Doc.: IEEE 802.11-13/0552r0 Submission Coexistence issues between 802.11p and 802.11ac in the proposed UNII-4 band Date: 2013-06-14 May 2013 Slide 1 Authors:

doc.: IEEE 802.11-13/0552r0

Submission

Coexistence issues between 802.11p and 802.11ac in the proposed UNII-4 band

Date: 2013-06-14

May 2013

Slide 1

Authors:

Name Company Address Phone email

Jim Lansford CSR Technology 100 Stirrup Cir, Florissant, Colorado 80816

+1-719-286-9277 [email protected]

John Kenney Toyota InfoTechnology Center, USA

465 Bernardo Avenue, Mountain View, CA

+1 650-694-4160 [email protected]

Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

May 2013

Jim Lansford (CSR Technology), John Kenney (Toyota ITC)Slide 2

Abstract

Discussion of possible coexistence techniques between 802.11p

(DSRC/WAVE) and 802.11ac extended into the proposed UNII-4 band

Disclaimer: This presentation is for discussion purposes only, and does not represent the official position of the presenters’ employers or any industry group

doc.: IEEE 802.11-13/0552r0

Submission

Overview• DSRC was designed for the 5.9GHz ITS band

– Licensed under FCC Part 90 and 95– Uses “communication outside the context of a BSS” defined in 802.11p– No coexistence mechanism with commercial 802.11 (≥ 20 MHz channels)– FCC designates certain channels, e.g. V2V safety, control, public safety

• 802.11ac was designed with coexistence mechanisms for mixed 20/40/80/dual 80/160 environments

• In NPRM 13-22, the FCC has proposed spectrum sharing between the 5.9GHz ITS band and unlicensed technologies such as 802.11ac

– This will be called the “UNII-4” band

– DSRC devices are “Primary”; DSRC and U-NII are not peers

• Since 802.11p and 802.11ac are both from the 802.11 family and have similarities, band sharing might be simpler than with non-802.11 incumbent technologies (e.g. radar)

– DSRC would take precedence in any band sharing proposal

May 2013

Slide 3 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

802.11p overview (1)• Based on 802.11a (and 802.11j)

– Uses 10 MHz channel option defined with 802.11j (½ clocked from 20 MHz)

– Tighter spectral mask– Slightly different MAC (1609.x

enhancements)– So it’s NOT just a minor tweak to

802.11g/n/ac– Differences in layers above PHY and

MAC as well• Special FCC channel designations:

– Ch. 172 is for vehicle collision avoidance communication

– Ch.178 is the control channel– Ch. 184 is for long distance public

safety communication

• Europe: Similar band/channelization• Japan: Uses 11p PHY in 700 MHz,

but higher layers quite different.

IEEE 1609.3

Non-Safety Applications

IETF RFC 2460

Safety Applications

IEEE802.2

PHY Layer

MAC Sublayer

MAC Sublayer Extension

LLC Sublayer

Application Layer

Network and Transport Layers - WSMP

Safety App. Sublayer

IEEE 802.11p

IEEE 1609.4

SAE J2735SAE J2945

IETF RFC 793/768

Transport Layer –

TCP/UDP

Network Layer –

IPv6

IEEE 1609.2

Security Services

Message Sublayer

DSRC/WAVE Protocol Stack

May 2013

Slide 4 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

802.11p overview (2)May 2013

Slide 5 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

DSRC Use Cases

doc.: IEEE 802.11-13/0552r0

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DSRC Spectrum

May 2013

Jim Lansford (CSR Technology), John Kenney (Toyota ITC)Slide 6

Frequency(GHz)

Ch 172BSMs

Ch 174 Ch 176 Ch 180 Ch 184Public Safety

Ch 182Ch 178CCH

Long Range

Intersections

Control

Channel

Designated Public Safety

Short Range

Service

Shared Public Safety /Private Service

40 dBm

33 dBm

23 dBm

40.0

33.0

23.0

44.8 dBm

Public limit

Private limit

Medium Range

Service

V2V and

Safety of Life

44.8

5.85

0

5.85

5

5.86

5

5.87

5

5.88

5

5.89

5

5.90

5

5.91

5

5.92

5

Power Limits (dBm EIRP)

doc.: IEEE 802.11-13/0552r0

Submission

DSRC Middle Layers

• Standardized by IEEE 1609 WG

• IEEE 1609.2 – Security– Defines authentication and encryption algorithms, data structures

• IEEE 1609.3 – Networking Services– Defines WAVE Short Message Protocol (WSMP) – lightweight

alternative to UDP/IP

– Defines WAVE Service Advertisement (WSA) – sent on CCH to advertise services in an area

• IEEE 1609.4 – Multi-Channel Operation– Defines time-division for rendezvous on CCH

May 2013

Slide 7 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

DSRC Traffic Types

• Communication at MAC sub-layer can be:– Unicast or Broadcast

– Single hop or multi-hop

• SAE standards define message formats and application requirements

• SAE J2735 DSRC Message Set Dictionary– Basic Safety Message

– 14 other message types

• SAE J2945 DSRC Minimum Performance Requirements– Data element accuracy and age (vehicle sensors)

– Transmission behavior (message frequency, modulation, Tx power)

– Protocol dialogues

May 2013

Slide 8 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

DSRC Device/Vehicle Types

• Light Vehicle

– Factory integrated (rich sensor data)

– “Aftermarket Safety Device” (ASD, usually relies on GPS)

– “Vehicle Awareness Device” (VAD, Tx only, full CSMA/CA MAC)

• Emergency Vehicle

– Police, Fire, Ambulance – special Tx permissions

• Commercial

• Transit

• Tracked (train, including light rail)

• Motorcycle

• Vulnerable Road User (road worker, pedestrian, bicycle)

May 2013

Slide 9 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

802.11p PPDU StructureMay 2013

Slide 10

Same as 802.11a, but twice the length

Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

802.11ac Coexistence Mechanisms

• This figure above from [2] illustrates how 20MHz systems can do CCA

• The figure below from [3] shows how an 80MHz system does CCA on multiple 20MHz preambles

May 2013

Slide 11 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

801.11ac techniques• 802.11ac in the UNII-4 band detects 802.11p preambles during

CCA– Pros:

• Leverages existing primary/secondary-n CCA

• 802.11p/DSRC doesn’t have to do anything

• Better solution than energy detection– False alarms from energy detection are very undesirable

– Cons:• Preambles of 802.11p are twice as long as 11a/n

• High power channels (178 and 184) will possibly cause adjacent and alternate channel interference that CCA may not detect

– After detection, what?• Channel transition interval

• Non-occupancy interval

May 2013

Slide 12 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

802.11p techniques

• Transmit an “intolerance” bit– No particular advantage – 11ac would have to be able to process

11p frames to do this, so 11ac might as well do CCA

• Use of Service Channels in the upper part of the band (Ch 180/182) first– Doesn’t solve channel 172 problem

• Others?

May 2013

Slide 13 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

Other issues• There has been some discussion about moving the collision

avoidance channel (CH 172) to the upper part of the band– Puts two high powered signals in adjacent channels

– Major change to existing DSRC channel definition

– Requires significant re-testing of DSRC safety functions

• The good news: If 802.11p and 802.11ac share a band, it creates the opportunity for a single chipset/module with collaborative coexistence like 802.11 – Bluetooth (adaptive frequencies and packet traffic arbitration)– Between adaptive frequency hopping and PTA, 802.11-Bluetooth coexistence

is pretty good

– 802.11p and 802.11ac aren’t equal in regulatory, so arbitration rules would be different

May 2013

Slide 14 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

Conclusion• Both 802.11ac and 802.11p are baked

– 802.11p wasn’t designed for band sharing– 802.11ac can’t process 10MHz channels

• 802.11p is the primary user in the band– Puts the burden on 802.11ac to adapt for sharing– 802.11ac has to protect 802.11p traffic

• 10MHz CCA in 802.11ac is one way forward– Double length preamble– Up to 7 possible channels to monitor– Adjacent/alternate channels are problematic

• NPRM process is rolling– Industry must come to consensus soon

May 2013

Slide 15 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

doc.: IEEE 802.11-13/0552r0

Submission

References

[1] ETSI DSRC standardhttp://www.etsi.org/deliver/etsi_en/302600_302699/302663/01.02.00_20/en_302663v010200a.pdf

[2] Perahia and Stacey presentation on 11ac at Globecomhttp://www.ieee-globecom.org/2012/private/T3M.pdf

[3] Minyoung’s paper on dynamic channel access in 11achttp://202.194.20.8/proc/ICC2011/DATA/03-063-02.PDF

May 2013

Slide 16 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)