Synchronous TransmissionSynchronous transmission is a data transfer method. It uses timing signals to make sure the sender and the receiver of the data signals are synchronized with one another. Data is sent in packets and frames. "Synchronous transmission sends data as one long bit stream or block of data. There are no gaps in transmission; each bit is sent one after the other. The receiver counts the bits and reconstructs bytes. It is essential that timing is maintained as there are no start and stop bits and no gaps. Accuracy is dependent on the receiver keeping an accurate count of the bits as they come in."
Bandwidth"The amount of data that can be transmitted in a fixed amount of time. For digital devices, the bandwidth is usually expressed in bits per second(bps) or bytes per second." Bandwidth measures how much data can be transferred along a communication channel.
Bandwidth LimitationsBandwidth limitations are the amount of data that can be downloaded or transferred from the internet. The higher the bandwidth limit, the more data can be downloaded/transferred.
Channel TypesTelephones are a device used to speak to other people over long distances using electric signals. The user will dial a number to directly send a signal to another specific telephone to talk to the person who answers the call.
A microwave is electromagnetic energy that has high frequency and short wavelengths. Microwave transmission is often used for transmitting mobile phone signals and sometimes can also be used to transmit data to satellites above the earths atmosphere.
Satellites can be man-made machines that are built to orbit the Earth and study weather, other planets, black holes, the sun or galaxies far away by taking pictures. Sometimes man-made satellites are also used for communications on Earth. For example, television signals, phone calls, and GPS' all use satellites to transmit signals around the world. Other satellites can be natural; for example, the moon and planets are satellites because they orbit something (the Earth orbits the sun, the moon orbits the Earth).
Data CompressionData compression is when the data file format is changed so that the data file can be saved. It is a way of reducing the storage space required by a file to be able to save it. "Compression is a reduction in the number of bits needed to represent data. Compressing data can save storage capacity, speed file transfer, and decrease costs for storage hardware and network bandwidth."
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Asynchronous TransmissionAsynchronous transmission is different to synchronous transmission because it doesn't need to rely on timing signals. "Asynchronous transmission is relatively slow due to the increased number of bits and gaps. It is a cheap and effective form of serial transmission and is particularly suited for low speed connections such as keyboard and mouse."
Digital Signalling MethodsDigital signalling methods are ways of transmitting a digital signal electrically, optically, through sound and through radio waves. "The process of converting analog transmissions into digital signals. The audio transmissions are processed in real-time and provide a clearer signal after the conversion."
Bandwidth NoiseRepresenting Data ElectronicallyData can be represented electronically using three different methods; these are bits, bytes and packet structures.
Bits: Bits have only two values - on (1) or off (0). It is the smallest piece of information in a computer. Bytes: A byte is made up of 8 bits. "In most computer systems, a byte is a unit of data that is eight binary digits long. A byte is the unit most computers use to represent a character such as a letter, number, or typographic symbol (for example, "g", "5", or "?")." Packet Structures: A packet is a unit of communication. They can also be called datagrams, segments, blocks, frames or cells. "Packets vary in structure depending on the protocols implementing them.The structure of a packet depends on the type of packet it is and on the protocol. An IP packet includes |
Error DetectionError detection is used to ensure that all data sent over communication channels are delivered correctly and are reliable sources of information. Examples of error detection in information technology include checksum, cyclic redundancy checks (CRC), repetition codes, parity bits, cryptographics hash functions and error-correcting codes.
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Error CorrectionError correction is vital within information technology when data is being delivered because without correcting detected errors, it will mean the user will receive unreliable information. Examples of error correction schemes are automatic repeat request (ARQ), error-correcting code and hybrid schemes.
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