V Propagation Effects Observed Indoors July

V. Propagation Effects Observed Indoors • • July 2003 Multipath fading for narrowband signals Wall loss and range dependence Spatial fading of pulsed signals Delay spread and coherence bandwidth 1 © 2003 by H. L. Bertoni

Multipath Fading for CW Signals • Fading at both ends of symmetric links •

Summary of Fading at Both Ends of the Link to an Elevated Base Station

Fading When Both Ends of Link in Clutter x. R x. T Receiver in

Measuring Fading on a Circular Path Antenna on a rotating arm RF Signal Spectrum Generator Analyzer GPIB/PCMCIA Interface Small area average is obtained in confined space by rotating the antenna in a circle with circumference ~ 20 July 2003 5 © 2003 by H. L. Bertoni

Fast Fading on a Non-LOS Indoor Link - Tx rotated around a circle of radius 1 m - One complete revolution corresponds to 300 samples of received signal f = 900 MHz W. Honcharenko, H. L. Bertoni, J. Dailing, "Bi-Lateral Averaging Over Receiving and Transmitting Areas for Accurate Measurements of Sector Average Signal Strength Inside Buildings, " IEEE Trans. on Ant. and Prop. , AP-43, pp. 508 -512, 1995. July 2003 6 © 2003 by H. L. Bertoni

Single and Double Ended Averages - Averages obtained rotating Tx only versus rotating both Tx and Rx around circles inside a building. Tx and Rx locate one floor apart in hallways - Resulting averages are plotted versus horizontal offset of the centers of the Tx and Rx circles. F = 879. 99 MHz R. A. Valenzuela, 0. Landron and D. L. Jacobs, "Estimating Local Mean Signal Strength of Indoor Multipath Propagation, " IEEE Trans. on Veh. Tech. , vol. VT-46, pp. 203 -212, 1997. July 2003 7 © 2003 by H. L. Bertoni

Averaging at One or Both Ends of Link Unfolded path length = Ln 0

Averaging at One End of Link July 2003 9 © 2003 by H. L.

Averaging at Both Ends of Link July 2003 10 © 2003 by H. L.

Double Ended and Frequency Averages July 2003 11 © 2003 by H. L. Bertoni

Fading on LOS and Non-LOS Indoor Links f = 5. 2 GHz Received Power (d. Bm) Rx rotated around a circle of 0. 4 m diameter in 1 min 600 samples taken of the received power H. K. Chung and H. L. Bertoni, "Indoor Propagation Characteristics at 5. 2 GHz in Home and Office Environments, " Journal of Communication and Networks; Vol. 4; No. 3; pp. 176 -188, 2002. Sample number around a 22 circle July 2003 12 © 2003 by H. L. Bertoni

CDF of Fading for LOS and Non-LOS Links f = 5. 2 GHz H. K. Chung and H. L. Bertoni, "Indoor Propagation Characteristics at 5. 2 GHz in Home and Office Environments, " Journal of Communication and Networks; Vol. 4; No. 3; pp. 176 -188, 2002. Normalized Power (d. B to mean) July 2003 13 © 2003 by H. L. Bertoni

Frequency Dependent Fading at 5. 2 GHz H. K. Chung and H. L. Bertoni, "Indoor Propagation Characteristics at 5. 2 GHz in Home and Office Environments, " Journal of Communication and Networks; Vol. 4; No. 3; pp. 176 -188, 2002. 10 - 15 d. B fades on LOS links 15 - 20 d. B fades on N-LOS links Fade separation ~ 25 MHz corresponds to path length differences Li - Lj ~ 12 m July 2003 14 © 2003 by H. L. Bertoni

Summary of Fading Characteristics for In-Building Links • Symmetric links experience fading at both ends • Motion at one end effects the spatial average at the other end • Double ended averaging is required to measure properties from one small area to another small area • Averaging over frequency is equivalent to a double ended average over space • Indoor spatial fading has Rayleigh, even for LOS links • Deep frequency fading with separation ~ 25 MHz July 2003 15 © 2003 by H. L. Bertoni

Amplitude Dependence of Indoor Signals • Wall and floor loss • Range dependence •

Approximate Measure of Wall Loss Receiving antenna on rotor is placed in Living Room and transmitting antenna placed at locations throughout building. The received power is averaged (in watts) over the rotor circle. Excess path loss is obtained by subtracting (in d. B) the calibrated free space path loss Calibrated free space loss is that measured with the antennas outdoors and adjusted to the actual antenna separation using 1/r 2 distance dependence H. K. Chung and H. L. Bertoni, "Indoor Propagation Characteristics at 5. 2 GHz in Home and Office Environments, " Journal of Communication and Networks; Vol. 4; No. 3; pp. 176 -188, 2002. July 2003 17 © 2003 by H. L. Bertoni

Excess Path Loss Measured at 5. 2 GHz One interior wall between Tx, Rx

Summary of Excess Wall Loss at 5. 2 GHz H. K. Chung and H. L. Bertoni, "Indoor Propagation Characteristics at 5. 2 GHz in Home and Office Environments, " Journal of Communication and Networks; Vol. 4; No. 3; pp. 176 -188, 2002. July 2003 19 © 2003 by H. L. Bertoni

Wall Loss at 2. 45 GHz July 2003 20 © 2003 by H. L.

Wall Loss at 900 - 1800 MHz • COST Action 231 (ISBN 92 -828 -5416 -7) for 900 - 1800 MHz: – Light wall loss = 3. 4 d. B – Concrete or brick wall loss = 6. 9 d. B – Floor penetration loss = 18. 3 d. B • D. Pena, et al, “…Losses in Brick and Concrete Walls for 900 MHz. . ”, IEEE Trans, AP-51, p. 31. – Brick wall loss ~ 5. 6 d. B – Reinforced concrete wall ~ 15 d. B • Lafortune and M. Lecours, “… Losses in a Building at 900 MHz, ” IEEE Trans, VT 39, p. 101. – Light concrete wall loss ~ 5 d. B – Reinforce concrete floor loss ~ 25 d. B July 2003 21 © 2003 by H. L. Bertoni

Floor Plan of an Academic Building J. Lafortune and M. Lecours, “Measurement and Modeling of Propagation Losses in a Building at 900 MHz, ” IEEE Trans. on Veh. Tech. , vol 39, pp. 101 -108, 1990. July 2003 22 © 2003 by H. L. Bertoni

Path Loss Over Floor of Academic Building July 2003 23 © 2003 by H.

Distance Dependence of Average Signal Inside Large Building at 850 MHz Devastravatham, et al.

Estimating Average Path Loss by Accounting for Wall Transmission Only R S July 2003

Walk. Abouts Inside a Building July 2003 26 © 2003 by H. L. Bertoni

Path Loss Between Floors 2. 62 m 9. 20 m TX 1. 3 m RX 2. 1 m 7. 50 m Number of floors separating Tx and Rx Other paths that go outside of the building will dominate the path gain when floor loss becomes large. July 2003 27 © 2003 by H. L. Bertoni

~ 20 d. B Fades Due to People Blocking Path Time in seconds Belt mounted Tx as wearer rotates while standing in same location Person crossing the path between Tx and Rx 70 cm in front of Tx July 2003 28 © 2003 by H. L. Bertoni

Summary of Amplitude Dependence Indoors • Wall and floor loss increase somewhat with frequency – Plaster board walls ~ 3 - 6 d. B, wood floors ~ 9 d. B – Concrete walls ~ 7 d. B, concrete floors ~ 10 - 20 d. B • Range dependence – Some guiding in hallways reduces loss compared with free space – Excess loss due to propagation through walls gives exponential decrease with distance – Propagation between floors may take diffraction paths when floor loss is high • Blockage by people moving close to one end of link results in 20 d. B fades July 2003 29 © 2003 by H. L. Bertoni

Spatial Fading of Pulsed Signals • • July 2003 Envelope Detector Impulse versus pulse

Detector Output for Pulsed Source Envelope of received voltage Ve(t) Transmitted Pulse p(t) e

Time Delay Profiles for Pulsed Sources Transmission in a large office building Transmission in a city of mixed size buildings Experimental License Progress Report to FCC from Telesis Technology Laboratory, August, 1991. July 2003 32 © 2003 by H. L. Bertoni

Impulse Response Due to Multipath Source d(t) V(t) t July 2003 33 © 2003

Multipath Response for Finite Width Pulse V(t) Source p(t) e jw t Overlapping Pulse

Spatial Fading of Ray Clusters Seen from Power Delay Profiles at 16 Points Along

Indoor Power Delay Profiles at 2. 4 GHz Line-of-Sight link Obscured link H. L. Bertoni, S. Kim and W. Honcharenko, "Review of In-Building Propagation Phenomena at UHF Frequencies, ", Proc. of the IEEE ASILOMAR-29, pp. 761 -765, 1996. July 2003 36 © 2003 by H. L. Bertoni

Determining the Fading Statistics of Individual Receive Pulses 1. Divide received signal into N time bins of duration Tc. 2. Average voltage envelope at each location xm over time bins 3. Normalize voltage in each time bin to the average over all locations xm 4. Construct CDF for the 16 N values of the random variable rm, n July 2003 37 © 2003 by H. L. Bertoni

CDF of Indoor Pulse Fading Statistics (a) Engineering Building (b) Retail Store S. Kim, H. L. Bertoni and A Stem, "Pulse Propagation Characteristics at 2. 4 GHz Inside Buildings, ” IEEE Trans. on Veh. Tech. , Vol. 45, pp. 579 -592, 1996. July 2003 38 © 2003 by H. L. Bertoni

Method for Finding Small Area Time Delay Profile Fixed Unit 1. 2 meter (4 Foot) Square Individual power delay profiles (offset 50 d. B) D. M. J. Devasirvatham, "Multipath Time Delay Spread in the Digital Portable Radio Environment, " IEEE Communications Magazine, vol. 25, pp. 13 -21, 1987. Average of power delay profiles July 2003 41 © 2003 by H. L. Bertoni

Delay Spread and Coherence Bandwidth • Measures of delay spread • Comparison of time

Excess Delay and RMS Delay Spread T. S. Rappaport, Wireless Communications, Prentice Hall PTR,

Delay Spread vs Distance and Room Size 50 House 4 40 House 3 House 2 Mean RMS Delay Spread (nsec) 30 20 10 0 2 4 6 8 10 Separation on LOS Paths (m) 70 60 50 40 30 House 20 Office 1 10 Office 2 0 100 200 300 400 Room Area (m 2) July 2003 44 H. K. Chung and H. L. Bertoni, "Indoor Propagation Characteristics at 5. 2 GHz in Home and Office Environments, " Journal of Communication and Networks; Vol. 4; No. 3; pp. 176 -188, 2002. © 2003 by H. L. Bertoni

Coherence Bandwidth of the Channel • Pulse response carries information about the frequency dependence of the channel – Fourier transform of the complex voltage envelope for pulsed source gives the channel transfer function over the bandwidth of the transmitted pulse Requires phase information of V ( t ). – Fourier transform of the received power envelope for pulse sources gives the coherence function for frequencies separated by w f Does not require phase information July 2003 45 © 2003 by H. L. Bertoni

Fourier Transform Pair of Channel Response Dominant ray on LOS path Multiple rays on non-LOS path A. A. M. Saleh, et al, “Distributed Antennas for Indoor Radio Communications, ”IEEE, CH 2424 -0/87/0000 -0076, 1987 July 2003 46 © 2003 by H. L. Bertoni

Coherence Function from Measured |H(f)| C(f, f) July 2003 47 © 2003 by H.

Coherence Bandwidth of Channels (f = 5. 2 GHz) July 2003 48 © 2003

Coherence Function from Impulse Response July 2003 49 © 2003 by H. L. Bertoni

Example of Coherence Function P(t) d. B t July 2003 50 © 2003 by

Measured Delay Profile and Its Transform (Retail Store, f = 2. 4 GHz) P(t) R( f) S. Kim, H. L. Bertoni and A Stem, "Pulse Propagation Characteristics at 2. 4 GHz Inside Buildings, ” IEEE Trans. on Veh. Tech. , Vol. 45, pp. 579 -592, 1996. July 2003 51 © 2003 by H. L. Bertoni

Coherence Bandwidth of Channels (Engineering Building and Retail Store, f = 2. 4 GHz) f 1 and f 2 are the values at which R( f) is 1/2 its maximum value S. Kim, H. L. Bertoni and A Stem, "Pulse Propagation Characteristics at 2. 4 GHz Inside Buildings, ” IEEE Trans. on Veh. Tech. , Vol. 45, pp. 579 -592, 1996. July 2003 52 © 2003 by H. L. Bertoni

Summary of Delay Spread and Coherence Bandwidth • Indoor LOS paths at 1. 5 and 2. 4 GHz – Impulse response and derived coherence function show dominant early arrival that has slow spatial fading – Weak frequency dependence of the channel transfer function H( jw ) and wide coherence bandwidth {for R( f)/R(0) = 1/2} • Indoor LOS paths at 5. 2 GHz – No dominant arrival, Rayleigh spatial fading, rapid variations of H( jw ) similar to n-LOS paths • N-LOS paths have many rays of nearly equal amplitudes – Many echoes stretched over time – Rapid spatial fading of individual peaks – Rapid frequency fading of H( jw ) – Narrow coherence bandwidth July 2003 53 © 2003 by H. L. Bertoni