Preliminary Coexistence Tests

• The same 802.11 wireless signal was used as the victim:– Power Level = 0 dBm– BW = 20 MHz– Center Frequency = 2.412 GHz– Orthogonal frequency-division multiplexing

(OFDM) Data Rate = 6 Mbps– BPSK

OFDM concept• Transmit data is spread over a number of

orthogonal subcarriers in the frequency domain

Error vector magnitude (EVM) measurement of the receive signal constellation

Comparing Impacts of Different Interference Modulation/Technologies

• Setup– Currently conductive – Eventually move to radiated

• Target protocol – WLAN• Interfering Modulation/Technologies – CW AM Signal– Bluetooth (BT)– LTE– WLAN

Peak Spectrum of 802.11 WLAN Test Signal

2.401 2.4034679492.4059358972.4084038462.4108717952.4133397442.4158076922.418275641 2.42074359-50

-45

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-25

-20

-15

-10

-5

0

Peak Power Spectrum of 802.11 WLAN Signal (0 dBm Power, 20 MHz BW)

WLAN

Frequency (GHz)

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Recieved WLAN Constellation, no interference.

Recieved WLAN EVM Spectrum with no Interfering signal

Interfering signal spectrums (with 20 MHz WLAN at center frequency = 2.417 GHz)

2.404 2.40525 2.4065 2.40775 2.409 2.41025 2.4115 2.41275 2.414 2.41525-100

-90

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-70

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-10

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Peak Power Spectrums of CW AM, Bluetooth, LTE, WLAN (all at -10 dBm Power setting)

LTE (10 MHz)BluetoothAMWLAN (20M, 2.417G)

Frequency (GHz)

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Interfering Signal 1: CW AM Signal

• Parameters:– Center Frequency = 2.41 GHz (within, but off

center, of WLAN band)– AM Modulation: 1 kHz and 80% (as in IEC 61000-

4-3, Annex A) – Power level = -10 dBm

• WLAN does not fail• RMS EVM of approx. -23 dBm (by inspection)

as an instant average over all subcarriers

Recieved WLAN Constellation from Interfering Signal 1

Recieved WLAN EVM spectrum from Interfering Signal 1

Interfering Signal 2: Bluetooth

• Parameters– Power Level = -10 dBm– Center Frequency = 2.41 GHz (same as Signal 1)– Max Payload length, Carrier Burst

• WLAN intermittently fails as a result of the BT signal• RMS EVM of WLAN is regularly about -50 dBm (by

inspection), with short periods of Higher EVM (at failure)– Consistently much lower EVM from signal 1

Received WLAN Constellation with Interfering Signal 2, WLAN Failure

Recieved WLAN EVM Spectrum with Interfering Signal 2, WLAN Failure

Interfering Signal 3: LTE

• Parameters– Power Level = -10 dBm– Center Frequency = 2.41 GHz– BW = 10 MHz

• With these Parameters the WLAN Receiver was never able to establish a link

Interfering Signal 3: LTE Cont.

• Highest 10 MHz LTE power that allowed the WLAN system to make a connection was -27 dBm– Consistent EVM of about -25 dBm (by inspection)– Large number of subcarriers are affected (see

following EVM plot) by this signal– This is due to the wider bandwidth of LTE

compared to Bluetooth or the CW AM signal

Received WLAN Constellation with Interfering Signal 3 (-27 dBm Power)

Recieved WLAN EVM Spectrum with Interfering Signal 3 (-27 dBm Power)

Interfering Signal 4: 802.11 WLAN

• The interfering WLAN is on the 802.11 band nearest the victim:– Power = -30 dBm– Center Frequency = 2.417 GHz– BW = 20 MHz

• -30 dBm interference power setting was the highest that allowed consistent victim connection

• Consistent average RMS EVM of about –29 dBm (from inspection)

Recieved WLAN Constellation from Interfering Signal 4

Recieved WLAN EVM spectrum from Interfering Signal 4

Backup Slides

Received WLAN Constellation with Interfering Signal 2, No WLAN Failure

Recieved WLAN EVM Spectrum with Interfering Signal 2, no WLAN Failure

Peak Spectrum Comparison of CW AM, Bluetooth , and LTE from Tests

2.404 2.40525 2.4065 2.40775 2.409 2.41025 2.4115 2.41275 2.414 2.41525-100

-90

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Peak Power Spectrums of CW AM, Bluetooth, LTE (all at -10 dBm Power setting)

LTE (10 MHz)BluetoothAM

Frequency (GHz)

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