In this paper, a Spectrum-Aware Routing (SAR) protocol for cognitive radio ad hoc networks, (CRAHN), is proposed which is robust to primary user activity and node failures. The protocol allows nodes to collect spectrum information during a spectrum management interval followed by a transmission period. Cognitive users discover routes by joint channel and next hop selection (synchronization) in the transmission intervals. A restricted geographical routing approach is adopted to avoid performance degradation specially due to routing overhead. We also add spectrum mobility capabilities to routes in our proposed method to provide robustness to primary user activity. SAR protocol performance is investigated through simulations of different scenarios and is compared with the most similar work, CAODV protocol. The results indicate that SAR can achieve significant reduction in control overhead as well as improved throughput.

Recently in ad hoc networks, routing schemes using location information which is provided by GPS (Global Position System) have been proposed. However, many routing schemes using location information assume that a source node has already known the location information of the destination node and they do not adapt to large ad hoc networks. On another front, the autonomous clustering scheme has been proposed to construct the hierarchical structure in ad hoc networks and adapt to large ad hoc networks. However, even when the hierarchical structure is introduced, there is some problem. The data delivery ratio becomes lower as the node speed becomes higher, and clusterheads have much overhead in the hierarchical routing scheme based on the autonomous clustering scheme. In order to cope with these problems, this paper proposes a new Hierarchical Geographical Routing with Alternative Paths (Hi-GRAP) using the autonomous clustering scheme and shows the effectiveness of the proposed hierarchical geographical routing in comparison with GPSR, Hi-AODV and AODV through simulation experiments with respect to the amount of control packets and the data delivery ratio.

The IEEE 802.15.4a standard enables geographical routing in ZigBee networks but previous geographical routing algorithms can suffer high packet loss due to the interference effects. This letter proposes an interference-aware energy-efficient geographical routing algorithm for the IEEE 802.15.4a networks. The proposed algorithm estimates the energy cost by considering the interference effects and forwards a packet to the neighbor with the lowest energy cost to advance. Experimental results show that the proposed algorithm outperforms the previous algorithms in terms of the delivery ratio and the energy consumption.

Recently, in mobile ad hoc networks, routing schemes using location information have been proposed. Most of these schemes assume that the source node already knows the location information of the destination node. However, since all nodes are always moving, it is difficult to apply this assumption to the real mobile ad hoc environment. In order to cope this difficulty, this paper presents a new routing scheme HGR (a Hybrid Greedy Routing with location and velocity information), which considers the location and velocity information of the destination node and the neighboring nodes. In HGR, when a source node creates a route to a destination node, the future location of neighboring nodes and the destination node predicted by the source node is calculated using these location and velocity information. And the source node sends data packets to the neighboring node that is the closest to the destination node based on these predicted location and velocity information. This paper shows that HGR achieves high data delivery ratio and fewer overheads for the route creation and maintenance through simulation experiments.