Study on the next generation ITS radio communication in Japan

Transcription

1 Study on the next generation ITS radio communication in Japan DSRC International Task Force, Japan Contents GHz DSRC in Japan (ARIB STD-T75) 2. Requirements for the next generation ITS radio communication 3. Candidate communication technologies for the next generation ITS radio communications. 4. OFDM (Orthogonal Frequency Division Multiplexing) 5. PSK-VP(Phase Shift Keying with Varied Phase) 6. Conclusion Sep DSRC International Task Force, Japan Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 1

2 1.1 Regional standards of DSRC Item Radio frequency band Europe (CEN) North America (ASTM) Japan (ARIB STD-T75) 5.8GHz GHz 5.8GHz Communication system Passive Active Active Data transmission rate Downlink:500kbps Uplink :250kbps Down/Uplink: 3-27Mbps Down/Uplink: 1 or 4 Mbps Duplex Half-duplex Half-duplex Half-duplex(OBU) Full-duplex (RSU) Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 2

3 2.1 ITS Standardization in ITU-R What is the next generation ITS radio communication? 1994, Question on ITS Recommendations (Answers to the Question) Objectives & Requirements Rec. ITU-R M ITU-R/SG8/WP8A/WG2: Standardization for ITS Functionalities Rec. ITU-R M Technologies Current Use of Spectrum Traffic & Spectrum Requirements Short-range Radar Rec. ITU-R M. 1452* 5.8GHz DSRC Rec. ITU-R M VICS(DSRC)? Next generation ITS radio communication?? Radio services - Broadcast - DSRC - Short-range radar - Short-range vehicle-tovehicle - Short-range continuous - Wide area * Rec. ITU-R M. 1453, Revised in Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 3

4 2.2Data transmission rate requirement for the next generation ITS radio communication Allowable traveling speed (mobility) [Km/h] 180 Information supply-type (high-speed traveling) ARIB STD-T75 generally satisfies the requirement except for the very small area shown below. 100 Image of a new portable telephone 20 Logistic Management Information supply-type (high-speed travelling) Parking lot Drive-through Specific region entry charging Information supply-type (semi-stationary) - high data rate highspeed traveling; Continuous communication - Very high data rate semi-stationary; Filling station Convenience store Pedestrian support On-demand information Video/music distribution Broadband ITS Radiocommunication (Resolution RAST 10/7) 0 Connection to Internet (IP) Data transmission rate 100K 1M 10M [bps] Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 4

5 2.3 Technical Requirement for the next generation ITS Radio Communication Area Extension :Spot Area Continuous or Wide Area 2High Reliability transmition to High Speed Vehicle in multi-path or/and Shadowing Situation Delayed wave 1 Direct wave Delayed wave 2 Multi-path Receive Level Shadowing Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 5

6 CDM (Code Division Multiplexing) DSRC International Task Force, Japan 3.1 Development status in ARIB* for the next generation ITS radio communication Technology Status Overview of the system Under Study Code 1 Code 1 OFDM (Orthogonal Frequency Division Multiplexing) a Under Study Developped OFDM Demonstration Finished Binary S/P Code 2 Low Binary Speed High Speed data data Code N Power QPSK QPSK QPSK Sum Power Code 2 Code N Binary high QPSK speed data Power S/P F3 SUM Transmit F1 F2 Power Fn Power F1 Power Fn F1 - Fn Symbol Frequency Time P/S Binary High Speed data PSK-VP (Phase Shift Keying with Varied Phase) Demonstration Finished * The road-vehicle communications technology group in the study group for Efficient Use of the Radio Spectrum for ITS Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 6

7 3.2 Countermeasures to Multi-path fading Delayed wave 1 Direct wave Delayed wave 2 Multi-path fading Available Technology CDM OFDM PSK-VP Features - RAKE / Path-Diversity - Low Inter-Symbol Interference (Low symbol rate) - Low Inter-symbol Interference (Low symbol rate) - Guard interval to reduce Inter Symbol and Inter Carrier Interference - Implicit RAKE / Path-Diversity Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 7

8 3.3 Countermeasures to Shadowing Technologies to realize reception from multiple antennas Available Technology CDM Features RAKE / Path-Diversity* f1 Shadowing f1 Developped OFDM PSK-VP Guard interval to reduce Inter Symbol Interference / Path-Diversity* Implicit RAKE / Path-Diversity* * ; Features to achieve continuous communication Avoidance of shadowing by reception from multiple Antennas Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 8

9 4.Modulation scheme and features of OFDM - Concept of OFDM modulation scheme Power QPSK Binary high QPSK speed data Power S/P F3 SUM Transmit QPSK QPSK F1 Power F2 Power Fn Power Power F1 - Fn Symbol Frequency - Anti-Multipath mechanism of OFDM Direct wave Direct wave Delayed wave Guard interval Symbol A Symbol B Symbol C F1 Fn Time Features of OFDM - Robustness against frequency selective fading (Narrow subcarrier) - High spectrum efficiency (Minimum carrier frequency spacing) - Low Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI): (Provision of Guard Interval) Delayed wave Delay time Symbol A Symbol B Symbol C Reduced ISI and ICI Guard interval Time Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 9

10 4.1 Specification of a basedofdm DSRC International Task Force, Japan Item a a/RA Std. Body IEEE ASTM Freq. Band 5 GHz band 5.9 GHz band GHz GHz GHz Com. Range* 100m(typ) ex. 35m(54Mbps) 200m( 6Mbps) 1,000m Modulation OFDM OFDM No of channels 12 ch 7 ch Channel separation 20 MHz 10 MHz Data rate 6-54 Mbps 3-27 Mbps Vehicle speed (Stationary) 200 km/h Others Spectrum mask - Severe than 11a TxPWR_level Adjacent ch Rej - Severe than 11a * depends on environment condition and data rate. Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 10

11 4.1.1 BER Simulation Results for a (Line Of Site model,16qam) Fd = 100Hz : 18km/h Rice K=5dB Fd = 200He :36km/h Fd = 300Hz :54km/h Fd = 400Hz :72km/h Fd = 500Hz :90km/h Delay Spread :10ns Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 11

12 4.1.2 BER Simulation Results for a (Line Of Site model,qpsk) Rice K=5dB Fd = 100Hz : 18km/h Fd = 200He :36km/h Fd = 300Hz :54km/h Fd = 400Hz :72km/h Fd = 500Hz :90km/h Delay Spread :10ns Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 12

13 4.1.3 BER Simulation Results for a (Non-Line Of Site model,16qam) Delay Spread :50ns Fd = 100Hz Fd = 200He : 18km/h :36km/h Delay Spread :100ns Fd = 300Hz :54km/h Fd = 400Hz :72km/h Fd = 500Hz :90km/h Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 13

14 4.1.4 BER Simulation Results for a (Non-Line Of Site model,qpsk) Eb/No[dB] 1.E BER 1.E-01 1.E-02 1.E Hz 400Hz 800Hz 1000Hz 1.E-04 1.E-05 a 10ns BER 1.E E-01 1.E-02 1.E-03 1.E-04 1.E-05 Eb/No[dB] BER Eb/No[dB] 1.E E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 b 50ns 1.E-06 c 100ns Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 14

15 4.2 Features of Developed OFDM systems - Parameters of the system Items Communication area Radio zone size Handover distance Channel separation Radio transmission rate (Up / Down) Modulation Error correction RSE TX power OBE TX power - Comparison with IEEE a Model system A 10mx300mxn 10mx(30m-60m) 300m 5MHz 3.253Mbps OFDM-DQPSK RS(31,19) 200mW 10mW Items Model system A IEEEE a Access method TDMAFDD CSMA/CA Modulation DQPSK BPSKQPSK16QAM 64QAM Symbol length µs 3.2µs Guard interval 1/16 1/4 Guard time 0.98µs 0.8µs Subcarrier spacing 64kHz 312.5Hz Number of subcarrier 27 52With 4 pilot carriers Bandwidth per channel 1728kHz About 17MHz Error collection RS(31,19) Convolutional coding R=1/22/33/4 Interleave Within slot Within symbol Number of subcarrier division 2 Features of the system - Seamless hand-over on single radio frequency by dividing the sub-carrier - Time interleave within the slot to compensate for time variation of the received signal - High mobility through adoption of differential PSK without pilot carriers Note; RLAN devices are generally not designed to be used at automotive or higher speeds. Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 15

16 4.2.1 System performance simulation (Developed OFDM systems) - Error rate under Rice (k=6db) type multipath interference, after error correction Maximum Doppler frequency=966hz < < 64,000Hz (Subcarrier spacing) at vehicle speed of 180km/h Parameters are as per listed on the slide No. 4.2 Delay difference=122ns Delay difference=488ns - Power spectrum (6dB Back-off, Class AB) Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 16

17 4.2.2 Hand-over on Single radio frequency by dividing the subcarrier (Developed OFDM systems) Channel No.1 Channel No.2 Divide subcarrier into two groups f Mechanism of high speed handover on single radio frequency - The roadside transmitter transmits subcarrier groups arranged in frequency domain - The roadside transmitters in a data zone simulcast the identical data to reduce shadowing effects - All roadside transmitters are synchronized - When a vehicle passes a boundary between data zones, the receiver demodulates the signal of the two data zones, and extracts suitable data zones (Handover) Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 17

18 4.2.3 An example of seamless hand-over (Developed OFDM systems) DSRC International Task Force, Japan RSE1 RSE 2 RSE 3 RSE 4 Channel No.1 Channel No.2 Divided Channel No.1 Divided Channel No.2 Frequency A B C B C B C D Dividing the subcarrier into two groups f Error free during hand-offs RSE Antenna - RSE Communication range: 30m - RSE Antenna height: 10m Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 18

19 4.2.4 An example of Continuous Communication (Developed OFDM systems) RSE1 RSE 2 RSE 3 RSE 4 Vehicle Speed: 120km/h RSE Antenna Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 19

20 5.1 PSK-VP Modulation Scheme Concept of PSK-VP (Phase Shift Keying with Varied Phase) An anti-multipath scheme by imposing phase-variation on the symbol of PSK Configuration cf. IEEE Trans. VT-42, No.4, pp IEEE Trans. VT-42, No.2, pp ITST2001 Proc., S3-3, pp Triple mode (QPSK-VP/QPSK/ASK) transceiver baseband is easily implemented into single FPGA chip. Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 20 Proto-Modem Example Multimode by swapping waveform tables / A common detector applies to PSK and PSK-VP

21 5.2 Anti-Multipath Mechanism of PSK-VP No complete cancel in multipath by imposed phase-variation, i.e., survivor somewhere exists. Implicit RAKE / Path-Diversity i) Vector Diagram for Conventional PSK ii) Vector Diagram for PSK-VP Total cancel over the effective area occurs when phase difference approaches. Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 21 No complete cancel over the effective area

22 5.4Structure and Specification for DSRC Basic Structure and Specification Main Specification Downlink (Road to Vehicle) Simultaneous transmission using path-diversity effect of PSK-VP Uplink (Vehicle to Road) cf. ITST2002 Proc., S7-1, pp ITST2002 Proc., S7-2, pp IP Application HTML HTTP TCP IPv4,IPv6 PPP, LAN Site-diversity using bit-error based data-combining scheme Non-IP Application Modified Part ETC Application Sub. Layer (ASL) AID=18 ARIB STD-T75 L7 ARIB STD-T75 L2 ARIB STD-T75 L1 ASK AID=14 QPSK-VP QPSK Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) (Downlink only) 22

23 DSRC International Task Force, Japan 5.5 System Performance Simulation (PSK-VP) Power Spectrum Calculation Result FER (Frame Error Rate) Performance Simulation Results i) Downlink MDC frame: 1576bits payload (=200nsfD=1000Hz corresponds to 180km/h) Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 23 ii) Uplink

24 DSRC International Task Force, Japan 5.6 Field Verification for Continuous Communication without Hand-Off Downlink (Road to Vehicle) Uplink (Vehicle to Road) QPSK (STD-T75) QPSK-VP Error! Error Free QPSK (STD-T75) + Data-Combining Starting Point Error Free Position of Roadside Antenna Position of Roadside Antenna Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 24

25 5.7 Field Verification for Anti-Shadowing Effect RFU2 RFU1 Single Transmission from RFU2 Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 25 Simultaneous Transmission from RFU1&2

26 DSRC International Task Force, Japan 5.7 Filed Verification for Realization of Long Radio Area by Simultaneous Transmission Diversity Level Diversity Vehicle Speed: 120km/h Roadside Antenna Setup BER Simultaneous Transmission from Both Antennas Single Transmission from Upper Antenna from Lower Antenna Upper Lower Error Free About 1km Distance [m] Distance [m] Distance [m] Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 26

27 5.8 Feature of PSK-VP in DSRC Application Applicable to simultaneous transmission in downlink by anti-multipath feature Robust for rapid fading by no adaptation process and highly-maintained symbol-rate Simple structure without large-scale circuit like equalizer or FFT Easy realization of multimode modem by swapping waveform tables / common detector for PSK and PSK-VP Easy extension from existing PSK-based standard of ARIB STD-T75 Full compatible in higher layer Major differences are in Downlink / RSU. (multiple RF units and additional waveform table for PSK-VP) Differences in OBU are minimized. (No change in transmission / A common detector is used for PSK-VP) Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 27

28 6. CONCLUSION New technologies have been studied for the Next generation ITS Radio communications In Japan. Simulation results showed a based OFDM technology has performance problem under high mobility Situation. Field test evaluation has already finished for OFDM and PSK-VP scheme. Sep , VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 28