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--- research:terms:monets [2006/07/11 18:15] – created tvcutsem
+++ research:terms:monets [2007/04/07 12:20] (current) – tvcutsem
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+==== Mobile Ad Hoc Networks ====
 In the general research area of pervasive computing and ambient intelligence, our research tends to focus on so-called **mobile networks**. Mobile networks fundamentally differ from traditional, stationary networks in the following two ways:
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   - In traditional distributed systems, components are interconnected via fast, wired, reliable communication links. In a mobile network, connections are usually **wireless**, slower and less reliable. Moreover, the biggest consequence of the wireless connections is that the communication //range// of devices becomes limited.
-Given these unavoidable, fundamental properties of mobile network, our research is founded on the observation of a number of so-called //hardware phenomena//: phenomena which have a profound impact on software, and which cannot be hidden from either developer or end-user because they are innate to the underlying hardware. The hardware phenomena we observer are:
+Given these unavoidable, fundamental properties of mobile network, our research is founded on the observation of a number of so-called //hardware phenomena//: phenomena which have a profound impact on software, and which cannot be hidden from either developer or end-user because they are innate to the underlying hardware. The hardware phenomena we observe are:
-  * **Natural Concurrency**:
+  * **Connection Volatility**: Two processes that perform a meaningful task together on two cooperating devices cannot assume a stable connection. The limited communication range of the wireless technology combined with the fact that users can move out of range can result in broken connections. However, upon re-establishing a broken connection, users typically expect the task to resume. In other words, they expect the task to be performed in the presence of a volatile connection.
-  * **Autonomous Devices**:
+  * **Ambient Resources**: If a user moves with his mobile device, remote resources become dynamically (un)available in the environment because the availability of a resource may depend on the location of the device. This is in contrast with stationary networks in which references to remote resources are obtained based on the explicit knowledge of the availability of the resource. In the context of mobile networks, the resources are said to be ambient.
-  * **Volatile Connections**:
+  * **Autonomy**: Most distributed applications today are developed using the client-server approach. The server often plays the role of a "higher authority" which coordinates interactions between the clients.  In mobile networks, and especially in mobile ad hoc networks, a connection to such a "higher authority" is not always possible. Every device acts as an autonomous computing unit.
-  * **Ambient Resources**:
+  * **Natural Concurrency**: In theory, distribution and concurrency are two different phenomena. For instance in a client-server setup, a client might wait for the results of a request to the server in order to resume its computation. Hence, in theory a distributed system is not necessarily a concurrent one. However, even in the extreme case where both communicating devices run a single threaded program, their autonomy implies that the resulting task is a concurrent one.  Moreover, the trend of software getting ever more multi-threaded will also manifest itself on mobile devices.  As a result, concurrency is a natural phenomenon in software running on mobile networks.