Monday, 8 April 2013

Mobile adhoc networks allow wireless connectivity directly between wireless nodes - without connecting through an access point (infrastructure mode networks).

Traditional wireless networks have at least one access point, which is usually connected to a wired network. The wireless nodes associate to the access point for their connectivity. Communication between wireless nodes occurs through the AP itself (if the AP allows peer-to-peer communications) or through the network that the AP is connected to. For the nodes to be able to communicate, they must remain within range of an AP.

Mobile adhoc networks (MANETs) are designed so that the wireless peers can communicate directly to/from each other without going through an AP. The peers form associations with, and validate each other directly. As long as the peers (nodes) are within range of each other, they can communicate.

Sunday, 7 April 2013

Fuzzy Logic


o   Fuzzy logic is a form of many-valued logic or probabilistic logic.
o   It deals with reasoning that is approximate rather than fixed and exact.
o   Compared to traditional binary sets (where variables may take on true or false values) fuzzy logic variables may have a truth value that ranges in degree between 0 and 1.
o   Fuzzy logic has been extended to handle the concept of partial truth, where the truth value may range between completely true and completely false.
o   Furthermore, when linguistic variables are used, these degrees may be managed by specific functions.
o   The term "fuzzy logic" was introduced with the 1965 proposal of fuzzy set theory by Lotfi A. Zadeh
o   Fuzzy logic has been applied to many fields, from control theory to artificial intelligence. Fuzzy logics however had been studied since the 1920s as infinite-valued logics notably by Łukasiewicz and Tarski.
o   Fuzzy logic has rapidly become one of the most successful of today's technologies for developing sophisticated control systems.
o   The reason for which is very simple. Fuzzy logic addresses such applications perfectly as it resembles human decision making with an ability to generate precise solutions from certain or approximate information.
o   It fills an important gap in engineering design methods left vacant by purely mathematical approaches (e.g. linear control design), and purely logic-based approaches (e.g. expert systems) in system design.

o  
While other approaches require accurate equations to model real-world behaviors, fuzzy design can accommodate the ambiguities of real-world human language and logic.
o   It provides both an intuitive method for describing systems in human terms and automates the conversion of those system specifications into effective models.
o   for example, the fuzzy washing machine . A load of clothes in it and press start, and the machine begins to churn, automatically choosing the best cycle.
o   The fuzzy microwave, Place chili, potatoes, or etc in a fuzzy microwave and push single button, and it cooks for the right time at the proper temperature.
o   The fuzzy car, maneuvers itself by following simple verbal instructions from its driver.
o   It can even stop itself when there is an obstacle immediately ahead using sensors.
o   But, practically the most exciting thing about it, is the simplicity involved in operating it.


o   Fuzzy logic is a form of many-valued logic or probabilistic logic.
o   It deals with reasoning that is approximate rather than fixed and exact.
o   Compared to traditional binary sets (where variables may take on true or false values) fuzzy logic variables may have a truth value that ranges in degree between 0 and 1.
o   Fuzzy logic has been extended to handle the concept of partial truth, where the truth value may range between completely true and completely false.
o   Furthermore, when linguistic variables are used, these degrees may be managed by specific functions.
o   The term "fuzzy logic" was introduced with the 1965 proposal of fuzzy set theory by Lotfi A. Zadeh
o   Fuzzy logic has been applied to many fields, from control theory to artificial intelligence. Fuzzy logics however had been studied since the 1920s as infinite-valued logics notably by Łukasiewicz and Tarski.
o   Fuzzy logic has rapidly become one of the most successful of today's technologies for developing sophisticated control systems.
o   The reason for which is very simple. Fuzzy logic addresses such applications perfectly as it resembles human decision making with an ability to generate precise solutions from certain or approximate information.
o   It fills an important gap in engineering design methods left vacant by purely mathematical approaches (e.g. linear control design), and purely logic-based approaches (e.g. expert systems) in system design.

o  
While other approaches require accurate equations to model real-world behaviors, fuzzy design can accommodate the ambiguities of real-world human language and logic.
o   It provides both an intuitive method for describing systems in human terms and automates the conversion of those system specifications into effective models.
o   for example, the fuzzy washing machine . A load of clothes in it and press start, and the machine begins to churn, automatically choosing the best cycle.
o   The fuzzy microwave, Place chili, potatoes, or etc in a fuzzy microwave and push single button, and it cooks for the right time at the proper temperature.
o   The fuzzy car, maneuvers itself by following simple verbal instructions from its driver.
o   It can even stop itself when there is an obstacle immediately ahead using sensors.
o   But, practically the most exciting thing about it, is the simplicity involved in operating it.


Saturday, 6 April 2013

ns-3
Overview
ns-3
is a discrete-event network simulator oriented towards network research and education, with a special focus on Internetbased
systems. The
ns-3 project is designing a follow-on successor to the popular ns-2 simulator.
In
ns-2, simulation scripts are written in OTcl. In ns-3, simulation scripts are written in C++, with support for extensions
that allow simulation scripts to be written in Python. These Python bindings have yet to be written, but the goal is for full or
near-full API support at the Python level.
ns-3
is intended to provide better support than in ns-2 for the following items:
Modularity of components
Scalability of simulations
Integration/reuse of externally developed code and software utilities
EmulationTracing and statistics

Wednesday, 3 April 2013

Definition of a Neural Network

           Neural networks have a large appeal to many researchers due to their great closeness to the structure of the brain, a characteristic not shared by more traditional systems.
In an analogy to the brain, an entity made up of interconnected neurons, neural networks are made up of interconnected processing elements called units, which respond in parallel to a set of input signals given to each.   The unit is the equivalent of its brain counterpart, the neuron.   A neural network consists of four main parts:

1. Processing units{uj}, where each uj has a certain activation level aj(t) at any point in time.

2. Weighted interconnections between the various processing units which determine how the activation of one unit leads to input for another unit.

3. An activation rule which acts on the set of input signals at a unit to produce a new output signal, or activation.

4. Optionally, a learning rule that specifies how to adjust the weights for a given input/output pair.
A processing unit uj takes a number of input signals, say a1j, a2j,...,anj with corresponding weights w1j, w2j,...,wnj, respectively. The net input to uj given by:
netj = SUM (wij * aij)
The new state of activation of uj given by:
aj(t+1) = F(aj(t),netj),
where F is the activation rule and aj(t) is the activation of uj at time t. The output signal oj of unit uj is a function of the new state of activation of uj:
oj(t+1) = fj(aj(t+1)).
One of the most important features of a neural network is its ability to adapt to new environments. Therefore, learning algorithms are critical to the study of neural networks.

MANET Features and Characteristics



What is a MANET ?
It is an infrastructureless IP based network of mobile and wireless machine nodes connected with radio. In operation, the nodes of a MANET do not have a centralized administration mechanism. It is known for its routeable network properties where each node act as a “router” to forward the traffic to other specified node in the network.

Types of MANET
There are different types of MANETs including:
o    InVANETs – Intelligent vehicular ad hoc networks make use of artificial intelligence to tackle unexpected situations like vehicle collision and accidents.
o    Vehicular ad hoc networks (VANETs) – Enables effective communication with another vehicle or helps to communicate with roadside equipments.
o    Internet Based Mobile Ad hoc Networks (iMANET) – helps to link fixed as well as mobile nodes.
Characteristics of MANET
o    In MANET, each node act as both host and router. That is it is autonomous in behavior. 
o    Multi-hop radio relaying- When a source node and destination node for a message is out of the radio range, the MANETs are capable of multi-hop routing.
o    Distributed nature of operation for security, routing and host configuration. A centralized firewall is absent here.
o    The nodes can join or leave the network anytime, making the network topology dynamic in nature.
o    Mobile nodes are characterized with less memory, power and light weight features.
o    The reliability, efficiency, stability and capacity of wireless links are often inferior when compared with wired links. This shows the fluctuating link bandwidth of wireless links.
o    Mobile and spontaneous behavior which demands minimum human intervention to configure the network.
o    All nodes have identical features with similar responsibilities and capabilities and hence it forms a completely symmetric environment.
o    High user density and large level of user mobility.
o    Nodal connectivity is intermittent.
Manet Challenges
A Manet environment has to overcome certain issues of limitation and inefficiency. It includes:
o    The wireless link characteristics are time-varying in nature: There are transmission impediments like fading, path loss, blockage and interference that adds to the susceptible behavior of  wireless channels. The reliability of wireless transmission is resisted by different factors.
o    Limited range of wireless transmission – The limited radio band results in reduced data rates compared to the wireless networks. Hence optimal usage of bandwidth is necessary by keeping low overhead as possible.
o    Packet losses due to errors in transmission – MANETs experience higher packet loss due to factors such as hidden terminals that results in collisions, wireless channel issues (high bit error rate (BER)), interference, frequent breakage in paths caused by mobility of nodes, increased collisions due to the presence of hidden terminals and uni-directional links.
o    Route changes due to mobility- The dynamic nature of network topology results in frequent path breaks.
o    Frequent network partitions- The random movement of nodes often leads to partition of the network. This mostly affects the intermediate nodes.

he application of this wireless network is limited due to the mobile and ad hoc nature. Similarly, the lack of a centralized operation prevents the use of firewall in MANETs. It also faces a multitude of security threats just like wired networks. It includes spoofing, passive eavesdropping, denial of service and many others. The attacks are usually classified on the basis of employed techniques and the consequences.

Tuesday, 2 April 2013

5 Top Windows 8 Features

5 Top Windows 8 Features
Following the release of Windows 8 Developer Preview, many sites have done reviews on what the next Windows system will be like. The reviews are mostly positive, with some hailing Windows 8 as the next revolution in the technology of computer operating systems (OS). Such may well be the ambition of Microsoft, and it shouldn’t surprise time it comes at a time when Apple’s share of the OS market is rising and pitting fiercely against them.
If there’s one thing great about competition, it is that it brings out the best product between companies. I’ve read up some of the features that Microsoft’s Windows 8 will be offering, and am now both intrigued and excited for what’s to come in the full version. It will even come with a new and unique kind of user interface (UI) known as the Metro.
Here are brief descriptions to some top features you would be keen to know about:

1. Speedy Boot Time

The load and boot up speed has improved significantly over Windows’ predecessors. This is partly due to the better resource allocations to applications and the system. When compared to Windows 7 desktop CPU, Windows 8 has an even speedier boot time.

(Image Source: Within Windows)
How did they improve so much over Windows 7? Well, Windows 8 employs a technique of hibernating the system kernel (think of it as your OS’s resource manager) when you shut down, such that it becomes almost like a partial hibernation each time. When you reboot the system, the ‘memory’ of your previous session gets reinitialized quicker.

2. Innovative & Dynamic Desktop

The tiles-based interface, or the Metro UI, will be the first thing you see upon logging in to Windows 8. At first glance, the UI seems to go intuitively with touchscreen devices like tablets and smartphones. Indeed, in such devices, you tap on those apps to open them. The grid layout seems to facilitate such interactions. Needless to say, you can customize your grid by adding and arranging applications.

(Image Source: JRtheTech)
The coolest thing, however, is that not only does Windows 8 allows you to personalize your desktop with the organization of the apps, it is also able display real-time information through them. Microsoft had demonstrated how the tile for a weather app could reveal the current temperature in a city without having to activate the app. The same goes for emails and such. In one glance over your tiles, you can have access to all that you need to be notified and take action on those which are urgent.

3. Improved Search Function

8 has no search box at the bottom of the Start menu. Heck, it doesn’t even have the trademark Start menu! That doesn’t mean that there’s no convenient search function available. All you need to do is to type anything, and a search box will appear from the right and give you the results. The search capability is even stronger this time, displaying all the matching apps and files instantaneously.

(Image Source: JaisonYR)
Unlike Windows 7, Windows
You can also search within apps that utilize Windows 8′s search function. The search pane that pops out on the right of your desktop will contain the list of apps which you can conduct the search in. For instance, if you’re looking for the emails sent by a particular contact, typing that name and clicking on the email app would allow you to search from within.

4. Windows To Go

Of the entire list here, this is one feature that offers the most convenience to users. Windows To Go allows users to make a copy of their OS complete with their settings, wallpapers, files and even apps, into a USB thumb drive. Plugged it into another computer with Windows 8 already installed, and you can boot up the PC and make it look exactly alike the OS you normally use, with all settings intact.

(Image Source: Engadget)
It sounds rather amazing, doesn’t it? The potential for such a feature is high and possibilities, many. For one, a virus-infected and crashed system could be revived by simply plugging in the USB thumbdrive with your last saved settings, inclusive of all your files, apps, etc. Users don’t have to worry about losing the ability to work on their projects just because their PC is down; they can always rely on plugging in that thumbdrive into another Windows 8-installed PC. Another is that users may simply bring back work from the office with that thumbdrive rather than a much bulkier laptop.

5. Windows Live Syncing

Similar to Windows To Go, the new Windows 8 will provide Windows Live syncing, such that users can login on any Windows 8 PC with ‘Live ID’ and get back their own personalized settings on it. The desktop will look the same every time the user login on a PC with their Windows Live account. Migrating to a new PC is probably made easier when the user has all the essential settings synced.

(Image Source: Windows 8)
How different will this be from Windows To Go? Well, Windows To Go seem to serve more as a controlled device for IT administrators to distribute to employees (with exact duplicates of Windows 8 with the same settings, wallpapers, apps, etc on thumbdrives), while Windows Live Syncing is more to allowing users to keep the basic settings and data available even if they’re away from their primary PC. We can only anticipate how the former and latter will be truly be like until they are unveiled by Microsoft in due course.