Potentiality of Interference Correction between FSS and FWA for Malaysia

Transcription

1 Ptentiality f Interference Crrectin between FSS and FWA fr Malaysia LWAY FAISAL ABDULRAZAK, ZAID A. SHAMSAN AND THAREK ABD. RAHMAN Wireless Cmmunicatin Center, Faculty f Electrical Engineering Universiti Teknlgi Malaysia Skudai 81310, Jhr, MALAYSIA Abstract: - This paper deals with the Interference between Fixed Satellite Service (FSS) and Fixed Wireless Access (FWA), fr Malaysian envirnment. The study began with a detailed calculatin f the current and mst useful frmulas path lss effect and clutter lss by using the existing parameters f bth services. Thereafter, FSS axis receiving gain and radiatin pattern had been cvered. Mrever, Site shielding, islatin, ff-axis, In-Band and ut f band have been discussed in several scenaris. Calculatins, analysis and simulatin have been dne by using Matlab sftware. Cnsequently, extracted cnclusins had highlighted the subsistent situatin and prpsal fr future wrk. Key-Wrds: - Interference, FSS, FWA, Malaysian envirnment, LNB and Saturatin. 1 Intrductin Living n a dynamic planet is big challenge fr wireless cmmunicatin [1]. Thugh, these rapid changes in services cverage are having a serius effect n each thers. With the increasing number f transmitters cming n the air, interference is becming mre prevalent in the wireless cmmunity. Therefre, encuraging the establishment f mdern legal and regulatry structures fr telecmmunicatins service delivery will be necessary t cntrl the interference. Recently Malaysia faced sme prblem regarding the interference between the Fixed Satellite Services and the Fixed Wireless access. Hwever, Malaysia has a trpical weather s it depends a lt n the C- Band fr the satellite cmmunicatin because it s immunity against the rain attenuatin. On the ther hand we have a Fixed Wireless Access have being deplyed t wrk n a part f C-band frm MHz [2], as clarify in Figure 1. The Internatinal Telecmmunicatin Unin (ITU) riginally allcated C-band fr use by the glbal satellite industry [3], massive deplyment f systems and services has been underway wrldwide, and millins f users nw rely upn satellites fr essential cmmunicatins. Hwever, the reprted impact n receptin f thse satellite services has been dramatic, including in-band interference, interference frm unwanted emissins (utside the signal bandwidth), and verdrive f lw-nise blck cnverters (LNBs saturatin) [3]. Key system characteristics had identified and discussed frm a radi frequency (RF) perspective. Accrdingly, nce the interference is identified, the characteristics f the interference shuld be nted. The signal s duratin, bandwidth, strength, sub-carriers, and time f ccurrence will help begin the prcess f eliminating interference suspects in the area and slving the interference prblem can dne by characterize the lcal envirnment; Find neighbring transmitters, Lcate the surce f the interference and identify the prblem and perfrm the separatin distance analysis based n transmitters in the area [4]. In rder t examine cexisting and sharing issues, it is necessary t clarify the parameters f FSS and FWA that will affect the interference level and criterin. Fig.1: Spectrum plan in Malaysia. 84 ISSN

2 2 Fixed Wireless access specificatins In Malaysia the frequency range ( ) GHz is allcated fr FWA systems, It is divided int subbands fr duplex use (nn duplex systems can still be used in this band), MHz paired with MHz. Hwever, Cuntries have varius frequency channel spacing within the 3.5 GHz bands 1.25, 1.75, 3.5, 7, 8.75, 10, 14, and 28 MHz can be used accrding t capacity needs. Alternatively, if we change the parameters defiantly we will gate a grate change in the interference upsht. S, we will be fcused n the parameters listed in Table 1 and we had cnsider that the center frequency f FWA is 3500 MHz fr GHz. Table 1 Fixed wireless access specificatins Specificatin FWA(CS) FWA(TS) Tx Peak utput pwer (dbm) Channel bandwidth 7 7 (MHz) Feeder lss (db) 1 1 Pwer cntrl(dbi) 0 12 Peak antenna gain (dbi) Antenna gain pattern ITU-R F.1336 ITU-R F.1336 Antenna height (m) Nise figure (db) 5 7 Receiver nise reference 3 Fixed Satellite services specificatins Fr Malaysia the fixed satellite service is allwed t wrk within 3.4 t 4.2GHz, and the frequency bandwidth is varying frm 4 KHz t 72MHz, base n different use. Flling table is describe the typical FSS earth statin already in use by petrnas (fuel statins) Table 2 Fixed satellite services specificatins Specificatins Satellite terminal Antenna diameter 2.4 (m) Gain (dbi) 38 Antenna diagram ITU RS.465 Nise temperature 114.8K Elevatin angle Azimuth Ntes: the azimuth and elevatin angle determined fr Wireless cmmunicatin center in UTM skudai, Jhr, Malaysia. 4 Determinatin f the maximum pssible level f in-band interference signal Accrding t ITU SF.1486 interference wuld be significant t FSS when the victim receiver subject t degradatin f thermal nise flr fr mre that 20% f any mnth. We cnsider the I/N t be 10 db accrding t ITU regulatin, then the limitatin f typical in band interference brder [6]. C / I (10 C / N) db (10 5.7) db 15.7 (1) Where C: Carrier pwer at the receiver, C/N is the required carrier t nise rati and C/ I: INBAND is the required prtectin rati I inband ( C 15.7) dbw (2) C C / N 10Lg( kbt) dbw (3) C C / N 10Lg( kbt) dbw 5.7 ( 156) dbw (4) dbw ( C 15.7) dbw I Inband 166dBW (5) S, the maximum pssible level f in-band interference is -166dB r -136dBm, and if the interference exceeds mre than -166 db, that will destry the received signal. Where I is the interference level in dbm, N is the thermal nise flr f receiver in dbm and α is the prtectin rati in db and here has value f -10 db which means that the interference must be apprximately 10 db belw thermal nise. Fig.2 shws the level f carrier, nise and interference [6]. C/I I/N C/N Fig.2 Interference prtectin criterins. C N I 85 ISSN

3 5 Determinatins near far radiatin pattern (fr satellite dish) The satellite antenna nrmally is a parablic antenna pinted t the sky. As lng as it s directed t the sky s we shuldn t wary abut the fixed satellite antenna. The fllwing figure shws the effect f the earth statin antenna with a 2.4 diameter n the frequency range GHz avidance, s mre bradly regarding the effect f FSS-ES n the ther services will be useless. 6 Path lss Effect The path lss calculatins between the FSS-ES and FWA-TS (transmitter) L FWA (d) is pedestal in ITU-R P.452. This is mdel which is used fr this cexistence study includes the attenuatin due t clutter in different envirnments L FWA ( d) lg d 20lg f Ah (6) Where d is the distance between interferer and victim receiver in kilmeters, f is the carrier frequency in GHz, and Ah is lss due t prtectin frm lcal clutter r called clutter lss, it is given by the expressin: Fig.3 near field effect f FSS-ES radiatin pattern. d h k Ah 10.25e 1 tanh ha (7) When we increase the antenna diameter emphatically we will gate swell in the radiatin pattern plus increasing the gain subsequently we will have lnger prtectin distance. Fig.4 shws fr different earth statin antenna diameter we shuld have different radiatin pattern as in the figure belw: Where d k is the distance (km) frm nminal clutter pint t the antenna, h is the antenna height (m) abve lcal grund level, and ha is the nminal clutter height (m) abve lcal grund level [5]. Clutter lsses are evaluated fr different categries: trees, rural, suburban, urban, and dense urban, etc. Increasing f antenna height up t the clutter height leads t decrease the clutter lss, as shwn in Table 3 and Fig. 2 which cntain the fur categries. In ur case, dense urban categry will be cnsidered. Table 3: ITU-R P.452, the Clutter Lss Clutter categry Clutter height ha Nminal distance d k Rural Suburban Urban Fig.4 Near Field behavir f FSS-Es fr different antenna diameter It s clear that the near field radiatin pattern f the fixed satellite earth statin des nt have that much effect n the services surrunding the system terminal. Hwever, fr typical antenna diameter 3 m which wrk n 3.5GHz, the near field effect will be 26m nly, fr the 2.4 separatin will be 16.8m and fr 1.8 the separatin will be 9.45m. The separatin distance that we have identified therefre assists in ur understanding f the rle f interference Dense urban Thereby, we can see the Clutter lss fr rural, suburban, urban, and dense urban areas effects base n different antenna height, as clarified in the figure bellw: 86 ISSN

4 using pwerful shielding technique (40dB) and 2 Km fr 30 db shielding lss. Fig.5 clutter lss base n ITU-R P Required prtectin distance Different available mitigatin techniques already existing like shielding, filtering, and separatin distance. Practically, prtectin by separatin distance is the mst expensive s we shuld fcus n it t find the mst suitable separatin between the services. Deferent cmpnents will add in way t calculate the separatin fr lcal envirnment. Hwever, the FSS statin ff Axis antenna receiving gain, fr given aff Axis angle frm main receiving beam f the statin, Gvs( ) fr a typical receiving antenna f 2.4m diameter is given by: G vs ( ) 32 25Lg ( ) dbi Where (8) G vs 10dBi where (9) And, we mentined fr the shielding cver as an attenuatin interference pwer (R), and R may take a value between 0dB t 40dB in the best cnditin. Nw we can d simple calculatins t fine that the required prtectin distance determine frm the fllwing frmula: Fig.6 separatin distances fr 2.4m FSS receiving antenna due t in-band interference frm single FWA. 9 FSS Saturatin 9.1 Different distance required base n different Off-Axis Angle f single FWA Interfere Withut any remedial measures, the required separatin distance shuld be25 300m base n the clear line f sight envirnment as shwn in fig.7. This result can be enhanced mre by using LNB filter. Nevertheless, this result shws hw the ffaxis tremendusly affects n the received signal frm victim FSS receiver. 20 Lg ( d ) I EIRP 20 Lg ( F ) A G h vs FWA 92.5 ( ) R (10) EIRP FWA : effective istrpic radiatin pattern, Shwn in Table 1. 8 In-band interference by single FWA If we cnsider an urban area within clutter lss abut 16 db which may turn ut t be a nrmal fr mst f Malaysian cities, the results f the simulatin Fig.6 reviles that minimum separatin distance fr In-band interference is 1.2Km if we are Fig.7 required separatin distances base n different ff-axis angle f FSS. When we applied the previus mathematical frmulas t calculate the interference fr the shrt distance which required fr the LNB saturatin pint we fund that the saturatin happen when I= dBm. 87 ISSN

5 T assuage the saturatin prblem, ne cunteractive measure wuld be using a suitable bandpass filter (with pass band in GHz) t reduce the level f the RF signals in 3.5 GHz t the LNB wrking in the entire C band ( GHz). 9.2 Multiple FWA interferers T examine the cumulative effects f interference frm multiple BWA transmitters, calculatin is made fr the required separatin distance fr cnsideratin f the wrst case scenari at NLOS; the aggregated interference is calculated by summatin f the interference pwer frm these transmitters f FWA received at the FSS statin input. The results as summarized in fig.8 shw that under the wrst case situatin, the required separatin distance is f the rder f 170m and 275m respectively fr FSS statin with LNB filter and withut LNB filter added at the frnt end. Fig.9: Separatin distance fr 2.4m FSS fr ut f band emissin case. The results shws that ut f band emissin f FWA limited f -69dBW/MHz, wuld nt cause interference t FSS statin if there is a separatin distance f 250m. the ut f band emissin f FSS limited f -48dBW/MHz wuld nt cause interference t FSS statin if there is a separatin distance f 650m. 4 Cnclusin Fig.8 separatin distances fr 2.4m FSS receiving antenna under LNB and Multiple FWA transmitters. If a LNB filter with sharper cut-ff characteristics is used, in additin t ther remedial measures that may be applied, it is pssible that the LNB verlad prblem shuld be further cntained r vercme even at the wrst case scenari. 10 Out f band emissin frm FWA The fllwing fig.9 shws the calculatin result f ut f band interference fr the emitted signal frm FWA transmitters within direct line f sight. In the absence f any crdinatin, FWA systems perating in the 3.5 GHz band will cause unacceptable interference t FSS statins in the extended C band ( GHz) if the tw systems perate n the same frequency channels. Over and abve, FWA systems in the 3.5 GHz band which are lcated nearby and with clear line-f-sight t FSS statins will cause interference t the latter perating in GHz band if the separatin distance is less than abut 275 meters and there are n prtectin measures. By adding a bandpass filter at the FSS statin frnt-end giving a 10 db lss t the received FWA signals, the required separatin distance abut 170 metes depending n the number f FWA interferers. In additin, ut-f-band emissins frm FWA systems in the 3.5 GHz band shuld nt cause unacceptable interference t FSS in GHz band if suitable emissin limits are adpted fr the BWA equipment. This assessment is dne in respnse t IMT-advanced threats t all the services wrk within same frequency. Hwever, ne f the mst expecting frequency ranges fr IMT- Advanced is C-Band. Cnsequently, as futures wrk the results in this study will be used t estimate and reduce the affect f IMT-Advanced n the existing services. 88 ISSN

6 References: [1] J. D. Laster and J. H. Reed, Interference rejectin in wireless cmmunicatins, IEEE Cmmun. Mag., vl. 14, pp , May [2] Lway Faisal Abdulrazak, Tharek Abd Rahman, Review Onging Research f Several Cuntries n the Interference between FSS and BWA, Internatinal Cnference n Cmmunicatin Systems and Applicatins (ICCSA'08) in China Hng Kng, cnference prceeding (ISBN: ), March [3] ITU-R WP 8F/TEMP 432 rev.2, Wrking dcument twards a PND reprt n sharing studies between IMT-ADVANCED and the Fixed Satellite Service in the and MHz bands, ITU-R Wrking Party 8F, August [4] ITU-R SF.1486, Sharing methdlgy between Fixed Wireless Access Systems in the Fixed Service and Very Small Aperture Terminals in the Fixed-Satellite Service in the MHz Band, ITU-R R WP4-9S, Geneva, Nvember [5] Electrnic Cmmunicatins Cmmittee (ECC), within the Eurpean Cnference f Pstal and Telecmmunicatins Administratins (CEPT), reprt 100, Cmpatibility studies in the band Mhz between Bradband Wireless Access (BWA) systems and ther services, Bern, February [6] Dcument AWF-3/17 Assessment f ptential interference between Bradband Wireless Access (BWA) in GHz band and Fixed Satellite Service (FSS) in GHz band, Office f the Telecmmunicatins Authrity (OFTA) Hng Kng, September ISSN