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Figure 6.7: Distorsion
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Figure 6.4 FDM (Frekvensdelningsmultiplex, frequency division multiplex) Exempel på FDM-teknik: ADSL-modem, kabel-TV-modem, trådlös kommunikation.
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Figure 6.5 FDM demultiplexing example
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Figure 6.19 T-1 line for multiplexing telephone lines
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Bandbredd = övre gränsfrekvens – undre gränsfrekvens
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Digital modulation För att överföra N bit/symbol krävs M=2 N Vid M symboler överförs N=log 2 M bit/symbol. Baudrate f s = antal symboler per sekund. Enhet: baud eller symboler/sekund. Symbollängd T s = 1/f s. f s = 1/T s Bitrate R = datahastighet. Enhet: bps eller bit/s. R= f s log 2 M
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Figure 3.6 Sine wave examples (continued)
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Figure 3.9 Three harmonics
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Figure 3.10 Adding first three harmonics
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Figure 3.11 Frequency spectrum comparison
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Point-to-point communication MikrofonHögtalare Source codingSource decoding Digitalizating compression 0110 Error managementError control. 0100010 Bitfel 0110010 Flow control ModulationDemodulation 0110010 NACK ACK Layer 6 Layer 2 Layer 1 Layer 7
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Aliasing
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Quantization noice
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Digital modulation methods Binär signal ASK = Amplitude Shift Keying (AM) FSK = Frequency Shift Keying (FM) PSK = Phase Shift Keying (PSK)
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Spread spectrum DS-CDMA = Direct Sequence Code Division Multiple Access Chip sequencies
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Figure 13.15 Encoding rules
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Figure 13.16 CDMA multiplexer
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Figure 13.17 CDMA demultiplexer
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