doc.: IEEE 11-13/1325r5
Nov 2013
802.11ai – Improving WLAN System Performance
Date: 2013-11-06
Authors:
Name
Company
Address
Jarkko Kneckt
Nokia Coroporation
Otaniementie 19B
02150 Espoo
Finland
Lei Wang
InterDigital Communications
Hitoshi Morioka
Alliedtelesis R&D center K.K.
Ping Fang
Huawei Technologies Co., Ltd.
René Struik
Struik Security Consultancy
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
Hiroshi Mano
Self-Employed & Allied Telesis
R&D Center
Alliedtelesis R&D center K.K.
Submission
Phone
email
[email protected]
m
781 Third Ave.
858-205-7286
King of Prussia, PA 19406
8F TOC2 Bldg. 7-21-11 NishiGotanda, Shinagawa-ku, Tokyo
141-0031 JAPAN
Bldg 7, Vision Software Park,
Road Gaoxin Sourth 9, Nanshan +86 755
District, Shenzhen, Guangdong, 36839346
China, 518057
Toronto ON, Canada
[email protected]
hmorioka@root-hqcom
[email protected]
[email protected]
[email protected]
8F TOC2 Bldg. 7-21-11 NishiGotanda, Shinagawa-ku, Tokyo
141-0031 JAPAN
Slide 1
[email protected]
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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.
Submission
Slide 2
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
Submission
Slide 3
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
Submission
Slide 4
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Hot Spot Environment 2/2
•Most of air time is occupied by management frame.
•Especially undesired Probe Response frames are overflowing
Frame type profile at metro station
KDDI’s report
Understanding the
current situation of
public Wi-Fi usage.
13/11-13-0523-02
Breakdown of Management frames
Submission
Slide 5
hew-understandingcurrent-situationof-public-wifiusage.pptx
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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.
Submission
Slide 6
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
Submission
Slide 7
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
AP1
AP2
AP3
AP1
STA
2
STA
1
Delay probe
request
transmission
Submission
AP3
Probe
Response
Probe
Request
STA
1
AP2
Slide 8
STA
2
Abort probe
request
transmission
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Active Scanning, Probe Response Collision Avoidance
•
AP avoids sending unnecessary Probe Responses:
Single copy of Probe Response or Beacon frame is enough
AP1
AP2
AP3
AP1
Submission
AP3
STA
2
STA
1
STA
2
AP1
AP2
AP3
Probe
Response
Probe
Request
Probe
Request
STA
1
AP2
STA2 send
Probe
Request for
same APs
Slide 9
STA
1
STA
2
Receive
probe
responses
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Active Scanning, Comprehensive Response
•
One Probe Response may contain information of multiple APs
The total number of Probe Request and Probe Responses is reduced
Chn 1
AP
1
Chn 6
AP
2
AP
3
Chn 1
AP
1
Submission
AP
2
Probe
Response +
Neighbor List
Probe
Request
STA
1
Chn 6
Request for
information of
other BSSs
STA
1
Slide 10
AP
3
Contains
information of itself
(AP 2), as well as
AP 1 and AP 3 of
Channel 1 and
Channel 6
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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.
AP1
AP2
AP3
AP1
Submission
AP3
Probe
Response
Probe Request
STA
1
AP2
Criteria for AP
delay
performance &
RSSI
Slide 11
STA
1
Probe
response is
transmitted if
all the criteria
are met
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
Submission
Slide 12
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Passive Scanning, Key Enhancements
FILS 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;
Beacon
Example
#1
T1
Example
#2
Example
#3
time
T2
T3
Submission
FD frame
Primary
channel of the
transmitter
time
Preamble
Payload of FD Frame
Preamble
Payload of FD Frame
Preamble
Payload of FD Frame
Preamble
Payload of FD Frame
time
Slide 13
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
Submission
Slide 14
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
Submission
Slide 15
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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.
Submission
Slide 16
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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
3rd Party
(DHCP Server)
DHCP Messages, etc.
Submission
Slide 17
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Link Setup States per 802.11ai
Submission
Slide 18
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
{(STA: KSTA),
(AP: KAP), …}
FILS Key Establishment with TTP
KSTA
KAP
STA
AP
Beacon/Probe Resp.
Authentication Request
Key
Establishment
Authentication Response
Association Request
Key
Confirmation
TTP
Secret
keys
Requires STA and AP
to share secret key
with same TTP (e.g.,
via ISPs that have preexisting business
relationships)
Association Request
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 recompute past sessions should node get compromised (in short: better security)
Submission
Slide 19
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
FILS Key Establishment w/o. TTP
CA root key
{CertSTA,
CertAP, …}
CA root key
STA
AP
Beacon/Probe Resp.
Authentication Request
Key
Establishment
Authentication Response
CA
Publi
c
keys
Requires STA and AP to
certify their own public
key with some CA (e.g.,
during manufacturing)
Association Request
Key
Confirmation
Association Request
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)
Submission
Slide 20
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Adding “piggy-backed info” to protocol flows …
STA
AP
TTP
Services
Beacon/Probe Resp.
Authentication Request
Key
Establishment
Authentication help
Authentication Response
Association Request
Key
Confirmation
+ piggy-backed info request Configuration help
Association Request
+ piggy-backed info response
IP address assignmen
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
Submission
Slide 21
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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-tgaiexperimental-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
Submission
Slide 22
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Trial report of feasibility study with FILS 2/2
• 20 FILS and 20 WPA2 are entering the
service area.
90% (18/20) FILS STA established link before
arriving at in the front of AP
• Measured the distance of STA and AP
where STA establish link successfully and
received http contents.
85% (17/20) WPA2 established link since they
passed in the front of AP
• Measured the time from Association/FILS
request to IP address assignment propriety
application.
•http://www.youtube.com/watch?v=xOKaVOPWXTU
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
Established
Link Point
FILS
非接続
歩
き
な
が
ら
移
動
非接続
Service Area
WPA2
Submission
Slide 23
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
ANNEX
USE CASE EXAMPLES THAT
BENEFIT FROM FILS
Submission
Slide 24
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
Alternative Use Cases
•
Automatic metering
•
• Power electric
• Water meter
• Gas meter
• etc..
Drive through
•
Digital Signage
•
V2V,V2X
Submission
Slide 25
Hiroshi Mano (ATRD)
doc.: IEEE 11-13/1325r5
Nov 2013
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.
Y: Number of exchanged messages
X: Communication time
2500
受信メッセージ数
FILS: it is available to exchange messages under short
communication time.
3000
2000
1500
通常接続（WPA2）
1000
高速接続（FILS）
500
This measurement did only consider the higher layer setup features while using legacy scanning.
We expect FURTHER performance increase if the
stations implemented the new scanning features.
Submission
Slide 26
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
通信時間 ［秒］
Hiroshi Mano (ATRD)