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Compare TDMA, CDMA, FDMA and SDMA

written 3.5 years ago by teamques10 ★ 68k

modified 3.0 years ago by pedsangini276 • 4.8k

wireless networks

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written 3.5 years ago by teamques10 ★ 68k

modified 2.5 years ago by sagarkolekar ★ 11k

Approach	SDMA	TDMA	FDMA	CDMA
Idea	Segment space into cells/sectors	Segment sending time into disjoint time-slots, demand driven or fixed patterns	Segment the frequency band into disjoint sub-bands	Spread the spectrum using orthogonal codes
Terminals	Only one terminal can be active in one cell/ one sector	All terminals are active for short periods of time on the same frequency	Every terminal has its own frequency, uninterrupted	All terminal can be active at the same place at the same moment, uninterrupted
Signal separation	Cell structure, directed antennas	Synchronization in the time domain	Filtering in the frequency domain	Code plus special receivers
Advantages	Very simple, increases capacity per km2	Established, fully digital, flexible	Simple established, robust	Flexible, less frequency planning needed, soft handover
Dis-advantages	Inflexible, antennas typically fixed	Quard space needed (multipath propogation), synchronization difficult	Inflexible,  frequencies are a scarce resource	Complex receivers, needs more complicate power control for senders
Comment	Only in combination with TDMA, FDMA or CDMA useful	Standard in fixed networks, together with FDMA/SDMA used in many mobile networks	Typically combined with TDMA (frequency hopping patterns) and SDMA (frequency reuse)	Still faces some problems, higher complexity, lowered expectations; will be integrated with TDMA/FDMA

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