24-03-2011, 02:13 PM
Prepared By
Shashank arora,
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Type of Multiplexing:
Frequency-Division Multiple Access (FDMA)
Time-Division Multiple Access (TDMA).
Code-division Multiple-Access (CDMA)
Frequency-Division Multiple Access (FDMA)
It is a communications technique that divides a communications channel into a number of equally spaced frequency bands
Time-Division Multiple Access (TDMA)
It is a digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference by allocating unique time slots to each user within each channel.
Code Division Multiple Access (CDMA)
is a wireless communications technology that uses the principle of spread spectrum communication.
There are three ways to spread the bandwidth of the signal:
Frequency hopping
Time hopping
Direct sequence
CDMA is a Direct Sequence Spread Spectrum system
CDMA Features:
o All users use same frequency and may transmit simultaneously
o Narrowband message signal multiplied by wideband spreading signal, or codeword
o Each user has its own pseudo-codeword (orthogonal to others).
o Receivers detect only the desired codeword. All others appear
as noise.
o Receivers must know transmitter’s codeword.
Advantages:
o Increased capacity
o Improved voice quality
o Eliminating the audible effects of multipath fading
o Enhanced privacy and security
o Reduced average transmitted power
o Reduced interference to other electronic devices
Disadvantages:
o Wide bandwidth per user required
o Precision code synchronization needed
o The Future Planning For Next Semester
o Study the capacity of CDMA
Study the interference rises from the increasing of capacity and how to reduce its effect
We will evaluate interference and capacity in CDMA system and analysize them using MatLab simulator