Multicast transport is a challenging problem because the source must provide congestion control and reliability for a tree, rather than a single path. This problem is made even more difficult in mobile ad hoc networks due to problems caused by contention, spatial reuse, and mobility. In this paper, we design a hop-by-hop multicast transport protocol, which pushes transport functionality into the core of the network. Although this requires per-flow state, a hop-by-hop approach simplifies congestion control, enables local recovery of lost packets, and provides low delay and efficient use of wireless capacity. We use a simulation study to demonstrate the effectiveness of this approach and compare its efficiency to application-layer multicast.

Routing in a mobile ad hoc network is challenging because nodes can move at any time, invalidating a previously-discovered route. Multicast routing is even more challenging, because a source needs to maintain a route to potentially many group members simultaneously. Providing scalable solutions to this problem typically requires building a hierarchy or an overlay network to reduce the cost of route discovery and maintenance. In this paper, we show that a much simpler alternative is possible, by using source specific semantics and relying on the unicast routing protocol to find all routes. This separation of concerns enables the multicast routing protocol to focus on minimizing join latency, repair latency, and control overhead. We design a routing protocol based on these principles and demonstrate its effectiveness through simulations.

In this paper we consider the problem of distinguishing whether frame loss at the MAC layer has occurred due to mobility or congestion. Most ad hoc routing protocols make the faulty assumption that all frame loss means the destination node has moved, resulting in significant overhead as they initiate the repair of routes that have not been broken. We design a mobility detection algorithm, MDA, that properly detects the cause of a lost frame, then coordinates with the routing protocol so that it reacts properly. This approach dramatically reduces routing protocol overhead and significantly increases application throughput. We use a simulation study to demonstrate the effectiveness of MDA and to determine the proper setting for MDA parameters.

Devices with multiple wireless interfaces are becoming increasingly popular. We envision that these devices will become the building block for future mesh networks, providing seamless connectivity across a range of heterogeneous devices. Although these devices typically implement frequency sharing, using either direct sequence spread spectrum (DSSS) or frequency hopping spread spectrum (FHSS), they may still interfere with one another. In this paper we provide a novel radio interference avoidance (RIA) algorithm that solves the problem of interference between IEEE 802.11 and Bluetooth. We then extend this algorithm to other types of DSSS and FHSS combinations. Though the algorithm is limited to devices with both of these interfaces, this is a very common case. We analytically derive the expected value of the response time for RIA and run simulations to demonstrate its effectiveness. Our results indicate that RIA is able to eliminate interference with a very short response time. RIA also outperforms adaptive frequency hopping, a solution proposed by the IEEE 802.15 co-existence working group.

WirelessUSB is built upon the premise that a complex and heavy networking protocol is not necessary for simple point-to-point and multi point-to-point applications like PC mice, keyboards, and sensor networks. WirelessUSB is a standard that fills this gap between Zigbee, Bluetooth, and proprietary point-to-point 2.4 GHz wireless technologies by providing a lightweight, low-latency protocol with interference immunity. In this paper, we propose and evaluate the WirelessUSB protocol. We use ns-2 based simulations to demonstrate the effectiveness of WirelessUSB in various network scenarios. In order to show the interference immunity of WirelessUSB, we implement trace-based models of cordless phones and microwave ovens. Our performance results indicate that WirelessUSB outperforms Bluetooth in terms of packet delivery ratio, latency, power consumption, and interference immunity

In this paper, we propose a unique set of pseudo noise (PN) codes, such that a large PN code can be split into two smaller PN codes. This allows a radio, to use both the large and the small PN codes, depending upon the desired code length if the large PN code is loaded into the radio. We refer to these codes as multiplicative PN codes. These codes would be especially useful in networks consisting of a master device connected to multiple slave devices. These codes enable slaves devices in the network to encode data with different PN codes of different lengths to trade off data rate and data integrity and yet be able to communicate with the master device. We first describe our motivation and methodology for generating multiplicative PN codes and then present an algorithm to span through the space of PN codes to provide a set with the maximum number of well-bounded multiplicative PN Codes. Our implementation results confirm the existence of a large number of such multiplicative PN codes

Current ad hoc multicast routing protocols have been designed to build and maintain a tree or mesh in the face of a mobile environment, with fast reaction to network changes in order to minimize packet loss. However, the performance of these protocols has not been adequately examined under realistic scenarios. Existing performance studies generally use a single, simple mobility model, with low density and often very low traffic rates. We explore the performance of ad hoc multicast routing protocols under scenarios that include realistic mobility patterns, high density and high traffic load. We use these scenarios to identify cases where existing protocols can improve their performance. Based on our observations, we make a series of recommendations for designers of multicast protocols.