TFRC-CR: An equation-based transport protocol for cognitive radio networks

Reliable and high throughput data delivery in cognitive radio networks remains an open challenge owing to the inability of the source to quickly identify and react to changes in spectrum availability. The window-based rate adaptation in TCP relies on acknowledgments (ACKs) to self trigger the sending rate, which are often delayed or lost owing to intermittent primary user (PU) activity, resulting in an incorrect inference of congestion by the source node. This paper proposes the first equation-based transport protocol based on TCP Friendly Rate Control for Cognitive Radio, called as TFRC-CR, which allows immediate changes in the transmission rate based on the spectrum-related changes in the network environment. TFRC-CR has the following unique features: (i) it leverages the recent FCC mandated spectrum databases with minimum querying overhead, (ii) it enables fine adjustment of the transmission rate by identifying the instances of true network congestion, as well as (iii) provides guidelines on when to re-start the source transmission after a pause due to PU activity. TFRC-CR is evaluated through an extensive set of module additions to the ns-2 simulator which is also released for further investigation by the research community.