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802.11ac Channel Modeling. Authors:. Topics. Introduction TGn Channel Model Applicability to TGac Conclusions & Next Steps Questions ?. Introduction. TGn has developed a comprehensive MIMO Broadband Channel Model

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topics
Topics
  • Introduction
  • TGn Channel Model Applicability to TGac
  • Conclusions & Next Steps
  • Questions ?

Names

introduction
Introduction
  • TGn has developed a comprehensive MIMO Broadband Channel Model
  • TGac can re-use the TGn channel models as a baseline with some minor changes to address possiblenew technology components such as
    • Higher order MIMO (> 4x4)
    • Spatial Division Multiple Access (SDMA) with > 4 AP antennas
    • Distributed MIMO
    • Higher Bandwidth (> 40 MHz)
    • OFDMA - Use multiple 20 MHz channels across multiple users.

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topics1
Topics
  • Introduction
  • TGn Channel Model Applicability to TGac
  • Conclusions & Next Steps
  • Questions ?

Names

measurement literature
Measurement Literature
  • Many studies of higher order indoor MIMO measurements found in literature. Examples include:
    • E. Bonek Ove, “Experimental validation of analytical MIMO channel models”, Vienna University of Technology, June 2005.
    • Ozcelik, H.; Herdin, M.; Hofstetter, H.; Bonek, E., "A comparison of measured 8 × 8 MIMO systems with a popular stochastic channel model at 5.2 GHz," Telecommunications, 2003. ICT 2003. 10th International Conference on , vol.2, no., pp. 1542-1546 vol.2, 23 Feb.-1 March 2003
    • Nielsen, J.O.; Anderson, J.B., “Indoor MIMO Channel Measurement and Modeling,” WPMC / IWS Conference, pp. 479-483, September 2005.
  • Qualcomm is also conducting 8x8 and 16x16 indoor channel measurements using a MIMO channel sounding system

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measurement setup
Measurement Setup
  • Indoor 8x8 and 16x16 MIMO 20 MHz channel measurements at 5.17 GHz performed at Qualcomm
  • Used a channel sounder built from off the shelf components
  • A mix of LOS and NLOS locations were chosen
  • Two independent channel measurements at each location (STA rotated 90°)

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example antenna configurations used
Example Antenna Configurations Used

8 Slot Antenna Array

Two V-H and two ±45° pairs

λ/2 separation between slot pairs

16 Linear Dipole Antenna Array

λ/2 separation between elements

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applicability to sdma distributed mimo ofdma
Applicability to SDMA, Distributed MIMO & OFDMA
  • Measurements indicate that users separated by a few l experience uncorrelated fading.
    • Spatial correlation coefficients across clients in the 0-0.2 range.
    • We welcome additional measurement results to validate this observation.
  • Recommend re-using the TGn channel models with the following notes:
    • Distributed MIMO, OFDMA: Use independent TGn MIMO channel realizations across links.
    • SDMA: Use zero spatial correlations for antennas corresponding to different clients.

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changes to bandwidth delay spread doppler spread parameters
Changes to Bandwidth, Delay Spread & Doppler Spread Parameters
  • TGn channel models are valid up to 100 MHz bandwidth.
  • TGac systems can use TGn models if system bandwidth <= 100 MHz.
    • If TGac systems include non-contiguous channels with total span > 100 MHz, then channel tap spacing needs to be decreased accordingly.
      • Example: Need 1ns channel tap spacing to accommodate 1 GHz. Recall that TGn channel tap spacing is 10nsec.
      • Need wider bandwidth channel measurements to validate channel models.
  • Measurements in literature do not invalidate TGn Delay spread model and Doppler spread models.
    • Suggest preserving these parameters, unless new measurements indicate otherwise.

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tgn channel capacity vs measured capacity
TGn Channel Capacity vs. Measured Capacity
  • 8x8 channel measurements indicate most locations have capacity CDFs that are bounded between 11n channel models B & D.
    • Assumed uniform linear isotropic antenna array (l/2 spacing) at AP and client.
  • Capacity calculation was performed as follows:
  • Calculate MMSE post-processing SINR at each tone, assuming 24 dB SNR per Rx antenna.
  • Convert SINR at each tone to capacity.
  • Average capacities across all tones across 20 MHz BW

Each CDF curve reflects a different test location/orientation

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tgn channel capacity vs measured capacity1
TGn Channel Capacity vs. Measured Capacity
  • 16x16 channel measurements indicate most locations have capacity CDFs that are bounded between 11n channel models B & D.
    • Assumed uniform linear isotropic antenna array (l/2 spacing) at AP and client.
  • Capacity calculation was performed as follows:
  • Calculate MMSE post-processing SINR at each tone, assuming 24 dB SNR per Rx antenna.
  • Convert SINR at each tone to capacity.
  • Average capacities across all tones across 20 MHz BW

Each CDF curve reflects a different test location/orientation

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cross polarized antennas
Cross-Polarized antennas
  • To minimize real estate and to improve LOS MIMO performance, OEMs may also use cross-polarized antennas, as shown in the below figure for 8 antennas
  • TGac may need to specify channel models that include dual-polarized antennas
    • Need to specify XPD, correlations between cross-polarized antennas etc.
    • Recall that TGn provided only a brief description of dual polarized antennas, but didn’t explicitly include dual pol channel models
  • TGac needs to agree on whether we need to include dual-pol antennas for proposal comparison /evaluation

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tgn channel capacity vs measured capacity2
TGn Channel Capacity vs. Measured Capacity
  • 8x8 cross-pol channel measurements show tightening of capacity CDF bounds across all locations and significant capacity improvement in LOS scenarios, w.r.t the linear dipole array measurements.
    • TGn channel models assume XPD = 3 dB and correlation between cross-pol antennas = 0.
  • Capacity calculation was performed as follows:
  • Calculate MMSE post-processing SINR at each tone, assuming 24 dB SNR per antenna.
  • Convert SINR at each tone to capacity.
  • Average capacities across all tones across 20 MHz BW

Each CDF curve reflects a different test location/orientation

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tgn channel capacity vs measured capacity3
TGn Channel Capacity vs. Measured Capacity
  • 16x16 cross-pol channel measurements show tightening of capacity CDF bounds across all locations and significant capacity improvement in LOS scenarios, w.r.t the linear dipole array measurements.
    • TGn channel models assume XPD = 3 dB and correlation between cross-pol antennas = 0.
  • Capacity calculation was performed as follows:
  • Calculate MMSE post-processing SINR at each tone, assuming 24 dB SNR per antenna.
  • Convert SINR at each tone to capacity.
  • Average capacities across all tones across 20 MHz BW
  • Conclusions & Next Steps

Each CDF curve reflects a different test location/orientation

Names

topics2
Topics
  • Introduction
  • TGn Channel Model Applicability to TGac
  • Conclusions & Next Steps
  • Questions ?

Names

conclusions
Conclusions
  • TGac can re-use the TGn channel models as a baseline.
    • TGn channel models seems to accurately bound the 8x8 and 16x16 channel capacities measured in enterprise environment.
  • Use of cross-polarized antennas improves system performance for 8x8 and 16x16.
  • TGac channel models may introduce Dual Pol channel models in addition to current models.
    • Need to agree on XPD, antenna correlation etc.

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next steps
Next Steps
  • Plan to submit a first-cut TGac channel model addendum document in March 2009 meeting.
    • Envision that the addendum and modifications thereof can be used as a supplement to TGn channel models for simulations.
  • We encourage participants to collaborate with us on:
    • Measurement results
    • TGac channel model addendum document.

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