A mobile ad hoc network is an autonomous system of infrastructureless, multihop wireless mobile nodes. Reactive routing protocols perform well in such an environment due to their ability to cope quickly against topological changes. In this paper, we propose a new routing protocol called Caching and Multipath (CHAMP) Routing Protocol. CHAMP uses cooperative packet caching and shortest multipath routing to reduce packet loss due to frequent route breakdowns. Simulation results reveal that by using a five-packet data cache, CHAMP exhibits excellent improvement in packet delivery, outperforming AODV and DSR by at most 30% in stressful scenarios. Furthermore, end-to-end delay is significantly reduced while routing overhead is lower at high mobility rates. 0-7803-7753-2/03/$17.00 (C) 2003 IEEE

Abstract-This paper presents a mobility-based d-hop clustering algorithm (MobDHop), which forms variable-diameter clusters based on node mobility pattern in MANETs. We introduce a new metric to measure the variation of distance between nodes over time in order to estimate the relative mobility of two nodes. We also estimate the stability of clusters based on relative mobility of cluster members. Unlike other clustering algorithms, the diameter of clusters is not restricted to two hops. Instead, the diameter of clusters is flexible and determined by the stability of clusters. Nodes which have similar moving pattern are grouped into one cluster. The simulation results show that MobDHop has stable performance in randomly generated scenarios. It forms lesser clusters than Lowest-ID and MOBIC algorithm in the same scenario. In conclusion, MobDHop can be used to provide an underlying hierarchical routing structure to address the scalability of routing protocol in large MANETs.

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Abstract-Underwater Sensor Networks are typically distributed in nature and the nodes communicate using acoustic waves over a wireless medium. Such networks are characterized by long and variable propagation delays, intermittent connectivity, limited bandwidth and low bit rates. Due to the wireless mode of communication between the sensor nodes, a Medium Access Control (MAC) protocol is required to coordinate access to the shared channel and enable efficient data communication. However, conventional terrestrial wireless network protocols that are based on RF technologies cannot be used underwater. In this paper, we propose PLAN -a MAC Protocol for Long-latency Access Networks that is designed for use in half-duplex underwater acoustic sensor networks. We utilize CDMA as the underlying multiple access technique, due to its resilience to multi-path and Doppler's effects prevalent in underwater environments, coupled with an RTS-CTS handshaking procedure prior to the actual data transmission. Using simulations, we study the performance and efficiency of the proposed MAC protocol in underwater acoustic networks.