'CDMA'에 해당되는 글 1건
- 11. spread spectrum communications: applications of spread spectrum - commercial
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- 2009. 1. 17. 14:30
11.5.2 commercial
multiple access communications
from the perspective of commercial applications, probably the most important use of spread spectrum communications is as a multiple accessing technique.
- SS technique and multiple access, CDMA
commonly used multiple access techniques: TDMA, FDMA, CDMA
in the CDMA, each signal in the set is given its own spreading sequence. all signals occupy the same bandwidth and are transmitted simultaneously in time: the different waveforms in CDMA are distinguished from one another at the receiver by the specific spreading codes they employ.
- CDMA detector
- CDMA application area: wireless communications
CDMA has been of particular interest recently for applications in wireless communications; including cellular communications, personal communications services (PCS), and wireless local area networks.
the reason for this popularity is primarily due to the performance that spread spectrum waveforms display when transmitted over a multipath fading channel, and concept known as the reuse factor, and property of achievable additional gain in the capacity by the use of voice activity detection.
- CDMA (SS technique) performance over multipath channel
- reuse factor
in conventional cellular systems, in order to avoid excessive interference from one cell to its neighbor cells, the frequencies used by a given cell are not used by its immediate neighbors. for CDMA, however, such spatial isolation is typecally not needed, so-called universal reuse is possible.
- voice activity detection
interference rejection
spread spectrum techniques are of interest in the commercial sector for basically the same reasons they are in the military community, namely their AJ and LPI characteristics.
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