Transcript Slide 1

Connecting to Multiple Networks using a Single Radio
Victor Bahl
Ranveer Chandra and Pradeep Bahl
MultiNet Approach
Applications
Switch the radio across multiple wireless networks.
Send packets when the network is active, otherwise
buffer. Buffered packets are sent when the network
gets activated.
Cisco Guy at
Microsoft
Buffering
Problem: Handle packets whose destination has
switched to another network using MultiNet. Packets are
lost if not unhandled
Solution: Buffer packets using PSM at APs for IS
networks, and end hosts for AH networks.
Microsoft Employee
Ad Hoc
Infrastructure
Microsoft Employee
Many more applications, such as:
• Gateway node of a wireless ad hoc network
• Bluetooth scatternets
• Extending the range of an infrastructure
network
Some Solutions
Switching Strategies
• Use Multiple Radios:
Have one radio for each desired network.
• Use a single radio
Software approach to stay connected to multiple
networks with a single radio.
Design Constraints
 Power:
Independent power consumption by multiple wireless
cards results in drastic reduction of battery life.
=> Use a single radio, but problems of
 MAC:
Wireless card can be associated to at most one
wireless network.
 Firmware:
Wireless cards send packets only after association to
a network.
Design Principles
 Transparency:
Switching across networks should be transparent
to the user.
 Scalability:
The proposed solution should scale with the
number of users in the network.
 Backward Compatibility:
The solution should work with legacy wireless
cards.
Switching strategies are application dependent.
MultiNet is implemented as a combination of NDIS IM
driver and a user level service
Driver:
 MMD: Miniport instances. One per network, and IP sees
each MMD as a different network card.
 MPD: Manages MMDs, switches card and buffers
packets.
Service:
 Maintains synchronization with other MultiNet nodes
 Sends signals to the IM driver using IOCTLs.
Screen Snapshot
Power (MultiNet vs Dual Radio)
MultiNet consumes around half the total power
consumed by the two radio approach for two networks.