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 Ra...[ Read more ]

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.