Events Calendar

WiFi-Nano : Reclaiming WiFi Efficiency through 800 ns slots

Speaker: Krishna Chintalapudi, Microsoft Research

Talk Title: WiFi-Nano : Reclaiming WiFi Efficiency through 800 ns slots

Abstract: The increase in WiFi physical layer transmission speeds from 1~Mbps to 1 Gbps has reduced transmission times for a 1500 byte packet from 12 ms to 12 us. However, WiFi MAC overheads such as channel access and acks have not seen similar reductions and cumulatively contribute about 150~$\mu s$ on average per packet. Thus, the efficiency of WiFi has deteriorated from over 80% at 1~Mbps to under 10% at 1~Gbps. WiFi-Nano, allows WiFi to to use 800 ns slots to significantly improve WiFi efficiency. Reducing slot time from 9 us to 800 ns makes backoffs efficient, but clear channel assessment can no longer be completed in one slot since preamble detection can now take multiple slots. Instead of waiting for multiple slots for detecting preambles, nodes speculatively transmit preambles as their backoff counters expire, while continuing to detect premables using self-interference cancellation. Upon detection of preambles from other transmitters, nodes simply abort their own preamble transmissions, thereby allowing the earliest transmitter to succeed. Further, receivers speculatively transmit their ack preambles at the end of packet reception, thereby reducing ack overhead. We validate the effectiveness of WiFi-Nano through implementation on an FPGA-based software defined radio platform, and through extensive simulations, demonstrate efficiency gains of up to 100%.

Biography: I am a researcher in the Mobility, Networks, and Systems group at Microsoft Research India. Prior to joining MSR I was a Senior Research Engineer at Bosch Research and Technology Center in Palo Alto, CA, USA. I graduated from University of Southern California with a PhD in Computer Science in 2005. My advisor was Prof. Ramesh Govindan. I obtained my Masters in Electrical Engineering from Drexel Univerity in 1999 and my B.Tech in Electrical Engineering from the Institute of Technology, Banaras Hindu University in 1997. My research interests broadly lie in the area of wireless networking systems. In the past I have worked on various aspects of wireless sensor networks, WiFi, Cognitive and WhiteSpace Networking and indoor localization of mobile devices.

Host: Urbashi Mitra, x0-4667, ubli@usc.edu

Location: Seaver Science Library (SSL) - 150

Audiences: Everyone Is Invited

Contact: Gerrielyn Ramos