A2-Radio Communication principles

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⌘ 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)

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