Submission Greg Breit, Qualcomm, et al. June 2009 doc.:IEEE /0699r0 Slide 1 Multi-User AoD Diversity Measurements Date: Authors:

Submission Greg Breit, Qualcomm, et al. June 2009 doc.:IEEE /0699r0 Slide 2 Abstract This contribution describes recent RF channel measurements at Qualcomm to assess DL AoD diversity of NLOS paths across spatially separated clients in a multi-user MIMO scenario. Measurements were performed in conference room, cafeteria, and auditorium settings. In each case, no evidence of consistent AoD clusters was observed between clients in NLOS conditions. This result suggests that a random per-user offset uniformly distributed over ±180° is appropriate for DL NLOS AoD clusters in the TGac MU-MIMO channel model.

Submission Greg Breit, Qualcomm, et al. Introduction NLOS AoD diversity parameter for MU-MIMO is currently “TBD” in the draft TGac channel model [1] AoD measurements were taken between a 16-antenna AP (ULA, λ/2 spacing) and 8 spatially separated 2- antenna clients (λ/2 spaced) –Testing performed in different environments Outdoors –Strong LOS environment –Intended for method validation Conference Room, Cafeteria, Auditorium –LOS and NLOS paths June 2009 doc.:IEEE /0699r0 Slide 3

Submission Greg Breit, Qualcomm, et al. Measurement Setup/Analysis AoD/AoA estimation can be treated as spectral estimation problem of channel estimates across a ULA –Multiple Signal Classification (MUSIC) algorithm used for spectral estimation Models signal as sum of discrete complex exponentials Better noise immunity than Fourier-based analysis –Arcsin of normalized frequency estimates used to get AoD –Range of measurements: ±90° relative to ULA broadside Cannot distinguish between rays in front vs. behind ULA Qualcomm channel sounding system used for AoD measurements –Center frequency: 5.17 GHz –64-tone OFDM over 20 MHz bandwidth Only 52 usable data tones: effective bandwidth is 16.3 MHz Time resolution: ~62ns –AoD analysis always performed on peak tap of channel impulse response June 2009 doc.:IEEE /0699r0 Slide 4

Submission Greg Breit, Qualcomm, et al. Outdoor LOS Verification Measurements Purpose of measurements was to verify AoD method AP placed at one end of circular courtyard on Qualcomm campus Clients placed around AP in a semicircular formation –Approximately 140° AoD variation across clients –Clients distributed approximately uniformly around semicircle –Good AoD agreement expected between antennas on same client Measurements taken with different orientations of the AP antenna array –Broadside of AP antenna array oriented toward specific clients –AoD spectra should “rotate” accordingly when AP is rotated June 2009 doc.:IEEE /0699r0 Slide 5

Submission Greg Breit, Qualcomm, et al. Outdoor Measurements – Client Locations June 2009 doc.:IEEE /0699r0 Slide

Submission Greg Breit, Qualcomm, et al. AoD Results for Outdoor Measurements AP Array Pointing at Client 5AP Array Pointing at Client 7 June 2009 doc.:IEEE /0699r0 Slide 7 Red and black curves represent AoD spectra to the two antennas at each client location Mean agreement (reference case): 7° AP rotation of ~30° evident in most results Larger measurement error and ambiguous results near ULA endfire

Submission Greg Breit, Qualcomm, et al. Indoor Measurements – Conference Room Clients placed in fixed locations around large conference table Measurements taken with AP in different locations/orientations –LOS – AP in same room as clients –NLOS – AP located in a seating area outside the conference room June 2009 doc.:IEEE /0699r0 Slide 8

Submission Greg Breit, Qualcomm, et al. Conference Room – Client Locations June 2009 doc.:IEEE /0699r0 Slide Red arrows denote broadside orientation of AP array

Submission Greg Breit, Qualcomm, et al. AoD Results – Conference Room Measurements LOS – AP inside roomNLOS – AP outside room June 2009 doc.:IEEE /0699r0 Slide 10 Evidence of common AoD values among different clients for LOS case All clients show peaks within ±30° of broadside (0°) NLOS AoD values show no evidence of common AoD clusters across clients

Submission Greg Breit, Qualcomm, et al. Indoor Measurements – Cafeteria Large open room Client antenna pairs placed in different fixed locations on dining tables around room Measurements taken with AP in different locations/orientations –LOS – Same room as clients, approx 20m range, ULA broadside oriented towards clients –NLOS – AP around an interior corner from main cafeteria room containing clients, no LOS path June 2009 doc.:IEEE /0699r0 Slide 11

Submission Greg Breit, Qualcomm, et al. Cafeteria – Client Locations June 2009 doc.:IEEE /0699r0 Slide AP placed around this corner for NLOS measurements

Submission Greg Breit, Qualcomm, et al. AoD Results – Cafeteria Measurements AP LOS to clientsAP around corner (NLOS) June 2009 doc.:IEEE /0699r0 Slide 13 Evidence of common AoD values among different clients for LOS case Most clients show peaks within ±30° of broadside (0°) NLOS AoD values show no evidence of common AoD clusters across clients

Submission Greg Breit, Qualcomm, et al. Indoor Measurements – Auditorium Clients distributed around auditorium seats –Antennas placed on seat tables –Three clients closely clustered (neighboring seats) –Remaining clients distributed in approximate semicircle relative to stage AP moved around to different locations within auditorium –LOS case – on stage, ULA broadside oriented towards seats –NLOS case – hallways and rooms adjacent to main auditorium June 2009 doc.:IEEE /0699r0 Slide 14

Submission Greg Breit, Qualcomm, et al. Test Locations June 2009 doc.:IEEE /0699r0 Slide 15

Submission Greg Breit, Qualcomm, et al. Client Placement June 2009 doc.:IEEE /0699r0 Slide

Submission Greg Breit, Qualcomm, et al. AoD Results – AP on stage (LOS) June 2009 doc.:IEEE /0699r0 Slide 17 Spectral peaks generally consistent between clients 1, 2, and 3 Other clients show gradual rotation with respect to AP

Submission Greg Breit, Qualcomm, et al. AoD Results – AP in passageway (NLOS) June 2009 doc.:IEEE /0699r0 Slide 18 Spectral peaks less distinct in NLOS conditions No evidence of common AoD clusters, despite proximity of Clients 1, 2, & 3

Submission Greg Breit, Qualcomm, et al. Discussion/Summary Results from outdoor LOS measurements validate the AoD estimation method used –Time resolution limited by measurement bandwidth Tap spacing: ~62ns AoD spectra probably represent several multipath clusters No evidence of common AoD clusters observed for NLOS measurements across spatially separated clients –Consistent with recent findings of ETRI [2] –Suggests that random per-client angle offsets uniformly distributed over ±180° is appropriate for NLOS AoD in the TGac MU-MIMO channel model Same assumption as AoAs and LOS AoD June 2009 doc.:IEEE /0699r0 Slide 19

Submission Greg Breit, Qualcomm, et al. References 1.Breit, G. et al., “TGac Channel Model Addendum.” Doc. IEEE /0308r5. 2.Kwak, B.-J. et al., “Measured Channel Capacity and AoD Estimation for Multi-User MIMO Scenarios.” Doc. IEEE /0543r1. June 2009 doc.:IEEE /0699r0 Slide 20