1. Submission doc.: IEEE 802.11-12/0416r1 Slide 1 Broadband Indoor TVWS Channel Measurement and Characterization at 670 MHz Date: 2012-03-14 Mar 2012 Ming-Tuo ZHOU, NICT

2. Submission doc.: IEEE 802.11-12/0416r1 Abstract An introduction to indoor TVWS channel measurement and results at 670 MHz Slide 2 Mar 2012 Ming-Tuo ZHOU, NICT

3. Submission doc.: IEEE 802.11-12/0416r1 Slide 3 Measurement Setup and Calibration Measurement targets: Multipath delay spread, particularly, RMS delay spread Channel impulse response Path loss properties Signaling: BPSK signal, 20 Mbps, 511-length pseudo random (PN) sequence, central frequency at 670 MHz CW signal, central frequency at 670 MHz, for path loss measurement Method: Custom designed receiver captures transmitted BPSK signal for measurement of multipath delay spread and channel impulse response For path loss measurement, the received signal power is measured by using a R&S FSU spectrum analyzer Mar 2012 Ming-Tuo ZHOU, NICT

4. Submission doc.: IEEE 802.11-12/0416r1 Measurement Setup and Calibration -- Instruments Used Transmitter Receiver & Spectrum Analyzer Mar 2012 Ming-Tuo ZHOU, NICTSlide 4

5. Submission doc.: IEEE 802.11-12/0416r1 Calibration Setup Slide 5 Mar 2012 Ming-Tuo ZHOU, NICT

6. Submission doc.: IEEE 802.11-12/0416r1 Measurement setup Mar 2012 Ming-Tuo ZHOU, NICTSlide 6

7. Submission doc.: IEEE 802.11-12/0416r1 Measurement Parameters Tx power23 dBm Cable loss3.45 dB AntennaMonopole type Antenna gain2.15 dBi ChannelIndoor LOS & NLOS BPSK data rate20 Mbps BW64 MHz (638-702 MHz,) Center frequency670 MHz Tx antenna height2.3 m / 2.6 m Rx antenna height0.7 m / 1.4 m Mar 2012 Ming-Tuo ZHOU, NICTSlide 7

8. Submission doc.: IEEE 802.11-12/0416r1 Measurement Scenarios 1 – Office 1 – small size office/lab 185 sqm (=14.52 m×12.74 m) Includes staff room, 3 experiment rooms, director room, meeting room, kitchen, reception, etc Walls material: plywood/concrete Three transmitter antenna locations Tx antenna – 2.3m, Rx antenna – 0.7m Mar 2012 Ming-Tuo ZHOU, NICTSlide 8

9. Submission doc.: IEEE 802.11-12/0416r1 Measurement Scenarios 2 – Office 2 – medium size office/lab Includes two hall rooms, a conference room, several experiment rooms, a big lab room, store room, staff cubicle area Walls material: plywood/concrete One transmitter antenna position Tx antenna – 2.6m, Rx antenna – 1.4m Mar 2012 Ming-Tuo ZHOU, NICTSlide 9

10. Submission doc.: IEEE 802.11-12/0416r1 Some Pictures of Measurement Scenarios Mar 2012 Ming-Tuo ZHOU, NICTSlide 10 Office 1, staff room Office 1, meeting room Office 2, Hall room 1 Office 2, office with staff cubicles

11. Submission doc.: IEEE 802.11-12/0416r1 Extracting Rays For each receiver location, BPSK signal is received and the normalized power delay profile is plot as function of time stamp A peak detection method is used to extract rays. First, the calibrated Nyquist pulse is normalized to the peak of received signal power delay profile, and then it is subtracted from the power delay profile Second, the calibrated Nyquist pulse is normalized to the peak of the remain part, and then it is subtracted from the remain part of power delay profile The above process is repeated until the peak power of the remain part is less than some threshold value, e.g., -30 dB Each peak represents a received ray (path). Power (path gain) and relative time delay of each peak with higher power than threshold (e.g., -30dB) are recorded Mar 2012 Ming-Tuo ZHOU, NICTSlide 11

12. Submission doc.: IEEE 802.11-12/0416r1 Extracting Rays (cont.) Example Mar 2012 Ming-Tuo ZHOU, NICTSlide 12 Ray Delay (ns)0.0037.575.00100125150187.5212.5 Ray relative power (dB)-26.73-13.500-2.14-5.68-11.11-12.55-21.41

13. Submission doc.: IEEE 802.11-12/0416r1 Extracting Rays (Cont.) The method extracting rays is verified by experiment of reconstructing the signal. Signal is reconstructed by summing copies of calibrated Nyquist pulses, each of which is weighted by a ray power (path gain) and delayed with ray delay The reconstructed signal is close to the measured one, as illustrated by following example Mar 2012 Ming-Tuo ZHOU, NICTSlide 13

14. Submission doc.: IEEE 802.11-12/0416r1 RMS Delay Spread RMS delay at each receiver location is calculated for each measurement scenario Median RMS delay is then calculated for each scenario (with different threshold) Scenario LOS (ns) (-30dB) LOS (ns) (-20dB) LOS (ns) (-10dB) NLOS (ns) (-30dB) NLOS (ns) (-20dB) NLOS (ns) (-10dB) Office 1 Tx-132.4231.3320.8841.0936.2027.44 Office 1 Tx-220.2018.9614.5436.0934.4318.24 Office 1 Tx-320.5118.7210.3432.3730.3626.48 Median for office 120.5118.9614.5436.0934.4326.48 Office 238.5234.6719.0442.4739.3228.19 Overall Median26.4725.1516.7938.5935.3226.96 Mar 2012 Slide 14Ming-Tuo ZHOU, NICT

15. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling We observed that rays arrive in clusters usually. Clusters may be formed by super-structures and walls inside buildings. In this study, super-structures may be metal cabinet or goods lift, and so on Clusters attenuate exponentially, because of propagation delay Mar 2012 Ming-Tuo ZHOU, NICTSlide 15

16. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) Comparison to S-V model Mar 2012 Ming-Tuo ZHOU, NICTSlide 16 New findings in this studySaleh-Valenzuela (S-V) model A cluster may appear before the strongest cluster in some cases The most left-side cluster is the strongest Inside a cluster rays power may increase with time delay Inside a cluster, rays power attenuate with time delay

17. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) A qualitative explain to the above new findings is that different rays/clusters may have different antenna gain, due to difference in angle-of-arrival (AoA) Lately arrived rays may have larger antenna gain, because of larger AoA Then although they have larger propagation delay, their power are larger than earlier rays An earlier cluster may have averagely smaller antenna gain than a later cluster, then later cluster may be stronger Mar 2012 Ming-Tuo ZHOU, NICTSlide 17

18. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) Illustration of qualitative explanation for rays arrival earlier may be weaker in power Mar 2012 Ming-Tuo ZHOU, NICTSlide 18

19. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) Proposed low-pass impulse response model Rays arrive in clusters, each cluster may consist of a group of rays. At middle is the strongest cluster, with cluster arrival time of 0 At the middle of each cluster is the strongest ray and it represents the cluster arrival time T l, which is arrival time relative to the strongest cluster Rays arrival time relative to the strongest ray is, where l is the cluster index, m is the ray index Cluster arrival time is modeled as Poisson arrival process with fixed arrival constant. Left side and right side clusters may have different cluster arrival time Rays arrival time is modeled as Poisson arrival process with fixed arrival constant, too Clusters decay exponentially with cluster arrival time, on both left and right sides (with possible different decay constant) Rays decay with ray arrival time Mar 2012 Ming-Tuo ZHOU, NICTSlide 19

20. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) Illustration of the proposed low-pass complex channel impulse response model (with comparison to S-V model) Mar 2012 Ming-Tuo ZHOU, NICTSlide 20

21. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) Mathematically, the low-pass complex channel impulse response model is given by Mar 2012 Ming-Tuo ZHOU, NICTSlide 21

22. Submission doc.: IEEE 802.11-12/0416r1 Channel Modeling (cont.) Parameters extracted from measurements Number of clusters: one left-side clusters occasionally, 2-4 right-side clusters Number of rays: 2-5 left-side rays in the strongest clusters, median of 0.67 for other clusters Cluster decay constant: left-side clusters 200ns to 1000ns, right-clusters: 25ns – 50 ns (median 33ns) Ray decay parameter: ranges between 16ns to 22ns if treat as constant, in small room or NLOS cases, rays decay faster Cluster arrival rate: both left-side and right-side clusters may have similar arrival rate, around 1/60ns Ray arrival rate: in LOS cases ray arrival rate is 1/12.5ns usually, NLOS case has smaller ray arrival rate (1/25ns, even 1/37.5ns) Mar 2012 Ming-Tuo ZHOU, NICTSlide 22

23. Submission doc.: IEEE 802.11-12/0416r1 Path Loss Properties Radio signals attenuate with distance exponentially For each measurement distance, we took median power of the received samples By fitting the path loss with minimum mean square error (MMSE), the exponential constant of LOS and NLOS in Office 1 is 2.02 and 2.09, respectively, indicating a strong waveguide effect In Office 2, LOS and NLOS has exponential constant of 3.16 and 3.56, respectively. Mar 2012 Ming-Tuo ZHOU, NICTSlide 23

24. Submission doc.: IEEE 802.11-12/0416r1 Conclusion Indoor channels at TVWS frequency of 670 MHz in both small- and medium-size mixed office/lab environment are measured and characterized (Overall) median of RMS delay spread for LOS with -30dB threshold is 26. 47ns, and is 38.59ns for NLOS with -30dB cutoff threshold. With smaller threshold, RMS delay spreads are smaller A low-pass complex impulse response model is proposed based on classic Saleh-Valenzuela (S-V) model and new findings Path loss constants are presented Mar 2012 Ming-Tuo ZHOU, NICTSlide 24