HAP – A Heterogeneous Ad hoc Protocol Arta Doci Colorado School of Mines Golden, Colorado adoci@mines.edu Leonard Barolli Fukuoka Institute of Technology Fukuoka, Japan barolli@fit.ac.jp Fatos Xhafa Technical University of Catalonia Barcelona, Spain fatos@lsi.upc.edu Abstract Ad hoc wireless networks are becoming an important infrastructure for developing networking applications due to their decentralized nature, improved scalability as com- pared to wireless managed networks, minimal configuration and fast deployment. However, such networks show several limitations regarding their capacity and are, in general, im- practical for stand alone commercial applications; in fact, such networks are mostly used for emergency applications. However, the features of ad hoc networks can be useful to extend the connectivity of wireless networks, while taking into account node mobility. In this paper we propose a Het- erogeneous Ad hoc Protocol (HAP), which aims to extend the connectivity of a wireless networks. HAP is a cross layer protocol that operates on the link, MAC, and network lay- ers, which takes into account the impact of the mobility on each of these layers. The objective of HAP is thus to over- come limitations of existing protocols, especially regarding mobility. HAP can be useful for developing applications in pedestrian and community networks. 1 Introduction Ad hoc networks have been proven useful in military and emergency applications, however they have been unable to take off as a business model for commercial applications. The main reasons for being unable to begone as commercial applications are the constraints of bandwidth, energy, and security. In addition, the scalability of these applications offers a trade off on protocol performance. Despite their limitations [1, 2, 3], their decentralized na- ture, improved scalability as compared to wireless man- aged networks, minimal configuration and fast deployment makes ad hoc networks an important network infrastructure. In this paper we show that ad hoc networks can be used to extend the connectivity between two wireless networks and can be proven very useful in the campus and community networks. Recent studies on extraction of the mobility prop- erties in the wireless networks for pedestrian [4] and vehic- ular [5] scenarios have revealed important findings. One such finding is that pedestrian and vehicular mobility mod- els have many similarities in common. First, they show that the wireless nodes tend to cluster around popular locations (hotspots). Second, the selection of the source and destina- tion pairs, as well as the movement from source toward the destinations is not at random, but rather it is activity based. For example, in Fig. 1, we display four hotspots on the Ohio State University student campus map, namely, R (Recreational/Athletics), H (Housing), W (Wireless) and L (Library). In general, due to the distributions of hotspots, there might be connectivity gaps between the hotspots, which could negatively impact on network connectivity and per- formance. This paper is motivated by the need to avoid connectivity gaps in wireless networks. To this end, we address the use ad hoc networks of mobile wireless de- vices to extend the connectivity among hotspots. To achieve this, we propose a Heterogeneous Ad hoc Protocol (HAP), which aims to extend the connectivity of a wireless net- works. HAP is a cross layer protocol that operates on the link, MAC, and network layers, which takes into account the impact of the mobility on each of these layers. The ob- jective of HAP is thus to overcome limitations of existing protocols, especially regarding mobility. HAP, first decides on the fly the number of hotspots that it is going to operate into. Next, within a hotspot, HAP con- siders the nodes to be stationary and connected using the wireless network with infrastructure. Therefore, the proto- 2009 International Conference on Network-Based Information Systems 978-0-7695-3767-2/09 $25.00 © 2009 IEEE DOI 10.1109/NBiS.2009.91 109