Transcript 802.11p

802.11 Enhancements and
Applications
802.11p, 802.11r, 802.11s,
802.11y
802.11p
802.11p
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“Dedicated Short Range Communications” (DSRC)
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Started in IEEE 1609, spun into 802.11p
Aka (WAVE) Wireless Access for Vehicular Environment
Goal
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Telematics (collision avoidance a big driver)
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54 Mbps, <50 ms latency
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Roadside-to-vehicle
Vehicle-to-vehicle environments
Possible competitor to cellular
Operates in 5.850 to 5.925GHz band
Draft under ballot
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Projected for March 2009
Broader Context
• 802.11p part of several standards which
will jointly enable widescale telematics
Intelligent Transportation Systems
doc.: IEEE 802.11-07/2045r0
802.11p Applications
• Applications
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Emergency warning system for vehicles
Cooperative Adaptive Cruise Control
Cooperative Forward Collision Warning
Intersection collision avoidance
Approaching emergency vehicle warning (Blue Waves)
Vehicle safety inspection
Transit or emergency vehicle signal priority
Electronic parking payments
Commercial vehicle clearance and safety inspections
In-vehicle signing
Rollover warning
Probe data collection
Highway-rail intersection warning
Example Application
COLLISION
IMMINENT
FRONT
COLLISION
In-Vehicle
Displays and
Annunciations
IMMINENT
LEFT
Note 1: The OBU in the vehicle recognizing the threat
transmits a WARNING and COLLISION PREPARATION
MESSAGE with the location address of the threat vehicle.
Note 2: Only the OBU in the threatening vehicle processes
the message because only it matches the threat address.
Note 3: COLLISION PREPARATION includes seat belt
tightening, side air bag deployment, side bumper
expansion, etc.
Car NOT Stopping
Radar Threat Identification
Traffic Signal
Traffic Signal
OBUs on Control Ch
From: IEEE 802.11- 04/ 0121r0
Available: http://www.npstc.org/meetings/Cash%20WAVE%20Information%20for%205.9%20GHz%20061404.pdf
Operation
• Spectrum divided into 7
bands
– 178 is control (safety)
– 2 edge channels are
reserved for future
– The rest are service
channels (not application
specific)
• IEEE 802.11a adjusted for
low overhead operations
Safety Messages
•Control Messaging
characteristics
–Most messages are single hop
–Some broadcasting (e.g.,
forwarding hazard warnings)
–No coordination for channel
access
–Messages targeted based on
vehicle location more so than
vehicle identity
–Short and mapped to a single
frame
–Arbitrary distances (100m is a
more practical distance)
–Vehicles in constant
communication
–Dedicated channel
•Messaging Principles
–Safety communication is not
application-to-application Instead,
an intermediate layer is
responsible for safety information
distribution and aggregation
among vehicles and infrastructure.
–Applications work by continuously
analyzing the aggregated
information to look out for potential
trigger conditions.
–Simply put, the sender of a safety
message cannot dictate how the
message should be processed
–“I-am-braking” vs “You have-tobrake” message. One particular
advantage
–Simplifies future enhancements
Reliability
• If cars are being
controlled wirelessly,
dropping packets
could cause accidents
• May need to signal a
long ways off
• Result of studies:
Free way conditions
– Errors not bursty
– Communications up to
1 km feasible
F. Bai, H. Krishnan, “Reliability Analysis of DSRC
Wireless Communication for Vehicle Safety Applications,”
IEEE ITSC 2006
Packet error distribution
Possible Deployments
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Good (though dated) schedule at
http://www.itsforum.gr.jp/Public/E4Meetings/P03/schnac
keTP74.pdf
US DoT planning to deploy as Vehicle Infrastructure
Integration project (VII)
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http://www.networkworld.com/news/2005/111405-vii.html
Widescale deployment decision in 2008
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GM possibly going its own route with “Vehicle to
Vehicle” which leverages OnStar
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First use in intersections
http://www.gm.com/company/gmability/safety/news_issues/rele
ases/sixthsense_102405.html
European Effort – Car-to-Car Communication
Consortium
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http://www.car-to-car.org/
802.11r
Support for Faster Roaming
802.11e overview
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Fast BSS Roaming/Transition within IEEE WLAN networks
– Preserve security with handovers <50ms
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Fast BSS Roaming is possible only within a certain area called the mobility
domain (MD), inter-MD cases are not covered
– Mobility Domain (MD): Set of BSS grouped together with the same 48bit MD
Identifier
– FT functionality seeks to provide handover performance for RT services
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Key Issues
– Resource Reservations
– Security
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Collapsed 5 step process down to 3
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Scanning – active or passive for other APs in the area
Authentication with a (one or more) target AP
Re-association to establish connection at target AP
Target 2008
http://www.cs.tut.
fi/kurssit/TLT6556/Slides/Lect
ure4.pdf
Resource Reservation (optional)
• Resource Reservation (RR) is to setup QoS resources in one or
more target AP during FT transition mechanism
– RR Setup only follows successful PTK derivation
• RR is based on one round-trip negotiation
• – STA requests certain QoS and t-AP provides as much or less QoS
• • Benefits
– No delay during re-association for RR (RIC) processing
– Better application service quality during FT roaming
– Without RR, STA may realize target AP does not have enough
resources at the time of reassociation
• Drawbacks
– STA may reserve at multiple AP but use only one => cost
– Increased AP complexity
• –Mechanism
– AP advertises the capability in the Beacon frame
– STA has the choice to initiate the RR procedure
Security
• New key hierarchy
• New
authentication
route
http://www.cs.tut.fi/kurssit/TLT-6556/Slides/Lecture4.pdf
http://www.networkcomputing.com/gallery/2007/0416/0416t
tb.jhtml;jsessionid=0CK4ZKR20HC5QQSNDLPCKHSCJU
NN2JVN
Reduction in Roaming Time
S. Bangolae, C. Bell, E.Qi, “Performance study of fast BSS
transition using IEEE 802.11r,” International Conference On
Communications And Mobile Computing, 2006
802.11s
Mesh Networking in WiFi
Objectives1
• Modify 802.11 MAC to create
dynamic self-configuring
network of access points (AP)
called and Extended Service
Set (ESS) Mesh
• Automatic topology learning,
dynamic path selection
• Single administrator for 802.11i
(authentication)
• Support up to 32 AP
• Support higher layer
connections
• Allow alternate path selection
metrics
• Extend network merely by
introducing access point and
configuring SSID
1. http://standards.ieee.org/board/nes/projects/802-11s.pdf
IP or
Ethernet
Conceptual Operation
http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf
• WLAN Mesh – An IEEE 802.11-based Wireless distribution service consisting
of a set of two or more Mesh Points interconnected via IEEE 802.11 links and
communicating via the WLAN Mesh Services.
• Mesh Point - A Mesh Services supporting device (bridge, access point)
• Mesh AP - Any Mesh Point that is also an Access Point.
• Mesh Portal - A boundary connection for the Mesh
Major Participants
WiMesh
• http://www.wi-mesh.org/
• Major Partners
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Nortel
InterDigital
Phillips
Mitre
Naval Research Lab
Thomson
SEEMesh
• Simple, Efficient and
Extensible Mesh
• No group site
• Major Partners
– Intel
– Motorola (purchased
MeshNetworks)
– Nokia
– Texas Instruments
1. http://grouper.ieee.org/groups/802/11/Reports/tgs_update.htm
Key Technologies
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Topology Formation
Internetworking
Routing
Security
Topology Formation
• Each Mesh Point may have one or more logical radio interface:
– Each logical interface on one (infrequently changing) RF channel,
belong to one “Unified Channel Graph”
– Each Unified Channel Graph shares a channel precedence value
• Channel precedence indicator – used to coalesce disjoint graphs
and support channel switching for DFS
http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf
Internetworking
• 1. Determine if the
destination is inside or
outside of the Mesh
– Leverage layer-2 mesh path
discovery
• 2. For a destination inside
the Mesh,
– a. Use layer-2 mesh path
discovery/forwarding
• 3. For a destination outside
the Mesh,
– a. Identify the “right” portal, and
deliver packets via unicast
– b. If not known, deliver to all
mesh portals
Default Routing: Hybrid Wireless
Mesh Protocol (HWMP)
• On demand routing is based on Radio
Metric AODV (RM-AODV)
– Based on basic mandatory features of
AODV (RFC 3561)
– Extensions to identify best-metric path with
arbitrary path metrics
– Destinations may be discovered in the
mesh on-demand
• Pro-active routing is based on tree
based routing
– If a Root portal is present, a distance vector
routing tree is built and maintained
– Tree based routing is efficient for
hierarchical networks
– Tree based routing avoids unnecessary
discovery flooding during discovery and
recovery
http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf
RA-OLSR – Key Features
(Optional Routing)
• Multi Point Relays (MPRs)
• – A set of 1-hop neighbor nodes
covering 2-hop neighborhood
• – Only MPRs emit topology
information and retransmit packets
• • Reduces retransmission
overhead in flooding process in
space.
• (Optional) message exchange
frequency control (fish-eye
state routing)
• – Lower frequency for nodes
within larger scope
• Reduce message exchange
overhead in time.
Security
• The MPs are no longer wired to one
another
• There is no intrinsic node hierarchy
• MPs need to maintain secure links with
many other MPs
• Transport security
– Mutually authenticate neighbor MPs
– Generate and manage session keys
and broadcast keys
– Data confidentiality over a link
– Detect message forgeries and replays
received on a link
• Authentication and Initial Key
Management
– Basic approach is to re-use
802.11i/802.1X
– Re-use of 802.11i facilitates
implementation
Usage Models
Combat Usage Case
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Vehicular mounted APs interconnected via WDS
(wide area data services)
Dismounted troops carry client STAs
APs & client STAs are communication endpoints
Occasionally a STA may need to switch roles and
become an AP in order to heal a bifurcated mesh
Predominance of multicast applications, e.g.,
situational awareness, conference mode VoIP, …
Type 1 encryption, e.g., Harris SecNet 11
Auto configuration
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Logica
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View
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plug and play, or nearly so
Multiple 802.11 ESS Meshes interconnected via
JTRS ELOS links
Mesh AP Links
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802.11 MAC/PHY
(4-addr data frames)
Some JTRS ELOS links may belong to the WDS
while others are external to the WDS, i.e., are
terminated via IP routers rather than by 802.11
APs.
802.11 ESS Mesh
JTRS ELOS Links
(Joint Tactical Radio System)
(Extended Line-of-Site)
Picture from: IEEE 802.11-04/1006r0
Client-to-AP Links
802.11 MAC/PHY
(3-addr data frames)
Slide from: J. Hauser, D. Shyy, M. Green, MCTSSA 802.11s
Military Usage Case
WiFi Mesh Products
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Motorola Mesh Networks
– www.motorola.com/mesh
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Tropos
– www.tropos.com
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PacketHop Communications
– www.packethop.com
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MeshDynamics
– www.meshdynamics.com
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SkyPilot Networks
– www.skypiilot.com
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Proxim Networks
– www.proxim.com/can/
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Nortel Networks
Wave Wireless
– www.wavewireless.com
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LocustWorld.com
FireTide Network
List from: http://www.cs.wustl.edu/~jain/cse574-06/ftp/j_jmesh/sld019.htm
802.11y
Dynamic Spectrum Access
Background
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FCC issued rules for novel “lite licensing” scheme for 3650-3700 MHz band
– Licensees
• pay small fee for nation-wide non-exclusive license
• Pay additional fee for each high-powered base station (up to 20 W)
– No need for license for clients nor operators, but devices must be “enabled”
– Devices must be identifiable (to find the culprit)
– Support contention based protocol to give opportunity to transmit to multiple
licensees
– Interference disputes between licensees must be resolved between themselves
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Applications
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Back haul for Municipal Wi-Fi networks
Industrial automation and controls
Campus and enterprise networking
Last Mile Wireless Broadband Access
Fixed Point to point links
Fixed point to mobile links
Public safety and security networks
802.11y
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Ports 802.11a to 3.65 GHz – 3.7 GHz (US Only)
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FCC opened up band in July 2005
Conditionally approved Summer 2007, to sponsor ballot, ready 2008
Intended to provide rural broadband access (distances up to 5 km)
Incumbents
– Band previously reserved for fixed satellite service (FSS) and radar installations –
including offshore
– Must protect 3650 MHz (radar)
– Not permitted within 80km of inband government radar
– Specialized requirements near Mexico/Canada and other incumbent users
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Leverages other amendments
– Adds 5,10 MHz channelization
(802.11j)
– DFS for signaling for radar
avoidance (802.11h)
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Database of existing devices
– Access nodes register at
http://wireless.fcc.gov/uls
– Must check for existing devices at
same site
Source: IEEE 802.11-06/0YYYr0
Key 802.11y technologies
• DFS (802.11h)
• Channelization (802.11j)
• Contention based protocol (CBP)
– geographic protection of the grandfathered satellite stations
– database for users to research other users in their area
– Location information
• Extended channel switch announcement (ECSA)
– Dependent notification of DFS
– Continuous adaptation
• Dependant station enablement (DSE)
Dependant station enablement
• DSE controls when a
dependant is allowed
to transmit in
licensed spectrum
– enabling station need
not be an access
point, may be
elsewhere
– Need not be
completed via a
direct link
DSE Enabling Process
https://edge.arubanetworks.com/article/
standards-corner-august-2007-ieee802-11y-3650-3700-mhz-operation-usa
Summary
• 802.11 is expanding into lots of applications
– VOIP roaming (802.11r)
– Cellular like ranges with dynamic spectrum access
(802.11y)
– Telematics (802.11p)
– Mesh networks (802.11s)
• Leverage and enhance previous amendments
• Expect to see cross-pollination of technologies
later.