Wireless technology

It's another brand new week!!!!

A new day brings new hope. So live the day to the fullest and hope to God that there's another day awaiting you. J

The topic for today was wireless technology. In this context, Dr Dayang taught us what is  the real definition for bluetooth.

Bluetooth

Bluetooth has becomes a part of our life now. However, all of you may wonder how exactly it works….So, here you go…. XD

How bluetooth work:

It utilizes a radio based, that means it does not require a line of sight connection in order to communicate.

2 bluetooth equipped devices simply have to come within 10 meter range of each other.

A device must request a connection either to accept or reject.

Concept:

Point to point and point to multiple connection with small network called piconets.

Each piconets hold up 8 active units.

When multiple network exist within the same room they become known as scatternet.

 To resist interference bluetooth employs spread-spectrum technique called frequency hoping.

Frequency hoping means several devices will be ON the same frequency at the same time.

Bluetooth and the future

The future of Bluetooth looks strong, with initiatives underway for higher throughput, more ubiquitous usage and links with Wifi and Ultra Wideband (UWB) broadcast technology.

Operating systems such as the Mac OS and Windows continue to have native support for Bluetooth.

The Bluetooth SIG partners are working on enabling Bluetooth information points, to enable advertising models based around users pulling information from ‘information points’, rather than having to ‘push’ information out.

Other emerging features include Bluetooth in cars; automatic configuration of piconets; and quality of service (QoS) improvements, for example enabling audio and video data to be transmitted at a higher quality.

Broadband

The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device (and the broader the band, the greater the capacity for traffic).

How is broadband different from dial-up service?

·         Broadband service provides higher-speed of data transmission. It allows more content to be carried through the transmission “pipeline.”

·         Broadband provides access to the highest quality Internet services—streaming media, VoIP (Internet phone), gaming, and interactive services. Many of these current and newly-developing services require the transfer of large amounts of data that may not be technically feasible with dial-up service. Therefore, broadband service may be increasingly necessary to access the full range of services and opportunities that the Internet can offer.

·         Broadband is always on. It does not block phone lines and there is no need to reconnect to network after logging off.

·         Less delay in transmission of content when using broadband.

Infrared

Infrared is a energy radiation with a frequency below our eyes sensitivity, so we cannot see it. Even that we cannot "see" sound frequencies, we know that it exist, we can listen them.

Infra-Red is interesting, because it is easily generated and doesn't suffer electromagnetic interference, so it is nicely used to communication and control, but it is not perfect, some other light emissions could contains infrared as well, and that can interfere in this communication. The sun is an example, since it emits a wide spectrum or radiation.

Infrared keyboard

The adventure of using lots of infra-red in TV/VCR remote controls and other applications, brought infra-red diodes (emitter and receivers) at very low cost at the market.

From now on you should think as infrared as just a "red" light.

This light can means something to the receiver, the "on or off" radiation can transmit different meanings.

Lots of things can generate infrared, anything that radiate heat do it, including out body, lamps, stove, oven, friction your hands together, even the hot water at the faucet. 

To allow a good communication using infra-red, and avoid those "fake" signals, it is imperative to use a "key" that can tell the receiver what is the real data transmitted and what is fake.  As an analogy, looking eye naked to the night sky you can see hundreds of stars, but you can spot easily a far away airplane just by its flashing strobe light.  That strobe light is the "key", the "coding" element that alerts us.

Before the end of our class, our classmates showed us how to use forum and chatting corner. They had provide us a lot of info about MSN,SKYPE and Yahoo Messenger. Thanks for their efforts!!! I had learnt a lot…..XD

MSN Messenger

Here's a video regarding the usage of infrared telescope to uncover hidden cosmic creatures, including the coolest stars, dark asteroids and the most luminous galaxies!!!

Unbounded /Unguided Media or Wireless Technology

The topic for this week’s lesson is unbounded /unguided media or as called as wireless technology. Unbounded / Unguided media or wireless media doesn't use any physical connectors between the two devices communicating. Usually the transmission is send through the atmosphere but sometimes it can be just across the rule. Wireless media is used when a physical obstruction or distance blocks are used with normal cable media.

TERRESTRIAL MICROWAVE

Terrestrial Micro waves are used are used to transmit wireless signals across a few miles. Terrestrial system requires that direct parabolic antennas can be pointed to each other. These systems operate in a low Giga Hertz range.

CHARACTERISTICS of terrestrial microwaves:

1)       Moderate to high cost.

2)       Moderately difficult installation

3)       1 M bps to 10 M bps capacity

4)       Variable attenuation

5)       Low immunity to EMI

6)       The taller the antenna, the longer the sight distance

There are 2 types of antenna:

ü  Parabolic dish

ü  Horn

PARABOLIC DISH

A parabolic dish is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves.  

The main advantage of a parabolic dish is that it is highly directive; it functions similarly to a searchlight or flashlight reflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only. Parabolic dish has some of the highest gains, that is they can produce the narrowest beam width angles, of any antenna type.

Parabolic Dish

HORN

A horn antenna is used for the transmission and reception of microwave signals. It derives its name from the characteristic flared appearance. The flared portion can be square, rectangular, or conical. The maximum radiation and response corresponds with the axis of the horn. In this respect, the antenna resembles an acoustic horn. It is usually fed with a wave guide.

Horn

In order to function properly, a horn antenna must be a certain minimum size relative to the wavelength of the incoming or outgoing electromagnetic field. If the horn is too small or the wavelength is too large (the frequency is too low), the antenna will not work efficiently.

SATELLITE

Satellite owns a similar principle as terrestrial microwave where it acts as a super tall antenna and repeater.

In general, a satellite is anything that orbits something else, as, for example, the moon orbits the earth. In a communications context, a satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth. There are hundreds of satellites currently in operation. They are used for such diverse purposes as weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global Positioning System, (GPS).

Transmission from earth to satellite----uplink

Transmission from satellite to earth---downlink

Satllite

RADIO FREQUENCY

How Does it Work	Radio frequency use electrical oscillation to transmit its signal. When an RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space.
Equipment	In order to receive radio signals an antenna must be used.
Distance covered	Different forms of electromagnetic energy are categorized by their wavelengths and frequencies. The RF part of the electromagnetic spectrum is generally defined as that part of the spectrum where electromagnetic waves have frequencies in the range of about 3 kilohertz (3 kHz) to 300 gigahertz (300 GHz).

Different Types of Radio Frequency

CELLULAR PHONE

How Does it Work	Make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile phone operator, allowing access to the public telephone network. By contrast, a cordless telephone is used only within the short range of a single, private base station.
Equipment	Cellular phone
Distance covered	As the cellular telephone user moves from one cell or area of coverage to another, the telephone is effectively passed on to the local cell transmitter.

Cellular Phone

WIFI

How Does it Work	Wifi allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet connections. The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards.
Equipment	A device that can use Wi-Fi (such as a personal computer, video game console, smartphone, tablet, or digital audio player) can connect to a network resource such as the Internet via a wireless network access point.
Distance covered	Access point (or hotspot) has a range of about 20 meters (65 feet) indoors and a greater range outdoors. Hotspot coverage can comprise an area as small as a single room with walls that block radio waves or as large as many square miles

I would like to share a video with you all. It is an interesting video regarding to the difference between 3G and 4G… J

CABLING

How time flies.....it’s coming to our 5th lecture class for telecommunication &networking .....

Yes, time is cruel, it doesn't wait for anyone. Can you believe that we 
had already go through almost 1 semester?? Can you believe that we 
had gone through the first quarter of 2012 already?

All assignments and homework suddenly say 'HI' to me and this had made me feel exhausted......T^T

I wish I can make the clock stop ticking right now.....>.<

So, I think it is the time for me to study hard since final exam is just around the corner…..

Ok, back to the topic…the topic for 5^th lecture class was CABLING…^^

Cabling sounds interesting for me..... o(^.^)o

First, you all may wonder what is the correct definition for cable……

Well, cable is the medium through which information usually moves

from one network device to another .

Several types of cable are commonly used with LANs.

In some cases, a network will utilize only one type of cable, while other networks will use a variety of cable types.

There are 4 types of cables:

1) Unshielded Twisted Pair (UTP) Cable

2) Shielded Twisted Pair (STP) Cable

3) Coaxial Cable

4) Fiber Optic Cable

Unshielded Twisted Pair (UTP) Cable

The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices.

The standard connector for unshielded twisted pair cabling is an RJ-45 connector. (RJ means registered jack)

A disadvantage of UTP is that it may be susceptible to radio and electrical frequency interference.

UTP Cable

Shielded Twisted Pair (STP) Cable

STP is a type of cable consists of two individual wires wrapped in a foil

shielding to help provide a more reliable data communication.

Hence, it is suitable for environments with electrical interference.

The disadvantage is the extra shielding can make

the cables quite bulky.

STP is often used on networks using Token Ring topology.

Coaxial Cable

Coaxial cabling has a single copper conductor at its center.

A plastic layer provides insulation between the center conductor and a

braided metal shield.

The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.

Fiber Optic Cable

Consists of a center glass core surrounded by several layers of protective materials

It transmits light rather than electronic signals eliminating the problem of

electrical interference.

It is ideal for certain environments that contain a large amount of electrical interference..

Fibre optic cable is superior than others since it is able to transmit signals over much longer distances than coaxial and twisted pair.

Fiber Optic Cable

Now, I am going to share a video so that all of you will be able to get a clearer image about fiber optics. 

Summary for Ethernet Cabling:

10 Base T: Unshielded Twisted Pair  :  100 meters

10 Base 2: Thin Coaxial  :  185 meters

10 Base 5: Thick Coaxial  :  500 meters

10 Base F: Fiber Optic  :  2000 meters

Cable and Topology:
Linear Bus : Coax, twisted pair, Fiber : Ethernet, Local Talk
Star : Twisted pair, Fier : Ethernet, Local talk
Star-Wired Ring : Twisted pair : Token Ring
Tree : Coax, Twisted Pair, Fiber ; Ethernet

That's all for this week's lecture.....see ya.....^^

Topology, Protocol, Architecture and ATM

HOORAY!!
It's coming to our 4th lesson for telecommunication &networking.
We are going to learn topology, protocol and architecture for this week's lesson.
At the beginning of the lesson, Dr Dayang showed us the definition of topology.


TOPOLOGY


Topology is the study of the arrangement or mapping of the elements such as links and nodes of a network.
Physical topology -The physical layout of devices on a network.It can also be defined as the way that the     devices on a network are arranged and how they communicate with each other

There are 6 types of physical topology:

1)Linear bus

2)Ring 

3)Star

4)Star-wired ring

5)Tree

6)Mesh

Linear bus topology

A linear bus topology consists of a main run of cable with a terminator at each end. All nodes are connected to the linear cable.

Ring topology

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either “clockwise” or “counterclockwise”). A failure in any cable or device breaks the loop and can take down the entire network.

Star topology

A star topology is designed with each node connected directly to a central network hub or concentrator.

Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer’s network access and not the entire LAN. 

Star wired topology

In the star-wired ring physical topology, the hubs are "intelligent." If the physical ring is somehow broken, each hub is able to close the physical circuit at any point in its internal ring, so that the ring is restored.

Tree topology

A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Mesh Topology

Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination.

PROTOCOL

Protocol is a set of rules that governs the communications between computers on a network.

Logical topology are bound to network protocols and describe how data is moved across the network.

Examples of protocol:

1. Ethernet

2. LocalTalk

3.Token Ring

4. FDDI


ETHERNET


Is a common logical bus topology protocol.
Early Ethernet network were half duplex, uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection), a system where each computer listens to the cable before sending anything through the network to avoid collisions.


LOCAL TALK

Is a network protocol that was developed Macintosh computers.

Used a method called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance), where a computer signals its intent to transmit before it actually does so.

The disadvantage of local talk is its slow speed (only 230 Kbps).

TOKEN RING

Its access method involves token-passing.

The computers are connected so that the signal travels around the network from one computer to another in a logical ring. 

FDDI

Fiber Distributed Data Interface is a network protocol that is used primarily to interconnect two or more local area networks, often over large distances.

A major advantage of FDDI is speed. It operates over fiber optic cable at 100 Mbps.

ARCHITECTURE

Network architectures are sometimes classified into two broad categories:

1）Peer to peer architecture 

2）Client server architecture

Peer to Peer architecture
In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network.

Client server architecture

Client server architecture allows the network to centralize functions

and applications in one or more dedicated file servers. The file servers become the heart of the

system, providing access to resources and providing security.

ATM (ASYNCHRONOUS TRANSFER MODE)

ATM is a network technology based on transferring data in cells or packets of a fixed size. The cell used with ATM is relatively small compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line.