CDMA concept (很基础)

CMDA-conceptConcepts of CDMA

1

22:48:24

Cellular Access Methods
Power Time Time Power

FDMA Power Time

Frequency

CDMA

Frequency

TDMA

Frequency
2

22:48:24

CDMA is Also Full Duplex
Amplitude
Reverse Link

US Cellular Channel 384
Forward Link

AMPS
836.52 MHz

45 MHz

Frequency
881.52 MHz

Amplitude
Reverse Link Forward Link

CDMA
836.52 MHz

45 MHz

Frequency
881.52 MHz

3

22:48:24

Cellular Frequency Reuse Patterns

1 2 6 5 7
FDMA Reuse

1

3 4 6 2
1

1 1 1 1

1 1 1

CDMA Reuse

4

22:48:24

CDMA Capacity Gains
(Chan BW) X _____ (1) Capacity = _____________ X (1) ____ X (Fr) (Data Rate) (S/N) (Vaf) (1,230,000) X _____ (1) CDMA = ____________ X (1) _____ X (0.67) (9,600) (5.01) (.40) CDMA = 42 Calls ( Using 1.5 MHz BW )

Processing Gain

AMPS = 1.5 MHz / 30 kHz = 50 Channels Capacity = 50