PLC Testing Update - EPRImydocs.epri.com/docs/publicmeetingmaterials/1112... · · 2011-12-16SAE...

SAE J2931 test plan:PLC Testing Results

Tim GodfreyArindam MaitraJohn HalliwellDaniel FosterJohn HardingSatish Rajagopalan12-14-2011

2© 2011 Electric Power Research Institute, Inc. All rights reserved.

Introduction

• SAE J2931 test plan (S316) was developed to test PLC communication technologies for the cordset– Test plan is based on requirements in J2931

• The objective is to test the communications technology, not a complete PEV or EVSE system implementation– Testing is done with a common reference point of the

IP layer. – IP layer testing allows the same tests to be run on

different communications technologies.– IPv6 is used because it is a requirement:

RD.UtilComm.5


Overview of test plan

• Tests– Bandwidth and Latency tests– Crosstalk Tests– Coexistence Tests– Interference Tests– Association Tests

• Technologies under test– HomePlug GreenPHY (PL-14, PL-15, and XAV2001)

• QCA7000 HPGP chipset available mid January– G3-FCC (Maxim 2992)

• (Autorem G3 Cenelec – discontinued testing )– TI Concerto G3-FCC expected mid January (IPv6 in question)


Differences between TCP and UDP testing

• TCP tests the available channel capacity. It pushes as much data through as possible. The result is the maximum data rate that can be carried.

• UDP tests whether a specific rate of packet flow can be carried through the channel. You tell the sender what rate to send at. At the receiver, the test result is how many packets made it through.

• CAN Tunneling would fall under the UDP test, where the application data flow determines the number of UDP packets that are sent. (Not part of test plan)


General Lab Setup


Test Setup for Bandwidth and Latency

• Bandwidth as measured by TCP throughput using IPv6

• PING script to test round trip time at IPv6– Script repeats test for packet sizes between 16 and

1024 bytes.


Results for Bandwidth

4509 Kbpsaverage

Std Dev 59

4550 Kbpsaverage

Std Dev 107

59.4 Kbpsaverage

Std Dev 30

HPGP on Mains, IPv6 TCP/IP throughput, kbps

HPGP on Pilot, IPv6 TCP/IP throughput, kbps

G3 on Pilot, IPv6 TCP/IP throughput, kbps


Combined results for Bandwidth

J2931 Test Limits: RD.UtilComm.3 MAC/PHY throughput shall be 100 kbps or greaterRD.DCComm.1 Application Data (payload) rate is 6 Kbps or greater concurrently (full-duplex)


Results for Latency (Ping Time) (HPGP)

• Results are Ping round trip time (RD.DCComm.2: 25mS round trip)• Different packet sizes are tested: 16 to 1024 bytes

(average value of 4 pings for each size)

4 mStypical

4 mS

1 mSvariance


Results for Latency (Ping Time) (G3)

• Results are Ping round trip time (RD.DCComm.2: 25mS round trip)• Different packet sizes are tested (average of 4 pings at each size)• 15mS subtracted off (red values) to compensate for serial link

50 mSat 16 and 32bytes

Inflectionabove 208

bytes


Summary results for Latency

Test Limit: 25mS

RD.DCComm.2

mS

Packet size,bytes

G3 latency is proportional to packet size, 50 –450mS

HPGP is constant latency, below 5mS


HPGP Association Testing – basic setup

• DUT is PL-15 with INT7400 chipset and special SLAC firmware.

• DUT3 not necessary


Association Tests – HPGP on Pilot (Untwisted)

Using PL-15

RSSI - Lower number is stronger signal. 0 – 60 is possible range. Each unit is 1 dB of attenuation Using 1.5nF coupling to Pilot. Average of 3 runs each.

RSSI Measurements:

EVSE2 PEV

EVSE1: 28EVSE2: 13 correct association.

EVSE1 PEV

EVSE1: 14EVSE2: 30correct association.


Association Tests – HPGP on Pilot (Twisted)

Using PL-15

RSSI Measurements (average of 3 runs each):

EVSE2 PEV

EVSE1: 29EVSE2: 14 correct association.

EVSE1 PEV

EVSE1: 14EVSE2: 28correct association.


Interference Testing

• Objective to determine system resilience to interference

• Interference testing is difficult with OFDM systems like HPGP and G3.– Wideband signal, adaptive modulation - work ‘around’ noise

• Interference tests used– White Noise – broadband, equal energy per Hz– Wideband FM – rapidly sweep interference across band

• Simulates short pulses of interference at various frequencies affecting the packets.

• Interference still to be done: Arc Lamp, DC Charger noise


General Setup for Interference Tests

• Interference is always injected on Mains• Measurement point is mains or pilot, depending on type of

PLC being tested.


AC Mains Interference Setup

Interference injection on Hot (L1) power conductor going to EVSE

(Someone didn’t pay attention to wire color standards)

Line Probefor spectrum measurement

Point of attachment for EVSE located Mains PLC (DUT2)L1 & L2 conductors in cordset)


Measuring Signal to Noise ratio

• Difficult to measure because spectrum is not flat

• Objective is to raise interference level until 50% packet loss or throughput drop is seen.

• Measure power spectrum of signal, power spectrum of noise at same physical connection point.

• SNR is difference, in dB.


HPGP MainsNoise floor and White Noise

White Noiseinterference

Noise Floor Signal Only

• Maximum output of signal generator – raise noise level to about -25dBm

• Above 10Mhz, noise floor is about -68dBm


HPGP Data

Wideband FMinterference • Maximum output of signal

generator. -10 to -20dBm

• Signal only, no noise. Ranges from -30 to -60dBm

HPGP MainsFM and PLC Data


White Noise

PLC Only

HPGP Mains White Noise Interference - SNR

>10dB

Noise is 0 to 20dB stronger than HPGP signal. No impairment of throughput or latency


HPGP Mains Wideband FM Interference - SNR

>30dB

Noise is 0 to 35dB stronger than HPGP signal. No impairment of throughput or latency

PLC Only WidebandFM Noise

~20dB


HPGP Mains interference results: Ping Latency

• Ping latency reveals MAC-layer retries– Even if there is no packet loss at the IP layer, interference may be

causing packet loss in the MAC and PHY layers. – An increase in MAC layer retries will be visible as increase in

round trip time.

NoMeasurable

Effect


HPGP Mains interference results: TCP throughput

NoMeasurable

Effect

No Noise 4607

White Noise 4595

Wide FM 4612


Setup for G3 Pilot Interference

• Pilot noise injection CT

• Maxim G3 Modem

• Spectrum Analyzer Active Probe


G3 PilotFM and PLC Data

G3 Data only

Wideband FMinterference

• Screen Range 100-500KHz– Signal range 160-478KHz– Noise Range 75% of signal

(200-438 KHz)

• Noise spectrum: Approx -28dBm

• Signal only, no noise. Approx -38dBm


G3 Pilot Wideband FM Interference - SNR

WidebandFM Noise

PLC Only

10dB

Noise is approx 10dB stronger than G3signal


G3 Pilot interference results: Ping Latency


G3 Pilot interference results: Ping Latency (zoom)


G3 Pilot interference results: Latency increase %

Approx 80% increase in latency with Interference


G3 Pilot interference results: TCP throughput

40.4 Kbps AverageNo Interference

18.9 Kbps AverageWith Interference


G3 Pilot interference results: TCP (avg) throughput

40.4 Kbps AverageNo Interference

18.9 Kbps AverageWith Interference

53% reduction


Interference Summary

• HPGP On Mains– SNR minus 20-30dB (Noise stronger than signal) for WB

FM interference– SNR minus 0-20dB (Noise stronger than signal) for White

Noise interference– No significant change in Ping latency or TCP throughput

beyond normal random variations.

• G3 on Pilot– SNR minus 10dB (Noise stronger than signal) for WB FM

interference– Approx 80% increase in Ping latency– Approx 53% reduction in TCP throughput


Schedule, Next Steps

• EPRI will complete Interference, Crosstalk, and coexistence tests for these platforms by Mid January

• Starting Mid-January, we will repeat tests with QCA7000 platform for HPGP

• If TI Concerto G3 platform is available with IPv6, they will be tested in parallel with QCA7000.

• Complete all testing by end of February

• At that point, SAE must make technology selection (if a decision has not been made by then)

• Once the technology has been selected, HAN testing may be conducted as needed.


Together…Shaping the Future of Electricity


QoS Test Results

Backup


DSCP Tagging

• Can be generated by JPERF application:– Consistent with test plan

• Results in packet tagged with DSCPvalue of 0x01:

• DSCP tag is upper 6 bitsof 8 bit field (0x04)

• Homeplug GreenPHY PIB configured like this toassign CAP 2 priority:


Baseline

• Two TCP streams over HPGP – no QoS tagging used• Right trace runs concurrently for 10 seconds in middle of left trace• Result – Bandwidth shared equally – 50% drop with 2nd TCP stream


One TCP stream with QoS priority

• Two TCP streams over HPGP: right trace stream tagged with DSCP 1• Right trace runs concurrently for 10 seconds in middle of left trace• Result – Most bandwidth goes to priority stream – approx 4.75 Mbps• Note that non-QoS stream is not excluded – it still gets 250 Kbps


Ping Tests

• Ping with DSCP Tag enabled (-v 4)– rtt increase from

13 to ~25mS

• HPGP TCP stream run in middle 10 seconds

• Ping with no QoS– rtt increase from

4 to ~100mS


HPGP 7% Bandwidth Limit

Backup


About the HPGP 7% Bandwidth limit

• A HPGP device may be limited to 7% of “time on wire” from a HPAV network on a shared medium under these conditions:– The HPAV network must be highly loaded, using 93% of time.

Otherwise HPGP is free to contend for more than 7% of time.– The limit only takes effect if coupling from HPAV network to

cordset is sufficient to decode the HPAV traffic.• If and only if these conditions are true, then:

– Basic HPGP PHY rate is 10Mbps, 7% is 700Kbps– HPGP TCP/IP throughput after MAC overhead is ~5Mbps, 7%

of that is 350Kbps.– J2931 test throughput is 100Kbps. (RD.UtilComm.1)– J2931 test data will not exceed 7% under any circumstances. – 7% of HPGP bandwidth is more than enough to meet J2931

requirements

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PLC Testing Update - EPRImydocs.epri.com/docs/publicmeetingmaterials/1112... · · 2011-12-16SAE...

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