Maintaining Performance while Saving Energy on Wireless LANs
+Ronny Krashinsky
Motivation
.Mobile devices limited by battery weight and lifetime
Wireless network access consumes a lot of energy
Want to disable the network interface card whenever its not in use
Basic problem: data may arrive from the network at any time
Focus of this work: a mobile client communicating with a wired base-station to perform request/response traffic (e.g. web browsing)
Not focusing on: ad hoc networks, mobile servers, real-time communication (voice)
Not relying on high-level knowledge of application state
802.11 Power-Saving Mode Overview (For Infrastructure Networks)
Network Interface Card power consumption:
Cisco Aironet: 1.7W Tx, 1.2W Rx, 1.1W Idle, 50mW Sleep
Basic idea: sleep to save energy, periodically wakeup to check for pending data
Clients go to sleep after sending or receiving data
Base-station buffers received data while client is asleep
Base-station sends out beacons every 100ms indicating whether or not the Client has pending data
Client wakes up to listen to beacon, then polls Base-station to receive data (ListenInterval can be less than BeaconPeriod)
Client can wake up to send data at any time
Talk Outline
Measured performance of TCP over 802.11 PSM (it’s not good)
Trace analysis for characteristics of client HTTP traffic (how to save energy)
Proposed enhancements to 802.11 PSM to improve performance and minimize energy
Simulation of web browsing traffic over existing 802.11 PSM and alternatives
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