Ranging detection algorithm for indoor UWB channels

Transcription

1 Ranging detection algorithm for indoor UWB channels Choi Look LAW and Chi XU Positioning and Wireless Technology Centre Nanyang Technological University

2 1. Measurement Campaign Objectives Obtain a database of UWB channel profiles in various indoor environments. Test UWB ranging accuracy in indoor environment with FCC PSD mask compliance UWB signal and Model the ranging error statistically. Analyze the UWB ranging performance in indoor environment and use the analysis to facilitate the ranging parameters setting in both LOS and NLOS cases. 2

3 Measurement System Setup 3

4 Measurement Setup Antenna Tx Setup Rx Setup 4

5 Biconical Antenna Pattern z θ r θ = 45 ϕ = 38.7 r= 1.4cm R= 3.2cm y 3.1GHz Azimuth Plane 1.6 GHz Azimuth Plane x R Coaxial cable 3.1GHz Elevation Plane 1.6 GHz Elevation Plane 5

6 Biconical Antenna Return Loss (2~11GHz) ----Reflection Loss <-1dB -1dB 6

7 ---- Test the Omni-directional properties of measurement setup Max-Min=.22V( = dB) θ Amplitude (V) Delay (ns) Max-Min=2ps Angle (Degree)

8 Measurement Environment Indoor Office Laboratory Room Open Hall Corridor 8

9 PWTC Layout with Measurement Routes Concrete Post Heavily Blocked Area Transmitting Antenna Position Receiving Antenna Route TX2L23 TX2L1 TX2L22 TX2L2 TX2 L8 TX2 L24 TX2L21 TX2L3 TX2 L12 TX2 L14 TX2 TX2L1 TX2 L2 TX2L4 TX2 L11 TX2 L13 TX2L19 TX2L5 TX2 L9 TX2 L15 TX2 L16 TX2L18 TX2L6 TX2L17 9 TX2L7

10 Campaign Summary Environment Sample Points Sample Spacing Maximum Distance Indoor Office 131.2m 26m LOS or NLOS LOS and NLOS* Lab 271.2m 5m LOS Open Hall 61.5m 3m LOS Corridor 31 1m 3m LOS Total 1664 * LOS Line of Sight NLOS Non Line of Sight 1

11 2. Results and Analysis 2.1: Pulse Shape Characterization ---- Signal before Tx antenna and power spectral density (PSD) after Tx antenna (including antenna gain) Power Spectral Denstiy (dbm/mhz) FCC PSD Mask For Indoor Application Frequency (GHz) 11

12 ---- Received direct path pulse shape with Tx-Rx distance of 1m Direct Path 12

13 2.2: Ranging Error Performance - Comparison of Coherent (CLEAN) and Non- coherent (Energy detection) Indoor Office Lab Open Hall Corridor LOS NLOS By Non-Coherent Detection Mean (m) STD. (m) Max (m) By Coherent Detection Mean (m) STD. (m) Max (m)

14 - CDF of ranging errors ε LOS NLOS Probability of ε < Abscissa Non-coherent Detection Coherent Detection ε (m) Probability of ε < Abscissa ε =.15m Non-coherent Detection Coherent Detection ε (m) 14

15 2.3 Ranging Performance Analysis for NLOS The received signal r(t) is modeled as, L () α ( τ ) α ( τ ) () r t = s t + p s t + n t d d i i i i= 1.. Eq (1) Whereα d and τ d are the amplitude and propagation delay of direct path α i and τ i are the amplitude and propagation delay of i th multipath p i is the polarity of i th multipath n(t) is the WGN process 15

16 After correlated with the pulse template, the resulting waveform within [τp -δ, τp] can be expressed M R t = α R t τ + pα R t τ + R t () ( ) ( ) () c d ss d i i ss i ns i= 1 ρ d =α d /α p β d = τ p - τ d Where R ss is the autocorrelation function of pulse template α M = α p and τ M =τ p Let us define:.. Eq (2) 16

17 Probability Density Curve Fitting Exp. Results Probability Density 5 x Curve Fitting Exp. Results f ρ d ρ d 1 d 1 = exp 2 πq( μ/ σρ) σρρd 2 x 1 x Q( x) = exp dx 2π 2 ( ρ ρ ) d, where βd βd f β ( β ) exp d d βd = η η β x 1-7 d (second) (( ln ρ ) ) 2 d μ 2σ.. Eq (4) 2 ρ.. Eq (3)

18 - Comparisons with previous reported results Channel Parameter Source P μ σ ρ η This Campaign [1] [1]. J. Y. Lee and R. A. Scholtz, Ranging in a dense multipath environment using an UWB radio link, IEEE J. Select. Areas Commun., vol. 2, pp , Dec

19 - Evaluate the performance by large error probability ( Estimated arrival time of direct path true arrival time of direct path > T c /2) - The large error probability is related to three events H1 = { βd > δ} H { β δ} { α n γ} = + < 2 d d ns H3 = { Zmax > γ } { αd + nns γ} Where, Zmax sup{ Rns () t } =, t [τp δ, τp ]and δ β d. n ns =R ns (τ p ), - Since three events are exclusive, the large error probability is Lgr ( γδ, ) = ( ) + ( ) + ( ) P P H P H P H Eq (5)

20 Ignoring the intermediate derivation process, the final equation will be, δ PLgr = 1 Pexp 1 Ψ m, P Γ m, PΨ m, η ( ( κ )) ( ) ( κ) ( κ) ( ) ( m κ ) ( m ) δ 2δ 2 ηp Ω, exp exp η Ω( m, κ) 2 η Ω, κ....eq (6) Where m = γ α is normalized threshold p κ α p = is signal-to-noise (SNR) ratio σ ns 2

21 -Comparison of simulation and analytical results, P Lgr Analy. (κ=15db) Analy. (κ=2db).2 Analy. (κ=3db) Sim. (κ=15db).1 Sim. (κ=2db) Sim. (κ=3db).2.4 m

22 Performance curves for various SNR κ=1db κ=15db κ=2db 22 κ=3db

23 2.3 Adaptive ranging parameters Setting For NLOS, if channel parameters are given, numerical search may be performed with Eq(6) to obtained the optimum setting 25.8 δ opt (ns) m opt κ (db) κ (db) 1-1 P min κ (db) 23

24 Conclusion on Ranging settings for NLOS For NLOS, If channel parameters are not available, a two-state threshold settings method is proposed: (1). δ is predefined and fixed. A worst-case false alarm rate P fls is predefined m = δλ 1 2ln ln 1 fls κ ( P ) λ is a parameter related to the RMS bandwidth of pulse template (2). If the calculated m for a particular κ is larger than 1, the largest path is taken as the direct path and the earliest path searching path does not initialized. 24

25 - Performance of optimum setting by numerical searching versus performance of two-state setting strategy with δ=5ns Optimum P fls =1-1 P fls =1-2 P fls =1-3 P fls =1-6 P Lgr κ (db) 25

26 Conclusion on Ranging settings for LOS - According to measurement results, the direct path is not the largest path in17 profiles out of 289 profiles. - For LOS, simple strategy is enough: setting search period δ>2ns and detection threshold γ =mα p with m=.5~ β d (ns) ρ d 26

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