1. Wireless CORBA
Richard Verhoeven

2. Content Quick Introduction to CORBA Wireless & Mobile Wireless CORBA
Test Case
Conclusions

3. What is CORBA? Common Object Request Broker Architecture
Distributed object-oriented middleware
Network abstraction of object location
Independent of programming language, platform or operating system
Set of open standards defined by the OMG
interface definition language (IDL)
interoperability standards (GIOP, IIOP)
collection of services

4. How does it work? Write the interface definition in IDL
Use the ORB-specific IDL compiler to generate client stubs and server skeletons
Use the stubs in the client application
Fill the skeletons with the server implementation
Compile everything

5. Example: IDL interface Account {
void deposit(in unsigned long amount);
void withdraw(in unsigned long amount);
long balance(); };

6. Example: client CORBA::Object_var
obj = orb->string_to_object( uri );
Account_var
account = Account::_narrow( obj );
...
if (account->balance() < 100) {
account->deposit( 500 );
} else {
account->withdraw( 100 ); }

7. Example: server (1) class Account_impl : virtual public POA_Account
{ ...
CORBA::Long _current_balance;
...
void deposit( CORBA::ULong amount)
{ _current_balance += amount; };
CORBA::Long balance()
{ return _current_balance; }; }

8. Example: server (2) … // orb, poa and mgr setup Account_impl*
servant = new Account_impl();
PortableServer::ObjectId_var
oid = poa->activate_object(servant);
… // construct object uri
mgr->activate();
orb->run();

9. Sizes of ORBs

10. Interoperability Timing

11. Wireless & Mobile Wireless protocols Wireless issues Mobile issues
InfraRed, BlueTooth, b, GSM, GPRS, UMTS
Wireless issues
packet loss, network congestion, packet cost
Mobile issues
hand-off, roaming, address changes
Location based services
wireless range, position & direction detection

12. MobileIP IETF solution (RFC 2002) Addresses macro-mobility
home-office, office-travel
Requires an active home agent

13. Wireless CORBA Issues MobileIP Architecture Mobile IORs
Handoff & Access Recovery

14. Wireless CORBA - Issues
CORBA relies on fixed end-points for connections
Nomadic computing
Wireless transport issues
Mobility transparency
Handoff
Backwards compatible

15. Why not MobileIP?
It only addresses macro-mobility, not the movement between small cells
The home agent is too important
It does not address wireless protocols
It hides all handoff events, thus making location-aware services difficult.

16. Architecture

17. Architecture Redirects requests for services on the terminal
Keeps track of the current
access bridge

18. Architecture Encapsulates, forwards or ignores incoming GIOP messages
Decapsulates and forwards
messages from the GIOP tunnel
Generates mobility events
Lists available services

19. Architecture Similar to the Access Bridge Does not provide forwarding
Generates mobility events
Does not list services

20. Architecture Abstract transport-independent tunnel for GIOP messages
Concrete tunnels for TCP/IP,
UDP/IP and WAP.
Protocol requires reliable and
ordered delivery

21. Handoff & Access Recovery
Network initiated handoff
started by an external application
optional to support make-before-break
Terminal initiated handoff
terminal discovered a new Access Bridge
make-before-break is required
Access recovery

22. Handoff Issues The Home Location Agent is informed
Old Access Bridges are informed to allow forwarding of open connection
Mobility events are generated in the visited domain and the terminal domain

23. Test Case ITEA Project “Vivian” Common platform for mobile phones
CORBA for distributed middleware
SOAP as alternative

24. Test Case Mobile device (Psion Revo) Java virtual machine Java ORB
XML sax parser
Remote User Interface Protocol
Conclusion: it works reasonable
(Wireless CORBA not used yet)

25. Conclusions
Wireless CORBA addresses wireless & mobility, not low resource constraints.
CORBA works on a mobile device, but it requires lots of resources
Handoff notification breaks the layered network model