International Journal of Interactive Mobile Technologies (iJIM) – eISSN: 1865-7923 – Vol 16 No 22 (2022) Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… Location Based Services for Remote Education and Health Institutes Using Sum-Difference Signal Patterns https://doi.org/10.3991/ijim.v16i22.35337 Muneer Ahmed Shaikh1, Sarmad Ahmed Shaikh1(), Fatima Zohra Shaikh2 1 Department of Computer Science, Sindh Madressatul Islam University, Karachi, Pakistan 2 Sindh Government Dispensary Bilawal Shah Noorani, District East Karachi, Pakistan sarmad@smiu.edu.pk Abstract—This paper presents a simple approach to providing location- based services (LBSs) for the remotely located educational and health institutes on demand, particularly in emergency situations i.e., COVID-19, using an an- tenna array. The proposed approach consists of the sum and difference patterns of the signal obtained from the antenna array at the base station of a wireless network. It provides the location of the targeting institute i.e., education and health, in terms of the angle-of-arrival (AoA) which can be used to steer the ra- diation beam in the targeted direction in order to provide the desired services i.e., emergency wireless communication link. In this way, fast and high band- width-based communication and networking can be possible for the mentioned organizations. We show antenna array design and location finding results in this paper. The obtained results in terms of antenna parameters and AoA show that the proposed approach is efficient, less complicated, and can be implemented in the next-generation wireless networks i.e., AI-enabled IoT and 6G systems, par- ticularly for the educational and health institutes. Keywords—location-based services, education and health institutes, and AoA 1 Introduction From the recent COVID-19 pandemic and big data volumes specially generated from educational and health organizations, it has appeared that there is a significant need for location-based services (LBSs) for efficient communication and networking among these organizations. Since educational and health institutes are mainly crowd- ed by many people for different purposes, they desire fast connectivity and services i.e., fast and high bandwidth wireless links. Therefore, LBSs from wireless networks, such as illustrated in Figure 1, have become a good option to address the challenge where we first find the location of the targeted site and then steer the transmission beam towards that site [1, 2, 3]. In this way, the total or the most of the electromag- netic (EM) energy can be diverted by forming a focused beam towards the targeted direction which will provide high data rates, secure communication, less interfer- ence/distortion, and improved performance (latency and robustness) [4, 5, 6]. 4 http://www.i-jim.org https://doi.org/10.3991/ijim.v16i22.35337 mailto:sarmad@smiu.edu.pk Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… Fig. 1. An overview of the location based services Radio localization is a concept in the wireless communication systems where the location of the terminals is estimated in various ways, for instance, angle of arrival (AoA)/direction of arrival (DoA) [7, 8, 9, 10, 11], time of arrival (ToA) [12], time- difference of arrival (TDoA) [13], and received signal strength (RSS) [14]. Among these techniques, particularly, the AoA estimation technique is used to estimate the location of the received signal in terms of angle (degrees) in azimuth and/or elevation axis using antenna array. The estimated direction of the targeting node can be used to steer the transmission in that specific direction in order to achieve the improved per- formance. Though there are numerous techniques available in the related literature to find the location information such as phased antenna arrays [13], multiple signal classification (MUSIC) [8], estimation of signal parameters via rotational invariance technique (ESPRIT) [15], and root MUSIC [16]. However, these methods involve complexity in terms of increased hardware and/or computations. Thus, in this paper, we propose a simple AoA estimation approach for LBS’s scenario which is based on utilizing the sum and difference patterns of the received signal. The proposed approach is capable of estimating the AoA with less complexity and good performance which can be real- ized in the LBS’s in education and health organizations. The paper is further arranged as follows. Section 2 describes the proposed method of location finding using antenna array and rat race coupler to achieve the sum and difference signal patterns followed by the AoA estimation expression. In Section 3, we demonstrate the obtained antenna parameters and the localization results, and discuss them in detail. Section 4 concludes the paper. iJIM ‒ Vol. 16, No. 22, 2022 5 Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… 2 Proposed methodology The proposed approach to find the location in terms of AoA includes a microstrip patch antenna array of two elements integrated with a rat race ring coupler in order to obtain the sum (∑) and difference (∆) signal patterns of the received signal, as shown in Figure 2. The obtained summed and differenced signals are then processed to ob- tain the desired AoA (θ�) in the azimuth plan such as given below: 𝜃𝜃� = 𝑠𝑠𝑠𝑠𝑠𝑠−1 � 𝜆𝜆 𝜋𝜋𝜋𝜋 𝑡𝑡𝑡𝑡𝑠𝑠−1 ∆ ∑ �, (1) where 𝜆𝜆, d, ∆, and ∑ represent the wavelength, distance between two antenna ele- ments, differenced signal pattern, and summed signal pattern, respectively. The ∆ and ∑ patterns are given below. ∆= 1 − 𝑒𝑒−𝑗𝑗𝑗𝑗𝜋𝜋 𝑠𝑠𝑠𝑠𝑠𝑠𝜃𝜃 , (2) ∑ = 1 + 𝑒𝑒−𝑗𝑗𝑗𝑗𝜋𝜋 𝑠𝑠𝑠𝑠𝑠𝑠𝜃𝜃. (3) The proposed antenna system has been designed at X-band of the frequency i.e., 10 GHz. We have used RT Duroid 5880 substrate for designing the antenna system whose properties are provided in Table 1. In this way, the simulated single antenna’s (quarter wave transformer matched patch antenna) layout design at 10 GHz frequency along with the following geometric parameters is illustrated in Figure 3. Free space wavelength (ℷ) = 𝑐𝑐 𝑓𝑓0 =30mm; c= speed of light in space = 3 X 108 m/sec Patch length = L = 9.0732 mm Patch Width = W = 11.8585 mm Patch input impedance = ZA= 212.50Ω Characteristic impedance of QWT = Z0′ = 103.07Ω QWT section length = lqw = 4.5886 mm QWT section width = wqw = 1.4 mm Width of 50Ω = w50= 5.0687 mm Length of 50Ω = l50= 5.3583 mm 6 http://www.i-jim.org Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… Fig. 2. Simulated design structure of the antenna array system Table 1. RT Duroid 5880 substrate properties Substrate permittivity εr 2.2 Substrate Thickness h 1.575 mm Substrate Tangent Loss 0.0004 Copper Conductivity 5.8 𝑒𝑒7 s/m Copper Thickness t 17 𝜇𝜇𝜇𝜇 Fig. 3. The layout design of the simulated single patch antenna iJIM ‒ Vol. 16, No. 22, 2022 7 Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… Moreover, the rat race coupler has been simulated at 10 GHz frequency using RT Duroid substrate with the same substrate properties as mentioned above. The simulat- ed layout design is shown in Figure 4, whereas the design parameters are also high- lighted. The s-parameters of the simulated coupler i.e., reflection loss coefficient and port isolation are shown in Figure 5 (a) and Figure 5 (b), respectively. The obtained reflection loss coefficient curves (S11, S22, S33, and S44) of coupler ports exhibit good matching having reflection loss of each port around -44.85 dB. Furthermore, the port isolations (between ∆ and ∑ ports and between two input ports), as shown in Figure 5 (b), are approximately -64 dB. The obtained phase differences between two input ports at ∆ and ∑ ports are 180.070 and 0.070, respectively, showing good per- formance of the coupler. Fig. 4. The layout design of the simulated rat race coupler a) 8 http://www.i-jim.org Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… b) Fig. 5. Simulated S-parameters of rat race couplers: a) reflection loss of each port, and b) port isolation 3 Results and discussions Initially, an antenna array consisting of two microstrip patch antenna elements has been designed on an EM simulator and integrated with a rat race coupler, as shown in Figure 2. The design principle for patch antenna and rat race coupler can be found in [13, 17, 18, 19]. The simulated scattering parameters (S-parameters) of the antenna array integrated with the coupler are depicted in Figure 6 where reflection loss for ∑ and ∆ ports is – 31 dB and -27 dB, respectively, which is less than – 10 dB desired value. Moreover, the obtained gain and directivity parameters are 9.47 dBi and 10.1 dBi, respectively. Furthermore, the same antenna array was excited with different angles powers on the ∑ and ∆ ports as given in the following Table 2 where the amplitude and phase of ∑ and ∆ ports are calculated using the ∑ and ∆ patterns expressions mentioned in Section 2. It is observed that as the angles of excitation vary between +450 and - 450, the beam steers accordingly between 00 (center) and ±450 with error less than ±50 which shows that the proposed circuit is working properly and the localization can be achieved. The radiation pattern (in terms of power versus excited angles) of ∑ and ∆ ports is shown in Figure 7. Moreover, received/estimated DoA angles versus the transmitted signal (true) angles are illustrated in Figure 8. iJIM ‒ Vol. 16, No. 22, 2022 9 Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… Table 2. Calculated absolute amplitude and phase of ∑ and ∆ θ [deg.] ∑ 𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀 ∑ 𝐏𝐏𝐏𝐏𝐏𝐏𝐏𝐏𝐀𝐀 ∆ 𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀 ∆ 𝐏𝐏𝐏𝐏𝐏𝐏𝐏𝐏𝐀𝐀 0 2 0 0 0 -15 1.667 -27.95 0.9375 62.04 15 1.667 27.95 0.9375 -62.04 -30 1.1756 -54 1.618 36 30 1.1756 54 1.618 -36 Fig. 6. Simulated S-parameters of ∆ and ∑ ports 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 x 10 10 -35 -30 -25 -20 -15 -10 -5 0 Simulated S-parameters (ckt1) Frequency S -p ar am et er [ dB ] Sum Difference 10 http://www.i-jim.org Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… Fig. 7. Radiation patterns of ∆ and ∑ ports Fig. 8. The estimated AoA/DoA versus Transmitted signal (true) angle 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 Estimated DOA Transmitted Signal Angle[deg.] D O A [ de g. ] of R ec ei ve d S ig na l iJIM ‒ Vol. 16, No. 22, 2022 11 Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… 4 Conclusion In this paper, we have demonstrated a simple approach, i.e., sum and difference patterns, towards the location based services system for the educational and health organizations. The proposed approach is capable of finding the direction of the de- sired organizations in terms of AoA within ±450 range which is in good agreement to other related works. The method is simple in the way that we perform most of the calculation of the sum and difference signal patterns in the RF domain which contrib- utes in reducing the computational cost. Therefore, the proposed approach can be applied for the remotely located institutes like education and health to provide them the location based fast and high bandwidth services. 5 Acknowledgement The authors acknowledge the Higher Education Commission (HEC) of Pakistan for the research grant to this work under National Research Program for Universities (NRPU) scheme with project No: 20- 15948/NRPU/R&D/HEC/2021. 6 References [1] Ni Lihao, Liu, Yanshen, and Liu, Yi , "Privacy Protection Model for Location-Based Services," Journal of Information Processing Systems, vol. 16, no. 1, pp. 96-112, 2020. https://doi.org/10.3745/JIPS.04.0163 [2] K. Witrisal, S.A. Shaikh, A. M. Tonello, et al, "Whitepaper on New Localization Methods for 5G Wireless Systems and the Internet-of-Things," in IRACON European Project, pp. 1-22, 2018. [3] M. N. Boulos , "Location-based health information services: a new paradigm in personalised information delivery," International journal of health geographics, vol. 2, no. 2, 2003. https://doi.org/10.1186/1476-072X-2-2 [4] D. Zhang, F. Xia, Z. Yang, L. Yao, and W. Zhao, "Localization technologies for indoor human tracking," in 5th International Conference on Future Information Technology, pp. 1-6, 2010. https://doi.org/10.1109/FUTURETECH.2010.5482731 [5] J. G. Andrews, et al, "What will 5G be?," in IEEE Journal on Selected Areas in Communications,, vol. 32, no. 6, p. 1065–1082, 2014. https://doi.org/10.1109/JSAC.2014. 2328098 [6] R. D. Taranto, et al, "Location-aware communications for 5G networks: How location information can improve scalability, latency, and robustness of 5G," in IEEE Signal Processing Magazine, vol. 31, no. 6, p. 102–112, 2014. https://doi.org/10.1109/MSP.2014. 2332611 [7] A. M. Tonello and D. Inserra, "Radio positioning based on DoA estimation:An implementation perspective," in IEEE International Conference on Communications Workshops (ICC), Budapest, pp. 27-31, 2013. https://doi.org/10.1109/ICCW.2013.66491 95 [8] S. A. Shaikh and A. M. Tonello, "DoA Estimation in EM Lens Assisted Massive Antenna System Using Subsets Based Antenna Selection and High Resolution Algorithms," in 12 http://www.i-jim.org https://doi.org/10.3745/JIPS.04.0163 https://doi.org/10.1186/1476-072X-2-2 https://doi.org/10.1109/FUTURETECH.2010.5482731 https://doi.org/10.1109/JSAC.2014.2328098 https://doi.org/10.1109/JSAC.2014.2328098 https://doi.org/10.1109/MSP.2014.2332611 https://doi.org/10.1109/MSP.2014.2332611 https://doi.org/10.1109/ICCW.2013.6649195 https://doi.org/10.1109/ICCW.2013.6649195 Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… International Journal of Radioengineering, vol. 27, no. 1, pp. 159-168, 2018. https://doi. org/10.13164/re.2018.0159 [9] S. A. Shaikh and A. M. Tonello, "Localization based on angle of arrival in EM lens- focusing massive MIMO," in IEEE 6th International Conference on Consumer Electronics (ICCE), Berlin, Germany, pp. 124-128, 09 2016. https://doi.org/10.1109/ICCE-Berlin. 2016.7684736 [10] X. Lan, L. Wang, Y. Wang, C. Choi, and D. Choi, "Tensor 2-D DOA estimation for a cylindrical conformal antenna array in a massive MIMO system under unknown mutual coupling," in IEEE Access, vol. 6, pp. 7864-7871, 2018. https://doi.org/10.1109/ACCESS. 2018.2799179 [11] X. Lan, Y. Li, and E. Wang, "A rare algorithm for 2D DOA estimation based on nested array in massive MIMO system," in IEEE Access, vol. 4, p. 3806–3814, 2016. https://doi. org/10.1109/ACCESS.2016.2583458 [12] M. I. Skolnik, Radar Systems, New York: McGraw-Hill, 2001. [13] C. A. Balanis, Antenna Theory and Analysis and Design, Newyork, USA: John Wiley and Sons Inc, 1997. [14] D. Laurijssen, J. Steckel, and M. Weyn, "Antenna arrays for RSS based indoor localization systems," in IEEE SENSORS Proceedings, pp. 261-264, 2014. https://doi.org/10.1109/ ICSENS.2014.6984983 [15] R. Shafin, L. Liu, and J. Zhang, "DoA estimation and RMSE characterization for 3D massive-MIMO/FD-MIMO OFDM system," in Proc. IEEE Global Commun. Conf. (GLOBECOM), 2015. https://doi.org/10.1109/GLOCOM.2015.7417413 [16] B. Allen and M. Ghavami, Adaptive Array Systems, England: John Wiley and Sons Inc., 2005. [17] D. M. Pozar, Microwave Engineering, 3rd Edi, John Wiley & Sons, New York, 2005. [18] S. A. Shaikh and A. M. Tonello, "Performance Analysis of 180 degree HRR Coupler Used for Direction Finding with an Antenna Array," in International Journal of Biomedical & Online Engineering (iJOE), vol. 13, no. 10, pp. 86-102, 2017. https://doi.org/10.3991/ijoe. v13i10.7410 [19] S.A. Shaikh, and et al, "An Educational Training Kit for an Efficient GPS Anti-Jamming System," in International Journal of Emerging Technologies in Learning (iJET), vol. 16, no. 06, pp. 231-244, 2021. https://doi.org/10.3991/ijet.v16i06.21251 7 Authors Dr. Sarmad Ahmed Shaikh was born in Pakistan. He received the Bachelors De- gree in Telecommunication Engineering from FAST-NUCES, Pakistan, in 2011, the M.S. degree in Electronics Engineering from Sabanci University, Istanbul, Turkey, in 2015, and the Ph.D. degree in Information Technology from the University of Kla- genfurt, Klagenfurt, Austria, in 2018. He is currently an Assistant Professor with the Faculty of Information Technology, Sindh Madressatul Islam University (SMIU), Karachi, Pakistan. His research interests include RF/microwave engineering, radio source localization, antenna arrays designing, and wireless sensor networking (IoT) & artificial intelligence. Mr. Muneer Ahmed Shaikh was born in Pakistan. He received the Bachelors De- gree in Computer Systems Engineering from Mehran University of Engineering & Technology Jamshoro, Pakistan, in 1994, the M.E. degree in Computer Systems En- iJIM ‒ Vol. 16, No. 22, 2022 13 https://doi.org/10.13164/re.2018.0159 https://doi.org/10.13164/re.2018.0159 https://doi.org/10.1109/ICCE-Berlin.2016.7684736 https://doi.org/10.1109/ICCE-Berlin.2016.7684736 https://doi.org/10.1109/ACCESS.2018.2799179 https://doi.org/10.1109/ACCESS.2018.2799179 https://doi.org/10.1109/ACCESS.2016.2583458 https://doi.org/10.1109/ACCESS.2016.2583458 https://doi.org/10.1109/ICSENS.2014.6984983 https://doi.org/10.1109/ICSENS.2014.6984983 https://doi.org/10.1109/GLOCOM.2015.7417413 https://doi.org/10.3991/ijoe.v13i10.7410 https://doi.org/10.3991/ijoe.v13i10.7410 https://doi.org/10.3991/ijet.v16i06.21251 Paper—Location Based Services for Remote Education and Health Institutes Using Sum-Difference… gineering from NED University, Karachi, Pakistan, in 2010, and the Ph.D. degree (Continued) in Computer Science from SMI University Karachi Pakistan. He is cur- rently an Assistant Professor in Computer Science, the College Education Depart- ment, Government of Sindh, Karachi, Pakistan. His research interests include RF/microwave engineering, radio source localization, antenna arrays designing, and wireless sensor networking (IoT) & artificial intelligence. Dr. Fatima Zohra was born in Pakistan. She received her MBBS degree from LUMHS Jamshoro, Pakistan in 2014. She did her training as a general physician at different tertiary care centers. Currently, she is working as a commissioned officer (WMO) in the health department of the Sindh Government, Pakistan. Her research interests include medicines. Article submitted 2022-09-14. Resubmitted 2022-10-18. Final acceptance 2022-10-18. Final version published as submitted by the authors. 14 http://www.i-jim.org