Wireless Internet Roaming(WiFi and Cellular integration)
December 7, 2002
Stuart JefferyTelecommunications Consultant
1072 Seena AveLos Altos, CA 94024Tel +1 650 966 8199Fax +1 408 850 1959
E-Mail: [email protected]
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Problem space• Wireless Carriers are in the Wireless Data
business– Yesterday – CDPD– Today – GPRS, 1XRTT (2.5G), iMode (in Japan)– Tomorrow – 3G
• Public Accss WiFi is developing very rapidly– Cheap, High Speed and Convenient– Users have device – PDA, Laptop, etc WiFi enabled– Ease of use, security all being solved
• From carrier’s perspective, wireless data is their business and these Public WiFi users are their customers!
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“Wireless Customer” wants….• Ubiquity – wants it to work everywhere• Same “user experience” - wherever they
are– Same “procedures”– Same “services”
• Economical / Affordable service -– In North America – internet data is “flat rate”– Data via cellular is $1 to 5 per MB (long term)
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Carrier’s dilemma: They must participate in this market
• WiFi is cheap, fast, but has limitation:– Cheap – no license fee, commodity equipment, and
simple network infrastructure (no central management)– Limitation - Short range and inefficient spectrum usage
• Carrier data- expensive, but ubiquitous – Expensive – complex infrastructure, QoS, exclusive
licenses– Slow – related to range and battery life– Advantage - Wide Area coverage
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Carrier’s positioning• “Value Add” possibilities
– Common Bill– Customer Care– Market promotion– Consistence of service (same user experience)
• Conundrum:
integratedIslandRoamingSlowFastSpeed
HighLowCost (per bit)Cellular DataWiFi
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Public WLAN
AP
Local LANAP
LocalAccessControl
INTERNET
CentralizedAAA
ServicesSignaling planeTransmission plane
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Public WLAN Roaming
Aggregators “Home”AAAVisited Network
Other HomesOther networksOther networks
Other Homes
Signaling planeTransmission plane
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Specific areas of integration• Back Office functions
– Billing –– Customer Care –
• Signaling plane functions – Registration / Authentication– Subscriber Data Base / service authorization
• Transmission plane functions – Services
• Mobility functions– Roaming– Handoff
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Signaling Plane• GSM and CDMA data networks are different
– CDMA – IETF Protocols – TCP / UDP, etc over IP
– GSM – GSM protocols – MAP over SS7• Signaling plane functions
– Authentication– Service profile- authorization of privileges for the
subscriber
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Cellular todayCDMA 2000
Signaling planeTransmission plane
PDSN
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Cellular todayCDMA 2000
XAggr.
Signaling planeTransmission plane
PDSN
Other Networks
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GSM
Signaling planeTransmission plane
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Public WLAN Roaming
Aggregators GSM“Home”
(GSM MAPVisited Network
Other HomesOther networksOther networks
Other Homes
IWF
GSM MAP over SS7
Signaling planeTransmission plane
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GSM
IWF
Signaling planeTransmission plane
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GSM Authentication with SIM
Secret Key (Ki) –each sub has own
Algorithm – A3Unique to Carrier
Home Network
Visited Network
RAND
Yes - Auth.No - DeniedMatch?
SRES
Algorithm – A3Unique to Carrier
Secret Key (Ki) –each sub has own
Mobile
Random numberGenerator
SRES
RA
ND
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Registration / Authentication• User name / password• SIM based
– Standard on mobiles– Higher risk on PDA and Laptops
Challenge from Network(sent in the clear)
Response to Network(sent in the clear)
Secret Key (Ki)
Algorithm
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SIM Adapters
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802.1x LAN Authentication Standard
• EAP that work with 802.1x• Large number of IETF Drafts• Several related to GSM and require SIM
on device– EAP-SIM – Nokia – EAP- SIM – GMM – Transat, Intel
• Adjungo’s EAP CAP – Works in pre 802.1x environments– Works with and without SIM on user device
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Companies IWF Gateways(probably not all of them)
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Services64 Billion $ Question is what are they?
• Walled Garden or Internet?– Information has a time value location value
• Why take traffic to the core? Take it directly to internet?• Problem statement
– There are many killer applications on the internet - most based on low cost transport
– Killer application for cellular data is different – because transport cost is not low - saving time or wasting time
EventTime
$ Value $
My LocationDistance
awayDistance
away
$ Value $
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Wireless Data Cost Comparison(prices as of Aug 2002)
~ $0.15 per min
Subscription plus $ 4.00 per MB
Subscription plus $0.30 to $0.50 per min
Cost(typical)
Cellular data card
Everywhere~ 1.5 X Dialup1XRTT
Very Localized
Everywhere
Available
WiFi Card10 to 20X Dialup
Hot Spots
Cellular data card
~ 1.5 X DialupGPRS
Equipment to connect
Speed vs. 45 Kbps
Tech.
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Cellular Data Cost Comparison(source data from RCR, August 19, 2002 page 26)
(T1 service ~ $0.167 per min)
$-
$10.00
$20.00
$30.00
$40.00
$50.00
1 2 5 7 10 20 30 40 50 100 150 200MB per month
$ pe
r mon
th
Verzion (heavy) ATT (heavy) Sprint (heavy) Cingular (med) Sprint (med)
T-Mobile (med) Verzion (light) ATT (med) T-Mobile (light) ATT (light)
Sprint (light) Cingular (light) T1 @ 2.5% T1 @ 5% T1 @ 10%
T1 backhaul
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RCR Data(source data from RCR, August 19, 2002 page 26)
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Mobility Functions
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Handoff• Disconnect and reconnect
– Rather simple approach– Creates disconnect –restart apps.
• Hurts VoIP• FTP• Streaming
– No problem to Web-browsing• True handoff
– Need mobile IP (hold address)– Need to communicate in advance to RAN
• For WLAN to WAN ok• For WAN to WLAN, issues
• But is there really a need?– Economics are very different– Cost of equipment much higher
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Roaming – Vertical(signaling plane)
GPRSRoamingNetworks
GSM Operator A
WiFi Network
GSM Operator B
GWGW
?
WiFi Network
Signaling planeTransmission plane
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Roaming – Horizontal(signaling plane)
WiFiRoamingNetworks
GSM Operator A
GSM Operator B
GWGW
WiFi Network
WiFi Network
Signaling planeTransmission plane
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Summary• Carrier’s can’t ignore WiFi• Many carrier’s are “dabbling” in this space
– T-mobile – Mobilestar– AWS – Denver Airport– Sprint – teaser announcements– Telia – Home Run– Asia – Many operators in Singapore, Korea, Taiwan, Japan
• Lot of standards working going on• Really big issue
– Cost is different– Speed is different– Maybe they are really different….
• How this will converge with 3 G is unclear
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Backup Material
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References
IEEE Communication, Feb 2002 –Pages 145-151
Interconnection of WLAN into 3 G networksGlobal Roaming in Next Gen networks
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IEEE Wireless Communications –October 2002 – Pages 112-124
Detailed paper on WLAN / GPRS integration. Good tutorial. Uses a lot of material from TR22.934
WLAN-GPRS Integration for Next-Generation Mobile Data Networks
5
http://www.ietf.org/internet-drafts/draft-buckley-pppext-eap-sim-gmm-00.txt
IETF Document on EAP-SIM-GMMEAP-SIM-GMM4
IETF Document on EAP-SIM
P.S0001-A v3.0 Wireless IP Network Standard (CDMA Based Document)
3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Feasibility study on 3GPP system to Wireless Local Area Network (WLAN)interworking;(Release 6) (GSM based document)
Description
http://www.ietf.org/internet-drafts/draft-haverinen-pppext-eap-sim-07.txt
EAP-SIM3
http://www.3gpp2.org/Public_html/specs/index.cfm
P.S0001-A v3.0 2
http://www.3gpp.org/ftp/Specs/archive/22_series/22.934/
3GPP TR 22.934 V2.0.0 (2002-09)
1
LocationTitleNr
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From 3GPP TR22-934
NOTE 1 : May also include WLAN 3 (Not Illustrated)
No coverageCoverage only available from WLAN3(s)
WLAN(s) coverage not interworked
12
No coverageCoverage available from WLAN1 & WLAN3
Multiple WLAN coverage
11
No coverageCoverage only available fromWLAN2(s)
Single WLAN2 network coverage
10
No coverageCoverage available from WLAN1(s) & WLAN2(s)
Multiple WLAN coverage
9
Coverage from Home and Visited Networks
WLAN1(s) & WLAN2(s) (NOTE 1):
Multiple 3GPP & Multiple WLANs
8
Coverage from visited network only
Coverage only available from WLAN2(s)
Overlapping 3GPP & WLAN coverage
7
Coverage from visited network(s) only
No coverageNetwork(s) 3GPP-V coverage (VPLMN)
6
Coverage from home network and other operator(s)
No coverageMultiple networks 3GPP coverage
5
Home network coverageNo coverageSingle network 3GPP-H coverage (HPLMN)
4
Home network coverageSingle network coverageOverlapping 3GPP & WLAN coverage
3
No coverageCoverage only available from WLAN1(s)
Single network WLAN1 coverage
2
No coverageNo coverageSwitch on1
3GPP PLMN CoverageWLAN CoverageDescriptionState
1
2
3
4 5 6
78
9 10
11
12
3GPP-H 3GPP-VHPLMN VPLMN
WLAN1 WLAN2
WLAN31
2
3
4 5 6
78
9 10
11
12
3GPP-H 3GPP-VHPLMN VPLMN
WLAN1 WLAN2
WLAN3