Figure 6.7: Distorsion
Figure 6.4 FDM (Frekvensdelningsmultiplex, frequency division multiplex) Exempel på FDM-teknik: ADSL-modem, kabel-TV-modem, trådlös kommunikation.
Figure 6.5 FDM demultiplexing example
Figure 6.19 T-1 line for multiplexing telephone lines
Bandbredd = övre gränsfrekvens – undre gränsfrekvens
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
Figure 3.6 Sine wave examples (continued)
Figure 3.9 Three harmonics
Figure 3.10 Adding first three harmonics
Figure 3.11 Frequency spectrum comparison
Point-to-point communication MikrofonHögtalare Source codingSource decoding Digitalizating compression 0110 Error managementError control Bitfel Flow control ModulationDemodulation NACK ACK Layer 6 Layer 2 Layer 1 Layer 7
Aliasing
Quantization noice
Digital modulation methods Binär signal ASK = Amplitude Shift Keying (AM) FSK = Frequency Shift Keying (FM) PSK = Phase Shift Keying (PSK)
Spread spectrum DS-CDMA = Direct Sequence Code Division Multiple Access Chip sequencies
Figure Encoding rules
Figure CDMA multiplexer
Figure CDMA demultiplexer