A New Method of Uplink Power Compensation of Rain Attenuation of Satellite Communication System Li Rong

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1 International Conerence on tomation, Mechanical Control and Comptational Engineering (MCCE 205) New Method o Uplink ower Compensation o Rain ttenation o Satellite Commnication System Li Rong College o Commnication and Inormation Engineering,Xi an University o Science and Technology, Xi an 70054,China Cold00@26.com Key words: Satellite commnication; Redction o rain attenation; Diversity reception; stract. In satellite commnication the signal ading may reach the maximm in rain weather. In this paper, an plink power redction rain ading method is pt orward to overcome the shortcoming o the traditional method. Throgh detection o satellite signal strength, the rain attenation in satellite commnication link can e calclated, and according to the rain attenation vales, grond station power will e adjsted to achieve the maximm compensation or the rain attenation, eectively redcing the inlence o rain attenation on the commnication qality. Introdction With the widespread application and high speed development o modern commnications, the demand o people or modern commnications is ecoming more anxios. Satellite commnication has ecome one o the most important technologies in recent years ecase o its eatres sch as wide coverage, no geographical limitations, cost eing nothing to do with distance []. The technology o satellite commnication resolves the prolems o traditional grond commnication systems which are restricted to geographical srronding and economic conditions, providing gloal seamless ll coverage networks. However, ecase o space radio transmission satellite commtation is highly ssceptile to clod, snow, og and rain, which leads to varios degree rain ading. The research indicates that the ading will reach the maximm in rainy weather. Conseqently, how to decrease the attenation and improve the commnication qality have ecome the hot isses. However, the traditional diversity reception technology is to choose two sites with certain distance y sing the space heterogeneity in rain areas and two earth stations are located. The two stations that have certain distance receive the signals o satellite commnication respectively. Then, the rain attenation vales o the signals are calclated. By comparison, the signal which has less attenation is selected as the ltimate reception signal. The method may redce the inlence o rain ading, t it cannot eectively remove the inlence o rain attenation. Based on aove prolems an plink power adjstment method is pt orward. Throgh detection o satellite signal strength, the rain attenation in satellite commnication link can e calclated, and according to the rain attenation vales, grond station power will e adjsted to achieve the maximm compensation or the rain attenation, eectively redcing the inlence o rain attenation on the commnication qality. The Inlence o rain ading on satellite commnication Satellite commnication technology that can keep two or more earth stations commnicate with each other throgh the relay o the manal commnication satellite. [3] The radio signals spread etween the grond stations and the satellite, travelling throgh the atmosphere. The signals, while spreading in the atmosphere, are inevitaly aected y the energy relection and asorption o ions and ree electrons in the atmosphere. Moreover, the troposphere has large amont o water vapor molecles, CO molecles, O molecles, and varios aerosols sch as snow, og, and rain. Ths, the radio signals, while spreading in the troposphere, are continally asored, relected and scattered, casing the energy redction The athors - lished y tlantis ress 28

2 mong the attenation, the rain ading or the signals most serios. In rainy days, the electromagnetic waves o satellite commnication are asored or relected y the rain drops, casing the attenation. The inlence extent is determined y the microscopic characteristics o the rain drops. The signal attenation vales with dierent powers are dierent, aected y dierent rainall intensity. In general, the rain attenation o signals ecomes particlarly serios when the power exceeds 0Hz [2]. Fig. shows the relationship etween the signal power and rain attenation. Fig.. the relationship etween the signal power and rain attenation Fig. indicates that the attenation vales o the radio signals are dierent with the dierent rainall intensity. The traditional diversity reception, as stated aove, is that two earth stations receive the radio signals relected y the satellite simltaneosly and the respective rain attenation o two stations is dierent ecase o the dierent rainall intensity. Then calclating the attenation degrees o the reception signals, the eqation is as ollows r( db) = kr Le () R represents the rate o rainall, coeicient o the rainall rate and L e transmission path o the signals in the rain areas. Ths, the respective rain attenation o the two stations is calclated and y comparison, the ltimate reception signals is selected which has less rain attenation. The eqation o the qality o satellite commnication is as Eq. 2 R Le log α = R r (2) s Eq.2 states, the qality o satellite commnication is inversely proportional to the rain attenation. It indicates that the less the signal is aected y rain ading, the etter the qality is. Thogh the signal with the less rain attenation is selected to redce the inlence o rain y traditional diversity reception, the attenation cannot e removed aectively, casing the redction o commnication qality. Thereore, in order to overcome the inlence o rain ading on commnication signals and the shortcoming o the traditional technology, the method o plink power control is pt orward. 282

3 Throgh detection o satellite signal strength, the rain attenation in satellite commnication link can e calclated, and according to the rain attenation vales, grond station power will e adjsted to achieve the maximm compensation or the rain attenation, eectively redcing the inlence o rain attenation on the commnication qality. The Method o Uplink ower Compensation o rain attenation The method o traditional diversity reception to redce rain attenation is to select the signal which is aected less y rain attenation and it cannot avoid the inlence o rain ading asoltely. So we pt orward the method o plink power control to completely remove the rain attenation, receiving high qality signals. The method o plink power control to redce rain ading will e introdced as ollows. the Fndamental Link rinciples Throgh the data o the plink and according to the link rain attenation vales calclated y commnication data, the grond station emission power can e adjsted y the inlence vale o rain ading. Then, to increase the transmitting power accordingly conteracts the power loss cased y rainall and the same signals as that in normal weathers can e received y the grond station to redce the rain attenation. The speciic principle is as ollows: as the plink rain ading vales cannot e calclated directly, the downlink rain ading vales that can e measred directly are sed to get the plink power estimated vales y reqency conversion. Then, the estimated vales are sent to the system processor to achieve the compensation or the rain attenation y power control. The lock diagram is shown in Fig.2 [4] Fig 2. The priciple lock diagram o plink power control 283

4 the Estimation and Transormation o the Link Rain Fading s the real-time link attenation cannot e measred directly, the attenation vale is predicted according to the experience vales. The prediction eqation ased on the rain attenation is as Eq.3 ˆ ( t t kt ) = ( ) ( ) () t t T + 20 t kt + e t (3) et () prediction error vale and T prediction intervals. In addition, () t real vale o the rain ading and ( t T) represents the real vale which was measred at a time eore this prediction. Ths, the prediction ormla can e transormed to get the real rain ading eqation as Eq.4 k ( ) k q t t kt = q i 20 ( t it) = 20 () t q k i= k prediction delay nmer and q delay actor. Moreover, the proportional actor will e when q is eqal to. The Eq.4 can e simpliied to Eq.5. ˆ ( t t kt ) = 20() t (5) now the prediction o the signal power is completed. ter the prediction o the downlink signal power, we will transorm the downlink power to the plink power. ccording to the rain attenation o the downlink power signals, the plink rain attenation can e estimated y employing dierent reqencies. The eqations o plink power rain ading are as ollows: R ϕ( ) = dr ϕ( d ) (6) ϕ( ).72 = (7) represents the emission power o the signal and R ( db ) and dr ( db ) indicate the plink rain attenation and the downlink rain attenation respectively. Moreover, and are d the plink power and downlink power respectively. Now the R can e calclated. Ths, the eqation o the whole attenation vale is Eq.8 L = R + S (8) L whole attenation vale. R is called the plink rain attenation and S power attenation when the signal travels in the atmosphere. the Compensation o the rain ading Now the whole power attenation is calclated as aove, so the emission power o the grond station may e adjsted according to the attenation vale, adding the attenation vale to the emission power. Eq.9 power calclation eqation. = 0 + L (9) ltimate signal power o the earth station and 0 power which is existed nder normal snny weather conditions. Ths, the compensation or the rain attenation will e inished in term o the Eq.9, eectively redcing the inlence o rain attenation on the commnication qality. Conclsions The signal qality in satellite commnication system will e aected y rain weather, so the rain attenation wold e overcome y sing the compensation methods. In the paper, a new method ased on plink power compensation or rain attenation is pt orward. ccording to the calclation o the plink rain ading y sing the downlink rain ading, the grond station emission (4) 284

5 power can e adjsted to achieve the maximm compensation or rain attenation. In a word, the new method overcomes the shortcoming o the traditional diversity reception and had high practical vale or ase-and digital signals. We will rther stdy on the ields o application and carrier reqency estimation hereater. Reerences [] Yao Jn, Li Baiping. Digital Microwave and Satellite Commnication[M](In Chinese).Beijing University o ost and Telecommnications press, 20,4 [2] Li Rong. Research o rain ttenation o Ka-and Satellite Commnication System [J]. ICNCE203, 203,8: [3]Sn Xekang, Zhang Zheng. Microwave and Satellite Commnication [M](In Chinese). ost and Telecommnications press, 2003,6 [4] Zhao Zhenwen, L Changsheng. rediction model o rain attenation or the earth-space links[j] (In Chinese). Diano Kexe Xeao/Chinese Jornal o Radio Science, v 28, n 3, p 42-49, Jne 203 [5] Badron K, Ismail.F. Evalation o RazakST's S-and link signal measrement with the radar derived rain attenation. International Conerence on Space Science and Commnication, IconSpace, p , 203 [6] Li Goliang. Satellite Commnication[M](In Chinese).Xidian University ress, 200 [7] Olrotimi E.O. Ojo J.S. Testing Rain Fall Models or Rain teenation rediction rposes in Tropical Climate[J]. 3th URSI General ssemly and Scientiic Symposim, p -4, 204 [8] Kamrzzaman M. Islam M.S. Rain ttenation recdiction or Sattelite Commnications Link at K and Ka Bands over Bangladesh[J]. ICEEICT 204: p-6. [9] Livierators Spiros N. Korogiorgas Charilaos I. On the rediction o Joint Rain ttenation Statistics in Earth-space Diversity Systems sing Coplas[J]. IEEE Transactions on ntennas and ropagation,v62, ,204. [0]Yss aoni Isiaka. Khamis NorHisham Haji. Rain ttenation rediction Model or Lagos at Millimeter Wave Band [J]. Jornal o tmospheric and Oceanic Technology,V3, p ,204 []Garcia Jose M. Riera Jose M. Rain attenation variaility calclated rom a slant-path Ka-and experiment[j]. 8th Eropean Conerence on ntennas and ropagation, p ,204. [2]dlrahman,Y. Rahman T.. Investigation o the Uniied Rain ttenation rediction Method with Data rom Tropical Climates[J]. IEEE ntennas and Wireless ropagation Letters, v 3, p 08-, 204. [3]Maekama Yasyki, Inamori Ytaka. Eects o Rain rea Motions and Grond Wind Velocities on Rain ttenation Characteristics o K-and Satellite Signals[J]. URSI GSS 204. [4]Kalogiros John, nagnosto Marios N. Evalation o a New olar metric lgorithm or Rain-path ttenation Correction o x-and Radar Oservations Ggainst Disdrometer[J]. IEEE Transactions on Geoscience and Remote Sensing, p ,204. [5]oolsawt Jirtchaya, Linpiti Tlaya. Short-term Rain-indced ttenation Model or Satellite Link Qality rediction[j]. ECTI-CON 204. [6]Sn Jiejing, Go Lixin, Ge Jianha. Eects o Rain ttenation on Ray-tracing rediction in Uran Microcelllar Environment at 20 GHz [J]. 204 IEEE International Wireless Symposim, p ,