doc.: IEEE 802.11-13/0364r1

Submission Eldad Perahia

, Intel Corpor

ation

Slide 1

Date: 2013-03-20

Name Company Address Phone email Eldad Perahia Intel

Corporation

2111 NE 25th Ave Hillsboro, OR 97124

503-712-8081 eldad.perahia@intel.com

Vinko Erceg Broadcom

Nihar Jindal Broadcom

Authors:

Antenna Array Gain from Measured Data for 802.11n/ac TxBF

March 2013

doc.: IEEE 802.11-13/0364r1

Submission

Abstract

• Theoretical calculation of antenna array gain is 10*log10(# of antenna elements)

• With 802.11n/ac MIMO/OFDM transmit beamforming (TxBF), antenna weights matrices are computed on a subcarrier basis

• In a multipath environment, while the TxBF PER performance gain will be substantial, the composite effective array gain will be much less than 10log10(N)

Eldad Perahia

, Intel Corpor

ation

Slide 2

March 2013

doc.: IEEE 802.11-13/0364r1

Submission

Measurements in an Office Environment

• Measurements captured in 802.11n test bed deployed on one floor of an occupied indoor office environment– Dimensions of the floor of the

building are 90 ft X 90 ft (~27.4 m X 27.4 m)

– In center of floor are labs, elevators, and a kitchen area

– Along the walls are workspaces with groups of cubicles and conference rooms

– Numbered circles indicate device locations

Eldad Perahia

, Intel Corpor

ation

Slide 3

doc.: IEEE 802.11-13/0364r1

Submission

Measurement Device Description

• Devices are actual 802.11n stations consisting of a desktop PC with an Intel Wi-Fi Wireless Link 5300 radio card and external antennas– 3 Tx antennas, 3 Rx antennas, 3

stream packet format– 5 GHz transmission on an empty

channel

Eldad Perahia

, Intel Corpor

ation

Slide 4

doc.: IEEE 802.11-13/0364r1

Submission

Captured Measurements• CSI is measured by having each device in turn

transmit a stream of 802.11n packets, while all the other devices on the floor receive the packets– Packets are transmitted every 0.8 ms– 3000 packets– measured from the long training field of each packet– 3x3 CSI matrix

• Received signal level data and noise level data also captured– Used to compute received SNR

Eldad Perahia

, Intel Corpor

ation

Slide 5

doc.: IEEE 802.11-13/0364r1

Submission

Antenna Gain Calculation

• 3x1 TxBF weights computed from CSI for each of the receive antennas

• Computation performed on each packet• Antenna gain computed from weights as shown on next slide• Computing statistics:

– antenna gain computed over 360 deg azimuth and 90 deg elevation for each subcarrier

– Average antenna gain (linear) computed over all subcarriers for each angle

– Maximum antenna gain found over all angles– Repeat for each time instance and CDF formed– Antenna gain reported at 50% and 90% probability point of CDF

Eldad Perahia

, Intel Corpor

ation

Slide 6

doc.: IEEE 802.11-13/0364r1

Submission

Transmission at angle φ, θ

TX ofAP

x

xk

x

x

w1,k exp(-j2πkΔf)

w2,k exp(-j2πkΔf)

w3,k exp(-j2πkΔf)

exp(jπ cos(φ) sin(θ))

1

exp(j 2π cos(φ) sin(θ))

Eldad Perahia

, Intel Corpor

ation

Slide 7

doc.: IEEE 802.11-13/0364r1

Submission

Summary of Array Gain Results (90% Prob)

Morning measurement Afternoon measurement

SRC Dest Rx ant 1 Rx ant 2 Rx ant 3 Rx ant 1 Rx ant 2 Rx ant 31 5 2.6 dB 2.3 dB 1.7 dB 2.5 dB 2.6 dB 2.0 dB

2 5 3.3 dB 3.2 dB 3.0 dB 2.0 dB 3.0 dB 1.0 dB

1 2 3.3 dB 2.1 dB 2.3 dB 1.5 dB 2.2 dB 2.5 dB

4 9 1.6 dB 2.9 dB 2.7 dB 1.6 dB 2.4 dB 2.0 dB

13 4 2.4 dB 3.3 dB 2.1 dB 2.7 dB 3.5 dB 2.0 dB

13 9 1.9 dB 2.3 dB 2.3 dB 1.9 dB 1.6 dB 2.3 dB

12 11 3.0 dB 1.9 dB 3.4 dB 2.3 dB 2.1 dB 1.6 dB

11 3 3.4 dB 2.3 dB 2.0 dB 3.4 dB 2.1 dB 2.1 dB

3 12 2.4 dB 2.5 dB 1.9 dB 2.6 dB 2.5 dB 2.7 dB

5 13 2.3 dB 2.5 dB 1.5 dB 1.5 dB 2.9 dB 2.3 dB

4 11 2.0 dB 1.9 dB 0.9 dB 1.1 dB 1.8 dB 2.1 dB

3 10 2.4 dB 3.1 dB 2.3 dB 1.9 dB 1.2 dB 2.4 dB

11 2 1.7 dB 2.0 dB 2.8 dB 1.5 dB 2.1 dB 2.7 dB

Eldad Perahia

, Intel Corpor

ation

Slide 8

doc.: IEEE 802.11-13/0364r1

Submission

Summary of Array Gain Results (50% Prob)

Morning measurement Afternoon measurement

SRC Dest Rx ant 1 Rx ant 2 Rx ant 3 Rx ant 1 Rx ant 2 Rx ant 31 5 2.1 dB 1.6 dB 1.1 dB 2.2 dB 2.3 dB 1.6 dB

2 5 2.4 dB 2.6 dB 1.2 dB 1.8 dB 2.9 dB 0.8 dB

1 2 2.7 dB 1.4 dB 1.8 dB 1.0 dB 1.5 dB 1.8 dB

4 9 1.1 dB 2.3 dB 2.2 dB 1.6 dB 2.2 dB 1.7 dB

13 4 2.1 dB 3.1 dB 1.9 dB 2.5 dB 3.0 dB 1.1 dB

13 9 1.2 dB 1.8 dB 2.2 dB 1.7 dB 1.3 dB 2.2 dB

12 11 2.9 dB 1.9 dB 3.4 dB 1.7 dB 1.3 dB 1.1 dB

11 3 3.3 dB 2.1 dB 2.0 dB 3.4 dB 2.0 dB 2.0 dB

3 12 2.1 dB 2.1 dB 1.4 dB 2.4 dB 2.4 dB 2.6 dB

5 13 1.9 dB 2.1 dB 1.2 dB 0.9 dB 2.4 dB 1.4 dB

4 11 1.6 dB 1.3 dB 0.6 dB 0.8 dB 1.4 dB 1.7 dB

3 10 1.9 dB 2.6 dB 2.2 dB 1.7 dB 1.1 dB 2.4 dB

11 2 1.3 dB 1.5 dB 2.3 dB 1.1 dB 1.7 dB 2.3 dB

Eldad Perahia

, Intel Corpor

ation

Slide 9

doc.: IEEE 802.11-13/0364r1

Submission

Observations• Array gain for 3 TX antennas is typically less that 3

dBi• Results can vary quite a bit even between RX antennas• Large variation in time

– 2-3 dB variation can occur over 2.5 sec• Results vary from morning measurements to

afternoon measurements• 90th percentile (spatially) over 50 percentile (temporal)

gain values (slide 8) – = 2.7 dB– 2 dB less than 10log(3)

Eldad Perahia

, Intel Corpor

ation

Slide 10

doc.: IEEE 802.11-13/0364r1

Submission

EXAMPLE ANALYSIS

Eldad Perahia

, Intel Corpor

ation

Slide 11

doc.: IEEE 802.11-13/0364r1

Submission

SRC = 1; Dest = 5RX antenna 1

Eldad Perahia

, Intel Corpor

ation

Slide 12

doc.: IEEE 802.11-13/0364r1

Submission

1

2

3

30

210

60

240

90

270

120

300

150

330

180 0

BW = 20 MHz, all subcarriers

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 13

doc.: IEEE 802.11-13/0364r1

Submission

0.5

1

1.5

2

2.5

30

210

60

240

90

270

120

300

150

330

180 0

One subcarrier

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 14

doc.: IEEE 802.11-13/0364r1

Submission

0 5 10 15 20 25 30-15

-10

-5

0

5BW = 20 MHz, single angle

Subcarriers

Arr

ay G

ain

(dB

)

Eldad Perahia

, Intel Corpor

ation

Slide 15

doc.: IEEE 802.11-13/0364r1

Submission

0.5

1

1.5

2

30

210

60

240

90

270

120

300

150

330

180 0

BW = 20 MHz, averaged over all subcarriers

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 16

doc.: IEEE 802.11-13/0364r1

Submission

max array gain over angles for each time instance; CDF over all instances

0 0.5 1 1.5 2 2.5 30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Array Gain (dB)

Pro

babi

lity

20 MHz

Eldad Perahia

, Intel Corpor

ation

Slide 17

doc.: IEEE 802.11-13/0364r1

Submission

SRC = 1; Dest = 5RX antenna 2

Eldad Perahia

, Intel Corpor

ation

Slide 18

doc.: IEEE 802.11-13/0364r1

Submission

1

2

3

30

210

60

240

90

270

120

300

150

330

180 0

BW = 20 MHz, all subcarriers

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 19

doc.: IEEE 802.11-13/0364r1

Submission

0.5

1

1.5

2

30

210

60

240

90

270

120

300

150

330

180 0

One subcarrier

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 20

doc.: IEEE 802.11-13/0364r1

Submission

0 5 10 15 20 25 30-8

-6

-4

-2

0

2

4

6BW = 20 MHz, single angle

Subcarriers

Arr

ay G

ain

(dB

)

Eldad Perahia

, Intel Corpor

ation

Slide 21

doc.: IEEE 802.11-13/0364r1

Submission

0.5

1

1.5

2

30

210

60

240

90

270

120

300

150

330

180 0

BW = 20 MHz, averaged over all subcarriers

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 22

doc.: IEEE 802.11-13/0364r1

Submission

max array gain over angles for each time instance; CDF over all instances

0.5 1 1.5 2 2.5 30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Array Gain (dB)

Pro

babi

lity

20 MHz

Eldad Perahia

, Intel Corpor

ation

Slide 23

doc.: IEEE 802.11-13/0364r1

Submission

SRC = 1; Dest = 5RX antenna 3

Eldad Perahia

, Intel Corpor

ation

Slide 24

doc.: IEEE 802.11-13/0364r1

Submission

1

2

3

30

210

60

240

90

270

120

300

150

330

180 0

BW = 20 MHz, all subcarriers

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 25

doc.: IEEE 802.11-13/0364r1

Submission

1

2

3

30

210

60

240

90

270

120

300

150

330

180 0

One subcarrier

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 26

doc.: IEEE 802.11-13/0364r1

Submission

0 5 10 15 20 25 30-25

-20

-15

-10

-5

0

5BW = 20 MHz, single angle

Subcarriers

Arr

ay G

ain

(dB

)

Eldad Perahia

, Intel Corpor

ation

Slide 27

doc.: IEEE 802.11-13/0364r1

Submission

0.5

1

1.5

30

210

60

240

90

270

120

300

150

330

180 0

BW = 20 MHz, averaged over all subcarriers

angle (deg)

Arr

ay G

ain

Eldad Perahia

, Intel Corpor

ation

Slide 28

doc.: IEEE 802.11-13/0364r1

Submission

max array gain over angles for each time instance; CDF over all instances

0 0.5 1 1.5 2 2.5 30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Array Gain (dB)

Pro

babi

lity

20 MHz

Eldad Perahia

, Intel Corpor

ation

Slide 29