Basics of WiMax and OFDMA

WiMAX 

World-wide Interoperability for microwave access [WiMAX]

As broadband wireless networks encompass various services such as www, voice, video and data network traffic becomes very dynamic and unbalanced between the Uplink and Down-link stream volumes.

To provide the highest transport efficiency in broadband network TDD [Time Division Duplex] is preferred over FDD [frequency division Duplex] because it offers more flexibility in changing up-link and down-link bandwidth ratio.

WiMAX is one of the wireless standard as wi-fi(wireless-fidelity) and is of standard (IEEE 802.16) for the 10 to 66 Ghz range. WiMAX and wi-fi both standards have different applications. 

WiMAX is a long range system, covering many kilometers that uses licensed or unlicensed spectrum to deliver point-to-point connection to the Internet from an ISP( Internet Service Provider) to an end user. Different 802.16 standards provide access to a network from mobile to fixed. Where as wi-fi is a shorter range system, typically hundreds of meters that uses unlicensed spectrum to provide access to a network. 

 The licensed spectrum for WiMAX profile is: 2.3 Ghz, 2.5 Ghz and 3.5 Ghz. 

One of the Advantages of WiMAX is spectral efficiency. VOIP ( Voice over Internet Protocol) is extra QOS ( Quality of Service) class for WiMAX technology.

WiMAX works on OFDMA scheme (Orthogonal Frequency Division Multiplexing).

OFDMA:

Orthogonal Frequency Division Multiple Access.

It is a multiplexing technique that subdivides the bandwidth in to multiple frequency sub-carriers. Here the input data stream is divided in to several parallel sub-streams of reduced data rate and each sub-stream is modulated and transmitted on a separate Orthogonal Sub carrier.

• It is a multi-user version of the popular Orthogonal Frequency Division Multiplexing (OFDM) digital modulation scheme. multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users.
• It is MIMO (multiple input and multiple output) friendly and advantage of channel frequency selecting.

 Advantage over TDM :

• It Allows simultaneous low-data-rate transmission from several users.
• Lower maximum transmission power for low data rate users.

Other Advantage :

• Flexibility of deployment across various frequency bands with little needed modification to the air interface.
• Averaging interference from neighboring cells, by using different basic carrier permutations between users in different cells.
• Enables Single Frequency Network coverage, where coverage problem exists and gives excellent coverage.

 
The WiMAX forum for this has published three Licensed Spectrum profile: 

2.3 Ghz, 2.5 GHz and 3.5 Ghz.

USES of OFDMA:

1.at IEEE 802.16 wireless MAN standard [WiMAX] .
2. at IEEE 802.20 mobile wireless MAN standard.
3. Ultra mobile Broadband [UMB] , Qualcomm.

-DR

Wi-Fi Security Basics

Wi-Fi Security

Wi-Fi security is the protection of devices and networks connected in a wireless environment. Without Wi-Fi security, a networking device such as a wireless access point or a router can be accessed by anyone using a computer or mobile device within range of the router's wireless signal.

Keeping wireless or wi-fi networks open or unsecure can be risky for users and organizations. So, Wi-Fi protection is designed to avoid unauthorized access to wireless devices. There are various types of wireless security protocols that have been developed for the safety of home wireless networks such as WEP, WPA, WPA2.

WEP (Wired Equivalent Privacy)

The Wired Equivalent Privacy (WEP) Protocol was a standard developed in 1999. WEP was using the data encryption scheme that was based on a combination of user and system generated key values. However, it was not stable, so officially it was discontinued. 

WPA (WI-FI PROTECTED ACCESS) 

After discontinuing WEP, WPA introduced with some additional feature for security. The new feature was Temporary Key Integrity Protocol (TKIP), where it came with 128-bit dynamic key. TKIP has other features such as Boosting encryption strength, preventing collision attacks without hardware replacement.

TKIP was useful for upgrading security on devices originally equipped with WEP, although it does not address all of the security issues facing WLANs and may not be reliable enough for sensitive data transmission. 

WPA2

WPA2 introduced with significant changes and more features to the wireless security posture. WPA2 replaced TKIP with the Counter Mode Cipher Block Chaining Message Authentication Code Protocol (CCMP) which is a far superior encryption tool. WPA2 has been taken as the industry standard since its commencement, on March 13, 2006.

WPA2-PSK

WPA2-PSK (Pre-Shared Key) requires only one password to connect to the wireless network. It is generally accepted that a single password to access Wi-Fi is safe but only as much as you trust those using it. WPA2-PSK is secure but shares a password to all the users connected to the network, leading to snoop on the network by the attacker.

SSID

SSID Stands for "Service Set Identifier." It is a unique ID that consists of 32 characters and is used for naming wireless networks. When multiple wireless networks overlap or present at a certain location, SSIDs make sure that data gets sent to the correct destination or need to distinguish which one is the right one to connect. 

-DR

Basics of Wi-Fi

Wi-Fi

Wi-Fi (Wireless Fidelity)

Wi-Fi is an IEEE 802.11 standard family of wireless network.

A wireless network uses radio waves, just like cell phones, televisions and radios do. A computer's or mobile’s wireless adapter translates data into a radio signal and communicates it using an antenna.

A wireless router receives the signal and decodes it. The router sends the information to the Internet using a physical, wired Ethernet connection.

The process also works in reverse, with the router receiving information from the Internet, translating it into a radio signal and sending it to the computer's wireless adapter.

The radios used for Wi-Fi communication are very like to the radios used for walkie-talkies, cell phones and other devices. They can transmit and receive radio waves, and they can convert 1s and 0s into radio waves and convert the radio waves back into 1s and 0s.

Wi-Fi Signal transmits at frequencies of 2.4 GHz or 5 GHz.

They use 802.11 networking standards, which come in several forms:

802.11a

802.11b

802.11g

802.11n

802.11ac

Wi-Fi Hot Spot

A Wi-Fi hotspot is basically an area with an accessible wireless network. The term is most often used to state that wireless networks in public areas like airports, railway stations, bus stops, shopping malls.

You can turn your mobile to a Wi-Fi Hotspot by enabling the hotspot option. So that other mobile users can connect with you through Wi-Fi to use internet.

Security is a major concern of a Wi-Fi hot spot. If you set your router to create an open hotspot, anyone who will be able to use your signal by using own Wi-Fi.

To connect to a Wi-Fi network, a user typically needs the network name (the SSID-Service Set Identifier) and a password. The password is used to encrypt Wi-Fi packets. Wi-Fi Protected Access (WPA) is intended to protect information moving across Wi-Fi networks.

-DR

Basics of Access Point - WAP

Access Point/ Wireless Access Point (WAP)

An Access point allows devices to connect to the wireless network without use of any cable. They can be connected through wi-fi.

• The access point connects to a LAN directly with cable (Ethernet).
• It is same as an amplifier, it extends the bandwidth from router to other devices in that network. 
• It Supports different IEEE standard. WAP have special security features as they come with encryption standards (WPA, WPA2). 
• Easy to access from anywhere from signal range.
• It have static and unique IP address.

On the other way its Simple, Secure and Flexible.

-DR

Know your BIOS

BIOS

BIOS is just a short form of Basic Input and Output system. The BIOS in Computer or system is stored in a ROM chip / IC chip found in motherboards that lets you access and setup your system. It is a kind of Firmware. 

This requires instructions on how to load basic computer hardware. It is a link between the operating system (OS) and Hardware components such as hard disks, keyboard, mouse etc. It includes a test known as a POST (Power-On-Self-Test) that helps verify the computer meets the requirements to boot up properly.

We must have heard about BIOS password at somewhere.

BIOS password is the extreme strong password that is used to lock the hardware in the system and makes your system completely unusable. 

How to access BIOS

To enter the BIOS screen you might have seen or know, some keys are pressed during booting time. Many of us aware, when we configure system for the first time, even we follow the same processing to load the booting sequence or selecting the booting device to external drive to install software. 

The key sometimes is F2, F8, Del, F12 depending upon the manufacturer. Read the instructions clearly before trying anything else.

That screen is known as BIOS screen. 

Options you can navigate on BIOS screen are Boot order, Time change, Drive Partition help, formatting requirement, general over clocking settings, secure boot and Fast booting, BIOS password.  

So, this was just a basic thing to know about BIOS. 

Thanks

-DR

Wide Area Network

Wide Area Network (WAN)

A wide-area network or WAN is a computer network that connects smaller networks or LANs. Since WANs are not tied to a specific location, they allow localized networks to communicate with one another across great distances. They also help communication and the sharing of information between devices from anywhere in the world.

For example, in an enterprise, a WAN is formed to connect branch offices with one another or to join remote employees working at home with the company's main office.

As WAN covers wide geographical area, it can be via wired or wireless. Wireless WAN can use, GSM, 3G, 4G, LTE network and in case of wired WAN, it can be used through copper wire, fibre wire through leased line connectivity, broadband connectivity.

As per studies found the first known WAN was created by the U.S. Air Force in the late 1950s to interconnect its several sites in the Semi-Automatic Ground Environment (SAGE) radar defense system. It was an enormous network of dedicated phone lines, telephones, and modems linked the sites together.

The foundation of the IP-based Internet started with the Advanced Research Projects Agency Network (ARPANET), the first wide-area packet-switching network with distributed control and the first network to implement TCP/IP protocol suite.

Designing WAN

Building a WAN requires the support of a third-party service provider or internet service provider (ISP) who will provide a link to your location. It also requires networking equipment like routers and switches at its all locations.

While designing the WAN network, it should be in such a way and capable of communication of voice, data and video in an efficient way. The internet bandwidth should be in optimized way.

The Network shall have industry efficient compression engine to optimize bandwidth utilization.

Advantages

• WAN generally covers large geographical areas.
• You can get benefit of having centralized data by using WAN you can share the data connected to all the devices in the respective network.
• Corporate LAN sometimes uses leased lines. By using leased lines means that there are more bandwidths compared to a standard broadband connection and can help in business improvement.

Disadvantages

• Security Issue
• Installation or implementation cost
• Down time issue or disconnection issue
• Maintenance problem

We will cover more later. 

-DR

Basics of Signal Duplexing

Signal Duplex

A duplex communication scheme is a point-to-point system composed of two or more connected devices that can communicate with one another in both directions.

Duplex systems are employed in many communications networks, either to allow for concurrent communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field.

There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX).

A full-duplex (FDX) system, allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously.

Land-line telephone networks are full-duplex since they allow both callers to speak and be heard at the same time, with the transition from four to two wires being achieved by a hybrid coil in a telephone hybrid. Modern cell phones are also full-duplex.

The Duplex Scheme Available for the Mobile Wimax are , FDD, TDD, H-FDD [Half Duplex FDD].

For the duplexing scheme FDD, TDD, H-FDD are available options in case of mobile wimax. 

• TDD: It has same frequency band for UL/DL.2. Frame is divided in to DL subframe & UL subframe in the time domain. 
• FDD: Different frequency band,2. UL/DL subframes are overlapped in the time domain. 
• H-FDD: Two different frequency bands for DLand UL .2. DL/UL subframes dont overlap in the time domain.

-DR

Basics of MAC Address

MAC Address

Media Access Control is a Physical Address of a System like the IP addresses. They are always represented by decimal value and is a 48 bit value.

A Sample MAC Address looks like: 00-02-A3-B2-67-68

Every piece of hardware on your local network has a MAC address in addition to the IP address assigned to it by the local router, switch or server.

An address system is required to uniquely identify computers and interfaces to allow for local delivery of frames on the Ethernet. Ethernet uses MAC addresses that are 48 bits in length and expressed as 12 hexadecimal digits. The first six hexadecimal digits, which are administered by the IEEE, identify the manufacturer or vendor. This portion of the MAC address is known as the Organizational Unique Identifier (OUI). The remaining six hexadecimal digits represent the interface serial number or another value administered by the manufacturer. MAC addresses are sometimes referred to as burned-in MAC addresses (BIAs) because they are burned into ROM and are copied into RAM when the NIC initializes. 

At the data link layer MAC headers and trailers are added to upper layer data. The header and trailer contain control information intended for the data link layer in the destination system. The data from upper layers is encapsulated within the data link frame, between the header and trailer, and then sent out on the network.

The NIC uses the MAC address to determine if a message should be passed on to the upper layers of the OSI model. The NIC does not use CPU processing time to make this assessment. This enables better communication times on an Ethernet network.

When a device sends data on an Ethernet network, it can use the destination MAC address to open a communication pathway to the other device. The source device attaches a header with the MAC address of the intended destination and sends data through the network. As this data travels along the network media the NIC in each device checks to see if the MAC address matches the physical destination address carried by the data frame. If there is no match, the NIC discards the data frame. When the data reaches the destination node, the NIC makes a copy and passes the frame up the OSI layers. On an Ethernet network, all nodes must examine the MAC header.

All devices that are connected to the Ethernet LAN have MAC addressed interfaces. This includes workstations, printers, routers, and switches.

Network cards each have a unique MAC address. Packets that are sent on the ethernet are always coming from a MAC address and sent to a MAC address. If a network adapter is receiving a packet, it is comparing the packet’s destination MAC address to the adapter’s own MAC address. If the addresses match, the packet is processed, otherwise it is discarded.

MAC Address of any network Card is 6 bytes and 48 bits long. 

Network switches store a list of MAC addresses seen at every port and only forward packets to the ports that need to see the packet.

DHCP servers use the MAC address to identify devices and give some devices fixed IP addresses.

Wanna Check?

Go to command prompt type: 

Start > Run > cmd 

ipconfig/all Enter

 

The network card is responsible for the determining whether the data is intended for it or for another network card. Each network card is given a set of rules that it follows.

 

 -DR

Basics of Network and Internet

01

Welcome to my First Blog!

Hello Readers! 

As I have started my career from this domain, so just wished to share the knowledge for understanding on basics of this domain. Hope it will help everyone to learn the domain. I have tried to keep all the relevant information in this entire blog. Please go to each post and read them. If you have any suggestions and comments on any section, please provide your valuable feedback or suggestion for improvement. 

Secondly this blog can be helpful for anyone who wanted to start a career in network domain, IT domain, Cyber security and Information Security domain. Because all the content were intended to cover those areas only. 

Lets start;

A Basic Computer Network 

A computer network is a group of computers connected together through wired or wireless medium. 

A basic network allows devices to share information or communicate with each other.

How they communicate ?

Language: Binary i.e. 0 and 1

Interface: Physical (Ports) / Wireless 

Medium: Cable / Wifi / Bluetooth / RF

Computers are generally connected from their Ethernet Port (RJ45 Interface/ Network Interface Card) via ethernet cable (UTP Cat cable/ Patch cord) to a LAN port (RJ45 interface) designated at table/wall or direct at Switch device port. 

 

In case of wireless connectivity they are connected through wireless NIC card. 

Basically there are three types of a computer network.

LAN: Local Area Network

MAN: Metropolitan Area Network

WAN: Wide Area Network

There are networks in other way as;

WLAN: Wireless Local Area Network

SAN: Storage Area Network

We will cover each sections in our coming next blogs. 

A computer network is used for following tasks to be performed.

• File Sharing and Transfer
• Browsing Internet and other stuffs.
• Allow user to access information. 

There are different designs of connectivity used such as;

Peer to peer and Client/ Server 

Peer to peer means one to one connectivity. Such as Switch to PC.

Client Server architecture means there is a primary server to which one or multiple PC can be connected through LAN or WAN. For example centralized Database Management Server, One Web application Server, etc. 

Topology: 

The term Network Topology is the logical arrangement of computer networking devices to the way in which the various nodes or hosts or computers of a network are linked together.

So, multiple devices connected with each other physically and logically with each other in various ways as mentioned below; 

• Mesh Topology
• Star Topology
• Bus Topology
• Ring Topology
• Tree Topology
• Hybrid Topology

To know how the network works or behaves, a topology is must required. There are many commercial software available in the market, who represent the network architecture or topology in graphical interface or dashboard for easy identification. 

There are many available tools and software for simulation of network such as Cisco Packet Tracer. It allows students and teachers to design, build, configure, and troubleshoot complex networks using virtual equipment.

Network Interface Card (NIC)/ LAN Card

A NIC (network interface card/ Network interface controller) is designed to connect over a computer network through Ethernet cable or wireless (In case of WNIC). A NIC card can transmit signals at the physical layer and deliver data packets at the network layer, it acts as a middleman between a computer/server and a data network. 

 

Internet

Internet, a system architecture that has modernized communications and methods of information exchange by allowing various computer networks around the world to interconnect. Sometimes known as a “network of networks”. 

It was first created by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense. ARPANET was one of the first general-purpose computer networks. It connected time-sharing computers at government-supported research sites, largely universities in United States using packet switching. Then it became a critical section of infrastructure for the computer science research community in the United States.

Bandwidth:

Bandwidth is calculated as the amount of data that can be transferred from one point to another within a network in a definite amount of time. It is expressed as a bitrate and measured in bits per second (bps). Similarly in today’s technology we are more familiar with higher values which are measured as Kbps, Mbps, Gbps, etc,.

The more bandwidth, the more data can be communicated or transferred. 

So this is just a basic and first writeup. Will update and come with new information in my next posts. Stay tuned. 

Thanks!

-DR