Analyi of eflection and Scattering Characteritic at the 6GH Frequency Myoung-Won Jung* Jong Ho Kim* Young Keun Yoon* Young Jun Chong* *Technology eearch Deartment TI 6 Gajeong-dong Yueong-gu Daejeon 35-7 KOA mwjung@etri.re.kr jonghkim@etri.re.kr ykyoon@etri.re.kr yjchong@etri.re.kr Abtract Thi aer reent the analyi reult of reflection and cattering characteritic for roagation rediction at the 6GH frequency. Becaue the millimeter wave band ha very hort wavelength within a few millimeter the cattering characteritic i occurred by the mall roughne of the urface of a wall on indoor environment. In addition becaue the roagation characteritic aear differently by the urface roughne of medium the roagation rediction i very difficult. Therefore the cattering characteritic according to the urface roughne hould be analyed for accurate roagation rediction. To redict the roagation characteritic in the indoor environment we hould have tudied change in the accordance with the rough urface. Thi aer analye the reflection and cattering characteritic by the urface roughne of medium in millimeter wave band and tudie the method for alying to the roagation rediction. Keyword millimeter wave cattering characteritic reflection characteritic urface roughne ray-tracing I. INTODUCTION ecently the demand for high data rate and large caacity i increaing in the millimeter wave band. Among them 6GH frequency i a good candidate for wide-band wirele communication in the indoor wirele environment. A communication technique for low-frequency efficiency can be eaily ued to contruct broadband communication in Multile Gigabit Wirele Sytem (MGWS). ecially hort-range communication between a TV and et-to bo for a ractical ue of the 6 GH band wa tudied. In the at there i no need for tudie on the reflection and cattering of radio wave in the 6 GH band becaue the communication range i very hort. However the communication range i gradually widening owing to advance in technology and thu reearch on the reflection and cattering of radio wave i needed. Generally the reflection characteritic i determined baed on the electrical characteritic of the medium but the reflection characteritic i determined by the cattering characteritic when the urface roughne of the medium i larger than the wavelength. Alo to redict the roagation characteritic in variou environment the channel model by variou meaurement or hyical channel model by ray tracing are neceary but tudie on thee model are incomlete Therefore the reflection characteritic of the rough urface hould be analyed for a more accurate analyi. In thi aer we analyed the reflection and cattering characteritic baed on the urface roughne of medium in the millimeter wave band and tudie a method for alication to roagation rediction uing a theoretical generaliation of thee characteritic II. TH FCTION AND SCATTING CHAACTISTICS AT TH MIIMT WAV BAND Generally a radio wave ha reflection and enetration characteritic according to a change in the medium. In the cae of reflection the direction of the reflected wave can be redicted to ome etent uing Snell law. However the redictable direction of the reflection wave uing Snell law i only oible when the urface of the obtacle i very mooth and there i therefore no diffuion. Many reearche on a rough urface have been conducted. Thee reearche are very imortant for a erformance verification of the roagation channel rediction model in ray tracing. A. ffective roughne () For a tudy on the cattering algorithm Italian V. D. Degli- oito and l-sallabi alied the cattering effect uing the face and volume of building in ray tracing. The model (or COST-73 cattering model) wa rooed through thee tudie and imlemented for 3D-ray tracing. Firt the definition of the cattering coefficient i neceary in order to draw the cattering attern in the model. The cattering coefficient i ereed baed on the ratio between the incident electric field and cattering electric field about the cattering urface area. S S. () i d According to thi definition and the rincile of the conervation of energy the total ower balance i a follow: S P / Pi G + + () ISBN 978-89-96865--5 44 February 6~9 4 ICACT4
where the reflection coefficient i Γ / and i the reflection attenuation coefficient by cattering. In addition P i the incident ower and P i the enetration ower. Alo Γ i determined baed on the Frenel reflection coefficient and P /P doe not change ignificantly from the non-uniformity of wall or obtacle [8]. Therefore equation () can be ereed again by auming the ideal lane (S ). P / Pi. G + (3) Under thi condition the relation between equation () and (3) i a follow. S @ -. (4) G The cattering coefficient of equation (4) ha to atify the cattering ower balance a follow: i W i i W S d r d r / q q f r in d d where Ω i the incident angle of the ray tube on the urface r and r are the ditance between the tranmitter and the cattering urface and between the receiving oint and the cattering urface reectively. The maimum cattering ower can be calculated by alying the cattering attern to equation (5). The cattering attern i determined by the non-uniformity of the obtacle and by the following two model. ) ambertian Model The maimum ower of the cattering wave in the ambertian model alway eit vertically in an obtacle and the cattering attern i a follow: S co. q Thu if the maimum ower i alied to equation (6) the cattering attern i a follow [][]: S æ KS ö ç è ri r coqi coq ds where i a contant determined by the incident wave. ) Directive Model In the directive model it i aumed that the maimum electric field of the cattering wave i formed to the direction of the regular reflection in the cattering environment. According to thi aumtion the cattering attern of the directive model i a follow: (5) (6) (7) a æ+ coy ö S ç è where i the angle between the cattering wave and the regular reflection and i a arameter determining the beam width of the cattering wave. The maimum cattering ower i calculated by ubtituting equation (8) with (5) a follow: where F I S a æ KS ö ç è ri r coqi ds F a (8) (9) a æa ö å Ii a ç j è j () æ j -(-) ö j- ç é w ùè æ wö in qi j ê q ú i w j ê åç w ú co. + ê è ë úû () B. Kirchhoff aroimation (KA) Many cattering theorie regarding a rough urface have been tudied for the olution uggetion of the cattering uing an aroimation of the boundary condition. The aroimation method vary and the KA method i baed on a Helmholt integration uing the boundary condition. Thi method i generally known a the Kirchhoff method or Method of Phyical Otic (PO). The theory of the Kirchhoff general olution of the rough urface i very imortant becaue it i a baic theory to elain the cattering of the articular urface uch a a eriodic or random area. III. COMPAISON BTWN THOTICA ANAYSS USING KICHHOFF APPOXIMATION AND TH MASUMNT SUTS In thi chater the cattering theory value of the millimeter wave band by the KA method mentioned in ection II are drawn and comared with the meaurement reult. A. The cattering characteritic of the rough urface The rough urface can be divided into eriodic and random tructure. Figure 3 how the geometric tructure of incident and cattering wave. If the radio wave ha incident angle about the -ai along the -ai it ha elevation angle in the - lane and aimuth angle in the -y lane and i cattered. Under thi condition the cattering coefficient for a rough urface of a eriodic tructure i a follow: ISBN 978-89-96865--5 443 February 6~9 4 ICACT4
I q Figure. Meurement ytem configuration - q iv+ iv r ( a - b) e d. 4 coq () In equation (9) the formula that have to be additionally calculated are a follow: v k(inq - in q ) - k(coq + co q ) v + v a ( - )in q + ( + )inq q 3 y S b ( + )co q - ( - )co q. (3) (4) quation () i a one-dimenional Kirchhoff general olution and the cattering urface can be etended to twodimenion uing equation (3). Therefore equation (5) which i the general olution of the one-dimenional rough urface i ereed a follow: r r iv r ( a + c y - b) e ddy. (6) 4XY coq - - X X Y Y In the cattering analyi of a random urface it i mot imortant to determine the roughne of the urface to model the robability ditribution and indicator variable. For the KA method the characteritic of a random urface can be ereed through a deviation of the urface height and the urface correlation ditance. In addition how the number of reflection within the urface i conidered i relevant to the accuracy of the modeling. Actually one to an infinite number of reflection can occur on a random urface and the more the reflection are analyed the more accurate the reult will be. However the greater the degree of the analyi i increaed the more the calculation comleity i increaed eonentially. Thi aer alie a two-degree analyi to the KA method becaue the reult i ignificantly accurate even though only two-degree reflection are analyed. The cattering coefficient by a one-degree Kirchhoff i drawn uing the cro ection of the follow equation: KA k co q < TKA > (7) < T > S( q q ) F KA æ ö dd ç è e[ -i( K - Ki ) d - ( K - K i ) ] e[ < f f > ( K + K i ) -] (8) where the cro ection indicate the reflected area to the articular cattering angle in the total area. The cattering coefficient by the two-degree Kirchhoff i determined by changing equation (7) a follow: KA k co q < TKA > < T > S( q ) S( q ) K da KA i (9) ' ' * ' K da JJ S ( a) S ( a ). () < > B. Meaurement camaign and reult To redict roagation characteritic at the 6 GH frequency we are ued KA aroimation. KA aroimation i given correlation on the rough urface of cattered ignal. In thi method reflection characteritic of rough urface at the 6 GH are comoed of the variable of MS height and correlation length. Baed on the above reult we made total 7 rough urface ( eriodic and 5 random amle). The Figure it how the meaurement ytem configuration to analye reflection characteritic on the rough urface. Figure. Meurement ytem configuration The carrier frequency wa et to 6 GH and we were intalled mall HPBW horn antenna and rough urface in the tand. Meaurement tructure wa T/ ditance.5m /urface interval m T/urface ga.3m/.6m ( kind of meaurement cae). We meaured reflection characteritic of rough urface in the ~8 incident angle( and 5 interval). We comared with imulation and meaurement reult. The Figure 3 how the reult of analyi on the rough urface. The analyi of the entire we how only following two cae...9.8.7.6.5.4.3..8.6.4... - -8-6 -4-4 6 8 -. - -8-6 -4-4 6 8 (a) degree in angle of incidence ISBN 978-89-96865--5 444 February 6~9 4 ICACT4
...8.6.4. - -8-6 -4-4 6 8...8.6.4. - -8-6 -4-4 6 8 (b) degree in angle of incidence (eft: and meaurement reult ight: meaurement and curb fitting reult) Figure 3. and meaurement reult C. Prooed roagation rediction method To redict roagation characteritic at the 6 GH frequency we are ued KA aroimation. KA aroimation i given correlation on the rough urface of cattered ignal. In thi method reflection characteritic of rough urface at the 6 GH are comoed of the variable of MS height and correlation length. A method for ray-tracing in a wideband Gbyte Gb communication ytem include deriving cattering ditribution characteritic of reflected ignal. An electromagnetic wave cattered in an electromagnetic wave incident to an interface in the indoor environment. Average cattering ower for the interface i calculated by the cattered electromagnetic wave. The roagation of the electromagnetic wave in the indoor area i analyed baed on the average cattering ower. In the Figure 3 it how the analyi roce accordance with the rough urface cattering. Figure 4. and meaurement reult Figure 4 i diagram chematically illutrating roagation of an electromagnetic wave in a radio wave ytem in accordance with the embodiment of the rooed method. The analyi of the entire we how only following two cae. (a) Incident angle degree (b) Incident angle 45 degree Figure 5. and meaurement reult IV. CONCUSION Proagation rediction i different flat urface and rough urface. It i deend on wave length from the urface roughne at the 6 GH frequency. To imrove thee roblem thi aer analyed the Kirchhoff olution of a rough urface and derived the Kirchhoff olution of a random rough urface with a normal ditribution function. Furthermore to decreae the comuting load uing aroimation and aly the rooed method to an indoor environment in the millimeter wave band thi aer rooed a cattering algorithm and analyed the cattering characteritic baed on the urface roughne. The reult of thi aer can increae the accuracy and reliability of ray tracing in a millimeter wave band. In addition a erformance imrovement of the roagation rediction model can be achieved by uing the frequency efficiently and the rooed technique can be alied to the develoment of other millimeter wave band. ACKNOWDGMNT Thi reearch wa funded by the MSIP(Minitry of Science ICT & Future Planning) Korea in the ICT &D Program 3 FNCS [] P. Beckmann and A. Siichino Scattering of letromagnetic Wave from ough Surface (Oford: Pergamon) 963. [] A. Ihmaru and J.S. Chen Scattering from very rough metallic and dielectric urface: a theory baed on the modified Kirchhoff aroimation Wave in andom Media vol.. -34 Jan. 99. [3] CMA TC48 CMA-387 High ate 6GH PHY MAC and HDMI PA Whiteaer nd ed. June 3th. [4] Wirele HD Alliance Overview of Wirele-HD Secification Verion.a Aug. 9. [5] K. ackowki et al. A Wideband Beamformer for a Phaed-Array 6GH eceiver in 4nm Digital CMOS Seion I Int. Solid-State Circuit Conf. Feb. 8th. 4-4. [6] W.. Chan et al. A 6GH-band Phaed-Array Tranmitter in 65nm CMOS Seion I Int. Solid-State Circuit Conf. Feb. 8th. 4-43. [7] TSI DT/M-M-49 (6) lectromagnetic Comatibility and adio Sectrum Matter (M): Sytem eference Document: Technical Characteritic of Multile Gigabit Wirele Sytem in the 6 GH ange Mar. 6. [8] M.W. Jung J.H. Kim Y.K. Yoon H.J. Hong Study of Proagation Characteritic Imrovement of ay-tracing Algorithm for MM ectrum Conference of Korea Intitute lectromagnetic ngineering Science 9. [9] M.W. Jung J.H. Kim Y.K. Yoon J.W. Kim S.C. Kim nhancement Aroach of ay-tracing Algorithm for MM-Wave Band International Conference on Infrared and Millimeter and Terahert Wave. [] M. W. Jung J. H. Kim J. I. Choi et al. An nhanced Aroach for a Prediction Method of the Proagation Characteritic in Korean nvironment at 78MH TI Journal vol. 34 no. 6.9-9 Dec.. ISBN 978-89-96865--5 445 February 6~9 4 ICACT4
Myoung-Won Jung received B.S. M.S. and Ph. D. degree in lectronic ngineering from Chungnam National Univerity Daejeon Korea in 6 8 and 4. Since 9 he ha been working for lectronic and Telecommunication eearch Intitute (TI) where he i a enior member of reearch taff of the adio Technology Deartment. Hi main interet are radio roagation tudy for mobile communication and millimeter wave roagation tudy in indoor and outdoor environment Young-Keun Yoon wa born in Chungbuk Korea. He received the B.. and M.. degree in radio engineering from National Chungbuk Univerity Korea in 997 999 reectively. Since he ha been worked in lectronic and Telecommunication eearch Intitute (TI). He ha been involved in the reearch of radio reource management and roagation ince 3. Hi main interet are radio roagation tudy for mobile communication and ectrum engineering tudy in indoor and outdoor environment Jong Ho Kim received hi BS MS and PhD in electronic engineering from Chungnam National Univerity Daejeon e. of Korea in 986 988 and 6 reectively. Since 989 he ha been working for TI Daejeon e. of Korea where he i a rincial member of the engineering taff of the adio Technology Deartment. Hi main interet are radio roagation and ectrum engineering. Young Jun Chong received the B.S. degree from the Jeju Univerity Jeju iland Korea in 99 and the M.S. degree in electronic engineering in 994 from Sogang Univerity. And Ph.D degree in lectronic ngineering from Chungnam National Univerity Daejeon Korea in 5 reectively. Since 994 he ha been with TI Dajeon Korea where he i a leader of ectrum engineering ection rincile member of the reearch taff of the adio Technology Deartment. He i currently involved in the develoment of the digital ultra-narrow band Walky-Talky. Hi reearch interet include F circuit and ytem. ISBN 978-89-96865--5 446 February 6~9 4 ICACT4