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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 November 17, 2006 Wireless Network Independent Hand-Off 2 802.21 Media Independent Hand-off (MIH) November 17, 2006 Wireless Network Independent Hand-Off 3 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 November 17, 2006 Wireless Network Independent Hand-Off 4 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 November 17, 2006 Wireless Network Independent Hand-Off 5 802.21 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 November 17, 2006 Wireless Network Independent Hand-Off 6 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) November 17, 2006 Wireless Network Independent Hand-Off 7 802.21 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 November 17, 2006 Wireless Network Independent Hand-Off Other 802 Standards 8 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) November 17, 2006 Mobility Management Protocol Stack (Heterogeneous Hand-off) Wireless Network Independent Hand-Off 9 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. November 17, 2006 Wireless Network Independent Hand-Off 10 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 November 17, 2006 Wireless Network Independent Hand-Off 11 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 November 17, 2006 Wireless Network Independent Hand-Off 12 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 November 17, 2006 Wireless Network Independent Hand-Off 13 802.21 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 November 17, 2006 Wireless Network Independent Hand-Off 14 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 November 17, 2006 Wireless Network Independent Hand-Off 15 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 November 17, 2006 Wireless Network Independent Hand-Off 16 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 November 17, 2006 Wireless Network Independent Hand-Off 17 802.21 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. November 17, 2006 Wireless Network Independent Hand-Off 18 802.16-2005 (802.16e) Wireless MAN/WiMAX November 17, 2006 Wireless Network Independent Hand-Off 19 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. November 17, 2006 Wireless Network Independent Hand-Off 20 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 November 17, 2006 Wireless Network Independent Hand-Off 21 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 November 17, 2006 Wireless Network Independent Hand-Off 22 802.16 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. November 17, 2006 Wireless Network Independent Hand-Off 23 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 November 17, 2006 Wireless Network Independent Hand-Off 24 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) November 17, 2006 Wireless Network Independent Hand-Off 25 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) November 17, 2006 Wireless Network Independent Hand-Off 26 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 November 17, 2006 Wireless Network Independent Hand-Off 27 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 November 17, 2006 Wireless Network Independent Hand-Off 28 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 November 17, 2006 Wireless Network Independent Hand-Off 29 Wireless Broadband (WiBro) November 17, 2006 Wireless Network Independent Hand-Off 30 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 November 17, 2006 Wireless Network Independent Hand-Off 31 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 November 17, 2006 Wireless Network Independent Hand-Off 32 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 November 17, 2006 Wireless Network Independent Hand-Off 33 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 November 17, 2006 Wireless Network Independent Hand-Off 34 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 November 17, 2006 Wireless Network Independent Hand-Off 35 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 November 17, 2006 Wireless Network Independent Hand-Off 36 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 November 17, 2006 Wireless Network Independent Hand-Off PSS 37 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 November 17, 2006 Wireless Network Independent Hand-Off 38