Potential DSRC Interference and some CV...

FLORIDA DEPARTMENT OF TRANSPORTATION

ITS CENTRAL OFFICE

Potential DSRC Interference and some CV updates

Presented at the 2013 Transportation Hazards and Security Summit and Peer Exchange,

AASHTO Special Committee Meeting on Wireless Communications Technology

August 19-23, 2013

Presented by Brian Kopp FDOT Telecommunications General Consulting Team

Cell Phone: 904-206-3453 Email: [email protected]


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• DEFINITIONS (so I don’t owe Randy money) – DSRC-Dedicated Short Range Communications: protocols and

dedicated spectrum (primarily 5.9GHz in the US) for vehicle communications

– CV-Connected Vehicle: Vehicle to Vehicle V2V and Vehicle to Infrastructure V2I communications

– V2V + V2I +I2V = “V2X” Concepts

• DSRC is one proposed way to implement CV • NHTSA - National Highway Transportation Safety

Administration: currently conducting a safety pilot that may result in DSRC being required in new cars (or not)


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• DSRC Status – 75 MHz (5.875-5.950 GHz) allocated by FCC in 1999 – FCC rules in place: Part 90, Subpart M and Part 95, Subpart L

• FCC rules for DSRC are tied to ASTM protocol!

– Protocols have been developed and are actively supported • American Society of Testing (ASTM), ASTM E2213-03 2003 • Institute of Electrical and Electronic Engineers (IEEE), 802.11-2012 • Society of Automotive Engineers (SAE), J2735 for message dictionary

– Infrastructure and Aftermarket Vehicle Products Available – NHTSA safety pilot implemented DSRC on 3000 vehicles around

Ann Arbor Michigan. Test is currently ongoing • OnBoard Units (OBUs) from DENSO, Cohda, and Savari and RoadSide

Units (RSUs) from Savari and Arada

– European and Japanese large-scale tests/implementations are also ongoing


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• DSRC Status: Products available from Savari, Arada, Cohda, DENSO, DGE, etc.


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• DSRC Status: Vehicle Manufacturers are not “OnBoard” – Vehicle manufacturers have not initiated DSRC Factory

installations as of 2014 model year – Vehicle manufacturers are implementing CV using 3G/4G LTE – In the US, Verizon (with BMW, Honda, Hyundai, Kia, and

Toyota) and AT&T (with GM) have formed alliances with Vehicle Manufacturers to implement internet connectivity in-vehicle

– LTE chipsets for vehicles: Qualcomm Gobi in the 2014 Audi A3 – Vehicle manufacturers are forming alliances to help application

developers for smart phones more easily interface with multiple proprietary interfaces (Peugeot, BMW, Volvo, Toyota, GM)


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• July 2013 Roadway Weather Management Stakeholder Conference (26 State DOTs, FHWA, USDOT, RITA Research and Innovative Technology Administration)

• Ongoing CV projects discussed • Nevada DOT, Michigan DOT (Not FHTSA Ann Arbor

Safety Pilot), Minnesota DOT, New York DOT • All projects focused on integrated mobile observations of

DOT vehicle telemetry and proximate environmental data

• Only NY DOT project is using DSRC. Others are using cellular modems and/or data radio (Nevada DOT tried state 800 MHz EDACS system but too slow)


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• February 20, 2013 FCC NPRM: – “Revision of Part 15 of the Commission’s Rules to Permit

Unlicensed National Information Infrastructure (U-NII) Devices in the 5 GHz Band”

• FCC wants to clarify existing rules and also add 195 MHz of spectrum to unlicensed broadband

• The problem for DSRC is that 75 MHz of the additional broadband spectrum would overlap with DSRC spectrum


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• FCC Proposed Spectrum Change


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• FCC proposal would share spectrum between U-NII and DSRC

• FCC proposes using U-NII-3 band rules in new U-NII-4 band (5.850-5.925 GHz) – 36 dBm (4 Watts) EIRP for Omni U-NII-4 users – 53 dBm (200 Watts) EIRP for Directional U-NII-4 users

• DSRC power limits are – Public safety RSUs limited to 44.8 dBm (30 Watts) EIRP – Private RSUs limited to 33 dBm (2 Watts) EIRP – Public safety mobile OBUs limited to 40 dBm (10 Watts) EIRP* – Private mobile OBUs limited to 33 dBm (2 Watts) EIRP* – Portable OBU limited to 0 dBm (0.001 Watts) EIRP

* Operational power limits also depend on range classification


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• DSRC Channels based on 802.11a (By FCC Rule) – EQ: 5 GHz + Channel Number * 5MHz = Channel Center Frequency

• CH 172: Basic Safety Messages (BSMs) are sent via a High-

Availability Low Latency (HALL) Channel • CH 184: Safety-of-life messages from public safety vehicles are sent

via a high-power channel • CH 178: Control channel gives direction regarding which services

are on which channels


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• U-NII Bands are NOT Channelized by FCC rule – Users must occupy at least 500 kHz of bandwidth – Many 5GHz equipment vendors use proprietary protocols for

Point to Point (PtP) operation

• 802.11 has channels and multiple bandwidth rules • Current 802.11n standard bonds as much as 40 MHz/CH • Draft 802.11ac standard will bond as much as 160 MHz

144

140

136

132

128

124

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116

112

108

104

100

165

161

157

153

149

64

60

56

52

48

44

40

36 IEEE channel #

20 MHz 40 MHz 80 MHz

160 MHz

UNII-1 UNII-2 UNII-2 UNII-3

5250 MHz

5350 MHz

5470 MHz

5725 MHz

NEW

96

92

88

84

80

76

72

68

169

173

177

181

5825 MHz

5925 MHz

NEW

Currently available channels

New channels


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• 802.11n Capability


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• 802.11ac Capability


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• What the FCC “sharing” would look like with 802.11

5850

DSRC[10 MHz]Service

Chan 184

DSRC[10 MHz]Service

Chan 182

DSRC[10 MHz]Service

Chan 180

DSRC[10 MHz]Control

Chan 178

DSRC[10 MHz]Service

Chan 176

DSRC[10 MHz] Service

Chan 172

DSRC[10 MHz] Service

Chan 174Res.

5840

5855

5860

5865

5870

5875

5880

5885

5890

5895

5900

5905

5910

5915

5920

5925

5845

Exp. UNII[160 MHz]

Center Chan 163

Exp. U-NII-4[40 MHz]

Center Chan 175


Center Chan 167


Center Chan 177


Cente Chan 173


Center Chan169


Center Chan 181

5850

5840

5855

5860

5865

5870

5875

5880

5885

5890

5895

5900

5905

5910

5915

5920

5925

5845

Frequency(MHz)

Frequency(MHz)

DSRC Band[10 MHz Channels]

ProposedU-NII-4 Expansion[20 MHz Channels]


ProposedU-NII-4 Expansion

[160 MHz Channels]


Center Chan 171



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• What the DSRC interference from WiFi might look like: – Assume BSM with 12Mbps, 16 QAM OFDM – DSRC specs requires minimum receiver sensitivity of -77dBm – Assume receiver minimum performance SNR of 20 dB – In an ideal channel without interference the noise floor would

need to be below -77dBm - 20 dB = -97 dBm to permit reception of a -77 dBm BSM signal

– Assume interference signal is flat in the 10 MHz of channel 172. – The interference signal would need to come within about 3 dB

below the noise floor to cause an impact. The interference signal need only be greater than -100dBm in the 10 MHz DSRC channel to potentially cause interference.

– Remember the interference problem is usually additive. Multiple U-NII users will be uncorrelated and will have an additive effect, aka “the cocktail party problem”


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• So for the proposed U-NII-4 users recall: – 36 dBm (4 Watts) EIRP for Omni U-NII-4 users – 53 dBm (200 Watts) EIRP for Directional U-NII-4 users

• An Omni U-NII-4 user occupying 40 MHz of overlapping bandwidth could present 30 dBm in the same channel as a DSRC safety message.

• Such a user would be transmitting 130 dB above the interference threshold.

• Considering only free-space path loss would require a “sharing” distance of 8 miles to avoid interference

• A similar calculation for directional 200 Watt EIRP U-NII-4 users would require a sharing distance of 50 miles


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• Why does this interference issue matter? • Consider some “sharing” scenarios


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• More “sharing” scenarios


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• More “sharing” scenarios – 36 dBm U-NII user at 3 meters (ground floor) and then at 30

meters (10th floor). Note the interference along ten miles of I-264


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• Conclusions – The FCC proposal in its current form would be very problematic

for DSRC – AASHTO and many other stakeholders filed comments and reply

comments in the NPRM recommending the FCC investigate the challenges and issues associated with sharing in the U-NII-4 band BEFORE making any decision.

Potential DSRC Interference and some CV...

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