1 Tor K Moseng, Handoff in Wireless Internet Access Trial Lecture Vertical and Horizontal Handoff in Wireless Internet Access Tor K Moseng Centre for Quantifiable Quality of Service in Communication Networks Dept. of Telematics, NTNU

2 Tor K Moseng, Handoff in Wireless Internet Access Outline Introduction Horizontal Handover –Handover in GSM –Handover in WiFi Vertical Handover –Handover UMTS-WiFi Handover Approaches Standards –IEEE –UMA –CALM Visions

3 Tor K Moseng, Handoff in Wireless Internet Access Wireless Internet Access Different wireless networks available –E.g. GSM/GPRS, UMTS, WiFi, WiMAX Mobility is Essential –Changes the users’ behavior –Internet access from any wireless device Always best connected –Multi-mode equipment Introduction Internet

4 Tor K Moseng, Handoff in Wireless Internet Access Wireless Internet Access What is handover? –Changing the point of connection while communicating Why is handover needed? –Mobility –User preferences What is the objective? –Handover procedure without a users notice  Seamless handover Introduction

5 Tor K Moseng, Handoff in Wireless Internet Access Network Coverage Introduction WPAN WLANWMANWWANSatellite Bluetooth RFID WiFi IEEE WiMAX IEEE GSM/GPRS UMTS GPS GALILEO Wireless Personal Area Network – In a person’s proximityWireless Local Area Network – Home, Hotel, AirportWireless Metropolitan Area Network – City wide Wireless Wide Area Network – Regional, Cellular systemsSatellite – Worldwide coverage

6 Tor K Moseng, Handoff in Wireless Internet Access Introduction – Use Case 1 BSC BS1BS2BS3 1. Connect to BS1 and start conversation2. Moving out of BS1’s coverage – connect to BS2 3. Moving out of BS2’s coverage – connect to BS34. Conversation ended – still within BS3’s coverage

7 Tor K Moseng, Handoff in Wireless Internet Access Introduction – Use Case 2 Ethernet WiFi UMTS Ethernet WiFi UMTS Ethernet WiFi UMTS Ethernet WiFi UMTS Ethernet WiFi UMTS 1. Wired connection at the working desk2. Moving indoor3. Moving outdoor4. Moving into a hot-spot

8 Tor K Moseng, Handoff in Wireless Internet Access Horizontal Handover Horizontal handover is when a mobile terminal changes its point of connection within the same type of network –E.g. from a cell to another in GSM –E.g. from an access point to another in WiFi Reasons for handover –Worse signal quality or loss of signal –Traffic load balancing –Cost Horizontal Handover

9 Tor K Moseng, Handoff in Wireless Internet Access Handover in GSM Network-controlled, mobile terminal assisted handover –The network takes the handover decisions –The mobile terminal supervises and reports its signal quality Three types of handover –Intra-BSC handover –Inter-BSC handover –Inter-MSC handover Horizontal Handover BSC MSC BSC

10 Tor K Moseng, Handoff in Wireless Internet Access Handover in WiFi Mobile terminal-controlled, network assisted handover –The mobile node chooses new AP to re-associate with –The network exchanges information after re-association Handover in four parts Horizontal Handover Distribution System AP1AP2 BSS1BSS2 IAPP (IEEE f) 1a. Probe request 1b. Probe response 2. Authentication 3. Re-association 4. Connection handover 1a. Probe request 1b. Probe response 2. Authentication 3. Re-association 4. Connection handover 1a. Probe request 1b. Probe response 2. Authentication 3. Re-association 4. Connection handover 1a. Probe request 1b. Probe response 2. Authentication 3. Re-association 4. Connection handover 1a. Probe request 1b. Probe response 2. Authentication 3. Re-association 4. Connection handover 1a. Probe request 1b. Probe response 2. Authentication 3. Re-association 4. Connection handover

11 Tor K Moseng, Handoff in Wireless Internet Access Vertical Handover Vertical handover is when a mobile terminal changes its point of connection in a different type of network –E.g. from a wired Ethernet connection to an access point in WiFi –E.g. from an access point in WiFi to a cell in UMTS Reasons for handover –Worse signal quality or loss of signal –Performance requirements (e.g. bandwidth) –Cost –Power consumption Vertical Handover

12 Tor K Moseng, Handoff in Wireless Internet Access Challenges in Vertical Handover Multi-mode devices Power consumption QoS –Available capacity –Security Timing The business model Session continuity Vertical Handover

13 Tor K Moseng, Handoff in Wireless Internet Access Handover UMTS-WiFi 1.Open coupling –No common subscriber database and billing –Poor handover performance 2.Loose coupling –Common subscriber database and billing –Improved handover performance 3.Tight coupling –UMTS core network interface must be supported  single operator –Improved handover performance Vertical Handover

14 Tor K Moseng, Handoff in Wireless Internet Access Handover UMTS-WiFi Vertical Handover Internet UMTS Core Network WiFi Gateway RNC 1.Open coupling 2.Loose coupling 3.Tight coupling 1.Open coupling 2.Loose coupling 3.Tight coupling 1.Open coupling 2.Loose coupling 3.Tight coupling AAA Node B AP

15 Tor K Moseng, Handoff in Wireless Internet Access Handover Approaches Handover objective is a seamless handover –Smooth handover: low loss –Fast handover: low delay  Smooth and fast handover gives a seamless handover Lower layers handover –Hard handover –Soft handover Network layer mobility –Mobile IP Handover Approaches

16 ”break before make” Tor K Moseng, Handoff in Wireless Internet Access Hard Handover Old connection is broken before a new connection is activated Primarily used in FDMA and TDMA systems (e.g. GSM) –Different frequency ranges used in adjacent cells to minimize the interference When to perform hard handover? –E.g. based on measurements of the signal quality –Different schemes to avoid unnecessary handovers Handover Approaches

17 ”make before break” Tor K Moseng, Handoff in Wireless Internet Access Soft Handover New connection is activated before the old is broken Used in UMTS to improve the signal quality –Uplink and downlink signals may be combined for better signal –A mobile may in UMTS spend a large part of the connection time in soft handover –Better connection reliability More seamless handover Handover Approaches

18 Tor K Moseng, Handoff in Wireless Internet Access Mobile IP Changing the point of connection may change the IP-address –Disrupting the on-going session Mobile IP is a network-layer mobility management solution –Hides the mobile node’s movement from its corresponding node Two IP-addresses involved –Home Address: the point of contact for corresponding nodes –Care-of-Address: the current point of connection Two agents involved –Home Agent: acts as a proxy and forwards packets to the CoA –Foreign Agent: allows mobile nodes to register in ”foreign” subnets Handover Approaches

19 Tor K Moseng, Handoff in Wireless Internet Access Mobile IP Handover Approaches 1. Session with Home Network 2. Move to a Foreign Network 3. Register its presence and Care-of-address 4. Session with Foreign Network Home Agent Foreign Agent Home Address Home Network Foreign Network Care-of-Address Corresponding Node Home Address  Care-of-Address

20 Tor K Moseng, Handoff in Wireless Internet Access Standards for vertical handover IEEE Unlicensed Mobile Access (UMA) Continous Air-Interface for Long and Medium range (CALM) Standards

21 Tor K Moseng, Handoff in Wireless Internet Access IEEE Support seamless vertical handover –Media Independent Handover (IEEE Std , January 2009) –Assess on-going work related to handover in IEEE, IETF and 3GPP –GSM/GPRS, UMTS, IEEE 802.3/11/15.3/16/20 Goals –Framework for vertical handover –Different vendors, operators and users Not covered –Handover policy –Security  What about the business model? Standards – IEEE

22 Tor K Moseng, Handoff in Wireless Internet Access Unlicensed Mobile Access (UMA) 3GPP standard for cellular systems and unlicensed wireless networks handover –A mobile centric version of IEEE The UMA Network Controller (UNC) –Provides an interface into mobile operators core network –Secure transport of mobile signaling over IP Extends a mobile operator’s services over IP-based access networks –Use WiFi to improve coverage and performance of 3G services Standards – UMA

23 Tor K Moseng, Handoff in Wireless Internet Access CALM ISO approved framework for continuous communication across various interfaces and media for vehicular users –ISO TC204/WG16 – Wide Area Communications –IEEE /11p/15/16e/20, 2G/3G, and ITS systems Application support –In-vehicle Internet access –ITS applications (focus on Vehicle Safety Communication) –V2V communication Vertical handover based on IPv6 protocols (ISO 21210) Standards – CALM

24 Tor K Moseng, Handoff in Wireless Internet Access Visions 4G network: Universal wireless access with much higher data rates than today Collection of technologies and protocols –Not just one single standard –Seamless handover and roaming –QoS support Prediction of availability is 2015 (ref:Phil Redman, Gartner) Visions ”Anytime, Anywhere”

25 Tor K Moseng, Handoff in Wireless Internet Access Visions The Wireless World Research Forum (WWRF) formulates visions on strategic future research directions in the wireless field Visions Networks for the Wireless World must enable application- and service-independent end-to-end reachability in the global network environment. Networks for the Wireless World should be capable to support both existing and new mobility mechanisms that enable terminals and networks to move around without being closely tied to so-called ”home” networks.

26 Tor K Moseng, Handoff in Wireless Internet Access References 3GPP, [Online]: Jacques De Kegel, IBM & Wireless 2004, Presentation WIreless e-business EBO, [Online]: Knut Evensen, CALM Architecture and CALM M5 Convenor, Presentation at IEEE 802 Plenary Tutorials, November 2006 Hussain et al., Mobility Management Challenges and Issues in 4G Heterogeneous Networks, In Proceedings of InterSense'06, May 2006 IEEE, [Online]: IETF, [Online]: Juha Korhonen, Introduction to 3G Mobile Communications, 2nd Ed, Artech House, 2003 Lim et al., SHARE: Seamless Handover Architecture for 3G-WLAN Roaming Environment, Wireless Networks, 15: , 2009 Network World, [Online]: Charles Perkins, Presentation at an IEEE 802 Handoff Tutorial, November 2002, [Online]: Bjørn Rønning, UMTS og WLAN - konkurrerende eller komplimentære systemer, Norsk UMTS-forum, Oktober 2001, [Online]: Sharma et al., OmniCon: A Mobile IP-based Vertical Handoff System for Wireless LAN and GPRS Links, In Proceedings of ICPP 2004 Workshops, 2004 UMA Today, [Online]: Wikipedia, The Free Encyclopedia, [Online]: Wireless World Research Forum, [Online]: Qing-An Zeng and D.P.Agrawal, Handoff in Wireless Mobile Networks, Chapter 1, Handbook of Wireless Networks and Mobile Computing, 2002 References