Approach
|
SDMA
|
TDMA
|
FDMA
|
CDMA
|
Idea
|
Segment spaced into cells(Tower) or
sectors.
|
Segments sending time into disjoint
time slots demand driven or fixed patterns.
|
Segment the frequency band into
disjoint subbands
|
Spread the spectrum using
orthogonal codes.
|
Terminals
|
Only one terminal can be active in
one cell or one sector.
|
All terminals are active for short
periods of time on same frequency.
|
Every terminal has its own
frequency uninterrupted
|
All terminals can be active at the
same place at the same moment uninterrupted.
|
Signal separation
|
Cell structure, directed antennas
|
Synchronization in time domain
|
Filtering in the frequency domain.
|
Code plus special receivers.
|
Transmission scheme
|
Continuous
|
Discontinuous
|
Continuous
|
Continuous
|
Cell capacity
|
Depends on cell area
|
Limited
|
Limited
|
No absolute limit on channel
capacity but it is an interference limited system
|
Advantages
|
Very simple, increases capacity per
|
Established fully digital, flexible
|
Simple, established, robust
|
Flexible, less frequency planning
needed, soft handover
|
Disadvantages
|
Inflexible, antennas typically
fixed
|
Guard space needed (multipath
propagation), synchronization difficult
|
Inflexible, frequencies are scarce
resource
|
Complex receivers, needs more
complicated power control for senders
|
Comment
|
Only in combination with TDMA, FDMA
or CDMA useful
|
Standards in fixed networks,
together with FDMA or SDMA used in many mobile networks
|
Typically combined with TDMA and
SDMA
|
Still faces some problems, higher
complexity, lowered expectations, will be integrated with TDMA or FDMA
|
Help others with accurate and useful information For more information please visit www.mamstricks.blogspot.in
Sunday 22 April 2018
Compare the features of SDMA, FDMA and CDMA
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