-1- NEC Europe Ltd. NDL-E Heidelberg MobiCom Group Seamless Handoffs in IP-Based Mobile...

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NEC Europe Ltd. NDL-E Heidelberg MobiCom Group

Seamless Handoffs in IP-Based Mobile Communication Networks

NEC Europe MobiCom GroupH. Hartenstein, F. Griffoul, K. Jonas,

W. Pokorski, S. Schaller, R. Schmitz

IPCN Paris, May 2000

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Outline

• Where and to what degree do we need IP-based micro-mobility support?– Wireless IP access scenarios– IP-based micro-mobility options – Our view (for discussion)

• Seamless inter-domain handoffs with simultaneous bindings– Assumptions, ‘architecture’, results, open

issues

• Network-assisted handoffs

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Overview scenarios: GSM-like networks

“Introduce IP to mobile communication networks”

access coreME BTS BSC MSC Node B RNC

MIPlink3GPP

MIPlink3GPP2

R-P interface

simple hierarchy

MWIF “IP in the RAN”

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Overview scenarios: existing IP networks

“add wireless access to IP networks”

(office/corporate environment, campus, ISP)• IP ‘plug-and play’ base stations• no dedicated access network• have to take into account existing subnet structure • extreme case: ‘neighborhood networks’

ISP1 ISP2

micro movement butmacro mobility!

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Coexistence/convergence of both scenarios ?

• future trend: ‘routable’ RAN? (comes later)• connection between private and public networks?

RNC

UTRAN

AAAHA

802.11

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Overview: IP-based micro-mobility methods

• Re-addressing-based methods:“keep routes, change address”

use of care-of address & tunnelsproposals: regional registrations, region-aware foreign agents,

Dynamics, hierarchical MIPv6 etc.

• Routing-based methods:“keep address, change routes”

no need for changing care-of address, no tunnels (within domain)

but “all or nothing” dilemmaproposals: CIP, HAWAII

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Which method for which scenario ?

For GSM/UTRAN type of networks:

• standard assumption ‘switching MA is far away’ not valid here

• one additional ‘FA’ level might be needed

• intra-RNC handoffs do not require new COA assignments

Simple Linux test example:

MA

RTT (MN-MA): <5ms

MA table update: 45ms (not optimized)

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For addition of wireless access to existing corporate/campus IP networks:

• Within a subnet there is no need for IP-based mobility management.

• Re-addressing-based methods introduce ‘functionality’ only at certain locations, while routing-based approaches suffer from the ‘all or nothing’ dilemma.

• Since RTTs are small in these environments, only small number of levels in the hierarchical setup are needed.

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For future trends:• Routable access networks:

– ‘IP up to the BS’

– MA still only some hops away, but COA assignments (or other negotiations) become bottleneck

– here, routing-based methods might be the choice when the access network is a ‘dedicated’ network

R-Point (e.g. Iu)

IP NETWORK

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Inter-domain handoffs

• Motivation: micro-mobility solutions only work within an ‘administrative’ domain

• We like to have seamless handoffs between different domains

• Simultaneous bindings: unicast - multicast - unicast handoff

• Finally, can we use this also within a domain?

Domain1 Domain2

HA

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Smooth handoff as a resource problem

Trade-off: degree of smoothness vs ‘costs’:

• How many independent receiver/sender at mobile terminal?– e.g. UMTS/GPRS WaveLAN handoff: seamless

handoff is easy since one has two independent receiver/sender; only critical point is processing at MA.

– e.g. WaveLAN WaveLAN adhoc + same freq.: zero loss, zero delay!

• How much bandwidth do we like to invest?• How many IP addresses?• Cell overlaps...?

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Our assumptions:

• one receiver/sender– e.g. intra-technology:

• UMTS operator UMTS operator• RNC RNC• WLAN WLAN (infrastructure, diff. freq.)

– one ‘software radio’• mobile terminal receives ‘control channel’ or

BS ID on link level– two options: MN scans like in 802.11 or gets

information from network (like in GSM)

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Seamless handoffs via simultaneous bindings

Set up (via old BS) sending of duplicate packets to new BS.

1. send reg. req. with S=1 and new COA

2. start sending duplicate packets

3. reg. reply

4. handoff

Domain1 Domain2

MA

1 23

4

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More detailed:

• we assume co-COA (but works also for FAs)• get BS ID from beacon/control channel• translate BS ID to IP subnet address• get new co-COA (via ‘address assignment server’,

DHCP?)• send reg. request with S=1 and new co-COA• get reply handoff

– local reconfiguration: change co-COA, tunnels

– ‘attach’ to new BS (e.g. unicast arp)

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Results, implementational issues, open issues

Our testbed: IPv4, Linux, Dynamics.

Packet duplication (at MA with sim. bindings): in user space using DIVERT sockets (easy but with performance penalty) or modifying kernel modules

Physical interruption: time needed for local

reconfiguration. In our tests: 10 ms (but this is a

system issue!)

Open issues: – address assignment, address leasing, when do we give the

address back?– multicast?– how to deal with ‘network unreachable’ at new BS?

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Physical interruption vs packet loss

Domain1 Domain2

MA

Physical interruption: 10 ms

But what about packet loss?

Depends on the delays of thedifferent streams betweenMA and MN!relativistic effects!

‘independent streams’

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Network-assisted handoffs

• what do we mean by ‘network-assisted’?– network decides/forces handoffs

– network helps to set up ‘resources’ before actual handoff: ‘make before break’

– simultaneous bindings are network-assisted

• why network-assisted handoffs?– traffic considerations, load balancing, interference

minimization etc.

– cost considerations...

– seamless handoffs (vs fast handoffs)

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Network-assisted handoffs: previous work

Calhoun/Kempf proposal: FA assisted handoff, defines a handoff request message.

HA

FA FA

1

2

1. binding udpate2. handoff request

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Network-assisted handoffs: our view

• de-couple handoff support from FA functionality• send ‘request’ over old BS and use sim. bindings

– otherwise one has to process two streams independently at the MN

– in the case of a breakdown of the connection to the old BS, the MN is the first to notice and has to find a new BS + has to send registration request

– handoff request only necessary when network wants the handoff or MN not aware of its options

• network layer - link layer interworking?– does the network need ‘measurement’ reports?

– if yes, how are they transported?

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Summary

• presented our view of the current micro-mobility landscape

• presented experiments for inter-domain handoffs using simultaneous bindings– set up everything via old BS

– physical interruption is small (10 ms)

– simultaneous bindings should be kept as an option

• presented ideas on a more general ‘network-assisted handoff’ framework

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References • 3GPP Technical Report 23.923 v1.0.0, Combined GSM and MobileIP Mobility Handling in UMTS IP

CN, October 1999• Y. Xu (ed.), Mobile IP Based Micro Mobility Management Protocol in The Third Generation Wireless

Network, internet draft, work in progress, March 2000• MWIF see http://www.mwif.org• E. Gustafsson, A. Jonsson, C. Perkins, Mobile IP Regional Registration, internet-draft, work in

progress, March 2000• S. F. Foo, K. C. Chu, Regional Aware Foreign Agent (RAFA) for Fast Local Handoffs, internet draft,

expired, November 1998• Dynamics HUT Mobile IP see http://www.cs.hut.fi/Research/Dynamics• C. Castellucia, A Hierarchical Mobile IPv6 Proposal, Raport technique no 0226, INRIA, November

1998• A. Campbell et al., Cellular IP, internet draft, work in progress, Oct. 1999• R. Ramjee et al., IP micro-mobility support using HAWAII, internet draft, work in progress, June

1999• another proposal employing sim. bind.: K. El Malki, H. Soliman, Hierarchical Mobile IPv4/v6 and

Fast Handoffs, internet draft, work in progress, March 2000 • J. Kempf, P. Calhoun, Foreign Agent Assited Hand-off, internet draft, work in progress, January

2000• a general paper on handoffs: N. Tripathi, J. Reed, H. VanLandingham, Handoff in Cellular Systems,

IEEE Personal Communications, December 1998, pp. 26-37

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