Download A Survey of Wireless Independent Hand-off

Wireless Network Independent
Hand-Off
Bill Phillips
17 November 2006
Outline
• Motivation/Overview
• Types of Hand-Off
• 802.21 MIH
–
–
–
–
Protocol Description
MIH Function and Key Services
Link Layer Event Triggers
References
• 802.16e/WiMAX
– Key Players
– Protocol Description
– References
• WiBro
– Comparison to WiMAX
– Hand-off Example
– References
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802.21 Media Independent
Hand-off (MIH)
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Motivation for Wireless Hand-Off
• Multiple Wireless Technologies Co-exist
–
–
–
–
WiMAX (802.16e)/WiBro
WLAN (802.11a,b,g)
Cellular (GPRS,CDMA-2000,3GPP)
Bluetooth
• Current technologies are limited to a
specific range
– WAN/MAN
– LAN
– PAN
• Users desire seamless wireless
connectivity
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Types of Hand-off
• Hard Hand-off
– Link is broken before new one is formed
• Soft Hand-off
– Link is established before old one is terminated.
• Seamless Hand-off
– Soft hand-off in which there is no loss of information
• Homogeneous (Horizontal) Hand-off
– Within Single Network (Localized Mobility)
• 802.11b to 802.11g
• One network access point to another in the same network.
– Limited opportunities (reliant on a single network)
• Heterogeneous (Vertical) Hand-off
– Across Different Networks (Global Mobility)
• Cellular to WIMAX to 802.11g
– 802.21 defines a framework for vertical handovers between
heterogeneous networks.
– Optimal Network Selection
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802.21 Overview
• Emerging IEEE Standard for Media Independent Hand-off
(MIH)
• First draft standard May ‘05/Current draft standard March ‘06
• Includes protocol specifications for:
–
–
–
–
Cellular (GSM/GPRS)
WiFi (802.11a,b,g)
WiMAX (802.16e)
Bluetooth (802.15.1)
• Protocol benefits
–
–
–
–
Seamless (low latency), vertical hand-off
Automatic detection and selection of network access points
Hand-off triggers that allow smooth, low loss network transitions
Automatic, intelligence selection of the optimal network based on
the user’s bandwidth and throughput requirements
– Supports both point-to-multipoint (user to access point) and peerto-peer (adhoc) connectivity
– Open source, compatible with other 802 standards
– Compatible with standard security algorithms
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Optimal Network Selection
• 802.21 specifies triggers that are used by the mobile
device to determine the optimal network when more
than 1 is present (network overlays)
–
–
–
–
–
signal quality
synchronization time differences
transmission error rates
available bandwidth
quality of service (QoS)
• Metrics are tracked in the mobile device, which
makes the determination to transfer to another
access point.
• The access point does not make the decision to
initiate hand-off (in the case of vertical hand-offs)
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802.21 Protocol Responsibility
Hand-off
Initiation
Hand-off
Preparation
Hand-off
Execution
Search
New Link
Setup
New Link
Transfer
Connection
Network Discovery
Network Selection
Hand-off Negotiation
Link Layer Connectivity
IP Layer Connectivity
Handover Signaling
Context Transfer
Packet Reception
802.21 Specification
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Other 802 Standards
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MIH Function
• MIH Function is
the set of handoff enabling
functions in the
protocol stack
(hand-off
intelligence).
• Primarily link layer
protocols
• Event Service info flows up
(detection)
• Command Service –
info flows down
(control)
• Information
Service – info
flows both ways
(query/response)
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Mobility Management Protocol Stack
(Heterogeneous Hand-off)
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MIH Services
• Media Independent Event Services (MIES)
– Triggered events corresponding to dynamic changes in the
link characteristics or status
• Media Independent Command Services (MICS)
– Used to manage and control link behavior relevant to handoffs and mobility
– Uses event service information as part of the subscription
and notification process
• Media Independent Information Services (MIIS)
– Provides an information model that passes on awareness
regarding the neighboring networks and their capabilities.
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MIES (Event Services)
Link State Changes
Event Services
Link Characteristics
Event Classification
Link Status
Event Filtering
Link Quality
Event Reporting
• Reports local and remote events to higher layers.
– Local Events: take place at mobile node.
– Remote Events: take place in other network elements (i.e.
link A going down at time t)
• Subscription/Notification Procedure
– MIES registers with MAC layer, and is notified if a
subscription event occurs.
– Trigger examples
• Link up/down
• Link parameters change
• Link hand-off imminent
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MICS (Command Services)
•
•
•
•
•
Controls MIH functions, and layer 2 services
Executes IP mobility and connectivity decisions
Both local and remote commands are possible
Includes link discovery and link configuration
Example commands:
–
–
–
–
MIH Poll
MIH Scan
MIH Configure
MIH Switch
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MIIS (Information Services)
• Link-Layer convergence zone for multiple
heterogeneous access technologies
• Unified presentation to upper layers of the mobilitymanagement protocol stack
• Awareness of neighboring networks and available
resources
• Facilitates effective network access
• Facilitates hand-off decisions
• Information discovery only/Does not make hand-off
decisions
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802.21 Test Bed
802.21 Test Bed Scenario
A.Dutta, S.Das, D. Famolari, Y.Ohba, K.Taniuchi, T.Kodama, H.Schulzrinne Seamless Handoff across Heterogeneous
Networks - An 802.21 Centric Approach IEEE WPMC 2005
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Scenario Setup
• Mobile node (network 1) is communicating with the
Correspondent node (network 4)
• Mobility management protocol: (SIP-M)
• Configuration protocol: DHCP
• Authentication agent: PANA Server
• Voice traffic protocol: RTP/UDP
– CODEC sampling speed: 20ms
• During simulation, the mobile node travels from
coverage area 1 to coverage area 2/3
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Scenario Results (baseline)
• Non-802.21 based hand-off (baseline)
–
–
–
–
Hand-off delay: 4 seconds
200 packets lost
Packet loss during mobile node’s movement
Delays
• IP address assignment (DHCP identification of duplicate IP
addresses)
• Post-authentication
• Mobility binding update
• Baseline repeated with CDMA and GPRS in coverage
area 2/3
– Hand-off delay: 15 seconds
– Lengthy authentication and connection establishment
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Scenario Results
• 802.21 based hand-off implementation
– Hand-off delay: 0 seconds
– 0 packets lost
– Advanced network discovery
• Access points, channels, Ethernet addresses, DHCP and PANA
servers
– Information
service:
RDF/XMLbased query
response
mechanism
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802.21 References
• IEEE 802.21, Media Independent Handover Services, Draft
Standard available at http://www.ieee802.org/21
• A.Dutta, S.Das, D. Famolari, Y.Ohba, K.Taniuchi, T.Kodama,
H.Schulzrinne Seamless Handoff across Heterogeneous
Networks - An 802.21 Centric Approach IEEE WPMC 2005
• A.Dutta, S.Das,
D.Famolari,Y.Ohba,K.Taniuchi,V.Fajardo,T.Kodama,H.Schulzrinne
Secured Seamless Convergence across Heterogeneous Access
Networks, World Telecommunication Congress 2006, Budapest,
Hungary, .
• C. Dannewitz, S. Berg, and H. Karl, "An IEEE 802.21-based
Universal Information Service", in Proc. of the Wireless World
Research Forum Meeting 16, April 2006.
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802.16-2005 (802.16e)
Wireless MAN/WiMAX
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Key Players Vital Statistics
• 16 IEEE articles published since 2004 on WiMAX
hand-off
– No articles prior to 2004 (year work began on 802.16e)
– 802.16 committee formed in 1999 and first iteration of the
standard was approved in 2002 (originally wired standard)
• 12 different research groups
• Spread across 6 different countries
–
–
–
–
–
–
USA (4 groups / 5 articles)
Korea (4 groups / 5 articles)
China (1 group / 3 articles)
France (1 group / 1 article)
Singapore (1 group / 1 article)
Sweden (1 group / 1 article)
No single
center of
research or
field leader
• Conclusion: 802.16 handoff to other wireless or wired
technologies is an emerging area of research.
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Primary Players
• Jing Nie, Xin He, JiangChuan Wen, Qi Dong, Zheng Zhou,
ChengLin Zhao
– Beijing University of Posts and Telecommunications, China
– 3 articles on 802.16 to/from 802.11 handoff
– All published in 2005
• Sunghyun Cho, Jonghyung Kwan, Chihyun Park, Jung-Hoon Cheon,
Ok-Seon Lee, Kiho Kim, Sik Choi, Gyung-Ho Hwang, Taesoo Kwon,
Ae-Ri Lim, Dong-Ho Cho
– Samsung Advanced Institute of Technology, Korea
– 2 articles on 802.16 hard/soft handoffs with simulations
– Published 2005 & 2006
• Kin K. Leung, Sayandev Mukherjee, George E. Rittenhouse
– Imperial College, England / Bell Labs, Lucent Technologies
– 2 articles on 802.16 mobile handoff and energy conservation
– All published in 2005
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Handoff Parameter Consideration
• How to determine the ”best” network when making a
vertical handoff decision?
–
–
–
–
–
–
–
Signal-to-interference ratio (or SNR or SSI)
Link/route cost (network policies)
Overall network performance (or capacity)
Power consumption/cost
Mobile host speed (small or large coverage foot print)
Traffic demand/speed-of-service (acceptable latency)
Quality of Service
• Algorithm should take all these parameters into
consideration
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802.16 QoS Features
• Differentiated levels of QoS.
• Demand Assigned Multiple Access (DAMA) allocates
time slots (bandwidth resources) based on demand
and QoS requirements.
• QoS is set at the time that the connection is
established, and cannot be adjusted.
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WiMAX Link Layer Specification
- Transformation of
external network data
into MAC SDUs;
- Payload header suppression
- System Access
- Bandwidth Allocation
- Connection set-up
- Connection maintenance
- QoS
- Authentication
- Secure key exchange
- Encryption
WiBro web site
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Convergence Sublayer
•
•
•
•
•
Funnel point between the Link Layer and Network Layer.
Data classification from higher layers
Ensures delivery to proper MAC SAP
Two sublayers specified: ATM and Packet
ATM CS features
– ATM cells mapped to MAC frames
– Several ATM cells with same connection ID may be packed to save
bandwidth
– Supports common channel signaling (CCS)
– Assigns channel ID (CID)
– Performs Payload Header Suppression (PHS)
• Packet CS features
– Used for all packet-based protocols (IP, Ethernet)
– Performs Payload Header Suppression (PHS)
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MAC Common Part Sublayer
• Defines multiple-access mechanism
• On downlink only base station transmitting
– no need for coordination
– base station broadcasts,
– stations retain only messages addressed to them
• On uplink user stations have to share bandwidth
– access determined by:
• unsolicited bandwidth grants
• polling procedures
• Contention procedures
– sharing dynamic and with on-demand basis
– sharing can depend on service classes (continuing rights to
transmit / transmit right only on request)
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Handoff Manager
• Located in network layer and interacts with both:
– the physical and data link layer, and
– the network layer
• Information collected:
– User preferences
– Network parameters (signal strength, available bandwidth,
network latency, and route cost)
Application
TELNET
Transport
TCP
Network
Data Link
IP
802.11n
FTP
HTTP
UDP
Handoff Manager
802.16e
Physical
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WiMAX References
•
•
•
Benefit-driven handoffs between WMAN and WLAN
Jing Nie; Xin He; Zheng Zhou; Cheng Lin Zhao;
Military Communications Conference, 2005. MILCOM 2005. IEEE
17-20 Oct. 2005 Page(s):2223 - 2229 Vol. 4
(ref A) Guo C, Guo Z, Zhang Q, Zhu W. A Seamless and Proactive Endto-End Mobility Solution for Roaming Across Heterogeneous Wireless
Networks. Selected Areas in Communications, IEEE Journal on, Volume:
22, Issue 5, June 2004, Pages 834-848
WiMAX Link Layer Overview
http://www.cs.tut.fi/~83180/83180_05_S8c.pdf
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Further Interest
•
•
•
•
•
•
•
•
In-vehicle secure wireless personal area network (SWPAN) Mahmud, S.M.; Shanker, S.;
Vehicular Technology, IEEE Transactions on
Volume 55, Issue 3, May 2006 Page(s):1051 - 1061
Hard Handoff Scheme Exploiting Uplink and Downlink Signals in IEEE 802.16e Systems
Sunghyun Cho; Kwun, J.; Chihyun Park; Jung-Hoon Cheon; Ok-Seon Lee; Kiho Kim;
Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd
Volume 3, 2006 Page(s):1236 – 1240
An Architecture for UMTS-WIMAX Interworking
Nguyen-Vuong, Q.; Fiat, L.; Agoulmine, N.;
Broadband Convergence Networks, 2006. BcN 2006. The 1st International Workshop on
07-07 April 2006 Page(s):1 - 10
A handover framework for seamless service support between wired and wireless networks
Ok Sik Yang; Seong Gon Choi; Jun Kyun Choi; Jung Soo Park; Hyoung Jun Kim;
Advanced Communication Technology, 2006. ICACT 2006. The 8th International Conference
Volume 3, 20-22 Feb. 2006 Page(s):6 pp.
Fast Handover Algorithm for IEEE 802.16e Broadband Wireless Access System
Doo Hwan Lee; Kyamakya, K.; Umondi, J.P.;
Wireless Pervasive Computing, 2006 1st International Symposium on
16-18 Jan. 2006 Page(s):1 - 6
Determining the best network to handover among various IEEE 802.11 and IEEE 802.16 networks by
a mobile device
Garg, A.; Kin Choong Yow; Mobile Technology, Applications and Systems, 2005 2nd International Conference
on 15-17 Nov. 2005 Page(s):1 - 6
Benefit-driven handoffs between WMAN and WLAN
Jing Nie; Xin He; Zheng Zhou; Cheng Lin Zhao;
Military Communications Conference, 2005. MILCOM 2005. IEEE
17-20 Oct. 2005 Page(s):2223 - 2229 Vol. 4
Communication with bandwidth optimization in IEEE 802.16 and IEEE 802.11 hybrid networks Jing Nie;
Xin He; Zheng Zhou; Chenglin Zhao;
Communications and Information Technology, 2005. ISCIT 2005. IEEE International Symposium on Volume
1, 12-14 Oct. 2005 Page(s):27 – 30
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Wireless Broadband
(WiBro)
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WiBro Overview
• WiBro – Korean Wireless
Broadband
telecommunications
technology.
• Cellular architecture where
base stations offer a 3050 Mbps aggregate data
throughput up to 5-km
(eventual goal).
• Supports mobile users.
• Supports different levels
of QoS.
• TDD Duplexing
• OFDMA Multiple Access
• 10-MHz Channel bandwidth
• Proprietary standard with
consortium consisting of primary
members: Korean Telecom, SK
Telecom, Samsung, LG Electronics,
and Intel Korea.
Wikipedia
WiBro web site
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WiBro Achievements
• Feb 2002 – Korean government allocated 100 MHz in
the 2.30 to 2.31-GHz band.
• Nov 2004 – WiMax and WiBro agree to make sure
that these technologies are interoperable.
• Nov 2005 – Korean Telecom successfully
demonstrated a WiBro network consisting of several
hundred PDA and laptop users.
• Feb 2006 – Telecom Italia successfully demonstrated
a WiBro network at the Winter Olympics with
10Mbps download speeds while moving at 120 km/h.
• Oct 2006 – WiBro conference hosted in Korea
iBizToday
Korean Times
Telcoeye
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WiBro Network Architecture
Public IP Network
HA
Operator’s
IP Network
AAA
ACR
ACR
RAS
PSS
RAS
PSS
RAS
RAS
PSS
• HA – Home
Agent
• AAA –
Authentication,
Authorization,
…
…
Accounting
Server
• ACR – Access
Control Router
• RAS – Radio
Access Station
• PSS – Personal
Subscriber
PSS
Station
WiBro web site
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Relationship between WiBro and WiMax
• WiBro is a complete subset of the 802.16 architecture /
Developed in conjunction with the 802.16e standard
– Supports IEEE Standard P802.16e (TDD, Freq Reuse
Factor=1, at least 60km/hr mobility support, Freq
Allocation >= 9 MHz, roaming between operators)
– Supports the mandatory features of IEEE 802.16 (i.e. QoS).
– WiBro Profile = the set of functionalities configuring every
mandatory feature and many optional features of 802.16e.
– WiBro Air Interface Specification is fully compatible with
IEEE P802.16e
– WiBro Profiles and Test Specifications will be harmonized
with WiMAX Forum’s currently developing Mobile WiMAX
Profiles and Test Specifications. (Most of the major
manufacturers are participating as the active members of
WiBro and WiMAX.)
WiBro web site
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WiBro Physical Layer Specification
• High spectrum efficiency
– TDD
– 10-MHz channels
• 8.447-MHz signal bandwidth
• 1.553-MHz guard band
– OFDMA multiple access scheme to support different
bandwidth needs/QoS
– QPSK, QAM-16 or QAM-64 modulation with convolution
turbo coding
• Less need for retransmission
• Improves effective range up to 5-km
• Wide coverage
– Frequency reuse factor = 1
– Reed Solomon orthogonal sequences minimize interference
between neighboring subscribers
WiBro web site
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WiBro Physical Layer Specification
• Mobility performance enhancement features
– Hybrid ARQ (H-ARQ) combines ARQ and FEC for better
efficiency
– Short OFDM symbol length in order to guarantee 60 km/h
mobility
• Supports multiple types of QoS
– Best effort
– Real-time polling
– Non real-time polling
• Power conservation
– Supports sleep mode
• Smart antenna
– Provides improved SNR and range extension (low mobility or
stationary)
WiBro web site
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Hand-off Example
Fr#(n)
RAS
#1
PSS
Fr#(n+1)
RAS
#1
Fr#(n+2) Fr#(n+3) Fr#(n+4) Fr#(n+5) Fr#(n+6) Fr#(n+7) Fr#(n+8) Fr#(n+9) Fr#(n+10)
RAS
#1
RAS
#1
RAS
#1
RAS#1 communicates
through the backbone with
RAS#2 and RAS#3
and decides which one to
recommend the PSS to
transition to
PSS
PSS
HO-REQ
Possible target RAS:
RAS#2: S/N=15dB
RAS#3: S/N=17dB
Time to HO: 7 Frames
PSS
RAS
#1
RAS
#1
RAS
#3
HO-IND
PSS
PSS
PSS
RAS
#3
PSS
RAS
#3
REG-REQ
RNG-RSP
DL-MAP
HO-RSP
Recommended target RAS:
RAS#3: S/N=17dB
Time to HO: 3 Frames
RAS
#3
RNG-REQ
HO-RSP
PSS
RAS
#3
Fr#(n+11)
PSS
REG-RSP
PSS
PSS
RAS 2
ACR
RAS 1
RAS 3
PSS
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PSS
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WiBro References
• Wikipedia entry on WiBro. http://en.wikipedia.org/wiki/WiBro
• iBizToday news article. “WiBro, WiMax Get Closer”.
http://www.ibiztoday.com/eng/articleviewer.html?art_id=50032
&lang=eng; November 15, 2004.
• Korean Times news article. “KT’s WiBro Broadens Wireless
Realm”.
http://times.hankooki.com/lpage/biz/200511/kt20051117161939
11860.htm; November 17, 2005.
• Italian Telecommunication Journal, Telcoeye. “WiBro a Torino:
10 Mbps in movimento”.
http://www.maxkava.com/2006/02/wibro-torino-10-mbps-inmovimento.html; February 10, 2006.
• WiBro offical site (English). http://www.wibro.or.kr/
• Richardson, Michael and Ryan, Patrick S., "WiMAX: Opportunity
or Hype?" . ITERA, 2006 Available at SSRN:
http://ssrn.com/abstract=892260
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