The magnetic induction communications for the wireless underground sensor networks

Transcription

1 International Journal of Intelligent Information Systems 2014; 3(6-1): Publishe online November 12, 2014 ( oi: /j.ijiis.s ISSN: (Print); ISSN: (Online) The magnetic inuction communications for the wireless unergroun sensor networks Farzam Saeenia 1, *, Shapour Khorshii 2, Mohssen Masoumi 3 1 Department Of Electrical Engineering, Kazerun Branch, Islamic Aza University, Kazerun, Iran 2 Air-Sea Science an Technology Acaemic Complex, Shiraz, Iran 3 Department Of Electrical Engineering, Jahrom Branch, Islamic Aza University, Jahrom, Iran aress: Farzam_2958@yahoo.com (F. Saeenia),khorshiy@yahoo.com(S. Khorshii), maesoumi@jia.ac.ir (M. Masoumi) To cite this article: Farzam Saeenia, Shapour Khorshii, Mohssen Masoumi. The Magnetic Inuction Communications for the Wireless Unergroun Sensor Networks. International Journal of Intelligent Information Systems. Special Issue: Research an Practices in Information Systems an Technologies in Developing Countries. Vol. 3, No. 6-1, 2014, pp oi: /j.ijiis.s Abstract: The most important ifference between the wireless unergroun sensor networks (WUSNs) anthe wireless groun sensor networksis the propagation environment of the signal.in fact, the unergroun environments consist of soil, rock an water instea of the air. The challenging reasons of these environments to propagate the wireless signal via the Electro Magnetic (EM) 2waves are consiere as: the high path loss, channel ynamic conitions an the high size of antenna. At the present stuy, the etails of Bit Error Rate (BER) 3 for 2PSK moulation, path loss an the banwith of the Magnetic Inuction (MI) 4Systems an Electro Magnetic (EM) Waveguie in the unergroun environment areevaluate. Meanwhile, a new metho isintrouce via MI waveguie that provie the constant conitions of channel by the small inuctive coils. At the en of this stuy,itisfoune that the transmission range in MI waveguie system woul be raise an the path loss in that system woul be ecline severely. Keywors: Channel Moulation, MI Waveguie Metho, Unergroun Communications, Wireless Sensor Networks, Magnetic Inuction 1. Introuction The Wireless Unergroun Sensor Networks (WUSNs) have the wireless sensors that are burie unergroun. WUSNs have so many applications such as the coverage, easy to use, appropriate ata, reliability an the cover ensity. The other applications are the control of the soil conitions, earthquake, lanslies forecast, the unergroun substructures control, the lanscapes management an security [1, 2]. It can be mentionethat the unergroun propagation environment consists of soil, rock an water instea of the air that confront us with three challenges if it is applie for the wireless communications via the Electro-Magnetic (EM) Waves: The high path loss, channel ynamic conitions, an Antenna size [3]. Akyiliizet.al,[2]evaluate the wireless communications networks installe in the unergroun an also the propagation via electromagneticwaves. Meanwhile,years later, Zhi Sun an Akyiliiz [9] compare the traitional methos an MI systems of the wireless unergroun communications.at the en of this stuy, the wireless unergroun communications were evaluate by a new metho calle MI Waveguie [9]. In the secon part, the theoretical structure of a new methocalle MI Waveguie was presente that use some inuctive coil.the thir section of simulation consiere the theory of secon section an the comparison of communication methos. 2. The MI Waveguie Characteristics As the unergroun route is limite in many WUSN applications such as the control of unergroun structure,the sensors must be place in the earth epths. The Magnetic Inuction (MI) is a physical layer metho for WUSN in high epths of soil[4]. Although the magnetic permeability of the soil, water an air is same, the MI channel conitions will be remaine the same because the magnetic fiels create slight changes in the loss of wave's strengthin the soil an water to the air. Furthermore, the transmission an reception of MI

2 110 Farzam Saeenia et al.: The Magnetic Inuction Communications for the Wireless Unergroun Sensor Networks waveguie are conucte by some small wire cores calle as Inuction coils (there is no multipath isappearance in MI waveguie) ue to the low resistance of the irraiation in the coil inuctance [2, 5, 6]. For MI Waveguie Metho,some multiple factors were applie such as the soil properties, soil size, number of rotations in each ring of coil, coil resistance in the operational frequency [6].Our analyses inicate that MI Typical Systems has a higher transmission range an lesser banwith than EM waveguies systems. But neither MI typical system nor EM waveguie system is able to provie enough communication range for the practical applications of WUSN. 3. The MI Waveguie for the Unergroun Communications The propagation characteristics of Electro Magnetic (EM) waves in the unergroun environment (soil, water, rock) were presente in fig.3. The analyses inicate that the path loss is much higher than the groun cases an its reason is the absorption in the elements of the unergroun environment. The success in the communications epenson the combination of operational frequency an soil. Thus, as the operational frequency ecreases, the path loss is ecrease too but we nee a larger antenna [3]. One suggeste solution is to apply some antenna with 0.3m length to receive 300 MHz signals. Meanwhile, the signal transmission rangeof these antennas is about 4 meter. Recently, the Magnetic Inuction metho has been use as a new physical layer metho for the wireless communications but it has isavantages as the high path loss an Low banwith.mi can be consiere as an alternative communication metho in Bluetooth. For the first time, MI was introuce in wireless unergroun communications. Accoring to the previous stuies, MI transmission isn t influence by the soil type, combinations, concentration or the moisture [7]. Although the channel is constant an the transmission range of the MI typical system is more than EM, its transmission range is still short for the operational applications. One suggeste solution is to apply several simple relay inuctioncoilswithout any energetic resourceanprocessing machine between the receiver an transmitter to conuct MI waves by EM Waves metho. The proceure is that at first, the sinusoial current in the transmitter scoil loop inuces a sinusoial current in the primary relay inuction coil point.then this sinusoial current in the coil loop of the primary relay inuces another sinusoial current in the seconary loop an this proceure continues until to reach the receiver. As it is shown in the first row in fig.1, a typical structure of n-2 coil loops has been place between the axis of receiver an transmitter. Thus, n,the total number of coil loop;r,the istance between the ajacentcoil loops/ringsan is the istance between the receiver an transmitter. D=(n-1)r ; a is the raius of coil loops. Accoring to the secon row in fig.1, it can be sai that each relay coil consists of the receiver an transmitter s coil loop that is loae via a capacitor, C. In orer to transmit the magnetic signals, an appropriate esign shoul be presente for the capacitor value an the effective value of the resonant coil loop to create the mutual inuction among each pair of coil loop that epens on the proximity of the loops. In the unergroun communications, we consiere the istance between two relay loops as 5meters. But that istance was higher than the maximum of the communication range in EM waves system. Despite this, the application of relay loop instea of the unergroun evices in MI system reuces the costs. In the next part, an appropriate istance is obtaine by analyzing the istance of MI waveguie relay loop. The istance of loops in comparison with the relay loop 0.15m is high enough an it causes that the coils only have a mutual self-inuction with their neighbors System Moeling For moeling the MI waveguie, all loops must have the same parameters (resistance, mutual inuctance an selfinuctance). M is the mutual inuctance between the ajacent coils, U a is the voltage of transmitter battery, L, the selfinuctance of the coils, R is the coil resistance, C is the loae capacitors in each coil an Z L is the impeance of the loa in the receiver.the equivalent circuit of the multistep transformer shown in the thir row in fig.1 is as follow: Z=R+jωL+ 1 jωc Z = ω M Z+Z i =2,3,,n 1 an Z =Z Z = ω M Z+Z i=3,4,.n an Z = ω M Z # Fig. 1. Communication Channels Moel for MI Waveguie. U % = jωm & '()* ++ (),()* i =2,3,.n an U % =U - (1)

3 International Journal of Intelligent Information Systems 2014; 3(6-1): whereas Z i 1 is the effect of i th coil on i 1./ loop anvice versa. Then the receive power in receiver is calculate as: 3.2. System Optimization, + 4.& '5 P 1 = Re3 + 5)*5 ++ 4, 6 (2) If the coil loops are resonate, U Mn value as the inuce voltage in the receiver will be reache to its maximum value that makes the receive power to reach to its maximum on the basis of equ.1.therefore, we shoul esign a capacitor to prevent from reucing the actual value of receive power severely because of self-inuction in the coil loops (jwl + 8 9: ;=0 By the self-inuction in equ.7, the capacitor value is calculate as: C= =, >,?@A When the coil loops are resonate,the receive power, U Mn can be extene as: U % = U - jωm R jωm R+ =, %, C =U - j F * F,.. jωm R+ =, %, C D, ', E.. (3) (4) F 5)* Accoring to the above-mentione equations, it can be sai that the multiplying operation, x,x,x H,,x is n-1 egree from x = R/ωM written as ξ 8 C ;,n 1, the :% following equation is : ζ8 C =%,n 1;=b 8 C =% ; +b 8 C =% ; + + b 8 C =% ; +b 8 C =% ;+b M (5) Nb Whereas,,i=1,2,,n 1O are the polynomial coefficients that aren t influence by the parameter for an special an constant n. Since the coil loop has been resonant, it causes that the loa impeance is matche with the pure strength. So, the loa impeance is regare as Z = PPPPPPPPPPPPPPP Z +R. Finally,in MI waveguie if the receiver is meter away from the transmitter an there is some loops with n-2 relay coil between them,the receive power will be written as: P 1 =. Q+ 5)*5 C &, R S, 8 E D',; (6) Whereas, is the transmission range, = (n-1) r. Like MI typical system, the transmitte an receive powers in MI system are reuce simultaneously as the transmission istanceincrease. Thus, MI waveguie loss, L MIG is efine as: L %TU = 10log P 1 P. r M 10log[ 4Z +R +20logζ\ R R ωm,n 1]^ a ` =10log4`1+ ` ` _ 1 8 C =% ; + * 8 E, D' ; e b *b..c * +20logfb 8 C =% ; + +b 8 C =% ;+b Mg (7) Whereas, P t (r D ) isefineas the transmission power when the transmitter is very close to the receiver an there is no inuction coil.on the basis of equ.7, the path loss in MI waveguie system is a function from R/ωM. Meanwhile, ξ C :%,n 1 is a polynomials that has a significant effect on the path loss. Thus, the path loss is a monotonic function with the increase performance from R/ωM. Thus, in orer to reuce the path loss, R/ωM must be reuce to the minimum value. By the wire resistance, R an the mutual inuctance, M in equ.4 an equ.6 [4],R/ωM is expresse as [9]: C =% = QC h =>?@.81 A ;H (8) Note that, the relay istance, r is 1/ (n-1) of the total transmission range,. By this metho, the effect of Cubic functionfor the path loss can be ecrease. With regar to this scheme, it is possible to ecrease the path loss by consiering the following items: - The ecrease of relay istance to the coil raius, r/a. -The increase of operational frequency, ω an the number of loops in the coil, N. - The ecrease of wire resistance, R D -But there are some other factors to minimize the path loss (the relay istance to raius). In orer to facilitate the eployment of coils, it is expecte to have a ecrease in the total transmission range. In this section, in orer to keep the avantages of the above case on the unergroun EM waveguie system, the relay istance is restricte to the minimum value, 4 m to have the maximum release in the transmission range. With regar to the coil raius, 0.15 meters, the relay istance to coil raius is very high. -There are other factors inclue in to this law an there isn t possibleto increase the operational frequency an the number of rotations in the coil loop. Thus, these two parameters can be restricte by equ.3. The capacitors with loas in each resonant coil shoul be more than 10PF. Furthermore, the ecrease of coil resistance can reuce the total path loss. In orer to obtain the practical value of the resonant capacitors in each resonant coil, it isn t possible to

4 112 Farzam Saeenia et al.: The Magnetic Inuction Communications for the Wireless Unergroun Sensor Networks maximize N an ω. Furthermore, very high operational frequency an the high number of coil rotations causes the severe operation arising from Parasitic Capacity[22].In this section, the operational frequency is 10 MHz,the number of rotations is 5 for each coil an the capacitor value is 35PF. Fig. 2. the comparison of the path loss in MI waveguie with EM,MI wave systems. Although the ecrease of coil resistance can reuces the path loss, two problems may occur: 1) in orer to ecrease the coil resistance, the wire iameter must be raise. It causes the costs increase an the loop becomesheavier. 2) The ecrease of coil resistance causes some fluctuations in the receive signal that make problems in receiving the signal in the receiver. In this stuy, the coil was mae of copper with 0.45mm iameter. With regar to the AWG stanar[8], the resistance of unit length, R D is 0.01 i j Numerical Analysis Path Loss The path loss in the MI waveguie system in Equ.7 were evaluate viamatlab software. The results were shown in fig.2. In orer to have a better comparison, the path loss of EM waves system with the operational frequency, 300MH in the soil with VWC, 0.5 an the path loss of typical MI system with the operational frequency, 10MHz were rawn. Accoring to the mentione iscussions in the fourth section, MI system operation can t influence on the soil properties. The soil environment has the permeability as the air (4k 10 l m/n). So in evaluating MI waveguie, there is no nee to consier the environmental parameters. Except the evaluation of the effects of special parameters, all available loops in the transmitter, receiver an relay points have some efault values: raius, a=0.15m an the number of rotationsin system, N=5.The resistance of unit length for the natural coil an the low resistance coils are R0=0.01Ω/m an R0=0.005Ω/m respectively. The operational frequency is set on 10MHz. The relay istance, r is also 5m.The total number of coil loops, n is etermine by the transmission istance, where = (n-1)r. The path loss of MI waveguie system, B with the ifferent transmission istances,, the ifferent relay istance, r an ifferent coil resistance, R D have been shown in fig.2. It can be foun that MI waveguie system has a lower path loss in 100 B an even with the transmission istance, 250m to EM magnetic an MI typical systems. But its path loss increases in more than 100 B with the istance, 5 m. Furthermore, the path loss can be obtaine via ecreasing the relay istances an the coil resistance Bit Error Rate The BER an MI waveguie characteristics were evaluate in fig.7. The analyses of thir section with 2PSK moulation were shown as the Scheme Moulation.Two noise levels were consiere which the noise moeratelevel, P n was regare in low parasite scenario, -103Bmwhile in high noise scenario, P n is -83 Bm. The transmission power value,p t is also set on 10 Bm. In fig.7, BER in MI waveguie system has been shown as a function of transmission istance, with the ifferent relay istances, r an ifferent wire resistance, R D.In fact, EM waveguie system an MI typical system has been rawn for comparison. by comparing the low transmission range of two other methos ( lower than 10m), it can be sai that even in high parasite scenarios, the transmission range of wave is about 250m.. It means that in comparison with two other systems, the transmission range in MI waveguie system will be raise for more than 25 times.in compliance with the analyses in the path loss, the transmission range of MI waveguie can be increase by ecreasing the relay istance an resistance of the coil Banwith Assuming that there is only one frequency in the transmission signals, thepath loss in high levels an in the transmission range of MI waveguie system is calculate. Accoring to this central frequency, all coils can be resonate.but if there is any kin of eployment from the central frequency, the resonance status of each coil will be isappeare. So, it is necessary to analyze the ban with in MI waveguie system. In fig.2, the frequency response of MI waveguie system was shown with ifferent relay istances, r an ifferent wire resistance, R D. The number of relay coilwas shown by constant 7.The results inicate that when the operational frequency is 10MHz, the ban with 3B in MI waveguie system will be place in a same range as MI typical system that is about 1 khz to 2 khz. Although the lower coil resistance can ecrease the path loss in the central frequency, thefluctuations of the frequency response is such a serious problem that may make some problems in the transferring the power to the receiver. The ban with can be increase as the relay istance reuces. But for a special transmission range, it can be sai that the reuction of relay istance means that we nee more relay loops. Two possible operational parameters are as follow: 1. The relay istance, r=5m an the resistance of unit length, R D,R D =0.01Ω/m that make the system conuctor in operation in 10KHz frequency,the raius, 250m an the ban with,1khz. 2. The relay istance, r=4m an the resistance of unit

5 International Journal of Intelligent Information Systems 2014; 3(6-1): length, R D,R D =0.01Ω/m that make the system conuctor in operation in 10KHz frequency,the raius, 400m an the ban with,2 KHz The Deployment Effect It must be mentione that the high operation of MI waveguie system is ieal in placement of the coils. All relay coils are place in it carefully as relay coil, N-2 is istribute in the transmission range uniformly between the transmitter an receiver that exactly consists of the same istances.the transmission range to temporal intervals is ivie to N-1. Thus, the mutual inuctances between the coils are the same. But in the operational applications, these conitions aren t operate because of the two following reasons: 1.in theinitial stage of placement, it isn t possible to place the coil in its exact position ue to some restrictions such as stones or rocks. 2. Perhaps, the position of loops is change ue to the groun pressure on the network or the soil motions. Thus, the operational status was analyze in figs.3, 4. It is assume that the relay coil loops isn t place in the accurate positions. So, the relay loop, n-2 between the receiver an transmitter is applie. Their esigne positions are as oi.,i = 1,2, n 2. p X j in the relay loop, i is a Gaussian ranom variable with the mean, i./(n-1) an the stanar eviation, σ r. After that, it can be sai that the transmission istance, is iviable to n-1 intervals with r 1,r 2,r n-1 whereas r =x x are the transmitter an receiver positions respectively. Itwas assume that the stanar eviation ha been esigne for the relay istances 5%,10% or 20%. The other simulation parameters were set on the efault values. The results were obtaine from 100 samples in average. Both the moerate value an the stanar eviation were rawn in the figure. It can be sai that operationally, there is also an aitional path loss. Furthermore, when the stanar eviation is 20%, the ban with ecreases severely.the level of aitional path loss an the reuction of ban with are etermine by the stanar eviation. The higher stanar eviation makes more problems in the system. Furthermore, as the transmission istance increases, the aitional path loss will be raise too. When the eployment increases, the stanar eviation of the path loss an the ban with are also raise severely.this inicates that as the eployment occurs, the reliability of MI waves system is also reuce. Meanwhile, as the stanar eviation is lesser than 10%, we can ignore the effect of eployment on the operation of MI waves system. 4. Discussion an Conclusion Fig. 3. The Comparison of Bit Error Rate of MI Waveguie with Different Relay Distances an Noises for EM an MI waves system. Fig. 4. The Frequency Response of MI Waveguie System with Different Wire an Remote Relay Resistances. In the unergroun wireless communications, the traitional methos via EM waves have three major challenges: the high path loss because of the material absorption, the channel ynamic conitions because of the various properties of the soil an the very high size of the antenna. MI is an alternative metho with the same channel conitionsan it can accomplish the communications with the small cores.at the present stuy, one analytic moel was shown that inicate the communicational unergroun channel characteristics of MI. Accoring to the channel analysis, we presente one MI wave metho that increase the transmission range. Our analysis inicate the following results: MI metho has the constant conitions of channel because the path loss only epens on the permeability of propagation environment. When the environment is the air, it remains the same but if the environment is the water or more kins of soils an rocks, this value is the same. The materials absorption is one of the most important parts in the path loss of EM system that may change in the various soil conitions. In the unergroun environments, the path loss of MI system is slightly lower than EM wave system in the natural an wet soils. But because of the high path loss, both systems can provie one transmission range that is more than 10m.Although the ban with of MI systeman MI waves system is only 1 to 2KHz (more lesser than EM waves system), these values are enough for monitoring few ata in the WUSNS applications. One of the other avantages of MI waves system is that as the transmission range increases, the

6 114 Farzam Saeenia et al.: The Magnetic Inuction Communications for the Wireless Unergroun Sensor Networks transmission power ecreases simultaneously with regar to the receive power.this is ieal for WUSNS restricte energy. MI Waves Metho ecreases the path loss effectively. It must be mentione that the cores of relay coil on t consume energy. hence, their costs are very low. The ban with of MI system is similar to one MI typical system. In comparison with MI typical system an EM waves, the transmission range of MI waves increases severely. References [1] I. F. Akyiliz, W. Su, Y. Sankarasubramaniam, an E. Cayirci, Wireless sensor networks: A survey, Computer Networks., vol. 38, no. 4, pp , March [2] I. F. Akyiliz an E. P. Stuntebeck, Wireless unergroun sensor networks: Research challenges, A Hoc Networks (Elsevier),vol. 4, pp , Jul [3] L. Li, M. C. Vuran, an I. F. Akyiliz, Characteristics of unergroun channel for wireless unergroun sensor networks, presente at the Me-Hoc-Net 07, Corfu, Greece, Jun [4] T. A. Milligan, Moern Antenna Design, 2n e. Piscataway, NJ: IEEE Press, [5] N. Jack an K. Shenai, Magnetic inuction IC for wireless communication in RF-impenetrable meia, presente at the IEEE Workshop on Microelectronics an Electron Devices (WMED 2007), Apr [6] J. J. Sojehei, P. N. Wrathall, an D. F. Dinn, Magnetoinuctive (MI) communications, presente at the MTS/IEEE Conf. an Exhibition (OCEANS 2001), Nov [7] A. R. Silva an M. C. Vuran, Development of a testbe for wirelessunergroun sensor networks, EURASIP J.WirelessCommun.Netw.(JWCN)[Online].Available: e.unl.eu/~mcvuran/ugtestbe.pf [8] Stanar Specification for Stanar Nominal Diameters an Cross- Sectional Areas of AWG Sizes of Soli Roun Wires Use as Electrical Conuctors, ASTM Stanar B , ASTM International, [9] Sun, Z. an Akyiliz, I. F.,"Magnetic Inuction Communications for Wireless Unergroun Sensor Networks,"IEEE Transactions on Antenna an Propagation, vol. 58, no. 7, pp , July 2010.