802.11 Enhancements and Applications

1
802.11 Enhancements and Applications

• 802.11p, 802.11r, 802.11s, 802.11y

2
802.11p
3
802.11p

• Dedicated Short Range Communications (DSRC)
• Started in IEEE 1609, spun into 802.11p
• Aka (WAVE) Wireless Access for Vehicular
  Environment
• Goal
• Telematics (collision avoidance a big driver)
• Roadside-to-vehicle
• Vehicle-to-vehicle environments
• 54 Mbps, lt50 ms latency
• Possible competitor to cellular
• Operates in 5.850 to 5.925GHz band
• Draft under ballot
• Projected for March 2009

4
Broader Context

• 802.11p part of several standards which will
  jointly enable widescale telematics

Intelligent Transportation Systems
doc. IEEE 802.11-07/2045r0
5
802.11p Applications

• Applications
• 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

6
Example Application
From IEEE 802.11- 04/ 0121r0 Available
http//www.npstc.org/meetings/Cash20WAVE20Inform
ation20for205.920GHz20061404.pdf
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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

8
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-applica
  tion 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-to-brake message.
  One particular advantage
• Simplifies future enhancements

9
Reliability

• If cars are being controlled wirelessly, dropping
  packets could cause accidents
• May need to signal a long ways off
• Result of studies
• Errors not bursty
• Communications up to 1 km feasible

Free way conditions
F. Bai, H. Krishnan, Reliability Analysis of
DSRC Wireless Communication for Vehicle Safety
Applications, IEEE ITSC 2006
Packet error distribution
10
Possible Deployments

• Good (though dated) schedule at
  http//www.itsforum.gr.jp/Public/E4Meetings/P03/sc
  hnackeTP74.pdf
• US DoT planning to deploy as Vehicle
  Infrastructure Integration project (VII)
• http//www.networkworld.com/news/2005/111405-vii.h
  tml
• Widescale deployment decision in 2008
• First use in intersections
• GM possibly going its own route with Vehicle to
  Vehicle which leverages OnStar
• http//www.gm.com/company/gmability/safety/news_is
  sues/releases/sixthsense_102405.html
• European Effort Car-to-Car Communication
  Consortium
• http//www.car-to-car.org/

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802.11r

• Support for Faster Roaming

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802.11e overview

• Fast BSS Roaming/Transition within IEEE WLAN
  networks
• Preserve security with handovers lt50ms
• 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
• Key Issues
• Resource Reservations
• Security
• Collapsed 5 step process down to 3
• 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/TLT-6556/Slides/Lectu
re4.pdf
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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
  gt cost
• Increased AP complexity
• Mechanism
• AP advertises the capability in the Beacon frame
• STA has the choice to initiate the RR procedure

14
Security

• New key hierarchy
• New authentication route

http//www.cs.tut.fi/kurssit/TLT-6556/Slides/Lectu
re4.pdf
http//www.networkcomputing.com/gallery/2007/0416/
0416ttb.jhtmljsessionid0CK4ZKR20HC5QQSNDLPCKHSCJ
UNN2JVN
15
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
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802.11s

• Mesh Networking in WiFi

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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

IP or Ethernet
1. http//standards.ieee.org/board/nes/projects/80
2-11s.pdf
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Conceptual Operation
http//ieee802.org/802_tutorials/nov06/802.11s_Tut
orial_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

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Major Participants

• WiMesh
• http//www.wi-mesh.org/
• Major Partners
• 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/t
gs_update.htm
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Key Technologies

• Topology Formation
• Internetworking
• Routing
• Security

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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_Tut
orial_r5.pdf
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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

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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_Tut
orial_r5.pdf
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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.

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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

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Usage Models
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Combat Usage Case

• 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
• plug and play, or nearly so
• Multiple 802.11 ESS Meshes interconnected via
  JTRS ELOS links
• 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.

Logical View
Mesh AP Links 802.11 MAC/PHY (4-addr data frames)
802.11 ESS Mesh
Client-to-AP Links 802.11 MAC/PHY (3-addr data
frames)
JTRS ELOS Links (Joint Tactical Radio
System) (Extended Line-of-Site)
Slide from J. Hauser, D. Shyy, M. Green, MCTSSA
802.11sMilitary Usage Case
Picture from IEEE 802.11-04/1006r0
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WiFi Mesh Products

• Motorola Mesh Networks
• www.motorola.com/mesh
• Tropos
• www.tropos.com
• PacketHop Communications
• www.packethop.com
• MeshDynamics
• www.meshdynamics.com
• SkyPilot Networks
• www.skypiilot.com
• Proxim Networks
• www.proxim.com/can/
• Nortel Networks
• Wave Wireless
• www.wavewireless.com
• LocustWorld.com
• FireTide Network

List from http//www.cs.wustl.edu/jain/cse574-06
/ftp/j_jmesh/sld019.htm
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802.11y

• Dynamic Spectrum Access

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Background

• 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
• Applications
• 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

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802.11y

• Ports 802.11a to 3.65 GHz 3.7 GHz (US Only)
• 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

• Leverages other amendments
• Adds 5,10 MHz channelization (802.11j)
• DFS for signaling for radar avoidance (802.11h)
• Database of existing devices
• Access nodes register at http//wireless.fcc.gov/u
  ls
• Must check for existing devices at same site

Source IEEE 802.11-06/0YYYr0
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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)

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Dependant station enablement
DSE Enabling Process

• 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

https//edge.arubanetworks.com/article/standards-c
orner-august-2007-ieee-802-11y-3650-3700-mhz-opera
tion-usa
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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.