Investigation of Performance Gain in n Systems due to Antenna Switching Using Simulated Radiation Patterns

Transkript

1 Investigation of Performance Gain in 80.n Systems due to Antenna Switching Using Simulated Radiation Patterns D. Kornek, H. Rabe, S.K. Hampel, O. Schmitz, G. Armbrecht, I. Rolfes Institut für Hochfrequenztechnik und Funksysteme

2 Outline. Introduction & motivation. Basics of MIMO channel-simulator 3. Investigation of simple antenna arrays 4. Conclusions

3 Introduction & motivation 3 Motivation modern communication systems include multiple antennas, e.g. IEEE 80.n investigation of performance gain due to antenna selection influence of real antennas on the system performance placing and design of antennas becomes more important [Source: antenna design antenna placing

4 Outline 4. Introduction & motivation. Basics of MIMO channel simulator 3. Investigation of simple antenna arrays 4. Conclusions

5 Basics of MIMO channel simulator 5 HFT Real Pattern Pattern Real Pattern commercial FEM-Solver pattern by Ansoft HFSS Channel modeling 3- dimensional Fix SNR per eigen-path Cluster & Taps 80. TGn Effects No Doppler No interferers Excitation & Excitation & Excitation & 4 Visualization CDF

6 Basics of MIMO channel simulator Correlation Coefficient ρ envelope correlation described by antenna correlation e ij ρ = R i ij σ σ j 6 R ij Kp ππ = K 0 0 ϑ, ϕ [ ( ) ( ) ( ) ( )] C ϑ, ϕ C ϑ, ϕ + XPR C ϑ, ϕ C ϑ, ϕ ϑ i r r ϑ jkrij ( ϑ, ϕ) e sin( ϑ) dϑ dϕ j ϕ i ϕ j K cross polarization ratio XPR= P P V H statistical channel modeling ( ) C ϑ, ϕ, ϑ ϕ radiation pattern of antenna (, ϕ) C ϑ = E ( ϑ, ϕ) E max Pattern diversity Polarization diversity Space diversity

7 Basics of MIMO channel simulator 7 Stochastic model for AoA environment, envelope fading Common channel parameters assumed Azimuth spectrum - Laplace Elevation spectrum - Gauß Channel Models IEEE 80.n (e.g.) Channel model A taps clusters Channel model F 8 taps 6 clusters

8 Basics of MIMO channel simulator 8 MIMO: Channel Capacity no interferers, AWGN ( σ N ) Used MIMO Channel Modell C equally distributed transmit power P T Including signal correlation MIMO PT = log det E + σ N M Subchannel capacity ~ ~ HH H Eigenvalue problem ~ H ~ h ~ = h M ~ hm ~ h O L K O L ~ h M M ~ h N MN C C i P = T log + σ N M min{ M, N} = Ci MIMO i= λi Mobile Channel narrow band Stochastic model for AoA environment, envelope fading channel coefficients uncorrelated including antenna correlation

9 Outline 9. Introduction & motivation. Basics of MIMO channel-simulator 3. Investigation of simple antenna arrays 4. Conclusions

10 Investigation of simple antenna arrays 0 Dipole-Array Power Correlation Coefficient scenario : weak scattering, scenario : rich scattering, σ ϕ σ ϕ =0 = 60 Topology optimal reference simulations in free space coupled and decoupled variation of inter element distance Effects decorrelation by coupling decorrelation by scattering decorrelation by distance d/λ

11 Investigation of simple antenna arrays Spherical Cut, ϑ=90 σ ϕ =0 : ρ e 0.5 σ ϕ =60 : ρ e 0.05 σ ϕ =0 : ρ e 0.34 d=0.5λ d=0.5λ d=λ Effects radiation pattern changes due to mutual coupling resulting in a better decorrelation performance gain due to diverse patterns

12 Investigation of simple antenna arrays real antenna pattern, element spacing 5.6 GHz channel model A, one tap m ϑ = 90 σϑ = 0 mϕ = 45 σϕ = 40 selection of 4 out of 8 antennas (in correspondence to 4 RF-chains) Simulation Model Outage Rate for Antenna Selection (4/8) choice of 4 antennas out of 8 (channel model A) choice from 4 antennas out of an array with 8 dipole antennas (channel model A) 0 best 3 : (357;368;468) worst 3 : (34;4567;345) -0,5 d d d d d d x - best 3 : (357;368;468) worst 3 : (34;4567;345) 45 log ( outage rate) -,5 - y b b b b z -, , channel capacity in bit/ s/ = 0 db

13 Investigation of simple antenna arrays 3 Analysis Method choice from 4 antennas choice of 4 out antennas of array out of with 8 (channel 8 dipole model antennas A) (channel (Kanalmodell A) A) 3 best 0,5 select antenna combination (abscissa) determine 6 correlation coefficients (left index) sort resulting 6 coefficients (right index) Antenna correlation index ,4 0,3 0, 0, absolute value of correlation coefficient ρ xy 70 3 worst index of antenna ensemble 0

14 Investigation of simple antenna arrays Simulation setup TX: 4 dipoles 5.6 GHz CM A: m ϑ = 90 σϑ = 0 mϕ = 45 σϕ = 40 all RX antenna combinations SNR = 0dB Size of PEC Box (90mm x 5 mm x 30mm) C_min for antenna combination (3,4,7,8) C_max for antenna combination (,3,6,8)

15 Investigation of simple antenna arrays Simulation setup TX: 4 dipoles 5.6 GHz CM A: m ϑ = 90 σϑ = 0 mϕ = 45 σϕ = 40 all RX antenna combinations SNR = 0dB C_min for antenna combination (,5,6,7) C_max for antenna combination (3,4,6,8) polarization diversity increases C_min

16 Investigation of simple antenna arrays Spherical Cut, ϑ=90 of E-Field Excitation 4 Excitation Excitation

17 Outline 7. Introduction & motivation. Basics of MIMO channel-simulator 3. Investigation of simple antenna arrays 4. Conclusions

18 Conclusions Conclusions 8 Higher accuracy due to 3D-modeling including real patterns of antennas Performance estimation for a given antenna setup and channel model (including switching) Future Work Gain of antenna needs to be included for real system modeling (no fix SNR) Mean effective gain MEG π π = 0 0 K p + ϑ, ϕ G XPR ϑ ( ϑ, ϕ) sin( ϑ) dϑ dϕ XPR + XPR ( ϑ, ϕ) + G ( ϑ, ϕ) ϕ K XPR= P V P H Goal: General antenna design criterions

19 9 Thanks for your attention