Seamless Handoffs in IP-Based Mobile Communication Networks

1
Seamless Handoffs in IP-Based Mobile
Communication Networks

• NEC Europe MobiCom Group
• H. Hartenstein, F. Griffoul, K. Jonas,
• W. Pokorski, S. Schaller, R. Schmitz
• IPCN Paris, May 2000

2
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

3
Overview scenarios GSM-like networks

• Introduce IP to mobile communication networks

simple hierarchy
access
core ME
BTS BSC
MSC Node B RNC

3GPP
3GPP2
R-P interface
MWIF
IP in the RAN
4
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

micro movement but macro mobility!
ISP1
ISP2
5
Coexistence/convergence of both scenarios ?

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

6
Overview IP-based micro-mobility methods

• Re-addressing-based methods
• keep routes, change address
• ? use of care-of address tunnels
• proposals 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 dilemma
• proposals CIP, HAWAII

7
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) lt5ms MA table update 45ms (not
optimized)
8
Which method for which scenario ?

• 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.

9
Which method for which scenario ?

• 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
10
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?

HA
Domain1
Domain2
11
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...?

12
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)

13
Seamless handoffs via simultaneous bindings

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

1. send reg. req. with S1 and new COA 2.
start sending duplicate packets 3. reg.
reply 4. handoff
14
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 S1 and new co-COA
• get reply ? handoff
• local reconfiguration change co-COA, tunnels
• attach to new BS (e.g. unicast arp)

15
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?

16
Physical interruption vs packet loss
independent streams
Physical interruption 10 ms But what about
packet loss? Depends on the delays of
the different streams between MA and
MN! relativistic effects!
?
17
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)

18
Network-assisted handoffs previous work

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

HA
1. binding udpate 2. handoff request
1
FA
FA
2
19
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?

20
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

21
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/Re
  search/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