none

Mobile ad hoc networks consist of potentially moving, computing nodes that communicate via radio and do not have access to any fixed infrastructure. The knowl- edge about nearby nodes is a fundamental requirement and is part of many of the known solutions to problems in mobile and wireless networks including routing, broad- casting, distributed token circulation, etc. The existing solutions for this problem of knowing about neighbors are probabilistic. In this thesis, we give a first step towards a distributed, deterministic algorithm for finding out about the neighboring nodes. In particular, we focus on the problem of maintaining information about neighboring nodes in a one dimensional mobile and wireless ad hoc environment. Under some simplifying assumptions, we give an algorithm for the problem and a proof of correctness for the algorithm. We deal with efficiency in terms of both time and space. We prove a tight bound on the speed of propagation of the message when the nodes are sufficiently dense. We also consider the case when multiple clusters merge together. Our algorithm is space efficient in that the nodes do not include information about all the nodes they know in their broadcast message at all times. Nodes also store only the information about relevant nodes in their local store and purge information about nodes that have moved out of range. Our work shows that it is possible to solve the problem deterministically, and with reasonable values of the parameters, under some simplifying assumptions. Numerous interesting open questions remain in the area regarding how to relax the assumptions to make the approach more practical.

In periodic wireless broadcasting, air behaves like a storage medium requiring new data organization and access methods.Due to power limit for the portable units (ex. the palmtop), how to design an energy-saving organization is a key issue.Imielinski et al. have proposed the hashing based schemes, including the Hashing A and Hashing B schemes, to save energy in the progress of getting data of interest. The Hashing B scheme improves the directory miss phenomenon in the Hashing A scheme, where the directory miss is that the client's initial probe comes before the bucket containing his key but after the bucket which contains a proper offset. However, based on these two schemes, if the differences between the minimum overflow and the other overflows are large extremely or the small overflows appear near the rear part of the broadcast file, both schemes have a poor performance. Therefore, in this thesis, we propose four multiple-hashing-functions-based schemes, including the FirstR, FirstL, AvgK and TopK schemes, to overcome such the situations. The basic idea is to use cutlines to divide the broadcast file with N logical buckets into several regions, and then each region may have the different minimum overflow. Since the minimum overflow in each region can be different, we can have different hashing functions for those regions to determine the positions of the designated buckets. Among the proposed schemes, the difference is how to determine the positions of the cutlines. The FirstR scheme finds those cutlines from the right end to the left whenever the difference of overflows of two adjacent logical buckets is greater than or equal to 1. The FirstL scheme finds those cutlines from the left end to the right whenever the difference of overflows of two adjacent logical buckets is greater than or equal to 1. In the AvgK scheme, we first calculate AvgD, the average of the differences of two consecutive overflows whose values are large than or equal to 1. Then we find cutlines from the left end to the right whenever the difference of two adjacent logical buckets is greater than or equal to AvgD. The TopK determines the cutlines by considering the descending order of the differences of overflows. From our performance analysis and simulation study, the performance of the TopK scheme is the best among the proposed schemes. Therefore, we then make a comparison between the TopK scheme and the Hashing B scheme. Since the number of the hashing functions in the TopK scheme is larger than those in the Hashing B, the physical bucket in the TopK scheme is somewhat bigger than that in the m Hashing B scheme. In our simulation, we have considered this factor as well. From our performance analysis and simulation study, we show that the performance of the TopK scheme performs better than that of the Hashing B scheme, even though the above factor about the storage size is considered. The TopK scheme improves the directory miss in the Hashing B scheme; therefore, the average access time is improved excellently.

Ad hoc wireless networks are quite convenient local area networks. Because ad hoc wireless networks have a property what its topology is changed as hosts move. In order to efficiently and quickly broadcasting data, it is very important to have efficacious protocols in MAC (Medium Access Control) layer. In this paper, we propose a new broadcast protocol, Contention-based Broadcast Protocol (CBP). CBP is a TDMA-based protocol. There are three characteristics which make CBP an efficient protocol. They are (1) CBP utilize a backoff algorithm and some mini slot in contention request phase to avoid collisions. Most protocols do not implement a backoff algorithm. (2) A host only reserves a data slot each time instead of many slots in most TDMA-based protocol. It has the advantage of reducing the influence of host mobility because the time between a data slot is reserved and the time the data slot is utilized has greatly decreased, and (3) CBP differentiates unicast data and broadcast data and allows a host to reuse by channel for a unicast if it is impossible for a broadcast.

In the environment of wireless sensor network, while one node want to send a message to another node, the most natural way is used broadcasting to distribute the message to the whole network. In the other words, as long as one node sends messages to the other node, its neighbor nodes can also listen to these messages, and then receive them. The advantage of broadcast networks is that can efficiently distribute data to multiple receivers. However, it has some drawbacks. A sensor network may be deployed in hostile environment where there are malicious attacks. The malicious attacker can send false messages to his neighbor nodes, and then rely on these neighbor nodes to distribute over the network. So if there are not any schemes of the security authentication in the message when a node wants to use broadcast, everyone can impersonate the sender and broadcast false messages. We call this a packet injection attack. So security is a main challenge in broadcast network. In order to authenticate a broadcast message¡Ait would conform to two conditions. First, insure that the data is transmitted from the claimed source. Second, the messages are not be modified en route. TESLA has been proposed to provide such services for sensor networks¡Ait mainly use time synchronization and delay disclosure key to protect encryption key¡CHowever, this scheme still has some drawbacks, so we propose some schemes to modify TESLA in this paper, and we will show these schemes can achieve better performance than previous ones.

Selbst im Bereich von Digital TV sitzt der Pinguin in der 1. Reihe. Mit einer DVB-Karte soll es möglich sein, digitale Programmvielfalt am PC zu erleben. Aber neben TV sind natürlich noch Funktionen wie Teletext verfügbar. Der PC läßt sich sogar in einen fernbedienbaren Videorecorder und DVD-Player verwandeln. Der Vortrag soll einen Überblick der unterstützten Hardware geben und ausgewählte Softwareentwicklungen vorstellen.

No description available.

Both House of Cards and Scandal have similar conceits (White House? Check. Sex? Check. Murder? Check.) but use different platforms: House of Cards is a Netflix Original production while Scandal is a broadcast television program on ABC. Through the course of this paper, I will examine how the platform and type of consumption affects the content and distribution of the show and the types of relationships they forge with their viewers.

A broadcast is a function f that assigns an integer value to each vertex of a graph such that, for each v ∈ V , f (v) ≤ e (v), where e(v) is the eccentricity of v. The broadcast number of a graph is the minimum value of ∑ f(v) among all broadcasts f with the property that for each vertex u ∈ V, there exists some v ∈ V with f(v) > 0 such that d(υ,v) ≤ f(v). We present a new upper bound for the broadcast number of a graph in terms of its irredundance number and a new dual property of the broadcast number called the multipacking number of a graph. / Graduate

This thesis focuses on the development of the Direct Broadcasting Satellite in Japan under its Kodo Johoka Shakai (Highly Advanced Information Society) policy. The field of new media policies is relatively new but very important in communications studies. The development of new media technologies changes into existing media systems, and profoundly influences economies which are increasingly dependent upon information services. / Japan's case is particularly interesting. Relatively little is known about its DBS policy compared to other industrialized countries, even though Japan has already begun to operate DBS under its own version of the "information society", the Kodo Johoka Shakai (Highly Advanced Information Society). The formulation of DBS policy is related to many factors, including space development, research and development, broadcasting, international telecommunications regulations and economic competition both in international and domestic markets. In order to take these factors into consideration, an historical approach and institutional analysis are used in this thesis.