A Parametric Characterization and Comparative Study of Okumura and Hata Propagation-lossprediction Models for Wireless Environment

Transcription

1 International Journal of Electronic Engineering Research ISSN Volume 2 Number 4 (2010) pp Research India Publications A Parametric Characterization and Comparative Study of Okumura and Hata Propagation-lossprediction Models for Wireless Environment Sagar Patel 1, Ved Vyas Dwivedi 2 and Y.P. Kosta 3 V.T. Patel Department of Electronics and Communication Engineering Charotar University of Science and Technology Changa, Gujarat, India 1 sbpatel_smart@yahoo.com, 2 vvdwivedi.ec@ecchanga.ac.in, 3 ypkosta@gmail.com Abstract Propagation-loss-prediction models play very vital roles in the characterization and design of precise cellular mobile radio communication systems for their specific technical parameters such as transmission power and frequency reuse. This paper presents a comprehensive review of the Okumura and Hata propagation-loss-prediction models for heterogeneous terrestrial wireless communication environments. We will accomplish the modifications by investigating the variations in the path loss between predicting values to improve the performance of the systems. Our numerical results prove that there occur similar changes with different frequencies for different distances under identical conditions. The power losses are calculated for various wireless parametric combinations such as the operating frequencies from 150 MHz 1.9 GHz, and the distances between transceivers from m. Other specific parametric combinations such as the electrical-physical-geographical factors, like different height for transceivers and the operating (suburban or urban) zone related issues are also considered. We analyze all the design features, modeling factors and application-issues of the Okumura and Hata models separately keeping the standard assumptions unchanged. Our simulation results show that these models are effectively applicable for efficient systems in the Indian wireless environments. Keywords: Propagation-path loss, suburban and urban wireless environment, Okumura and Hata prediction model

2 454 Sagar Patel et al Introduction The prediction of propagation loss is the central question in the radio services and no of statistical model and approaches are available in the literature for the prediction and calculation of transmission loss in different conditions [1]. In this paper, comparisons are made between the prediction methods of Okumura and Hata models for different parameters. Mobile communication is currently at its fastest growth-period in history. Due to the emerging technologies that permit for wider deployment. Technological advancements in wireless communication field has resulted into number of wings such as mobile terminals, infrared sensors, satellite and radar applications.the need for high quality and high capacity networks, estimating coverage accurately has become a extremely important. Therefore, for more accurate design coverage of modern cellular network, signal strength measurement must be taken in to consideration in order to provide an efficient and reliable coverage area. This article addresses the comparisons between the theoretical and the empirical propagation model. It was achieved that, the most extensively used propagation data for mobile communication is okumura s measurement and it is recognized by the International Telecommunication Union (ITU) [1]. Initially, the cellular concept could solve the problem of spectral congestion and user s capacity and offer high capacity with a limited spectrum allocation without any major technological change. In this system a single high power transmitter for large cell is replaced with many low power transmitters (base stations - BTS) for smaller cells. The power loss occurred in terms of path loss depends on the antenna height, carrier frequency and distance. Due to reduced level of path loss at higher frequencies more number of cells is required. In section II we explain and describe the application based model using a selection flow chart that comprises of Okumura and Hata models. Section III presents the attenuation (path loss) values in tabulated form for Okumura model used in urban and suburban geographic areas. This also presents the attenuation (path loss) values in tabulated form for Hata model used in urban, suburban and open areas. Section IV discusses about the simulation results in graphical form for Okumura while section V deals with simulation results in graphical form for Hata model. Conclusively section VI highlights the investigations carried out in this paper and the future perspectives for the aspirants. Model Description and Selection Okumura Propagation Model [3] Okumura s model is most widely used for signal predictions in urban and suburban areas operating in the range of 150MHz to 1.92 GHz and up to 3GHz with BTS antenna heights from 30m to 1Km. Okumura curves were developed from extensive measurement using vertical omni-directional antenna at both the base and mobile, and are plotted as a function of the operating frequency and the distance from the base station in the range of 100m to 100Km. It gives the relative attenuation values for the free space medium of urban area over quasi-smooth terrain with a BTS effective

3 A Parametric Characterization and Comparative Study of Okumura 455 antenna height of 200m and a mobile antenna height of 3m. To determine path loss using Okumura s model, the free space path loss between the points of interest is first determined, and then the value of A mu (f, d) is added to it along with correction factors to account for the type of terrain as expressed in (1). L ( ) 50 db = L f + Am u G H G te H G re area 2 λ L f 10 log 10 2 ( 4 π ) d G G H H te re = 2 = 20 log 10 = 10 log 10 H 200 H 3 re te Here, L ( db) is the 50 percentile value of propagation path loss, 50 L f is propagation loss of free space, Amu is the median attenuation relative to free space, G H te, G H re, Garea are BTS antenna height gain factor, mobile antenna height gain factor and gain due to the type of environment. Hata Propagation Model [2] Hata model is based on Okumura s field test results and it predicts various equations for path loss with different types of clutters. Limitations of the Hata Model test results include its carrier frequency (150 MHz to 1.8 GHz), the distance from BTS (50m to 20Km), and the height of base station antenna (30m to 200m) and the height of mobile antenna (1m to 10m). Mathematically, the Hata model path loss is expressed for different environments such as the urban, suburban and open country in (2-4). Hata model may not produce good results for the hilly rural terrains because the geographic details for this environment are not specified. The path loss for urban clutter is expressed as: L p(urban) = log(f) 13.82log(h b ) a(h m )+( log(h b ))log(d); Where, the a(h m ) = (1.11log(f)-0.7)h m (1.56 log(f)-0.8) (2) Path loss for suburban clutter is expressed as: 2 L p(suburban) Lp(urban) -2{log(f/28)} -5.4 = (3) Path loss for the open country is expressed as: 2 L p(open) Lp(urban) -4.78{log(f)} 18.33log(f) = + (4) (1) Flow Chart for Selection of Model To characterize a prediction loss model a large number of permutations and combinations are needed depending upon the environmental conditions and application requirements. Flow chart in figure 1 presents a simple guidance for the selectors and designers.

4 456 Sagar Patel et al Figure 1: Calculation flow for proposed method [6]. Statistical Estimation of Path Losses The path loss values for the Okumura and Hata models are statistically estimated through numerical analysis methods. These results for the accuracy of two decimal points are produced in tables 1 and 2. The assumptions made for these computations are; A mu =35, H te =100m, H re =2m, G area =9(suburban), 15(urban), h b =100m, h m =2m, f= MHz (for Okumura) and f = MHz (for Hata). The parametric comparative analysis for the results is shown in table 1.a and table 1.b. It proves that the power attenuation-variation for the urban and suburban zones for Okumura model operating under similar conditions such as specified frequency and distance between the transceivers are quite consistent. The results of attenuation taking place for Hata model operating in the urban, suburban and open zones are enlisted in table 2.a, 2.b and 2.c. A parametric comparative analysis is presented in the table 3. It justifies that the attenuation level between the Okumura and Hata models for suburban and urban zones vary randomly for different combinations of frequency and distance. Results for Okumura suburban and urban Environment Table 1: (a)attenuation (Path Loss) for 150 MHz 1.92 GHz versus Distance (50-200m) for suburban environment (b) Attenuation (Path Loss) for 150 MHz 1.92 GHz versus Distance (50-200m) for urban environment. Sr No. Frequency (MHz) Distance (m) (a) L 50 (db) Attenuation (b) L 50 (db) Attenuation

5 A Parametric Characterization and Comparative Study of Okumura Results for Hata urban, suburban and open Environment Table 2: (a) Attenuation (Path Loss) for 150 MHz 1.8 GHz versus Distance (50-200m) for urban environment (b) Attenuation (Path Loss) for 150 MHz 1.8 GHz versus Distance (50-200m) for suburban environment (c) Attenuation (Path Loss) for 150 MHz 1.8 GHz versus Distance (50-200m) for open environment. Sr No. Frequency (MHz) Distance (m) (a) L-urban Attenuation (b) L- suburban Attenuation (c)l-open Attenuation

6 458 Sagar Patel et al Table 3: Comparison between Okumura and Hata Models for the Path-loss levels. Freq Distance L (suburban) L (urban) Okumura Hata L (suburban) (db) Okumura Hata L (urban) (db) Okumura Simulation Results The graphical simulation results are shown in figure 2,3,4,5,6,7,8 and 9 for Okumura model operating under various combinations of Indian environmental and specific electrical conditions such as different frequencies, distances, urban and suburban zones. Figrue 2: Distance vs. L 50 Attenuation for Sub-Urban Area (with Different frequencies). Figrue 3: Distance versus L 50 Attenuation for Urban Area (with Different frequencies).

7 A Parametric Characterization and Comparative Study of Okumura 459 Figure 4: Distance vs. Received Power (db) for suburban Area (with 50m Suburban Area). Figure 5: Distance vs. Received Power (db) for suburban Area (with 100m Suburban Area). Figure 6: Distance vs. Received Power (db) for suburban Area (with 150m Suburban Area). Figure 7: Distance vs. Received Power (db) for suburban Area (with 200m Suburban Area). Figure 8: Frequencies vs. L 50 Attenuation for Sub-Urban Area (with Different Distances). Figure 9: Frequencies vs. L 50 Attenuation for Urban Area (with Different Distances).

8 460 Sagar Patel et al Hata Simulation Results The graphical simulation results are shown in the figure 10, 11 and 12 for Hata model operating under various combinations of Indian environmental and specific electrical conditions such as different frequencies, distances, urban, suburban and open zones. Figure 10: Distance vs. L 50 Attenuation for open Area (with Different frequencies). Figure 12: Distance vs. L 50 Attenuation for Sub-Urban Area (with Different frequencies). Figure 12: Distance vs. L 50 Attenuation for Urban Area (with Different frequencies). Conclusion and Future Scopes The Okumura and Hata prediction-loss models are investigated for their electrogeographic performance for their specific electrical operating conditions. The comparative analysis was carried out for the simulated results by varying the distance between the transceivers and the frequency of operation for urban, suburban and open terrains. This model based study results into the conclusion that the better prediction propagation loss for the concerned area can be selected and then get optimized. Accordingly the variations in the prime factors affecting the end-user-performance of

9 A Parametric Characterization and Comparative Study of Okumura 461 the selected wireless systems including both, the transmitters and receivers, and the environment can also be programmed. This investigation and simulation will be highly useful to the future research aspirants working in the areas of wireless and telecommunication. Acknowledgment The authors are very much thankful to the CHARUSAT management for encouraging them to complete this research work in time. References [1] Nazar. Elfadhil, M.A. salam, Modification of an open area okumura-hata propagation model suitable for Oman IEEE-TENCON, 2005, Australia. [2] Z.Nadir, Pathloss Determination Using Okumura-Hata Model and Spline Interpolation for Missing Data for Oman. WCE 2008, July 2-4, 2008, London, U.K. [3] A Final Report on city RF propagation models page no.9, Saudi Arabia, [4] Gilles Y.Delisle, Michel Lecours Propagation Loss Prediction: A Comparative Study with Application to the Mobile Radio Channel IEEE Transactions on Vehicular Technology, Vol. VT-34, no.2, May [5] V.S. Abhayawardhana, I.J. Wassell Comparison of Empirical Propagation Path Loss Models for Fixed Wireless Access Systems May, 2005, UK. [6] Michifumi Miyashita, Takashi Terada An optimum model to estimate path losses for 400MHz band land mobile radio Central Research Institute of Electric Power Industry Journal, 2003 page.16. Bibliography Dr. Y. P. Kosta is earned his M. Tech. and Ph. D. degrees all in Electronics and Communication Engineering in 1991 and 1998 respectively. He joined ISRO and worked towards the design and development of INSAT satellite Communication payloads. He also worked as a Sr. Design Engineer at Teledyne in California, USA. He is a member of professional bodies like IEEE, IETE, ISTE and CSI. He has written books, articles and research papers for journals and conferences of repute. Dr Kosta is an SCPM from Stanford University. Presently he is Principal of CIT and Dean of faculty of Engineering and Technology, Charotar University of Science and Technology Changa. His research and interest areas are RF, Wireless Satellite Systems and Information Communications. He has guided more than twelve M. Tech. dissertations and is guiding 06 Ph.D. theses. He has delivered more than a dozen of his expert talks. He is member of various academic and research bodies in India and abroad.

10 462 Sagar Patel et al Ved Vyas Dwivedi is a life member of IETE, the IE (India) and Member IEEE ( 03, 04, 08). He earned B.E. in Electronics Engineering and P.G.D. in E.C. (Microwave) Engg. He did M.E. E.C. Engineering from BIT Mesra, Ranchi, India. Presently, he is with this department accredited by NBA and TCS, ISO 9000:2001 certified. To pursue Ph.D., he is researching on DNG microstrip antenna. He is coordinator of IETE Student Forum. He has published 09 journal research papers (05 in international journals), 12 papers in recognized international conference proceedings (06 in IEEE) and 15 recognized national proceedings (4-IETE, 5-IEEE). He is associated with electromagnetic engineering, antenna, microwave and satellite communication industries. He is full time UG-PG recognized teacher and has guided and evaluated 23 UG and 14 PG projects in his research projects. He has delivered 13 expert talks. Sagar Patel did his B.E. in Electronics and Communication Engineering from North Maharashtra Uni. His research areas are wireless communication engineering, especially prediction propogation model loss with different parameter. He is presently serving in the department of EC engineering at Charotar University of Science and Technology Changa Gujarat India since Oct He is teaching the subjects of under graduate engineering students of this university.