SAE J2931 test plan: PLC Testing Results. Tim Godfrey Arindam Maitra John Halliwell Daniel Foster John Harding Satish Rajagopalan

Transcription

1 SAE J2931 test plan: PLC Testing Results Tim Godfrey Arindam Maitra John Halliwell Daniel Foster John Harding Satish Rajagopalan

2 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 2

3 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) 3

4 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) 4

5 General Lab Setup 5

6 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. 6

7 Results for Bandwidth HPGP on Mains, IPv6 TCP/IP throughput, kbps 4509 Kbps average Std Dev Kbps average Std Dev 107 HPGP on Pilot, IPv6 TCP/IP throughput, kbps 59.4 Kbps average Std Dev 30 G3 on Pilot, IPv6 TCP/IP throughput, kbps 7

8 Combined results for Bandwidth J2931 Test Limits: RD.UtilComm.3 MAC/PHY throughput shall be 100 kbps or greater RD.DCComm.1 Application Data (payload) rate is 6 Kbps or greater concurrently (full-duplex) 8

9 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 ms typical 1 ms variance 4 ms 9

10 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 Inflection above 208 bytes 50 ms at 16 and 32 bytes 10

11 Summary results for Latency ms G3 latency is proportional to packet size, mS HPGP is constant latency, below 5mS Test Limit: 25mS RD.DCComm.2 Packet size, bytes 11

12 HPGP Association Testing basic setup DUT is PL-15 with INT7400 chipset and special SLAC firmware. DUT3 not necessary 12

13 Association Tests HPGP on Pilot (Untwisted) Using PL-15 RSSI - Lower number is stronger signal 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: 28 EVSE2: 13 correct association. EVSE1 PEV EVSE1: 14 EVSE2: 30 correct association. 13

14 Association Tests HPGP on Pilot (Twisted) Using PL-15 RSSI Measurements (average of 3 runs each): EVSE2 PEV EVSE1: 29 EVSE2: 14 correct association. EVSE1 PEV EVSE1: 14 EVSE2: 28 correct association. 14

15 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 15

16 General Setup for Interference Tests Interference is always injected on Mains Measurement point is mains or pilot, depending on type of PLC being tested. 16

17 AC Mains Interference Setup Line Probe for spectrum measurement Interference injection on Hot (L1) power conductor going to EVSE (Someone didn t pay attention to wire color standards) Point of attachment for EVSE located Mains PLC (DUT2) L1 & L2 conductors in cordset) 17

18 Measuring Signal to Noise ratio 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. Difficult to measure because spectrum is not flat 18

19 HPGP Mains Noise floor and White Noise Above 10Mhz, noise floor is about -68dBm Noise Floor Signal Only Maximum output of signal generator raise noise level to about -25dBm White Noise interference 19

20 HPGP Mains FM and PLC Data Wideband FM interference Maximum output of signal generator. -10 to -20dBm Signal only, no noise. Ranges from -30 to - 60dBm HPGP Data 20

21 HPGP Mains White Noise Interference - SNR White Noise >10dB PLC Only Noise is 0 to 20dB stronger than HPGP signal. No impairment of throughput or latency 21

22 HPGP Mains Wideband FM Interference - SNR ~20dB >30dB PLC Only Wideband FM Noise Noise is 0 to 35dB stronger than HPGP signal. No impairment of throughput or latency 22

23 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. No Measurable Effect 23

24 HPGP Mains interference results: TCP throughput No Measurable Effect No Noise 4607 White Noise 4595 Wide FM

25 Setup for G3 Pilot Interference Pilot noise injection CT Maxim G3 Modem Spectrum Analyzer Active Probe 25

26 G3 Pilot FM and PLC Data Wideband FM interference Screen Range KHz Signal range KHz Noise Range 75% of signal ( KHz) Noise spectrum: Approx -28dBm Signal only, no noise. Approx -38dBm G3 Data only 26

27 G3 Pilot Wideband FM Interference - SNR Wideband FM Noise PLC Only 10dB Noise is approx 10dB stronger than G3signal 27

28 G3 Pilot interference results: Ping Latency 28

29 G3 Pilot interference results: Ping Latency (zoom) 29

30 G3 Pilot interference results: Latency increase % Approx 80% increase in latency with Interference 30

31 G3 Pilot interference results: TCP throughput 40.4 Kbps Average No Interference 18.9 Kbps Average With Interference 31

32 G3 Pilot interference results: TCP (avg) throughput 40.4 Kbps Average No Interference 18.9 Kbps Average With Interference 53% reduction 32

33 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 33

34 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. 34

35 Together Shaping the Future of Electricity 35

36 Backup QoS Test Results 36

37 DSCP Tagging Can be generated by JPERF application: Consistent with test plan Results in packet tagged with DSCP value of 0x01: DSCP tag is upper 6 bits of 8 bit field (0x04) Homeplug GreenPHY PIB configured like this to assign CAP 2 priority: 37

38 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 2 nd TCP stream 38

39 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 39

40 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 40

41 Backup HPGP 7% Bandwidth Limit 41

42 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 42