secton. The propagaton paths of electromagnetc wave between submerged antennas near deep-sea bottom are shown n Fg.. Electromagnetc wave whch belongs to unform planar electromagnetc wave emtted by the antenna s oblquely njected nto the seabed-rock-layer through seawater. In any polarzaton, the wave can be decomposed Optcally denser medum Incdent wave Optcally thnner medum Reflected wave Refracted wave Fg.. Schematc dagram of Snell' s law. nto two orthogonal lnearly polarzed waves [6]. The polarzaton drecton of one s perpendcular to the ncdent plane known as vertcal polarzaton wave E s ; another polarzaton drecton n the ncdent plane known as parallel polarzaton wave E p, that s: E = E s + E p. The schematc dagram of Snell's law s shown n Fg.. Snell' s law [5] s defned as: k sn k sn (7) c c t where kc w c, θ s ncdent angle, θ t s refracton angle, and ε c = ε jσ /ω s complex permttvty, =, represents seawater and seabed-rock-layer, respectvely. The crtcal angle of total reflecton s defned as c arcsn c / c, ε c s a complex number, so the crtcal angle s also a complex angle. When f <<.5 MHz, we obtan σ /ωε >>, ndcatng that the seabed-rock-layer s also good conductve medum, and there s a real crtcal angle j / c arcsn arcsn.866 j / (8) showng that a very small angle wll cause the total reflecton at the nterface. When θ θ c cos sn j sn. (9) t t Consderng the electrc feld n the nfnty tends to, we take the negatve sgn. Then where = sn /. cos j () t Fg.. Propagaton paths between submerged antennas near deep-water bottom. For the two knds of non-ferromagnetc and conductve medums, the transmsson coeffcent and the reflecton coeffcent of vertcal polarzed wave (TE wave) and parallel polarzed wave (TM wave) are slghtly dfferent at the nterface [6]. For TE wave, the transmsson and the reflecton coeffcent are, respectvely:

434 Z. Q. NIE, S. L. WANG, D. H. CHEN, T. DENG, SEABED-ROCK-LAYER ELECTROMAGNETIC COMMUNICATION CHANNEL cos s, cos j sn cos j sn s s s cos j sn exp j. () () Hence the ampltude and phase of the reflecton coeffcent are obtaned, respectvely s, (3) sn s arctan. cos (4) For TM wave, the transmsson and the reflecton coeffcent are, respectvely cos p, cos j sn cos j sn jp p = p e. cos j sn (5) (6) Hence the ampltude and phase of the reflecton coeffcent are obtaned, respectvely: p arctan s, (7) sn cos (8) where j ( j ) s the phase of the reflecton coeffcent, j = s, p represents TE wave and TM wave, respectvely. From the above equatons of TE wave and TM wave we can see when the total reflecton occurs between the two conductve medums (seawater and seabed-rock-layer) nterface, we get j, It ndcates that there s transmsson wave n seabed-rock-layer that s dfferent from the total reflecton on the deal conductor surface (no transmsson wave). Furthermore, the phase of the reflected wave s changed. Under the precondton of total reflecton, the electrc feld ntensty of the transmtted wave n seabedrock-layer s: E E exp jk r E exp jk a r (9) t c kt where E s electrc feld ntensty of ncdent wave, a kt = a x sn t + a z cos t s the unt propagaton vector of plane electromagnetc wave and r = a x x + a z z s the vector of equal phase plane. Combnng () and (9), the electrc feld ntensty of the transmsson wave can be expressed as: E () E exp j z exp jsnx and the magnetc feld ntensty of transmsson wave can be expressed as: a H E () kt c j where / = e s complex ntrnsc mpedance. c c c Therefore, the power flow densty n seabed-rocklayer can be expressed as: av, Re S E H a E x cosexp z snx snt c () From () we can see that the power flow of the transmsson wave goes along the tangental drecton (xaxs) that s the seabed-rock-layer surface; the feld ampltude attenuates exponentally along the normal z-drecton (z-axs) whose effectve depth generally has the same order of magntude of skn depth [6]. Wthn the effectve depth, the nstantaneous power of transmsson wave s not, but n the extremely thck seabed-rock-layer the mean power along the z-axs s, whch ndcates that the exponental attenuaton along the z-axs s dfferent from attenuaton caused by ohmc-loss, there s no real power propagaton. The transmsson wave cannot penetrate nto seabedrock-layer whch merely belongs to the pure wave effect, and s named evanescent wave. From () and (), we can see that the propagaton drecton of evanescent wave s along the x-axs, and ts attenuaton constant, phase constant and propagaton velocty are expressed as sn, (3) r sn, (4) v r p /. (5) The propagaton characterstcs of electromagnetc wave n seabed-rock-layer are closely related to the ncdent angle. As sn, the path loss n seabed-rocklayer path s smaller and the propagaton velocty s faster than that n seawater path. When the deeply submerged transmttng and recevng antennas are extremely far apart away from each other, r

RADIOENGINEERING, VOL. 7, NO., JUNE 8 435 the sgnal n the LOS-seawater path wll be severely attenuated and can be gnored, thus the propagaton mechansm can be regarded as the followng processes: Frstly, the electromagnetc waves travel through the nsulatng shell outsde the antenna nto seawater. Secondly, the waves whch cross the nterface between seawater and seabed-rock-layer are very sharply refracted and establsh evanescent wave feld n seabed-rock-layer. Thrdly, the waves wll be guded along the seabedrock-layer surface wth attenuaton, and are completely absorbed wthn the effectve depth. Fourthly, the absorbed energy stmulates the forced vbratons of the molecules or atoms n the medum, resultng n Raylegh scatterng. Ffthly, the Raylegh waves generated by scatterng are coherent, and fnally the waves return to the seawater through the nterface. 3. Achevable Communcaton Range The lateral shft of evanescent wave on the seabedrock-layer surface s closely related to the earlest researcher F. Goos and H. Hanchen [7] who took experment wth multple reflecton method to prove when the total reflecton occurs at the nterface of two medums, the actual reflecton pont has a lateral shft from the ncdent pont, and later the lateral shft was named Goos-Hanchen (GH) Shft [8]. Accordng to Statc Phase Method [9], we can derve GH Shft expressed as: d r j j (6) where the subscrpt r j = r s, r p. d r j = d r s, d r p represent GH Shft of TE wave and TM wave, respectvely. Therefore the GH Shft s related to the polarzaton state of ncdent wave []. We can derve GH Shft of TE wave and TM wave, respectvely: d sn r-s / sn cos sn d r-p / sn where sn sn sn. c sn, (7) (8) Obvously, the GH Shft s determned by the ncdent angle. If the ncdent angle s just equal to the crtcal angle c, the lateral GH Shft wll reach nfnty and the penetraton depth wll be nfnte thus no more evanescent wave occurs. Only when the ncdent angle s larger than the crtcal angle, the lateral GH Shft exsts, but the larger the ncdent angle s, the smaller the lateral GH Shft s. Therefore, when the ncdent angle s larger than and close to the crtcal angle, the lateral GH Shft of the wave at the seabedrock-layer surface can reach up to several klometers. Theoretcally ths method can solve the problem of range-lmtaton n the seawater. Through the above-mentoned dervaton and analyss about the total reflecton, we can conclude that the achevable horzontal communcaton range of the deeply submerged transcever can be expressed as: Los r-j d = d + h+ r tan r (9) where r s the radus of the nsulatng shell and h s the vertcal range of antennas from seabed-rock-layer. 3.3 Path Loss Frs propagaton equaton can be expressed as [] db db db db db P P G G L (3) r t t r Loss where P t and P r are transmtted and receved power, respectvely. G t and G r are the antenna gans of the transmtter and recever, respectvely. And L Loss s path loss. For the seabed-rock-layer channel model, the path loss s related to absorpton loss L att (db) and spread loss L spread (db) n two medums. L db L db + L db. (3) Loss att spread The absorpton loss n the conductve medums exsts n three stages: seawater, seabed-rock-layer and returnseawater. The propagaton range n seawater s set as d s = [(h + r)/cos r] and the attenuaton constant s α. And n seabed-rock-layer, the propagaton range s GH Shft d r and the attenuaton constant s α r. Hence, the absorpton loss can be calculated as: dsrdr Latt db log e. (3) Most of the prevous studes have focused on shortrange underwater wreless transmsson scenaros and the spread loss s neglected. In ths secton, we deduce and analyze the characterstcs of spread loss n long-range seabed-rock-layer channel model theoretcally. The nsulatng shell outsde the antenna matches the mpedance of the seawater, so the wavelength n both medums s same. However, the permttvty and conductvty of seabed-rock-layer are dfferent from those of seawater, so the wavelength wll change due to the change of the phase constant caused by the propagaton of evanescent wave on the seabed-rock-layer surface. The path loss n vacuum s L db =log 4 d / (33)

436 Z. Q. NIE, S. L. WANG, D. H. CHEN, T. DENG, SEABED-ROCK-LAYER ELECTROMAGNETIC COMMUNICATION CHANNEL Attenuaton constant (db/m) 8 6 4 Seawater Seabed-rock-layer 3 4 5 6 7 8 9 Incdent angle (degree) Fg. 3. Attenuaton constant at frequency khz. Propagaton velocty (m/s) x 6 9 8 7 6 5 4 3 Seawater Seabed-rock-layer 3 4 5 6 7 8 9 Incdent angle (degree) Fg. 4. Propagaton velocty at frequency khz. where λ = c/f s wavelength n vacuum. The loss due to the change of the transmsson medum [] s db =log / L (34) c where λ s wavelength n conductve medum. Substtutng (34) nto (33) yelds L db = L + L log 4 d /. (35) spread c Combnng (5) and (35), the spread loss of electromagnetc wave n conductve medum can be expressed as: d Lspread db =log. (36) Snce the propagaton of electromagnetc wave n the seabed model wll go through fve processes ncludng nsulatng shell, seawater, seabed-rock-layer, return-seawater and nsulatng shell. Thus the spread loss can be corrected as: Lspread db =log r ds dr. (37) It s obvous that the nfluence factors of the path loss are not only the permttvty, conductvty, permeablty of the conductve medum, but also the launch frequency, the ncdence angle of electromagnetc wave, and the radus of the nsulaton cylnder shell as well as the vertcal heght of the antennas from the seabed-rock-layer surface. 3.4 Channel Response Combnng (9), (3), (3) and (37), we can get the receved electrc feld ntensty, expressed as: E jkds jkdr E e e rds dr E e rds dr e e e E rd d s r ds jds dr jdr d sn d j d sn d s r s r e e. (38) Thus the ampltude-frequency response and phasefrequency response of the communcaton channel model can be obtaned, respectvely: s r e d sn d H f, (39) rd d s r f d d sn. (4) s r 4. Smulaton Results and Analyss TE wave and TM wave are dfferent only n GH Shft equatons, but ther characterstcs are same. In ths secton, TE wave s utlzed for smulaton verfcaton and analyss. The radus of the nsulatng shell s consdered to be 9 6 mm [3]. For the frequency less than GHz, the spread loss n the nsulatng shell s small enough to be gnored. In the deep sea, the vertcal heght of the antennas from the seabed-rock-layer surface s generally set to 3 m, and we adopt the frequency of khz prmarly for smulaton. From Fg. 3, we can know that the attenuaton constant n seawater s of db/m or so. When the ncdent angle s greater than and close to the crtcal angle, t s about.5 db/m n seabed-rock-layer whch s only / of the attenuaton n the seawater path. As can be seen from Fg. 4, the propagaton velocty of electromagnetc wave n seawater s.5 6 m/s. However, wth the same frequency and angle of ncdence, the correspondng velocty n seabed-rock-layer can reach 9.8 6 m/s. It ndcates that the communcaton range and propagaton velocty wll ncrease about tmes through the seabed-rock-layer path. In Fg. 5, the lateral GH Shft along the seabed-rocklayer surface s shown as a functon of the ncdent angle. When the ncdent angle s greater than 3 degrees, the GH Shft s so small that there s no dsplay. The sotropc antenna can emt the omn-drectonal waves, whch wll cause dfferent GH Shfts when arrvng at the nterface between seawater and seabed-rock-layer. The larger the ncdent angle s, the smaller the lateral GH Shft s. When the ncdent angle s larger than and close to the crtcal angle, the lateral GH Shft can reach 3 meters at frequency khz and more than two klometers at frequency khz.

RADIOENGINEERING, VOL. 7, NO., JUNE 8 437 3 5 KHz KHz KHz 8 Path Loss Absorpton Loss Spread Loss Lateral GH Shft (m) 5 Loss (db) 6 4 8 5 6 4.9.9.93.94.95.96.97.98.99 3 Incdent angle (degree) Fg. 5. Lateral GH Shft along the seabed-rock-layer surface at frequency khz, khz and khz. 3 5 h=m h=m h=m h=3m.9.9.93.94.95.96.97.98.99 3 Incdence angle (degree) Fg. 7. The loss ncludng path loss, absorpton loss, spread loss n seabed-rock-layer communcaton channel model at frequency khz. KHz KHz KHz Path Loss (db) 5 Path Loss (db) 8 6 4 5.9.9.93.94.95.96.97.98.99 3 Incdence angle (degree) Fg. 6. Path loss n seabed-rock-layer communcaton channel model at frequency KHz wth the dfferent heghts. Fgure 6 shows the characterstcs of the path loss n the seabed-rock-layer communcaton channel model wth dfferent antenna heghts. The hgher the antenna, the greater s the path loss. As the heght ncreases, the path loss ncreases by about 5 db for each addtonal heght of m. Ths s because the hgher the heght, the longer s the oblque range through the seawater before the electromagnetc wave arrves at the seabed-rock-layer, resultng n larger loss, especally the absorpton loss. So much closer the antenna to the seabed-rock-layer, the more advantages of ths channel model have. Takng nto account the case where the transmttng and recevng antennas are n contact wth the seabed (h = ), the analyss of the characterstcs of path loss s carred out. The results are shown n Fg. 7. It s found that the absorpton loss of the conductve medum s smaller than the spread loss when the ncdent angle s greater than.97 degrees; the reason s that the GH Shft gets shorter when the ncdent angle s greater from Fg. 5. A slght change of the ncdent angle wll cause a dramatc change n path loss. When the ncdent angle s about.9 degrees, the path loss s about 7 db. Accordng to Fg. 8 we can also see that f we adopt the lower frequency for communcaton, khz for example, 8 6 5 5 5 3 Communcaton Range (m) Fg. 8. Path loss n seabed-rock-layer communcaton channel model at frequency khz, khz and khz. Ampltude-Frequency Response H(f) - - -3-4 m 4m -5 8m m 6m -6 5 5 Frequency (KHz) Fg. 9. Ampltude-frequency response. the communcaton range can reach m farther, whch s very mportant to break through the lmtaton of range when electromagnetc wave propagate n seawater. Then, the channel response of the seabed-rock-layer communcaton channel s analyzed by the case where the transcever s n contact wth the seabed (h = m). Fgure 9 shows the smulaton results of ampltude-frequency response n the case of communcaton range of m, 4 m,

438 Z. Q. NIE, S. L. WANG, D. H. CHEN, T. DENG, SEABED-ROCK-LAYER ELECTROMAGNETIC COMMUNICATION CHANNEL Phase-Frequency Response φ(f) (rad) 6 4 - -4 m 4m 8m m 6m -6 5 5 Frequency (KHz) Fg.. Phase-frequency response. 8 m, m and 6 m n the operatng frequency range of ~5 khz. It can be observed that the ampltude-frequency response of the channel exhbts a smlar exponental trend, and the sgnal fadng at dfferent frequences s dfferent, the fadng of the hgh-frequency sgnal s more serous than the low-frequency sgnal. In the case of communcaton range of m, the characterstc of the channel fadng s relatvely flat, and the maxmum fadng dfference s only about.4 tmes. When the communcaton range s expanded to 8 m, the fadng dfference s only about 4 tmes. Fgure shows the smulaton results of the phasefrequency response n the case of communcaton range of m, 4 m, 8 m, m and 6 m n the operatng frequency range of ~5 khz. As can be seen from the fgure, wth the ncrease of the communcaton range n the smulated operatng frequency range, the phase-frequency response curve s steeper, so that the speed of phase change s accelerated. For example, n the case of communcaton range of m, the phase dfference between the 8~ khz s only.39 rad, and n the case of the communcaton range of m, the dfference s.545 rad. In the case of the range of 6 m, the dfference s close to.53 rad. Accordng to the smulaton results, we can see that the ampltude dfference and phase dfference are not serous n the short range, so that the transmsson sgnal wll not be severely affected. 5. Concluson In ths paper, our research starts the analyss about the propagaton characterstcs of electromagnetc wave n seawater, we explot the evanescent wave effect generated by total reflecton to deduce and analyze the lateral GH Shft of electromagnetc wave on the seabed-rock-layer surface whose man component s basalt theoretcally. A low loss seabed-rock-layer communcaton channel model for hgh speed communcatons has been establshed n ths paper, whose propagaton velocty can be ncreased tmes and path loss can also be reduced to / of the seawater condton. If we choose the approprately lower frequency, communcaton range can be extended to several hundred meters or even several klometers. Ths model s a breakthrough n the problem of lmted communcaton range when electromagnetc wave propagates n seawater and also has certan sgnfcance for underwater shortrange and hgh speed relable transmsson. References [] RHODES, M. Electromagnetc propagaton n sea water and ts value n mltary systems. In SEAS DTC Techncal Conference. 7, p. -6. [] SOZER, E. M., STOJANOVIC, M., PROAKIS, J. G. Underwater acoustc networks. IEEE Journal of Oceanc Engneerng,, vol. 5, no., p. 7 83. DOI:.9/48.8738 [3] CHITRE, M., SHAHABUDEEN, S., STOJANOVIC, M. Underwater acoustc communcatons and networkng: Recent advances and future challenges. 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RADIOENGINEERING, VOL. 7, NO., JUNE 8 439 Conference on Systems, Man and Cybernetcs. San Antono (USA), 9, p. 33 38. DOI:.9/ICSMC.9.534598 [5] KELLEY, B., NAISHADHAM, K. RF multcarrer sgnalng and antenna systems for low SNR broadband underwater communcatons. In IEEE Topcal Conference on Bomedcal Wreless Technologes, Networks, and Sensng Systems (BoWreleSS). Austn (USA), 3, p. 4 4. DOI:.9/BoWreleSS.3.66379 [6] MICHALSKI, K. A. Electromagnetc wave theory. Proceedngs of the IEEE, 987, vol. 75, no. 6, p. 86 863. DOI:.9/PROC.987.388 [7] GOOS, F., HANCHEN, H. En neuer und fundamentaler Versuch zur Totalreflexon. Annalen Der Physk,, vol. 436, no. 7, p. 333 346. DOI:./andp.94743674 [8] SNYDER, A. W., LOVE, J. D. Goos-Hanchen shft. Appled Optcs, 976, vol. 5, no., p. 36 38. DOI:.364/AO.5.36 [9] RESCH, K. J., LUNDEEN, J. S., STEINBERG, A. M. Total reflecton cannot occur wth a negatve delay tme. IEEE Journal of Quantum Electroncs,, vol. 37, no. 6, p. 794 799. DOI:.9/3.9777 [] LIU, X. B., CAO, Z. Q., ZHU, P. F., et al. Smultaneously large and opposte lateral beam shfts for TE and TM modes on a double metal-claddng slab. Chnese Physcs Letters, 6, vol. 3, p. 77 79. DOI:.88/56-37X/3/8/3 [] STUBER, G. L. Prncples of Moble Communcaton. Kluwer Academc Publshers, 996. ISBN: 978--4757-668-6 [] WANG, W. C. Electromagnetc Wave Theory. 986. Avalable at: http://depts.washngton.edu/mctech/optcs/me557/week.pdf. [3] SHI, J., ZHANG S., YANG, C. J. Hgh frequency RF based noncontact underwater communcaton. In IEEE Oceans. Yeosu (South Korea),, p. 6. DOI:.9/OCEANS- Yeosu..66343 About the Authors... Zhqang NIE was born n 993. He receved hs B.S. degree n Communcaton Engneerng from Hunan Unversty n 5 and currently s a master student at the Dept. of Electronc Scence, Natonal Unversty of Defense Technology, Chna. Hs research nterest s underwater electromagnetc communcaton. Shlan WANG (correspondng author) was born n 976. He receved hs Ph.D. degree n Informaton and Communcaton Engneerng from the Natonal Unversty of Defense Technology, Chna n 4. Currently he s a professor at the Dept. of Electronc Scence, Natonal Unversty of Defense Technology. Hs prmary nterest s n the area of underwater communcaton and network confrontaton. Daha CHEN has receved the B.E. degree, M.E. degree and D.E. degree n Electronc Engneerng from the Unversty of Electronc Scence and Technology n Chengdu (UESTC), Chengdu, Chna, n 993,, 8, respectvely. He joned the Insttute of Electronc Engneerng, Chna Academy of Engneerng Physcs snce July, 993. Hs man research nterests are n the area of hgh data rate transmsson systems desgn and mplementaton. Tan DENG was born n 993. She receved her B.S. degree n Communcaton Engneerng from Hunan Unversty n 5 and currently s a master student at the Dept. of Electronc Scence, Natonal Unversty of Defense Technology, Chna. Her research nterest s modern communcaton technology.