What is LED

Definition of LED :

Nowadays the light is collected from the edge of the full form of an LED, in order to reduce the losses caused by absorption in the active layer and to make the beam more directional. Such a device is known as an edge emitting LED or LED.

Light emitting diode (LED) is a component 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 system. Essentially LED is a PN junction diode. LED has two types of LED structure called has Heterojunction and double heterojunction diode.

One of the major characteristics of an LED is a different color. Initially, various types of LED colors were restricted only red LEDs were available but after semiconductor processes were improved and new research was undertaken to investigate in direction of new LEDs many different colors were available.

Features of LED : 

• A linear relationship between optical output and current. 
• Spectral width is 25 to 40 nm or lambda equal to around 0.8 - 0.9 µm.
• Modulation bandwidth is much large. 
• Not affected by catastrophic gradation mechanisms hence LEDs are more reliable. 
• Better coupling efficiency than the surface emitter.
• Less temperature was sensitive. 

Usage :

• It is most commonly used for short-range narrow and medium bandwidth links. 
• Long distance analog links.
• Suitable for digital systems up to 140 Mb/sec.

Light source material :

In light source material the spontaneous emission due to carrier recombination is called carrier recombination electroluminescence.

To encourage electroluminescence, so it is necessary to select an appropriate semiconductor material. The semiconductors depending on energy bandgap can be categorized into the following way,

• Direct bandgap semiconductors 
• Indirect bandgap semiconductors. 
• In the direct bandgap semiconductors, the electrons, and holes on either side of band gap have the same value of crystal momentum. Hence, direct recombination is ban possible
• In the direct gap of semiconductors, the maximum and minimum energies occur at different values of crystal momentum. The recombination in these semiconductors is quite slow.
• The active layer semiconductor material must have a direct band gap to shown in the figure. In the direct bandgap semiconductor, electrons and holes recombine directly without need of the third particle to conserve momentum.
• In these materials, the optical radiation is sufficiently too much high. 
• The peak output power is obtained around 810 nm. The width of emission at half power (0.5) is referred to as (full-width half maximum- FWHM) spectral width. For the given LED FWHM is 36 nm.

The fundamental quantum mechanical relationship between gap energy E and the frequency of  v is given as a formula in this form;

 E = hv

 E = hc / ɣ

 ɣ = hc / E

Where energy E is in joules and wavelength is measured in a meter. Expressing the gap energy in electron volts and wavelength in micrometers for this formula.

Types of LEDs according to color:

• Gallium Arsenide (GaAs) - Infrared
• Gallium Arsenide  photo-side (GAAsP) - Red to inferred, orange
• Zine selenide (ZnSe) - Blue
• Aluminium Gallium  Nitride (ALGaN) - Ultraviolet
• Silicon Carbide (SiC) - Blue as a substrate
• Aluminium Gallium Phosphide (AlGaP) - Green
• Gallium Indium Nitride (GalnN) - Near ultraviolet, bluish-green and blue
• Zinc Selenide (ZnSe) - Blue
• Gallium Phosphide (GaP) - Red, yellow, and green 
• Multicolor LEDs

LED can be used in a variety of application like automotive, mobile devices, Backlighting and projection, General illumination etc. This articles also gives information about various types of application in LED to know more details about LED.

1. Automotive :

• Headlights
• Instrument panel
• Infotainment backlighting
• Interior lighting
• RCL
• General lighting
• Camera flashes
• Lighted wallpaper
• traffic signal

2. Mobile devices :

• Display back-lighting
• Mobile phones and display messages
• Camera flash

3. Back-lighting and projection :

• The large format TV display
• Laptop
• Pocket and data projector

4. General illumination :

• Residential
• Industrial
• Medical data display board
• Retail display
• Signs and channel lettering

LED colors

One of the major characteristics of an LED uses a different color. Initially what is full form of LED colors were restricted only red LEDs were available. But after semiconductor processes were improved and new research was undertaken to investigate in direction of new LEDs many different colors were available. 

Different types of LED colors with wavelength given below :

1. Infrared 

Wavelength - > 760

Voltage drop -  < 1.9

Semiconductor material - Gallium arsenide, Aluminium gallium arsenide

2.  Red

Wavelength - 610-760

Voltage drop - 1.6 TO 2.0

Semiconductor material - Galium arsenide phosphide, Aluminium gallium arsenide

3. Violet

Wavelength - 400-450

Voltage drop - 2.8 to 4.0

Semiconductor material - Indium gallium nitride

4. Purple

Wavelength - multi types

Voltage drop - 2.4 to 3.7

Semiconductor material - Blue with red phosphor, White with purple plastic, Dual blue/red LEDs

5. Ultraviolet

Wavelength - <400

Voltage drop - 3.1 to 4.4

Semiconductor material - Diamond, boron nitride, aluminium nitride

6. Pink

Wavelength - Multi types

Voltage drop - 3.3

Semiconductor material - Blue with phosphor, white with pink pigment, yellow with red, orange, or pink phosphor

7. White 

Wavelength - Broad spectrum

Voltage drop - 3.5

Semiconductor material - Silicon. silicon carbide, Zinc selenide

8. Orange 

Wavelength - 590-610

Voltage drop - 2.0 to 2.1

Semiconductor material - Gallium arsenide phosphide, Gallium phosphide

9. Yellow 

Wavelength - 570-590

Voltage drop - 2.1 to 2.2

Semiconductor material - Gallium arsenide phosphide, Gallium phosphide

10. Green

Wavelength - 500-570

Voltage drop - 1.9 to 4.0

Semiconductor material - Aluminium gallium phosphide, Gallium indium phosphide, Indium gallium nitride

Types of LED

There are many LEDs meaning available are not only useful to decorate your home with small glittering LEDs or vehicles to give extra gorgeous look but they are also emerging out as a reliable and eco-friendly light solution in many applications too. One of the major characteristics of an LED is a different color. Initially colors of LED  were restricted only red LEDs were available. Let we check the different types of LED are following below :

Types of LEDs available in market :

• Miniature LEDs
• Application specific LEDs for banner and brand promotions 
• LED strips 
• Directional and Reflector LED lamps 
• Conversion kits & down lights
• LED spots 
• LED candle bulbs 
• LED corn bulbs 
• LED-G bulbs 
• R7S LED lamp 
• LED tubes 
• LED panel lights 
• LED track lights 
• LED flat tubes 
• LED industrial high bay lights 
• LED stage lights 
• LED flood lights 
• LED street lights 

Types of LEDs according to colour :

• Gallium Arsenide (GaAs) - Infrared
• Gallium Arsenide  photo-side (GAAsP) - Red to inferred, orange
• Zinc selenide (ZnSe) - Blue
• Aluminium Gallium  Nitride (ALGaN) - Ultraviolet
• Silicon Carbide (SiC) - Blue as a substrate
• Aluminium Gallium Phosphide (AlGaP) - Green
• Gallium Indium Nitride (GalnN) - Near ultraviolet, bluish-green and blue
• Zinc Selenide (ZnSe) - Blue
• Gallium Phosphide (GaP) - Red, yellow, and green 
• Multicolor LEDs

Types of LED strip light :

• Digital RGB LED strip
• Flexible LED strip
• Waterproof SMD LED strip
• Phillips lines LED light strip
• Philips lines flexible LED strip
• ACE gold LED strip light
• A decorative blue colored self-adhesive LED strip
• Water proof SMD LED strips
• Decorative red colored self-adhesive LED strip
• Multi-color five-meter waterproof flexible LED light strip
• Hit light weather proof green flexible ribbon LED strip light

LED application

Before we learn about LED application first let we check it out a short form of LED. LED can be used in a variety of application like automotive, mobile devices, Backlighting and projection, General illumination etc. This article gives information about various types of application in LED to know more details about LED.

1. Automotive :

• Headlights
• Instrument panel
• Infotainment backlighting
• Interior lighting
• RCL
• General lighting
• Camera flashes
• Lighted wallpaper
• traffic signal

2. Mobile devices :

• Display back-lighting
• Mobile phones and display messages
• Camera flash

3. Back-lighting and projection :

• The large format TV display
• Laptop
• Pocket and data projector

4. General illumination :

• Residential
• Industrial
• Medical data display board
• Retail display
• Signs and channel lettering

WiMAX technology

WiMAX is similar to Wi-Fi technology. both create hot-spots. Wi-Fi can cover several hundred meters while WiMAX covers a range of 40-50 km. It provides a wireless alternative to cable, DSL, and also have broadband access.

WiMAX can be used as a complementary technology to connect 802.11 hotspots to the internet. Mobile-Fi is the mobile version of WiMAX. It is used to provide internet access to mobile users at data rates even higher than available in today broadband links.

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

A Mobile-Fi user can enjoy broadband internet access even while traveling in a moving car or train. WiMAX could potentially be deployed in a variety of spectrum bands like in different range 2.3 GHz, 2.5 GHz, 3.5 GHz, and 5.8 GHz.

A WiMAX architecture consists of two major parts: Main part is to be (i) A WiMAX base station (ii) A WiMAX receiver.

Following Major principles :

• Spectrum is − able to be deployed in both licensed and unlicensed spectra.
• Topology − supports different Radio Access Network topology.
• IP connectivity network − supports a mix of IPv4 and IPv6 network interconnects in application and clients servers.
• Mobility management − It is a possibility to extend the fixed access to broadband multimedia services delivery.
• Interworking − WiMAX support independent RAN architecture to enable seamless integration and interworking with 3GPP2, 3GPP, and  WiFi networks.

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

• WiMAX support multipath.
• WiMAX must be provided 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 a WiMAX system to optimize the throughput based on the when propagation conditions apply.
• Very scalable bandwidth and high-speed data rate.
• WiMAX benefits are that it is 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.
• The most important application of WiMAX technology offered by  is business, Multiplayer interactive gaming, backhaul, consumer connectivity, large area coverage access

WiMAX standard :

These standards were issued by IEEE 802.16 into the subgroup of 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 802.16a as an amendment to IEEE  802.16 defining as a line of sight capability (LOC).

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

WiMAX supported to different frequency band considered as a different range.

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

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

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 256 subscriber, 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 - 256 subscriber, OFDM using QPSK16, QAM, 64 QAM, 256-QAM
• Completion - 2nd half of 2005

WiMAX architecture :

A WiMAX system consists of two major parts: Main part is to be (i) A WiMAX base station (ii) 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 other networks.

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

Each base station provides wireless coverage over an area called a cell. The WiMAX base station also uses a multiple antennas point in a different direction. This area covered by one antenna signal is called a sector.

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

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

A WiMAX receiver : 

A WiMAX receiver 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 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.

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.

                   WiMAX architecture

Application of WiMAX :

• It is a wireless alternative to many existing wired and late miles coverage deployments such as cable modem, digital subscriber line, T and E-carrier system and optical carrier technologies.
• The most important application offered by WiMAX technology is business, Multiplayer interactive gaming, backhaul, consumer connectivity, large area coverage access.
• Using WiMAX technology it can offer broadband wireless access at data rates of multiple Mbit/second to the end user and also within a range of several kilometers. So in this technology, the same radio technology will also offer high-speed data services to all the nomadic terminal like laptops. PDAs, and several other devices. 
• IEEE 802.16 -Fixed users.
• IEEE 802.16e - portable user.
• Backhaul side - Point to point antenna is used to connect base station located across a long distance.
• Last mile side - Residential and business subscriber are connected to the base station using point to multi-point antennas.
• Large area coverage access side - WiMAX also offer broadband connectivity in larger areas.

Wi-Fi and WiMAX offer complementary solutions with Wi-Fi being suitable for short range and WiMAX being suitable for long-range outdoor connection.

Zigbee protocol

Some of the technical details of the Zigbee protocol given below :

• Zigbee offers a wireless range of 70m indoors and 400m outdoor
• Zigbee protocol operates on a single frequency of only 2.4 GHz.
• Low latency and low duty cycle lead to achieving low power consumption giving sensors and the long-lasting battery life
• DSSS helps to the offers data rate for quicker response
• Cater to thousand of devices for spread networks
• It offers network flexibility to cover homes of all size by offering for multiple networks like point-to-point, point-to-multipoint mesh network
• Zigbee can easily integrate monitoring and control of light systems, security system, as well as motion detection

Zigbee protocol operate 802.15.4 physical layer specification and operate even in the unlicensed band including 2.4 GHz, 868 MHz, and 900 MHz 

Different types of layers :

1. Physical layer: This layer consists of modulation and demodulation operation upon transmitting and receiving signal respectively.

2. MAC layer: This layer can be used for synchronizing communication. It is a reliable transmission of data by accessing different network with CSMA.

Different types of a layer in the Zigbee network

3. Network layer: This layer can be used for network set up, such as disconnect network, routing, device configuration, network set up, etc.

4.Application support sub-layer: This layer interface with the network layers for data managing services.

5. Application framework: This layer is responsible for detecting, initiating and binding other devices.

WiMAX frequency

WiMAX could potentially be deployed in a variety of spectrum bands uses like 2.3 GHz, 2.5 GHz, 3.5 GHz, and 5.8 GHz. There are different types of WiMax frequency range listed below:

1. IEEE 802.16d (Fixed WiMAX)

Frequency band - 2-66 GHz

Range - 31 miles

Number of users - 1000

2. IEEE 802.16e (Mobile WiMAX)

Frequency band - 2-11 GHz

Range - 31 miles

Number of users - 1000

3. IEEE 802.11 (WLAN)

Frequency band - 2.4 -5.8 GHz

Range - 100 meters

Number of user - Dozens

4. IEEE 802.11  (Bluetooth)

Frequency band - 2.4 GHz

Range - 10 meters

Number of users - Dozens

Zigbee technology

Zigbee is a wireless protocol used for wireless networking and also have connectivity. Zigbee network is the wireless language that every device used to connect to one another. It is the recently emerged technology of network communication based on the IEEE 802.15.4 standard where IEEE stands for Institute of electrical and also have electronic engineers. Zigbee is a new standard developed by the Zigbee alliance for full form of PAN personal area network, consisting of more than 270 companies and many more. Let us now check it out basic features of Zigbee network to know more details about the Zigbee network.

Feature of Zigbee

• It incorporates power saving mechanisms for all device classes
• Discovery mechanism with full application confirmation
• Pairing mechanism with full application confirmation
• Various transmission option included broadcast
• It uses a small packet compared with other technology WiFi and Bluetooth
• Low data rate
• Low battery consumption
• The maximum range of operation for a Zigbee device is 250 feet
• Easy to implement
• Low cost
• It supports up to 65000 nodes connected in a network
• Support alliance standard or manufacturer specific profiles
• Zigbee uses small packets compared with  other technology WiFi and Bluetooth
• Multiple star topology and interpersonal area network communication
• It supports up to 65000 nodes connected in a network
• Zigbee can automatically establish its network

Zigbee network consists of three different types of devices such as like:

• Router
• Zigbee coordinator and 
• End devices.

At least one ZigBee coordinators are acts as root and bridge of the network. The coordinator is responsible for handling and storing the information while transmitting and receiving operation.

Coordinator and end devices always depend on the Different types of Zigbee topology like star, tree, and mesh.

Zigbee router is internal devices while end devices have limited functionality to communicate with parent nodes. So battery power is saved.

Zigbee architecture consists of various layers where IEEE 802.15.4 is defined as two layers a physical layer and MAC layers.

Zigbee specification has two implementation options or feature sets: 1. Zigbee and 2. Zigbee PRO. Zigbee feature set is designed to support smaller networks with more than hundreds of devices in a single network. Zigbee PRO feature set is the most popular device for the choice of developer and the specification used for most alliance developed standard. This article gives some basic feature of Zigbee networks, advantages and disadvantages and application of Zigbee networks.

Different types of layers :

1. Physical layer: This layer does modulation and demodulation operation upon both side transmitting and receiving signal respectively.

2. MAC layer: This layer can be used for synchronizing communication. It is a reliable transmission of data by accessing different network with CSMA.

Different types of a layer in Zigbee network

3. Network layer: This layer can be used for network set up, such as disconnect network, routing, device configuration, network set up etc.

4. Application support sub-layer: This layer interface with the network layers for data managing services.

5. Application framework: This layer is responsible for detecting, initiating and binding other devices.

Zigbee topology:

There are different types of topology like a star, mesh, tree topology.

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. The end device must be communicated only with the coordinator. So any packet exchange between end devices first must go through the Zigbee coordinator.

The advantages of 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 go 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 total 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 a cluster type tree topology. In it, a parent with its children is called a cluster, as shown in the figure.

One of the 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 looks like a tree structure, in which some leaves are directly linked. A message can travel across the tree when a suitable route is available.

It is also called peer to peer topology. It consists 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 of a device can communicate with any destination in the network
• It uses a more complex routing protocol in comparison to the star topology

                              Zigbee topology

Zigbee is a wireless protocol used for wireless networking and connectivity. Zigbee is the wireless language that every device used to connect to one another. It is the recently emerged technology of network communication based on the used IEEE 802.15.4 standard where IEEE stands for Institute of electrical and also for electronic engineers. Zigbee is a new standard developed by the Zigbee alliance for used personal area network (PAN), Consisting of more than 270 companies. 

Let us now check it out the application of the Zigbee network to know more details about the Zigbee network.

Home automation :

• Heating, lighting
• Cooling, door locking mechanisms
• Home security system
• Smoke detector

Telecom application :

• Used to transmit and receive the message
• Share ring tone, images, and contacts
• Emergency services

Industrial automation :

• Personal tracking
• Livestock tracking
• Record and transmit critical data like pressure, temperature and also a vibration

Security :

• Home security
• Fire detection

Some other applications :

• Health care
• Smart energy
• Remote control for consumer electronics 
• Hotel room access
• Smart metering

Zigbee architecture

Zigbee network consists of three different types of devices following below :

• Router
• Zigbee coordinator and 
• End devices

At least one zigbee coordinators are acts as a root and bridge of the network. The coordinator are responsible for handling and storing the information while transmitting and receiving operation.

Coordinator and end devices always depends on the types of topology like star, tree and mesh.

Zigbee router are internally devices while end devices have limited functionality to communicate with parent nodes. So battery power is saved.

Zigbee architecture consists of various layes where IEEE 802.15.4 is defined as a physical layer and MAC layers.

Different types of layers :

Physical layer : This layer does modulation and demodulation operation up on transmitting and receiving signal respectively.

MAC layer : This layer can be used for synchronizing communication. It is releible transmission of data by accessing different network with CSMA.

Different types of layer in Zigbee network

Network layer : This layer can be used for network set up, such as disconnect network, routing, device configuration, network set up etc.

Application support sub layer : This layer interface with the network layers for data managing services.

Application framework : This layer is responsible for detecting, initiating and binding other device.