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  Progress In Electromagnetics Research, Vol. 125, 559–581, 2012  EXPERIMENTAL INVESTIGATION OF GSM 900MHzRESULTS OVER NORTHERN INDIA WITH AWAS ELEC-TROMAGNETIC CODE AND OTHER PREDICTIONMODELSM. V. S. N. Prasad 1,* , P. K. Dalela 2 , and C. S. Misra 3 1 CSIR-National Physical Laboratory, Dr. K S Krishnan Road, NewDelhi 110012, India 2 C-DOT, Mandigaon Road, Opp. New Manglapuri, Chatterpur,Mehrauli, New Delhi 110030, India 3 Aircom International Pvt Ltd., Gurgaon 122001, India Abstract —Recent trends in propagation modeling indicate thestudy of mobile radio propagation modeling with the help of electromagnetic formulations which traditionally has been explainedwith empirical methods. These empirical methods were preferred bythe cellular operators in their radio planning tools due to their easeof implementation and less time consumption. In the present study,AWAS electromagnetic code and conventional prediction methods havebeen employed to explain the observed results of ten base stationsmainly in the near field zones of GSM 900MHz band situated in theurban and suburban regions around Delhi in India. The suitability of the above models in terms of prediction errors and standard deviationsare presented. Path loss exponents deduced from the observed datahave been explained by Sommerfeld’s formulations. 1. INTRODUCTION In order to design high quality and high capacity cellular networks,a thorough understanding of propagation channel is necessary, andsignal strength measurements should be conducted to delineate cellradii and assess reliable coverage area [1]. It is established thatpropagation phenomena can cause unexpectedly poor performancein cellular networks. These are manifested in reduced coverage, Received 30 December 2011, Accepted 25 February 2012, Scheduled 12 March 2012  * Corresponding author: M. V. S. N. Prasad (mvsnprasad@gmail.com).  560 Prasad, Dalela, and Misra dropped calls and unexpected hand overs [2]. The performance of thecellular network can be assessed, or new networks can be designedwhen different models are tested with observed results. Arijit Deet al. pointed out [3] that in cellular communication scenario notmuch attention is paid to the relationship between the height of thetransmitting antenna and the distance of transition from near field tofar field region. In the near field, the strength of the field oscillateswildly with large nulls and peaks. They indicated that larger was theheight of transmitting antenna, greater would be the near field region,and the performance of cellular communication systems was degradedappreciably in near field region rather than in the far field region.They positioned the antenna closer to ground and also deployed ahorizontally polarized antenna for mobile communications as the fieldsradiated by a horizontally polarized antenna not to vary too muchwith the height of the antenna in the near field region. Gutierrez-Meana et al. [4] used deterministic radio electric coverage tool for thecomputation of electromagnetic fields based on modified equivalentcurrent approximation method. They illustrated the applicability in arural scenario, where a GSM base station at 900MHz is located, andan urban scenario to test the acceleration technique.Most of the statistical propagation models used in radio planningtools for the design of cellular radio networks refer to the periodof GSM where antennas are located far above the roof top, andcells were large [5]. Latest developments in mobile radio technologyand introduction of smaller cells, lower antennas necessitated thedevelopment of models applicable to many situations. The specialfeature in Delhi urban environment is that most of the buildingsare non uniformly spaced, and results reported elsewhere might notbe totally applicable to this type of environment. In this context,it is worthwhile to investigate how numerical electromagnetic codescompete with the statistical propagation models in the 900MHz band.Prasad et al. reported the investigation of eleven base station results inthe 1800MHz band with AWAS code and other models [6]. To verifythe suitability of AWAS electromagnetic code in the 900MHz band,field strength measurements were conducted utilizing the followingGSM base stations situated in national capital region of Delhi. Theyare 1. Paschimvihar (PVR) 2. University Area (UA) 3. Nandanagari-1(NN-1). 4. Nandanagari-2 (NN-2) 5. Satyaniketan (SNT) 6. Faridabad(FBD) 7. Vinayak Hospital (VKH) in the urban region and threesuburban base stations namely 1. Tradex tower (TXT), 2. Meethapur(MTR) 3. Gurgaon (GRN). The measured values of signal strengthhave been compared with the prediction methods of AWAS, Hata,COST 231 Walfisch & Ikegami, Dmitry and ITU-R. The models have  Progress In Electromagnetics Research, Vol. 125, 2012 561 been chosen so that they are applicable to the environments wheremeasurements were conducted. 2. ENVIRONMENTAL DESCRIPTIONS 1. Both the NN-1 and NN-2 base stations are surrounded by denseurban areas on three sides and medium urban environment onthe other side. The average building height is around 6 to 9m.PVR base station is surrounded by medium urban environmentwith slight open areas in between. Far away from the base stationon the left side, low tree density is seen. On the southern sideof the base station, a small water canal flows. UA base stationis surrounded by medium urban environment, and from east tosouth of the base station, a thick patch of tree density is seen.At a distance 2km away from the base station, dense urbanenvironment prevails on the southern side of the base station. (a)(b)  562 Prasad, Dalela, and Misra (c)(d) Figure 1. (a) Photographs of the environment. (b) Photographs of the environment. (c) Photographs of the environment. (d) Googlemap showing the locations of base stations.MPR base station is surrounded by low density urban area (mainlysuburban) with small patches of green vegetation in between.SNT base station is surrounded by medium urban environmentand small patches of greenery in between, denoting some kindof low urban residential environment. Figures 1(a) to 1(c) showthe photographs of the environment where measurements wereconducted. A google map showing the locations of 10 base stationsis shown in Figure 1(d). The three photographs in Figures 1(a) to1(c) were taken from the close surrounding area of base stationsVKH, FBD and SNT. Since the environmental features of otherbase stations are more or less similar, they are described in detail.
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