Envelope correlations (5/5) The higher the coherence distance Le the lower the angle spread All considered we have: B DS
Envelope correlations (5/5) The higher the coherence distance Lc the lower the angle spread. All considered we have: B c 0.1 1 DS L c 0.1 ≈ λ 4 1 σ Ω
Multidimensional parameters and MIMO (1/2) For optimum antenna/space diversity performance the received signal at the different antennas should be incorrelated,i.e.the signal envelope should have fast changes with space (along s). Therefore the power-angle profile should be very spread-there must be a large angle spread. To achieve good spatial multiplexing there must be a large number of strong paths well spaced(independent)in the angle domain in order for the MIMO matrix to have high rank-there must be a large angle spread. In other words there must be a high multipath richness Also absolute-time and Doppler domains(not considered here)are very important for space-time coding,i.e.transmit diversity and other MIMO coding techniques
Multidimensional parameters and MIMO (1/2) For optimum antenna/space diversity performance the received signal at the different antennas should be incorrelated, i.e. the signal envelope should have fast changes with space (along s). Therefore the power-angle profile should be very spread → there must be a large angle spread. To achieve good spatial multiplexing there must be a large number of strong paths well spaced (independent) in the angle domain in order for the MIMO matrix to have high rank → there must be a large angle spread. In other words there must be a high multipath richness Also absolute-time and Doppler domains (not considered here) are very important for space-time coding, i.e. transmit diversity and other MIMO coding techniques
Multidimensional parameters and MIMO (2/2) Angle spread and delay spread are two possibile measures of multipath richness. SNR remains however the most important parameter for the performance pf small-size MIMO schemes(i.e.2x2 or 4x4 etc) Recent studies have shown that for unnormalized channel,the channel capacity usually rises when moving from NLOS into LOS since the loss in multipath richness is more than compensated for by an increase in SNR. Dual-polarized MIMO schemes are very attractive as a doubling in the MIMO order is achieved with a less-than-proportional increase in the antenna size. In Dual polarized MIMO schemes the XPD(Cross-Polarization Discrimination) is very important.If the XPD is high (low correlation btw polarization states) then multiplexing is possible,otherwise polarization diversity is preferable
Multidimensional parameters and MIMO (2/2) Angle spread and delay spread are two possibile measures of multipath richness. SNR remains however the most important parameter for the performance pf small-size MIMO schemes (i.e. 2x2 or 4x4 etc) Recent studies have shown that for unnormalized channel, the channel capacity usually rises when moving from NLOS into LOS since the loss in multipath richness is more than compensated for by an increase in SNR. Dual-polarized MIMO schemes are very attractive as a doubling in the MIMO order is achieved with a less-than-proportional increase in the antenna size. In Dual polarized MIMO schemes the XPD (Cross-Polarization Discrimination) is very important. If the XPD is high (low correlation btw polarization states) then multiplexing is possible, otherwise polarization diversity is preferable