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Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 1
DSRC International Task Force, Japan
Study on the next generation ITS radio communication in Japan
Contents1. 5.8GHz DSRC in Japan (ARIB STD-T75) 2. Requirements for the next generation ITS radio
communication3. 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.4 2003 DSRC International Task Force, Japan
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 2
DSRC International Task Force, Japan
1.1 Regional standards of DSRC
ItemItem EuropeEurope(CEN)(CEN)
North America (ASTM)
Japan Japan ((ARIB STD-T75)
Radio frequency band
Communication system
Data transmission rate
Duplex
5.8GHz 5.8 - 5.9GHz 5.8GHz
Passive Active
Downlink:500kbpsUplink :250kbps
Half-duplex
Down/Uplink:3 - 27Mbps
Down/Uplink:1 or 4 Mbps
Half-duplexHalf-duplex(OBU)Full-duplex (RSU)
Active
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 3
DSRC International Task Force, Japan
2.1 ITS Standardization in ITU-R“What is the next generation ITS radio communication?”
1994, Question on ITS Recommendations (Answers to the Question)
Rec. ITU-R M. 1310
1996 1997 1998 2000 2001
Objectives& Requirements
Functionalities
Current Useof Spectrum
Traffic & SpectrumRequirements
Technologies
Short-range Radar
VICS(DSRC)
1995
Next generation ITS radio communication
Radio services- Broadcast- DSRC- Short-range radar- Short-range vehicle-to-
vehicle- Short-range continuous- Wide area
Rec. ITU-R M. 1451
Rec. ITU-R M. 1452*Rec. ITU-R M. 14535.8GHz DSRC
ITU-R/SG8/WP8A/WG2:Standardization for ITS
* Rec. ITU-R M. 1453, Revised in 2002.
? ??
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 4
DSRC International Task Force, Japan
2.2 Data transmission rate requirement for the next generation ITS radio communication
Allowabletraveling speed(mobility)
[Km/h]
Information supply-type(high-speed traveling)
Information supply-type(semi-stationary)
Data transmissionrate
100K 1M 10M [bps]
Image of a newportable telephone
20
0
100
180
Convenience store
Filling station
Parking lot
Drive-through
Logistic Management
Connection to Internet (IP)
Video/music distributionPedestrian
support
Information supply-type(high-speed travelling)
On-demand information
Specific region entry
charging
ARIB STD-T75 generally satisfies the requirement except for the very small area shown below.
- high data rate high-speed traveling;
Continuous communication
- Very high data rate semi-stationary;
Broadband ITS Radiocommunication(Resolution RAST 10/7)
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 5
DSRC International Task Force, Japan
2.3 Technical Requirementfor the next generation ITS Radio Communication
1.Area Extension : Spot Area ⇒Continuous or Wide Area
2.High Reliability transmition to High Speed Vehicle in multi-path or/and Shadowing Situation
Shadowing
Delayed wave 1
Direct wave
Delayed wave 2
Multi-pathReceive Level
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 6
DSRC International Task Force, Japan
3.1 Development status in ARIB* for the next generation ITS radio communication
Technology Status Overview of the system CDM (Code Division Multiplexing)
Under Study
802.11a Under Study
OFDM (Orthogonal Frequency Division Multiplexing)
Developped OFDM
Demonstration Finished
PSK-VP (Phase Shift Keying with Varied Phase)
Demonstration Finished
Sum Binary High Speed
data
S/P P/S
Code 1
Code 2
Code N
Binary Low Speed
data
Code 1
Code 2
Code N
Binary High Speed
data
QPSK
Binary high speed data
QPSK
QPSK
QPSK
S/P SUM Transmit
Power
Power
F1
F2
F3
Fn
Power
Power
F1 - Fn Power
Power Symbol
Time
Frequency
F1
Fn
* The road-vehicle communications technology group in the study group for ”Efficient Use of the Radio Spectrum for ITS”
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 7
DSRC International Task Force, Japan
3.2 Countermeasures to Multi-path fading
Delayed wave 1
Direct wave
Delayed wave 2
Multi-path fading
AvailableTechnology
Features
CDM - RAKE / Path-Diversity- Low Inter-Symbol Interference (Low symbol rate)
OFDM - Low Inter-symbol Interference (Low symbol rate)- Guard interval to reduce Inter Symbol and InterCarrier Interference
PSK-VP - Implicit RAKE / Path-Diversity
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 8
DSRC International Task Force, Japan
3.3 Countermeasures to Shadowing
Shadowing
f1
f1
f1 f1
×
×
f1
f1
f1
f1
f1 f1
×
×
f1 f1
×
×
Avoidance of shadowing by reception from multiple Antennas
Technologies to realize reception from multiple antennas
Available Technology
Features
CDM RAKE / Path-Diversity*
Developped OFDM
Guard interval to reduce Inter Symbol Interference / Path-Diversity*
PSK-VP Implicit RAKE / Path-Diversity* * ; Features to achieve continuous communication
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 9
DSRC International Task Force, Japan
4. Modulation scheme and features of OFDM
Q PSK
Binary high speed data
Q PSK
Q PSK
Q PSK
S/P SUM Transm it
Power
Power
F1
F2
F3
Fn
Power
Power
F1 - Fn Power
Power Symbol
Time
Frequency
F1
Fn
- Concept of OFDM modulation scheme
- Anti-Multipath mechanism of OFDM
Guard interval
Direct wave Delayed wave
Direct wave
Delayed wave
Symbol A Symbol B Symbol C
Symbol A Symbol B Symbol C
Delay time Reduced ISI and ICI Guard interval
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)
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 10
DSRC International Task Force, Japan
4.1 Specification of 802.11a based OFDM
Item 802.11a 802.11a/RA Std. Body IEEE ASTM Freq. Band 5 GHz band
5.15–5.35 GHz 5.725–5.825 GHz
5.9 GHz band 5.850-5.925 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?
Spectrum mask - Severe than 11a TxPWR_level 1 - 8 1 - 64
Others
Adjacent ch Rej - Severe than 11a
* depends on environment condition and data rate.
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 11
DSRC International Task Force, Japan
4.1.1 BER Simulation Results for 802.11a(Line Of Site model ,16QAM)
10-6
10-5
10-4
10-3
10-2
10-1
100
0 5 10 15 20 25 30 35 40
fd=100Hzfd=200Hzfd=300Hzfd=400Hzfd=500Hz
Average Eb/N0 [dB]
10-6
10-5
10-4
10-3
10-2
10-1
100
0 5 10 15 20 25 30 35 40
fd=100Hzfd=200Hzfd=300Hzfd=400Hzfd=500Hz
Average Eb/N0 [dB]
Rice K=5dB Delay Spread :10ns
Fd = 100Hz : 18km/h
Fd = 200He :36km/h
Fd = 300Hz :54km/h
Fd = 400Hz :72km/h
Fd = 500Hz :90km/h
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 12
DSRC International Task Force, Japan
4.1.2 BER Simulation Results for 802.11a(Line Of Site model ,QPSK)
Rice K=5dB Delay Spread :10ns
10-6
10-5
10-4
10-3
10-2
10-1
100
0 5 10 15 20 25 30 35 40
fd=100Hzfd=200Hzfd=300Hzfd=400Hzfd=500Hz
Average Eb/N0 [dB]
10- 6
10- 5
10- 4
10- 3
10- 2
10- 1
100
0 5 10 15 20 25 30 35 40
fd=100Hzfd=200Hzfd=300Hzfd=400Hzfd=500Hz
Average Eb/N0 [dB]Fd = 100Hz : 18km/h
Fd = 200He :36km/h
Fd = 300Hz :54km/h
Fd = 400Hz :72km/h
Fd = 500Hz :90km/h
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 13
DSRC International Task Force, Japan
4.1.3 BER Simulation Results for 802.11a(Non-Line Of Site model ,16QAM)
Delay Spread :50ns
10-6
10-5
10-4
10-3
10-2
10-1
100
0 5 10 15 20 25 30 35 40
fd=100Hzfd=200Hzfd=300Hz
Average Eb/N0 [dB]
Delay Spread :100ns
10-6
10-5
10-4
10-3
10-2
10-1
100
0 5 10 15 20 25 30 35 40
fd=100Hzfd=200Hzfd=300Hz
Average Eb/N0 [dB]
Fd = 100Hz : 18km/h
Fd = 200He :36km/h
Fd = 300Hz :54km/h
Fd = 400Hz :72km/h
Fd = 500Hz :90km/h
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 14
DSRC International Task Force, Japan
4.1.4 BER Simulation Results for 802.11a(Non-Line Of Site model ,QPSK)
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+0010 15 20 25 30 35 40
平均Eb/No[dB]
BER
100Hz400Hz800Hz1000Hz
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+0010 15 20 25 30 35 40
平均Eb/No[dB]
BER
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+0010 15 20 25 30 35 40
平均Eb/No[dB]
BER
(a)σ:10ns
(b)σ:50ns (c)σ:100ns
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 15
DSRC International Task Force, Japan
4.2 Features of Developed OFDM systems
Items Model system A Communication area 10mx300mxn
Radio zone size 10mx(30m-60m) Handover distance 300m Channel separation 5MHz
Radio transmission rate (Up / Down) 3.253Mbps Modulation OFDM-DQPSK
Error correction RS(31,19) RSE TX power 200mW OBE TX power 10mW
- Parameters of the system
- Comparison with IEEE 802.11a
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 carriersNote;RLAN devices are generallynot designed to be used at automotive or higher speeds.
Items Model system A
IEEEE 802.11a
Access method TDMA/FDD CSMA/CA Modulation DQPSK BPSK,QPSK,16QAM,
64QAM Symbol length 15.625µs 3.2µs Guard interval 1/16 1/4
Guard time 0.98µs 0.8µs Subcarrier spacing 64kHz 312.5kHz
Number of subcarrier 27 52(With 4 pilot carriers) Bandwidth per channel 1728kHz About 17MHz
Error collection RS(31,19) Convolutional coding(R=1/2,2/3,3/4)
Interleave Within slot Within symbol Number of subcarrier division 2
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 16
DSRC International Task Force, Japan
4.2.1 System performance simulation (Developed OFDM systems)
- Error rate under Rice (k=6dB) type multipath interference, after error correction
Delay difference=122ns Delay difference=488ns
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
- Power spectrum(6dB Back-off, Class AB)
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 17
DSRC International Task Force, Japan
4.2.2 Hand-over on Single radio frequency by dividing the subcarrier (Developed OFDM systems)
Mechanism of high speed hand-over 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)
Channel No.1 Channel No.2
f
Divide subcarrier into two groups
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 18
DSRC International Task Force, Japan
4.2.3 An example of seamless hand-over (Developed OFDM systems)
Channel No.1 Channel No.2
f
Dividing the subcarrier into two groups
RSE Antenna
- RSE Communication range: 30m- RSE Antenna height: 10m
A C
BB
RSE1 RSE 2 RSE 3 RSE 4
Divided Channel No.1
Divided Channel No.2
B
C C
D
Frequency
Error free during hand-offs
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 19
DSRC International Task Force, Japan
-110.0
-90.0
-70.0
-50.0
-30.0
-10.0
10.0
30.0
Distance[m]
RX L
eve
l[dB
m]
BE
R
1
10-5
10-10
-500 -375 -250 -125 0
RSE1 RSE2 RSE3 RSE4
RSE1 RSE 2 RSE 3 RSE 4
Vehicle Speed: 120km/h
4.2.4 An example of Continuous Communication (Developed OFDM systems)
RSE Antenna
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 20
DSRC International Task Force, Japan
5.1 PSK-VP Modulation Scheme
cf. IEEE Trans. VT-42, No.4, pp. 625-640IEEE Trans. VT-42, No.2, pp. 177-185ITST2001 Proc., S3-3, pp. 625―639
◆ Concept of PSK-VP (Phase Shift Keying with Varied Phase)
◆ Configuration
An anti-multipath scheme by imposing phase-variation on the symbol of PSK
θ: Information Phase-Shift φ(t): Imposed Phase-Variation
ROMD/A
Ex. QPSK ⇒ QPSK-VPVary Phase
D
LPFTXdata
RXdata
Diff. Det.
φ(t)θ
Symbolactually
D/A
conceptually
Chirp Sig.Generator
CoderDiff.
Proto-Modem Example
Triple mode (QPSK-VP/QPSK/ASK)transceiver baseband is easily
implemented into single FPGA chip.
Multimode by swapping waveform tables / A common detector applies to PSK and PSK-VP
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 21
DSRC International Task Force, Japan
5.2 Anti-Multipath Mechanism of PSK-VP
Phase of1st. Wave
Phase of2nd. Wave
τ0
π
π+αα
RX Signal
α
Effective Area
Phase of1st. Wave
Phase of2nd. Wave
RX Signal
τ0
π
π+αα
RX Signal
α
RX Signal
Effective Area
NG
OK1st.Wave
2nd.Wave2nd.
Wave
1st.Wave
2nd.Wave
1st.Wave
2nd.Wave
1st.Wave
NGOK
i) Vector Diagram for Conventional PSK ii) Vector Diagram for PSK-VP
Total cancel over the effective area occurswhen phase difference α approaches π. No complete cancel over the effective area
No complete cancel in multipath by imposed phase-variation,i.e., survivor somewhere exists. ⇒ Implicit RAKE / Path-Diversity
×Error due toinherent multipath
PSK
○No errorby utilizing anti-multipath feature
PSK-VP
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 22
DSRC International Task Force, Japan
5.4 Structure and Specification for DSRC
◇ Downlink (Road to Vehicle)
◇ Uplink (Vehicle to Road)
Simultaneous transmissionusing path-diversity effect of PSK-VP
Site-diversity using bit-error baseddata-combining scheme
DET DET DET
RX data
TX data
������
�������
����
�����
RFU RFU RFU BSU-1 -2 -n
QPSK-VPModulator
CombinerData-
DET
MODQPSK
Coder
CRC
BCHor
OBU
TXdata
RXdata
◆ Basic Structure and Specification
Main Specification
Channel Spacing 5MHzDownlink π/4-QPSK-VP (3.072Mbps)
Uplink π/4-QPSK (4.096Mbps)+BCH(63,51)
Radio Area Size typ. 30~50m×n
+ ARIB STD-T75 Higher Layer
in conformity to ARIB STD-T75
cf. ITST2002 Proc.,
S7-1, pp.233―237ITST2002 Proc.,
S7-2, pp.239―244
← QPSK
ARIB STD-T75 L2ARIB STD-T75 L7
Modified Part
Application Sub. Layer(ASL) AID=18 AID=14
ETCNon-IPApplicationPPP, LAN
IPv4,IPv6TCP
HTTPHTML
IPApplication
ASKQPSK-VPARIB STD-T75 L1
(Downlink only)
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 23
DSRC International Task Force, Japan
5.5 System Performance Simulation (PSK-VP)
100
10
1
0.1
0.01
without data combining
with data combining
MDCACTCACKC
MDCACTCACKC
FER
[%
]
π/4-QPSK(4.096Mbps)fD=800Hz
Eb/No [dB]5 10 15 20 25 30 35
100100
10
1
0.1
0.01
without data combining
with data combining
MDCACTCACKC
MDCACTCACKC
FER
[%
]
π/4-QPSK(4.096Mbps)fD=800Hz
Eb/No [dB]5 10 15 20 25 30 35
100
1.0E-03
1.0E-02
1.0E-01
1.0E+00
10 20 30 40Eb/No (dB)
FER
(%)
fD=1000Hz
fD=800Hz
fD=400Hz
fD=100Hz
fD=1000Hz
fD=800Hz
fD=400Hz ____
fD=100Hz
fD=800Hz, Exp.
fD=400Hz, Exp.
fD=100Hz, Exp.
10
100
1
0.1
QPSKwith BCH
QPSK-VPw/o FEC
QPSK-VP
QPSK
(τ=200ns,fD=1000Hz corresponds to 180km/h)
◆ FER (Frame Error Rate)Performance Simulation Results
i) Downlink
MDC frame: 1576bits payload
ii) Uplink
◆ Power Spectrum Calculation Result
QPSK-VP 3Mbps( Class-AB )
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
-15 -10 -5 0 5 10 15
Frequency (MHz)
Pow
er
Spe
ctr
um
Densi
ty (
dB)
OBO=2dB
OBO=3dB
OBO=4dB
OBO=5dB
OBO=6dB
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 24
DSRC International Task Force, Japan
5.6 Field Verification for Continuous Communicationwithout Hand-Off
◇ Downlink (Road to Vehicle) ◇ Uplink (Vehicle to Road)
▲: Position of Roadside Antenna
-90
-70
-50
-30
-10
10
30
50
Distance(m)
Rx
Lev
el(dB
m) B
ER
B
ER
187.5 250.00.0 62.5 125.0
1
10-5
10-10
1
10-5
10-10
Error Free
Error !
QPSK-VP
QPSK (STD-T75)
1.3E+02
1
10-10
10-5
誤り
率
×:アンテナ位置測定開始ポイント
Error FreeBER
▲: Position of Roadside Antenna
Starting Point
QPSK (STD-T75) + Data-Combining
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 25
DSRC International Task Force, Japan
5.7 Field Verification for Anti-Shadowing Effect
1.2m
40m62m
13.0°RFU2
13.0°
大型トラック
55m
4.9m 7.1m
11.0m
0.7m
RFU1
1.2m
40m62m
13.0°
Start Point
13.0°
Large Truck
55m
4.9m 7.1m
11.0m
0.7m
End Point
Traveling Line of Right Side of Large Truck
Traveling Direction
OBU Antenna PositionObstacle (Truck)
Vehicle with OBU
Roadside Antenna
-100
-80
-60
-40
0 5 10 15測定経過時間(秒)
RX L
eve
l [d
Bm
]B
ER 1
10-5
10-10
Shadowing area
Time [s]
-100
-80
-60
-40
0 5 10 15
1
10-5
10-10
Shadowing area
Time [s]
RX L
eve
l [d
Bm
]B
ER
RFU1RFU2
◇ Single Transmission from RFU2 ◇ Simultaneous Transmission from RFU1&2
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 26
DSRC International Task Force, Japan
国総研 ロング ダイバー/上/下 変調VP DL 100Km 真中 DL直結 アンテナ前向き 方位角1°俯角1° アンテナ位置3cm前+下
-100.0
-90.0
-80.0
-70.0
-60.0
-50.0
-40.0
-1400 -1200 -1000 -800 -600 -400 -200 0 200
距離 [m]
受信
レベ
ル
ダイバー上のみ下のみ
5.7 Filed Verification for Realization of Long Radio Areaby Simultaneous Transmission Diversity
国総研 ロング(RFU3のみ) 変調VP DL 100Km 真中 DL直結 アンテナ前向き 方位角1°俯角1° アンテナ位置3cm前+下
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
-1400 -1200 -1000 -800 -600 -400 -200 0 200距離 [m]
B
BER
◇ Single Transmission
◇ SimultaneousTransmission
from Upper Antenna
from Lower Antenna
from Both Antennas
国総研 ロング(RFU4のみ) 変調VP DL 100Km 真中 DL直結 アンテナ前向き 方位角1°俯角1° アンテナ位置3cm前+下
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
-1400 -1200 -1000 -800 -600 -400 -200 0 200距離 [m]
B
BER
Distance [m]
Distance [m]
Roadside Antenna Setup国総研 ロング(ダイバー) 変調VP DL 100Km 真中 DL直結 アンテナ前向き 方位角1°俯角1° アンテナ位置3cm前
+下
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
-1400 -1200 -1000 -800 -600 -400 -200 0 200距離 [m]
BE
BER
Distance [m]
Error Free
About 1km
Level
BER
Vehicle Speed: 120km/hDiversity
LowerUpper
Sep 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 27
DSRC International Task Force, Japan
5.8 Feature of PSK-VP in DSRC Application
◆ Simple structure without large-scale circuit like equalizer or FFT
◆ Applicable to simultaneous transmissionin downlink by anti-multipath feature
◆ Robust for rapid fadingby no adaptation process and highly-maintained symbol-rate
◆ Easy extension from existing PSK-based standard of ARIB STD-T75
◆ Easy realization of multimode modem by swapping waveform tables / common detector for PSK and PSK-VP
・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 4 2003, VSC Session5-4-1 Communication for Vehicle Safety (Field Test) 28
DSRC International Task Force, Japan
6. CONCLUSION
◆ Simulation results showed“802.11a based OFDM technology has performance problem
under high mobility Situation”.
◆ New technologies have been studiedfor the Next generation ITS Radio communications In Japan.
◆ Field test evaluation has already finishedfor OFDM and PSK-VP scheme.
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