Engineer's Pride : October 2013

Thursday 31 October 2013

POWER LINE COMMUNICATION

It is the most advanced and emerging technology today.
What is it??? It is nothing but sending data and electric power in the same line that is used for power line.
The data are internet communication, telephone communication, etc.
We know that the above mentioned communication takes conductor as medium to travel.
Here that property is used for sending simultaneously AC electric power and data.
Mostly they are used within a building for example home automation.
Typically transformer prevents the propagation of signal, so it requires multiple technologies to form very large networks.
Data rates and distances limits vary widely over many power line communication standards
Low frequency impressed on high voltages, high data rate only used for short distance.

ADVANTAGE:

It reduces the cost of communication.
No need of building any external setup we can use already existing features.

USES:

It enable in vehicle network communication of data voice, music & video signal by digital mean over direct current from battery.

Wednesday 30 October 2013

Flying Robot

Here is the robot that can fly.
Wondered by reading it...??? Keep reading...
It just identifies the barrier in its way then it changes its orientation of flying.
It can display an image of the building in which it present.
It can be used for many rescue process.
It can also be used in military applications.
Also it is widely used in many other applications.
You can get more information about this flying robot by the following link... (Don’t ignore it)

http://www.youtube.com/watch?v=4ErEBkj_3PY

Thursday 24 October 2013

Li-Fi

LI-FI

Chinese scientist introduce a new thing Li-Fi instead of Wi-Fi
It is nothing but Wi-Fi connectivity through light bulb.
A Micro chipped bulb can produce data speed of up to 150Mbps.
If we use this technique, only one watt led bulb would be enough to provide net connectivity to 4 computers.
It is also known as visible light communication (VLC).
Li-Fi promises to be cheaper and more energy efficient than existing wireless radio system ubiquity of LED bulbs.
Visible light is a part of EM spectrum & 10,000 times bigger than radio spectrum affording potentially unlimited capacity.

HOW IT IS USED FOR INTERNET CONNECTION?

Data from the internet and the local network is used to modulate the intensity of the LED light source in a way undetectable to the human eye.
The photo detector picks up the signal, which is converted back into a data stream and sent to the client.
The client can communicate through its own LED output or over the existing network.

ADVANTAGE:

It can be used under the sea using conduction property of salt water.
It can be used in planes because it won’t interfere with radio waves.
The data is blocked by walls so there is no chance of external data leakage.

DISADVANTAGE:

If light is blocked then the signal transmission is also blocked.
It can also be taken as advantage in security purposes.

Sunday 20 October 2013

GPS

GPS - Global Positioning System.

GPS is a space based satellite system that provides the information about exact position on the Earth, anywhere and anytime in all weather conditions.
It is maintained by the US government and is freely accessible by anyone having a GPS receiver.
GPS was developed by the Department of Defense (DoD) and it consists of 24 satellites.

BASIC CONCEPT:

A GPS receiver calculates its position by timing the signals sent by the GPS satellites above the Earth. Each satellite message contains

Time of the transmitted message
Satellite position at the time of message transmission.

Using this message, the receiver determines the transit time of each message and computes the distance of each satellite in the speed of light.
From this information, the location of the receiver was determined.
Then the location is displayed using a moving map display or latitude and longitude.
Elevation, altitude, direction and speed information may also be included.

STRUCTURE:

GPS consists of 3 segments:

Space segment
Control segment
User segment

SPACE SEGMENT:

Space segment composed of orbiting GPS satellite or Space Vehicles (SVs) which is 24 in number having six orbital planes with 4 satellites each.
The orbital planes are inclined at 55°. Orbital period is one half a sidereal days i.e., 11 hours & 58 minutes.
Hence each SV makes 2 complete orbits each sidereal day.
There are about 32 satellites in GPS constellation by Dec 2012.
The additional satellites are used to improve the accuracy of the GPS receiver.

CONTROL SEGMENT:

The control segment is composed of

a master control station (MCS),
an alternate master control station,
four dedicated ground antennas and
Six dedicated monitor stations.

GPS control segment consists of monitor stations located around the world.
The monitor station receives the signal from the SV and computes the orbital data and clock correction for each satellite sends it to SVs within a nano seconds.

USER SEGMENT:

User segment composed of receiver that are now available in variety of formats which can be integrated into cars, phones, watches, etc.
It consists of an antenna that can be tuned to the transmitting frequency of satellite, receiver processor and highly stable clock.
It consists of displays for giving speed and location information to the user.
Receiver is usually described by its number of channels which indicates the number of satellites that it can monitor simultaneously.

APPLICATIONS:

Civilian:
Many civilian applications use one or more GPS components.
Some of the civil applications are astronomy, automated vehicle, cartography, cellular telephony, clock synchronization, disaster relief, GPS for mining, navigation, Robotics, Surveying, Tectonics, Telematics, etc.
Military:
It is used for navigation, Target tracking, Missile & Projectile guidance, Search & Rescue, Reconnaissance.

Thursday 17 October 2013

WIRELESS TECHNOLOGY

From the word Wireless we can understand, this communication doesn't require any wire.
Electromagnetic waves are used to carry the information from one point to other in this communication.

What is the need for Wireless Communication?

For communicating with people from one end to other end of the world we need wired connection.
But the cost for connecting entire world by cables will be high. Also it is impossible.
If there causes any damage in the wire we cannot identify the place of the fault.
Due such a kind of problems we go for wireless communication which is of low cost.

Advantages of Wireless communication:

Flexibility: Flexibility is one of the biggest advantages.
Ease of use: wireless networks are easy to setup and handle.
Place devices: These devices won't occupy much place as that of wired devices.
Durability: It has long lasting capability.
Prices: The prices of wireless networks are very low.

Various wireless communications:
Read the following posts to know more about wireless communication:

Wi-Fi - http://digitalnativeengg.blogspot.in/2013/06/wifi.html
GSM - http://digitalnativeengg.blogspot.in/2013/10/gsm.html
GPRS - http://digitalnativeengg.blogspot.in/2013/10/gprs.html
IR - http://digitalnativeengg.blogspot.in/2013/10/ir-communication.html
RF - http://digitalnativeengg.blogspot.in/2013/10/rf-communication.html
Bluetooth - http://digitalnativeengg.blogspot.in/2013/06/bluetooth.html

Zigbee - http://digitalnativeengg.blogspot.in/2013/10/zigbee.html

Wednesday 16 October 2013

IR COMMUNICATION

IR-Infrared Communication. It uses infrared light to transfer data.
Infrared light is a wavelength of energy that is invisible to the human eye.
It is a point-to-point communication i.e. it has line of sight.
The most popular application of IR is the TV Remote Control.

Why it is called Infrared?

IR is a part of the electromagnetic spectrum.
Infrared waves lie between microwaves and visible light waves in the electromagnetic spectrum.
The prefix infra means "below", the infrared means "below red". This indicates its position in the electromagnetic spectrum.

Won’t the IR Rays affect human?

Yes probably the IR rays affect the humans if it is used in higher wavelength.
But most of the electronic devices make use of IR at lower wavelength or near infrared wavelength.
So it won't affect the human.

Advantages of using Infrared Communication:

SECURITY: Infrared communication has high directionality and can identify the person whom you are communicating with.
COMMUNICATION SPEED: Infrared communication has a maximum speed of about 1Gbps.

Tuesday 15 October 2013

GPRS

GPRS stands for General Packet Radio Service.
GPRS is a mobile data service that provides e-mail and Internet access for 2G and 3G mobiles.
It is also called as 2.5G technology, that is, a technology between 2G and 3G.
GPRS is usually charged based on amount of data transferred whereas circuit-switched data is billed per min of connection time.
GPRS is a best service that has variable throughput and latency that depends on number of users sharing the service at the same time.

CHARACTERISTICS:

Data rate - 115kbps
Speed - 40 to 50kbps
Latency is very high.
Roundtrip time - 600 to 700ms and often 1s is achieved.

SERVICES OFFERED:

GPRS offers services like SMS, MMS, P2P service, P2M service, Push to Talk, Instant Messaging, etc..
In GPRS, an SMS transmission speed of about 30 SMS per minute can be achieved and it is fast enough technology for MMS and browsing.

PROTOCOLS SUPPORTED:

Internet Protocol (IP) - It is built in mobile browsers and it uses IPv4.
Point to point protocol (PPP) – It is not supported by mobile phones but it is used to provide IP to the phone when it is used as modem to the computer.

HARDWARE SUPPORTED:

CLASS A – It can be connected to GPRS and GSM service using both at a time.
CLASS B – It can be connected to GPRS and GSM service using only one at a time. Most of the GPRS mobile services are Class B.
CLASS C – It can be connected to either GPRS or GSM service.

ACCESSING METHOD:

Multiple Access method used in GSM with GPRS is based on Frequency Division Duplex(FDD) and Time Division Multiple Access(TDMA).
Hence it is possible that the several users can share the same frequency channel.

Monday 14 October 2013

RF COMMUNICATION

What is RF Communication?

RF -Radio Frequency communication. It is a wireless communication.
It makes use of Electromagnetic waves that is available in the free space for its communication.
The biggest advantage of RF communication is that it does not have Line of Sight. (No need of Transmitter and Receiver to be in straight line)
Like all other communication it also has source, medium and destination.
The Radio Transmitter is the source, Radio Receiver is the destination and the Free Space is the medium through which the electromagnetic wave travels.
In free space, there is more probability of message signal to get mixed with noise.
In order to avoid the mixing up of noise the message signal is modulated with a carrier signal in the transmitter end.
Again in the receiver end the reverse process takes place i.e. the original message signal is recovered by demodulation.

MODULATION:

The message signal is normally low frequency signal it cannot travel longer distance also have high chance of mixing up with noise.
To make the message signal travel longer distance without interruption it is modulated with high frequency signal called carrier signal.
The process of changing the characteristics of carrier signal with respect to the message signal is called modulation.
It is done in the transmitter.

DEMODULATION:

The process of recovering the message signal from the modulated signal is called demodulation.
It is done in the receiver.

TYPES OF MODULATION:

Amplitude Modulation: The process of changing the amplitude of the carrier signal with respect to the amplitude of the message signal is called Amplitude Modulation.
Frequency Modulation: The process of changing the frequency of the carrier signal with respect to the frequency of the message signal is called Frequency Modulation.
Phase Modulation: The process of changing the phase of the carrier signal with respect to the phase of the message signal is called Phase Modulation.

Radio Transmitter:

Before transmitting data it is encoded for safety transmission by encoder.
The transmitter contains modulator, amplifier and antenna.
The message that has to be transmitted is modulated and transmitted by means of the antenna.
The modulated signal is amplified to make it travel for long distance.

Radio Receiver:

The receiver contains antenna, amplifier and demodulator.
The transmitted signal is received by the antenna.
Even though the message signal is amplified and then transmitted the signal received in the receiver side is very low hence it is amplified once again.
The amplified signal is demodulated by the demodulator.
The encoded data is decoded here in the decoder unit.
NOTE: The modulator and demodulator should have same carrier for getting correct message signal.

Sunday 13 October 2013

ZIGBEE

Zigbee is a wireless technology used for communication.
It is a low cost and low power consumption technology.
It is developed to meet the low power requirements of the devices.
The zigbee standard is regulated by a group known as the ZigBee Alliance.
Zigbee operates on IEEE 802.15.4 specification, which is the standard for wireless protocol.
    -IEEE stands for Institute of Electrical and Electronics Engineers
    -802 groups denote the section of the IEEE involved in network operations and technologies.
    -15 groups denote wireless networking technologies.
Zigbee and Bluetooth are nearly same technology. Bluetooth connects large packet user devices whereas Zigbee connects small packet devices.
The data rate of Zigbee is 250 Kbps and operates on the 2.4 GHz ISM band, which is available throughout most of the world.
The maximum range of operation for ZigBee devices are 250 feet i.e., 76 m.
Due to low power consumption Zigbee devices withstand for long period of time.

LAYERS IN ZIGBEE:

The layers in Zigbee are
    1. Physical Layer
    2. MAC Layer
    3. Network Layer

1. Physical Layer

The Physical Layer satisfies the need of low cost.
It uses DSSS (Direct Sequence Spread Spectrum) modulation scheme.
Because of this modulation the circuits used will also be simple thus reduces the cost.

FREQUENCY BANDS AVAILABLE FOR ZIGBEE:

The Zigbee has three frequency bands for its operation.
    -868.3 MHz for Europe, it has one channel at 868.3 MHz and data rate of 20 kb/s
    -915 MHz for North American, it has 10 channels between 902.0 and 928.0 MHz and data of 20 kb/s
    -2.400 GHz for world wide application, it has 16 channels between 2.4 and 2.4835 GHz and data rate of 250 kb/s

The transmitter in 868 and 915MHz bands uses BPSK, whereas the transmitter in 2.450 GHz band uses offset-QPSK.

2. MAC Layer

The MAC layer in Zigbee controls the accessing channels by means of CSMA-CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism.
MAC Layer initially transmits beacon frames and provides necessary synchronization for a reliable transmission.
It has two modes, Beacon-enabled (slotted) and Non Beacon-enabled mode (unslotted).
In Beacon-enabled mode, periodic data is transmitted to all devices. The device will wake up for that beacon, check for any messages and then go back to sleep.
In Non Beacon-enabled mode, device has to be awake all the time in order to receive new messages.

3. Network Layer

The Network layer in Zigbee tells about addressing mechanisms, security of transmitted frames and relay of frames to their destinations.
Network Layer's security is responsible for authentication, encryption and message integrity.
The way of communication between devices is also included in this network layer.
There are three types of network topologies in Zigbee. They are Star, Cluster Tree and Mesh.
In Star Topology, the nodes have to communicate via the coordinator.
In Cluster Tree Topology, the communication takes place in hierarchical manner. The node that wants to send data should first send it to router, the router will send it to coordinator and then the coordinator will distribute it to corresponding node.
In Mesh Topology, mostly all the nodes are interlinked so any node can communicate with any other. For this advantage only we are mostly using mesh topology.