Concepts include: - Uploading and Downloading
- Serial and Parallel Transmissions
- Simplex, Half Duplex and Full Duplex
- Synchronous vs Asynchronous transmission
- Measurement of Speeds (bit rates, baud rates and bandwidth)
Bandwidth The difference between the highest and lowest frequencies in a transmission channel. Hence bandwidth is expressed in hertz (Hz), usually kilohertz (kHz) or megahertz (MHz).
The term bandwidth is often used incorrectly, people make statements such as “video requires much more bandwidth than text” or “my bandwidth decreases as more people use the Internet”. - Statements such as these are incorrect, they are using bandwidth when they really mean speed or bps.
- Bandwidth is not a measure of speed at all, rather it is the range of frequencies used by a transmission channel.
- Presumably misunderstandings have occurred because the theoretical maximum speed does increase as the bandwidth of a channel increases.
- However, it is simply impossible for the bandwidth of most channels to change during transmission.
- Each channel is assigned a particular range of frequencies when it is first setup, unless you run a high-speed Internet company or are creating your own hardware transmitters and receivers, then altering bandwidth is really beyond your control.
So what is bandwidth? It is the difference between the highest and the lowest frequencies used by a transmission channel. - Frequency is measured in hertz (Hz), meaning cycles per second.
- Each cycle being a complete wavelength of an electromagnetic wave, so 20Hz means 20 complete wavelengths occur every second.
- As frequency is expressed in hertz then so to is bandwidth.
- For example, standard telephone equipment used for voice operates within a frequency range from about 200Hz to 3400Hz, so the available bandwidth is approximately 3200Hz.
- As high-speed connections routinely use bandwidths larger than 1,000Hz or even 1,000,000Hz, bandwidth is usually expressed using kilohertz (kHz) or megahertz (MHz).
- For example 3200Hz would be expressed as 3.2kHz.
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