GRaTIS: Sensing and intelligence for performance in the presence of legacy networks

Recent work has examined techniques to estimate the “best” modulation rate for data networks such as OFDM-based 802.11a/g. Each rate is effective in a range of signal-to-noise ratios (SNRs) but the limited number of practical rates often force the transmitter to “step down” to a lower data rate despite having higher SNR to the receiver. In this paper we describe, evaluate and implement a practical multiuser communication scheme that transmits two packets in the time normally needed to transmit a single packet, increasing aggregate throughput precisely when it is most needed — when the network is busy and suffers from rate unfairness. Because the method transmits a group of packets simultaneously, we call this scheme Group Rate Transmission with Intertwined Symbols, or GRaTIS. This method uses SNR sensing and knowledge about the network to achieve improved performance in the presence of legacy network members.