Gaillot, Davy P

Joseph, Wout

Laly, Pierre

Liénard, Martine

Martens, Luc

Tanghe, Emmeric

Tran, Viet-Chi

Vin, Isabelle K

English

Ghent University Academic Bibliography

Polarimetric Characteristics of Specular and DenseMultipath Components in an Industrial HallE. Tanghe1, D. P. Gaillot2, W. Joseph1, I. K. Vin2, P. Laly2, V.-C. Tran2, M. Lie´nard2, and L. Martens11INTEC/WiCa, Ghent University, Ghent, Belgium, emmeric.tanghe@intec.ugent.be2IEMN/TELICE, University of Lille 1, Lille, France, davy.gaillot@univ-lille1.frAbstract—This contribution analyzes the cross-polarizationdiscrimination and the co-polar ratio of channel sounding datain a large industrial hall. The polarimetric parameters arecalculated for the complete channels including measurementantennas, and for the specular and dense multipath componentsestimated with the RiMAX algorithm. The main observation isthat horizontally polarized waves in the specular and dense partof the channel undergo an equal amount of depolarization whilethe depolarization of vertically polarized waves seems to be morepronounced in the dense part. A physical explanation for thisobservation based on the hall’s high ceiling is given.Index Terms—radio channel modeling, propagation parameterestimation, polarization.I. INTRODUCTIONOver the course of the last decade, the modeling of theradio channel has undergone an important change. Before that,the radio channel was commonly modeled as a collectionof Specular Multipath Components (SMC) that each havewell-defined discrete locations in the angular and time-delaydomains. However, it is also widely recognized that part of theradio channel appears to be continuous across these domains.This part is put under the umbrella of Dense Multipath Compo-nents (DMC) [1]. Among other sources, DMC originates fromdistributed diffuse scattering on electrically small objects.In this contribution, we analyze the polarization propertiesof the SMC and DMC in a large industrial hall. The analysisis based on frequency-domain channel sounding experiments.The polarization characteristics of the radio channel arequantified and analyzed by means of the cross-polarizationdiscrimination (XPD) and co-polar ratio (CPR) parameters.II. MATERIALS AND METHODSThe propagation environment under consideration is a largeindustrial hall located in Zwijnaarde, Belgium. The hall hasdimensions 21.3 x 77.2 x 12.2 m3. The main inventory consistsof large metallic machinery used for conducting experimentson concrete structures. The dominant building material forwalls, floor, and ceiling is concrete. Fig. 1(a) presents a viewof the industrial hall.Multidimensional channel sounding measurements wereperformed in the industrial hall. A 4-port vector networkanalyzer was used to probe the full polarimetric radio channelin a 22 MHz bandwidth centered around 1.3 GHz (MF =1601 frequency points). At both link ends, a virtual uniformcircular antenna array was created by a dual-polarized squarepatch antenna mounted on an automated rotating arm installedat 1.60 m above ground level. MT = MR = 12 is the numberof array elements at the Tx and Rx, respectively. In total 29Tx-Rx links were measured, shown in Fig. 1(b). The locationsof the Tx and Rx are shown as blue circles and red squares,respectively. Tx and Rx locations sharing the same numberform a Tx-Rx measurement pair. The shadowing conditionsfor the links were either Line-Of-Sight (LOS) or ObstructedLine-Of-Sight (OLOS).(a) Industrial hall(b) Tx (circles) - Rx (squares) measurement pairsFig. 1. Measurement environmentThe RiMAX maximum-likelihood estimator is used to ex-tract the full-polarimetric SMC and DMC from the channelsounding data [1]. The de-embedding of the full polarimetriccomplex radiation patterns of the measurement antennas isbased on the effective aperture distribution function in [2].III. RESULTS AND DISCUSSIONA. XPD/CPR of measured channel gainsThe XPD and CPR values are calculated directly fromthe measured polarimetric channels hXY which include theSMC/DMC contribution and antenna effects. The expectationE{·} is taken over the MTMR spatial subchannels to removesmall-scale fading. X and Y denote the transmit and receivepolarization, respectively (either H or V ). The XPD for Hand V , and the CPR for a certain Tx-Rx link are given by:XPDH = 10 log10(E{|hHH |2|hHV |2})(1)XPDV = 10 log10(E{|hV V |2|hVH |2})(2)CPR = 10 log10(E{|hHH |2|hV V |2})(3)Table I presents the measured XPD and CPR values aver-aged over the LOS and OLOS Tx-Rx links separately. Thereappears to be slightly more depolarization for V than for H .However, this could be attributed to the 1 dB gain differencebetween the H and V ports of our patch antennas instead ofto the radio channel (also notice the CPR values are close to1 dB).XPDH [dB] XPDV [dB] CPR [dB]LOS 12.2 11.05 0.97OLOS 8.48 7.58 0.5TABLE IMEAN OF THE MEASURED XPDS AND CPRSB. XPD/CPR of SMC and DMCIn this section, the SMC and DMC are de-embedded fromthe measured channels while taking the radiation patterns ofthe measurement antennas into account. The SMC XPD andCPR are calculated per path p of each Tx-Rx link. The averagenumber of paths per Tx-Rx links is around 200. The per-pathXPD and CPR are given by (γpXY denotes the path’s estimatedcomplex amplitude):XPDpH = 10 log10(|γpHH |2|γpHV |2)(4)XPDpV = 10 log10(|γpV V |2|γpV H |2)(5)CPRp = 10 log10(|γpHH |2|γpV V |2)(6)Table II presents the mean and deviation of the per-pathXPDs and CPRs. For this, all paths were grouped accordingto whether they originated from a LOS or an OLOS link. Itis found that the per-path XPDs and CPRs are well-describedby a Gaussian distribution. The results demonstrate that thepolarimetric characteristics are rather different between Vand H polarized paths: H polarized paths suffer more fromdepolarization than V polarized paths (see e.g., the negativevalues of the mean CPR). This behavior is not observed in themeasured channels (Table I).This behavior of the SMC may be explained as follows.For specular paths with low elevation (i.e., nearly parallelto azimuthal plane), the H polarization will undergo moredepolarization than the V polarization because of the Brewsterangle effect [3]. Conversely, for specular paths with highelevation, the Brewster angle effect will cause V polarizedpaths to depolarize more than H polarized paths. The pathswith high elevation in the latter case are commonly those thatreflect off the high ceiling. These paths are characterized bya large path length and thus low power. One can thus arguethat the XPD for V polarized paths is generally higher thanfor H polarized paths because V depolarization occurs morefrequently for insignificant low-power paths. This leads us toconclude that buildings with high ceilings, such as industrialhalls, favor V polarization over H polarization for the SMC.XPDpH[dB] XPDpV[dB] CPRp [dB]mean std mean std mean stdLOS 7.41 3.25 11.6 2.94 -4.65 3.24OLOS 4.66 3.24 10.11 2.96 -6.15 3.25TABLE IIMEAN AND STANDARD DEVIATION OF THE SMC XPDS AND CPRSTable III presents the average XPDs of the DMC for theLOS and OLOS links separately. In contrast to the SMC, theDMC depolarization is nearly the same for LOS/OLOS andH /V polarization. The SMC and DMC average XPD valuesfor H are within 2.2 dB from each other which may indicatethat they undergo similar interactions with the environment(i.e., reflect largely of the same objects with similar inci-dent angles). In contrast, a larger average depolarization isobserved for V polarized DMC than for V polarized SMC.A possible explanation is that the DMC contains a lot of thehigh-elevation low-power paths that are largely absent fromthe SMC (cf. previous paragraph). The depolarization of Vpolarized waves is thus predominantly effectuated by the DMCprocess.XPDH [dB] XPDV [dB]LOS 5.29 5.17OLOS 6.84 4.16TABLE IIIMEAN OF THE DMC XPDSIV. CONCLUSIONThis contribution presented empirically obtained values ofthe cross-polarization discrimination and the co-polar ratio ina large industrial hall. The main finding is that horizontallyand vertically polarized waves appear to undergo an amountof depolarization that is dependent on whether they belong tothe specular or the dense part of the channel.REFERENCES[1] A. Richter, “Estimation of radio channel parameters: Models and algo-rithms,” Ph.D. dissertation, Technische Universita¨t Ilmenau, Faku¨ltat fu¨rElektrotechnik und Informationstechnik, Ilmenau, DE, 2005.[2] M. Landmann, “Limitations of experimental channel characterisation,”Ph.D. dissertation, Technische Universita¨t Ilmenau, Faku¨ltat fu¨r Elek-trotechnik und Informationstechnik, Ilmenau, DE, 2008.[3] P. Kyritsi and D. Cox, “Propagation characteristics of horizontally andvertically polarized electric fields in an indoor environment: simple modeland results,” in IEEE 54th Vehicular Technology Conference, vol. 3, 2001,pp. 1422–1426.

Polarimetric characteristics of specular and dense multipath components in an industrial hall

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Polarimetric characteristics of specular and dense multipath components in an industrial hall

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