44,318 research outputs found
Optimal Schedules for Asynchronous Transmission of Discrete Packets
In this paper we study the distribution of dynamic data over a broadcast channel to a large number of
passive clients. Clients obtain the information by accessing the channel and listening for the next available
packet. This scenario, referred to as packet-based or discrete broadcast, has many practical applications such
as the distribution of weather and traffic updates to wireless mobile devices, reconfiguration and reprogramming
of wireless sensors and downloading dynamic task information in battlefield networks.
The optimal broadcast protocols require a high degree of synchronization between the server and the
wireless clients. However, in typical wireless settings such degree of synchronization is difficult to achieve
due to the inaccuracy of internal clocks. Moreover, in some settings, such as military applications, synchronized
transmission is not desirable due to jamming. The lack of synchronization leads to large delays
and excessive power consumption. Accordingly, in this work we focus on the design of optimal broadcast
schedules that are robust to clock inaccuracy. We present universal schedules for delivery of up-to-date
information with minimum waiting time in asynchronous settings
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Collision Avoidance Tree networks
The Collision Avoidance Tree is a new local area network based on a hardware device called collision avoidance switch, which arbitrates random access to a shared communications channel. Collision Avoidance Tree combines the benefits of random access (low delay when traffic is light; simple, distributed, and therefore robust, protocols) with concurrency of transmission, excellent network utilization and suitability for the domain of high-speed, optical networking.The Collision Avoidance Tree is classified in two classes: the Collision Avoidance Single Broadcast (CASB) Tree and the Collision Avoidance Multiple Broadcast (CAMB) Tree. The CASB Tree allows only a single transmission on the network at a given time, while the CAMB Tree is more general and allows concurrent transmissions on the network.This paper describes network architectures (e.g., station and switch protocols) and designs and implementations of the CASB and CAMB Trees. Performance results derived from analyses, simulations, measurements of experimental networks are also presented
Data Dissemination in Unified Dynamic Wireless Networks
We give efficient algorithms for the fundamental problems of Broadcast and
Local Broadcast in dynamic wireless networks. We propose a general model of
communication which captures and includes both fading models (like SINR) and
graph-based models (such as quasi unit disc graphs, bounded-independence
graphs, and protocol model). The only requirement is that the nodes can be
embedded in a bounded growth quasi-metric, which is the weakest condition known
to ensure distributed operability. Both the nodes and the links of the network
are dynamic: nodes can come and go, while the signal strength on links can go
up or down.
The results improve some of the known bounds even in the static setting,
including an optimal algorithm for local broadcasting in the SINR model, which
is additionally uniform (independent of network size). An essential component
is a procedure for balancing contention, which has potentially wide
applicability. The results illustrate the importance of carrier sensing, a
stock feature of wireless nodes today, which we encapsulate in primitives to
better explore its uses and usefulness.Comment: 28 pages, 2 figure
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