Submission doc.: IEEE 11-13/1325r5 Hiroshi Mano (ATRD) Nov 2013 802.11ai – Improving WLAN System...

Submission

doc.: IEEE 11-13/1325r5

Hiroshi Mano (ATRD)

Nov 2013

802.11ai – Improving WLAN System PerformanceDate: 2013-11-06Authors:

Slide 1

Name Company Address Phone emailJarkko Kneckt Nokia Coroporation Otaniementie 19B

02150 EspooFinland

[email protected]

Lei Wang InterDigital Communications781 Third Ave.King of Prussia, PA 19406

858-205-7286 [email protected]

Hitoshi Morioka Alliedtelesis R&D center K.K. 8F TOC2 Bldg. 7-21-11 Nishi-Gotanda, Shinagawa-ku, Tokyo 141-0031 JAPAN

hmorioka@root-hqcom

Ping Fang Huawei Technologies Co., Ltd.

Bldg 7, Vision Software Park, Road Gaoxin Sourth 9, Nanshan District, Shenzhen, Guangdong, China, 518057

+86 755 36839346

[email protected]

René Struik Struik Security Consultancy Toronto ON, Canada [email protected]

Santosh Pandey Cisco Systems 170 W Tasman Dr, San Jose, CA, 95134, USA

+1-408-8535990 [email protected]

Cherian, George Qualcomm 5775 Morehouse Dr, San Diego, CA, USA

+1 858 651 6645 [email protected]

Marc Emmelmann Self-Employed & Allied Telesis R&D Center

[email protected]

Hiroshi Mano Alliedtelesis R&D center K.K. 8F TOC2 Bldg. 7-21-11 Nishi-Gotanda, Shinagawa-ku, Tokyo 141-0031 JAPAN

[email protected]

Submission

doc.: IEEE 11-13/1325r5

Agenda

• Introduction to IEEE802.11ai, FILS• Key use case for 11ai• 802.11ai features in details • Trial report of the FILS feasibility study• Current status of IEEE802.11ai

Note:This presentation has not been approved by IEEE802.11ai task group as an official overview document. It has been proposed by the authors based on the approved submissions as of Nov 2013.

Slide 2 Hiroshi Mano (ATRD)

Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Today’s Market Trends

Growth of portable device market - Majority of the Wi-Fi are portable devices .

True mobile usage: Users frequently pass through (isolated) hot spots while on the move

The dwell time of an user within a cell is short

Isolated hot spots cause frequent initial association /authentication (link setup)

New application’s request (Twitter, Facebook…)

Push Notification Service

Short and quick updates

High bandwidth

Very SMALL CELL of each AP

So even with short dwell time under a given AP, always-on connectivity is a must


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Hot Spot Environment 1/2• Dense deployment: The famous “Tokyo Metro Station”

Increasing amount of spectrum & number of networks & number of devices

• Signaling overhead, exchange of unnecessary information

QoS violation

• Use of WLAN offloading is increasing

• It is equally important to shorten the link setup time as it is to shorten the data transmission time

• Shorter scanning reduces power consumption of the device


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Hot Spot Environment 2/2

•Most of air time is occupied by management frame.

•Especially undesired Probe Response frames are overflowing

KDDI’s report

Understanding the current situation of public Wi-Fi usage.

13/11-13-0523-02

hew-understanding-current-situation-of-public-wifi-usage.pptx


Nov 2013

Breakdown of Management framesBreakdown of Management frames

Frame type profile at metro station Frame type profile at metro station

Submission

doc.: IEEE 11-13/1325r5

Introduction to 11ai Fast Initial Link Setup (FILS)

The initial link setup includes all operations required to enable packets exchange. The main operations include:

• Network and BSS discovery• Authentication and association • Higher layer setup such as IP address configuration

FILS focuses on an environment where mobile users are constantly entering and leaving the coverage area of an existing extended service set (ESS). Every time the mobile device enters an ESS, the mobile device has to do an initial link set-up. This requires efficient mechanisms that:

(a) scale with a high number of users simultaneously entering an ESS

(b) minimize the time spent within the initial link set-up phase

(c) securely provide initial authentication.


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Network and BSS discovery: Scanning procedure changes• More control to scanning procedures:

Terminating the ongoing scan

More reporting options of the scanning result

• Immediate reporting

• Reporting after a channel is scanned

• Legacy, reporting after scanning is completed

• Announcing one or more neighbor BSS or channel information in Beacon, Probe Response and Fast Discovery (FD) frame

Reduce chances of scanning channels with no AP

BSSID of neighbor AP enables more precise active scanning

More information on neighbor BSSs may be provided


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Active Scanning, Expedited Scanning Procedure

• STA avoids sending unnecessary Probe Request:

If a device has received a Probe Request, it should avoid transmitting of a Probe Request for same APs


Nov 2013

STA 1

STA 1

Probe RequestProbe

Request

STA 2

STA 2

Delay probe request

transmission

Delay probe request

transmission

AP1AP1 AP2AP2 AP3AP3

STA 1

STA 1

Probe Response

Probe Response

STA 2

STA 2

Abort probe request

transmission

Abort probe request

transmission


Submission

doc.: IEEE 11-13/1325r5

Active Scanning, Probe Response Collision Avoidance

• AP avoids sending unnecessary Probe Responses:

Single copy of Probe Response or Beacon frame is enough


Nov 2013

STA 1

STA 1

Probe RequestProbe

Request

STA 2

STA 2 STA2 send

Probe Request for same APs

STA2 send Probe

Request for same APs


STA 1

STA 1

Probe Response

Probe Response

STA 2

STA 2

Receive probe

responses

Receive probe

responses


STA 1

STA 1

Probe RequestProbe

Request

STA 2

STA 2


Submission

doc.: IEEE 11-13/1325r5

Active Scanning, Comprehensive Response

• One Probe Response may contain information of multiple APs

The total number of Probe Request and Probe Responses is reduced

STA 1

STA 1

Probe RequestProbe

Request

Chn 1Chn 1 Chn 6Chn 6

Request for information of other BSSs

Request for information of other BSSs


STA 1

STA 1

Probe Response + Neighbor List

Probe Response + Neighbor List Contains

information of itself (AP 2), as well as AP 1 and AP 3 of

Channel 1 and Channel 6

Contains information of itself (AP 2), as well as AP 1 and AP 3 of

Channel 1 and Channel 6

Chn 1Chn 1 Chn 6Chn 6


Nov 2013


Submission

doc.: IEEE 11-13/1325r5

Active scanning, New Response Criteria

• Probe Request contains criteria to transmit Probe Response. Response is transmitted only if the criteria is met

• Criteria include:

• Reception power

• AP’s channel access delay, capabilities

• STA’s QoS requirement

• Vendor specific information etc.

STA 1

STA 1

Probe RequestProbe Request

Criteria for AP delay

performance & RSSI

Criteria for AP delay

performance & RSSI


STA 1

STA 1

Probe Response

Probe Response

Probe response is

transmitted if all the criteria

are met

Probe response is

transmitted if all the criteria

are met


Nov 2013


Submission

doc.: IEEE 11-13/1325r5

Active scanning, Probe Response Reception Time Element

• The transmitters of the Probe Request may indicate how long the transmitter will be available to receive Probe Responses

• Probe Response Reception Time is set to MAX_Probe_Response_Time


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Passive Scanning, Key EnhancementsFILS Discovery (FD) frame: a new public action frame

• Small-size: MAC headers + FD frame body, 40 to 55 bytes for typical uses;

• Only one mandatory information element: SSID;

• Optional information items: AP’s Next TBTT, AP-CCC, Access Network Options, Capability, Security, Neighbor AP information.

• FD frame is transmitted between Beacon frames, for a fast AP/Network discovery;

• FD frame may be transmitted as a non-HT duplicate PPDU, enabling a larger channel than 20MHz;


Nov 2013

Payload of FD Frame Primary channel of the transmitter

Primary channel of the transmitter

Preamble

Payload of FD Frame

Payload of FD Frame

Payload of FD Frame

Preamble

Preamble

Preamble

T2 time

Example #1 T1 time

T3time

Example #2

Example #3

Beacon FD frame

Submission

doc.: IEEE 11-13/1325r5

Reducing Sizes of the Responses

• AP Configuration Change Count (CCC) keeps track of changes of the parameters in Probe Response and Beacon

One octet in length

AP-CCC does not consider changes of BSS Load, Average Access Delay and other rapidly changing parameters


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Control allowed STAs for concurrent initial links

Differentiated Initial Link Setup element can be set by AP to control allowed STA for concurrent initial links

Conditions for STAs can be set by AP including:

ILS User Priority

MAC Address Filter

Vendor Specific Category

Link Setup Bursty


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Network Discovery, Key Enhancements

GAS query enhancement by using an AP white-list

A new IE with one or multiple 6-byte BSSIDs in GAS request to indicate the AP(s) that the requesting STA wants to query.

GAS traffic reduction by using GAS Configuration Sequence Number

A new IE with an 1-byte unsigned integer:indicating the version number of AP’s GAS configuration information

set;

monotonically incrementing whenever there is any change in the AP’s GAS configuration information set;

Used in Beacon and/or Probe Response.


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Feature of IEEE802.11ai (Higher layer setup) Significant reduction in setup signaling: Authentication, 4-way

handshake, Association & Higher layer setup including IP address assignment completed in 2 roundtrip signaling messages

Fast authentication & FILS IP address assignment speeds up the authentication & IP Address assignment procedure


Nov 2013

3rd Party(DHCP Server)3rd Party(DHCP Server)

DHCP Messages, etc.

Submission

doc.: IEEE 11-13/1325r5

Link Setup States per 802.11ai


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

FILS Key Establishment with TTP

STASTA APAP

Association Request

Beacon/Probe Resp.

Authentication Request

Authentication Response

Association Request

Key Establishment

Key Confirmation

Secret keys

TTPTTP

{(STA: KSTA), (AP: KAP), …}

FILS authentication with online TTP: TTP actively assists STA and AP in deriving shared keying material (hence, “online”) Two flavors: with or without “Perfect Forward Secrecy” (PFS)NOTE: With “PFS”, TTP usually does not learn shared key STA-AP, nor can re-compute past sessions should node get compromised (in short: better security)

Requires STA and AP to share secret key with same TTP (e.g., via ISPs that have pre-existing business relationships)

KAPKSTA

Nov 2013


Submission

doc.: IEEE 11-13/1325r5

FILS Key Establishment w/o. TTP

STASTA APAP

Association Request

Beacon/Probe Resp.



Association Request

Key Establishment

Key Confirmation

Public

keys

CACA

{CertSTA, CertAP, …}

FILS authentication without online TTP: STA and AP can derive shared keying material and authentication directly, via use of certificates (so, no need for any active involvement third party for authentication) Third party may still be involved for authorization or for configuration (as with all FILS key establishment protocols)

Requires STA and AP to certify their own public key with some CA (e.g., during manufacturing)

CA root key CA root key

Nov 2013


Submission

doc.: IEEE 11-13/1325r5

Adding “piggy-backed info” to protocol flows …

STASTA APAP

Association Request

Beacon/Probe Resp.



Association Request

Key Establishment

Key Confirmation

TTPTTPServicesServices

+ piggy-backed info response

+ piggy-backed info request

Authentication help

Configuration help

IP address assignment

Authorization

Subscription credentials

Piggy-backing info along FILS authentication protocol: Higher-layer set-up, including IP address assignment Authorization functionality, subscription credentials, etc.

See details elsewhere in presentation

Nov 2013


Submission

doc.: IEEE 11-13/1325r5

Trial report of FILS feasibility study

The effect of reducing packet exchange was evaluated by field test in Japan

The details are reported in IEEE802.11 as, https://mentor.ieee.org/802.11/dcn/13/11-13-0323-02-00ai-tgai-experimental-test-report-of-fils.pptx

FILS STAs completed the association process in significantly less time than WPA STAs

More time within the AP coverage for (user) data exchange

The large number of link setup frame exchanges for WPA2 STAs (as compared to FILS STAs) made them vulnerable.

If retransmission of a lost frame did not succeed after three attempts, the association process had to restart from the beginning

This field trial did only consider the higher layer set-up features while using legacy scanning. We expect FURTHER performance improvement when the FILS scanning features are in use


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Trial report of feasibility study with FILS 2/2• 20 FILS and 20 WPA2 are entering the service area.

• Measured the distance of STA and AP where STA establish link successfully and received http contents.

• Measured the time from Association/FILS request to IP address assignment propriety application.

•http://www.youtube.com/watch?v=xOKaVOPWXTU

90% (18/20) FILS STA established link before arriving at in the front of AP

85% (17/20) WPA2 established link since they passed in the front of AP

Average link setup time from FILS request to IP address assignment is 0.742 Sec

Average link setup time from Association request to IP address assignment is 21.599 Sec

FILSFILS

Service Area

歩きながら移動

WPA2

WPA2

非接続

非接続

Established Link PointEstablished Link Point

Nov 2013


Submission

doc.: IEEE 11-13/1325r5

ANNEX

USE CASE EXAMPLES THAT BENEFIT FROM FILS


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Alternative Use Cases• Automatic metering

• Power electric

• Water meter

• Gas meter

• etc..

• Drive through

• Digital Signage

• V2V,V2X


Nov 2013

Submission

doc.: IEEE 11-13/1325r5

Feasibility Study of Automobile Application

Fast initial link setup enables opportunistic vehicle to vehicle communication.

Toyota InfoTechnology Center measured the number of user text message exchanges during specific time period.

Assumption

Air coverage: 50m

Vehicle speed: 40km/h （ 11m/Sec ）

Available communication time : 5Sec

WPA2: More than 4Sec communication time is required to exchange messages.

FILS: it is available to exchange messages under short communication time.

Y: Number of exchanged messages

X: Communication time

This measurement did only consider the higher layer set-up features while using legacy scanning.

We expect FURTHER performance increase if the stations implemented the new scanning features.


Nov 2013

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Submission doc.: IEEE 11-13/1325r5 Hiroshi Mano (ATRD) Nov 2013 802.11ai – Improving WLAN System...

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