Performance Enhancement by Using PHY Layer Information in Wireless Networks

MPhil Thesis Defence


Title: "Performance Enhancement by Using PHY Layer Information in
Wireless Networks"

By

Mr. Haochao Li


Abstract

In recent years, the increasing demand for mobility over the world has caused a 
proliferation of using wireless network. Though the current wireless 
technologies have been developed rapidly, the intrinsic characteristics of 
wireless communication itself have largely limited its development in the near 
future. The interference caused by wireless’s broadcast nature and its 
fragility due to the environment changes limit the transmission capacity and 
quality of today’s wireless network. Thus accurately determining an instant 
wireless link quality is essential for most protocol and application designs 
and becomes a big challenge for the further development in wireless 
communications. In previous studies, packet-level metrics are utilized to 
reflect the link quality, e.g., Packet Reception Rate (PRR). In practice, 
however, these metrics exhibit many limitations and could be misleading without 
regarding the dynamics in wireless. Motivated by this, I propose to use more 
fine-grained information from the physical layer for link quality estimation 
purpose. Further inspired by the idea in Side Channel, the designated 
interference patterns retrieved from physical layer can be used for encoding 
extra information without degrading the effective throughput of the original 
transmission. However, this idea is currently only based on the coding 
redundancy in Direct Sequence Spread Spectrum (DSSS). In order to realize it in 
a more general scheme, i.e., OFDM-based WLANs, I then propose a new 
communication model, hJam that explores the physical layer information in an 
entirely different way. In hJam, the control messages in a multiple-user 
wireless network will be “attached” to the normal data transmission. hJam is 
implemented on the GNU Radio testbed consisting of eight USRP2 nodes. My 
comprehensive simulations and the experimental results show that hJam can 
improve the WLANs efficiency by up to 200% compared with the existing 802.11 
family protocols.


Date:			Wednesday, 6 July 2011

Time:			2:00pm – 4:00pm

Venue:			Room 5508
 			Lifts 25/26

Committee Members:	Prof. Lionel Ni (Supervisor)
 			Dr. Huamin Qu (Chairperson)
 			Dr. Lei Chen


**** ALL are Welcome ****