Enhanced Blind Reception of WiGig ad Multicarrier PHY using MIMO Beam Analysis

Transcription

1 Institute for Critical Technology and Applied Science Enhanced Blind Reception of WiGig ad Multicarrier PHY using MIMO Beam Analysis Joseph F Ziegler Research Associate Electronic Systems November /31/2016 hume@vt.edu WiGig PHY Presentation

2 Presentation overview Introduction and motivation Technical approach Link geometry example Problem statement and research goals Summary of legacy results Parameter estimation examples Anticipated results of proposed research 10/31/2016 WiGig PHY Presentation 2

3 Introduction/motivation Blind demodulation of ad signal at an unintended receiver MIMO transmission introduces intentional multipath to enhance reception at the intended receiver However this adds distortion at the non-cooperative receiver Blind OFDM characterization Estimation of all modulation and channel parameters from the received samples Includes BW, N FFT, subcarrier spacing and modulation, baud rate, cyclic prefix, CFO, pilots MIMO beam analysis can provide insight into the link geometry Number of spatial streams and antennas employed Direction/angle of arrival Proper application of derived channel state can actually improve disadvantaged Rx performance over SISO channel through guaranteed spatial diversity 10/31/2016 WiGig PHY Presentation 3

4 Technical approach Related work in the field includes: OFDM characterization using maximum likelihood, cyclostationary, HOSA/moments, MAP, subspace decomposition, ICA techniques MIMO joint detection & DOA estimation using PCA, bilinear & trilinear (PARAFAC) decomposition, MUSIC/subspace algorithms MIMO blind source separation using CMA, HOSA, ICA, Generalized EM algorithm Eigenvalue and information theoretic approaches for estimating the number of antennas Combined approach to use MIMO beam analysis and blind OFDM characterization together to build an enhanced blind receiver for OFDM-MIMO waveforms Exploit overlapping algorithms where possible, e.g. ICA and matrix decomposition techniques span both problem spaces Leverage experience with blind OFDM signal parameter estimation Must determine the modulation coding scheme currently in use, albeit restricted to the set of ad MCS /31/2016 WiGig PHY Presentation 4

5 Link geometry example MIMO beam energy received due to sidelobe and reflected paths 10/31/2016 WiGig PHY Presentation 5

6 Problem statement and research goals Goal is to fully identify any OFDM and MIMO channel parameters required to decode a bit stream, given no a priori information about the transmitter s current MCS selection or spatial geometry Development tasks Simulate representative ad PHY waveforms Apply & modify legacy blind OFDM characterization algorithms to new MCS modes Develop MIMO beam analysis techniques to determine what can be learned about the channel Reconstruct all relevant modulation parameters and channel model from joint effort of blind OFDM characterization and MIMO beam analysis Apply gained knowledge of estimated parameters to build enhanced ad blind receiver 10/31/2016 WiGig PHY Presentation 6

7 Summary of legacy results Blind OFDM parameter estimation prototype applied to representative OFDM signals (WiFi, WiMax and LTE-like PHY) Successful recovery of all OFDM parameters at reasonable SNR, including pilot symbol mask for continuous framed transmission Frame headers Amplitude and phase raster vs time Fixed pilot subcarriers 10/31/2016 WiGig PHY Presentation 7

8 Parameter estimation examples Bandwidth, subcarrier spacing, & N FFT estimation Bandwidth estimate 1/Δf 10/31/2016 WiGig PHY Presentation 8

9 Parameter estimation examples Baud rate and cyclic prefix estimation Baud acquisition using conjugate delay multiply PSD R s 3*R s 10/31/2016 WiGig PHY Presentation 9

10 Anticipated results of proposed research Expanded blind OFDM characterization capability to include some ad MCS modes Develop an understanding of how MIMO beam analysis can be applied to the thirdparty receiver problem And how practical/realistic MIMO channels scale with # of antennas relative to the theoretical performance Long term goal is to apply gained knowledge of MIMO channel/geometry to use coherent combining of reflected energy from multiple transmission paths at the disadvantaged receiver Technology transfer may involve use cases such as cochannel interference mitigation and emitter identification and geolocation 10/31/2016 WiGig PHY Presentation 10