802 11ac channel modeling
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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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802.11ac Channel Modeling

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802 11ac channel modeling

802.11ac Channel Modeling

Authors:

Names


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.

Names


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

Names


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°)

Names


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

Names


Cross pol antenna array radiation pattern

Cross-Pol Antenna Array Radiation Pattern

Names


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.

Names


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.

Names


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

Names


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

Names


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

Names


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

Names


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.

Names


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.

Names


Questions

Questions ?

Names


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