WiMAX features

A wireless broadband solution that offers various features with a lot of flexibility in terms of potential service offering is WiMAX technology.

• WiMAX support multipath.
• IT provide up to 50 km of service area range.
• WiMAX uses OFDM technology.
• WiMAX support TDD and FDD.
• WiMAX offer modulation and error correction.
• Adaptive modulation enables while using WiMAX system to optimize the throughput based on the propagation conditions.
• Very scalable bandwidth and high-speed data rate.
• Flexible and dynamic per-user resource allocation.
• Support for advanced antenna techniques.
• Support for mobility.
• Portable internet usage.
• Quality of service support.
• It is IP based architecture.
• WiMAX is always best connected.

WiMAX architecture

As we know that the WiMAX system consists of two major parts: Main part is to be (i) A WiMAX base station (ii) And a WiMAX receiver.

Let us take a look at the WiMAX architecture to shown in the figure.

A WiMAX base station :

WiMAX base station is very similar to accessing a wireless access point in a Wi-Fi network, but the coverage is greater than to another network.

WiMAX base station can provide a very large area up to a radius of around 6 miles. A WiMAX base station(BS) consists of indoor electronics and as we know that WiMAX tower similar look like to a cell phone tower.

Each base station(BS) can provide wireless coverage over an area called a cell. The WiMAX base station can also use a multiple antennas point in a different direction. This area covered by one antenna signal called sector.

The uplink and also a downlink channel are shared among the many subscriber stations in a given sector. WiMAX can also have support bursty data and also provide high-quality telephone and high volume multimedia.

The uplink and also for downlink channels are divided into slots of equal size. A WiMAX frame takes multiple slots. Different frame takes a different number of slots. The downlink channel easy to subdivide into connection as only the base station sends on that channel.

A WiMAX receiver : 

A WiMAX receiver side may have a separate antenna or could be a stand-alone box or a PCMCIA card present in your laptop or any other device. It is called as customer premise equipment (CPE).

In most of the cases, a simple plug and play terminal, similar to a DSL modem provides connectivity as shown in the figure given below.

For customer located several kilometers from the WiMAX base station, a self-install outdoor. The antenna may be required to improve transmission quality. 

For customer requesting a voice in addition to broadband services, specific CPE will allow the connection of standard or VoIP phones device.

WiMAX architecture

WiMAX standard

We all know that the WiMAX system has been supporting IEEE 802.16, This standard is called IEEE  called 802.16, it was associated with 802.16a / REV d / e standard.

These standards were issued by IEEE standard 802.16 into the subgroup called  (802.16a/REV d/e) standard that originally covered the Wireless local loop (WLL) technologies with radio spectrum from 10 to 66 GHz. Recently were extended below 10 GHz.

In the year of January 2003, the approved IEEE standard 802.16a as an amendment to IEEE  standard 802.16 defining line of sight capability.

In the year of 2004, the IEEE 802.16 standard Revd was introduced to support basically indoor customer premises equipment through additional radio capabilities like antenna beamforming and OFDM sub channeling.

In the year of 2005, an IEEE standard 802.16e variant was developed for supporting mobility device.

Following are the details of various IEEE 802.16 standard related to WiMAX system listed below.

1. 802.16

• Spectrum - 10-66 GHz
• Configuration  - Line of sight
• Mobility - Fixed
• Channel bandwidth - 20,25 MHz
• Typical cell radius - 1-3 miles
• Modulation - QPSK-16 QAM 64 QAM
• Completion  - December 2001

2. 802.16a

• Spectrum - 2-11 GHz
• Configuration  - Non-Line of sight
• Mobility - Fixed
• Channel bandwidth - Selectable, 1.25-20 MHz
• Typical cell radius - 3-5 miles
• Modulation - total number of 256 subscribers, OFDM using QPSK, 16 QAM, 64 QAM, 256-QAM
• Completion - January 2003

3. 802.16e

• Spectrum - <6 GHz
• Configuration  - Non-Line of sight
• Mobility - Fixed
• Channel bandwidth - 5 MHz planned
• Typical cell radius - 1-3 miles
• Modulation - total number of 256 subscribers, OFDM using QPSK16, QAM, 64 QAM, 256-QAM
• Completion - 2nd half of 2005

GSM handover

Definition of handover : 

Handover is the process of transferring a mobile station from one channel to another channel side.

This system can be defined as a mechanism to hand over the mobile device to the neighboring cell.

Basically, handover is a core element that can be planned and deployed cellular system based network. It must be efficiently done using different strategies.

In the handover process, if the mobile device moves out the range of one cell, a different base station provides it with a use of the stronger signal.

In this process, if the channel of the base station is busy then the nearby base station can provide service to the device.

Types of handover :

There are two types of handover :

1. Hard Handover
2. Soft Handover

1. Hard handover :

In hard handover, the radio link must be dropped for a small amount of time before it can be taken over by another base station.

So the call process not from only one base station (BS) to another base station but from current transmits to receiver frequency pair to another frequency pair. A break in call transmission is called as a call drop.

In general, the handover occurs in a very few milliseconds. The GSM system performs hard handovers.

2. Soft handover :

While in soft handover indicates an MS full form is a mobile station at the boundary of two adjacent cells does not call drop because of handover in the boundary region. 

A mobile can be connected easily to several base station (BS full form) is base stations simultaneously. The 3D CDMA support soft handover.

Photo detector

The photodetector is also called an optical receiver. It converts the variation in optical power into a corresponding variation in the electric current. As compare to the optical transmitter the design of optical receiver is more complicated just because the receiver must detect weak, distorted signals and then make decisions on what type of data was sent based on an amplified version of this totally distorted signal.

Photodiodes are one type of photodetector, is capable of converting light into either voltage or current. That depends upon the mode of operation. In photodetector cut off wavelength and quantum efficiency can be defined as λc and ȵ

The requirement of the ideal photodetector 

• High sensitivity at the operating wavelength 
• Spectral response: This parameter also describe the efficiency of the photodetector as a function of wavelength.
• Size: Photodetector size must be small
• Voltage: It must be work on small voltage 
• High fidelity: The received signal must be reproduced as it as far as possible
• Cost: Cost of the photodetector must be less
• Noise: Minimum noise must be introduced by the detector device
• Stability: Performance characteristics of photodetector should not change with a change in ambient conditions

Types of photodetector 

• LDR
• the p-n junction semiconductor photodetector
• Traveling wave photodetector
• PIN diode
• Avalanche photodiode
• Phototransistor

Full form of LED

What is the full form of LED?

Answer :

• Light Emitting Diode

What does LED mean?

LED is a component is its convert the electrical signal into a corresponding light that is injected into the fiber. Basically, the light emitter is a key element in any fiber optic technology. Nowadays the light has collected the edge of LED, in order to reduce the losses caused by absorption the active layer and to make the beam more directional, such a device is known as edge emitting LED or ELED.

Properties of light

Light is electromagnetic radiation that has wave properties. Light waves can travel in a straight line. The light rays travel at the speed 3×10⁸ or 186000 miles/sec. in free space. Light is a basic form of energy produced by the luminous object. It can travel through a vacuum. A light source needs characteristics of light must be possible to operate the device continuously at a variety of temperatures for many years.

Let us now check it out the primary definitions which we will be using while discussing optical fiber.

1. Refractive Index :

Refraction is the bending of a light ray that occurs when a light ray passes from one medium to another.

So it usually happens when the light to them from one medium to the next. The measure of how much light refract in a medium call index of refraction.

Refractive index can be defined as, n of an optical parameter of a material or substance as the ratio of the speed of light(c) in the air to the speed of light(v) in another medium, such as glass, water etc.

Where, 

Refractive index  n = Speed of light in air (c) / speed of light in a material (glass-v)

n = Refractive index

c = Speed of light,  speed of light in free space = 3×10⁸ or 186000 miles/sec

v = speed of light in a material

Now will discuss the index of refraction in a different material

• Air - 1.003
• Vacuum - 1
• Water - 1.33
• Glass fiber - 1.5-1.9
• Diamond - 2.0 - 2.42
• Silicon - 3.4
• Gallium arsenide - 2.6

Due to the refraction of light, we have to observe the various effect in our daily life. The following some example of them.

• A stick partially dipped in water seems to be sent
• A clear pool of water always appears to be shallower than compare it actually is.

2. Reflection :

The law of reflection state that when the light ray incident upon a reflective surface at some of the incident angle i from imaginary perpendicular normal, the ray will be reflected from the surface at some angle r^r from normal which is equal to the angle of incident.

The angle of reflection =  r^r  = the angle at which the light is reflected from a surface is called the angle of reflection

                                                                  i =  r^r 

                           ^{The angle of incidence  is the same as = the angle of reflection}

The angle at which the light strikes a surface of the mirror with respect to the normal is called the "angle of incidence". The figure shows that the law of refraction and reflection.

 

3. Diffraction :

Diffraction is the slight bending of light as it passes around the edge of an object side. It refers to various phenomena that occur when a wave encounters an obstacle or silt. It is also defined as the bending of light around the corners of an obstacle or aperture into the region of the geometrical shadow of the obstacle. every cloud is a silver lining is the example of diffraction.

4. Dispersion :

The process on which light is separated into its colors due to the different degree of refraction, so the separation of visibility into its different colors is known as dispersion.

Full form of SONET

What is the full form of SONET?

Answer :

• Synchronous  Optical Network

What does SONET mean?

SONET is standing for the synchronous optical network. It is most commonly transmit data at a speed between the range of around 155 megabits per second and 2.5 gigabits per second.  To build these high bandwidth data streams, SONET  multiplexer together channels having bandwidth as low as 64 kilobits per second into data frames sent at fixed intervals.

SONET interface defines all layers, from the physical to the application layers, while SDH is a set of standard interfaces in a network of elements that conform to these interfaces.

Advantages and disadvantages of SONET

SONET has commonly transmitted data at speed between 155 megabits per second and 2.5 gigabits per second. To the build these high bandwidth data streams, for SONET multiplexer techniques together channels having bandwidth as low as 64-kilobits per second into data frames sent at fixed intervals. So now let us check out the advantages and disadvantages of SONET to know more details about SONET.

Advantages of SONET :

• Reduced cost
• It offers network survivability features
• It is compatible with legacy and future network
• Very high efficiency
• Allows transportation of all  forms of traffic
• Standard optical interference
• De-multiplexing is easy
• Remote operation capabilities. remotely provisioned, tested, inventoried, customized and also reconfigured
• Can we used in SONET networks for fast restoral and protection
• Out of band management system

Disadvantages of SONET :

• No interoperable standard
• Tributary services require SONET mux services
• Low cost effective for low channel numbers.
• SONET/SDH network management system not well equipped to handle the DWDM method and management
• Bandwidth efficiency is a problem at higher capacity
• More overhead is required

Application of SONET

SONET has commonly transmitted data at speed between 155 megabits per second and 2.5 gigabits per second. To the build these high bandwidth data streams, the SONET multiplexer together channels having the bandwidth as low as 64-kilobits per second into data frames sent at fixed intervals. So now let us check out the application of SONET to know more details about SONET.

• SONET was originally designed for the public telephone network.
• SONET acts as a carrier of multiple higher-level application protocol.
• SONET provides a layer 1 or interfaces layer technology also termed physical layer in the OSI model.
• SONET is used to Multipoint configurations, enhanced performance, monitoring, and enhanced and integrated OAM.

What is SONET

Nowadays carrier synchronous digital hierarchy  (SDH) is an international standard for high-speed telecommunication networks. It is a synchronous system which provides simple network infrastructure and it is a more flexible network. SONET is very similar to SDH. SONET is the standard used in the US where SDH is the standard used outside the US also. Before we started the details about SONET/ SDH first we will discuss why using SONET/ SDH and also a full form of SONET.

• In SONET yield thinner cable than copper
• The lower bit error rate
• Higher bandwidth per fiber
• Higher transmission reliability 

SONET network is a transmission interface originally proposed by the broadband ISDN network. Now in this article, we talk about some important characteristics, similarities, major difference between SONET and SDH, SONET network topology. first, now let us check it out some important point SONET as well as SDH.

• SONET is a synchronous network while SDH is also synchronous network with an optical interface.
• SONET interface defines all layers, from the physical to the application layers, while SDH is a set of standard interfaces in a network of elements that conform to these interfaces.

SONET has commonly transmitted data at speed between 155 megabits per second and 2.5 gigabits per second. To the build these high bandwidth data streams, SONET  is multiplexer together channels having the bandwidth as low as around 64-kilobits per second into data frames sent at fixed intervals.

This article gives information about both SONET and SDH  are based on a structure that has a basic frame format and speed. All the base signaling level called STS-1, SONET support 51.84 Mbps and this STS-1 frame can be carried in an OC-1 signal. The SDH level and frame format used by the synchronous transport module(STM).

SONET versus SDH :

• Bitrate and frame format organization
• Frame synchronization schemes
• Error control
• Multiplexing and demultiplexing rules

SONET and SDH rates :

SONET Signal - STS-1, Optical carrier - OC-1

Data rate - 51.84 Mbps

Payload rate - 50.112 Mbps

SONET signal - STS-3,Optical carrier - OC-3,

SDH ITU-T - STM-1

Data rate - 155.52 Mbps

Payload rate - 150.336 Mbps

SONET Signal - STS-9, Optical carrier - OC-9,

SDH ITU-T - STM-3

Data rate - 466.56 Mbps

Payload rate - 451.008 Mbps

SONET signal - STS-12, optical carrier- OC-12
SDH ITU-T - STM-4
Data rate - 622.08 Mbps
Payload rate - 601.344 Mbps

STS-1 - Synchronous transport signal -1 

OC - Optical carrier

STM - Synchronous transport module

ITU-T - International telecommunication union telecommunication standardization sector.

Application of SONET :

• Used for the public telephone network.
• SONET acts as a carrier of multiple higher-level application protocol.
• SONET provides a layer 1 or interfaces layer technology also termed physical layer in the OSI model.
• Used to Multipoint configurations, enhanced performance, monitoring, and enhanced and integrated OAM.

You may also check it out :

Advantages and disadvantages of SONET

What is DWDM

Before we learn about the DWDM first let it check out the full form of DWDM. DWDM stands for dense wavelength division multiplexing. Hence the dense means the wavelength channel is very narrow and also very close to each other. 

Dense wavelength division multiplexing(DWDM) is technology put data from different sources together in an optical fiber, which uses single-mode fiber to carry multiple light waves of different frequencies.

For 100 GHz dense WDM, the interval between the adjacent channel is only 100 GHz, for example, the adjacent channels could be 1533.33 nm, 1533,12 nm, 1531.90 nm.

DWDM is widely used for the 1550 nm band so as to help the capabilities of EDFA full form. EDFA as are commonly used for the 1525 nm - 1565 nm.

Dense wavelength division multiplexing is an important innovation in optical network and provides many benefits of DWDM. It can be used various applications like  utilize the existing thin fiber and building or expanding a network

DWDM system structure :

DWDM system consists of transmitter, receiver, Multiplexer, optical amplifier (EDFA), demultiplexer. The figure shows a typical application of a DWDM system

Transmitter: Laser that transmits data with a very accurate wavelength each laser is configured to transmit in a certain wavelength.

Receiver: Component that receives the signal and transmits them into a de-multiplexer.

DWDM system

EDFA: Erbium-doped fiber amplifier. Optical repeater device that amplifies the optical signal, It is a silica-based optical fiber that doped with erbium that boosts the power of the wavelength.

Add and drop: Component that receives a fiber optic with some wavelength multiplexed, and can drop or add a certain lambda from the signal.

DWDM multiplexers: Receive many optical signals, each one is a different wavelength, and transmit the entire wavelength in one optic fiber.

DWDM de-multiplexer: Receive all the signal in one optic fiber, and transmit each wavelength in a different fiber.

DWDM applications:

• It can be used for signal transmission
• It is ready to make for long distance, Telecommunication operator that use either point to point or ring topology 
• Utilize the existing thin fiber
• Building or expanding network
• The transparency of the DWDM system to  various bit-rate and protocols
• Network wholesalers can lease capacity rather than entire fiber cable

Full form of DWDM

What is the full form of DWDM?

Answer :

• Dense Wavelength Division Multiplexing

What does DWDM?

DWDM stand for dense wavelength division multiplexing. Hence dense means the wavelength channel is very narrow and close to each other.

Dense wavelength division multiplexing is technology put data from different sources together in an optical fiber, which uses single-mode fiber to carry multiple light waves of different frequencies.

Dense wavelength division multiplexing is a data transmission technology having large capacity and efficiency.

A better is a solution is to use dense wavelength division multiplexing, which effectively increases the useable bandwidth in a system without electronic repeaters.

What is WDM

In this method, the scheme of combining a number of wavelength over a single fiber called wavelength division multiplexing. In this techniques fiber optic transmission using multiple light wavelength to send the data over the same medium or device. In fiber optic, two or more wavelength (colors) of light can travel on one fiber and several signals can be transmitted in optical waveguide at differing wavelengths. 

So the combining a number of wavelengths over a single fiber called WDM full form is wavelength division multiplexing.

In WDM each input generated by a separate optical source with a unique wavelength. An optical multiplexer couples light from individual sources to the transmitting fiber shown in the figure. 

At the receiving station, an optical demultiplexer is required to separate the different carriers before photodetection of the individual signal.

WDM scheme

To prevent spurious signal to enter into receiving channel, the demultiplexer must have a narrow spectral operation with sharp wavelength cut-offs. The acceptable limit of cross talk is -30 dB. 

Features of WDM :

The following features of WDM are given below:

• Capacity upgrade for the system - Each wavelength support independent data rate in Gbps.
• Wavelength routing for the device - Link capacity and flexibility can be increased by using multiple wavelengths.
• Transparency of the system - WDM can carry fast asynchronous, slow synchronous, synchronous analog and digital data.
• Wavelength switching for the system - WDM can add or drop multiplexer, cross-connects and wavelength converters.

WDM has wide application in the communication system because of this useful feature details we show above. Other method called DWDM, it's different from WDM. The main difference between WDM and DWDM is DWDM has a greater overall capacity so DWDM spaces the wavelength more closely than WDM.

Application of WDM :

• SONET network
• Dense WDM allows to muxed and de-muxed numbers of channel closer to one another to achieve greater efficiency
• FDM to an optical fiber
• Optical transport network
• Local exchange network

WDM driver:

WDM driver is classified into three types :

• Bus driver
• Function driver
• Filter driver

Function driver :

• A function driver is a specific individual device, such as a printer.

Bus driver :

• Bus driver uses individual buses like PCI, SCSI, and USB, adapter or bridges. It is reported to the child device that is connected to the bus.

Filter driver :

•  It is I/O request for a device, which is a class of device or bus device.

Full form of WDM

What is full form of  WDM  ?

Answer :

• Wavelength division multiplexing

The scheme of combining a number of wavelength over a single fiber called wavelength division multiplexing. In this techniques fiber optic transmission using multiple light wavelength to send the data over the same medium or device. In fiber optic, two or more wavelength (colors) of light can travel on one fiber and several signal can be transmitted in optical wave guide at differing wavelengths. 

Features of Bluetooth

Bluetooth technology is an open standard that provides an ad-hoc way for connecting devices in the 10 m range. Bluetooth in the 2.4 GHz band and uses a frequency hopping TDD method for each radio channel. Now let us check it out features of Bluetooth to know more details about Bluetooth. 

• Better IOT
• Quick data transfer
• Better audio quality
• Easy transport 
• Greater flexibility
• Available everywhere
• Up to eight devices can be a network in the piconet
• The device does not need to be a point at each other, as a signal is OMNI directional 
• Increases numbers of advertising packets
• Provide location-based services
• Government  worldwide regular it, so it is possible to utilize the same standards wherever one travel
• Sending the information between the two devices which are close to each other

Bluetooth architecture

Bluetooth architecture defines two types of structure :

1. Piconet
2. Scatternet

1. Piconet 

• Eight devices are connected in a Bluetooth network called as a piconet, so the piconet has up to eight active nodes 
• One of them acts as a master and others act as slaves.
• In piconet communication between the primary and secondary can be one to one or one to many forms. 
• All communication is done between master and slave. slave-slave or master-master communication is not possible

2. Scatternet

• A scatternet is formed when two more piconets connect through a bridge node. 
• It is combining various piconet.
• In scattered addition to be seven active slaves, there can be up to 255 parked nodes in the net that can only respond to a beacon signal from the master.
• The slaves are also dumb devices that do the task that the master tells them to do.
• Mater controlling the clock and it is determining in which slave gets to communicate in which time slot.
• All the communication is between the master and slave and but not between the slaves.

Bluetooth architecture

Bluetooth frame structure

Access code: It identifies the master so that slaves within the radio range of two masters can tell which is traffic for them. It is a 72-bit field, that contains synchronization bits.

Header: The 54-bit header contains an 18-bit header that is repeated 3 times for a total of 54 bits. It allows the receiver to remind all three copies of each beat and reject the ones that do not have a majority.

Address field: The address field in the header identifies which of the eight devices the frame is intended for.

Types field: Types field identifies whether it is an ACL, SCO, pull or null frame types, the types of error correction used in the data field and how many slots long the frame is

Flow bit: It is used for primitive types of flow control and is asserted by the slave when its buffer is full and cannot receive any more data.

ACK bit: ACK bit is used to piggyback an acknowledgment onto a frame

Sequence bit: It is used to number the frame to detect re-transmission in a stop and wait for a protocol. It is followed by an 8-bit checksum.

Bluetooth frame structure

Application of Bluetooth

Bluetooth system is an open standard that provides an ad-hoc way for connecting devices in the 10 m range. Bluetooth in the 2.4 GHz band and uses a frequency hopping TDD method for each radio channel. Let us now check it out the application of Bluetooth to know more details about Bluetooth. 

• Medical requirement
• Vending machines
• Office requirement, faxes, PCs, laptops, handset, pager, etc
• Bluetooth car kit
• Vending machines
  DVD player cameras refrigerators
• In the parking and vehicle communication system
• Microwave ovens
• Electronic payment system
• Banking and other electronic systems
• Headsets and pagers
• Office and conference rooms with wireless devices

Zigbee topology

Zigbee is network technology. Here this article gives information about Zigbee topology to know more details about it. 

1. Star topology :

A star network has a central node, which is linked to all other nodes in the networks. All messages travel via the central node.

The star topology consists of a coordinator and several end devices as shown in the figure. In this topology, the end device communicates only with the coordinator. So any packet exchange between end devices must go through the ZigBee coordinator.

The advantages of the star topology are that it is simple and packet go through at most two hopes to reach their destination.

2. Tree topology :

A tree network has a top node with a branch like structure as shown in the figure. To reach its destination, a message travels up the tree and then down the tree.

As shown in the figure, the network terminal consists of a central node, which is a coordinator, several routers and end device.

So in this topology, the task of the router is to extend the coverage of the network. The end nodes connected to the routers or the coordinator are referred to as children. Only the coordinator and the routers can have children like that.

The coordinator and the routers can have children. Hence only they can be parents. A special case of tree topology is called as cluster tree topology. In it, a parent with its children is called a cluster, as shown in the figure.

One of disadvantages of tree topology is that if two nodes are located close to each other, they can not directly communicate.

3. Mesh topology :

A mesh topology look like a tree structure, in which some leaves are directly linked. Message can travel across the tree, when a suitable route is available.

It is also called peer to peer topology. It consist of one coordinator several routers , and end device as shown n figure. 

Following characteristics of a mesh topology

• Dead zone eliminated in this topology
• In this topology the device can be placed close to each other so that they use less power
• Adding or removing a device is very easy in this topology
• Any source device can communicate with any destination in the network
• It uses a more complex routing protocol in comparison to the star topology

Zigbee topology