Difference between revisions of "A2-Radio Communication principles"
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| − | + | =⌘ Coding and Modulation= | |
| − | + | A modulated radio signal can be written in a general form: | |
| − | + | <math> C(t) = A(t) cos(2\pi f(t) t + \varphi(t)) </math> | |
| − | + | Any of these three parameters can be varied: amplitude-, frequency- or phase-modulation. | |
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| − | + | * Channel-coding is used to reduce bit-error-rate, e.g. through forward error correction. | |
| − | + | * Multiplexing is used to split the total amount of radio into smaller pieces. Typical: time, frequency or code multiplex. <span style="color:#000B80">examples | |
| − | + | [Source:K.E. Walter, Basics of Mobile Communications] | |
| + | |||
| + | == Comments == | ||
| + | [[File:F3-7.png|550px|right]] | ||
| + | Figure: A frequency band consists of ''n'' channels. | ||
| + | |||
| + | Example GSM: the upload band is from 880-915 Unik/MHz, which is 35 Unik/MHz. With a carrier of 200 kHz we have 175 channels, which have to be divided between the various operators. | ||
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| + | =⌘ Modulation types = | ||
| + | [[File:WalterModulation.png|450px|right]] | ||
| + | |||
| + | * Amplitude shift keying (ASK) | ||
| + | * Frequency shift keying (FSK) | ||
| + | * Phase shift keying (PSK) | ||
| + | [Source:K.E. Walter, Basics of Mobile Communications] | ||
| + | |||
| + | =⌘ Frequency and time division multiplexing = | ||
| + | [[File:WalterMultiplexing.png|450px|right]] | ||
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| + | [[File:WalterGSM.png|450px|right]] | ||
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| + | * Time domain, e.g. 8 slots in GSM | ||
| + | * Frequency domain, e.g. up- and downlink in specific bands | ||
| + | * Code division (CDM), specific codes | ||
| + | |||
| + | [Source:K.E. Walter, Basics of Mobile Communications] | ||
| + | |||
| + | =⌘ Code division multiple access = | ||
| + | |||
| + | <span style="color:#0B0080"> UMTS as an example (in one of the future lectures) | ||
Latest revision as of 19:32, 21 September 2014
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Contents
⌘ Coding and Modulation
A modulated radio signal can be written in a general form:
Any of these three parameters can be varied: amplitude-, frequency- or phase-modulation.
- Channel-coding is used to reduce bit-error-rate, e.g. through forward error correction.
- Multiplexing is used to split the total amount of radio into smaller pieces. Typical: time, frequency or code multiplex. examples
[Source:K.E. Walter, Basics of Mobile Communications]
Comments
Figure: A frequency band consists of n channels.
Example GSM: the upload band is from 880-915 Unik/MHz, which is 35 Unik/MHz. With a carrier of 200 kHz we have 175 channels, which have to be divided between the various operators.
⌘ Modulation types
- Amplitude shift keying (ASK)
- Frequency shift keying (FSK)
- Phase shift keying (PSK)
[Source:K.E. Walter, Basics of Mobile Communications]
⌘ Frequency and time division multiplexing
- Time domain, e.g. 8 slots in GSM
- Frequency domain, e.g. up- and downlink in specific bands
- Code division (CDM), specific codes
[Source:K.E. Walter, Basics of Mobile Communications]
⌘ Code division multiple access
UMTS as an example (in one of the future lectures)
