A HF Frequency Prediction Method of Engineering Calculation in the Asia Pacific Region Chao LI, Yun-jiang LIU, Xiao-peng YANG and Feng WANG

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1 8 nternational Conerene on Computer, Eletroni normation and Communiations (CEC 8 SBN: A HF Frequeny Predition Method o Engineering Calulation in the Asia Paii Region Chao L, Yun-jiang LU, Xiao-peng YANG and Feng WANG The normation and Navigation College, Air Fore Engineering University, Xi an, Shanxi, 777, China Keywords: onosphere harateristi parameters, HF requeny predition, TS. Abstrat. On the premise o omprehending the ionosphere predition method in the Asia Oeania region, HF requeny predition method reommended by the nternational Teleommuniation Union (TU is improved in this paper, and the engineering alulation method o prediting HF requeny in the Asia Paii region is onluded and summarized. Comparing with the TS (the nstitute or Teleommuniation Siene sotware s prediting result, the method is improved to some extent in time availability and SNR in the reeiving point. ntrodution As to the maximum usable requeny(muf predition o HF ommuniation, the key ator is the ionosphere. With development o the ionosphere physis, and requirements o theoretial researh and pratial appliation, the ionospheri model was attrating inreasing attention or nearly years. The model an be expressed as some ionospheri harateristis, or Curve or ormula about some ators, suh as the related itting urve o ritial requeny and sunspot numbers, et al. Currently, the most representative is the nternational Reerene onosphere (R [], not only applied to HF predition, but also to the ionosphere physis researh. The R model predition is also alled the global F and M ( F predition. But the preision o the R predition is restrited to used material time and geographi span, espeially Chinese ionospheri measured data are absent, thereore the ionospheri F layer predition error in Chinese region (espeially south China is bigger. The ionosphere workers o China Researh nstitute o Radiowave Propagation (CRRP statistially researhed long-term observation data o 9 stations in the Asia Oeania region, then an ionospheri F layer predition method suitable or Chinese region(cr was presented, and the main predition harateristis are F and M ( F. Based on CR method, the major idea in this paper is prediting the MUF, and ompare with the TS s prediting result. Predition Method o MUF Empirial HF predition models are some derived parameters equations with the atual observation data. n many ases, these equations have no physial signiiane, but an provide various parameters values in a ertain time. The MUF empirial predition is generally by the ollowing steps: [] A. Calulate the great irle entral angle and distane between two endpoints o the ommuniation link. B. Take the great irle diretion, whih is transmitting antenna to reeiving antenna. C. Take the longest distane o one hop under the lowest elevation, and obtain the least number o the ionosphere reletion. Separately predit primary transmission parameters o the ionospheri E and F layer, and alulate MUF aording to experiene ormula, then hoie the propagation mode(e or F. D. Take the available requeny: to one hop ommuniation, the obtained result is MUF rom ; to multiple hops, repeat steps -, and take minimum.

2 Now, The HF MUF predition method in this paper is presented as ollowing steps: Calulate Shortwave Communiation Link Lengths n Figure, it is supposed that HF link is built between A and B station, and great irle distane is the propagation path between A and B, and the great irle entral angle is expressed as long, we an get: os long sin Xsin X + os( Y Y ( X, Y is the latitude and longitude o A station Separately, and X, Y is the latitude and longitude o B station Separately. Deine east longitude, north latitude or positive diretion. The great irle distane o A and B is: D long π R 8. 7 long ( R 78.km, earth radius. onosphere α h ( X,Y A D B( X,Y R Calulate the Azimuth R d Figure. HF ommuniation hannel parameters shemes. When Calulate the azimuth, we use the international ompass sale (rom to, i.e. or north diretion, Clokwise or positive diretion. The azimuth between A and B an be desribed as []: sin sin C AB C BA O sin( Y Y ( sin long sin( Y Y ( sin long Calulate the Position The latitude o the releting point: o lat m 9 aros(os long sin x + sin long os x os C (. AB The longitude o the releting point: long m y aros[(os long sin lat. m sin x / os lat. m os ] (. x F Layer MUF The F layer MUF an be desribed as[][]: Cd H d nf ( D MUF [ + ( ( B ] of + ( (7 C d max 7

3 height. is the magnetism irle requeny o the ionosphere virtual reletion point (H is the H (8 R H sin lat. m R + H d 78 + ( + / x 97/ x + 889/ x (/ B. (9 max 7.8 {[ M ( F] }. +.sin(.9 B M ( F. + x n ormula (7, d D/n or dmax, the unit is km; whend km, then Cd C; x of/oe or, hoose the bigger value; F and M ( F will be introdued in F. Estimation o F and M ( F n CR, the dedued predition exponent rom the ionosphere station s observation data will take the plae o sunspots low average o months (R. n the Asia Oeania region, the orrelation o and is better than and R, espeially in Chinese region [][7]. an be desribed as: F + i + i n F ( + n ( n n+ Where n denotes the nth month in time series, and denotes the average o F month median o Monthly hours. The F and ( M F s initial value Γ o the same loation, the same month, the same hour, and the related an be onneted with the ollowing equation: Γ M i A i i ( (MHz ( The oeiients o F and M ( F an be determined by least-square method, then this F (o this loation, this month, this hour an be alulated when the value o is, 9 and, and M ( F an be alulated when the value o is and 9. When we have known the reletion loation, the orreted magnetism irle requeny and, the estimation o F is: and M ( F an be obtained with ormula (7. To, the parameter matrix A A + + ( F F9 F ( 9( ( 8 ( ( ( 9 ( ( 9 ( To M ( F 8 M + M, the parameter matrix B is: B (7 ( (8 F 8

4 ( (9 Calulate the Frequeny o Optimum Trai (FOT Aording to above alulation, the MUF predition o E layer or F layer reletion an be obtained. But the time availability o MUF is just %, we should lower the requeny appropriately, and raise the time utilization rate o 9%, i.e. alulating the FOT. FOT.8MUF ( Example Simulation Based on R model, the empirial predition sotware TS is exploited by the nstitute or Teleommuniation Siene, used or prediting the ommuniation perormane o HF (~MHz. t is supposed that we should predit the MUF between Peking(. E, 9.9 N and Guangzhou (. E,. N. To ompare the FOT perormane between the method in this paper and TS, two requenies are hosen o UT :(Namely Beijing time pm: the predition FOT o the method in this paper is 7.7MHz, and TS is 9.7MHz. We will ompare the time availability and SNR by illustration. Figure. The time availability in 7.7MHz. Figure. The time availability in 9.7MHz. n Figure and Figure, the lowest time availability is 97.8% when FOT is 7.7MHz, while the lowest time availability is 9.% when FOT is 9.7MHz. Figure. SNR in 7.7MHz. Figure. SNR in 9.7MHz. n Figure and Figure, the lowest SNR is 7.dB when FOT is 7.7MHz, while the lowest SNR is.7db when FOT is 9.7MHz. Comparison o these igures, the time availability o our prediting FOT is better than the TS over perentage points, and SNR raise nearly db. Thereore, we an draw a onlusion: the perormane index o the method in this paper is superior to the TS sotware, and this method an be used or engineering alulation through omputer programming. 9

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