Taku Yamazaki

Forwarding mechanism using prioritized forwarders for opportunistic routing

In ad hoc networks, backoff-based OR (opportunistic routing) protocols, which autonomously selects a forwarder among the potential forwarders based on a random backoff time, have been proposed. However, each potential forwarder must wait for the backoff time to avoid packet collisions among receivers. In addition, the terminal density strongly affects the performance since the backoff-based OR protocols improve the performance by using multiple terminals. In this paper, we propose a novel OR protocol called PRIOR (prioritized forwarding for opportunistic routing). In PRIOR, a terminal called prioritized forwarder, which forwards packets without using a backoff time, is selected among neighbours. In addition, we propose a hop-by-hop retransmission control that performs the retransmission terminal selection on the basis of a neighbour relation with the PFs. Moreover, we introduce an explicit acknowledgement mechanism on the basis of the difference of hop counts to alleviate the bad effect of the retransmission control in dense environments. Finally, we evaluate PRIOR in comparison with conventional backoff-based OR protocols in computer simulation.

Opportunistic Routing Using Prioritized Forwarders with Retransmission Control

Abstract In ad hoc networks, broadcast-based forwarding protocols called opportunistic routing have been proposed. In general backoff-based opportunistic routing protocols, each receiver autonomously makes a forwarding decision using a random backoff time based on logical distance. However, each potential forwarder must wait for the expiration of the backoff timer before the packet forwarding. Moreover, they cannot gain forwarding path diversity in sparse environments. In this paper, we propose a novel forwarder selection method for opportunistic routing. In the proposed method, a terminal called, a prioritized forwarder, and which is selected from among neighbours and can forward packets without using the backoff time. In addition, we integrate a hop-by-hop retransmission control in the proposed method, which improves the packet transmission success rate in sparse environments. We evaluate the proposed method in comparison with the conventional protocols in computer simulations.

Performance Analysis of Fixed Node Assisted Opportunistic Routing for Ad Hoc Networks

In ad hoc networks, we can achieve better performance if we use fixed nodes besides mobile nodes. In this paper, we first present a network model comprised of fixed nodes with enough network resource as well as mobile nodes. Then, we propose a novel routing method that opportunistically selects the most stable links through fixed nodes in preference to links through mobile nodes based on the mobility information of neighbouring nodes. The proposed method also relieves packet losses due to its simple retransmission function among fixed nodes. The simulation results show that the proposed method opportunistically selects stable links and able to improve the performance with higher packet delivery rate and lower control message overhead.