IEEE 802.11g

Wi-Fi is abbrevasion from Wireless Fidelity, have a undestanding namely a set of standard that use for local network nircable (Wireless Local Area Network - WLAN) that based on specification IEEE 802.11.

IEEE 802.11g is a standard niscable network that work on frequency 2,45 GHz and used modulation method OFDM. 802.11 that on publication on june 2003 capable achieve apeed until 54 Mb/s on frequence ribbon 2,45 GHz, like same as IEEE 802.11 ordinary IEEE 802.11b.

excess 802.11g have speed spedy maximum, reach signal is good and not easy hampered. whereas shortage from 802.11g is cost more from 802.11b, equipment can interfere signal on frequence that not to controle.

IEEE 802.11g is a standard nircable Network that work on frequence 2,45 GHz and makemodulation method OFDM. Orthogonal frequency-division multiplexing (OFDM) is a frequence-division multiplexing (FDM) that be used for scema multi-carrier digital modulation method.

Orthogonal Frequency Division Multiplexing is new teknology just start achieve LAN nircable (WLAN) market in form device IEEE 802.11g that be operation on 5 GHZ band. OFDM is a "muty-carrier" modulation scema. data be devided on between some of adjacent "subcarriers"
provide from OFDM is :
- can with easy to adapt with condition channel severe without complexs equalization.
- stronger against narrow-band co-channel interference.
- stronger against interference intersymbol (ISI) and fading caised by multipath propagation.
- high spectrum efficience than with conventional modulation scema, spreat spectrum etc.
- low cencitiveto time sincronisation false.
shortage of OFDM is:
- sensitive against shift doppler.
- sensitive against problem sincronisation frequence.
- Peak-to-rata-Power Ratio (PAPR), require emission circuit
linier, that suffer from efisience power that bad.
- almost a lot of from efisiece spectrume that offered by vestigial sideband modulation for example used in ATSC sistem TV digital.

Aplication on Computer Network

Arcitek Network And Layer OSI

On computer network,osi(open systems interconnection) that may to interconnection doing, OSI creative force by ISO on the  year 1984 for arcitect comunication model intercompter. OSI stack in layer form and a layer have self fungtion that have be  connected until one to other one. aim from make a layer is for decrease difficulty in comunication. layer association and  this protocol called for network arciterct. 

A layer having an axcel on layer that are in under and send service on layer in on. protocol on layer from a device will be to  comucation with protocol on the layer that same on other device. 

Phisical Payer

            this layer duty for send data to aim bit by bit. comunication media can  pass through cabel or air. that happen   focus on this layer is processing signal that doing with logic reprecetation, speed transfer, etc.

            are three terminolog in thik to transmition data,  that is :

                        - simplex*

                        - half duplex*

                        - full duplex*

            are two kind signal that can be transmission, thas is:

                        -analog signal*

                        -digital  signal*

component network that do on this layer            is repeater, multiplexer, hub,osiloscop,amplifier. this protocol that use on  t his layer be based on IEEE 802.

 be baset  explaination about it, physical layer have some fungtion, that is:

-  encoding / decoding signal

-  biginning / discharge trigger (for sincronitation)

-  transmotion / receive bit

on time transmition be doing  are three kind interference that may happen, that is :

- attenuation : become weak signal energy in effort reach aim.

- Delay distortion : because are data transmition  that be different speed

- noise : into energy that not be hope on transmission phase besides that origin from transmiter.

Data Link Layer

Data link layer be devide become two sub layer : MAC* and LLC*. both of them be legal separation but running the fungtion  that bedifferent  

Layer Network

network lyer for take package from source and sending to aim. on this layer segment data to be change becomepackage  and may  be have exceed some hop before reach aim. fungtion network layer be defferent with layer data link, taht have aim more simple  that is only to move data from tip cable that one to other.

Transport Layer

connected with isu mainsty quallity, channel reins, and false corected sevice. on this layer a data that will sending to  broken become parts that more little and give header add for known. form from cuts that give header this give name datagram.

Layer On TCP/IP

concept TCP/IP infact use concept that same  with OSI. TCP/IP brief 7 layer PSI become 4 layer. this time TCP/IP concept  more popular, this TCP/IP model be creative force , but want to be design network that holdout in anywhere condition.  inclouded, nucleur war.  

types of transmission media

transmission media is media that can making for send information from one place to other place. In networking, all media that can conected electricity wave or electromagnetic or light can make for sending media, good for sending or receiving data. choice media transmission (sending) for need comunication data depend on many factor, like cost, network perfomance that desired, there is or not that medium.
A. Copper Media
Copper media form all media transmissin data that made from copper material. people usually call with cabel name. Data that sending through cable, form is electricity signals (tension or current)  digital.

Type of cable that making for data transmission on network:

1. Coaxial Cable

This cable often make for antenna TV cable. Also called to BNC cable (byonet Naur Connector). This cable form cable that most
many make to LAN, but have protected to noise that more tall, cheap, and capable/can send data with standa speed.

4 type coaxial cable, namely :
  Thinnet or RG-58 (10Base2)
Thicnet atau RG-8 (10Base5)
RG-59
RG-6

there is 3 connector pada kabel Coaxial, namely T connector (socket) and BNC connector. Profit making the coaxial cable is more cheaper from to fiber optic cable and distance reach enaugh far from type cable UTP/STP that make repeater as stronger/amplifier. shortage hard on time installation, good connector installation although cable.  for this time coaxial cable have been not recomendation again for network installation.

2. Twisted-Pair cable
Twisted Pair be composed from 2 type :

STP cable (Shielded Twisted Pair)

Profit making STP cable is more stand to wave interferece electromagnetic good from within or from outside. shortage is expensive cost, hard in time installation (especially problem grounding), and distanse reach/distance range only 100m.

there is some category for Twisted Pair cable, namely :
- category One (Cat-1).

usually make a heavy conductor AWG standar many/as much as 22 or 24 pin with impedance range that width. making on the telephone connection and not for recomendation for data transmition.

-  category Two (Cat-2).

Impedance range that width, often make on the PBX system and alarm system. Data transmission ISDN making two category cable, with maximum bandwidth 1 MBps.

- category tree (Cat-3).

Often called voice grade cable, use heavy conductor some 22 or 24 pin with impendence 100 ampere and fungtion until 16 MBps. Can make network 10BaseT and token Ring with bandwidth 4 Mbps.

- four category (Cat-4).

like category three with banwidth 20 MBps, to applied on the TOken Ring network with bandwidth 16 Mbps.

- Category five (Cat-5).
Is good Twister pair cable (grade data) with bandwidth 100 Mbps and maxsimum transmission reach 100m.

B.Optical Media

there is three fiber optic cable that usually use namely singgle mode, multy mode and plastic optical fiber that fungtion for light code from end cable to end cable other, from transmitter* receiver, that change electric pulse to light and otherwise, in form light-emitting diode or laser. Fiber cable optic singgle mode form singgle fiber glass with diameter 8.3 to 10 cilometres, have one type transmission that can receive data big capasity with hig speed to far distance, and smaller. Ability cable singgle mode type in deliver transmission is 50 times faster from multimode cable type, but have core that smaller so that can to lost every distortion and pulse light that overlapping.
Fiber optic multimode cable made from fiberglass with diametres bigger, namely 50 to with 100 micrometre that can deliver big capasity data be not acurate. being plastic optical fiber is cable new plastic basis that guarantee perform level that same with fiber glass in sort distance with much cheaper cost. this time, fiber optic have been use for standart cable data in biding physical layer telecomunication or network, like device cable TV, also protecting system  that used Closed Circuit television (CCTV), and etc. materia basic from optical media is glass with that very small size (micron scale). Usually known with fiber optic name (fiber optic). Data that passed on this medium in light form (laser or infrared).

One cfiber optic cable consist of two fiber, one fungtion for Transmit (Tx) and only/one again for Recive(Rx) so that comunication with fiber optic can be doing two way in together (fullduplex).

C.Wireless Network

this time been many to used network without cable (wireless networking),  data transmission use infra red ray or micro wove for delivery a data. although practice heard, problem yet that to deal here is a problem in distance , bandwidth, and cost cheap. yet such for need LAN in the building, this time been expending wireless technology for active hub (wireless acces point) and wireless LAN card (change NIC), until can minus broken in cable transmission data on computer network. wireless acses point can connectet to (up link) whit activehub from network that be on.

transmission media wireless use radio phase hight frequence. usually phase electronic with frequence 2.4 Ghz and 5 Ghz.digital data's that sending to way this wireless will to modulation to in this electronic phase.