DATA COMMUNICATION SYSTEM AND COMPUTER NETWORKS

DATA COMMUNICATION SYSTEM AND COMPUTER NETWORKS


11.1Pendahuluan

current communications technology advances have an influence to the development of data processing. Data sent from one place to another by means of communication.

To use the computer data, sending data using electronic transmission system, usually referred to as data communications (Data Communication).



Data Communications 11.2


To communicate data from one place to another, the three elements of the system must be available, the data source (source), transmission media (transmision media), the recipient (receiver). if one element is missing, the communication will not be done.



11.2.1Tranmisi Data


Data transmission is the process of sending data from one source to the receiver data.

for menetahui of complete data transmission there are several processes that need to be in the know.

these concerns:

- Transmission media are used

- The capacity of transmission channels

- The type of transmission channels

- The code used transmission

- Transmission mode

- Protocol

- Handling of transmission errors



11.2.1.1 Media Transmission

Several media can be used as a transmission channel (path) or carrier transmission of data that can be transmitted to cable or electromagnetic radiation.


KABEL

cable can be used as a data source and the recipient is not too far away and in the local area.


1. Coaxial Cable

Cable Coaxial cable is wrapped with a soft metal.

Coaxial Cable have a data transmission rate higher than the normal cable, but more expensive.




2. Fiber Optic Cable

Fiber Optic Cable is made of glass fibers (optical fibers) are thin in diameter and the diameter of human hair.

Fiber Optic Cable have a data transmission speeds up to 10x greater than the Coaxial Cable.




Electromagnetic Radiation

If the data source and recipient data a long distance, communication channels may be a radiation media. Electromagnetic emitted through the open air, which can be a microwave (microwave), satellite system (satellite system), or laser system (laser system).


1. Microwave

Microwave is a high frequency radio waves emitted from one station to another station. The nature of microwave radiation and is line-of-sight is not obstructed. Because of the buildings are tall, hill-proof or the mountains, the microwave is usually used for distances close to it.


For a far distance, should be used relay station, a distance of 30 to 50 kilometers. Kaerna relay station is required to strengthen the signal received from the previous relay station and continue to the next relay station.


2. Satellite System


Because the microwave should not be blocked, then the distances to far used the satellite system (satellite system). Satellite will receive a signal transmitted from the microwave station on earth and send it back to another earth station. Satellites act as relay stations in space letaknnya.


3. Laser System

Laser communications technology is widely used for research. Communications experts predict the days to come yagn using laser technology will be expanded and will dramatically reduce transmission costs.

And now it is in fact a laser system used, such as wireless.


What is wireless?

Media transmission of electromagnetic radiation is emitted through the open air which can be mikrogelombang (microwave), satellite system (satellite system), infrared light / laser system (laser system)


Benefits of wireless!

1.Pembangunan integrated computer network infrastructure that conditions make it impossible to pull the cable

2.Tepat to users who have high mobility

3.Tepat for users temporary (not permanent)


Wireless LAN technology became very popular today in many application. After evaluation of these technologies do, make the users feel satisfied and realiability believe this technology and ready for use in large scale and complex in the network without wires.


11.2.1.2 CHANNEL TRANSMISSION CAPACITY




Bandwidth (wide band) shows a number of data that can be transmitted to one unit of time is expressed in units of bits per second (bps) or characters per second (cps). Bandwidth in bps or cps units declare the size of the transmission channel capacity, not the size of speed. transmission of data with size 1000 bits per second can not be faster than the transmission of data with size 200 bits per second.Kapasitas or transfer rate (distribution rate) or band transmission rate of the channel can be classified in the narrowband channel. Channel 3 transmission is divided:




1) Narrowband CHANNEL

Narrowband channels or subvoice grade transmission channel is a channel with low bandwidth, approximately 50-300 bps.Biaya of transmission through the lower narrowband. But the average cost per bitnya more expensive with the possibility of errors besar.jalur telegraph is an example of the narrowband channel.




2) VOICE BAND CHANNEL




Voice band channel or voice grade transmission channel is a channel that has greater bandwidth than the narrowband channel, and it ranged from 300-500 bps.Jalur call is an example of the voice band channel.




3) WIDE BAND CHANNEL


Wide band channel or a broad band transmission channels are used for the transmission of large volumes of data with a bandwidth up to 1 million bps. In general, the data transmission channels widwband very expensive, but if calculated perbitnya costs would be cheaper and probably a small transmission errors. Public telephone lines using widwband channels, ie using coaxial cable media that lies under the sea or microwafe system or satellite system.


CHANEL TYPE OF TRANSMISSION




A transmission channel may have a transmission TPE:

One-Way Transmision

Type of transmission is one-way transmission can only carry data information in the form of one direction only, can not dibolak back.

Examples are radio or television signal is sent from one station can only be received by the catcher plane broadcast, but broadcast catcher aircraft were unable to send back information kestasiun transmitter.


2. Either-Way Transmision

Type two-way alternate transmission is the transmission channels of information where data can flow in both directions alternately.

For example walkie talkie CB radio that can listen or speak in turn.

Both-Way Transmision

Type two-way simultaneous transmission is a dual channel data transmission in which information can flow in two directions simultaneously. Communication by telephone merupan samples from Both Way Transmision.


TRANSMISSION CODE

Transmission codes that can be used are as follows:

Boudot cod, using a combination of 5 bits to represent a character, which is supposed to be able to represent as many as 32 characters. These 32 kinds of characters tidk enough to represent all alphanumeric characters, so the code is divided into 2 parts namely character and character shapes.

ASCII code, ASCII code can be shaped 7-Bitt or code 8-bit ASCII

SCBDIS code, consisting of a combination of 6 bits

EBCDIC code, consisting of a combination of 8 bits


11.MODE TRANSMISSIONS

Data transmission via the transmission channel may take the form:

Parallel Transmission

In this mode all the bits of the character represented by a code, simultaneously transmitted one character at any time.

Serial Transmission

Transmission in series is a common mode of transmission ddipergunakan. In this mode each bit of a character is sent in sequence, ie bits per byte.


Syncrhronous Transmision

Delivery time is the bits in the source must be synchronized with the sender when receiving the bits are received by the recipient.


Bit synchronization, related to the time when the source of the sender must put the bits that are sent to the channels of transmission and receiver must know when exactly to take the bits that sent it.

This problem can be solved with the clock in and clock source of the sender in the recipient post. When bit synchronization problem has been resolved with the clock at the source and the receiver, still other problems arise, the character synchronization. This solution can be overcome by preceding each block of data to be sent denagn a form of specific transmission control characters. In the ASCII code of the transmission control characters is in the form of a SYN with binary numbers .. If only used a SYN character transmission control of a course, the possibility may be happen false synchronization and to prevent, control 2 SYN fruit characters can be used at the beginning of the transmitted data blocks.


Asyncronous Transmission


Asyncronous transmission is transmission of data transmitted each time a character tertentu.Penngirim can transmit characters in bsrbeda intervals, or in other words do not have the time between sending singkron a character with character, each character berikutnya.Tiap transmitted yangn as a stand alone unit and the recipient must be able to recognize each character yersebut.Untuk overcome this, then each character kasin preceded by an additional bits, the start bit or start pulseyang a bit value 0 and the stop bit or stop pulse is a bit value 1 is placed at the end of each character.

Asyncronous transmission more secure than the transmission syncronous transmission.Pada Asyncronous if an error occurs in the transmitted data, will only, only erusak a character, is the transmission Syncronous will destroy a block of data.Akan However, transmission Asyncronous less efficient than transmission syncronous because it needs additional bits for each character, the start bit and stop bit.


PROTOCOL

Protocol is a set of rules associated with data communication between communication devices so that data communication can be done by hand benar.Jabatan an example of protocol between two people who will berkomunikasi.Di handshake computer terms (handshaking) shows a protocol of the data communication when two devices are connected to each other to determine that they are compatible.

To be compatible, then the transmission of data, they must have a transfer rate (transmission rate) the same, have the same data format, must be the same type of transmission and the transmission mode must also be a sama.Protokol generally mengaturkomunikasi software data.


TRANSMISSION ERROR HANDLING

In a data transmission can occur such defects is called the noise, then the transmitted data will occur in the transmission kesalahan.Di important data, transmission errors must be detected and dibetulkan.Pendeteksian transmission errors can be done with teknilk reflection (echo technique ), checking pariti two coordinates (two-coordinate) or cyclic redundancy checking.


ECHO TECHNIQUE

Echo technique is also called an echoplex error detection how to listen, how data is transmitted reflected or sent back (echo) by the recipient back to pengirim.Pengirim then comparing the results are sent back to what was sent, when both are fit, then do not occur error, if not suitable, then there jesalahan in transmission.


TWO-Coordinate Parity Checking

Two-coordinate detection checkingmelakukan parity data transmitted by pariti examined from two directions, each character koordinat.Tiap transmitted given a bit extra that serves as a parity check and a block of transmitted characters were given an extra character that serves as a block check character ( BCC). BCC is also the longlitudinal redundancy check character (LRCC).

Pariti bits (parity bits) for each character in this way is called a character or horizontal parity bits parity bits parity bits or transverse or lateral row parity bits or parity bits bit.Sedang parity in the BCC called peryti character block check bits or longlitudinal or column parity check parity check parity check or vertical.

If there is a wrong bit in a character, then these bits can be detected and corrected automatically, because the character parity bit (horizontal parity bits) and block parity check bits Charakter (paerity vertical check) for the bits that will not true.

11.22.PERANGAKAT HARD DATA COMMUNICATION

In addition to major hardware, such as input devices, processing devices, output devices and mass storage, data communication systems needed some other hardware used to facilitate the process of data transmission.

MODEM

Generally, the data channel transmission lines in the form of analog data, the data were generated by the source sending digital data form. A modulator-demodulator (better known by abbreviation modem) or also called data sets can be used to transform data from digital form into analog form. Special type of modem called the acoustic coupler can be used to alter the digital signal from the terminal to the tone of voice will be transmitted via the modem telepon.Selain using telephone lines, is now also available that do not use a modem or telephone cable, called: the wireless modem. Esteem Wireless modem using VHF FM radio frequencies with specifikasi as follows:


* Type of transmission channels used are full duplex.
* Mode is a serial asynchronous transmission.
* The capacity of the transmission channel is 110 to 9600 bands to choose from.
* Handling of transmission errors using the CRC.


Multiplexer

Multiplexer or mux is a device that allows multiple communication signals using respective terminal low capacity transmission channels can be combined together dikirimin through high-capacity transmission channel (eg, voice grade), so it is more efficient (total cost would be cheaper).


Concentrator

Concentrator has the same function as multiplexer, which combines some of the data signal transmission channel low capacity to high-capacity transmission channel. Concentrator can be set from the current form data before it merged into the high-capacity transmission channel and usually have an outer self storage (mass storage).


COMUNIKASI PROSCESSOR

Communication processors are also called communication controller or the communication front-end or front-end processor or front-end devices that can be a minicomputer or a microcomputer as his successor. Communication processor is designed to perform tasks like setting the data flow is sent, error detection and correction of errors if possible to be formed. Its main objective is to ensure that the central computer CPU can perform other processes, and does not interfere with these additional duties.


11.2.3. FORM DATA SYSTEM KOMUNIASI

A data communication system can be shaped off_line communicationSystem or on_line communication system.


11.2.3.1 OFF_LINE COMMUNICATION SYSTEM

A form of data communication system which can form off_line simple communication system, the transmitted data is not directly processed by the receiver CPU.


11.2.3.2. ON_LINE COMMUNICATION SYSTEM

On_line a communication system, the data will be sent directly received by the central computer for processing. on_line communication system can be shaped remove job entry (RJE) system, real-time system, time-sharing systems, client server system or a distributed data processing system.


REMOVE JOB ENTRY SYSTEM

This system of processing called the batch processing system. Results from a general psngolahan computer data centers and can not be directly dihasilkannya.Karena immediately to the central computer processing and data collection large enough.



RealTime SYSTEM

A realtime system allows to send data to a computer center, computer center processed immediately at the time of the data received and sends the results back to the sender data processing immediately.


SHARING SYSTEM TIMER


Timer-sharing system allows some use of computers (multi user) together using the computer and the computer will divide his time alternately for each user. Because the development process faster CPU, while the tools I / O can not keep up kecepan of CPU, the speed of the CPU can be used efficiently to serve some of the tools I / O turns. Cristopher starchy in 1959 has given an idea of the division of time by the CPU. And in 1961 the first system that really shaped time-sharing system at MIT conducted (Massachusetts Institute of technology) that can serve as many users by using the IBM 7090 computer.


Each user is served by the computer take turns in a very fast time. So that each computer user does not feel that computers serve several users at once turns.


Client Server System

Time sharing system generally involves a mainframe computer that is connected with many terminals. Terminal used is dumb terminal that serves as a tool saja.Terrminal inputs and outputs are called dumb terminals that do not have a processor so that all data processing done mainframe computer. Therefore, the mainframe computer to divide waktuknya (time sharing) to serve a lot of dumb terminals.

Computer center that serves as a provider of data and the program is called with the server. Computer-micro computer that serves as the terminal is called the client and the network system is called the client server system.



Distributed Data Processing System

DDP system can didevenisikan as an interactive computer system that glows in geogerafi and telkomunikasi networks associated with each computer capable of processing data indevenden and able to connect with other Computer into one system.


NETWORK

Network is a network of data communication systems involving one or more computer systems on transmission lines connecting with the communication devices to form a single system





II. Network components 13


components of nodes and links. Nnode is a point that can accept dat input into an output network or information or both. Node can be a printer or other equipment.

Link is: chanenel or transmission lines or carrier to have the information or data may be a cable between. Microwave system. Which each node is a remote location with each other. And use the links in the form of long-distance transmission lines is called a WAN. (Wide area network) network are each separate node in the local distances and using a link cable transmission lines is called a LAN (local area network)


II. 3.2.wan and Ian

WAN (wan and Ian) is a network of data communication systems, each node is located far away (remote location) to each other. WAN is also the name of the remote network or network or exsternal long distane.

Local Area Network (LAN) is a limited network seuat within the local area (local). This network is widely used in a company that connects between the departments in the building swatu.


Fransmisi data in a LAN speeds vary and can be dikatagorikan as follows:

1. HIGH SPEED NETWORK (greater than 20 MBps)

2. MEDIUM SPEED NETWORK (1 MBps, 20 MBps)

3. LOW SPEED NETWORK (less than 1 MBps)


In the LAN, the central computer called a server network that can be associated with several computer terminals or micro form a network. Micro computer can be connected to the network server using regular cable or Coaxial Cable denagn.



Network Topology



Topology: a network based on how to contact a number of nodes or central in forming a network system.



1. STAR NETWORK (NETWORK STAR)


. Connect all the cables on the host to one main point. This point is usually used Hub or Switch



Pros:
- The most flexible for easy wiring
- The addition or reduction of the terminal is very easy and does not interfere with other parts of the network
- Centralized control so as to facilitate the detection and isolation of errors and facilitate network management


Weaknesses:
- Wasteful cable
- Centralized control (HUB) to be a critical element

2. Hierarchical TREE NETWORK

Connected to a computer system that controls traffic on the topology.


Network Keungguluan tree model like this is, can the formation of a group that needed at any time. For example, companies can form a group consisting of terminal accounts, as well as on other groups formed for the sale terminals. The weakness is, if the node is higher then does not work, then another group who are below it eventually also became ineffective. How a network of this tree relative to lambat.puter





3. LOOP NETWORK

Loop network is a relationship between nodes in a series in the form of a closed circle. In this form there is no central node or host note, all have the same status


Pros:

-All the nodes have the same status


Weaknesses:

-If one node will not disturb the damaged another node


4. BUS NETWORK

Using a single segment (cable length) backbone, ie all hosts that connect directly


Pros:

-Low power

-Easy to be developed

-No need of central control

-Simple Layout

- The addition and reduction of the terminal can be done without disturbing the operation running.


Weaknesses:

- Fault detection and isolation of very small

- High traffic density

- Lack of data security guaranteed

- The speed will decrease when the number of users (users) increases

- Required for long-distance repeater


5. RING NETWORK

Connecting a host to host after and before. Physically, the ring-shaped network (circles).


Pros:
- Efficient cable
- Do not need a special cable bundle handling
- Can serve the data traffic is dense


Weaknesses:

- Sensitive to errors

- Development of more rigid network

- Slow

- Damage to the media sender / terminal could paralyze the entire network work


6. WEB NETWORK

Connecting one point to another. Condition where there is no relationship is absolutely cut off communication between computer nodes.


Advantages of mesh network is a single node may be associated with the other nodes are free and if a node is damaged, the other can still relate. The weakness of this mesh networks are too many links so that the cost is expensive and difficult to control because of decentralized management


7. META NETWORK

Meta-network or hybrid network is a network from a network or a combination of several network