Progresses about Indoor Positioning Techniques Innovations

Transcription

1 Progresses about Indoor Positioning Techniques Innovations Alessandro NERI*, Roberto CAPUA**, Massimo MASSARO*, Pietro SALVATORI* *Università ROMA TRE **SOGEI

2 Contents Indoor Localization Techniques LTE Localization Services Architecture Indoor Localization Challanges Mutipath Performance Conclusions

3 Indoor Localization Technologies

4 Time of Arrival Indoor Localization The target location can be computed by solving the pseudorange equations by means of the Bancroft Algorithm. S 3 ρ 1 S 1 S 2 ρ 3 ρ 2 r 3 S 3 r 1 S 1 ρ 4 S 4

5 Performance Performance evaluation can be carried out by resorting to the Taylor s expansion of the pseudorange equations 1 ek, x + tr + nk c 1 τ e x e x e x t n c k k,1 1 k,2 2 k,3 3 R k x ˆR R e k S k Line of Sight unit vector [ c ] H = P 1 M R 2 T 1 1 t c x HRn H, R = if R Rn 2 = σ τ I 2 2 T 1, t c σ x τ HH =

6 Performance Cramèr Rao lower bound where σ 2 τ (2 π ) SNR Weff W 2 eff def f S( f ) df + 2 = S( f) df for S( f )=const we obtain 2 2 B W eff = 3

7 UMTS LTE Advanced Very high bit rate Down Link 3 Gb/s, Up Link: 1.5 Gb/s High spectral efficiency 30 bit/(s x Hz) Large number of simultaneous users Main Functionalities Carrier aggregation Mutiple antennas (MIMO) Relay Nodes (RN). Max 5 Component Carrier (CC), Max 100 MHz Bandwidth CC: 1.4,3,5,10,15,20 MHz f

8 LTE Location services In principle the enodeb synch signals could be used for localization Due to the intercell interference, only in a few cases at least 4 different signals useful for localization are available Thus, 3GPP introduced the Positioning Reference Signal (PRS) for measuring the Difference of Time of Arrival (DTOA)

9 LTE Downlink Resource grid Down link Channels Physical Downlink Shared Channel, PDSCH Physical Broadcast Channel, PBCH Physical Multicast Channel, PMCH Physical Control Format Indicator Channel, PCFICH Physical Downlink Control Channel, PDCCH Physical Hybrid ARQ Indicator Channel, PHICH Enhanced Physical Downlink Control Channel, EPDCCH

10 LTE-Advanced - PRS To allow joint transmission from several enodeb (up to 6), each node employes only an interlaced subset of the OFDM subcarriers, The other enbs apply radio silence. enodeb #1 t enodeb #2 enodeb #6 f f f

11 IEEE IEEE ac and IEEE ad adopt a Physical Layer based on WideBand OFDM IEEE ac Carrier frequency band: 5 GHz Bandwidth: 80 MHz (mandatory) 160 MHz (optional) IEEE ad Carrier frequency band: 60 GHz Bandwidth: 2.16 GHz

12 Outdoor: weakness Short ambiguity distance due to puncturing LOS required Multipath mitigation required

13 Test Bed

14 Signal Bandwidth: 100 MHz # of carriers= 2048 Trasmitter 1

15 Signal Bandwidth: 100 MHz # of carriers= 2048 Transmitter 2

16 Received Signals Rx #0 Rx #1

17 Indoor: Multipath In indoor applications the localization accuracy strongly depends on multipath because of the small path differences. S k Es. 2 paths zt () = α st ( τ ) + α st ( τ ) f j2π s j2π f τ α 1 2 c H( f) = α1e 1+ e α1 R

18 Multipath Model Multipath channel based on parametric model Parameter identification based on 100 MHz measurement campaign. d(m) Material Cammini riflessi Δ path (m) Δτ (ns) Γ LOS 5, Path concrete Right Wall Path glass Left Wall Path concrete Ceil Path concrete Floor Path concrete Front/Rear Wall

19 Approach Under Multipath the received signal is M zt () = α st ( τ ) + nt () k= 1 k When OFDM or SC-FDM is employed it is more convenient to resort to the Discrete Fourier Transform M ( ) = αk j2π f τk ( ) + ( ) k= 1 Z f e S f N f If we set S(f)=cost=b for data sub-carriers f m =m f we have (A k =α k b): [ M ] = k j2πm f τk + [ ] k= 1 Z m Ae N m Thus the problem reduces to the detection and estimation of M complex exponentials in white Gaussian noise k

20 Approach Let R Z be the correlation matrix We have RZ H { } = E ZZ RZ = RS + RN noise H 2 = Akee k k +σ NI k Signal with thus jωk j2 ωk j( M 1) ω H k = 1 ek e e e H 2 RZ = EΛ E +σ NI

21 Approach: ESPRIT Algorithm SVD Conjecture: Let R = UΛ U Highest Autovalues pertain to signal Small Autovalues pertain to noise We have 1 K 1 ( K 1) 1 ( K 1) K Z Z Γ = I 0 Γ 2 = 0( K 1) 1 I K 1 ( K 1) H K with [ Γ U] Φ=Γ 2 2 U Φ= diag e e e e jω jω j ω jω M

22 INDOOR - Performance Room size 2m x 8m x 2.5m target height 0.8 m wall Side wall Floor/ceil entrance Reflection Coeff

23 INDOOR - Performance Room size 2m x 8m x 2.5m target height 0.8 m wall Side wall Floor/ceil entrance Reflection Coeff

24 INDOOR - Performance Room size 2m x 8m x 2.5m target height 0.8 m wall Side wall Floor/ceil entrance Reflection Coeff

25 INDOOR - Performance Room size 2m x 8m x 2.5m target height 2.0 m wall Side wall Floor/ceil entrance Reflection Coeff

26 INDOOR - Performance Room size 2m x 8m x 2.5m target height 2.0 m wall Side wall Floor/ceil entrance Reflection Coeff

27 INDOOR - Performance Room size 2m x 8m x 2.5m target height 2.0 m wall Side wall Floor/ceil entrance Reflection Coeff

28 INDOOR - Performance Room size 2m x 8m x 2.5m target height 0.5 m wall Side wall Floor/ceil entrance Reflection Coeff

29 INDOOR - Performance Room size 2m x 8m x 2.5m target height 0.5 m wall Side wall Floor/ceil entrance Reflection Coeff

30 INDOOR - Performance Room size 2m x 8m x 2.5m target height 0.5 m wall Side wall Floor/ceil entrance Reflection Coeff

31 Conclusions OFDM-based digital signals have shown to be used to indoor localization where the multipath represents a major threat to be accounted. Spectral Estimation techniques, typical in Digital Signal Processing, can be used to estimate the time of first arrival. The current bandwidth foreseen in LTE-Advanced standard seems to be compliant with a decimetre accuracy. IEEE ac standard, also based on OFDM, foresees aggregate bands till 160 MHz operating in free frequencies being considerable as a valid alternative to LTE. Moreover, IEEE ad operating at 60 GHz adopts even larger bandwidth (2.16 GHz) major drawback is the limited range.