TP-CRAHN: a Transport Protocol for Cognitive Radio Ad-Hoc Networks

Abstract

Abstract-Existing research in transport protocols for wireless ad-hoc networks has focused on reliable end-to-end packet delivery under uncertain channel conditions, route failures due to node mobility and link congestion. In a cognitive radio (CR) environment, there are several key challenges that must be addressed apart from the above concerns. The intermittent spectrum sensing undertaken by the CR users, the activity of the licensed users of the spectrum, large-scale bandwidth variation based on spectrum availability, and the channel switching process need to be considered in the transport protocol design. In this paper, a window-based Transport Protocol for CR Ad-Hoc Networks, TP-CRAHN, is proposed that distinguishes each of these events by a combination of explicit feedback from the intermediate nodes and the destination. This is achieved by adapting the classical TCP rate control algorithm running at the source to closely interact with the physical layer channel information, the link layer functions of spectrum sensing and buffer management, and a predictive mobility framework that is developed at the network layer. To the best of our knowledge, this is the first work on the transport layer to specifically address the concerns of the CR ad-hoc networks and our approach is thoroughly validated by simulation experiments.

An Experimental Implementation of a Cross-Layer Approach for Improving TCP Performance over Cognitive Radio Networks

“…Recently, a few approaches [5][6][7][8] have been proposed for improving TCP performance in CRNs through cross-layering. However, all of them are evaluated via simulations with somewhat optimistic and convenient assumptions.…”

“…However, all of them are evaluated via simulations with somewhat optimistic and convenient assumptions. For instance, perfect knowledge on the channel state [5], error-free control channel [7,8], statistical knowledge on the behavior of PU's transmission [6][7][8] and static channel gain during a single RTT [5]. For all of that, it is still challenging to implement cross-layer schemes in general computer systems since it is inevitable to manipulate the TCP stack and device driver in an operating system.…”

Adaptive Communication Techniques for the Internet of Things

“…TP-CRAHN, TCP adapted for ad hoc network nodes with spectrum-sensing capability, is proposed in [117] in order to deal with disruptions caused by spectral availability variation and node mobility, together with two additional challenges, namely the route suspension caused by spectrum sensing and tradeoff between throughput and sensing accuracy [43,117]. The strategy of [117] is to make spectrum-related events and parameters explicitly known to the TCP protocol.…”

“…The strategy of [117] is to make spectrum-related events and parameters explicitly known to the TCP protocol. In contrast to [116], configuration details such as sensing duration and commencement times are exchanged during connection establishment.…”

“…As a step further than [116], each node during normal communication collects the received signal strength (RSS) of acknowledgment packets from its next hop and compares the values with minimum device reception power. By applying such information to an estimation framework based on the Kalman filter [117], the mobility of nodes is predicted and the congestion window is limited as a precaution of probable disconnections [43].…”