802.11 Enhancements and Applications

802.11n, 802.11p, 802.11r, 802.11s, 802.11y

802.11n

802.11

802.11n

• Overview

• Certification, Products

• Performance

• Summary

802.11n overview• Adds MIMO to WLAN OFDM• Operate in either UNII or ISM bands• Status:

–In Ballot–May get held up by IP

• http://arstechnica.com/news.ars/post/20070924-dark-australian-patent-cloud-looms-over-802-11n-spec.html

• CSIRO (http://www.csiro.au/) holds some key IP, hasn’t signed letter of assurance, has history of WiFi lawsuits and seeking injunctions

• Last publicly available draft–Enhanced Wireless Consortium (merger of TGnSync and WWiSE)

–http://www.enhancedwirelessconsortium.org/home/EWC_PHY_spec_V127.pdf (PHY)

–http://www.enhancedwirelessconsortium.org/home/EWC_MAC_spec_V124.pdf (MAC)

Source: http://www.tgnsync.org/products

Streaming Home Multimedia (HDTV)

802.11n PHY (in 1 slide)•MIMO evolution of 802.11 OFDM PHY

–Up to 4 antennas per device• 20 and 40MHz channels

–Fully interoperable with legacy 802.11a/b/g

–288 Mbps in 20MHz and 600 Mbps in 40MHz (64 QAM, 4 spatial streams, 1/2 guard interval)

–Claim of 100 Mbps in real throughput

•Optional enhancements–Transmit beamforming with negligible overhead at the client

–Advanced channel coding techniques (RS)

–Space Time Block Coding (Alamouti and others)

–1/2 guard interval (i.e., 400ns instead of 800 ns)

–7/8 rate coding

http://www.enhancedwirelessconsortium.org/home/EWC_PHY_spec_V127.pdf

802.11n MAC Features• Supports 802.11e (QoS)• Frame aggregation

– Single and multiple destinations• Bi-directional data flow• Link adaptation with explicit

feedback and control of channel sounding packets

• Protection mechanisms– For seamless interoperability and

coexistence with legacy devices• Channel management

– Including management of 20/40MHz operating modes

– Channel estimation and feedback• Power management for MIMO

receivers• Data aggregation

Broadcom, “802.11n: Next-Generation Wireless LAN Technology,” White Paper, April 06

Legacy Support• Distributed coordination function will

fail if devices cannot interpret packets

• Much more spectrum used by 802.11n

• Three packet modes to support legacy equipment

– Legacy (all legacy)– Mixed (some legacy, some 802.11n)– Green Field (all 802.11n)

• Spectrum usage–LM – Legacy Mode – equivalent to

802.11a/g–HT-Mode – In HT mode the device operates

in either 40MHz bandwidth or 20MHz bandwidth and with one to four spatial streams.

–Duplicate Legacy Mode – in this mode the device operates in a 40MHz channel composed of two adjacent 20MHz channel. The packets to be

–sent are in the legacy 11a format in each of the 20MHz channels. To reduce the PAPR the upper channel (higher frequency) is rotated by 90º

–relative to the lower channel.–40 MHz Upper Mode – used to transmit a

legacy or HT packet in the 16 upper 20MHz channel of a 40MHz channel.

–40 MHz Lower Mode – used to transmit a legacy or HT packet in the lower 20MHz channel of a 40MHz channelLM is mandatory and HT-Mode for 1 and 2 spatial streams are also mandatory.

802.11n PLCP Formathttp://www.enhancedwirelessconsortium.org/home/EWC_PHY_spec_V127.pdf

Some 802.11 performance results

From IEEE 802.11-04/1369r0

Comparison with 802.11a/gThroughput Enhancements

IEEE 802.11-04/1369r0

Relative Cost to Implement

Peak Rates

PHY Throughput

• Link adaptation is based on long term average SNR sub-optimum inferior bound

• Finer grid possible with more modes

Simulation results

• Diversity gain for 2 streams, but not for 3 streams• 120 Mbps lowers SNR ~ 36dB 26dB

Mode/

Mbps

SNR for PER=10-1

180 (effect)

36dB

180 36dB

120 35dB 25.5dB

96 27.5dB 21dB

48 18dB 14dB

12 5dB 4.5dB

doc.: IEEE 802.11-04/1369r0

Mixed traffic handling

• Capacity usage at MAC-SAP vs. Number of VoIP sessions– 1 TCP data flow transmitted using MIMO 3x3_64QAM2/3 (Ns=3)

[144Mbit/s]– VoIP: 120-byte packets emitted every 10 ms (2x96kbit/s)– n VoIP sessions, using either 2x2_64QAM2/3 (Ns=1) [48Mbit/s] or

2x2_16QAM1/2 (Ns=1) [24 Mbit/s]

• MAC Efficiency between 78% and 55%

• 30 VoIP sessions + at least 65 Mbit/s of TCP traffic

VoIP Scenario Performance

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70

Number of VoIP terminals

TC

P A

gg

reg

ate

d g

oo

dp

ut

(M

bit

/s)

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

MA

C E

ffic

ien

cy

TCP Throughput

MAC Efficiency

doc.: IEEE 802.11-04/1369r0

Delay performances

• IEEE TGn Usage models : Scenario I (Home)• Traffic classification based on priority level (VoIP > TCP)

• Delay comparison for different error rate [cdf(d>D)]

• Strong QoS constraints of VoIP reached:– with a simple centralised

scheduling – an efficient ARQ

• Max delay below 20 ms for QoS traffic

IEEE Usage model: Scenario I (Home)Distribution of delay

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 10 20 30 40 50 60 70 80

Delay (ms)

cd

f(d

>D

)

TCP (No Error)

TCP (PER=3.10-2)

TCP (PER=10-1)

VoIP (No Error)

VoIP (PER=3.10-2)

VoIP (PER=10-1)

doc.: IEEE 802.11-04/1369r0

802.11n Certification

• Wi-Fi Alliance– Certifying to Draft 2.0

while draft is approved– Certify to Ratified

Standard when available

– 22 August 2007 - Almost 70 products certified for compliance with Draft 2.0 of the 802.11n

• http://www.wi-fiplanet.com/news/article.php/3578886

Key Certification Features

Wi-Fi CERTIFIED™ 802.11n draft 2.0: Longer-Range, Faster-Throughput, Multimedia-Grade Wi-Fi® Networks

Pre-802.11n deployments• Belkin (pre-802.11n)

– 8x coverage, 6x speed of 802.11g– 3 antennas

• Netgear (pre-802.11n)– 7 antennas– 43.2 Mbps (measured)

http://www.theregister.co.uk/2005/06/07/review_netgear_mimo_router/page2.html

• Linksys (Cisco)– 802.11g with Speed and Range eXpansion (802.11g SRX)– 8x speed, 3 times range– 3 antennas

• Airgo (chip vendor, “True MIMO”)– SOHOware, Planex– Linksys

• Dell– Optional Pre-N with Broadcom adapter– http://biz.yahoo.com/prnews/060717/nym115.html?.v=38

802.11n Summary

• By adding antenna arrays to WiFi, significant improvements possible without exponential increases in complexity– Most people using it for range extension

• Thin pipe into the house• High SNRs needed for peak rates

• Designed to co-exist with 802.11 a/b/g

• WiFi Alliance certifying to draft 2.0 now

802.11p

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, <50 ms latency• Possible competitor to cellular

• Operates in 5.850 to 5.925GHz band• Draft under ballot

– 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

S. Biswas, R. Tatchikou, F. Dion, “Vehicle-to-vehicle wireless communication protocols for enhancing highway traffic safety,” IEEE Comm Mag, Jan 06, pp. 74-82.

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

Example Application

IMMINENT

FRONT

COLLISION

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.

In-Vehicle Displays and Annunciations

Traffic Signal

Traffic Signal

OBUs on Control Ch

~ ~~ ~

~ ~

IMMINENT

LEFT

COLLISION

Radar Threat Identification

Note 2: Only the OBU in the threatening vehicle processes the message because only it matches the threat address.

up to 100 m (328 ft)Note 3: COLLISION PREPARATION includes seat belt tightening, side air bag deployment, side bumper expansion, etc.

Car NOT Stopping

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

D. Jiang, V. Taliwal, A. Meier, W. Holfelder, R. Herrtwich, “Design of 5.9 ghz dsrc-based vehicular safety communication,“ IEEE Wireless Comm, Oct 06, pp. 36-43

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-to-brake” 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:– Errors not bursty– Communications up to

1 km feasible

Free way conditions

Packet error distribution

F. Bai, H. Krishnan, “Reliability Analysis of DSRC Wireless Communication for Vehicle Safety Applications,” IEEE ITSC 2006

Possible Deployments

• Good (though dated) schedule at http://www.itsforum.gr.jp/Public/E4Meetings/P03/schnackeTP74.pdf

• US DoT planning to deploy as Vehicle Infrastructure Integration project (VII)– http://www.networkworld.com/news/2005/111405-vii.html – 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_issues/rele

ases/sixthsense_102405.html• European Effort – Car-to-Car Communication

Consortium– http://www.car-to-car.org/

802.11r

Support for Faster Roaming

802.11r overview• Fast BSS Roaming/Transition within IEEE WLAN networks

– Preserve security with handovers <50ms• 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/Lecture4.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/2007/0416/0416ttb.jhtml;jsessionid=0CK4ZKR20HC5QQSNDLPCKHSCJUNN2JVN

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

• 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

Objectives1

• 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

Conceptual Operation of 802.11s

http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf

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/tgs_update.htm

Major Participants

Key Technologies

• 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

http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf

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.

http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf

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

http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf

Usage Models

http://ieee802.org/802_tutorials/nov06/802.11s_Tutorial_r5.pdf

• 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.

Picture from: IEEE 802.11-04/1006r0

802.11 ESS Mesh802.11 ESS Mesh

Mesh AP LinksMesh AP Links802.11 MAC/PHY802.11 MAC/PHY

(4-addr data frames)(4-addr data frames)

Client-to-AP LinksClient-to-AP Links802.11 MAC/PHY802.11 MAC/PHY

(3-addr data frames)(3-addr data frames)

JTRS ELOS LinksJTRS ELOS Links((JJoint oint TTactical actical RRadio adio SSystem)ystem)

((EExtended xtended LLine-ine-oof-f-SSite)ite)

Log

ical

Vie

w

Slide from: J. Hauser, D. Shyy, M. Green, MCTSSA 802.11sMilitary Usage Case

Combat Usage Case

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

802.11y

Dynamic Spectrum Access

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

• 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/uls

– Must check for existing devices at same site

Source: IEEE 802.11-06/0YYYr0

802.11y

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

https://edge.arubanetworks.com/article/standards-corner-august-2007-ieee-802-11y-3650-3700-mhz-operation-usa

DSE Enabling Process

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.