An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. In such an environment, it may be necessary for one mobile host to enlist the aid of other hosts in forwarding a packet to its destination, due to the limited range of each mobile host’s wireless transmissions. This paper presents a protocol for routing in ad hoc networks that uses dynamic source routing. The protocol adapts quickly to routing changes when host movement is frequent, yet requires little or no overhead during periods in which hosts move less frequently. Based on results from a packet-level simulation of mobile hosts operating in an ad hoc network, the protocol performs well over a variety of environmental conditions such as host density and movement rates. For all but the highest rates of host movement simulated, the overhead of the protocol is quite low, falling to just 1 % of total data packets transmitted for moderate movement rates in a network of 24 mobile hosts. In all cases, the difference in length between the routes used and the optimal route lengths is negligible, and in most cases, route lengths are on average within a factor of 1.01 of optimal. 1.

The widespread distribution and availability of smallscale sensors, actuators, and embedded processors is transforming the physical world into a computing platform. One such example is a sensor network consisting of a large number of sensor nodes that combine physical sensing capabilities such as temperature, light, or seismic sensors with networking and computation capabilities. Applications range from environmental control, warehouse inventory, and health care to military environments. Existing sensor networks assume that the sensors are preprogrammed and send data to a central frontend where the data is aggregated and stored for offline querying and analysis. This approach has two major drawbacks. First, the user cannot change the behavior of the system on the fly. Second, conservation of battery power is a major design factor, but a central system cannot make use of in-network programming, which trades costly communication for cheap local computation.

We evaluate several routing protocols for mobile, wireless, ad hoc networks via packet level simulations. The protocol suite includes routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, end-to-end delay and routing load for a given traffic and mobility model. It is observed that the new generation of on-demand routing protocols use much lower routing load. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and delay performance. 1. Introduction A mobile, ad hoc network [4] is an autonomous system of mobile hosts connected by wireless links. There is no static infrastructure such as base stations. If two hosts are not within radio range, all message communication between them must pass through one or more intermediate hosts that double as router...

Mobile wireless networks pose interesting challenges for routing system design. To produce feasible routes in a mobile wireless network, a routing system must be able to accommodate roving users, changing network topology, and fluctuating link quality. We discuss the impact of node mobility and wireless communication on routing system design, and we survey the set of techniques employed in or proposed for routing in mobile wireless networks.

Channel assignment problems in the time, frequency and code domains have thus far been studied separately. Exploiting the similarity of constraints that characterize assignments within and across these domains, we introduce the first unified framework for the study of assignment problems. Our framework identifies eleven atomic constraints underlying most current and potential assignment problems, and characterizes a problem as a combination of these constraints. Based on this framework, we present a unified algorithm for efficient (T/F/C)DMA channel assignments to network nodes or to inter-nodal links in a (multihop) wireless network. The algorithm is parametrized to allow for tradeoff-selectable use as three different variants called RAND, MNF, and PMNF. We provide comprehensive theoretical analysis characterizing the worst-case performance of our algorithm for several classes of problems. In particular, we show that the assignments produced by the PMNF variant are proportional to the thickness of the network. For most typical multihop networks, the thickness can be bounded by a small constant, and hence this represents a significant theoretical result. We also experimentally study the relative performance of the variants for one node and one link assignment problem. We observe that the PMNF variant performs the best, and that a large percentage of unidirectional links is detrimental to the performance in general.

MMWN is a modular system of link- and network-layer algorithms that enables a multihop mobile wireless network to support distributed, real-time multimedia applications. In this paper, we describe three key components of this system: the clustering procedures for defining a virtual, hierarchical control structure superimposed on a large network of mobile switches and endpoints; the location management procedures for determining the current locations of mobile endpoints relative to the hierarchical control structure; and the virtual circuit management procedures for setting up and repairing virtual circuits as switches and endpoints move. We also provide performance results, obtained through simulation and analysis, which show the robustness of each of these components with respect to a broad spectrum of transmission ranges and relative mobility of switches and endpoints. 1 Introduction The evolution of mobile computing and communications technology has been shaped predominantly by th...

| Several routing algorithms for mobile ad hoc networks (MANETs) have been proposed in the recent past [1], [2], [3]. With the exception of a few, these protocols (i) involve all nodes in the route management process, (ii) rely on the use of broadcast relays for route computation, and (iii) are primarily reactive in nature. Related work [4], [5] has shown that the capacity utilization in ad hoc networks decreases signicantly when broadcast relays or \broadcast storms" are performed frequently. This eect is compounded when all nodes in the network take part in the route computation. We propose and study an approach based on overlaying a virtual infrastructure (adaptation of the core, proposed in [3]) on an ad hoc network and operating routing protocols over the infrastructure. The core enables routing protocols to use only a subset of nodes in the network for route management and avoid the use of broadcast relays. Using the ns-2 simulator [6] , we evaluate the performance of two ad hoc routing protocols, DSR [1] and AODV [2], when they are operated over the core and compare their performance against those of their basic versions. Keywords| Virtual Infrastructures, Ad hoc Routing. I.

Channel assignment problems in the time, frequency and code domains have hitherto been studied separately. Exploiting the similarity of constraints that characterize assignments within and across these domains, we introduce the first unified framework for the study of assignment problems. Our framework identifies eleven atomic constraints underlying most current and potential assignment problems, and characterizes a problem as a combination of these constraints. Based on this framework, we present a unified algorithm for efficient (T/F/C)DMA channel assignments to network nodes or to inter-nodal links in a (multihop) wireless network. The algorithm is parametrized to allow for use as three different variants - RAND, MNF, and PMNF. We provide comprehensive theoretical analysis characterizing the worst-case performance of our algorithm for several classes of problems. In particular, we show that the assignments produced by the PMNF variant are proportional to the thickness of the network...

This thesis addresses the problems of managing the transmissions of stations in a spread-spectrum packet radio network so that the system can remain effective when scaled to millions of nodes concentrated in a metropolitan area. The principal difficulty in scaling a system of packet radio stations is interference from other stations in the system. Interference comes both from nearby stations and from distant stations. Each nearby interfering station is a particular problem, because a signal received from it may be as strong as or stronger than the desired signal from some other station. Far-off interfering stations are not individually a problem, since each of their signals will be weaker, but the combined effect may be the dominant source of interference. The thesis begins with an analysis of propagation and interference models. The overall noise level in the system (mainly caused by the many distant stations) is then analyzed, and found to remain manageable even as the system scales ...

Busy tone multiple access protocols have been used in multihop networks to reduce the effect of the hidden terminal problem. This paper demonstrates another approach to reduce the effect of the hidden terminal problem namely the use of multiple channel schemes. A protocol that uses both the busy tone and the multiple channel techniques achieves the best performance. Using a Markov chain model and an approximation, the throughput performance of the multiple channel nonpersistent CSMA protocol and the multiple channel conservative BTMA protocol in a large network is evaluated and compared. The results show that the multichannel CSMA and BTMA schemes exhibit a better performance over their single channel counterparts in a multihop network. 2 1. Introduction In a companion paper[1], we have analyzed the performance of the nonpersistent CSMA, conservative BTMA and idealistic destination based BTMA protocols in large multihop networks. It was assumed that around each terminal, a single ch...