Beach, MA

Faulkner, M

Martin, GT

English

A wideband channel sounder was used to measure the complex impulse response of the radio channel. The sounder has a resolution of 10 ns, equivalent to a path length difference of 3 metres. Indoor measurements were made in the Engineering School building, which has a mixture of small offices, and large open plan lab spaces, together with long corridors. Outdoor measurements were done within the campus, a compact collection of buildings of irregular shape. Ray tracing simulations for the same environments used the Microcell Communication Simulator (MCS), marketed by EDX Engineering, Inc., Oregon, USA. This paper compares simulated delay spreads with the measured values, in a variety of locations. An indoor measurement was done for a single receiver location within a large lecture room, with the transmitter in a nearby corridor. A series of indoor measurements was also done with the transmitter in a single location in a side corridor and the receiver moving along a route following a main corridor. Outdoor measurements were done on the university campus in a large courtyard-like area, completely surrounded by irregular shaped buildings, and complicated by the three dimensional factors of sloping ground levels, and various elevated pedestrian bridges, which could not be included in the two dimensional ray tracing database. Measured rms delay spreads were generally larger than the ray tracing predicted values, except for outdoor situations of simple building geometry, where agreement with averaged measured values over most of the route was goo

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                          Martin, G. T., Faulkner, M., & Beach, M. A. (1995). Wide band propagationmeasurements and ray tracing simulations at 1890 MHz. In InternationalConference on Universal Personal Communications, Tokyo, Japan. (pp. 283 -287). Institute of Electrical and Electronics Engineers (IEEE).10.1109/ICUPC.1995.496905Link to published version (if available):10.1109/ICUPC.1995.496905Link to publication record in Explore Bristol ResearchPDF-documentUniversity of Bristol - Explore Bristol ResearchGeneral rightsThis document is made available in accordance with publisher policies. Please cite only the publishedversion using the reference above. Full terms of use are available:http://www.bristol.ac.uk/pure/about/ebr-terms.htmlTake down policyExplore Bristol Research is a digital archive and the intention is that deposited content should not beremoved. However, if you believe that this version of the work breaches copyright law please contactopen-access@bristol.ac.uk and include the following information in your message:• Your contact details• Bibliographic details for the item, including a URL• An outline of the nature of the complaintOn receipt of your message the Open Access Team will immediately investigate your claim, make aninitial judgement of the validity of the claim and, where appropriate, withdraw the item in questionfrom public view.Wide Band Propagation Measurements and Ray Tracing Simulations at 1890 MHz G.T.Martin*, M.Faulkner* and M.A.Beach** *Mobile Communications and Signal Processing Group, Department of Electrical and Electronic Engineering Victoria University of Technology, PO Box 14428MMC Melbourne, Victoria 3000, AUSTRALIA Tel: +61 3 9688 4454 Fax: +61 3 9688 4908 email: greg@cabsav.vut.edu.au ** Centre for Communications Research, University of Bristol Queen's Building, University Walk, Bristol BS8 lTR, UNITED KINGDOM Introduction A wideband channel sounder was used to measure the complex impulse response of the radio channel, using the swept time delay cross correlator method. The sounder uses a chipping rate of 100 MHz, and has a resolution of 10 nS, equivalent to a path length difference of 3 metres. Omnidirectional vertically polarised antennas were used for both the transmitter and receiver. Indoor measurements were made in the Engineering School building, which has a mixture of small offices, and large open plan lab spaces, together with long corridors. Outdoor measurements were done within the campus, a compact collection of buildmgs of irregular shape. Ray tracing simulations for the same environments used the personal computer-based Microcell Communication Simulator (MCS), marketed by EDX Engineering, Inc., Oregon, USA This simulator makes a number of simplifying assumptions, works only in two dimensions, and only allows one wall transmission per ray. Simplifying assumptions must also be made for the &electric properties of the wall building materials. This paper compares simulated delay spreads with the measured values, in a variety of locations. An indoor measurement was done for a single receiver location within a large lecture room, with the transmitter in a nearby corridor. A series of indoor measurements was also done with the transmitter in a single location in a side corridor and the receiver moving along a route following a main corridor. Most of this route was non-line-of-sight, apart from a short section as the side corridor was passed. Outdoor measurements were done on the university campus in a large courtyard-like area, completely surrounded by irregular shaped buildings, and complicated by the three dimensional factors of sloping ground levels, and various elevated pedestrian bridges, which could not be included in the two dimensional ray tracing database. Measured rms delay spreads were generally larger than the raytracing predicted values, except for outdoor situations of simple building geometry, where agreement with averaged measured values over most of the route was good, within +I- 10 nS. Ray Tracing The EDX Engineering Inc. MCS software uses point to point ray tracing techniques to idenm the multipath propagation arriving at the receiver. Thus idealised approach results in infinite impulse resolution, corresponding to unlimited system bandwidth. Multiple generation wall reflections, up to ten, and up to two corner diffractions, may be included, together with diffuse wall scattering if desired. For fixed transmitter and receiver locations, plots of the channel impulse response and angle of arrival are generated, and the rms delay spread is calculated. If a route along which the receiver moves is specified, a plot of rms delay spread verses distance along the route results. Grid study plots can also be done. The software has other features described in the user manual. Limitations Some limitations arise from the software, and from unavoidable simplification of the database information. The version of MCS used (Version 1.0) works essentially in 2 dimensions, apart from including one ground reflection. Terrain height variation is not included, and in the case of indoor applications, ceiling effects are not considered. Only one wall transmission of a ray is included, and this path is not onward propagated. The database describing the environment is a text file made up of coordinates locating each buildmg corner, an angle indicating the direction the corner faces, and a category for each wall section describing the electrical properties of the building material used. Buildings, or internal walls and partitions, are thus described in two Qmensional plan form as outlines. The number of wall sections and corners must not exceed 500 within the cell radius, which can be chosen as either 500 or 1000 metres. So the complexity and detail of buildings is reduced to an over-simplified two dimensional outline. For the indoor case, walls are treated as infinitely h g h  with no ceiling. Items such as steel fluorescent light units, whch may be strong reflectors, cannot be included, and detail such as furniture, although many wavelengths in size, is not included in this study. The electrical properties (permittivity and conductivity) used for the building wall materials are, at best, an approximate estimate. Windows within walls are difficult to include, except by the token gesture of modifying the average electrical parameters. In the case of internal partition walls, the electrical parameters are also in doubt, especially where the wall construction is non-homogeneous, such as with steel framework plasterboard walls. 0-7803-2955-4/95/$4.00 OIEEE 283 Wall Types and Estimated Electrical Properties The estimates below are based on anechoic chamber measurements done at Bristol University, and from results inRef. 1. 1 2 3 4 5 6 I Wall type I Description I reinforced concrete, half height windows solid reinforced concrete plasterboard and steel frame plasterboard and timber frame metal timber door Number wall cond- re1 surface thick- type uctivity permit- rough- ness S tivity ness m m wall atten. dB Channel Sounder The sliding correlator channel sounder measures the complex impulse response of the rad0 channel (Ref. 2,3,4), and uses a PN sequence of length 1023 and chip rate 100 MHz, an RF bandwidth of 200 MHz and a centre frequency of 1890 MHz. The sliding correlation time scale factor is 20,000. Back to Back Tests Laboratory back-to-back tests were done to investigate the linearity, dynamic range and resolution of the Channel Sounder. In these tests, the transmitter and receiver are connected via coaxial cable, fixed and variable attenuators, and an artificial channel which splits the signal into three paths, delaying the second path by 50 nS and the k r d  path by 100 nS relative to the main path. Compared with the main path, the second path has an additional loss of 4.5dB and the third path an additional loss of 8.5dB. The Channel Sounder receiver polar output voltage is linear for RF input levels of <-lo0 dBm to -60 dBm, and for input levels between -90 dBm and -60 dBm the dynamic range between the output level and the approximate noise floor is >25 dE3. Each peak of the power delay profile has a -3 dE3 width of 10 nS, confirming the expected resolution. Small spurs on the skirts of the peaks are probably caused by reflections in the approximately 5 metre cable used for back-to-back testing. Channel Sounder Accuracy Amplitude accuracy is within +/- 1.5 dl3 over the whole dynamic range, based on back-back linearity tests. Timing accuracy is precise, locked to a rubid" oscillator. Measurement Method The battery powered transmitter is mounted on a small trolley, with the discone antenna mounted 1.8 metre above ground level. The receiver is also battery powered and trolley mounted with 1.8 metre antenna height. Data is collected using a portable notebook computer. Transmitter output power is adjusted to keep the receiver input power within a favourable range at each measurement point. At each measurement point, between 3 and 6 measurements are taken, moving the receiver trolley randomly within a radius of approximately 2 wavelengths from the initial position. Measurements were done on Sunday evening, when the campus and building concerned were almost deserted, avoiding effects from pedestrians or vehicles. Rms Delay Spread A threshold of 15dB below the main peak is used (Ref 5). All components below this threshold are set to zero. A range threshold is also used, with all signals arriving more than 1 microsecond after the main peak being disregarded. Calculation of the delay spread is corrected for the finite but small width of the channel sounder impulse response. Indoor Measurements Indoor measurements were done on Level 7 of the Engineering School. This is an L shaped buildmg, with a central corridor of approximately 70 metres along the longer leg. Side passages, large lecture rooms and labs, and small offices open off the main corridor. The floor is reinforced concrete. A suspended plaster ceiling with a light steel frame is at 2.4 metre height above floor level. Reinforced concrete pillars are distributed throughout the floor. Partition walls are a mixture of concrete, plaster on a timber frame, and plaster with a steel frame, with various styles of internal windows, typically in the upper one third of the walls. Doors are of timber. In the raytracing plan, with the exception of doorways into some of the lecture rooms, only the comdor outlines are included because rays with more than one wall transmission are disregarded. Single Point Measurement For both the single point and route measurements, the transmitter is located in a wide side corridor, opposite steel lift doors. Measurements were made at a single location in a lecture theatre, with the receiver moved randomly between each of 9 measurements within a 5 wavelength radius of the initial point. Rms Delay Spread values varied between 21 and 33 nS, with an average value of 26 nS and standard deviation of 4 nS. The raytracing plot for this situation is shown in Figure 1, and gave a delay spread of 32 nS, 23% or 6 nS greater than the average measured value of 26 nS. 284 ENGINEERING SCHOOL Single location raytrace rms Delay Spread = 32 nS Number of ravs = 10 F I I  ,lo metre? Figure 1 Route Measurement The receiver route, up the corridor past the transmitter, and then turning left into a right angle corridor, is shown in Figure 2. Measurements were made every 1.5 metres, with between 3 and 5 measurements around each point. ENGINEERING SCHOOL q:m 10 metre, Receiver Route along Indoor Corridors Figure 2 Figure 3 compares measured results with raytracing results. Generally the measured delay spreads are greater than the raytrace values, by a large amount in some cases. Ceiling reflections, and reflections from steel lockers and other furniture not accounted for in raytracing would also be expected to increase delay spread values. Note that after the corner is turned in the corridor, the raytrace simulation signal soon vanishes. Measured delay spreads can vary by large amounts with small position changes because fast fading causes large alterations in the power delay profile . Results should show this spread of delays, rather than being based on averaged profiles, because a user will actually experience this effect [6]. Figure 3 250 - 200 U (D Q 150 5 2 P 5 100 U) 0 U) E 50 0 0 20 40 60 80 100 distance along route (metre) Outdoor Measurements The receiver route is shown in Figure 4, and Figure 5 compares measured delay spreads with raytrace values. In most cases 4 measurements were made around each point. Over the first 20 metres of the route, agreement is poor, with averaged measured delay spreads being up to 90 nS greater than the raytrace values. From 20 metres to 70 metres, the curves approximately follow the same shape with delay spread agreement within 15 nS, apart from the region around 50 metres, where the discrepancy reaches 35 nS. Some significant reinforced concrete elevated pedestrian walkways and supporting pillars were omitted from the raytrace database. Apart from the pillars, the 2 dimensional raytracing software cannot cope with the elevated structures. The under surface of these is between 4 and 5 metres above ground level. At the start of the route, ground altitude is about 3 metres below ground level at the transmitter, and the level gradually rises along the route. The early part of the route is most influenced by the elevated walkways and lower ground level, probably contributing to the greater measured delays. Towards the end of the route, on more level ground and with a line-of- sight component, agreement with raytracing results is good, within 5 nS. Figure 6 shows the location of the elevated walkways. Figure 7 shows a measured power delay profile for the start of the route where delay spreads are much larger than raytrace values. Conclusions In view of the uncertainty in the estimates used for building material electrical properties, simplifications and omissions made with raytracing plans, and the 2 dimensional limitation of the raytracing software, it is perhaps surprising that the raytracing simulations can produce useful estimates of delay spreads in the outdoor case. Performance indoors is poor with the delay spread being underestimated. The raytracing program is not really aimed at indoor use. In outdoor use, if the building geometry is 285 simple with vertical walls and a plan representable in 2 dimensions, the raytracing simulations can produce guideline predictions of delay spread. P BLOCK U - U G B L O C A  outdoor + route + C BLOCK * + + +  I I i I ENGINEERING SCHOOL D BLOCK I 100 metres I Figure 4 MCS & Measured values VUT Campus Outdoors 1890MHz RMS Delay Spread (nS) 150 140 130 120 110 100 90 80 70 60 50 40 30 20 IC ............ * ........... i ...... .... I ............. i .... . :  ............. i ..... : *b *. I I I I I I I I c Distance along route (metres) Acknowledgements Thls project is funded by a research grant from Ericsson Australia F‘ty.Ltd., and their support of this work and permission to publish ~s paper is gratefully acknowledged. The valuable workshop assistance of Mr.P.Izzard, is much appreciated. Thanks also go to Professor J.P.McGeehan, Dr.Richard Davies, Mr.P.Guemas, and other members of the CCR at the University of Bristol. Power Delay Profile rms delay spread 126nS VUT Campus position 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Excess Delay US Figure 7 + Footscray Campud- Showing overhead walkways overhead walkway 4 to 5 metres above ground - reinforced concrete Figure 6 References [l] S.Jenvey, ‘Ray Optics Modelling for Indoor Propagation at 1.8 Ghz.”, IEEE 44th Vehicular Technology Conference Proceedings, Vol.3, pp.1750-1753, June 8-10, 1994, Stockholm Sweden. Figure 5 286 [2] D.C.Cox, "Delay Doppler Characterisation of Multipath Propagation at 910 MHz in a Suburban Mobile Radio Environment", IEEE Transactions on Antennas and Propagation, Vol AP-20, NOS, pp.625-635, September 1972. [3] J.D.Parsons, D. A.Demery, A.M.D.Turkmani, "Soundmg Techniques for Wideband Mobile Radio Channels: A Review", IEE Proceedings-I, pp.437-446, Vol 138, NOS, October 1991. [4] G.T.Martin & M.Faulkner," Delay Spread Measurements at 1890 Mhz in Pedestrian Areas of the Central Business District in the City of Melbourne", IEEE 44th Vehicular Technology Conference Proceedings, Vol. 1, pp. 145-149, June 8-10, 1994, Stockholm Sweden [5] J.D.Parsons, The Mobile Radio Propagation Channel, Chapter 8, Halstead Press, 1992. [6] G.E.Athanasiadou, A.R.Nix , J.P.McGeehan, 'A Ray Tracing Algorithm for Microcellular Wideband Propagation Modelling", IEEE 45th Vehicular Technology Conference Proceedings, Vol. 1, pp.261-264, July 25-28, Chcago, USA. 287 

Optics Modelling for Indoor Propagation at 1.8 Ghz.”,

Wide band propagation measurements and ray tracing simulations at 1890 MHz

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Wide band propagation measurements and ray tracing simulations at 1890 MHz

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