Wireless protocols IEEE 802.11 A B G N compared

When buying a wireless router or a wireless network card, have you ever wondered what do these letters next to the protocol 802.11 (a, b, g, and n) really mean? What is the difference between these protocols?

IEEE 802.11 is a set of standards for wireless local area network (WLAN) computer communication. The terms 802.11 and Wi-Fi are often used interchangeably but there is slight difference between the two.

(A) 802.11a
Frequency- 5 GHz  
Typical Data Rate - 23 Mbit/s  
Max Data rate – 54 Mbit/s  
Range – 115 feet

(B) 802.11b
Frequency - 2.4 GHz  
Typical Data Rate - 4.5 Mbit/s  
Max Data rate – 11 Mbit/s  
Range - 115 feet

(G) 802.11g
Frequency - 2.4 GHz  
Typical Data Rate – 19 Mbit/s  
Max Data rate - 54 Mbit/s  
Range – 125 feet

(N) 802.11n
Frequency - 5GHz and/or 2.4GHz  
Typical Data Rate - 74 Mbit/s  
Max Data rate - 300 Mbit/s (2 streams)
Range – 230 feet

Linux: Setting JAVA_HOME for a single user and all users

Here is how to setup JAVA_HOME and PATH environment variables for a single user or all users on Fedora Linux system

Setting JAVA_HOME and PATH for a single user

# vi ~/.bash_profile
# export JAVA_HOME=/opt/jdkx.x.x_xx
# export PATH=$PATH:$JAVA_HOME/bin

Setting JAVA_HOME and PATH for all users

# vi /etc/profile
# export JAVA_HOME=/opt/jdkx.x.x_xx
# export PATH=$PATH:$JAVA_HOME/bin

Linux – How to find out which Shell you are using?

Here are three quick ways to find out which shell you are currently using:

Method 1:

command:

# echo $SHELL

output:

/bin/bash

Method 2:

command:

# echo $0

output:

-bash

Method 3:

command:

# ps -p $$

output:

 PID TTY               TIME CMD
1447 tty1          00:00:01 bash

Creating Linux style symbolic links in Windows Vista

Windows Vista supports symbolic links (soft links). One way of creating these links is using the command line utility called MKLINK.

Run Command Prompt and type the comman MKLINK.

If the system warns saying…“You do not have sufficient privilege to perform this operation”. Run the Command Prompt as Administrator

Usage:

MKLINK [[/D] | [/H] | [/J]] Link Target
        /D      Creates a directory symbolic link.  Default is a file
                symbolic link.
        /H      Creates a hard link instead of a symbolic link.
        /J      Creates a Directory Junction.
        Link    specifies the new symbolic link name.
        Target  specifies the path (relative or absolute) that the new link
                refers to.

Example: To create a directorty link called src what points to c:\users\foo\src

     mklink /D src c:\users\foo\src
Thats it!

Top 4 micro-blogging tools – Twitter, Pownce, Tumblr and Jaiku

Twitter

Twitter is a free social networking and micro-blogging service that allows users to send updates (otherwise known as tweets) which are text-based posts of up to 140 characters in length.

Updates are displayed on the user’s profile page and delivered to other users who have signed up to receive them. The sender can restrict delivery to those in his or her circle of friends (delivery to everyone being the default). Users can receive updates via the Twitter website, instant messaging, SMS, RSS, email or through an application such as Twitterrific or Facebook.

Pownce

Pownce is a free social networking and micro-blogging site started by Internet entrepreneurs Kevin Rose, Leah Culver, Daniel Burka.[2] Pownce is centered around sharing messages, files, events, and links with already-established friends. The site launched on June 27, 2007, and was opened to the public on January 22, 2008.

Tumbler

tumblr is a tumblelog site. A tumblelog is a variation of a blog that favors short-form, mixed-media posts over the longer editorial posts frequently associated with blogging. Common post formats found on tumblelogs include links, photos, quotes, dialogues, and video. Unlike blogs, tumblelogs are frequently used to share the author’s creations, discoveries, or experiences while providing little or no commentary.

Jaiku

Jaiku is a social networking, micro-blogging and lifestreaming service comparable to Twitter. Jaiku was founded in February 2006 by Jyri Engeström and Petteri Koponen from Finland and launched in July of that year. It was purchased by Google on October 9, 2007.