Cognitive radio-aware transport protocol for mobile ad hoc networks

With the proliferation of new wireless service, a scarcity of wireless resources will arise and become a critical issue. For this reason, cognitive radio mobile ad hoc networks (CogMANET) are being developed as a promising solution to this problem. However, in CogMANET, channel switching is inherently necessary whenever a primary user with a license appears on the channel. Allowing secondary users to choose an available channel from among a wide range of the spectrum thus enables reliable communication in this context. In such cases, the communication characteristics also change in terms of bottleneck bandwidth and RTT. In response to this change, TCP has to adaptively update its congestion window size (cwnd) to make an efficient use of the available wireless resources. For this purpose, TCP CRAHN was proposed for CogMANET. In this paper, TCP CRAHN is first evaluated in cases where bottleneck bandwidth and RTT drastically change during communication. Based on these results, a new TCP, TCP CoBA, is proposed to further improve the throughput performance in the above cases. TCP CoBA updates the cwnd based upon the available buffer space in the relay node having changed its channels as well as other communication characteristics. Through simulations, it is shown that compared with TCP CRAHN, TCP CoBA improves the throughput performance by up to 42%. In addition, the case where sensing and data transmission processes were done in parallel on devices dedicated (DD model) to each instead of on one shared device (SD model) was considered In this case, TCP CoBA with a DD model attains excellent throughput performance of twice that of the SD model.