R F 2008 IEEE INTERNATIONAL RF AND MICROWAVE CONFERENCE PROCEEDINGS
December 22-4, 2008, Kuala Lumpur, MALAYSIA
M 08
Novel Computation of Expecting Interference between FSS and IMTAdvanced for Malaysia Lway Faisal Abdulrazak, Zaid A. Shamsan, Ali K. Aswad and Tharek Abd. Rahman Wireless Communication Center, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Skudai 81310, Johor, MALAYSIA.
[email protected],
[email protected],
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[email protected].
Abstract - This paper deals with the Interference between Fixed Satellite Service (FSS) and IMTAdvanced (4G) for Malaysian environment. The study initiated within detailed calculations of the current and most useful formulas for path loss effect and clutter loss by using the existing parameters of FSS and the most expected parameters for the IMT-Advanced. Thereafter, FSS axis received gain and radiation pattern had been covered. Furthermore, Site shielding, isolation, off-Axis, In-Band and out of band have been discussed in several scenarios. Calculations, analysis and simulation have been done by using Matlab software. Consequently, extracted conclusions had highlighted the subsistent situation and proposal for future work. Keywords: ITU; FSS receiver; IMT-Advanced; mitigation techniques; interference.
1. Introduction Challenging in a wireless communication services lurk in dynamically changes of the services in response to the market demanding [1]. With the increasing number of transmitters coming on the air, interference is becoming more prevalent in the wireless community. Recently Malaysia faced some problem regarding the interference between the Fixed Satellite Services and the Fixed Wireless access. However, Malaysia has a tropical weather so it depends a lot on the C-Band for the satellite communication because it’s immunity against the rain attenuation. On the other hand we have a Fixed Wireless Access have being deployed to work on a part of C-band from 34003.600MHz [2], the International Telecommunication Union (ITU) originally allocated C-band for use by the global satellite industry [3]. In extra, according to World Radiocommunication Conference (WRC-07) for high system capacity, sufficient mobility support, reasonable coverage area and cost purpose it is suggested that the suitable frequency range for IMTAdvanced services is below 5 GHz. Most probably that C-band and extended C-band are the candidate for potential upcoming technology. Massive deployment of systems and services has been underway worldwide, some times earth stations deployed ubiquitously and
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without individual licensing or registration. It’s difficult to provide a protection for this type because it’s likely to be deployed in large numbers and their location is not known. Others are individually licensed earth stations, location of these earth stations is known and site shielding and other mitigation techniques can be taken into account. Millions of users now rely upon satellites for essential communications. Motivated by emergence of protecting radio waves, this article is about understanding of new class of communication system where pairs of transmitters and receivers can adapt there modulation/demodulation method in presence of interference to achieve the better performance due the coexistence. Since IMTAdvanced systems targets (100 Mb/s and 1 Gb/s with high mobility and low mobility, respectively) defined by the international telecommunication union (ITU) [4], many bands are allocated for more than one radio service and therefore the sharing is necessity. The 3400–4200 MHz overlapping with the potential nominee bands for 4G systems is currently allocated to fixed satellite service (FFS). Consequently, the impact of the interference of 4G on FFS systems needs to be studied. However, the expected impact on reception of those satellite services has been dramatic, including inband interference, interference from unwanted emissions (outside the signal bandwidth), and overdrive of low-noise block converters (LNBs saturation) [5]. Key system characteristics had identified and discussed from a radio frequency (RF) perspective, by counting the power transmit interference to the FSS receiver. Solving the interference problem can be done by characterize the local environment; Find neighboring transmitters, Locate the source of the interference and identify the problem and perform the separation distance analysis based on transmitters in the area [6].
2. IMT-Advanced signal specifications The IMT-Advanced term has been introduced for “beyond IMT-2000” system [7]. The target peak data rates are 100 Mbps for high mobility systems and 1 Gbps for low mobility of fixed and nomadic systems. The required channel bandwidths is ranging between 20-100 MHz where 50 MHz for suburban and 100
MHz for urban coverage [8]. Table 1 contains the IMT-Advanced parameters assumed for the comparison of the different studies.
According to ITU SF.1486 interference would be significant to FSS when the victim receiver subject to degradation of thermal noise floor for more that 20% of any month. The separation distance will be come a very huge distance which is impossible we rely on because of the high sensitivity of FSS receiver, figure below (Figure 1) shows the maximum acceptable inband interference between the two services.
Table 1: IMT-Advanced specification. Parameter Center frequency of operation (MHz) Base station transmitted power (dBm) Minimum Coupling Loss ( (dB) Base station antenna gain (dBi) Base station antenna height (m) Interference Limit Power (dBm) EIRP density range: macro base station scaled to 1 MHz bandwidth Maximum EIRP2 (Transmitter output power + antenna gain – feeder loss) Antenna type (Tx/Rx) (the gain is assumed to be flat within one sector) Protection criterion (I/N) VS satellite systems
4. Determination of the maximum possible level of in-band interference
Value 3500 43 30 18 30 -109 39 to 46 dBm/MHz 59 dBm Sectored for macrocell –10 dB
3. Fixed Satellite services specifications For Malaysia the fixed satellite service is allowed to work within 3.4 to 4.2GHz, and the frequency bandwidth is varying from 4 KHz to 72MHz, base on different use. Following table is describing the typical FSS earth station receiver already in use by petronas (fuel stations).
Satellite terminal 3400-4200 MHz 40KGz-72MHz 2.4-3(m) 38(dBi) ITU RS.465 114.8oK 75.95
Elevation angle
50
Off-axis
14.5
263.7 100 200
7.0
-0.5
5. Path loss Effect The channel parameters for individual snapshots are determined stochastically, based on statistical distributions extracted from channel measurement. Channel realizations are generated with geometrical principle by summing contributions of rays with specific small scale parameters like delay, power, angle-of-arrival (AoA) and angle-of-departure (AoD). Equations are given for mean path loss as a function of distance for each of the terrestrial environments the slow variation is considered to be log-normally distributed. Path-loss models at 2 to 6 GHz have been developed based on literature [9] [10]. Free space attenuation is
Table 2: Fixed satellite services specifications. Specification Frequency Emission bandwidth Antenna diameter Gain Antenna diagram Noise temperature Elevation angle Azimuth Earth station off-axis gain towards the local horizon (dBi)
Figure 1: Maximum acceptable in-band interference between FSS and FWA, when I: is the interference level, C is the carrier signal, N is the receiver noise level.
PLfree = 46.4 + 20log10 (d [m]) + 20log10 ( f [GHz]/5.0) 300
-4.9
(1)
>850
0
The path loss calculations between the FSS-ES and IMT-Advanced (transmitter) Loss (d) is pedestal in IEEE L802.16-07/070r1 [11]. This is model which is used for this coexistence study includes the attenuation due to clutter in different environments Loss ( d ) = 101.04 − 7.1logW + 7.5 log < H >
Notes: the azimuth and elevation angle determined for Wireless communication center in UTM skudai, Johor, Malaysia.
− {24.37 − 3.7(< H > / hb ) 2 }log hb + (43.42 − 3.1log hb ) log d + 20 log f c − Ah (2)
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Where hb, , W denote the BS antenna height, the average building height, and the street width, respectively. fc denotes the carrier frequency in GHz. Where d is the distance between interferer and victim receiver in kilometers and Ah is loss due to protection from local clutter or called clutter loss, it is given by the expression:
h Ah = 10.25e −d k 1 − tanh 6 − 0.625 − 0.33 ha
most suitable separation between the services. Deferent components will add in way to calculate the separation for local environment. However, the FSS station off Axis antenna receiving gain, for given aff Axis angle from main receiving beam of the station, Gvs( α ) for a typical receiving antenna of 2.4m diameter is given by:
Gvs (α ) = 32 − 25Log (α )dBi Where3.6o < α < 48o (4) (3)
Where dk is the distance (km) from nominal clutter point to the antenna, h is the antenna height (m) above local ground level, and ha is the nominal clutter height (m) above local ground level [12]. Clutter losses are evaluated for different categories: trees, rural, suburban, urban, and dense urban, etc. as shown in Table 3 and Figure 2 which contain the four categories.
G vs = −10 dBi
where48o < α < 180o (5)
For the shielding cover as attenuation to the interference power (R) which takes a value between 0dB to 40dB in the best condition. Now we can do simple calculations to fine that the required protection distance determine from the following formula: 20Log(d ) = −I + EIRPIMT − 46.4 − 20Log( F ) − Ah + Gvs (α ) − R (6)
EIRPIMT: effective isotropic radiation pattern, Shown in Table 1 (we considered it 46 dBm/MHz). Table 3: ITU-R P.452, the Clutter Loss Clutter category
Clutter height ha
Nominal distance dk
Rural Suburban Urban Dense urban
4 9 20 25
0.1 0.025 0.02 0.02
7. In-band interference by single IMT-BS
Thereby, we can see the Clutter loss for rural, suburban, urban, and dense urban areas effects base on different antenna height, as clarified in the figure bellow:
If we consider a suburban area within clutter loss about 16 dB, the results of the simulation Figure 3 reviles that minimum separation distance for In-band interference is 42Km if we are using powerful shielding technique (40dB) and 68 Km for 30 dB shielding loss.
Figure 3 separation distances for 2.4m FSS receiving antenna due to in-band interference from single IMTAdvanced BS. Figure 2: clutter loss base on ITU-R P.452
8. FSS Saturation 6. Required protection distance Practically, protection by separation distance is the most expensive so we should focus on it to find the
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When we applied the previous mathematical formulas (2-6) to calculate the interference for the short distance which required for the LNB saturation
point we found that the saturation happen when I=65.92dBm. To assuage the saturation problem, one counteractive measure would be using a suitable bandpass filter (with pass band in 3.6 – 4.2 GHz) to reduce the level of the RF signals in 3.5 GHz to the LNB working in the entire C band (3.4 – 4.2 GHz).
9. Multiple IMT-Advanced BS interferers To examine the cumulative effects of interference from multiple IMT-Advanced BS transmitters, calculation is made for the required separation distance for consideration of the worst case scenario at NLOS for the nonlinearity saturation situations of LNB; the aggregated interference is calculated by summation of the interference power from these transmitters of IMTAdvanced BS received at the FSS station input. The results as summarized in figure 4 show that under the worst case situation, the required separation distance is of the order of 1.75Km and 3Km respectively for FSS station with LNB filter and without LNB filter added at the front end.
Figure 5: Separation distance for 2.4m FSS for out of band emission case.
The results shows that out of band emission of IMT-Advanced BS limited of -69dBW/MHz, would not cause interference to FSS station if there is a separation distance of 50Km. the out of band emission of FSS limited of -59dBW/MHz would not cause interference to FSS station if there is a separation
distance of 50Km.
11. Conclusions
Figure 4 separation distances for 2.4m FSS receiving antenna under LNB and Multiple IMT transmitters.
If a LNB filter with sharper cut-off characteristics is used, in addition to other remedial measures that may be applied, it is possible that the LNB overload problem should be further contained or overcome even at the worst case scenario.
10. Out of band emission from IMT The following figure 5 shows the calculation result of out of band interference for the emitted signal from IMT-Advanced BS transmitters within direct line of sight.
If we reduce IMT radiated power to 25dB the same power will be -50dB after 500m and -166dB required for the FSS to not interrupt the signal which make the coexistence bump of phantom. In the absence of any coordination, IMTAdvanced systems will be more capable in the 3.4-4.2 GHz band will cause unacceptable interference to FSS stations in the C band if the two systems operate on the same frequency channels. Over and above, IMTAdvanced systems in the 3.5 GHz band which are located nearby and with non line-of-sight to FSS stations will cause interference to the latter operating in 3.6 – 4.2 GHz band if the separation distance is less than about 3 Kilometers and there are no protection measures. By adding a bandpass filter at the FSS station front-end giving a 10 dB loss to the received FWA signals, the required separation distance about 1.75 Kilometers depending on the number of IMTAdvanced interferers. In addition, out-of-band emissions from IMT systems in the 3.5 GHz band should not cause unacceptable interference to FSS in 3.6 – 4.2 GHz band if suitable emission limits are adopted for the IMT equipment. This assessment is done in response to IMT-advanced threats to all the services work within same frequency. Consequently, as futures work the results in this study will be used to developing mathematical approach to prevent the interference between tow services in order to develop
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some mitigation technique to reduce it to the minimum level.
Acknowledgment The authors thank the the Malaysia Communication and multimedia commission (MCMC) for providing financial support and wonderful hospitality where this work was completed. References [1] J. D. Laster and J. H. Reed, “Interference rejection in wireless communications”, IEEE Commun. Mag., vol. 14, pp. 37-62, May 1997. [2] Lway Faisal Abdulrazak, Tharek Abd Rahman, “Review Ongoing Research of Several Countries on the Interference between FSS and BWA”, International Conference on Communication Systems and Applications (ICCSA'08) in China Hong Kong, conference proceeding (ISBN: 978988-98671-8-8) volum I, March 2008. [3] ITU-R WP 8F/TEMP 432 rev.2, “Working document towards a PND report on sharing studies between IMT-ADVANCED and the Fixed Satellite Service in the 3 400- 4 200 and 4 500-4 800 MHz bands”, ITU-R Working Party 8F, August 2006. [4] “Methodology for the calculation of IMT-2000 terrestrial spectrum requirement,” ITU-R Recommendation M.1645, Jan. 1999. [5] ITU-R SF.1486, “Sharing methodology between Fixed Wireless Access Systems in the Fixed Service and Very Small Aperture Terminals in the Fixed-Satellite Service in the 3 400-3 700 MHz Band,” ITU-R R WP4-9S, Geneva, November 2000. [6] Electronic Communications Committee (ECC), within the European Conference of Postal and Telecommunications Administrations (CEPT), report 100, “Compatibility studies in the band 3400- 3800 Mhz between Broadband Wireless Access (BWA) systems and other services,” Bern, February 2007. [7] ITU-R Document 8F/1015-E, “sharing studies between FSS and IMT-Advanced systems in the 3400-4200 and 4500-4800 MHz bands”, 2006. [8] “PROPOSED MIMO CHANNEL MODEL APPROACH FOR EVALUATION OF AIR INTERFACE PROPOSALS FORIMTADVANCED”, Document 8F/1148-E, Question ITU-R 229/8, ITU-R WP8F Meeting in Cameroon, January 2007. [9] Document AWF-3/17 “Assessment of potential interference between Broadband Wireless Access (BWA) in 3.4-3.6 GHz band and Fixed Satellite Service (FSS) in 3.4-4.2 GHz band”, Office of the
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Telecommunications Authority (OFTA) Hong Kong, September 2006. [10] Report ITU-R M. [LMS.CHAR.BWA], “Characteristics of broadband wireless access systems operating in the mobile service for frequency sharing and interference analyses”. [11] J. D. Laster and J. H. Reed, “Interference rejection in wireless communications”, IEEE Commun. Mag., vol. 14, pp. 37-62, May 1997. [12] ITU-R Recommendation F.1402, “Frequency sharing criteria between a land mobile wireless access system and a fixed wireless access system using the same equipment type as the mobile wireless access system”, 1999.
