January 2013 doc.: IEEE 802.11-13/0153r0 May 2013 Coexistence issues between 802.11p and 802.11ac in the proposed UNII-4 band Authors: Date: 2013-06-14 Jim Lansford (CSR Technology), John Kenney (Toyota ITC) Clint Chaplin, Chair (Samsung)

January 2013 doc.: IEEE 802.11-13/0153r0 May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC) Clint Chaplin, Chair (Samsung)

Overview DSRC was designed for the 5.9GHz ITS band May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

Non-Safety Applications May 2013 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 IEEE 802.2 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 J2735 SAE J2945 IETF RFC 793/768 Transport Layer –TCP/UDP Network Layer – IPv6 IEEE 1609.2 Security Services Message Sublayer DSRC/WAVE Protocol Stack Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

802.11p overview (2) DSRC Use Cases May 2013 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

DSRC Spectrum May 2013 Shared Public Safety /Private Service Designated Public Safety Control Channel Medium Range Service Short Range Service V2V and Safety of Life Long Range Intersections Power Limits (dBm EIRP) 44.8 44.8 dBm 40.0 Public limit Private limit 40 dBm 33.0 33 dBm 23.0 23 dBm Frequency(GHz) 5.850 5.855 5.865 5.875 5.885 5.895 5.905 5.915 5.925 Ch 172 BSMs Ch 174 Ch 176 Ch 178 CCH Ch 180 Ch 182 Ch 184 Public Safety Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

DSRC Middle Layers Standardized by IEEE 1609 WG IEEE 1609.2 – Security May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

DSRC Traffic Types Communication at MAC sub-layer can be: May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

DSRC Device/Vehicle Types May 2013 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) Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

802.11p PPDU Structure Same as 802.11a, but twice the length May 2013 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

802.11ac Coexistence Mechanisms May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

802.11p techniques Transmit an “intolerance” bit May 2013 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? Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

Conclusion Both 802.11ac and 802.11p are baked May 2013 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 Jim Lansford (CSR Technology), John Kenney (Toyota ITC)

References [1] ETSI DSRC standard May 2013 References [1] ETSI DSRC standard http://www.etsi.org/deliver/etsi_en/302600_302699/302663/01.02.00_20/en_302663v010200a.pdf [2] Perahia and Stacey presentation on 11ac at Globecom http://www.ieee-globecom.org/2012/private/T3M.pdf [3] Minyoung’s paper on dynamic channel access in 11ac http://202.194.20.8/proc/ICC2011/DATA/03-063-02.PDF Jim Lansford (CSR Technology), John Kenney (Toyota ITC)