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Saturday, February 21, 2009


Here is a short guide to help have the benefits of a wifi router without actually having it on Windows XP.


1. Go to Control Panel -> Network Connection.
2. Right click on Your Ethernet connection and click on Properties.
3. Go toAdvanced Tab.
4. Check Allow Other NEtwork¦.. Internet Connection
5. In the Drop down Below select the Wifi connection of your pc. If it is disabled, it will be showing your wifi connection already.
6. Click on Settings
7. Check the protocols you need to share. Jamal has explained on them.I normally use only http and https.
8. Click on reach the network connection page. The sharing part is now over.


1. Click on Start -> Run
2. Type in cmd in the Run prompt
3. In the new window type ipconfig /all and press enter.
4. Note down your DNS server ip address from the screen.


1. Go again to Control Panel -> network connections.
2. Right click on your WIFI connection and click properties.
3. Go to Wireless Network Tab.
4. The use windows to configure my wireless network connection should be checked.
5. In the preferred network connection section click on add button
6. Enter a name of your wish to the network name.
7. Network authentication is open
8. Change Data Encryption to Disabled
9. Check the this is a computer to computer . not used connection.
10. Click Ok
11. Click on general tab. select internet protocol(tcp/ip) and click on properties button.
12. Now type in ip address, in subnet mask, leave default gateway empty.
13. Fill in the DNS server entry which you had noted down earlier.
14. Click on OK and your network is set.

Your network should appear on the wifi network list now. Search for wlan on your phone. Connect and enjoy browsing on your phone.

Friday, October 24, 2008

Baseband Communication

Baseband communication refers to the transmission over a baseband channel or a low pass channel. Low pass channel refers to channels that support only low frequency signals such as twisted pair, coaxial cable etc. The digital signals are sent through the medium without modulation on a high frequency carrier. Two major constraints for baseband communication are channel noise and intersymbol interference(ISI) that will result in bit errors in the received signal. Channel noise is assumed to be additive white Gaussian noise AWGN whose spectral density is independent of the frequency. The effects of channel noise on the information can be minimized by using a matched filter. Intersymbol interference is due to the dispersive nature of the channel and it will degrade the performance considerably. ISI can be controlled by adopting the raised cosine spectrum with the optimum roll-off factor. Eye patterns are used to study the combined effects of channel noise and ISI on the received signal.

Tuesday, August 12, 2008

IP Address

Just like every home has an address every node in the network has a unique address. IP address is the address used for communication between the computers at the network layer level. Every computer linked to the web will be allotted a 32 bit IP address during start up. The IP address can be broadly classified as two types namely classful and classless addressing. Let us take a look at the classful addressing

Every IP address can be dissected into two parts as netid and hostid. The netid identifies the network and the hostid identifies the host on the network.

Class A can be allocated to large size universal networks and they can accommodate a whopping 16,777,216 computers.

Class B addresses can incorporate 65,536 hosts and are most commonly allocated for intermediate size networks like MAN etc.

Class C addresses can support only 256 hosts and they are allocated to many small organizations with lower number of terminals.

Class D address serve as multicast addresses which are used to send data to several nodes at the same time.

Class E addresses are reserved for future use. Recently Classless addresses are being used. IP addresses are often used conservatively with the help of techniques like Network Address Translation(NAT) and Subnetting.

Saturday, August 9, 2008

ALOHA protocol

Aloha means "Hello". Aloha is a multiple access protocol at the datalink layer and proposes how multiple terminals access the medium without interference or collision. The protocol was developed by Norman Abramson and his colleagues at the University of Hawaii. The protocol allows every system to send a frame if it ready to send. But when a collision occurs the node will wait for a random amount time and then send the frame again. The process continues till the node has sent all the frames. Since the nodes send their frames without sensing the medium there is a high probability for collisions to occur. The maximum success rate or throughput that can be achieved with Aloha protocol is only 18%.

In 1972 Roberts developed a protocol that would increase the capacity of aloha two fold. The Slotted Aloha protocol involves dividing the time interval into discrete slots and each slot interval corresponds to the time period of one frame. This method requires synchronization between the sending nodes to prevent collisions.

Thursday, August 7, 2008

Home Area Networks

The Home Area Network (HAN) is a technology that interconnects all the home appliances and also links them to the internet via a central home portal. Devices such as personal computers, laptops, telephones, washing machines, security systems and entertainment systems can be tied together with the internet to facilitate remote controlling and inter-operation. The application diversity and dissimilar bandwidth requirements of each device are the constraints in HAN design. A HAN is meant to be user friendly, low cost, flexible and scalable without significant performance degradation.

There are different technologies adopted to develop the HAN infrastructure. Home Phone Network Access (HPNA) aims at providing internet access to home appliances through the single Telephone wiring. This is possible by using different frequencies for different applications on the same wire employing frequency division multiplexing. Power Line Modems is yet another HAN technology that tries to deliver broadband via power lines supplied to our homes. But the medium is noisy and the cost associated is high. Therefore we need to look out wireless solution alternatives. Home Access Networks are wireless networks that provide wireless internet connection to homes directly and enable communication of devices.

Tuesday, August 5, 2008

Mac frame format

Medium access control is very important to prevent collisions and delays. The data link layer is responsible for medium access control and several protocols are used for this purpose. Carrier sense multiple access is one way of controlling access to the medium. In CSMA/CD the system first senses the carrier before transmitting when the carrier is idle the system sends the data. When the carrier is busy the system backs of for a certain period of time before sensing the carrier again.

let us take a closer look at the Mac frame format

The Preamble is a seven byte field made up of alternating 0's and 1's which is very essential for synchronization between the transmitter and the receiver.

Start frame delimiter has a fixed sequence 10101011 which indicates the start of a frame and identifies the first bit for the receiver.

The Destination address is either 2byte or 6byte which refers to the address of the receiving system.

The Source address is either 2byte or 6byte which refers to the address of the sending system.

The length field provides the length of the data field of the logical link control layer.

The data from the LLC layer is encapsulated in to the Mac frame.

There are some extra bits needed for padding to ensure that the frame is matching the size perfectly.

A 32 bit CRC is provided at the end of the frame for error detection.

Sunday, August 3, 2008

Internet Services

Lets look at the services offered by the internet at the application level. The internet has changed our life and we use internet applications in our daily life directly or indirectly. The power of internet lies in its interoperability wherein multiple systems communicate with each other in solving multiple problems and tasks.

The worldwideweb is a repository of information allowing the users to access text, graphics and multimedia instantly. The users can follow hyperlinks to other websites.

Electronic mail has revolutionised the way people communicate with each other. The user can send messages and files as attachments via email. Every user is presented with an inbox to store incoming mails for free by all leading companies.

File transfer allows users to send/receive a copy of a file online. Small files can be attached to emails and large files can also be shared online.

Remote login allows users to sit at home and access the files in a remote computer by logging on to the system as a guest or registered user.