The potential of time reversal in multiple antenna systems

1. The potential of time reversal in multiple antenna systems Persefoni Kyritsi, George Papanicolaou (Stanford University) Hung Tuan Nguyen, Jørgen Bach Andersen, Gert Frølund Pedersen, and Patrick Eggers (Aalborg University)

2. TR can achieve delay spread reduction and spatial focusing. • Delay spread* study: TR for fixed wireless applications (FWA) • Spatial focusing study: TR in a multi-user context • Discussion • Normalizations and objectives • What kinds of measurements do we need? *Delay spread:

3. TX1 TX2 User j sj TXNT MISO TR to a single user

4. TR with antenna weighting: • Weight selection algorithms

5. FWA: Measurement equipment • Carrier frequency: 5 GHz • Transmitted power: PT = 100mW • 3dB bandwidth = 25MHz • 8 element uniform linear arrays (ULA) • Spacing: s = /2 • Vertical polarization • Vertical (V) or Horizontal (H) orientation

6. 29 floors (5, 19, 28) Balconies SW & NE 28 floors (19, 29) 7 floors (roof) FWA: Measument locations

7. Clear to cluttered Cluttered to clear Classification of MISO situations

8. Delay spread reduction: heq/h

9. Spatial focusing in MISO TR to multiple users • Each receiving antenna represents one of the Nr users

10. Interference calculation • Signal on target user • Interference from other users • The SIR

11. BS Reminder: The near-far problem U1 U2

12. Power control scenarios • The scaling factors normalize so that the total transmitted power is kept constant • Additional constraints • No power control across users • Simple power control across users

13. BS d d Multi-user operation • Nu=2 • Antennas of 2 different terminals at locations along the route separated by distance d Measurement route

14. Measurements • fc=2.14GHz, • BW > 7MHz • 2 measurement routes of l=1km • Transmitter • 8 TX antennas • htx=20m (Balcony on 5th floor) • Receiver _ On a trolley pulled by a van • Velocity 20-40km/hr • 4 RX antennas: A1, A2, B1, B2 at the four corners

15. Route 2 20 20 15 18 10 16 A1 14 5 A2 Mean B1 12 SIR in dB B2 0 A1 A2 10 SIR in dB B1 -5 B2 8 -10 Min 6 -15 4 -20 2 0 -25 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Distance in meters Distance in meters Route 1 20 20 15 18 Mean 10 16 A1 5 A2 14 B1 0 12 B2 SIR in dB SIR in dB A1 10 A2 -5 B1 8 B2 -10 6 -15 Min 4 -20 2 -25 0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Distance in meters Distance in meters Results for NR=2, multi-user Route 1 Mean Min With power control Without power control Route 2 Mean Min

16. Conclusions • Spatial focusing achieved to different users with the mean SIR of up to 18dB for 8 transmitting antennas and 2 users. • Multi-stream operation to a single user is not always possible