Efficient integration of a multi-hop wireless network with the Internet is an important research problem, and benefits several applications, such as wireless neighborhood networks and sensor networks. In a wireless neighborhood network, a few Internet Transit Access Points (ITAPs), serving as gateways to the Internet, are deployed across the neighborhood; houses are equipped with low-cost antennas, and form a multi-hop wireless network among themselves to cooperatively route traffic to the Internet through the ITAPs. In a sensor network, sensors collect measurement data and send it through a multi-hop wireless network to the servers on the Internet via ITAPs. For both applications, placement of integration points between the wireless and wired network is a critical determinant of system performance and resource usage. However there has been little work on this subject. In this paper, we explore the placement problem under three wireless link models. For each link model, we develop algorithms to make informed placement decisions based on neighborhood layouts, user demands, and wireless link characteristics. We also extend our algorithms to provide fault tolerance and handle significant workload variation. We evaluate our placement algorithms using both analysis and simulation, and show that our algorithms yield close to optimal solutions over a wide range of scenarios we have considered. 1.

This paper presents a novel slotted ALOHAbased protocol for use in ad hoc networks where nodes are equipped with adaptive array smart antennas. The protocol relies on the ability of the antenna and DoA (Direction of Arrival) algorithms to identify the direction of transmitters and then beamform appropriately to maximize SINR (Signal to Interference and Noise Ratio) at the receiver. The performance of the protocol is evaluated using analytical modeling as well as detailed simulation in OPNET and Matlab where we demonstrate the benefits of using smart antennas. The impact of using different number of antenna elements is also studied for this environment.

Smart antennas enable a receiver to determine the Direction of Arrival (DOA) of multiple transmissions as well as to form nulls in some number of directions to maximize SINR (Signal to Interference and Noise Ratio) of the received signal. We utilize the benefits of these capabilities to develop a simple modified version of the popular 802.11b protocol. This protocol exhibits high throughput under a variety of network conditions and is fair. The performance of the protocol is examined exhaustively using joint simulation in OPNET and Matlab.